CT Technique Flashcards
What reconstruction thickness and interval would you use for CT Brain bone reconstruction?
0.6/0/4
What reconstruction thickness and interval would you use for CT Brain cerebrum reconstruction?
0.75/0.6
What reconstruction thickness and interval would you use for a CT chest, neck or abdomen/pelvis?
1.0/0.8
What reconstruction thickness and interval would you use for CT cervical spine?
0.6/0.4
What reconstruction thickness and interval would you use for PTB or inner ear?
0.5/0.3
What reconstruction thickness and interval would you use for wrist or elbow?
0.6/0.4
What reconstruction thickness and interval would you use for CT COW, Carotid angio or neuroperfusion?
0.5/0.3
What reconstruction thickness and interval would you use for CT calcium score?
1.0/1.0
What reconstruction thickness and interval would you use for renal angio or leg run off?
0.75/0.6
What are the indications of cardiac CT?
CAD, chest pain, family history, SOBOE, chest tightness, increased troponin, irregular ECG
What is the patient preparation for cardiac CT?
Fasted 4 hours, no tea/coffee morning of appointment, BP and heart rate observations, list all medications, GTN (unless viagra or cialis in 48 hoursor BP below 105 systolic)
What is prospective gating?
Monitoring RR intervals either previous 3 (mean) or 5 (median) and exposing only at selected range
What is retrospective gating?
Retrospectively selecting data to be included in reconstructed range, beam is always on and pitch must be appropriate for heart rate
Which scanning mode results in higher radiation dose?
Retrospective
When is helical scanning useful?
Uncooperative patients, irregular heart rates
When is sequential scanning useful?
Younger patients (where radiation dose is a concern), regular heart rates,, cooperative patients, calcium deposits
What are the indications of CT calcium score?
Family history, hypercalcaemia
What are the indications of a CT colonoscopy?
Unsuitable for anaesthetics, failed colonoscopy, iron deficient anaemia, positive FOBT
What are the benefits of CT colonoscopy?
Less invasive, extracolonic findings, highly sensitive and specific
What is the role of CT perfusion?
Differentiate salvagable ischaemic brain tissue (penumbra) from the damaged infarcted brain (infarct core)
Which groups can result in overestimated MTT and underestimated CBF?
Poor cardiac output, AF, arterial stenosis
What are the indications for CT neuroperfusion?
Acute infarction,
Assessment of reperfusion after treatment of acute stroke
New neurological symptoms after subarachnoid haemorrhage
Evaluation of haemodynamic significance of carotid stenosis
Transient ischaemic attack
Significant head trauma
Brain tumor
What is mean transit time?
Average time in seconds that red blood cells spend within a determinate volume of capillary circulation
How is mean transit time calculated?
MTT=CBV/CBF
