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MI6 Medical Imaging Toronto Notes 2023
legend
a I anterior 1st rib
»2 anterior 2nd rib
aortic arch
apw aorto'pulmonarv window
anterior airspace
carina
clavicle
coracoid process
costophrenic angle
diaphragm
gastric bubble
inferior vena cava
left atrium
Ibr left mainstem bronchus
Ipa left pulmonary artery
left ventricle
mf major fissure
minorftssuro
p3 posterior 3rd rib
p4 posterior 4th nb
main pulmonary artery
right atrium
rbr right mainstem bronchus
rpa right pulmonary artery
right ventricle
scapula
spinous process
sternum
sve supenorvenacava
trachea
vb vertebral body
aa
as
ca
cl
co
epa
di
9
VC
la
v
mi
pa
ra
rv
sc
sp
St
PA view Lateral view tr
Figure 2. Location of fissures, mediastinal structures,and bony landmarks on CXR
Note that anterior space is also commonly called retrosternal space
LUL
LLL
t
1
r~ m\
Right-Lateral
^
RUL Right Upper Lobe; RML:Right Middle Lobe; RLL:Right Lower Lobe; LUL:Left Upper Lobe; LLL:Left Lower Lobe
Front AP Back AP Left-Lateral
< w
Jf
Figure 3
fW £ \
. Location of lobes of the lung
\
i
*
Chest Computed Tomography — BooeWiidow
Approach to CT Chest
• soft tissue window
• thyroid, chest wall, pleura
heart: chambers, coronary artery calcifications, pericardium
• vessels: aorta, pulmonary artery, smaller vasculature
• lymph nodes: mediastinal, axillary, hilar
• bone window
vertebrae,sternum, ribs: fractures, lytic lesions,sclerosis
• lung window
trachea: patency,secretions
bronchi:anatomic variants, mucus plugs,airway collapse
• lung parenchyma: nodules,fibrosis, interstitial changes, consolidation, atelectasis
pleural space: effusions, thickening
Figure 4. CT thorax windows in axial
view
Table 4. Types of CT Chest
Advantage Disadvantage Contrast Indication
Standard Scans lull lung very quickly (<1 mm)
i high resolution reconstructions
CXR abnormality
Pleural and mediastinal abnormality
lung cancerstaging
Cancer follow up
Empyema vs.abscess
lung cancer screening
Follow up Inlections, lung transplant,
metastases
Radiation i
LJ
low Dose 1/Slh the radiation Decreased detail No
+
CIA lodinated contrast highlights
vasculature (scan timed for maximum
opacification of vessel being studied)
Contrast can causesevere Yes
allergic reaction and can
cause acute kidney injury
PE
Aortic aneurysms
Aortic dissection
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MI7 Medical Imaging Toronto Notes 2023
Lung Abnormalities
Atelectasis
• pathogenesis: collapse of lung tissue due to restricted breathing, blockage of bronchi, external
compression, or poor surfactant
• findings
increased opacity of involved segment/lobe, vascular crowding,silhouette sign, air bronchograms
volume loss:fissure displacement,hilar/mediastinal displacement, diaphragm elevation
compensatory hyperinflation of remaining normallung
• differential diagnosis
obstructive (most common):alveolar air distal to obstruction is resorbed causing alveolar
collapse
post-surgical, endobronchial lesion, foreign body,inflammation (granulomatous infections,
pneumoconiosis,sarcoidosis, radiation injury),or mucous plug (cystic fibrosis)
compressive:tumour, bulla, effusion, enlarged heart,lymphadenopathy
traction (cicatrization):due to scarring, which distorts alveoli and contractsthe lung
adhesive:due to lack ofsurfactant
hyaline membrane disease, prematurity
passive (relaxation): a result of air or fluid in the pleural space preventing full aeration
pleural effusion, pneumothorax
• management: in the absence of a known etiology, persisting atelectasis must be investigated (i.e.CT
thorax or bronchoscopy) to rule out bronchogenic carcinoma centrally
Consolidation
• pathogenesis:air in alveoli replaced by fluid (transudate,blood),inflammatory exudates, protein,or
tumour
• findings
air bronchograms: lucent branching bronchi visible through opacification
airspace nodules:fluffy, patchy, poorly defined margins with later tendency to coalesce, may take
on lobar or segmental distribution
silhouette sign
• differential diagnosis
fluid:transudate (pulmonary edema),blood (trauma,vasculitis,bleeding disorder,pulmonary
infarct)
inflammatory exudates: bacterial infections, TB, allergic hypersensitivity alveolitis, COP
(cryptogenic organizing pneumonia), allergic bronchopulmonary aspergillosis, aspiration,
sarcoidosis
protein: pulmonary alveolar proteinosis
tumour:adenocarcinoma, lymphoma
• management:varies depending on the pattern of consolidation, which can suggest different etiologies;
should also be done in the context of clinical picture
Interstitial Disease
• pathogenesis: pathological process involving pulmonary interstitium (i.e."lung scaffolding")
• findings
septal thickening:fine lines caused by thickened connective tissue septae (most commonly due to
pulmonary edema or lymphangitis carcinomatosis)
these manifest on CX R as:
- Kerley A:long thin linesin upper lobes
- Kerley B:short horizontal lines extending from lateral lung margin
- Kerley C: diffuse linear pattern throughout lung
• nodular pattern: 1 -5 mm well-defined or ill
-defined nodules distributed throughout lung or with
a lung zone predominance
» seen in metastases, pneumoconiosis, granulomatous disease (e.g.sarcoidosis, miliary TB)
reticular pattern:fine curvilinear opacities
seen in interstitial lung diseases (pulmonary fibrosis)
watch for pneumothorax as a complication
reticulonodular: combination of reticular and nodular patterns
may also see signs of airspace disease (atelectasis, consolidation)
• differential diagnosis
occupational/environmental exposure
inorganic: asbestosis, coal miner'
s pneumoconiosis,silicosis, berylliosis, talc pneumoconiosis
organic:hypersensitivity pneumonitis, bird fancier’
slung,farmer’s lung (mouldy hay), and
other organic dust
autoimmune:connective tissue diseases(e.g.rheumatoid arthritis,scleroderma,SLE,
polymyositis, mixed connective tissue disease), 1BD, celiac disease, vasculitis
• drug-related:antibiotics(cephalosporins, nitrofurantoin), NSAlDs, phenytoin, carbamazepine,
fluoxetine, amiodarone, chemotherapy (e.g. methotrexate), immunotherapy, heroin, cocaine,
methadone
• infections:TB, non-tuberculous mycobacteria, certain fungal infections, viral infections
Figure 5. Atelectasis: RML collapse
DDx of Airspace Disease
. Pus (e.g.infectionssuch as
pneumonia)
• Fluid (e.g. pulmonary edema)
• Blood (e.g. pulmonary hemorrhage)
• Cells (e.g. bronchioalveolar
carcinoma, lymphoma)
• Protein (e.g.alveolar proteinosis)
Figure 6. Air bronchograms inright
lung
Figure 7. Consolidation:bacterial
pneumonia
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MI8 Medical Imaging Toronto Notes 2023
idiopathic:1PF, nonspecific interstitial pneumonia (NSIP), organizing pneumonia
for causes of interstitial lung disease classified by distribution,see Respirology, R13
• management: high-resolution CT thorax and ± open lung biopsy, multidisciplinary team discussions
Pulmonary Nodule
• findings
round opacity <3 cm (>3 cm is considered a mass) ± silhouette sign
note:do not mistake nipple shadows for nodules;if in doubt,repeat CXR with nipple markers
• differential diagnosis
cxtrapulmonary density: nipple,skin lesion, electrode, pleural mass, bony lesion
solitary nodule
tumour:carcinoma,hamartoma, metastasis, bronchial adenoma
infection/inflammation: histoplasmoma, tuberculoma, coccidioidomycosis
vascular: AV fistula, pulmonary varix (dilated pulmonary vein), infarct, septic embolus
multiple nodules: metastases, abscess, granulomatous lung disease (TB,fungal,sarcoid,
rheumatoid nodules,silicosis,GPA),septic emboli
• management:clinical information and CT appearance determine level of suspicion of malignancy
if high probability of malignancy, invasive testing (transbronchial or CT-guided transthoracic
biopsy) ± PET/CT isindicated
if low probability of malignancy,follow-up imaging as per Fleischner guidelines 2017
Figure 8.Interstitial disease:fine
reticular pattern
Table 5. Characteristics of Benign and Malignant Pulmonary Nodules
Malignant Benign
Figure 9. Interstitial disease:
medium reticular pattern
Margin
Contour
Calcification
Doubling Time
Other Features
lll-defined/spiculated (“corona radiata")
lobulalod
Eccentric or stippled
20-460 d
Cavitation, collapse,adenopathy, pleural effusion,lytic bone
lesions,smoking history
>3cm
Yes. especially withwall thickness >15 mm.eccentric cavity,and No
shaggy internal margins
Well-defined
Smooth
Diffuse,central,popcorn, concentric
<20dor >460 d
ODx of Interstitial lung Disease
FASSTEN (upper lung disease)
Farmer- slung (hypersensitivity
pneumonitis)
Ankylosing spondylitis
Sarcoidosis
Silicosis
Size <3 cm
Cavitation
Satellite lesions No Yes
TB
Eosinophilic granuloma (langerhans cell
histiocytosis)
Neurofibromatosis
Pulmonary Vascular Abnormalities
Pulmonary Edema
• pathogenesis:fluid accumulation in the airspaces of the lungs
• findings
vascular redistribution/enlargement, cephalization, pleural effusion, cardiomegaly (may be
present in cardiogenic edema and fluid overloaded states)
fluid initially collects in interstitium
loss of definition of pulmonary vasculature
peribronchial cuffing
KerleyBlines
ret iculonodular pattern
• thickening of interlobar fissures
as pulmonary edema progresses,fluid collects in alveoli and causes diffuse airspace disease,often
in a “bat wing” or “butterfly"
pattern in perihilar regions (outermost lung fields tend to be spared)
• differential diagnosis: cardiogenic (e.g.CHF), renal failure, volume overload, non-cardiogenic (e.g.
ARDS)
BAD RASH (lower lung disease)
Bronchiolitis obliterans organizing
pneumonia (BOOP)
Asbestos
Drugs (nitrofurantoin, hydralazine,
isoniazid. amiodarone, many
chemotherapy drugs)
Rheumatological disease
Aspiration
Scleroderma
Hamman Rich and idiopathic pulmonary
fibrosis(IPF)
<§>
DDx for Cavitating Lung Nodule
WEIRD HOLES
GPA (Wegener'
s)
Embolic (pulmonary,septic)
Infection (anaerobes, pneumocystis.
Pulmonary Embolism
• pathogenesis:blockage in the pulmonary arteries due to emboli from pelvic or leg veins,rarely from
central venous catheters,air,fat,or amniotic fluid
• findings
generally not possible to definitively diagnose on plain film; diagnosis made by O'
pulmonary
angiography or ventilation/perfusion scintigraphy (VQ scan)
CXR:Westermark sign (localized pulmonary oligemia), Hampton’
s hump (triangular peripheral
infarct), enlarged right ventricle and right atrium, atelectasis, pleural effusion, and rarely
pulmonary edema
definitive imagingstudy:CT pulmonary angiography to look for filling defect in contrast-filled
pulmonary arteries
VQ scan:can be used in patients with impaired renal function or in pregnancy
re)
Rheumatoid (necrobiotic nodules)
Developmental cysts(sequestration)
Histiocytosis
Oncological
Lymphangioleiomyomatosis
Environmental, occupational
Sarcoidosis
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MI9 Medical Imaging Toronto Notes 2023
Pleural Abnormalities
Pleural Effusion
Table 6. Sensitivity of Plain Film Views for Pleural Effusion
X-Ray Projection Minimum Volume to Visualize
25 mL:most sensitive
50 ml:meniscus seen in the posterior costophrenic sulcus
200ml
Variable (May appear as diffuse haziness)
lateral decubitus
Upright lateral
PA
Supine
Figure 10. LUL mass:bronchogenic
carcinoma •a horizontal fluid level isseen only in a hydropneumothorax (i.e.both fluid and air within pleural
cavity)
•effusion may exert mass effect,shift trachea and mediastinum to opposite side,or cause atelectasis of
adjacent lung
•U/S is superior to plain film for detection of small effusions and may also aid in thoracentesis; FOCUS
is now standard of care in acute situations
Pneumothorax
•pathogenesis: gas/air accumulation within the pleural space resulting in separation of the lung from
the chest wall
•findings
upright chest film allows visualization of visceral pleura as curvilinear line paralleling chest wall,
separating partially collapsed lung from pleural air
• more obvious on expiratory (increased contrast between lung and air) or lateral decubitusfilms
(air collectssuperiorly)
more difficult to detect on supine film;look for the “deep (costophrenic)sulcus” sign, “double
diaphragm" sign (dome and anterior portions of diaphragm outlined by lung and pleural air,
respectively), nyperlucent hemithorax,sharpening of adjacent mediastinal structures
contralateral tracheal and mediastinal shift may occur in tension pneumothorax
•differential diagnosis:spontaneous (tall and thin males,smokers), iatrogenic (lung biopsy, ventilation,
central venous catheter insertion, thoracentesis), trauma (associated with rib fractures), emphysema,
malignancy,honeycomb lung
•management:supplemental oxygen and observation, chest tube insertion in 5th ICS anterior axillary
line, or emergent needle decompression in 2nd ICS middavicular line if tension pneumothorax
(followed by chest tube insertion); repeat CXR to ensure resolution
Asbestos
•asbestos exposure may cause various pleural abnormalities including benign plaques (most common;
these may calcify),diffuse pleural fibrosis, effusion, and malignant mesothelioma
Figure 11. Peribronchial cuffing:
interstitial edema
Mediastinal Abnormalities
Mediastinal Mass
• Felson’
s method of division outlines three compartments, which provides an approach to the
differential diagnosis of a mediastinal mass
• anterior compartment is bordered anteriorly by the sternum and posteriorly by the heart and great
vessels
4 T
'
s: thyroid, thymic neoplasm, teratoma,terrible lymphoma
cardiophrenic angle mass differential:thymic cyst, epicardial fat pad,foramen of Morgagni
hernia
• middle compartment extendsfrom the posterior border of anterior mediastinum to a line 1 cm
posterior to the anterior edge of thoracic vertebral bodies
esophageal carcinoma, esophageal duplication cyst, metastatic disease,lymphadenopathy (all
causes), hiatus hernia, bronchogenic cyst
• posterior border (posterior to the middle line described above)
neurogenic tumour (e.g. neurofibroma,schwannoma), neurenteric cyst, thoracic duct cyst, lateral
meningocele, Bochdalek hernia, extramedullary hematopoiesis
• any compartment may give rise to lymphoma,lung cancer, aortic aneurysm or other vascular
abnormalities, abscess, or hematoma
Figure 12.Pleural effusion inlateral
view
n
Enlarged Cardiac Silhouette
• heart borders
on FA view, right heart border is formed by right atrium;left heart border isformed by left atrium
and left ventricle
on lateral view, anterior heart border isformed by right ventricle; posterior border is formed by
left atrium (superior to left ventricle) and left ventricle
Figure 13.Pneumothorax
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MHO Medical Imaging Toronto Notes 2023
• cardiothoracic ratio = greatest transverse dimension of the central shadow relative to the greatest
transverse dimension of the thoracic cavity
using a good quality erect PA chest film in adults, cardiothoracic ratio of >0.5 is abnormal
differential of ratio >0.5
cardiomegaly (myocardial dilatation or hypertrophy)
pericardial effusion
poor inspiratory effort/low lung volumes
pectus excavatum
ratio <0.5 does not exclude enlargement
• pericardial effusion: globular heart with loss of indentations on left mediastinal border
• RA enlargement:increase in curvature of right heart border and enlargement of SVC
• LA enlargement:straightening of left heart border;increased opacity of lower rightside of
cardiovascularshadow (double heart border);elevation of left main bronchus (specifically,the upper
lobe bronchus on the lateral film); distance between left main bronchus and “double"heart border >7
cm;splayed carina (late sign)
• KV enlargement: elevation of cardiac apex from diaphragm; anterior enlargement leading to loss of
retrosternal airspace on lateral; increased contact of right ventricle against sternum
• LV enlargement:rounding of the cardiac apex;displacement of left cardiac border leftward,inferiorly,
and posteriorly
Elevated Hemidiaphragm Suggests
PAL DIP
Pregnancy
Atelectasis
Lung resection
Diaphragmatic paralysis
Intra-abdominal process
Pneumonectomy
Pleural effusion also may result In
apparent elevation
Depressed Hemidiaphragm Suggests
fALC
Tumour
Asthma
Large pleural effusion
COPD
DD
*
Anterior Mediastinal Mass
4 Ts
Tubes, Lines, and Catheters Thyroid
Thymic neoplasm
Teratoma
•ensure appropriate placement and assess potential complications of lines and tubes Terrible lymphoma
•avoid mistaking a line/tube for pathology (e.g. oxygen rebreather mask for pneumothoraces)
Central Venous Catheter
•used for fluid and medication administration, vascular access for hemodialysis, and CVP monitoring
•ideally located at the SVC/atrial junction to prevent inducing arrhythmias or perforating wall of
atrium
if monitoring CVP, catheter tip must be proximal to venous valves
•tip of well-positioned central venous catheter projects over silhouette of SVC in a zone demarcated
superiorly by the anterior first rib end and clavicle, and inferiorly by top of RA
•course should parallel that of the SVC; if appears to bend as it approaches wall of SVC or appears
perpendicular, catheter may damage and ultimately perforate wall of SVC
•complications:pneumothorax,bleeding (mediastinal, pleural),malposition (artery, pleura), air
embolism
Endotracheal Tube
•frontal chest film: tube projects over trachea and shallow oblique or lateral chest radiograph will help
determine position in 3 dimensions
•progressive gaseous distention of stomach on repeat imaging is concerning for esophageal intubation
•tip should be located 2-4 cm above tracheal carina (avoids bronchus intubation and vocal cord
irritation)
•maximum inflation diameter <3cm to avoid necrosis of tracheal mucosa and rupture; ensure
diameter of balloon is less than tracheal diameter above and below balloon
•complications: aspiration (parenchymal opacities), pharyngeal perforation (subcutaneous
emphysema,pneumomediastinum, mediastinitis)
Figure14. Lateral CXR showing three
mediastinal compartments
Nasogastric Tube
•tip and side port should be positioned distal to esophagogastric junction and proximal to gastric
pylorus
•radiographic confirmation of tube is mandatory because clinical techniques for assessing tip position
may be unreliable
•complications:aspiration (parenchymal opacities), pneumothorax
Swan-Ganz Catheter
•to monitor pulmonary capillary wedge pressure and estimate diastolic filling of left heart
•tip should be positioned within right or left main pulmonary arteries or in one of their large, lobar
branches
•if tip islocated more distally,increased risk of prolonged pulmonary artery occlusion resulting in
pulmonary infarction or,rarely, pulmonary artery rupture/aneurysm
•complications:pneumothorax, bleeding (mediastinal, pleural), air embolism
r -i
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Figure15. CXR showing well- Chest Tube positioned central venous catheter
•in dorsal and caudal portion of pleural space to evacuate fluid
•in ventral and cephalad portions of pleural space to evacuate pneumothoraces
•tube may lie in fissure as long as functioning
•complications:bleeding, infection,lung laceration
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Mil1 Medical Imaging Toronto Notes 2023
Abdominal Imaging
Abdominal X-Ray
Indications
• acute abdomen:bowel perforation, toxic megacolon, bowel ischemia,small bowel obstruction, large
bowel obstruction
• chronic symptoms:constipation, calcifications (gallstones, renal stones, urinary bladderstones, etc.)
• not useful in:G1 bleeds, chronic anemia,vague Gl symptoms
Anatomy
• the abdomen is divided into 2 cavities:
• peritoneal cavity:lined by peritoneum that wraps around most of the bowel, the spleen, and most
of the liver;forms a recesslateral to both the ascending and descending colon (paracolic gutters)
retroperitoneal cavity:containsseveral organssituated posterior to the peritoneal cavity;the
contour of these can often be seen on radiographs
3 Views of AXR
• Erect/Upright
• Supine
• Left lateral decubitus
Table 7. Differentiating Small and Large Bowel
Property Small Bowel Large Bowel
Mucosal Folds Uninterrupted valvulae conniventes(or plicae
circulates)
Central
Interrupted hauslra extend only partway acrosslumen 3-6-9 Rule of Dilation
• Small bowel (>3 cm)
. Large bowel (>6 cm)
• Cecum (>9cm)
Location Peripheral (picture frame)
6cm (9cm al cecum)
5 mm
Commonly containssolid lecal material
Maximum Diameter
Maximum Fold Thickness
Other
3 cm
3mm
Rarely containssolid fecal material
Approach to Abdominal X-Ray
• mnemonic:“Free ABDO"
• “Free”:free air and fluid
free fluid
small amounts of fluid:increased distance between lateral fatstripes and adjacent colon may
indicate free peritoneal fluid in the paracolic gutters
large amounts of fluid:diffuse increased opacification on supine film;bowel floats to centre of
anterior abdominal wall
ascites and blood (hemoperitoneum) are the same density on the radiograph and cannot be
differentiated
free intraperitoneal airsuggests rupture of a hollow viscus (anterior duodenum, transverse colon,
etc.), penetrating trauma,or recent (<7 d) surgery
• “A”:air in the bowel (can be normal,ileus, or obstruction)
volvulus-twisting of the bowel upon itself resulting in obstruction;from most to least common:
1. sigmoid:massively dilated sigmoid projects to right or mid-upper abdomen with proximal
dilation (“coffee bean" sign)
2. cecal:massively dilated bowel loop projecting to left or mid- upper abdomen with small bowel
dilation
3. gastric:rare
4. transverse colon: rare (usually in younger individuals)
5. small bowel: “corkscrew” sign (rarely diagnosed on plain films,seen best on CT)
toxic megacolon
manifestation of fulminant colitis
extreme dilatation of colon (>6.5 cm) with mucosal changes (e.g. foci of edema, ulceration,
pseudopolyps) and loss of normal haustral pattern
• “B": bowel wall thickening
increased soft tissue density in bowel wall, thumb-like indentations in bowel wall (“thumbprinting"), or a picket-fence appearance of the valvulae conniventes (“stacked coin"
appearance)
may be seen in 1BD, infection, ischemia,hypoproteinemic states, and submucosal hemorrhage
• “D”:densities
bones:look for gross abnormalities of lower ribs, vertebral column, and bony pelvis
• abnormal calcifications: approach by location
RUQ:renal stone, adrenal calcification, gallstone, porcelain gallbladder
RLQ: ureteral stone, appendicolith, gallstone ileus
« LUQ: renal stone, adrenal calcification, tail of pancreas
LLQ: ureteral stone
central:aorta/aortic aneurysm, pancreas,lymph nodes
pelvis: phleboliths(i.e.calcified veins), uterine fibroids, bladder stones
LJ
• “0”:organs +
• kidney,liver,gallbladder,spleen, pancreas, urinary bladder, psoasshadow
• outlines can occasionally be identified because they are surrounded by more lucent fat, but all are
best visualized with other imaging modalities(CT, MRI )
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MI12 Medical Imaging Toronto Notes 2023
Biliary vs. Portal Venous Air
"Go with the flow":air follows the flow
of bile or portal venous blood
Biliary air is most prominent centrally
over the liver
Portal venous air is most prominent
peripherally
Figure 16. Normal AXRs: (left) supine anteroposterior AXR, (middle) upright anteroposterior AXR, and (right)
left lateral decubitus AXR
Table 8. Abnormal Air on Abdominal X-Ray
Air Appearance Common Etiologies
Extraluminal Intraperitoneal
(pneumoperitoneum)
Upright film: air under diaphragm
Left lateral decubitusfilm:air between liver
and abdominal wall
Supine film:gas outlines of structures not
normally seen:
Inner and outer bowel wall (“Rigler’s" sign)
Falciform ligament
Peritoneal cavity ("football''sign)
Gas outlining retroperitoneal structures
allowing increased visual ballon:
Psoasshadows
Renal shadows
Lucent air streaksin bowel wall. 2 types:
1.Linear
2. Rounded (cystoides type)
Dilated loops of bowel, air-fluid levels
Perforated viscus
Postoperative (up to10 d to be resorbed)
Perforation of retroperitoneal segments of
bowel: duodenal ulcer, postcolonoscopy
Retroperitoneal
Intramural ( pneumatosisintestinalis) 1. Linear:ischemia, necrotizing enterocolitis
2. Rounded/cystoides (generally benign):
primary (idiopathic),secondary (COPO)
Adynamic (paralytic) Ileus, mechanical bowel
obstruction
Abscess
Intraluminal
Loculated Mottled, localized in abnormal position
without normal bowelfeatures
Biliary Air centrally over liver Sphincterotomy, gallstone ileus, erosive
peptic ulcer, cholangitis, emphysematous
cholecystitis
Portal Venous Air peripherally over liver in branching patlern Bowel ischemiafinlardion
Table 9. Adynamic Ileus vs. Mechanical Obstruction
Feature Adynamic Ileus Mechanical Obstruction
Calibre ol Bowel loops
Air-fluid Levels
(erect and left lateral decubitus films only)
Normal or dilated
Same level in the same single loop
Usually dilated
Multiple air fluid levelsgiving "step ladder"
appearance, dynamic (indicating peristalsis
present),“string of pearls" (rovr of small
gas accumulations in the dilated valvulae
conniventos)
Distribution ol Bowel Gas Air throughout Gl trad is generalized or
localized
In a localized ileus(e.g.pancreatitis,
appendicitis), dilated “sentinel loop" remains “Hairpin" (180°) turns in bowel
in the same location onserial films, usually
adjacent lo the area of inflammation
Dilated bowel up lo the point of obstruction
(i.e. transition point)
No air distal to obstructed segment
Abdominal Computed Tomography
• indications for plain CT: renal colic, hemorrhage
• indications for CT with contrast:
IV contrast given immediately before or during CT to allow identification of arteries and veins
portal venous phase:indicated for majority of cases
biphasic (arterial and portal venous phases):liver, pancreas, bile duct tumours
caution: contrast allergy (may pre-medicate with steroids and antihistamine)
contraindication: impaired renal function (eGl'R <30 mL/min/1.73 m 2 )
• oral contrast: barium or water-soluble (water soluble if suspected perforation ) given in most cases
to demarcate Gl tract
• rectal contrast:given for investigation of colonic lesions
r1
L J
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Figure 18. Sigmoid volvulus on plain
film, “coffee bean” sign
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MI13Medical Imaging Toronto Notes 2023
Approach to Abdominal Computed Tomography
• look through all images in gestalt fashion to identify any obvious abnormalities
• look at each organ orstructure individually,from top to bottom, evaluating the size and shape of each
area of increased or decreased density
• evaluate the following:
• soft tissue window
liver,gallbladder,spleen, and pancreas
adrenals, kidneys, ureters, and bladder
stomach, duodenum,small bowel mesentery, and colon/appendix
retroperitoneum (aorta, vena cava, and mesenteric vessels; look for adenopathy in vicinity of
vessels)
peritoneal cavity for fluid or masses
abdominal wall and adjacent soft tissue
lung window
» visible lung (bases)
bone window
vertebrae,spinal cord,and bony pelvis
Figure 19. Axial abdominal computed tomography
CT and Bowel Obstruction
• cause of bowel obstruction is rarely found on plain films; CT is the best imaging modality
• the “3,6,9" rule is a very useful guide for determining when the bowel is dilated; the maximum
diameter for thesmall bowel isI cm,for large bowel is 6cm, and for cecum is 9 cm; this can also be
useful to distinguish small and large bowel, and to assess for‘impending’cecal perforation (e.g. postuntreated Ogilvie'
ssyndrome)
• closed-loop obstruction: an obstruction in two locations (usually small bowel) creating a loop of bowel
obstructed both proximally and distally; complications (e.g. ischemia, perforation, necrosis) may
occur quickly
CT Colonography (Virtual Colonoscopy)
• emerging imaging technique for evaluation of intraluminal colonic masses (i.e. polyps, tumours)
• two CT'
scans of the abdomen (prone and supine) after the instillation of carbon dioxide into a prepped
colon
• computer reconstruction of 2D CT images into a 3D intraluminal view of the colon
• lesionsseen on 3D images correlated with 2D axial images
• indications:surveillance in low-risk patients, incomplete colonoscopy,orstaging of obstructing
colonic lesions
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Mil l Medical Imaging Toronto Notes 2023
Contrast Studies
Colorectal Cancer:Cl Colonography and
Colonoscopy lor Detection-Systematic Review
a nd Meta-Analysis
Radiology 2011;259:393- 405
Purpose: loassessthe sensitivityo!computed
tomography|CI|colonography and optical
colonoscopy|0C)for colorectal cancer (CRC)
detection.
Methods: Systematic rev ew and meta-analysis
ol diagnostic studies evaluating Cl colonography
detection of CRC based on a priorieligibly criteria,
m particular requiting both 0C andhistological
confirmation oldsease.Studies that also assessed
true-positiveandfalse-negativedagnoseswithOC
were used to calculate 0C sensitivity.Sensitivity of
CIC and 0C for CRC was the main outcome.
Results: 49 studes on11.151patents undergoing
diagnostic study lor detection olCRC were included.
CIC has a sensitivityof 96.19,(95% Cl 93.8V9)J%|
and OC has a sensitivity of 94.
)% (95% Cl 90.4%,
97.2%) for the detectionof CRC.
Conclusion CIC is highly sensitive for the detection
of CR C and may be a hetter modality for the iniliaI
investigation of suspected CRC.assuming reasonat e
specificity.
Table 10. Types of Contrast Studies
Study Organ Procedure
Description
Assessment Findings
Cine Esophagogram Cervical esophagus Contrast agent swallowed
Recorded for later
playback and analysis
Dysphagia,swallowing
incoordination,recurrent
aspiration, postoperative
deft palate repair
Aspiration, webs
Ipartial occlusion).
Zenker's diverticulum,
cricopharyngeal bar.
laryngeal tumour
Achalasia, hiatus hernia,
esophagitis,cancer,
esophageal tear
Ulcers,neoplasms,filling
defects
Barium Swallow Thoracic esophagus Contrast agentswallowed
under fluoroscopy,
selective images captuied
Double contrast study:
1. Barium to coat mucosa
2. Gas pills fat distention
Patient HPO alter midnight
Enterography:patient
drinks 1-2 L of sorbitol,
psyllium,or barium
solution to distend small
bowel
Enterodysis:NJ tube used
to pump barium,psyllium,
or sorbitol contrast media
directly into small bowel
Dysphagia,rule outGERD.
post- esophageal surgery
Upper GlSeries Thoracic esophagus,
stomach, and duodenum
Dyspepsia, investigate
possible upper Gl bleed,
weight loss/anemia,postgastric surgery
I80.malabsorption,
weight loss/anemia.
Meckel’s diverticulum
Enterographyand Entire small bowel
Enterodysis (MRI orCT)
Neoplasms. IBD.
malabsorption, infection
Prophylactic Hydration to Protect Renal Function
from Intravascular Contrast Material inPatients
a t High-Risk ol Contrast-InducedNephropathy
IAMACING)
lancet 2011:389:1312-1322
Purpose: Determine the clinical eflectiveness
and cost-eHectntness ol prophylactic hydration
treatment in protecting renal function.
Methods: AMAQHG is a prospective,randomised,
non-inferiority trial.High-nsk patients (with an eGFR
ol 30 -59) >18 yr.undergoing an elective procedure
requiring iodmated contrast wererandomly assigned
(1:1) to receiveN0.9% NaCl or noprophylaxis.The
primary outcome was incidence of contrast-induced
nephropathy. deSned at an intitase instium
creatinine from baseline of >25% or 44 pmol.
'
lwithin
2-6d of contrast exposure,and cost-effectiveness
of nD prophylaxis comparedwith IY hydration in
the prevention ofcontrast-mduced nephropathy.
Oeatinine was measured before. 26 d. and 2-35 d
after contrast-material exposure.
Results:660 consecutive patients were randomly
assignedto receive no prophylaxis (n-332) or IV
hydration (n*328).No hydration and prophylaxis
had srnidar rates olnephropathy.No hydration was
cost-savmg relative to hydration.No haemodialysis
ot related deaths occnrred withm 35 days.5.5%
of patients hadcorspllcations associated with
intravenous hydration.
Conclusion:No prophylaxis was found to be
ron-inferior and cost-saving in preventng contrastinduced nephropathy compared with IV hydration.
Specific Visceral Organ Imaging
•for the management of urgent and emergent peritoneal masses
Liver
•U/S: assessment of cysts, abscesses, tumours, biliary'tree
•CT ± IV: most popular procedure for imaging the liver parenchyma (primary liver tumours,
metastases, cysts, abscesses, trauma, cirrhosis)
•MRI: excellent in evaluation of primary liver tumours, liver metastases, other parenchymal
conditions; particularly helpful in differentiating common benign hepatic hemangiomas from
primary liver tumours and metastases
•elastography: measures shear wave velocity by U/S (l ibroScan) or MRI (MR elastography) to noninvasively quantify liver fibrosis
•findings:
• advanced cirrhosis: liver small and irregular (fibrous scarring, segmental atrophy, regenerating
nodules)
porto-systemic shunts: caput medusae, esophageal varices, spontaneous spleno-renal shunt
• U/S: cirrhosis appears nodular and hvperechoic with irregular areas of atrophy of the right lobe
and hypertrophy of the caudate or left lobes
CT: fatty infiltration appears hvpodense
•some masses require contrast to be visualized
•upon identifying a liver lesion on imaging (e.g. U/S), the follow-up imaging modality should he CT or
MRI. CT would be four-phase non-contrast, arterial, venous, and delayed to distinguish the common
benign liver lesion hemangioma from other tumours
Spleen
•U/S, CT, nuclear medicine scan (nuclear medicine only to distinguish ectopic splenic tissue from
enhancing tumours)
•CT for splenic trauma (hemorrhage) Normal liver appears more dense than
spleen on CT.If less dense, suspect fatty
infiltration
Liver Mass DDx r “i
L J
SHs
HCC
Hydatid cyst
Hemangioma
Hepatic adenoma
Hyperplasia (focal nodular)
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M115 Medical Imaging Toronto Notes 2023
Table 11.Imaging of Liver Masses
u/s CT Re« ised (stimotcs of Diagnostic TcstSensitivity
and Specificity in Suspected Biliary Trad Disease
*
rcli Intern Med 1998:15425732581
Purpose:In assessthe sensitivity and specificity
of tests used to diagnose choleithiasis and acute
cholecystitis, including U/5, oral cholecystography,
rad or jdeotide scanning with lech'et um, MRI.
Benign Mass
Hepatic Adenoma Well-defined mass with hyperechoic areas due Well-defined hypervascular lesion with
to hemorrhage enlarged central vessel becoming slightly
Isoattenuating in venous phase
Hemangioma Peripheral globular enhancement in arterial
phase scans:ccnlral filling and persislcnl
enhancement on delayed scans
Hypervascular mass in arterial phase and
isoattenuation to liver in portal venous phase
Low attenuation lesion with an irregular
enhancing wall
low attenuation simple or mulliloculalcd cyst:
calcification
Homogeneous hyperechoic mass
or Cl.
Methods: Meta -analysts of studiesevalualing the
use of different imaging moda > tiesin the diagnosis n!
biliary tract disease.Main outcomes were sensitivity
and specificity of the different imaging modalities,
usng the gold standard of surgery,autopsy, or 3
mo clinical follow- up for cholelithiasis.Foi acute
cholecystitis, pathologic findings,confirmation of
an alteriutedisease. or cbmcal resolution during
hospdaluation for cholecysbtn were used as the
standard.
Results: thirty studies were included. For evaluating
choletthiasis, U/S had the best unadiusted sensitivity
(0.97; 95% Cl 0.95-0.99) and speeiWy (0.95,
0.88-1.00) and ad|usted (for indication bias)
sensitivity (0.84; 0.76-0.92) and specificity I0.99;
95% CI 0.97-1.00). lor evaluating acute cholecystitis,
radionudeotide scanning has the best sensitivity
(0.97:0.96-0-98)and specificity (0.90; 0.86-0.95).
Conclusion: U /S is the test of choce for degnosmg
cholelithiasis and radionudeotide scanning is the
superior test lor dug nos ng acute cholecystitis.
Well- defined mass, centralscar seen in 50%
of cases
Ill-defined, irregular margin, hypoechoic
contents
Simplc/mulliloculatedcysl
Focal Nodular Hyperplasia
Abscess
Hydatid Cyst
Malignant Mass
Single/multiple masses,or diffuse infiltration Hypervascular; enhances in arterial and
washes out in venous phase with portal venous
tumour thrombus
Multiple masses of variable cchotcxturc Usually low attenuation on contrast-enhanced
HOC
Mctastascs
scan
Pancreas
• tumours
• U/S: mass is more echogenic than normal pancreatic tissue
• CT:preferred modality for diagnosis/staging
• ductal dilation secondary to stone/tumour
MRCP:imaging of ductal system using MR I cholangiography; no therapeutic potential
• ERCP:endoscopic injection of dye into the biliary tree and x-ray imaging to assess pancreatic and
biliary ducts;therapeutic potential (stent placement,stone retrieval)
acute pancreatitis is a complication in 5% of diagnostic procedures and 10% of therapeutic
procedures
Biliary Tree Gallbladde
• U/S; bile ducts usually visualized only if dilated,secondary to obstruction (e.g.choledocholithiasis,
benign stricture, mass)
• CT:dilated intrahepatic ductules seen as branching, tubularstructures following pathway of portal
venoussystem
• MRCP, ERCP, PTC:further evaluation of obstruction and possible intervention
Figure 20. ERCP;biliary tree (A)
common bile duct (B) cystic duct
(C) common hepatic duct (D) right
hepatic duct (E) left hepatic duct
“itis” Imaging
Acute Cholecystitis
• pathogenesis: inflammation of gallbladder resulting from sustained gallstone impaction in cystic duct,
or in the case of acalculous cholecystitis, due to gallbladder ischemia or cholestasis (see General and
Thoracic Surgery, GS56 )
• best imaging modality: U/S (best sensitivity and specificity); nuclear medicine (H1DA scan) can help
diagnose cases of acalculous or chronic cholecystitis
• findings: most sensitive findings are presence of gallstones and positive sonographic Murphy’
ssign
(tenderness from pressure of U/S probe over visualized gallbladder). Secondary findings include
thickened gallbladder wall (>3 mm), dilated gallbladder, and pericholecystic fluid
• management: admit, NPO, IV fluids, analgesia, cefazolin, and early laparoscopic cholecystectomy
mm.
Figure 21. Ultrasound:longitudinal
view of aninflamed gallbladder
Arrowheads show thickened walls
and pericholecystic fluid
Acute Appendicitis
• pathogenesis:luminal obstruction -> bacterial overgrowth > inflammation/swelling > increased
pressure > localized ischemia > gangrene/perforation > localized abscess or peritonitis(see General
and Thoracic Suruerv. GS35)
• best imaging modality: U/S or CT
• findings:
U/S:thick-walled appendix, appendicolith, dilated fluid-filled appendix, non-compressible;may
also demonstrate signs of other causes of RLQ pain (e.g.ovarian abscess, 1BD, ectopic pregnancy)
CT:enlargement of appendix (>6 mm in outer diameter), enhancement of appendiceal wall,
adjacent inflammatory stranding, appendicolith; also facilitates percutaneous abscess drainage
• management: admit, NPO, IV fluids, analgesia, cefazolin t metronidazole, and appendectomy
-
r "i
L J
Acute Diverticulitis
• pathogenesis: erosion of the intestinal wall (most commonly rectosigmoid) by increased intraluminal
pressure or inspissated food particles -> inflammation and local necrosis -> micro- or macroscopic
perforation (see General and Thoracic Suruerv, GS39)
• best imaging modality:CT, although U/S is sometimes used
• contrast: oral and rectal contrast given before CT to opacify bowel
+
Figure 22. Ultrasound:inflamed
appendix
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MI16 Medical Imaging Toronto Notes 2023
•findings:
cardinal signs:thickened wall, mesenteric infiltration, gas-filled diverticula, abscess
CT can be used for percutaneous abscess drainage before or in lieu ofsurgical intervention
• sometimes difficult to distinguish from perforated cancer (send abscess fluid for cytology and
follow up with colonoscopy)
if chronic, may see fistula (most common to bladder) or sinustract (linear or branching
structures)
•management:rangesfrom antibiotic treatment to surgical intervention:can use imaging to follow
progression
Conput'
d Tomography and Ullrasonogtaphy
to Detect Acute Appendicitis in Adults and
A dolescenls
Ann Intern Med 2004;M1:537-5d6
Purpose: To review tile diagnostic accuracy of CT and
lift in thediagnosrsotacute appendicitis.
Methods: Meta analyst of prospective studies
evaluating the use of Clor ll/S,followed try surgical
or cinkal follow-up io patientswith suspected
appendicitis. Patients >Uyt with a clinicalsuspicion
ol appendicitiswere eligible.Sensitivity and
specificity using surgery or clinical lollow-upas the
gold standard were the main outcomesstudied.
Results:Twenty-two studieswere included.CT [12
studies) had an overallsensitivity ol0.94 (95% Cl
0.91-0.95) and a specificity ol 0,95[0.93-0.96). 0)5
[14states) had an overallsensitivity of 0.86 (0.83-
0.88)and a specificity of 0.81 (0.78-0.84).
Conclusion:CT ismoreaccurate lor diagnosing
appendicitis in adults and adolescents, allhough
verification biasand inappropilale blinding ol
reference standardswere noted in the included
si-Ces
Acute Pancreatitis
•pathogenesis: activation of proteolytic enzymes within pancreatic cellsleading to local and systemic
inflammatory response (see Gastroenterology,G48);a clinical/biochemical diagnosis
•best imaging modality:imaging used to support diagnosis and evaluate for complications(diagnosis
cannot be excluded by imaging alone)
• U/S good for screening and follow-up
CT is useful in advanced stages and in assessing for complications (1st line imaging test)
•findings:
n U/S:hypoechoic enlarged pancreas (if ileus present, gas obscures pancreas)
n CT:enlarged pancreas, edema, fatstranding with indistinct fat planes, mesenteric and Gerota’
s
fascia (renal fascia) thickening, pseudocyst in lesser sac, abscess (gas or thick-walled fluid
collection), pancreatic necrosis (low attenuation gas-containing non-enhancing pancreatic
tissue), hemorrhage
•management:supportive therapy
n CT-guided needle aspiration and/or drainage of abscess when clinically indicated
pseudocyst may be followed by CT and drained ifsymptomatic Ultrasound
©,Computed Tomography or Magnetic
Resonantelmaging fur Acute Appendicitis in
Children
Pediatr Radiol 2097;47:186-196
Purpose:Compare the accuracies of IKS.Cl.and MRI
for clinically suspected acute appendicitisin children.
Methods: Search and meta-analysis.Ihe sensitivity,
specificity, and the acta under the curve o(summary
receiver operating characteristics were calculated
and compared.
Results:19 studiesof UTS,6stud iesof CT.and 4
studiesof MRI. Ihe analysisshowed that Ihe area
under Ihe receiver operator charictenstcs curve ol
MRI I0.99S) was a title higher than thatol US [0.987)
and Cl(0.982; P>0.0S).
Conclusion:US.CT.and MRI have high diagnostic
accuracies ol clinically suspected acute appendicitis
in chiMten overall with no significant difference.
Chronic Pancreatitis
•pathogenesis:(see Gastroenterology. G50)
•best imaging modality:MRCP (can show calcification and duct obstruction)
•findings: U/S, CT scan, and MKI may show calcifications, ductal dilatation, enlargement of the
pancreas, and fluid collections(c.g. pseudocysts) adjacent to the gland
Angiography of Gastrointestinal Tract
• anatomy of the arterial branches of the G1 tract
celiac artery:hepatic,splenic, gastroduodenal,left/right gastric
superior mesenteric artery:jejunal, ileal,ileo-colic, right colic, middle colic
inferior mesenteric artery:left colic,superior rectal
• imaging modalities
conventional angiogram:invasive (usual approach via femoral puncture),catheter used
flush aortographv: catheter injection into abdominal aorta,followed by selective
arteriography of individual vessels
CT angiogram:modality of choice, non-invasive using IV contrast (no catheterization required)
Angiography requires active blood loss
1-1.5 ml/min under optimal conditions
for a bleeding site to be visualized in
cases of lower Gl bleeding
Genitourinary System and Adrenal
Imaging Modafity Based on
Presentation
• Acute testicular pain - Doppler. UTS
• Amenorrhea -U/S, MRI (brain)
. Bloating -Plain film/CT (if abnormal)
. Flank pain =U/S,CT
• Hematuria - U/S. Cystoscopy. CT
. Infertility - HSG. MRI
• Lower abdominal mass U/S. CT
• Lower abdominal pain -U/S,CT
• Renal colic =U/S. KUB, CT
• Testicular mass *
U/S
• Urethral stricture ~ Urethrogram
Urological Imaging
Kidney, Ureter, and Bladder (KUB) X-ray
• a frontalsupine radiograph of the abdomen
• indication: useful in evaluation of radiopaque renal stones (exceptions: uric acid and indinavir stones),
indwelling ureteric stents/catheters, and foreign bodies in abdomen
• findings:addition of IV contrast excreted by the kidney (intravenous urogram) allows better
visualization of the urinary tract hut has been largely replaced by CT urography
Abdominal CT
Renal Masses
• Bosniak classification for cystic renal masses
• class l-ll: benign and can be disregarded
• class Ill
-:should be followed
• class 11I-1V:suspiciousfor malignancy,requiring additional workup
n
LJ
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MI17 Medical Imaging Toronto Notes 2023
Table 12. Bosniak Classification for Cystic Renal Masses
Classes Definition
Simple RenalCysts
ClassI
Class II
Fluid-attenuating well-defined lesion,no septation.no cakificatioo.no solid components,hailine-thm wall
Same as classI•
*
fine calcification or moderately thickened calcification inseptae or walls:also includes
hyperdense cysts|<3 cm)that do not enhance with contrast
•Class IIF:multiple hairline-thin septa withminimal thickening,no enhancingsoft tissue components,
completely intrarenalnon-enhancing high-attenuating renal lesions>3cm
Complex Renal Cysts
Class III Thick irregular wallsicalcifications ±septated.enhancingwalls,or septa withcontrast
Renal CellCarcinoma
Class IV Same as classIII soft tissue enhancement with contrast(defined as >10 Hounsfield unit increase,
characterizing vascularity) withde-enhancement in venous phase ±areas of necrosis
•plain CT KUB indications:general imaging of renal anatomy,renal colic symptoms, assessment
of renal calculi (size and location) and potential sequalae (infection and obstruction),and
hydronephrosis prior to urological treatment
•CT urography indications:investigation of cause of hematuria,detailed assessment of urinary tracts
(excretory phase), high sensitivity (95%) for uroepithelial malignancies of the upper urinary tracts,
assessment of renal calculi
phases: unenhanced, excretory
•renal triphasic CT indications:standard imaging for renal masses, allows accurate assessment of renal Figure 23.Triphasic CT of an
arteries and veins, better characterization ofsuspicious renal masses- especially in differentiating
renal cell carcinoma from more benign masses, and preoperative staging
phases:unenhanced, arterial and venous(nephrographic), excretory
angiomyolipoma:showing fat
density with non-contrast scan,
mildly enhancing with contrast
Ultrasound
•indications:initialstudy for evaluation of kidney size and nature of renal masses (solid vs.cystic
masses,simple vs. complicated cysts);modality of choice forscreening patients with suspected
hydronephrosis (no IV contrast injection, no radiation exposure,and can be used in patients with
renal failure);TRUS useful to evaluate prostate gland and guide biopsies;Doppler VIS to assess renal
vasculature
•findings:solid renal masses are echogenic (bright on U/S), cystic renal masses have smooth welldefined walls with anechoic interior (dark on U/S),and complicated cysts have internal echoes within
a thickened, irregular wall
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