Interstitial Gynecologic Brachytherapy Research Articles

Design approach and benefits of the 3D-printed vaginal individualized applicator (VIA)

PURPOSEInterstitial gynecologic brachytherapy necessitates precise needle placement, requiring time and expertise. We aimed to simplify interstitial procedures and facilitate optimal needle distribution with individualized vaginal templates to guide interstitial needles. MATERIALS/METHODSWe developed the 3D-printed vaginal individualized applicator (VIA), a cylindrical template containing individualized internal channels that guide interstitial needles to cover the tumor extent. Eight patients underwent VIA only interstitial implants (VIA only), and five intact cervical cases were treated using tandem and customized VIA (VIA + T). Procedure length, number of needles utilized and dosimetric measures were evaluated. RESULTSVIA was successfully designed and used clinically for 24 procedures (8 VIA only, 16 VIA + T). Average procedure needle insertion time reduced from 80.9 min for traditional interstitial to 42.9 min for VIA only, approximately 47% shorter with a similar mean high risk CTV volume (28.3 cc VIA only vs. 32.4 cc) and excellent dosimetry with average CTV V100% (94.3% and 94.4%). VIA + T was particularly useful in patients with small vaginal canals and large tumor size. For the five VIA + T patients average tumor size was 68.0cc (range 26.6–143.5 cc). VIA + T procedures were approximately 20% shorter than hybrid procedures with other applicators with mean length of 20.1 min and an average of 6.8 needles (range 3–12). CONCLUSIONOur novel 3D-printed VIA facilitates gynecologic interstitial brachytherapy by simplifying needle placement, reducing procedure time, and maintaining excellent dosimetry. VIA can be customized for various clinical scenarios, particularly beneficial for large tumors or small vaginal canals.

Development and clinical implementation of simple needle attachment post placement interstitial template (SNAPP-IT) enabling a shorter, more direct needle path while preserving tumor visualization

Purpose: Historical gynecologic interstitial brachytherapy templates block direct tumor visualization during needle placement, presenting an opportunity for clinical innovation to develop a novel interstitial template allowing direct tumor visualization during needle insertion. Methods: We designed and implemented a novel interstitial template, Simple Needle Attachment Post Placement Interstitial Template (SNAPP-IT), that allowed direct visualization of the target vaginal tumor during interstitial needle placement while maintaining the ability to individually secure needles to the template, allow a vaginal cylinder, suture holes for securing to the perineum, MRI compatibility and sterilizable for repeat use. Procedure outcomes including procedure time, needle path lengths, and plan dosimetry were prospectively captured in a patient database. Results: Forty gynecologic interstitial brachytherapy cases were recorded (20 SNAPP-IT, 20 traditional templates). Needle insertion depth was reduced using the SNAPP-IT in comparison with traditional interstitial templates (11.8cm vs 3.6cm, p<0.0001). The average CTV volume was 25.6 cc for SNAPP-IT and 20.7 cc for traditional; both methods averaged a similar number of needles (15.8, 15.6). Dosimetric constraints were similarly met in both treatment groups. Procedures performed using the SNAPP-IT were shorter compared with those performed with traditional interstitial devices (83.4 minutes vs 100.7 minutes) and there were no post-operative infections in the SNAPP-IT group. Conclusion: Implementation of a novel gynecologic interstitial brachytherapy template (SNAPP-IT) reduced procedure times, allowed direct tumor visualization, and decreased needle insertion depth. SNAPP-IT provides a useful alternative approach for vaginal interstitial brachytherapy, may increase brachytherapist efficiency with complex procedures and potentially expands access to interstitial brachytherapy.

Accuracy of an electromagnetic tracking enabled afterloader based on the automated registration with CT phantom images.

Electromagnetic tracking (EMT) has been researched for brachytherapy applications, showing a great potential for automating implant reconstruction, and overcoming image-based limitations such as contrast and spatial resolution. One of the challenges of this technology is that it does not intrinsically share the same reference frame as the patient's medical imaging. To present a novel phantom that can be used for a comprehensive quality assurance (QA) program of brachytherapy EMT systems and use this phantom to validate a novel applicator-based registration method of EMT and image reference frames for gynecological (GYN) interstitial brachytherapy. Eleven 6F-catheters (20cm long), one 6F round tip catheter (29.4cm long) and a tandem and ring gynecological applicator (Elekta, CT/MR 60°, 40mm long tandem, 30mm diameter ring) were placed in a rigid custom-made phantom (Elekta Brachytherapy, Veenendaal, The Netherlands) to reconstruct their geometry using a five-degree of freedom EMT sensor attached to an afterloader's check cable. All EMT reconstructions were done in three different environments: disturbance free (no metal nearby), computed tomography (CT)-on-rails brachytherapy suite and magnetic resonance imaging (MRI) brachytherapy suite. Implants were placed parallel to a magnetic field generatorand were reconstructed using two different acquisition methods: step-and-record and continuous motion. In all cases, the acquisition is performed at a rate of approximately 40Hz. A CT scan of the phantom inside a water cube was obtained. In the treatment planning system (TPS), all catheters in the CT images were manually reconstructed and the applicator reconstruction was achieved by manually placing its solid 3D model, found in the applicator library of the TPS. The Iterative Closest Point and the Coherent Point Drift algorithms were used, initialized with four known points, to register both EMT and CT scan reference frames using corresponding points from the EMT and CT based reconstructions of the phantom, following three approaches: one gynecological applicator, four interstitial catheters inside four calibration plates having an S-shaped path, and four 5mm diameter ceramic marbles found in each of the four calibration plates. Once registered, the registration error (perpendicular distance) was computed. The absolute median deviation from the expected value for EMT measurements in the disturbance free environment, CT-on-rails brachytherapy suite, and MRI-brachytherapy suite are 0.41, 0.23, and 0.31mm, respectively, while for the CT scan it is 0.18mm. These values significantly lie below the sensor's expected accuracy of 0.70mm (p<0.001), suggesting that the environment did not have a significant impact on the measurements, given that care is taken in the immediate surroundings. In all three environments, the two acquisitions and three registration approaches have mean and median registration errors that lie at or below 1mm, which is lower than the clinical acceptable threshold of 2mm. The novel phantom allowed to successfully evaluate the accuracy of EMT-based reconstructions of catheters and a GYN tandem and ring applicator in different clinical environments. A registration method based only on the applicator geometry, reconstructed withan EMT sensor and the TPS solid applicator library, was validated and shows clinically acceptable accuracy, comparable to CT-based reconstruction but within a few minutes. Since the applicator is also visible in MRI, this method could potentially be used in clinics in an EMT-MR interstitial GYN brachytherapy workflow.

Can Volume-Based MRI-Guided Planning for Interstitial Gynecologic Brachytherapy Overcome Clinicopathologic Risk Factors for Fistula Formation?

Tumor and patient factors requiring an interstitial (IS) approach for gynecologic tract brachytherapy (BT) may be associated with high morbidity despite the conformality maximizing effect of ISBT. We reviewed outcomes from a diverse, high-volume center to evaluate the association of clinical features and planning parameters with toxicity, with the hypothesis that MRI-guided volume-based planning mitigates clinicopathologic risk factors associated with treatment related fistula (TRF) after ISBT. We retrospectively reviewed patients treated with Syed-based ISBT at a single institution from 2014-2019. Fisher's exact was used for group comparison with p<0.05. Kaplan-Meier method was used to estimate local control (LC), overall survival (OS), and fistula-free survival (FFS). Cox regression was used for univariate (UVA) and multivariate analysis (MVA) to estimate hazard ratios (HR). Collinearity was assessed using variable inflation factor and Pearson's correlation. A total of 54 patients (median age 58 [IQR 46-67], 54% Caucasian, 39% African American, 15% Hispanic) treated with ISBT (89% MRI-guided) with median follow-up 32 months had initial (89%) or recurrent (11%) disease from cervical (70%), vaginal (15%), urethral (6%), and other cancers. At presentation 5.5% had clinically evident fistula. There was radiographic rectal and bladder involvement in 22.0% and 19.2%, respectively. 89% received concurrent chemotherapy and 98% received EBRT prior to ISBT with a cumulative median high-risk CTV (HRCTV) dose 80.8 Gy (IQR 76.8-84.3), bladder D2cc 84.3 Gy (IQR 75.8-89.0), and rectal D2cc 73.8 Gy (IQR 67.7-80.0 Gy). All 7 patients who developed a TRF (rectovaginal in 6/7 and vesicovaginal in 5/7) were former or current smokers, had primary cervical cancer, and received chemotherapy. Management included surgical intervention in 6 (85.7%). LC, OS, and FFS at 2-years was 89.3% (95% CI 75.9-95.4%), 87.8% (95% CI 66.9-89.8%), and 85.2% (95% CI 69.9-93.1%), respectively. On UVA, current smoking (HR 4.60, 95% CI 1.02-20.74), BT bladder D2cc (HR 1.63, 95% CI 1.07-2.47) and BT rectal Dmax (HR 1.30, 95% CI 1.07-1.58) predicted for increased risk of TRF. Most factors were non-significant including Charlson Comorbidity Index, age, BMI, surgical history, extent of vaginal involvement, race, HRCTV volume and number of needles used. No patients with radiographic bladder or rectal invasion developed TRF. On MVA, only smoking status (HR 14.05, 95% CI 1.48-133.1) remained significant. 0% of never (0/26), 20% of former (3/15) and 31% of current (4/13) smokers developed fistulas from toxicities (p<0.05). In patients with locally advanced cancers of the gynecologic tract treated with MRI-guided volume-based ISBT, smoking was the only factor predictive of TRF formation, occurring primarily in cervical cancer patients. This highlights the importance of smoking cessation during treatment and appropriately counseling patients at high risk for this morbidity.

Real-Time Precision Needle Tracking for Gynecological Interstitial Brachytherapy: A Phantom Feasibility Study

To determine if an advanced needle navigation and real-time precision tracking system developed for prostate biopsies can be used for the purpose of real-time guidance of interstitial needles in modern image-guided gynecologic brachytherapy. An agarose gel pelvic phantom was previously designed using 3D Slicer and Autodesk Fusion360 to model an average uterus from a 50-patient dataset, a vaginal canal from KleenSpec (TM, Welch Allyn) speculum dimensions, and a rectum to accommodate a BK 8848 endocavity biplane ultrasound [US] probe. After manufacturing the phantom with a 7.2cm x 3.7cm x 4.4cm (LxWxH) uterus and an attached 2.7cm x 1.4cmx 1.7cm (LxWxH) focal HR-CTV target, the model was imaged using MRI. The uterus and HR-CTV were contoured on MRI to aid in registration with US and provide a target for needle placement. The tracking system with endorectal probe was then used to image the phantom. Ultrasound images from a 180-degree sweep were acquired and a 3D Ultrasound-based volume was generated. Using the commercially available system, the MRI was imported and an MRI-Ultrasound fusion performed based on the uterus contours and then refined using contour-based deformable registration. Three desired locations for needle placement were defined to test the ability of the system to guide needles at these locations: one in the most lateral aspect of the HRCTV, one at the HRCTV-uterus interface, and one inside the uterus. The needle tracking sleeve that was indexed to the probe was used in conjunction with the software interface to guide the 17-gauge titanium needle placement in real time. The distance between actual needle and the intended needle location was measured for each successful needle placement. When possible, needles were removed and reinserted at the same desired location to test the reproducibility of insertion under US guidance. Two of the three intended needles were successfully placed using real-time US guidance. The most lateral needle in the HRCTV was not inserted due to limitations of the phantom design, specifically inaccessibility to the agarose phantom through the phantom wall supports. The inserted needles were visible and tracked to the desired location within 0.6 mm (needle located at HRCTV-uterus interface), and 2.2 mm (needles inserted centrally in the uterus). For the target within the uterus, needles were reinserted at the same target of interest with a ∆ 0.15mm in greatest range between attempts. We have demonstrated a proof of concept in which existing technology for prostate biopsies can be utilized for the application of interstitial gynecologic brachytherapy with a high degree of fidelity. Ongoing modifications to our validation phantom and the tracking system are needed to allow for variations in uterine anatomy, more rigorous evaluation of reproducibility, and multi-catheter placement.

188 Development and Evaluation of a GUI Using AI-Assisted Algorithm for Catheter Reconstruction in MR-Only Gynecological Interstitial HDR Brachytherapy

188 Development and Evaluation of a GUI Using AI-Assisted Algorithm for Catheter Reconstruction in MR-Only Gynecological Interstitial HDR Brachytherapy

GSOR03 Presentation Time: 12:10 PM: The Impact of MRI-tracking Technology on Procedural Time for Patients Undergoing Perineal Template-Based Interstitial Gynecologic Brachytherapy Implants

GSOR03 Presentation Time: 12:10 PM: The Impact of MRI-tracking Technology on Procedural Time for Patients Undergoing Perineal Template-Based Interstitial Gynecologic Brachytherapy Implants

PP03 Presentation Time: 10:18 AM: 3D-Printed Vaginal Individualized Applicator (VIA) Simplifies Needle Insertion, Guides Needle Distribution, Facilitates Procedure Efficiency and Optimizes Dosimetry for Gynecologic Interstitial Brachytherapy

PP03 Presentation Time: 10:18 AM: 3D-Printed Vaginal Individualized Applicator (VIA) Simplifies Needle Insertion, Guides Needle Distribution, Facilitates Procedure Efficiency and Optimizes Dosimetry for Gynecologic Interstitial Brachytherapy

GPP10 Presentation Time: 10:10 AM: Using 3D Printed Vaginal Individualized Applicator (VIA) to Simplify Needle Insertion, Guide Needle Distribution and Optimize Dosimetry for Gynecologic Interstitial and Cervix Hybrid Brachytherapy

<h3>Purpose</h3> Optimally placing interstitial needles either as part of hybrid procedures for the treatment of cervical cancer or for interstitial only gynecologic brachytherapy requires time and expertise. Individualized templates to guide needles to dosimetrically beneficial positions could simplify interstitial and hybrid procedures, decrease procedure time, improve needle distribution and optimize dosimetry. <h3>Materials and Methods</h3> We developed a novel approach using 3D printed Vaginal Individualized Applicator (VIA) templates that contain internal channels that guide interstitial needles from the vaginal introitus to the desired locations within the tumor. The use of 3D printing allows for curved and angled needle trajectories allowing needle distribution to be individualized based on patient and tumor anatomy, such as having a narrow vaginal applicator with needle paths to cover a much wider tumor diameter. The channel directions and needle depths are based on a pre-planning approach. Following a pre-procedure MRI, CTV contours are drawn and converted to a Computer Aided Design (CAD) format. Within the 3D design software, a simple 25 mm diameter cylinder is used to start. Needle paths are manually designed to cover the target following a set of basic rules, which include needle spacing and bending angles. The cylinder with curved needle paths is intended to be slid over the tandem after insertion, or used on its own with a needle in the central location (Figure 1A). The resulting design is 3D printed with biocompatible materials and sterilized pre-procedure. Depending on the printing options (in-house printer or external vendor), the process takes from one week to 24 hours, thereby enabling fraction-to-fraction modifications. <h3>Results</h3> We have created and used clinically 3D printed VIA templates for both hybrid cervix brachytherapy for patients with narrow vaginal canals and for interstitial only gynecologic brachytherapy. The VIA design allows for dwell times within the needles and also within the cylinder component. By allowing the placement of needles from the vaginal introitus, the VIA increases the ease and simultaneously decreases the complexity of optimally placing interstitial needles within the region of the tumor. This design approach also allows additional needles to be placed through available potential channels, if found to be needed, following 3D imaging with CT or MRI, without removing any of the applicator (Figure 1B). For hybrid procedures (n=7), use of the VIA decreased procedure time by 45% (from 33.1 to 18.3 minutes) and improved or maintained excellent dosimetry with an average CTV V100% of 93.4% vs. 90.9% for other hybrid applicators. Similarly, in using the VIA for interstitial-only cases (n=1), we found that needle placement was reduced by 30 minutes or 33% quicker than standard interstitial procedures with similar dosimetry (CTV V100% 95.4 % for VIA vs. 93.4%). <h3>Conclusions</h3> Our team developed a novel 3D printed VIA template that significantly facilitates gynecologic interstitial and cervix hybrid brachytherapy by simplifying the placement of needles, decreasing procedure time and optimizing dosimetry. The clinical data above demonstrates the benefits of this approach for patients with narrow vaginal canals that do not accommodate commercial hybrid applicators. The VIA can easily be designed to facilitate interstitial gynecologic brachytherapy for multiple clinical situations.

PO36 Presentation Time: 10:30 AM: Rates of Toxicity Associated with Bowel or Bladder Needle Intrusion During Gynecologic Interstitial Brachytherapy: An Institutional Series

<h3>Purpose</h3> Interstitial brachytherapy (ISBT) is an important treatment technique in the treatment of gynecologic cancers. However, there are concerns about potential complications from needle intrusion of visceral organs. The purpose of this study is to evaluate the rates of acute and late complications from needle intrusion of the bladder or bowel. <h3>Materials and Methods</h3> Records from thirteen patients with gynecological cancers treated with ISBT at a single institution from July 2020 to April 2022 were reviewed. Post-procedure CT images were reviewed to identify cases that had radiographic evidence of bladder or bowel needle intrusion. Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 was used to grade complications/toxicities. <h3>Results</h3> Median follow-up was 7.6 months; the crude local control rate was 92%. One patient (8%) had local recurrence, one patient (8%) had regional recurrence, and two patients (15%) had distant recurrences. In total, four patients (31%) had radiographic evidence of needle intrusion(s). Three patients (23%) had evidence of needle intrusion into the bowel and one patient (8%) had evidence of needle intrusions into both the bladder and bowel. Radioactive source dwell times were minimized in these areas. A total of one toxicity (8%) from needle intrusion was noted: acute grade one hematuria in the patient with bladder needle intrusion. There were no grade ≥2 acute or late toxicities from needle intrusion(s) found. One patient developed a vesicovaginal fistula from disease recurrence; there was no bladder needle intrusion in this patient. One patient developed a colovaginal fistula from disease recurrence; there was bowel needle intrusion in this patient. <h3>Conclusions</h3> ISBT is an effective treatment for gynecologic cancers. Despite occasional radiographic evidence of bladder/bowel needle intrusion, the rates of organ complications are low; disease recurrence represents the major cause of morbidity. These data suggest that needle intrusion of visceral organs in the absence of radioactive source loading is associated with a low risk of morbidity; this is in accordance with the existing literature.

Saturday, June 18, 20227:40 AM - 5:00 PMPO22 Presentation Time: 7:40 AM: A Novel Algorithm for Automatic Interstitial Needle Tracking on PETRA MRI for HDR Brachytherapy

<h3>Purpose</h3> Current practice for interstitial high-dose-rate (HDR) brachytherapy treatment planning involves manual tracking of needle positions on CT images. Recently, PETRA MRI showed the potential to detect empty interstitial gynecological brachytherapy needles owing to low needle signal, intermediate tissue contrast and high spatial resolution. We aimed to develop an algorithm for automatic interstitial needle tracking on PETRA images by employing their negative contrast against surrounding tissue. <h3>Materials and Methods</h3> Fourteen ProGuide Sharp Needles 6Fx294mm were implanted in an endometrial adenocarcinoma patient using a Syed-Neblett template. One of the needles lay in the obturator center, and six inside the obturator slots. The patient underwent standard CT imaging with copper-filled needles. After marker removal, 3D PETRA images of the patient's pelvis (TR\TE 3.32\0.07 ms, voxel size 0.9 mm³ isotropic, 416 slices) were acquired on a 3T Siemens Vida MR scanner. PETRA MR images were analyzed for interstitial needle detection using custom code in MATLAB R2022a. A rectangular part of all axial slices where needles may be contained (slices 149-310) was selected. For each slice part, corner points were extracted from the original part and from its sharpened gradient magnitude image by detecting Harris features. Points found within Euclidean distance (ED) of 3 pixels on both images were matched, and the pixel with minimum signal intensity closest to each such point on the original part was selected. Minimum intensity points lying within 2 pixels ED between subsequent slices were considered as possible catheter coordinates. Such points appearing on at least 10 continuous slices were designated as true catheters, and their positions were compared to those visible on CT. <h3>Results</h3> Figure 1a) displays the selected MR image parts for two example slices. Pixels with detected Harris features and their closest signal minima are marked by red and green crosses, respectively, in b). Pixels accepted as needle positions are shown as magenta crosses in c). Matching CT image parts with bright marker-filled needles are displayed in d). Empty interstitial catheters on PETRA images corresponded to local minima of signal intensity, located near Harris features. The assumption of needle position continuity within an allowed distance along subsequent slices helped avoid spurious signal minima, while following needle position variations caused by different deflection angles. Needles guided through the obturator grooves and the central needle were detected only after they became detached from the obturator (ex. figure left). All 14 needles were tracked along their visible length inside tissue (ex. figure right). Visual comparison to CT images confirmed interstitial catheter detection on MRI. Selecting a range of slices and zooming on a part of each slice for analysis reduced computational time and output data size. <h3>Conclusions</h3> Automated detection of interstitial needles is feasible on PETRA MR images and may facilitate MR-only treatment planning in interstitial HDR brachytherapy. The newly developed algorithm was able to track all needles inside tissue based on their signal intensity characteristics, without requiring manual seed position placement.

GPP07 Presentation Time: 9:40 AM: Investigating the Efficacy of Simulation-Based Education for Interstitial Gynecologic Brachytherapy Using a Novel US/MR/CT-Compatible Gynecologic Phantom

<h3>Purpose</h3> Brachytherapy is an essential component of curative treatment for cervical cancer. Simulation-based education using models is an effective method for teaching intracavitary (IC) brachytherapy skills. While the use of interstitial (including hybrid) applications is increasing among physicians, simulation training for gynecologic interstitial brachytherapy has been unsatisfactory. This is in part due to the limitations of current simulation models, including unsuitable material for needle placement and incompatibility with ultrasound (US), CT and/or MRI imaging. We present here the results from a simulation-based hybrid brachytherapy workshop held in March 2022, in which we seek to validate a novel, commercially available US/CT/MRI-compatible gynecologic phantom for its use in gynecologic brachytherapy training. <h3>Materials and Methods</h3> The SIM (Simulated Inanimate Models, Pittsford, NY) gynecological trainer phantom modeled a uterus, cervix, and vaginal canal within a block of tissue-like colloid material. The model also contained a gel-filled bladder and air-filled rectum. The phantom was US, CT, and MRI-compatible with realistic visualization of the pelvic organs, pubic bones, and sacral bones on imaging due to variable physical and hydrogen densities. We CT simulated the phantom with a tandem-and-ovoid applicator with 20 mm ovoids and a 30-degree curved tandem in place. We segmented the bladder and rectum and created a cervical HR-CTV with dimensions of 35 × 35 × 40 mm³. We then simulated the model again with 2 free-hand interstitial needles alongside the tandem-and-ovoids to improve geographic coverage of the HR-CTV. We designed a workshop incorporating the phantom and simulated datasets, during which trainees performed the following elements: 1- IC placement; 2- review of the IC-alone optimized plan treatment planning system; 3- schematic mapping on 3D diagrams of the HR-CTV in axial, coronal, and sagittal orientations; 4- pre-planning of location and depth of desired interstitial needles; 5- interstitial needle labeling and placement; 6- evaluation and modification of needle placement with imaging; 7- plan review and DVH comparison of HR-CTC coverage and organ-at-risk limits with and without the supplemental needles. Pre- and post-workshop surveys with Likert-style questions were administered. A Wilcoxon matched-pairs signed-rank test was used to assess statistical differences between pre- and post-workshop responses. <h3>Results</h3> Thirteen residents (PGY 2-5) participated in the workshops over the course of 3 separate 1-hour sessions. Seven residents reported performing 2 or more intracavitary procedures, and 6 reported performing 2 or more interstitial gynecologic procedures prior to workshop participation. All eligible residents completed each component of the workshop. Responses to questions ascertaining knowledge, preparedness, comfort, confidence, and ability in planning and executing IC and hybrid interstitial brachytherapy procedures all demonstrated significant improvement from pre- to post-workshop (Figure 1). In response to whether the session was an effective learning experience, all 13 residents rated the workshop with a score of 9 (n=1) or 10 (n=12) out of 10, with a score of 10 indicating ‘strongly agree.' Suggested improvements to the model included increasing dimensions of the vagina, angling of the cervix/uterus, and adding a visible/palpable tumor. <h3>Conclusions</h3> The novel gynecologic phantom simulates live tissue, permits needle placement, is US/CT/MR-compatible, and is commercially available. The improvements seen in trainee knowledge, skills, and confidence validate the novel gynecologic phantom for interstitial brachytherapy skills training. Based on responses from the workshop, improvements to the model are currently in progress, with modified model expected by the ABS annual meeting.

Deep-learning-assisted algorithm for catheter reconstruction during MR-only gynecological interstitial brachytherapy.

Magnetic resonance imaging (MRI) offers excellent soft‐tissue contrast enabling the contouring of targets and organs at risk during gynecological interstitial brachytherapy procedure. Despite its advantage, one of the main obstacles preventing a transition to an MRI‐only workflow is that implanted plastic catheters are not reliably visualized on MR images. This study aims to evaluate the feasibility of a deep‐learning‐based algorithm for semiautomatic reconstruction of interstitial catheters during an MR‐only workflow. MR images of 20 gynecological patients were used in this study. Note that 360 catheters were reconstructed using T1‐ and T2‐weighted images by five experienced brachytherapy planners. The mean of the five reconstructed paths were used for training (257 catheters), validation (15 catheters), and testing/evaluation (88 catheters). To automatically identify and localize the catheters, a two‐dimensional (2D) U‐net algorithm was used to find their approximate location in each image slice. Once localized, thresholding was applied to those regions to find the extrema, as catheters appear as bright and dark regions in T1‐ and T2‐weighted images, respectively. The localized dwell positions of the proposed algorithm were compared to the ground truth reconstruction. Reconstruction time was also evaluated. A total of 34 009 catheter dwell positions were evaluated between the algorithm and all planners to estimate the reconstruction variability. The average variation was 0.97 ± 0.66 mm. The average reconstruction time for this approach was 11 ± 1 min, compared with 46 ± 10 min for the expert planners. This study suggests that the proposed deep learning, MR‐based framework has potential to replace the conventional manual catheter reconstruction. The adoption of this approach in the brachytherapy workflow is expected to improve treatment efficiency while reducing planning time, resources, and human errors.

Gynecologic interstitial brachytherapy curriculum using a low-cost phantom with ultrasound workshop and a treatment planning workshop is effective

PURPOSE/OBJECTIVE(S)Standardized simulation training geared towards interstitial brachytherapy (IS BT) for gynecologic malignancies is lacking in radiation oncology resident education. We developed and implemented a curriculum for IS BT training with (1) lecture on equipment, workflow, and guidelines, (2) hands-on ultrasound-guided IS BT workshop, and (3) treatment planning workshop. METHODS AND MATERIALThe cost in materials of each phantom was approximately $66. After a lecture, two alternating workshops were performed. The first session consisted of a hands-on ultrasound-guided IS BT workshop with one resident imaging the phantom with a transabdominal ultrasound probe and the other resident implanting the phantom with needles. A second session consisted of a hands-on treatment planning workshop using BrachyVision and an l-Q spreadsheet with the following objectives: coverage goal, meeting D2cc constraints, and minimizing V200. The primary outcome was improvement in knowledge assessed with Likert-style questions and objective knowledge-based questions (KBQs). RESULTSFour of the seven medical residents that participated in this curriculum had prior IS BT experience. Residents reported significantly improved knowledge regarding gynecologic IS BT equipment and procedure, evaluating gynecologic anatomy using ultrasound, CT simulation, contouring, and plan review (overall median pre-session subjective score 2 (1) −(3) versus post-session score 4 (3) −(4, p < 0.01). Residents demonstrated improvement in answering KBQs correctly from 44% correct at baseline to 88% after completion of the curriculum (p < 0.01). All residents “Agree” and “Strongly Agree” the session was an effective learning experience. CONCLUSIONSResidents participating in phantom training with an ultrasound curriculum and a treatment planning session is effective for improving knowledge and skills in IS BT for radiation oncology residents.

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.

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

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.

Evaluation Of MR Only Trans-Perineal Interstitial Gynecological HDR Brachytherapy Workflow Using MR-Line Marker And MR Template

There is a growing interest in using MR-only trans-perineal gynecological interstitial brachytherapy because it offers excellent soft-tissue contrast due to MR imaging while reducing the resources required for planning and uncertainty due to registration with CT. The purpose of this work is to evaluate the variation in MR-only workflow in comparison to CT guided approach in gynecological trans-perineal interstitial high dose rate (HDR) brachytherapy. An in-house MR-line marker was designed and created to provide positive contrast on T1W MR images for delineating 6F interstitial catheters (Elekta), replacing the need for CT. A marker plate filled with contrast was affixed to the trans-perineal template, providing a clear reference plane for planning on T1W MR images. Ten patients diagnosed with locally advanced cervical cancer treated with HDR brachytherapy were retrospectively evaluated. An MR-only workflow was developed that used the positive contrast from the MR-markers on T1W images in conjunction with negative contrast on T2W images, to robustly and accurately delineate the interstitial catheters. Inter-observer variability in delineated catheter paths and time required to delineate the catheters were evaluated for 3 therapists and 2 medical physicists. A dosimetric comparison of the plans in the MR-only workflow was made with those in CT based workflow. The contrast in the MR-line marker was stable over time. MR-line markers were visible on planning T1-3D MR images but the complementary information from co-registered T2-3D images were needed at some anatomical locations where the background signal was comparable to that of the markers. MR-template helped to make quality assurance of reconstructed catheter lengths and hence to locate the first dwell point reliably. More than about 97% of catheter reconstruction variations were within 2mm. There were no statistical differences in gross tumor volume (GTV) D98 and High-risk clinical target volume (HR-CTV) D90 and the organs at risk (Bladder, sigmoid, rectum and bowel) D2cc between MR-only and hybrid CT/MR workflow. The average catheter reconstruction time was 51 ± 10 minutes across all ten patients for all observers. The results of this study show that the MR-only workflow is feasible. The use of MR markers enabled accurate and reproducible delineation of the catheters. Furthermore, it was also demonstrated that an MR-only workflow is dosimetrically equivalent to a CT based approach.

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

PurposeMagnetic 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 MaterialsTen 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. ResultsMore 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. ConclusionThe 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.

A semiautomatic segmentation method for interstitial needles in intraoperative 3D transvaginal ultrasound images for high-dose-rate gynecologic brachytherapy of vaginal tumors

PurposeThe purpose of this study was to evaluate the use of a semiautomatic algorithm to simultaneously segment multiple high-dose-rate (HDR) gynecologic interstitial brachytherapy (ISBT) needles in three-dimensional (3D) transvaginal ultrasound (TVUS) images, with the aim of providing a clinically useful tool for intraoperative implant assessment. Methods and MaterialsA needle segmentation algorithm previously developed for HDR prostate brachytherapy was adapted and extended to 3D TVUS images from gynecologic ISBT patients with vaginal tumors. Two patients were used for refining/validating the modified algorithm and five patients (8–12 needles/patient) were reserved as an unseen test data set. The images were filtered to enhance needle edges, using intensity peaks to generate feature points, and leveraged the randomized 3D Hough transform to identify candidate needle trajectories. Algorithmic segmentations were compared against manual segmentations and calculated dwell positions were evaluated. ResultsAll 50 test data set needles were successfully segmented with 96% of algorithmically segmented needles having angular differences <3° compared with manually segmented needles and the maximum Euclidean distance was <2.1 mm. The median distance between corresponding dwell positions was 0.77 mm with 86% of needles having maximum differences <3 mm. The mean segmentation time using the algorithm was <30 s/patient. ConclusionsWe successfully segmented multiple needles simultaneously in intraoperative 3D TVUS images from gynecologic HDR-ISBT patients with vaginal tumors and demonstrated the robustness of the algorithmic approach to image artifacts. This method provided accurate segmentations within a clinically efficient timeframe, providing the potential to be translated into intraoperative clinical use for implant assessment.