Retrospective analysis of treatment-positioning accuracy and dose error in boron neutron capture therapy using a sitting-position treatment system for head and neck cancer.

The neutron beam in boron neutron capture therapy (BNCT) exhibits poor directionality and significantly decreasing neutron flux with increasing distance. Therefore, the treatment site must be close to the irradiation aperture. Some patients with head and neck cancer may benefit from a sitting-position setup. The study aim was to evaluate the treatment-positioning accuracy and dose error in sitting patients receiving BNCT. Thirty-two patients with head and neck cancer who underwent sitting-position BNCT at Southern Tohoku BNCT Research Center were included in the study. Horizontal (ΔX) and vertical (ΔY) errors were defined as the displacement between the treatment planning system (TPS) digital reconstructed radiograph and the pre-treatment X-ray image. Using in-house software, image matching was performed. The beam-axial directional (ΔZ) error was compared with the parameters entered into the TPS and the actual pre-treatment measured values. The translational-position error was reflected in the TPS's patient coordinate system with respect to the reference plan. Re-dose calculations were performed to evaluate the effect of positional error on tumor and normal-tissue doses. The [ΔX, ΔY, ΔZ] DRR-CR mean ± 1SD were - 0.40 ± 2.0, 0.30 ± 2.3, and - 1.4 ± 1.5 mm, respectively. The Dmean and D98% tumor-dose errors were 1.22 % ± 1.44 % and 0.99 % ± 1.63 %, respectively. The D2% pharyngeal and oral mucosal-dose errors were 0.98 % ± 1.91 % and 1.21 % ± 1.78 %, respectively. The tumor- and normal-tissue dose errors were typically < 5 %. High-precision treatment was feasible in sitting-positioned BNCT.

Performance of dual-energy subtraction in contrast-enhanced mammography for three different manufacturers: a phantom study.

BACKGROUND: Dual-energy subtraction (DES) imaging is critical in contrast-enhanced mammography (CEM), as the recombination of low-energy (LE) and high-energy (HE) images produces contrast enhancement while reducing anatomical noise. The study's purpose was to compare the performance of the DES algorithm among three different CEM systems using a commercial phantom. METHODS: A CIRS Model 022 phantom, designed for CEM, was acquired using all available automatic exposure modes (AECs) with three CEM systems from three different manufacturers (CEM1, CEM2, and CEM3). Three studies were acquired for each system/AEC mode to measure both radiation dose and image quality metrics, including estimation of measurement error. The mean glandular dose (MGD) calculated over the three acquisitions was used as the dosimetry index, while contrast-to-noise ratio (CNR) was obtained from LE and HE images and DES images and used as an image quality metric. RESULTS: On average, the CNR of LE images of CEM1 was 2.3 times higher than that of CEM2 and 2.7 times higher than that of CEM3. For HE images, the CNR of CEM1 was 2.7 and 3.5 times higher than that of CEM2 and CEM3, respectively. The CNR remained predominantly higher for CEM1 even when measured from DES images, followed by CEM2 and then CEM3. CEM1 delivered the lowest MGD (2.34 ± 0.03 mGy), followed by CEM3 (2.53 ± 0.02 mGy) in default AEC mode, and CEM2 (3.50 ± 0.05 mGy). The doses of CEM2 and CEM3 increased by 49.6% and 8.0% compared with CEM1, respectively. CONCLUSION: One system outperformed others in DES algorithms, providing higher CNR at lower doses. RELEVANCE STATEMENT: This phantom study highlighted the variability in performance among the DES algorithms used by different CEM systems, showing that these differences can be translated in terms of variations in contrast enhancement and radiation dose. KEY POINTS: DES images, obtained by recombining LE and HE images, have a major role in CEM. Differences in radiation dose among CEM systems were between 8.0% and 49.6%. One DES algorithm achieved superior technical performance, providing higher CNR values at a lower radiation dose.

Quantitative CT imaging and radiation-absorbed dose estimations of 166Ho microspheres: paving the way for clinical application.

BACKGROUND: Microbrachytherapy enables high local tumor doses sparing surrounding tissues by intratumoral injection of radioactive holmium-166 microspheres (166Ho-MS). Magnetic resonance imaging (MRI) cannot properly detect high local Ho-MS concentrations and single-photon emission computed tomography has insufficient resolution. Computed tomography (CT) is quicker and cheaper with high resolution and previously enabled Ho quantification. We aimed to optimize Ho quantification on CT and to implement corresponding dosimetry. METHODS: Two scanners were calibrated for Ho detection using phantoms and multiple settings. Quantification was evaluated in five phantoms and seven canine patients using subtraction and thresholding including influences of the target tissue, injected amounts, acquisition parameters, and quantification volumes. Radiation-absorbed dose estimation was implemented using a three-dimensional 166Ho specific dose point kernel generated with Monte Carlo simulations. RESULTS: CT calibration showed a near-perfect linear relation between radiodensity (HU) and Ho concentrations for all conditions, with differences between scanners. Ho detection during calibration was higher using lower tube voltages, soft-tissue kernels, and without a scanner detection limit. The most accurate Ho recovery in phantoms was 102 ± 11% using a threshold of mean tissue HU + (2 × standard deviation) and in patients 98 ± 31% using a 100 HU threshold. Thresholding allowed better recovery with less variation and dependency on the volume of interest compared to the subtraction of a single HU reference value. Corresponding doses and histograms were successfully generated. CONCLUSION: CT quantification and dosimetry of 166Ho should be considered for further clinical application with on-site validation using radioactive measurements and intra-operative Ho-MS and dose visualizations. RELEVANCE STATEMENT: Image-guided holmium-166 microbrachytherapy currently lacks reliable quantification and dosimetry on CT to ensure treatment safety and efficacy, while it is the only imaging modality capable of quantifying high in vivo holmium concentrations. KEY POINTS: Local injection of 166Ho-MS enables high local tumor doses while sparing surrounding tissue. CT enables imaging-based quantification and radiation-absorbed dose estimation of concentrated Ho in vivo, essential for treatment safety and efficacy. Two different CT scanners and multiple acquisition and reconstruction parameters showed near-perfect linearity between radiodensity and Ho concentration. The most accurate Ho recoveries on CT were 102 ± 11% in five phantoms and 98 ± 31% in seven canine patients using thresholding methods. Dose estimations and volume histograms were successfully implemented for clinical application using a dose point kernel based on Monte Carlo simulations.

Can physical parameters from radiation simulation scan with deep inspiratory breath hold predict magnitude of heart dose reduction?

INTRODUCTION: Deep inspiratory breath hold is one of the techniques for reducing the heart doses for left breast cancers. This study was conducted to confirm use of physical parameters from DIBH simulation CT scan like DIBH amplitude alongside several novel parameters to predict the heart dose reduction. MATERIALS AND METHODS: Segmentation and planning of radiation to the left breast on the free breathing (FB) and DIBH simulation scan was performed for 50 left-sided breast cancer patients treated with DIBH technique. Physical parameters, namely DIBH amplitude, anterior sternal displacement, diaphragmatic excursion, ratio of lung volume (cc) in DIBH scan to lung volume in FB scan (cc), and delta heart volume in field (DHVIF), were extracted and were compared with magnitude of heart dose reduction (mean heart dose, V30Gy, and D5%). RESULTS: Forty-eight (96%) patients achieved reduction in the mean heart dose with DIBH technique, while all patients had reduction in V30Gy. The median reduction was 41%, 89.7%, and 63% in the mean dose, V30Gy, and D5%, respectively. While DIBH did not correlate with heart dose reduction, ratio of lung volumes and DHVIF showed a strong positive correlation with heart dose reduction (P < 0.05). Sternal displacement correlated weakly with heart dose reduction but strongly with DHVIF, demonstrating to be an indirect predictor. CONCLUSIONS: Physical parameters like anterior sternal displacement, ratio of lung volumes of DIBH to FB, and possibly diaphragmatic movement can predict the dose reduction before the dose calculations by the physicist. These parameters can be used to construct a model to predict heart dose reduction.

[Influencing factors of occupational health of clinical nuclear medical staff].

Objective: To analyze the characteristics and its influencing factors of occupational injury among clinical nuclear medicine staff, and to put forward suggestions for formulating relevant radiation protection intervention measures. Methods: In March 2022, a study was conducted involving 12 medical institutions engaged in nuclear medicine in Gansu Province. The occupational health examination data of 1451 clinical nuclear medicine staff were analyzed. The study subjects were divided into two groups based on the median annual effective dose of external exposure in 2022: Group A (annual effective dose ≤0.2 mSv, n=927) and group B (annual effective dose >0.2 mSv, n=524). The effects of annual effective dose, age, seniority, gender and occupational category on occupational health of clinical nuclear medicine staff were analyzed. Classification variables between groups were compared with Pearson χ(2) test. Multivariate logistic regression was used to analyze the influencing factors of the abnormal results. Results: The abnormal rates of white blood cell count (WBC), red blood cell count (RBC) and hemoglobin (HGB) in female clinical nuclear medical staff were higher than those in males, and the differences were statistically significant (P<0.001). The abnormal rates of WBC and HGB in clinical nuclear medicine staff of different occupational categories were statistically significant (P<0.05). The abnormal rates of RBC and HGB of clinical nuclear medicine staff in annual effective dose group B were higher than those in group A, and the differences were statistically significant (P<0.05). Multivariate logistic regression results showed that the abnormal risks of RBC in annual effective dose group B was 2.465 times of that in group A, the abnormal risks of RBC, WBC and HGB in females were 9.354, 2.939 and 6.760 times of those in males, respectively. The abnormal risk of WBC in the radiotherapy group was 2.334 times of that in general radiotherapy group. The abnormal risk of lens in nuclear medicine group was 2.459 times of that in general radiotherapy group. The abnormal risk of ECG and lens in ≥35 years old age group were 1.814 times and 1.969 times of those in <35 years old age group, respectively. The abnormal risk of lens of the ≥10 working years group was 1.899 times of that in the <10 working years group. The risk of lymphocyte micronucleus abnormality in the interventional group was 1.481 times of that in the general radiotherapy group, the risk of lymphocyte micronucleus abnormality in females was 2.215 times of that in males. The risk of lymphocyte micronucleus abnormality and lymphocyte chromosome aberration in ≥35 years old age group were 2.552 and 2.266 times of those in <35 years old age group, respectively. The risk of lymphocyte micronucleus abnormality in the group with≥10 working years was 1.443 times of that in<10 working years group (P<0.05) . Conclusion: Long-term low-dose ionizing radiation has a certain effect on the lens and genetic indexes of clinical nuclear medicine staff.

Comparison of deep-learning multimodality data fusion strategies in mandibular osteoradionecrosis NTCP modelling using clinical variables and radiation dose distribution volumes.

Objective.Normal tissue complication probability (NTCP) modelling is rapidly embracing deep learning (DL) methods, acknowledging the importance of spatial dose information. Finding effective ways to combine information from radiation dose distribution maps (dosiomics) and clinical data involves technical challenges and requires domain knowledge. We propose different multi-modality data fusion strategies to facilitate future DL-based NTCP studies.Approach.Early, joint and late DL multi-modality fusion strategies were compared using clinical and mandibular radiation dose distribution volumes. These were contrasted with single-modality models: a random forest trained on non-image data (clinical, demographic and dose-volume metrics) and a 3D DenseNet-40 trained on image data (mandibular dose distribution maps). The study involved a matched cohort of 92 osteoradionecrosis cases and 92 controls from a single institution.Main results.The late fusion model exhibited superior discrimination and calibration performance, while the join fusion achieved a more balanced distribution of the predicted probabilities. Discrimination performance did not significantly differ between strategies. Late fusion, though less technically complex, lacks crucial inter-modality interactions for NTCP modelling. In contrast, joint fusion, despite its complexity, resulted in a single network training process which included intra- and inter-modality interactions in its model parameter optimisation.Significance.This study is a pioneering effort in comparing different strategies for including image data into DL-based NTCP models in combination with lower dimensional data such as clinical variables. The discrimination performance of such multi-modality NTCP models and the choice of fusion strategy will depend on the distribution and quality of both types of data. Multiple data fusion strategies should be compared and reported in multi-modality NTCP modelling using DL.

Factors affecting radiation exposure in patients undergoing endoscopic treatment for urolithiasis.

Imaging techniques, such as computed tomography (CT) and fluoroscopy, are essential for the diagnosis and treatment of urolithiasis. There is increasing concern regarding the cumulative radiation dose associated with medical imaging and its adverse effects. This study aimed to assess radiation exposure in patients undergoing endoscopic management of urolithiasis and to identify factors associated with increased exposure.A retrospective analysis of all consecutive symptomatic urolithiasis cases who underwent endoscopic surgery over a two-year period at a tertiary referral center was performed. The cumulative radiation dose was recorded per stone episode, and the effective dose (ED) then calculated. Multivariable regression analysis was performed to determine the association between ED and patient, stone, and procedural characteristics.Between January 2020 and December 2021, 250 patients underwent endoscopic intervention for urolithiasis; 71% (n = 178) were male with a median age of 48 years (IQR 35-59). The median stone size was 6 mm (IQR, 5-8 mm) and the median stone volume was 110 mm3 (IQR, 60-206 mm3). Most stones were located in the distal ureter (46%, n = 114). The median ED received per stone episode was 3.99 mSv (IQR 2.9-7 mSv). On multivariable analysis, BMI, number of CT scans performed, CT protocol used, and repeat procedures strongly predicted increased radiation dose (p < 0.01).It is important for urologists to consider the cumulative radiation dosage in patients with urolithiasis. Strategies to minimize exposure, such as avoiding re-imaging, low-dose CTs, and collimation of the region of interest with judicious magnification, should be considered during treatment.

Co-designing of a prototype mobile application for fetal radiation dose monitoring among pregnant radiographers using a design thinking approach.

This study aimed to develop a prototype mobile application to enhance fetal dosimetry among pregnant radiographers in #### through a design thinking approach. Eleven participants were recruited to engage in a participatory design workshop, which encompassed five stages: Empathise, Ideate, Define, Prototype and Test. The participants were divided into two teams. Qualitative datasets from the workshop included field notes and FIGMA screens. The data were analysed through thematic analysis, from which three major themes emerged: (1) Unsafe working environments for pregnant radiographers, (2) The need for enhanced fetal radiation dose monitoring by pregnant radiographers as an occupational health and safety requirement, and (3) Co-designing of the prototype mobile application, PregiDose. The participants contributed towards a prototype mobile application which addressed challenges experienced in the real-life setting. Hence, the prototype can be used as an effective framework by which to guide the development of the final artefact.

Dose-rate effects and tumor control probability in177Lu-based targeted radionuclide therapy: a theoretical analysis.

Objective.177Lu-based targeted radionuclide therapy (TRT) has become an important cancer treatment option in recent years, in particular in the treatment of advanced prostate cancer and metastasized neuroendocrine tumors. Although it is known from conventional radiotherapy that the temporal dynamics of the dose-rate can be of relevance for tumor cell survival, the analysis of TRT efficacy usually considers only the absorbed dose. Thus, the aim of this theoretical analysis is to shed light on the possible effects of the pattern of dose-rate in TRT on tumor control probability (TCP).Approach.For this purpose, TCP is studied numerically in a typical four-cycle treatment regime based on the mechanistic lethal-potentially lethal model and the Zaider-Minerbo model for TCP including repopulation of tumor cells.Main results.It is shown that the dose-rate pattern in TRT can have a substantial effect on TCP even though the absorbed dose in the tumor lesion is unchanged. These dose-rate effects are particularly evident when repair of potentially lethal lesions is slow.Significance.The results indicate that in some situations in the analysis of the efficacy of TRT it is necessary to consider the full dose-rate pattern instead of the absorbed dose alone. This can be highly relevant for optimization and further development of TRTs. In particular, it could be of relevancy in studying the efficacy of newly emerging treatment concepts that combine the use of TRT and drugs that inhibit DNA damage repair.

Assessment of cone beam computed tomography use in pediatric and adolescent patients: a cross-sectional study.

BACKGROUND: The use of cone beam computed tomography (CBCT) for dentomaxillofacial diagnostics in pediatric dentistry is expanding and concerns have been raised about the radiation risks associated with this imaging modality, especially for children. Dentomaxillofacial paediatric imaging: an investigation towards low-dose radiation induced risks (DIMITRA) is a multidisciplinary project focused on optimizing CBCT exposure for children and adolescents. This study aims to clarify the indications behind CBCT scans in children aligned with DIMITRA's recommendations. METHODS: For each CBCT examination, data were collected on patient age at the time of the CBCT examination, gender, reason for request, referring department, CBCT-requested region, and the field of view (FOV) dimension of imaging. The CBCT indications were categorized under six headings according to an adaptation of the DIMITRA project recommendations: impacted teeth, dentoalveolar trauma, orofacial clefts, dental anomalies, bone pathology, syndromes. Indications not categorized in DIMITRA were recorded below the heading "other". RESULTS: The most common indication was the "other" category (34.8%), which included implant, temporomandibular joint dysfunction, orofacial anomalies, foreign object and root canal morphology. The least common indication was "orofacial cleft" (1.9%) and no requests were made for cases related to syndromes. Detection of supernumerary tooth in dental anomalies (68.6%) was the most common CBCT indication, while dentigerous cysts (37.6%) were among the most common CBCT indication in bone pathologies and orofacial anomalies (68.1%) in the other category. The most common size was External Center (15 × 15 cm) (27%) and the least common size was Both Arches/small (8 × 8 cm) (0.4%) when the CBCT FOV was analysed. CONCLUSIONS: Although the option of a smaller FOV size was available, the larger FOV size that included the both jaws were most frequently used. When justifying CBCT requests, patient-specific radiation dose risks should be considered and specific guidelines should be followed.

Cavity ionization chamber responses in the JAEA and the NMIJ high-energy photon reference fields for radiation protection.

A dosimeter should ideally be calibrated in a reference field with similar energy and doserate to that which the dosimeter is being used to measure. Environments around nuclear reactors and radiation therapy facilities have high-energy photons with energies exceeding that of60Co gamma rays, and controlling exposure to these photons is important. The Japan Atomic Energy Agency and National Metrology Institute of Japan have high-energy reference fields with energies above several megaelectronvolts for different types of accelerators. Their reference fields have different fluence-energy distributions. In this study, the energy dependencies of the two-cavity ionization chambers, which are often used by secondary standard laboratories, were experimentally and computationally evaluated for each high-energy field. These results agreed well within the relative expanded uncertainties (k= 2), and their capabilities for air kerma measurements in each high-energy reference field were confirmed. Therefore, the capabilities of the air-kerma measurements were verified in the two high-energy reference fields.

Radiation dose reduction and image quality in pediatric paranasal sinus CT: with automatic tube current modulation and iterative reconstruction technique.

Our objective is to evaluate radiation dose and image quality in pediatric paranasal sinus computed tomography (CT) with automatic tube current modulation (ATCM) and sinogram-affirmed iterative reconstruction algorithm (SAFIRE). CT scans from 80 patients were divided into two groups: Group A [80 kVp, pitch 1.5, 40 mAs, the filtered back projection (FBP) algorithm] and Group B (70 kVp, pitch 3, ATCM with reference at 40 mAs, SAFIRE strengths 1-5). We have evaluated image quality and radiation dose. Group B demonstrated significantly lower volume computed tomography dose index, dose-length product, and effective dose than Group A (0.13 ± 0.03 vs. 1.57 ± 0.01 mGy, 2.27 ± 0.82 vs. 19.88 ± 2.01 mGy·cm, and 0.0081 ± 0.0017 vs. 0.079 ± 0.013 mSv, respectively; P < .001). Increasing SAFIRE strengths correlated with noise reduction and SNR enhancement. Group B's noise and SNRsoft at SAFIRE strength 5 were comparable with Group A. Images reconstructed with SAFIRE strength 5 in Group B exhibit comparable image quality with FBP in Group A.

Virtual reality training for radiation safety in cardiac catheterization laboratories - an integrated study.

The advent of fluoroscopically guided cardiology procedures has greatly improved patient outcomes but has also increased occupational radiation exposure for healthcare professionals, leading to adverse health effects such as radiation-induced cataracts, alopecia, and cancer. This emphasizes the need for effective radiation safety training. Traditional training methods, often based on passive learning, fail to simulate the dynamic catheterization laboratory environment adequately. Virtual Reality (VR) offers a promising alternative by providing immersive, interactive experiences that mimic real-world scenarios without the risks of actual radiation exposure. Our study aims to assess the effectiveness of VR-based radiation safety training compared to traditional methods. We conducted a prospective cohort study involving 48 healthcare professionals in a catheterization lab setting. Participants underwent a 1-hour self-directed VR training session using Virtual Medical Coaching's RadSafe VR software, which simulates real-world clinical scenarios. Pre- and post-intervention radiation dose levels were measured using personal dosimeters at the eye, chest, and pelvis. Knowledge and skills were assessed through tests, and feedback was gathered through surveys and interviews. Statistical analysis revealed significant reductions in radiation exposure across all professional groups after VR training. For cardiologists, the eye dose dropped by 21.88% (from 2.88 mSv to 2.25 mSv), the chest dose decreased by 21.65% (from 4.11 mSv to 3.22 mSv), and the pelvis dose went down by 21.84% (from 2.06 mSv to 1.61 mSv). Perioperative nurses experienced similar reductions, with eye doses decreasing by 14.74% (from 1.56 mSv to 1.33 mSv), chest doses by 26.92% (from 2.6 mSv to 1.9 mSv), and pelvis doses by 26.92% (from 1.3 mSv to 0.95 mSv). Radiographers saw their eye doses reduced by 18.95% (from 0.95 mSv to 0.77 mSv), chest doses by 42.11% (from 1.9 mSv to 1.1 mSv), and pelvis doses by 27.63% (from 0.76 mSv to 0.55 mSv).Participants reported enhanced engagement, improved understanding of radiation safety, and a preference for VR over traditional methods. A cost analysis also demonstrated the economic advantages of VR training, with significant savings in staff time and rental costs compared to traditional methods. Our findings suggest that VR is a highly effective and cost-efficient training tool for radiation safety in healthcare, offering significant benefits over traditional training approaches.

Low-dose high-resolution chest CT in adults with cystic fibrosis: intraindividual comparison between photon-counting and energy-integrating detector CT.

BACKGROUND: Regular disease monitoring with low-dose high-resolution (LD-HR) computed tomography (CT) scans is necessary for the clinical management of people with cystic fibrosis (pwCF). The aim of this study was to compare the image quality and radiation dose of LD-HR protocols between photon-counting CT (PCCT) and energy-integrating detector system CT (EID-CT) in pwCF. METHODS: This retrospective study included 23 pwCF undergoing LD-HR chest CT with PCCT who had previously undergone LD-HR chest CT with EID-CT. An intraindividual comparison of radiation dose and image quality was conducted. The study measured the dose-length product, volumetric CT dose index, effective dose and signal-to-noise ratio (SNR). Three blinded radiologists assessed the overall image quality, image sharpness, and image noise using a 5-point Likert scale ranging from 1 (deficient) to 5 (very good) for image quality and image sharpness and from 1 (very high) to 5 (very low) for image noise. RESULTS: PCCT used approximately 42% less radiation dose than EID-CT (median effective dose 0.54 versus 0.93 mSv, p < 0.001). PCCT was consistently rated higher than EID-CT for overall image quality and image sharpness. Additionally, image noise was lower with PCCT compared to EID-CT. The average SNR of the lung parenchyma was lower with PCCT compared to EID-CT (p < 0.001). CONCLUSION: In pwCF, LD-HR chest CT protocols using PCCT scans provided significantly better image quality and reduced radiation exposure compared to EID-CT. RELEVANCE STATEMENT: In pwCF, regular follow-up could be performed through photon-counting CT instead of EID-CT, with substantial advantages in terms of both lower radiation exposure and increased image quality. KEY POINTS: Photon-counting CT (PCCT) and energy-integrating detector system CT (EID-CT) were compared in 23 people with cystic fibrosis (pwCF). Image quality was rated higher for PCCT than for EID-CT. PCCT used approximately 42% less radiation dose and offered superior image quality than EID-CT.

Application of motion prediction based on a long short-term memory network for imaging dose reduction in real-time tumor-tracking radiation therapy.

PURPOSE: To demonstrate the possibility of using a lower imaging rate while maintaining acceptable accuracy by applying motion prediction to minimize the imaging dose in real-time image-guided radiation therapy. METHODS: Time-series of three-dimensional internal marker positions obtained from 98 patients in liver stereotactic body radiation therapy were used to train and test the long-short-term memory (LSTM) network. For real-time imaging, the root mean squared error (RMSE) of the prediction on three-dimensional marker position made by LSTM, the residual motion of the target under respiratory-gated irradiation, and irradiation efficiency were evaluated. In the evaluation of the residual motion, the system-specific latency was assumed to be 100 ms. RESULTS: Except for outliers in the superior-inferior (SI) direction, the median/maximum values of the RMSE for imaging rates of 7.5, 5.0, and 2.5 frames per second (fps) were 0.8/1.3, 0.9/1.6, and 1.2/2.4 mm, respectively. The median/maximum residual motion in the SI direction at an imaging rate of 15.0 fps without prediction of the marker position, which is a typical clinical setting, was 2.3/3.6 mm. For rates of 7.5, 5.0, and 2.5 fps with prediction, the corresponding values were 2.0/2.6, 2.2/3.3, and 2.4/3.9 mm, respectively. There was no significant difference between the irradiation efficiency with and that without prediction of the marker position. The geometrical accuracy at lower frame rates with prediction applied was superior or comparable to that at 15 fps without prediction. In comparison with the current clinical setting for real-time image-guided radiation therapy, which uses an imaging rate of 15.0 fps without prediction, it may be possible to reduce the imaging dose by half or more. CONCLUSIONS: Motion prediction can effectively lower the frame rate and minimize the imaging dose in real-time image-guided radiation therapy.

Feasibility of the analytical dose calculation method for Au-198 brachytherapy.

PURPOSE: A dose calculation algorithm Computed Tomography (CT)-based analytical dose calculation method (CTanly), which can correct for subject inhomogeneity and size-dependent scatter doses, was applied to the 198Au seed. In this study, we evaluated the effectiveness of the CTanly method by comparing the gold standard Monte Carlo (MC) method and the conventional TG43 method on two virtual phantoms and patient CT images simulating oral cancer. METHODS: As virtual phantoms, a water phantom and a heterogeneous phantom with soft tissue inserted cubic fat, lung, and bone were used. A 2-mm-thick lead plate was also inserted into the heterogeneous phantom as a dose attenuator. Virtual 198Au seeds and a 2-mm-thick lead plate were placed on the patient CT images. Dose distributions obtained via the TG43 and CTanly methods were compared with those of the MC by gamma analysis with 2%/2-mm thresholds. The computation durations were also compared. RESULTS: In the water phantom, dose distributions comparable to those obtained via the MC method were obtained regardless of the algorithm. For the inhomogeneity phantom and patient case, the CTanly method showed an improvement in the gamma passing rate and dose distributions similar to those of the MC method were obtained. The computation time, which was days with the MC method, was reduced to minutes with the CTanly method. CONCLUSIONS: The CTanly method is effective for 198Au seed dose calculations and takes a shorter time to obtain the dose distributions than the MC method.

Radiation dose analysis in interventional neuroradiology of unruptured aneurysm cases.

This study aimed to evaluate the radiation doses (peak skin dose (PSD) and bilateral lens dose) for each interventional neuroradiology procedure. A direct measurement system consisting of small radiophotoluminescence glass dosimeter chips and a dosimetry cap made of thin stretchable polyester was used for radiation dosimetry. The mean PSDs for each procedure were 1565 ± 590 mGy (simple technique coil embolization (STCE) cases), 1851 ± 825 mGy (balloon-assisted coil embolization (BACE) cases), 2583 ± 967 mGy (stent-assisted coil embolization (SACE) cases), 1690 ± 597 mGy (simple flow-diverter stenting (FDS) cases), and 2214 ± 726 mGy (FDS + coiling cases). The mean PSD was higher in SACE cases than in STCE, BACE, and simple FDS cases. Moreover, the PSD exceeded 2000 mGy and 3000 mGy in 46 (67.6%) and 19 (27.9%) SACE cases, respectively. The left lens doses for each procedure were 126 ± 111 mGy (STCE cases), 163 ± 152 mGy (BACE cases), 184 ± 148 mGy (SACE cases), 144 ± 60 mGy (simple FDS cases), and 242 ± 178 mGy (FDS + coiling cases). The left lens dose in SACE cases was higher than that in STCE cases and exceeded 500 mGy in 3 (4.4%) patients. In FDS + coiling cases, the mean PSD and left lens dose were 2214 ± 726 mGy and 242 ± 178 mGy, respectively. The left lens dose was higher than that in the STCE and BACE cases, with two (15.4%) patients receiving doses >500 mGy in FDS + coiling cases. The detailed data obtained in this study are expected to contribute to the promotion of radiation dose optimization.

Deep learning-based segmentation for high-dose-rate brachytherapy in cervical cancer using 3D Prompt-ResUNet.

Objective.To develop and evaluate a 3D Prompt-ResUNet module that utilized the prompt-based model combined with 3D nnUNet for rapid and consistent autosegmentation of high-risk clinical target volume (HRCTV) and organ at risk (OAR) in high-dose-rate brachytherapy for cervical cancer patients.Approach.We used 73 computed tomography scans and 62 magnetic resonance imaging scans from 135 (103 for training, 16 for validation, and 16 for testing) cervical cancer patients across two hospitals for HRCTV and OAR segmentation. A novel comparison of the deep learning neural networks 3D Prompt-ResUNet, nnUNet, and segment anything model-Med3D was applied for the segmentation. Evaluation was conducted in two parts: geometric and clinical assessments. Quantitative metrics included the Dice similarity coefficient (DSC), 95th percentile Hausdorff distance (HD95%), Jaccard index (JI), and Matthews correlation coefficient (MCC). Clinical evaluation involved interobserver comparison, 4-grade expert scoring, and a double-blinded Turing test.Main results.The Prompt-ResUNet model performed most similarly to experienced radiation oncologists, outperforming less experienced ones. During testing, the DSC, HD95% (mm), JI, and MCC value (mean ± SD) for HRCTV were 0.92 ± 0.03, 2.91 ± 0.69, 0.85 ± 0.04, and 0.92 ± 0.02, respectively. For the bladder, these values were 0.93 ± 0.05, 3.07 ± 1.05, 0.87 ± 0.08, and 0.93 ± 0.05, respectively. For the rectum, they were 0.87 ± 0.03, 3.54 ± 1.46, 0.78 ± 0.05, and 0.87 ± 0.03, respectively. For the sigmoid, they were 0.76 ± 0.11, 7.54 ± 5.54, 0.63 ± 0.14, and 0.78 ± 0.09, respectively. The Prompt-ResUNet achieved a clinical viability score of at least 2 in all evaluation cases (100%) for both HRCTV and bladder and exceeded the 30% positive rate benchmark for all evaluated structures in the Turing test.Significance.The Prompt-ResUNet architecture demonstrated high consistency with ground truth in autosegmentation of HRCTV and OARs, reducing interobserver variability and shortening treatment times.

Effects of tube voltage, radiation dose and adaptive statistical iterative reconstruction strength level on the detection and characterization of pulmonary nodules in ultra-low-dose chest CT.

OBJECTIVE: To explore the effects of tube voltage, radiation dose and adaptive statistical iterative reconstruction (ASiR-V) strength level on the detection and characterization of pulmonary nodules by an artificial intelligence (AI) software in ultra-low-dose chest CT (ULDCT). MATERIALS AND METHODS: An anthropomorphic thorax phantom containing 12 spherical simulated nodules (Diameter: 12 mm, 10 mm, 8 mm, 5 mm; CT value: -800HU, -630HU, 100HU) was scanned with three ULDCT protocols: Dose-1 (70kVp:0.11mSv, 100kVp:0.10mSv), Dose-2 (70kVp:0.34mSv, 100kVp:0.32mSv), Dose-3 (70kVp:0.53mSv, 100kVp:0.51mSv). All scanning protocols were repeated five times. CT images were reconstructed using four different strength levels of ASiR-V (0%=FBP, 30%, 50%, 70%ASiR-V) with a slice thickness of 1.25 mm. The characteristics of the physical nodules were used as reference standards. All images were analyzed using a commercially available AI software to identify nodules for calculating nodule detection rate (DR) and to obtain their long diameter and short diameter, which were used to calculate the deformation coefficient (DC) and size measurement deviation percentage (SP) of nodules. DR, DC and SP of different imaging groups were statistically compared. RESULTS: Image noise decreased with the increase of ASiR-V strength level, and the 70 kV images had lower noise under the same strength level (mean-value 70 kV: 40.14 ± 7.05 (dose 1), 27.55 ± 7.38 (dose 2), 23.88 ± 6.98 (dose 3); 100 kV: 42.36 ± 7.62 (dose 1); 30.78 ± 6.87 (dose 2); 26.49 ± 6.61 (dose 3)). Under the same dose level, there were no differences in DR between 70 kV and 100 kV (dose 1: 58.76% vs. 58.33%; dose 2: 73.33% vs. 70.83%; dose 3: 75.42% vs. 75.42%, all p > 0.05). The DR of GGNs increased significantly at dose 2 and higher (70 kV: 38.12% (dose 1), 60.63% (dose 2), 64.38% (dose 3); 100 kV: 37.50% (dose 1), 59.38% (dose 2), 66.25% (dose 3)). In general, the use of ASiR-V at higher strength levels (> 50%) and 100 kV provided better (lower) DC and SP. CONCLUSION: Detection rates are similar between 70 kV and 100 kV scans. The 70 kV images have better noise performance under the same ASiR-V level, while images of 100 kV and higher ASiR-V levels are better in preserving the nodule morphology (lower DC and SP); the dose levels above 0.33mSv provide high sensitivity for nodules detection, especially the simulated ground glass nodules.