This document provides an overview of imaging techniques for evaluating soft tissues, including radiography, ultrasound, CT, MRI, and radionuclide imaging. It discusses the advantages and limitations of each technique. It also reviews common radiographic observations of soft tissue abnormalities like calcification, ossification, and conditions that cause generalized soft tissue changes such as metabolic disorders, infections, and congenital disorders. The level of detail provided is intended to help radiologists and clinicians understand the diagnostic potential and appropriate clinical application of various imaging modalities for soft tissue evaluation.

2. Introduction
• The imaging evaluation of the soft tissues has
undergone a rapid evolution with the application
of computed tomography (CT), magnetic
resonance imaging (MRI), and recently high
resolution ultrasound (US).
• Consideration must be given to the financial costs
and invasiveness of each technique balanced
against the diagnostic reward.
• No examination should be reported in isolation
without knowledge of relevant clinical details and
results of previous investigations.

3. What is Soft Tissue???
• Soft tissue
– derived primarily from mesenchyme and
– consists of
• skeletal muscle,
• fat,
• fibrous tissue,
• the vascular structures
• the peripheral nervous system.

4. IMAGING TECHNIQUES

5. Radiography
• The relative lack of soft tissue contrast
resolution is a well-recognized limitation of
radiography.

6. Only those structures exhibiting a radiodensity
sufficiently different to that of water can be
distinguished from other soft tissues.
Less than muscle - fat and gas
Increased radiodensity - haemosiderin deposition,
mineralization, be it calcification or ossification, and
certain foreign bodies

7. • A low kilovoltage technique will accentuate the
density differences between fat and muscle.
• Density differences can also be maximized with
digital radiography where the broad exposure
range means that it is difficult to make an
inadequate exposure. A free choice of data
processing allows control of the grey scales,
contrast, etc., which can be optimized to
highlight soft tissue disease.

8. Radiograph - Caution!!!
• When evaluating a radiograph it is important to
remember that numerous extraneous factors
may mimic soft tissue abnormalities. These
include skin folds, clothing, hair artefacts and
companion shadows.
• Also, iatrogenic conditions may pose diagnostic
problems to the unwary such as the sites of old
bismuth injections in the buttocks and tantalum
gauze previously used in hernia repairs.

9. Ultrasound
• Diagnostic ultrasound has been applied to the musculoskeletal system since B-mode techniques
became available. There have been rapid developments in ultrasound technology over recent years
and these, along with the have resulted in a vast expansion in the evaluation of the soft tissues.
• Advantages of ultrasound include
– widespread availability of ultrasound and
– relatively low cost,
– solid from cystic
– abnormal tissue from normal variants such as accessory muscles
– its real-time ability to assess structures dynamically,
– its capability, using Doppler technology, to assess vascular flow and
– to guide interventional procedures such as joint aspirations and soft tissue biopsies.

10. • The advent of high frequency
(>10 MHz) transducers with
their improved spatial
resolution, along with other
developments such as
multifrequency transducers,
compound imaging and beam
steering, has meant that
further applications for
musculoskeletal ultrasound
continue to be introduced.
• Tendons, ligaments, nerves
and muscle are now readily
shown with ultrasound.

11. Ultrasound - Trade off!!!
• The physics of ultrasound means there will always be a trade-off
between image resolution and depth of penetration.
• Nevertheless the majority of musculoskeletal soft tissue structures
lie superficially and are readily amenable to high resolution
ultrasound assessment.
• Disadvantages:
– some deeper structures, such as the deep musculature about the
adult hip, remain difficult to assess
– larger patients.
– unable to see behind or into bone.
– relatively limited field of view (extended field of view imaging has
gone some way to resolve this issue)
– marked operator dependency
– poor demonstration of findings on hard copy images;

12. Computed tomography
• The introduction of computed
tomography (CT) proved a
revolution in the detection of soft
tissue masses and the
preoperative staging of soft tissue
tumours.
• CT, by virtue of its ability to assign
a numerical value (Hounsfield
number) to X-ray attenuation,
produces good qualitative and
quantitative assessment of soft
tissues, offering an opportunity to
distinguish the nature of a mass
whether it is muscle, fat, fluid or
tumour, and not solely on
morphology.

13. • The high spatial resolution of CT, of
the order of 1 mm, allows for masses
as small as 1 cm to be detected,
depending on differential attenuation
between the lesion and the
surrounding soft tissues.
• The contrast sensitivity and cross-sectional
ability of CT will reveal soft
tissue masses and calcifications that
are not visible on conventional
radiography.
• Lesion conspicuity can be increased
with intravenous (IV) iodinated
contrast medium.
• Narrow window settings are required
for small density differences.
• The full extent of a lesion can be
displayed by performing multiplanar
reconstructions.

14. Magnetic resonance imaging
• advantage
– not using ionizing radiation.
– superior soft tissue contrast resolution and
– multiplanar capability
• Soft tissue lesions can be categorized by MRI
according to
– site,
– morphological changes and
– signal characteristics – helped by multitude of
sequences.

15. • Contrast enhancement following the IV injection of a gadolinium chelate
will result in a decrease in the T1 relaxation time and show up soft tissue
lesions due to their different vascularization and perfusion. Enhancement
can be most clearly identified on fat-suppressed T1-weighted images but
enhancement is rarely necessary in the detection of soft tissue
abnormalities where fat-suppressed T2-weighted or STIR sequences will
suffice without the additional expense of the contrast medium.
• Similarly, many soft tissue abnormalities can be adequately categorized
on MRI without contrast medium, e.g. ganglion, lipoma, haemangioma,
etc. In equivocal cases, contrast agents can be of value in helping to
distinguish cystic from solid lesions and thereby identifying the most
appropriate portion of a lesion to biopsy.
• MRI is the best technique for staging soft tissue tumours and for follow-up.
With the increasing use of adjuvant chemotherapy for soft tissue
sarcomas, dynamic contrast-enhanced techniques will be increasingly
used to assess angiogenesis and response.

16. Radionuclide imaging
• Numerous soft tissue lesions concentrate bone-seeking radiopharmaceuticals. Any soft tissue
abnormality with the propensity to develop mineralization can show ectopic activity on
skeletal scintigraphy. These include congenital abnormalities such as fibrodysplasia ossificans
progressiva , collagen vascular disorders such as dermatomyositis, trauma as in myositis
ossificans and neoplasia as in extraskeletal osteosarcoma and synovial sarcoma.
• Skeletal scintigraphy may be helpful in assessing the maturity of ectopic ossification as can
be seen with spinal cord injuries. In this situation surgical resection is best deferred until the
ossification becomes stable to minimize the risk of recurrence.
• Scintigraphy is not routinely indicated in the surgical staging of soft tissue sarcomas. Local
osseous extension is uncommon and is best demonstrated by MRI. Bone metastases from
soft tissue sarcomas are rare in the absence of disseminated disease elsewhere, notably the
lungs, but can be seen in alveolar soft part sarcoma and rhabdomyosarcoma.
• Positron emission tomography (PET) with [F-18] fluorodeoxyglucose has not yet been widely
studied for soft tissue lesions; it can be used to assess soft tissue tumour metabolism in order
to grade tumours and to assess relapse. It may also be helpful in assessing malignant
transformation of peripheral nerve sheath tumours in neurofibromatosis

17. RADIOGRAPHIC OBSERVATIONS

18. Calcification And Ossification
• The deposition of amorphous calcium salts within
the soft tissues is variously called mineralization
or calcification.
• Two forms of calcium salts may be found in the
soft tissues: calcium pyrophosphate dihydrate
and calcium hydroxyapatite.
• If bony trabeculae are discernible within the
mineralized focus the term ‘ossification’ is used,
sometimes prefixed with the terms ectopic or
heterotopic.

19. • There is a wide differential diagnosis, which
can be divided into
– generalized calcification,
– localized calcification and
– ossification

20. Generalized Conditions

21. Generalized Conditions

22. Metabolic disorders
• Prolonged elevation of the serum calcium or, more importantly, the
serum phosphate.
• In primary hyperparathyroidism
– typically seen in arteries, cartilage (chondrocalcinosis) and the
periarticular tissues.
– uncommon today as primary hyperparathyroidism is usually detected
by identification of serum biochemical abnormalities before the more
florid radiographic abnormalities have the opportunity to develop.
• In secondary hyperparathyroidism, typically associated with renal
failure,
– arterial and soft tissue calcification are frequent findings.
– Periarticular calcification is a prominent feature, particularly in those
on long-term renal dialysis.
– Conversely, chondrocalcinosis is an infrequent finding in secondary
hyperparathyroidism

23. Chronic renal failure (two different cases).
(A) PA hand radiograph showing the florid features of secondary
hyperparathyroidism including terminal phalangeal resorption, soft tissue
calcification, subperiosteal resorption, vascular calcification and osteopenia.
(B) Tumoral calcinosis with heavy periarticular calcification

24. • In hypoparathyroidism there is a deficiency in parathormone (PTH),
usually secondary to excision or surgical trauma but rarely
idiopathic. Subcutaneous calcification, basal ganglia calcification,
osteosclerosis and premature closure of epiphyses are typical of the
primary disease. Occasionally, band-like paraspinal calcification may
be seen mimicking diffuse idiopathic skeletal hyperostosis.
• Pseudohypoparathyroidism, a rare inherited X-linked dominant
disease in which there is end-organ resistance to PTH, exhibits
similar features to hypoparathyroidism. Features that distinguish it
from hypoparathyroidism are growth deformities, with broad bones
and cone epiphyses, brachydactyly with short metacarpals and
metatarsals, especially the first, fourth and fifth, and small
exostoses projected at right angles from the bone.
• In pseudopseudohypoparathyroidism, in which the serum calcium
and phosphate levels are normal, the radiographic abnormalities
are identical to those of pseudohypoparathyroidism.

25. • Hypervitaminosis D usually occurs due to the administration of excessive levels of the vitamin in
the treatment of rickets and osteomalacia but can also be found in granulomatous diseases, Paget's
disease and rheumatological conditions such as rheumatoid arthritis and gout. Smooth, lobulated
amorphous masses of calcium, usually calcium hydroxyapatite, occur in the periarticular regions,
bursae, tendons sheaths, and both within the capsule and cavity of joints. The bony manifestations
of vitamin D intoxication depend on the age of the patient, with dense metaphyseal bands and
cortical thickening with or without generalized osteosclerosis seen in infants and children. Adults
merely show varying degrees of osteoporosis.
• A generalized increase in bone density is a feature of idiopathic infantile hypercalcaemia where
there are associated clinical manifestations of hypotonia and mental and physical retardation. The
condition is thought to be due to inappropriate sensitivity to vitamin D.
• Milk-alkali syndrome is reported in patients with chronic peptic ulcer disease and renal impairment
in whom the excessive ingestion of alkali, usually calcium carbonate, and milk leads to diffuse
calcifications in the soft tissues, kidneys and eyes. Reversibility depends on the chronicity of the
disorder. The soft tissue calcifications are typically periarticular, amorphous and vary in size from
small nodules to large masses. Similar deposits may be seen in renal osteodystrophy, collagen
vascular disorders, hypervitaminosis D and idiopathic tumoral calcinosis.
• Deposits of monosodium urate in gout, so-called ‘tophi’, are not radio-opaque. However,
calcification within the tophi can occur as a secondary phenomenon. The incidence of chronic
tophaceous gout has decreased considerably with the introduction of effective anti-uricaemic
drugs.

26. Generalized Conditions

27. Arterial calcification
• Some degree of arterial disease is an almost
inevitable part of the ageing process in the
developed world so that atheromatous
calcification is considered a normal variant
on most radiographs in middle-aged and
elderly patients. The spectrum of
calcification ranges from irregular plaques to
extensive tramline calcification
predominantly affecting the aorta and pelvic
and lower limb arteries.
• Finer ‘pipe-stem’ calcification is seen in
medial degeneration (Mönckeberg's
arteriosclerosis) which also shows a similar
propensity for the lower limbs, as does the
calcification associated with diabetes
mellitus.
• A finer more generalized pattern of arterial
calcification is seen in renal failure and
hyperparathyroidism.
• Rounded, curvilinear or crescentic
calcification is a typical feature of aneurysms
on radiographs irrespective of site.

28. Venous calcification
• Venous mural calcification is rare
• Small circular calcified densities,
phleboliths, are common, especially
in the pelvic veins.
– also seen in chronic varicosities and
haemangiomas, most frequently
cavernous ( Fig.A ).
• Phleboliths may be the only
radiographic soft tissue abnormality
indicative of haemangiomas in
patients with Maffucci's syndrome,
which is the combination of multiple
enchondromas (Ollier's disease) and
haemangiomas ( Fig.B ).
• Subcutaneous calcification and
organized periosteal new bone
formation may occur in chronic
oedema associated with venous
incompetence.

29. Generalized Conditions

30. Bacterial
• Diffuse calcification is
extremely rare in bacterial
infection. Dystrophic
calcification may occur in
resolving abscesses,
particularly in tuberculosis of
the spine.
• Extensive calcified
lymphadenitis is highly
suggestive of an old
tuberculous infection and, in
endemic areas, the fungal
infections histoplasmosis and
coccidioidomycosis.
• Leprosy is a rare cause of
nerve calcification.

31. Parasitic
Cysticercosis Guinea worm

32. Generalized Conditions

33. Congenital
• Fibrodysplasia ossificans
progressiva
– Previously known by the synonym
myositis ossificans progressiva
– inherited autosomal disorder.
– progressive swelling and
ossification of the fascia,
aponeuroses, ligaments, tendons
and connective tissue of skeletal
muscle,
– entirely unrelated to myositis
ossificans.
– The initial manifestation is swelling
of the muscular fascial planes,
usually affecting the neck and
shoulder girdle first, before the
onset of multifocal calcification
progressing to ossification.
Fibrodysplasia ossificans progressiva.
(A) Posterior 3-h skeletal scintigram of the trunk showing
linear foci of increased activity corresponding to the soft
tissue ossification. (B) Chest radiograph showing bilateral
chest wall ossification.

34. Congenital
• Fibrodysplasia ossificans
progressiva
– Early changes can be detected by
CT, MRI and skeletal scintigraphy
– The progressive ossification
produces large masses that can
bridge between bones, which in
the thorax can result in respiratory
compromise.
– The disorder can be suspected
before the development of soft
tissue swellings by identification of
associated skeletal abnormalities.
• short first metacarpals and
metatarsals
• small cervical vertebral bodies
with relative prominence of the
pedicles.
Fibrodysplasia ossificans progressiva.
(A) Posterior 3-h skeletal scintigram of the trunk showing
linear foci of increased activity corresponding to the soft
tissue ossification. (B) Chest radiograph showing bilateral
chest wall ossification.

35. Acquired
Crystal deposition diseases
Crystal deposition in a joint will stimulate a synovitis
due to one of the following crystalline
arthropathies:
1. gout
2. calcium pyrophosphate dihydrate deposition disease
(CPPD)
3. calcium hydroxyapatite deposition disease (HADD)
4. mixed crystal deposition disease.

36. CPPD
• CPPD is the general term for the deposition of
calcium pyrophosphate dihydrate crystals in and
around joints, and in the annulus of the
intervertebral disc.
 The latter is a useful distinguishing feature from ochronosis
which involves the nucleus pulposus.
• There are three manifestations of CPPD,
– acute intermittent synovitis (pseudogout),
– chronic pyrophosphate arthropathy and
– chondrocalcinosis

37. • Pyrophosphate arthropathy has many similar
radiographic appearances to osteoarthritis.
• It is for this reason that many cases will pass through
orthopaedic clinics simply labelled as osteoarthritis.
• Features suggestive of pyrophosphate arthropathy
include
– unusual distribution (e.g. patellofemoral, radiocarpal and
elbow joints),
– prominent subchondral cyst formation and
– relative paucity of osteophytes.

38. • Chondrocalcinosis affects
both fibrocartilage (menisci,
triangular fibrocartilage,
symphysis pubis and
annulus fibrosus) and
hyaline cartilage of the
knee, wrist, elbow and hip.
• CPPD is associated with
many conditions, such as
hyperparathyroidism,
haemochromatosis, gout,
Wilson's disease and
diabetes mellitus. Chondrocalcinosis of the menisci.
Ossification adjacent to the medial femoral
condyle indicates old medial collateral
ligament injury (Pellegrini–Stieda lesion).

39. Calcium hydroxyapatite deposition disease
(HADD)
• HADD typically has a
monoarticular presentation in
the middle-aged and elderly.
• It is characterized by
homogeneous cloud-like
periarticular calcification, most
commonly affecting the shoulder
in and around the supraspinatus
tendon.
• Aetiology is thought to be related
to repetitive minor trauma with a
cycle of necrosis and
inflammation leading to
dystrophic calcification.
• Over time, dependent on the
clinical course, the calcifications
may increase in size, remain
unchanged or regress.
Calcium hydroxyapatite deposition disease
(HADD). Heavy calcification in the distal
supraspinatus tendon.

40. Dermatomyositis
• This is a condition of unknown aetiology
that produces inflammation and muscle
degeneration.
• It is frequently associated with
nonspecific subcutaneous calcification
with less common, albeit characteristic,
sheet-like calcification along fascial and
muscle planes, particularly involving the
proximal large muscles.
• The major differential diagnoses
– idiopathic calcinosis universalis
– hyperparathyroidism.
• The childhood form may be associated
with hypogammaglobulinaemia or
leukaemia.
• In older patients it may be associated
with malignancy; the most common
associations are with carcinoma of the
bronchus, breast, stomach and ovary.

41. Progressive systemic sclerosis
(scleroderma)
• This condition, with unknown aetiology, causes
small vessel disease and fibrosis in several
organs.
• Scleroderma is the cutaneous manifestation of
the disease.
• It often presents with Raynaud's phenomenon
and skin changes.
• Typical features in the hands are terminal
phalangeal resorption (acro-osteolysis) due to
pressure atrophy, discrete dense plaques of
calcification (calcinosis circumscripta) and
occasional intra-articular calcification.
• Erosive changes can occur which may be due to
concurrent rheumatoid arthritis or some form
of overlapping condition.
• The related CREST syndrome is due to the
combination of calcinosis, Raynaud's
phenomenon, oesophageal dysmotility,
scleroderma and telangiectasia.
• The only radiographic difference from that
described above is that the calcification may
also involve the tendon sheaths.
Scleroderma.
Widespread digital calcification (calcinosis circumscripta).

42. Generalized Conditions

43. Tumoral calcinosis
• Autosomal dominant condition,
• biochemical defect of phosphorus
metabolism.
• normal serum calcium level
• renal, metabolic and collagen vascular
disorders have been excluded.
• It leads to large multilocular juxta-articular
cystic lesions filled with calcific
fluid (calcium hydroxyapatite) with or
without fluid–fluid levels.
• By virtue of their site and size, these
masses can lead to restricted joint
motion, bone erosion and superficial
ulceration and secondary infection.
• Treatment relies on phosphate depletion.
• Surgery is frequently associated with
recurrence of the mass.
Tumoral calcinosis with heavy
periarticular calcification.

44. Localized Conditions

45. CALCIFICATION—LOCALIZED
• The first radiographic sign of soft tissue
mineralization will be faint calcification.
• In time this may become more extensive and
therefore more conspicuous.
• Alternatively, in certain conditions the
mineralization can develop into woven bone.
Therefore, localized calcification may be the
precursor of conditions typically associated
with ossification.

46. Trauma
• Any condition that results in focal soft tissue necrosis may
predispose to calcification.
– These include injection sites, radiation damage to the soft
tissues and thermal injuries, both burns and frost-bite.
• Blunt trauma may cause fat necrosis within the
subcutaneous tissues with areas of dystrophic calcification.
• Calcification of atrophic muscles may be seen 1–2 months
after severe crush injury (calcific myonecrosis).
• Any haematoma, particularly if in a subperiosteal location,
may calcify.
– This includes the subperiosteal (pericranial) haematoma seen in
the skull of babies, usually as a result of birth trauma.

47. Tumours
• Widespread soft tissue calcification is a rare
manifestation of disseminated malignancies
(e.g. metastases, leukaemia and myeloma)
where there is hypercalcaemia associated with
extensive bone destruction.
• Localized intratumoral calcification may occur
within any soft tissue tumour due to
haemorrhage and/or necrosis.
• Benign soft tissue tumours with the propensity
to mineralize include soft tissue chondromas
(punctate or ‘ring-and-arc’ calcification),
lipomas, particularly if in a parosteal location
(ossification), haemangiomas (phleboliths) and
soft tissue aneurysmal bone cyst.
• The typical malignant soft tissue tumours that
calcify are extraskeletal osteosarcoma,
extraskeletal chondrosarcoma and synovial
sarcoma . In the latter entity calcification occurs
in approximately 30% of patients with a central
rather than a peripheral distribution.
• A rare benign tumour that can mimic myositis
ossificans with peripheral calcification is the
ossifying fibromyxoid tumour of soft parts.
Synovial sarcoma.
Axial CT demonstrating a soft tissue mass
lateral and posterior to the femur
containing calcifications.

48. OSSIFICATION
• Many calcifying lesions may proceed to
ossification with the production of woven
bone.
• The deposits of calcium salts tend to be more
densely sclerotic than comparable amounts of
bone. If there is doubt, CT can readily
distinguish the amorphous quality of calcium
salts from the trabecular pattern of ossification.
• Heterotopic ossification is a common
complication of many conditions and is thought
to be due to inappropriate differentiation of
fibroblasts into osteoblasts in response to a
local inflammatory process.
• Developmental causes include fibrodysplasia
ossificans progressiva, melorheostosis and
progressive osseous heteroplasia.
• The majority of other causes of heterotopic
ossification are traumatic in origin.

49. • Soft tissue ossification as a
result of surgery is well
recognized, particularly after
total hip arthroplasty.
– In most cases the ossification is
of little clinical significance.
• Post-traumatic or post-surgical
ossification is common
in tendons and ligaments.
– Examples include the Achilles
tendon and the medial
collateral ligament of the knee
(Pellegrini–Stieda lesion).
• Ossification may occur in
patients with severe thermal
and electrical burns.

50. • Acute detachment or repeated
trauma to a tendino-osseous
junction can lead to soft tissue
ossification with underlying
cortical irregularity.
• In the skeletally immature, an
avulsed ossification centre may
continue to grow, presenting at
a later stage with a large
ossified mass in the soft tissues.
• These types of avulsion injury
classically affect the pelvis,
particularly the origin of the
hamstrings.
Ischial avulsion.
(A) Radiograph at presentation shows
the avulsed ischial apophysis lying
in the soft tissues.
(B) Three years later the apophysis
has continued to grow to form a
large ossified mass

51. • Trauma can also be an indirect
cause of soft tissue ossification
when associated with injuries to
the central nervous system, be it
prolonged unconsciousness or
spinal trauma.
• In this situation it is known as
neurogenic heterotopic
ossification.
• It typically exhibits a periarticular
distribution with the hips most
commonly affected.
• The shoulders and elbows are
usually only involved with head or
higher spinal injuries.
• Surgical excision is frequently
associated with recurrence.

52. • Heterotopic bone formation in
muscles, tendons and fascia following
trauma is known as myositis
ossificans.
• A very similar condition
(radiographically and pathologically)
occurring in the absence of trauma is
the pseudomalignant osseous
tumour of soft tissues; this is also
known as pseudomalignant myositis
ossificans.
Myositis ossificans.
(A) Axial CT at presentation showing early
peripheral mineralization.
(B) Six weeks later there has been
maturation with well-organized
peripheral ossification

53. • Initially there is interstitial haemorrhage
with subsequent mineralization.
• The mineralization is seen first in the
periphery; there is a gradual reduction in
size of the mass .
• Both are helpful distinguishing features
from a mineralizing soft tissue sarcoma.
• The lesions will appear hypervascular on
angiography and show increased activity
on bone scintigraphy.
• Where possible, early biopsy should be
avoided as the immature lesion can
pathologically resemble a soft tissue
osteosarcoma.
• The MRI features of the early lesion can
also be confusing showing florid
perilesional oedema involving the whole
affected muscle compartment on T2-
weighted or STIR images
Myositis ossificans.
(A) Axial CT at presentation showing early
peripheral mineralization.
(B) Six weeks later there has been
maturation with well-organized
peripheral ossification

54. GAS IN SOFT TISSUES
• Gas/air may be introduced into the soft tissues
from within and without the body.
• It may also be formed directly within the soft
tissues. Gas in the soft tissue can be recognized
radiographically by increased radiolucency
outlining the soft tissue planes.
• Care should be taken not to confuse ectopic
viscera with soft tissue gas. A prime example
would be bowel gas within an inguinal hernia
which can overlie the soft tissues of the groin or
scrotum.

55. Gas introduced from within
• Air may enter the soft tissues
whenever there is a breach in the
integrity of the lining of either the
respiratory or gastrointestinal tract.
• In the chest and retroperitoneum
this is known as surgical
emphysema.
• Common causes in the chest
include
– blunt trauma with a fractured rib
puncturing the lung,
– penetrating lung trauma and
– following chest surgery.
– complication of interventional
procedures such as the insertion of
central lines and biopsy and drainage
procedures.

56. Gas introduced from without
• Air may be introduced into the
soft tissues as a result of
penetrating injuries or
compound fractures.
• This can be distinguished from
infection in that it is present
on the initial radiograph,
whereas the gas associated
with infection usually takes
several days to develop.
• Frequently, air can be
identified within joints and
soft tissues following
therapeutic injections and
surgical procedures.

57. Gas arising within the body
• Gas formed within the soft tissues is
a manifestation of infection.
• The classic example is gas gangrene
which is a bacterial infection caused
by several clostridial species. The
infection usually follows open,
contaminated wounds with
concomitant vascular compromise.
• Another form of clostridial infection
is anaerobic cellulitis where the gas
is confined to the subcutaneous and
superficial fascial layers.
• Other anaerobic infections producing
gas include coliforms, anaerobic
Streptococcus, Bacteroides and
Aerobacter aerogenes.
– less severe
– more localized collections of gas.
Clostridial osteomyelitis.
The axial CT shows the relatively hypodense abscess
collection surrounding the abnormal femur
containing multiple loculi of gas.

59. SOFT TISSUE INFECTION
• Infections in the soft tissues are common and may
require percutaneous or surgical intervention.
• Gas may be seen in the soft tissues in association with
infection
• The appearance of soft tissue calcification seen with
parasitic infections, healing abscesses and tuberculosis.
• With the exception of soft tissue swelling and blurring
of normal fat planes, most soft tissue infections do not
give rise to radiographic changes and cross-sectional
imaging techniques are required.

60. Abscess
• Abscesses may develop in the soft tissues
either from extrinsic sources, for instance
following a puncture wound, or from an
intrinsic source either via haematogenous
spread or direct spread from a nearby
source such as a bowel fistula or infected
joint.
• US - appear as predominantly cystic
structures, often of a complex
multiloculated nature with posterior
acoustic enhancement. The cyst contents
can vary considerably in echogenicity
depending on the nature of the collection
and on the amount of soft tissue debris
present, and may be shown to swirl
around with gentle probe pressure.
• Although the collection itself will not show
any Doppler signal, the tissues
surrounding the collection may appear
markedly hypervascular
Abscess collection.
Transverse US with power Doppler. A largely anechoic
collection lying in the thigh of this diabetic patient was
found to contain pus. Note the marked vascularity of the
soft tissues surrounding the collection shown

61. • In cases where the
infection has resulted
from the introduction of a
foreign body, this may be
still present.
• Although radio-opaque
matter may be seen on
conventional radiographs,
ultrasound is excellent for
looking for non-radio-opaque
foreign bodies
Wooden foreign body.
Transverse US. A piece of bamboo cane seen here in
transverse section (arrow) is located in an abscess collection
in the subcutaneous tissues of the upper arm. Note the
acoustic shadowing behind the foreign body.

62. • MRI and CT will also both show abscess
collections and may be required for deep-seated
abscesses such as those in the psoas
muscle or deep gluteal region.
• US or CT is ideally suited for guiding aspiration
and drainage of soft tissue abscess collections.

63. • CT will usually show
abscesses as
– a nonenhancing area of
lower attenuation than the
surrounding tissues,
although the presence of
haemorrhage or very
proteinaceous fluid may
result in increased
attenuation.
– The surrounding tissues
may enhance following
intravenous contrast
medium.

64. • On MRI the collection will
be of
– low to intermediate signal
on T1 weighting and
– high signal on T2 weighting
and
– peripheral enhancement
with gadolinium.
– Oedematous change in the
surrounding tissues often
with a rather feathery
appearance.

65. Pyomyositis
• In the western world pyomyositis is most frequently
seen in immunocompromised individuals.
• MRI best shows
– generalized change seen throughout the affected muscle
– heterogeneous increased signal on T2-weighted imaging,
• Ultrasound will also show
– generalized alteration in echogenicity.
• As the disease progresses, small pockets of fluid form
within the muscle with similar imaging characteristics
to abscesses.
• MRI is the most sensitive investigation in pyomyositis.

66. Cellulitis
• Cellulitis represents a superficial infection involving the subcutaneous
tissues.
• Clinically the tissues appear erythematous and swollen.
• Imaging reveals thickening of the skin and subcutaneous tissues. Fluid is
seen tracking between the lobules of subcutaneous fat.
• On Ultrasound
– low reflective septa,
• On T2-weighted MRI
– these thickened septa yield increased signal.
– Increased signal is also seen in the skin itself and underlying fascia.
• Since these changes are nonspecific and will be seen with noninfective
causes of soft tissue oedema, clinical correlation is essential.
• Imaging remains useful to demonstrate any associated abscess
formation and may be required to exclude involvement of other local
structures such as bone or joint.

68. NEUROMUSCULAR DISORDERS
• A wide-ranging and diverse group of conditions can be considered under
the broad heading of neuromuscular disorders. These include the
congenital and acquired myopathies and neuropathies, all of which bring
about muscle changes as their end point.
• Conditions include
– those affecting the nerve supply to muscles, such as the congenital and
acquired spinal muscle atrophies and peripheral neuropathies, and
– those affecting the muscles themselves such as the congenital, inflammatory
and metabolic dystrophies and myopathies.
• The key changes seen in muscle pathology (seen on imaging) are
– hypertrophy and atrophy,
– oedema-like change
– fat infiltration and
– calcification.
 The term ‘oedema-like’ change is preferred to oedematous, as muscles
showing this change on MRI are not actually oedematous when examined
histologically.

69. Conventional radiographs
• Limited role to play in the diagnosis of these
conditions.
– Fat atrophy may be apparent on plain radiography
– Calcification within skeletal muscle can be seen
both following trauma (as in myositis ossificans)
and in inflammatory conditions such as
dermatomyositis.

70. Ultrasound
• Hypertrophy and atrophy may be detected
– difficult to appreciate when generalized.
• Fat infiltration is easier to recognize on US
– normal striated architecture of the muscle is lost and the
affected muscles show an increase in reflectivity.
• Advantages:
– when nerve compression is suspected as many of the
peripheral nerves can be easily followed and causes of nerve
entrapment may be identified.
– role in guiding muscle biopsies.
• The main disadvantage of US
– small field of view, which makes it a difficult tool for examining
generalized muscle conditions.

71. CT
• Atrophy, hypertrophy and fat infiltration are easier
to identify on CT
• larger areas of muscle can be screened effectively.

72. MRI
• Normal muscle shows intermediate signal on both T1- and
T2-weighted imaging.
• Indeed, when MRI changes are reported as showing high or
low signal, this is usually assessed relative to skeletal
muscle.
• Fat appears bright on T1-weighted imaging and its signal
can be suppressed using standard techniques such as
inversion recovery and spectral fat suppression.
• Consequently fat infiltration of muscle is easy to recognize
on MRI.
• Oedema-like change in muscle will appear as increased
signal on T2-weighted imaging, and this is most clearly
shown on fat-suppressed T2 and STIR imaging.

73. MRI - technique
• T1 and fat-suppressed T2 (or STIR) sequences are
fundamental to the diagnosis of neuromuscular
disorders.
• coronal and sagittal imaging
– useful in assessing the longitudinal extent of muscle
involvement,
• axial imaging
– demonstration of the muscle compartments for identifying
patterns of muscle involvement and the individual muscles
or muscle groups involved.
– making comparisons with contralateral side in
asymmetrical disease.

74. MRI in neuromuscular pathology
• The signal changes seen on MRI in neuromuscular
pathology are nonspecific
• Generally not helpful in distinguishing between
different types of disease.
• The pattern of signal intensity does give some
useful information about the chronicity of a
muscle disorder.
– Fat infiltration represents a long-standing irreversible
process,
– while oedema-like signal change represents acute or
subacute and potentially reversible muscle damage.

75. Muscle denervation
• MRI is not very sensitive to early changes in
muscle following denervation.
• The earliest reliable changes are seen after
around 1 month
– the affected muscle or muscles yielding increased
signal on T2-weighted and STIR imaging.
• About a year after denervation
– fatty infiltration becomes apparent

77. SOFT TISSUE INJURY
• The advent of MRI and high resolution US has
revolutionized our ability to image soft tissue
injury.
• Soft tissue injuries can be grouped into acute
injuries or more chronic injuries which
generally occur as a result of sustained or
repetitive trauma.
• A brief overview of the role of imaging in
tendon and muscle injury is given here.

78. Normal Tendon
• On US, tendons are
visualized as linear
structures comprising
multiple parallel echogenic
bands representing the
interfaces between collagen
bundles. Vascular flow is
not shown in the normal
tendon.
• Using MRI the normal
tendon is visualized as a
nonenhancing low signal
structure on all
conventional sequences.

79. A word of caution!!!
• Tendons are comprised of highly organized linear bundles of collagen microfibrils with an
extremely regular and ordered structure.
• The regular structure results in an alteration in the imaging characteristics of tendons on US
depending on the tendon alignment relative to the ultrasound beam.
• This property is known as ANISOTROPY.
• To see the normal echogenic fibrillar pattern in tendons on US the tendon must be aligned
perpendicular to the ultrasound beam.
• Any significant angulation of the incident ultrasound beam to the tendon will result in echoes
generated by the tendon being reflected back at an angle and not returned to the transducer.
This leads to the tendon appearing hypo- or even anechoic.
Long head of biceps tendon shown on ultrasound. .

80. A word of caution!!!
• The anisotropy of tendons on MRI is the result of the so-called ‘magic angle phenomenon’.
• This can result in artefactual increased signal from tendons on short TE imaging sequences.
• Normally tendons have an extremely short T2 relaxation time, giving them the signal void seen with conventional
MRI techniques. However, when the alignment of the tendon (and therefore the collagen bundles within it)
approaches 55 degrees to the static magnetic field (B0), known as the magic angle, the T2 relaxation lengthens and
signal is seen from within the tendon. This effect is only seen on short TE imaging sequences (T1 and proton
density) and is important because tendon abnormalities usually yield increased signal from within the tendon on
short TE imaging. Lesions can be distinguished from the magic angle effect by the persistence of abnormal signal
on long TE sequences. The magic angle effect is not exclusive to tendons and may also be seen in ligaments,
menisci and articular cartilage

81. Chronic tendon injury
• Chronic or repetitive trauma to a tendon
results in degenerative change within the
tendon which has become known as
tendinopathy or tendinosis.
• Changes seen within the tendon include
degeneration and disorganization of the
collagen bundles along with vascular
ingrowth.

82. Tendinopathic Tendons
• Ultrasound
– thickening of the affected
tendon.
– areas of low reflectivity
will be seen within the
tendon
– loss of the normal
fibrillar architecture.
– Neovascularization may
also be seen with
Doppler techniques
demonstrating blood
flow within the normally
avascular tendon
Patellar tendinopathy.
(A) Longitudinal US shows the thickened patellar tendon
(between the arrowheads) at its insertion into the
patella (P). Note the low reflective change within its
substance.
(B) A similar section, this time with power Doppler,
shows the intense neovascularization seen within
the tendinopathic tendon. Normal tendon is
avascular.

83. Tendinopathic Tendons
• MRI
– thickening of the
affected tendon.
– increased signal will be
seen within the tendon
on both short and long
TE sequences.
Patellar tendinopathy.
Sagittal proton density MR image of the patellar
tendon shows thickening and increased
intrasubstance signal at its proximal insertion
(arrow).

84. • Some tendons, such as the extensors and
flexors of the hand and foot, have a synovial
tendon sheath; where this becomes involved
in the process the condition is known as
tenosynovitis.

85. • Tenosynovitis will be
seen on US and MRI as
– synovial thickening and
– fluid surrounding the
tendon.

86. • Many tendons do not have a tendon sheath
(for instance the Achilles and patellar tendons)
and are instead surrounded by loose
connective tissue known as the paratenon.
This may also become involved, a condition
known as paratenonitis.

87. • Paratenonitis is seen
– on US as a low reflective
‘halo’ surrounding the
tendon and
– on MRI as a thin high
signal rim on T2 imaging
which enhances with
gadolinium on T1
imaging.

88. • Calcific deposits may form within the tendon
– demonstrated on conventional radiographs.
– shown on US as bright reflective foci.
– low signal on MRI although there may be increased
signal in the surrounding tissues due to inflammatory
response.
– Tendon calcification can cause susceptibility artefact.
– In acute calcium deposition the calcific material is
liquid or semiliquid and may show fluid–fluid levels on
MRI.

89. Tendon tears
• Tendon tears are
unusual in an otherwise
normal tendon.
• When a tendon
undergoes
tendinopathic change it
becomes weaker and at
this point tears may
occur.

90. Tendon tears - Full or partial thickness.
• Full thickness tears are
generally easily
recognized at US and
MRI.
– Retraction of the torn
ends will be seen
– haematoma or fluid will
be seen filling the gap
(depending on how acute
the tear is).
• Assessment of the tendon
dynamically with US helps
confirm the full thickness
nature of the tear.

91. • Disruption of a tendon
without tendinopathic
change is usually the
result of avulsion of the
tendon from the bone.
• In this case the avulsed
bone fragment may be
seen on conventional
radiographs, but its
tendon attachment can
be confirmed at US or
MRI.

92. Partial thickness tears
• The distinction between a partial thickness
tear and tendinopathy may be difficult at US
and MRI.
• US
– well-defined low reflective areas or clefts
extending into the substance of the tendon,
– Doppler will help distinguish a tear from vessels
formed in an area of tendinopathy.

93. Partial thickness tears
MRI
presence of high signal on T2-weighted MRI extending to a tendon surface is also
indicative of a partial thickness tear.

94. In general, studies would suggest that in many
cases there is little to choose between MRI and
US when diagnosing tendon abnormalities

95. Muscle injury
• Muscle injuries are common,
especially in those undertaking
athletic activities.
• Movement in muscle is
transmitted to the skeleton
through the kinetic chain
comprising muscle connecting
to tendon connecting to bone.
• The majority of ‘muscle’ tears
in fact represent tears at the
myotendinous junction where
the tendon arises from the
muscle, a relatively weak point
in the kinetic chain.
myotendinous junction,
a relatively weak point in the
kinetic chain.

96. Muscle Tears
• The diagnosis of muscle tears is normally a
clinical one.
• Imaging can be helpful
– indication of the degree of severity of the muscle
injury
– Helpful in predicting the likely time before the
athlete can return to competition.

97. Acute muscle injury – Grade 1
• A grade 1 tear or strain
– microscopic tearing of muscle fibres, usually
without loss of muscle strength.
– No macroscopic tear in the muscle fibres is
seen
– oedema and haemorrhage may occur within
the muscle.
• USG –
– usually normal
– occasionally a mild increase in reflectivity
can be seen.
• MRI
– depend on the relative amount and age of
haemorrhage and oedema.
– Majority appear as intermediate signal on T1
and increased signal on T2-weighted
imaging.
– poor relationship between the severity of
the patient's symptoms and the MRI findings

98. Acute muscle injury – Grade 2
• Partial tears where there is macroscopic but incomplete separation of
muscle or muscle and tendon.
• The muscle belly will be retracted at the site of the tear, opening a gap
which will be filled with haematoma or fluid.
• USG / MRI –
– Depending on the age of the tear the haematoma may appear anechoic or
more complex.
– The demonstration of muscle retraction may be helped by examining the area
dynamically.
– fluid tracking around the muscle adjacent to the covering fascia.
Longitudinal extended field of view US
demonstrates a grade 2 muscle tear of
the medial head of gastrocnemius in a
different patient. The retracted medial
head of gastrocnemius muscle (G) is
seen separated from the underlying
tendon aponeurosis (arrow) and soleus
muscle (S) by haematoma (H).

99. Grade 3 tears represent a full thickness tear of the muscle with
complete separation of the torn ends of the muscle, or more
commonly the muscle from the tendon.
Biceps brachii tendon tear.
Longitudinal scan of the bicipital groove shows
proximal retraction of the biceps muscle (long
arrow). A fluid-filled gap with echogenic clots
(small arrow) at the myotendinous junction.
Tendoachilles tear at the myotendinous
junction.

100. Blunt trauma to a muscle
• Haemorrhage into the muscle (often with some
swelling).
• Where muscles overlie each other, two or more
muscles (or even muscle groups) may be
involved.
• The diagnosis is normally clear from the history,
but imaging will show haemorrhage and oedema
within the muscle.
• This is often subtle on US and the characteristic
finding is increased reflectivity and some focal
swelling of the muscle.

101. Chronic muscle injuries
• Disuse atrophy of muscle may be seen from a
variety of causes including chronic muscle or
tendon injury and denervation.
• The loss of muscle bulk may be obvious on
cross-sectional imaging. In addition the
muscle undergoes a process of fatty
infiltration seen as increased signal on T1-
weighted MRI, as increased echogenicity on
US, and as areas of fat attenuation on CT.

102. Delayed onset muscle soreness
(DOMS)
• DOMS is a well-recognized phenomenon where
muscular pain develops hours or days after muscle
activity.
• It remains poorly understood but is manifest on MRI as
oedematous change (increased signal on T2 weighting
and STIR imaging) in the affected muscles.
• The appearances are therefore similar to those of a
muscle strain, but the clinical picture differs in that the
symptoms come on some time after the exercise.
• As with muscle strains, the MRI findings take longer to
resolve than the muscular pain.

103. Myositis ossificans
• Myositis ossificans may develop following
muscle trauma.
• In this condition ossification occurs in the
muscle and may be visible on plain
radiography and CT .
• Ultrasound will show the area of
ossification as a dense reflection from
within the muscle with posterior acoustic
shadowing.
• MRI initially shows oedema-type change
in the muscle. This gradually organizes,
becoming better defined. Cortical bone
developing around the edges of the lesion
is of low signal intensity on all sequences.
In the mature lesions the centre of the
area becomes filled with bone trabeculae
surrounded by fatty bone marrow. The
latter will show signal characteristics of
fat.
Early
peripheral
mineralizatio
n.
Six weeks
later there
has been
maturation
with well-organized
peripheral
ossification

104. Muscle hernias
• Muscle hernias usually present as
a lump which the patient may
notice becomes more prominent
when the muscle is tensed. They
represent muscle fibres
herniating out through a tear or
weakness in the muscular fascia.
Such weaknesses are often
associated with perforating veins
in the lower limb.
• Ultrasound during muscle
contraction is readily able to
show muscle hernias and provide
reassurance that the palpable
mass is composed of normal
muscle tissue.
Tibialis Anterior – muscle hernia

106. Soft Tissue???
• Soft tissue
– derived primarily from mesenchyme and
– consists of
• skeletal muscle,
• fat,
• fibrous tissue,
• the vascular structures
• the peripheral nervous system.

107. General Concepts
• Soft-tissue tumors are classified histologically on the
basis of the adult tissue they resemble.
– Eg: liposarcoma does not indicate a lesion arose from fat,
but rather that it is a malignant mesenchymal tumor that
has differentiated into tissue that microscopically
resembles normal adult fat.
• Many sarcomas are poorly differentiated and,
consequently, lack the microscopic features required to
make a specific diagnosis.
• In such cases, immuno-histochemical stains have aided
pathologists in identifying their pattern of
differentiation, allowing accurate classification.

108. General Concepts
• Soft-tissue sarcomas
– relatively uncommon and are estimated to
represent about 1% of all malignant tumors.
– two to three times as common as primary
malignant bone tumors.
• The annual clinical incidence of benign soft-tissue
tumors is estimated at 300 per 100,000,
and these tumors are about 100 times more
common than malignant soft-tissue tumors.

109. The World Health
Organization (WHO)
classification system for
soft-tissue tumors

110. Additional soft-tissue lesions are not included in the
WHO classification

112. A SYSTEMATIC APPROACH FOR
CHARACTERIZATION OF SOFT-TISSUE MASSES

113. • Given the wide variety of masses and the
overlap that exists between the imaging
characteristics of benign and malignant
masses, it is impossible to arrive at a single
diagnosis for many of the lesions
encountered.

114. Then what is the role of imaging?
• By applying a systematic approach, one
– can arrive at a diagnosis for the subset of lesions that have
characteristic appearances and
– can narrow the differential diagnosis for lesions that
demonstrate indeterminate characteristics.
• In the appropriate clinical setting, excluding a benign
diagnosis (eg, lipoma or ganglion) can aid in clinical
decision making.
• Ultimately, if a lesion cannot be characterized as a
benign entity, the lesion should be reported as
indeterminate and the patient should undergo biopsy
to exclude malignancy.

115. Clinical History and Physical
Examination
• Evaluation of a soft-tissue mass begins with
the clinical history and physical examination.
• Clinical history regarding
– age,
– recent trauma,
– fluctuating mass size,
– history of malignant cancer
and familial syndromes,
– single or multiple lesions

116. Clinical History and Physical
Examination
At physical examination, determining whether the
• mobile or fixed.
– In general, masses that are
mobile are more suggestive of a
benign diagnosis, while masses
that are fixed to surrounding
tissues are more suggestive of
malignancy.
• skin changes
– such as ecchymosis related to
trauma or inflammatory changes
from cellulitis and soft-tissue
abscess, can aid in establishing
an appropriate differential
diagnosis.

117. Location
• Certain masses occur in specific locations in
the body, aiding in lesion characterization.

118. Origin of the lesion
• Recognizing that a lesion arises from a specific structure (eg,
nerves, vessels, or tendons) can help in lesion characterization.
• Tumors arising from nerves are typically benign PNSTs, which include schwannomas
and neurofibromas. If there is a history of type 1 neurofibromatosis, a malignant PNST
should be considered. Occasionally, fat-containing tumors can also arise from nerve.
This type of lesion, previously known as a fibrolipomatous hamartoma, has been
designated as lipomatosis of the nerve by the WHO in the 2002 classification.
• Vascular neoplasms typically have dilated tortuous vessels entering and/or exiting the
lesion and include hemangiomas, lymphangiomas, and angiosarcomas .
Hemangiomas are the most common of the vascular lesions and contain serpentine
vessels, areas of fat, and phleboliths. Besides true vascular tumors, several additional
vascular lesions should be included in the differential diagnosis of a soft-tissue mass
arising from vessels. Pseudoaneurysms can occur in the setting of trauma, such as
femoral vessel injury from cardiac catheterization. In these cases, it is important to
make the diagnosis prospectively and to avoid biopsy. Another group of masses
characteristically arise from tendon sheaths.
• Lesions arising from tendons are most commonly GCTs of the tendon sheath;
however, ganglia, lipomas, and fibromas are all masses that may arise from a tendon
sheath.

119. IMAGING

120. Radiography
• The radiologic evaluation of a suspected soft-tissue
mass must begin with the radiograph.
• Radiographs may be diagnostic of a palpable
lesion caused by an underlying skeletal deformity
(such as exuberant callus related to prior trauma)
or exostosis, which may masquerade as a soft-tissue
mass.

121. • Radiographs may also reveal
soft-tissue calcifications, which
can be suggestive and, at
times, very characteristic of a
specific diagnosis.
– phleboliths within a
hemangioma ,
– juxtaarticular
osteocartilaginous masses of
synovial chondromatosis,
– peripherally more mature
ossification of myositis
ossificans, or
– characteristic bone changes of
other processes with
associated soft-tissue
involvement.

122. • When not characteristic
of a specific process,
soft-tissue calcification
can suggest certain
diagnoses.
– nonspecific dystrophic
calcifications in a slowly
growing lower extremity
mass in a young adult
should suggest a synovial
sarcoma as the diagnosis
of exclusion.
17-year-old girl with synovial sarcoma of foot
who presented with slowly growing painless
mass.

123. • In addition, radiographs are the best initial method of
assessing coexistent osseous involvement, such as
remodeling, periosteal reaction, or overt osseous
invasion and destruction.
• However, unlike bone tumors, the biologic activity of a
soft-tissue mass cannot be reliably assessed by its
growth rate. A slowly growing soft-tissue mass that
may remodel adjacent bone (causing a scalloped area
with well-defined sclerotic margins) may still be highly
malignant on histologic examination.

124. • A soft-tissue mass may also be the initial presentation
of a primary bone tumor or inflammatory process.
– In such cases, the radiograph may be useful in identifying
the osseous origin of the lesion. The diagnosis of a
malignant bone tumor such as Ewing's sarcoma or primary
lymphoma of the bone should be considered when there is
a large circumferential soft-tissue mass in association with
an underlying destructive permeative bone lesion.
• A subtle radiologic feature, which may help to separate
inflammatory and neoplastic processes, is that an
inflammatory process typically obliterates fascial
planes rather than displaces them.

125. Role of CT
• CT may be a useful adjunct
in specific circumstances.
• We generally reserve CT for
patients in whom
radiographs do not
adequately depict the lesion,
its pattern of mineralization,
or its relationship to the
host.
• This inadequacy typically
occurs in areas in which the
osseous anatomy is complex,
such as the pelvis, shoulder,
and paraspinal regions.

126. MR Imaging
• MR imaging has emerged as the preferred modality for
evaluating soft-tissue lesions.
• It provides
– superior soft-tissue contrast,
– allows multiplanar image acquisition,
– its capability in imaging superficial and deep soft tissues over
both large and small fields of view
– obviates iodinated contrast agents and ionizing radiation, and
– is devoid of streak artifacts commonly encountered with CT.
• Although initial investigations maintained that CT was
superior to MR imaging in detecting destruction of cortical
bone, later studies suggest that these two modalities are
comparable in this regard.

127. • Evaluation with MR images allows
– tumor staging,
– detection of neurovascular involvement,
– identification of tumor necrosis, and
– preoperative planning.

128. Newer Techniques
• The use of techniques such as MR
spectroscopy and diffusion imaging has been
reported for the evaluation of soft-tissue
masses and, in particular, for assessing
response to therapy.
• These techniques offer intriguing potential for
interrogation of soft-tissue masses but are not
yet in routine clinical use.

129. • The utility of MR imaging in the assessment of
soft-tissue masses is predicated on the
generation of diagnostic images of good
quality.
• A brief discussion of technical considerations
as they relate to MR imaging of soft-tissue
masses is therefore presented.

130. TECHNICAL CONSIDERATIONS FOR MR
IMAGING OF SOFT-TISSUE MASSES

131. General Considerations
• Given the variety of sizes and locations of soft-tissue
masses, it is difficult to prescribe a single
imaging protocol.
• The lesion should be demarcated prior to
imaging, but care should be taken not to
compress or distort the mass, either with the skin
markers or by imaging the mass dependently
against the table.
• Images should be of sufficiently high spatial
resolution to demonstrate relevant morphologic
features and local anatomic detail.

132. Imaging Plane
• Lesions should be imaged in at least two orthogonal
planes, using conventional T1-weighted and T2-
weighted spin-echo MR pulse sequences in at least one
of these planes.
• Axial images
– For demonstrating relevant anatomy and
– helping to determine whether the mass is confined to a
single compartment and
– whether it is invading or encasing surrounding structures.
• Longitudinal plane—coronal, sagittal, or oblique
– help demonstrate the extent of the mass and
– its relationship to anatomic landmarks.

133. Imaging Strategy
• Field of view is dictated by the size and location
of the lesion.
• large field of view
– where the goal is to establish the presence of a mass.
– sacrificing spatial resolution.
• smaller field of view
– where detailed assessment of the mass is needed
– delineate its features and
– assess its proximity to surrounding structures.

134. Imaging Sequences
• Standard spin-echo MR images are most useful in
establishing a specific diagnosis.
– the most reproducible technique
– the most often referenced in the tumor imaging literature.
– the imaging technique with which we are most familiar for
tumor evaluation,
– established as the standard by which other imaging
techniques must be judged.
• The main disadvantage of spin-echo MR imaging
remains
– the relatively long acquisition times, especially for double-echo
T2-weighted MR imaging sequences .

135. • Fast scanning techniques may be useful in the
evaluation of soft-tissue masses.
– shorter imaging times,
– decreased motion artifacts, and
– increased patient tolerance, as well as patient
throughput.
• Gradient-echo imaging may be a
– useful supplement in revealing hemosiderin because
of the greater magnetic susceptibility of hemosiderin.
– showing the lesion—fat interfaces and
– depicting small surrounding vessels.

136. 27-year-old woman with foreign body
and associated abscess.
A, Oblique radiograph of foot shows
irregular opacity (arrow ), initially
interpreted as calcification.
B, Coronal T1-weighted spin-echo MR
image (600/15, TR/TE) shows prominent
signal void (asterisk ), with “parenthetic”
artifact, compatible with foreign body.
C, Corresponding conventional T2-
weighted spin-echo MR image (2500/80)
shows foreign body (asterisk ) with
associated inflammatory change.
D, Gradient-echo MR image (15/12, 15°
flip angle) shows “blooming” (asterisk )
caused by greater magnetic susceptibility.

137. • STIR imaging can be an adjunct in selective cases.
– produces fat suppression and
– enhances the identification of abnormal tissue with
increased water content and,
– as a result, is useful to confirm subtle areas of soft-tissue
abnormality
– increases lesion conspicuity
• but
– lower signal-to-noise ratio
– more susceptible to degradation by motion.

138. • Fat suppression on T2-weighted MR images
– increase lesion-to-background signal intensity differences
for high-signal-intensity lesions within the marrow or fatty
soft tissue.
– decreasing or eliminating the MR signal from fat,
– allowing increased conspicuity of lesions containing
paramagnetic substances (such as methemoglobin) on T1-
weighted MR images, and
– revealing contrast enhancement.
• However
– decreases variations in tumor signal intensities, and hence
not used in place of conventional T2-weighted MR
imaging.

139. Describing Masses
• The SI of masses should be described in
relation to an internal standard.
• Most often, a mass is described as being hypo-
, iso-, or hyperintense to muscle on both T1-
and T2-weighted images.
• Some authors describe the SI of a mass on T2-
weighted images in relation to subcutaneous
fat; however, the relative SI of fat differs
between SE and fast SE techniques.

140. MR Imaging Contrast Enhancement
• controversial.
– enhance the signal intensity of many tumors on T1-weighted spin-echo
MR images,
– enhancing the demarcation between tumor and muscle and tumor
and edema
– providing information on tumor vascularity.
• In actuality, differentiation between tumor and muscle is usually
quite well delineated without contrast-enhanced imaging on T2-
weighted MR images, and
• the accurate distinction between tumor and edema is probably of
little practical value. Edema, which is infrequent without
superimposed trauma or hemorrhage, is considered to be part of
the reactive zone around the neoplasm and, as a result, is removed
en bloc with the tumor.

141. • Disadvantages:
– increases the length and cost of the examination.
– not been shown to increase lesion conspicuity or
to replace conventional T2-weighted MR imaging .
– contrast reaction (even though small)
• Consequently, gadolinium-enhanced imaging
should be reserved for cases in which the
results would influence patient care.

142. Contrast: Useful situations
• evaluation of hematomas.
– may reveal a small tumor nodule that may have
been inapparent within the hemorrhage on
conventional MR imaging.
Caution is required, however, because the
fibrovascular tissue in organizing hematomas may
show enhancement.

143. Contrast: Useful situations….
• differentiate solid from cystic (or necrotic) lesions
or
• identify cystic or necrotic areas within solid
tumors,
– these necrotic or cystic areas showing no
enhancement.
In general, sonography is fast and inexpensive and is
an ideal method for differentiating solid and cystic
lesions when the lesion is in an anatomic location
accessible to sonographic evaluation.
• guide biopsy

145. Contrast: Useful situations….
• Evaluation of tumor recurrence
Enhancing tumor nodule in a post operative desmoid tumor, suggestive of recurrence

146. Technical considerations in contrast imaging
• Intravenous gadolinium-based contrast agent is
generally administered in a nondynamic fashion.
• Contrast-enhanced images are often obtained with
fat suppression to suppress fat and highlight the
presence of the gadolinium-based contrast agent.

147. Technical considerations…..
In choosing to use fat-suppressed T1-weighted MR sequences for this
purpose, several considerations apply:
1. Images obtained before and after contrast agent administration must be
obtained with identical imaging parameters to allow adequate
assessment of enhancement.
2. For similar reasons, transmit gain cannot be allowed to change between
nonenhanced and contrast-enhanced images. To maintain the same
transmit gain, no preliminary imaging should take place between
nonenhanced and contrast-enhanced imaging.
3. If, on nonenhanced images, fat suppression proves to be
inhomogeneous, consideration should be given to acquiring the
nonenhanced and contrast-enhanced images without fat suppression.
4. Image subtraction can help to address the problem of inhomogeneous
fat suppression, but this technique depends on the absence of patient
motion between the nonenhanced and contrast-enhanced sequences.

148. LESION CHARACTERIZATION ON THE
BASIS OF MR IMAGES

149. T1 Hypo- or Isointense Lesions
• Most soft-tissue masses are iso- or hypointense to
muscle on T1-weighted images;
– limited ability to distinguish or characterize lesions on the
basis of low T1 SI alone.
• The differential diagnosis for these masses is extensive
and includes both benign and malignant lesions.
– For example, ganglia, fibrosarcomas, and pleomorphic
sarcomas can all demonstrate T1 hypo- or isointensity.
• Lesions that are iso- or hypointense to muscle on T1-
weighted MR images should be further evaluated with
T2-weighted MR images.

150. T1 Hyperintense Lesions
• Higher in SI than skeletal muscle on T1-
weighted images.
• SI should be determined on images that are
obtained without fat suppression because
some masses may be isointense to muscle on
T1-weighted images without fat suppression
but relatively hyperintense to muscle on fat-suppressed
T1-weighted images.

151. T1 Hyperintense…..
• Substances that are associated with T1 shortening include
– fat,
– methemoglobin,
– proteinaceous fluid, and
– melanin
• Fat has intrinsically short T1 relaxation times due to its molecular
structure.
• Methemoglobin causes shortening of T1 relaxation times due to a
paramagnetic effect.
• Proteinaceous fluid is characterized by relative T1 shortening due to
accelerated relaxation of water molecules bound to proteins .
• Although one report of T1 shortening in melanomas ascribed the effect
directly to paramagnetic radicals associated with melanin itself, a later
report theorized that it was owing to other sources, such as biological
paramagnetic metals that become bound by the melanin.

153. • If the mass has areas of hyperintense T1
signal, the next step is to evaluate suppression
on fat-suppressed T1-weighted images.
– It is important to perform the sequence with
frequency-selective (also known as chemically
specific) fat suppression.
– Inversion-recovery fat suppression is nonspecific
and can cause loss of signal of not only fat but also
of other short-T1 substances.

154. Fat suppression +
• If the hyperintense area is suppressed, then
the lesion contains fat, and the most likely
diagnoses include
– lipoma,
– lipoma variant,
– well-differentiated liposarcoma,
– hemangioma, and
– mature ossification.

155. Fat suppression +
• If the mass is composed
entirely of fat, with only
minimal thin septations
and without nonfatty
nodular components,
then a diagnosis of
lipoma can be made.

156. If the lesion is greater than 10 cm in diameter, contains septa
greater than 2 mm thick and/or globular or nodular nonfatty
components, or is comprised of less than 75% fat, then a
diagnosis of well-differentiated liposarcoma is likely.
59-year-old woman with well-differentiated liposarcoma.

157. Fat suppression +
• Some lipomatous masses,
including some lipomas
and lipoma variants, have
a complex appearance
because they contain
benign soft-tissue
constituents; thus, it may
be difficult to distinguish
these entities from well-differentiated
liposarcomas.
28-year-old woman with chondroid lipoma.
Sagittal T1-weighted image (TR/TE, 600/10)
obtained through left chest shows mass
posteriorly, which is predominantly high in
signal but contains nodular foci of low signal
(arrow).

158. Fat suppression +
• Hemangiomas with fatty components will have
suppressed SI on fat-suppressed MR images but
should have a distinct appearance from lipomas.
– lobulated
– have high-SI vascular channels on T2-weighted MR
images (due to slow intravascular flow),
– may contain rounded low-SI phleboliths on T1- and
T2-weighted MR images, (more apparent on
radiographs)
– may cause fatty atrophy in surrounding muscles or
reactive sclerosis in abutting bones.

159. 10-year-old boy with hemangioma of lower extremity.
• Axial T1-weighted MR image (TR/TE, 500/16) shows low signal
intensity of tumor (arrows) with interspersed areas of high signal
intensity representing fat.
• Axial T2-weighted MR image (4000/85) shows lobulated high-signal-intensity
lesion. Note several central low-signal-intensity dots
(arrows).
• Gadolinium-enhanced T1-weighted MR image (500/16) shows marked
enhancement of lesion. Central low-intensity dots seen on B are not
seen after contrast administration, suggesting vascular nature.

160. Fat suppression +
• Ossification, seen with mature
myositis ossificans or
heterotopic ossification, can
appear to be T1 hyperintense
owing to fatty marrow.
• Again, reviewing the
radiographs for evidence of
mature ossification is helpful;
however, ossification may not
be apparent on radiographs,
especially in the early stage of
myositis ossificans.
• In these cases, CT images may
be helpful for identifying early
mineralization.

161. Mature (late) myositis ossificans in
popliteal fossa of a man 35 years of
age.
A: Radiograph shows a densely
mineralized mass in the popliteal
fossa.
B: Axial CT scan displayed at bone
window shows irregular diffuse
mineralization throughout the mass.
The attenuation coefficient of the
nonmineralized area is difficult to
assess, but areas imaging similar to fat
can be seen.
C,D: Axial T1-weighted (C) and T2-
weighted (D) spin-echo MR images
show a well-defined mass (arrows) in
the popliteal fossa. Areas of increased
signal within mass (asterisk) have a
signal intensity similar to that of
subcutaneous fat.

162. Fat suppression (-)
• If the lesion does not lose SI on the fat-suppressed
T1-weighted MR images, then it is
composed of another substance that causes
T1 shortening, such as
– methemoglobin,
– proteinaceous fluid, or
– melanin.

163. Fat suppression (-)
• A history of trauma may account for a
hematoma with methemoglobin.
• However, a hematoma might also occur
secondary to bleeding from a tumor.
• So a hematoma should be followed up with
imaging to resolution to exclude an underlying
sarcoma or other malignant lesion as the
source of the hematoma.

164. 8-year-old woman with subacute
hematoma adjacent to lipoma.
T1-weighted axial image shows subacute hematoma (white arrow)
with relatively increased signal intensity due to extracellular hemoglobin. Compare
hematoma with higher signal intensity mass (black arrow), which is lipoma.
T1-weighted fat-suppressed MR image shows
that signal intensity of subacute hematoma (white arrow) remains
bright, whereas that of lipoma (black arrow) “drops out.”

165. Fat suppression (-)
• Any mass containing sufficient fluid with an
appropriate concentration of protein can have
high T1 SI.
• These masses include ganglia, abscesses, and
epidermoid inclusion cysts with high protein
content.

166. Fat suppression (-)
• If the patient has a history of melanoma and a
mass with high T1 SI, the possibility of a
melanoma metastasis should be considered
• It should be noted, however, that not all
melanotic lesions are characterized by
substantial T1 shortening .

169. T2 Hypointense Lesions
• A mass that is lower in SI than skeletal muscle
on T2-weighted MR images is considered to be
hypointense .
• Substances that appear hypointense on T2-
weighted images include
– fibrosis,
– hemosiderin, and
– calcification (distinct from ossification).

170. T2 Hypointense….
• Lesions with fibrotic components tend to have low T2 SI because of a
relative lack of mobile protons associated with their hypocellular densely
collagenous matrix.
• Hemosiderin, a nonspecific end-product from the breakdown of
hemorrhage, is T2 hypointense due to magnetic susceptibility. When
present in sufficient quantities, hemosiderin can appear more prominent
(blooming) on T2*-weighted MR images than on T2-weighted MR images .
• Calcifications are typically T2 hypointense because the protons are
immobilized within a crystalline structure and cannot contribute to the
signal.
 Paradoxically, calcifications may appear as higher SI when calcium crystals are
surrounded by a hydration shell, which provides a source of mobile protons .
• Substances that have intrinsic low proton density, such as air and some
foreign bodies, also can appear to be T2 hypointense.
 Foreign bodies can be deceptive, as small foreign bodies may be surrounded by
a hyperintense area from reactive fluid or inflammatory tissue, which can
obscure the underlying foreign body and mimic a neoplasm.

172. • Masses that are composed of fibrotic material represent
– broad spectrum of benign and malignant lesions,
– ranging from fibrotic scars to fibromas and some fibrosarcomas.
• T2 hypointensity in lesions such as GCT of the tendon
sheath, amyloid deposits, long-standing rheumatoid
pannus, soft-tissue callus, leiomyoma, and lymphoma has
been ascribed to the presence of hypocellular fibrosis.
 However, not all fibrous masses have low T2 SI;
hypercellular fibrous masses, such as desmoids and
leiomyomas, may demonstrate higher T2 SI.

174. Masses that contain large amounts of hemosiderin include pigmented
villonodular synovitis, GCT of the tendon sheath, and a variety of
hemorrhagic masses.

175. • Masses that are diffusely calcified may also
appear to have low T2 SI.
• However, the SI will depend on
– the extent and distribution of calcification,
– whether the calcification is hydrated, and
– whether there is associated edema or
inflammatory reaction

177. mass with low T2 SI
• first step is to review the radiographs for the
presence of calcifications, which are often
difficult to identify on MR images alone.
• On radiographs, calcifications may have a
characteristic pattern, such as the
– cloudlike paraarticular calcifications seen in gout
or
– the flocculent calcifications seen in tumoral
calcinosis.

178. • If there are no calcifications on the radiographs, then a mass with
low T2 SI will most likely either be focal fibrosis or a tumor with
substantial fibrous content.
• In these cases, lesion location can be helpful for further
characterization.
– Single or multiple masses within a joint may reflect the presence of
pigmented villonodular synovitis.
– Similarly, if a well-circumscribed noncalcified mass abuts a tendon, it
may be a GCT of the tendon sheath.
– A history of prior surgery at the lesion site could suggest the presence
of fibrous scar tissue.
– A nodular mass that is adjacent to the plantar fascia of the foot most
likely is a plantar fibroma.
– Similarly, a mass along the superficial palmar fascia of the hand can
suggest Dupuytren disease.

180. T2 Hyperintense (Cystlike) Lesions
• Many T2 hyperintense lesions are
heterogeneously hyperintense.
– difficult to specifically characterize.
• A subset of lesions that are relatively
homogeneously hyperintense
– can be further characterized.

181. T2 hyperintense…..
• Thus, the differential diagnosis for lesions that
are predominantly T2 hyperintense includes
– fluid-filled lesions (eg, ganglia, synovial cysts, and
seromas)
– solid lesions (eg, myxomas, myxoid sarcomas,
some PNSTs, and small synovial sarcomas).
• Some are relatively homogeneous hyperintense,
• mistaken for fluid-filled structures
• have been termed cystlike lesions by some authors.
– hyperemic synovium and
– hyaline cartilage.

183. True Cysts vs Cyst like lesions
• Administering an intravenous gadolinium-based contrast agent is an
important step to distinguish between true cysts and solid lesions.
• Cysts and fluid-filled components of masses
– will NOT demonstrate internal enhancement whereas
• solid (Cyst like) structures
– will usually demonstrate internal enhancement.
• Note!!!
– given sufficient time, gadolinium-based contrast agents can diffuse
into the center of a cyst from the periphery.
– Thus, internal enhancement can be seen in a true cyst if it is imaged
late after contrast agent administration .
– Although there are no well-formulated rules for this phenomenon, we
typically evaluate enhancement on MR images obtained within 6
minutes after contrast agent administration.

185. Peripheral enhancement
• If a T2 hyperintense mass has a thin even rim of
enhancement and no internal enhancement, then it is
a cyst of some kind.
– Ganglia are very common and should be considered
whenever a periarticular hyperintense mass is identified
on T2-weighted MR images.
– Postoperative seromas, posttraumatic cysts, epidermoid
inclusion cysts, lymphoceles, and lymphangiomas are
other lesions that may demonstrate a thin rim of
peripheral enhancement .
• When the peripheral rim of enhancement is thick
and/or irregular,
– other diagnoses must be considered, including inflamed or
infected ganglia, abscesses, hematomas, and necrotic
tumor masses.

186. Internal enhancement
• If a mass that is T2 hyperintense demonstrates
internal enhancement, either homogeneous
or heterogeneous, then soft-tissue masses
(eg, intramuscular myxomas, myxoid
sarcomas, PNSTs, and synovial sarcomas)
should be considered.
• Myxoid material because of its high water
content appears hyperintense on T2-weighted
MR images.

187. Lesions showing internal enhancement…..
• Intramuscular myxomas
– benign masses
– typically have uniform hyperintensity on nonenhanced T2-weighted MR
images
– demonstrate internal enhancement on contrast-enhanced MR images.
• Myxoid sarcomas
– can be homogeneously T2 hyperintense but also
– demonstrate internal contrast enhancement.
• Synovial sarcoma should be considered
– an enhancing hyperintense lesion is paraarticular.
– Irregular calcifications, erosion of the bone, and cystic components may be
associated.
• PNST is suggested
– lesion is fusiform and
– is associated with a nerve

188. Axial fat-suppressed MR images in 56-year-old woman show palpable lesion in groin.
(a) T2-weighted MR image shows a hyperintense cystlike lesion (arrow) in the left upper thigh.
(b) Nonenhanced T1-weighted SPGRMRimage at level of lesion (arrow).
(c) Contrast-enhanced T1-weighted SPGRMR image shows wispy internal enhancement
(arrow).
Intramuscular myxoma was identified at biopsy.

190. Benign Versus Malignant
• Diagnostic value of MR imaging
– general agreement
• Reliably distinguish benign from malignant???
– less clear.

191. • When not sufficiently characteristic to suggest a specific
diagnosis,
– a conservative approach is warranted.
• Malignancies are generally
– larger and
– more likely to outgrow their vascular supply with subsequent
infarction, necrosis, and heterogeneous signal intensity on T2-
weighted spin-echo MR imaging.
• Consequently, the larger a mass is, the greater its
heterogeneity, the greater is the concern for malignancy.
– Only 5% of benign soft-tissue tumors exceed 5 cm in diameter.
– Only about 1% of all benign soft-tissue tumors are deep.
• Superficial sarcomas have less aggressive biologic behavior
than do deep lesions.

192. • As a rule, most malignancies grow as
– deep space-occupying lesions,
– enlarging in a centripetal fashion,
– pushing rather than infiltrating adjacent structures (although
clearly there are exceptions to this general rule).
– as sarcomas enlarge, a pseudocapsule of fibrous connective
tissue is formed around them by compression and layering of
normal tissue, associated inflammatory reaction, and
vascularization.
– generally, they respect fascial borders and
– remain within anatomic compartments until late in their course.
• It is this pattern of growth that gives most sarcomas
relatively well-defined margins, in distinction to the
general concepts of margins used in the evaluation of
osseous tumors.

193. • Metastatic carcinoma to soft tissue
– appear more infiltrative with ill-defined margins
– often violating fascial planes and anatomic
compartments.
• This pattern of growth is quite different from
that seen in most primary soft-tissue tumors.

194. • Increased signal intensity in the skeletal muscle
surrounding a musculoskeletal mass on T2-
weighted spin-echo MR images or other fluid-sensitive
sequences (i.e., STIR)
– suggested as a reliable indicator of malignancy.
– quite nonspecific.
– more commonly suggests an inflammatory process,
abscess, myositis ossificans, local trauma,
hemorrhage, biopsy, or the effect of radiation therapy
rather than a primary soft-tissue neoplasm.

195. 14-year-old boy with myositis ossificans in forearm.
A, Axial fast spin-echo T2-weighted spin-echo MR image (2600/80, TR/TE) shows poorly defined mass in
extensor compartment of forearm and adjacent to ulna. Lesion predominantly involves extensor carpi ulnaris,
although there is abnormal signal in and between adjacent muscles.
B, Corresponding axial T1-weighted spin-echo MR image (650/20) shows only minimal signal alteration with
effacement of subcutaneous adipose tissue (arrow )

196. Benign vs Malignant - Role of Gadolinium
• Malignant lesions show
– greater enhancement as well as
– greater rate of enhancement.
• Enhancement reflects tissue vascularity and
tissue perfusion.
• Considerable overlap – little practical value.

197. • When a lesion has a nonspecific MR imaging
appearance, one is ill-advised to suggest a
lesion is benign or malignant solely on the
basis of its MR imaging characteristics and
rate or degree of enhancement.

198. • DeSchepper et al. performed a multivariate statistical
analysis of 10 imaging parameters, individually and in
combination.
• Highest sensitivity for malignancy
– high signal intensity on T2-weighted MR images,
– larger than 33 mm in diameter,
– heterogeneous signal intensity on T1-weighted MR images.
• Greatest specificity for malignancy
– tumor necrosis,
– bone or neurovascular involvement, and
– mean diameter of more than 66 mm

199. 15-year-old girl with rhabdomyosarcoma of leg.
A, Sagittal T1-weighted spin-echo MR image shows large mass with bone invasion.
B, Corresponding contrast-enhanced MR image shows nonenhancing area compatible
with necrosis. Bone invasion and necrosis are both specific for malignancy. Note nodal
involvement (arrows ).

200. 57-year-old woman with liposarcoma of thigh.
A, Axial fast spin-echo T2-weighted MR image (3200/102, TR/TE) shows large mass
with mixed intermediate signal intensity.
B and C, Corresponding coronal unenhanced (B) and contrast-enhanced (C) T1-
weighted spin-echo MR images (600/16) show adipose tissue within lesion,
compatible with fat differentiation. Enhancement in portions of tumor is extensive.
Large size and deep location with adipose differentiation suggest diagnosis of
liposarcoma.

201. Staging
• Purpose of a staging system
– the state of a malignancy,
– defining the extent of the local and distant tumor
– critical for optimum patient care and
– planning of percutaneous biopsy.
• Local staging is best accomplished using MR
imaging, which can accurately depict the
anatomic spaces (compartments) involved by
the tumor.

202. The Indeterminate Lesion
• Identify the lesion as a benign determinate
lesion.
• Provide a succinct differential diagnosis on the
basis of the available characteristics.
• However, if the lesion cannot be confidently
characterized as a benign entity, then it is an
indeterminate lesion and requires further
evaluation.
• This concern should be discussed with the
ordering clinician, and a biopsy should be strongly
considered.

203. The Indeterminate Lesion
• The WHO recommends that
• “soft tissue masses that do not demonstrate
tumor-specific features on MR images should
be considered indeterminate and biopsy should
always be obtained to exclude malignancy”.
• In some instances, especially in patients with
comorbidities or relative contraindications to
biopsy, short-term imaging follow-up may be
an alternative.

204. Conclusion
• MR imaging is the preferred modality for the evaluation of a soft-tissue
mass after radiography.
• The radiologic appearance of certain soft-tissue tumors or tumorlike
processes, such as myositis ossificans, fatty tumors, hemangiomas,
peripheral nerve sheath tumors, pigmented villonodular synovitis, and
certain hematomas may be sufficiently unique to allow a strong
presumptive radiologic diagnosis.
• It must be emphasized that MR imaging cannot reliably distinguish
between benign and malignant lesions
• When radiologic evaluation is nonspecific, one is ill-advised to suggest
that a lesion is benign or malignant solely on its MR imaging appearance.
• When a specific diagnosis is not possible, knowledge of tumor prevalence
by location and age, with appropriate clinical history and radiologic
features, can be used to establish a suitably ordered differential
diagnosis.