Current Clinical Concerns in CT: Results : Protocols
Upper extremity CT angiography
1. I currently have a 4 slice Marconi scanner. We have a large dialysis population and have a peripheral vascular surgeon wanting to start using our MDCT scanner for preoperative upper extremity venograms. I have Silverman's protocol book which I have used in addition to your website and lecture notes from 2 Johns Hopkins courses I have attended. Still, I have been unable to get a diagnostic exam.
Answer: See my reply below. What technique have you used to date? Has it been a problem of being too early or too late? Let me know. |
2. I could not find a CT angiography protocol for upper extremity with 16 detector CT. Do you have a protocol and for which applications do you use it? We are planning to use it for upper extremity fistula dysfunction of hemodialysis patients.
Answer: We use a 15-18 second delay and for a fistula inject the same side as the suspected problem. I use a lower contrast concentration (100 cc Omnipaque-300) and inject 3-4 cc/sec. I use a .75 mm thick section, reconstructed at .5 mm intervals to get a great 3D. For the 3D, I use both MIP and VRT. |
3. How would you approach CTA of the brachiocephalic veins? I am inclined to think that waiting for recirculation would not yield optimal opacity. Any tricks? We have a Siemens 16.
Answer: In order to get good venous opacification, I would do a 30 second delay and scan from beneath the arch superiorly (inferior to superior). |
4. I have a thin, female patient with a post-traumatic right subclavian pseudoaneurysm. Are there any recommendations for modified aortic or cerebral protocol for such a study?
Answer: Just the usual of arterial phase, thin sections. In this case I would also do a scan at venous phase to see if there is any late filling of the pseudoaneurysm. |
5. Would you recommend having patients arms up or down for CTA of the brachiocephalic artery? Also, how important is contralateral (left arm) injection for this exam?
Answer: I do like contralateral arm injection to decrease the artifact in axilla. I also like to do the studies arms up to decrease beam attenuation artifacts. |
6. Is there a protocol for CTA of the hand on a 16 slice CT scanner?
Answer: Our protocol is to inject in the contralateral arm and do a 25 - 30 second delay. We will scan from proximal to distal direction. |
References
Lawler LP, Corl FM and Fishman EK. Multi-detector row and volume-rendered CT of the normal and accessory flow pathways of the thoracic systemic and pulmonary veins. Radiographics 2002; 22: S45-S60.
- Summary: This article includes images displaying systemic and pulmonary veins with 4 slice MDCT and volume rendering. A discussion of acquisition timing tailored to the region of interest is provided. The sample protocol for this type of scanner included 1 mm collimation (2.5 mm in those who can not hold their breath), 1.25 mm section thickness, 1 mm recontruction interval. This article provides CME credit.