Objective: It is well established that computer based models of x-ray imaging systems are basic and very important tools\r\nfor developing and evaluating new emerging x-ray imaging techniques, optimizing technical parameters, and performing\r\nfeasibility studies prior to implementation in clinical practice. Such models are essential for the development and the\r\nestablishment of new breast x-ray imaging modalities that aim to detect and better characterize breast lesions in their early\r\nstage. This work presents a complete software package, called BreastSimulator, dedicated for breast x-ray imaging\r\nresearch.\r\nMethods: The package consists of four modules used to create three-dimensional breast models in compressed and\r\nuncompressed state, simulate x-ray mammographic images and visualize the results of the simulations. The module that is\r\nused to generate breast models, Breast Modeling Module, consists of several sub-modules that are utilized to model the\r\ndifferent breast components: external shape, glandular and adipose tissue, breast lesion, skin, pectoralis and lymphatics.\r\nThe Compression Module is dedicated to simulate the mechanical compression of the breasts. Mammographic projection\r\nimages are obtained with simulation of x-ray photon transport starting from the x-ray source, passing through the breast\r\nmodel and reaching the detector. This is accomplished in the Image Generation Module. Finally, the results of the\r\nsimulations, i.e. breast models and mammographic images can be seen with the Visualization Module.\r\nResults: Here, we demonstrate the application of the software package in conventional and dual-energy mammography as\r\nwell as compression studies, as examples to highlight basic functions and applications of Breast Simulator. The first study\r\naimed to define the optimal pair of ââ?¬Ë?lowââ?¬â?¢ and ââ?¬Ë?highââ?¬â?¢ monochromatic x-ray energies for dual-energy mammography. It\r\ninvolved the synthesis of 225 dual-energy images obtained from combinations of ââ?¬Ë?lowââ?¬â?¢ and ââ?¬Ë?highââ?¬â?¢ energy images acquired\r\nin the energy range 14 to 28 keV. Images were generated from a medium sized dense breast model that contained one\r\ncalcification. The study showed that 17/28 keV incident monoenergetic beams are optimal to obtain maximal calcification\r\ndetectability for this breast. The second study demonstrated the effect of breast compression on the quality of the obtained\r\nmammograms. It included a breast model based on breast CT slices subjected to simulated compression and generation of\r\nmammographic images. Increased image quality is observed for mammograms obtained from breasts with reduced\r\nthickness. The characteristics of the x-ray beams that exit a small dense breast model were investigated in the third study.\r\nFor two mammographic spectra used in mammography imaging, the mean energy of the transmitted x-rays and the mean\r\nexit angle of the scattered radiation increase as the incident x-ray energy increases.\r\nConclusions: We believe that this tool and its functionalities will speed up the development, testing and optimization of\r\nnew breast imaging modalities such as breast tomosynthesis, cone-beam CT and advanced two-dimensional techniques\r\nlike dual-energy as well as specific parts of imaging chain, such as x-ray source, detector and acquisition geometry.
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