| Naval Medical Center San Diego Cuts CT Scan Radiation Exposure In Half

By Mass Communication Specialist 2nd Class Chelsea A. Radford, NMCSD Public Affairs Office


SAN DIEGO - The radiology department at Naval Medical Center San Diego (NMCSD) has cut the radiation doses in half from the national average given to patients through a new Flash computed axial tomography (CT) scanner.


NMCSD purchased a new CT scanner, costing approximately 2.5 million dollars, in order to provide the most advanced imaging capabilities in addition to minimizing the radiation dosage on patients.


“Radiation dosing has become a hot topic,” said Cmdr. (Dr.) Ronald J. Boucher, Chairman of the NMCSD and Radiology Assistant Specialty Leader. “Half of the ionizing radiation exposure that the American public receives comes from natural background radiation while the other half comes from man-made sources, where medical imaging procedures account for nearly all of this type exposure. It is this area where we can control and minimize radiation dose delivered to the patient through our technology.” NMCSD is the only Department of Defense hospital in the country to have the new Flash CT scanner. NMCSD has effectively cut the radiation doses in half in the span of five years, and up to 95% in most cardiac scans, from a nationwide average of 21 millisieverts (mSv) to one or two mSv. A millisievert is the way to measure radiation doses.


“A legacy CT scan will traditionally put out a higher dose of radiation-until recently. The increased use of CT scanning has largely been driven by the better diagnostic capabilities of this tool” said Dr. Gilbert Boswell, NMCSD’s Senior Body Imager. “What is new is that we now have ways to more specifically tailor exams to lower radiation doses.”


The most common CT scan performed is of a patient’s head followed by CT of the abdomen or pelvis and chest. The amount of radiation required is determined by the body part that is being imaged (due to different tissue density) and the required image quality needed to diagnose the problem. Radiologists follow the “ALARA” principle, which means the radiation they use is “as low as reasonably achievable.”


“A long time ago, if someone had suspicion of appendicitis, the diagnosis would be based on a physical exam and the patient would be sent to the operating room. We know that up to a quarter of these patients may not have had appendicitis. Now that number is much lower because CT scans have totally changed the process. We use it to identify things we could never identify before, like appendicitis and kidney stones for example,” said Boswell.


NMCSD tracks and records radiation doses in order to find trends. The new Flash CT scanner has two X-Ray tubes configured to scan a patient much more quickly and efficiently compared to the single tube the original CT scanner had. Providers are able to significantly lower radiation doses with this faster scan along with techniques to filter the radiation delivered. A CT scanner without the new technology would produce a head-to-toe image in about 30 seconds, while the new Flash CT scanner will produce the same image in five seconds.


“The two tubes allow us to increase the speed of the scan,” said Boswell. “It also allows us to minimize the dose duration, while still creating a high quality image.”


There are three steps to lowering the radiation dose. The first step is finding out if the patient medically requires a CT scan. The referring doctor obtains a detailed medical history, which allows the radiologists to create an appropriate protocol for scanning. The second step is to individualize the dose for each patient. The radiologist will find out the height, weight, age and body mass index , along with the reason for the study, of the patient to discern how much radiation is needed. The third step is using the technology to capitalize on the advanced dose reduction techniques to take the scan.


“We want to do whatever we can at our level to minimize radiation dose to the patient without compromising the image quality to produce an accurate diagnosis,” said Boucher.


NMCSD’s radiology department performs more than 100 CT scans per day, with three modern CT scanners including the newest Flash CT scanner. The Flash CT Scanner was implemented in May of this year and placed in the emergency department to improve patient throughput and physician interaction.


For more information on Radiology, please visit www.navy.mil/local/sd or call the Radiology Department at (619) 532-8666.