Photon counting CT is a new technology that enables us to improve the quality of images by a conventional CT, in which the detection of transmitted photons is conducted by an integration of photon energies. This paper describes the features and advantages of the photon counting detection compared to the energy integration detection. They are (1) reduction of electrical noise and improvement of the signal-to-noise ratio, (2) improvement of the image contrast using the weighting factors to images acquired with energy bins, (3) k-edge imaging by setting two energy bins at the k-edge of some contrast media such as gadopenteto megruminacid and gold-nanoparticles, and (4) material decomposition using the data acquired with multiple energy windows. For the material decomposition, the principal component analysis, singular value decomposition method, and the application of the artificial neural network are described. The photon counting CT technique has a potential to improve the diagnostic accuracy and introduce new clinical methods, however, much efforts are required to use this technology in the clinical situation.

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Innovation is the key to future success for Japan that is slowly falling behind. Industries targeted by the “Abenomics” growth strategy include healthcare and medicine. Since cancer is the leading cause of death in Japan, the development of a system that can detect and treat early stage cancers will be very valuable for patient QOL and reducing health care costs. Although the effectiveness of radiation therapy for treating early stage cancer is widely recognized, there has been no system to treat small, moving tumors with sub millimeter accuracy. A project supported by NEDO develops a “Next-Generation Radiation Therapy System” that uses high energy, narrow X-rays beams that can be accurately pinpointed deep inside the body. Performance testing of a prototype system is currently underway at the National Center for Global Health and Medicine in Tokyo.

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Four-dimensional radiation therapy (4DRT) and adaptive radiation therapy (ART) are treatments to account for respiratory motion and anatomical changes during a course of treatment, respectively. Recent development of both imaging and delivery techniques made these radiation therapy possible. In these planning, dose distributions are calculated with multiple image sets for example each respiratory phase constituting 4-dimensional computed tomography and cone-beam computed tomography acquired on each treatment day. To evaluate overall dose distributions, we need to accumulate dose distributions calculated with multiple image sets. However, pixel-wise dose accumulation is impossible because it does not accumulate dose based on anatomy if image sets are different. Deformable image registration (DIR) is used to find corresponding anatomical points between image sets. Thus, dose accumulation based on DIR is a promising technology to enable us to evaluate overall dose distributions of 4DRT and ART. In this article, I will briefly introduce dose accumulation based on DIR and its application to 4DRT and ART.

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For practical energy-resolved computed tomography (CT), a transXend detector is proposed. The transXend detector consists of several segment detectors which are aligned along the direction of X-ray incidence. With response functions of segment detectors, the energy distribution of incident X-rays is obtained after unfolding process. Because the transXend detector measures X-rays as electric currents, it has no limit of counting rate : the number of X-rays in medical diagnosis ranges 10⁶∼10⁹ n/mm²/s, measuring energy of each X-ray is not practical at this stage.
The operation principle and ways of application of the transXend detector are described. With defining narrow energy ranges in an unfolding process, effective atomic numbers are estimated with using white X-rays: the transXend detector can cut out quasi-monochromatic X-rays out of white X-rays. With the transXend detector with absorbers among the segment detectors, the directions of material thickness increment are shown different in the graph made of electric current ratios measured by the segment detectors. Using the current ratio graph, the thicknesses of the materials along the line X-rays passed are estimated. In other words, cancers marked by contrast agent can be detected with one transmission measurement, and possibly are measured and positioned by transmission measurements from two directions.

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In 1953 F. Daniels et al. used the property of thermoluminescence in dosimetry for the first time. Since then, numerous TLD have been developed. 2D TLD was investigated for the first time in 1972 by P Broadhead. However, due to excessive fading, difficulties with handling and the time required for measurements, development stalled. At the current time, the majority of TLD are used in small scale, localized dosimetry with a wide dynamic range and personal dosimeters for exposure management.
Urushiyama et. al. have taken advantage of the commoditization of CCD cameras in recent years—making large area, high resolution imaging easier—to introduce and develop a 2D TLD. It is expected that these developments will give rise to a new generation of applications for 2D TL dosimetry.
This paper introduces the “TL Slab Dosimeter” developed jointly by Urushiyama et. al. and our team, its measurement system and several typical usage scenarios.

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