Characteristics of a real-time radiation exposure dosimetry system using a synthetic ruby for radiotherapy.

Radiotherapy-related medical accidents are frequently caused by planning problems, excessive irradiation during radiotherapy, or patient movement. This is partly because the local exposure dose cannot be directly monitored during radiotherapy. This article discusses the development of our recent real-time radiation exposure dosimetry system that uses a synthetic ruby for radiation therapy. Background noise was observed before the measurement of the short-term characteristic features. Regarding the relationship between the number of photons and dose rate, using 100 monitor units (MU)/min as the measurement value, the counts decreased by approximately 10% at 600 MU/min. A clear correlation was observed between the MU value and the number of photons (R2 = 0.9987). The coefficient of variation (%CV) was less than ± 1.0% under all the irradiation conditions. Slight differences were observed between the ion chamber and the synthetic ruby dosimeters in the measurement of the percentage depth dose. However, this difference was almost matched by correcting for the Cherenkov light. Although some problems were observed with the synthetic ruby dosimeter system, our results indicate that the developed dosimeter can be used to measure the irradiation dose of patients in real time, with no significant impact on the data, as any effect would be masked by the larger effect of the ruby; however, the impact requires a detailed assessment in the future.

Mirror writing and cortical hypometabolism in Parkinson's disease.

Mirror writing (MW) is the production of individual letters, words, or word strings in the reverse direction. Parkinson's disease (PD) is a progressive neurodegenerative disorder, and high MW rates have been reported in patients with PD. Thus, the present study sought to identify the factors that cause MW in patients with PD. We examined the frequency of MW in patients with PD and investigated the area of the brain where such frequency inversely correlates with reduced regional cerebral metabolic rates of glucose (rCMRglc). We also examined whether this area satisfied the motor and visual monitoring hypotheses of MW that have been presented in previous studies. Thirty-six subjects with idiopathic PD and 23 healthy controls were included in the study. We asked the participants to write down words, numerals, and sentences from left to right using their dominant and non-dominant hands. Patients with PD underwent an 18F-fluorodeoxyglucose positron emission tomography scan to measure the rCMRglc. Neither the patients with PD nor the healthy subjects exhibited MW in the use of the right hand. In the use of the left hand, MW occurred in 15 of the 36 patients with PD, but in none of the healthy controls. The right intraparietal sulcus was identified as the area where rCMRglc was inversely correlated with the number of left-right reversed characters. Previous functional imaging studies have suggested that the right superior parietal cortex and intraparietal sulcus play an important role in recognizing left-right reversed letters. Therefore, dysfunction in the intraparietal sulcus may hinder the recognition of left-right reversed characters, resulting in MW. Consequently, our findings in patients with PD are consistent with the visual-monitoring hypothesis of MW.

Impaired perception of illusory contours and cortical hypometabolism in patients with Parkinson's disease.

Neuroimaging evidence suggests that areas of the higher-order visual cortex, including the lateral occipital complex (LOC), are engaged in the perception of illusory contours; however, these findings remain unsubstantiated by human lesion data. Therefore, we assessed the presentation time necessary to perceive two types of illusory contours formed by Kanizsa figures or aligned line ends in patients with Parkinson's disease (PD). Additionally, we used 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to measure regional cerebral glucose metabolism in PD patients. Although there were no significant differences in the stimulus durations required for perception of illusory contours formed by aligned line ends between PD patients and controls, PD patients required significantly longer stimulus durations for the perception of Kanizsa illusory figures. Difficulty in perceiving Kanizsa illusory figures was correlated with hypometabolism in the higher-order visual cortical areas, including the posterior inferior temporal gyrus. These findings indicate an association between dysfunction in the posterior inferior temporal gyrus, a region corresponding to a portion of the LOC, and impaired perception of Kanizsa illusory figures in PD patients.

Neural substrates underlying progressive micrographia in Parkinson's disease.

INTRODUCTION: The neural substrates associated with the development of micrographia remain unknown. We aimed to elucidate the neural substrates underlying micrographia in Parkinson's disease (PD) patients. METHODS: Forty PD patients and 20 healthy controls underwent handwriting tests that involved free writing and copying. We measured the size of each letter and the resting cerebral glucose metabolic rate of the PD patients and another group of age- and sex-matched 14 healthy controls (HCs), who had not participated in the writing tests, using resting-state 18F-fluorodeoxyglucose positron emission tomography. RESULTS: In the PD patients, the prevalence of consistent micrographia (CM) associated with free writing was 2.5% for both tasks. Alternatively, the prevalence of progressive micrographia (PM) was 15% for free writing and 17.5% for copying. In the PD patients, there was no significant difference in the letter sizes between these tasks, whereas the variability of the letter sizes for copying was significantly different from that for free writing. The means and decrements in letter sizes in either task were not significantly correlated with the severity of brady/hypokinesia in the PD patients. For free writing, the PD patients with PM showed glucose hypometabolism in the anterior part of the right middle cingulate cortex, including the rostral cingulate motor area, compared with those without PM. For copying, the PD patients with PM showed glucose hypometabolism in the right superior occipital gyrus, including V3A, compared with those without PM. CONCLUSIONS: These findings suggest that PM in free writing in PD patients is caused by the difficulty of monitoring whether the actual handwriting movements are desirable for maintaining letter size during self-paced handwriting. By contrast, PM in copying in PD patients is evoked by a lack of visual information about the personal handwriting and hand motions that are used as cues for maintaining letter sizes.

Clinical and Cerebral Metabolic Changes in Parkinson's Disease With Basal Forebrain Atrophy.

BACKGROUND: Cholinergic dysfunction plays a key role in cognitive dysfunction in Parkinson's disease (PD). Recent studies revealed that atrophy in the nucleus basalis of Meynert (NBM), the largest cholinergic nucleus in the basal forebrain, heralds cognitive decline in PD. Despite clinical importance of NBM atrophy in PD, clinical and radiological correlates of NBM atrophy remains to be elucidated. OBJECTIVE: We investigated the longitudinal changes in clinical and cerebral glucose metabolic characteristics in PD with atrophy in the NBM. METHODS: We analyzed the 3-year longitudinal data of 56 PD patients who underwent motor, nonmotor, and imaging evaluations at baseline. The patients were classified into PD with and without NBM atrophy based on the results of magnetic resonance imaging volumetry. We compared clinical characteristics and cerebral glucose metabolic changes between PD with and without NBM atrophy. RESULTS: At baseline, 20 patients and 36 patients were classified into PD with and without NBM atrophy groups, respectively. At follow-up, the data of the 14 PD patients in the NBM atrophy group and the 18 patients in the group without NBM atrophy completed full assessments and were available for the analysis. The PD with NBM atrophy group showed severe cognitive dysfunction and psychiatric symptoms both at baseline and follow-up. The NBM volume significantly correlated with motor and nonmotor functions. The PD with NBM atrophy showed significantly reduced metabolism in the parietal and occipital cortices both at baseline and follow-up. CONCLUSIONS: Basal forebrain atrophy is a simple and sensible marker of faster disease progression and cortical hypometabolism in PD. © 2020 International Parkinson and Movement Disorder Society.

Comparison of Count Normalization Methods for Statistical Parametric Mapping Analysis Using a Digital Brain Phantom Obtained from Fluorodeoxyglucose-positron Emission Tomography.

OBJECTIVES: Alternative normalization methods were proposed to solve the biased information of SPM in the study of neurodegenerative disease. The objective of this study was to determine the most suitable count normalization method for SPM analysis of a neurodegenerative disease based on the results of different count normalization methods applied on a prepared digital phantom similar to one obtained using fluorodeoxyglucose-positron emission tomography (FDG-PET) data of a brain with a known neurodegenerative condition. METHODS: Digital brain phantoms, mimicking mild and intermediate neurodegenerative disease conditions, were prepared from the FDG-PET data of 11 healthy subjects. SPM analysis was performed on these simulations using different count normalization methods. RESULTS: In the slight-decrease phantom simulation, the Yakushev method correctly visualized wider areas of slightly decreased metabolism with the smallest artifacts of increased metabolism. Other count normalization methods were unable to identify this slightly decreases and produced more artifacts. The intermediate-decreased areas were well visualized by all methods. The areas surrounding the grey matter with the slight decreases were not visualized with the GM and VOI count normalization methods but with the Andersson. The Yakushev method well visualized these areas. Artifacts were present in all methods. When the number of reference area extraction was increased, the Andersson method better-captured the areas with decreased metabolism and reduced the artifacts of increased metabolism. In the Yakushev method, increasing the threshold for the reference area extraction reduced such artifacts. CONCLUSION: The Yakushev method is the most suitable count normalization method for the SPM analysis of neurodegenerative disease.

A quantitative morphological analysis of three-dimensional CT coxal bone images of contemporary Japanese using homologous models for sex and age estimation.

Sexual dimorphisms and age-dependent morphological features of the human coxal bone were quantitatively analyzed using homologous models created from three-dimensional (3D) computed tomography images of the pelvis (male: 514 samples, female: 388 samples, age 16-100). Bilateral average coxal images of each sex and age decade were generated separately through principle component analyses (PCA). By measuring average point-to-point distances of 8472 corresponding points (average corresponding point differences [ACPDs]) between each homologous coxal image and the average images, the sex of more than 93% of the samples was correctly assigned. Some principal components (PCs) detected in PCA of the homologous models of the samples correlated fairly well with age and are affected by features of the curvature of the iliac crest, the arcuate line and the greater sciatic notch. Moreover, separate PCA using the average images of each age decade successfully detected the first PCs, which were strongly correlated with age. However, neither multiple regression analysis using PCs related to age nor comparison of ACPDs with the average images of each age decade could produce accurate results for age decade assignment of unknown (blind) samples. Therefore, more detailed analysis of age-dependent morphological features would be necessary for actual age estimation. In addition, some laterality or left and right shape difference of the coxal bone images was also elucidated, and was more significant in females. Analysis of 3D structures using homologous models and PCA appears to be a potential technique to detect subsistent morphological changes of bones.

Defining visual illusions in Parkinson's disease: Kinetopsia and object misidentification illusions.

OBJECTIVE: To identify the phenomenological features and neural correlates of visual illusions in Parkinson's disease (PD). METHODS: Ninety-three patients with PD were assessed via questionnaires regarding visual illusions and behavioral symptoms, and neuropsychological tests, motor assessments and 18-F fluorodeoxyglucose-positron emission tomography (FDG-PET) were performed. The relationship between visual illusions or hallucinations and regional cerebral glucose metabolism was investigated using partial least squares (PLS) correlation and conventional mass-univariate analyses. RESULTS: Kinetopsia, in which stationary objects are perceived as being in motion, and object misidentification illusions, in which objects are misperceived as different objects, were the most common types of visual illusions. Kinetopsia and object misidentification illusions were identified in 24 patients (25.8%) and 17 patients (18.3%), respectively. Eleven patients with kinetopsia and 9 patients with object misidentification illusions had visual hallucinations. Kinetopsia and visual hallucinations were associated with hypometabolism in the temporo-parietal cortices, whereas object misidentification illusions were associated with hypometabolism in the early visual cortex, as well as the temporo-parietal cortices. CONCLUSIONS: Our findings suggest that kinetopsia and object misidentification illusions are the most common types of visual illusions in PD. Despite the phenomenological diversity of visual illusions and hallucinations in PD, all of these symptoms are associated with dysfunction of the temporo-parietal cortices, which support visual spatial processing, rather than dysfunction of the ventral temporo-occipital cortices, which supports visual object recognition.

Investigation of fMRI Analysis Method to Visualize the Difference in the Brain Activation Timing.

RATIONALE AND OBJECTIVES: In general functional magnetic resonance imaging (fMRI) analysis, the task onset time of the statistical model is typically set according to the timing of stimulation. In this study, using a high temporal resolution fMRI data, we examined the way of dynamically visualizing the difference in the activation timing between the brain activation areas by analyzing the task onset time of the statistical model shifted from the actual stimulation timing. MATERIALS AND METHODS: fMRI data with high temporal resolution was acquired using 3 T magnetic resonance imaging for 10 right-handed healthy volunteers. While being scanned, the volunteers completed a task that comprised two sets of a rest and right hand grip movement task. Statistical Parametric Mapping 12 (SPM12) software was used to analyze fMRI data. After preprocessing, statistical analyses were performed by shifting the task onset time on the statistical model by about 1 second forward or backward from the actual stimulation timing. Activation maps of multiple time phases were then created. RESULTS: Activity was observed to the left of the primary motor area and the supplementary motor area and to the right of the cerebellum (familywise error rate, P < .05). In the right hand grip movement, the primary motor area and the supplementary motor area were activated from 1.12 to 4.48 seconds earlier than the cerebellum. CONCLUSIONS: Using this analysis method, we visualized the differences in activation timings of different areas of the brain.

Motion-frozen Imaging by Gated Myocardial Perfusion Single Photon Emission Computed Tomography Using Multi-focus Fan Beam Collimator in Thallium-201 Study.

PURPOSE: This study aimed to evaluate the statistical noise of motion-frozen (MF) image generated by gated myocardial perfusion single photon emission computed tomography (SPECT) imaging using IQ · SPECT and to determine the optimal acquisition and reconstruction parameters for MF image using IQ · SPECT. METHODS: A movement cardiac phantom and static cardiac phantom were used to acquire the MF images. The acquisition times used were different in 8 and 16 frames per R-R interval, and varying reconstruction parameters (subset and iteration) were used. We determined the %CV value, contrast, and normalized mean square error (NMSE) to evaluate the image quality. RESULTS: The %CV value for a MF image with IQ · SPECT was lower than that for a conventional non-gated myocardial perfusion SPECT (MPS) image with low energy high resolution (LEHR). With regard to the acquisition parameters, the contrast did not change when the acquisition time was increased in 8 and 16 frames per R-R interval. NMSE converged in 56 beats/view in 8 frames per R-R interval. With regard to the reconstruction parameters, the contrast and the %CV value of the anterior and septal wall converged in update 40. The minimum NMSE in subsets 1, 2, and 3 were almost similar. CONCLUSIONS: Uniformity in the MF image with IQ · SPECT was higher than that in the conventional image. The results of this MF image with IQ · SPECT study suggest that the optimal acquisition parameter should be 56 beats/view in 8 frames per R-R interval, and the optimal reconstruction parameters should be subset 3 and iteration 14.

Longitudinal study of cognitive and cerebral metabolic changes in Parkinson's disease.

OBJECTIVE: To investigate the cortical metabolic alterations that precedes longitudinal cognitive decline in Parkinson's disease (PD). METHODS: We analyzed the data of 46 PD patients who did not have dementia at baseline and completed 3-year follow-up. Based on the results of general cognitive, memory and visuospatial tests, patients were classified into cognitively normal PD (PD-CogNL), PD with mild cognitive impairment (PD-MCI), and PD dementia (PDD). The regional cerebral glucose metabolism at rest was measured using 18F-fluorodeoxyglucose positron emission tomography. Voxel-wise effect size analyses were performed to delineate abnormal metabolic patterns associated with changes in cognitive status in PD. RESULTS: At baseline, 29 patients had PD-CogNL, and 17 patients had PD-MCI. At follow-up, 28 patients had PD-CogNL, 12 patients had PD-MCI, and 6 patients developed PDD. Seventeen of 29 PD-CogNL patients remained to be PD-CogNL, and 9 PD-CogNL patients converted to PD-MCI. Eleven PD-MCI patients reverted to normal cognition during follow-up. 3 PD-CogNL and 3 PD-MCI patients developed PDD. Cognitively stable PD-CogNL group had frontal predominant hypometabolism. PDD converters showed parieto-occipital hypometabolism at baseline regardless of whether a patient's initial cognitive status is PD-CogNL or PD-MCI. CONCLUSIONS: Parieto-occipital hypometabolism is a good predictor of early dementia conversion in PD.

A Case Report of Postmortem Radiography of Acute, Fatal Abdominal Distension After Binge Eating.

This case report describes a woman who developed fatal gastric dilatation after binge eating. She called an ambulance because of stomach pain. When she arrived at the hospital, she did not look seriously ill. However, she rapidly became unconscious and collapsed immediately after she was laid on the examination table in a supine position. Postmortem chest x-ray and computed tomography showed right shift of the mediastinum and raised left diaphragm caused by massive gastric distension. Computed tomography showed no visible inferior vena cava. We think that her sudden deterioration was caused by movement of her stomach contents. Radiographic images provided some clues to the cause of her rapid collapse and death.

A case of fatal sigmoid volvulus visualized on postmortem radiography: The importance of image optimization with multidetector computed tomography.

This report describes the case of a man who developed fatal sigmoid volvulus that was identified on postmortem radiography before forensic autopsy. Postmortem radiography is useful for visualizing the body prior to autopsy. We discuss postmortem multidetector computed tomography that was tailored for optimum image quality to allow reconstruction of the fatal findings in multiple axes and in three dimensions, helping to pinpoint the anatomical sites of interest. This involves techniques such as manipulation of the scanning beam pitch and overlapping CT section acquisition. These techniques are best performed by personnel with CT technology training.

Rectal temperature-based death time estimation in infants.

In determining the time of death in infants based on rectal temperature, the same methods used in adults are generally used. However, whether the methods for adults are suitable for infants is unclear. In this study, we examined the following 3 methods in 20 infant death cases: computer simulation of rectal temperature based on the infinite cylinder model (Ohno's method), computer-based double exponential approximation based on Marshall and Hoare's double exponential model with Henssge's parameter determination (Henssge's method), and computer-based collinear approximation based on extrapolation of the rectal temperature curve (collinear approximation). The interval between the last time the infant was seen alive and the time that he/she was found dead was defined as the death time interval and compared with the estimated time of death. In Ohno's method, 7 cases were within the death time interval, and the average deviation in the other 12 cases was approximately 80 min. The results of both Henssge's method and collinear approximation were apparently inferior to the results of Ohno's method. The corrective factor was set within the range of 0.7-1.3 in Henssge's method, and a modified program was newly developed to make it possible to change the corrective factors. Modification A, in which the upper limit of the corrective factor range was set as the maximum value in each body weight, produced the best results: 8 cases were within the death time interval, and the average deviation in the other 12 cases was approximately 80min. There was a possibility that the influence of thermal isolation on the actual infants was stronger than that previously shown by Henssge. We conclude that Ohno's method and Modification A are useful for death time estimation in infants. However, it is important to accept the estimated time of death with certain latitude considering other circumstances.