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Improving CT Safety

Improving CT Safety

CT is a powerful diagnostic technology, but it is also associated with risks. Ionizing radiation can damage cells and act as a weak carcinogen. The challenge is to find the optimal x-ray dose for each CT exam. “About 80 million CTs are performed each year in the United States,” says John M. Boone, PhD. “The higher the dose, the better the images, but we also want the lowest possible dose so that patients are protected from unnecessary radiation exposure. The key is to find the balance between acceptable image quality and acceptable doses.” New Strategies The Journal of the American College of Radiology (JACR) recently devoted an entire issue to CT safety. Dr. Boone and other specialists from the University of California, Davis contributed three studies to the special issue. In one of the JACR papers, the need to improve dose calculations was discussed. Manufacturers use phantoms along with instruments to measure radiation, but different companies use phantoms of different sizes, making comparisons problematic in some cases. To prevent these problems, a new metric, the size-specific dose estimate (SSDE), is recommended. “SSDEs can provide a better way to estimate patient doses and can help compare scanners from different companies,” says Dr. Boone. SSDEs may also address the need to more accurately estimate CT doses from a range of patient sizes, especially in pediatric patients. The second JACR paper addressed the challenges of optimizing different CT machines. Automatic exposure protocols must be set up, but this can vary doses based on tissue thickness. “Transferring these settings between machines can be difficult and time consuming,” Dr. Boone says. To overcome this...
Safety of Contrast Agents in the Critically Ill

Safety of Contrast Agents in the Critically Ill

Ultrasound contrast agent safety in critically ill patients undergoing echocardiography has been questioned by the FDA. This controversy was the result of rare reports showing that deaths or life-threatening adverse reactions occurred in close proximity to the administration of ultrasound contrast agents. “Since these reports surfaced around 2007, many studies have been conducted to better define the safety profile of these agents,” says Michael L. Main, MD. An Observational Analysis In a large observational study published in JACC: Cardiovascular Imaging, Dr. Main and colleagues compared 48-hour all-cause mortalities and hospital stay mortalities among critically ill patients who underwent echocardiography either with or without an ultrasound contrast agent. Data were collected on more than a million participants through discharge information from a database that included information on primary and secondary diagnoses, procedure billing codes, and demographic and baseline patient information in addition to hospital characteristics. At discharge, more than 990,000 patients underwent echocardiography without a contrast agent, whereas 16,222 received a contrast agent for their exam. According to the results, ultrasound contrast agent use was associated with a 28% lower mortality rate at 48 hours among critically ill patients undergoing echocardiography when compared with no ultrasound contrast agent use. Recipients of ultrasound contrast agents also had significantly lower mortality rates over their entire hospital stay when compared with those who did not receive one (14.85% vs 15.66%). “Importantly, our findings were consistent across a wide variety of major comorbidities and important demographic subgroups, such as age and gender,” says Dr. Main. Overall, there were no groups with significantly greater odds for mortality after receiving a contrast agent. Impactful Findings Data...
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