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Weight-Based PET-CT Protocols Seem to Cut Radiation Risk
Study shows 43% reduction in dose during whole-body imaging
by Ed Susman, Contributing Writer, MedPage Today November 29, 2015
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Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
CHICAGO -- Reductions in radiation dose may be achieved by using a patient-specific, weight-based protocols during whole-body FDG PET/CT imaging, researchers reported here.
The radiation dose can be reduced by 43% (P<0.0001), according to Charbel Saade, PhD, of the American University in Beirut, and colleagues.
That dose reduction translated to a 69% in the lifetime attributable risk to female patients and a 21% reduction is radiation-related injury to male patients, Saade's group reported at the Radiological Society of North America (RSNA) meeting.
"With the expanding use of PET/CT, ionizing radiation may eventually result in an increased incidence of cancer in the exposed population. This problem can be minimized by optimizing the CT protocol to achieve optimal image quality with the lowest possible radiation dose," the authors wrote.
For the study, more than 500 consecutive patients were referred for FDG- PET-CT studies. The heights and weights of each group was about the same, and Saade said there were no significant differences in body mass index, body surface area, and lean body weight for men or women.
Patients were allocated to one of two scanning protocols: A conventional protocol with a 120 kVp and 120 mAs dose (group A), and a weight-based protocol (group B), as follows:
60 kg (about 132 lbs): 140 kVp, 35 mAs
60-80 kg: 140 kVp, 50 mAs
80-100 kg: 140 kVp, 65 mAs
>100 kg: 140 kVp, 100 mAs
"Age and sex-specific lifetime attributable risk (LAR) of individual cancers were estimated using the approach of BEIR VII and summed to obtain whole body LAR," the authors explained.
The mean effective volume CT dose index (CTDIvol) and dose length product (DLP) was significantly reduced in group B (CTDIvol 4.60, DLP 823.35 mSv) versus group A (CTDIvol 7.36, DLP 1,260.96 mSv, P<0.0001).
Mean FDG administration demonstrated no significant differences in each protocol (P=0.873), the authors reported. In addition, the contrast-to-noise ratio demonstrated no differences between each group (P<0.21).
The mean LAR cancer risk was significantly reduced for women by 35% and for men by 125% in group B versus group A (P<0.04).
Saade stated that the differences in the doses did not appear to affect the imaging results, but his group is now assessing if the lower dose had an impact on image quality.
"Dose reduction is a very hot topic, and the question is whether or not to adopt these protocols in cancer patients who are undergoing CT, and whether the reductions are really that acute in this population," commented RSNA session moderator Andrew Quon, MD, of Stanford University in Stanford, Calif.
Quon told MedPage Today that the use of weight-based protocols is on the rise, but pointed out that when patients with cancer undergo imaging, "optimal imaging quality should be the first goal, and dose reduction should be second. The most important thing we can do is have sharper images so we know more about how to treat the patients."
Quon added that weight-based protocols to reduce radiation exposure among pediatric patients could be meaningful.
Saade and co-authors disclosed no relevant relationships with industry.
Quon disclosed no relevant relationships with industry.
Radiological Society of North America
Source Reference: Saade C, et al "Body Weight-based Protocols during Whole Body FDG PET/CT Significantly Reduces Radiation Dose without Compromising Image Quality" RSNA 2015; SSA015-09.