Current Clinical Concerns in CT: Results : Protocols
Routine abdomen
1. Our poor elderly PACS chokes on multi-hundred slice CT's. For routine work, such as the usual abdomen and pelvis scan to evaluate for abdominal pain, what parameters are necessary? Can we get by with 5 mm @ 5 mm reconstruction, which yields about 90 or so images? One of our sites does 2.5 @ 2.5 mm yielding 300 slices for ROUTINE abdomen and pelvis CT. The images are spectacular, but would we risk missing much to back down to the thicker slices?
| Answer: We routinely do a 3 x 3, but in most cases, 5 x 5 will work and you can get additional cuts as needed. This is for the routine, "search and seek", studies, and not for tumor staging. |
2. We use your abdomen protocol: 120 cc, 2 cc/sec, 60 second delay. It is perfect. However, some radiologists say there is no good contrast in the IVC. I was wondering if you have any recommendation to have good contrast in aorta, IVC and other organs in the abdomen. We do delayed cuts on the kidney to see the renal pelvis and ureters.
| Answer: IVC enhancement is good at 60-80 seconds, as you note. Enhancement of various organs is of course related to arterial and venous phase imaging. |
3. What are your thoughts on routine delayed scanning of the kidneys and bladder on routine abdomen/pelvis studies for non-renal work ups
| Answer: I think on routine cases, delayed scans are not necessary. If there is any possibility of renal disease (pyelonephritis), then I would always get delayed scans (4 min delay). In your experience, have you found any significant finding on routine delayed scans? |
4. I am a diagnostic physicist. One of the CT technologists in our hospital came to me confused as to why one of the radiologists had set an abdomen protocol in a Quad GE Lightspeed to acquiring four 2.5 mm slices/rotation and then reconstructing two 5 mm slices/rotation. My question is what advantage does this have over just acquiring two 5 mm slices or better yet four 5 mm slices. I see where there is no difference in spatial resolution or low contrast object detectability between the two end result images.
| Answer: The reason is that the smaller the detectors, the better the resolution. Also perhaps that radiologist prefers to do multiplanar reconstructions or 3D, and you can create thinner sections from that dataset. |
5. Since we got a helical CT I used to inject 15-20 cc before the main portal venous bolus, in all abdominal CT examinations, except for evaluating trauma, renal calculi and suspected renal lesion. I do it for opacification of the collecting system without delayed scans, based on an article published by Dinkel HP et al, European Radiology 1999; 9: 1579-1585. What is your opinion?
| Answer: Although it has some merit, we don't do it. It may hide some lesions and make detection more difficult for others. I would not recommend that protocol. |
References
Ros PR, Ji H. Special focus session: Multisection (Multidetector) CT: Applications in the abdomen. Radiographics 2002; 22: 697-700.
- Summary: This review article discusses advantages, disadvantages and clinical applications for abdominal multidetector row CT. Acquisition parameters including collimation, pitch, reconstruction interval and contrast administration are addressed.
- Summary: Acquisition protocol design for specific clinical applications are reviewed, including hepatic, pancreatic and renal imaging, as well as trauma.