<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 mm<sup>3</sup>. 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.
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Dec 1, 2022
Emad Mikhail 
Open Access