Characterization of novel 3D-printed metal shielding for brachytherapy applicators.

PURPOSE: To characterize 3D-printed stainless steel metal samples in the presence of an Iridium-192 source for organ-at-risk sparing in gynecologic brachytherapy. METHODS: Samples of 3D-printed stainless steel (5.5 × 5.5 cm2, thickness range 1-5 mm) were embedded in a solid water phantom at varying distances from source catheters. An Ir-192 brachytherapy source was passed through the phantom and the dose was measured using EBT3 Gafchromic film. The film was initially positioned in the sagittal plane 2 cm away from the catheters, with the metal directly below and then 1 cm from the film. A uniform dose was delivered at the film plane. A second setup measured a depth dose curve in solid water with film in the transverse plane directly above the metal samples. This setup was recreated using Monte Carlo simulations (EGSnrc egs_brachy). Validation between methods was performed with unshielded (solid water only) measurements. RESULTS: The planar dose passing through the metal samples (thickness 1-5 mm) at the midpoint between the film and catheters, decreased compared to solid water by 7.4% ± 6.9% to 26.5% ± 5.5%. Dose enhancement on the order of 5% was noted when metal was directly adjacent to the film. The average decrease in depth dose from a single dwell position ranged from 10.0% ± 5.9% (1 mm) to 21.1% ± 5.3% (5 mm) as measured with film, and from 3.8% ± 0.9% (1 mm) to 16.3% ± 0.9% (5 mm) using MC simulation. The average depth dose values were measured using a line width of 2.5 mm for film, and 3 mm for MC simulation, and the measurements generally agree within standard error. CONCLUSIONS: The 3D-printed metal samples show potential for personalized applicators. Maximum dose reduction of 26.5% ± 5.5% compared to solid water was measured at 2 cm from the source using the 5 mm sample. An outer layer of solid water could potentially be used to reduce dose enhancement due to increased scatter near the metal.

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

PURPOSE: To design, manufacture, and validate a female pelvic phantom for multi-modality imaging (CT, MRI, US) to benchmark a commercial needle tracking system with application in HDR gynecological (GYN) interstitial procedures. MATERIALS AND METHODS: A GYN needle-tracking phantom was designed using CAD software to model an average uterus from a previous patient study, a vaginal canal from speculum dimensions, and a rectum to accommodate a transrectal ultrasound (TRUS) probe. A target volume (CTVHR ) was designed as an extension from the cervix-uterus complex. Negative space molds were created from modeled anatomy and 3D printed. Silicone was used to cast the anatomy molds. A 3D printed box was constructed to house the manufactured anatomy for structural integrity and to accommodate the insertion of a speculum, tandem, needles, and TRUS probe. The phantom was CT-imaged to identify potential imperfections that might impact US visualization. Free-hand TRUS was used to guide interstitial needles into the phantom. The commercial tracking system was used to generate a 3D US volume. After insertion, the phantom was imaged with CT and MR and the uterus and CTVHR dimensions were verified against the CAD model. RESULTS/CONCLUSIONS: The manufactured phantom allows for accurate visualization with multiple imaging modalities and is conducive to applicator and needle insertion. The phantom dimensions from the CAD model were verified with those from each imaging modality. The phantom is low cost and can be reproducibly manufactured with the 3D printing and molding processes. Our initial experiments demonstrate the ability to integrate the phantom with a commercial tracking system for future needle tracking validation studies.

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.

Automated treatment planning framework for brachytherapy of cervical cancer using 3D dose predictions.

Objective. To lay the foundation for automated knowledge-based brachytherapy treatment planning using 3D dose estimations, we describe an optimization framework to convert brachytherapy dose distributions directly into dwell times (DTs).Approach. A dose rate kerneld(r,θ,φ)was produced by exporting 3D dose for one dwell position from the treatment planning system and normalizing by DT. By translating and rotating this kernel to each dwell position, scaling by DT and summing over all dwell positions, dose was computed (Dcalc). We used a Python-coded COBYLA optimizer to iteratively determine the DTs that minimize the mean squared error betweenDcalcand reference doseDref, computed using voxels withDref80%-120% of prescription. As validation of the optimization, we showed that the optimizer replicates clinical plans whenDref= clinical dose in 40 patients treated with tandem-and-ovoid (T&O) or tandem-and-ring (T&R) and 0-3 needles. Then we demonstrated automated planning in 10 T&O usingDref= dose predicted from a convolutional neural network developed in past work. Validation and automated plans were compared to clinical plans using mean absolute differences (MAD=1N∑n=1Nabsxn-xn') over all voxels (xn= Dose,N= #voxels) and DTs (xn= DT,N= #dwell positions), mean differences (MD) in organD2ccand high-risk CTV D90 over all patients (where positive indicates higher clinical dose), and mean Dice similarity coefficients (DSC) for 100% isodose contours.Main results. Validation plans agreed well with clinical plans (MADdose= 1.1%, MADDT= 4 s or 0.8% of total plan time,D2ccMD = -0.2% to 0.2% and D90 MD = -0.6%, DSC = 0.99). For automated plans, MADdose= 6.5% and MADDT= 10.3 s (2.1%). The slightly higher clinical metrics in automated plans (D2ccMD = -3.8% to 1.3% and D90 MD = -5.1%) were due to higher neural network dose predictions. The overall shape of the automated dose distributions were similar to clinical doses (DSC = 0.91).Significance. Automated planning with 3D dose predictions could provide significant time savings and standardize treatment planning across practitioners, regardless of experience.

Implementing a simulation-based curriculum for hybrid intracavitary/interstitial brachytherapy using a new, commercially available, US/MR/CT-compatible gynecologic phantom.

PURPOSE: To establish a simulation-based workshop for teaching hybrid intracavitary/interstitial (IC/IS) brachytherapy skills using a new, commercially available US/CT/MRI-compatible gynecologic phantom prototype. METHODS AND MATERIALS: The VIOMERSE gynecological trainer phantom consisted of tissue-like colloid material and was US, CT, and MRI-compatible. We designed a hands-on workshop incorporating the phantom prototype to teach skills for hybrid IC/IS brachytherapy including pre-implant planning, procedural steps of implant placement, and post-implant evaluation. The workshop impact was evaluated with pre- and post-workshop surveys and responses were analyzed with Wilcoxon matched-pairs signed-rank test. RESULTS: Thirteen residents, divided into small groups, attended one of three separate 1-h workshop sessions held during the gynecologic education block. Workshop steps included IC applicator placement, tumor mapping and pre-planning desired location and depth of needles for hybrid IC/IS application, IS needle labelling and insertion, image review of needle placements, comparison of IC-alone versus IC/IS brachytherapy plans. Responses to questions ascertaining knowledge, confidence, and ability in planning and executing hybrid IC/IS procedures all demonstrated significant improvement from pre- to post-workshop. In response to whether the session was an effective learning experience, all 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." CONCLUSIONS: Implementation of a hybrid IC/IS brachytherapy workshop utilizing a new, commercially-available phantom prototype was successful, with clear, subjective benefit for the residents in our program. This experience may inform continued efforts towards standardizing brachytherapy curricula across programs and increasing trainee exposure to interstitial procedures.

3D-printed Magnetic Resonance (MR)-based gynecological phantom for image-guided brachytherapy training.

PURPOSE/OBJECTIVES: There is a clinical need to develop anatomic phantoms for simulation-based learning in gynecological brachytherapy. Here, we provide a step-by-step approach to build a life-sized gynecological training phantom based on magnetic resonance imaging (MRI) of an individual patient. Our hypothesis is that this phantom can generate convincing ultrasound (US) images that are similar to patient scans. METHODS: Organs-at-risk were manually segmented using patient scans (MRI). The gynecological phantom was constructed using positive molds from 3D printing and polyvinyl chloride (PVC) plastisol. Tissue texture/acoustic properties were simulated using different plastic softener/hardener ratios and microbead densities. Nine readers (residents) were asked to evaluate 10 cases (1 ultrasound image per case) and categorize each as a "patient" or "phantom" image. To evaluate whether the phantom and patient images were equivalent, we used a multireader, multicase equivalence study design with two composite null hypotheses with proportion (pr) at H01: pr ≤ 0.35 and H02: pr ≥ 0.65. Readers were also asked to review US videos and identify the insertion of an interstitial needle into the pelvic phantom. Computed Tomography (CT) and magnetic resonance (MR) images of the phantom were acquired for a feasibility study. RESULTS: Readers correctly classified "patient" and "phantom" scans at pr = 53.3% ± 6.2% (p values 0.013 for H01 and 0.054 for H02, df = 5.96). Readers reviewed US videos and identified the interstitial needle 100% of the time in transabdominal view, and 78% in transrectal view. The phantom was CT and MR safe. CONCLUSIONS: We have outlined a manufacturing process to create a life-sized, gynecological phantom that is compatible with multi-modality imaging and can be used to simulate clinical scenarios in image-guided brachytherapy procedures.

Transvaginal artificial ascites infusion as a spacer in gynecological brachytherapy: a novel technique.

This is a first paper to report on artificial ascites infusion via vaginal wall for pelvic interstitial brachytherapy. Artificial ascites is commonly used for treating liver tumors, with radiofrequency ablation and percutaneous artificial ascites infusion through the abdominal wall for pelvic brachytherapy has been previously reported by our group. However, the trans-abdominal needle approach under ultrasound guidance is unreliable due to poor visualization resulting in fluid injection into the abdominal wall or mesenterium and the rate of successful artificial ascites infusion was low. Target tumor of the vaginal cuff brachytherapy is usually adjacent to the intestine, and transvaginal artificial ascites infusion under trans-rectal ultrasonography is considered as a rational and simpler method to create a space between target volume and organs at risk, such as intestines or sigmoid colon, by increased visualization of the needle compared to trans-abdominal approach. Here, we report a practical experience of transvaginal artificial ascites infusion.

O significado da dor para mulheres em braquiterapia ginecológica: abordagem fenomenológica na consulta de enfermagem / El significado del dolor para las mujeres en la braquiterapia ginecológica: enfoque fenomenológico en la consulta de enfermería / The meaning of pain for women in gynecological brachytherapy: phenomenological approach in nursing consultation

Objetivo: Identificar a percepção da dor para mulheres em braquiterapia ginecológica na consulta de enfermagem. Método: Estudo qualitativo, realizado entre fevereiro a novembro de 2012, apoiado na abordagem da Fenomenologia Sociológica Compreensiva de Alfred Schutz. Treze mulheres participaram, maiores de dezoito anos, submetidas à braquiterapia ginecológica de dois serviços de radioterapia localizados no Rio de Janeiro e outro em São Paulo. Resultados: Uma característica que sobressaiu a partir dos depoimentos se referiu à dor na braquiterapia ginecológica, em que as mulheres revelaram o anseio por superá-la. Conclusão: Tal anseio independe da idade e do grau de instrução, é comum a todas e oriundo do vivido com o câncer. O que modifica é a maneira como se apresenta e a sua intensidade, que variam conforme a singularidade de cada sujeito

Objetivo: Identificar la percepción del dolor para las mujeres en braquiterapia ginecológica en la consulta de enfermería. Método: Estudio cualitativo, realizado de febrero a noviembre de 2012, a favor del enfoque de la fenomenología sociológica Integral de Alfred Schutz. Los participantes fueron trece las mujeres mayores de dieciocho años sometidos a la braquiterapia ginecológica dos servicios de radioterapia ubicadas en Río de Janeiro y otro en Sao Paulo. Resultados: Una característica que se destacó de los estados mencionados dolor en la braquiterapia ginecológica, en el que las mujeres revelan el deseo de superación. Conclusión: Este deseo es independiente de la edad y nivel de educación, es común a todos y procedentes de los vivos con el cáncer. Lo que cambia es la forma en que se presenta y su intensidad, que varían de acuerdo a la singularidad de cada sujeto

Objective: The study's goal has been to identify the perception of pain for women in gynecological brachytherapy in nursing consultation. Methods: It a qualitative study, carried out from February to November 2012, supported in the approach of the Sociological Phenomenology Comprehensive Alfred Schutz. Participants were thirteen women over eighteen years submitted to gynecological brachytherapy two radiotherapy services located in Rio de Janeiro and another in Sao Paulo. Results: One characteristic that emerged from the statements referred to pain in gynecological brachytherapy, in which women revealed the desire to overcoming it. Conclusion: This desire is independent of age and level of education; it is common to all and coming from the living with cancer. What changes is the way it is presented and its intensity, which vary according to the uniqueness of each subject