Breast Radiation Too High for Routine FDG-PET/CT

A recent study was conducted to determine the average radiation to breast tissue from combined FDG-PET/CT imaging.

FDG-PET/CT radiation to breasts is higher than the ACR recommendations; therefore, this modality should be limited to only necessary imaging.

Methodology
This retrospective study included 21 female patients (age range, 25 to 77 years; mean age, 50.8 +/- 16.23 years) with both breasts, who voluntarily underwent combined FDG-PET/CT imaging.
Each patient had been administered 50 mL of oral contrast diluted in 1500 mL of water at midnight before imaging. Thermoluminescence dosimeters (TLDs) were taped onto each breast and were sensitive to 100 mGy or 10 mrad to 1 Gy of radiation and were removed 24 hours after FDG-PET/CT imaging. Any nervous or shivering patient was also given 5 mg of Valium prior to FDG injection.
Each patient was administered approximately 14.0 mCi (522 MBq) of F-18 FDG intravenously with imaging (extending from the top of the head to mid-thighs) 60 minutes later. To determine the average breast radiation dose from low-dose CT scanning, an anthropomorphic dosimetric phantom, with its tissue-equivalent breast, was imaged with the same CT protocol, with TLDs placed on its surface.

Results
The mean superficial breast dose was found to be 14.42 +/- 2.41 mGy. For the phantom study, the average breast radiation dose with the low-dose CT for skin and glandular breast tissue was 9.50 mGy and 5.94 mGy, respectively. For each PET/CT study, the total effective dose was determined by summing the external transmission and internal emission components. These Results showed that this radiation exposure greatly exceeds the American College of Radiology (ACR) recommendation of 3 mGy (0.300 rad) or less for standard two-view mammography.

Reviewer’s Comments
The radiation dose to breasts during combined FDG-PET/CT imaging is higher than the ACR recommended doses; therefore, this type of imaging should be performed only when it is essential and can be justified.

The authors believed this to be particularly true in women of reproductive age.
Author: Twyla Bartel, DO

Reference:
Halac M, Yilmaz MH, et al. Female Breast Surface Radiation Exposure During FDG PET/CT Examinations.
Nucl Med Communications; 2007; 28 (December): 924-928