Development and clinical applications of digital tomosyuthesis system with the capabilities of dual energy subtraction and multi-directional tomography

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We have developed a digital tomosynthesis system, which incorporates an x-ray fluororadiographic TV unit and has the capabilities to perform multi-directional tomography and to expose pulsed x-rays with rapid kV switching between low energy and high energy, a digital image processing unit and display unit, including a high-resolution CRT monitor and a lase printer. We have studied the methods of re-constructing digital tomographs of multilayrs, utilizing image data obtained from a single multi-directional tomographic movement, and of improving image quality of those reconstructed tomographs by means of several digital image processing techniques. The basic processing technique in our system was spatial frequency filtration, although dual energy and blurred mask layr-subtractions were the optional techniques and showed the distinct advancements shown in this study. Clinical applications of this modality has proved a number of advantages as listed below :1) Longitudinal format of the reconstructed tomographs facilitated an easy interpretation of the tomographs and helped comparison against conventional radiographs2) Digital reconstruction of multiple tomographs from a single set of tomographic image data shortened examination time and lowered patient radiation exposure. Moreover it helped three-dimensional recognition of the object when multiple tomographs were displayd on a CRT in cine mode3) Image processing was effective to improve image quality of the tomograph and enhanced some specific image informations pertinent to the clinical problem at hand4) Dual energy subtraction digital tomosynthesis was effective to clearly demonstrate bony structures or a small calcification in the lesion and permitted discrimination of calcifications from dense fibrotic lesions5) Digital angiotomosynthesis permitted a detailed observation of vascular disorders and was promising for dynamic vascular study