Molecular breast imaging shows promise for surgical planning, screening

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An evolving nuclear medicine imaging technology, molecular breast imaging (MBI), is showing promise in the evaluation of diagnosed breast disease and as a breast cancer screening tool, according to studies presented at the American Society of Breast Surgeons Annual Meeting, held April 30 - May 4.
MBI visualizes disease through the functional uptake of radiotracer sestamibi (Tc-99m) using specialized breast imaging protocols and new high-resolution gamma cameras specifically engineered for breast applications, according to researcher Judy Boughey, MD, of the Mayo Clinic, who provided a review of several studies conducted at the Mayo clinic during the past six years.

MBI provides significantly higher resolution images than available in the early 1990s, when the radiotracer was first used in breast applications with more primitive cameras and techniques. Boughey believes that MBI is emerging as a useful modality in surgical treatment planning by finding multi-focal cancers in women diagnosed with only a single tumor through mammography. 

In a study of 53 breast cancer patients previously diagnosed with mammography and ultrasound, using a single-head gamma camera, MBI picked up 57 of 67 cancers for an overall sensitivity of 85 percent, she noted.

Additional research examined 120 diagnosed breast cancer patients imaged with the assistance of trained mammography technologists using a more advanced dual-head camera.  MBI delivered a 92 percent sensitivity overall in the detection of tumors and a significantly improved ability to pick up smaller cancers.

Boughey said in yet another study, 650 asymptomatic women at high risk for cancer were screened with the advanced camera.  MBI detected seven cancers, while conventional mammography picked up only two of these. Only one cancer was detected by mammography but not MBI.

An analysis of breast cancer cases across all studies found that MBI detected 187 cancers in 146 patients and was highly reliable for all forms of the disease.  Twenty-one of these lesions had not been found earlier using mammography, she said.

In all studies, Boughey said that breast cancers were eventually confirmed through pathology reports, suggesting that MBI may be a “useful surgical planning tool for further evaluation of women diagnosed with breast cancer.”

Boughey notes that the new dual-head cameras have been responsible, in part, for recent advances in MBI sensitivity.  The system, which was developed by Mayo Clinic physicists Michael O’Connor, PhD, and Carrie Hruska, PhD, uses recently developed, compact semiconductor-based gamma cameras incorporated into a newly designed breast imaging system.  Each breast is lightly compressed between the gamma cameras with enough pressure to stop movement during the five- to ten-minute imaging process, Boughey said.