Mixed Reality Visualization of Radiation Dose for Health Professionals and Patients in Interventional Radiology.

For interventional radiology, dose management has persisted as a crucially important issue to reduce radiation exposure to patients and medical staff. This study designed a real-time dose visualization system for interventional radiology designed with mixed reality technology and Monte Carlo simulation. An earlier report described a Monte-Carlo-based estimation system, which simulates a patient's skin dose and air dose distributions, adopted for our system. We also developed a system of acquiring fluoroscopic conditions to input them into the Monte Carlo system. Then we combined the Monte Carlo system with a wearable device for three-dimensional holographic visualization. The estimated doses were transferred sequentially to the device. The patient's dose distribution was then projected on the patient body. The visualization system also has a mechanism to detect one's position in a room to estimate the user's exposure dose to detect and display the exposure level. Qualitative tests were conducted to evaluate the workload and usability of our mixed reality system. An end-to-end system test was performed using a human phantom. The acquisition system accurately recognized conditions that were necessary for real-time dose estimation. The dose hologram represents the patient dose. The user dose was changed correctly, depending on conditions and positions. The perceived overall workload score (33.50) was lower than the scores reported in the literature for medical tasks (50.60) for computer activities (54.00). Mixed reality dose visualization is expected to improve exposure dose management for patients and health professionals by exhibiting the invisible radiation exposure in real space.

Calculating and estimating second cancer risk from breast radiotherapy using Monte Carlo code with internal body scatter for each out-of-field organ.

Out-of-field organs are not commonly designated as dose calculation targets during radiation therapy treatment planning, but they might entail risks of second cancer. Risk components include specific internal body scatter, which is a dominant source of out-of-field doses, and head leakage, which can be reduced by external shielding. Our simulation study quantifies out-of-field organ doses and estimates second cancer risks attributable to internal body scatter in whole-breast radiotherapy (WBRT) with or without additional regional nodal radiotherapy (RNRT), respectively, for right and left breast cancer using Monte Carlo code PHITS. Simulations were conducted using a complete whole-body female model. Second cancer risk was estimated using the calculated doses with a concept of excess absolute risk. Simulation results revealed marked differences between WBRT alone and WBRT plus RNRT in out-of-field organ doses. The ratios of mean doses between them were as large as 3.5-8.0 for the head and neck region and about 1.5-6.6 for the lower abdominal region. Potentially, most out-of-field organs had excess absolute risks of less than 1 per 10,000 persons-year. Our study surveyed the respective contributions of internal body scatter to out-of-field organ doses and second cancer risks in breast radiotherapy on this intact female model.

Characteristic asymmetric limbic and anterior temporal atrophy in demented patients with pathologically confirmed argyrophilic grain disease.

PURPOSE: The purpose of this study is to clarify the characteristic structural magnetic resonance imaging (MRI) findings in demented patients with pathologically confirmed argyrophilic grain disease (AGD). METHODS: Nine pathologically confirmed AGD patients with cerebral three-dimensional T1-weighted MRI were evaluated in this study. In addition to visual rating scales of atrophic and asymmetric changes in the limbic and temporal lobes, voxel-based morphometry (VBM) was performed to assess group difference between pathologically confirmed AGD and Alzheimer's disease (AD) patients. RESULTS: On visual analyses of AGD patients, the medial temporal, anterior temporal, and posterior temporal atrophy scores were 3.3 ± 0.7, 1.7 ± 0.5, and 1.0 ± 0.7, respectively. Asymmetric scores of the hippocampus and parahippocampal gyrus, amygdala and ambient gyrus, anterior temporal, and posterior temporal lobes were rated as 1.1 ± 0.7, 1.6 ± 0.5, 1.3 ± 0.8, and 0.4 ± 0.7, respectively. In spite of no statistical differences in atrophic scores, AGD patients showed the higher score and proportion of anterior temporal asymmetric score than AD (p = 0.03 and 0.02). Compared with controls, VBM analysis revealed left dominant asymmetric atrophy predominantly in the limbic and anterior temporal lobe in AGD patients. By contrast, there was no significant gray matter reduction between AGD and AD patients. CONCLUSIONS: Asymmetric atrophy relatively localized to the anterior temporal and limbic lobes including the amygdala and ambient gyrus is a characteristic MRI finding of AGD. For the precise antemortem diagnosis, especially to differentiation from AD, it is important to pay attention to this asymmetric change.

Multifaceted structural magnetic resonance imaging findings in demented patients with pathologically confirmed TDP-43 proteinopathy.

This short report clarifies the heterogeneity of structural magnetic resonance imaging (MRI) findings in seven demented patients due to pathologically accumulated TAR DNA-binding protein-43 (TDP-43) protein using visual analyses including visual rating scales (i.e., global cortical atrophy and medial temporal atrophy scales). In addition to the well-known frontotemporal lobar atrophy, structural MRI has revealed multifaceted imaging findings including asymmetric atrophy of the frontoparietal lobe and cerebral peduncle, midbrain atrophy, and localized or diffuse white matter T2 hyperintensity. Understanding of these multifaceted neuroimaging findings is important for the precise antemortem diagnosis of TDP-43 proteinopathy.

A case of new PCDH12 gene variants presented as dyskinetic cerebral palsy with epilepsy.

Here we report a Japanese patient with new compound heterozygous truncating variants in the PCDH12 gene. As compared to the previously reported families who had congenital microcephaly, intrauterine growth retardation, intracranial calcification, and neonatal seizure associated with dysplasia of the midbrain-hypothalamus-optic tract, the present patient showed no midbrain-hypothalamus dysplasia or congenital/postnatal microcephaly, but dyskinetic cerebral palsy and severe intellectual disability as well as multifocal epilepsy. To understand phenotypic spectrum associated with PCDH12 variants, more reports are needed.

High Signal Intensity in Dentate Nucleus on Unenhanced T1-weighted MR Images: Association with Linear versus Macrocyclic Gadolinium Chelate Administration.

PURPOSE: To assess whether an association exists between hyperintensity in the dentate nucleus (DN) on unenhanced T1-weighted magnetic resonance (MR) images and previous administration of gadolinium-based contrast agents (GBCAs) that contain different types of gadolinium chelates. MATERIALS AND METHODS: The institutional review board approved this study. Written informed consent was waived because this was a retrospective study. Evaluated were 127 cases among 360 consecutive patients who underwent contrast agent-enhanced brain MR imaging. Two radiologists conducted visual evaluation and quantitative analysis on unenhanced T1-weighted MR images by using regions of interest. DN-to-cerebellum (DN/cerebellum) signal intensity ratios were calculated and the relationship between DN/cerebellum and several factors was evaluated, including the number of previous linear chelate and/or macrocyclic GBCA administrations by using a generalized additive model. The Akaike information criterion was used in model selection. Interobserver correlation was evaluated with paired t tests and the Lin concordance correlation coefficient. RESULTS: The images of nine patients (7.1%) showed hyperintensity in the DN. Twenty-three patients (18.1%) received linear GBCAs (median, two patients; maximum, 11 patients), 36 patients (28.3%) received macrocyclic GBCAs (median, two patients; maximum, 15 patients), 14 patients (11.0%) received both types of GBCA (linear [median, two patients; maximum, five patients] and macrocyclic [median, three patients; maximum, eight patients]), and 54 patients (42.5%) had no history of administration of gadolinium chelate. Interobserver correlation was almost perfect (0.992 [95% confidence interval: 0.990, 0.994]). The DN/cerebellum ratio was associated with linear GBCA (P < .001), but not with macrocyclic GBCA exposure (P = .875). According to the Akaike information criterion, only linear GBCA was selected for the final model, and the DN/cerebellum ratio had strong association only with linear GBCA. CONCLUSION: Hyperintensity in the DN on unenhanced T1-weighted MR images is associated with previous administration of linear GBCA, while the previous administration of macrocyclic GBCAs showed no such association.

Gadolinium-based Contrast Agent Accumulates in the Brain Even in Subjects without Severe Renal Dysfunction: Evaluation of Autopsy Brain Specimens with Inductively Coupled Plasma Mass Spectroscopy.

PURPOSE: To use inductively coupled plasma mass spectroscopy (ICP-MS) to evaluate gadolinium accumulation in brain tissues, including the dentate nucleus (DN) and globus pallidus (GP), in subjects who received a gadolinium-based contrast agent (GBCA). MATERIALS AND METHODS: Institutional review board approval was obtained for this study. Written informed consent for postmortem investigation was obtained either from the subject prior to his or her death or afterward from the subject's relatives. Brain tissues obtained at autopsy in five subjects who received a linear GBCA (GBCA group) and five subjects with no history of GBCA administration (non-GBCA group) were examined with ICP-MS. Formalin-fixed DN tissue, the inner segment of the GP, cerebellar white matter, the frontal lobe cortex, and frontal lobe white matter were obtained, and their gadolinium concentrations were measured. None of the subjects had received a diagnosis of severely compromised renal function (estimated glomerular filtration rate <45 mL/min/1.73 m(2)) or acute renal failure. Fisher permutation test was used to compare gadolinium concentrations between the two groups and among brain regions. RESULTS: Gadolinium was detected in all specimens in the GBCA agent group (mean, 0.25 µg per gram of brain tissue ± 0.44 [standard deviation]), with significantly higher concentrations in each region (P = .004 vs the non-GBCA group for all regions). In the GBCA group, the DN and GP showed significantly higher gadolinium concentrations (mean, 0.44 µg/g ± 0.63) than other regions (0.12 µg/g ± 0.16) (P = .029). CONCLUSION: Even in subjects without severe renal dysfunction, GBCA administration causes gadolinium accumulation in the brain, especially in the DN and GP.

Percutaneous Covered Stenting in Splenic Vein for Left-sided Portal Hypertension Caused by Chronic Splenic Vein Obstruction.

Left-sided portal hypertension (LSPH), an uncommon manifestation of portal hypertension, is characterized by conditions such as isolated gastric varices and splenomegaly, which result from impeded splenic venous drainage in the presence of pancreatic disease. We employed a percutaneous transhepatic technique to achieve regression of isolated gastric varices by implanting a covered stent within a blocked splenic vein and by embolizing the posterior gastric vein and varices using N-butyl-2-cyanoacrylate. We report the successful treatment of stenting for LSPH by the covered stent placement.

Evaluation of deep learning reconstruction on diffusion-weighted imaging quality and apparent diffusion coefficient using an ice-water phantom.

This study assessed the influence of deep learning reconstruction (DLR) on the quality of diffusion-weighted images (DWI) and apparent diffusion coefficient (ADC) using an ice-water phantom. An ice-water phantom with known diffusion properties (true ADC = 1.1 × 10-3 mm2/s at 0 °C) was imaged at various b-values (0, 1000, 2000, and 4000 s/mm2) using a 3 T magnetic resonance imaging scanner with slice thicknesses of 1.5 and 3.0 mm. All DWIs were reconstructed with or without DLR. ADC maps were generated using combinations of b-values 0 and 1000, 0 and 2000, and 0 and 4000 s/mm2. Based on the quantitative imaging biomarker alliance profile, the signal-to-noise ratio (SNRs) in DWIs was calculated, and the accuracy, precision, and within-subject parameter variance (wCV) of the ADCs were evaluated. DLR improved the SNR in DWIs with b-values ranging from 0 to 2000s/mm2; however, its effectiveness was diminished at 4000 s/mm2. There was no noticeable difference in the ADCs of images generated with or without implementing DLR. For a slice thickness of 1.5 mm and combined b-values of 0 and 4000 s/mm2, the ADC values were 0.97 × 10-3and 0.98 × 10-3mm2/s with and without DLR, respectively, both being lower than the true ADC value. Furthermore, DLR enhanced the precision and wCV of the ADC measurements. DLR can enhance the SNR, repeatability, and precision of ADC measurements; however, it does not improve their accuracies.

Impact of arm position on vertebral bone marrow proton density fat fraction in chemical-shift-encoded magnetic resonance imaging: a preliminary study.

Arm positions employed during magnetic resonance imaging (MRI) can affect magnetic field distribution, which may result in variability in proton density fat fraction (PDFF) measurements. This study evaluated the effect of arm position on lumbar PDFF measured using chemical-shift-encoded MRI (CSE-MRI). Fifteen healthy volunteers from a single-center underwent lumbar CSE-MRI at two different arm positions (side and elevated) using a single 3T scanner. Scans were performed twice in each position. PDFFs of the L1-L5 vertebrae were independently measured by two readers, and reader measurements were compared by calculating intraclass correlation coefficients (ICC). We compared PDFF measurements from two arm positions and from two consecutive scans using the Wilcoxon test and Bland-Altman analysis. Measurements from the two readers were in high agreement [ICC =0.999; 95% confidence interval (CI), 0.998-0.999]. No significant difference was observed between PDFFs from the first and second scans of all vertebrae for each reader (all P>0.05); however, PDFF for the elevated arm position was significantly higher than that for the side arm position (37.9-44.8% vs. 37.0-43.8%; all P<0.05), except at the L2 level by reader 2. The mean differences in PDFF measurements from the first and second scans [0.1%; 95% limits of agreement (LoA), -1.8% to 1.9%] and from the side arm and elevated arm positions (0.8%; 95% LoA, -1.6% to 3.2%) were small. In conclusion, these preliminary data suggest that different arm positions during CSE-MRI can slightly affect lumbar PDFF; however, the mean absolute differences were very small.

A preliminary study on predictors of treatment response to repetitive transcranial magnetic stimulation in patients with treatment-resistant depression in Japan.

BACKGROUND: Brain imaging studies have reported that the effect of repetitive transcranial magnetic stimulation (rTMS) is associated with the activities of the dorsolateral prefrontal cortex (DLPFC) and ventral medial prefrontal cortex (VMPFC). However, few studies have been conducted in Japanese patients. AIM: We aimed to identify brain regions associated with depressive symptom changes by measuring regional cerebral blood flow (rCBF) in the DLPFC and VMPFC before and after the high-frequency rTMS to the left DLPFC in Japanese patients with treatment-resistant depression. METHOD: Fourteen patients participated in the rTMS study and were assessed with the 17-item Hamilton depression rating scale (HAM-D17 ). Among them, 13 participants underwent magnetic resonance imaging scan of the brain using the arterial spin labeling method. The rCBF was calculated using the fine stereotactic region of interest template (FineSRT) program for automated analysis. We focused on eight regions reported in previous studies. RESULTS: Depression severity significantly decreased after 2 week (HAM-D17 :11.4 ± 2.8, P = 0.00027) and 4 week (HAM-D17 : 11.0 ± 3.7, P = 0.0023) of rTMS treatment. There was no significant change in rCBF at each region in the pre-post design. However, there was a significantly negative correlation between baseline rCBF in the right DLPFC and the improvement in HAM-D17 score (r = -0.559, P = 0.047). CONCLUSION: We obtained supportive evidence for the effectiveness of rTMS to the prefrontal cortex in treatment-resistant depression, which may be associated with reduced rCBF of the right DLPFC before initiation of rTMS.

Magnetic resonance imaging changes in Asian people living with HIV.

BACKGROUND: Previous studies have reported a significant increase in age-related magnetic resonance imaging (MRI) changes in relatively younger people living with HIV (PLWH). However, there is little data available for brain changes in Asian PLWH. The data to differentiate HIV specific brain change from usual aging change was also sparse. To clarify them, we assessed the presence of leukoaraiosis and brain atrophic changes on MRI in young and middle-aged Japanese PLWH. METHODS: We reviewed data from well-controlled PLWH (age: 20-64 years) and coeval controls. We evaluated the presence of leukoaraiosis, as well as the extent of whole-brain grey matter (GM) atrophy and parahippocampal atrophy on brain MRI and determined between-group differences. Moreover, we evaluated the severity of parahippocampal atrophy based on the voxel-based specific regional analysis system for Alzheimer's disease. RESULTS: We enrolled 40 PLWH and 33 controls (median age: 40.15 and 48.00 years, respectively, [p = .3585]). Leukoaraiosis was significantly more prevalent among the PLWH (20 cases [50%]) than in the controls (9 cases [27.3%]) (univariate: p = .0483, multivariate: p = .0206). The extent of whole-brain GM atrophy was significantly greater in the PLWH than in the controls (univariate: p < .001, multivariate: p = .0012). Contrastingly, there was no significant between-group difference in the extent and severity of parahippocampal atrophy. CONCLUSIONS: Aging changes in the brain were significantly more prevalent in well-controlled Japanese PLWH. However, the process of atrophic brain changes might differ between HIV and one of age-related diseases, Alzheimer's disease.

Intranodal Embolization for Groin Lymphocele.

Purpose: Intranodal embolization using n-butyl cyanoacrylate glue is an emerging treatment option for persistent lymphatic leakage. This report describes the procedure details of intranodal embolization for groin lymphocele and evaluates the efficacy of intranodal embolization at our institution via retrospective chart review. Material and Methods: Nine consecutive patients (six men and three women; median age, 77.4 years; range, 43-95 years) who underwent intranodal embolization for groin lymphocele between January 2017 and December 2019 were included as study subjects. Intranodal lymphangiography with iodinated contrast was performed to confirm lymphatic leakage, followed by intranodal embolization using n-butyl cyanoacrylate glue mixed with iodized oil for all nine patients. The etiologies of lymphocele, technical and clinical success rates of intranodal embolization, duration of treatment, follow-up period, and acute and chronic complications were retrospectively investigated. Results: The etiologies of groin lymphoceles were the cutdown access of inguinal vessels (n = 7), lymph node biopsy (n = 1), and trauma (n = 1). The technical and clinical success rates of both lymphangiography and subsequent intranodal embolization were 100%. For intranodal embolization, 16.7%-33.3% n-butyl cyanoacrylate glue was used. The median duration of treatment was 2 days (range, 1-13 days). The follow-up period lasted 0-895 days (median, 9 days). No acute or chronic complications were observed. Conclusions: In this study, intranodal embolization showed promising results for groin lymphocele with a short duration of treatment with a median of 2 days. Intranodal embolization using n-butyl cyanoacrylate glue could be a treatment option for persistent groin lymphocele. However, further research is warranted to further evaluate the efficacy of intranodal embolization.

Imaging spectrum of abnormal subcutaneous and visceral fat distribution.

Adipose tissue plays multiple and complex roles not only in mechanical cushioning and energy storage but also as an important secretory organ that regulates energy balance and homeostasis multilaterally. Fat tissue is categorized into subcutaneous fat tissue (SCAT) or visceral fat tissue (VSA) depending on its distribution, with the two having different metabolic functions. Near-total lack of fat in congenital/acquired generalized lipodystrophy, cachexia, or any other severe malnutrition condition induces severe multi-organ dysfunction due to lack of production of leptin and other adipokines. Increased visceral fat tissue secondary to obesity, hypercortisolism, or multiple symmetric lipomatosis raises the risk of insulin resistance, cardiac complications, and airway or spinal canal stenosis, although the fat distribution pattern differs in each condition. Partial abnormal fat distribution conditions such as HIV/HAART therapy-associated lipodystrophy, familial partial lipodystrophies, and acquired partial lipodystrophy frequently show a mixture of lipoatrophy and lipohypertrophy with metabolic dysfunction. Characteristic imaging features in conditions with local abnormal fat distribution can provide information about a patient's co-existent/unrecognized disease(s), past medical history, or lifestyle. Knowledge of characteristic abnormal fat distribution patterns can contribute to proper and timely therapeutic decision-making and patient education.

Immersive Radiation Experience for Interventional Radiology with Virtual Reality Radiation Dose Visualization Using Fast Monte Carlo Dose Estimation.

For interventional radiology (IR), understanding the precise dose distribution is crucial to reduce the risks of radiation dermatitis to patients and staff. Visualization of dose distribution is expected to support radiation safety efforts immensely. This report presents techniques for perceiving the dose distribution using virtual reality (VR) technology and for estimating the air dose distribution accurately using Monte Carlo simulation for VR dose visualization. We adopted an earlier reported Monte-Carlo-based estimation system for IR and simulated the dose in a geometrical area resembling an IR room with fluoroscopic conditions. Users of our VR system experienced a simulated air dose distribution in the IR room while the irradiation angle, irradiation timing, and lead shielding were controlled. The estimated air dose was evaluated through comparison with measurements taken using a radiophotoluminescence glass dosimeter. Our dose estimation results were consistent with dosimeter readings, showing a 13.5% average mutual difference. The estimated air dose was visualized in VR: users could view a virtual IR room and walk around in it. Using our VR system, users experienced dose distribution changes dynamically with C-arm rotation. Qualitative tests were conducted to evaluate the workload and usability of our VR system. The perceived overall workload score (18.00) was lower than the scores reported in the literature for medical tasks (50.60) and computer activities (54.00). This VR visualization is expected to open new horizons for understanding dose distributions intuitively, thereby aiding the avoidance of radiation injury.