Master List

Volume 5

Number 3

Fall 1999

IN THIS ISSUE

UAB and Kirklin CT now move at "LightSpeed®"

Publications and Presentations

1. Targeted maximum intensity projection of CT angiogram on a renal donor patient shows anomalous renal artery and vein supplying the lower pole of the left kidney. 2. Targeted Maximum intensity projection of hepatic donor patient shows normal hepatic arterial anatomy and patent portal vein. 3. Maximum intensity projection of CT angiogram of abdominal aorta from an inferior to superior point of view shows proximal right renal artery stenosis.

UAB and Kirklin CT now move at "Lightspeed®"

New multislice CT scanners improve CT quality and add new applications - CT aortography with peripheral runoff aortic stent-graft planning renal and liver donor evaluation coronary calcification screening CT colography

J. Kevin Smith, MD, PhD

Two new state-of-the art GE Lightspeed" Helical CT scanners that have recently been added to the UAB hospital and Kirklin Clinic CT departments should improve the quality and timeliness of CT exams in both facilities and provide exciting new types of CT examinations. The only two in north and central Alabama, these GE Lightspeed" Helical CT scanners are based on a radically new design of X-ray detector that allows the collection of four image "slices" for every rotation of the scanner. This, coupled with faster rotation times, allows the new scanners to image patients up to six times faster than existing helical scanners, with better image quality. Some of this increased speed can be traded for additional improvements in image quality while still imaging three times faster than current scanners. Patients should see many immediate benefits as the increased exam capacity eliminates significant waiting times in both the inpatient and outpatient facilities. Patients getting their CT on the newer machine will see improvement in the quality of even "routine" types of CT exams. Much shorter scan time will translate into shorter breath hold times for chest, abdomen, and pelvis exams with increased patient comfort and decreased motion and misregistration artifacts. Patients getting multiple exams, such as acute trauma patients, will also benefit greatly. The new machine's increased efficiency in using X-rays and new, higher capacity x-ray tubes eliminate the need to decide between long waiting times for the x-ray tube to cool or getting unacceptable image noise because the output of the scanner is decreased to keep the x-ray tube from overheating. With previous ER and inpatient exam load distributed to only two single slice helical scanners, it was not uncommon for trauma patients to wait 10-15 minutes for tube cooling during their exams - up to one fourth of their "golden hour." These immediate benefits of shorter exam times and decreased patient waiting benefit all of the UAB health		system patients, but many patients will also benefit as the dramatic increase in speed makes possible many new types of CT examinations. The extreme speed and decreased x-ray tube heating translates directly into the ability to scan whole anatomic regions with much thinner slices than previously possible, or to scan practically the whole patient with what was formerly considered "thin" slices. This makes it possible to extend the range of exams that pushed the limits of single slice CT scanners such as CT angiography to routinely examine smaller vessels or cover the whole aorta as well as the runoff vessels of the leg. For CT angiography, "you can never be too fast or too thin." Preliminary studies at other institutions with these CT scanners indicates that CT angiography of the aorta and runoff vessels using multislice CT scanners may actually be superior to the diagnostic capabilities of catheter aortography and runoff, showing more of the distal runoff segments, especially if there is proximal occlusive disease. The scan time is typically less than a minute with the whole exam taking less than ten minutes. Since contrast is injected via vein rather than by catheterizing the artery, there is no need for prolonged observation or risk of arterial access complications. The true 3D volume imaging of CT angiography is also proving essential for evaluation and surgical planning for patients having aortic aneurysms treated with the recently approved stent-grafts. These stent-grafts allow repair of life-threatening aortic aneurysms through small incisions to the arteries at the groin and placement of a tube inside the aneurysm with a catheter. CT not only provides information about the shape and size of the inside of the aneurysm or "flow lumen" like catheter angiography, but also about the shape and size of the aneurysm outside the flow lumen, which may be significantly different. Since patients treated with stent-grafts do not have abdominal surgery, this detailed information about the size and shape of the outside of the aneurysm would not be available at all without CT.
CT aortogram and runoff on a patient with aortoiliac disease and a right external iliac stent. Distal vessels are normal. Right renal artery is stenotic. Top of Page	The ability to scan whole anatomic regions with very thin slices during a single breath hold allows routine visualization of very small vessels during CT angiography. This makes CT angiography a viable alternative to catheter angiography for screening for renal artery stenosis, for example, or for evaluating renal and hepatic organ donors for variant arterial anatomy. It also extends visualization of the pulmonary arteries during CT pulmonary angiography, demonstrating emboli routinely in the 3rd and 4th order branches. Cancer patients will also see benefits from the increased speed and image quality of the new multislice CT scanners. Three phase hepatic CT, which can be useful in improving the detection and characterization of many primary hepatic tumors and selected types of hepatic metastases, is routinely available now, but pushes the technical limitations of our existing scanners and may require long breath hold times. The new scanners will allow thinner, less noisy images with very manageable breath hold times, even for sick patients.	Surface rendering of CT arteriogram showing right subclavian artery aneurysm. Some institutions are currently experimenting with adding additional phases to try to further improve lesion detection. Additional imaging immediately after contrast injection can also be useful for surgical planning, showing the arterial anatomy and relationships of tumor and arteries. In the pancreas, for example, early scans show arterial anatomy and islet cell tumors best, while slightly later "parenchymal phase" images contrast adenocarcinoma best against the enhancing pancreas tissue. Images in the even later routine, "hepatic" phase show hepatic metastases best. With current single slice CT scanners it is not possible to image the liver and pancreas in all of these phases. As urologists become more aggressive with nephron sparing renal tumor surgeries, arterial anatomy has become more important to their patients since tumor location and arterial anatomy will determine whether a patient is a candidate for segmental nephrectomy rather than traditional radical nephrectomy. Renal CT with CT angiography has the potential to provide "one stop imaging shopping" for the pre-surgical planning in these patients.
Other types of CT examinations that are currently in the research stage but may have tremendous future utility, such as CT colography and coronary artery calcium scoring, will also benefit from the new speed enhancements available with multislice CT. In CT colography (sometimes called "virtual colonoscopy"), CT is performed of the abdomen and pelvis after inflation of the colon with rectal air. CT colography can detect colon cancers and many small, pre-cancerous polyps, but may involve prohibitively long breath holding, or the selection of thicker slices that can mean missing some significant polyps with single slice CT. The speed and image quality available with the multislice CT will likely make this exam a practical test for colorectal carcinoma screening and UAB is currently enrolling in a multi-institution study to evaluate its effectiveness. Coronary artery calcium scoring involves obtaining a cardiac gated CT through the base of the heart and analyzing the volume of calcium in the proximal coronary arteries. This "calcium score" has been shown to correlate well with risk of future coronary events, and may prove to be an important test, comparable to lipid profile measurements. This calcium scoring has traditionally been performed on "ultrafast" electron beam CT scanners, but these scanners are expensive and have had disappointing image quality for other types of exams, limiting their usefulness. Preliminary research from Europe indicates that coronary artery calcium scoring with multislice CT scanners may actually be superior to scoring with the electron beam CT, making this test much more economically feasible. A coronary calcium scoring package should be available on our GE Lightspeed" scanners early in 2000. One unfortunate side effect of the new technology is that the number of images generated for some of these studies may be prohibitive for film-based viewing, so some exams will not have all images filmed (for example, an aortogram with runoff may have 400-500 images). This will necessitate review of some exams on a computer workstation in the CT area. A new Vitrea" volume rendering workstation soon to be installed in the CT area at UAB will allow more rapid 3D reconstructions with interactive viewing. The volume rendering technique allows display of various tissue densities with color and partial transparency to provide surgical landmarks without obscuring the internal items of interest, and also of various perspectives, including from within the body. Please do not hesitate to consult the CT radiologist for help determining the optimal imaging strategy for your individual patient, or if you have questions about these new techniques or wish to review exams on your patients.
Publications and Presentations Dubovsky EV, Russell CD. Advances in radionuclide evaluation of urinary tract obstruction. Abdom Imaging 1998;23:17-26 Russell CD, Dubovsky EV. Single-sample 99Tcm-MAG3 renal clearance in long-term management of patients with spinal cord injury. 10th International Symposium on Radionuclides in Nephrourology. Nucl Med Commun 1998;19(5):494 Russell CD, Yang H, Diethelm AG, Dubovsky EV. Prediction of renal transplant survival from early post-operative ERPF measurement. 10th International Symposium on Radionuclides in Nephrourology. Nucl Med Commun 1998;19(5):504 Dubovsky EV. Consensus: Radionuclide evaluation of the transplanted kidney. 10th International Symposium on Radionuclides in Nephrourology. Copenhagen, Denmark, May 14-16, 1998. Junck KL, Berland LL, Bernreuter WK, McEachern M, Grandhi, Lewey G. PACS and CR implementation in a level I trauma center emergency department. J Dig Imaging 1998;11(3):Suppl 1: pp159-162 Berland LL, Smith JK. Editorial: Multidetector-Array CT: Once again, technology creates new opportunities. Radiology 1998;209:327-329 Berland LL, Weber TM. 1998. Chapter 31: Carotid. In: Diagnostic Ultrasound - A Logical Approach. Ed: Goldberg BB, McGahan JP. JB Lippincott. pp.1009-1036 Berland LL, Bridges MD, Weber TM, Junck KL. Measuring effects of implementing CT in the emergency department as part of a cost-effectiveness analysis. Presented at Annual Meeting of RSNA, Chicago, December, 1998. Baron TH, Dean PA, Yates MR, Canon CL, Koehler RE. Expandable metal stents for the treatment of colonic obstruction: techniques and outcomes. Gastrointest Endosc 1998; 47(3):277- 285 Canon CL. The continued debate on the radiologic evaluation of Crohn's disease. Invited Commentary. Advances in Gastroenterology, Hepatology & Clinical Nutrition 1998;3(3):132-133 Wu X. Spin relaxation for laser-pumped hyperpolarized spins. Proc SPIE 1998;3548:67-74 Barnes GT, Wu X. Mammography Dosimetry: Historical, Theoretical and Practical Considerations. Medical Physics 1998;25:A125 Barnes GT, Lakshminarayanan AV. 1998. Conventional and Spiral Computed Tomography: Physical Principles and Image Quality Considerations. In: Computed Body Tomography with MRI Correlation. JKT Lee, SS Sagel, RJ Stanley, JP Heiken (eds) Lippincott-Raven Publishers, Philadelphia, PA, pp 1-20. Bass WB Jr, Barnes GT. 1998. Medical Center Personnel Monitoring: Operational Considerations. In: Good Practices in Health Physics. Komp GR, Thompson MA(eds) Medical Physics Publishing, Madison, WI, pp 23-27.

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UAB Radiology Home Page: www.rad.uab.edu Visions In UAB Radiology is published quarterly by the University of Alabama Hospital, Department of Radiology. Professor and Chairman: Robert J. Stanley, MD; Vice-Chairman for Operations and Academic Affairs: Robert E. Koehler, MD; Vice-Chairman for Planning and Administration: Lincoln L. Berland, MD; Director of Outpatient Services: Peter Dempsey, MD. Visions Staff: Managing Editor/Layout: Pat Moore; Editors: Lincoln L. Berland, MD; Robert Lopez, MD; Hrudaya Nath, MD; Rachel Oser, MD. Web Master: J. Kevin Smith, MD, PhD. Please direct questions, comments, and suggestions as follows: Attention: Pat Moore or Lincoln L. Berland, MD. Fax: (205) 975-7213; Address: JT N 348A; E-Mail lberland@uabmc.edu