HDR Brachytherapy For Cancer Research Articles

PO0311: Clinical Outcome Modelling Indicates Minimum Dose to be a Good Predictor in Evaluating Cervical Cancer HDR Brachytherapy Plans

PO0311: Clinical Outcome Modelling Indicates Minimum Dose to be a Good Predictor in Evaluating Cervical Cancer HDR Brachytherapy Plans

PO29: Multi-Center Investigation of Inter-Observer Variability of a Novel Mobile CBCT Ring for Gynecological Cancer HDR Brachytherapy

PO29: Multi-Center Investigation of Inter-Observer Variability of a Novel Mobile CBCT Ring for Gynecological Cancer HDR Brachytherapy

PO-1791 Lumbosacral plexus dose with CT pelvimetry correlation in cervical cancer HDR brachytherapy

PO-1791 Lumbosacral plexus dose with CT pelvimetry correlation in cervical cancer HDR brachytherapy

PO-0203 Range of intra-fraction dose uncertainty in cervical cancer HDR brachytherapy.

PO-0203 Range of intra-fraction dose uncertainty in cervical cancer HDR brachytherapy.

PO-0225 Automatic reporting of vaginal dose points for cervical cancer HDR-brachytherapy

PO-0225 Automatic reporting of vaginal dose points for cervical cancer HDR-brachytherapy

Reduction of applicator displacement in MR/CT-guided cervical cancer HDR brachytherapy by the use of patient hover transport system.

PurposeTo quantify the reduction of relative displacement between the implanted intracavitary applicator and the patient bony anatomy, due to the use of a hover transport system during the patient transports between the imaging table and the treatment table.Material and methodsThe displacement of the applicator inside the patient was measured by comparing the distance between the tip of the tandem and the pubic bone on X-ray radiography images taken before and after moving a patient to magnetic resonance/computed tomography imaging. Displacements were evaluated for 27 fractions of treatment using hover transport and 185 fractions of treatment using manual transport.ResultsThe use of hover transport system reduced the percentage of fractions with displacements greater than 5 mm from 22.7% to 7.4%. The reduction of applicator displacement using hover transport is statistically significant, compared to the manual transport method (p-value 0.0086; mean displacement 3.41 mm [95% CI: 2.96-3.97] for manual transport, and 2.27 mm [95% CI: 1.71-2.97] for hover transport fractions).ConclusionsThis study indicates that the hover transport system is effectively reducing displacement between tandem and patient bony anatomy during patient transports. The potential improvement in dosimetric accuracy due to this reduction warrants further study.

SU‐C‐202‐02: A Comprehensive Evaluation of Adaptive Daily Planning for Cervical Cancer HDR Brachytherapy

Purpose:To evaluate adaptive daily planning for cervical cancer patients who underwent high‐dose‐rate intra‐cavitary brachytherapy (HDR‐ICBT).Methods:This study included 22 cervical cancer patients who underwent 5 fractions of HDR ICBT. Regions of interest (ROIs) including high‐risk clinical tumor volume (HR‐CTV) and organs‐at‐risk (OARs) were manually contoured on daily CT images. All patients were treated with adaptive daily plans, which involved ROI delineation and dose optimization at each treatment fraction. Single treatment plans were retrospectively generated by applying the first treatment fraction's dwell times adjusted for decay and dwell positions of the applicator to subsequent treatment fractions. Various existing similarity metrics were calculated for the ROIs to quantify interfractional organ variations. A novel similarity score (JRARM) was established, which combined both volumetric overlap metrics (DSC, JSC, and RVD) and distance metrics (ASD, MSD, and RMSD). Linear regression was performed to determine a relationship between inter‐fractional organ variations of various similarity metrics and D2cc variations from both plans. Wilcoxon Signed Rank Tests were used to assess adaptive daily plans and single plans by comparing EQD2 D2cc (α/β=3) for OARs.Results:For inter‐fractional organ variations, the sigmoid demonstrated the greatest variations based on the JRARM and DSC similarity metrics. Comparisons between paired ROIs showed differences in JRARM scores and DSCs at each treatment fraction. RVD, MSD, and RMSD were found to be significantly correlated to D2cc variations for bladder and sigmoid. The comparison between plans found that adaptive daily planning provided lower EQD2 D2cc of OARs than single planning, specifically for the sigmoid (p=0.015).Conclusion:Substantial inter‐fractional organ motion can occur during HDR‐BT, which may significantly affect D2cc of OARs. Adaptive daily planning provides improved dose sparing for OARs compared to single planning.

Can Bladder Late Complications Be Predicted in Cervical Cancer HDR Brachytherapy?

Can Bladder Late Complications Be Predicted in Cervical Cancer HDR Brachytherapy?

Reproducibility of Immobilization Balloons Used Sequentially for Cervical Cancer HDR Brachytherapy

Reproducibility of Immobilization Balloons Used Sequentially for Cervical Cancer HDR Brachytherapy

SU‐C‐16A‐07: Sculpting Isodose Lines: Design of An Internally Shielded Tandem for Cervical Cancer Brachytherapy

Purpose:With the prescription method moving from point A to 3D volume based in cervical cancer HDR brachytherapy, the traditional pear‐shaped isodose lines are desired to be sculptured to conform to the irregular shaped target. The standard single channel tandem cannot generate asymmetric isodose lines. Most of the directionally shielded sources proposed in literature are challenging to manufacture and operate. In this study, we proposed a novel internally shielded tandem applicator design which gave users more freedom to manipulate isodose lines while planning.Methods:The proposed tandem design has one centrally located lead cylindrical rod of 8 mm in diameter serving as the internal shield. Multiple source channels with the diameter of 2 mm are evenly spaced and engraved on the central cylindrical rod. The overall diameter of the tandem with polymer encapsulation was kept to be 10 mm. Various number of channels and engraving depths have been tested in the design process. Geant4 Monte Carlo toolkit was used for dose calculation assuming a Varian VS2000 source was placed inside the applicator. A Monte Carlo based planning system has been developed in‐house to generate brachytherapy plans. Test plans by using this internally shielded tandem were generated for 3 clinical cases.Results:Water phantom results shown the dose distribution from a VS2000 source in the tandem was strongly distorted towards one direction due to the presence of shielding material. Conformal plans with asymmetric isodose distributions around the tandem can be generated by optimizing dwell times in different channels.Conclusion:An effective and easy‐to‐use internally shielded tandem was developed. It gave user the freedom to sculpt isodose lines to generate conformal plans for cervical cancer brachytherapy.

SU‐F‐BRF‐09: A Non‐Rigid Point Matching Method for Accurate Bladder Dose Summation in Cervical Cancer HDR Brachytherapy

Purpose:To propose and validate a deformable point matching scheme for surface deformation to facilitate accurate bladder dose summation for fractionated HDR cervical cancer treatment.Method:A deformable point matching scheme based on the thin plate spline robust point matching (TPSRPM) algorithm is proposed for bladder surface registration. The surface of bladders segmented from fractional CT images is extracted and discretized with triangular surface mesh. Deformation between the two bladder surfaces are obtained by matching the two meshes' vertices via the TPS‐RPM algorithm, and the deformation vector fields (DVFs) characteristic of this deformation is estimated by B‐spline approximation. Numerically, the algorithm is quantitatively compared with the Demons algorithm using five clinical cervical cancer cases by several metrics: vertex‐to‐vertex distance (VVD), Hausdorff distance (HD), percent error (PE), and conformity index (CI). Experimentally, the algorithm is validated on a balloon phantom with 12 surface fiducial markers. The balloon is inflated with different amount of water, and the displacement of fiducial markers is benchmarked as ground truth to study TPS‐RPM calculated DVFs' accuracy.Results:In numerical evaluation, the mean VVD is 3.7(±2.0) mm after Demons, and 1.3(±0.9) mm after TPS‐RPM. The mean HD is 14.4 mm after Demons, and 5.3mm after TPS‐RPM. The mean PE is 101.7% after Demons and decreases to 18.7% after TPS‐RPM. The mean CI is 0.63 after Demons, and increases to 0.90 after TPS‐RPM. In the phantom study, the mean Euclidean distance of the fiducials is 7.4±3.0mm and 4.2±1.8mm after Demons and TPS‐RPM, respectively.Conclusions:The bladder wall deformation is more accurate using the feature‐based TPS‐RPM algorithm than the intensity‐based Demons algorithm, indicating that TPS‐RPM has the potential for accurate bladder dose deformation and dose summation for multi‐fractional cervical HDR brachytherapy.This work is supported in part by the National Natural ScienceFoundation of China (no 30970866 and no 81301940).

EP-1895: Treated volumes comparison for different fractionation regimens of cervical cancer HDR brachytherapy

EP-1895: Treated volumes comparison for different fractionation regimens of cervical cancer HDR brachytherapy

SU-E-T-299: Sensitivity Analysis of the Radiobiological Parameters Used to Examine the Effectiveness of Different Fractionation Schedules in Prostate Cancer HDR Brachytherapy

Purpose: The aim of the present study is to evaluate the robustness of the effectiveness of different fractionation schemes of HDR brachytherapy (to be applied as monotherapy for low-risk prostate cancer) by using radiobiological models and dosimetric measures. Methods: In this study, the treatment plans of 12 patients who had undergone clinical implants for HDR brachytherapy of prostate cancer were evaluated using the response probabilities of the individual organs, the complication-free tumor control probability (P+), the total tumor control probability (PB), the total normal tissue complication probability (PI), the biologically effective uniform dose (BEUD) and the generalized equivalent uniform dose (gEUD) as measures. These indices use the D50, γ, s, α/β and alpha radiobiological parameters together with the corresponding tissue DVH data. The values of those parameters were varied around their reference values in order to examine the impact of their uncertainty on the values of the radiobiological measures in the evaluation of four fractionation schemes. Results: For the four examined fractionation schemes, the tumor control probabilities are 98.5% in 1×20Gy, 98.6% in 2×14Gy, 97.5% in 3×11Gy and 97.8% in 4x9.5Gy. The corresponding total normal tissue complication probabilities are 9.7% in 1×20Gy, 14.6% in 2×14Gy, 11.5% in 3×11Gy and 15.6% in 4×9.5Gy. The complication-free tumor control probabilities are 88.8% in 1x20Gy, 83.9% in 2×14Gy, 86.0% in 3×11Gy and 82.3% in 4×9.5Gy. The sensitivity analysis showed that the values of P+, PB, PI and BEUD varied by 6.1–7.3%, 5.8–9.3%, 5.6–7.2% and 7.6–9.0 Gy, respectively. Conclusion: The present analysis indicates that among the fractionation schemes of 1×20Gy, 2×14Gy, 3×11Gy and 4×9.5Gy the first scheme is more effective. The sensitivity analysis shows that the variation of the radiobiological parameters considerably affects the values of the response indices, especially the α/β parameter.

SU-E-T-586: Utrecht Applicator Reconstruction in MRI-Based Cervix Gynaecological Brachytherapy

Purpose: GYN GEC-ESTRO recommendations stated the convenience of performing a 3D magnetic resonance imaging (MRI)—based treatment planning for brachytherapy in cervical cancer. Several applicators have been developed for combining intracavitary/interstitial brachytherapy like the Utrecht applicators consisting of a tandem plus colpostats with plastic needles inserted for which no dummies have been developed. The objective of this work is to describe our experience in the MRI-based reconstruction of the Utrecht applicators. Methods: At our department Utrecht applicators are used in cervical cancer HDR brachytherapy (4 fractions of 7 Gy), after 45–50 Gy of 3DCRT. For each application, MR scans with applicator in situ are made. Two different MRI modalities have been used to acquire the images that are imported in Oncentra MasterPlan (OMP) treatment planning system. a) Firstly, the sequence of images was acquired in a GEMS SIGMA EXCITE MRI Unit (strength 1.5T). See Perez-Calatayud et al. (R&O 2009) for the details of the process for intracavitary catheters. b) Lately the acquisition is done in a Siemens TrioTim MRI unit (strength 3T), using a 3D sequence based on acquired coronal images (dedicated to the geometric reconstruction), in conjunction with transverse images (intended to the definition of the VOI). Regarding the reconstruction of the needles, the retraction is set on OMP with the measuring distance tools on the paracoronal/parasagital reconstructed planes that contain the needle. The black hole corresponding to the needle position in the transverse view is also used.Results: Several examples are presented to illustrate the described process, which allows the reconstruction of the Utrecht applicators without any dummy phantom. With the 3T technique the image quality has been improved and the reconstruction has been enhanced. Conclusions: A fast and efficient method for the Utrecht applicator reconstruction based on 3T MRI data acquisition has been established.

3D Image-based Customized Treatment Planning versus Standard Plans for Cervix Cancer HDR Brachytherapy

3D Image-based Customized Treatment Planning versus Standard Plans for Cervix Cancer HDR Brachytherapy

SU-GG-T-47: Dosimetric Equivalence of Non-Standard Brachytherapy Needle Patterns

Purpose: To determine whether alternative prostate brachytherapy needle patterns can result in similar or improved dose distributions while providing better access and reducing trauma in the treatment of HDR prostate brachytherapy.Method and Materials: Standard prostate cancer HDR brachytherapy uses a regular grid of parallel needle positions to guide the catheter insertion. This geometry does not easily allow the physician to avoid piercing the penile bulb nor does it provide position flexibility in the case of pubic arch interference. In this study, CT datasets from 10 previously‐treated patients were used and catheters were digitized by following three hypothetical catheter patterns: conical, bi‐conical, and fireworks. The conical patterns were used to accommodate a robotic delivery using a single entry point. The bi‐conical and fireworks patterns were specifically designed to avoid the bulb. For each catheter distribution, a plan was optimized with the inverse planning algorithm, IPSA, and compared with the plan used for treatment. Irrelevant of geometry, a plan must fulfill the RTOG‐0321 dose criteria for target dose coverage (V100>90%) and organ‐at‐risk dose sparing (V75<1cc for the bladder and rectum, V125<<1cc for the urethra). Results: The three non‐standard catheter patterns used 16 non‐parallel, straight divergent catheters, with the focal point(s) in the perineum. 30 plans from 10 patients with prostate sizes ranging from 26 to 89 cc were optimized. All non‐standard patterns fulfilled the RTOG criteria when the clinical plan did. In some cases, the dose distribution was improved by better sparing the organs‐at‐risk. Conclusion: Alternative needle patterns can provide the physician with additional ways to treat patients previously considered unsuited for brachytherapytreatment (pubic arch interference) and to improve patient quality of life (avoidance of penile bulb), while fulfilling the RTOG criteria. Conflict of Interest: Research sponsored by the Nucletron Corporation.

SU‐EE‐A1‐04: Integrated Complementary IMRT Combined with Image‐Guided HDR Brachytherapy for Cancers of the Uterine Cervix

Purpose: Conventional HDR (CHDR) brachytherapy for cervical cancers often fails to cover the entire gross tumor volume (GTV). CT/MRI‐based 3‐D planning allows optimization of dwell times for improved target coverage, but often at the cost of substantially higher doses to organs at risk (OARs). In the present study, we integrate image‐guided HDR brachytherapy with concomitant complementary IMRT to boost target coverage and maintain low doses to OARs. Method and Materials: Treatment planning CT and MRI images of 6 patients were acquired with CT/MRI‐compatible carbon‐fiber applicator. HDR plans were obtained by modifying CHDR plans to keep bladder and rectum dose below 80%. Based on these HDR plans, IMRT plans were subsequently optimized to complement the dose coverage of GTV with 3‐mm margin (GTV+) and the uterus. To prevent anatomical deformation, IMRT plans were to be delivered immediately following image‐guided HDR treatment with applicator in place. V95% (Target volume receiving 95% prescription dose) and D2 (minimum dose in 2.0‐cm3 OAR volume receiving the highest dose) were used to compare IMRT‐HDR technique with CHDR and HDR optimized for target coverage (OHDR). Results: The MRT‐HDR technique substantially improved target coverage while maintaining bladder and rectum doses at acceptable low level. For the six patients, V95% for GTV+ and the uterus improved from the average of 56.8% and 51.4% in CHDR to 92.5% and 95.3% in IMRT‐HDR, respectively. Average D2 doses to bladder and rectum were 88.7% and 65.2% for CHDR and 72.4% and 71.4% for IMRT‐HDR. In contrast, OHDR improved target coverage, but D2 doses to bladder (&gt;119%) and rectum (87.3% to &gt; 200%) were unacceptably high. Conclusion: Integrated complementary IMRT combined with image‐guide HDR significantly improves dose coverage to the targets while maintaining low doses to OARs. It is dosimetrically and logistically feasible to clinically implement this technique for potentially improved outcome.

25 MRI assisted 3D treatment planning in intracavitary and interstitial cervix cancer HDR brachytherapy and its impact on local tumour control: Vienna experience in 145 patients treated from 1998–2003

25 MRI assisted 3D treatment planning in intracavitary and interstitial cervix cancer HDR brachytherapy and its impact on local tumour control: Vienna experience in 145 patients treated from 1998–2003

Results of interstitial HDR brachytherapy for cancer of the lower lip

Summary Background HDR brachytherapy has been employed in the treatment of cancers in numerous locations around the body, however, few publications have dealt with primary carcinomas of the head and neck. To our knowledge, only one paper concerns the use of this technique in the treatment of cancers of the lower lip. Furthermore, the recommendations given by the American Association of Brachytherapy do not appear to elaborate on the subject. Aim To analyse the treatment of lower lip carcinoma by interstitial HDR brachytherapy. Materials/Methods Retrospective analysis of the results of treatment was carried out among a group of 24 consecutive patients, of whom 18 were treated by brachytherapy alone while 6 others were treated after surgery. Fifteen patients were classified as T1, nine patients as T2. 23 patients were classified as N0 and one as N1. Each patient had histologically confirmed squamous cell carcinoma. Radiotherapy involved interstitial, high dose rate brachytherapy with an iridium-192 source. Post-operative brachytherapy was indicated in cases of microscopically incomplete excision. The dose was determined using the Paris method, the reference dose being 80% or at a point 3–5 mm from the macroscopic lesion or tumour bed. The mean total dose was 35 Gy, the mean number of fractions was 7, and the mean fraction dose was 5.7 Gy. The total treatment time was 12 days, on average, whereas the mean follow-up was 32 months. Results Local control was obtained after 24 months in 21 patients (87.5%). All patients developed a severe early reaction. Three patients with mouth corner infiltration (100%) failed to show complete regression. Two of these patients underwent additional irradiation to the residual lesion, resulting in cures. The third patient underwent successful surgical treatment. The cosmetic and functional effect was very good. Conclusuions Interstitial HDR brachytherapy is an effective and safe method for the treatment of carcinoma in the lower lip.