Early clinical results from PEM 1: a high resolution system for positron emission mammography

The authors report first results of the stage one clinical trial performed with the Positron Emission Mammography-1(PEM-1) scanner. Patients selected are >20 years of age with no history of treatment for cancer, recently diagnosed with an unclassified tumour mass of <2 cm diameter in one breast. A 2 mCi (74 MBq) injection of 2-[18F]-fluoro-deoxy-2-D-glucose (FDG) is given 40 minutes prior to scanning. The scan is a two step process. (1) The patient´s mammogram is obtained with the tumour and a co-registration tool in the field-of-view (FOV). (2) Without moving the patient, the PEM detectors are moved in and emission data is collected for up to 5 minutes. The mammogram is digitized and fused with the reconstructed PEM image. To date, the authors have scanned eleven patients. In one subject a tumour <1 cm in diameter was localised visually as a hot spot 1.2 cm×0.8 cm in two dimensions. There was close to 4:1 increase in the focal uptake of FDG at the tumour site. Knowing the thickness of the compressed breast one can locate the tumour depth within the breast. There have been five true-positive results×these subjects were all correctly diagnosed by PEM-1 as having breast cancer; four true-negative results these subjects tested negative for breast cancer with PEM-1 and were surgically confirmed as being cancer free. There have been two false-negative results-the reasons for these are discussed in the text. The PEM-1 system is a high resolution, high efficiency and affordable system which can produce emission images accurately co-registered with X-ray mammographic images using at most 1/5 the F18-FDG and imaging for at most 1/5 the time required when conventional PET instruments are used