Tandem-ring Applicator Research Articles

PO0115: Validation of Scintillator-Based In Vivo Dosimetry for Pulsed Dose Rate Brachytherapy with Tandem Ring Applicators for Cervical Cancer

PO0115: Validation of Scintillator-Based In Vivo Dosimetry for Pulsed Dose Rate Brachytherapy with Tandem Ring Applicators for Cervical Cancer

Clinical outcomes using a 3D printed tandem-needle-template and the EMBRACE-II planning aims for image guided adaptive brachytherapy in locally advanced cervical cancer

Background Extensive local disease or narrow vagina may compromise brachytherapy (BT) in patients with cervical cancer. This is the first study to analyze long-term outcomes of using 3D printed vaginal tandem-needle templates (3DP TNT) for transvaginal insertion of needles in parallel (P) or parallel and oblique (P&O) direction to the tandem. Material and methods All patients treated with BT using 3DP TNT from 2015-2020 were included. Decision to use a 3DP TNT and preplanning were made after 4-5 weeks of external beam radiotherapy, based on gynecological examination and MRI with a tandem-ring applicator in situ. The TNT was 3D-printed in house consisting of a circular template with P&O holes for guidance of plastic needles and a shaft fitting the uterine tandem. Thus, the radioactive source was never in direct contact with the 3DP TNT. The TNT was 3D printed in a standard or personalized configuration. Planning aims were based on the Embrace II protocol. Results 101 patients (median age of 63 years) were included: 49 with P needles only and 52 with P&O needles. Personalized TNT was used in 19 patients in the P&O group. Performance status (WHO) was > 0 in 48%. FIGO2018 stage III-IV was present in 77%. T-score at diagnosis and BT was 9.1 and 6.3 respectively, with a significantly higher T-score in the P&O compared to P group. The mean high-risk CTV D90 was 93 Gy with no significant difference between the two groups. Three-year local control rates were 85%, 95%, 75% for the overall, P- and P&O group respectively and 68%, 80% and 56% for cancer specific survival. Grade ≥3 treatment related complications were observed in 10 (10%) patients. Conclusions 3DP TNT for BT in cervical cancer provides successful management of very extensive local disease and/or unfavorable anatomy with the possibility for treatment individualization.

Intracavitary brachytherapy with additional Heyman capsules in the treatment of cervical cancer

PurposeBrachytherapy is a mandatory component of primary radiochemotherapy in cervical cancer. The dose can be applied with a traditional intracavitary approach (IC alone) or with multiple catheter brachytherapy to optimize dose distribution in an individual concept. We therefore evaluated whether the utilization of a tandem–ring applicator plus additional intracavitary applicators (add IC) provides an advantage over the traditional IC alone approach, as this method is less time consuming and less invasive compared to a combined intracavitary/interstitial brachytherapy.MethodsTwenty three procedures of intracavitary brachytherapy for cervical cancer with additional intracavitary applicators performed in seven patients treated between 2016 and 2018 in our institution were included in this study. Plans were optimized for D90 HR-CTV with and without the utilization of the additional applicators and compared by statistical analysis.ResultsD90 for HR-CTV was 5.71 Gy (±1.17 Gy) for fractions optimized with add IC approach and 5.29 Gy (±1.24 Gy) for fractions without additional applicators (p < 0.01). This translates to a calculated mean EQD2 HR-CTV D90 of 80.72 Gy (±8.34 Gy) compared to 77.84 Gy (±8.49 Gy) after external beam therapy and four fractions of brachytherapy for add IC and IC alone, respectively (p < 0.01). The predictive value of improved coverage of HR-CTV in the first fraction was high.ConclusionIn a subgroup of cases, the addition of intracavitary Heyman capsules can be an alternative to interstitial brachytherapy to improve the plan quality compared to standard IC alone brachytherapy. The benefit from the addition of applicators in the first fraction is predictive for the following fractions.

Dose to pelvic lymph nodes in locally advanced cervical cancer during high-dose-rate brachytherapy with tandem-ring applicators.

PurposeThe present study aimed to assess the correlation between dose to pelvic lymph nodes and to point B with tandem-ring (TR) applicators for intra-cavitary brachytherapy treatment of locally advanced cervical cancer.Material and methodsCervical cancer patients treated at brachytherapy department of Lucien Neuwirth Cancer Center, from 2015 to 2018, were included. Target delineation was performed in compliance with GEC-ESTRO guidelines. Revised American Brachytherapy Society (ABS) point A was determined (ARN (right) and ALN (left)) as well as Manchester point B. Prescription dose was 25-35 Gy in 5 fractions. Pelvic lymph nodes were delineated, then dose to points A and B, and dose-volume histogram (DVH) parameters of delineated lymph nodes were extracted. Significant relationships or correlations between lymph nodes reference points, dosage to points B, and their DVH parameters were investigated.ResultsThe mean dose and mean percentage of the prescription dose to the left and right points B were 4.6 ±0.18 Gy and 82.08 ±0.72%, respectively. Pearson correlation coefficient R = 0.81 (p-value = 0.00) between dose to ARN and ALN points and prescription dose was obtained. Negative correlation between CTVHR volume and difference between French and ABS prescription points was found.ConclusionsDose to point B can be a moderate surrogate for maximum, minimum, and median dose to the internal iliac and presacral lymph node, but cannot be for maximum dose to the obturator lymph node. Points B cannot be a reliable substitute for common and external iliac chains.

The dosimetric comparison between tandem-ovoid and tandemring applicator in cervical cancer brachytherapy

The dosimetric comparison between tandem-ovoid and tandemring applicator in cervical cancer brachytherapy

Comparative dosimetry of brachytherapy treatment planning between a volume-based plan by CT and a point-based plan by TAUS in CT datasets for brachytherapy

Abstract Aim: To evaluate comparative dosimetry of brachytherapy treatment planning between a volume-based plan by computed tomography (CT) and a point-based plan by transabdominal ultrasound (TAUS) in CT datasets for brachytherapy. Materials and methods: From 2019 to 2021, 59 different datasets of CT images were collected from 38 patients treated by intracavitary brachytherapy with tandem ovoid or tandem ring applicators. At that time, TAUS was performed to prevent uterine perforation and to evaluate topography of the cervix during application. In volume-based planning by CT, the target dose was used to keep the dose at 90% of high-risk clinical target volume (HR-CTV), to give a dose of at least 7Gy, while in the point-based plan by TAUS, the target dose was used to keep the minimum dose to eight cervix reference points (measured by TAUS), to give a dose of at least 7Gy. The doses to targets and organs at risk were evaluated and compared between volume-based planning by CT and the point-based plan by TAUS. Results: Of 59 fractions, a tandem ovoid applicator was used in 48 fractions (81·3%). In the volume-based plan by CT, the mean doses to HR-CTV(D90), intermediate-risk clinical target volume (IR-CTV)(D90), bladder(D2cc), rectum(D2cc) and sigmoid colon(D2cc) were 7·0, 3·9, 4·9, 2·9 and 3·3 Gy, respectively, while in the point-based plan by TAUS, the mean doses to HR-CTV(D90), IR-CTV(D90), bladder(D2cc), rectum(D2cc) and sigmoid colon(D2cc) were 8·2, 4·6, 5·9, 3·4 and 3·9 Gy, respectively. The percentages of mean dose differences between TAUS and CT of HR-CTV(D90), IR-CTV(D90), bladder(D2cc), rectum(D2cc) and sigmoid colon(D2cc) were 17·7, 19·5, 20·5, 19·5, 21·3 and 19·8%, respectively. With the target dose to the point-based plan by TAUS (7 Gy to the cervix reference points), this was close to D98 of HR-CTV with a mean percentage of difference of 0·6%. Findings: The point-based plan by TAUS showed higher values to targets and organs at risk than the volume-based plan by CT. With the point-based plan by TAUS, it was close to D98 of HR-CTV.

Dosimetric evaluation of image based brachytherapy using tandem ovoid and tandem ring applicators

The aim of the study is to evaluate the differences in dosimetry between tandem-ovoid and tandem-ring gynaecologic brachytherapy applicators in image based brachytherapy. Traditionally, tandem ovoid applicators were used to deliver dose to tumor in intracavitary brachytherapy. Tandem-ring, tandem-cylinder and hybrid intracavitary, interstitial applicators are also used nowadays in cervical cancer brachytherapy. 100 CT datasets of cervical cancer patients (stage IB2 - IIIB) receiving HDR application (50 tandem-ovoid and 50 tandem-ring) were studied. Brachytherapy was delivered using a CT-MRI compatible tandem-ovoid (50 patients) and a tandem-ring applicator (50 patients). DVHs were calculated and D2cc was recorded for the bladder and rectum and compared with the corresponding ICRU point doses. The point B dose, the treated volume, high dose volume and the treatment time were recorded and compared for the two applicators. The mean D2cc of the bladder with TR applicator was 6.746Gy. TO applicator delivered a mean D2cc of 7.160Gy to the bladder. The mean ICRU bladder points were 5.60 and 5.63Gy for TR and TO applicator, respectively. The mean D2cc of the rectum was 4.04Gy and 4.79Gy for TR and TO applicators, respectively. The corresponding ICRU point doses were 5.10Gy and 5.66Gy, respectively. The results indicate that the OAR doses assessed by DVH criteria were higher than ICRU point doses for the bladder with both tandem-ovoid and tandem-ring applicators whereas DVH based dose was lower than ICRU dose for the rectum. The point B dose, the treated volume and high dose volume was found to be slightly higher with the tandem-ovoid applicator. The mean D2cc dose for the bladder and rectum was lower with tandem-ring applicators. The clinical implication of the above dosimetric differences needs to be evaluated further.

Impact of heterogeneity-corrected dose calculation using a grid-based Boltzmann solver on breast and cervix cancer brachytherapy.

PurposeTo analyze the impact of heterogeneity-corrected dose calculation on dosimetric quality parameters in gynecological and breast brachytherapy using Acuros, a grid-based Boltzmann equation solver (GBBS), and to evaluate the shielding effects of different cervix brachytherapy applicators.Material and methodsCalculations with TG-43 and Acuros were based on computed tomography (CT) retrospectively, for 10 cases of accelerated partial breast irradiation and 9 cervix cancer cases treated with tandem-ring applicators. Phantom CT-scans of different applicators (plastic and titanium) were acquired. For breast cases the V20Gyαβ3 to lung, the D0.1cm3, D1cm3, D2cm3 to rib, the D0.1cm3, D1cm3, D10cm3 to skin, and Dmax for all structures were reported. For cervix cases, the D0.1cm3, D2cm3 to bladder, rectum and sigmoid, and the D50, D90, D98, V100 for the CTVHR were reported. For the phantom study, surrogates for target and organ at risk were created for a similar dose volume histogram (DVH) analysis. Absorbed dose and equivalent dose to 2 Gy fractionation (EQD2) were used for comparison.ResultsCalculations with TG-43 overestimated the dose for all dosimetric indices investigated. For breast, a decrease of ~8% was found for D10cm3 to the skin and 5% for D2cm3 to rib, resulting in a difference ~ –1.5 Gy EQD2 for overall treatment. Smaller effects were found for cervix cases with the plastic applicator, with up to –2% (–0.2 Gy EQD2) per fraction for organs at risk and –0.5% (–0.3 Gy EQD2) per fraction for CTVHR. The shielding effect of the titanium applicator resulted in a decrease of 2% for D2cm3 to the organ at risk versus 0.7% for plastic.ConclusionsLower doses were reported when calculating with Acuros compared to TG-43. Differences in dose parameters were larger in breast cases. A lower impact on clinical dose parameters was found for the cervix cases. Applicator material causes systematic shielding effects that can be taken into account.

Our Experience Using HDR Brachytherapy for Cervical Cancer in Albania

Purpose: The purpose of this study was to determine our examined and evaluated the Dosimetry aspect and the early local results of cervical cancer. Methods and Materials: Between April 2009 to January 2012, a total of 122 patients were treated with HDR Ir-192 following EBRT radiotherapy treatment, (FIGO stage IIa-IIIa patients were treated with EBRT plus concomitant chemotherapy platine based, 60% of patients had radical hysterectomy after EBRT, 27% of the patients were treated with EB and were given 12Gy in 2 fractions, 73% of the patients were treated with EB using 3 fractions with 7Gy, 40% of cervical cancer patients were treated using the tandem ring applicator, while the other 60%were treated through the use of the vaginal applicator. Results: A total of 100% of patients completed their treatment on average, 122 cases received a total of 80 Gy to the CTV from EBRT and Endocavitary Brachytherapy. Conclusion: The combination of EBRT surgery and EB remains the best options of cervical cancer treatment.

MRI-assisted cervix cancer brachytherapy pre-planning, based on application in paracervical anaesthesia: final report.

BackgroundOptimal applicator insertion is a precondition for the success of cervix cancer brachytherapy (BT). We aimed to assess feasibility and efficacy of MRI-assisted pre-planning, based on applicator insertion in para-cervical anaesthesia (PCA).Patients and methods.Five days prior to BT, the pre-planning procedure was performed in 18 cervix cancer patients: tandem-ring applicator was inserted under PCA, pelvic MRI obtained and applicator removed. Procedure tolerability was assessed. High risk clinical target volume (HR CTV) and organs at risk were delineated on the pre-planning MRI, virtual needles placed at optimal positions, and dose planning performed. At BT, insertion was carried out in subarachnoidal anaesthesia according to pre-planned geometry. Pre-planned and actual treatment parameters were compared.ResultsPre-planning procedure was well tolerated. Median difference between the pre-planned and actual needle insertion depth and position were 2 (0–10) mm and 4 (0–30) degrees, respectively. The differences between the pre-planned and actual geometric and dosimetric parameters were statistically non-significant. All actual needles were positioned inside the HR CTV and outside the organs at risk (OAR).ConclusionsOur pre-planning approach is well tolerated and effective. Pre-planned geometry and dose distribution can be reproduced at BT.

CT and MR image fusion of tandem and ring applicator using rigid registration in intracavitary brachytherapy planning

The purpose of this study is to find the uncertainties in the reconstruction of MR compatible ring‐tandem intracavitary applicators of high‐dose rate image‐based brachytherapy treatment planning using rigid registration of 3D MR and CT image fusion. Tandem and ring reconstruction in MR image based brachytherapy planning was done using rigid registration of CT and MR applicator geometries. Verifications of registration for applicator fusion were performed in six verification steps at three different sites of tandem ring applicator set. The first site consists of three errors at the level of ring plane in (1) cranio–caudal shift (Cranial Shift) of ring plane along tandem axis, (2) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (3) lateral shift (Lat Shift) perpendicular to the plane containing the tandem at the level of ring plane. The other two sites are the verifications at the tip of tandem and neck of the ring. The verification at the tip of tandem consists of two errors in (1) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (2) lateral shift (Lat Shift) perpendicular to the plane containing the tandem. The third site of verification at the neck of the ring is the error due to the rotation of ring about tandem axis. The impact of translational errors from −5 mm to 5 mm in the step of 1 mm along x‐, y‐, and z‐axis and three rotational errors about these axes from −19.1° to 19.1° in the step of 3.28° on dose‐volume histogram parameters (D2cc,D1cc,D0.1cc, and D5cc of bladder, rectum, and sigmoid, and D90 and D98 of HRCTV were also analyzed. Maximum registration errors along cranio–caudal direction was 2.2 mm (1 case), whereas the errors of 31 out of 34 cases of registration were found within 1.5 mm, and those of two cases were less than 2 mm but greater than 1.5 mm. Maximum rotational error of ring about tandem axis was 3.15° (1.1 mm). In other direction and different sites of the ring applicator set, the errors were within 1.5 mm. The impacts of registration errors on DVH parameters of bladder, rectum, and sigmoid were very sensitive to antero–posterior shift. Cranio‐caudal errors of registration also largely affected the rectum DVH parameters. Largest change of 17.95% per mm and 20.65% per mm in all the DVH parameters of all OARs and HRCTV were observed for ϕ and Ψ rotational errors as compare to other translational and rotational errors. Catheter reconstruction in MR image using rigid registration of applicator geometries of CT and MR images is a feasible technique for MR image‐based intracavitary brachytherapy planning. The applicator registration using the contours of tandem and neck of the ring of CT and MR images decreased the rotational error about tandem axis. Verification of CT MR image fusion using applicator registration which consists of six steps of verification at three different sites in ring applicator set can report all the errors due to translation and rotational shift along θ,ϕ, and Ψ. ϕ and Ψ rotational errors, which produced potential changes in DVH parameters, can be tackled using AP Shift and Lat Shift at the tip of tandem. The maximum shift was still found along the tandem axis in this technique.PACS number: 87.55.km

Long Term Outcome of CT-Based Image-Guided Brachytherapy for Cervix Cancer Using the Tandem-Ring Applicator

Objectives: To evaluate the long term outcome of CT-based image-guided brachytherapy (IGBT) for cervix cancer using the tandem-ring applicator. Methods: Between February 2005 and December 2008, 40 patients were treated with chemo-radiotherapy and high dose rate CT-based IGBT. A manually optimized dosimetry plan was created for each fraction. The planning aims were to deliver a point A dose ≥ 74 Gy10, D90 of the high-risk clinical target volume (HR-CTV) ≥ 74 Gy10, V100 HR-CTV ≥ 95%, D2cc rectum/sigmoid ≤ 75 Gy3 and D2cc bladder ≤ 95 Gy3. Results: Median follow-up was 61 months. The 3-year and 5-year cancer-specific survival was 80% (tumors 2-5 cm=87%, >5 cm=59%) and 74% (tumors 2-5 cm=87%, >5 cm=52%). The 3-year and 5-year local control was 89% (tumors 2-5 cm=96%, >5 cm=76%). The mean D90 for patients with and without local recurrence was 70.8 Gy10 and 85.2 Gy10 respectively. The 3-year and 5-year rate of G3 complications was 10% and 15%. Manual optimization could not improve the dosimetry in 96 (85%) fractions. Conclusions: CT-based IGBT improves local control compared to conventional BT, particularly for small tumors.

Image guided adaptive brachytherapy for cervical cancer: dose contribution to involved pelvic nodes in two cancer centers.

PurposeThe goal of this study was to determine the dose contributions from image guided adaptive brachytherapy (IGABT) to individual suspicious pelvic lymph nodes (pLNN) in cervical cancer patients. Data were collected in two cancer centers, University of Pittsburgh Cancer Institute (UPCI) and University Medical Center Utrecht (UMCU).Material and methods27 and 15 patients with node positive cervical cancer treated with HDR (high dose rate) or PDR (pulsed dose rate)-IGABT were analyzed. HDR-IGABT (UPCI) was delivered with CT/MRI compatible tandem-ring applicators with 5.0-6.0 Gy × five fractions. PDR-IGABT (UMCU) dose was delivered with Utrecht tandem-ovoid applicators with 32 × 0.6 Gy × two fractions. Pelvic lymph nodes with short axis diameter of ≥ 5 mm on pre-treatment MRI or PET-CT were contoured for all BT-plans. Dose contributions to individual pLNN expressed as D90 (dose to 90% of the volume) were calculated from dose-volume histograms as absolute and relative physical dose (% of the reference dose) for each fraction. For each node, the total dose from all fractions was calculated, expressed in EQD2 (equivalent total dose in 2 Gy fractions).ResultsFifty-seven (UPCI) and 40 (UMCU) individual pLNN were contoured. The mean D90 pLNN was 10.8% (range 5.7-25.1%) and 20.5% (range 6.8-93.3%), respectively, and therefore different in the two centers. These values translate into 2.7 Gy (1.3-6.6 Gy) EQD2 and 7.1 Gy (2.2-36.7 Gy) EQD2, respectively. Differences are caused by the location of the individual nodes in relation to the spatial dose distribution of IGABT, differences in total dose administered and radiobiology (HDR versus PDR).ConclusionsThe IGABT dose contribution to individual pelvic nodes depends on patient and treatment related factors, and varies considerably.

Uncertainty analysis for 3D image-based cervix cancer brachytherapy by repetitive MR imaging: Assessment of DVH-variations between two HDR fractions within one applicator insertion and their clinical relevance

PurposeTo investigate dosimetric uncertainties of MRI-based cervix cancer brachytherapy, when applying two HDR fractions for each applicator insertion and their clinical relevance. Methods21 patients with 84 MRI-examinations and fractions were investigated. After insertion of the MRI compatible tandem-ring applicator, an MRI-set was recorded and the treatment plan optimised for the first fraction. Prior to the second fraction 16–20h later a second MRI-set was recorded, and the dose distribution from the plan of the previous day superimposed and analysed. The same procedure was repeated for fractions 3 and 4. Dose from EBRT and brachytherapy was normalised to 2Gy-fractionation (EQD2), added up to a total dose, and compared to a calculated total dose if only 1 MRI-examination per insertion is available. ResultsThe total D90 for High risk (HR) CTV was 1.2±2.7Gyαβ10 (1±3%) (mean±1SD) lower by individual MRI-evaluation of each fraction compared to 1 MRI per insertion. The D2cm3 increased by 0.7±4.7Gyαβ3 (1±6%) for bladder, 1.1±2.4Gyαβ3 (2±4%) for rectum and decreased by 0.8±3.4Gyαβ3 (1±5%) for sigmoid. For HR CTV the individual approach did not identify any case with a decrease of D90 >5Gyαβ10. For the bladder 3 cases, for the rectum no case and for the sigmoid 1 case was identified with an increase of D2cm3 >5Gyαβ3. For the bladder all dose variations of more than 5Gyαβ3 could have been avoided by ensuring a constant bladder filling. Individual MRI-evaluation did not determine any case where dose constraints were not fulfilled. ConclusionsFor the treatment schedule as applied in this study, geometric differences between applicator, target and OAR result in overall dosimetric changes, which seem to be of minor relevance in regard to clinical dose volume constraints applied at present.

Identifying afterloading PDR and HDR brachytherapy errors using real-time fiber-coupled Al2O3:C dosimetry and a novel statistical error decision criterion

Background and purposeThe feasibility of a real-time in vivo dosimeter to detect errors has previously been demonstrated. The purpose of this study was to: (1) quantify the sensitivity of the dosimeter to detect imposed treatment errors under well controlled and clinically relevant experimental conditions, and (2) test a new statistical error decision concept based on full uncertainty analysis. Materials and methodsPhantom studies of two gynecological cancer PDR and one prostate cancer HDR patient treatment plans were performed using tandem ring applicators or interstitial needles. Imposed treatment errors, including interchanged pairs of afterloader guide tubes and 2–20mm source displacements, were monitored using a real-time fiber-coupled carbon doped aluminum oxide (Al2O3:C) crystal dosimeter that was positioned in the reconstructed tumor region. The error detection capacity was evaluated at three dose levels: dwell position, source channel, and fraction. The error criterion incorporated the correlated source position uncertainties and other sources of uncertainty, and it was applied both for the specific phantom patient plans and for a general case (source-detector distance 5–90mm and position uncertainty 1–4mm). ResultsOut of 20 interchanged guide tube errors, time-resolved analysis identified 17 while fraction level analysis identified two. Channel and fraction level comparisons could leave 10mm dosimeter displacement errors unidentified. Dwell position dose rate comparisons correctly identified displacements ⩾5mm. ConclusionThis phantom study demonstrates that Al2O3:C real-time dosimetry can identify applicator displacements ⩾5mm and interchanged guide tube errors during PDR and HDR brachytherapy. The study demonstrates the shortcoming of a constant error criterion and the advantage of a statistical error criterion.

Implementation of Image-guided Brachytherapy for Cervix Cancer in the UK: Progress Update

Aims Image-guided brachytherapy (IGBT) is the new gold standard for cervix cancer brachytherapy. In 2009, the Royal College of Radiologists (RCR) published a guidance document to facilitate the implementation of IGBT for cervix cancer in the UK. This paper reports the progress since the publication of the RCR document. Materials and methods Questionnaires were sent to 45 UK centres known to offer brachytherapy for cervix cancer in 2011. Replies were received from 43 (96%) centres. Details collected included brachytherapy machine, imaging technique for brachytherapy planning, applicator design and total dose to point A from external beam radiotherapy and brachytherapy. The results were compared with the 2008 survey reported in the RCR document. Results The number of centres offering computed tomography (CT) or magnetic resonance imaging (MRI)-based IGBT for cervix cancer has increased to 32 (71%) in 2011 compared with 12 (26%) in 2008. Although the most common applicator design in 2011 remains the tandem-ovoid applicator (71%), more respondents are using the tandem-ring applicator (29% versus 9% in 2008). Only seven (16%) centres are routinely prescribing <70 Gy 10 to point A in 2011 compared with10 (22%) in 2008. Conclusion Considerable progress with implementing IGBT for cervix cancer has been made in the UK since the publication of the RCR guidance document.

Dosimetric Impact of Interfraction Tandem-Ring Applicator and Catheter Movement in High-Dose-Rate Brachytherapy for Gynecology Patients

Purpose: Prior studies have reported the interfraction motion of the ring-tandem applicator, but the resulting dosimetric impact has not been quantified. The goal of our study was to determine the dosimetric impact of interfraction tandem-ring (T&R) applicator and interstitial catheter movement in high-dose-rate (HDR) brachytherapy treatment for cervical cancer.

Variation of treatment planning parameters (D90 HR-CTV, D 2cc for OAR) for cervical cancer tandem ring brachytherapy in a multicentre setting: Comparison of standard planning and 3D image guided optimisation based on a joint protocol for dose–volume constraints

Purpose To perform a qualitative and quantitative comparison of different treatment planning methods used in different centres for MRI-based brachytherapy (BT) of cervical cancer. Materials and methods Two representative patients with advanced cervical cancer (1 “limited volume case”; 1 “extensive volume case”) were planned for brachytherapy (BT) with a tandem-ring applicator by six different centres. During a workshop all centres produced an institutional standard plan and an MRI-based adaptive treatment plan for each case. Optimisation was based on the fractionation schedule (HDR, PDR) and method according to the institutional protocol. Results The loading pattern, dwell times, shape of the point A isodose varied considerably between institutional standard plans, as did dose–volume parameters for high risk CTV (HR-CTV) and also for the D 2cc for OAR, violating the dose–volume constraints in many situations. During optimisation, the centres stayed as close as possible to the standard loading pattern and dwell times. The dose distributions and dose–volume parameters between the plans from the different centres became much more comparable after optimisation. The prescribed dose to the HR-CTV could be achieved in the limited volume case by all centres, in the extensive case only if additional needles were applied. Conclusion Treatment planning for gynaecologic brachytherapy based on different traditions shows less variation in regard to target coverage and OAR dose, when 3D image-based optimisation is performed with a uniform prescription protocol.

Direct reconstruction of the Vienna applicator on MR images

Purpose To introduce and test a direct reconstruction concept for intracavitary tandem ring applicators in MR image-based brachytherapy treatment planning. Materials and methods Optical measurements of transparent ring-phantoms provided the geometric relation between source path and the Vienna ring applicator as visible on MRI. For the manual direct reconstruction method (PLATO), the geometry plotted on a transparency was placed on the screen and rotated to fit with visible ring holes. With the software-integrated reconstruction method (OncentraGYN), the applicator geometry was directly used when placing the visible parts of the applicator in the 3D dataset. Clinical feasibility was tested in 10 clinical insertions. Reconstruction and dose calculation were performed independently on two treatment planning systems (PLATO and OncentraGYN) using MRI alone. DVH parameters for targets and organs at risk were analysed and compared to the clinically used radiograph/MRI registration-based method. Results The direct reconstruction concept for both methods was feasible and reduced treatment planning time. Evaluated DVH parameters for plans using direct reconstruction methods differed from clinically used plans (traditional reconstruction) in mean differences ⩽0.2 Gy for plans with 7 Gy prescribed dose. Conclusion If the relation between applicator shape visible on MRI and the source path is defined once, the reconstruction process can be performed by directly placing the applicator in the MRI dataset.

Clinical Impact of Computed Tomography-based Image-guided Brachytherapy for Cervix Cancer using the Tandem-ring Applicator — the Addenbrooke's Experience

Aims We report our initial 3-year experience of chemoradiotherapy for cervical cancer with computed tomography-based image-guided high dose rate (HDR) brachytherapy using the tandem-ring applicator. Materials and methods Twenty-eight patients were treated between February 2005 and December 2007. All patients received initial external beam radiotherapy (EBRT) followed by HDR brachytherapy (planned dose 21 Gy to point A in three fractions over 8 days). For each insertion, a computed tomography scan was obtained with the brachytherapy applicator in situ. The cervix, uterus and organs at risk (OAR) were contoured on the computed tomography images to create an individualised dosimetry plan. The D 90 (the dose delivered to 90% of the tumour target), V 100 (the percentage of tumour target volume receiving 100% of the prescribed dose) and the minimum dose in the most exposed 2 cm 3 volume ( D 2cc) of rectum, bladder and bowel were recorded. The equivalent dose in 2 Gy fractions delivered by EBRT and brachytherapy was calculated. Results The 3-year cancer-specific survival was 81%, with a pelvic control rate of 96%. In 24 patients, a D 90 ≥74 Gy α/β10 was achieved. The only patient with local recurrence had a D 90 of 63.8 Gy α/β10. The overall actuarial risk of serious late morbidity was 14%. Seventeen patients had satisfactory OAR doses using the standard loading pattern. Seven patients had modifications to reduce the risk of toxicity, whereas two had modifications to improve the tumour dose. Comparison with a previous cohort of patients treated with chemoradiotherapy and a conventionally planned low dose rate triple source brachytherapy technique showed an improvement in local pelvic control of 20% ( P = 0.04). Conclusions The implementation of a computed tomography-based tandem-ring HDR brachytherapy technique in conjunction with individual dose adaptation has resulted in a significant improvement in local control at Addenbrooke's without increasing the risk of serious toxicity, and with little effect on radiotherapy resources.