CT is a investigation of choice for knowing the degree and extent of involvement of disease process.
In plain radiograph soft tissue density is seen but bony changes is not clearly visualised.
In CT mucoperiosteal thickening and bony sclerosis is clearly visualised on wide window setting of 2000-2500 WW.
In MRI, high signal on T2W of the sinus mucosal layer and some time no signal is seen in dessicated state where sinus is mimicked aerated
polyps result from an expansion of fluids in the deeper lamina propria of the Schneiderian mucosa in the nasal fossa and paranasal sinuses.
The polyps in sinonasal polyposis are soft-tissue pedunculated masses of oedematous hyperplastic upper respiratory mucosa.
The cause remains unclear but there is an association with atopic rhinitis (allergic and non-allergic), asthma, infection, cystic fibrosis, aspirin intolerance and Kartagener's syndrome.
The commonest site of sinonasal polyposis is the ethmoids, followed by the maxillary antra and then the sphenoid sinus.
occur as a result of obstruction of the ducts of the mucosal glands.
usually small, have a well-defined outline and are seen in approximately 10% of the population.
may occasionally enlarge to fill the sinus.
The intrasinus polyp and the retention cyst cannot be differentiated on either plain films or sectional imaging.
Plain radiograph and CT appearance is of a smooth, broad-based soft-tissue mass with outwardly convex and borders a well-defined outline.
On MRI these are usually of low intensity on T1, and bright on T2, but may appear bright on T1, depending on the concentration of entrapped secretions.
is a permanent injury that occurs when tissue perfusion is decreased long enough to cause necrosis, typically as the result of occlusion of the feeding artery.
two thirds of infarcts are caused by thrombi and one third are caused by emboli
Vasculitis, vasospasm, coagulopathies, global hypoperfusion, and venous thrombosis each account for 5% or fewer of acute strokes, but are important to recognize because of differing treatment and prognosis
Imaging Findings in Acute Ischemia
Ischemia causes a cascade of cellular level events leading to the gross pathologic changes detected in clinical imaging .
Failure of membrane pumps permits efflux of potassium ions (K+) and simultaneous influx of calcium ions (Ca2+), sodium ions (Na+), and water
This leads to cellular (“cytotoxic”) edema, observed clinically as increased water content in the affected region.
Even a small increase in water content causes characteristic decreased attenuation on CT, low signal on T1WIs, and high signal on T2- and diffusion-weighted MR.
Hemorrhage occurs when an artery or vein ruptures, allowing blood to burst forth into the brain parenchyma or subarachnoid spaces
Although mixed patterns occur, hemorrhages are most conveniently divided into subaracnoid and parenchymal categories .
Imaging studies are critical in determining the source of bleeding and in showing any associated complications.
astrocytomas tend to occur in younger patients, usually children and adults 20 to 40 years old
are usually well-demarcated tumors without necrosis or neovascularity, rarely hemorrhage, and are often cystic
show calcification in 20% of cases and rarely have surrounding edema
On CT, they are hypodense with little or no enhancement. On MR, compared to gray matter, they are hypointense on T1WIs, hyperintense on T2WIs, and show minimal enhancement
the higher-grade astrocytomas tend to occur in patients older than 40 years of age
tumors are poorly delineated microscopically, although they may appear well-circumscribed grossly. Necrosis, hemorrhage, and neovascularity are common, particularly in the GBM.
On CT, they are typically heterogeneous. On MR they are isointense to hypointense compared to gray matter on T1WIs and hyperintense on T2WIs. A ringlike pattern on postcontrast imaging may be seen
most common extra-axial neoplasm of adults and accounts for 15% of all intracranial neoplasms, second only to gliomas in overall prevalence
The peak age of presentation is 50 to 60 years of age.
On CT, a well-defined hyperdense (85%) mass with variable surrounding edema and intense and homogeneous enhancement on postcontrast studies is highly characteristic . Hyperostosis of the adjacent inner table is noted about 40% of the time. Calcification is seen in 10% to 20% of cases.
On MR, the tumor is typically isointense to hypointense to gray matter on T1WIs and isointense to hyperintense to gray matter on T2WIs
account for about 10% to 15% of all intracranial tumors and constitute the most common sellar masses
Based on their size, they are considered either microadenomas (10 mm or smaller) or macroadenomas (>10 mm).
MR is the imaging modality of choice to detect pituitary tumors.
Microadenomas are usually best detected on coronal T1WIs as focal areas of hypointensity (on noncontrast studies) compared tothe rest of the pituitary gland
most common pediatric CNS malignancy and, along with the pilocytic astrocytoma, the most common pediatric posterior fossa tumor
majority (85%) arise from the cerebellar vermis
Extension into the adjacent fourth ventricle and subsequent development of hydrocephalus is common
is a highly malignant neoplasm (WHO grade IV) with rapid growth
Most medulloblastomas manifest as solid, hyperdense masses on CT. Cystic change or necrosis occurs in up to 60% of cases and calcification is noted in 20%
On MR, the tumor is usually isointense to hypointense compared to white matter on T1WIs and has a more variable appearance on T2WIs
Following administration of contrast, the tumor demonstrates intense although usually heterogeneous enhancement
Simple Renal Cyst
are the most common type renal mass
They are found in half the population older than age 55
Small cysts are asymptomatic
Large cysts (>4 cm) occasionally cause obstruction, pain, hematuria, or hypertension
Cysts are commonly multiple and bilateral
US, CT, and MR can each make a definitive diagnosis
Plain film -Often no abnormal finding.
-A bulge in renal outline for very large cyst.
Intravenous pyelography- Displacement and stretching of calyces
-Clubbing of calyces
Simple Renal Cyst
CT signs include :
sharp margination with the renal parenchyma,
no perceptible wall,
homogeneous attenuation near water density (-10 to +10 H)
absence of contrast enhancement
MR criteria include:
homogeneous, sharply defined, round or oval mass;
homogeneous low signal intensity on T1WIs; and
homogeneous high signal intensity similar to that of urine on T2WIs. No enhancement should be seen after gadolinium administration
-Enlargement and lobulation of the renal shadows
-Stretching of the calyces and calyceal stem which are large crescentic and sharply defined
-Enlargement of both kidneys
-The number, size, shape and the nature of the cysts are well demonstrated.
is an uncommon (1% to 3% of renal neoplasms) benign mesenchymal tumor composed of varying amounts of fat, smooth muscle, and abnormal blood vessels lacking elastic tissue.
Most (80%) are solitary unilateral tumors; they are discovered most commonly in middle-aged women.
Plain film ：
-Changes of renal outline
Intravenous pyelography ：
-Depress and displacement of calyces and pelvis with smooth margin.
-Low or mix-dense mass with clear margin. The most important sign is the fat tissue within the mass with very low density.
-Unevenly enhancement of the mass on the contrast enhanced scan
Renal cell carcinoma (RCC)
accounts for 85% of all renal neoplasms
more common in men (male-to-female ratio = 3:1) aged 50 to 70 years and is bilateral in 2% of cases
Hemorrhage and necrosis are common, and cystic and multicystic forms
Stippled central or peripheral calcifications are present in 10% of cases
The tumors are commonly hypervascular, with numerous abnormal feeding vessels visualized.
Tumor growth into the renal vein occurs in 30% of cases and extends into the IVC in 5% to 10% of cases
The tumor metastasizes most commonly to lung, local lymph nodes, liver, bone, adrenal glands, and the opposite kidney
C/F: painless hematuria
Renal cell carcinoma
Plain film ：
Generalized enlargement of renal outline ， local bulge
Irregular or linear calcification
Little changes in small tumor
Displace, stretch and destroy calyceal stems and calyces
Dilatation of some calyces
Renal cell carcinoma
CT : Local bulge or irregular mass
Slightly low, iso- or high dense mass, which will be enhanced in contrast enhanced scans.
Destruction and displacement of calyces and pelvis
MRI: RCC is isointense or hyperintense compared with renal parenchyma on T1WIs and shows distinct enhancement with gadolinium administration.
Hyperintensity on T1WIs usually reflects tumoral hemorrhage, but fat-suppression sequences should be used to ensure the high signal is not because of fat
S lightly hyperintense on T2-weighted sequences.
Contrast: Heterogeneous enhancement occurs immediately, decreasing on delayed images
Basic imaging signs of GIT diseases
1 ） evection (protrude)
- Filling defect is a term used to describe something occupying space within the bowel thereby preventing the normal filling of the lumen with barium. This creates an area of total or relative radiolucency within the barium column.
-The common cause includes tumor 、 granuloma etc.
2 ） indentation
- an outward projection from the barium-filled lumen
ulcer is common
Basic imaging signs of GIT diseases
（ 3 ） thickening the wall of the bowel
the wall of esophagus>5mm
the wall of stomach>10mm
the wall of small intestine>5mm
the wall of large intestine>5mm, suspected ； >10mm ， confirmed
squamous cell carcinoma in 85% to 90% of cases
Tumor assumes four basic radiographic patterns:
annular constricting lesion, appearing as an irregular ulcerated stricture, is most common
polypoid pattern causes an intraluminal filling defect
infiltrative variety grows predominantly in the submucosa and may simulate a benign stricture
least common pattern is that of an ulcerated mass
COMPLICATIONS : Perforation leading to abscess,fistula.
Metastasis to lymph node
the third most common GI malignancy, following colon and pancreatic carcinoma
Most (95%) are adenocarcinomas; the remainder are diffuse anaplastic (signet-ring) carcinoma, squamous cell carcinoma, or rare cell types
2.localized and ulcerated
3.ulcerated and infiltrative
stricture of gastral cavity, rigidity wall （ leather bottle ）
niche ： irregular morphous, meniscus sign
destroyed 、 interrupted or abnormally thickened mucosal folds
CT : CT examination has limited value in detecting gastric ulcer , duodenal ulcer or early gastric cancer, whereas it is good at observing lesion range and metastasis of lymph node.
IBD- Crohn disease
involves the colon in two thirds of cases and is isolated to the colon in approximately one third of all cases
Is a inflammatory disease
Hallmarks of Crohn colitis include early aphthous ulcers, later confluent deep ulcerations, predominant right colon disease, discontinuous involvement with intervening regions of normal bowel, asymmetric involvement of the bowel wall, strictures, fistulas, and sinus formation
Imaging manifestations ：
1 、 aphthoid ulcer 、 longitudinal ulcer
2 、 cobblestone filling defect
3 、 segmented and dissymmetry distribution
4 、 pseudodiverticula at opposing mesentry
5 、 thickening 、 hardened intestinal wall
6 、 CT can demonstrate mural abscess 、 sinus tract
adenocarcinoma is the most common malignancy of the GI tract and the second most common malignant tumor
Approximately 50% arise in the rectum and rectosigmoid area. Another 25% occur in the sigmoid colon, and the remaining 25% are evenly distributed throughout the remainder of the colon
1. annular constricting lesions most common type, 2 to 6 cm in diameter, with raised everted edges and ulcerated mucosa 2. Polypoid tumors are less common,3. Infiltrating scirrhous tumors
irregular filling defect
annular stricture of lumens
rigidity of the bowel wall, aperistalsis
N aso p haryngeal c arcinoma
Squamous cell carcinoma (SCC) accounts for about 70% of the malignancies arising in the nasopharynx in adults.
Type l, keratinized squamous cell carcinoma (25%)
Type 2, nonkeratinized carcinoma (12%) (sometimes called transitional cell carcinoma) Type 3, undifferentiated carcinomas (63%)
Most tumors arise in the fossa of Rosenmuller and tend toward submucosal spread to infiltrate the palatal muscles and eustachian tube orifice.
Genetic susceptibility .
Environmental factors (including chemical carcinogens)
Exposure to Epstejn-Barn virus
(with types 2 and 3 of nasopharyngeal SCC)
Highest incidence found in southern china (Guangdong)
Risk factors include chronic sinonasal infection, nitrosamines ( in dry-salted fish), polycyclic hydrocarbons, and poor living conditions.
C/F : more common in men.
Early stage is asymptomatic and usually overlooked for simple postnasal drip and nasopharyngeal irritation.
Middle ear effusion
Advance disease present with nasal obstruction, epistaxis, trismus, proptosis, various cranial nerve palsies (mostly trigeminal)
MRI is a choice to see the soft tissue and neuro vascular extension where as CT is valuable to visualise bone invasion.
MRI: in early stage obliteration of fat strip between the tensor and levator veli palatini muscles, on T1W obliteration of bright signal on this area.
Middle ear and mastoid air cell signal changes.
1997 AMERICAN JOINT COMMITTEE ON CANCER STAGING FOR EPITHELIAL TUMORS OF THE NASOPHARYNX:
T1 Tumor confined to the nasopharynx
T2 Tumor extends to soft tissues of oropharynx and/or nasal fossa.
T2a Without parapharyngeal extension
T2b With parapharyngeal extension
T3 Tumor invades bony structures and/or paranasal sinuses
T4 Tumor with intracranial extension and/or involvement of cranial nerves, infratemporal fossa, hypopharynx, or orbit.
Associated cervical lymphadenopathy, intermediate T1W and high T2W.
On CT in early stage, soft tissue isodense mass on the Fossa of Rosenmuller , doesnot show marked enhancement.
MRI on advance stage shows isotense to adjacent muscle on T1W. On T2W intermediate to high signal. Solid part of tumor shows significant enhancement on T1W.
On advance stage CT can demonstrate erosion of bones of skull base, paranasal sinus, orbits.
is the irreversible dilatation of one or more bronchi,and is usually the result of severe,recurrent,or chronic infection.
Morphologically, bronchiectasis is divided into three groups: cylindric, varicose, and saccular (cystic).
Bronchography is gold standard but it is invasive so CT is the choice of investigation.
Plain x-ray is not reliable due to unclear feature unless it is prominent,eg may be incresed lung markings or atelectasis or consolidation on basal regions.
The CT appearance of bronchiectasis depends on the site of involvement and the type of bronchiectasis
Cylindric bronchiectasis in upper & lower lobe regions appears as multiple dilated thick-walled circular lucencies, with the adjoining smaller artery giving each dilated bronchus the appearance of a “signet ring.”
In the mid-lung, where the bronchi course horizontally, the appearance is that of parallel linear opacities (tram tracks).
Cystic bronchiectasis in any region is easily recognized as clusters of rounded lucencies, often containing air–fluid levels; this appearance has been likened to a “cluster of grapes ”
Lobar pneumonia/segmental pneumonia
Bronchopneumonia/ Lobular pneumonia
Lobar pneumonia/segmental pneumonia
Exudation & consolidation
Acute inflammation of the entire lobe/lung
Caused by Streptococcus pneumoniae
Congestion 24hrs .
Red hepatisation a few days
Grey hepatisation a few days
Resolution 8~10 days later
c/f: Fever, cough, rusty sputum, pleurisy
Typical X-ray ： exudation & consolidation
Uniform opacity – alveolar consolidation
lobar ： confined within the boundaries of the lobe
segmental ： ill-defined
The lobe volume normal / slight loss
Air-bronchonogram, no lung markings can be seen
Absorption – patchy shadows with blur lung markings
Pleural reaction: pleural effusion,empyema
Incomplete resolution ： fibrosis
Necrosis ： lung abscess
Is a multifocal process which commences in the terminal and respiratory bronchioles.
Cause S.aureus and Gram-negative bacteria
clinical ： elderly people, infant, Complication with other disease, Fever, cough.
X-ray ： site ： inner and middle parts of both lower lobes
Alveolar inflammation: small patchy (1 ～ 2 cm) opacities blur and exaggerated lung markings, lobular consolidation
Abscess, pleural effusion
pathology ： Interstitial inflammation
Mostly due to viral infection eg,influenza,HVC
Involved: Small bronchioles, Adjacent alveoli, Lymphangitis, Bronchiole obstruction.
X-ray: Bilateral,lower field and near the hilum
Blur and exaggerated lung markings ， form diffuse reticulation, with spot opacities
Hilum enlargement ：
Pul. artery congestion
Lymph nodes enlarged
Chronic infectious disease caused by mycobacterium tuberculosis
classification(1998 China ）
Ⅰ ： primary tuberculosis
Ⅱ ： disseminated TB
Ⅲ ： postprimary TB
Ⅳ ： TB pleurisy
Ⅴ ： extra-pulmonary TB
primary tuberculosis (type I) primary syndrome Pathology X-ray Parenchyma exudation Ill-defined parenchyma opacity, Cloudy shadow lymphangitis Strip and liner shadows between the lesion and the hilar lymph-nodes lymphadenopathy Hilar & right paratracheal region lymphadenopathy
primary tuberculosis paratracheal region lymphadenopathy
Lymph nodes enlargement ：
Lymph nodes caseous necrosis
Can cause middle lobe collapse
disseminated TB （ typeⅡ ）
Acute disseminated TB (homogenous pattern)
large amount of mycobacterium TB spread into the blood and seed in lung in short period
Chronic disseminated TB (heterogenous pattern)
minority mycobacterium TB spread into the lung in a long period recurrently
* Acute disseminated TB *
X-ray ： Homogenous millet-like nodules (1.5~2mm)
disseminated in both lung fields, with similar density and size ,can be accumulated and fused to patchy shadow
Lung markings disappear
recover ： disappear 、 fibrosis 、 calcification
worse ： exudation 、 cavity formation
* Chronic disseminated TB *
X-ray ： heterogeneous
distribution ： upper middle lung field
Size ： varies
Density ： acinus nodules 、 calcification
Clinical ： adult （ reactivation ） or reinfection ， c/f cough and constitutional symptoms, including chills, night sweats, and weight loss
Common site ： 2 nd ~3 rd anterior costal space 、 lung apex