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4. Medical Imaging > Emergency Imaging : Chest, Abdomen And Neuro > Flashcards

Emergency Imaging : Chest, Abdomen And Neuro Flashcards

1
Q

What are the leading imaging modalities in emergency chest imaging?

A
  • CT angiography
  • DSA (coronography)
  • Chest X Ray
  • MRI (only if we have time)
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2
Q

What is a triple rule out CT?

A

Protocol that assesses 3 different problems at the same time : coronary artery disease, aortic dissection and pulmonary embolism

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3
Q

Absolute contraindication of using iodine contrast agent

A

Documented previous severe reaction to iodinated contrast media

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4
Q

Relative contraindication to using iodine contrast agent

A
  • Mild reactions
  • Renal impairment / failure (GFR under 30)
  • Risk factors for adverse reaction like hyperthyroidism, allergy, asthma
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5
Q

What is the CT angio sign of PE?

A

Hypodense filling defect in primary and secondary pulmonary arterial vessels

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6
Q

How to tell difference between chronic and acute PE in CT angi?

A

As it gets older, the thrombus will shrink and won’t fill the whole lumen

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7
Q

What additional examination needs to be done in PE after CT?

A

Doppler US of the lower extremities to exclude deep vein thrombosis

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8
Q

Imaging modalities in suspected PE

A
  • Chest X-Ray
  • CTA with IV contrast
  • CT chest with IV contrast
  • Tc99m V/Q scan lung
  • US doppler scan of lower extremities
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9
Q

Imaging modalities in suspected aortic aneurysm

A
  • US of aorta / abdomen
  • CT(A) of abdomen with IV contrast
  • MRA abdomen without and with IV contrast (alternative to CT if there’s a contraindication)
  • DSA
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10
Q

What does DSA stand for?

A

Digital substraction angiography

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11
Q

How can aortic dissection cause ischemia?

A
  • If an artery arises from the false lumen, which has less oxygenated blood
  • The flap can cause obstruction
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12
Q

Types of aortic dissections

A
  • Stanford type A : absolute emergency, involves aortic arch +/- more
  • Stanford type B : can be treated conservatively, doesn’t involve the arch
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13
Q

Treatment of aortic dissection

A

Stent implantation

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14
Q

Imaging recommendations for aortic dissection

A
  • Chest XRAY
  • CTA chest and abdomen, with IV contrast
  • MRA chest and abdomen +/- IV contrast
    (MRA can replace CTA in hemodynamically stable patients, if available)
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15
Q

What are some life threatening acute abdomen situation?

A
  • Aortic aneurysm rupture
  • Pancreatitis
  • Bowel Ischemia
  • Perforation
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16
Q

X RAY signs of bowel obstruction

A
  • Bowel distension
  • Multiple air / fluid levels
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17
Q

How to prepare patient for abdominal US?

A
  • Fasting for 6 hours (so air doesn’t obstruct visibility and gallbladder isn’t constructed)
  • Patient can drink still water only
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18
Q

What is US used for in the abdomen?

A
  • Assesment of pelvis
  • Ascitis
  • Fluid collection (abscess)
  • Parenchymal organs (kidney, liver, spleen)
  • Biliary system (gallbladder is best seen in US)
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19
Q

Limitations of US in abdomen

A
  • Meteoristic patient
  • Obesity
  • Postoperative bandage and drains
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20
Q

When is CT the first option in abdominal pain?

A

When there is suspected aortic occlusion, ischemia - emergency situation

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21
Q

Why would US be prefered to XRAY in acute appendicitis?

A

Because of the risk of perforation and air that would be a problem on X RAY but is not visible on ultrasound

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22
Q

Signs of inflammed appendix on US

A
  • Periappendiceal fluid or abscess (hypogenic)
  • Increased vascularisation in doppler
  • Diameter over 6mm
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23
Q

Acute appendix on CT morphology

A
  • Peri appendicular fat can be inflammed (brighter)
  • Thickened appendix
24
Q

Imaging modalities for right upper quadrant pain (usually suspected biliary disease)

A
  • US abdomen
  • CT abdomen with IV contrast
  • MRI abdomen
25
Q

What are the advantages of CT compared to US in right upper quadrant pain?

A

CT is more sensitive than US in the depiction of pericholecystic abscesses, gas and stones in the biliary tract

26
Q

Sign of biliary disorders on US

A
  • Highly reflective echogenic gallstone
  • Thickened gallbladder wall with increased vascularization
  • Sonographic Murphy sign
27
Q

When is MRI used in biliary issues?

A
  • Pregnant patients
  • To get more precise depiction than CT, especially in chronic biliary disorders and stones (because can’t see non calcified stones on CT)
28
Q

What do stones look like on T2W MRI?

A

Gallstones are dark, with no signal

29
Q

Do we need contrast MR for biliary system?

A

No, in T2W the fluid structures are easily visible and bright

30
Q

How can we differenciate blood vessels from bililary ducts on US

A

When we use doppler, there won’t be a signal in the ducts

31
Q

Limitation of CT on cholecysto-pancreatography

A

CT cannot see stones that don’t contain calcium

32
Q

What is the first imaging modality in suspected bowel loop, ileus…

A

Abdominal XRAY to confirm dilated bowel

33
Q

How to tell if it’s small or large bowel obstruction on XRAY?

A
  1. Location : if it’s in the center, it’s the small bowel. If it’s peripheral it’s large bowel
  2. Wall of bowel : kerkring folds and haustrae
34
Q

What is the next step after XRAY in bowel obstruction?

A

Contrast enhanced CT to localize and determine the underlying cause

35
Q

Signs of bowel wall necrosis on CT

A
  • Distended bowels because of edema
  • No contrast enhancement
36
Q

Most common causes of small and large bowel obstruction

A

Small : adhesions, Crohn, herniation, tumors
Large : colorectal adenocarcinoma, diverticulitis, herniation, volvulus (in children)

37
Q

How can we tell if the bowel obstruction if recent or not?

A

When the bowel has been obstructed for a long time, it cannot constrict (because of the blockage) so it will increase secretions of fluid

38
Q

When can we use US in bowel obstruction?

A

In very advanced obstruction, when there is a lot of fluid (because if it’s just air then US can’t see it)

39
Q

What is the use of small bowel follow through?

A
  • can offer additional information regarding degree and level of obstruction (ie ileus if contrast doesn’t reach large bowels in 3 hours)
  • can have therapeutic effect (pushes bowel, has a diarrhea effect)
40
Q

Limitations of small bowel follow through

A
  • Takes 6-24 hours
  • Inability to drink in case of severely ill patients
41
Q

Important questions for imaging of bowel obstruction?

A
  • Mechanical or functional?
  • Small or large bowel?
  • Cause of ileus?
  • Necrosis? Perforation?
42
Q

When is imaging necessary in pancreatitis?

A
  • CT to rule out complications (abscess, thrombosis, necrosis)
  • US to detect biliary stone or duct dilation in early phae

(But usually we mostly rely on lab results)

43
Q

Imaging modalities for kidney stones

A
  • Low dose enhanced CT : gold standard, very specific and sensitive
  • US : can visualize stones in the pelvis, calyxes
  • XRAY : high false negatives
44
Q

Neurological reasons for imaging

A
  • Vascular (stroke, aneurysm)
  • Trauma (risk of bleeding)
  • Tumor
  • Infections (encephalitis, abscess)
  • Spine (trauma, disc herniation)
45
Q

What are the 2 types of strokes

A
  • Ischaemic (85%)
  • Hemorrhagic (15%)
46
Q

Early signs of brain infarct on CT

A
  • Hyperdense sign (Gacs sign) for MCA
  • Loss of gray/white matter differentiation
  • Less visible sulci because of edema

-> but changes are barely visible in the acute phase on CT

47
Q

What MRI is used for showing infarcts?

A

Diffusion weighed imaging (DWI) will have high signal intensity areas in ischemia

48
Q

Why is diffusion perfusion mismatch useful in strokes?

A

The mismatch on the fusion image of diffusion and perfusion shows the parts of the brain that can still be saved

49
Q

What is an acute epidural hematoma?

A

An absolute emergency, bleeding between dura and skull, usually due to meningeal artery rupture after trauma

50
Q

How do hematomas change on CT over time?

A

Start as hyperdense (compared to cortex), and become hypodense after 10-14 days

51
Q

What is a subdural hematoma?

A

Less urgent bleeding in between the dura and the arachnoid space, often due to tearing of bridging cortical veins

52
Q

Which imaging modality can accurately determine age / stage of hemorrhage?

A

MRI

53
Q

What is brain herniation?

A

Life threatening emergency most probably due to space occupying lesions and / or increased intracranial pressure.

54
Q

What is the most dangerous brain herniation that needs to be ruled out?

A

Tonsillar herniation

55
Q

Why is MRI necessary for diagnosis of encephalitis?

A

Because of the very good soft tissue resolution (CT wouldn’t work)

56
Q

Signs of encephalitis on MRI

A

T2W, ADC, FLAIR : edema, restricted diffusion in temporal lobe - looks hyperdense

4. Medical Imaging (7 decks)

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