Andrew Polemi, Zongyi Gong, Tushita Patel, Kelly Klanian, Jonathan Nguyen, Luke Lancaster, Carrie Rochman, Matthew Miller, Jennifer Harvey, Patrice Rehm, Heather Peppard, Gina Petroni, Mark Williams
KEYWORDS: Digital breast tomosynthesis, Breast, Biopsy, Nuclear medicine, Scanners, Diagnostics, Breast imaging, Cameras, Image quality, Digital mammography
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.
A new low profile gamma camera is being developed for use in a dual modality (x-ray transmission and gamma-ray
emission) tomosynthesis system. Compared to the system’s current gamma camera, the new camera has a larger field of
view (~20x25 cm) to better match the system’s x-ray detector (~23x29 cm), and is thinner (7.3 cm instead of 10.3 cm)
permitting easier camera positioning near the top surface of the breast. It contains a pixelated NaI(Tl) array with a crystal
pitch of 2.2 mm, which is optically coupled to a 4x5 array of Hamamatsu H8500C position sensitive photomultiplier
tubes (PSPMTs). The manufacturer-provided connector board of each PSPMT was replaced with a custom designed
board that a) reduces the 64 channel readout of the 8x8 electrode anode of the H8500C to 16 channels (8X and 8Y), b)
performs gain non-uniformity correction, and c) reduces the height of the PSPMT-base assembly, 37.7 mm to 27.87 mm.
The X and Y outputs of each module are connected in a lattice framework, and at two edges of this lattice, the X and Y
outputs (32Y by 40X) are coupled to an amplifier/output board whose signals are fed via shielded ribbon cables to
external ADCs. The camera uses parallel hole collimation. We describe the measured camera imaging performance,
including intrinsic and extrinsic spatial resolution, detection sensitivity, uniformity of response, energy resolution for
140 keV gamma rays, and geometric linearity.
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