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Amide proton transfer-weighted (APTw) 7-T MRI enables monitoring of changes in amide proton concentration in the brain regions of demyelination and remyelination.

Although diffusion tensor imaging (DTI) has been widely used for the quantitative analyses of the integrity of white matter in the brain in clinical and research fields, quality assurance (QA) for DTI has not been fully established. Thus, we suggest a QA guideline for DTI using the American College of Radiology (ACR) Magnetic resonance imaging (MRI) head phantom. In this study, the geometric accuracy, slice-position accuracy, image intensity uniformity, percent signalghosting, low-contrast object detectability, image distortion, fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were measured and evaluated in 1.5T and 3.0T MRI scanners equipped with an 8-channel SENSE head coil. The standard axial spin echo (SE) T1-weighted MR images and DTI with 6, 15 and 32 directions were obtained. Concerning geometric accuracy, image twisting in the three directions was observed due to the inhomogeneity of echo planar imaging (EPI). Image intensity uniformity was significantly lower for DTI than for the standard SE T1-weighted MR images. Percent signal ghosting was higher for images from 3.0T MRI than for images from 1.5T MRI. Low-contrast object detectability was visually identified and measured at a low contrasttonoise ratio (CNR) and a low signaltonoise ratio (SNR). Image distortion changed remarkably to the phaseencoding direction. The present study using the ACR MRI phantom suggests a QA method for DTI with high reproducibility and easy accessibility.

In megavoltage X-ray imaging (MVI), computed radiography (CR) has required a very simple and general quality assurance (QA) method based on a radiotherapy imaging technique. The purpose of this study was to develop a general QA method for evaluating the modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) for MVI. Thus, a simple and compact edge block made of tungsten, with dimensions of 19 × 10 × 1 cm3, was efficiently designed and developed. The pre-sampling MTF was evaluated with the following settings: a 6 megavoltage (MV) energy, four different types of detectors, CR-IP (image plate: photo-stimulable phosphor screen), CR-IP-Lead (image plate + lead screen), CR-IP-Regular (fast front screen + image plate + fast front screen) and CR-IP-Fast (fast back screen + image plate + fast front screen). The MTF values at 1 mm−1for CR-IP-Regular showed the highest resolution of 0.18. The best noise distribution was observed in the measurement of the NPS with CR-IP-Regular. With increasing spatial frequency, our results showed that value of the DQE for the four types of detectors was approximately 1.0 mm−1, which is comparable to the values reported in the literature. In this report, measurements for megavoltage imaging based on line-pair modulations by using an edge block are presented. When the wide side of the tungsten block was reduced, the accuracy of the edge measurement was improved to match those offered by edge techniques. The present study demonstrates that the QA method with our home-made edge block can be used to evaluate the MTF, NPS and DQE for MVI.

Neuroprotective therapeutics slows down the degeneration process in animal models of Parkinson’s disease (PD). The neuronal survival in PD animal models is often measured by using immunohistochemistry. However, dynamic changes in the pathology of the brain cannot be explored with this technique. Application of in-vivo1H magnetic resonance spectroscopy (1H MRS) can cover this shortcoming, as these techniques are non-invasive and can be repeated over time in the same animal. Thus, the sensitivity of both techniques to measure changes in the PD pathology was explored in an experiment studying the neuroprotective effects of the vigilance enhancer bee-venom (BV) in a mouse model of PD. The mice were pre-treated with 0.02-ml BV administered to the acupuncture point GB34 (Yangneungcheon) once every 3 days for 2 weeks. Three groups were classified as control, MPTP-intoxicated PD model and BV-treated mice. Outer volume suppression combined with the ultra-short echo-time STEAM (TE = 2.2 ms, TM = 20 ms, TR = 5000 ms) was used for localized in-vivo1H MRS. Based on the 1H MRS spectral analysis, substantial changes of the neurochemical profiles were evaluated in the three investigated groups. In particular, the glutamate complex (Glx)/creatine (Cr) ratio (7.72 ± 1.25) in the PD group was significantly increased compared to that in the control group (3.93 ± 2.21, P = 0.001). Compared to the baseline values, the Glx/Cr ratio of the BV-treated group was significantly decreased 2 weeks after MPTP intoxication (one-way ANOVA, p < 0.05). In conclusion, the present study demonstrated that neurochemical alterations occurred in the three groups and that the neuroprotective effects of the BV acupuncture in a mouse model of PD could be quantified by using immunohistochemistry and 1H MRS.

Abstract: The noise power spectrum (NPS) is one of the most general methods for measuring the noise amplitude and the quality of an image acquired from a uniform radiation field. The purpose of this study was to compare different NPS methodologies by using megavoltage X-ray energies. The NPS evaluation methods in diagnostic radiation were applied to therapy using the International Electrotechnical Commission standard (IEC 62220-1). In order to measure the region of interest (ROI) of the NPS, we used the following five factors: the overlapping impact, the non-overlapping impact, the penumbra, the flatness and different ROI sizes. We used NPS from four different types of detectors, the CR-IP (computed radiography image plate: photo-stimulable phosphor screen), the CR-IP-lead (hexalon lead screen), the CR-IP-back [lanex TM fast back screen: {terbium-doped gadolinium oxysulfide granular phosphor screen (Gd2O2S:Tb,133 mg/cm2)} + 1-mm-thick copper plate and the CR-IP-front (lanex TM fast front screen). A Kodak 2000 RT photo-stimulable phosphor-based computed radiographic (CR) system showed that the normalized noise power spectrum (NNPS) curve gradually decreased, in compliance with increasing spatial resolution. In addition, each detector showed a different reactivity of the NPS to megavoltage. The results of multivariate analysis of variance (MANOVA) test (methods × detectors) revealed significant main effects of the methods [F(1, 4) = 53.543, P = 0.001 and of the detectors [F(1, 4) = 17.556, P = 0.001]. The present study revealed that various factors could be employed to produce megavoltage imaging (MVI) of the NPS and as a baseline standard for NPS control in MVI.