Proper CT positioning dramatically cuts patient dose

May 17, 2007

Vendors are pouring money into R&D aimed at reducing radiation dose to patients when a simpler, more immediate answer might be at hand: positioning patients correctly before scanning.

Vendors are pouring money into R&D aimed at reducing radiation dose to patients when a simpler, more immediate answer might be at hand: positioning patients correctly before scanning.

Research conducted at Massachusetts General Hospital in Boston suggests that the vast majority of patients undergoing CT may be exposed to much more radiation than needed because technologists don't center them appropriately on the scanner gantry table. Proper positioning can reduce radiation dose by as much as 56%, according to the MGH research.

The researchers' conclusions are based on a study of 63 CT patients. Forty-two of the 45 patients undergoing abdominal CTs and all of the 18 patients undergoing chest CT were found to be off center, according to Dr. Mannudeep Kalra, a radiology fellow at MGH in Boston.

As part of the study, the 63 patients were positioned on the scanner gantry table by a radiology technologist following standard department protocol. An x-ray was taken of the initial positioning of the patient. The CT scanner's laser guidance system estimated the point where the patient would be centered on the gantry table. The researchers then used an automatic centering technique to determine the true center point.

Patients were off center by 5.5 mm to as much as 64 mm for chest CT examinations and from 5.5 mm to 56 mm for abdominal CT exams, he said.

When the automatic centering technique was used to center the patients appropriately, radiation dose was cut anywhere from 7% to 29.9% in chest CT examinations and 5.5% to 56% for abdominal CT exams, he said.

"This study emphasizes that radiologists and technologists must pay close attention to patient centering," Kalra said. "In addition, vendors are encouraged to develop and assess techniques that aid the technologist in accurate patient centering."