Accurate dosimetry is particularly difficult for low- to medium-energy x-rays as various interaction processes with different dependences on material properties determine the dose distribution in tissue and radiation detectors. Monoenergetic x-rays from synchrotron radiation offer the unique opportunity to study the dose response variation with photon energy of radiation detectors without the compounding effect of the spectral distribution of x-rays from conventional sources. The variation of dose response with photon energies between 10 and 99.6 keV was studied for two TLD materials (LiF:Mg,Ti and LiF:Mg,Cu,P), MOSFET semiconductors, radiographic and radiochromic film. The dose response at synchrotron radiation energies was compared with the one for several superficial/orthovoltage radiation qualities (HVL 1.4 mm Al to 4 mm Cu) and megavoltage photons from a medical linear accelerator. A calibrated parallel plate ionization chamber was taken as the reference dosimeter. The variation of response with x-ray energy was modelled using a two-component model that allows determination of the energy for maximum response as well as its magnitude. MOSFET detectors and the radiographic film were found to overrespond to low-energy x-rays by up to a factor of 7 and 12 respectively, while the radiochromic film underestimated the dose by approximately a factor of 2 at 24 keV. The TLDs showed a slight overresponse with LiF:Mg, Cu, P demonstrating better tissue equivalence than LiF:Mg, Ti (maximum deviation from water less than 25%). The results of the present study demonstrate the usefulness of monoenergetic photons for the study of the energy response of radiation detectors. The variations in energy response observed for the MOSFET detectors and GAF chromic film emphasize the need for a correction for individual dosimeters if accurate dosimetry of low- to medium-energy x-rays is attempted.

The synchrotron radiation system may be useful for evaluating microcirculatory disorders and early-stage malignant tumors in various human organs.

The small collateral artery network was angiographically visualized with a resolution limit < 100 microns. The linear collaterals appeared to result from an opening of preexisting vessels. The undulating, unbranched vessels were not observed in the normal limbs and seemed to be vessels that were newly formed after limb ischemia. Synchrotron radiation microangiography appears to be a powerful means of assessing the development of small collateral arteries, which may help to provide a basis for understanding of the collateral circulation.

A two-dimensional clinical intravenous coronary angiography system, comprising a large-size view area produced by asymmetrical re¯ection from a silicon crystal using intense synchrotron radiation from a multipole wiggler and a two-dimensional detector with an image intensi®er, has been completed. An advantage of the imaging system is that two-dimensional dynamic imaging of the cardiovascular system can be achieved due to its two-dimensional radiation ®eld. This world-®rst two-dimensional system has been successfully adapted to clinical applications. Details of the imaging system are described in this paper.

Abstract-This paper presents a wearable upper body exoskeleton system with a model based compensation control framework to support robot-aided shoulder-elbow rehabilitation and power assistance tasks. To eliminate the need for EMG and force sensors, we exploit off-the-shelf compensation techniques developed for robot manipulators. Thus target rehabilitation tasks are addressed by using only encoder readings.A proof of concept evaluation was conducted with 5 able-bodied participants. The patient-active rehabilitation task was realized via observer-based user torque estimation, in which resistive forces were adjusted using virtual impedance. In the patient-passive rehabilitation task, the proposed controller enabled precise joint tracking with a maximum positioning error of 0.25 degrees. In the power assistance task, the users' muscular activities were reduced up to 85% while exercising with a 5 [kg] dumbbell. Therefore, the exoskeleton system was regarded as being useful for the target tasks; indicating that it has a potential to promote robot-aided therapy protocols.

The intramural coronary artery (IMCA) with a diameter of 50–500 μm is critical for blood supply to the inner layers of heart muscle. We introduced digital measurement to microangiography using monochromatic synchrotron radiation and quantified branching patterns of the IMCA, the epicardial coronary artery (EPCA), and the distal ileal artery (DIA). The pre- and postbranching diameters were measured (95–1,275 μm) in seven dogs. A typical arterial segment divided into two nearly equivalent branches, and a regression line of daughter-to-mother diameter plots was almost identical among the EPCA ( y = 0.838 x − 16.7 in μm), IMCA ( y = 0.737 x− 2.18), and DIA ( y = 0.755 x + 8.63). However, a considerable difference was present at a segment where a proximal IMCA branched off from an EPCA ( y = 0.182 x + 90.2). Moreover, a proximal IMCA diameter had no relationship to the branching order from an EPCA. The precision of this method was confirmed by the good correlation of diameter measurements between two independent observers ( r = 0.999, y = 1.02 x − 1.07). In conclusion, using digital microangiography we demonstrated that the self-similar branching pattern of coronary arteries was discrete at the connection between the IMCA and EPCA.

Coronary angiogram by means of monochromatic x-ray is useful for a precise evaluation of coronary circulation, both in clinical setting and in physiological animal experiments.

Fluorescent scanning (FS) x-ray tomography was developed to detect nonradioactive tracer materials (iodine and gadolinium) in a living object. FS x-ray tomography consists of a silicon (111) channel cut monochromator, an x-ray shutter, an x-ray slit system and a collimator for detection, a scanning table for the target organ, and an x-ray detector with pure germanium. The minimal detectable dose of iodine in this experiment was 100 ng in a volume of 2 mm3 and a linear relationship was shown between the photon counts of a fluorescent x ray and the concentration of iodine contrast material. A FS x-ray tomographic image was clearly obtained with a phantom.