The potential role of positron emission mammography for detection of breast cancer. A phantom study

Positron emission mammography (PEM) is a new, specialized imaging modality utilizing PET radiopharmaceuticals to detect breast cancer. The capabilitie s and limitations of PEM in detecting breast tumors were investigated with a series of phantom experiments. The PEM imager was mounted on a standard L orad biopsy table (separated by 18 cm). In the initial phase of the investi gation, basic scanner parameters (resolution, sensitivity, and scatter frac tion) were measured. The effects of a number of breast imaging parameters ( length of acquisition, breast thickness, and breast density) on detection o f breast lesions were then explored utilizing special phantoms. Moderately compressed breasts were simulated with a block of gelatin containing amount s of FDG consistent with 370 MBq injections. Lesions were simulated with fo ur hollow spheres (inner diameters=5 mm, 8 mm, 12 mm, and 15 mm) filled wit h amounts of FDG representative of uptake in malignant breast tumors (targe t-to-background concentration ratio=8.5:1). Resolution at the center of the imager was 3.9 mm, sensitivity was 0.059 kcps/kBq/ml and the Compton scatt er fraction was similar to 12%. Objects as small as 8 mm in diameter could be detected after 30 s of data acquisition; 5 mm spheres were detectable af ter 300 s. Object detection capabilities were reduced with increasing breas t thickness. In thin compressed breasts (2 cm) even the smallest sphere (5 mm in diameter) could be detected; increasing breast thickness increased th e minimum detectable sphere diameter to 8 mm. increased background activity caused by FDG uptake in metabolically active normal tissue more prevalent in radiodense breasts compared to "fatty" breasts was simulated and shown t o reduce the minimum detectable lesion size to 12 mm for the densest breast s. These results demonstrate the potential of PEM for the detection of brea st lesions. The addition of the system to a standard biopsy apparatus indic ates its potential for use to guide some core biopsies of breast cancers. ( C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)0300 8-X].