Brachytherapy最新文献

{"title":"PO38","authors":"Bethel Adefres, Christopher Jason Tien, Shari Damast","doi":"10.1016/j.brachy.2023.06.139","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.139","url":null,"abstract":"Purpose Adjuvant vaginal cuff brachytherapy (VCB) for endometrial cancer (EC) is typically delivered with single-channel vaginal cylinders with diameters ranging from 2.0 to 4.0 cm. Due to the unfavorable dosimetry of 2.0 cm diameter cylinders, larger diameter cylinders are used whenever possible. There are, however, occasional patients with narrow vaginal anatomy for whom only a 2.0 cm cylinder can be accommodated. In this unique population, in addition to the dosimetric challenges for a typical prescription to 5 mm depth (ie., heterogeneity of about 170% and 210% of prescription dose at the surface of the cylinder lateral walls and tip, respectively), there tend to be clinical challenges as well such as insertional pain or difficulty with procedural tolerance. This study reports the clinical outcomes of an EC cohort that received VCB with cylinder size 2.0 cm at a single institution. Materials and Methods From an IRB-approved institutional database of EC patients treated with VCB between 07/01/2014-11/30/2022, all patients that were fitted with 2.0 cm cylinder were retrospectively reviewed. Although our institutional prescriptions for cylinders larger than 2.0cm are at 5mm depth (6-7 Gy x 3 fractions weekly), for the 2.0cm cylinder patients, VCB prescriptions are to the vaginal surface (10Gy x 3 fractions weekly), to avoid issues resulting in unacceptably high surface dose. Patient demographics, disease and treatment characteristics, recurrence rates and complications were descriptively analyzed. Toxicity was recorded via the CTCAE v4.0. The Kaplan-Meier method was used to assess freedom from vaginal recurrence. All computations were performed in IBM SPSS Statistics 28. Results Among 655 consecutive EC patients treated with VCB, there were 36 women (5%) that were treated with cylinder size 2.0 cm. Median age was 68.5 years (range: 46-95 years). The majority were nulliparous (77.8%) and 15 women (42%) had documented baseline pain or anxiety related to pelvic examination prior to VCB. Median BMI was 39 (range: 19-62). Baseline vaginal length was 8.3cm (range: 5-14cm). 78% had stage I-II, 14% had stage IIIA, and 8% had stage IVB EC. The histological subtypes included endometrioid adenocarcinoma (69%), mixed (11%), serous (8%), clear cell (6%) and de-differentiated (6%). 42% of the patients received chemotherapy. None received external beam radiotherapy. Median interval from surgery to VCB was 54 days (range: 43-119 days). All received 10Gy x 3 fractions prescribed to vaginal surface, and active length was 3cm (5.6%), 4cm (63.9%) or 5cm (30.6%). 3D planning was performed in 58% of the cohort, while 2D planning was used in the remainder due to issues related to body habitus and/or poor mobility. Median follow-up was 17.5 months (range: 3-76 months). The 2-year freedom from vaginal recurrence was 96%. There was only 1 vaginal recurrence, which was out of field. 5 patients died from disease, unrelated to radiation treatment. There were no grade 2 or h","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"135 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO42","authors":"Ria Mulherkar, Hong Wang, Mark Jelenik, Hayeon Kim, Christopher J. Houser, Elangovan Doraisamy, Madeleine Courtney-Brooks, Alexander Olawaiye, John Comerci, Michelle Boisen, Jessica Berger, Joseph Kelley, Paniti Sukumvanich, Sarah Taylor, Robert Edwards, Lan Coffman, Ronald Buckanovich, Jamie Lesnock, Haider Mahdi, Shannon Rush, John Austin Vargo, Sushil Beriwal, Parul Barry","doi":"10.1016/j.brachy.2023.06.143","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.143","url":null,"abstract":"Disparities in race and socioeconomic factors affect patient access to cancer screening, treatment, and clinical outcomes. The aim of this project was to evaluate relationship between race and socioeconomic factors including insurance status, employment status, disability status, and distance from brachytherapy center on clinical outcomes including stage at presentation, number of nodes positive, brachytherapy technique, progression-free survival (PFS), and overall survival (OS). All cervical cancer patients treated with brachytherapy at our institution from 2007-2017 were identified. Race and socioeconomic factors including insurance status, employment status, disability status, and distance from brachytherapy center were recorded. Clinical characteristics including stage at presentation, number of involved nodes, and brachytherapy technique were also recorded. PFS and OS were calculated from date of last brachytherapy fraction, with censorship at date of last follow-up. Correlation was tested between racial and socioeconomic factors and survival outcomes (i.e., PFS and OS) using Cox regression models. Their association with other outcomes was examined with Wilcoxon rank sum tests, Fisher's exact tests, and Spearman's rank correlation coefficients where appropriate. 251 cervical cancer patients were identified, with median follow-up 5.2 years (IQR 2.0-7.7 years). On univariate analysis (UVA), there was no correlation between brachytherapy technique utilized, number of nodes positive, or stage at presentation and race, distance from treatment center, insurance status, employment status, or disability status. UVA did show a significant correlation between PFS and race, insurance status, employment status, and disability status. Significantly worse PFS was seen in non-white group (p=0.036), uninsured group (p<0.001), unemployed group (p<0.001), and disabled group (p=0.041). Similarly, there was significant correlation between OS and race, insurance status, employment status, and disability status. Significantly worse OS was seen in non-white group (p=0.005), uninsured group (p<0.001), unemployed group (p<0.001), and disabled group (p=0.008). On multivariate analysis (MVA), there was no significant correlation between race or disability status and PFS, but there was significantly improved PFS seen in patients with insurance (p < 0.001) and patients who were employed (p = 0.002). MVA showed no correlation between disability status and OS, but significantly worse OS in patients who were non-white (p=0.039) and significantly improved OS in patients with insurance (p<0.001), and patients who were employed (p-0.001). MVA showed no significant correlation between stage and insurance or employment status. MVA showed no significant correlation between histology and employment status; on MVA patients with government insurance were less likely to have squamous histology compared with no insurance (p=0.002). Insurance and employment status are significant pred","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO121","authors":"Hari Menon, Charles R. Wallace, Jessica M. Schuster, Kristin A. Bradley, Bethany M. Anderson","doi":"10.1016/j.brachy.2023.06.222","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.222","url":null,"abstract":"","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO34","authors":"Devin Van Elburg, Sarah Quirk, Kevin Martell, Tyler Meyer, Michael Roumeliotis","doi":"10.1016/j.brachy.2023.06.135","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.135","url":null,"abstract":"","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO61","authors":"Fada Guan, Emily Draeger, David Carlson, Zhe Chen, Christopher Tien","doi":"10.1016/j.brachy.2023.06.162","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.162","url":null,"abstract":"Purpose In the conventional fractionation schemes of high-dose-rate (HDR) brachytherapy, the intra-fractional and inter-fractional DNA damage repair and repopulation of tumor cells are neglected in calculating the biologically effective dose (BED). This may result in inaccurate model prediction of the theoretical tumor control probability (TCP). Notwithstanding, current prostate brachytherapy prescriptions may still be large enough to theoretically overcome these effects, among others. The purpose of this study was to recalculate the theoretical TCP, accounting for intrafraction DNA damage repair and 192Ir source decay for prostate cancer treated using HDR brachytherapy as the monotherapy, compared against common 1-, 2-, and 9-fraction prescription schemes. Materials and Methods We incorporated the Lea-Catcheside dose protraction factor g, the effective tumor doubling time Td, the total elapsed time of the treatment course T, and the onset or lag time of cell repopulation Tk, into the full-form BED calculation, in contrast to the simple form BED which only includes the total dose, dose per fraction and α/β. The Poisson model relating the surviving fraction and the number of tumor clonogens (K) was used to calculate TCP. The parameter set α = 0.15 Gy-1, α/β = 3.1 Gy, τ = 0.27 h (DNA damage repair half time), Td = 42 days, and Tk = 0 was used for the full-form BED calculation. K = 1.1 × 107 from the high-risk group was used in the TCP calculation. The new 192Ir source (40,700 U, 10 Ci, 1.27 Gy/min) and the 90-day source (17,470 U, 4.3 Ci, 0.55 Gy/min) were used to investigate the source decay effect on TCP. Three different fractionation schemes n = 1, 2, and 9 fraction(s) were studied. Simple BED, full-form BED (both 10 Ci and 4.3 Ci), TCP50 (total dose at TCP = 50%), and TCP90 (total dose at TCP = 90%) were calculated for each setup. 1 x 21 Gy, 2 x 13.5 Gy, and 9 x 6 Gy prescriptions were selected to evaluate the robustness of different fractionation schemes on TCP impacted by DNA damage repair and source decay. Results TCP50 and TCP90 using the simple BED, the full-form BED at 10 Ci and 4.3 Ci were calculated. In the single-fraction group, TCP50 = 17.0, 18.6, and 21.2 Gy, and TCP90 = 18.0, 19.9, and 22.8 Gy. In the 2-fraction group, TCP50 = 23.3, 24.7, and 26.8 Gy, and TCP90 = 24.7, 26.3, and 28.7 Gy. In the 9-fraction group, TCP50 = 43.3, 44.3, and 45.6 Gy, and TCP90 = 46.3, 47.4, and 48.9 Gy. For 1 × 21 Gy, the simple BED and full-form BED (10 Ci and 4.3 Ci) = 163.3, 134.8, and 109.0 Gy, and TCP = 99.9%, 98.2%, and 41.9%. For 2 × 13.5 Gy, the simple BED and full-from BED (10 Ci and 4.3 Ci) = 144.6, 128.5, and 112.0 Gy, and TCP = 99.6%, 95.4%, and 57.4%. For 9 × 6 Gy, the simple BED and full-from BED (10 Ci and 4.3 Ci) = 158.5, 151.4, and 143.4 Gy, and TCP = 99.9%, 99.9%, and 99.5%. In general, we have observed: (1) using the simple BED overestimated the TCP compared to the full-form BED, (2) with the source decay, a higher total dose was needed","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO59","authors":"Jiheon Song, Mark Corkum, Andrew Loblaw, Hans Tse-Kan Chung, Chia-Lin Tseng, Patrick Cheung, Ewa Szumacher, Stanley Liu, William Chu, Melanie Davidson, Matt Wronski, Liying Zhang, Alexandre Mamedov, Gerard Morton","doi":"10.1016/j.brachy.2023.06.160","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.160","url":null,"abstract":"Purpose High dose-rate (HDR) brachytherapy as monotherapy is an effective treatment for patients with low- and intermediate-risk prostate cancer and is increasingly being offered as a 2-fraction protocol. There is a lack of consensus on the optimal dosimetric planning parameters to use, or whether there is any benefit summating dosimetric parameters from more than one implant. Our goal is to determine planning parameters associated with disease control, toxicity and health-related quality of life (HRQOL). Materials and Methods Data were collected on 83 patients with low- and intermediate-risk prostate cancer who received 2 fractions of 13.5 Gy HDR brachytherapy without androgen-deprivation therapy or external beam radiotherapy as part of a randomized phase II clinical trial. An in-house deformable, registration algorithm was used to co-register and dose-summate the plans from both for each patient. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were measured using Common Toxicity Criteria for Adverse Events (CTCAE) 4.0 and HRQOL was measured in urinary, bowel, sexual and hormonal domains using the expanded prostate cancer index composite (EPIC) scores. Treatment efficacy was assessed through PSA measurement and imaging with or without biopsy where indicated. Covariates included baseline clinical factors, disease characteristics and treatment dosimetric parameters. Cox proportional hazards was performed to evaluate covariates impact on treatment toxicity and efficacy, and logistic regression analysis evaluated covariates impact on HRQOL. Results Among the 83 patients, median prostate volume was 46.7cm3. Median summated planning target volume receiving 100% prescription dose (PTV V100%) was 97.4%, median PTV V150% 42.4% and median PTV V200% 15.5%. Median highest dose to the 1cm3 rectum (D1cc) was 66.9% of the prescription dose and median rectum V80% was 0.008cm3. Median urethral D1cc was 99.0% of the prescription dose, median urethral Dmax 121.7% and median urethral D10% 116.2%. Grade ≥2 GI toxicity was uncommon (3.7% acute and 8.5% late), but grade ≥2 GU toxicity was reported in 73.2% (acute) and 46.3% (late) patients. Rectum D1cc and V80% were found to be significantly associated with grade 2 or higher acute GI toxicity, while use of α-blocker at baseline was associated with grade ≥2 acute GU toxicity. Similarly, higher percentage of Gleason 4 disease and use of α-blocker were associated with late grade ≥2 GU toxicity. No other variables were associated with treatment-related toxicities. Only rectum D1cc was significantly associated with changes in bowel EPIC scores. Dosimetric parameters did not predict disease recurrence. Estimated 5-year biochemical disease-free survival was 93.9% and 5-year cumulative incidence of local failure was 3.8%. Conclusions HDR monotherapy with 27 Gy delivered in 2 fractions in treatment of prostate cancer is well tolerated with high rates of disease control and minimal toxicity. Dose summatio","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO53","authors":"Andre Karius, Claudia Schweizer, Vratislav Strnad, Michael Lotter, Stephan Kreppner, Rainer Fietkau, Christoph Bert","doi":"10.1016/j.brachy.2023.06.154","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.154","url":null,"abstract":"Purpose Permanent prostate brachytherapy with seeds represent a standard of care procedure for low to intermediate risk prostate cancer. It is known to provide high cure rates and disease-free survival with tolerable toxicity. One disadvantage is that the implant arrangement cannot be altered after implantation. However, it is known that seed-displacements against their implant location may occur during the treatment course. The scope of this work was to perform a comparative analysis of seed-displacements within the prostate until day 1 and day 30 after implantation. This aimed to assess geometric and dosimetric implant variations and to identify possibilities for corresponding stability enhancements. Materials and Methods Seed-displacements between intraoperative transrectal ultrasound (TRUS) (day 0 of brachytherapy), quality assurance computed tomography (CT) (day 1), and post-plan CT (day 30) were analyzed for 21 consecutive patients. The implant arrangement observed at day 1 and 30 was registered to the day 0 and day 1 implant, and a corresponding 1:1 seed assignment was performed using the Hungarian method. These procedures were done on a pure seed-only level, i.e. without resorting to patient anatomy. Seed-displacements were evaluated depending on strand-length and implant location within the prostate. Corresponding dosimetric effects were assessed. Correlations of implant variations with patient-specific factors as prostate volume (change), dosimetric effects, as well as number of used needles and seeds were evaluated. Results Seed-displacements in the immediate post-implant phase until day 1 of brachytherapy (median displacements: 3.9±3.4 mm) were stronger than in the time to post-plan CT (2.3±2.6 mm). Implant variations occurred enhanced along the cranial-caudal direction, i.e. along the implantation direction. Seeds in base and apex tended to move towards the prostate midzone in both examined time periods. No dependency of seed-displacements on seed strand-length was observed until day 30, but strands containing one (7.0±4.5 mm) or two (8.0±5.7 mm) seeds showed larger positional deviations than strands of higher lengths (up to 4.2±7.0 mm) from day 0 to day 1. D90 (dose that 90% of prostate receives) was with variations of 2±17 Gy more stable from day 1 to 30 than in the immediate post-implant phase (-18±10 Gy). Seed-displacements were correlated with both dosimetric variations as well as prostate volume changes and the number of implanted seeds and needles. Conclusions Seed-displacements were stronger in the immediate post-implant phase than from day 1 to 30. Based on our observations, this may result from uncertainties in the gold-standard TRUS-guided implantation process. Our findings suggest a high importance of achieving a dose coverage close to 100% during intra-operative treatment planning, to ensure sufficient prostate dose coverage even after corresponding coverage declines originating from edema or systematic uncertainties. Im","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO40","authors":"Diana Lucia Guevara-Barrera, Silvia Rodriguez Villalba, Luis Suso-Martí, Enrique Sanchis-Sánchez, Francisco Blazquez Molina, Maria José Pérez-Calatayud, José Pérez-Calatayud, Manuel Santos Ortega","doi":"10.1016/j.brachy.2023.06.141","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.141","url":null,"abstract":"Purpose Tumor coverage with conventional MRI compatible combined intracavitary/interstitial (IC/IS) applicators is scarce in some patients with locally advanced gynecological malignancies. In these cases, it is recommended to add a larger interstitial component using transperineal templates (P-ISBT). Our department has been performing this type of implant since 2005 using MUPIT applicator and CT-based planning. In 2013 we switched to MRI-based planning and a compatible applicator had to be developed. It combines an IC component (intrauterine tandem) with a perineal template and Titanium needles. It is an attempt to combine the technical advantages of the MUPIT and of the MRI, while preserving the stability, geometry, and robustness of the implant. In contrast with the CT, MRI provides an excellent visibility of soft tissue, allowing a better delineation of residual tumor at the time of BT, resulting in more accurate and generally smaller treatment volumes. The aim of this work is to present the impact and benefice of MRI implementation in P-ISBT. For this purpose, the two groups of patients (pre- and post-2013) were compared in terms of CTV volume and late toxicity. Materials and Methods From 2005 to 2022, 169 patients diagnosed with primary/recurrent gynecological tumors were treated with P-ISBT. 80 patients, without dosimetric data (planned in a retired TPS) were excluded, leaving 89 patients for analysis. Patients were treated with either MUPIT or MRI-based applicator. Implants were performed by the same team of radiation oncologists, and following the same delineation and prescription protocols. Dose prescription was 24 Gy in 6 fractions for CT-based plans, and 25.5 Gy in 6 fractions for MRI-based plans. Fractions were administered twice daily. Dosimetric planning is also homogeneous within the two patient groups plan optimization was performed through the help of geometrical optimization, followed by a fine-tuning manual optimization, in order to avoid inner over-dose volumes.The CTV volumes of both groups of patients have been compared. Similarly, to demonstrate homogeneity in dosimetric planning, CTV overdose volumes V120%, V150% and V200% were compared. Finally, toxicity outcomes were analyzed using CTCAE v5.0. SPSS Statistics was used for analysis. Results 24 patients treated with MUPIT were compared to 65 patients treated with MRI- applicator. Mean CTV volumes were compared in Table 1 for patients with primary cervical cancer and in other cases (vaginal primary or recurrent), showing a halved volume in favor of MRI.Overdose volumes were compared for different CTV volume categories (image 1). The results for the 3 indices are fully equivalent for the different volume ranges As for late toxicities: G1-2 rectal toxicity was 37.5% in MUPIT vs. 7.7% in MRI-based applicator (P=0.0006); G3 rectal toxicity was 12.5% vs. 6.2% respectively (ns). G1-2 urinary toxicity was 8.3% in MUPIT vs. 6.2% in MRI-based applicator (ns); G3 urinary toxicity was","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO89","authors":"Ming Xu","doi":"10.1016/j.brachy.2023.06.190","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.190","url":null,"abstract":"The objective was to evaluate radioactive angles and dose distribution of partially shielded GYN cylinders during HDR Brachytherapy in a commercial treatment planning system (TPS). Patient treatment plans with partial shielded cylinders were generated in Brachytherapy planning using Eclipse TPS. The AAPM TG-43 dose calculation formalism was commonly used to provide rapid patient treatment. The Acuros algorithm in AAPM TG-186 MBCDAs with the same source position and planned dwell time was used to compare shielding effects and unblocked dose distributions. Acuros calculations employed solid applicators with shielded angles of 90°, 180°, and 270° from the TPS library, with tungsten alloy shielded segments. All calculations were performed in the water phantom. The differences between the AAPM TG-43 and TG-186 algorithms in these applicators were evaluated in terms of shielded angle, radioactive range, low dose bath background, and dose distribution. Patient planning using various shielded angle cylinders anteriorly or posteriorly to minimize local bladder or rectal dose on patient CT images for vaginal cuff treatment. The dwell time at the source position was calculated according to the 3D TG-43 algorithm, ignoring the shielding effect of the applicator to result in a cylindrically symmetrical dose distribution along the cylinder axis. Acuros dose calculation implemented Monte-Carlo (MC) algorithm approach. The 3D asymmetric dose distribution was shown in the sagittal view as expected. Low dose bath in the shielded areas was observed at approximately 10-15% of the prescribed dose. The low dose bath level changed slowly with shielding angle. The physical shielding angle was effectively shielded within the dose distribution range. The radioactive angle can be defined as the angle of the radioactive coverage portion from the source, or the angle between the designed isodose points to the center of cylindrical section. As showed in the figure below, a 180° shielded cylinder can shield a maximum range of about 210° in the posterior portion. When the sum of the shieling angle and radioactive angle was 360°, the radioactive angle was equal to 150°. This behavior was confirmed for shielding angles of 90°, 180°, and 270°, respectively in Acuros calculations. The radioactive angle was found to be smaller than the physical shielding angle. The presence of the metal block appeared to prevent deposition of scattered doses to unshielded tissue. This reduced scatter made the blocking angle projection wider than its physical angle. A slightly longer Acuros dwell time at a few percent was required to achieve the same dose level calculated for TG-43. Acuros calculations for shielded cylinder suggest that the shielded region in dose distribution is wider than the physically shielded part of segment. The radioactive angle is smaller than the physical shielded angle. Shielded areas are kept in low dose baths of prescribed doses. A slightly longer dwell time is required t","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PO04","authors":"Yixiang Liao, Ken Tatebe, Julius Turian","doi":"10.1016/j.brachy.2023.06.105","DOIUrl":"https://doi.org/10.1016/j.brachy.2023.06.105","url":null,"abstract":"Purpose The conventional vaginal cylinder design consists of cylindrical segments and a hemi-spherical top, with a diameter matched to the cylinder portion. This design is driven primarily by geometric simplicity, without much consideration for the dose distribution around the brachytherapy source, nor the anatomy of patients. Careful plan optimization is required to make the prescription isodose line conform to the surface of the cylinder. However, the conformity is not optimal due to the discrepancy between the cylinder shape and the intrinsic dose anisotropy of the source perpendicular to the azimuthal plane. We propose an alternative design for an ergonomic vaginal applicator (EVA), which requires minimal optimization, provides a more natural dose conformity, and is more ergonomic for the patient. Materials and Methods In treating with brachytherapy alone for postoperative endometrial cancer, our typical prescription is 6 Gy x 5 fractions to the surface, covering the top 4 cm of the vaginal cuff. To create the proposed applicator, the existing cylinder channel, using the first 10 dwell positions (5mm-interval), are uniformly loaded for 17.33 seconds with nominal 10 Ci Ir-192 HDR source (GammaMedPlusiX and Eclipse). The prescription isodose line then takes the shape of an ovoid, with 3 cm diameter at middle length, paralleling a typical size used for cylinder applicator treatments. Similarly, uniform loading times of 10, 13.6, 21.8, and 26.5 seconds correspond to maximal diameters of 2, 2.5, 3.5, and 4 cm, respectively. The prescription isodose line is converted to a contour that can be exported and used to construct an applicator. The surface of this applicator naturally conforms to the prescription isodose line, which removes the need for any further plan optimization. Dose along the surface and at 5mm distance from the applicator equator to the tip of the dome are reported. Results Using the 3 cm diameter case as an example, the average surface dose (± Std. Dev) is 100% ± 3.2% with the EVA, compared to 100% ± 5.5% with the conventional cylinder, showing improved surface dose homogeneity with EVA, even after extensive optimization of the cylinder plan. The doses at 5mm depth are comparable: 57.3 ± 6.8% and 57.9 ± 6.2%, respectively. In addition, the tapered tip of EVA is likely easier to implant and would cause less discomfort for patients. Another potential benefit of the EVA is that its tapered tip may be less likely to trap air bubbles between the applicator and the vaginal cuff. Conclusions A novel design for a vaginal applicator is achieved that requires minimal planning optimization, with improved surface dose homogeneity, and better ergonomics. These are expected to provide both superior dosimetry and better overall clinical experience. The conventional vaginal cylinder design consists of cylindrical segments and a hemi-spherical top, with a diameter matched to the cylinder portion. This design is driven primarily by geometric simplic","PeriodicalId":93914,"journal":{"name":"Brachytherapy","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135434529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}