Setup Reproducibility Research Articles

To Assess the Effect of BMI on Patient Setup Reproducibility in Hypofractionation of Breast Cancer to Establish an Imaging Protocol

Objectives: To analyze the setup accuracy among patients treated for breast cancer with hypofractionation radiation therapy (HFRT) regimen (five fractions instead of 15-16 fractions in standard regimen) and predict the necessity of performing the setup imaging in the 4th and 5th fractions as a function of setup accuracy in the first three fractions. Methods: This retrospective study reviewed setup displacements in each direction (lateral, longitudinal, and vertical) for 51 women with breast cancer treated with HFRT at the Radiation Therapy Unit between September 2020 and May 2022. Besides the five fractions (#1– # 5), the mean setup error was computed for the first three fractions (AVG-III) for each direction. Setup accuracy rates were computed for each direction and fraction as the percentage of fractions with setup error ≤ 0.5 cm. The correlations of #1, #2, #3, and AVG-III setup errors and their value in indicating #4 and #5 setup error and accuracy were analyzed using Pearson's coefficient and Receiver Operating Characteristics (ROC) curve, respectively. Furthermore, the effect of body mass index (BMI) on setup reproducibility was analyzed using logistic regression Result: The mean (SD) age of the participants was 54.41 (11.46) years. There was a high percentage of overweight (25.5%) and obese (53.0%). The mean setup error was 0.05) and #5 (r = -0.128–0.254; p>0.05) within any of the first three fractions or AVG-III, in any of the directions. In the ROC curve, only #5 accuracy was indicated by #3 in the longitudinal direction (AUC=0.89, p=0.025). BMI was only associated with inaccurate setup for fraction #3 in the lateral direction, in a positive relationship (OR=1.15, 95% CI = 1.01–1.30; p=0.031). Conclusion: Setup accuracy in the first fractions of HFRT does not predict accuracy in the two last fractions nor is predicted by the patient’s BMI. Consequently, women with breast cancer treated with HFRT require daily imaging for optimal setup before each radiotherapy fraction.

Technical note: Multi-MATE, a high-throughput platform for automated image-guidedsmall-animal irradiation.

Small animal irradiation is essential to study the radiation response of new interventions before or parallel to human therapy. Image-guided radiotherapy (IGRT) and intensity-modulated radiotherapy (IMRT) are recently adopted in small animal irradiation to more closely mimic human treatments. However, sophisticated techniques require exceedingly high time, resources, and expertize that are often impractical. We propose a high throughput and high precision platform named Multiple Mouse Automated Treatment Environment (Multi-MATE) to streamline image-guided small animal irradiation. Multi-MATE consists of six parallel and hexagonally arranged channels, each equipped with a transfer railing, a 3D-printed immobilization pod, and an electromagnetic control unit, computer-controlled via an Arduino interface. The mouse immobilization pods are transferred along the railings between the home position outside the radiation field and the imaging/irradiation position at the irradiator isocenter. All six immobilization pods are transferred to the isocenter in the proposed workflow for parallel CBCT scans and treatment planning. The immobilization pods are then sequentially transported to the imaging/therapy position for dose delivery. The positioning reproducibility of Multi-MATE are evaluated using CBCT and radiochromic films. While parallelizing and automating the image-guided small animal radiation delivery, Multi-MATE achieved the average pod position reproducibility of 0.17 ± 0.04 mm in the superior-inferior direction, 0.20 ± 0.04 mm in the left-right direction, and 0.12 ± 0.02mm in the anterior-posterior direction in repeated CBCT tests. Additionally, in image-guided dose delivery tasks, Multi-MATE demonstrated the positioning reproducibility of 0.17 ± 0.06 mm in the superior-inferior direction, 0.19 ± 0.06 mm in the left-right direction. We designed, fabricated, and tested a novel automated irradiation platform, Multi-MATE to accelerate and automate image-guided small animal irradiation. The automated platform minimizes human operation and achieves high setup reproducibility and image-guided dose delivery accuracy. Multi-MATE thus removes a major barrier to implementing high-precision preclinical radiation research.

PO-2264 Assessment of weight loss and setup reproducibility in nasopharyngeal cancer patients.

PO-2264 Assessment of weight loss and setup reproducibility in nasopharyngeal cancer patients.

A fast and effective approach for classification medical data sets

This study's objective is to offer a practical computer method for handling classification problems on large datasets. The aim of this study is to offer a practical computer approach for handling classification tasks on big datasets. We show that using Python’s built-in parameters to balance classes can improve the accuracy and the metrics of a classification task. We employ logistic regression, support vector machines, decision trees, and random forest classifier. We use the parameter “class_weight='balanced'” to run each classification model as well as stratified train/test splitting to ensure that relative class frequencies are approximately preserved in each train and set subsets. We use our methods on medical datasets because class imbalance is frequently a problem there. Our research shows that the proposed algorithms can improve the accuracy and classification metrics of the given medical datasets. We propose an effective and easy-to-apply alternative to improve the prediction ability of the presented classification models in medical datasets. We test an easily reproducible set-up where any classification model can be used to model imbalanced classes. The key tuning of the model lies in the stratified train/test split as well as the parameter “class weight='balanced'”. By combination of parameter tuning, better classification performance can be obtained in a quick and simple manner. It is simple and quick to replicate our algorithms to examine various medical datasets and determine which model best fits the data. It can be reproduced in biostatistical laboratories and by medical companies. Because it is simple to comprehend, medical researchers can swiftly review the information and determine the best course of action.

Impact of the Extremities Positioning on the Set-Up Reproducibility for the Total Marrow Irradiation Treatment

Total marrow (lymph node) irradiation (TMI/TMLI) delivery requires more time than standard radiotherapy treatments. The patient's extremities, through the joints, can experience large movements. The reproducibility of TMI/TMLI patients' extremities was evaluated to find the best positioning and reduce unwanted movements. Eighty TMI/TMLI patients were selected (2013-2022). During treatment, a cone-beam computed tomography (CBCT) was performed for each isocenter to reposition the patient. CBCT-CT pairs were evaluated considering: (i) online vector shift (OVS) that matched the two series; (ii) residual vector shift (RVS) to reposition the patient's extremities; (iii) qualitative agreement (range 1-5). Patients were subdivided into (i) arms either leaning on the frame or above the body; (ii) with or without a personal cushion for foot positioning. The Mann-Whitney test was considered (p < 0.05 significant). Six-hundred-twenty-nine CBCTs were analyzed. The median OVS was 4.0 mm, with only 1.6% of cases ranked < 3, and 24% of RVS > 10 mm. Arms leaning on the frame had significantly smaller RVS than above the body (median: 8.0 mm/6.0 mm, p < 0.05). Using a personal cushion for the feet significantly improved the RVS than without cushions (median: 8.5 mm/1.8 mm, p < 0.01). The role and experience of the radiotherapy team are fundamental to optimizing the TMI/TMLI patient setup.

Use of Thermoluminescence Dosimetry for QA in High-Dose-Rate Skin Surface Brachytherapy with Custom-Flap Applicator

Surface brachytherapy (BT) lacks standard quality assurance (QA) protocols. Commercially available treatment planning systems (TPSs) are based on a dose calculation formalism that assumes the patient is made of water, resulting in potential deviations between planned and delivered doses. Here, a method for treatment plan verification for skin surface BT is reported. Chips of thermoluminescent dosimeters (TLDs) were used for dose point measurements. High-dose-rate treatments were simulated and delivered through a custom-flap applicator provided with four fixed catheters to guide the Iridium-192 (Ir-192) source by way of a remote afterloading system. A flat water-equivalent phantom was used to simulate patient skin. Elekta TPS Oncentra Brachy was used for planning. TLDs were calibrated to Ir-192 through an indirect method of linear interpolation between calibration factors (CFs) measured for 250 kV X-rays, Cesium-137, and Cobalt-60. Subsequently, plans were designed and delivered to test the reproducibility of the irradiation set-up and to make comparisons between planned and delivered dose. The obtained CF for Ir-192 was (4.96 ± 0.25) μC/Gy. Deviations between measured and TPS calculated doses for multi-catheter treatment configuration ranged from -8.4% to 13.3% with an average of 0.6%. TLDs could be included in clinical practice for QA in skin BT with a customized flap applicator.

Cross-link augmentation enhances CFR-PEEK short fixation in lumbar metastasis stabilization.

Introduction: Spinal stability plays a crucial role in the success of the surgical treatment of lumbar vertebral metastasis and, in current practice, less invasive approaches such as short constructs have been considered. Concurrently, carbon fiber-reinforced (CFR) poly-ether-ether-ketone (PEEK) fixation devices are expanding in oncologic spinal surgery thanks to their radiotransparency and valid mechanical properties. This study attempts to provide an exhaustive biomechanical comparison of different CFR-PEEK surgical stabilizations through a highly reproducible experimental setup. Methods: A Sawbones biomimetic phantom (T12-S1) was tested in flexion, extension, lateral bending, and axial rotation. An hemisome lesion on L3 vertebral body was mimicked and different pedicle screw posterior fixations were realized with implants from CarboFix Orthopedics Ltd: a long construct involving two spinal levels above and below the lesion, and a short construct involving only the levels adjacent to L3, with and without the addition of a transverse rod-rod cross-link; to provide additional insights on its long-term applicability, the event of a pedicle screw loosening was also accounted. Results: Short construct reduced the overloading onset caused by long stabilization. Particularly, the segmental motion contribution less deviated from the physiologic pattern and also the long-chain stiffness was reduced with respect to the prevalent long construct. The use of the cross-link enhanced the short stabilization by making it significantly stiffer in lateral bending and axial rotation, and by limiting mobiliza-tion in case of pedicle screw loosening. Discussion: The present study proved in vitro the biomechanical benefits of cross-link augmentation in short CFR-PEEK fixation, demonstrating it to be a potential alternative to standard long fixation in the surgical management of lumbar metastasis.

Commissioning, clinical implementation, and initial experience with a new brain tumor treatment package on a low-field MR-linac.

To evaluate the image quality, dosimetric properties, setup reproducibility, and planar cine motion detection of a high-resolution brain coil and integrated stereotactic brain immobilization system that constitute a new brain treatment package (BTP) on a low-field magnetic resonance imaging (MRI) linear accelerator (MR-linac). Image quality of the high-resolution brain coil was evaluated with the 17cm diameter spherical phantom and the American College of Radiology (ACR) Large MRI Phantom. Patient imaging studies approved by the institutional review board (IRB) assisted in selecting image acquisition parameters. Radiographic and dosimetric evaluation of the high-resolution brain coil and the associated immobilization devices was performed using dose calculations and ion chamber measurements. End-to-end testing was performed simulating a cranial lesion in a phantom. Inter-fraction setup variability and motion detection tests were evaluated on four healthy volunteers. Inter-fraction variability was assessed based on three repeat setups for each volunteer. Motion detection was evaluated using three-plane (axial, coronal, and sagittal) MR-cine imaging sessions, where volunteers were asked to perform a set of specific motions. The images were post-processed and evaluated using anin-house program. Contrast resolution of the high-resolution brain coil is superior to the head/neck and torso coils. The BTP receiver coils have an average HU value of 525 HU. The most significant radiation attenuation (3.14%) of the BTP, occurs through the lateral portion of the overlay board where the high-precision lateral-profile mask clips attach to the overlay. The greatest inter-fraction setup variability occurred in the pitch (average 1.08 degree) and translationally in the superior/inferior direction (average 4.88mm). Three plane cine imaging with the BTP was able to detect large and small motions. Small voluntary motions, sub-millimeter in magnitude (maximum 0.9mm), from motion of external limbs were detected. Imaging tests, inter-fraction setup variability, attenuation, and end-to-end measurements were quantified and performed for the BTP. Results demonstrate better contrast resolution and low contrast detectability that allows for better visualization of soft tissue anatomical changes relative to head/neck and torso coil systems.

Improving total body irradiation with a dedicated couch and 3D-printed patient-specific lung blocks: A feasibility study.

Total body irradiation (TBI) is an important component of the conditioning regimen in patients undergoing hematopoietic stem cell transplants. TBI is used in very few patients and therefore it is generally delivered with standard linear accelerators (LINACs) and not with dedicated devices. Severe pulmonary toxicity is the most common adverse effect after TBI, and patient-specific lead blocks are used to reduce mean lung dose. In this context, online treatment setup is crucial to achieve precise positioning of the lung blocks. Therefore, in this study we aim to report our experience at generating 3D-printed patient-specific lung blocks and coupling a dedicated couch (with an integrated onboard image device) with a modern LINAC for TBI treatment. TBI was planned and delivered (2Gy/fraction given twice a day, over 3 days) to 15 patients. Online images, to be compared with planned digitally reconstructed radiographies, were acquired with the couch-dedicated Electronic Portal Imaging Device (EPID) panel and imported in the iView software using a homemade Graphical User Interface (GUI). In vivo dosimetry, using Metal-Oxide Field-Effect Transistors (MOSFETs), was used to assess the setup reproducibility in both supine and prone positions. 3D printing of lung blocks was feasible for all planned patients using a stereolithography 3D printer with a build volume of 14.5×14.5×17.5 cm3. The number of required pre-TBI EPID-images generally decreases after the first fraction. In patient-specific quality assurance, the difference between measured and calculated dose was generally<2%. The MOSFET measurements reproducibility along each treatment and patient was 2.7%, in average. The TBI technique was successfully implemented, demonstrating that our approach is feasible, flexible, and cost-effective. The use of 3D-printed patient-specific lung blocks have the potential to personalize TBI treatment and to refine the shape of the blocks before delivery, making them extremely versatile.

Proof of concept for measuring growth of shelf marine calcifiers: ‘a Bryozoan odyssey’

Context The variation observed in growth rate estimates of bryozoans raise questions regarding the validity of the methods used to measure growth in these animals. Naturally, the best way for measuring growth rate is to understand the growth in situ, but access is not always straightforward. Aims This study assesses a field experiment for measuring in situ growth of heavily calcified bryozoans in the open ocean at 56 m, the deepest such deployment attempted for bryozoans. Methods Cellaria immersa colonies were collected by dredge from the continental shelf off Otago, marked using calcein, mounted on a purpose-built frame, called ‘Odyssey’, and returned to the shelf for 3 months in the Austral summer (November–February). Key results Data from 10 internodes indicated that growth was, on average, 0.97 ± 0.84 mm year−1 and showed some interesting intracolonial growth patterns. Conclusions and implications The data obtained from this study are only indicative at this stage, but we have succeeded in developing a reproducible experimental set-up for in situ growth experiments of shelf bryozoans, enabling us to record growth, lifespan, and calcification rates of heavily calcified and ecologically important species. Understanding such key species is critical to identifying their role in the ecosystem and providing valuable information for future conservation initiatives.

Use of Scanning Laser Technology to Obtain the Erhu Vibroacoustic

The aim of this research is to develop and validate an experimental model testing method in the erhu instrument. The model analysis is dependent on the dynamic behavior of materials which results the relationships to be naturally excited due to the structure. There are three major factors which would directly affect the performance of erhu vibroacoustic: (1) string, (2) vibrating skin, and (3) wooden soundbox. However, the transducer mass effect is the significant impact factor in the membrane vibration measurement. The attention is focused on the erhu skin vibration modes by using the scanning laser method. The method for experimental mode shapes of erhu skin was notable in that the equipment assembled a loudspeaker, a signal point laser, and a scanning laser vibrometer. The mode shapes can be excited depending on the white noise with plane acoustic wave to push on the skin surface. The scanning laser method is content two types of laser doppler vibrometer for various purpose. The single point laser measured the driving point vibration as the reference in the center of the skin surface. The responses were measured by the scanning laser vibrometer with 276 measuring points on the surface. The results showed the vibroacoustic of erhu skin which the various mode shapes are dependent on the frequency diversifications. The mode shapes of the erhu skin can be characteristic into five vibroacoustic patterns by the various frequency ranges (20 to 5,000 Hz). Obviously, the scanning laser method is a convenient and readily reproducible setup to evaluate in the erhu vibroacoustic properties. As an engineering application, the proposed method can be served as a fundamental tool when predicting or even suppressing the possible excitations associated with particular vibration modes in the mechanical designs of the instruments.

A versatile physical phantom design and construction for I-125 dose measurements and dose-to-medium determination

In this paper we present a phantom designed to provide conditions to generate set of "true" independent reference data as requested by TG-186, and mitigating the scarcity of experimental studies on brachytherapy validation. It was used to perform accurate experimental measurements of dose of 125I brachytherapy seeds using LiF dosimeters, with the objective of experimentally validating Monte Carlo (MC) calculations with model-based dose calculation algorithm (MBDCA). In addition, this work intends to evaluate a methodology to convert the experimental values from LiF into dose in the medium. The proposed PMMA physical phantom features cavities to insert a LiF dosimeter and a 125I seed, adjusted in different configurations with variable thickness. Monte Carlo calculations performed with MCNP6.2 code were used to score the absorbed dose in the LiF and the dose conversion parameters. A sensitivity analysis was done to verify the source of possible uncertainties and quantify their impact on the results. The proposed phantom and experimental procedure developed in this work provided precise dose data within 5.68% uncertainty (k = 1). The achieved precision made it possible to convert the LiF responses into absorbed dose to medium and to validate the dose conversion factor methodology. The proposed phantom is simple both in design and as in its composition, thus achieving the demanded precision in dose evaluations due to its easy reproducibility of experimental setup. The results derived from the phantom measurements support the dose conversion methodology. The phantom and the experimental procedure developed here can be applied for other materials and radiation sources.

PO18: An Efficient and Reproducible Autoradiography Technique for HDR-Gynecological Applicators Commissioning

<h3>Purpose</h3> High Dose Rate (HDR) brachytherapy commissioning of Elekta's gynecological (Gyn) applicator sets include a large inventory of CT/MR compatible plastic, applicator tubes of varying shapes and sizes. This often present a challenge to the efficiency of source autoradiography - an essential test to determine and verify final dwell position of the HDR source and its positioning/stepping accuracy. We present a technique of acquiring radiograph-autoradiograph combinations of HDR-Gyn applicators that allows testing of several applicators simultaneously, in a rigid and reproducible set-up. <h3>Materials Methods</h3> Elekta provides x-ray catheter (marker) sets as a required accessory to verify source positioning inside Gyn applicators. Once the markers are calibrated & Final Marker Position (FMP) characterized, using Elekta's Source Position Check Ruler & CT-scans, the technique of radiograph-autoradiograph superposition is recommended for determination of final dwell position (FDP) & verification of source positioning accuracy. To ensure a rigid & reproducible set-up, template trays to hold multiple applicator tubes & Gafochromic EBT3 film for recording multiple radiographs in unison were built using Styrofoam. Channels were carved in styrofoam creating tight narrow groves fitting applicators in place. Applicators were taped with tips laid flat & flush with the film secured to styrofoam base independently. Primary advantage of using styrofoam is that it offers no backscatter to radiography as well as gamma photons from the Ir-192 source. Additionally, it is readily available and easy to work with. Each tray held 4-6 applicators with markers allowing a simultaneous radiograph acquisition, &∼ 5 cm lateral spacing enabled independent images. Truebeam^TM Linear accelerator was used for radiography. Multiple pre-prepared template trays with applicators were exposed at a source-to-film-distance of 100 cm with 400 monitor units using 2.5 MV imaging beam. This technique provided best visualization of the plastic applicator & marker on a gafochromic EBT3 film. Once the multiple-applicator-radiograph is acquired, templates were transported to adjacent HDR suite, set on a rigid couch, markers carefully removed & transfer tube connected for acquisition of autoradiograph coincident with recently acquired radiograph, using Flexitron afterloader. For Ir-192 source's autoradiograph, a 10-15 seconds dwell time is adequate to darken film with marker visualization reasonably intact for analysis. Pre-prepared templates and availability of personnel allowed simultaneous use of linear accelerator & afterloader, for radiograph & autoradiograph acquisition, adding further efficiency. Source positioning & stepping accuracy was verified by coincidence of center of darkening at the exposed dwell-position & center of visualized markers, on a viewbox illuminator. <h3>Results</h3> Using techniques and workflow developed, 60 CT/MR compatible HDR-Gyn plastic applicators were commissioned. Autoradiography-radiography superposition with x-ray markers enabled verification of Elekta specified distances between the outer tip of the IU/ovoid tubes, inner tip & the final dwell position, & HDR source positioning & stepping accuracy within 1 mm. Figure 1-A shows Styrofoam templates with multiple channels for affixing applicators over EBT3 Gafochromic film for radiography, 1-B is HDR room setup for autoradiography and 1-C shows images of multiple different applicator tubes depicting the radiograph-autoradiograph overlay with marker visualization and HDR source positioning. <h3>Conclusion</h3> We present an efficient autoradiography technique for commissioning of a large inventory HDR-Gyn plastic applicators using a linear accelerator & HDR afterloader.

PO10: Case Presentation and Workflow for a 3D Printed Mold for HDR Brachytherapy of the Lower Lip

<h3>Introduction</h3> Interstitial head and neck brachytherapy is a versatile tool but requires intense patient and clinical resources as well as a high level of physician skill. For certain lesions, 3D printed brachytherapy molds may provide an "easier" alternative to interstitial brachytherapy. Recently, a patient presented with a progressive recurrent squamous cell carcinoma (SCC) in situ of the lower lip two years after prior Mohs surgery. As surgery for removal of the lesion would be disfiguring, radiotherapy was pursued. Electron radiotherapy would be difficult due to the curved surface. Thus, brachytherapy options were considered, however the use of interstitial brachytherapy would have been technically difficult as well as invasive. Commercial surface brachytherapy applicators would not fit the lesion and location, and therefore, a 3D printed brachytherapy applicator was utilized. <h3>Materials and Methods</h3> To create the 3D printed mold, two CT scans were required prior to mold design - one scan with radiopaque wires to define the target volume on the CT scan, and a second scan without wires, used to accurately define the patient surface for the 3D-printed mold. In this instance, the lower lip had to be rolled outward to expose the lesion and had to be immobilized in this position. Immobilization of the lower lip was achieved with adhesive attached to the lip and chest (Figure 1.a.). A standard bite block was inserted into the patient's mouth to keep the teeth in a reproducible position with the final intent that the 3D mold could be designed to attach to this bite block. CT scans were acquired at 1.25 mm thickness. A 3D mold was designed using our standard process in the Adaptiiv 3D bolus software. A pre-plan was created with the mold design in BrachyVision (Varian, Palo Alto, CA) to determine if the desired dosimetry to the target volume was achievable. Once a final mold design was approved, printing utilized an Axiom20 3D printer with Cheetah TPU. <h3>Results</h3> The final mold is shown in Figure 1.b and 1.c., illustrating that the mold was designed to fit over the pegs of the bite block. Several mold designs were considered, and ultimately an open bottomed mold was selected (Figure 1.d.) to allow for visualization of setup and also in case the lip swelled during treatment. A final CT of the patient with the mold in place was obtained to evaluate final mold fit and perform final CT planning (Figure 1.f.), as well as to acquire setup measurements (Figure 1.e.). Air gaps were minimal and only in two locations over the treatment volume which were all ≤1.5mm. The patient received 40 Gy in 10 fractions every other day. Near the end of treatment, topical lidocaine was applied to the patient's lip to help with applicator tolerance. Follow-up pictures are shown in Figure 1.g-i. Some moist desquamation was visible at the 1 week follow-up but resolved by six weeks posttreatment. At 10 months, the patient shows no signs of recurrence and no significant treatment-related toxicities. <h3>Conclusions</h3> A recurrent SCC in situ of the lower lip was successfully immobilized, planned, and treated with HDR brachytherapy using a custom 3D-printed mold. The benefits of the 3D mold allow for rigid immobilization of the lip for a reproducible and comfortable setup. Further research is needed into the optimal indications and applicator designs for 3D-printed applicators for head and neck brachytherapy.

Ultrasound Guided Hysteroscopy in the Complex Uterine Isthmus

<h3>Study Objective</h3> To demonstrate clinical considerations, operative setup and techniques for a reproducible method of achieving safe hysteroscopic access to the endometrial cavity using multimodal imaging techniques to navigate the complex uterine isthmus. <h3>Design</h3> Educational and stepwise instructional narrated surgical video. <h3>Setting</h3> Community Gynecologic Surgery Referral Practice <h3>Patients or Participants</h3> A 31-year-old G1P1 patient with severe cervical stenosis and high-grade isthmocele is referred for assistance with cervical dilation prior to planned embryo transfer. <h3>Interventions</h3> The patient underwent combined simultaneous hysteroscopic and ultrasonographic visualization to safely access the endometrial cavity. <h3>Measurements and Main Results</h3> A reproducible procedural setup and workflow is described in depth including positioning of patient, assistants and technology as well as detailed stepwise procedure instructions to obtain endometrial access without perforation. <h3>Conclusion</h3> As recognition of isthmocele and other anatomic pathology increases alongside high rates of cesarean section, the gynecologic surgeon must command careful perioperative planning, multimodal imaging techniques and a firm grasp of instrumentation safety parameters as part of the advanced endoscopic skill set required to navigate this complex anatomic area.

Laparoscopic Suturing of the Vaginal Cuff: A Surgical Education Module for Obstetrics and Gynecology Residents

<h3>Study Objective</h3> We aim to review the assembly of a laparoscopic box trainer with a validated vaginal cuff model and to highlight principles for efficient two-handed laparoscopic vaginal cuff closure using three unique port configurations (ipsilateral, contralateral, and midline). This video was created as part of a surgical education module for Obstetrics and Gynecology residents. <h3>Design</h3> Surgical education video. <h3>Setting</h3> Laparoscopic box trainer with a validated vaginal cuff model. <h3>Patients or Participants</h3> Education module for Ob/Gyn resident physicians. <h3>Interventions</h3> The validated vaginal cuff model incorporates multiple layers to represent the vaginal epithelium and vaginal wall. We demonstrate laparoscopic suturing using a running technique from ipsilateral, contralateral, and suprapubic port configurations. A braided suture with a knot at the end simulates a unidirectional barbed suture that does not require knot tying. Critical steps needed for proper cuff closure are highlighted. <h3>Measurements and Main Results</h3> In this video, we highlight a reproducible setup of a validated vaginal cuff model within a laparoscopic box trainer. We demonstrate correct needle loading for enhanced accuracy in needle entry and exit. Efficient techniques to achieve adequate exposure, incorporation of vaginal epithelium, appropriate suture tension, and optimized ergonomics are also reviewed. <h3>Conclusion</h3> We present a surgical education video to teach safe and efficient laparoscopic suturing techniques to Ob/Gyn resident physicians using multiple two-handed port configurations. Key surgical principles include proper needle loading, needle entry, exposure, and optimized ergonomics.

A Prospective, Randomized, Controlled Clinical Study of Cervical Muscle Group Training Improving Radiotherapy Setup Accuracy Repeatability for Head and Neck Tumors

<h3>Purpose/Objective(s)</h3> Studies have shown that head and neck tumors are impossible to achieve an ideal match over the entire length of the neck due to the wide range of radiotherapy target areas. Previous studies have shown random deformation errors of 0.5 to 3.6 mm in the head and neck, the difference between any two different matched areas can reach 2 to 6 mm. we aimed to evaluate the role of neck muscle group training on the repeatability of the pose in patients treated with radiotherapy for head and neck tumors. <h3>Materials/Methods</h3> Patients treated with radiotherapy for head and neck tumors were randomly assigned (1:1) to a study group and a control group. The study group started cervical spine exercises+massage training one week before the start of radiotherapy until the end of radiotherapy. In the control group, conventional treatment without specific interventions was performed. The primary endpoint was the difference in the reproducibility of cervical spine set-up between the two groups, and the secondary endpoints were the differences in cervical curvature changes on lateral cervical radiographs before and after treatment between the two groups, and the differences in the timing and extent of side effects before, during, and after treatment between the two groups. <h3>Results</h3> A total of 947 CBCT scans were performed in 166 patients, including 479 CBCTs in 83 patients in the study group and 468 CBCTs in 83 patients in the control group. 26.51% (22/83) of the study group and 33.73% (28/83) of the control group had an error of ≥3 mm during the first treatment, (P=0.31). Patients with clivus and neck error >3mm in anterior-posterior direction during treatment accounted for 8.43% (7/83) of the study group and 26.51% (22/83) of the control group(P=0.002). The number of repeated setups except the first treatment was 2.42% in the study group and 7.02% in the control group (P=0.01). The error range from clivus to neck was (7, 3, 7) mm. setup error: in the clivus position of the two groups in the X, Y, Z three directions of the Setup error were (0.95 ± 0.89, 1.09 ± 0.94, 1.62 ± 1.18) mm vs (1.02 ± 0.94, 1.14 ± 0.96, 1.82 ± 1.21) mm, p in the z-direction is statistically significant (p = 0.01); The position of the 4,7th cervical vertebra also had statistical significance in the Z direction. Comparison between the surgical study group and non-surgical study group, the errors in the x and Z directions of the clivus and the 7th cervical vertebra were (0.99±0.96, 1.65±1.36 and 1.64±1.23, 1.61±1.37) mm vs (0.80±0.77, 1.85±1.44 and 1.67±1.07, 1.95±1.60) mm, P = 0.02, 0.11, 0.77, 0.01; the results were similar to it when comparing surgical controls to non-surgical controls. It can be seen from the data that in the X and Z directions from the clivus to the neck, the error change of the surgical group is smaller than that of the non-surgical group. There was no difference in toxicity and side effects. <h3>Conclusion</h3> The results show that neck muscle training can improve the anterior and posterior neck deformation error, improve the radiotherapy accuracy and setup efficiency.

Preclinical Research Platform for Ocular FLASH Irradiation

<h3>Purpose/Objective(s)</h3> Normal tissue sparing effects from FLASH radiotherapy (RT) are potentially transformative for the treatment of ocular cancers. Reducing damage to the abundant at-risk structures within the eye can prospectively increase visual retention rates, relax treatment margins, and eliminate the need for motion tracking by surgically implanted fiducials. To date, no prior work has explored FLASH-RT effects in the context of the eye. In this work, we have conducted a pilot study of x-ray FLASH effects for ocular irradiation in a preclinical mouse model by measuring the functional and pathological changes in healthy eyes following FLASH or conventional (CONV) dose rate irradiation. <h3>Materials/Methods</h3> An immobilization device was designed to enable focal irradiation to a single mouse eye using a FLASH-capable rotating anode x-ray tube. A 5 mm diameter lead collimator was manufactured to encompass the 3 mm target of the entire eye. Dose and dose rate measurements were performed with calibrated radiographic EBT3 films. Cone-beam CTs were acquired of four C57BL6J mice in immobilization to confirm setup reproducibility, quantified by the mean Hausdorff distance between bone segmentations. Healthy 8-week-old C57BL6J mice were irradiated with 150 kVp x-rays to doses of 21 Gy or 34 Gy at FLASH (right eye) and CONV (left eye) dose rates, respectively. Both eyes were irradiated to limit the influence of varying baseline vision between animals in our analysis. Visual acuity was assessed in 3 mice per dose level using scotopic electroretinography (ERG) up to 2 months post irradiation. Histopathological changes were assessed through H&E staining of harvested eyes. <h3>Results</h3> Mouse setup in our immobilization device was highly reproducible, with a mean Hausdorff distance of 0.34 ± 0.10 mm. Measured dose rates within the field were 67.0 ± 1.9 Gy/s and 1.2 ± 0.1 Gy/s at FLASH and CONV settings, respectively. ERGs revealed that FLASH-irradiated eyes at 21 Gy retained visual function up to 2 months post irradiation, while 21 Gy CONV induced blindness at all sampled time points with more severe surrounding skin effects. At 34 Gy, all eyes were blinded within 1 week, with comparable skin toxicities in the irradiated areas regardless of dose rate. Pathological assessment showed a loss of the photoreceptor layer of the retina from CONV irradiation, which remained intact in FLASH-treated mice. <h3>Conclusion</h3> We have developed a novel platform to study x-ray FLASH effects from ocular irradiation in mice. Functional ERG assay revealed a preservation of visual function from 21 Gy at FLASH dose rates that was not present from 21 Gy CONV. Differential damages between FLASH and CONV irradiations were confirmed through histopathology. This first demonstration of FLASH normal tissue sparing effects in a mouse eye model presents a unique and promising translation opportunity for clinical FLASH treatment. Further studies are ongoing to explore the long-term effects of FLASH radiation on vision and its efficacy on intraocular tumors.

Cervical Spine Setup Reproducibility Using Standard Headrests vs. Custom Headrests in Head and Neck Cancer Patients

Cervical Spine Setup Reproducibility Using Standard Headrests vs. Custom Headrests in Head and Neck Cancer Patients

Retrospective Analysis of Replan Frequency and Causes in Esophageal Cancer Patients Treated with Spot Scanned Proton Therapy

<h3>Purpose/Objective(s)</h3> For patients with esophageal cancer treated with intensity-modulated proton therapy (IMPT) at our institution, weekly verification CT scans are obtained to ensure that the plan is still acceptable. If unacceptable deviations from the intended dose are observed, replanning is performed. This study aims to investigate the frequency and causes of replans to determine the appropriate frequency of performing verification scans. <h3>Materials/Methods</h3> Data from a cohort of 205 esophageal cancer patients treated with IMPT between 2015 and 2020 were retrospectively analyzed. Patients were typically positioned head first supine with arms up in a vacuum immobilization device, and a four-dimensional CT (4DCT) simulation scan was obtained. The typical prescription was 50 Gy in 25 fractions over 5 weeks, with contours delineated as per consensus guidelines. For tumor motion ≤ 10 mm, patients were treated free-breathing with isolayer repainting, while for motion > 10 mm, gating was also added. Two posterior oblique beams were typically used, and single field optimization was performed. Robust optimization was utilized with 5-mm translational perturbations and 3% range uncertainty, with dose evaluation, also performed on the extreme respiratory phases. Weekly 4DCT verification scans in treatment position were acquired. Rigid image registration to the original planning CT image set was performed, and the care team reviewed the recalculated dose distributions to determine the need for replan. CTV (V95%) % was selected as a metric to compare the difference in target volume dose between verification scans that did [CTV_replan (V95%) %], versus did not [CTV_no-replan (V95%) %], lead to a replan. <h3>Results</h3> The primary tumor location was upper/middle esophagus (16%) or lower/gastroesophageal junction (83%). 21 patients (10%) required replanning, including 3 patients with 2 replans. Replans occurred during the 1^st (20%), 2^nd (33%), 3^rd (20%), or 4^th (25%) weeks of treatment. Primary reasons for replanning were a superior shift of the diaphragm baseline position affecting the range of the beams entering near this interface (46%), changes in tumor size or position (17%), new or resolving pleural effusion affecting the range of beams (13%), changes in stomach filling affecting the target geometry (13%), and patient setup reproducibility issues (13%). The average value of CTV_no-replan (V95%) % = 98% ± 3% vs. CTV_replan (V95%) % = 96% ± 1%. The modest size of this difference suggests that other factors, including poor fidelity of rigid CTV contours, also contribute to clinical decision-making. <h3>Conclusion</h3> In this large cohort of patients with esophageal cancer treated with robustly planned IMPT, the rate of adaptive replanning was 10% and resulted from 5 discrete changes as described above. Every other week frequency of verification scans should be considered.