Development of a multiple view limited angle dual modality breast imaging system

Nuclear medicine breast imaging techniques are being considered as complementary modalities to x-ray mammography for breast cancer diagnosis and characterization, for evaluation of metastases, and as an aid in the selection of appropriate therapies. Because the positive predictive value of x-ray mammography is only 20%--30%, nuclear medicine imaging is a way of obtaining functional or metabolic information that could potentially decrease the number of unnecessary biopsies performed, by helping to characterize the lesion and may also act as an adjunct detection modality for patients with radiodense breasts. Conventional gamma cameras used for breast imaging (scintimammography) have shown to suffer from low sensitivity for small lesions due to poor spatial resolution. Also, scintimammography is performed with the patient prone and the breast uncompressed making it difficult to correlate structures seen on the gamma images with those seen in the mammogram. This has motivated the need for dedicated breast imagers that have improved intrinsic spatial resolution, that can be positioned close to the breast and that can be integrated with x-ray mammography.; A novel dual modality breast scanner has been developed that can acquire x-ray transmission and gamma ray emission images in succession at multiple viewing angles with the breast held in a fixed configuration under mild compression. These views are then reconstructed and fused to obtain three-dimensional images that combine structural and functional information. Results are presented from phantom experiments designed to test the system's ability to obtain volumetric dual modality data sets from a limited number of projections, acquired over a limited (less than 180 degrees) angular range. These results demonstrate that limited angle tomography can reduce the negative impact of the overlying tissue on lesion detectability and improve the image contrast of deep-seated lesions. Analysis of the lesion contrast and signal to noise ratio as a function of angular range with a fixed number of equally spaced views, shows that both the contrast and SNR decrease with increasing angular range. On the other hand, the spatial resolution in the direction parallel to the direction of compression improves with increasing angular range. Based on the results so far, it is encouraging that diagnostically useful three-dimensional volumes might be reconstructed using as few as 5 views. (Abstract shortened by UMI.)...