Quantitative Breast Imaging using Photon Counting Detector

Possible limitations of current dual energy Contrast Enhanced Digital Mammography(CEDM) are that overlapping normal breast tissue structures can obscure the visualization of iodine, and that the only two images acquired provide solution for two variable equations while three variables are required as the breast consists of three materials - adipose and glandular tissues and iodine. To solve this problem with dual energy CEDM, it requires knowledge of the breast thickness at each pixel. However, in many clinical mammography systems employing a spring-loaded paddle, the physical thickness of the breast may not be uniform due to deformation and tilt of the compression paddle. Therefore, we chose to use triple energy CEDM to overcome these limitations, which can provide a third image. However, the radiation dose can remain a major concern due to three exposures. Photon counting detector(PCD) can provide triple energy radiography without mentioned extra exposures. For triple energy CEDM, an iodine quantification method for breast imaging was suggested in this research. We acquired triple energy images of calibration phantom of different iodine concentrations first, using PCD. Then, intensity values at each energy of imaging object could be mapped pixel by pixel to different locations on the calibration phantom images of different iodine thicknesses(concentrations). Interpolation surface of iodine concentration was constructed from the mapped locations at each energy. Resultant triple surfaces were combined to find out the intersection of the three iodine thickness surfaces from the three energy images, which tells the estimated iodine thickness from the input intensity value. The result shows that the proposed method could quantify iodine inserts in breast phantom accurately, which simulate lesions in breast filled with different iodine concentrations.