Synchrotron based planar imaging and digital tomosynthesis of breast and biopsy phantoms using a CMOS active pixel sensor.

The SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline at Elettra is performing the first mammography study on human patients using free-space propagation phase contrast imaging. The stricter spatial resolution requirements of this method currently force the use of conventional films or specialized computed radiography (CR) systems. This also prevents the implementation of three-dimensional (3D) approaches. This paper explores the use of an X-ray detector based on complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology as a possible alternative, for acquisitions both in planar and tomosynthesis geometry. Results indicate higher quality of the images acquired with the synchrotron set-up in both geometries. This improvement can be partly ascribed to the use of parallel, collimated and monochromatic synchrotron radiation (resulting in scatter rejection, no penumbra-induced blurring and optimized X-ray energy), and partly to phase contrast effects. Even though the pixel size of the used detector is still too large - and thus suboptimal - for free-space propagation phase contrast imaging, a degree of phase-induced edge enhancement can clearly be observed in the images.

Dual-modality breast tomosynthesis.

PURPOSE: To evaluate the clinical performance of a hybrid scanner that uses dual-modality tomosynthesis (DMT) and technetium 99m sestamibi to provide coregistered anatomic and functional breast images in three dimensions. MATERIALS AND METHODS: A prospective pilot evaluation of the scanner was performed in women scheduled to undergo breast biopsy after institutional review board approval and informed consent were obtained. All subject data were handled in compliance with the rules and regulations concerning the privacy and security of protected health information under HIPAA. The study included 17 women (mean age, 53 years; age range, 44-67 years) and 21 biopsy-sampled lesions. Results of DMT scanning were compared with histopathologic results for the 21 lesions. RESULTS: Of the 21 lesions, seven were malignant, and 14 were benign. Among the 13 subjects with one lesion each, three had positive biopsy results, and 10 had negative biopsy results. Among the four subjects with two lesions, the biopsy results were as follows: bilateral in one, both negative; bilateral in one, both positive; unilateral in two, one positive and one negative. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of DMT scanning were 86%, 100%, 100%, 93%, and 95%, respectively. CONCLUSION: Pilot clinical evaluation of the DMT scanner suggests that it is a feasible and accurate method with which to detect and diagnose breast cancer. Systems such as the DMT scanner that are designed specifically for three-dimensional multimodality breast imaging could make possible some of the advances in tumor detection, localization, and characterization of breast cancer that are now being observed with whole-body three-dimensional hybrid systems, such as positron emission tomography/computed tomography (CT) or single photon emission computed tomography/CT.

Introducing DeBRa: a detailed breast model for radiological studies.

Currently, x-ray mammography is the method of choice in breast cancer screening programmes. As the mammography technology moves from 2D imaging modalities to 3D, conventional computational phantoms do not have sufficient detail to support the studies of these advanced imaging systems. Studies of these 3D imaging systems call for a realistic and sophisticated computational model of the breast. DeBRa (Detailed Breast model for Radiological studies) is the most advanced, detailed, 3D computational model of the breast developed recently for breast imaging studies. A DeBRa phantom can be constructed to model a compressed breast, as in film/screen, digital mammography and digital breast tomosynthesis studies, or a non-compressed breast as in positron emission mammography and breast CT studies. Both the cranial-caudal and mediolateral oblique views can be modelled. The anatomical details inside the phantom include the lactiferous duct system, the Cooper ligaments and the pectoral muscle. The fibroglandular tissues are also modelled realistically. In addition, abnormalities such as microcalcifications, irregular tumours and spiculated tumours are inserted into the phantom. Existing sophisticated breast models require specialized simulation codes. Unlike its predecessors, DeBRa has elemental compositions and densities incorporated into its voxels including those of the explicitly modelled anatomical structures and the noise-like fibroglandular tissues. The voxel dimensions are specified as needed by any study and the microcalcifications are embedded into the voxels so that the microcalcification sizes are not limited by the voxel dimensions. Therefore, DeBRa works with general-purpose Monte Carlo codes. Furthermore, general-purpose Monte Carlo codes allow different types of imaging modalities and detector characteristics to be simulated with ease. DeBRa is a versatile and multipurpose model specifically designed for both x-ray and gamma-ray imaging studies.

Mean glandular dose estimation using MCNPX for a digital breast tomosynthesis system with tungsten/aluminum and tungsten/aluminum+silver x-ray anode-filter combinations.

Breast cancer screening with x-ray mammography, using one or two projection images of the breast, is an indispensible tool in the early detection of breast cancer in women. Digital breast tomosynthesis (DBT) is a 3D imaging technique that promises higher sensitivity and specificity in breast cancer screening at a similar radiation dose to conventional two-view screening mammography. In DBT a 3D volume is reconstructed with anisotropic voxels from a limited number of x-ray projection images acquired over a limited angle. Although the benefit of early cancer detection through screening mammography outweighs the potential risks associated with radiation, the radiation dosage to women in terms of mean glandular dose (MGD) is carefully monitored. This work studies the MGD arising from a prototype DBT system under various parameters. Two anode/filter combinations (W/Al and W/Al+Ag) were investigated; the tube potential ranges from 20 to 50 kVp; and the breast size varied between 4 and 10 cm chest wall-to-nipple distance and between 3 and 7 cm compressed breast thickness. The dosimetric effect of breast positioning with respect to the imaging detector was also reviewed. It was found that the position of the breast can affect the MGD by as much as 5% to 13% depending on the breast size.