Stationary digital breast tomosynthesis system with a multi-beam field emission x-ray source array

Abstract

A stationary tomosynthesis mammography system with a carbon nanotube-based x-ray source array can shorten imaging time and improve image quality.Mammography is currently the most effective screening and diagnostic tool for early breast cancer detection. In fact, the recent reduction in the breast cancer mortality rate has been attributed to increased mammographic screening 1 . However, mammography suffers from several limitations. It is very difficult to distinguish cancer from overlying breast tissues on two-dimensional mammograms, and radiologists' interpretation of the images may vary. There are also higher rates of false-positive and falsenegative test results because dense tissues interfere with the identification of abnormalities associated with tumors. To solve this problem, researchers in the late 1990s developed a novel technique called x-ray digital breast tomosynthesis (DBT).DBT is a three-dimensional imaging technique that uses a series of projection images acquired at different angles to provide reconstruction planes in the breast. Several commercial vendors, including GE 2 , Hologic 3 , and Siemens 4 , have manufactured prototype DBT scanners that are based on full-field digital mammography (FFDM) systems. To generate the series of projection images, a conventional x-ray tube mounted on a rotating gantry fixes the imaging beam on the breast, while the tube moves in an arc to generate images at multiple angles. A typical tomosynthesis scan can take anywhere from 20 seconds to more than 1 minute. Compared with conventional mammography, the prolonged imaging time introduces patient motion blur on the images. Moreover, gantry motion leads to a larger effective x-ray focal spot size, which degrades the image quality.To overcome this problem, we proposed a stationary digital breast tomosynthesis system using a carbon nanotube-based field emission x-ray source array 5,6 . The device, called Argus, uses spatially distributed x-ray sources, so it acquires the projection images without source or detector movement. It reduces the total imaging time and potentially improves image quality.We have designed and constructed a prototype system composed of a 25-pixel x-ray source array, a flat panel detector for full-field mammography, a control unit for x-ray sources, and a computer work station. As shown in Figure 1, the geometry of the Argus system, including source-to-object distance, angle coverage, and view number, is comparable to that of conventional mammography and DBT systems. Table 1 shows a comparison between Argus and other prototype systems. Our target goal is the acquisition of 25 projection images in 11 seconds at 0.2mm resolution. By contrast, the Siemens system at the same dose requires 20 seconds to take 25 images with ∼0.3mm focal spot size-and additional blur due to gantry motion ranges from 0.2mm to 1mm depending on the rotation speed.The key component of the Argus system is the 25-pixel x-ray source array. Other medical applications like micro-CT 7 have Continued on next page

High resolution stationary digital breast tomosynthesis using distributed carbon nanotube x‐ray source array

“…28 Instead of mechanically moving a single x-ray tube to the multiple viewing angles, s-DBT employs a stationary x-ray source array, which generates x-ray beams from different viewing angles by electronically activating the individual sources (beams) prepositioned at the corresponding viewing angles without mechanical moving the x-ray tube, therefore eliminating the focal spot motion blurring. 29,30 The scanning speed is determined only by the x-ray tube flux (which determines the exposure time per view) and the detector readout time and is independent of angular coverage. Here, we report our recent progress in this technology development.…”

Tomosynthesis imaging: At a translational crossroads

“…One example is the development of novel x-ray sources using carbon nanotube field-emission cathodes. 54 If these devices are successful and reasonably priced, they may enable very rapid collection of tomosynthesis projection images that would eliminate the need for lengthy compression. A second example is the use of iodinated contrast in breast imaging.…”

Evaluation of Back Projection Methods for Breast Tomosynthesis Image Reconstruction

“…A new multi-beam breast tomosynthesis prototype system, invented by Zhou et al [18], was used for our phantom experiments. The system used static multi-beam X-ray emitters as the sources and controlled the X-ray sources by electronic switches.…”