Brachytherapy Procedures Research Articles

Multipurpose ultrasound-based prostate phantom for use in interstitial brachytherapy

PURPOSEWhile brachytherapy is an effective treatment for localized prostate cancer, there has been a noticeable decline in its use. Training opportunity for prostate brachytherapy has been in steady decline, with some residents receiving little to no hands-on training. This work was developed to design a training environment that uses a phantom-based simulator to teach the process of TRUS-based prostate brachytherapy METHODS AND MATERIALSA prostate phantom was fabricated from a representative prostate patient TRUS scan. Three materials were used: gelatin powder, graphite powder, and water. The prostate was developed using 9% gelatin and 0.3% graphite per 100 ml water. Five radiation oncologists were asked to qualitatively score the phantom according to image quality, haptic feedback, needle insertion quality, and its compatibility with operative tools. The contrast-to-noise ratio (CNR) was estimated using different concentrations of graphite. The elasticity of the phantom was evaluated based on ultrasound elastography measurements RESULTSThe prostate phantom had an average CNR of 3.94 ± 1.09 compared to real prostate images with a CNR of 2 ± 1.8. The average Young's modulus was computed to be 58.03 ± 6.24 kPa compared to real prostate tissue (58.8 ± 8.2 kPa). Oncologists ranked the phantom as “very good” for overall quality of the phantom. They reported that needle insertion quality was “very good” during a simulated brachytherapy procedure. CONCLUSIONWe have developed a 3D printing prostate phantom to be used for training purposes during prostate brachytherapy. The phantom has been evaluated for image quality and elasticity. The reconstructed phantom could be used as an anthropomorphic surrogate to train residents on prostate brachytherapy procedures.

Utilization of brachytherapy in Quebec, Canada

Despite the excellent clinical outcomes from brachytherapy treatments compared with other modalities and the low associated costs, there have been reports of a decline in utilization of brachytherapy. The aim of this study was to investigate in detail the trend in utilization of brachytherapy in the province of Québec, Canada, from 2011 to 2019. All radiotherapy clinics in the province of Quebec, and among these the clinics that provide brachytherapy treatments, were identified. This observational retrospective cohort study involved analysis of data compiled by the Ministère de la Santé et des Services Sociaux du Québec for the period of 2011 to end of 2019 on all brachytherapy procedures performed in the province of Quebec. Time series graphs were used to describe the number of high dose rate (HDR) and low dose rate (LDR) brachytherapy treatments during the studied time period. Statistical analysis was conducted using R statistical software. Between 2011 and 2019, 12 hospitals in the province of Québec provided radiotherapy treatments, and all of them offered brachytherapy services. The median annual number of brachytherapy sessions was 4413 (range 3930-4829). HDR brachytherapy represented over 90% of all brachytherapy treatments throughout the study period. Significant changes over time were observed in the number of treatments: at least 5% change was seen only for the two most common subtypes of brachytherapy, HDR interstitial and HDR intracavitary, with an increase of 9.6% and a decrease of 9.2%, respectively. The use of other subtypes of brachytherapy (HDR-plesiotherapy, LDR-interstitial, LDR-intracavitary, LDR-eye plaque) was stable between 2011 and 2019, with ≤ 2.5% variation. This study demonstrates an overall steady use of brachytherapy between 2011 and 2019 in Quebec. Brachytherapy offers numerous advantages for the treatment of diverse cancer sites. Although more sophisticated external beam radiotherapy treatments have emerged in the last decades, the precision and cost-effectiveness of brachytherapy remain unbeaten. To ensure the continued use and availability of brachytherapy, governments must put in place policies and regulations to that effect. Training and exposure of future health care professionals to brachytherapy within Quebec and Canada is essential to provide all patients the same access to this life saving modality.

3D model of deflection of an asymmetrical needle during motion in soft tissues

This study describes a mathematical model of deflection of a steel medical injection needle during its motion in the soft tissue phantom (imitation of human tissues). This model is necessary for adjustment of robotically assisted systems during brachytherapy procedures or similar operations where high precision needle tip positioning is prerequisite. Since the needle tip is asymmetrical, the needle will deform when moving in human tissues and consequently deflect from the rectirectilinear motion. Thus, by inserting and rotating the needle around its axis the needle tip can be led along the predetermined path. This study adopts a new approach to describe an external impact on the needle when it moves inside human tissues and also describes 2D and 3D models, a process of selection of coefficients for 3D models, and provides simulation results.

Analysis of Applicator Insertion Related Acute Side Effects for Cervical Cancer Treated With Brachytherapy.

PurposeTo report applicator insertion-related acute side effects during brachytherapy (BT) procedure for cervical cancer patients.Materials and MethodsBetween November 2017 and December 2019, 407 BT fractions were performed in 125 patients with locally advanced cervical cancer. Acute side effects recorded comprised anesthesia-related side effects, mechanical-related side effects and infection, whose frequency and degree were recorded. Pain was assessed using numeric rating scale; vaginal bleeding volume was counted by weighing gauze pieces used in packing. The BT procedure comprised eight stages: anesthesia, applicator insertion, image acquisition, transport, waiting for treatment, dose delivery, applicator removal, and removed which denoted 0.5–12.0 h period after removal, with time of each stage recorded. Factors influencing acute side effects were assessed by Spearman correlation and Mann–Whitney U test.ResultsThe most common acute side effect was pain, followed by vaginal bleeding. The mean scores for pain were highest during removal time, 4.9 ± 1.6 points. The mean vaginal bleeding volume was 44.4 ml during removal time. Mean total procedure time was 218.8 (175–336) min, having positive relationship with frequency of acute side effects. The total procedure time with acute side effects was longer than that without acute side effects. The longest procedure time was waiting time, 113.0 (91.0–132.0) min. More needles generated higher pain scores and larger volume of vaginal bleeding.ConclusionPain and vaginal bleeding were the most common acute side effects, especially during removal time, which physicians should focus on. Shortening patients’ waiting time helps to reduce the total procedure time, thus, reduce acute side effects. While meeting dose requirement, less needles are helpful to reduce acute side effects.

Development of a yz scan system for the improvement of an automatic system of radioactive seed implants in prostate brachytherapy

Brachytherapy is the use of radiotherapy with insertion of radiation sources close to the site that needs treatment. It has become an extremely sought-after option by research fields for its impressive efficiency and practicality. In addition to being a fast-paced procedure, it allows patients to leave hospital care very soon after it is done, without pain or with minor discomfort, which can be considered an advantage.The brachytherapy procedure is divided into two stages, obtaining images of the region where seed implantation will take place and the application itself. The images are obtained by ultrasonography, which will guide the insertion of the needle into the patient's body. During the injection, the patient is anesthetized and immobilized, so that movements that compromise the accuracy of the needle, which, by the current manual method, are already subject to oscillations are avoided.Currently the application of radioactive seeds is done manually by a clinician who uses needles and monitors their positions through the images generated by ultrasound equipment. Thus, the main objective of this project was to improve the prototype of the Prostate Seed Implantation System (SISP), developed by the Nuclear Engineering Department of the UFMG (Nuclear Engineering Department). Thus, the device allows automated scanning on x, y and z axes, facilitating the application of radioactive seeds in prostate brachytherapy treatments, which in current treatments are done manually by the clinician. And the possibility of controlling this movement via BLUETOOTH technology.

Artificial intelligence in brachytherapy: a summary of recent developments.

Artificial intelligence (AI) applications, in the form of machine learning and deep learning, are being incorporated into practice in various aspects of medicine, including radiation oncology. Ample evidence from recent publications explores its utility and future use in external beam radiotherapy. However, the discussion on its role in brachytherapy is sparse. This article summarizes available current literature and discusses potential uses of AI in brachytherapy, including future directions. AI has been applied for brachytherapy procedures during almost all steps, starting from decision-making till treatment completion. AI use has led to improvement in efficiency and accuracy by reducing the human errors and saving time in certain aspects. Apart from direct use in brachytherapy, AI also contributes to contemporary advancements in radiology and associated sciences that can affect brachytherapy decisions and treatment. There is a renewal of interest in brachytherapy as a technique in recent years, contributed largely by the understanding that contemporary advances such as intensity modulated radiotherapy and stereotactic external beam radiotherapy cannot match the geometric gains and conformality of brachytherapy, and the integrated efforts of international brachytherapy societies to promote brachytherapy training and awareness. Use of AI technologies may consolidate it further by reducing human effort and time. Prospective validation over larger studies and incorporation of AI technologies for a larger patient population would help improve the efficiency and acceptance of brachytherapy. The enthusiasm favoring AI needs to be balanced against the short duration and quantum of experience with AI in limited patient subsets, need for constant learning and re-learning to train the AI algorithms, and the inevitability of humans having to take responsibility for the correctness and safety of treatments.

Quantifying risk using FMEA: An alternate approach to AAPM TG-100 for scoring failures and evaluating clinical workflow

Renovation of the brachytherapy program at a leading cancer center utilized methods of the AAPM TG-100 report to objectively evaluate current clinical brachytherapy workflows and develop techniques for minimizing the risk of failures, increasing efficiency, and consequently providing opportunities for improved treatment quality. The TG-100 report guides evaluation of clinical workflows with recommendations for identifying potential failure modes (FM) and scoring them from the perspective of their occurrence frequency O, failure severity S, and inability to detect them D. The current study assessed the impact of differing methods to determine the risk priority number (RPN) beyond simple multiplication. The clinical workflow for a complex brachytherapy procedure was evaluated by a team of 15 staff members, who identified discrete FM using alternate scoring scales than those presented in the TG-100 report. These scales were expanded over all clinically relevant possibilities with care to emphasize mitigation of natural bias for scoring near the median range as well as to enhance the overall scoring-system sensitivity. Based on staff member perceptions, a more realistic measure of risk was determined using weighted functions of their scores. This new method expanded the range of RPN possibilities by a factor of 86, improving evaluation and recognition of safe and efficient clinical workflows. Mean RPN values for each FM decreased by 44% when changing from the old to the new clinical workflow, as evaluated using the TG-100 method. This decreased by 66% when evaluated with the new method. As a measure of the total risk associated with an entire clinical workflow, the integral of RPN values increased by 15% and decreased by 31% with the TG-100 and new methods, respectively. This appears to be the first application of an alternate approach to the TG-100 method for evaluating the risk of clinical workflows. It exemplifies the risk analysis techniques necessary to rapidly evaluate simple clinical workflows appropriately.

Prostate permanent implant brachytherapy with BARC I-125 Ocu-Prosta seeds.

The aim of this study is implementation and establishment of standard operating procedure for permanent prostate implant brachytherapy technique using BARC I-125 Ocu-Prosta seeds. The transrectal ultrasound (US)-guided procedure was used for permanent implant procedure. The Best® Sonalis™ US Imaging System and Best NOMOS™ Treatment Planning system was used for volume study and implant procedure. The BARC provided I-125 Ocu-Pro radioactive seeds were implanted into the patient with help of Mick@ Applicator. The implant was performed based on pre-implant dosimetry and intraoperative planning performed during implant procedure. The necessary quality assurance tests were performed for US system before clinical use. The boost dose of 110 Gy was prescribed to the prostate volume of 34.71 cc. About 48 seeds with activity of 0.35 mCi (each) implanted into the prostate volume with reference to intraoperative planning. At the end of procedure, the patient underwent abdomen fluoroscopic examination, to ensure the seed counts in the prostate volume. The day after the implant, the patient was discharged. One month later a planning computed tomography and treatment planning was performed for seed position and dose verification. Low dose rate permanent implant brachytherapy has the advantage of being a one-time procedure and the existing long term follow-up supports its excellent outcome and low morbidity. BARC-BRIT is supplying the loose 125I seeds. These seeds can be easily implanted into the patient using Mick applicator. However, the pre-implant seed preparation and implant procedure may result some radiation exposure to staff involved. The radiation dose can be minimized with good practice. This report is one patient pilot study and intended to test the implant systems and standard operative procedure henceforth for permanent implant brachytherapy procedure.

Intraoperative optimization of seed implantation plan in breast brachytherapy.

Low-dose-rate permanent-seed (LDR-PS) brachytherapy has shown a great potential for treating breast cancer. An implantation scheme indicating the template pose and needle trajectories is determined before the operation. However, when performing the pre-planned scheme intraoperatively, a change of the patient's posture will cause seed placements away from the desired locations. Hence, the implantation scheme should update based on the current patient's posture. A numerical method of optimizing the implantation scheme for the LDR-PS breast brachytherapy is presented here. The proposed algorithm determines the fewest needle trajectories and template poses for delivering the seeds to the intraoperative desired locations. The clinical demand, such as the minimum distance between the chest wall and the needle, is considered in the optimization process. The method was simulated for a given LDR-PS brachytherapy procedure to evaluate the optimal scheme as the number of the template poses changing. The optimization parameters of the needles' number and the implantation errors are used to adjust the algorithm outcome. The results show that the implantation schemes obtained by our method have a satisfactory accuracy in the cases of 2 or 3 template poses. The computation time is about 76s to 150s according to the number of the template poses from 1 to 3. The proposed method can find the optimal implantation scheme corresponding to the current desired seed locations immediately once there is a change of patient's posture. This work can be applied to the robot-assisted LDR-PS breast brachytherapy for improving the operation accuracy and efficiency.

Comparison of ketofol versus propofol for procedural sedation and analgesia in cervical cancer brachytherapy: A prospective, randomized double blind study

Most common drug used for outpatient procedural sedation and analgesia is propofol, with limitations like systemic hypotension. Combining propofol with ketamine preserves sedation efficacy, minimizing their respective adverse effects. So, we aimed to compare ketofol (ketamine+propofol) versus propofol regarding their total drug consumption, recovery profile, effect on haemodynamic and respiratory parameters in brachytherapy patients. A prospective, randomized, controlled double blind study was carried out in 100 female patients between 20-60 years, 30-70kg, ASA I-III undergoing brachytherapy as outpatient procedure on elective basis, after ethical clearance from institutional committee. These were randomly divided into 2 groups (50 each). Group P-Injpropofol (10mg/ml) 2mg/kg for induction and 20mg as supplementation. Group K-Injketofol (10mg/ml) (ketamine 50mg+propofol 100mg, 1:2) 2mg/kg for induction and 20 mg as supplementation.The supplementation dose required was significantly higher in propofol group (800mg) as compared to ketofol group (20mg) (p=0.00). Also, the fall in SBP and DBP was significantly less in ketofol group than propofol group (p<0.01). The mean awakening time (time from end of procedure to MRSS =3) andmean recovery time (time from end of procedure to achievement of Aldrete score 10) was more in ketofol group than propofol group (p<0.003), the difference was less than 1-2 min, so it was clinically not significant. Ketamine-propofol combination in 1:2 ratio in a single syringe as ketofolis better alternative to propofol in providing sedation and analgesia with better haemodynamic stability, for outpatient brachytherapy procedure in cancer cervix patients.

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.

Feasibility and Clinical Value of CT-Guided 125I Brachytherapy for Pain Palliation in Patients With Breast Cancer and Bone Metastases After External Beam Radiotherapy Failure.

Objectives: To evaluate the feasibility and clinical value of CT-guided iodine-125 (125I) brachytherapy for pain palliation in patients with breast cancer and bone metastases after external beam radiotherapy failure.Methods: From January 2014 to July 2016, a total of 90 patients, who had received the standard therapies for bone metastases but still suffered moderate-to-severe pain, were retrospectively studied. About 42 patients were treated with both 125I brachytherapy and bisphosphonates (Group A), and 48 patients were treated with bisphosphonates alone (Group B).Results: In Group A, 45 125I brachytherapy procedures were performed in 42 patients with 69 bone metastases; the primary success rate of 125I seed implantation was 92.9%, without severe complications. Regarding pain progression of the two groups, Group A exhibited significant relief in “worst pain,” “least pain,” “average pain,” and “present pain” 3-day after treatment and could achieve a 12-week-remission for “worst pain,” “least pain,” “average pain,” and “present pain.” The morphine-equivalent 24-h analgesic dose at 3 days, 4 weeks, 8 weeks, and 12 weeks was 91 ± 27, 53 ± 13, 31 ± 17, and 34 ± 12 mg for Group A, and 129 ± 21, 61 ± 16, 53 ± 15, and 105 ± 23 mg for Group B. Group A experienced a lower incidence of analgesic-related adverse events and better quality of life than Group B.Conclusion: The CT-guided 125I brachytherapy is a feasible and an effective treatment for the palliation of pain caused by bone metastases from breast cancer after external beam radiotherapy failure.

Design, Fabrication, and Testing of a Flexible Three-Dimensional Printed Percutaneous Needle With Embedded Actuators

Abstract Percutaneous needle-based procedures have replaced open surgeries in cancer treatments to perform the tasks with minimal invasiveness to the tissue. Precise placement of the needle at target positions in cancer diagnostic (e.g., breast biopsy) or therapeutic (e.g., prostate brachytherapy) procedures governs the success of such procedures. Also, in many needle insertion applications, it is desired to steer away from critical organs or to maneuver around anatomical obstacles in tissue. This work introduces a flexible three-dimensional (3D) printed percutaneous needle with embedded actuators for improved navigation inside the tissue toward the target. The needle is manipulated via a programmed portable motorized control unit to realize an average angular deflection of about 15 and 14 deg in air and a tissue-mimicking phantom, respectively. We demonstrated the needle's capability to reach the target, while avoiding obstacles. We also demonstrated that the flexible needle can be guided through a desired trajectory by controlling its angular deflection and axial movement. The 3D deflection of the needle is expected to assist in breast cancer lumpectomy for multiple extractions of tissue samples or in prostate brachytherapy via a curvilinear approach. The flexible needle may help reducing the complexity of current path planning algorithms, and thereby improve efficiency of closed-loop control systems in needle steering.

Development and Preliminary Evaluation of an Anthropomorphic Trans-rectal Ultrasound Prostate Brachytherapy Training Phantom

The quality of the trans-rectal ultrasound (TRUS) image, and thus seed placement during the prostate brachytherapy (PBT) procedure, relies on the user's technical and clinical competency. Simulation-based medical education can provide a structured approach for the acquisition of clinical competencies, but the efficacy of the training relies on the fidelity of the training simulators. In this work, the design, development and preliminary evaluation of an anthropomorphic training phantom for TRUS PBT is described. TRUS clinical patient data informed the design of 3-D printed moulds to fabricate prostate targets. Tissue-mimicking materials were included that had the sonographic characteristics of the prostate and overlying tissues, as well as the clinically relevant physical response, to provide haptic feedback to the user. Through an iterative design process, prototypes were constructed. These prototypes were quantitatively evaluated using a specification list and evaluated by an experienced clinical brachytherapy oncologist; their feedback was implemented, and the results of this evaluation are presented.

Brachytherapy quality assurance in the PORTEC-4a trial for molecular-integrated risk profile guided adjuvant treatment of endometrial cancer

ObjectiveThe PORTEC-4a trial investigates molecular-integrated risk profile guided adjuvant treatment for endometrial cancer. The quality assurance programme included a dummy run for vaginal brachytherapy prior to site activation, and annual quality assurance to verify protocol adherence. Aims of this study were to evaluate vaginal brachytherapy quality and protocol adherence. MethodsFor the dummy run, institutes were invited to create a brachytherapy plan on a provided CT-scan with the applicator in situ. For annual quality assurance, institutes provided data of one randomly selected brachytherapy case. A brachytherapy panel reviewed and scored the brachytherapy plans according to a checklist. ResultsAt the dummy run, 15 out of 21 (71.4%) institutes needed adjustments of delineation or planning. After adjustments, the mean dose at the vaginal apex (protocol: 100%; 7 Gy) decreased from 100.7% to 99.9% and range and standard deviation (SD) narrowed from 83.6–135.1 to 96.4–101.4 and 8.8 to 1.1, respectively. At annual quality assurance, 22 out of 27 (81.5%) cases had no or minor and 5 out of 27 (18.5%) major deviations. Most deviations were related to delineation, mean dose at the vaginal apex (98.0%, 74.7–114.2, SD 7.6) or reference volume length. ConclusionsMost feedback during the brachytherapy quality assurance procedure of the PORTEC-4a trial was related to delineation, dose at the vaginal apex and the reference volume length. Annual quality assurance is essential to promote protocol compliance, ensuring high quality vaginal brachytherapy in all participating institutes.

Deep learning-based digitization of prostate brachytherapy needles in ultrasound images.

PurposeTo develop, and evaluate the performance of, a deep learning‐based three‐dimensional (3D) convolutional neural network (CNN) artificial intelligence (AI) algorithm aimed at finding needles in ultrasound images used in prostate brachytherapy.MethodsTransrectal ultrasound (TRUS) image volumes from 1102 treatments were used to create a clinical ground truth (CGT) including 24422 individual needles that had been manually digitized by medical physicists during brachytherapy procedures. A 3D CNN U‐net with 128 × 128 × 128 TRUS image volumes as input was trained using 17215 needle examples. Predictions of voxels constituting a needle were combined to yield a 3D linear function describing the localization of each needle in a TRUS volume. Manual and AI digitizations were compared in terms of the root‐mean‐square distance (RMSD) along each needle, expressed as median and interquartile range (IQR). The method was evaluated on a data set including 7207 needle examples. A subgroup of the evaluation data set (n = 188) was created, where the needles were digitized once more by a medical physicist (G1) trained in brachytherapy. The digitization procedure was timed.ResultsThe RMSD between the AI and CGT was 0.55 (IQR: 0.35–0.86) mm. In the smaller subset, the RMSD between AI and CGT was similar (0.52 [IQR: 0.33–0.79] mm) but significantly smaller (P < 0.001) than the difference of 0.75 (IQR: 0.49–1.20) mm between AI and G1. The difference between CGT and G1 was 0.80 (IQR: 0.48–1.18) mm, implying that the AI performed as well as the CGT in relation to G1. The mean time needed for human digitization was 10 min 11 sec, while the time needed for the AI was negligible.ConclusionsA 3D CNN can be trained to identify needles in TRUS images. The performance of the network was similar to that of a medical physicist trained in brachytherapy. Incorporating a CNN for needle identification can shorten brachytherapy treatment procedures substantially.

Automated Needle Digitization in Ultrasound-based Prostate High Dose-rate Brachytherapy Using a Deep Learning Algorithm

Prostate high dose-rate brachytherapy (HDR) delivers the radiation using a radioactive Ir-192 seed through interstitial needles and the needle implants are guided by a real-time ultrasound (US) imaging system. The success of this therapy relies highly on accurate digitization of the needles in the treatment planning US images. In current clinical procedures, the needles' trajectories are manually labeled by physicists, which is time-consuming and prone to errors. In recent years, deep learning techniques have brought many breakthroughs, especially in medical imaging processing. We thus propose a deep learning-based method to segment the needles accurately in the US images. The training data including the US images, needle positions and treatment plans were collected from the clinical database with IRB approval. Before training, images in the Cartesian coordinate were transferred into the polar plane and then split into smaller batches so that each contains one needle. Data augmentation techniques were used to avoid overfitting. The needle segmented neural network was based on U-Net with an encoder-decoder structure and shortcuts connecting directly the encoder layers and the corresponding decoder ones. The network structure and parameters were optimized for the needle segmentation problem. To estimate the positions of the needle tips, a separate convolutional neural network with the architecture of Vgg16 was developed and the 3D position accuracy was obtained. Data from 441 patients and 13200 needles was utilized. The needle trajectories were successfully segmented with mean errors of 0.67 mm and 0.32 mm in left-right (X) and anterior-posterior (Y) directions of the original US images and the estimation errors within 2 mm in X and Y directions are 95.4% and 99.2%, respectively. As for the needle tip localization, the positioning accuracies in X, Y, and Z (superior-inferior) are 0.72 mm, 0.37 mm and 1.88 mm, with 94.2%, 98.3% and 67.5% of the data have error of less than 2 mm, respectively. A novel method based on deep learning and neural networks was successfully developed to digitize HDR brachytherapy needles automatically. This method can be served as a valuable tool during brachytherapy procedures and has the potential to improve the efficiency and quality of treatment delivery, contributing overall to the patient care.

Multi-material 3D Printing in Brachytherapy– Prototyping Teaching Tools

The utilization of brachytherapy for cervical cancer has been declining, resulting in worsening survival. To improve resident confidence in performing of intracavitary and interstitial HDR brachytherapy procedures, an educational multi-material modular 3D printed gynecologic pelvic phantom training kit simulating both normal and pathological conditions has been developed. The implementation of this phantom in resident education is intended to allow for a more thorough and comprehensive training in tandem and ovoid and needle insertions. CT and MR scans from 50 patients with locally advanced cervical cancer were analyzed. Dimensions of the uterine bodies and canals were measured from the T2 weighted MRI images. These measurements were used to construct four model uteri based off of averages and standard deviations. The vaginal canal was constructed based on standard gynecological speculum dimensions. Individual STL files were imported into Autodesk Meshmixer and manipulated to include features such as hollowed out cavities and canals to allow for applicator placement. Modular components of the phantom were designed and integrated into patient anatomy using CAD 3DShapr. Five HRCTVs were extracted from patient scans to be incorporated into the uterine body. Elasticity properties of tissues were used to calculate appropriate flexible and rigid shore values (0-100) to assign to each anatomical structure for multi-material printing. Average dimensions and SD from the 50-patient study are presented in Table 1 for the anatomical structures considered. The finalized prototype kit consists of three anteverted uteri based on the smallest, the average, and the largest dimensions from our patient set. The fourth uterus is retroverted and uses average dimensions. Clip-on HRCTV attachments expanding outside of the uterine body are included to mimic different pathology. Color staining with different shore values within the uterus was done to represent internal HRCTVs. All uterus bodies and the vaginal canal were printed using Agilus (shore 30A) in clear as a means of evaluation for tandem/ovoid and needle placement. The rectum and HRCTVs were printed using a blend of polymers that allow for variable stiffness (Vero and Agilus, shore 70A and 40A respectively). The bladder was printed using pure Agilus (shore 30A). A multi-material modular 3D printed pelvic phantom training kit simulating normal and cervix pathological conditions has been developed for practicing tandem and ovoid insertions. This tool may be used to help address a gap in decreased resident confidence in performing brachytherapy procedures.Tabled 1Abstract 2983; TableCanal Length [cm]Canal Width [cm]Body Length [cm]Body Width (top) [cm]Body Width (midpoint) [cm]Canal Angle [deg]U15.810.345.812.023.1519.1U26.230.427.872.744.4527.6U37.630.3439.933.455.7436.1U4*6.230.427.872.744.4527.6∗Retroverted Open table in a new tab

Endobronchial HDR Brachytherapy for Post-Transplant or Wegener’s Granulomatosis Associated Bronchial Stenosis

Bronchial stenosis is a clinically challenging problem following lung transplant and in Wegener’s Granulomatosis. Despite laser, stenting, balloon dilation among other interventions, worsening of stenosis often occurs. Endobronchial brachytherapy has been implemented for treatment refractory stenotic areas based on limited data. We hypothesize that high dose rate (HDR) Brachytherapy using 3Gy x1 fraction is effective in alleviating treatment refractory stenosis of bronchus. Patients who underwent endobronchial HDR Ir-192 brachytherapy from January 2016 to January 2020 for bronchial stenosis were retrospectively reviewed. Patients were selected for HDR brachytherapy if they had treatment refractory symptomatic re-stenosis. On day of brachytherapy, a flexible bronchoscopy was performed and a brachytherapy catheter was inserted. Intraoperative fluoroscopic imaging confirmed catheter positioning. Treatment length ranged from 3-5cm. The dose of 3Gy in 1 fraction was prescribed 1cm from the catheter surface. Patients were followed with bronchoscopies and pulmonary function testing (PFTs). Four patients were included with median follow-up of 5.2m (range: 0.9-16.8). One patient received brachytherapy 12Gy in 4 fractions 12 years prior to re-treatment. The same patient received a second double lung transplant due to bronchiolitis obliterans. All patients had initial clinical & bronchoscopic improvement with brachytherapy. The one Wegener’s Granulomatosis patient required an additional two courses of brachytherapy due to residual granulation tissue found proximally outside of the prior radiation treatment fields. Median time to next endobronchial intervention after brachytherapy was 5.2m [0.9-18.8]. The median number of interventions pre and post brachytherapy are listed below (Table 1). FEV1 prior to brachytherapy was 33% predicted [27-65] and PFT after brachytherapy was 40% predicted [25-72]. The one Wegener granulomatosis patient had a balloon dilation procedure induced grade 4 bronchopulmonary hemorrhage three months after 3rd brachytherapy treatment, requiring bronchial artery embolization. They were subsequently discharged 36 hours after the initial bleed and remains free of stenosis. Table 1 Endobronchial HDR brachytherapy utilizing 3Gy x 1 fraction was safe and effective in resolving refractory re-stenotic areas of bronchus caused by granulation tissue. There were no toxicities associated with lung transplant patients. The Wegener’s Granulomatosis patient had a potential G4 toxicity after a third brachytherapy treatment. Caution needs to be applied in the setting of repeated endobronchial brachytherapy procedures. More robust follow up is needed to assess long term success.Abstract 2512; TablePatientNumber of Pre-Brachytherapy InterventionNumber of Post-Brachytherapy Intervention12-6 months6-0 months0-6 months6-12 months194191221311303442042900Median [range]6.5 [2-13]6.5 [4-11]2.5 [0-19]0 [0-12] Open table in a new tab

An Analysis of Learning Curve Effect on the Speed and Quality of High Dose Rate Prostate Brachytherapy Procedures

To evaluate the impact of learning curve effect on the provision of High Dose Rate (HDR) prostate brachytherapy boost at a recently initiated program within a smaller Canadian Academic Cancer Center. From 2015 to 2019, 266 patients with intermediate or unfavorable risk prostate cancer were treated with single fraction HDR prostate brachytherapy boost (15 Gy), followed by combination external beam radiation therapy (37.5 – 46 Gy) at a single Canadian cancer institution. Detailed time records were recorded for all phases of the procedures including: total procedure time, catheter insertion / placement, contouring, second oncologist check, catheter reconstruction, planning / dose optimization, QA / second checks, and treatment delivery. Dosimetric values from the delivered plans were also analyzed, including metrics for: Prostate (D90, V100, V150, V200), urethra (D10, max), and rectum (V75, V80, V100, max). The experience of each team member (previous number of procedures performed since program inception) was also recorded. Radiation Oncologist (RO) experience was not a significant predictor of total procedure time (p = 0.163) nor total catheter placement time (p = 0.583). Planner experience was significantly correlated with reduced catheter reconstruction time, and consequently, total procedure time (β = -0.376 minutes / case experience, P<0.001). There were statistically significant differences in mean prostate D90 (105.36 vs 106.05%, p = 0.04), V100 (94.69% vs. 95.31%, p = 0.014), and urethra D10 (113.61 vs. 112.74%, p = 0.008) when comparing dosimetry from an oncologist’s first 20 cases compared to those afterwards. RO experience was correlated with improvement in prostate D90 (β = 0.000156, p = 0.008), V100 (β = 0.000144, p = 0.001), and V200 (β = -0.000152, p = 0.008), and urethra D10 (β = -0.000159, p = 0.011). HDR Prostate brachytherapy can provide radiotherapy with excellent dosimetric characteristics regardless of previous institutional experience. In our study, institutional oncologist experience provided a modest, but measurable improvement in dosimetric quality. Institutional experience reduced total procedure time; this improvement was mainly attributable to the planner. These findings support the use of HDR prostate brachytherapy as a robust technique even for newer adopters, and may further inform cancer centers initiating new HDR Brachytherapy programs or training new staff.