Intracavitary Brachytherapy Planning Research Articles

Vaginal Dose Reduction by Changing the Ovoid Loading Pattern in Image Guided Intracavitary Brachytherapy of Cervix.

Locally advanced cervical cancer is frequently treated using a combination of external beam radiotherapy and brachytherapy. Radiotherapy often leads to vaginal morbidity, which poses a significant problem. This study aims to analyze the impact of reducing ovoid loading on dosimetry. We analyzed forty-five CT-based intracavitary brachytherapy plans from fifteen patients. Three plan sets were created for the 45 applications: a standard loading plan (A), a plan with reduced ovoid loading (B), and a tandem-only loading plan (C). We generated Dose-Volume Histograms and recorded dose volume parameters for the three plan sets. The D90 for the Clinical Target Volume (CTV) did not show significant differences among the three plan sets (p = 0.20). The average D90 values for plans A, B, and C were 8.15Gy, 8.16Gy, and 7.4Gy, respectively. No statistically significant differences were observed in D2cc bladder (p = 0.09) (average values: 6.8Gy, 6.5Gy, and 5.9Gy for plans A, B, and C, respectively) and D2cc sigmoid (p = 0.43) (average values: 2.8Gy, 2.6Gy, and 2.4Gy, respectively) among the three plan sets. However, there was a statistically significant difference in D2cc rectum (p < 0.001) (average values: 4Gy, 3.3Gy, and 1.8Gy, respectively), as well as in vaginal dose points (p < 0.001). Reducing ovoid loading significantly decreased the doses to vaginal dose points and the rectum without compromising the dose to the Clinical Target Volume (CTV). Therefore, in carefully selected cases, the adoption of tandem-only loading or reduced ovoid loading could be considered to minimize vaginal morbidity following high dose rate intracavitary brachytherapy.

IMRT as an Alternative Technique for Intracavitary Brachytherapy in Patients with Carcinoma of the Cervix: A Feasibility Study Using Unified Dosimetric Index.

Intracavitary brachytherapy (ICBT) plays an important role in the management of carcinoma of the cervix. This study attempts to find the feasibility of intensity-modulated radiation therapy (IMRT) as a boost for patients who are not suitable for ICBT in order to improve their disease-free and overall survival. Twenty patients with carcinoma of the cervix were included in this study. Nine fields of IMRT and ICBT plans were generated for PTVBoost. Various dosimetric indices like coverage, conformity, homogeneity, and gradient index were calculated, and the corresponding unified dosimetric index (UDI) values were generated. Plans were classified based on combined UDI, and the UDI values were compared with those of ICBT. In addition, rectum and bladder doses were compared. All the dosimetric indices were within acceptable limits except for the gradient index. The gradient index of the IMRT and ICBT plans were 8.77 ± 0.26 and 1.33 ± 0.06 respectively (p < 0.0001). The mean of combined UDI with standard deviation was 32.557 ± 8.940 and plan quality was calculated from these values. Rectum and bladder doses for ICBT were lesser than IMRT (p < 0.0001). ICBT is the gold standard for boost RT in carcinoma of the cervix patients. IMRT boost is feasible for patients who are unsuitable on medical grounds for brachytherapy.

Prospective Dosimetric Comparison Study Between Volumetric Modulated Arc Therapy and Intracavitary Brachytherapy for Cervical Cancer

Although volumetric modulated arc therapy (VMAT) boost can achieve highly conformal dose distributions for cervical cancer, VMAT has the disadvantage of requiring set-up and organ motion margins. This study prospectively recruited patients with the cervical cancer and compared VMAT plan with intracavitary brachytherapy (ICBT) plan. All patients treated with ICBT for locally advanced cervical cancer between April 2020 and September 2022 were enrolled. Patients had whole-pelvis radiotherapy, followed by CT scans with and without the tandem and ovoid in the same session (for the planning of ICBT and VMAT, respectively). ICBT planning characterizes the high-risk clinical target volume (HR-CTV) as the target volume and the bladder, rectum, sigmoid colon and small bowel loop as the organ at risk (OAR). VMAT planning defines the HR-CTV + 3 mm as the target volume and bladder, rectum + 3 mm (planning organ at risk volume (PRV) rectum), sigmoid colon + 3 mm (PRV sigmoid) and bowel bag as the OAR to account for set-up and organ motion. ICBT and VMAT plans were optimized for maximal dose received by at least 90% (D90%) of the target volume without impairing the dose constraints for the OARs. The prescribed dose (PD) was 26 Gy in 4 fractions. The dose constraints were determined as 25.2 Gy for D2 ml in the bladder and 20 Gy for D2 ml in the other OARs. The D90% and D100% of the target volume and D2 ml of OARs were compared between 2 plans using paired two-tailed Student's t test. Seventeen patients were enrolled. Dose and volume parameters for the 2 plans are shown in Table 1. Of the 17 patients, D90% of the target volume received 100% PD in 4 cases with ICBT plans, in 6 cases for VMAT plans, and in 2 cases with both methods. For D90% of the target volume, ICBT plans were greater than VMAT plans in 4 cases, with a maximum difference of 5.6 Gy (ICBT: 26.0 Gy, SBRT: 20.4 Gy). VMAT plans were higher than ICBT plans in 11 cases, with a maximum difference of 10.3 Gy (ICBT: 14.5 Gy, SBRT: 24.8 Gy). The dose-limiting OARs to attain D90% of target volume were bladder in 12 cases and small bowel loop in 1 case for ICBT plans, while PRV rectum in 11 cases, PRV sigmoid in 4 cases and bowel bag in 1 case for VMAT plans. This prospective study with 17 ICBT-eligible patients revealed D90% of the target volume demonstrated no substantial difference between VMAT and ICBT plans, while D100% showed a significant increase in VMAT plan compared to ICBT plan. Even with a set-up and organ motion margins on the HR-CTV and OARs, VMAT may have a dosimetric advantage over ICBT if the target geometry is complicated and close to the OARs.

Determination of variation in dosimetric parameters of treatment planning with Co-60 and Ir-192 sources in high dose rate brachytherapy of cervical carcinoma

AimTo determine the differences in dosimetric parameters in patients of intracavitary brachytherapy and interstitial HDR brachytherapy using Co-60 and Ir-192 sources. Materials and methodsComputed tomography (CT) based treatment plans of 20 cervical carcinoma patients treated with intracavitary and interstitial high dose rate brachytherapy were retrospectively studied. Patients were planned using Co-60 and Ir-192 sources, keeping the same dwell positions and dose objectives. The dosimetric parameters such as V100, D90, homogeneity index (HI) and conformal index (CI) for target and D2cc, D1cc and D0.1cc for organs at risk (OAR) were compared for both sources. ResultsFor interstitial brachytherapy plans, HR-CTV mean V100 values for Co-60 and Ir-192-based plans were 97.03 ± 1.93% and 96.42 ± 2.18%, respectively. There was no significant difference found in target coverage (p = 0.370). Ir-192 based plans were more homogeneous (HI = 0.68 ± 0.09) than the Co-60 plans (HI = 0.59 ± 0.10). However, the conformity was similar with both the sources. No significant difference was found between D2cc, D1cc, and D0.1cc values of bladder and rectum. In intracavitary brachytherapy plans, we did not find any significant difference in the dosimetric parameters such as point A values, D90, V100, and OAR doses on comparing plans from both sources. ConclusionThere are no significant differences in dosimetric parameters and no clinical advantage of using Co-60 over Ir-192-based brachytherapy. However, when it comes to cost management, Co-60 has a longer half-life, which reduces the cost of frequent source replacement and disposal.

A mathematical model to predict the different isodose volumes using TRAK value in HDR intracavitary brachytherapy for revised Manchester and ICRU-89 based Point A plans using computer tomography images

To find out the simple relationship between Total Reference Air Kerma (TRAK) and various isodose volumes. Calculated isodose volumes were compared with experimental data for revised Manchester and International Commission on Radiation Units and measurements (ICRU)-89 Point A-based treatment plans. The accuracy of the formula was compared with the results of other relationships available in the literature. Dosimetric data from 62 intracavitary brachytherapy (ICBT) treatment plans of 31 patients with cervical cancer were studied. Each patient had treatment plans normalized to revised Manchester and ICRU-89 Points A (Aflange and Aicru89). For each treatment plan, TRAK values, V350, V700, V1050, and V1400 were obtained. The modeling curve was plotted between Isodose volume (Vd) and the ratio of d/TRAK obtained from Aflange plans to get a mathematical relation. The results of this formula were compared with the experimental data and outcomes of other formulas available in the literature. A paired-sample t-test was performed to assess the statistical significance. In the case of revised Manchester-based Aflange normalization plans, the mean isodose volume of V350, V700, V1050, and V1400 were 285.98 ± 32.3 cm3, 101.96 ± 10.63 cm3, 52.71 ± 4.72 cm3, and 31.44 ± 2.33 cm3 respectively. Likewise, for ICRU-89 based Aicru89 normalization plans, the mean isodose volumes of V350, V700, V1050, and V1400 were 304.11 ± 26.17 cm3, 108.88 ± 8.29 cm3, 56.62 ± 3.69 cm3 and 34 ± 2.23 cm3 respectively. The mean difference was significant. The Mathematical relationship developed was [INLINE:1]. No correlation was found between TRAK and D0.1cm3,D2cm3 for organs at risk. The developed formula calculated isodose volumes within the accuracy of ± 3% in ICBT plans.

Plan optimization with L0-norm and group sparsity constraints for a new rotational, intensity-modulated brachytherapy for cervical cancer.

The aim of this work is to build a framework that comprehends inverse planning procedure and plan optimization algorithm tailored to a novel directional beam intensity-modulated brachytherapy (IMBT) of cervical cancer using a rotatable, single-channel radiation shield. Inverse planning is required for finding optimal beam emitting direction, source dwell position and dwell time, which begin with creating a kernel matrix for each structure based on Monte-Carlo simulated dose distribution in the rotatable shield. For efficient beam delivery and less transit dose, the number of source dwell positions and angles needs to be minimized. It can be solved by L0-norm regularization for fewest possible dwell points, and by group sparsity constraint in L2,p-norm (0≤p<1) besides L0-norm for fewest active applicator rotating angles. The dose distributions from our proposed algorithms were compared to those of conventional tandem-based intracavitary brachytherapy (ICR) plans for six cervical cancer patients. The algorithmic performance was evaluated in delivery efficiency and plan quality relative to the unconstrained algorithm. The proposed framework yielded substantially enhanced plan quality over the conventional ICR plans. The L0-norm and (group sparsity+L0-norm) constrained algorithms reduced the number of source dwell points by 60 and 70% and saved 5 and 8 rotational angles on average (7 and 11 angles for highly modulated cases), relative to the unconstrained algorithm, respectively. Though both algorithms reduced the optimal source dwell positions and angles, the group sparsity constrained optimization with L0-norm was more effective than the L0-norm constraint only, mainly because of considering physical constraints of the new IMBT applicator. With much fewer dwell points compared to the unconstrained, the proposed algorithms led to statistically similar plan quality in dose volume histograms and iso-dose lines. It also demonstrated that the plan optimized by rotating the applicator resulted in much better plan quality than that of conventional applicator-based plans.

Dosimetric research into target regions and organs at risk in three-dimensional intracavitary brachytherapy techniques for Chinese patients with cervical carcinoma.

The present study aimed to compare the dosages of target regions and organs at risk (OARs) in 3D intracavitary brachytherapy (ICBT) and conventional 2D ICBT for Chinese patients with cervical carcinoma. ICBT was performed in a total of 66 patients with Stage IB to IVA cervical carcinoma who had not received surgery but who had received whole-pelvic external-beam radiotherapy (EBRT). Plans for the 3D-ICBT and the conventional 2D-ICBT were individually designed for every patient. The dosages differences between the target regions and the OARs in patients with each of the various stages of cervical carcinoma were compared between the two ICBT plans. There was no significant difference in the dose at Point A between the two ICBT plans. However, the CTVhr-D90, CTVhr-D100 and CTVir-D90 in 3D-ICBT were much higher than in 2D-ICBT, especially in Stage IIB (P < 0.05). As compared with conventional 2D-ICBT, the dosages of DICRU and D2.0cm3 in the rectum/bladder, and D2.0cm3 in the sigmoid/small bowel were decreased significantly in 3D-ICBT (P < 0.05). For patients with Stage IIA, IIB and IIIB, the D2.0cm3 in the rectum/bladder was significantly reduced in 3D-ICBT (P < 0.05). It was demonstrated that, in Chinese patients, 3D-ICBT for cervical carcinoma could optimize the target coverage and reduce the dosages to the OARs compared with conventional 2D-ICBT.

Study of the effects of dwell time deviation constraints on inverse planning simulated annealing optimized plans of intracavitary brachytherapy of cancer cervix.

High Dose Rate (HDR) remote afterloading brachytherapy machine and advanced treatment planning system have made it possible to make variations in individual dwell times across a catheter according to tumour density and for sparing normal structures. New inverse planning technique such as Inverse Planning Simulated Annealing (IPSA) has also been introduced. But very few institutions are venturing towards volume based IPSA optimised intracavitary brachytherapy. This study focuses on dwell time deviation constraint (DTDC) feature of IPSA based optimization which restricts the large variation of dwell time across the catheter. For this retrospective study we have generated IPSA optimised intracavitary brachytherapy plans for 20 cancer cervix applications. The initial DTDC value of each IPSA plan was kept 0.0. Later on gradual increment was made in DTDC values in step of 0.2. Plan modulation index (M) defined by Ryan L. Smith et al was used for characterising the variation of dwell time modulation with respect to gradual increase in DTDC parameter. Plan modulation index gradually decreases with increasing value of DTDC from 0.0 to 1.0. There was the 83% decrease in M value from IPSA of DTDC 0.0 to fully constrained IPSA of DTDC1.0. There is reduction of 8.26% and 6.95% for D2cc values of rectum and bladder respectively for DTDC 1.0 compared to DTDC 0.0. One of the benefits of applying DTDC constrained in IPSA plan is that, it removes local hot spots. It's another advantage is the reduction in rectum and bladder dose.

Dose comparison between prescription methods according to anatomical variations in intracavitary brachytherapy for cervical cancer

PurposeWe compared how doses delivered via two-dimensional (2D) intracavitary brachytherapy (ICBT) and three-dimensional (3D) ICBT varied anatomically.Materials and MethodsA total of 50 patients who received 30 Gy of 3D ICBT after external radiotherapy (RT) were enrolled. We compared the doses of the actual 3D and 2D ICBT plans among patients grouped according to six anatomical variations: differences in a small-bowel V2Gy, small bowel circumference, the direction of bladder distension, bladder volume, sigmoid V3.5Gy, and sigmoid circumference. Seven dose parameters were measured in line with the EMBRACE recommendations.ResultsIn terms of bladder volume, the bladder and small-bowel D2cc values were lower in the 150–250 mL bladder volume subgroup; and the rectum, sigmoid, and bladder D2mL values were all lower in the >250 mL subgroup, for 3D vs. 2D ICBT. In the sigmoid V3.5Gy >2 mL subgroup, the sigmoid and bladder D2mL values were significantly lower for 3D than 2D ICBT. The bladder D2mL value was also significantly lower for 3D ICBT, as reflected by the sigmoid circumference. In patients with a small bowel V2.0Gy >10 mL or small bowel circumference >15%, most dose parameters were significantly lower for 3D than 2D ICBT. The bladder distension direction did not significantly affect the doses.ConclusionCompared to 2D ICBT, a greater bladder volume can reduce the internal 3D ICBT organ dose without affecting the target dose.

A Clinical Evaluation of American Brachytherapy Society Consensus Guideline for Bulky Vaginal Mass in Gynecological Cancer.

ObjectivesAmerican Brachytherapy Society (ABS)-recommended interstitial brachytherapy (IBT) should be considered for bulky vaginal tumor thicker than 5 mm. The aim of this study was to evaluate the ABS consensus guideline for patients with severe vaginal invasion based on our long-term follow-up results.Methods/MaterialsThe study included 7 patients with vaginal cancer and 14 patients with cervical cancer invading to the lower vagina. Based on prebrachytherapy magnetic resonance imaging findings, patients received intracavitary brachytherapy (ICT) for vaginal tumors 5 mm or less or IBT for vaginal tumors less than 5 mm. Nine patients received ICT and the remaining 12 patients received IBT. For dosimetric comparison, an experimental recalculation as the virtual IBT for patients actually treated by ICT, and vice versa, was performed.ResultsThe 5-year local control rate for all tumors was 89.4%. No differences in local control between ICT- and IBT-treated groups were observed (P = 0.21). One patient experienced a grade 3 rectal complication. There were no significant differences in the CTV D90 and rectum D2cc between the 2 groups (P = 0.13 and 0.39, respectively). In the dosimetric study of ICT-treated patients, neither the actual ICT plans nor the experimental IBT plans exceeded the limited dose for organs at risk, which were recommended in the guideline published from the ABS. In the IBT-treated patients, D2cc for bladder and rectum of the experimental ICT plans was significantly higher than for the actual IBT plans (P < 0.001 and <0.001, respectively), and 11 experimental ICT plans (92%) exceeded the limited dose for bladder and/or rectum D2cc.ConclusionsTumor control and toxicity after selected brachytherapy according to vaginal tumor thickness were satisfactory; IBT instead of ICT is recommended for patients with vaginal tumor thickness greater than 5 mm to maintain bladder and/or rectum D2cc.

Dosimetric evaluation of Point A and volume-based high-dose-rate plans: a single institution study on adaptive brachytherapy planning for cervical cancer.

PurposeExternal beam radiation therapy (EBRT) and brachytherapy (BT) with concurrent cisplatin is the standard of care for locally advanced cervical cancer. The applicability of image-guided adaptive volume-based high-dose-rate (HDR) intracavitary brachytherapy planning is an active area of investigation. In this study, we examined whether volume-based HDR-BT (HDRVOL) plans leads to more conformal plans compared to Point A (HDRPointA)-based plans.Material and methodsTwo hundred and forty HDRPointA plans from 48 cervical cancer patients treated with chemoradiotherapy were retrospectively collected. Point A plans were renormalized with respect to the high-risk clinical target volume (HR-CTV) for the HDRVOL plans. The doses to organs at risk (OAR; rectum, sigmoid, and bladder), and HR-CTV and the conformal index were compared between HDRPointA and HDRVOL plans.ResultsHDRVOL plans resulted in a 6-12% reduction in the total dose (EBRT + HDR-BT) to 0.1 cc, 1.0 cc, and 2.0 cc of the OAR as well as an 8-37% reduction in the dose to 2 cc of OAR per HDR-BT fraction compared to HDRPointA plans. Differences in the conformal indexes between the two groups of plans showed an 18-31% relative increase per HDR-BT fraction for HDRVOL plans. The D90 of the HR-CTV was reduced by 11% by HDRVOL planning and had a median dose of 86 Gy.ConclusionsOur study reports the relative improvement in OAR doses per HDR-BT fraction by HDRVOL planning compared to HDRPointA planning and demonstrates the dosimetric advantages of volume-based HDR-BT planning in creating more conformal plans.

Organ at Risk Doses during High Dose Rate Intracavitary Brachytherapy for Cervical Cancer: A Dosimetric Study

Background: Treatment of Cervical cancer includes a combination of external beam radiotherapy (EBRT) with intracavitary brachytherapy (ICBT). ICBT helps to boost radiation dose to primary disease. Organs like rectum, bladder, sigmoid and small bowel lie close to the cervix region and these organs receive dose from EBRT as well as ICBT and we want to know the dose to these organ at risk (OAR). Materials & Methods: Dosimetric details of 174 ICBT applications done in 58 patients were retrospectively analysed. All patients received EBRT dose of 50.4 Gy in 28 fractions. All patients had ICBT, three sessions with 7 Gy prescribed to point A. Dosimetric data including dose to right and left point A and dose to OARs were recorded from Oncentra Planning System. Results: Mean dose to point A on right side was 6.89 Gy and left side was 6.91 Gy. Mean D2cc dose to rectum, bladder, sigmoid and small bowel was 3.5 Gy, 5.25 Gy, 4.75 Gy and 4.2 Gy respectively. Mean EQD2 dose combining EBRT and ICBT in point A was 78.7 Gy on right side and 79 Gy on left side. Mean EQD2 doses to D2cc of rectum, bladder, sigmoid and small bowel was 62 Gy, 74.4 Gy, 70.5 Gy and 66.5 Gy respectively. Conclusion: From the results of this dosimetric study it is evident that OARs like rectum, sigmoid, bladder & bowel are receiving only acceptable doses of radiation using point A prescribed CT based ICBT planning. Hence with regards to OAR doses, CT based ICBT planning with dose prescribed to point A is a feasible option.

Interfractional dosimetric study of target volume and organs at risk following intracavitary brachytherapy for cervical cancer

Objective To examine the interfractional dosimetric variations among inverse three-dimensional (3D) plan, forward 3D plan, and two-dimensional (2D) plan of intracavitary brachytherapy for cervical cancer, and to discuss the risk of implementing the interval plan on different implantation applicators at short time intervals. Methods Twenty-five groups of CT-guided intracavitary brachytherapy (two consecutive radiations at ≤4 d apart) plans from 11 cervical cancer patients who received radical radiation therapy in our hospital were reviewed and compared. The dwelling location and time of the first intracavitary brachytherapy plan (Plan-1) were simulated on the CT image of the second intracavitary brachytherapy to form Plan-1-S. The target coverage indices and D 2 cc of organs at risk (OARs) of Plan-1-S and Plan 2(actual plan of the second intracavitary brachytherapy) under the three planning modes were recorded and compared using the paired t-test, Wilcoxon signed rank test, and ANOVA. Results The D90, D100, and V100 of high-risk CTV were significantly lower in Plan-1-S created under the inverse mode in the actual plan (-9.11±13.46%, -13.16±18.79%, and -7.80±13.34%, P=0.002, 0.002, and 0.005, respectively). D90, D100, and V100 of the interval plan had the greatest reduction under the inverse mode (76%, 80%, and 76%, respectively). The maximum reductions in D90, D100, and V100 were 332.14 cGy (2D), 244.12 cGy (forward), and 41.76%(inverse). OAR overdose occurred most frequently under the forward mode; the rates of D90, D100, and V100 reductions accompanied by one OAR overdose were 29.41%, 37.50%, and 25.00%, and the rates of D90, D100, and V100 reductions by two OAR overdoses were 5.88%, 12.50%, and 6.25%, respectively. Overdose occurred most frequently in the small intestine (36%). Comparison of the three planning modes showed that the inverse plan had a greater reduction in each target coverage index than the 2D plan. Conclusions The simulated interval plan can significantly reduce target coverage and increase the risk of OAR overdose regardless of the planning mode and the short time intervals, and is therefore not recommended for clinical application. Key words: Cervical neoplasms/brachytherapy; Interfractional dosimetric; Interval model plan

Investigation of fusion dose distribution for locally advanced cervical cancer under different bladder statuses for intensity‐modulated radiotherapy combined with intracavitary brachytherapy

Investigation of fusion dose distribution for locally advanced cervical cancer under different bladder statuses for intensity‐modulated radiotherapy combined with intracavitary brachytherapy

Dosimetric Comparison between Three-Dimensional Magnetic Resonance Imaging-Guided and Conventional Two-Dimensional Point A-Based Intracavitary Brachytherapy Planning for Cervical Cancer

ObjectiveThe purpose of this study was to comprehensively compare the 3-dimensional (3D) magnetic resonance imaging (MRI)-guided and conventional 2-dimensional (2D) point A-based intracavitary brachytherapy (BT) planning for cervical cancer with regard to target dose coverage and dosages to adjacent organs-at risk (OARs).MethodsA total of 79 patients with cervical cancer were enrolled to receive 2D point A-based BT planning and then immediately to receive 3D planning between October 2011 and April 2013 at the First Hospital Affiliated to Xi’an Jiao Tong University (Xi’an, China). The dose-volume histogram (DVH) parameters for gross tumor volume (GTV), high-risk clinical target volume (HR-CTV), intermediate-risk clinical target volume (IR-CTV) and OARs were compared between the 2D and 3D planning.ResultsIn small tumors, there was no significant difference in most of the DVHs between 2D and 3D planning (all p>0.05). While in big tumors, 3D BT planning significantly increased the DVHs for most of the GTV, HR-CTV and IR-CTV, and some OARs compared with 2D planning (all P<0.05). In 3D planning, DVHs for GTV, HR-CTV, IR-CTV and some OARs were significantly higher in big tumors than in small tumors (all p<0.05). In contrast, in 2D planning, DVHs for almost all of the HR-CTV and IR-CTV were significantly lower in big tumors (all p<0.05). In eccentric tumors, 3D planning significantly increased dose coverage but decreased dosages to OARs compared with 2D planning (p<0.05). In tumors invading adjacent tissues, the target dose coverage in 3D planning was generally significantly higher than in 2D planning (P<0.05); the dosages to the adjacent rectum and bladder were significantly higher but those to sigmoid colon were lower in 3D planning (all P<0.05).Conclusions3D MRI image-guided BT planning exhibits advantages over 2D planning in a complex way, generally showing advantages for the treatment of cervical cancer except small tumors.

Dose–volume histogram analysis of composite EQD2 dose distributions using the central shielding technique in cervical cancer radiotherapy

PurposeTo analyze the dose–volume histogram of the central shielding technique for cervical cancer radiotherapy by computing the composite three-dimensional EQD2 dose distributions of external-beam radiotherapy plus intracavitary brachytherapy. Methods and MaterialsOn a phantom, three patterns of high-risk clinical target volume (HR-CTV) with right–left diameters of 3, 4, and 5 cm were created using clinical data. Four patterns of combinations of whole-pelvis irradiation plus “pelvis irradiation using the central shielding technique” (CS) (shielding width, 3 or 4 cm) were created: 20 Gy/10 fractions + 30 Gy/15 fractions, 30 Gy/15 fractions + 20 Gy/10 fractions, 40 Gy/20 fractions + 10 Gy/5 fractions, and 50 Gy/25 fractions + 0 Gy. The intracavitary brachytherapy plan was set as 24 Gy/4 fractions prescribed to the Point A. The HR-CTV D90/D98 and modeled bladder/rectum D2cc were computed using the composite EQD2 dose distributions of all the treatment combinations. ResultsIf appropriate combinations of the treatment plans were selected on the basis of the CS doses and the HR-CTV sizes, the D90/D98 of HR-CTV 3 cm, HR-CTV 4 cm, and HR-CTV 5 cm were 89.7 Gy/80.6 Gy, 77.3 Gy/72.0 Gy, and 73.0 Gy/69.2 Gy in the case of CS width 3 cm, respectively; and 86.2 Gy/76.0 Gy, 73.3 Gy/67.6 Gy, and 70.9 Gy/67.1 Gy in the case of CS width 4 cm, respectively. The contributions of CS to the HR-CTV D90/bladder D2cc/rectum D2cc values were 24–56%/28–32%/9% of the CS plan doses for shielding width of 3 cm and were 13–35%/11–16%/5–6% for shielding width of 4 cm. ConclusionThe dose contributions of CS were variable but not negligible when analyzing the total doses delivered to the HR-CTV.

Treatment optimization with concurrent SBRT and intracavitary brachytherapy for locally advanced cervical cancer.

This work is aimed at investigating treatment planning strategies to optimally combine stereotactic body radiation therapy (SBRT) with intracavitary brachytherapy (ICBT) for the treatment of locally advanced cervical cancer. Forty patients (stage IIB – IIIB) previously treated with combined SBRT and ICBT were randomly selected for this retrospective study. All patients were CT‐ and MR‐scanned with a ring applicator in situ. HR‐CTV and OARs were contoured according to fused CT and MR images. Several ICBT plans were generated for each patient based on different dose prescription points, and then a matching SBRT plan was generated for each ICBT plan. The dose distribution of each composite plan was analyzed with a focus on the doses received by 90% and 100% of the target volume (D90 and D100), the target volume receiving 100% of the prescription dose (V100%), and the doses received by 2 cc and 40% of the OARs (D2cc and D40). As the distance, d, between the prescription point and the tandem varied within 1.0 and 1.9 cm, the D90, D100 and V100% for the target, as well as D2cc and D40 for the bladder and rectum approached their optimal values for d value between 1.0 and 1.4 cm. When designing a combined ICBT+SBRT plan, one should measure the size of the cervix and set the prescription isodose line 1.0 to 1.4 cm away from the tandem for the ICBT plan first and then optimize the SBRT plan based on the ICBT dose distribution to achieve the best target coverage and critical structures sparing.PACS number: 87.53.jw; 87.55.D‐

Optimizing packing contrast for MRI-based intracavitary brachytherapy planning for cervical cancer.

We prospectively tested five variations in vaginal gauze packing in an effort to improve contrast between the packing, cervix, and applicator for MRI-based intracavitary brachytherapy planning. Five patients enrolled on a prospective study from May 2013 to October 2013 received MRI-based intracavitary brachytherapy for cervical cancer with variations of impregnated gauze packing. Substances tested included antibiotic cream alone, antibiotic cream mixed with ultrasound gel, conjugated estrogens cream mixed with ultrasound gel, ultrasound gel alone, and gadolinium. Images from the T2-weighted pelvic MRI were used to obtain signal intensity measurements at points within the packing, cervix, and applicator. Signal intensity values were normalized using the signal-to-noise ratio and compared using an unpaired t-test. Ultrasound gel-impregnated gauze allowed for the greatest contrast between the packing and the cervix with a difference in mean normalized signal intensity of 38.2 (p < 0.01). Conjugated estrogens cream mixed with ultrasound gel and gadolinium also provided contrast when compared with cervix, with differences in mean normalized signal intensity of 25.3 and -16.2, respectively (p < 0.01 for both). For all variations but gadolinium, the normalized mean signal intensity of the packing was found to be significantly different from the applicator, with the ultrasound gel again demonstrating the greatest contrast with a difference of 42.5 (p < 0.01). Gauze impregnated with ultrasound gel, conjugated estrogens cream mixed with ultrasound gel, and gadolinium allowed for a significant difference in MRI signal intensity between the packing and the cervix. With respect to both the cervix and the applicator, ultrasoundgel-impregnated gauze provided the best contrast overall.

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

Comparison of high‐dose‐rate intracavitary brachytherapy dosimetry with and without anesthesia in patients with cervical carcinoma

This study compares the dosimetry of high‐dose‐rate intracavitary brachytherapy (HDR‐ICBT) performed with and without general anesthesia/spinal anesthesia (GA/SA) in patients with cervical carcinoma. We retrospectively retrieved the records of 138 HDR‐ICBT applicator insertions performed in 46 patients: 69 performed with GA/SA (anesthesia group known as AG) in 23 patients, and 69 performed without GA/SA (nonanesthesia group known as NAG) in 23 patients. The intracavitary brachytherapy (ICBT) application was done with central tandem and two vaginal ovoids. For each ICBT plan, a high‐dose‐rate (HDR) dose of 7 Gy was prescribed to point A. From each plan, the doses to Point B right (BR), Point B left (BL), bladder and rectal reference points (Bladderref and Rectalref) were recorded and compared in the two groups. Student's t‐test was applied to find out the significance of difference. The two groups were comparable in terms of demography and clinical characteristics. Mean Point BL doses in AG and NAG were 1.89 Gy (27% of Point A dose) and 1.82 Gy (26% of Point A dose), respectively. Mean Point BR doses in AG and NAG were 1.91 Gy (27% of Point A dose) and 1.85 Gy (26% of point A), respectively (p‐value 0.7). The mean dose to Bladderref in AG and NAG was 5.03 Gy and 4.90 Gy, respectively (p‐value 0.6). The mean dose to Rectalref was significantly higher in AG than NAG (5.09 Gy vs. 4.49 Gy, p‐value 0.01). Although based on conventional 2D dosimetry planning, our study has demonstrated that avoiding GA/SA does not result in inferior HDR‐ICBT dosimetry.PACS number: 87.53.Jw, 87.50.cm