3D image-based adapted high-dose-rate brachytherapy in cervical cancer with and without interstitial needles: measurement of applicator shift between imaging and dose delivery (original) (raw)
Related papers
Journal of Contemporary Brachytherapy
Purpose: Hybrid intracavitary and interstitial (IC/IS) applicators improve dose distribution compared to traditional IC applicators in cervical high-dose-rate (HDR) brachytherapy. There is a learning curve to these applicators, and initial standard needle insertion patterns have not been well-established. In this study, we quantified dosimetric benefits of IC/IS applicators, and offer practical initial interstitial needle-selection, insertion depths, and dwell position recommendations. Material and methods: Fifteen patients previously treated with a tandem and ring IC applicator and magnetic resonance (MR)-guidance were re-planned at first fraction using a digital template of Vienna-style interstitial needles. IC/IS plans maintained identical high-risk clinical target volume (HR-CTV) D 90% while reducing dose to organs at risk (OARs). To assess the validity of planning using virtual needles, virtual needle templates were overlaid on twelve clinical IC/IS plans, and the displacements between 40 physical and virtual needles were measured at 3 cm depth. Results: The median HR-CTV volume in the present study was 19.6 cc (range, 6.6-60.5 cc). HR-CTV D 90% was maintained in all re-plans. Median bladder D 2cc decreased from 5.4 Gy per fraction to 4.8 Gy (p = 0.003); median rectum D 2cc decreased from 2.4 Gy per fraction to 2.0 Gy (p = 0.007). We suggest that a standard loading pattern should include needles in lateral channels 4, 5, and 9, 10 inserted 3 cm deep, with dwell times < 20% of the combined tandem and ring dwells. The mean displacement between planned and physical needles was 1.8 mm. All needles but three deviated less than 3.3 mm, demonstrating the validity of re-planning with virtual needles. Conclusions: Hybrid IC/IS applicators maintain excellent D 90% coverage while improving dose to OARs compared to IC-only applicators, even in non-bulky HR-CTVs. We offer practical recommendations for needle selection, insertion depth, and relative weighting for Vienna-style applicators in small HR-CTVs. These results support previous publications, offering practical recommendations for users of Vienna-style hybrid applicators.
Journal of Contemporary Brachytherapy
Purpose: Novel hybrid Venezia applicator enables intracavitary and interstitial brachytherapy (BT) for locally advanced cervical cancer. However, the method to determine the optimal interstitial needle number, position, and depth using this applicator is unknown. Therefore, we aimed to establish a method for reliable needle optimization. Material and methods: We produced a template model of the Venezia applicator with whole needles, and acquired computed tomography (CT) images (template CT). Using this template CT as a map, clinicians could define interstitial needle's insertion route in advance. During treatment, we first placed tandem and ovoid, and acquired a CT (tandem + ovoid CT). This was fused to the template CT by matching the contour of applicators with high accuracy. Then, we determined the optimal interstitial needle number, position, and depth to fit high-risk clinical target volume (HR-CTV) and avoid organs at risk (OARs) on the fused CT (intra pre-plan). Next, we re-inserted the tandem and ovoids with interstitial needle into patient's uterus and vagina. We inserted the optimized interstitial needle using insertion tool of optimal depth immediately following the applicator insertion. Lastly, a real-time treatment planning CT was performed, followed by planning and treatment. Results: We achieved a good dose distribution of Venezia applicator BT using intra pre-plan method to optimize the number of interstitial needles, position, and depth. Conclusions: This novel intra pre-plan method of interstitial needle optimization using template CT fusion provides high reproducibility, efficiency, and safety for patients with cervical cancer treated with brachytherapy using Venezia applicator.
DOAJ (DOAJ: Directory of Open Access Journals), 2010
Purpose: In order to know the effect of variation in position of applicators to the dose received by the tumor volume, critical organs such as rectum and bladder and the correlation of variation on the clinical outcome. Material and methods: 36 patients with histologically proven cervical cancer, undergoing intracavitary brachytherapy (ICBT) from October 2005 to December 2006 were the subjects of the study. Two pairs of orthogonal X-ray films were taken: one prior to loading of sources and the other after removal of sources. These patients were followed up as per the RTOG criteria. Results: The median duration of insertion was 25 hours with a median follow up period of 6.7 months. The translational variation of the applicator position for all patients was 3 mm and 1 mm (2 SD), respectively, in the patient's lateral and antero-posterior direction. The rotational variation was 3 and 4 degrees (2 SD) in the patient's transverse and sagittal planes. Detailed analysis of source movement showed following changes in median dose: point A: 14%, point B: 2%, point P: 1%, Rectum 1: 3.5%, Rectum 2: 4% and Bladder: 9.1%. The incidence of rectal toxicity was 6/36 (16.7%) and that of bladder was 1/36 (2.8%). When the variables were grouped to evaluate the relationship, our study showed statistically significant relationship between: R2 and rectal toxicity (p value: 0.002), point A and rectal toxicity (Pearson: 0.792), lateral displacement/anteroposterior displacement and rectal toxicity (p value: 0.012/0.003), beta angle and R2 (p value: 0.002). Conclusions: The geometric relationships between the ICBT applicators and the critical structures vary during the course of low dose rate brachytherapy. Source movement does result in significant dose alterations in terms of increased rate of complications, but its impact on cure rates needs to be studied in the future.
2021
Purpose: There are no international guidelines for optimal needle insertion during interstitial intracavitary brachytherapy (IS-ICBT) for cervical cancer. We aimed to investigate the clinical feasibility and added value of computed to mography (CT) guidance to optimize needle insertion in IS-ICBT using the Utrecht appli cator and to evaluate needle shifts. Methods and Materials: We enrolled 24 patients who were treated with IS-BT . Two CT scans each were performed for every patient: 1) aft er applicator insertion without needles (CTpreneedle ); 2) after needle insertion (CT postneedle ). In addition to magnetic resonance imaging (MRI) after external-beam radiotherapy, CT preneedle was used to determine optimal needle locations and insertion lengths based on applicator nd organs at risk positioning on the day of treatment; CTpostneedle was used for IS-ICBT planning. The needle-channel axis was used as a reference to determine needle-shift evolution. Results: A total of 266 interstiti...
Journal of contemporary brachytherapy, 2015
The path of subsequent dwell positions of an afterloader source being moved through a ring applicator for cervix cancer brachytherapy deviates from an ideal circle and the position of marker wires. This can lead to deviations of several millimetres between real and assumed dwell positions for treatment planning with simplified source path models. The aim of this study was to test video- and autoradiography-based methods for source path determination, and to study the influence of dwell position accuracy on dose-volume histogram (DVH)-parameters. Videos of the exact motion of the source wire through three different (r = 26, 30, 34 mm) computed tomography/magnetic resonance (CT/MR) compatible plastic ring applicators were recorded. Observed dwell positions covering the whole length of each applicators channel were used to adjust the circular source path model. The agreement of the true source positions derived from video analysis with those of the corrected circular source path was ve...
International Journal of Radiation Oncology*Biology*Physics, 2020
The aim of this study was to investigate the influence of brachytherapy technique and applicator type on target dose, isodose surface volumes, and organ-at-risk (OAR) dose. Methods and Materials: Nine hundred two patients treated with tandem/ovoids (T&O) (n Z 299) and tandem/ring (T&R) (n Z 603) applicators from 16 EMBRACE centers were analyzed. Patients received external beam radiation therapy and magnetic resonance imaging guided brachytherapy with dose prescription according to departmental practice. Centers were divided into 4 groups, according to applicator/technique: Ovoids and ring centers treating mainly with the intracavitary (IC) technique and ovoids and ring centers treating routinely with the intracavitary/interstitial (IC/IS) technique. V85Gy EQD2 10 , CTV HR D 90% (EQD2 10), and bladder, rectum, sigmoid, and vaginal 5-mm lateral-point doses (EQD2 3) were evaluated among center groups. Differences between T&O and T&R were tested with multivariable analysis. Results: For similar point A doses, mean CTV HR D 90% was 3.3 Gy higher and V85Gy was 23% lower for ring-IC compared with ovoids-IC centers (at median target volumes). Mean bladder/rectum doses (D 2cm3 and ICRU-point) were 3.2 to 7.7 Gy smaller and vaginal 5-mm lateral-point was 19.6 Gy higher for ring-IC centers. Routine use of IC/IS technique resulted in increased target dose, whereas V85Gy was stable (T&R) or decreased (T&O); reduced bladder and rectum D 2cm3 and bladder ICRU-point by 3.5 to 5.0 Gy for ovoids centers; and similar OAR doses for ring centers. CTV HR D 90% was 2.8 Gy higher, bladder D 2cm3 4.3 Gy lower, rectovaginal ICRU-point 4.8 Gy lower, and vagina 5mm lateral-point 22.4 Gy higher for ring-IC/IS versus ovoids-IC/IS centers. The P values were <.002 for all comparisons. Equivalently, significant differences were derived from the multivariable analysis. Conclusions: T&R-IC applicators have better target dose and dose conformity than T&O-IC in this representative patient cohort. IC applicators fail to cover large target volumes, whereas routine application of IC/IS improves target and OAR dose considerably. Patients treated with T&R show a more favorable therapeutic ratio when evaluating target, bladder/rectum doses, and V85Gy. A comprehensive view on technique/applicators should furthermore include practical considerations and clinical outcome.
International Journal of Radiation Oncology*Biology*Physics, 2006
Purpose: To present a combined intracavitary and interstitial dedicated applicator and magnetic resonance imaging (MRI) treatment planning for cervical cancer brachytherapy. Methods and Materials: A modified ring applicator allows interstitial needles to be implanted in parallel to the intrauterine tandem. MRI treatment planning based on a standard loading pattern with stepwise dwell weight adaptation and needle loading is performed to achieve optimal dose coverage and sparing of organs at risk. Dose constraints are applied for dose-volume histogram parameters. Results: The use of additional interstitial needles provides prescription dose up to 15 mm lateral to point A. Twenty-two patients with high-risk clinical target volumes of mean 44 cm 3 were treated with a mean prescribed total dose of 85 Gy (biologically equivalent to 2 Gy fractionation, ␣/ ؍ 10 Gy) and 93% coverage (V100). The dose to organs at risk was within standard limits for intracavitary brachytherapy alone.
Indian Journal of Pathology and Oncology, 2020
Background: Interfraction variations occur due to tumour regression during cervical intarcavitary brachytherapy (ICR) requiring replanning with every fraction. This study aimed to determine the correlation of interfraction variations in positioning of applicator and its relationship with relative dosimetry if the dwell time and source positions of the plan of first fraction were applied to other subsequent fractions. Materials and Methods: This is a retrospective review of the orthogonal radiographs of cervical cancer patients treated from 2013 to 2016 in our institute, receiving ICR with the same dose prescription to point A using a tandem and two ovoids applicators. A hypothetical second and third plan were obtained by applying the same source positions and dwell time as in the first fraction plan. The dose delivered to point A, point B, cervical point, bladder point and rectal point were determined. The actual doses in the treated second and third fractions were compared with these hypothetical plans for any significant change in relative dosimetry. Statistical differences between groups were analysed using 2 tailed paired t test. Results: There was consistant increase in the doses to the point B, bladder point and rectal point in all the hypothetical plans with statistically significant difference observed for point B (p=0.001), rectal point (p=0.000) and bladder point(p=0.041). Conclusion: The conception of avoiding the replanning if similar interfraction conditions are achieved looks promising but the significant findings observed in this study warrants strongly to continue as per current recommendation of replanning with every fraction of brachytherapy.
Applicator reconstruction in MRI 3D image-based dose planning of brachytherapy for cervical cancer
Brachytherapy, 2008
Background and purpose: To elaborate a method for applicator reconstruction for MRI-based brachytherapy for cervical cancer. Materials and methods: Custom-made plastic catheters with a copper sulphate solution were made for insertion in the source channels of MR-CT compatible applicators: plastic and titanium tandem ring applicators, and titanium needles. The applicators were CT and MR scanned in a phantom for accurate 3D assessment of applicator visibility and geometry. A reconstruction method was developed and evaluated in 19 patient MR examinations with ring applicator (plastic: 14, titanium: 5). MR applicator reconstruction uncertainties related to inter-observer variation were evaluated. Results: The catheters were visible in the plastic applicator on T1-weighted images in phantom and in 14/ 14 clinical applications. On T2-weighted images, the catheters appeared weaker but still visible in phantom and in 13/14 MR clinical applications. In the titanium applicator, the catheters could not be separated from the artifacts from the applicator itself. However, these artifacts could be used to localize both titanium ring applicator (5/5 clinical applications) and needles (6/6 clinical applications). Standard deviations of inter-observer differences were below 2 mm in all directions. Conclusion: 3D applicator reconstruction based on MR imaging could be performed for plastic and titanium applicators. Plastic applicators proved well to be suited for MRI-based reconstruction. For improved practicability of titanium applicator reconstruction, development of MR applicator markers is essential. Reconstruction of titanium applicator and needles at 1.5 T MR requires geometric evaluations in phantoms before using the applicator in patients.
Brachytherapy
To evaluate the role of 3T-MRI-guided adaptive high-dose-rate (HDR) combined intracavitary and interstitial brachytherapy for cervical cancer using a novel intracavitary split-ring (ICSR) applicator adapter. We retrospectively reviewed all HDR brachytherapy cases from 2013 to 2015 using an ICSR applicator. Initial optimization was performed using 3T multiparametric MRI (mpMRI) series with an applicator in place. The mpMRI series were discretionarily acquired before subsequent fractions for possible target adaptation. When necessary, interstitial needles (ISNs) were inserted through a novel ICSR adapter or freehand. Dosimetric parameters, clinical outcomes, and toxicities were compared between groups. Seventeen patients were included, with a mean followup of 32 months. An mpMRI series preceded each initial fraction and 52.9% of patients underwent ≥1 additional pretreatment mpMRI. Among these subsequent fractions, the high-risk clinical target volume was reduced in 80% vs. 41% without...