CT abdo protocols Flashcards
CT portal venous abdo indications
Acute abdo pain Trauma Oncology staging/follow up ? Mass Abscess Ascites Diverticulitis Appendicitis and other non-descript abdo symptoms
CT portal venous abdo protocl
Most common type of abdominal scan
Scans performed supine feet first arms raised out of FOV
Scan on inspiration
AP or duel scanogram
Scan from 2cm above diaphragm to base of pelvis
Slices overlapping 1-1.5mm thick
Standard recon algorithm and S.T. window approx. WW 400 WL 40
MPR’s Ax, Sag and Cor 2-5mm
CT portal venous abdo contrast requirements
Oral contrast usually used (water or opaque as per department protocol)
IV contrast via cannula. 50-75ml @ 2.5-3.5 ml/sec
Timing of scan is 70-80 sec post inj.
If bolus tracking, place tracker over descending aorta just above diaphragm with a delay between 40-50 sec post threshold
This timing allows for optimal enhancement of internal organs
Portal venous abdo possible pathologies
Mass Abscess Ascites Diverticulitis Appendicitis
CT post contrast abo indications (15)
Injuries following trauma Masses Ascites Abscess or intra-abdominal collection Initial staging of Lymphoma/Oncology/Metastases staging Inflammatory bowel disease i.e. Crohn’s disease Colon cancer Acute cholecystitis Acute appendicitis Bleeding Unexplained abdominal pain Melanoma Ovarian cancer Testicular cancer Bowel obstruction
CT post contrast protocl
Scans performed supine feet first arms raised out of FOV
Scan on inspiration
AP or duel scanogram
Scan from 2cm above diaphragm to base of pelvis
Slices overlapping 1-1.5mm thick
Standard recon algorithm and S.T. window approx. WW 400 WL 40
MPR’s Ax, Sag and Cor 2-5mm
CT post contrast, contrast requirements
Oral contrast usually used (water or opaque as per department protocol)
IV contrast via cannula. 50-75ml @ 2.5-3.5 ml/sec
Timing of scan is 70-80 sec post inj.
If bolus tracking, place tracker over descending aorta just above diaphragm with a delay between 5-10 sec post threshold
This timing allows for optimal enhancement of internal organs
Possible CT abdo post contrast pathologies
mass ascites abscess Crohn's disease colon cancer melanoma ovarian cancer testicular cancer bowel obstruction
CT urogram or CT IVP indications
Evaluation and detection of renal mass Bladder pathology Complex cysts Neuroblastoma Haematuria Hydronephrosis
CT urogram or CT IVP protocol
Scans performed supine feet first arms raised out of FOV
Scan on inspiration
AP or duel scanogram
Scan from:
Non contrast scan of the complete abdomen
Arterial scan of the upper abdomen to crests only
Delayed phase is through the complete abdomen
Slices overlapping 1-1.5mm thick
Standard recon algorithm and S.T. window approx. WW 400 WL 40
MPR’s Ax, Sag and Cor 2-5mm
CT urogram or CT IVP contrast requirements
Oral contrast usually used (water or opaque as per department protocol)
IV contrast via cannula. 50-75ml @ 2.5-3.5 ml/sec
If bolus tracking, place tracker over descending aorta just above diaphragm:
Arterial 5 - 10 second
Delayed approx. 10 minutes
CT urogram or CT IVP possible pathologies
RCC
Neuroblastoma
Heamaturia
Hydronephrosis
3 phase liver/pancreas indications (8)
Hepatic cell carcinoma Pancreatic Cancer Pancreatitis Metastases Cirrhosis / Alcoholic liver disease Haemangioma / Hyper-vascular lesions Pancreatic abscess or Pseudocyst Jaundice - Obstructive and non-obstructive jaundice
3 phase liver/pancreas protocol
Scans performed supine feet first arms raised out of FOV
Scan on inspiration
AP or duel scanogram
Scan from:
Non contrast, delayed phase and arterial of the upper abdomen to crest
Portal venous through the complete abdomen
Slices overlapping 1-1.5mm thick
Standard recon algorithm and S.T. window approx. WW 400 WL 40
MPR’s Ax, Sag and Cor 2-5mm
3 phase liver/pancreas contrast requirements
Oral contrast usually used (water or opaque as per department protocol)
IV contrast via cannula. 50-75ml @ 2.5-3.5 ml/sec
If bolus tracking, place tracker over descending aorta just above diaphragm:
Arterial 5 - 10 second
Venous 45 - 70 second
Delayed 5 minutes
3 phase liver/pancreas possible pathologies
hepatic cell carcinoma pancreatic ca pancreatitis mets cirrhosis pancreatic abscess jaundice
possible protocol alterations for trauma
Trauma patient: lots of staff, quick scan, organised room ready to scan
Fast non-con scan to prevent patient movement and risk of repeating
- If patient hard on hearing turn auto instructions up as you need to remove hearing aids
- Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
Possible protocol alterations for paediatrics
- Paediatric patient: parent in the room, sedations/ GA, secure head, organised and quick scan, simple explanation
- Fast non-con scan to prevent patient movement and risk of repeating
- If patient hard on hearing turn auto instructions up as you need to remove hearing aids
- Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
Possible protocol alterations for geriatrics
- Geriatrics: secure head, explain simply, organised and quick scan
- Fast non-con scan to prevent patient movement and risk of repeating
- If patient hard on hearing turn auto instructions up as you need to remove hearing aids
- Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
Possible protocol alterations for uncooperative patients
- Uncooperative: immobilisation devices, alter parameters for a fast scan, staff to help
- Contrast volume dependent on patient size
- Fast non-con scan to prevent patient movement and risk of repeating
- If patient hard on hearing turn auto instructions up as you need to remove hearing aids
- Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
Dose reduction strategies
- Appropriate scan range: image relevant anatomy
- Pitch closer to 1 to decrease scan time (critical cases)
- Making the non con scan a fast scan: reducing dose and reducing risk of having to repeat scan
- Change contrast volume (dependent on patient size)
- Change technical factors dependent on patient size: reduce kV, mAs
- Change tube rotation time (slow down to gain appropriate exposure)
- Reduce scan range to reduce radiation exposure and maximise resolution
- SFOV is appropriate: tight to maximise spatial resolution
- Automatic exposure control: Automatically adjusts exposure (mA) for attenuation differences of tissue types and thicknesses. Tight collimation: Accurate pre-patient collimation reduces dose post-patient collimation picks up unhelpful scatter and improves image quality
- Bowtie filter: shape’s and hardens the beam increasing uniformity, removes low energy x-rays and increases average energy beam; lower absorbed dose to patient
- Centre patient in isocentre correctly
- Lead shielding if needed
What protocol would you do for the following and what are possible pathologies?
- 58 year old male
- 5 days of dull abdominal pain with diarrhoea
- Fevers for 2 days (indicates inflammatory response)
- Heart rate 98 bpm
- Blood pressure 100/75
- Respiration rate 32
- On examination; tenderness left lower quadrant
- Nil per rectum blood
Portal venous abdomen due to left lower quadrant pain: suggestive of any abdominal pathology (most likely bowel related)
- Diverticulitis: fevers associated with abdominal pain
- Bowel obstruction: dull bowel pain
- Early stage of bowel cancer: dull abdo pain, diarrhoea
- Pt History: previous surgery, urology? Risk of perforation
- Ulcerative colitis
- Crohn’s disease
Indications of a CTA AAA
? Aneurysm
? Dissection
Surgical planning
Contrast of CTA AAA
75-100mL @4-5mL/sec
18g cannula
ROI over descending aorta
