Synchrotron radiation has been employed to analyze cross-bridge dynamics chiefly in isolated papillary muscle using x-ray diffraction techniques. Here we showed that these techniques can detect regional changes in rat left ventricle (LV) contractility and myosin lattice spacing in in situ ejecting hearts in real time. Further, we examined the sensitivity of these indices to changes in intracellular Ca²⁺ concentration with dobutamine or ryanodine, regional ischemia, and muscular hypertrophy with hypertension. The LV free wall of spontaneously beating rat hearts were directly exposed to brief high-flux, low-emittance x-ray beams provided at SPring-8. Myosin mass transfer to actin filaments (the number of cross-bridges) was determined as the decrease in reflection intensity ratio (intensity of 1,0 plane over the 1,1 plane) between end-diastole and end-systole. The distance between 1,0 reflections was converted to a lattice spacing between myosin filaments. We found that LV end-systolic pressure changed in proportion to mass transfer (cross-bridge formation) in response to changes in Ca²⁺ transients. Left coronary occlusion eliminated increases in myosin lattice spacing and severely reduced mass transfer in the ischemic region. In the hypertrophic LV, the periodic changes in reflection intensity ratio corresponding with cardiac cycle were maintained at the posterior wall regions, but not at the anterior wall regions. Our results suggest that x-ray diffraction techniques permit real time in situ analysis of regional cross-bridge dynamics at the molecular and fiber levels that might also facilitate investigations of ventricular output regulation by the Frank-Starling mechanism.

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Positron emission tomography (PET) provides qualitative and quantitative information about the distribution over space and time of a given radiotracer within the body. Due to the ability to produce fused PET/CT images, combined PET/CT scanners have been rapidly replacing dedicated PET cameras in the market. A new technology named SYNETRAC has led to a new type of whole-body PET/CT that can perform CT scanning only for cancer localized areas previously determined by whole-body PET scanning. This PET/CT can significantly reduce radiation dose without compromising patient throughput. With requirement of both high sensitivity and high spatial resolution, organ-specific PET with depth-of-interaction (DOI) detector system is now under development. The first development target is high-resolution positron emission mammography (PEM) for improving sensitivity and specificity of breast cancer diagnosis. The DOI detector technology has also be applied to small animal PET for laboratory rodents used in basic medical research and drug discovery. The scanner consisting of DOI detector modules with a large axial extent provides significant advantages in fine-structure imaging and quantitative kinetics measurements. We believe that these new PET technologies will be widely used for early diagnosis, effective treatment assessment, and drug discovery.

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Coherent-scatter computed tomography (CT) is a technique that produces images based on low-angle X-ray coherent scatter. The number of coherent-scatter photons corresponding to the scattered angles is sensitive to the molecular structure, and hence, their contrast properties on CT images are expected to be higher at specific angles. However, very few studies have reported such image contrasts. Therefore, we attempted to evaluate and compare the contrast properties of coherent-scatter CT images with those of conventional CT images. First, simulation studies using coherent-scatter distributions were performed with monoenergetic beams of 30, 60, and 90 keV, and a polyenergetic beam of 40 kV. This was followed by an experimental study using coherent-scatter CT images with a plastic phantom measuring 6 cm in diameter radiated by a polyenergetic beam of 40 kV. The relative contrast in coherent-scatter CT images at a low-scatter angle was higher than that in conventional CT images. This result suggests that coherent-scatter CT is useful in the detection of low-contrast lesions.

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The purpose of our study is to evaluate restricted diffusion of the water molecules caused by the trabecular bone structure of the vertebra using a phantom. On a 1.5-T MRI, single shot diffusion echo planar imaging was used with b factors of 0, 500, and 1000s/mm², effective TE of 80 ms, and TR of 2000ms. We determined ADC values with an original phantom, which consists of sponges with different space diameters and dry vertebral bone into the container filled with pure water We assessed the effects of values (0, 500, 1000s/mm²) and acquisition matrix (64×64, 128×128, 256×256) . ADC of the sponge increased as space diameter due to change in restricted diffusion of the water molecules, and was the same level of the dry vertebral bone. Moreover, ADC varied with b values and matrix sizes. Our original phantom enables to analyze restricted diffusion, and ADC is affected by the trabecular bone structure.

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