Breast-specific gamma imaging shows better sensitivity than other methods

Breast-specific gamma imaging demonstrates better specificity and sensitivity than mammography, ultrasound, and MRI, according to several studies presented at the RSNA meeting.

Dr. Rachel Brem, director of breast imaging and intervention at George Washington University Medical Center, and colleagues conducted a retrospective multicenter study on 26 women with biopsy-proven invasive lobular carcinoma. BSGI had the greatest sensitivity at 93%. Mammography, ultrasound, and MRI had sensitivities of 79%, 68% and 83%, respectively. BSGI also detected an additional suspicious occult lesion in 29% of women.

Dr. Leora Lanzkowsky, former medical director of the Eisenhower Medical Center in Rancho Mirage, CA, and colleagues conducted BSGI and breast MRI on patients with complex, inconclusive mammographic and/or ultrasonic findings. The researchers examined 48 patients and found 63 abnormalities.

BSGI and MRI yielded consistent results in 37 of these areas and were inconsistent in 26. MRI was inconclusive in a greater number of benign cases: 10 versus three on BSGI. The sensitivities of BSGI and MRI were 96% and 88%, respectively, with specificities of 46% and 27%.

The gamma technique images breast cancer differently from MRI, mammography, or ultrasound. Instead of approaching breast cancer in an anatomic way, BSGI examines how breast cancer functions differently from surrounding tissue. Due to an increased rate of metabolic activity, cancerous cells in the breast absorb a greater amount of the pharmaceutical tracing agent injected into patients than does the normal surrounding tissue. In this way, BSGI can find occult lesions as small as 1 mm.

The radiation dose of BSGI is similar to that of mammography, according to Bob Moussa, president and CEO of Dilon Technologies, a manufacturer of a BSGI camera.

"Our BSGI imaging room is directly across from our reading room. We don't have any extra shielding. Patients can just leave and come into the general public. It's a very low dose of radiation," Brem said.