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Leading the News
Study Fuels Discussion about Radiation Risk from Imaging Procedures
Imaging procedures are a significant source of ionizing radiation in the United States and can result in high cumulative effective doses of radiation. This conclusion was based on an observational study of 952,420 adults, 68.8 percent of whom underwent at least one imaging procedure associated with radiation exposure. The annual average radiation exposure was less than 3 millisieverts. However, about 20 percent of study participants had moderate exposure (3 to 20 millisieverts) and 2 percent had high exposure (20 to 50 millisieverts). Given these findings, the researchers estimated that medical imaging exposes 4 million nonelderly adults to radiation doses greater than 20 millisieverts a year. The annual safe limit is 50 millisieverts. In the research, routine X-rays for the chest and ankle made up 71 percent of the procedures, but only 11 percent of the radiation exposure. By contrast, computed tomographic (CT) and nuclear imaging accounted for 21 percent of total procedures and 75 percent of the radiation exposure. Nuclear tests to detect heart problems made up 22 percent of the radiation exposure, while CT scans of the abdomen, pelvis, and chest accounted for nearly 38 percent. Far more women had imaging procedures than men - 79 percent versus 58 percent. This is a concern because women live longer and face a higher risk of developing radiation-induced cancer. Dr. James Thrall, chief radiologist at Massachusetts General Hospital, notes a major limitation of the study was the lack of information about why the tests were done, and without that, it is impossible to know whether the test was medically necessary. "There's a risk that people who need a lifesaving or life-improving imaging procedure might not get one" because of radiation worries, says Thrall, who is also chairman of the American College of Radiology's board of chancellors.
From "Two-Thirds Get Medical Tests With Radiation Dose"
Associated Press (08/27/09) Chang, Alicia
Research
PET Used to Identify Blood Flow Metabolism Mismatch That Predicts Pancreatic Tumor Aggressiveness
Researchers in Finland have identified a blood flow glucose consumption mismatch that predicts pancreatic tumor aggressiveness. For the purposes of their study, the researchers used positron emission tomography to measure blood flow and glucose consumption in 26 patients with pancreatic cancer. Results showed that patients with benign and malignant tumors had decreased blood flow of the lesion by 48 percent and 60 percent, respectively, compared to patients with normal pancreatic tissue. These findings may help explain the lack of success some patients experience with radiotherapy and chemotherapy, according to the researchers. They suggest that the composite measurement of blood flow and metabolism in pancreatic cancer could serve as a novel tool in the planning of treatments targeting vasculature.
From "Decreased Blood Flow With Increased Metabolic Activity: A Novel Sign of Pancreatic Tumor Aggressiveness"
Clinical Cancer Research (08/09)
Prostate Cancer Patients Treated With IMRT Remain Disease-Free
A group of researchers conducted a study to assess prostate-specific antigen (PSA) bounce in patients treated exclusively with intensity-modulated radiotherapy (IMRT). From January 1997 to July 2002, 102 patients with clinically localized prostate cancer were treated with IMRT alone. No patients received androgen ablation. Average follow-up was 76 months, and the median length of time until the first PSA bounce was 13.6 months. About 32 percent of patients had a minimum of one PSA bounce, while 5.9 percent had two bounces, and 2 percent had four bounces. No significant association was perceived between PSA and biochemical evidence of disease survival, clinical stage, pretreatment PSA, Gleason combined score, prostate planning target volume, PSA nadir, or mean dose to the prostate. The study verifies that most patients with a bouncing PSA remain biochemically and clinically free of disease with extended follow-up.
From "Prostate-Specific Antigen Bounce After Intensity-Modulated Radiotherapy for Prostate Cancer"
UroToday (08/25/2009) Sheinbein, C.; Teh, B.S.; Mai, W.Y.; et al.
Musculoskeletal CT Scans Linked to Elevated Radiation
Computerized tomographic (CT) scans are routinely obtained to evaluate a number of musculoskeletal conditions. However, since CT scans expose patients to the greatest amounts of radiation of all imaging modalities, the physician must be cognizant of the effective doses of radiation that are administered. Researchers at the Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, and the Yale-New Haven Hospital attempted to quantify the effective doses of CT scans that are performed for various musculoskeletal applications. The digital imaging archive of a single institution was retrospectively reviewed to identify helical CT scans that were completed to visualize the extremities or spine. The mean effective doses for CT scans of the chest, abdomen, and pelvis (5.27, 4.95, and 4.85 mSv, respectively) were consistent with those of previous investigations. The highest mean effective doses were recorded for studies evaluating the spine (4.36, 17.99, and 19.15 mSv for the cervical, thoracic, and lumbar spines, respectively). In the upper extremity, the effective dose of a CT scan of the shoulder (2.06 mSv) was higher than those of the elbow (0.14 mSv) and wrist (0.03 mSv). The researchers concluded that CT scans of the axial and appendicular skeleton are associated with substantially elevated radiation exposures, but the effective dose declines substantially for anatomic structures that are further away from the torso.
From "Radiation Exposure From Musculoskeletal Computerized Tomographic Scans"
Journal of Bone and Joint Surgery (08/01/2009) Biswas, Debdut; Bible, Jesse; Bohan, Michael; et al.
fMRI Reveals That Alzheimer's Patients Have Hyperactive Brain Function
Researchers using functional magnetic resonance imaging (fMRI) have found that a low-effort, high-accuracy semantic memory activation task is sensitive to Alzheimer's disease risk factors in a dose-related manner. This increased activation in at-risk individuals may reflect a compensatory brain response to support task performance in otherwise asymptomatic older adults. This conclusion is based on a study of 69 individuals. The researchers divided the patients into three groups: those who had no risk factors for Alzheimer's, those who had a family history of disease but no genetic indicators of it themselves, and those who had both family members with Alzheimer's as well as a version of a gene for apolipoprotein E4. These patients all underwent fMRI and were shown both familiar and unfamiliar names. Those who displayed risk factors associated with Alzheimer's displayed greater activation in recognizing famous relative to unfamiliar names than a group without risk factors, especially in the bilateral posterior cingulate/precuneus, bilateral temporoparietal junction, and bilateral prefrontal cortex. fMRI revealed the control group demonstrated greater activation for unfamiliar than familiar names, predominately in the supplementary motor area, bilateral precentral, left inferior frontal, right insula, precuneus, and angular gyrus.
From "Semantic Memory Activation in Individuals at Risk for Developing Alzheimer Disease"
Neurology (08/25/2009) Seidenberg, M.; Guidotti, L.; Nielson, K. A.; et al.
Technology
Computer-Aided Kinetic Information Useful for Differentiating MRI-Detected Breast Lesions
A group of researchers compared a trio of computer-aided evaluation (CAE) kinetic features of suspicious breast lesions detected by magnetic resonance imaging (MRI) to determine associations with benign or malignant outcomes. The study involved 1,532 MRI examinations in which all suspicious breast lesions initially spotted with MRI and having CAE kinetics and subsequent biopsy were identified. Initial phase peak enhancement, delayed phase enhancement classified by a single type of kinetics comprising the largest percentage of enhancement, and delayed phase enhancement categorized by single most suspicious type of kinetics were compared for benign and malignant lesions. The analysis set was composed of 42 malignant and 83 benign lesions, and no significant disparities in initial peak enhancement or delayed kinetics categorized by largest percentage enhancement types between benign and malignant lesions were identified. A significant difference in delayed kinetics categorized by the most suspicious enhancement types was recorded, however. Almost 46 percent of lesions with washout as most suspicious were malignant, versus 20 percent with plateau and 13.3 percent with fully persistent enhancement. The researchers observed that only delayed enhancement categorized by most suspicious type was significantly different between benign and malignant lesions, and this supports the American College of Radiology BI-RADS Breast MRI Lexicon recommendation to disclose the "worst looking" kinetic curve.
From "MRI-Detected Suspicious Breast Lesions: Predictive Values of Kinetic Features Measured by Computer-Aided Evaluation"
American Journal of Roentgenology (09/01/2009) Vol. 193, No. 3, P. 826; Wang, Lilian C.; DeMartini, Wendy B.; Partridge, Savannah C.; et al.
Clinical Practice
DSCT and MRA Are Both Effective in Imaging CAS Patients
A group of researchers conducted a study to assess the potential of dual-source computed tomography angiography (DSCT) and 3T-magnetic resonance angiography (MRA) in the preoperative evaluation of the vascular anatomy and lesions within the extra- and intracranial arteries. Contrast-enhanced DSCT and 3T-MRA examinations were performed in 16 patients with carotid artery stenosis (CAS), and all examinations were analyzed for relevant morphologic and pathologic features or aberrations. A total of 624 vessel segments were scored. Imaging of almost all intracranial arteries was better through MRA versus CTA, but DSCT permitted further morphological carotid stenosis description, especially with respect to calcification. All pre-interventionally relevant information could be visualized from DSCT. DSCT and MRA may both be considered a dependable, expedient, pre-interventional imaging investigation in CAS patients.
From "Comparison of Dual-source CT Angiography and MR Angiography in Preoperative Evaluation of Intra- and Extracranial Vessels: A Pilot Study"
European Radiology (08/21/09) Muhlenbruch, Georg; Das, Marco; Mommertz, Gottfried; et al.
Interventional Radiologists Treat Ruptured Brain Aneurysms With Stent-Assisted Coil Embolization
Researchers in Finland have found that stent-assisted coil embolization provides effective new treatment option for patients who have suffered a ruptured brain aneurysm. The researchers studied the effects of stent-assisted embolization in 61 patients, who were treated for subarachnoid hemorrhage at three Finnish hospitals over a 4.5-year period. In the study, interventional radiologists performed coil embolization by first placing a stent, a small wire mesh tube, over the neck of the aneurysm to keep the coils within the aneurysmal sac. The procedure was a technical success in 72 percent of the 61 patient cases and adequate blood flow was restored in 64 percent of the patients. The study was published at Radiology Online on August 25, 2009.
From "Wide-Necked Intracranial Aneurysms: Treatment With Stent-Assisted Coil Embolization During Acute (<72 Hours) Subarachnoid Hemorrhage"
Radiology Online (08/25/09) Tahtinen, Olli I.; Vanninen, Ritva L.; Manninen, Hannu I.; et al.
Industry News
Dutch Reactor Resumes Output of Medical Isotope
The High-Flux Reactor in the Netherlands is back online to produce medical isotopes and the global manufacturer Covidien was expected to begin receiving molybdenum 99 in late August, helping to alleviate the shortage caused by the unexpected shutdown of the Chalk River reactor in Canada earlier this year. "This worldwide shortage affects the entire chain ... generator manufacturers, radiopharmacies, clinicians, and, most importantly, the patients," says John Collins, vice president of U.S. commercial operations for Covidien. "Though it comes at a cost, each of us is doing our part to maximize the availability of this crucial isotope to minimize patient impact."
From "Dutch Reactor Resumes Output of Medical Isotope"
Modern Healthcare (08/23/09) Zigmond, Jessica
Workload of Radiologists Increases in United States
In 2006-2007, the average annual workload per full-time equivalent (FTE) radiologist was 14,900 procedures, an increase of 7 percent since 2002-2003 and 34 percent since 1991-1992, according to a study published in the August 2009 issue of Radiology. Annual relative value units for each FTE radiologist were 10,200, an increase of 10 percent since 2002-2003 and 70.3 percent since 1991-1992. Academic practice performed approximately one-third fewer procedures per FTE radiologist than others. In the majority of practice types, radiologists in a 75th-percentile practice performed at least 65 percent more procedures annually than radiologists in a 25th-percentile practice. Additionally, regression analysis showed that practices using external off-hours teleradiology services performed 27 percent more procedures than otherwise similar practices that did not use these services.
From "Workload of Radiologists in United States in 2006-2007 and Trends Since 1991-1992"
Radiology (08/01/09) Vol. 252, No. 2, P. 458; Bhargavan, Mythreyi; Kaye, Adam H.; Forman, Howard P.; et al.
RSNA Weekly is a briefing of the latest radiology-related news selected from hundreds of sources by the editors of Information, Inc. While care is taken to use good sources, inaccuracies in source material are not the responsibility of RSNA or Information, Inc.
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