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Radiologist seeks to clarify benefits of CTs   by U. Joseph Schoepf, M.D. MUSC Department of Radiology During the past decades, we have seen scores of new developments that have fundamentally increased our quality of life, improved our health and expanded our life expectancy as compared to only 50 years ago. Medical research has brought us cleaner water, better drugs to ward off previously fatal diseases, and fascinating new technologies to diagnose and treat the human body.   One area that is setting the pace like no other medical specialty is radiology. Medical imaging has become such a vital part of modern medicine that hardly any condition is being treated today without prior imaging with X-rays, computed tomography (CT or CAT) scans, ultrasound, nuclear imaging, or magnetic resonance. These technologies provide fascinating insights into the human body and save countless lives on a daily basis.   The imaging test that has seen the most rapid growth over the last decade is computed tomography. Spurred by quickly advancing scanner technology, CT has become the work-horse in emergency departments around the world, enabling rapid assessment of trauma victims for life-threatening injuries or to quickly evaluate patients with symptoms of stroke. Thanks to evermore sophisticated technology, computed tomography now also allows generation of crisp and clear images of the human heart and particularly of the heart vessels (coronary arteries). For the longest time, patients with suspected narrowing or blockage of the heart vessels had to undergo cardiac catheterization, an invasive procedure in which a catheter is inserted in the groin and snaked up to the heart to directly inject dye (contrast material) into the heart vessels. While this is generally a fairly safe procedure, about two out of 100 patients undergoing this procedure experience major complications such as stroke, heart attacks or tears in their major blood vessels.   One out of every 1,000 patients dies during cardiac catheterization. CT of the heart has the potential to do away with a large percentage of these invasive procedures, particularly in patients with vague symptoms that may or may not be a sign of heart disease, but who would still undergo invasive catheterization just to rule out the possibility that something is wrong with their heart vessels.   MUSC has been very much at the forefront of implementing this test. MUSC faculty are among the pioneers and most recognized experts in the field. Meanwhile, an active core group of MUSC radiologists and cardiologists are exhaustively researching the appropriate use of CT of the heart and are continuously refining scan technology.   Their work resulted in a series of three major articles, all published in the July issue of the Journal of Radiology, the most esteemed and influential publication in medical imaging. In those articles, they reported preliminary data on a group of 115 patients who underwent CT of the heart vessels in comparison with traditional invasive cardiac catheterization. The MUSC researchers showed that in this group CT did not miss a single patient who had significant narrowing or blockages of the heart vessels, demonstrating the power of CT to replace invasive catheterization in appropriate patients. In one of the flagship articles of the journal,  and “How I Do It” section, they shared the MUSC expertise on performing this test with the vast, global readership of Radiology. In this contribution, they particularly focused on strategies for lowering the use of radiation during the scan acquisition. Like invasive heart catheterization, CT uses X-rays to generate exceedingly thin and detailed images of the human body with a resolution that far exceeds what can be achieved with other techniques for imaging the heart, such as magnetic resonance or nuclear scans. Particularly for diagnosing diseases of the heart vessels that are minute, and fast moving structures, no other non-invasive test currently features the combination of speed and spatial resolution provided by CT.   Although the radiation exposure from a CT scan of the heart is far too low to result in any direct effects on the human body and several magnitudes lower than what is routinely applied during radiation therapy, for instance, MUSC doctors have strived to keep the radiation exposure to patients as low as reasonably achievable while maintaining sufficient diagnostic accuracy. In their endeavors to lower radiation during medical testing, MUSC physicians are supported and monitored by some of the most acclaimed medical physicists worldwide, such as Donald Frey, Ph.D., a member of the board of directors of the American Board of Radiological and the International Organization for Medical Physics and past president of the American Association of Physicists in Medicine and newly recruited Walter Huda, Ph.D., author of the premier textbook on medical physics.   The need to keep radiation as low as possible is based on the concern that even low level radiation has the potential to cause cancer. While a direct connection between radiation applied during medical imaging tests and cancer has never been established, researchers have tried to calculate the risk of cancer from any type of radiation, largely based on data from the A-bomb survivors of Hiroshima and Nagasaki. This topic was most recently revisited in a study published in the current issue of the Journal of the American Medical Association, entitled “Estimating Risk of Cancer Associated with Radiation Exposure from 64-Slice Computed Tomography Coronary Angiography.” In this article, the authors calculate the theoretical risk of developing cancer from the radiation applied during CT of the heart. Publication of this article has helped to further heighten public awareness concerning radiation exposure and adds additional justification to the endeavors of MUSC physicians to ensure the appropriate use of this test. MUSC’s policies on accepting only appropriate patients for undergoing CT of the heart have traditionally been very conservative and even more restrictive than the recommendations of the pertinent professional societies. MUSC does not allow self-referral of patients (“walk-ins”) like other, less restrictive and more commercial institutions, but requires physician referral in all cases ensuring that only such patients get scanned who would otherwise need traditional catheterization. Avoiding an invasive procedure that also involves radiation should outweigh radiation exposure from the non-invasive CT scan in most cases.    Most importantly, MUSC is in a fortunate situation to be leading the nation in scanner technology and moved on from the previous scanner generation on which the now published calculations are based. MUSC was among the very first institutions nationwide to start operations of the most advanced scanner generation, the Dual-Source CT. This scanner enables a hereto unprecedented temporal resolution, or “shutter-speed” to obtain crisp and clear images of the heart. More importantly, this scanner features very novel and sophisticated approaches to further lower radiation. Thus, depending on the patient’s body type and heart rate, the radiation dose can be significantly lowered – sometimes to about one-fifth of the exposure of previous scanner generations, so that radiation from a CT scan of the heart roughly equals the exposure that every American receives each year from environmental sources. In collaboration with their partners in industry, MUSC doctors and researchers will continue the tradition of excellence in providing the highest level of responsible patient care with the best equipment available and lead the field in cutting-edge research. About the author: U. Joseph Schoepf, M.D., from the MUSC Department of Radiology,  has helped develop CT of the heart for 10 years and has published several books and more than 100 articles in peer-reviewed journals primarily on this topic. He was cited by Medical Imaging Magazine among the world's Top 10 cardiovascular imagers for the second year in a row.     Friday, Aug. 3, 2007 Catalyst Online is published weekly, updated as needed and improved from time to time by the MUSC Office of Public Relations for the faculty, employees and students of the Medical University of South Carolina. Catalyst Online editor, Kim Draughn, can be reached at 792-4107 or by email, catalyst@musc.edu. Editorial copy can be submitted to Catalyst Online and to The Catalyst in print by fax, 792-6723, or by email to catalyst@musc.edu. To place an ad in The Catalyst hardcopy, call Island Publications at 849-1778, ext. 201.