Combining transrectal ultrasound and CT for image-guided adaptive brachytherapy of cervical cancer: Proof of concept

Integration of Ultrasound in Image-Guided Adaptive Brachytherapy in Cancer of the Uterine Cervix

Cervical cancer continues to be a public health concern, as it remains the second most common cancer despite screening programs. It is the third most common cause of cancer-related death for women, and the majority of cases happen in developing nations. The standard treatment for locally advanced cervical cancer involves the use of external beam radiation therapy, along with concurrent chemotherapy, followed by an image-guided adaptive brachytherapy (IGABT) boost. The five-year relative survival rate for European women diagnosed with cervical cancer was 62% between 2000 and 2007. Updated cervical cancer treatment guidelines based on IGABT have been developed by the Gynecological working group, which is composed of the Group Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology. The therapeutic strategy makes use of three-dimensional imaging, which can be tailored to the target volume and at-risk organs through the use of computed tomography or magnetic resonance imaging. Under anaesthesia, the brachytherapy implantation is carried out. Ultrasonography is utilised to assess the depth of the uterine cavity and to facilitate the dilation of the uterine canal during the application insertion. In this study, we examine data from the international literature regarding the application of ultrasound in cervical cancer brachytherapy.

First implementation of an innovative infra-red camera system integrated into a mobile CBCT scanner for applicator tracking in brachytherapy-Initial performance characterization

PURPOSE

To enable a real-time applicator guidance for brachytherapy, we used for the first time infra-red tracking cameras (OptiTrack, USA) integrated into a mobile cone-beam computed tomography (CBCT) scanner (medPhoton, Austria). We provide the first description of this prototype and its performance evaluation.

METHODS

We performed assessments of camera calibration and camera-CBCT registration using a geometric calibration phantom. For this purpose, we first evaluated the effects of intrinsic parameters such as camera temperature or gantry rotations on the tracked marker positions. Afterward, calibrations with various settings (sample number, field of view coverage, calibration directions, calibration distances, and lighting conditions) were performed to identify the requirements for achieving maximum tracking accuracy based on an in-house phantom. The corresponding effects on camera-CBCT registration were determined as well by comparing tracked marker positions to the positions determined via CBCT. Long-term stability was assessed by comparing tracking and a ground-truth on a weekly basis for 6 weeks.

RESULTS

Robust tracking with positional drifts of 0.02 ± 0.01 mm was feasible using the system after a warm-up period of 90 min. However, gantry rotations affected the tracking and led to inaccuracies of up to 0.70 mm. We identified that 4000 samples and full coverage were required to ensure a robust determination of marker positions and camera-CBCT registration with geometric deviations of 0.18 ± 0.03 mm and 0.42 ± 0.07 mm, respectively. Long-term stability showed deviations of more than two standard deviations from the initial calibration after 3 weeks.

CONCLUSION

We implemented for the first time a standalone combined camera-CBCT system for tracking in brachytherapy. The system showed high potential for establishing corresponding workflows.

Current Status and Future Directions of Image-Guided Adaptive Brachytherapy for Locally Advanced Cervical Cancer

PURPOSE

The standard of care for patients with locally advanced cervical cancer is definitive chemoradiation followed by a brachytherapy boost. This review describes the current status and future directions of image-guided adaptive brachytherapy for locally advanced cervical cancer.

METHODS

A systematic search of the PubMed and Clinicaltrials.gov databases was performed, focusing on studies published within the last 10 years. The search queried "cervical cancer [AND] image-guided brachytherapy [OR] magnetic resonance imaging (MRI) [OR] adaptive brachytherapy".

DISCUSSION

The retroEMBRACE and EMBRACE-I trials have established the use of MRI as the standard imaging modality for brachytherapy application and planning. Quantitative imaging and radiomics have the potential to improve outcomes, with three ongoing prospective studies examining the use of radiomics to further risk-stratify patients and personalize brachytherapy. Another active area of investigation includes utilizing the superior soft tissue contrast provided by MRI to increase the dose per fraction and decrease the number of fractions needed for brachytherapy, with several retrospective studies demonstrating the safety and feasibility of three-fraction courses. For developing countries with limited access to MRI, trans-rectal ultrasound (TRUS) appears to be an effective alternative, with several retrospective studies demonstrating improved target delineation with the use of TRUS in conjunction with CT guidance.

CONCLUSIONS

Further investigation is needed to continue improving outcomes for patients with locally advanced cervical cancer treated with image-guided brachytherapy.

Transrectal ultrasound for intraoperative interstitial needle guidance in cervical cancer brachytherapy

OBJECTIVE

This study aimed to prospectively assess the visibility of interstitial needles on transrectal ultrasound (TRUS) in cervical cancer brachytherapy patients and evaluate its impact on implant and treatment plan quality.

MATERIAL AND METHODS

TRUS was utilized during and after applicator insertion, with each needle's visibility documented through axial images at the high-risk clinical target volume's largest diameter. Needle visibility on TRUS was scored from 0 (no visibility) to 3 (excellent discrimination, margins distinct). Quantitative assessment involved measuring the distance between tandem and each needle on TRUS and comparing it to respective magnetic resonance imaging (MRI) measurements. Expected treatment plan quality based on TRUS images was rated from 1 (meeting all planning objectives) to 4 (violation of High-risk clinical target volume (CTVHR) and/or organ at risk (OAR) hard constraints) and compared to the final MRI-based plan.

RESULTS

Analysis included 23 patients with local FIGO stage IB2-IVA, comprising 41 applications with a total of 230 needles. A high visibility rate of 99.1% (228/230 needles) was observed, with a mean visibility score of 2.5 ± 0.7 for visible needles. The maximum and mean difference between MRI and TRUS measurements were 8 mm and -0.1 ± 1.6 mm, respectively, with > 3 mm discrepancies in 3.5% of needles. Expected treatment plan quality after TRUS assessment exactly aligned with the final MRI plan in 28 out of 41 applications with only minor deviations in all other cases.

CONCLUSION

Real-time TRUS-guided interstitial needle placement yielded high-quality implants, thanks to excellent needle visibility during insertion. This supports the potential of TRUS-guided brachytherapy as a promising modality for gynecological indications.

High-Dose-Rate Three-Dimensional Image-Guided Adaptive Brachytherapy (3D IGABT) for Locally Advanced Cervical Cancer (LACC): A Narrative Review on Imaging Modality and Clinical Evidence

Background: Brachytherapy (BT) is a critical component of radiotherapy for locally advanced cervical cancer (LACC), and it has rapidly developed in recent decades. Since the advent of three-dimensional image-guided adaptive brachytherapy (3D-IGABT), magnetic resonance imaging (MRI) has emerged as the primary modality for image guidance. Meanwhile, other imaging modalities, such as computed tomography, 18F-fluorodeoxyglucose positron emission tomography, ultrasound, and their combinations have also been widely studied. Materials and methods: We reviewed studies on different imaging modalities utilized for target delineation and planning. Emerging techniques in IGABT like real-time image guidance and 3D printing were also included. We summarized research on their feasibility and concentrated on their clinical outcomes. Results: MRI-guided BT was the gold standard, and CT-guided BT was the most widely applied. Other modalities have shown feasibility and promising efficacy in dosimetry studies and preliminary outcomes. The longer-term clinical outcomes associated with these approaches require further elucidation. Conclusions: As 3D-IGABT was validated by promising clinical outcomes, the future of BT for LACC is expected to progress toward the refinement of more effective image-guided procedures. Moreover, achieving operational consensus and driving technological advancements to mitigate the inherent limitations associated with different imaging modes remain essential.

Clinical implementation of 3D transvaginal ultrasound for intraoperative guidance of needle implant in template interstitial gynecologic high-dose-rate brachytherapy

PURPOSE

To demonstrate novel clinical implementation of a 3D transvaginal ultrasound (3DTVUS) system for intraoperative needle insertion guidance in perineal template interstitial gynecologic high-dose-rate brachytherapy and assess its impact on implant quality.

METHODS AND MATERIALS

Interstitial implants began with preimplant 3DTVUS to visualize the tumor and anatomy, with intermittent 3DTVUS to assess the implant and guide needle adjustment. Analysis includes visualization of the implant relative to anatomy, identification of cases where 3DTVUS is beneficial, dosimetry, and a survey distributed to 3DTVUS clinicians.

RESULTS

Seven patients treated between November 2021 and October 2022 were included in this study. Twenty needles were inserted under 3DTVUS guidance. The tumor and vaginal wall were well-differentiated in four and all seven patients, respectively. Patients with tumours below the superior aspect of the vagina are suited for 3DTVUS. Four radiation oncologists responded to the survey. There was general agreement that 3DTVUS improves implant and anatomy visualization and is preferred over standard 2D ultrasound guidance techniques.

CONCLUSIONS

Based on qualitative feedback from primary users and a small preliminary patient cohort, 3DTVUS imaging improves tumor and vaginal wall visualization during gynecologic perineal template interstitial needle implant and is a powerful tool for implant assessment in an intraoperative setting.

A novel multi-modality imaging phantom for validating interstitial needle guidance for high dose rate gynecological brachytherapy

PURPOSE

To design, manufacture, and validate a female pelvic phantom for multi-modality imaging (CT, MRI, US) to benchmark a commercial needle tracking system with application in HDR gynecological (GYN) interstitial procedures.

MATERIALS AND METHODS

A GYN needle-tracking phantom was designed using CAD software to model an average uterus from a previous patient study, a vaginal canal from speculum dimensions, and a rectum to accommodate a transrectal ultrasound (TRUS) probe. A target volume (CTVHR ) was designed as an extension from the cervix-uterus complex. Negative space molds were created from modeled anatomy and 3D printed. Silicone was used to cast the anatomy molds. A 3D printed box was constructed to house the manufactured anatomy for structural integrity and to accommodate the insertion of a speculum, tandem, needles, and TRUS probe. The phantom was CT-imaged to identify potential imperfections that might impact US visualization. Free-hand TRUS was used to guide interstitial needles into the phantom. The commercial tracking system was used to generate a 3D US volume. After insertion, the phantom was imaged with CT and MR and the uterus and CTVHR dimensions were verified against the CAD model.

RESULTS/CONCLUSIONS

The manufactured phantom allows for accurate visualization with multiple imaging modalities and is conducive to applicator and needle insertion. The phantom dimensions from the CAD model were verified with those from each imaging modality. The phantom is low cost and can be reproducibly manufactured with the 3D printing and molding processes. Our initial experiments demonstrate the ability to integrate the phantom with a commercial tracking system for future needle tracking validation studies.

ESGO/ESTRO quality indicators for radiation therapy of cervical cancer

BACKGROUND

The European Society of Gynaecological Oncology (ESGO) has previously defined and established a list of quality indicators for the surgical treatment of cervical cancer. As a continuation of this effort to improve overall quality of care for cervical cancer patients across all aspects, ESGO and the European SocieTy for Radiotherapy and Oncology (ESTRO) initiated the development of quality indicators for radiation therapy of cervical cancer.

OBJECTIVE

To develop a list of quality indicators for radiation therapy of cervical cancer that can be used to audit and improve clinical practice by giving to practitioners and administrators a quantitative basis to improve care and organizational processes, notably for recognition of the increased complexity of modern external radiotherapy and brachytherapy techniques.

METHODS

Quality indicators were based on scientific evidence and/or expert consensus. The development process included a systematic literature search for identification of potential quality indicators and documentation of scientific evidence, consensus meetings of a group of international experts, an internal validation process, and external review by a large international panel of clinicians (n = 99).

RESULTS

Using a structured format, each quality indicator has a description specifying what the indicator is measuring. Measurability specifications are detailed to define how the quality indicators will be measured in practice. Targets were also defined for specifying the level which each unit or center should be aiming to achieve. Nineteen structural, process, and outcome indicators were defined. Quality indicators 1-6 are general requirements related to pretreatment workup, time to treatment, upfront radiation therapy, and overall management, including active participation in clinical research and the decision making process within a structured multidisciplinary team. Quality indicators 7-17 are related to treatment indicators. Quality indicators 18 and 19 are related to patient outcomes.

DISCUSSION

This set of quality indicators is a major instrument to standardize the quality of radiation therapy in cervical cancer. A scoring system combining surgical and radiotherapeutic quality indicators will be developed within an envisaged future ESGO accreditation process for the overall management of cervical cancer, in an effort to support institutional and governmental quality assurance programs.

ESGO/ESTRO quality indicators for radiation therapy of cervical cancer

BACKGROUND

The European Society of Gynaecological Oncology (ESGO) has previously defined and established a list of quality indicators for the surgical treatment of cervical cancer. As a continuation of this effort to improve overall quality of care for cervical cancer patients across all aspects, ESGO and the European SocieTy for Radiotherapy and Oncology (ESTRO) initiated the development of quality indicators for radiation therapy of cervical cancer.

OBJECTIVE

To develop a list of quality indicators for radiation therapy of cervical cancer that can be used to audit and improve clinical practice by giving to practitioners and administrators a quantitative basis to improve care and organizational processes, notably for recognition of the increased complexity of modern external radiotherapy and brachytherapy techniques.

METHODS

Quality indicators were based on scientific evidence and/or expert consensus. The development process included a systematic literature search for identification of potential quality indicators and documentation of scientific evidence, consensus meetings of a group of international experts, an internal validation process, and external review by a large international panel of clinicians (n=99).

RESULTS

Using a structured format, each quality indicator has a description specifying what the indicator is measuring. Measurability specifications are detailed to define how the quality indicators will be measured in practice. Targets were also defined for specifying the level which each unit or center should be aiming to achieve. Nineteen structural, process, and outcome indicators were defined. Quality indicators 1-6 are general requirements related to pretreatment workup, time to treatment, upfront radiation therapy, and overall management, including active participation in clinical research and the decision making process within a structured multidisciplinary team. Quality indicators 7-17 are related to treatment indicators. Quality indicators 18 and 19 are related to patient outcomes.

DISCUSSION

This set of quality indicators is a major instrument to standardize the quality of radiation therapy in cervical cancer. A scoring system combining surgical and radiotherapeutic quality indicators will be developed within an envisaged future ESGO accreditation process for the overall management of cervical cancer, in an effort to support institutional and governmental quality assurance programs.

Application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer

BACKGROUND

Three-dimensional (3D) imaging has an important role in brachytherapy and the treatment of cervical cancer. The main imaging methods used in the cervical cancer brachytherapy include magnetic resonance imaging (MRI), computer tomography (CT), ultrasound (US), and positron emission tomography (PET). However, single-imaging methods have certain limitations compared to multi-imaging. The application of multi-imaging can make up for the shortcomings and provide a more suitable imaging selection for brachytherapy.

PURPOSE

This review details the situation and scope of existing multi-imaging combination methods in cervical cancer brachytherapy and provides a reference for medical institutions.

MATERIALS AND METHODS

Searched the literature related to application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer in PubMed/Medline and Web of Science electronic databases. Summarized the existing combined imaging methods and the application of each method in cervical cancer brachytherapy.

CONCLUSION

The current imaging combination methods mainly include MRI/CT, US/CT, MRI/US, and MRI/PET. The combination of two imaging tools can be used for applicator implantation guidance, applicator reconstruction, target and organs at risk (OAR) contouring, dose optimization, prognosis evaluation, etc., which provides a more suitable imaging choice for brachytherapy.

Embracing a future of progress in gynecologic brachytherapy

In the last 20 years, gynecologic brachytherapy has made tremendous advancements, most prominently evidenced by the evolution of cervical cancer brachytherapy. In its 20 year history, Brachytherapy has become known as a journal of science, education, and advocacy for our specialty and for our patients. In this review, we celebrate the 25 most impactful manuscripts in gynecologic brachytherapy in the journal's history.

A new technique for performing interstitial implants for gynecologic malignancies using transvaginal ultrasound guidance

Objectives

This study concerns a new technique that aims to achieve precise interstitial brachytherapy of pelvic recurrent tumors under transvaginal ultrasound (US) guidance, enhance the conformity index of the brachytherapy (BT), and improve the curative effect of radiotherapy for gynecological oncology patients with pelvic relapse.

Methods

A real-time transvaginal US-guided interstitial implant device was developed to assist in implant BT. Prior to implant brachytherapy, the size and location of the tumor in the pelvis and the interrelationship with adjacent organs were first assessed with intracavitary ultrasound. The transvaginal US-guided interstitial implant device was then placed on the endoluminal ultrasound probe, the probe was oriented intravaginally to determine a safe needle path, the implant needle was placed into the needle passage of the device, and the implant needle was inserted into the tumor tissue in the direction guided by the ultrasound puncture guide line. After the implant needle was placed in place, the cover of the transvaginal US-guided interstitial implant device was opened perpendicular to the ultrasound probe, and the needle was separated from the ultrasound probe smoothly, and then the cover was re-covered for subsequent implantation.

Results

In this study, 56 patients who underwent real-time transvaginal ultrasound-guided implantation for gynecologic oncology were enrolled, and insertion of 736 implant needles was completed. Among them, 13 patients had recurrent pelvic tumors after cervical cancer surgery and 6 patients had recurrent pelvic tumors after endometrial cancer surgery. Thirty-two patients who underwent radical radiation therapy for cervical cancer did not have adequate regression of parametrial invaded tissue after completion of standard EBRT treatment; and 5 patients had recurrent tumors in the radiation field after previous standard course of pelvic radiotherapy. The accuracy of the implant therapy was improved. The radiotherapy dose for recurrent pelvic masses was successfully increased, and the cumulative dose of external irradiation combined with BT was augmented to 80–100 Gy. The use of a new device for transvaginal implant for recurrent masses located in the lateral wall of the pelvic cavity was successful.

Conclusion

This intravascular US-guided interstitial implant device can realize interstitial implant with the shortest path under transvaginal US guidance. With convenient operation, high precision, and good security, the device not only improves the accuracy of implant therapy, but it also reduces the risks of anesthesia and organ injury, so it is suitable for widespread promotion and use.

Ultrasound guidance for cervical implantation

Ultrasound can provide real-time imagery without the risk of radiation exposure, and it is widely available at a relatively low cost. It can provide updated three-dimensional information that can improve the physician’s spatial awareness during a brachytherapy procedure for cervical cancer. There is mounting evidence demonstrating the numerous benefits of ultrasound-guided brachytherapy in the published literature. This evidence supports its routine use to improve the safety and the effectiveness of cervical brachytherapy. In this report we will review various methods in which ultrasound imaging has been used during cervical brachytherapy. We also include a description of our own institutional approach to ultrasound-guided cervical implementation that has been in use for all cervical brachytherapy procedures over the past two decades.

Image-guided brachytherapy in cervical cancer including fractionation

Image-guided brachytherapy in cervical cancer has been developed to be a feasible and very efficient component of the treatment of locally advanced cervical cancer in addition to concurrent chemoradiation treatment. This technique allows effective dose coverage of the target while sparing the organs at risk through adjustment of the implants (intracavitary and interstitial needles) and multi-pararametric three-dimensional treatment planning. Emerging evidence from prospective studies shows a high rate of local control throughout all stages, superior to two-dimensional brachytherapy, with limited toxicity for each organ site. This is associated with a high rate of pelvic control and overall survival. Based on clinical evidence, there is a dose–effect relationship for both disease and morbidity endpoints from which clear dose constraints for the target and organs at risk were derived. This review gives an overview of the major milestones that occurred in the development of image-guided adaptive brachytherapy in the last two decades, including outcome data and a summary of the hard and soft dose constraints recommended for targets and organs at risk.

Technical Note: Commissioning of an ultrasound-compatible surrogate vaginal cylinder for transvaginal ultrasound-based gynecologic high-dose-rate brachytherapy

PURPOSE

To provide a comprehensive set of commissioning tests for clinical implementation of three-dimensional transvaginal ultrasound (3D TVUS) as a replacement of computed tomography (CT) for applicator reconstruction in gynecologic intracavitary high-dose-rate brachytherapy with a multi-channel vaginal cylinder.

METHODS

We introduce an ultrasound-compatible "surrogate" vaginal cylinder (SVC) for reconstruction of Elekta's CT-MR Multi Channel Applicator (MCVC) in 3D TVUS. The MCVC is digitized over the SVC in 3DUS using digital library model overlay. Consulting guidelines from various sources (CPQR, GEC-ESTRO, AAPM), we identify and describe three tests specific to commissioning the SVC: 1) verification of SVC outer dimensions, 2) source position accuracy of MCVC digitization over the SVC in 3D TVUS, and 3) MRI/US registration error.

RESULTS

The SVC outer dimensions (diameter and A-D marker locations) were well matched to the MCVC, however a 0.6 mm discrepancy in length between cylinder tips was observed. Source position accuracy was within 1 mm (tolerance recommended by CPQR) when reconstructing the MCVC in 3D TVUS. Dice similarity coefficients and target registration error for MRI/3D TVUS registration was similar to MRI/CT registration, which is the clinical standard.

CONCLUSIONS

These commissioning tests are performed using institutional equipment but provide the framework for any practitioners to repeat in their own setup, to demonstrate safe adoption of the 3D TVUS system for patient treatments. We demonstrate that MRI/US-based workflow achieves similar source position accuracy and image registration error as standard MRI/CT, which is consistent with standard tolerances. This is a critical step towards replacement of CT with US in gynecologic high-dose-rate brachytherapy treatments with the MCVC. This article is protected by copyright. All rights reserved.

Dosimetric impact of target definition in brachytherapy for cervical cancer – Computed tomography and trans rectal ultrasound versus magnetic resonance imaging

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This study evaluated the dosimetric impact of target volume delineation in Computed Tomography (CT) with assistance from Trans Rectal Ultrasound (TRUS) as compared to Magnetic Resonance Imaging (MRI) image-based brachytherapy for cervical cancer.

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No statistically significant systematic difference was found between MRI and CT for target structures.

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However, considerable variations were seen on individual patient level which needs to be considered during clinical practice, which also needs further investigations.

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Current findings provide useful information to optimally utilize various imaging modalities for brachytherapy planning.

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Although, CT + TRUS based delineation of target volume, appear promising, MRI remains the gold standard.

Background and Purpose

Magnetic Resonance Imaging (MRI) based target definition in cervix brachytherapy is limited by its availability, logistics and financial implications, therefore, use of computed tomography (CT) and Trans Rectal UltraSonography (TRUS) has been explored. The current study evaluated the dosimetric impact of CT + TRUS based target volumes as compared to gold standard MRI.

Methods and Materials

Images of patients (n = 21) who underwent TRUS followed by MRI and CT, were delineated with High-Risk Clinical Target Volume in CT (CTV_HR-CT) and in MRI (CTV_HR-MR). CTV_HR-CT was drawn on CT images with TRUS assistance. For each patient, two treatment plans were made, on MRI and CT, followed by fusion and transfer of CTV_HR-MR to the CT images, referred as CTV_HR-MRonCT. The agreement between CTV_HR-MRonCT and CTV_HR-CT was evaluated for dosimetric parameters (D₉₀, D₉₈ and D₅₀; Dose received by 90%, 98% and 50% of the volumes) using Bland-Altman plots, linear regression, and Pearson correlation.

Results

No statistically significant systematic difference was found between MRI and CT. Mean difference (±1.96 SD) of D₉₀, D₉₈ and D₅₀ between CTV_HR-MRonCT and CTV_HR-CT was 2.0, 1.2 and 5.6 Gy respectively. The number of patients who have met the dose constraints of D₉₀ > 85 Gy were 90% and 80% in MR and in CT respectively, others were in the borderline, with a minimum dose of 80 Gy. The mean ± SD dose-difference between MR and CT plans for bladder was significant (5 ± 13 Gy; p = 0.12) for D_0.1cm3, while others were statistically insignificant.

Conclusion

CT + TRUS based delineation of CTV_HR appear promising, provide useful information to optimally utilize for brachytherapy planning, however, MRI remains the gold standard.

Toward 3D-TRUS image-guided interstitial brachytherapy for cervical cancer

PURPOSE

To qualitatively and quantitatively analyze needle visibility in combined intracavitary and interstitial cervical cancer brachytherapy on 3D transrectal ultrasound (TRUS) in comparison to gold standard MRI.

METHODS AND MATERIALS

Image acquisition was done with a customized TRUS stepper unit and software (Medcom, Germany; Elekta, Sweden; ACMIT, Austria) followed by an MRI on the same day with the applicator in place. Qualitative assessment was done with following scoring system: 0 = no visibility 1 (= poor), 2 (= fair), 3 (= excellent) discrimination, quantitative assessment was done by measuring the distance between each needle and the tandem two centimeters (cm) above the ring and comparing to the respective measurement on MRI.

RESULTS

Twenty-nine implants and a total of 188 needles (132 straight, 35 oblique, 21 free-hand) were available. Overall, 79% were visible (87% straight, 51% oblique, 76% free-hand). Mean visibility score was 1.4 ± 0.5 for all visible needles. Distance of the visible needles to tandem was mean ± standard deviation (SD) 21.3 millimeters (mm) ± 6.5 mm on MRI and 21.0 mm ± 6.4 mm on TRUS, respectively. Difference between MRI and TRUS was max 14 mm, mean ± SD -0.3 mm ± 2.6 mm. 11% differed more than 3 mm.

CONCLUSIONS

Straight needles were better detectable than oblique needles (87% vs. 51%). Detectability was impaired by insufficient rotation of the TRUS probe, poor image quality or anatomic variation. As needles show a rather indistinct signal on TRUS, online detection with a standardized imaging protocol in combination with tracking should be investigated, aiming at the development of real time image guidance and online treatment planning.

Clinical values of transrectal ultrasound in judging GTV of cervical cancer

PURPOSE

To investigate the clinical value of transrectal ultrasound in judging the Gross Target Volume (GTV) of cervical cancer (CC).

METHODS

A total of 196 CC patients admitted to the Department of Radiotherapy, China-Japan Union Hospital, Jilin University, from January 2016 to June 2019 were selected as the study subjects. The GTVs before and after applicator insertion were determined by transrectal ultrasound and compared with those judged by MRI.

RESULTS

All 196 patients were successfully undergoing applicator insertion according to the pretreatment plan. The GTV doses reached the clinical requirements during treatment. There was no significant difference between the GTVs judged by MRI and ultrasound before insertion in terms of upper/lower diameter (MRI Before 1 vs. Ultrasound Before 1) (MB1 vs. UB1), left/right diameter (MB2 vs. UB2), or ventral/dorsal diameter (MB3 vs. UB3), and the intragroup correlation coefficients (ICC) were 0.59, 0.77, and 0.66, respectively; moreover, there was no significant difference between the GTVs judged by MRI and ultrasound after insertion in terms of MRI After one vs. Ultrasound After one (MA1 vs. UA1), MA2 vs. UA2, and MA3 vs. UA3, and the ICC values were 0.62, 0.79, and 0.76, respectively.

CONCLUSIONS

Transrectal ultrasound can satisfactorily determine the GTV of CC and has certain value in brachytherapy for CC.

Feasibility of fusing three-dimensional transabdominal and transrectal ultrasound images for comprehensive intraoperative visualization of gynecologic brachytherapy applicators

PURPOSE

In this study, we propose combining three-dimensional (3D) transrectal ultrasound (TRUS) and 3D transabdominal ultrasound (TAUS) images of gynecologic brachytherapy applicators to leverage the advantages of each imaging perspective, providing a broader field-of-view and allowing previously obscured features to be recovered. The aim of this study was to evaluate the feasibility of fusing these 3D ultrasound (US) perspectives based on the applicator geometry in a phantom prior to clinical implementation.

METHODS

In proof-of-concept experiments, 3D US images of application-specific multimodality pelvic phantoms were acquired with tandem-and-ring and tandem-and-ovoids applicators using previously validated imaging systems. Two TRUS images were acquired at different insertion depths and manually fused based on the position of the ring/ovoids to broaden the TRUS field-of-view. The phantom design allowed "abdominal thickness" to be modified to represent different body habitus and TAUS images were acquired at three thicknesses for each applicator. The merged TRUS images were then combined with TAUS images by rigidly aligning applicator components and manually refining the registration using the positions of source channels and known tandem length, as well as the ring diameter for the tandem-and-ring applicator. Combined 3D US images were manually, rigidly registered to images from a second modality (magnetic resonance (MR) imaging for the tandem-and-ring applicator and X-ray computed tomography (CT) for the tandem-and-ovoids applicator (based on applicator compatibility)) to assess alignment. Four spherical fiducials were used to calculate target registration errors (TREs), providing a metric for validating registrations, where TREs were computed using root-mean-square distances to describe the alignment of manually identified corresponding fiducials. An analysis of variance (ANOVA) was used to identify statistically significant differences (p < 0.05) between the TREs for the three abdominal thicknesses for each applicator type. As an additional indicator of geometric accuracy, the bladder was segmented in the 3D US and corresponding MR/CT images, and volumetric differences and Dice similarity coefficients (DSCs) were calculated.

RESULTS

For both applicator types, the combination of 3D TRUS with 3D TAUS images allowed image information obscured by the shadowing artifacts under single imaging perspectives to be recovered. For the tandem-and-ring applicator, the mean ± one standard deviation (SD) TREs from the images with increasing thicknesses were 1.37 ± 1.35 mm, 1.84 ± 1.22 mm, and 1.60 ± 1.00 mm. Similarly, for the tandem-and-ovoids applicator, the mean ± SD TREs from the images with increasing thicknesses were 1.37 ± 0.35 mm, 1.95 ± 0.90 mm, and 1.61 ± 0.76 mm. No statistically significant difference was detected in the TREs for the three thicknesses for either applicator type. The mean volume differences for the bladder segmentations were 3.14% and 2.33% and mean DSCs were 87.8% and 87.7% for the tandem-and-ring and tandem-and-ovoids applicators, respectively.

CONCLUSIONS

In this proof-of-concept study, we demonstrated the feasibility of fusing 3D TRUS and 3D TAUS images based on the geometry of tandem-and-ring and tandem-and-ovoids applicators. This represents a step toward an accessible and low-cost 3D imaging method for gynecologic brachytherapy, with the potential to extend this approach to other intracavitary configurations and hybrid applicators.

IBS-GEC ESTRO-ABS recommendations for CT based contouring in image guided adaptive brachytherapy for cervical cancer

MR Imaging is regarded asthe gold standardfor Image Gudied Adaptive Brachytherapy (IGABT) for cervical cancer. However, its wide applicability is limited by its availability, logistics and financial implications. Use of alternative imaging like CTand Ultrasound (US) for IGABT has been attempted. In order to arrive at a systematic, uniform and international approach for CT based definition and contouring of target structures, GEC ESTRO, IBS and ABS agreed to jointly develop such recommendations based on the concepts and terms as published in the ICRU Report 89. The minimum requirements are clinical examination & documentation, CT or MR imaging at diagnosis and at a minimum, CT imaging with the applicator in place. The recommendations are based on (i) assessment of the GTV at diagnosis and at brachytherapy, (ii) categorizing the response to external radiation into different clinical remission patterns, (iii) defining various clinico-radiological environments and (iv) definition & delineation of a target on CT imaging at the time of brachytherapy with the applicator in situ. CT based target contouring recommendations based on 4 remission categories within 8 defined environments, aim at improving the contouring accuracy for IGABT using CT, US and MRI as available. For each clinico-radiological environment, there is an attempt to minimize the specific uncertainties in order to arrive at the best possible contouring accuracy. Evaluating feasibility & reproducibility, to achieve a benchmark towards a gold standard MR IGABT and further clinical research including outcomes with CT Based IGABT will become the next steps.

Integration of functional imaging in brachytherapy

Functional imaging allows the evaluation of numerous biological properties that could be considered at all steps of the therapeutic management of patients treated with brachytherapy. Indeed, it enables better initial staging of the disease, and some parameters may also be used as predictive biomarkers for treatment response, allowing better selection of patients eligible for brachytherapy. It may also improve the definition of target volumes with the aim of dose escalations by dose-painting. Finally, it could be useful during the follow-up to assess response to treatment. In this review, we report how functional imaging is integrated at the present time during the brachytherapy procedure, and what are its potential future contributions in the main tumour locations where brachytherapy is recommended. Functional imaging has great potential in the contact of brachytherapy, but still, several issues remain to be resolved before integrating it into clinical practice, especially as a biomarker or in dose painting strategies.

Advantages of real-time transabdominal ultrasound guidance in combined interstitial/intracavitary cervical brachytherapy: a case-based review

Sub-optimal placement of both intracavitary devices and interstitial needles is a relatively common occurrence in cervical brachytherapy, which may reduce the accuracy of dose distribution and contribute to adverse toxicities. To mitigate complications, improve target dose coverage, and verify proper device placement, implants may be placed under real-time image guidance. Traditionally, transrectal ultrasound has been used for needle guidance. However, we have utilized transabdominal ultrasound (TA-US) in our brachytherapy center. The purpose of this pictorial essay was to provide a pictorial description of TA-US technique, present a retrospective review of our preliminary outcomes adopting TA-US into routine practice, and to discuss the advantages of real-time ultrasound image guidance for placement of intrauterine tandem and interstitial needles.

Ultrasound-guided Brachytherapy for Cervix Cancer

Radiotherapy and brachytherapy are the definitive treatments for locally advanced cervix cancer. The use of soft-tissue imaging, particularly magnetic resonance imaging, has enhanced their effectiveness and improved clinical outcomes. However, the use of magnetic resonance imaging is largely restricted to well-resourced centres in both the first and developing world and remains elusive to many less advantaged centres, particularly those in areas with a high burden of cervix cancer. Ultrasound is an accessible, affordable and accurate imaging modality that can be used throughout the brachytherapy procedure. Ultrasound is primarily used to ensure safe insertion of the applicator but can also be used to guide planning. The methods used to utilise ultrasound images for planning are described. Ultrasound is particularly useful as a verification aid to confirm applicator placement after patients are moved and transferred around the radiotherapy department. It can also be used to verify the dimensions of treatment volumes over the course of brachytherapy. There is a crucial unmet need for an accessible economical soft-tissue imaging modality in cervical brachytherapy. Ultrasound has the potential to meet this need.

Quality Assurance in Modern Gynecological HDR-Brachytherapy (Interventional Radiotherapy): Clinical Considerations and Comments

Simple Summary

This is a focused review discussing quality assurance during interventional brachytherapy in gynecological cancers. This topic is very large and is usually addressed from the technical and physical sides, therefore, we decided to select “hot-spots” under this large title and discuss them from the point of view of clinicians. We hope that this concise and focused review will help clinicians in improving their quality assurance protocols and draw attention to the discussed issues.

Abstract

The use of brachytherapy (interventional radiotherapy) in the treatment of gynecological cancers is a crucial element in both definitive and adjuvant settings. The recent developments in high-dose rate remote afterloaders, modern applicators, treatment-planning software, image guidance, and dose monitoring systems have led to improvement in the local control rates and in some cases improved the survival rates. The development of these highly advanced and complicated treatment modalities has been accompanied by challenges, which have made the existence of quality assurance protocols a must to ensure the integrity of the treatment process. Quality assurance aims at standardizing the technical and clinical procedures involved in the treatment of patients, which could eventually decrease the source of uncertainties whether technical (source/equipment related) or clinical. This commentary review sheds light (from a clinical point of view) on some potential sources of uncertainties associated with the use of modern brachytherapy in the treatment of gynecological cancers.

Application of transrectal ultrasound in guiding interstitial brachytherapy for advanced cervical cancer

Purpose

To investigate the role of transrectal ultrasound guidance in interstitial brachytherapy for cervical cancer.

Material and methods

Forty-eight patients who underwent interstitial brachytherapy treatment for cervical cancer between January 2017 and January 2018 were enrolled in the study. The distances between each inserted needle and the lesion were measured at seven sites by ultrasound (D1-D7) and compared to the corresponding distances (M1-M7) when visualised with nuclear magnetic resonance imaging (MRI). Measurements were paired on the basis of the observation sites, e.g. D1 and M1, D2 and M2. The statistical differences, intraclass correlation coefficients (ICCs), and linear relationships for the paired measurements were calculated.

Results

No significant differences were found between the paired M and D measurements, with all ICCs showing high levels of concordance (0.81-0.93).

Conclusions

Transrectal ultrasound showed strong agreement with MRI results in determining the position of the inserted needles. Transrectal ultrasound is a useful tool for guided interstitial brachytherapy and is appropriate for widespread use in the treatment of locally advanced cervical cancer.

Dosimetry of a sonolucent material for an ultrasound-compatible gynecologic high-dose-rate brachytherapy cylinder using Monte Carlo simulation and radiochromic film

PURPOSE

he purpose of this study was to study the dosimetric characterization of sonolucent material "TPX" to be used toward gynecologic high-dose-rate brachytherapy treatments using ultrasound-compatible cylinders in non-model-based dose calculation workflows.

METHODS

Monte Carlo simulations were performed using EGSnrc application egs_brachy in cylinders of polymethylpentene (TPX) plastic, water, and PMMA. Simulations were performed of five 192Ir sources placed longitudinally in ∼3.7 cm diameter, 5.0 cm length cylinders (matching physical cylinders used in film measurements). TPX and PMMA dose distributions and percentage depth dose curves were compared relative to water. Film measurements were performed to validate egs_brachy simulations. TPX and PMMA cylinders were placed in a water tank using 3D-printed supports to position film radially and touching the surface of the cylinders. The same five 192Ir dwell positions were delivered as simulated in egs_brachy.

RESULTS

The egs_brachy and film percentage depth doses agreed within film uncertainties. The egs_brachy relative dose difference between TPX and water was (0.74 ± 0.09)% and between PMMA and water was (-0.79 ± 0.09)% over the dose scoring phantom. Dose differences for TPX and PMMA relative to water were less than ± 1% within 5 cm of the cylinder surface.

CONCLUSIONS

In a solid sonolucent sheath of TPX, the dosimetric differences are comparable with PMMA and other applicator materials in clinical use. No additional uncertainty to dose calculation is introduced when treating through TPX cylinders compared with current applicator materials, and therefore, it is acceptable to perform gynecologic brachytherapy treatments with a sonolucent sheath inserted during radiation delivery.

Evaluation of an MR-only interstitial gynecologic brachytherapy workflow using MR-line marker for catheter reconstruction

PURPOSE

Magnetic resonance imaging (MRI) offers excellent soft-tissue contrast enabling the contouring of targets and organs at risk (OARs) during gynecological interstitial brachytherapy procedure. Despite its benefit, one of the main challenges toward MRI-only workflows is that the implanted catheters are not reliably visualized on MR images. This study aims to evaluate the feasibility of MR-only workflow using an in-house MR line marker during interstitial gynecological high-dose-rate (HDR) brachytherapy.

METHODS AND MATERIALS

Ten patients diagnosed with locally advanced cervical cancer treated with HDR brachytherapy were included in this study. The hybrid CT/MR-treated plan was used as the study reference plan. Five users manually reconstructed the catheter's path on MR images (3D T1- and T2-weighted). Subsequently, the dwell positions from the users' plans were superimposed on the reference plans to evaluate the dosimetric impact of the using MR-only for catheter reconstruction in comparison with hybrid CT/MR approach. Variability of dwell positions between users and reconstruction time was also evaluated.

RESULTS

More than 96.90% of catheter reconstruction variations were < 2 mm. No statistical differences were reported between MR-only and hybrid CT/MR in gross tumor volume D₉₈ and high-risk clinical target volume D₉₀, respectively. For the OARs (bladder, sigmoid, rectum, and bowel), no significant changes were observed in any dose metrics between MR-only and hybrid CT/MR. The average reconstruction time was 51 ± 10 minutes across all ten patients.

CONCLUSION

The feasibility of MR-only workflow using MR line marker during interstitial gynecological HDR brachytherapy has been validated in this study. The results show that the MR-only workflow is equivalent to the conventional hybrid CT/MR approach in terms of gross tumor volume and high-risk clinical target volume coverage and respecting of OARs dose limits.

Hybrid TRUS/CT with optical tracking for target delineation in image-guided adaptive brachytherapy for cervical cancer

Objective

To prospectively compare the interobserver variability of combined transrectal ultrasound (TRUS)/computed tomography (CT)- vs. CT only- vs. magnetic resonance imaging (MRI) only-based contouring of the high-risk clinical target volume (CTV_HR) in image-guided adaptive brachytherapy (IGABT) for locally advanced cervical cancer (LACC).

Methods

Five patients with LACC (FIGO stages IIb–IVa) treated with radiochemotherapy and IGABT were included. CT, TRUS, and T2-weighted MRI images were performed after brachytherapy applicator insertion. 3D-TRUS image acquisition was performed with a customized ultrasound stepper device and software. Automatic applicator reconstruction using optical tracking was performed in the TRUS dataset and TRUS and CT images were fused with rigid image registration with the applicator as reference structure. The CTV_HR (based on the GEC-ESTRO recommendations) was contoured by five investigators on the three modalities (CTV_HR_CT, CTV_HR_TRUS-CT, and CTV_HR_MRI). A consensus reference CTV_HR_MRI (MRIref) was defined for each patient. Descriptive statistics and overlap measures were calculated using RTslicer (SlicerRT Community and Percutaneous Surgery Laboratory, Queen’s University, Canada), comparing contours of every observer with one another and with the MRIref.

Results

The interobserver coefficient of variation was 0.18 ± 0.05 for CT, 0.10 ± 0.04 for TRUS-CT, and 0.07 ± 0.03 for MRI. Interobserver concordance in relation to the MRIref expressed by the generalized conformity index was 0.75 ± 0.04 for MRI, 0.51 ± 0.10 for TRUS-CT, and 0.48 ± 0.06 for CT. The mean CTV_HR_CT volume of all observers was 71% larger than the MRIref volume, whereas the mean CTV_HR_TRUS-CT volume was 15% larger.

Conclusion

Hybrid TRUS-CT as an imaging modality for contouring the CTV_HR in IGABT for LACC is feasible and reproducible among multiple observers. TRUS-CT substantially reduces overestimation of the CTV_HR volume of CT alone while maintaining similar interobserver variability.

Clinical Application of Ultrasound Guidance for Parametrial Treatment of Advanced Cervical Cancer

OBJECTIVES

To evaluate the accuracy of ultrasound (US) in determining the positions of parametrial implants by comparing US with magnetic resonance imaging (MRI) for advanced cervical cancer.

METHODS

Patients undergoing brachytherapy with parametrial implantation for cervical cancer from February 2017 to February 2019 were involved in the study. The transverse section of the cervix (surface S₁ ) and the transverse section 1 cm above the external cervix (surface S₂ ) were selected from MRI and US images as the observation planes. In the MRI observation plane, the distances between the uterine titanium needles and the uterine tube/implanter were set as M₁ to M₄ ; in the US observation plane, the distances between the uterine titanium needles and the uterine tube/implanter were set as D₁ to D₄ . The differences and consistency in M and D of each group were then compared.

RESULTS

There were no significant differences between M and D in each group (P = .058; P = .821; P = .870; and P = .936, respectively). The intraclass correlation coefficients of M and D in each group were 0.970, 0.968, 0.952, and 0.956. A regression analysis showed that the relationships between M and D in each group were as follows: M₁ = 0.9449D₁  + 0.1812; M₂ = 0.9463D₂  + 0.0965; M₃ = 0.9176D₃  + 0.1233; and M₄ = 0.9253D₄  + 0.1224.

CONCLUSIONS

In parametrial brachytherapy for cervical cancer, US can accurately determine the positions of parametrial implantation needles, which is already applicable on MRI, and can provide assistance in parametrial brachytherapy for advanced cervical cancer.

GEC-ESTRO/ACROP recommendations for quality assurance of ultrasound imaging in brachytherapy

Ultrasound (US) is an important imaging modality in brachytherapy (BT). In particular for low-dose-rate (LDR) and high-dose-rate (HDR) prostate implants transrectal ultrasound (TRUS) is widespread. Besides the common use of US for prostate implants, US can also be applied in gynecological and anal cancer therapies as examples amongst others. The BRAPHYQS (BRAchytherapy PHYsics Quality assurance System) and UroGEC (urology) working groups of GEC-ESTRO (GEC: Groupe Européen de Curiethérapie, committee of ESTRO: European SocieTy for Radiotherapy & Oncology) elaborated upon guidelines describing quality assurance (QA) methods for US in BT. The total quality management (QM) for the unit includes acceptance testing, commissioning and periodic image testing. In 2008, the AAPM (American Association of Physicists in Medicine) published the TG (Task group) 128 report. Whereas the TG 128 focuses on US systems and prostate BT, the current recommendations also cover tests for stepping devices and include other interstitial or intracavitary treatment sites in BT, such as anal implants and gynecological BT. The recommendations presented herein do not replace regular maintenance for the US devices performed by the vendor. They are the QA of US in BT but are not sufficient for the whole maintenance of medical US devices. Moreover, national regulations and recommendations should also be followed. For the tests presented in this report tolerances or action limits are given. These recommendations explain practical test procedures of US devices in BT. They will help the clinics to perform a high level of quality in the use of US for BT in Europe.

Radical radiotherapy in patients with cervix uteri carcinoma: experience of Ondokuz Mayis University

Background

Radical radiotherapy is the standard treatment for patients with locally advanced cervix uteri carcinoma (FIGO stage IB2–IVA). Worldwide, incidence and mortality rates vary among regions because of differences in lifestyles and treatment standards. Herein, we evaluated the outcomes of radical radiotherapy in patients with locally advanced cervix uteri carcinoma from the middle Black Sea region of Turkey.

Methods

We retrospectively reviewed the records of 64 consecutive patients with locally advanced cervix uteri carcinoma who were treated from January 2013 to 2016 in our radiation oncology department. All patients staging and radiotherapy planning were performed with modern imaging techniques including magnetic resonance imaging and positron-emission-tomography/computed tomography before radical radiotherapy. Thereafter, all of them were treated with external beam radiotherapy and concurrent cis-platinum-based chemotherapy followed by three-dimensional intra-cavitary high-dose-rate brachytherapy.

Results

The median age at diagnosis was 54.5 years. The median follow-up period was 21 months. Acute grade 3 toxicity was detected in 3.1% of patients. Late toxicity was not detected in any patient. The 1- and 3-year progression-free survival rates were 83.6 and 67.5%, respectively. The 1- and 3-year overall survival rates were 95.7 and 76.9%, respectively. The most important prognostic factor was the FIGO stage. Distant metastasis was the most common cause of death in patients with locally advanced cervix uteri carcinoma despite radical radiotherapy.

Conclusions

In patients with locally-advanced cervix uteri carcinoma from the middle Black Sea region of our developing country, acceptable toxicity and survival rates are achieved similar to the recent literature from developed countries with using of modern staging, planning and radical radiotherapy techniques. However, recurrence was mostly in the form of distant metastases and further investigations on systemic therapies are required.

Prospective intra/inter-observer evaluation of pre-brachytherapy cervical cancer tumor width measured in TRUS and MR imaging

BACKGROUND

Ultrasound (US) imaging has been proved as an excellent diagnostic tool in gynecology and, due to its wide availability and limited cost, is under intense investigation as base for dose adaptation in cervical cancer brachytherapy. Purpose of this work is to test inter/intra-observer uncertainties between magnetic resonance (MR) and trans-rectal ultrasound (TRUS) imaging in defining maximum tumor width before first brachytherapy (BT) application in a prospective cohort of cervical cancer patients undergoing image-guided adaptive brachytherapy (IGABT).

METHODS

One hundred ten consecutive cervical cancer patients treated between 2013 and 2016 were included. Before the first BT implant patients underwent MR and TRUS scan with no applicator in place. Images were independently analyzed by three examiners, blinded to the other's results. With clinical information at hand, maximum tumor width was measured on preBT TRUS and MR. Quantitative agreement analysis was undertaken. Intra-class correlation coefficient (ICC), Passing-Bablok and Bland Altman plots were used to evaluate the intra/inter-observers measurement agreement.

RESULTS

Average difference between tumor width measured on MR (HRCTV_MR) and TRUS (HRCTV_TRUS) was 1.3 ± 3.2 mm (p <  0.001); 1.1 ± 4.6 mm (p = 0.01) and 0.7 ± 3 mm (p = 0.01). The error was less than 3 mm in 79, 82 and 80% of the measurements for the three observers, respectively. Intra-observer ICC was 0.96 (CI95% 0.94-0.97), 0.93 (CI95% 0.9-0.95) and 0.96 (CI95% 0.95-0.98) respectively. Inter-observer ICC for HRCTV_MR width measures was 0.92 (CI95% 0.89-0.94) with no difference among FIGO stages. Inter-observer ICC for HRCTV_TRUS was 0.86 (CI95% 0.81-0.9). For FIGO stage I and II tumors, ICC HRCTV_TRUS values were comparable to respective HRCTV_MR ICC values. For larger tumors HRCTV_TRUS inter-observer ICC values were lower than respective HRCTV_MR although remaining acceptable.

CONCLUSIONS

Our results suggest that TRUS is equivalent to MR in assessing preBT tumor maximum width in cervical cancer FIGO stage I/II. In more advanced stages TRUS seems to be slightly inferior to MR although maintaining a good agreement to gold standard imaging.

Indian Brachytherapy Society Guidelines for radiotherapeutic management of cervical cancer with special emphasis on high-dose-rate brachytherapy

Brachytherapy (BT) for locally advanced cervical cancer is vital for optimal outcomes. There is heterogeneity in brachytherapy treatment practice for cervical cancer across India. In an attempt to standardize various processes involved in cervical cancer brachytherapy, the expert members of the Indian Brachytherapy Society (IBS) developed a document related to radiation therapy treatment of cervical cancer with special emphasis on brachytherapy. The guidelines are based on high quality clinical evidence, expert opinion and consensus wherever evidence was lacking. The document provides a guide for external beam radiation and details of all the processes involved in high-dose-rate (HDR) brachytherapy including patient selection, preparation, principles and technique of BT applications, target and normal tissue definition, dose prescriptions, BT planning, reporting parameters, common complications of BT and their management, scope for research, etc. In summary, we present here practical tips and tricks, recording and reporting of cervical cancer brachytherapy, which can be implemented in various clinical environments and forms the basis of this report.

Review of strategies for MRI based reconstruction of endocavitary and interstitial applicators in brachytherapy of cervical cancer

Brachytherapy plays an essential role in the curative intent management of locally advanced cervical cancer. The introduction of the magnetic resonance (MR) as a preferred image modality and the development of new type of applicators with interstitial components have further improved its benefits. The aim of this work is to review the current status of one important aspect in the cervix cancer brachytherapy procedure, namely catheter reconstruction. MR compatible intracavitary and interstitial applicators are described. Considerations about the use of MR imaging (MRI) regarding appropriate strategies for applicator reconstruction, technical requirements, MR sequences, patient preparation and applicator commissioning are included. It is recommendable to perform the reconstruction process in the same image study employed by the physician for contouring, that is, T2 weighted (T2W) sequences. Nevertheless, a clear identification of the source path inside the catheters and the applicators is a challenge when using exclusively T2W sequences. For the intracavitary component of the implant, sometimes the catheters may be filled with some substance that produces a high intensity signal on MRI. However, this strategy is not feasible for plastic tubes or titanium needles, which, moreover, induce magnetic susceptibility artifacts. In these situations, the use of applicator libraries available in the treatment planning system (TPS) is useful, since they not only include accurate geometrical models of the intracavitary applicators, but also recent developments have made possible the implementation of the interstitial component. Another strategy to improve the reconstruction process is based on the incorporation of MR markers, such as small pellets, to be used as anchor points. Many institutions employ computed tomography (CT) as a supporting image modality. The registration of CT and MR image sets should be carefully performed, and its uncertainty previously assessed. Besides, an important research work is being carried out regarding the use of ultrasound and electromagnetic tracking technologies.

Research on pseudo-CT imaging technique based on an ultrasound deformation field with binary mask in radiotherapy

This study aimed to investigate the reliability of pseudo-computed tomography (pseudo-CT) imaging based on ultrasound (US) deformation fields under different binary masks in radiotherapy.We used 3-dimensional (3D) CT and US images, including those acquired during CT simulation positioning, and cone-beam CT (CBCT) and US images acquired 1 week after treating 3 patients with cervical cancer. Image data of 3 different layers were selected from the US images, and 3D CT images of each patient were selected. For US image registration, the following were created and applied: binary masks of the region of interest overlapping (ROIO) between the US image based on simulation positioning and US image for positioning verification, region of interest (ROI), whole overlapping (wholeO), and whole imaging region (whole). Accordingly, the deformation field was obtained and applied to CT images (CTsim), and different pseudo-CT images were acquired. Similarities between the pseudo-CT and CBCT images were compared, and registration accuracies between pseudo-CT images under different binary masks and CTsim were compared and discussed.A pair t test was conducted to normalized mutual information values of the registration accuracy between the pseudo-CT image based on ROIO binary mask and CTsim with other methods (P < .05), and the difference was statistically significant. A pair t test of normalized gray mean-squared errors was also performed (P < .05), and the difference was statistically significant. The similarity function means between pseudo-CT, that is, based on ROIO, ROI, wholeO, whole, and no binary mask, and CBCT were 0.9084, 0.8365, 0.7800, 0.6830, and 0.5518, respectively.Pseudo-CT based on ROIO binary mask best matched with CTsim and achieved the highest similarity with CBCT.

A Prospective Comparison of Computed Tomography with Transrectal Ultrasonography Assistance and Magnetic Resonance Imaging-Based Target-Volume Definition During Image Guided Adaptive Brachytherapy for Cervical Cancers

PURPOSE

Although magnetic resonance imaging (MRI) represents the gold standard for image guided adaptive brachytherapy (IGABT) for cervical cancer, the majority of brachytherapy (BT) continues to be guided by computed tomography (CT). However, CT seems to overestimate the target-volume definition, and the potential of transrectal ultrasonography (TRUS) needs further evaluation. This prospective, comparative study aimed to evaluate CT-based target contouring with the incorporation of TRUS during BT.

METHODS AND MATERIALS

Patients with locally advanced cervical cancer undergoing magnetic resonance IGABT between January 2013 and March 2014 were included. During the BT procedure, TRUS imaging with central tandem in situ was acquired at 3 representative levels. Reference points/dimensions (D1-D4) of the hypoechoic region on TRUS images with respect to the central tandem were recorded. CT and magnetic resonance BT planning imaging was performed after BT application. The high-risk clinical target volume (HR-CTV) was contoured on CT scans with incorporation of clinical and TRUS imaging findings and was compared with the gold standard MRI-based target approach.

RESULTS

The image sets of 25 patients (International Federation of Gynecology and Obstetrics clinical stage IIB [11; 44%] and IIIB [14; 56%]) were evaluable. The mean (±standard deviation) volumes of HR-CTV on CT and MRI imaging were 39.1 (±20) cm³ and 39 (±19) cm³, respectively (r = 0.92; P < .001)_. A significant correlation was found between the HR-CTV dimensions (width and thickness) of CT and MRI scans at various levels (r = 0.70-0.80; P < .001)_. In addition, the absolute differences in target dimensions between CT and MRI were <0.5 cm. A strong correlation was seen between CT and MRI for patients with medial and lateral parametrial invasion (P < .05) compared with no parametrial disease at BT. Furthermore, the mean differences in HR-CTV width between CT and MRI contours at various levels, irrespective of parametrial involvement, was only 0.1 to 0.4 cm.

CONCLUSIONS

This study suggests that a CT-based target and organ-at-risk delineation using MRI at diagnosis and real-time TRUS information during BT seems comparable with the gold standard MRI-based approach in IGABT for cervical cancer.

The EMBRACE II study: The outcome and prospect of two decades of evolution within the GEC-ESTRO GYN working group and the EMBRACE studies

The publication of the GEC-ESTRO recommendations one decade ago was a significant step forward for reaching international consensus on adaptive target definition and dose reporting in image guided adaptive brachytherapy (IGABT) in locally advanced cervical cancer. Since then, IGABT has been spreading, particularly in Europe, North America and Asia, and the guidelines have proved their broad acceptance and applicability in clinical practice. However, a unified approach to volume contouring and reporting does not imply a unified administration of treatment, and currently both external beam radiotherapy (EBRT) and IGABT are delivered using a large variety of techniques and prescription/fractionation schedules. With IGABT, local control is excellent in limited and well-responding tumours. The major challenges are currently loco-regional control in advanced tumours, treatment-related morbidity, and distant metastatic disease. Emerging evidence from the RetroEMBRACE and EMBRACE I studies has demonstrated that clinical outcome is related to dose prescription and technique. The next logical step is to demonstrate excellent clinical outcome with the most advanced EBRT and brachytherapy techniques based on an evidence-based prospective dose and volume prescription protocol. The EMBRACE II study is an interventional and observational multicentre study which aims to benchmark a high level of local, nodal and systemic control while limiting morbidity, using state of the art treatment including an advanced target volume selection and contouring protocol for EBRT and brachytherapy, a multi-parametric brachytherapy dose prescription protocol (clinical validation of dose constraints), and use of advanced EBRT (IMRT and IGRT) and brachytherapy (IC/IS) techniques (clinical validation). The study also incorporates translational research including imaging and tissue biomarkers.

Use of 3D transabdominal ultrasound imaging for treatment planning in cervical cancer brachytherapy: Comparison to magnetic resonance and computed tomography

PURPOSE

To evaluate if the addition of 3D transabdominal ultrasound (3DTAUS) imaging to computed tomography (CT) can improve treatment planning in 3D adaptive brachytherapy when compared with CT-based planning alone, resulting in treatment plans closer to the ones obtained using magnetic resonance imaging (MRI)-based planning.

METHODS AND MATERIALS

Five patients with cervical cancer undergoing brachytherapy underwent three imaging modalities: MRI, CT, and CT-3DTAUS. Volumes were delineated by a radiation oncologist and treatment plans were optimized on each imaging modality. To compare treatment plans, the dwell times optimized on MRI were transferred on CT and CT-3DTAUS images and dose parameters were reported on volumes of the receiving imaging modality. The plans optimized on CT and CT-3DTAUS were also copied and evaluated on MRI images.

RESULTS

Treatment plans optimized and evaluated on the same imaging modalities were clinically acceptable but statistically different (p < 0.05) from one another. MR-based plans had the highest target coverage (98%) and CT-based plans the lowest (93%). For all treatment plans evaluated on MRI, the target coverage was equivalent. However, a decrease in target coverage (V100) was observed when MR-based plans were applied on CT-3DTAUS (6%) and CT (13%) with p < 0.05. An increase in the rectum/sigmoid dose (D2cc) was observed with both CT-3DTAUS-based (0.6 Gy) and CT-based planning (1 Gy) when compared with MR-based plans, whereas bladder dose stayed similar.

CONCLUSIONS

When compared with CT-based planning, the addition of 3DTAUS to CT results in treatment plans closer to MR-based planning. Its use reduces the high-risk clinical target volume overestimation typically observed on CT, improving coverage of the target volume while reducing dose to the organs at risk.