Clinical Research Supports Promising Outlook for Low-Dose Molecular Breast Imaging

Dr. Marcela Bohm-Velez and her colleagues from Weinstein Imaging Associates (Pittsburgh, PA, USA) shared preliminary findings from a prospective study on low-dose MBI, specifically breast-specific gamma imaging (BSGI), at the SNM (Society of Nuclear Medicine) Breast Cancer Imaging: State of the Art 2011. Their results suggest it may be possible to reduce the radiation dose patients receive from a BSGI procedure by up to 60%.

The tracer used in this procedure, technetium Tc99m sestamibi (MIBI), has typically been used in cardiac studies for a long time and was cleared by the US Food and Drug Administration (FDA) in the mid-1990s for diagnostic breast imaging. The recommended dose (20 mCi - 30 mCi) was established using an older, larger, less sensitive whole body imaging system. Newer breast-optimized imaging systems have an inherently higher photon sensitivity that may allow a lesser dose to be used.

At the Weinstein Imaging Center, BSGI has become a valuable diagnostic tool, especially for patients with dense breast tissue that limits the effectiveness of mammography. "In order to optimize care and use BSGI to screen specific populations, we wanted to examine the possibility of using a lesser dose," said Dr. Bohm-Velez. "The present challenge for the clinician is that the use of lower doses is currently an off-label use of the pharmaceutical."

The study compared breast tissue uptake at low-dose levels of 5 mCi, 10 mCi, and 15 mCi to those obtained with the traditional 20 mCi (740 MBq) injections. According to Dr. Bohm-Velez, "Although these are early results, we were quite surprised to see that we can reduce the dose to 15 mCi without any substantial impact on breast tissue uptake or image quality. Moreover, a 10-mCi image still provided a very good, clinically viable image. The good news is that at lower doses, the breast tissue uptake is still sufficient; leading us to believe that a dose of 8 mCi is likely possible with the current instrumentation."

Dr. Bohm-Velez also mentioned current studies are underway at the University of Virginia (Charlotte, VA, USA) to allow potentially doses as low as 2-4 mCi to be used, making the radiation dose a patient receives from a BSGI/MBI study equivalent to that from a mammogram. According to Dr. Bohm-Velez, "The next steps are to gain the funding needed to expand this to a multicenter trial, investigate the impact of these optimizations, and hopefully, in the end, change the drug insert package to include low-dose breast imaging."

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Weinstein Imaging Associates