Imaging CT US abdomen and pelvis

Question 1

Recall general considerations for imaging

Answer 1

• always identify
  
  • type of imaging modality
  • plane (coronal, sagittal, axial OR longitudinal/transverse)
  • sequences and windows where relevant
  • region imaged

Question 2

Recall densities on US

Answer 2

• Us measures how fast sound travels in tissue
• assigns echoness a shade of grey
• water is black
• air and bone are both white, and both create a black shadow

US cheat sheet
- Very white = air, calcium or bone
- Quite white = fat
- Grey = soft tissue – blacker, = soggier’, brighter = more fatty/cellular
- Very black = fluid or shadow from air or bone

Question 3

What organs might you be able to identify from abdomen/pelvis US?

Answer 3

Identifying organs eg
- kidney: cortex and pelvis/hilar fat - which is echogenic
- spleen: typically hidden under ribs
- aorta: dark linear structure
- liver, gall bladder and duct
- stomach
- bladder (volume can be used to see deeper structures)
- pancreas - doesn’t visualise well
Recall that organs don’t shadow

Can also be used eg with doppler to measure blood flow in portal vein (can measure direction, speed etc). Can also be used to distinguish bile duct/blood vessels (bile duct will have no flow)

Question 4

What are some common conditions that can be seen on US?

Answer 4

• chronic cholecystitis
• ![[Pasted image 20240509131135.png]]
• gall bladder calculus, CBD calculus - these do shadow
• RIF pain
  -can see bowel layers - doesn’t collapse on compression which indicates inflammation
  
  • ## note also increased water content also indicative of inflammation ![[Pasted image 20240509131149.png]]

Question 5

Summarise some tips for interpreting US

Answer 5

US summary
- The tissue of interest is probably in the centre of the image
- Read around the image for clues
- TS = transverse section = axial
- LS = longitudinal section = sagittal
- Look for very black things
- A ‘target’ of concentric rings is probably bowel/stomach
- A circular black object in all planes is a sphere ie a cyst
- A black stripe is probably a blood vessel – put on a Doppler gate
- “Fluid” on ultrasound =
- Blood vessel (a stripe or a circle)
- Fresh blood in a haematoma
- Bile
- Urine
- Ascites
- Pus
- Pleural effusion
- Amniotic fluid
- Cyst fluid etc

Question 6

Recall densities on CT

Answer 6

• measures density and assigns density a shade of grey
• uses XR
• recall: air -> fat -> water -> organs ->bone -> metal
  
  • blood, 65, white

Question 7

What organs might be identifiable on CT?

Answer 7

• vertebra and spinal canal
• liver (metastases, fluid etc) note steatohep makes liver less dense
• kidney
• aorta - can inform if/no contrast
• IVC- can inform if/no contrast
• pancreas
• skin and subcut fat
• mesenteric fat
• stomach
• spleen

Question 8

List some common conditions that might be seen on CT

Answer 8

• chronic hepatitis B
• ## renal tract calculus

Question 9

What is the underlying principle behind MRI?

Answer 9

• Detects the number of mobile protons (H+) in a tissue
• Assigns their radio waves a shade of grey

Question 10

What is MRI used for in this context?

Answer 10

• planning pelvic surgery e.g. gynaecological, oncological surgery
• characterising abdominal organ lesions
• MRCP: occult stones and tumours
• follow-up for younger people and chronic bowel conditions