The value of adding 99mTc- sestamibi MBT to the current clinical standard of DBT plus 2D digital mammography (MM) was assessed. Images were acquired using a dual modality tomosynthesis (DMT) scanner designed to obtain superimposable DBT and MBT images. Seventy-five subjects with 83 biopsied lesions were scanned prior to biopsy. A blinded MQSA-certified breast radiologist with limited nuclear medicine (NM) experience viewed the images in the following sequence: 1) DBT alone, 2) add MM, and 3) add MBT (equivalent to DMT+MM). MM images were from each subject’s most recent clinical mammographic exam. At each stage, all findings were scored using a 5-point suspicion scale ranging from 1=definitely benign, to 5=definitely malignant. Independently, a blinded, experienced NM radiologist scored all MBT scans without access to the DBT or MM images, using the same suspicion scale. The NM results were provided to the breast radiologist reader following their 3-stage evaluation, and a fourth suspicion score was recorded for all findings. Using location-confirmed biopsy results as ground truth, ROC curves and the areas under the curves, Az were generated for each of the four stages, and for MBT alone. Compared to DBT+MM, the changes in Az for MBT alone, DBT, and DMT+MM were +21.4% (p<0.02), -22.1% (p<0.01), +25.2% (p<0.002), respectively. Addition of the NM report to DMT+MM had no measurable effect on ROC shape or Az value. These results suggest that hybrid tomosynthesis can potentially improve DBT diagnostic performance; that breast radiologists with limited nuclear medicine experience might nevertheless effectively utilize MBT information; and that stand-alone MBT could be a valuable complementary tomographic modality.
This work describes a methodology for efficient removal of scatter radiation during digital breast tomosynthesis (DBT). The goal of this approach is to enable grid image obscuration without a large increase in radiation dose by minimizing misalignment of the grid focal point (GFP) and x-ray focal spot (XFS) during grid reciprocation. Hardware for the motion scheme was built and tested on the dual modality breast tomosynthesis (DMT) scanner, which combines DBT and molecular breast tomosynthesis (MBT) on a single gantry. The DMT scanner uses fully isocentric rotation of tube and x-ray detector for maintaining a fixed tube-detector alignment during DBT imaging. A cellular focused copper prototype grid with 80 cm focal length, 3.85 mm height, 0.1 mm thick lamellae, and 1.1 mm hole pitch was tested. Primary transmission of the grid at 28 kV tube voltage was on average 74% with the grid stationary and aligned for maximum transmission. It fell to 72% during grid reciprocation by the proposed method. Residual grid line artifacts (GLAs) in projection views and reconstructed DBT images are characterized and methods for reducing the visibility of GLAs in the reconstructed volume through projection image flat-field correction and spatial frequency-based filtering of the DBT slices are described and evaluated. The software correction methods reduce the visibility of these artifacts in the reconstructed volume, making them imperceptible both in the reconstructed DBT images and their Fourier transforms.