Dose Difference Research Articles

Patient specific quality assurance of volumetric modulated arc therapy of synchronous bilateral breast cancer

Synchronous bilateral breast cancers (SBBC) present a considerable issue in external beam radiotherapy because of large fields size and large target volumes. Mono-isocentric volumetric modulated arc therapy (VMAT) appears as an appropriate irradiation technique for these types of tumors. The aim of this study was to demonstrate the utility of a 3D DVH pretreatment quality assurance program in VMAT of SBBC cases. Twenty SBBC patients who underwent radiation therapy in our department were retrospectively enrolled in this study. Fifteen patients were treated exclusively to the mammary glands. Five patients benefited from a dose boost on the tumor bed (60Gy). Nine patients were irradiated on the supraclavicular nodes (50Gy). This dose was delivered in 25 fractions and integrated boost was used when appropriate. Depending on the complexity of the treatment plans; 2 or 4 arcs VMAT plans were used in a mono-isocentric technique. The patient specific quality assurance (PSQA) was evaluated using COMPASS measured data, COMPASS reconstructed (CR) and COMPASS computed (CC) dose compared to treatment planning system (TPS) dose. Clinical evaluation was based on DVH metrics for target volumes and organ at risks.The maximum average dose deviation between TPS, CC, and CR was below 3%. The paired t-test between TPS, CC, and CR shows a strong agreement (p < 0.001). The 3DVH dose distribution comparison between TPS and COMPASS were also performed with good gamma score for global analysis.COMPASS was successfully evaluated as a 3DVH pretreatment system for SBBC despite the large fields size and complex target volumes. It allows the verification of the plan in 3D patient anatomy and the evaluation of dose discrepancies.

Clinical Use of a Commercial Artificial Intelligence-Based Software for Autocontouring in Radiation Therapy: Geometric Performance and Dosimetric Impact.

When autocontouring based on artificial intelligence (AI) is used in the radiotherapy (RT) workflow, the contours are reviewed and eventually adjusted by a radiation oncologist before an RT treatment plan is generated, with the purpose of improving dosimetry and reducing both interobserver variability and time for contouring. The purpose of this study was to evaluate the results of application of a commercial AI-based autocontouring for RT, assessing both geometric accuracies and the influence on optimized dose from automatically generated contours after review by human operator. A commercial autocontouring system was applied to a retrospective database of 40 patients, of which 20 were treated with radiotherapy for prostate cancer (PCa) and 20 for head and neck cancer (HNC). Contours resulting from AI were compared against AI contours reviewed by human operator and human-only contours using Dice similarity coefficient (DSC), Hausdorff distance (HD), and relative volume difference (RVD). Dosimetric indices such as Dmean, D0.03cc, and normalized plan quality metrics were used to compare dose distributions from RT plans generated from structure sets contoured by humans assisted by AI against plans from manual contours. The reduction in contouring time obtained by using automated tools was also assessed. A Wilcoxon rank sum test was computed to assess the significance of differences. Interobserver variability of the comparison of manual vs. AI-assisted contours was also assessed among two radiation oncologists for PCa. For PCa, AI-assisted segmentation showed good agreement with expert radiation oncologist structures with average DSC among patients ≥ 0.7 for all structures, and minimal radiation oncology adjustment of structures (DSC of adjusted versus AI structures ≥ 0.91). For HNC, results of comparison between manual and AI contouring varied considerably e.g., 0.77 for oral cavity and 0.11-0.13 for brachial plexus, but again, adjustment was generally minimal (DSC of adjusted against AI contours 0.97 for oral cavity, 0.92-0.93 for brachial plexus). The difference in dose for the target and organs at risk were not statistically significant between human and AI-assisted, with the only exceptions of D0.03cc to the anal canal and Dmean to the brachial plexus. The observed average differences in plan quality for PCa and HNC cases were 8% and 6.7%, respectively. The dose parameter changes due to interobserver variability in PCa were small, with the exception of the anal canal, where large dose variations were observed. The reduction in time required for contouring was 72% for PCa and 84% for HNC. When an autocontouring system is used in combination with human review, the time of the RT workflow is significantly reduced without affecting dose distribution and plan quality.

Influence of eye lens dosimeter positioning in a realistic dosimetric phantom in reference radiation beams

This paper presents a novel approach to dosimeter placement evaluation for personal eye lens dosimetry. A new assembly, known as the “Eye-Band”, and an anthropomorphic phantom containing two “Real Eye Dosimeters”, referred to as REDs, are proposed. The purpose of this study is to compare the energy and angular responses of the Eye-Band dosimeter assembly with those of an anthropomorphic dosimeter holder (RED-holder) placed inside a phantom. The objective is to analyze the maximum deviations between these measurements to determine the ideal placement of the holders from a metrological point of view. The commercially available BeOSL Eye Lens Dosimeters were also used for comparison, placed near each eye. BeO OSL EzClips were used as the sensitive elements in all three holders. Overall, except for 24 keV and 33 keV at 90° incidence, the differences between the dosimeters worn on the most exposed side of the head (Eye-Band or the standard commercial casings) and the estimated dose at the most exposed lens inside the anthropomorphic phantom were less than ∼20%. Results for the energy dependence of the central Eye-Band dosimeter at each angle of incidence (0°, 30°, 60° and 90°) showed that the deviation in dose to the most exposed eye (right eye) between RED and the central Eye-Band dosimeter ranged from 0% to ∼20% across all energies and angles from 0° to 90°. These results show that the angular dependence of the dosimeter on the most exposed side of the head is critical to ensure adequate results between the doses registered by the worn dosimeters at the side or center positions and the actual dose delivered to the most exposed eye. For the least exposed eye on the exit beam, the dosimeters worn on the left side (the left Eye-Band and the left standard commercial casing dosimeter worn near the left eye) are shown to be inadequate in representing the dose at the left eye position, even at a slight angle of incidence of 30°. This is due to partial shielding of the left dosimeters by the operator's head as the head rotates to the left. Anthropomorphic eye lens dosimeters have proven to be an invaluable tool for gaining a comprehensive understanding of the various factors influencing dose estimation in ocular lens dosimetry from a metrological perspective. This approach effectively bridges the gap between the controlled type testing conditions of dosimeters and real-world workplace conditions, while maintaining standard radiation beam conditions.

Perbandingan Dosis Radiasi Pemeriksaan Radiografi Thoraks PA Menggunakan Faktor Eksposi: Standar dan High kVp Berdasarkan Database DRL Si-INTAN BAPETEN

The usage of high kV has yet to be debated, so it is not fully used in PA chest radiographic examinations. However, The World Health Organization (WHO) and the Commission of European Communities (CEC) recommend using high kV, which can reduce the radiation dose to a minimum while maintaining the quality of the radiographic image. This study aimed to analyze the radiation dose for posterior-anterior (PA) chest radiography examinations using exposure factors: standard and high kV. This research method uses a retrospective study of the results of PA chest radiography examinations database diagnostic reference level (DRL) BAPETEN between 2018-2022. The PA chest examination data are the procedure, patient position, age, body weight, exposure factors (kVp and mAs), and ESAK dose (mGy). Then, use a standard exposure factor between 60-75 kVp and tube current-time of 6-12 mAs, while the exposure factor is high kV between 90-109 kVp and tube current-time of 0.7-4 mAs. After that, statistical analysis was carried out using IBM SPSS version 26 and Microsoft Excel. Determination of the average value and percentage difference in radiation dose of standard exposure factors and high kV. Then, proceed with statistical tests mann-whitney to determine the difference in the average radiation dose value between standard and exposure factors high kVp. The study showed that the average radiation dose for the standard kV exposure factor for the PA chest radiography examination was 0.179 mGy, while the high kV was 0.146 mGy. The dose difference between standard kV and high kV is 18.43%, with exposure factor radiation dose high kV lower than the standard exposure factor. For statistical test results, mann-whitney results p-value &lt; 0,000. High kV could be a procedure to optimize exposure factors for PA chest radiography examination. Keywords: Exposure factors, High kV, Optimization, DRL, Chest PA

The effect of vaginal cylinder inhomogeneity on the HDR brachytherapy dose calculations using Monte Carlo simulations.

To analytically assess the heterogeneity effect of vaginal cylinders (VC) made of high-density plastics on dose calculations, considering the prescription point (surface or 5mm beyond the surface), and benchmark the accuracy of a commercial model-based dose calculation (MBDC) algorithm using Monte Carlo (MC) simulations. The GEANT4 MC code was used to simulate a commercial 192 Ir HDR source and VC, with diameters ranging from 20 to 35mm, inside a virtual water phantom. Standard plans were generated from a commercial treatment planning system [TPS-BrachyVision ACUROS (BV)] optimized for a treatment length of 5cm through two dose calculation approaches: (1) assuming all the environment as water (i.e., Dw,w-MC & Dw,w-TG43 ) and (2) accounting for the heterogeneity of VC applicators (i.e., Dw,w-App-MC & Dw,w-App-MBDC ). The compared isodose lines, and dose & energy difference maps were extracted for analysis. In addition, the dose difference on the peripheral surface, along the applicator and at middle of treatment length, as well as apical tip was evaluated. The Dw,w-App-MC results indicated that the VC heterogeneity can cause a dose reduction of (up to) % 6.8 on average (for all sizes) on the peripheral surface, translating to 1mm shrinkage of the isodose lines compared to Dw,w-MC . In addition, the results denoted that BV overestimates the dose on the peripheral surface and apical tip of about 3.7% and 17.9%, respectively, (i.e., Dw,w-App-MBDC vs Dw,w-App-MC ) when prescribing to the surface. However, the difference between the two were negligible at the prescription point when prescribing to 5mm beyond the surface. The VCs' heterogeneity could cause dose reduction when prescribing dose to the surface of the applicator, and hence increases the level of uncertainty. Thus, reviewing the TG43 results, in addition to ACUROS, becomes prudent, when evaluating the surface coverage at the apex.

Jelly snakes to reduce early postoperative vomiting in children after adenotonsillectomy: The randomized controlled snakes trial

BackgroundDespite the use of dual antiemetic agents, postoperative nausea and vomiting (PONV) occurs in an unacceptably large number of patients post-tonsillectomy. There has been increased interest in alternative and non-pharmacological treatments for PONV e.g., chewing gum. We investigated if chewing a large confectionary jelly snake had prophylactic antiemetic effects postoperatively in young children. MethodsProspective, open-label randomised controlled trial of 240 patients, 2–16 years. Patients administered a confectionary jelly snake to chew postoperatively were compared with a control group. The primary outcome was the number of episodes of vomiting within 6 h of the operation on an intention-to-treat basis. Secondary outcomes: incidence of nausea, vomiting at 6 and 24 h, rescue antiemetic use, acceptability, delayed discharge. Results233 patients were randomised to receive the confectionary snake (snake group, 118) or standard care (control group, 115). The number of vomiting episodes in 6 h was similar between groups on an intention-to-treat basis, with 39 episodes across 22 (19%) patients in the control group and 31 across 19 (16%) patients in the snake group (p = 0.666). From post anaesthetic care unit until 24 h there was no difference in doses of antiemetics or delayed discharge due to PONV. A secondary as per protocol analysis did not change this result. ConclusionsChewing of confectionery jelly snakes within one hour of waking following adenotonsillectomy with vapour-maintained anaesthesia and two prophylactic antiemetics did not further reduce the incidence of early vomiting. Registrationprospective registration at the Australia and New Zealand Clinical Trials Registry (ACTRN12618000637246).

Crude protein and crude fiber content of fish silage fermented with kombucha tea

Fish silage production using mineral acid is considered to have a negative effect because it is highly corrosive. As an alternative, kombucha tea which contains several organic acids and microorganisms can be used as a starter for fish silage fermentation. This study aims to determine the effect of different doses and duration of fermentation on the crude protein and crude fiber content of fish silage. The research method used was a factorial completely randomized design (CRD) method with 2 factors, namely factor A (dose) and factor B (fermentation time). The results showed that the difference in the dose of kombucha tea was not significantly different (p>0.05) on the increase in crude protein, while the difference in fermentation time was considerably different (p<0.05). Meanwhile, the difference in kombucha tea dose was not significantly different (p>0.05) on the decrease in crude fiber, but the difference in fermentation time was significantly different (p<0.05). Based on these results, there was an interaction between the dosage and the length of fermentation time on the crude protein content, while there was no interaction in crude fiber content. In conclusion, fermentation of fish silage using kombucha tea increased crude protein content while decreasing crude fiber content.

Dosimetric impact of CT metal artifact reduction for spinal implants in stereotactic body radiotherapy planning.

Metal artifacts due to spinal implants may affect the accuracy of dose calculation for radiotherapy. However, the dosimetric impact of metal artifact reduction (MAR) for spinal implants in stereotactic body radiotherapy (SBRT) plans has not been well studied. The objective of this study was to evaluate the dosimetric impact of MAR in spinal SBRT planning with three clinically common dose calculation algorithms. Gammex phantom and 10 patients' computed tomography (CT) images were studied to investigate the effects of titanium implants. A commercial orthopedic MAR algorithm was employed to reduce artifacts. Dose calculations for SBRT were conducted on both artifact-corrected and uncorrected images using three commercial algorithms [analytical anisotropic algorithm (AAA), Acuros XB (AXB), and Monte Carlo (MC)]. Dose discrepancies between artifact-corrected and uncorrected cases were appraised using a dose-volume histogram (DVH) and 3-dimensional (3D) gamma analysis with different distance to agreement (DTA) and dose difference criteria. The gamma agreement index (GAI) was denoted as G(∆D, DTA). Statistical analysis of t-test was utilized to evaluate the dose differences of different algorithms. The phantom study demonstrated that titanium metal artifacts can be effectively reduced. The patient cases study showed that dose differences between the artifact-corrected and uncorrected datasets were small evaluated by gamma index and DVH. Gamma analysis found that even the strict criterion local G(1,1) had average values ≥93.9% for the three algorithms. For all DVH metrics, average differences did not exceed 0.7% in planning target volume (PTV) and 2.1% in planning risk volume of spinal cord (PRV-SC). Statistical analysis showed that the observed dose differences of MC method were significantly larger than those of AAA (P<0.01 for D98% of PTV and P<0.001 for D0.1cc of spinal cord) and AXB methods (P<0.001 for D98% and P<0.0001 for D0.1cc). Dosimetric impact of artifacts caused by titanium implants is not significant in spinal SBRT planning, which indicates that dose calculation algorithms might not be very sensitive to CT number variation caused by titanium inserts.

#145 : Effect of Intra-Ovarian Instillation of Autologous Platelet Rich Plasma on Live Birth Rate in POSEIDON 3 versus POSEIDON 4 Group: A Prospective Follow-Up Study

Background and Aims: Various anecdotal cases have been reported regarding platelet rich plasma (PRP), demonstrating successful pregnancy outcomes. But the data still remains elusive, especially for women of Asian ethnicity, who have a rapid decline in ovarian reserve when compared to the Caucasian population. We aim to study the effect of intra-ovarian PRP on live birth rate (LBR) in POSEIDON-3 versus POSEIDON-4 group. Method: Prospective interventional study conducted at tertiary care institute (July 2020-April 2022). 72-women between 20-40 years with idiopathic poor ovarian reserve (AMH[Formula: see text]1.2 ng/ml; AFC[Formula: see text]5) and a normal uterine cavity were enrolled. A 1.5 ml-PRP prepared from 30 ml venous-blood, was instilled in each ovarian stroma between day 6-10 of menses with 3-consecutive months follow-up to assess ovarian-reserve parameters (FSH, AMH, AFC). Patients showing improvement (AFC[Formula: see text] 5) were enrolled in antagonist-IVF cycles and categorised into two groups: POSEIDON-3 vs 4 groups. Paired/signrank test and Independent/ranksum test compared clinical parameters between the two-groups. Results: Out of 72 participants, 16.67% responded in 1 [Formula: see text] month of follow-up (AFC: 5 vs 3, p[Formula: see text]0.001), 43% in 2 [Formula: see text] month (AFC: 6 vs 3, p[Formula: see text]0.001) and 12.5% in 3 [Formula: see text] month (AFC:4 vs 3, p[Formula: see text]0.001). 20 participants showed no improvement. Excluding one, 43 underwent antagonist-cycle. Although number of oocytes retrieved was similar (6.35 ± 1.83 vs 5.75 ± 1.35, p=0.21), the dose of HMG requirement was higher in POSEIDON-4 (1450 ± 96.53 vs 1190.3 ± 66.49, p=0.04) thus depicting the effect of advanced age. There was no significant difference in dose of rFSH requirement (2705.6 ± 48.93 vs 2737 ± 54.74, p=0.71), fertilisation rate (60.86% vs 57.86%, p=0.66), CPR (25% vs 25.8%, p=0.95) and LBR (22.6% vs 16.66%, p=0.66) between the two-groups. Conclusion: Intra-ovarian PRP improves the LBR in low-prognosis patients irrespective of age. PRP improves the ovarian reserve which translates into better reproductive outcomes in a population of women who were planned and counselled for donor-oocyte IVF.

A modified U-net with graph representation for dose prediction in esophageal cancer radiotherapy plans

The manual design of esophageal cancer radiotherapy plan is time-consuming and labor-intensive. Automatic planning (AP) is prevalent nowadays to increase physicists’ work efficiency. Because of the intuitiveness of dose distribution in AP evaluation, obtaining reasonable dose prediction provides effective guarantees to generate a satisfactory AP. Existing fully convolutional network-based methods for predicting dose distribution in esophageal cancer radiotherapy plans often capture features in a limited receptive field. Additionally, the correlations between voxel pairs are often ignored. This work modifies the U-net architecture and exploits graph convolution to capture long-range information for dose prediction in esophageal cancer plans. Meanwhile, attention mechanism gets correlations between planning target volume (PTV) and organs at risk, and adaptively learns their feature weights. Finally, a novel loss function that considers features between voxel pairs is used to highlight the predictions. 152 subjects with prescription doses of 50 Gy or 60 Gy are collected in this study. The mean absolute error and standard deviation of conformity index, homogeneity index, and max dose for PTV achieved by the proposed method are 0.036 ± 0.030, 0.036 ± 0.027, and 0.930 ± 1.162, respectively, which outperform other state-of-the-art models. The superior performance demonstrates that our proposed method has great potential for AP generation.

Joint Exposure‐Response Analysis of PET Amyloid Plaque Data from the BACE1 Inhibitor Verubecestat and Amyloid mAbs Trials in Prodromal to Moderate Alzheimer’s Disease

AbstractBackgroundPositron‐emission tomography (PET) with amyloid radiotracers allows the quantification of pathological amyloid deposition in brain tissues. An exposure‐response (E‐R) analysis of individual study data of the β‐secretase‐1 inhibitor verubecestat and summary level data of four amyloid mAbs in patients with Alzheimer’s disease (AD) was conducted, to quantify the drug effects and plaque turnover rates and facilitate prediction of unstudied regimens.MethodIndividual (n = 188) verubecestat amyloid‐PET plaque data and exposures from APECS [Egan et.al, 2019] were pooled with summary. amyloid‐PET data and serum exposures from literature for aducanumab [Sevigny J, et al. 2016], donanemab [Lowe SL, et al. 2021, Lily ADPD, 2021], gantenerumab [Klein G, et al. 2019, Portron A, et al. 2020] and lecanemab [Swanson CJ, et al. 2021]. Amyloid plaque levels in SUVR units were converted to Centiloid [Klunk WE, et al. 2015]. All data were fit simultaneously in a joint model by nonlinear mixed‐effects modelingResultAn indirect response (turnover) model with verubecestat inhibiting plaque formation, and amyloid mAbs stimulating plaque removal well represented the available data (Figure 1). All plaque time course data from natural progression (control arms), β‐secretase‐1 inhibition and amyloid mAb treatment arms were well described by a joint model. The plaque turnover was estimated to be 0.00028 per day, corresponding to a half‐life of plaque of ∼ 6.8 years. Verubecestat AUC50 was estimated as 0.313 uM*h, commensurate to a 93.5% reduction in plaque formation at the typical 40 mg exposure and consistent with the &gt;60% reductions in CSF Aβ40 and 42 observed in APECS. Aducanumab 10 mpk Q4W, donanemab 1400 mg Q4W, lencanemab 10 mpk Q2W, and gantenerumab 1200 mg SC Q4W were estimated to results in 13.5‐, 16.4‐, 16.6‐, and 12.6‐fold increases in plaque removal rate, respectively.ConclusionThe joint turnover model, linking drug exposure with amyloid plaque load, was adequate to describe natural progression and treatment response, and allows for estimation of the underlying turnover rate. This approach improves cross‐study comparisons and prediction of alternative regimens and therapeutic approaches by accounting for differences in baseline plaque load, dosing and titration regimens, and mechanism of action.

Modeling and Simulation to Inform Potential New Strategies for BACEi in Treatment of Alzheimers Disease

AbstractBackgroundThe β‐secretase‐1 inhibitors (BACEi), including verubecestat, were extensively studied in prodromal to moderate AD and demonstrated early cognitive decline at doses achieving &gt;50% inhibition of amyloid production. Questions remain as to whether BACEi may still have utility, if used earlier in disease, in combination with other therapies, and/or at lower doses. Modeling and simulation approaches were used to maximize learnings from the prior trials and to make predictions around potential alternative therapeutic approaches.MethodTwo models were developed: 1) A joint plaque turnover model, linking drug exposure with amyloid plaque load (PET data in centiloids), to describe natural progression and treatment response to BACEi and amyloid mAb therapies. All plaque data from natural progression (control arms), BACEi and amyloid mAb treatment arms were well described by a joint model, after accounting for differences in baseline plaque load, dosing and titration regimens, and mechanism of action. 2) Disease progression models for the clinical efficacy outcomes (ADAS‐cog11, CDR‐SB) were developed using a methodology similar to Ref. Evidence for BACEi drug effects (on progression rate and/or early detrimental offset) was tested and dependencies on dose, drug exposure and patient characteristics were explored.ResultThe joint plaque turnover model well described natural progression and treatment response to BACEi and amyloid mAb and allows for prediction of alternative regimens and therapeutic approaches. Simulations indicate that 20‐30% inhibition of BACE would be sufficient to stabilize plaque loads in prodromal patients. Disease progression results for ADAS‐cog11 and CDR‐SB identified a verubecestat drug effect of early detrimental offset with no effect on rate of disease progression supported. The magnitude of the early detrimental offset was small relative to the overall progression seen over 18‐24 months and results suggested that this effect may be reduced in advanced AD patients. A simulation engine utilizing the progression model allows for estimation of sample size needed to check for the detrimental effect in future trials.ConclusionModel‐based simulations can help inform future BACEi therapeutic strategies and trial designs. Reference: Clin Pharmacol Ther. 2015 Mar;97(3):210‐4

Is single-catheter technique for coronary angiography an optimal tool for beginners in interventional cardiology?-randomized controlled study TRACT 2: Transradial Coronary Angiography Trial 2.

Transradial coronary angiography can be performed using a dual-catheter technique (DCT) or single-catheter technique (SCT). The current study aimed to compare DxTerity SCT Ultra and the Trapease curve SCT catheters with DCT catheters in procedures performed by young, less experienced, interventional cardiologists. For this prospective, single-blinded, randomized study 107 were enrolled and assigned to 1 of 3 groups. They underwent planned coronary angiography at the Second Department of Cardiology Jagiellonian University in Kraków. In groups 1 (n=37) and 2 (n=35), DxTerity SCT Ultra catheters and the Trapease curve were used, respectively. In control group 3 (n=35), standard DCT Judkins catheters were applied. One patient was excluded from group 2, bringing the total number of cases analysed to 106. The study endpoints comprised the percentage of optimal stability, proper ostial artery engagement, a good quality angiogram, the duration of each procedure stage, the amount of contrast and the radiation dose. The highest percentage of optimal stability was observed in group 1 for the right coronary artery (RCA): 94%, and in group 3, for the left coronary artery (LCA): 85%. The necessity to change the catheter was most common in group 2. Group 1 was characterised by a shorter total procedural time. The contrast volume was higher in group 2, while there were no differences in radiation dose. SCT is at least as adequate as DCT for young cardiologists. SCT was associated with lower necessity of catheter exchange during RCA visualization. The DxTerity Ultra curve catheter allows shortening the total procedure time.

Impact of Prepectoral vs. Subpectoral Tissue Expander Placement on Post-mastectomy Radiation Therapy Delivery: A Retrospective Cohort Study.

Implant-based reconstruction is the most common method of postmastectomy reconstruction. Many patients require postmastectomy radiation (PMRT). Tissue expanders (TEs), typically inserted as a first stage, have historically been placed subpectorally. More recently, prepectoral reconstruction has gained popularity, but its impact on PMRT is unknown. Prior studies focus on complication rates and aesthetic outcomes. This study examines whether there is a difference in radiation dosimetry among patients undergoing prepectoral versus subpectoral TE reconstruction. Electronic medical records and radiation plans of 50 patients (25 prepectoral, 25 subpectoral) who underwent mastectomy with immediate TE reconstruction at our institution or affiliate site were reviewed. Pectoralis major muscle and chest wall structures were contoured and mean percentage volumes of these structures receiving less than 95%, 100%, and more than 105% target radiation dose were calculated, as were heart and ipsilateral lung doses. Welch two sample t test, Fisher exact test, and Pearson chi-squared tests were performed. The groups had comparable patient and tumor characteristics and underwent similar ablative and reconstructive procedures and radiation dosimetry. Subpectoral patients had larger mean areas receiving less than 95% target dose ("cold spots"); prepectoral patients had larger mean areas receiving greater than 105% ("hot spots") and 100% target doses. There were no differences in chest wall, heart, and lung doses. Our results demonstrate an increased mean percentage area of pectoralis cold spots with subpectoral reconstruction and increased area of hot spots and 100% dose delivery to the pectoralis in prepectoral patients. Larger studies should analyze long-term effects of prepectoral reconstruction on radiation dosing and recurrence rates.

Threshold in breast compression reduction for full-field digital mammography and digital breast tomosynthesis

IntroductionBreast compression is essential in mammography to improve image quality and reduce radiation dose. However, it can cause discomfort or even pain in women which could discourage them from attending future mammography examinations. Therefore, this study aims to explore the maximum reduction in breast compression in full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) that is achievable without impacting on image quality and dose. MethodsTen compression force (CF) levels (20N–110N, with 10N intervals) were assessed on Siemens MAMMOMAT Inspiration with Nuclear Associates 18–228 phantom. Imaging was carried out in craniocaudal projection using Automatic Exposure Control at 28 kVp with a Tungsten/Rhodium anode/filter combination, and at 50° sweep angle for DBT. Using ImageJ software, image quality of the acquired mammograms and central tomosynthesis slices were examined based on mass conspicuity (MC) and microcalcification conspicuity (MicroC). Entrance skin dose (ESD) and mean glandular dose (MGD) were recorded from Digital Imaging and Communication in Medicine image header. Linear regression was performed to examine the relationship between CF with ESD, MGD, MC and MicroC. Differences in image quality and radiation dose were assessed with one-way analysis of variance and Kruskal-Wallis H test. ResultsSignificant correlations were noted between CF with ESD and MicroC for FFDM and DBT, with DBT also demonstrating associations with MGD and MC. No significant differences were observed for ESD, MGD, MC and MicroC when CF was reduced to 40N and 80N in FFDM and DBT respectively. ConclusionThis study demonstrated that CF can be reduced as low as 40N and 80N in FFDM and DBT respectively, without significant impact on image quality and radiation dose. Implications for practiceReduced mammographic compression may reduce discomfort or pain in women, which may improve attendance rate in breast screening programmes. Findings from this study will provide reference for future work examining breast compression in mammography.

Outcomes of Proton Therapy to Infradiaphragmatic Sites in Pediatric Hodgkin Lymphoma Patients

Purpose: When treating pediatric patients with radiotherapy (RT), an important area of optimization is reducing integral dose with the goal of minimizing toxicity. As a result, proton radiation (PT) is a well-established RT modality for certain clinical indications within pediatrics. However, there is limited data on outcomes of PT in pediatric patients with Hodgkin lymphoma who receive RT to infradiaphragmatic targets. We report on radiation planning details, doses achieved to organs at risk (OARs), and outcomes for this population, and additionally provide comparative dosimetric data between photon and proton plans for a patient subset. Methods: This is a single-institution retrospective study of pediatric patients with Hodgkin lymphoma who received curative intent PT to infradiaphragmatic targets between 2011-2022. Demographic and clinical factors were collected from the electronic medical record, and toxicity was reported using CTCAE version 5.0. Dosimetric and clinical factors associated with toxicity and oncologic outcomes were assessed via Cox regression, while the paired t-test or Wilcoxon signed rank sum test was used for dosimetric analyses. Photon comparison plans were generated for a subset of 10 patients who received PT to a range of infradiaphragmatic subsites, and doses to key OARs were compared across modalities via the Wilcoxon signed rank sum test. Results: Twenty-one patients comprising 22 PT courses were included. Median follow-up was 4.8 years. Mean age at the time of RT was 14.2 years (range 4-22 years) and 48% were male. Median dose was 21 Gray equivalent (GyE) over 14 fractions. 50% of patients received PT to multiple subdiaphragmatic sites, and top locations treated in single-target PT courses included spleen (32%), retroperitoneum (14%), and pelvis (3%). Most common acute grade 1 (G1) toxicities were fatigue (59%) and anorexia (36%). Rates of acute G2 and G3+ toxicity were 18% and 0%, respectively. The average maximum dose (Dmax) to the spinal cord was 15.3 Gy and bowel bag (BB) was 19.9 Gy. Multiple BB metrics were significantly different between patients who developed nausea and those who did not: V5 Gy (median 42% vs. 2%, p=.0068), V15 Gy (median 30% vs. 1%, p=.0056), V20 Gy (median 26% vs. 0%, p=.0038), mean (median 949 vs. 35 cGy, p=.0063), and Dmax (median 2295 vs. 2184 cGy, p=.0301). Rectum Dmax also significantly varied between those who did or did not develop abdominal discomfort (median 119 vs. 0 cGy, p=.0071). No other OAR metrics were significantly different based on acute toxicity. Following PT, two patients developed persistent gastrointestinal issues of unclear etiology, and one patient developed chronic kidney disease (CKD). No statistically significant differences in doses to BB (V5 Gy, V15 Gy, V20 Gy, Dmax, or mean) or kidney (mean or V5 Gy) were detected between these patients and those without chronic abdominopelvic sequelae. Kidney V18 Gy and V20 Gy for the patient with subsequent CKD was 2% and 0%, respectively. No patients developed a second malignancy after PT, and 0% experienced progression of disease (POD) after final course of PT. In our 10 patient subset with photon comparison plans, protons achieved numerically lower averages for all OARs assessed with the exception of spinal cord Dmax (889 vs. 851 cGy), although these differences were not statistically significant (all p&amp;gt;0.05). Conclusions: PT is well-tolerated when utilized to target single or multiple infradiaphragmatic locations in pediatric Hodgkin lymphoma patients and leads to excellent oncologic and toxicity outcomes with long-term follow-up. PT may confer dosimetric advantages when compared to photons, although larger patient subsets are needed.

A deep learning model to generate synthetic CT for prostate MR-only radiotherapy dose planning: a multicenter study

IntroductionFor radiotherapy based solely on magnetic resonance imaging (MRI), generating synthetic computed tomography scans (sCT) from MRI is essential for dose calculation. The use of deep learning (DL) methods to generate sCT from MRI has shown encouraging results if the MRI images used for training the deep learning network and the MRI images for sCT generation come from the same MRI device. The objective of this study was to create and evaluate a generic DL model capable of generating sCTs from various MRI devices for prostate radiotherapyMaterials and methodsIn total, 90 patients from three centers (30 CT-MR prostate pairs/center) underwent treatment using volumetric modulated arc therapy for prostate cancer (PCa) (60 Gy in 20 fractions). T2 MRI images were acquired in addition to computed tomography (CT) images for treatment planning. The DL model was a 2D supervised conditional generative adversarial network (Pix2Pix). Patient images underwent preprocessing steps, including nonrigid registration. Seven different supervised models were trained, incorporating patients from one, two, or three centers. Each model was trained on 24 CT-MR prostate pairs. A generic model was trained using patients from all three centers. To compare sCT and CT, the mean absolute error in Hounsfield units was calculated for the entire pelvis, prostate, bladder, rectum, and bones. For dose analysis, mean dose differences of D99% for CTV, V95% for PTV, Dmax for rectum and bladder, and 3D gamma analysis (local, 1%/1 mm) were calculated from CT and sCT. Furthermore, Wilcoxon tests were performed to compare the image and dose results obtained with the generic model to those with the other trained models.ResultsConsidering the image results for the entire pelvis, when the data used for the test comes from the same center as the data used for training, the results were not significantly different from the generic model. Absolute dose differences were less than 1 Gy for the CTV D99% for every trained model and center. The gamma analysis results showed nonsignificant differences between the generic and monocentric models.ConclusionThe accuracy of sCT, in terms of image and dose, is equivalent to whether MRI images are generated using the generic model or the monocentric model. The generic model, using only eight MRI-CT pairs per center, offers robust sCT generation, facilitating PCa MRI-only radiotherapy for routine clinical use.

Prediction of patient-specific quality assurance for volumetric modulated arc therapy using radiomics-based machine learning with dose distribution.

We sought to develop machine learning models to predict the results of patient-specific quality assurance (QA) for volumetric modulated arc therapy (VMAT), which were represented by several dose-evaluation metrics-including the gamma passing rates (GPRs)-and criteria based on the radiomic features of 3D dose distribution in a phantom. A total of 4,250 radiomic features of 3D dose distribution in a cylindrical dummy phantom for 140 arcs from 106 clinical VMAT plans were extracted. We obtained the following dose-evaluation metrics: GPRs with global and local normalization, the dose difference (DD) in 1% and 2% passing rates (DD1% and DD2%) for 10% and 50% dose threshold, and the distance-to-agreement in 1-mm and 2-mm passing rates (DTA1 mm and DTA2 mm) for 0.5%/mm and 1.0%.mm dose gradient threshold determined by measurement using a diode array in patient-specific QA. The machine learning regression models for predicting the values of the dose-evaluation metrics using the radiomic features were developed based on the elastic net (EN) and extra trees (ET) models. The feature selection and tuning of hyperparameters were performed with nested cross-validation in which four-fold cross-validation is used within the inner loop, and the performance of each model was evaluated in terms of the root mean square error (RMSE), the mean absolute error (MAE), and Spearman's rank correlation coefficient. The RMSE and MAE for the developed machine learning models ranged from<1% to nearly<10% depending on the dose-evaluation metric, the criteria, and dose and dose gradient thresholds used for both machine learning models. It was advantageous to focus on high dose region for predicating global GPR, DDs, and DTAs. For certain metrics and criteria, it was possible to create models applicable for patients' heterogeneity by training only with dose distributions in phantom. The developed machine learning models showed high performance for predicting dose-evaluation metrics especially for high dose region depending on the metric and criteria. Our results demonstrate that the radiomic features of dose distribution can be considered good indicators of the plan complexity and useful in predicting measured dose evaluation metrics.

Influence of minimum segment width on intensity-modulated radiotherapy plan for left-sided breast cancer after breast conserving surgery.

To research the influence of the minimum segment width (MSW) on intensity-modulated radiotherapy (IMRT) plan for left breast cancer after breast conserving surgery and provide a reference for plan optimization. Ten patients with left-sided early-stage breast cancer after breast-conserving surgery (BCS) were selected for postoperative radiotherapy. The Monaco 5.11 treatment planning system (TPS) was used, and the optimization parameters of the plan were fixed, while MSW were set to 0.5, 1, 1.5, and 2 cm, and four 5 field-IMRT plans were designed for every patient. The plan quality and execution efficiency of each plan were compared, including planning target volume (PTV) dose, organs at risk (OAR) dose, segments number (SN), monitor units (MU), delivery time (DT), and dose verification results. With the increase of the MSW, the dose indexes of the OAR were similar (P > .05). The D2%, D98%, and D50% of the PTV gradually deviated from the prescription dose, and the uniformity gradually deteriorated (P < .05). The gamma passing rates (GPR) of dose verification and the dose deviation of the PTV were similar (P > .05). The SN, MU, and DT gradually decreased (P < .05), but the amplitude change caused by each increase of 0.5 cm gradually decreased, the decrease of 0.5 to 1 cm was the largest, reaching 16.41%, 21.25%, and 0.35 minutes, respectively, while the 3 values of 1.5 and 2 cm were close. When using Monaco 5.11 TPS to design IMRT plan for left breast cancer after BCS, 1.5 cm MSW could ensure better dose coverage and uniformity of the PTV, as little as possible exposure dose to the OAR, and high dose verification accuracy. The SN, MU, and DT were significantly reduced, and the treatment efficiency was improved.

Evaluation of a novel CBCT conversion method implemented in a treatment planning system

BackgroundTo evaluate a novel CBCT conversion algorithm for dose calculation implemented in a research version of a treatment planning system (TPS).MethodsThe algorithm was implemented in a research version of RayStation (v. 11B-DTK, RaySearch, Stockholm, Sweden). CBCTs acquired for each ten head and neck (HN), gynecology (GYN) and lung cancer (LNG) patients were collected and converted using the new algorithm (CBCTc). A bulk density overriding technique implemented in the same version of the TPS was used for comparison (CBCTb). A deformed CT (dCT) was created by using deformable image registration of the planning CT (pCT) to the CBCT to reduce anatomical changes. All treatment plans were recalculated on the pCT, dCT, CBCTc and the CBCTb. The resulting dose distributions were analyzed using the MICE toolkit (NONPIMedical AB Sweden, Umeå) with local gamma analysis, with 1% dose difference and 1 mm distance to agreement criteria. A Wilcoxon paired rank sum test was applied to test the differences in gamma pass rates (GPRs). A p value smaller than 0.05 considered statistically significant.ResultsThe GPRs for the CBCTb method were systematically lower compared to the CBCTc method. Using the 10% dose threshold and the dCT as reference the median GPRs were for the CBCTc method were 100% and 99.8% for the HN and GYN cases, respectively. Compared to that the GPRs of the CBCTb method were lower with values of 99.8% and 98.0%, for the HN and GYN cases, respectively. The GPRs of the LNG cases were 99.9% and 97.5% for the CBCTc and CBCTb method, respectively. These differences were statistically significant. The main differences between the dose calculated on the CBCTs and the pCTs were found in regions near air/tissue interfaces, which are also subject to anatomical variations.ConclusionThe dose distribution calculated using the new CBCTc method showed excellent agreement with the dose calculated using dCT and pCT and was superior to the CBCTb method. The main reasons for deviations of the calculated dose distribution were caused by anatomical variations between the pCT and the corrected CBCT.