A Novel Detection System Consisting of a Large Area Sensor and a Multi-Cell Si-Pad Array Operated in Spectroscopic Mode for X-Ray Breast Imaging

The ability of coherent x-ray scatter to provide the molecular structure of breast tissues could add a new dimension in x-ray breast imaging capable of tracking the molecular structural changes during disease progression and (if improving the sensitivity to low-contrast lesions without increasing the radiation dose. Work is under way to build a laboratory prototype dual-sensor breast-imaging scanning system, which combines the diagnostic information from both the transmitted primary and the forward scattered x-rays. This required the design and development of a coherent x-ray scatter detection system based on a high-resistivity multi-element 2D Si-pad array, a multi-channel low-noise pulse processing front-end electronics chip, the XA1.3, and a new DAQ system. Results on the characterization and optimization of the detector-readout electronics-DAQ system and its performance to measure diffraction signatures are presented.</p

Image-quality performance of an a-Si: H-based X-ray imaging system for digital mammography

We have been investigating the potential of large area active matrix flat-panel a-Si : H imaging arrays for full-field digital X-ray mammography. To optimise the overall performance of such an imaging system under mammographic conditions, four different Gd2O2S : Tb phosphor screens (i.e. Lanex Fast-Back, Regular, Fine and MinR-2000) were employed and our full-field detector was integrated with the Feinfocus DIMA (Direct Magnification) PLUS MII mammographic unit. The spatial resolution and the image noise of the digital detector were measured and the X-ray imaging performance of the whole system was also evaluated with two mammographic phantoms. It was deduced from the results of this study that Regular screen offers the best compromise between sensitivity and spatial resolution and exhibits better overall image-quality performance than that of a conventional mammography system

Development of a patient-specific two-compartment anthropomorphic breast phantom

PURPOSE: To develop a technique for the construction of a two-compartment anthropomorphic breast phantom specific to an individual patient’s pendant breast anatomy. METHODS: Three-dimensional breast images were acquired on a prototype dedicated breast computed tomography (bCT) scanner as part of an ongoing IRB-approved clinical trial of bCT. The images from the breast of a patient were segmented into adipose and glandular tissue regions and divided into 1.59 mm thick breast sections to correspond to the thickness of polyethylene stock. A computer controlled water-jet cutting machine was used to cut the outer breast edge and the internal regions corresponding to glandular tissue from the polyethylene. The stack of polyethylene breast segments was encased in a thermoplastic “skin” and filled with water. Water-filled spaces modeled glandular tissue structures and the surrounding polyethylene modeled the adipose tissue compartment. Utility of the phantom was demonstrated by inserting 200 μm microcalcifications as well as measuring point dose deposition during bCT scanning. RESULTS: Rigid registration of the original patient images with bCT images of the phantom showed similar tissue distribution. Linear profiles through the registered images demonstrated a mean coefficient of determination (r(2)) between grayscale profiles of 0.881. The exponent of the power law describing the anatomical noise power spectrum was identical in the coronal images of the patient’s breast and the phantom. Microcalcifications were visualized in the phantom at bCT scanning. Real-time air kerma rate was measured during bCT scanning and fluctuated with breast anatomy. On average, point dose deposition was 7.1% greater than mean glandular dose. CONCLUSIONS: A technique to generate a two-compartment anthropomorphic breast phantom from bCT images has been demonstrated. The phantom is the first, to our knowledge, to accurately model the uncompressed pendant breast and the glandular tissue distribution for a specific patient. The modular design of the phantom allows for studies of a single breast segment and the entire breast volume. Insertion of other devices, materials, and tissues of interest into the phantom provide a robust platform for future breast imaging and dosimetry studies

Contrast cancellation technique applied to digital x-ray imaging using silicon strip detectors

Dual-energy mammographic imaging experimental tests have been performed using a compact dichromatic imaging system based on a conventional x-ray tube, a mosaic crystal, and a 384-strip silicon detector equipped with full-custom electronics with single photon counting capability. For simulating mammal tissue, a three-component phantom, made of Plexiglass, polyethylene, and water, has been used. Images have been collected with three different pairs of x-ray energies: 16–32 keV, 18–36 keV, and 20–40 keV. A Monte Carlo simulation of the experiment has also been carried out using the MCNP-4C transport code. The Alvarez-Macovski algorithm has been applied both to experimental and simulated data to remove the contrast between two of the phantom materials so as to enhance the visibility of the third one