Evaluation of In-room Volumetric Imaging Doses for Image-guided Radiotherapy: A Multi-institutional Study.

Aims: We investigated imaging dose and noise under clinical scan conditions at multiple institutions using a simple and unified method, and demonstrated the need for diagnostic reference levels in image-guided radiotherapy (IGRT). Materials and Methods: Nine cone-beam and helical computed tomography (CT) scanners (Varian, Elekta, Accuray Inc., and BrainLAB) from seven institutions were investigated in this study. The weighted cone-beam dose index (CBDIw) was calculated for head and pelvic protocols using a 100 mm pencil chamber under the conditions used in actual clinical practice at each institution. Cone-beam CT image noise was evaluated using polymethylmethacrylate head and body phantoms with diameters of 16 and 32 cm, respectively. Results: For head and pelvic protocols, CBDIw values ranged from 0.94-6.59 and 1.47-20.9 mGy, respectively. Similarly, standard deviation (SD) values ranged from 9.3-34.0 and 26.9-97.4 HU, respectively. The SD values tended to increase with decreasing imaging dose (r = -0.33 and -0.61 for the head and pelvic protocols, respectively). Conclusions: Among the nine machines, the imaging dose for high imaging dose institutions was approximately 20 mGy to the pelvic phantom, and there was a 14-fold difference in dose compared with the other institutions. These results suggest the need to establish DRLs for IGRT to guide clinical decision-making.

[Questionnaire Survey of Hands-on Seminar Using a Web Conferencing System in the COVID-19 Pandemic].

The purpose of this study was to evaluate the effectiveness of a hands-on seminar using a Web conferencing system, based on the post-event questionnaires of the face-to-face and online seminars of the hands-on seminar. For participants to feel realistic training in the online seminars, four educational videos explaining the procedure of the practical skill were created. We compared results of questionnaires acquired from participants after the face-to-face and online seminars. The questions about expectation, comprehension, satisfaction level, and lecture time for the seminars were graded on a 5-point scale. The higher the scores, the higher the rating, except for lecture time. A score of 3 was appropriate for the lecture time, with a higher score indicating that the seminar felt longer and a lower score indicating that the seminar felt shorter. In the evaluation of classroom lectures, such as expectation, comprehension, and satisfaction level for the seminars, there were no significant differences between the face-to-face and online seminars, and both achieved high scores of 4 or more. There was a significant difference in the evaluation of lecture time for classroom lectures, with participants feeling that it was too short in the face-to-face but just right in the online. In all evaluations for hands-on training and discussion, there were no significant differences between the face-to-face and online seminars, and both achieved high scores of 4 or more and time was short. It was concluded that our proposed online seminar approach could achieve a high level of evaluation as face-to-face seminars.

[Usefulness of an Ultrasound System with Automatic Bladder Urine Volume Measurement Using Artificial Intelligence Technology in Radiotherapy].

PURPOSE: We aimed to investigate the usefulness of iViz air ver.4 Convex (FUJIFILM, Tokyo) as a tool to determine the bladder capacity before prostate radiotherapy by comparing it with the existing BladderScan BVI 6100 (Verathon Inc., Bothell, Washington). METHODS: We investigated the usefulness of iViz air as a tool to determine the bladder capacity before prostate radiotherapy by comparing it with the current BladderScan. RESULTS: The absolute value of each error rate was approximately 30.9%±27.2% and 26.4%±18.9% for the BladderScan and iViz air, respectively, with no significant differences between the instruments (p=0.16). Evaluated by urine volume, the mean error rates for bladder volumes >50 ml were 26.9%±19.0% and 26.1%±18.5% for the Bladder Scan and iViz air, respectively, with no significant differences (p=0.56). However, the BladderScan and iViz air had significantly higher error rates of 89.5%±52.5% and 31.5%±25.1%, respectively, if the bladder volume was <50 ml (p=0.005). CONCLUSION: The iViz air has limited measurement error to confirm images, especially in limited volumes, suggesting that it is a useful bladder capacity measurement device in performing prostate radiotherapy.

A novel real-time shapeable soft rubber bolus for clinical use in electron radiotherapy.

We have developed soft rubber (SR) bolus that can be shaped in real-time by heating flexibly and repeatedly. This study investigated whether the SR bolus could be used as an ideal bolus, such as not changing of the beam characteristics and homogeneity through the bolus and high plasticity to adhere a patient in addition to real-time shapeable and reusability, in electron radiotherapy. Percentage depth doses (PDDs) and lateral dose profiles (LDPs) were obtained for 4, 6, and 9 MeV electron beams and were compared between the SR and conventional gel boluses. For the LDP at depth of 90% dose, the penumbra as lateral distance between the 80% and 20% isodose lines (P80-20) and the width of 90% dose level (r90) were compared. To evaluate adhesion, the air gap volume between the boluses and nose of a head phantom was evaluated on CT image. The dose profiles along the center axis for the 6 MeV electron beam with SR, gel, and virtual boluses (thickness = 5 mm) on the head phantom were also calculated for the irradiation of 200 monitor unit with a treatment planning system and the depth of the maximum dose (dmax) and maximum dose (Dmax) were compared. The PDDs,P80-20, andr90between the SR and gel boluses corresponded well (within 2%, 0.4 mm, and 0.7 mm, respectively). The air gap volumes of the SR and gel boluses were 3.14 and 50.35 cm3, respectively. Thedmaxwith SR, gel and virtual boluses were 8.0, 6.0, and 7.0 mm (no bolus: 12.0 mm), and theDmaxvalues were 186.4, 170.6, and 186.8 cGy, respectively. The SR bolus had the equivalent electron beam characteristics and homogeneity to the gel bolus and achieved excellent adhesion to a body surface, which can be used in electron radiotherapy as an ideal bolus.

[Application of Real-time Variable Shape Tungsten Rubber for Nail Radiation Protection in the Total Skin Electron Beam (TSEB) Therapy].

PURPOSE: This study investigated whether real-time variable shape tungsten rubber (STR) could be applied for nail radiation protection in total skin electron beam (TSEB) therapy. METHODS: Simulated finger phantoms were made from syringes filled with physiological saline of volumes 5, 10, 20, and 30 ml (inner diameters of 14.1, 17.0, 21.7, and 25.3 mm, respectively). Gafchromic film was applied to the phantom, and lead (thickness 1-3 mm) or STR (thickness 1-4 mm) with an area of 4´1.5 cm was used to cover the film. A 6 MeV electron beam with an 8 mm acrylic board was then used to irradiate the phantom. The source-surface distance (SSD) was 444 cm, the field size was 36´36 cm at SSD of 100 cm without an electron applicator, and the monitor unit was 2000 MU. The shielding rates were obtained from the dose profiles. RESULTS: The mean values of the shielding rate values for all phantoms were 50.1, 97.6, and 98.7% for 1, 2, and 3 mm of lead, respectively, and -13.6, 53.9, 91.2, and 99.4% for 1, 2, 3, and 4 mm of STR, respectively. CONCLUSION: STR with a thickness of 4 mm had the same shielding properties as lead with a thickness of 3 mm, which was an approximately 100% shielding rate. STR could therefore be used in TSEB therapy instead of lead.

Dosimetric evaluation of skin collimation with tungsten rubber for electron radiotherapy: A Monte Carlo study.

PURPOSE: Skin collimation provides a sharp penumbra for electron beams, while the effect of bremsstrahlung from shielding materials is a concern. This phantom study was conducted to evaluate the safety and efficacy of a real-time variable shape rubber containing-tungsten (STR) that can be placed on a patient's skin. METHODS: Electron beam profiles were acquired with the STR placed on a water-equivalent phantom and low melting-point alloy (LMA) placed at the applicator according to commonly used procedures (field sizes: 20- and 40-mm diameters). Depth and lateral dose profiles for 6- and 12-MeV electron beams were obtained by Monte Carlo (MC) simulations and were benchmarked against film measurements. The width of the off-axis distance between 80% and 20% doses (P80-20 ) and the maximum dose were obtained from the lateral dose profiles. Bremsstrahlung emission was analyzed by MC simulations at the depth of maximum dose (R100 ). RESULTS: The depth dose profiles calculated by the MC simulations were consistently within 2% of the measurements. The P80-20 at R100 for 20- and 40-mm diameters were 4.0 mm vs. 7.6 mm (STR vs. LMA) and 4.5 mm vs. 9.2 mm, respectively, for the 6-MeV electron beam with 7.0-mm-thick STR, and 2.7 mm vs. 5.6 mm and 4.5 mm vs. 7.1 mm, respectively, for the 12-MeV electron beam with 12.0-mm-thick STR. A hotspot was not observed on the lateral dose profiles obtained with the STR at R100 . The bremsstrahlung emission under the region shielded by the STR was comparable to that obtained with the LMA, even though the STR was placed on the surface of the phantom. CONCLUSIONS: Skin collimator with STR provided superior dosimetric characteristics and comparable bremsstrahlung emission to LMA collimator at the applicator. STR could be a new tool for the safe and efficient delivery of electron radiotherapy.

Dose reduction potential of using gold fiducial markers for kilovoltage image-guided radiotherapy.

This study aimed to evaluate the possibility of reducing the imaging dose for image-guided radiotherapy by using planar kilovoltage orthogonal imaging and fiducial markers (kV-FM). We tested kilovoltage planar images under clinical imaging conditions for the pelvis (75 kVp, 200 mA, 50 ms) at a decreasing tube current (from 200 to 10 mA). Imaging doses were measured with a semiconductor detector. The visibility of the kV-FM, aspects of image quality (spatial resolution, low contrast resolution), and the resultant image registration reproducibility were evaluated using various shapes (folded, linear, tadpole-like) of fiducial markers containing 0.5% iron [Gold Anchor™ (GA); Naslund Medical AB, Huddinge, Sweden]. The GA phantom was created by placing these variously shaped GAs in an agar phantom. The imaging doses with 200 and 10 mA were approximately 0.74 and 0.04 mGy and they were correlated to the tube current (R2  = 0.999). Regardless of the marker's shape, the GA phantom ensured visibility even when the tube current was reduced to the minimum value (10 mA). The low contrast resolution was gradually decreased at less than 50 mA, but the spatial resolution did not change. Although the auto-registration function could not be used, manual-registration could be achieved with an accuracy of within 1 mm, even when the imaging dose was reduced to 1/20 of the clinical imaging condition for the pelvis. When using the GA as the fiducial marker, the imaging dose could be reduced to 1/20 of that used clinically while maintaining the accuracy of manual-registration using the kV-FM for image-guided radiotherapy of the pelvis.

Feasibility of using tungsten functional paper as a thin bolus for electron beam radiotherapy.

Containing 80% tungsten by weight, tungsten functional paper (TFP) is a radiation-shielding material that is lightweight, flexible, disposable, and easy to cut. Through experimental measurements and Monte Carlo simulations, we investigated the feasibility of using TFP as a bolus in electron beam radiotherapy. Commercial boluses of thickness 5 and 10 mm and from one to nine layers of TFPs (0.3-2.7 mm) were positioned on the surface of water-equivalent phantoms. The percentage depth dose curves and transverse dose profiles were measured using a 9-MeV electron beam from a clinical linear accelerator. Normalized to the value at the depth of maximum dose without bolus, the relative doses at the phantom surface for no bolus, 5-mm bolus, 10-mm bolus, 1 TFP, 3 TFPs, 6 TFPs, and 9 TFPs were 78%, 88%, 92%, 84%, 92%, 102%, and 112%, respectively; the therapeutic depths corresponding to a 90% dose level were 29.1 mm, 22.7 mm, 17.7 mm, 26.6 mm, 23.2 mm, 19.3 mm, and 15.8 mm, respectively. The TFP contributed to increased skin dose and provided dose uniformity within the target volume. However, it also resulted in increased lateral constriction and penumbra width. The results of Monte Carlo simulation produced similar trends as the experimental measurements. Our findings suggest that using TFP as a novel thin and flexible skin bolus for electron beam radiotherapy is feasible.

Registration accuracy with the low dose kilovoltage cone-beam CT: A phantom study.

OBJECTIVE: The aim of this study was to investigate low-dose kilovoltage cone-beam CT (kV-CBCT) for image-guided radiotherapy, with a particular focus on the accuracy of image registration with low-dose protocols. METHODS: Imaging doses were measured with a NOMEX semiconductor detector positioned at the front of head, thorax, and pelvis human body phantoms while kV-CBCT scans were acquired at different tube currents. Aspects of image quality (spatial resolution, noise, uniformity, contrast, geometric distortion, and Hounsfield unit sensitivity) and image registration accuracy using bone and soft tissue were evaluated. RESULTS: With preset and the lowest tube currents, the imaging doses were 0.16 and 0.08 mGy, 5.29 and 2.80 mGy, and 18.23 and 2.69 mGy for head, thorax, and pelvis, respectively. Noise was the only quality aspect directly dependent on tube current, being increased by 1.5 times with a tube current half that of the preset in head and thorax, and by 2.2 times with a tube current 1/8 of the preset in the pelvis. Accurate auto-bone matching was performed within 1 mm at the lowest tube current. The auto-soft tissue matching could not be performed with the lowest tube current; however, manual-soft tissue matching could still be performed within 2 mm or less. CONCLUSION: Noise was the only image quality aspect dependent on the imaging dose. Auto-bone and manual-soft tissue matching could still be performed at the lowest imaging dose. ADVANCES IN KNOWLEDGE: When optimizing kV-CBCT imaging dose, the impact on bone and soft tissue image registration accuracy should be evaluated.

AIM1 and LINE-1 epigenetic aberrations in tumor and serum relate to melanoma progression and disease outcome.

Aberrations in the methylation status of noncoding genomic repeat DNA sequences and specific gene promoter region are important epigenetic events in melanoma progression. Promoter methylation status in long interspersed nucleotide element-1 (LINE-1) and absent in melanoma-1 (AIM1; 6q21) associated with melanoma progression and disease outcome was assessed. LINE-1 and AIM1 methylation status was assessed in paraffin-embedded archival tissue (PEAT; n = 133) and in melanoma patients' serum (n = 56). LINE-1 U-Index (hypomethylation) and AIM1 were analyzed in microdissected melanoma PEAT sections. The LINE-1 U-Index of melanoma (n = 100) was significantly higher than that of normal skin (n = 14) and nevi (n = 12; P = 0.0004). LINE-1 U-Index level was elevated with increasing American Joint Committee on Cancer (AJCC) stage (P<0.0001). AIM1 promoter hypermethylation was found in higher frequency (P = 0.005) in metastatic melanoma (65%) than in primary melanomas (38%). When analyzed, high LINE-1 U-Index and/or AIM1 methylation in melanomas were associated with disease-free survival (DFS) and overall survival (OS) in stage I/II patients (P = 0.017 and 0.027, respectively). In multivariate analysis, melanoma AIM1 methylation status was a significant prognostic factor of OS (P = 0.032). Furthermore, serum unmethylated LINE-1 was at higher levels in both stage III (n = 20) and stage IV (n = 36) patients compared with healthy donors (n = 14; P = 0.022). Circulating methylated AIM1 was detected in patients' serum and was predictive of OS in stage IV patients (P = 0.009). LINE-1 hypomethylation and AIM1 hypermethylation have prognostic utility in both melanoma patients' tumors and serum.

Perforation of Meckel's diverticulum with enteroliths.

Perforation of Meckel's diverticulum with enteroliths is a rare complication. Here, we report a case of perforation of Meckel's diverticulum with enteroliths, which could be accurately diagnosed by the preoperative computed tomography (CT). A 46-year-old man with acute onset of severe abdominal pain, and a localized muscle guarding in the right hypochondrium, had a solitary stone detected in the right abdomen by the radiography. The abdominal CT revealed a saclike outpouching of the small intestine, containing air/fluid levels and an enterolith, with surrounding free air and mesenteric inflammatory change in the right paraumbilical area. He was diagnosed as the perforation of Meckel's diverticulum with enterolith, and the emergency operation was indicated. The perforated Meckel's diverticulum was identified approximately 90 cm proximal to the ileocecal valve. The diverticulum was transected at the base, and removed. The patient's postoperative course was uneventful. This case strongly suggested the ability of CT enterography to accurately diagnose pathologies involving the small intestine, such as the perforation of Meckel's diverticulum, which open premises for its use in the diagnosis of acute abdomen preoperatively.

Optimal timing of MR sialography by use of a simple method of stimulating the salivary gland: a preliminary report.

The present study was performed for determining the optimal timing of MR sialography by use of the Japanese pickled plum (umeboshi) for promoting secretion by the salivary glands. MR sialography was performed in four healthy male volunteers. The four volunteers were examined before and 10 min after stimulation with umeboshi. On the next examination, three volunteers were examined before and after umeboshi stimulation every 1 min up to 5 min to allow assessment of the temporal changes in duct visualization. Dilatation of the salivary gland ducts and improvement of the visualization of the ducts were obtained after stimulation with umeboshi. The difference in the dilatation of the parotid duct was statistically significant. In the temporal study, the salivary gland ducts were shown to be dilated at 2 min after stimulation. As a result, 2 min after stimulation is the optimal timing for MR sialography by use of umeboshi as a stimulator of salivary secretion.