Flat Panel X-ray Sources for Digital Breast Tomosynthesis System

DESCRIPTION (provided by applicant): X-ray mammography continues to be the primary tool for breast cancer screening and plays an important role in the diagnosis and management of breast cancer. However, the difficulty in resolving overlapping structures in a 2D projection image leads to reduced sensitivity. A number of research groups and companies are developing dedicated breast tomographic systems to overcome this problem. Most of the systems are based on the conventional mammographic tube mounted on a rotating gantry. These systems have long acquisition times and are hence prone to motion blur. Here we propose to develop novel digitally addressable x-ray source (DAXS) panels suitable for use in a prototype digital breast tomosynthesis (DBT) system to be built in Phase II in collaboration with MD Anderson Cancer Center (MDACC). The DAXS uses an innovative architecture in which field emission current from arrays of cold cathode field emitters formed in pixel configurations on the source exit window generates x-ray flux from a target opposite the exit window. The flux then passes through the emitters, out the window and on to the subject. The metal x-ray target is a broad, flat sheet or slab which forms part of the vacuum envelope. Depending on the pitch between emitters, over 10,000 emitters can be patterned per mm2. We have demonstrated in previous work currents of over 505A from single emitters, so high current densities (e.g. 500 mA per mm2, or about 50mA from the typical 0.3 mm spot size in mammography) are possible. Here we will continue to improve the current density and will also test the use of electron hop funnel, which can both further concentrate current and collimate the x-ray flux. Pixel flux levels can be modulated over a broad range by varying the emitter cathode-gate voltage. The ability to address x-ray pixels, and vary intensity, will offer new flexibility in delivering precise amounts of x-ray flux to target locations for dose modulation. Pixel address speeds will be well under 1ms, so motion blurring will be reduced. MDACC will demonstrate basic imaging capability using a flat panel detector and phantoms and help with system design in Phase I. DBT systems to be designed in Phase II based on the DAXS panels will lead to a new generation of compact, fast, affordable and transportable breast tomographic systems for breast cancer screening, diagnosis and management. The primary impact of the proposed work will be to make breast cancer screening more accessible and convenient, and provide motion-free 3-D breast images to radiologists, surgeons, radiation oncologists, for better detection, diagnosis and staging of breast cancers. PUBLIC HEALTH RELEVANCE: The digital breast tomosynthesis system to be developed here is based on novel digitally addressable x-ray source panels which offer unique capabilities not available with current mammography x-ray sources. Since the x-ray pixels can be addressed electronically in nanoseconds no gantry motion is required and these can help reduce exposure time and dose and eliminate motion blurring problems associated with 3-D imaging. Such a device will make 3-D imaging mobile and affordable and increase breast cancer survival rates by making more widely available to practitioners new tools and methodologies for early detection and more accurate diagnosis of breast cancer.