Instrumentation for Positron Emission Mammography

Feasibility and promise of early instruments

Through a collaboration with Weinberg, the first experiments to examine the concept were published in 1993 [5], and the name “positron emission mammography” (PEM) was coined to represent this technique. The concept was to place two planar detectors capable of detecting the 511 keV annihilation photons in a conventional mammography unit. Placing the breast on a “magnification table” sometimes used in these instruments provides the possibility of having one detector between the radiograph tube

Evolution of positron emission mammography instruments

When performing WB-PET scans, it is a simple matter to overscan the regions most likely to harbor metastases, and to overlap the bed positions to compensate for the reduced sensitivity toward the axial ends of each set of slices caused by the fall-off in three dimensional (3D) sensitivity in the scanner. When imaging the breast with PET detectors in a mammographic configuration, this is not possible, as illustrated in Fig. 2. Even when the detectors are placed very close to the chest wall, some

Early clinical findings

In 1999, the author's group published the results of the first clinical trial of any PEM instrument [12]. During the clinical trial of the PEM-1 scanner, we studied 14 patients, 10 of whom had various breast cancers confirmed by pathological investigation of the surgically excised specimens. Only 5 of these had a clearly focal uptake (with a mean contrast of 5.8:1 with respect to the surrounding breast tissue). Three other patients were considered PEM-positive on the basis of a significant

Recent clinical findings

The first report of clinical results from PEM Flex was published by Weinberg and coworkers earlier this year [14]. They reported on 94 cases performed at four different sites during the first year of use of the instrument. Analysis of these cases showed a sensitivity of 93% and a specificity of 83%.

Fig. 6 is an example of a PEM image from this instrument. Unlike the PEM-1 scanner, the field of view is much larger, 24 × 18 cm rather than 5.5 × 6.0 cm. The device also employs a sophisticated

Future prospects for positron emission mammography

In the United States, Medicare approval for use of PET imaging of breast cancer was given in late 2003 [17]. Unlike the approvals granted for PET in other forms of malignant disease, the approval document refers to three specific areas: initial staging of axillary lymph nodes, detection of loco-regional recurrence or distant metastasis/recurrence, and evaluating response to treatment. Although this is intended for the use of conventional WB-PET scanners, there is an opportunity for the

Acknowledgments

The author gratefully acknowledges support from the Natural Science and Engineering Council of Canada over the last 15 years. PEM research at the McGill University teaching hospitals has been a team effort. The work of Dr. R Lisbona, Chairman of the Radiology Department, and Dr. Antoine Loutfi of the Surgical Oncology unit of the McGill University Health Centre: Royal Victoria Hospital played vital roles in the success of this project. Students Kavita Murthy, Yani Picard, James Robar, Alanah