Analysis of x-ray spectra is important for quality assurance (QA) and quality control (QC) of radiographic systems. This is especially true for mammographic x-ray imaging systems which require low-contrast detectability. Under clinical conditions, the measurement of diagnostic x-ray spectra is difficult because of pulse pile-up due to the high fluence rate of incident x-ray photons. However, it is difficult to set a long sourceto-detector distance to reduce the number of photons detected per unit time for mammographic x-ray units. Compton spectroscopy is a suitable tool to deal with this problem. Detection of 90-degrees scattered photons only, energy correction and reconstruction are easy using the Klein-Nishina formula. However, x-ray spectra measured by this method have lower energy resolution, because of the geometrical irradiation angle or electron movement in the scatterer. Moreover, spectra measured with a compound semiconductor detector, such as a high resolution Schottky Cdte detector like we used, are distorted by the detector response, which is based on detecting x-ray photon interactions and charge carrier trapping in the semiconductor crystal. While the distortion of spectra caused by the response can be easily corrected by applying a stripping procedure, it is very difficult to reconstruct the broad spectra measured by Compton spectroscopy as sharp spectra such as obtained when directly measured. Some complicated reconstruction algorithms have been reported to fit the shape of spectra obtained by the Compton spectroscopy to sharp standard spectra. However, for QA / QC of the radiographic system, it is not necessary to correct the spectra sharply if the spectral broadening is at a tolerable level and the properties of the broad spectra acquired by the Compton spectroscopy agree with those of the sharp spectra measured directly; i. e. evaluations are necessary only for estimation of spectral shape.
In this paper, we compared attenuation curves calculated using Hubbell's attenuation coefficients to estimate the coincidence or difference of spectra measured by the Compton spectroscopy and directly measured in the primary beam. Our results showed that the attenuation curves acquired from the reconstructed spectra measured by the Compton spectroscopy agreed with that acquired from corrected spectra that were directly measured. Moreover, the attenuation curves acquired from the spectra actually measured by adding aluminum attenuators agreed with theoretically calculated curves.

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An advantage of heavy - ion therapy is its good dose concentration. A limit for full use of this desirable feature comes from range ambiguities in treatment planning. The treatment planning is based on X-ray CT measurements, and the range ambiguities are mainly due to an error in calibration of the CT number. The heavy - ion ranges are related to electron density of the medium while the CT numbers are defined using the X - ray attenuation coefficient.
The range verific ation method using positron emitter beams has been developed to reduce the range ambiguities. In this verification, probing beams of positron emitters are implanted into the tumor, and pairs of annihilation gamma rays are detected with a positron camera.
This paper demonstrates an application to verify [P1]treatment planning. [P2] Here, the treatment planning was made on a head phantom and the ranges estimated from the CT-number were compared with the ranges measured with the positron camera. As a result, disagreements were detected between the planned ranges and the measured ones; these were 1.6mm at maximum. [P3] The disagreements were due to an error of transformation of CT - number to range for[P4] the phantom material in the water-column depth - dose measurement. The disagreements could be lowered to 0.4mm by using the calibrated water - equivalent lengths. It was confirmed that the range verification system has a designed measurement accuracy of 1 mm and is useful for verifying irradiation fields on heavy - ion radiotherapy.

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Recently, the number of scans for X-ray computed tomography (CT) examinations has been rising due to the wide-spread use of multi-slice CT (MSCT) scanners. There is a concern that the total medical exposures will be increased by these examinations. In order to lower exposures, routine parameters for head CT examinations done at several hospitals in Gunma were investigated. In this study, the computed tomography dose index (CTDI100c, [P1]), noise, and low contrast resolution were measured. The CTDIloo, c for all the hospitals exceeded the guideline (40mGy) suggested by the Japan Association of Radiological Technologists (JART). Low contrast resolution showed the coefficient of variation of ± 5%[P2] between hospitals. In conclusion, it was proposed that the technologists should reconsider the parameters of the head X-ray CTs, in cases where their output dose far exceeds the standard.

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We compared estimated axes obtained from the upper arm outline, which changes during movement, with the skeleton axis obtained from an x-ray image in terms of range of motion.
Statistical analysis showed that the estimated axes corresponded to the skeleton axis in each range of motion of the hand. The analysis was superior to the conventional approach.

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