Abdomen + Pelvis Procedures Flashcards
positioning
supine, arm above head
head first or feet first?
feet first but will be cephalocaudal
purpose of positive oral contrast
to differentiate a fluid-filled loop of bowel from a mass or abnormal collection of fluid
what are examples of positive oral contrast used
- barium sulfate
- water-soluble contrast
example of low attenuation oral contrast
water
what are the advantages of using low attenuation contrast > positive contrast?
- won’t obscure mucosal surfaces
- won’t obscure abdominal vessels
- better spatial reso on reconstructed images
- doesn’t mask radiopaque stones
why is rectal contrast used?
- staging colon ca
- penetrating trauma, fistulas, anastomotic leaks
example of rectal contrast
CO2
purposes of IV contrast
- opacify vessels
- increase CT density of vascular organs
- improve image contrast between lesions and normal anatomy
when are multi-phase scans usually performed?
imaging liver, pancreas, kidneys
algorithms
WW 450 WL 50
standard soft tissue
algorithms
WW 150 WL 70
liver
algorithms
WW 1500 WL -700
lungs
algorithms
WW 2000 WL 600
bone
typically, DFOV is set to…
just include skin surface
indications for CECT Routine Abdomen + Pelvis (RAP)
- abdominal mass
- tumour staging
- abscess
- non-specific abdominal symptoms
type of contrast used for RAP
IV contrast or oral
what flow do you set the IV contrast for RAP
125 ml at 3.0 ml/sec, 50 ml NaCl flush
scan delay for RAP
65 secs - portal venous phase
volume of oral contrast used for RAP
675 ml barium sulfate (1.5 bottles) over 2 hours
(final 225 ml just prior to scanning)
anatomy region for venous chest
above lung apices to below costophrenic angles
anatomy region for venous abdomen only
above diaphragm to 1cm below iliac crest
anatomy region for venous abdomen and pelvis
above diaphragm to pubic symphysis
mA for CECT CAP
avg 230
reconstruction slice thickness/increment for CAP
5mm/5mm
indications for CECT chest, abdomen, pelvis (CAP)
- infection
- mass
- trauma
what are the two scans done for CAP
- venous chest
- venous ab/pelvis
IV contrast rate for CAP
125 ml at 3.0ml/sec, 50 ml NaCl flush
scan delay for CAP - Chest
35 secs - late arterial/venous phase
scan delay for CAP - ab/pel
65 secs - portal venous phase
volume of oral contrast for CAP
900 ml 1 hour prior
what does appendicitis look like on a ct scan?
- dilated, non-opacified appendix
- fat stranding
- appendicolith
4 indications on a ct scan to rule out appendicitis
- appendiceal lumen contains air or contrast
- <6mm in diameter
- appendiceal wall <2mm thick
- no “stranding”
anatomy included for appendicitis scan
above diaphragm to below pubic symphysis
is contrast used for appendicitis scans?
yes - IV and oral
algorithm used for appendicitis scans
standard soft tissue
mA for appendicitis scan
avg 230, atcm (btw 100-575)
reconstruction of appendicitis scan
slice thickness/interval
2.5mm/1.25mm
algorithm(s) used for CAP
soft tissue and lung
rate of IV contrast for appendicitis scans
125 ml at 3ml/sec, 50 ml NaCl flush
scan delay for appendicitis
65 secs
HU for normal liver
38-70 HU
indications for liver imaging
- fatty infiltration
- cavernous hemangioma
- hypervascular tumor
- liver mets
how do you most accurately assess the liver?
NECT abdomen
how do you diagnose livers?
comparison of HU of liver to spleen
hepatic arterial phase
17-25 secs
late hepatic arterial phase
40-55 secs
portal venous phase
65-80 secs
hepatic venous phase
75-85 secs
early delayed hepatic phase
3-5 mins
vascular equilibrium phase
3-5 mins
late delayed hepatic phase
10-15 mins
parenchymal equilibrium phase
10-15 mins
how does cavernous hemangioma look on NECT
well-defined and hypodense of same density as other fluid-filled spaces
how does cavernous hemangioma look on CECT
progressive pooling of contrast at lesion’s peripheral (centripetal filling)
enhancement for hypervascular tumors
late arterial phase (35-45 secs)
liver mets are (hyper/hypo)vascular
hypovascular
enhancement for liver mets
portal venous phase (60-80 secs)
anatomy for CECT arterial venous liver
just above diaphragm to iliac crests
algorithms used for CECT arterial venous liver
soft tissue and liver
reconstruction slice thickness/interval for CECT arterial venous liver
2.5mm/2.5mm
rate for IV contrast for CECT arterial venous liver
125 ml at 4 ml/sec, 50 ml NaCl flush
IV contrast scan delay for arterial (CECT arterial venous liver)
35 secs
IV contrast scan delay for venous (CECT arterial venous liver)
65 secs
oral contrast used for CECT arterial venous liver scans = 900 ml water, how much do we give 30 mins prior? 10 mins prior? just prior?
30 mins - 450 ml
10 mins - 225 ml
just - 225 ml
what scans use water as oral contrast?
pancreas and arterial venous liver scans
indication for NECT pancreas
calculi in pancreatic or common bile duct
indication for CECT pancreas
pancreatitis, mass/tumors
what can be done if scans can’t differentiate pancreas from duodenum
scan RLAT decubitus position
difference between arterial venous pancreas scan delay for arterial vs. arterial venous liver scan delay for arterial
pancreas - scan delay art = 40 secs
liver - scan delay art = 35 secs
why CT for urinary tract calculi?
- high diagnostic accuracy
- most types of stones are visible
- can undergo 3d reconstruction
- give info on degree of obstruction
slice thickness needed to identify stones for calculi scans
<2.5mm
indications for NECT ab/pel for calculi
- urinary tract calculi
- renal colic
- flank pain
KUB
NECT ab/pel for calculi
anatomy region for nect ab/pel calculi
2cm above kidneys to symphysis pubis
mA for nect ab/pel calculi
100 mA if pt <165lb otherwise, 0.7*pt weight (lbs)
indications for CT colongraphy
- positive FIT test
- contraindication/failed/incomplete colonoscopy
contraindications for CT colonography
- bowel obstruction
- toxic megacolon
- acute abdomen or acute diverticulitis
what prep is required for ct colonography
clear liquid diet with laxatives, oral contrast and suppositories
double contrast is required for CT colonography. which two?
- rectal contrast - co2
- oral contrast - barium and water-soluble agent
anatomy region for ct colonography
just above diaphragm to lesser trochanters
mA for ct colonography
120