MRI uses magnetic fields and radio waves to produce detailed images of organs and tissues inside the body. An MRI scanner contains magnetic coils, radiofrequency coils, gradient coils, and a computer display unit. MRI works by aligning atomic nuclei such as hydrogen in a magnetic field and inducing resonance with radio pulses. When the pulses are removed, the nuclei release energy that is detected as signals providing data to create digital images. MRI can produce different types of weighted images like T1, T2, STIR, and gradient echo that highlight various tissues. MRI is useful for imaging musculoskeletal injuries, tumors, infections and other orthopedic conditions due to its excellent soft tissue contrast without ionizing radiation.

1. MRI
IN ORTHOPAEDICS
MODERATOR:DR.SANTOSH
PRESENTER:DR.MD AAMIR MALLIK

2. MAGNETIC
RESONANCE
IMAGING
(MRI)
●Introduction
●Components of MRI scanner system
●Basic principle of MRI
●What are MRI images?
●MRI signal production
●T1 vs T2 Images
●Specialised MRI sequences
●Contrast agents
●Systematic approach
●MRI safety and limitations

3. Introduction
●It is a technique that uses a magnetic field and radiofrequency
waves to create detailed images of the organs and tissues
within the body.
●Nikola tesla invented the rotating magnetic field in 1882 in
Hungary.
●All MRI machines are caliberated in “Tesla” units.
●The strength of a magnetic field is measured in Tesla or Gauss
units.

4. Components
of MRI System
●The system includes:
1. Magnetic coil
2. RadioFrequency coils (transmitter and receiver),
3. Gradient coils, and
4. Computer display unit with digital storage facilities.

5. Basic Principle
of MRI
●The ability of MRI to image body parts depends on the intrinsic spin of
atomic nuclei with an odd number of protons and/or neutrons (e.g.,
hydrogen), thus generating a magnetic moment. Atomic nuclei of tissues
placed within the main magnetic field from the usual random alignment of
their magnetic poles tend to align along the direction of that field.
●The application of RF pulses causes the nuclei to absorb energy and induces
resonance of particular sets of nuclei, which causes their orientation to the
magnetic field.
●The required frequency of the pulse is determined by the strength of the
magnetic field and the particular nucleus undergoing investigation.

6. ●When the RF field is removed, the energy absorbed during the transition from a high to
low-energy state is subsequently released, and this can be recorded as an electrical
signal that provides the data from which digital images are derived.
●Signal intensity refers to the strength of the radio wave that a tissue emits after
excitation. The strength of this radio wave determines the degree of brightness of the
imaged structures.

7. MRI signal
production
(Principle)

8. What are MRI
Images?
●X-ray and CT images can be considered to be a map of density of tissues
in the body
●MRI images can be considered as a map of proton energy within tissues
of the body. A variety of MRI images can be produced which emphasise
different tissue types, in particular those that contain a large amount of fat
or water.
●Bright areas on an MRI image represent high ‘signal’ given off by protons
in the body during the scanning process.
●White areas on an X-ray or CT image = high density structures
●White areas on an MRI image = high signal intensity structures

9. Systematic
approach to
interpretation
of MRI images
●Check image and patient details over the film
●Check MRI planes
●Check MRI sequences(T1,T2,STIR)
●Check for abnormal MRI signal
●Compare with previous radiologic images(MRI/X-
ray/CT/USG)
●Co-relate with clinical findings

12. T1 vs T2
Images
●It’s all about FAT and WATER
●The two basic types of MRI images are T1-weighted
and T2-weighted images, often referred to as T1 and
T2 images.
●The timing of radiofrequency pulse sequences used to
make T1 images results in images which highlight fat
tissue within the body.
●The timing of radiofrequency pulse sequences used to
make T2 images results in images which highlight
fat AND water within the body.
●So, this makes things easy to remember.
●T1 images – 1 tissue type is bright – FAT
●T2 images – 2 tissue types are bright –
FAT and WATER
TISSUE T1 T2
Fluid Dark Bright(ww2)
Fat Bright Intermediate
Tendon/
ligament
Dark dark
Air Black Black

13. ,

17. Specialised
MRI sequences

18. STIR(Short Tau
Inversion Recovery):
• STIR (Short Tau Inversion Recovery) images
are highly water-sensitive and the timing of
the pulse sequence used acts to suppress
signal coming from fatty tissues – so ONLY
WATER is bright
• A combination of standard T1 images and
STIR images can be compared to determine
the amount of fat or water within a body part
• In these MRI images abnormal signal is seen
in the vertebral bodies and intervertebral disc
• Abnormal low signal on the T1 image and
abnormal high signal on the STIR image –
indicates abnormal fluid
• These are typical appearances of
spondylodiscitis (also known as discitis)

19. Proton density weighted image
Preoperative magnetic resonance imaging depicted as a proton
density weighted coronal section showing a cartilage defect

20. Fat suppressed T2W image
Sagittal fat-suppressed T2-weighted (T2W) image demonstrating oedema at the
anterior aspects of the femoral and tibial condyles due to a hyperextension injury in
a 24-year-old soccer player (arrows)

21. Gradient echo(T2*) image
IDEAL gradient-recalled echo (GRE) image
shows bright synovial fluid (arrow)

22. MRI Arthrogram
•Fluid containing gadolinium has been injected into the
shoulder joint revealing displacement of the anterior glenoid
labrum in this patient with recurrent shoulder dislocation
•G = Glenoid of scapula
•H = Head of humerus

23. Advantages of
MRI
●Images can be obtained in any plane and provide
superb soft tissue contrast,anatomic detail and
simultaneous demonstration of bones and soft
tissues.As a result,it is the best single modality for
evaluating most types of musculoskeletal pathology.
●The most useful modality for detecting marrow
pathology(neoplastic marrow infiltration,bone
contusion,occult fracture,tumour).
●The test of choice for evaluating neurologic deficits
related to spinal trauma and neoplasm.
●Can be used in combination with contrast
agents(gadolinium)
●No ionising radiation.

24. Uses of MRI
●MRI excels in the display of soft tissue detail.It is widely
used in the diagnosis of sports injuries because of its ability
to differentiate b/w the different soft tissues and distinguish
partial tears of tendons and ligaments from complete tears.
●MRI is very sensitive for detecting changes and variations in
bone marrow. This is important in the diagnosis of bone
tumors,stress fractures and avascular necrosis.
●In some cases,MRI has replaced invasive diagnostic
procedures such as arthroscopy ,as in the detection of
meniscal tears.
●MRI is the best modality for evaluation of disc herniations
and other potential causes of nerve root impingement.
●MRI has the ability to stage neoplasms in bone and soft
tissues as well as evaluate the extent of tissue invasion
before surgery.It is more sensitive than bone scan for
detecting bone metastases,although bone scan is more
effective as a screening technique.

25. General Spine Anatomy
Intervertebral Disc complex has three components:
● Cartilaginous end plate
● Annulus fibrosus
● Nucleus pulposus
● intervertebral discs show intermediate signal intensity on T1-weighted images and
high signal intensity on T2-weighted images.The outer annulus appears
hypointense on T2.

26. ● As the disc degenerates and as patients age, the signal intensity of the
nucleus pulposus decreases.
● The ligamentum flavum connects the lamina of adjacent vertebrae and
is seen as a hypointense band posterior to the dura.
● nerve roots have intermediate signal intensity and are surrounded by
high signal intensity fat on T1-weighted images and by high signal
intensity CSF on T2-weighted images..

29. MRI Spine indications:
▪Evaluation of intervertebral disk disease
▪Evaluation of nerve roots, posterior longitudinal
ligament and intervertebral foramen
▪Postoperative back pain (failed-back surgery)
▪Pyogenic and tuberculous infections
▪Epidural hematoma or abscess
▪Primary and metastatic tumors of the vertebral column
▪Spinal cord injury
▪Spinal cord tumors (extradural and intradural)
▪Abnormalities of thecal sac
▪Developmental deformities of the spinal cord and
vertebral column.

30. CERVICAL SPINE
AXIAL
VIEW
SAGITTAL VIEW

31. THORACIC SPINE
AXIAL
VIEW
SAGITTAL
VIEW

32. SAGITTAL IMAGE
Mid
sagittal
Parasagital
Foraminal sagital

33. Lumbar Spine
● The midsagittal
image should be
evaluated first,then
sequentially
evaluated toward
each side to assess
the facet joints and
neural foramina.
● sagittal images can
be concurrently
evaluated with the
axial sequence to
confirm laterality.

36. AXIAL
IMAGES
● the degree of
contribution of the
three primary
contributors to
spinal stenosis (disc
pathology, facet
arthropathy, and
ligamentum flavum
hypertrophy) should
be noted

37. ● Herniation is defined as a
localized displacement of disc
contents beyond the borders
of the intervertebral disc
space
● disc material may include
● nucleus
● cartilage
● fragmented apophyseal bone
● annular tissue or a
combination

38. DISC DEGENERATION DISEASE

39. Disc protrusion Disc extrusion

40. Lumbar disc protrusion. Sagittal (A) and axial (B) T2-weighted images
showing a central disc protrusion at the L4-L5 level (arrow
on each).

41. Disc herniation

44. Lumbar Spinal Stenosis
● compression
of the neural
elements in
the spinal
canal, lateral
recesses, or
neural
foramina.

45. Spinal canal stenosis

46. TB SPINE

47. ●Meniscal lesion
●Cruciate ligament tears
●Collateral ligament tears
●Cartilage lesions: arthritis,osteochondritis dissecans
●Inflammatory changes: Synovitis
●Changes in bone: oedema, necrosis, fracture
●Cysts : baker cyst
●Tumors
●Intra-articular loose bodies
●Soft tissue envelope: tear ,hematoma, tumor.
MRI Knee joint indications

48. ACL
● Course
● Composed of the antero-
medial and posterolateral
bundles.
● Intraarticular but
extrasynovial
● Should not show marked
increased signal on T2-
weighted imaging, but it
may have minimally
increased signal on T1-
weighted images because
of the presence of fatty
tissue

50. PCL
● PCL curves anteriorly
to insert on the
anterolateral aspect of
the medial femoral
condyle
● appears as a thicker,
darker, curved band
compared with the
ACL.

51. NORMAL MENISCI
low intensity signals on both T1w and T2w
• Mensici are best seen in sagittal view
• In central cuts-triangle,in peripheral cuts-Bow tie appearance
• Lesions-areas of increased signal
• Sensitivity and specificity of MRI >90%

52. ▪ MENISCAL INJURIES:
Lesions are seen as areas of
increased signal and are
classified:
Grade 1- Globular signal
within the meniscus.
Grade 2- Linear signal within
the meniscus not reaching the
articular surface.
Grade 3- Linear signal within
the meniscus reaching the
articular surface. surface.

53. GRADE-1 GRADE-2 GRADE-3

55. ● Most tears
involve the
medial
meniscus, but
most acute
tears involve
the lateral
meniscus
● chronic ACL
tears associated
with meniscus
tears.
posterior horn of the medial meniscus

56. medial meniscus and
displaced inferior to the
PCL (arrow-
head), exhibiting the
double-PCL sign

57. complete radial tear - empty meniscus sign

58. ACL TEARS
● H/o twisting or valgus
injury to the knee with a
planted foot and often
describes sensing a
“pop” inside the knee.
● adult ACL usually
avulses from its femoral
attachment or develops
an intrasubstance tear.
● The tendon does not
have to dissociate
completely to become
incompetent. In skeletally immature patients,
the ACL may remain intact and avulse a fragment of
bone off of the attachment.

62. normal
acute
avulsio
n
chronic
ACL
Tear

63. ● sagittal fat-suppressed proton-density image shows
advanced degeneration (marked thickening) of the
ACL
Segond fracture

64. PCL Tear
▪ Seen as a curving band of
fibrous tissue appearing
homogeneously hypointense
on sagittal MRI series.
▪ Discontinuity of the ligament
or fluid signal within its
substance indicates a tear.

65. Partial PCL tear Complete PCL tear PCL avulsion

66. MRI Shoulder

67. NORMAL SHOULDER MRI

68. ROTATOR CUFF TEAR
•MR abnormalities
• Full-thickness tear: high SI on
T2WI
• Direct signs
Tendon discontinuity
Fluid signal in tendon gap
Retraction of
musculotendinous junction
• Associated findings
Subacromial/ subdeltoid
bursal fluid
Muscle atrophy
SUPRASPINATUS TEAR

69. Biceps tendon tear

70. Subscapularis Tendon Tear
•MRI:
• Detachment from lesser tuberosity
• Increased SI, thin/thick
• Contrast over the lesser tuberosity

71. Adhesive capsulitis (Frozen shoulder)
• Inflammatory process ->
progressive capsular retraction, scar
tissue
MRI
• Complete obliteration of the fat
triangle under the coracoid process
(subcoracoid triangle sign)
• Scar tissue
• Thickening of the CHL
• Axillary recess thickening
• Arthrography:
• Decreased joint capacity
• Small capsular recesses
• Serrated appearance of capsular
attachments
.

72. MRI Hip indications
• Avascular necrosis of femoral head
• Transient osteoporosis of the hip
• Occult fractures
• Evaluation of the acetabular labrum

73. • Avascular necrosis is the most
frequent indication for hip imaging.
Even when initial roentgenograms
show normal images MRI may be
positive for AVN.
• In T1-weighted images,intensity is
decreased in areas affected by
AVN. The surrounding ischemic
bone is seen as a low-signal band.
• In T2 images, a second inner band
of high intensity is seen which is
the “double line” sign diagnostic of
AVN
AVN of femoral head

74. Transient osteoporosis
• self-limited process of uncertain etiology related to reflex
sympathetic dystrophy and regional migratory
osteoporosis.
• MRI shows diffuse edema in the femoral head, extending
into the intertrochanteric region.
• This is seen as a low signal area onT1 when compared to the
normal bone marrow,
• whereas on T2
it becomes hyperintense.

75. Occult fractures
• MRI changes are apparent immediately, with linear areas of low
signal easily seen in the fatty marrow on T1- weighted images, and
surrounding edema seen with T2- weighted images

76. Contraindications
of MRI
1. Intra cerebral aneurysm clips
2. Internal hearing aids
3. Middle ear prosthesis
4. Cardiac pacemakers
5. 1st trimester pregnancy
6. Metallic orbital foreign bodies
Orthopaedic implants and prosthetics are
safe on MRI

77. Limitations of
MRI
●Fractures on the posterior elements of the
spine are difficult to detect with MRI(more
cortical bone)
●Assessment of fracture healing
●Hardware (depending on type,may produce
severe artifact,obscuring adjacent tissues.
●More time consuming than CT
●Claustrophobia
●Even the slight movements of the patient on
the examination bed can distort the MRI
image.
●More costlier than USG,CT.

78. MRI safety
warnings

79. REFERENCES
●Fundamentals of musculoskeletal imaging-
Lynn.N.Mckinnis
●Essential orthopaedics;Imaging of the
Musculoskeletal system-Mark.D.Miller
●Turek’s Orthopaedics;Imaging in
Orthopaedics
●Essential orthopaedics-Manish kumar
varshney
●www.radiologymasterclass.co.uk

80. “THANK YOU”