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.

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.

A case of ß-catenin-positive hepatocellular adenoma with MR imaging sign of diffuse intratumoral fat deposition.

Hepatocellular adenoma (HCA) is a rare primary benign tumor of the liver, which occurs predominantly in young and middle-aged women. Recently, the subclassification of HCA was proposed by the Bordeaux group. Subsequently, characteristic radiological and clinical features have been revealed in each HCA subtype. According to the previous literature, diffuse intratumoral fat deposition is a very common finding in hepatocyte nuclear factor 1α-negative HCA, but this finding has been reported in ß-catenin-positive HCA in the literature for only one case. In this case report, we report the second case of ß-catenin-positive HCA with MR imaging sign of diffuse intratumoral fat deposition, confirmed immunohistologically on the basis of a surgical specimen. In addition, our case showed hypovascularity and isointensity on the hepatobiliary phase which have been reported as characteristic findings in ß-catenin-positive HCA. Diffuse intratumoral fat deposition can be observed in ß-catenin-positive HCA, which has a greater probability of malignant transformation than other types of HCA.

Usefulness of proton magnetic resonance spectroscopy in predicting positive biopsy after high-intensity focused ultrasound for treatment of localized prostate cancer.

OBJECTIVES: To investigate the clinical effectiveness of proton magnetic resonance spectroscopy in predicting local recurrence or residual disease after high-intensity focused ultrasound for treatment of localized prostate cancer. METHODS: The present study included patients with localized prostate cancer who underwent high-intensity focused ultrasound of whole-gland ablation as primary therapy. Clinicopathological variables including proton magnetic resonance spectroscopy, T2-weighted magnetic resonance imaging, and prostate-specific antigen and its derivatives were analyzed to predict the positive prostate biopsy results using univariate and multivariate analyses. Furthermore, the presence of tumor in each of the 12 prostate sectors by T2-weighted magnetic resonance imaging and proton magnetic resonance spectroscopy were evaluated and compared with prostate biopsy results in each of the 12 prostate sectors in order to evaluate the local cancer distribution in the prostate after high-intensity focused ultrasound. RESULTS: Overall, we carried out 85 prostate biopsies in 52 patients. Multivariate logistic regression analysis showed that the positive finding of proton magnetic resonance spectroscopy was the only statistically significant prognostic parameter of pathological tumor progression in patients after high-intensity focused ultrasound. Prostate biopsy cores were obtained from 952 prostate sectors of 52 patients and 85 prostate biopsies. Compared with T2-weighted magnetic resonance imaging, proton magnetic resonance spectroscopy (sensitivity 52.8%, specificity 97.4%, positive predictive value 44.2% and negative predictive value 98.1%, P < 0.001) has higher values to predict local tumor progression in prostate sectors after high-intensity focused ultrasound. CONCLUSIONS: Proton magnetic resonance spectroscopy is a useful, non-invasive diagnostic modality that predicts local tumor progression in patients after high-intensity focused ultrasound, as well as local cancer distribution at each of the prostate sectors with pinpoint accuracy.

Three cases of collagenous fibroma with rim enhancement on postcontrast T1-weighted images with fat suppression.

Collagenous fibroma, also known as desmoplastic fibroblastoma, is a benign fibrous soft tissue tumor showing gradual growth, commonly without aggressive local infiltration. Today, preoperative radiological diagnosis is important to avoid over-treatment and unnecessary extensive procedures, but is difficult because diagnostic imaging findings for collagenous fibroma have not been established. We report MR imaging findings of three collagenous fibromas in correlation with their histopathology. The characteristic rim enhancement on post-contrast T1-weighted images with fat suppression was present in all three cases, and we consider this to represent the difference in vascularity between the outer capsule-like fibrous tissue and the inside of the tumor.

Celiac artery dissection seen with ruptured pancreaticoduodenal arcade aneurysms in two cases of celiac artery stenosis from compression by median arcuate ligament.

We report two cases of ruptured pancreaticoduodenal arcade aneurysms that were successfully treated by embolotherapy. In these cases, contrast-enhanced computed tomography, sagittal reformed images, and angiography revealed celiac artery stenoses due to compression by the median arcuate ligament. Computed tomography also showed acute localized dissection in the distal celiac axis, suggesting that aneurysmal rupture had occurred immediately after development of the dissection. When unruptured pancreaticoduodenal arcade aneurysms are identified in the context of celiac artery dissection, the possibility of rupture may be high and requires strict observation and consideration of embolotherapy.

[Prevention of radiation damage in interventional radiology (IVR)].

With the development of interventional radiology, radiation protection has become increasingly important for both patients and medical staff in interventional radiology. Sometimes, long fluoroscopy times and repeated angiography lead to higher radiation doses, limited to a small area of the patient's skin surface. This becomes the potential for deterministic effects of the skin and also may lead to an increased risk of stochastic effects. The entrance skin dose and effective dose can be deduced from the dose area product. It should be noted that minimizing patient dose leads to reduction of staff dose. Here we briefly explain radiation protection in interventional radiology.

Entrance skin dose during radiofrequency catheter ablation for tachyarrhythmia: a multicenter study.

BACKGROUND: To assess the entrance skin dose (ESD) during radiofrequency catheter ablation procedures for tachyarrhythmia including atrial fibrillation (Af). METHODS: This study focused on 99 consecutive patients who underwent procedures for tachyarrhythmia (Af; n = 34, non-Af; n = 65) in three institutions. The non-Af group included atrial flutter, atrial tachycardia, paroxysmal supraventricular tachycardia, ventricular tachycardia, ventricular premature contraction, atrial premature contraction, atrioventricular nodal reentry tachycardia, and Wolff-Parkinson-White syndrome. In two of the three institutions, the procedures were performed for both Af and non-Af. The ESDs were measured using 100 radiosensitive indicators attached to the back of each patient's jacket at 5-cm intervals. For statistical analyses, multiple regression analysis (the dependent variable, Max-ESD; and the independent variables, dose area product [DAP], total fluoroscopic time [TFT], body mass index, etc.), Pearson's correlation test, and the Mann-Whitney test were employed. RESULTS: The overall averages for the TFTs, the DAPs, and the Max-ESDs were 49.9 ± 28.2 minutes, 71.2 ± 73.7 Gy cm(2) , and 0.57 ± 0.51 Gy, respectively. DAP was positively related to the Max-ESD and was significant in stepwise multiple regression analysis (P < 0.0001). There was a significant association between TFT and Max-ESD in five of the six kinds of angiographic unit, and between DAP and Max-ESD in all three systems with available DAP measures. In one institution, TFT, DAP, and Max-ESD differed significantly between the Af and non-Af groups (P = 0.0002, P < 0.0001, and P < 0.0001). CONCLUSIONS: During the cardiac catheter ablation, ESDs of only a few patients exceeded the thresholds of radiation skin injuries, and the DAP proved useful to estimate each patient's Max-ESD.

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.

Enhanced structural connectivity within the motor loop in professional boxers prior to a match.

Professional boxers train to reduce their body mass before a match to refine their body movements. To test the hypothesis that the well-defined movements of boxers are represented within the motor loop (cortico-striatal circuit), we first elucidated the brain structure and functional connectivity specific to boxers and then investigated plasticity in relation to boxing matches. We recruited 21 male boxers 1 month before a match (Time1) and compared them to 22 age-, sex-, and body mass index (BMI)-matched controls. Boxers were longitudinally followed up within 1 week prior to the match (Time2) and 1 month after the match (Time3). The BMIs of boxers significantly decreased at Time2 compared with those at Time1 and Time3. Compared to controls, boxers presented significantly higher gray matter volume in the left putamen, a critical region representing motor skill training. Boxers presented significantly higher functional connectivity than controls between the left primary motor cortex (M1) and left putamen, which is an essential region for establishing well-defined movements. Boxers also showed significantly higher structural connectivity in the same region within the motor loop from Time1 to Time2 than during other periods, which may represent the refined movements of their body induced by training for the match.

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.

First experience of 192Ir source stuck event during high-dose-rate brachytherapy in Japan.

PURPOSE: To share the experience of an iridium-192 (192Ir) source stuck event during high-dose-rate (HDR) brachytherapy for cervical cancer. MATERIAL AND METHODS: In 2014, we experienced the first source stuck event in Japan when treating cervical cancer with HDR brachytherapy. The cause of the event was a loose screw in the treatment device that interfered with the gear reeling the source. This event had minimal clinical effects on the patient and staff; however, after the event, we created a normal treatment process and an emergency process. In the emergency processes, each staff member is given an appropriate role. The dose rate distribution calculated by the new Monte Carlo simulation system was used as a reference to create the process. RESULTS: According to the calculated dose rate distribution, the dose rates inside the maze, near the treatment room door, and near the console room were ≅ 10-2 [cGy · h-1], 10-3 [cGy · h-1], and << 10-3 [cGy · h-1], respectively. Based on these findings, in the emergency process, the recorder was evacuated to the console room, and the rescuer waited inside the maze until the radiation source was recovered. This emergency response manual is currently a critical workflow once a year with vendors. CONCLUSIONS: We reported our experience of the source stuck event. Details of the event and proposed emergency process will be helpful in managing a patient safety program for other HDR brachytherapy users.

Cerebral blood flow in young and middle-aged people living with HIV.

Purpose: Neurocognitive disorder has been noted as a long-term complication in individuals with HIV. In people living with HIV, regardless of treatment, age-related changes like arteriosclerosis are well-known to be accelerated. Such accelerated aging changes may decrease cerebral blood flow in younger generations with HIV, increasing the rate of occurrence of neurocognitive disorders. We investigated regional cerebral blood flows in well-controlled Japanese people living with HIV under 65 years old to clarify whether age-related changes in regional cerebral blood flows are accelerated in people living with HIV.Method: Japanese male HIV patients >20 years old but <65 years old who visited Teikyo University Hospital between August 2013 and September 2015 were recruited to and enrolled in this study. Healthy coeval male volunteers during the same period were recruited as controls. Magnetic resonance imaging was performed. Twelve regional cerebral blood flows were calculated from pseudocontinuous arterial spine labelling data.Results: Participants in this study comprised 40 individuals with HIV (HIV-positive group) and 33 non-HIV individuals (Control group). Median age was 40.15 years [interquartile range (IQR), 32.80-50.55 years] for the HIV-positive group and 48.00 years [IQR, 37.75-59.25 years; p = 0.3585] for the Control group. No significant differences in regional cerebral blood flows were seen between groups. In the HIV-positive group, cerebral blood flows decreased with age in the neocortex, although no significant decrease was observed in any of the regions in the control group.Conclusions: Significant age-related declines in cerebral blood flows in the neocortex may occur earlier in HIV patients.

Effective dose during abdominal three-dimensional imaging with a flat-panel detector angiography system.

The purpose of this study was to measure the effective dose during abdominal three-dimensional imaging obtained with an angiography unit with a digital flat-panel system on a phantom and to determine dose-area product (DAP)-to-effective dose conversion factors. DAPs and effective doses were evaluated for 163-cm-tall human-shaped phantoms with estimated body weights of 54, 64, and 77 kg, and the effective doses were 2.1, 3.2, and 4.2 mSv, respectively. The DAP-to-effective dose conversion factors were 0.28-0.29 mSv x Gy(-1) x cm(-2). In conclusion, the DAPs were useful for estimating the effective dose during abdominal three-dimensional angiographic imaging.

Radiation exposure to patients' skin during cardiac resynchronization therapy.

AIMS: The purpose of the current study is to evaluate the patients' entrance skin dose (ESD) during cardiac resynchronization therapy (CRT). METHODS AND RESULTS: Entrance skin doses were assessed during 16 CRT procedures. Seven of the 16 patients were upgrade of conventional pacemaker to CRT. The patients wore jackets which had 100 radiosensitive indicators placed on the back during the procedures. After the procedure, the patients' ESDs were calculated from the colour difference of the indicators. Eleven of the 16 patients were implanted devices with a defibrillator, and three patients those without a defibrillator. In the other two, the procedures failed. The average total fluoroscopic time (TFT), total numbers of cine frames, and the maximum ESDs were 56.7 +/- 28.0 min, 674 +/- 342 frames, and 1.0 +/- 0.6 Gy, respectively. Of the 16 patients, six received ESDs exceeding 1 Gy, TFT, total number of cine frames, and the maximum ESD tended to decrease as the operator experience increased. CONCLUSION: The patients' ESDs during CRT procedures can exceed the thresholds for radiation skin injuries due to prolonged fluoroscopic times. Therefore, interventionalists should estimate the doses.