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Robots reduce radiation exposure. (Research And Technology).

Robot guidance during interventional procedures could significantly reduce radiation exposure to both personnel and patients, according to a study in the October issue of the journal Radiology.

The study involved 16 patients scheduled for interventional procedures guided by computed tomography (CT) fluoroscopy. In each case, needles were placed with robotic assistance using a joystick or other remote-control device.

Normally, a physician positions the needle manually, with his or her hands near the scanning plane. Radiation exposure for physician and patient can be high. Lead drapes sometimes can be used to reduce physician exposure, but also tend to be cumbersome.

Using the robotic technique, physicians' radiation exposure was negligible, researchers reported. Radiation exposure to the patient also may be reduced because continuous imaging is not necessary with robotic positioning. Furthermore, needle placement is more accurate with a robot's assistance.

False Positive Rates Vary With Radiologist's Age

Younger radiologists are 2 to 4 times more likely to identify false-positive findings on mammograms than radiologists trained more than 15 years ago, a study published in the September 18 issue of the Journal of the National Cancer Institute suggests.

The comparison of 24 radiologists' readings of 8734 screening mammograms revealed widely differing reporting rates for masses, calcifications and fibrocystic changes. False-positive rates ranged from 2.6% to 15.9%.

Radiologists with higher false-positive rates tended to be younger, male and more recent graduates of medical school. The researchers speculated that this may be related to a fear of malpractice lawsuits due to delayed detection of breast cancer. In addition, "Younger doctors may have had training that concentrated on finding cancer without emphasizing that false positives can cause a lot of women who don't have breast cancer to be called back for additional tests," said Joanne Elmore, M.D., one of the study's authors.

In an editorial that accompanied the report, researchers from the Fred Hutchinson Cancer Research Center in Seattle, Wash, recommended changes that could help reduce false-positive rates and improve accuracy, such as double reading of mammograms.

CT Beats Pyelograms For Finding Stones

Noncontrast helical CT is significantly better than intravenous pyelography (IVP) at detecting calculi in the urinary tract, according to a meta-analysis of 4 previously published studies. The analysis, published in the September issue of the Annals of Emergency Medicine, also noted that CT exams are faster, require no contrast media and can be used to evaluate disease outside the urinary tract.

The 4 studies included in the meta-analysis involved 296 patients with suspected acute urolithiasis. All of the patients underwent CT first, followed by an IVP. Because patients may have passed stones between the 2 examinations, the results may be biased in favor of CT, the researchers noted.

Equation Trumps Ultrasound For Predicting Birth Weight

A mathematical formula based on an expectant mother's height and weight plus several pregnancy-specific factors allows physicians to more accurately predict a baby's birth weight than a prenatal ultrasound examination, according to a report in the September issue of the Journal of Reproductive Medicine.

Physicians at Duke University and California State University predicted birth weights within an average of [+ or -] 8% of actual birth weights in 244 full-term infants born to nonhypertensive, nondiabetic women. The formula they used factors in the woman's rate of weight gain during the third trimester, number of previous births, the fetus' sex and gestational age at the time of delivery, as well as maternal height and weight.

"This equation turns out to be a costless way to estimate birth weights very accurately," coauthor Gerard G. Nahum, M.D., told Reuters Health. "It's better than ultrasound, it doesn't require any special testing or equipment and it is calculable with 1 to 2 minutes by anybody who plugs in the numbers." The formula could be used to easily and inexpensively determine women who are at risk of delivering very large babies and may need early induction of labor, the researchers said.

CT Screening for Lung Cancer Needs More Study, Researchers Caution

Preliminary results of a large randomized trial indicate that CT scans used for lung cancer screening yield many false-positive findings and should not be recommended to the public without further study, researchers reported in the October issue of the American Journal of Roentgenology.

"The bottom line is that we (as doctors) must be sure that we are not doing more harm than good," said Stephen Swensen, M.D., chairman of radiology at the Mayo Clinic in Rochester, Minn. Dr. Swensen is a principal investigator for the National Lung Screening Trial, the randomized trial of CT screening for lung cancer conducted by the National Cancer Institute. The trial will involve 50 000 participants at 30 clinical sites, including the Mayo Clinic. Results will be published by 2009.

Proponents of CT screening for lung cancer argue that early detection gives patients the best chance of survival. Critics point out that there is no proof that early detection prolongs survival for lung cancer patients. CT screening also carries risks, including radiation exposure and possible false-positive results, which may lead to unnecessary worry and distress for patients, potential surgical complications and costly follow-up tests. Patients should be warned of such risks, Dr. Swensen said.

Study Finds Moving-bed MR Effective In Diagnosing Peripheral Vascular Disease

Magnetic resonance (MR) imaging using a moving bed may one day displace digital subtraction angiography (DSA) as the gold standard for diagnosing vascular disease in the pelvis, legs and feet. Not only is the MR technique safer and more comfortable for the patient, it also offers diagnostic accuracy greater than 95%, according to researchers at the University of Vienna in Austria. Their study, published in the October issue of the American Journal of Roentgenology, examined 106 patients using both moving-bed MR angiography (MRA) and DSA.

In moving-bed MRA, patients are placed on a table that moves through the MR machine. The pelvis, thighs and calves can be imaged in a single 15-minute procedure with one injection of contrast media. MRA is an outpatient procedure, whereas DSA may require a hospital stay.

Another advantage of moving-bed MRA is that unlike DSA it requires no radiation. Because peripheral vascular disease tends to recur, patients often undergo repeated imaging procedures and radiation exposure is an important concern.

In the Austrian study, MRA failed to show the severity of vascular disease in the calves of a few patients. "This is due, in part, to the fact that the calf region was the last area to be imaged and the contrast media was less effective in enhancing the image," explained the study's lead author, Christian Loewe, M.D. Researchers are studying ways to speed up the imaging process to avoid this problem.

Between 4% and 9% of men older than 55 are affected by peripheral vascular disease. Some of them are not good candidates for moving-bed MRA, including those with pacemakers, defibrillators and other implanted devices.

Research & Technology showcases the latest findings of research as well as industry news and new product and materials development in the radiologic sciences. Health and research organizations and commercial interests should send information to Managing Editor Katie Racette, c/o The American Society of Radiologic Technologists, 15000 Central Ave. SE, Albuquerque, NM 87123-3917.
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Author:Racette, Katie
Publication:Radiologic Technology
Geographic Code:1USA
Date:Nov 1, 2002
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