CT colonography Flashcards
(28 cards)
what is CT colonography for
examine LARRGE intestine for cancer and polyps
(minimally invasive procesdure)
areas for referral for CTC:
Gastrointerology
colorectal
GP
failed colonoscopy
bowel cancer screening program (BCSP)
what 2 drugs are given to a patient as prep (prior to CTC) (given along with appointment letter)
100mls gastrograffin
sachet of pico lax (laxative)
2 days prior to CTC, what must the patient do
low fibre and low fat diet
when should patient take the gastrograffin
50mls morning and evening 1 day before examination
- light meal only
on the day of CTC, patients advised not to eat but are invited to drink more water
note: laxative is not routinely used when gastrograffin is available as prep (Derriford)
what 2 drugs are IV inserted for CTC
- Omnipaque 350 (iohexol drug) (IV contrast for bowel) (70ml)
- buscopan (20mg/1ml)
give some reasons why u wouldn’t give contrast
- bad egfr (and on metformin (can induce acute kidney injury))
- allergy to iodine/contrast
- asthma severe
- over/under active thyroid
normal side effects to contrast:
- warm feeling
- metallic taste
- flushed
why wouldn’t you prescribe buscopan
- allergy
- heart issues e.g angina
- hypertension
- on blood thinners
side effects of buscopan
- dry mouth
- blurred vision
- constipation
- increased heart rate
who do you speak to if a patient hasn’t prepped accordingly for CTC
gastroenterology unit (DFR)
what is insufflation in CTC, why is this done
- reduce pain and discomfort during CTC by opening up the bowel
- colonic distension with CO2 gas for CT colonography (tube stuck up backside and inflates with c02)
what position is the patient required to lie in for insertion of the insufflation
left lateral decubitus position
what is the technique from start to end of the CTC
- left lateral decubitus position
- tube inserted and balloon inflated
- gas started
- buscopan then given
- wait for bowel to inflate
- back in supine position
- connect patient to contrast
- insufflating radiographer leaves
- abdomen and pelvis scounts retrieved
how thick are the imaging slices in CTC
1.25mm
what contrast timing are the images retrieved in
portal venous
why would the ideal position for CTC be prone
- improved colonic distention
- better visualisation of colonic walls
(reduced residual fluid and collapsed areas of colon due to gravity)
- if not prone then left lateral decubitus or right
the 2nd and 3rd views of CTC are reduced dose, so higher noise index resulting in 1/3 of dose of initial scan. why is this
- to minimize overall radiation exposure to patient
- as initial view provides comprehensive assessment of colon, the additional views are just to clarify potential findings or areas of concern
what do you do once the CTC is complete
- vent gas on insufflator
- disconnect patient from contrast
- deflate balloon and remove catheter
what all the parts to the insufflator used in ctc
gas source (inflates colon)(typically c02)
pressure regulator = controls and maintains desired pressure of gas delivered
flow control valve = regulates flow rate of gas entering colon
humidifier (optional) = comfort
delivering tube = connects insufflator and rectal catheter
pressure monitoring system = monitors pressure in colon is in safe limits
display screen = shows current pressure and flow settings
safety features = alarms and automatic shut down mechanisms to prevent over inflation
after CTC what must you do with the patient
get them to wait 15-20 mins (check no side effects)
give them safety sheet outlining possible side effects / tell them what next
post processing includes:
documenting is buscopan was given
writing provisional report
regular post processing on images
writing provisional report:
view images in multiple planes at once
did patient need thorax CT too
