Vaginal Cylinder Research Articles

Experimental verification of Advanced Collapsed-cone Engine for use with a multichannel vaginal cylinder applicator.

Model‐based dose calculation algorithms have recently been incorporated into brachytherapy treatment planning systems, and their introduction requires critical evaluation before clinical implementation. Here, we present an experimental evaluation of Oncentra® Brachy Advanced Collapsed‐cone Engine (ACE) for a multichannel vaginal cylinder (MCVC) applicator using radiochromic film. A uniform dose of 500 cGy was specified to the surface of the MCVC using the TG‐43 dose formalism under two conditions: (a) with only the central channel loaded or (b) only the peripheral channels loaded. Film measurements were made at the applicator surface and compared to the doses calculated using TG‐43, standard accuracy ACE (sACE), and high accuracy ACE (hACE). When the central channel of the applicator was used, the film measurements showed a dose increase of (11 ± 8)% (k = 2) above the two outer grooves on the applicator surface. This increase in dose was confirmed with the hACE calculations, but was not confirmed with the sACE calculations at the applicator surface. When the peripheral channels were used, a periodic azimuthal variation in measured dose was observed around the applicator. The sACE and hACE calculations confirmed this variation and agreed within 1% of each other at the applicator surface. Additionally for the film measurements with the central channel used, a baseline dose variation of (10 ± 4)% (k = 2) of the mean dose was observed azimuthally around the applicator surface, which can be explained by offset source positioning in the central channel.

Impact of vaginal cylinder diameter on outcomes following brachytherapy for early stage endometrial cancer.

ObjectiveTo examine the outcomes (tolerability, toxicity, and recurrence) of vaginal brachytherapy (VBT) among endometrial cancer (EC) patients treated with small cylinder size.MethodsPatients with EC who received adjuvant VBT between September 2011 and December 2015 were reviewed. Patients were fitted with the largest vaginal cylinder they could comfortably accommodate, from 2.0–3.0 cm diameter. Small cylinders were defined as size 2.3 cm or less. Patient, tumor, or treatment characteristics were correlated with need for small cylinders. Treatment tolerability, measures of gastrointestinal (GI), genitourinary (GU), and vaginal toxicity, and rates of recurrence were analyzed.ResultsThree hundred four patients were included. Small cylinders were used in 51 patients (17%). Normal body mass index (BMI; p<0.001), nulligravidity (p<0.001), and shorter vaginal length (p<0.001) were associated with small cylinder size. There was no acute or late grade 3 toxicity. Rates of acute (grade 1–2) GI, GU, or vaginal symptoms were low (10%, 11%, and 19%, respectively). Small cylinder size was associated with increased likelihood of reporting acute GI (p<0.05) but not GU or vaginal symptoms. Small cylinder size was associated with higher risk of grade 1–2 vaginal stenosis (odds ratio [OR]=4.7; 95% confidence interval [CI]=1.5–14.7; p=0.007). There was no association between cylinder size and recurrence rate (p=0.55).ConclusionVBT is generally very well tolerated, however, patients fitted with smaller cylinders (commonly nulligravid and low BMI) may have increased side effects. Further study to improve the dosimetry of VBT for patients requiring small cylinders may be worthwhile.

Effects of vaginal cylinder position on dose distribution in patients with endometrial carcinoma in treatment of vaginal cuff brachytherapy.

PurposeTo investigate the impact of different cylinder positions on dosimetry of critical structures in patients with endometrial carcinoma undergoing three-dimensional image-based vaginal cuff brachytherapy (VCB).Material and methodsWe delivered VCB at a dose of 4 Gy to a depth of 5 mm in the vaginal cuff of 15 patients using three different cylinder positions (neutral [N], parallel [P], and angled [A]) according to the longitudinal axis of the patient. We analyzed the dose-volume distribution and volumetric variability of the rectum and bladder. We converted the total doses to equivalent doses in 2 Gy (EQD2) using a linear-quadratic model (a/b = 3 Gy).ResultsThe mean rectum volume for the N, P, and A positions was 68.2 ± 22.7 cc, 79.3 ± 33.7 cc, and 74.2 ± 29.6 cc, respectively. The mean rectum volume for the P position was significantly larger than that for the N position (p = 0.03). Relative to the N position, the A position resulted in a lower total EQD2 in the highest irradiated 2 cc (D2cc; p = 0.001), 1 cc (D1cc; p = 0.004), and 0.1 cc (D0.1cc; p = 0.047) of the rectum. Similarly, the P position resulted in a lower EQD2 in the D2cc (p = 0.018) and D1cc (p = 0.024) of the rectum relative to the N position. In the bladder, the P position resulted in a higher EQD2 in the D2cc relative to the N position (p = 0.02). There was no dosimetric difference between the P and A positions in either the rectum or the bladder.ConclusionsVaginal cuff brachytherapy in the P and A positions is significantly superior to that in the N position in terms of rectum dosimetry. The bladder dose in the N position is considerably lower than that in the other positions.

Comparing organ-at-risk doses for high-dose-rate vaginal brachytherapy between three different planning workflows

PurposeThe aim of this study was to compare the organ-at-risk doses to the rectum and the bladder in postoperative endometrial cancer patients who receive high-dose-rate vaginal brachytherapy (HDR-VB), when using three different methods of treatment planning: (Workflow A) individualized treatment planning before every fraction, (Workflow B) individualized treatment planning for first fraction only), and (Workflow C) using a template plan based on applicator choice and prescription specifics without patient-specific imaging or planning (standardized template approach). Methods and MaterialsAlternative plans were retrospectively created using workflows B and C for 22 patients who previously received postoperative HDR-VB using a vaginal cylinder and planned using Workflow A for endometrial cancer. The rectum and bladder were contoured on the CTs used for each fraction for dose comparison between the three methods. D50, D2cc, D1cc, D0.1cc, and V100 of the bladder and the rectum were compared using the two-sided Wilcoxon signed-rank test. ResultsA total of 123 fractions were available for comparison. For Workflow A vs. Workflow B, there was no significant difference for any rectal or bladder dosimetric parameter. For Workflow A vs. Workflow C, Workflow A delivered a significantly higher median dose to the rectum than Workflow C for D50, D2cc, D1cc, and V100. Workflow C delivered a significantly higher dose to the bladder than Workflow A: D2cc, D1cc, D0.1cc, and V100. However, the magnitudes of the differences were small; the dose index difference was >75 cGy for only two fractions. ConclusionPlan standardization in HDR-VB may result in considerable time and cost savings with minimal organ-at-risk dose differences.

6th Annual Conference of Indian Brachytherapy Society 2016 (IBSCON 2016) Proceedings

PurposeTo report the incidence, severity, and time of onset of late toxicities in patients of endometrial adenocarcinoma (EA) treated with external beam radiotherapy (EBRT) + brachytherapy (BT), or vaginal brachytherapy (VBT) alone.Material and methodsArchives of a single institution from 2008-2015 were studied. The indications for EBRT and VBT were based on standard recommendations. EBRT was planned to 50 Gy/25 fractions/5 weeks/3DCRT with 4-field ‘box’ technique on a dual energy linear accelerator. VBT was planned using appropriate vaginal cylinder treating upper half of vaginal cuff, prescribed 5 mm from vaginal surface using Ir-192 micro-Selectron to doses of 4 Gy x 4 fractions/4 days or 6 Gy x 5 fractions/ 7 days with or without EBRT, respectively. Intra-cavitary BT (ICBT) was prescribed to point A to 7 Gy x 3 fractions once weekly. Survival was calculated from Kaplan-Meier curves, and toxicity was recorded using CTCAE V3.ResultsOf 120 patients registered, 19 were excluded due to inadequate follow-up. Among the 63 patients who received RT, 18 received VBT alone and 40 received adjuvant EBRT + VBT. Five patients received definitive EBRT + ICBT, all of whom are disease free with median follow-up of 36.5 (range: 18-76) months. With median follow-up of 30 (range: 0.8-81) months, median DFS and OS were 79.2% and 75.7%, respectively in the adjuvant RT setting. Cystitis, proctitis, and enteritis was reported in 7% (all grade I/II), 17% (9% grade I/II and 8% grade III), and 5% (all grade I/II), respectively. All toxicities were seen in the EBRT arm. EBRT resulted in significantly higher proctitis than VBT alone (p = 0.02). The median time to cystitis, proctitis, and enteritis were 27, 17, and 28 months, respectively.ConclusionWith the use of 3D-CRT in endometrial adenocarcinoma, late toxicity rates appear low and mild, however EBRT leads to significantly higher proctitis than VBT alone.

Small Vaginal Cylinder Size Predicts for Reduced Tolerance of Brachytherapy in Endometrial Cancer

Small Vaginal Cylinder Size Predicts for Reduced Tolerance of Brachytherapy in Endometrial Cancer

The effect of pelvic radiotherapy on vaginal brachytherapy cylinder diameter: Implications for optimal treatment order

PurposeTo determine the factors that correlate with cylinder size in vaginal brachytherapy (VB) after hysterectomy for endometrial carcinoma. Methods and MaterialsPatients treated for endometrial cancer from January 1, 2003 to December 31, 2013 were reviewed from a single institution. Patients included underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy followed by high-dose-rate VB with or without external beam pelvic radiotherapy (EBRT). According to institutional guidelines, the vaginal cylinder size selected was the largest diameter cylinder the patient could comfortably accommodate. Patient, tumor, and treatment factors were recorded and compared with cylinder size. ResultsThree hundred eighty-one eligible patients were identified, including 121 patients treated with pelvic radiotherapy (RT) before VB and 260 treated with VB alone. On univariate analysis, weight (p = 0.0004), body mass index (BMI) (p = 0.001), and receipt of pelvic RT (p ≤ 0.0001) were the only statistically significant factors correlated with vaginal cylinder size. On multivariate analysis, receipt of EBRT retained significance after adjusting for weight or BMI. In patients receiving VB alone, median cylinder size was 3 cm; after pelvic RT, it was 2.5 cm. ConclusionsHigher weight and BMI correlated with accommodation of larger cylinder size. Accounting for this, the receipt of EBRT before VB was associated with smaller cylinder size. Dosimetric data show that larger cylinder size provides superior dose distribution. Although historically the VB boost follows EBRT, reversal of this order may be preferred.

SU-F-P-61: Does It Matter Not to Use Optimization Points at the Apex for Vaginal Cylinder HDR Brachytherapy Planning?

Purpose: To test the impact of the use of apex optimization points for new vaginal cylinder (VC) applicators. Methods: New “ClickFit” single channel VC applicators (Varian) that have a different top thicknesses but the same diameters as the old VC applicators (2.3 cm diameter, 2.6 cm, 3.0 cm, and 3.5 cm) were compared using phantom studies. Old VC applicator plans without apex optimization points were also compared to the plans with the optimization points. The apex doses were monitored at 5 mm depth doses (8 points) where a prescription dose (Rx) of 6Gy was prescribed. VC surface doses (8 points) were also analyzed. Results: The new VC applicator plans without apex optimization points presented significantly lower 5mm depth doses than Rx (on average −31 ± 7%, p <0.00001) due to their thicker VC tops (3.4 ± 1.1 mm thicker with the range of 1.2 to 4.4 mm) than the old VC applicators. Old VC applicator plans also showed a statistically significant reduction (p <0.00001) due to Ir-192 source anisotropic effect at the apex region but the % reduction over Rx was only −7 ± 9%. However, by adding apex optimization points to the new VC applicator plans, the plans improved 5 mm depth doses (−7 ± 9% over Rx) that were not statistically different from old VC plans (p = 0.923), along with apex VC surface doses (−22 ± 10% over old VC versus −46 ± 7% without using apex optimization points). Conclusion: The use of apex optimization points are important in order to avoid significant additional cold doses (−24 ± 2%) at the prescription depth (5 mm) of apex, especially for the new VC applicators that have thicker tops.

SU‐G‐TeP2‐10: Feasibility of Newly Designed Applicator for High Dose Rate Brachytherapy Treatment of Patients with Vaginal Vault Recurrence

Purpose:To compare the dose of an in‐house 3D‐printed gynecology applicator (TMHGA) for vaginal vault recurrence of corpus cancer patients after operation for high dose rate brachytherapy treatment with commercially available applicators.Methods:A newly designed applicator is made from 3D‐printing methods using ABSM30i. The isodose of the applicator is compared with Elekta multi‐channel (MC) applicator and titanium Rotterdam applicator with coupling central tube and vaginal cylinder (RC). Three plans are created using three applicators in a CT set of water phantom. The applicators are anchored using the applicator library and implant library in the Elekta Oncentra treatment planning system (ver.4.5). The rectum is mimicked by creating a 2cm diameter cylinder, with a distance 1mm posteriorly away from the high risk CTV (HR‐CTV). Similarly, the bladder is replicated by a 6cm diameter cylinder with distance 1mm anteriorly from the HR‐CTV. Three plans are all normalized 1.5cm superior, 0.5cm anterior and 0.5cm posterior of the applicator surface. By fixing D90 of HR‐CTV to 6Gy, the D2cc of rectum and bladder of three plans are compared.Results:The D2cc of the bladder for using TMHGA is lower than MC and RC by 14.0% and 11.9% respectively. While the D2cc of the rectum for using TMHGA is lower than MC and RC by 18.9% and 12.4% respectively. The total treatment time of TMHGA plan is shorter than MC and RC by 11.2% and 12.9%.Conclusion:The applicator created via 3D printing delivers a lower dose to the bladder and the rectum while keeping the same coverage to HR‐CTV as other commercially available applicators. Additionally, the new applicator resulted in a reduction of treatment time, which is always welcome.

SU‐F‐T‐47: MRI T2 Exclusive Based Planning Using the Endocavitary/interstitial Gynecological Benidorm Applicator: A Proposed TPS Library and Preplan Efficient Methodology

Purpose:ABS and GEC‐ESTRO have recommended MRI T2 for image guided brachytherapy. Recently, a new applicator (Benidorm Template, TB) has been developed in our Department (Rodriguez et al 2015). TB is fully MRI compatible because the Titanium needles and it allows the use of intrauterine tandem. Currently, TPS applicators library are not currently available for non‐rigid applicators in case of interstitial component as the TB.The purpose of this work is to present the development of a library for the TB, together with its use on a pre‐planning technique. Both new goals allow a very efficient and exclusive T2 MRI based planning clinical TB implementation.Methods:The developed library has been implemented in Oncentra Brachytherapy TPS, version 4.3.0 (Elekta) and now is being implemented on Sagiplan v 2.0 TPS (Eckert&amp;Ziegler BEBIG). To model the TB, free and open software named FreeCAD and MeshLab have been used. The reconstruction process is based on three inserted A‐vitamin pellets together with the data provided by the free length. The implemented preplanning procedure is as follow: 1) A MRI T2 acquisition is performed with the template in place just with the vaginal cylinder (no uterine tube nor needles). 2) The CTV is drawn and the required needles are selected using a developed Java based application and 3) A post‐implant MRI T2 is performed.Results:This library procedure has been successfully applied by now in 25 patients. In this work the use of the developed library will be illustrated with clinical examples. The preplanning procedure has been applied by now in 6 patients, having significant advantages: needle depth estimation, needle positions and number are optimized a priori, time saving, etcConclusion:TB library and pre‐plan techniques are feasible and very efficient and their use will be illustrated in this work.

SU-G-201-07: Dosimetric Verification of a 3D Printed HDR Skin Brachytherapy Applicator

Purpose: The use of radiation as a treatment modality for skin cancer has increased significantly over the last decade with standardized applicators. Utilizing 3D printing, the ability to make applicators specifically designed for each patient's anatomy has become economically feasible. With this in mind it was the aim of this study to determine the dosimetric accuracy of a 3-D printed HDR brachytherapy applicator for the skin. Methods: A CT reference image was used to generate a custom applicator based on an anthropomorphic head and neck phantom. To create the applicator a 1cm expansion anteriorly with 0.5cmX0.5cm trenches on the outer surface that were spaced 1cm sup-inf to accommodate standard 6F flexible catheters. The applicator was printed using PLA material using a printrbot simple printer. A treatment plan optimized to deliver a clinically representative volume was created in Oncentra and delivered with a nucletron afterloader. Measurements were made using TLDs and EBT3 gafchromic film that were placed between the applicator and the phantom's forehead. An additional piece of film was also used to qualitatively asses the dose distribution in the transverse plane. Using a standard vaginal cylinder and bolus, a standardized curve correlating TLD and film exposure-to-radiation dose was established by irradiating film to known doses (200,500,700 cGy) at a 3.5 cm radius distance. Results: Evaluated TLDs showed the absolute dose delivered to the skin surface using the 3-D printed bolus was 615cGy±6%, with a mean predicted TPS value in the measured area of 617.5±7%. Additionally, planar dose distributions had good qualitative agreement with calculated TPS isodoses. Conclusion: This work demonstrates patient specific 3-D printed HDR brachytherapy applicators for skin cancer treatments are practical and accurate in TPS calculations but additional measurements are needed to verify additional sites and dose at depth.

SU‐F‐T‐65: AutomaticTreatment Planning for High‐Dose Rate (HDR) Brachytherapy with a VaginalCylinder Applicator

Purpose:High dose rate (HDR) brachytherapy treatment planning is conventionally performed in a manual fashion. Yet it is highly desirable to perform computerized automated planning to improve treatment planning efficiency, eliminate human errors, and reduce plan quality variation. The goal of this research is to develop an automatic treatment planning tool for HDR brachytherapy with a cylinder applicator for vaginal cancer.Methods:After inserting the cylinder applicator into the patient, a CT scan was acquired and was loaded to an in‐house developed treatment planning software. The cylinder applicator was automatically segmented using image‐processing techniques. CTV was generated based on user‐specified treatment depth and length. Locations of relevant points (apex point, prescription point, and vaginal surface point), central applicator channel coordinates, and dwell positions were determined according to their geometric relations with the applicator. Dwell time was computed through an inverse optimization process. The planning information was written into DICOM‐RT plan and structure files to transfer the automatically generated plan to a commercial treatment planning system for plan verification and delivery.Results:We have tested the system retrospectively in nine patients treated with vaginal cylinder applicator. These cases were selected with different treatment prescriptions, lengths, depths, and cylinder diameters to represent a large patient population. Our system was able to generate treatment plans for these cases with clinically acceptable quality. Computation time varied from 3–6 min.Conclusion:We have developed a system to perform automated treatment planning for HDR brachytherapy with a cylinder applicator. Such a novel system has greatly improved treatment planning efficiency and reduced plan quality variation. It also served as a testbed to demonstrate the feasibility of automatic HDR treatment planning for more complicated cases.

Standard High Dose Rate Brachytherapy Plan Template Generation as Part of a Comprehensive Brachytherapy Program

Standard High Dose Rate Brachytherapy Plan Template Generation as Part of a Comprehensive Brachytherapy Program

Vaginal Cylinders in High Dose Rate Brachytherapy - Do Different Point Prescriptions Affect Results?

Vaginal Cylinders in High Dose Rate Brachytherapy - Do Different Point Prescriptions Affect Results?

Evaluation of the Surface Dose around a Multi-Channel Vaginal Cylinder Using Radiochromic Film and ACE Algorithm

Evaluation of the Surface Dose around a Multi-Channel Vaginal Cylinder Using Radiochromic Film and ACE Algorithm

Improved Dose Conformality in Non-Image Based Treatment Planning for Vaginal Cylinders Using Shallower Dose Optimization Points

Improved Dose Conformality in Non-Image Based Treatment Planning for Vaginal Cylinders Using Shallower Dose Optimization Points

Dosimetric Comparison of Interstitial Brachytherapy with Multi-Channel Vaginal Cylinder (MCVC) Plans in Patients with Vaginal Cancers

Dosimetric Comparison of Interstitial Brachytherapy with Multi-Channel Vaginal Cylinder (MCVC) Plans in Patients with Vaginal Cancers

Quantification & Dosimetric Consequences of Air Gaps Surrounding Vaginal Cylinders in Women Undergoing Vaginal HDR Brachytherapy. Final Report of a Prospective Study

Quantification & Dosimetric Consequences of Air Gaps Surrounding Vaginal Cylinders in Women Undergoing Vaginal HDR Brachytherapy. Final Report of a Prospective Study

Clinical Outcomes with Definitive Treatment of Vaginal Cancer with Image-Based Multichannel Vaginal Cylinder Brachytherapy

Clinical Outcomes with Definitive Treatment of Vaginal Cancer with Image-Based Multichannel Vaginal Cylinder Brachytherapy

3d Image-Based Auto-Planning and Quality Assurance for High-Dose Rate (HDR) Brachytherapy with a Vaginal Cylinder Applicator

3d Image-Based Auto-Planning and Quality Assurance for High-Dose Rate (HDR) Brachytherapy with a Vaginal Cylinder Applicator