Gynecologic Brachytherapy Research Articles

Multidisciplinary Consensus and Evaluation of Gynecological High-Dose-Rate (HDR) Brachytherapy

To improve the consistency and quality of gynecological HDR brachytherapy through multidisciplinary evaluation of implants and treatment plans.A quality assurance (QA) task force initiated in 2020 consisting of radiation oncologists, physicists, and radiation therapists reviewed applicator implant and treatment plan quality convened monthly for 48 gynecology patients undergoing high-dose-rate (HDR) brachytherapy. Each implant was scored based on the location and symmetry of applicators (tandem and ovoids/ring), interstitial needle location (if applicable), and packing quality as previously described (PMID: 22193645, 29705049). Treatment plans were evaluated based on contouring quality and dosimetry (target dose and OAR doses). Each quality measure was scored from 0 (inadequate) to 1 (excellent) to and a mean score for implant and treatment plan was calculated for each patient. The assigned scores represent a consensus among task force members who provided feedback according to their areas of expertise. Individual measures, implant types and mean scores were analyzed at the mid-year-mark.QA evaluation proved more beneficial for implant placement compared to treatment planning. Mean implant scores increased by 15% with significant improvements in needle positions (P = 0.02) and nonsignificant increases in packing scores (P = 0.09). In contrast, mean treatment plan scores remained unchanged throughout the year (P = 0.56). No differences were noted in the scores assigned for dosimetry, contouring, OAR doses or target doses after the mid-year mark.The QA initiative enabled the interprofessional team to share knowledge and resources to facilitate immediate mid-course changes in implant and planning strategy. The feedback generated encouraged members to alter practices and expand their understanding of treatment goals and limitations. Specific criteria for the scoring of individual quality measures should be developed to improve objectivity. The utility of HDR QA should be correlated with tumor control, recurrence, and OAR toxicity to bolster patient safety and treatment outcomes. QA sessions require quantifiable measures such as team member satisfaction and ongoing assessment due to the multidisciplinary nature of the process.C.Y. Mollings Puentes: Independent Contractor; UWorld. T. Banks: Develop/vet educational website content; AAPM.B.A. Hrycushko: None. X. Jia: None. C.R. Nwachukwu: Scientific Advisory board; Boston Scientific. K.V. Albuquerque: Research Grant; Astra Zeneca. Honoraria; ACR, ARRT. Travel Expenses; ACR, ARRT, ASCO.

Gynecologic Interstitial Brachytherapy Curriculum Using a Low-Cost Phantom With Ultrasound Workshop and a Treatment Planning Workshop is Feasible and Effective

<h3>Purpose/Objective(s)</h3> There is no standard simulation training geared towards interstitial brachytherapy (IS BT) for gynecologic malignancies. Most residents perform few IS cases during residency. However, IS BT is an integral part of care for locally advanced gynecologic malignancies. We developed and implemented a workshop curriculum for IS BT with: 1) lecture on equipment, workflow, and guidelines, 2) hands-on ultrasound-guided IS BT workshop, and 3) treatment planning workshop. <h3>Materials/Methods</h3> The cost of each gynecologic phantom was approximately $70; phantoms were composed of an acrylic vase cube, rigid PETG tubes, modeling clay, agar, glass microspheres, a custom molded cervix/uterus structure, and a water-filled condom to mimic the bladder. A hands-on ultrasound-guided IS BT workshop was performed with residents in two small groups, where they imaged the gynecologic phantom using a transabdominal ultrasound probe. Participants alternated roles of sonographer or brachytherapist, implanting the phantom using custom stainless-steel needles machined in-house. A second workshop with hands-on treatment planning was performed in planning software using a L-Q spreadsheet with the following objectives: coverage goal of D90, meeting D2cc constraints of bladder and rectum, and minimizing V200 to qualitatively involve a small volume. All residents filled out a pre- and post-survey with subjective (4 demographics; 12 Likert-style) and objective knowledge-based (13) questions about GYN IS-BT. Paired subjective data were compared with the Wilcoxon signed ranks test. Paired objective data were compared with the McNemar's test of paired proportions. All statistical analysis was performed with a 2-sided <i>P</i>-value at the 0.05 significance level. <h3>Results</h3> Four residents had prior IS BT experience. After the workshop, residents reported significantly improved comfort with skills and knowledge regarding GYN IS BT equipment and procedure, evaluating GYN anatomy using ultrasound, and CT Simulation, contouring, and plan review (median pre-session Likert score 2 [1-3] vs post session 3 [3-4], <i>P</i> < 0.05). The overall rate of percent correct items assessing objective radiation oncology knowledge at baseline was 44%, Following completion of the curriculum, the overall percent correct items was 88% (<i>P</i> < 0.0001). All residents "Agree" (2/7) and "Strongly Agree" (5/7) the session was an effective learning experience. Qualitative feedback primarily asked for more time with treatment planning and educational content beforehand. <h3>Conclusion</h3> Residents participating in phantom training with an ultrasound curriculum and a treatment planning session is both feasible and effective. Similar strategies should be considered to enhance and standardize radiation oncology education initiatives for gynecologic IS BT training.

An endovaginal MRI array with a forward-looking coil for advanced gynecological cancer brachytherapy procedures: Design and initial results.

To develop an endovaginal MRI array that provides signal enhancement forward into the posterior parametrium and sideways into the vaginal wall, accelerating multiple-contrast detection of residual tumors that survive external beam radiation. The array's enclosure should form an obturator for cervical cancer brachytherapy, allowing integration with MRI-guided catheter placement, CT, and interstitial radiation dose delivery. The endovaginal array consisted of forward-looking and sideways-looking components. The forward-looking element imaged the cervix and posterior endometrium, and the sideways-looking elements imaged the vaginal wall. Electromagnetic simulation was performed to optimize the geometry of a forward-looking coil placed on a conductive-metallic substrate, extending the forward penetration above the coil's tip. Thereafter, an endovaginal array with one forward-looking coil and four sideways-looking elements was constructed and tested at 1.5 Tesla in saline and gel phantoms, and three sexually mature swine. Each coil's tuning, matching, and decoupling were optimized theoretically, implemented with electronic circuits, and validated with network-analyzer measurements. The array enclosure emulates a conventional brachytherapy obturator, allowing use of the internal imaging array together with tandem coils and interstitial catheters, as well as use of the enclosure alone during CT and radiation delivery. To evaluate the receive magnetic field ( ) spatial profile, the endovaginal array's specific absorption-rate (SAR) distribution was simulated inside a gel ASTM phantom to determine extreme heating locations in advance of a heating test. Heating tests were then performed during high SAR imaging in a gel phantom at the predetermined locations, testing compliance with MRI safety standards. To assess array imaging performance, signal-to-noise-ratios (SNR) were calculated in a saline phantom and in vivo. Swine images were acquired with the endovaginal array combined with the scanner's body and spine arrays. Simulated profiles for the forward-looking lobe pattern, obtained while varying several geometric parameters, disclosed that a forward-looking coil placed on a metal-backed substrate could double the effective forward penetration from approximately 25 to ∼40mm. An endovaginal array, enclosed in an obturator enclosure was then constructed, with all coils tuned, matched, and decoupled. The ASTM gel-phantom SAR test showed that peak local SAR was 1.2 W/kg in the forward-looking coil and 0.3 W/kg in the sideways-looking elements, well within ASTM/FDA/IEC guidelines. A 15-min 4 W/kg average SAR imaging experiment resulted inless than2o C temperature increase, also within ASTM/FDA/IEC heating limits. In a saline phantom, the forward-looking coil and sideways-looking array's SNR was four to eight times, over a 20-30mm field-of-view (FOV), and five to eight times, over a 15-25mm FOV, relative to the spine array's SNR, respectively. In three sexually mature swine, the forward-looking coil provided a 5+0.2 SNR enhancement factor within the cervix and posterior endometrium, and the sideways-looking array provided a 4+0.2 SNR gain factor in the vaginal wall, relative to the Siemens spine array, demonstrating that the array could significantly reduce imaging time. Higher SNR gynecological imaging is supported by forward-looking and sideways-looking coils. A forward-looking endovaginal coil for cervix and parametrium imaging was built with optimized metal backing. Array placement within an obturator enhanced integration with the brachytherapy procedure and accelerated imaging for detecting postexternal-beam residual tumors.

80: Development and Design of Custom 3D Printed Cylindrical Templates for Interstitial Gynecological Brachytherapy

80: Development and Design of Custom 3D Printed Cylindrical Templates for Interstitial Gynecological Brachytherapy

Skin dose measurement and estimating the dosimetric effect of applicator misplacement in gynecological brachytherapy: A patient and phantom study.

To evaluate skin dose differences between TPS (treatment planning system) calculations and TLD (thermo-luminescent dosimeters) measurements along with the dosimetric effect of applicator misplacement for patients diagnosed with gynecological (GYN) cancers undergoing brachytherapy. The skin doses were measured using TLDs attached in different locations on patients' skin in pelvic regions (anterior, left, and right) for 20 patients, as well as on a phantom. In addition, the applicator surface dose was calculated with TLDs attached to the applicator. The measured doses were compared with TPS calculations to find TPS accuracy. For the phantom, different applicator shifts were applied to find the effect of applicator misplacement on the surface dose. The mean absolute dose differences between the TPS and TLDs results for anterior, left, and right points were 3.14±1.03, 6.25±1.88, and 6.20±1.97 %, respectively. The mean difference on the applicator surface was obtained 1.92±0.46 %. Applicator misplacements of 0.5, 2, and 4 cm (average of three locations) resulted in 9, 36, and 61%, dose errors respectively. The surface/skin differences between the calculations and measurements are higher in the left and right regions, which relate to the higher uncertainty of TPS dose calculation in these regions. Furthermore, applicator misplacements can result in high skin dose variations, therefore it can be an appropriate quality assurance method for future research.

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

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. 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. 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 ± 1.35mm, 1.84 ± 1.22mm, and 1.60 ± 1.00mm. Similarly, for the tandem-and-ovoids applicator, the mean ± SD TREs from the images with increasing thicknesses were 1.37 ± 0.35mm, 1.95 ± 0.90mm, and 1.61 ± 0.76mm. 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. 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.

Readability of a Radiotherapy Graphic Narrative Patient Education Guide Series in English and Spanish

Communicating the External Beam Radiotherapy Experience (CEBRE) and Communicating the Gynecologic Brachytherapy Experience (CoGBE) are novel graphic narrative patient education guides developed to facilitate doctor-patient communication during radiotherapy consultations.1 The guides were developed by designers and physicians with the goal of creating accessible, readable, and patient-centered tools for a range of disease sites and practice settings. Given the need for improved radiotherapy education resources for Spanish-speaking patients in the United States, we sought to develop versions of CEBRE and CoGBE in Spanish.

Knowledge-based dose prediction models to inform gynecologic brachytherapy needle supplementation for locally advanced cervical cancer

PURPOSEThe use of interstitial needles, combined with intracavitary applicators, enables customized dose distributions and is beneficial for complex cases, but increases procedure time. Overall, applicator selection is not standardized and depends on physician expertise and preference. The purpose of this study is to determine whether dose prediction models can guide needle supplementation decision-making for cervical cancer. MATERIALS AND METHODSIntracavitary knowledge-based models for organ-at-risk (OAR) dose estimation were trained and validated for tandem-and-ring/ovoids (T&R/T&O) implants. Models were applied to hybrid cases with 1–3 implanted needles to predict OAR dose without needles. As a reference, 70/67 hybrid T&R/T&O cases were replanned without needles, following a standardized procedure guided by dose predictions. If a replanned dose exceeded the dose objective, the case was categorized as requiring needles. Receiver operating characteristic (ROC) curves of needle classification accuracy were generated. Optimal classification thresholds were determined from the Youden Index. RESULTSNeedle supplementation reduced dose to OARs. However, 67%/39% of replans for T&R/T&O met all dose constraints without needles. The ROC for T&R/T&O models had an area-under-curve of 0.89/0.86, proving high classification accuracy. The optimal threshold of 99%/101% of the dose limit for T&R/T&O resulted in classification sensitivity and specificity of 78%/86% and 85%/78%. CONCLUSIONSNeedle supplementation reduced OAR dose for most cases but was not always required to meet standard dose objectives, particularly for T&R cases. Our knowledge-based dose prediction model accurately identified cases that could have met constraints without needle supplementation, suggesting that such models may be beneficial for applicator selection.

PD-0927 MRI-based deep learning auto-contouring for organs-at-risk in gynecological brachytherapy

PD-0927 MRI-based deep learning auto-contouring for organs-at-risk in gynecological brachytherapy

Abstract 105: Communicating the Gynecologic Brachytherapy Experience (CoGBE): Clinician Perceived Benefits of a Graphic Narrative Patient Education Tool

Abstract Purpose: Radiotherapy patient education materials fail to meet readability standards, impairing access for patients with low educational attainment, disabilities, or limited-English proficiency. Design professionals and physicians developed graphic narrative discussion guides, Communication of the Gynecologic Brachytherapy Experience (CoGBE), for cylinder, intracavitary, and interstitial high-dose rate (HDR) gynecologic brachytherapy. This study assesses perceived clinical benefits, usability, and anxiety-reduction of CoGBE. Methods: An electronic survey was sent to members of the American Brachytherapy Society. Participants were assigned to assess one of the three modality-specific CoGBE guides using a modified Systems Usability Scale (mSUS), modified state-trait anxiety index (mSTAI), and Likert-type questions. Free response data was analyzed using modified grounded theory. Results: Median mSUS score was 76.3 (interquartile range [IQR], 71.3-82.5) and there were no significant differences between guide types. Median mSTAI was 40 (IQR, 40-43.3) for all guides collectively. The cylinder guide had a significantly higher median mSTAI than the intracavitary and interstitial guides (41.6 vs 40.0 and 40.0; p=0.04) suggesting the cylinder guide may have less impact on reducing anxiety. 72.7% rated CoGBE as “quite” or “extremely” helpful compared to a text-only pamphlet. When compared to their current education practices, 77.3% reported patients would understand “more” or “a lot more” after initial consultation and 81.8% reported CoGBE would be at least moderately helpful in making initial consultations more memorable for patients. Lastly, 79.5% reported at least a moderate likelihood of using CoGBE. Qualitative analysis themes included personalization, relatability, and graphic narrative (positive domains); generalizability and character affect (negative domains). Conclusion: Clinicians rate CoGBE as usable with potential to reduce patient anxiety, especially with more invasive treatment modalities including intracavitary or interstitial HDR. The CoGBE guides (including multilingual versions) have global applicability, in low resource settings with high cervical cancer burdens and patient populations that may benefit from the graphic narrative format. Citation Format: Santiago Avila, María J. Ruiz, Ritu Arya, Brian Callender, Yasmin Hasan, Josephine S. Kim, Nita Lee, Anne McCall, Christina H. Son, Kate Stack, Sabah Asif, Tyler Besecker, Arushi Juneja, Zhongyang Li, Pinakee Naik, Tanvi Ranka, Prachi Saxena, Brian Siegfried, Tomoko Ichikawa, Daniel W. Golden. Communicating the Gynecologic Brachytherapy Experience (CoGBE): Clinician Perceived Benefits of a Graphic Narrative Patient Education Tool [abstract]. In: Proceedings of the 9th Annual Symposium on Global Cancer Research; Global Cancer Research and Control: Looking Back and Charting a Path Forward; 2021 Mar 10-11. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2021;30(7 Suppl):Abstract nr 105.

Design and evaluation of 3D printable patient-specific applicators for gynecologic HDR brachytherapy.

The purpose of this study is to improve dose distribution and organ-at-risk sparing during gynecologic HDR brachytherapy with patient-specific applicators. The majority of applicators used today are generic in design and do not allow for dose modulation for patient-specific shaping of dose distributions. Their performance might be adjusted with commercially available wedge shields; however, this provides dose modulation in the orthogonal plane only and does not allow for variation along the length of the applicator. Generic applicators are available only in standard sizes and geometries, and provide suboptimal patient fit with limited dose modulation. In this paper we use Monte Carlo modeling for comprehensive characterization of radiologic properties of various 3D printable biocompatible and sterilizable materials with comparison to water. Based on these results, we choose the optimal set of materials for a patient-specific applicator. We develop a novel method to design the patient-specific applicator without incurring a significant increase in treatment time or changes to clinical workflow. Finally, using an example of two selected vaginal cancers, we compare the performance of patient-specific and water-equivalent applicators in terms of target coverage and rectum sparing. In the energy range from 1MeV to 4MeV, all materials have similar attenuation coefficients. In the range from ~2keV to 1MeV and above 4MeV, tungsten-polylactic acid composite (WPLA) was seen to have the highest attenuation coefficient. The dose distribution of the water-equivalent applicator was found to be symmetric about its central axis. At the same time patient-specific shielded applicators exhibit well-modulated dose distributions. Their isodose lines are seen to spread radially into the patient, while merging close to the applicator surface, where WPLA shielding has been applied. The patient-specific cylinders provide comparable dose to the target, while offering advanced healthy tissue sparing, not achievable with the generic design.

PHSOR09 Presentation Time: 10:40 AM: Implementation of MRI-Only Treatment Planning (MRTP) for Gynecologic HDR Brachytherapy Using PETRA Sequence

Purpose: Current protocol in interstitial HDR brachytherapy requires CT imaging post MRI-guided needle/applicator insertion to visualize and localize needles for treatment planning. MRI is routinely acquired for segmentation of both the clinical target volumes (CTV) and the organs at risk (OARs), following CT-MRI registration. The purpose of this study is to develop and implement an MRI-only treatment planning (MRTP) approach that can potentially improve the clinical treatment planning process for interstitial HDR brachytherapy.

PHSOR09 Presentation Time: 10:40 AM: Implementation of MRI-Only Treatment Planning (MRTP) for Gynecologic HDR Brachytherapy Using PETRA Sequence

PHSOR09 Presentation Time: 10:40 AM: Implementation of MRI-Only Treatment Planning (MRTP) for Gynecologic HDR Brachytherapy Using PETRA Sequence

PP26 Presentation Time: 11:00 AM: New Gynecologic Brachytherapy Interstitial Template Enabling a Shorter and More Direct Needle Path While Preserving Tumor Visualization

Purpose: Existing interstitial brachytherapy approaches rely on attaching the interstitial template to the perineum and have needles traverse a long distance of normal tissue to reach the tumor. In clinical practice, we frequently found that tumors requiring interstitial brachytherapy are relatively easily visualized with vaginal speculum exam, but classical interstitial templates hinder this direct visualization when sutured in place and force the user to insert needles far from the target tumor.

PP26 Presentation Time: 11:00 AM: New Gynecologic Brachytherapy Interstitial Template Enabling a Shorter and More Direct Needle Path While Preserving Tumor Visualization

PP26 Presentation Time: 11:00 AM: New Gynecologic Brachytherapy Interstitial Template Enabling a Shorter and More Direct Needle Path While Preserving Tumor Visualization

Plenary Session Thursday, June 24, 2021 1:15 PM - 2:15 PM PLEN01 Presentation Time: 1:15 PM: Virtual Reality-Based Simulation Improves Gynecologic Brachytherapy Proficiency, Engagement, and Trainee Self-Confidence

Plenary Session Thursday, June 24, 2021 1:15 PM - 2:15 PM PLEN01 Presentation Time: 1:15 PM: Virtual Reality-Based Simulation Improves Gynecologic Brachytherapy Proficiency, Engagement, and Trainee Self-Confidence

PLEN01 Presentation Time: 1:15 PM: Virtual Reality-Based Simulation Improves Gynecologic Brachytherapy Proficiency, Engagement, and Trainee Self-Confidence

Purpose: Brachytherapy is an integral component in treatment of gynecologic malignancies. Intracavitary brachytherapy has the highest rates of local control and survival in cervical cancer. Classical brachytherapy training requires 1-on-1 instruction during patient encounters. This training is resource intensive and variable based on the type/frequency of the procedures performed by the attending physician/facility. Consequently, exposure to brachytherapy varies among residency programs. Even with Accreditation Council for Graduate Medical Education mandated requirements, only about 50% of graduating residents express confidence to develop a brachytherapy practice with caseload as the greatest barrier. The use of simulation-based education has been shown to increase confidence, applicator placement quality, and decrease implant time and errors.

Patient-controlled epidural analgesia, patient-controlled intravenous analgesia, and conventional intravenous opioids for gynecologic interstitial brachytherapy: A single-center retrospective study

PURPOSE Interstitial brachytherapy for gynecologic malignancies is stressful physically and mentally; however, optimal analgesic methods remain unclear. We investigated the effect of analgesic methods on pain and adverse events during interstitial brachytherapy for gynecologic malignancies.METHODS The data of 73 patients who underwent interstitial brachytherapy for gynecologic malignancies between April 2015 and March 2020 were retrospectively analyzed. Patient-controlled epidural analgesia (PCEA), patient-controlled intravenous analgesia (PCIA), and conventional intravenous opioid administration were used for analgesia during treatment. We compared the analgesic effects based on a numerical rating scale (NRS), the number of additional analgesics, and the adverse events associated with analgesia. The NRS score was calculated as an average value for every 12 h (NRS1: treatment on the 1st day from 12 to 24 o'clock; NRS2: treatment on the 2nd day from 0 to 12 o'clock; NRS3: treatment on the 2nd day from 12 to 24 o'clock). The mean NRS score differences between the methods were evaluated using mixed models for repeated-measures analyses.RESULTS The NRS score was significantly lower at all times for PCEA (NRS1: p = 0.003; NRS2: p = 0.011; NRS3: p < 0.001). NRS2 and NRS3 were significantly lower for PCIA (NRS2: p = 0.043; NRS3: p < 0.001) than for the conventional method. The NRS scores for PCEA and PCIA were not significantly different. Moreover, additional analgesics and adverse events did not differ between the three treatments.CONCLUSION PCEA and PCIA were superior to conventional intravenous opioids for analgesia in interstitial brachytherapy for gynecologic malignancies. However, adverse events associated with PCEA and PCIA were not reduced.

Verification of Guiding Needle Placement by Registered Ultrasound Image During Combined Intracavitary/Interstitial Gynecologic Brachytherapy.

PurposeOur previous research demonstrated that under ideal conditions, rigid registration between MRI images and US images had high accuracy for real-time image guidance. The work presented in this paper focused on the application of the previously established procedures to a new context, including preoperative CT images.Materials and MethodsWe used a template to calibrate the US probe and completed the registration between preoperative CT images and US images. Marker experiments on the accuracy of real-time needle trajectories in CT images were performed using micro electromagnetic sensors. Pelvic phantom experiments were carried out to test the registration accuracy between CT and US images, in addition to registration accuracy between US images and real-time needle trajectories (real-time space model).ResultsThe US probe calibration error in CT images was 0.879 ± 0.149 mm. The difference of registration between US images and CT images was 0.935 ± 0.166 mm in the axial plane (n = 30) and 0.916 ± 0.143 mm in the sagittal plane (n =12). The difference of registration between US images and the needle’s real-time trajectories was 0.951 ± 0.202 mm.ConclusionUnder ideal conditions, rigid registration between CT images and US images had high accuracy for real-time image guidance.

Complications of intracavitary brachytherapy for gynecologic cancers and their management: A comprehensive review

Intracavitary gynecologic brachytherapy in the form of tandem-based brachytherapy and vaginal cylinder–based brachytherapy represents a fundamental component of the treatment of women with cervical or uterine cancer due to the ability to deliver a therapeutic dose of radiation with sharp dose falloff. This results in highly effective treatment in terms of oncologic outcomes with an overall favorable toxicity profile. Still, complications and side effects of brachytherapy do exist. While advances in brachytherapy techniques have led to a significant decrease in the rates of toxicity, a thorough understanding of the potential complications is crucial to ensuring optimal outcomes for women with gynecologic cancer undergoing brachytherapy. Use of equivalent dose at 2 Gy per fraction (EQD2) models has allowed incorporation of external beam radiotherapy dose to the brachytherapy dose leading to development of consolidated dose constraints for organs-at-risk in the modern era. This manuscript offers a comprehensive review of potential complications associated with intracavitary brachytherapy for gynecologic cancer including predictive factors, mitigation tactics, and management strategies.