To compare the geometric accuracy of two Asia‑developed AI auto‑contouring systems (RatoGuide and OncoStudio) for prostate radiotherapy planning CT, including performance in clinical edge cases. Planning CT data from 45 patients were stratified into four groups (Normal, Spacer, Seed/Spacer, GM/Spacer). Manual contours of prostate, rectum, bladder, seminal vesicles, and femoral heads served as reference. Segmentation accuracy was assessed using DSC and 95

This study aimed to establish the diagnostic reference levels (DRLs) of imaging doses for image-guided radiotherapy (IGRT) used in intensity-modulated radiotherapy for prostate cancer in Japan. A nationwide survey was conducted to gather data on image acquisition conditions, parameters, and frequencies across 193 radiation therapy institutions using intensity-modulated radiotherapy. IGRT modalities, such as kilovoltage and megavoltage cone-beam computed tomography (CBCT), two-dimensional imaging, and in-room computed tomography (CT), were targeted. Data analysis focused on image acquisition parameters displayed by the devices, such as tube voltage, current, and imaging dose, along with the CT dose index volume (CTDIvol) and dose-length product (DLP), were collected from 222 radiotherapy devices. The results showed that kV-CT/CBCT was the most frequently used modality, used in 94% of the institutions. Imaging dose-reduction techniques were adopted by over half of the institutions, with 56% optimizing imaging parameters and 45% reducing the imaging field size or scan length. The 75th percentile for CTDIvol was 16.0 mGy, while that for DLP was 263 mGy·cm, with considerable variation among devices and institutions. This study provides the first large-scale reference data for IGRT imaging doses used for prostate cancer treatment in Japan. These results are critical for improving patient safety by optimizing imaging protocols and establishing DRLs tailored to IGRT. These findings will serve as a basis for further refinement of radiological protection practices in Japan.

PURPOSE:177 Lu-DOTATATE-targeted radionuclide therapy (TRT) is effective for patients with somatostatin receptor (SSTR)-positive neuroendocrine tumors; however, radiation safety regulations often necessitate hospitalization, particularly in countries with stringent discharge criteria. This study aimed to identify pretreatment factors predicting outpatient eligibility. METHODS:We retrospectively analyzed 26 patients who underwent their first cycle of 177 Lu-DOTATATE TRT with complete data for analysis. The external dose rate at 1 m (EDR-1 m) was measured 6 h after administration. Patients were divided into two groups: EDR-1 m greater than or equal to 18 μSv/h and less than 18 μSv/h. Characteristics, including age, sex, BMI, body surface area, estimated glomerular filtration rate, administered dose, and tumor site, were compared. In addition, the whole-body washout rate from pretreatment SSTR imaging was evaluated as a potential predictor. Logistic regression and receiver operating characteristic (ROC) analyses were conducted. RESULTS:Fourteen of the 26 (53.8%) patients met the discharge criterion at 6 h. No significant differences were observed in demographic or clinical characteristics between groups. The median washout rate was significantly higher in those meeting the criterion (57.6 vs. 35.0%; P  < 0.001). The area under the ROC curve for the washout rate was 0.929, indicating excellent predictive ability. An optimal cut-off value of 53.5% predicted same-day discharge with a sensitivity of 92.9% and specificity of 91.7%. CONCLUSION:The whole-body washout rate derived from pretreatment SSTR imaging is a strong, practical predictor for outpatient eligibility following 177 Lu-DOTATATE TRT. Incorporating this simple, noninvasive marker into clinical workflow could support individualized discharge planning and improve patient access under strict radiation safety regulations.

Background: Accurate absolute dosimetry is essential for achieving high-precision proton beam therapy. Consequently, a comprehensive characterization of the ionization chamber’s response properties is necessary. Purpose: This study aimed to evaluate the average fQ using Monte Carlo (MC) code PHITS to assess uncertainties among different MC simulation tools. Additionally, PQ values for PTW 30013, NACP-02, and PTW 31013 ionization chambers are calculated using PHITS to provide new reference data for PQ. Furthermore, a new kQ factor for PTW 31013 chamber is established using MC method, contributing to advancements in proton beam dosimetry protocols. Methods: Monoenergetic proton beams were employed to calculate fQ, kQ, and PQ for Farmer, Semiflex, and plane‐parallel chambers. The absorbed dose deposited within the sensitive volume of each chamber was determined via simulations employing PHITS, thereby providing the basis for the estimation of these factors. Computed fQ values were compared with previous reports, while kQ and PQ were benchmarked against literature and Technical Reports Series No. 398 (TRS-398) Rev.1 guideline. Results: Incorporating PHITS‐derived fQ values reduced the uncertainty of f¯QPHITS compared to previous findings. The kQ factor for PTW 31013 followed trends observed in cylindrical chambers with varying sensitive volumes; notably, this study represents the first MC estimation of kQ for this chamber. PQ values for values deviated by up to 1.7% from unity. Conclusion: The data generated in this study provide important insights for refining proton beam dosimetry, contributing to the improvement of treatment precision.

Stereotactic body radiation therapy (SBRT) has emerged as a promising and minimally invasive treatment option for patients with renal cell carcinoma (RCC). This study presents our initial clinical experiences with treatments following our center's protocol, which was formulated based on both national and international evidence. Six patients who had undergone renal SBRT at our center from January 2021 to December 2023 were included. Treatment planning used computed tomography (CT) and magnetic resonance imaging, with respiratory management conducted through breath-hold or free-breathing techniques. The prescribed dose was primarily 48 Gy in three fractions, with increased fractionations when dose constraints were challenging to achieve. Dose constraints were met for all patients, and treatment planning adhered to protocol guidelines. After the confirmation of cone-beam CT (CBCT) images by physicians, radiation was delivered. Five out of six patients completed the planned treatment, whereas one discontinued the treatment midway (the causal relationship to radiation therapy was unclear). Dose-volume histogram analysis revealed that doses to organs at risk depended on the position and size of the planning target volume but remained within acceptable limits for all cases. The intrafractional patient motion was 2.7 mm, as calculated from the pre- and post-CBCT images, confirming the appropriateness of a 3-mm setup margin. Although this study provides initial insights, further clinical trials are warranted to establish standardized protocols and optimize treatment strategies for RCC. In the future, it is also necessary to generate evidence that is tailored to the current situation in Japan.

This study evaluates current practices and challenges associated with computed tomography number-to-mass density (CT-MD) conversion tables in helical tomotherapy across Japan and explores directions for standardization and quality improvement amid the increasing adoption of adaptive radiotherapy (ART). A nationwide web-based survey was conducted across 34 institutions utilizing the Radixact system. Data were collected on CT acquisition protocols, calibration phantoms, density plugs, reconstruction algorithms, table registration timing and quality assurance (QA) frequency. Registered CT-MD tables were categorized by CT modality: Simulation CT (SimCT), ClearRT and CTrue. ClearRT tables were analyzed by phantom setup (full vs half), and CTrue tables by reconstruction method [filtered back projection (FPB) vs iterative reconstruction (IR)]. Inter-institutional variations in CT numbers and the number of data points were assessed. SimCT tables exhibited the widest variation in the number of data points (median = 10) and high-density CT numbers. ClearRT tables (median = 8) showed variations of up to 300 Hounsfield units (HU) in cortical bone; the half-phantom setup reduced inter-institutional variability. CTrue tables (median = 8) demonstrated high consistency, with negligible differences between IR and FPB. All plug CT numbers of CTrue remained within the tolerance defined by the American Association of Physicists in Medicine Task Group 148. However, CT numbers for air plugs varied by ~±30 HU, indicating inconsistent handling of air reference values. Additionally, 43% of institutions did not perform routine QA. Standardizing phantom geometry, air CT number handling and QA protocols-particularly using half-phantom calibration-may improve CT-MD table consistency and dose accuracy in ART.

PurposeIn linear accelerators, deviations in the x-ray focal spot position significantly affect the accuracy of radiation therapy. However, as the focal spot position in bore-type linac systems such as the Radixact system, cannot be assessed using conventional methods, a new evaluation method is required. This study aimed to develop a novel method to measure the focal spot position of Radixact and evaluate any deviations from the ideal x-ray focal spot position.MethodsA structurally simplified measurement system was developed to evaluate the focal spot position of the Radixact system. This system consisted of a vertically aligned metal bar and an ionization chamber, which was moved stepwise to acquire the beam profiles. The focal spot position deviation was calculated based on the center differences of the profiles obtained from two different upstream and downstream locations of the metal bar.ResultsThe measurement results indicated that the focal spot position shift was 0.42 mm and -0.36 mm at the target height in the IEC-X and -Y directions, respectively. The measurement uncertainty was 0.187 mm, confirming a slight deviation from the ideal focal position.ConclusionsThis study developed a novel method to accurately evaluate the x-ray focal spot position of the Radixact system, which can potentially be applied to other conventional linear accelerators and bore-type systems, such as Halcyon, to improve the accuracy of radiotherapy. However, its generalizability and applicability to different radiotherapy machines must be explored further.

BACKGROUND:Accurate dosimetry is important in radiotherapy, and all equipment used for radiotherapy shoud be audited by an independent external dose audit. Radiophotoluminescence glass dosimeter (RPLD) has excellent characteristics and is widely used for postal dose audit; however, postal dose audit for proton therapy using RPLD has not been established. PURPOSE:This study aims to develop a postal dose audit procedure for scanning proton beams using RPLD, estimate uncertainties, and conduct a multicenter pilot study to validate the methodology. METHODS:A postal toolkit was developed and a postal dose audit procedure for RPLD measurements of scanning proton beams was established in cooperation with several facilities that employ various accelerators, irradiation equipment, and treatment planning systems (TPS) for clinical use. Based on basic and previous studies, an uncertainty budget was developed for estimating relative uncertainty and pilot studies were conducted at each site. A method for postal dose audits was developed in a multicenter collaboration to develop an approach suitable for implementation across multiple facilities. RESULTS:The relative response of 60 RPLDs for scanning proton beam examined in this study was 1.00 ± 1.28% mean ± standard deviation. The combined relative standard uncertainty of postal dosimetry for scanning proton beams using the RPLD was 2.97% (k = 1). Under the reference condition, the maximum differences between the ionization chamber measurement (IC) and TPS, RPLD and TPS, and RPLD and IC were 0.97, 1.88, and 2.12%, respectively. The maximum differences between the RPLD and ionization chamber for plateau measurements at 3 cm depth using single-energy and non-reference conditions were 11.31 and 4.02%, respectively. CONCLUSION:We established a procedure for the postal dose audits of proton beams using RPLD and presented the results of a multicenter pilot study. By standardizing the reference conditions, the dosimetry uncertainty was estimated at 2.92%. The results demonstrated the feasibility of performing an independent third-party dose audit of scanning proton beams using RPLD, and for such postal dose audits for proton beams, the irradiation conditions should be standardized to reduce uncertainties. These results are expected to contribute to the development of proton beams.

ABSTRACT The patient setup using the surface‐guided radiation therapy (SGRT) system differs from conventional surface marker procedures. Owing to the abundance of three‐dimensional information, there may be operator variability in where to focus during the patient setup. This study aimed to clarify the differences between expert and novice operators in SGRT positioning for head and neck cases by tracking their eye movements, thereby providing data for developing efficient patient setup procedures. Six radiation therapists set up a simulated patient on the SGRT system while recording eye movements on the screen using the QG‐PLUS eye‐tracking system. The positioning time and number of gaze fixations on the screen were analysed, and the relationship between years of experience with SGRT, positioning time and number of gaze fixations was evaluated. No significant correlation was found between SGRT experience and positioning time ( r = −0.67, p = 0.15). However, more experienced radiation therapists exhibited fewer gaze fixations per positioning session ( r = −0.81, p < 0.05), indicating that they efficiently identified key positioning points. Additionally, experienced radiation therapists focused more intently on a specific screen during the latter half of positioning, suggesting a refined approach for final patient alignment verification. More experienced radiation therapists showed fewer gaze fixations and demonstrated increased attention to a specific screen during the latter half of the patient setup process, suggesting that eye‐tracking technology may provide useful data for standardising patient setup procedures in SGRT patient setups.

This study aimed to evaluate the recent trends in single-fraction conventional radiotherapy (CRT) as palliative treatment in Japan, using data from the National Database published by the Ministry of Health, Labor, and Welfare. Data from fiscal year (FY) 2014 to FY2022, specifically related to the utilization of single-fraction CRT, were analyzed. Multi-fraction CRT, stereotactic body radiotherapy (SBRT), intensity-modulated radiotherapy (IMRT), and brachytherapy were excluded. The primary outcome was the cumulative and annual number of single-fraction CRT courses. Additionally, quarterly course data from FY2019 to FY2022, the period for which monthly data were available, were assessed to evaluate the impact of the coronavirus disease 2019 (COVID-19) pandemic on single-fraction CRT utilization. Of the total 2 315 607 radiotherapy courses, we identified 33 221 single-fraction CRT courses after excluding multi-fraction CRT (n = 1 835 650), SBRT (n = 33 935), IMRT (n = 332 827), and brachytherapy (n = 113 195). The annual number of single-fraction CRT courses increased from 1730 in FY2014 to 5642 in FY2022, with an average annual growth rate of 0.28 (range: -0.07 to 0.65). Outpatient courses significantly increased, particularly from FY2019 onward, surpassing inpatient courses in FY2022 (2914 vs 2728). The highest annual increase was observed in FY2020, particularly from April to December, although this upward trend did not persist in 2021. In conclusion, single-fraction CRT has exhibited a consistent upward trend, highlighting its expanding role in palliative radiotherapy. Although the COVID-19 pandemic temporarily accelerated this trend, its impact has already subsided, with growth rates returning to pre-pandemic levels.

To quantify radiation dose reduction in radiotherapy treatment-planning CT (RTCT) using a deep learning-based reconstruction (DLR; AiCE) algorithm compared with adaptive iterative dose reduction (IR; AIDR). To evaluate its potential to inform RTCT-specific diagnostic reference levels (DRLs). In this single-institution retrospective study, 4-part RTCT scans (head, head and neck, lung, and pelvis) were acquired on a large-bore CT. Scans reconstructed with IR (n = 820) and DLR (n = 854) were compared. The 75th-percentile CTDIvol and DLP (CTDIIR, DLPIR vs. CTDIDLR, DLPDLR) were determined per site. Dose reduction rates were calculated as (CTDIDLR – CTDIIR)/CTDIIR × 100

BACKGROUND:Despite advances in treatment for unresectable locally advanced non-small cell lung cancer (LA-NSCLC), overall survival (OS) remains poor. The effects of coronary artery calcification (CAC) and heart radiation doses on OS in LA-NSCLC patients, especially their combined impact, have not been thoroughly investigated. This study aimed to examine the individual and combined effects of CAC and heart dose on OS in LA-NSCLC patients treated with radiotherapy over a 3-year follow-up period. PATIENTS AND METHODS:The study included 140 patients who received definitive radiotherapy for LA-NSCLC (stage III, 92.1%) from 2015 to 2021. The endpoint was OS, with each patient followed for a fixed 3-year period. RESULTS:Univariate Cox regression analysis identified mean heart dose (MHD; hazard ratio [HR], 4.0 [2.2-7.3]; P < .001) and CAC in multiple vessels (HR, 2.6 [1.5-4.8]; P = .001) as significant predictors of worse OS, both serving as independent predictors of poorer outcomes in multivariate analysis. Kaplan-Meier analysis revealed that combining MHD and CAC in any coronary artery, each specific artery, and multivessels provided enhanced risk stratification for OS (P < .001 for all combinations). Among patients with higher MHD, those with calcification in the left main trunk (LMT) had the highest annual event rate (28.2%), showing a significant difference (P < .001) compared to patients with lower MHD (4.4%). CONCLUSION:Combination of CAC and heart dose enhanced risk stratification for 3-year OS in LA-NSCLC patients treated with radiotherapy. Importantly, patients with calcification in the LMT derived the greatest benefit from reducing heart doses.

We aimed to investigate the impact of concurrent antibody–drug conjugates (ADC) and radiotherapy on symptomatic radiation necrosis (SRN) in breast cancer patients with brain metastases (BM). This multicenter retrospective study uses four institutional data. Eligibility criteria were histologically proven breast cancer, diagnosed BM with gadolinium-enhanced MRI, a Karnofsky performance status of 60 or higher, and radiotherapy for all BM lesions between 2017 and 2022. Patients with leptomeningeal dissemination were excluded. Concurrent ADC was defined as using ADC within four weeks before or after radiotherapy. The cumulative incidence of SRN until December 2023 with death as a competing event was compared between the groups with and without concurrent ADC. Multivariable analysis was performed using the Fine-Gray model. Among the 168 patients enrolled, 48 (29

Purpose We aimed to evaluate the efficacy and safety of re-irradiation stereotactic body radiation therapy (SBRT) in patients with metastatic epidural spinal cord compression (MESCC) following high-dose conventional radiotherapy. Materials and methods Twenty-one patients met the following eligibility criteria: with an irradiation history of 50 Gy 2 equivalent dose in 2-Gy fractions (EQD2) or more, diagnosed MESCC in the cervical or thoracic spines, and treated with re-irradiation SBRT of 24 Gy in 2 fractions between April 2018 and March 2023. Prior treatment was radiotherapy alone, not including surgery. The primary endpoint was a 1-year local failure rate. Overall survival (OS) and treatment-related adverse events were assessed as the secondary endpoints. Since our cohort includes one treatment-related death (TRD) of esophageal perforation, the cumulative esophageal dose was evaluated to find the dose constraints related to severe toxicities. Results The median age was 68, and 14 males were included. The primary tumor sites (esophagus/lung/head and neck/others) were 6/6/7/2, and the median initial radiotherapy dose was 60 Gy 2 EQD2 (range: 50–105 Gy 2 , 60–70/ > 70 Gy 2 were 11/4). Ten patients underwent surgery followed by SBRT and 11 SBRT alone. At the median follow-up time of 10.4 months, 17 patients died of systemic disease progression including one TRD. No radiation-induced myelopathy or nerve root injuries occurred. Local failure occurred in six patients, with a 1-year local failure rate of 29.3% and a 1-year OS of 55.0%. Other toxicities included five cases of vertebral compression fractures (23.8%) and one radiation pneumonitis. The cumulative esophageal dose was recommended as follows: D max < 203, D 0.035 cc < 187, and D 1cc < 167 (Gy 3 in biological effective dose). Conclusion Re-irradiation spine SBRT may be effective for selected patients with cervical or thoracic MESCC, even with high-dose irradiation histories. The cumulative dose assessment across the original and re-irradiated esophagus was recommended to decrease the risk of severe esophageal toxicities.

This retrospective study aimed to assess the efficacy and safety of palliative radiotherapy for painful non-bone lesions in patients with advanced cancer. We enrolled patients with painful non-bone lesions who underwent conventional palliative radiotherapy between September 2018 and September 2022. The treatment targets included primary tumor lesions, lymph node metastases, non-bone hematogenous metastases, and other lesions. The primary endpoint was the overall pain response rate in evaluable patients, determined based on the International Consensus Pain Response Endpoint criteria. The secondary endpoints included overall survival, pain recurrence, and adverse events. Of the 420 screened patients, 142 received palliative radiotherapy for painful non-bone lesions, and 112 were evaluable. A pain response was achieved in 67 patients (60

Continuous-rotation computed tomography (CT) fluoroscopy is an imaging modality widely used in interventional radiology (IR) procedures, facilitating precise punctures even into small lesions and lesions deep within the body by rapid, real-time, and high-resolution tomographic images (1Knott E.A. Rose S.D. Wagner M.G. et al.CT fluoroscopy for image-guided procedures: physician radiation dose during full-rotation and partial-angle CT scanning.J Vasc Interv Radiol. 2021; 32: 439-446Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar,2Nakatani M. Kariya S. Ono Y. et al.Radiation exposure and protection in computed tomography fluoroscopy.Interv Radiol. 2022; 7: 49-53Crossref Google Scholar). However, this modality has the drawback of high radiation exposure to the eye lens of the interventional radiologist (1Knott E.A. Rose S.D. Wagner M.G. et al.CT fluoroscopy for image-guided procedures: physician radiation dose during full-rotation and partial-angle CT scanning.J Vasc Interv Radiol. 2021; 32: 439-446Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar,2Nakatani M. Kariya S. Ono Y. et al.Radiation exposure and protection in computed tomography fluoroscopy.Interv Radiol. 2022; 7: 49-53Crossref Google Scholar). The installation of a radioprotective shield with an attached lead drape in front of the scan plane was reported to be one of the easiest ways to reduce the scattered radiation (3Kikuchi K. Takaki H. Matsumoto K. et al.Radioprotective effects of a semicircular X-ray shielding device for operators during CT fluoroscopy-guided interventional procedures: experimental and clinical studies.Cardiovasc Interv Radiol. 2023; 46: 770-776Crossref Scopus (0) Google Scholar), but it was not quantitatively compared with a radioprotective shield without a lead drape. Thus, this study compared radiation exposure to the interventional radiologist in conditions using the radioprotective shield with and without a lead drape during continuous-rotation CT fluoroscopy–guided IR procedures. This study was approved by the authors' institutional review board (IRB) (Aichi Cancer Center Hospital) as a cohort study to evaluate the occupational radiation dose during IR procedures. Written informed consent was obtained from the interventional radiologist performing the procedure before measuring the radiation dose. Informed consent to perform lung nodule localization under continuous-rotation CT fluoroscopy, which provides medical exposure, was obtained from each patient. Radiation doses were measured during preprocedural localization of the lung nodules because the fluoroscopy time was relatively short and did not vary in each procedure. A radioprotective shield with an attached lead drape (Kyowaglass XA-III; Kuraray Trading, Osaka, Japan) was installed as a temporary sample in the IR procedure room at the authors' institution between October 2021 and December 2021 and changed to the equivalent radioprotective shield without a lead drape (Kyowaglass XA-I; Kuraray) thereafter. During the period with the lead drape, 20 sessions of lung nodule localization were performed. The radiation doses in this period were evaluated and compared with those of the initial consecutive 20 sessions using the radioprotective shield without a lead drape conducted until March 2022. The procedures were performed percutaneously using continuous-rotation CT fluoroscopy (Aquilion Prime; Canon Medical Systems, Otawara, Japan). Real-time continuous fluoroscopic images were obtained with a tube voltage of 120 kV and a tube current of 10 mA. The radioprotective shield was placed within 30 cm of the caudal side of the scan plane (Fig 1). The radiation dose was measured using small optically stimulated luminescence dosimeters (OSLDs) (Nanodot; Nagase Landauer, Tsukuba, Japan) taped outside the left surface of the radioprotective glasses (Panoramashield; Toray Industries, Tokyo, Japan) (Fig 2). Taped OSLDs were removed from the radioprotective glasses immediately after each session, and the data were read using a microSTAR reader (Nagase Landauer).Figure 2Small optically stimulated luminescence dosimeters were taped outside the left surface of the radioprotective glasses.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The procedural details are summarized in Table. There were no significant differences between the procedures with and without lead drape within any variables, including dose-length product to the patients. The measured radiation doses of the OSLDs were 3.7 μGy (SD ± 1.5; range, 1.7–6.8 μGy) at the procedure using the radioprotective shield with a lead drape and 12.8 μGy (SD ± 4.1; range, 5.1–19.6 μGy) without the lead drape (Fig 3). The radiation dose was significantly lower when using the radioprotective shield with a lead drape by Welch's t test (P < .001).TableProcedure DetailsVariablesRadioprotective boardPWith lead drapeWithout lead drapeSex Female7 (35)9 (45)0.75 Male13 (65)11 (55)Age (y) Mean ± SD63.5 ± 11.166.0 ± 11.40.49 Range31–7841–77BMI Mean ± SD20.9 ± 2.321.5 ± 3.30.52 Range15.5–24.716.6–26.1Tumor size (cm) Mean ± SD1.2 ± 0.51.2 ± 0.50.92 Range0.5–2.10.7–2.1Body position Supine6 (30)10 (50)0.24 Prone9 (45)8 (40) Left lateral decubitus3 (15)1 (5) Right lateral decubitus2 (10)1 (5)Continuous-rotation CT fluoroscopy duration (s) Mean ± SD47.5 ± 15.346.7 ± 10.30.86 Range25.7–76.935.9–69.7Patients' DLP by continuous-rotation CT fluoroscopy (mGy∗cm) Mean ± SD94.7 ± 42.992.9 ± 41.60.89 Range27.6–224.035.2–179.6Note–Numbers in parentheses are percentages.BMI = body mass index; CT = computed tomography; DLP = dose-length product; SD = standard deviation. Open table in a new tab Note–Numbers in parentheses are percentages. BMI = body mass index; CT = computed tomography; DLP = dose-length product; SD = standard deviation. The result of this study showed that attachment of the lead drape to the radioprotective shield was effective in reducing radiation exposure to the eye lens of the interventional radiologist during clinical continuous-rotation CT fluoroscopy–guided IR procedures. Reducing radiation exposure in sessions by using a radioprotective shield with a lead drape will contribute to the ability to perform more procedures while remaining within regulated limits for occupational radiation exposure. Kikuchi et al (3Kikuchi K. Takaki H. Matsumoto K. et al.Radioprotective effects of a semicircular X-ray shielding device for operators during CT fluoroscopy-guided interventional procedures: experimental and clinical studies.Cardiovasc Interv Radiol. 2023; 46: 770-776Crossref Scopus (0) Google Scholar) also reported the usefulness of radioprotective shield with lead drape. They used a semicircular type of shield and proved that use of this tool significantly reduced the radiation exposure to the interventional radiologist compared with no shielding. In addition to their research, the present study showed the usefulness of a radioprotective shield with a lead drape compared with that without a drape. Neeman et al (4Neeman Z. Dromi S.A. Sarin S. Wood B.J. CT fluoroscopy shielding: decreases in scattered radiation for the patient and operator.J Vasc Interv Radiol. 2006; 17: 1999-2004Abstract Full Text Full Text PDF PubMed Google Scholar) reported the usefulness of introducing a fenestrated drape hung from the CT gantry and a corner drape attached to the table, reducing the radiation dose from 564.6 to 38.81 μGy. Although scanner technical developments and differences in measurement conditions may limit direct comparison, the radiation doses in the present study were lower than those in their study. This study has several limitations. First, radiation doses measured using small OSLDs were environmental radiation doses; therefore, the results did not entirely match the dose to the eye lens. Second, the distances between the scan plane, the interventional radiologist, and the radioprotective shield were not constant, which may affect measured radiation dose. Despite these limitations, this study has shown the effectiveness of using a radioprotective shield with an attached lead drape to reduce the radiation exposure to the eye lens of the interventional radiologist during continuous-rotation CT fluoroscopy–guided procedures. This work was supported by the Aichi Cancer Research Foundation.

Purpose: Total body irradiation before bone marrow transplantation for hematological malignancies using Radixact, a high-precision radiotherapy machine, can potentially reduce side effects and the risk of secondary malignancies. However, stable control of couch speed is critical, and direct assessment methods outlined in quality assurance guidelines are lacking. This study aims to develop a real-time couch speed verification system for the Radixact. Methods: The developed system used a linear encoder to measure couch speed directly. Accuracy was verified via a linear stage, comparing measurements with a laser distance sensor. After placing a phantom simulating the human body on the Radixact couch, the couch speed was verified using predefined speed plans. Results: Operating the linear stage at 0.1, 0.5, and 1.0 mm/s revealed that the maximum position error of the developed verification system compared to the laser distance sensor was nearly equivalent to the distance resolution of the system (0.05 mm/pulse), with negligible average speed error. When the Radixact couch operated at 0.1, 0.5, and 1.0 mm/s, the values obtained by the verification system agreed with the theoretical values within the sampling period (0.01 s) and distance resolution (0.05 mm). Conclusion: The verification system developed provides real-time monitoring of the speed of the Radixact table, ensuring treatment effectiveness and patient safety. It would guarantee the couch speed's soundness and contribute to the "visualization" of safety.