Patient Setup Research Articles

First-in-human trial using mixed-reality visualization for patient setup during breast or chest wall radiotherapy

Abstract Background The purpose of this study is to assess the feasibility of mixed-reality (MixR) visualization for patient setup in breast and chest wall radiotherapy (RT) by performing a first-in-human clinical trial comparing MixR with a 3-point alignment. Methods IRB approval was granted for a study incorporating MixR during the setup process for patients undergoing proton (n = 10) or photon (n = 8) RT to the breast or chest wall. For each patient, MixR was utilized for five fractions and compared against another five fractions using 3-point alignment. During fractions with MixR, the patient was aligned by at least one therapist wearing a HoloLens 2 device who was able to guide the process by simultaneously and directly viewing the patient and a hologram of the patient’s surface derived from their simulation CT scan. Alignment accuracy was quantified with cone-beam CT (CBCT) for photon treatments and CBCT plus kV/kV imaging for proton treatments. Registration time was tracked throughout the setup process as well as the amount of image guidance (IGRT) utilized for final alignment. Results In the proton cohort, the mean 3D shift was 0.96 cm using 3-point alignment and 1.18 cm using MixR. An equivalence test indicated that the difference in registration accuracy between the two techniques was less than 0.5 cm. In the photon cohort, the mean 3D shift was 1.18 cm using 3-point alignment and 1.00 cm using MixR. An equivalence test indicated that the difference in registration accuracy was less than 0.3 cm. Minor differences were seen in registration time and the amount of IGRT utilization. Conclusions MixR for patient setup for breast cancer RT is possible at the level of accuracy and efficiency provided by a 3-point alignment. Further developments in marker tracking, feedback, and a better understanding of the perceptual challenges of MixR are needed to achieve a similar level of accuracy as provided by modern surface-guided radiotherapy (SGRT) systems. Trial registration ClinicalTrials.gov, UFHPTI 2015-BR05: Improving Breast Radiotherapy Setup and Delivery Using Mixed-Reality Visualization, NCT05178927.

Quantification of uncertainties in reference and relative dose measurements, dose calculations, and patient setup in modern external beam radiotherapy.

Uncertainties in the steps of external beam radiotherapy (EBRT) affect patient outcomes. However, few studies have investigated major contributors to these uncertainties. This study investigated factors contributing to reducing uncertainty in delivering a dose to a target volume. The EBRT process was classified into four steps: reference dosimetry, relative dosimetry [percentage depth doses (PDDs) and off-center ratios (OCRs)], dose calculations (PDDs and OCRs in a virtual water phantom), and patient setup using an image-guided radiation therapy system. We evaluated the uncertainties for these steps in conventionally fractionated EBRT for intracranial disease using 4-, 6-, and 10-MV flattened photon beams generated from clinical linear accelerators following the Guide to the Expression of Uncertainty in Measurement and an uncertainty evaluation method with uncorrected deflection. The following were the major contributors to these uncertainties: beam quality conversion factors for reference dosimetry; charge measurements, chamber depth, source-to-surface distance, water evaporation, and field size for relative dosimetry; dose calculation accuracy for the dose calculations; image registration, radiation-imaging isocenter coincidence, variation in radiation isocenter due to gantry and couch rotation, and intrafractional motion for the patient setup. Among the four steps, the relative dosimetry and dose calculation (namely, both penumbral OCRs) steps involved an uncertainty of more than 5% with a coverage factor of 1. In the EBRT process evaluated herein, the uncertainties in the relative dosimetry and dose calculations must be reduced.

Impact of deep inspiration breath hold, surface-guided radiotherapy, and daily CBCT on the organs at risk in breast cancer radiotherapy.

The goal of the study was to assess the impact of deep inspiration breath hold technique (DIBH), surface-guided radiotherapy (SGRT), and daily kilovoltage cone-beam computed tomography (kV-CBCT) on the dose to organs at risk (OAR) in left-sided breast cancer radiotherapy. Twenty-six consecutive left-sided breast cancer patients treated using Volumetric Intensity Modulated Arc Therapy (VMAT), DIBH, SGRT, and a hypofractionated regimen were retrospectively evaluated in this study. Dose parameters were extracted from dose-volume histograms (DVH). The Wilcoxon Matched Pairs test was used to test dose parameters obtained in free breathing (FB) and DIBH for statistical significance. Multivariable analysis of variance (ANOVA) and receiver operating characteristics (ROC) analysis were used to identify parameters and cut-off points associated with the reduction of the mean heart dose (MHD) by DIBH. Based on published models, the risk of cardiac and lung toxicity (pneumonitis) using SGRT or daily kV-CBCT was estimated and compared. DIBH substantially reduced the MHD (median, 43.6%; range, 4.2% to 75.1%; P < 0.00001). The risk of cardiac toxicity using SGRT increased by 1%, compared to 3.6% to 20.5% using daily kV-CBCT. No significant difference in the risk of radiation-induced pneumonitis using SGRT versus daily kV-CBCT was detected. The ANOVA revealed the relative increase of the left lung volume by DIBH as the only significant impact factor for the MHD. The ROC analysis of this parameter showed an area under the curve (AUC) of 0.89 (95%CI, 0.71 to 0.98; P < 0.0001). DIBH can substantially reduce the MHD in left-sided breast cancer patients treated with modern radiotherapy techniques and hypofractionation. Patient setup using SGRT compared to daily kV-CBCT may be the preferred option for many patients. In our patient cohort, the relative reduction of the left lung volume by DIBH can be used as a predictor to select patients who benefit from DIBH.

Deep learning prediction of scenario doses for direct plan robustness evaluations in IMPT for head-and-neck

Objective. Intensity modulated proton therapy (IMPT) is susceptible to uncertainties in patient setup and proton range. Robust optimization is employed in IMPT treatment planning to ensure sufficient coverage of the clinical target volume (CTV) in predefined scenarios, albeit at a price of increased planning times. We investigated a deep learning (DL) strategy for dose predictions in individual error scenarios in head and neck cancer IMPT treatment planning, enabling direct evaluation of plan robustness. The model is able to differentiate between scenarios by using embeddings of the scenario index.Approach. To accommodate resolution disparities in planning CT-scans and accommodate the setup error scenarios, we introduced scenario-specific isocentric distance maps as inputs to the DL models. For 392 H&N cancer patients, high-quality 9-scenario ground truth (GT) robust plans were generated with wish-list driven fully automated multi-criteria optimization. The scenario index is converted to one-hot-vector that is used to derive the scenarios embeddings through the training of the DL model, aiding the model to predict a scenario specific dose distribution.Main results. The model achieved within 1%-point of agreement with the GT the predictedV95%of the voxelwise minimum dose for CTV Low and CTV High for 96% and 75% respectively of the test patients. Considering all robustness scenarios, median differences were 0.035%-point for CTV HighV95%, 0.11%-point for CTV LowV95%, 0.29 GyE for parotidsDmean, 0.7 GyE for submandibular glandsDmeanand 0.9 GyE for oral cavityDmean. Prediction of full 3D dose distributions for all scenarios took around 14 s.Significance. Predicting individual scenarios for robust proton therapy using DL dose prediction is feasible, enabling direct robustness evaluation of the predicted scenario doses.

Optimisation of cone beam CT radiotherapy imaging protocols using a novel 3D printed head and neck anthropomorphic phantom

Objective.This study aimed to optimise Cone Beam Computed Tomography (CBCT) protocols for head and neck (H&N) radiotherapy treatments using a 3D printed anthropomorphic phantom. It focused on precise patient positioning in conventional treatment and adaptive radiotherapy (ART).Approach.Ten CBCT protocols were evaluated with the 3D-printed H&N anthropomorphic phantom, including one baseline protocol currently used at our centre and nine new protocols. Adjustments were made to milliamperage and exposure time to explore their impact on radiation dose and image quality. Additionally, the effect on image quality of varying the scatter correction parameter for each of the protocols was assessed. Each protocol was compared against a reference CT scan. Usability was assessed by three Clinical Scientists using a Likert scale, and statistical validation was performed on the findings.Main results. The work revealed variability in the effectiveness of protocols. Protocols optimised for lower radiation exposure maintained sufficient image quality for patient setup in a conventional radiotherapy pathway, suggesting the potential for reducing patient radiation dose by over 50% without compromising efficacy. Optimising ART protocols involves balancing accuracy across brain, bone, and soft tissue, as no single protocol or scatter correction parameter achieves optimal results for all simultaneously.Significance.This study underscores the importance of optimising CBCT protocols in H&N radiotherapy. Our findings highlight the potential to maintain the usability of CBCT for bony registration in patient setup while significantly reducing the radiation dose, emphasizing the significance of optimising imaging protocols for the task in hand (registering to soft tissue or bone) and aligning with the as low as reasonably achievable principle. More studies are needed to assess these protocols for ART, including CBCT dose measurements and CT comparisons. Furthermore, the novel 3D printed anthropomorphic phantom demonstrated to be a useful tool when optimising CBCT protocols.

Six-degrees-of-freedom pelvic bone monitoring on 2D kV intrafraction images to enable multi-target tracking for locally advanced prostate cancer.

Patients with locally advanced prostate cancer require the prostate and pelvic lymph nodes to be irradiated simultaneously during radiation therapy treatment. However, relative motion between treatment targets decreases dosimetric conformity. Current treatment methods mitigate this error by having large treatment margins and often prioritize the prostate at patient setup at the cost of lymph node coverage. Treatment accuracy can be improved through real-time multi-target adaptation which requires simultaneous motion monitoring of both the prostate and lymph node targets. This study developed and evaluated an intrafraction pelvic bone motion monitoring method as a surrogate for pelvic lymph node displacement to be combined with prostate motion monitoring to enable multi-target six-degrees-of-freedom (6DoF) tracking using 2D kV projections acquired during treatment. A method to monitor pelvic bone translation and rotation was developed and retrospectively applied to images from 20 patients treated in the TROG 15.01 Stereotactic Prostate Ablative Radiotherapy with Kilovoltage Intrafraction Monitoring (KIM) trial. The pelvic motion monitoring method performed template matching to calculate the 6DoF position of the pelvis from 2D kV images. The method first generated a library of digitally reconstructed radiographs (DRRs) for a range of imaging angles and pelvic rotations. The normalized 2D cross-correlations were then calculated for each incoming kV image and a subset of DRRs and the DRR with the maximum correlation coefficient was used to estimate the pelvis translation and rotation. Translation of the pelvis in the unresolved direction was calculated using a 3D Gaussian probability estimation method. Prostate motion was measured using the KIM marker tracking method. The pelvic motion monitoring method was compared to the ground truth obtained from a 6DoF rigid registration of the CBCT and CT. The geometric errors of the pelvic motion monitoring method demonstrated sub-mm and sub-degree accuracy and precision in the translational directions ( , , ) and rotational directions ( , , ). The 3D relative displacement between the prostate and pelvic bones exceeded 2, 3, 5, and 7mm for approximately 66%, 44%, 12%, and 7% of the images. Accurate intrafraction pelvic bone motion monitoring in 6DoF was demonstrated on 2D kV images, providing a necessary tool for real-time multi-target motion-adapted treatment.

Quality management of head and neck patient treatments using statistical process control techniques.

The treatment, planning, simulation, and setup of radiotherapy patients contain many processes subject to errors involving both staff and equipment. Cone-beam-CT (CBCT) provides a final check of patient positioning and corrections based on this can be made prior to treatment delivery. Statistical Process Control (SPC) techniques are used in various industries for quality management and error mitigation. The utility of SPC techniques to monitor process and equipment changes in our Head and Neck patient treatments was assessed by application to CBCT results from a quality-focused longitudinal study. Individuals and moving range (XmR) as well as exponentially-weighted moving average (EWMA) techniques were explored. The SPC techniques were sensitive to process changes and trends over the 12 years of data collected. A reduction in the random component of patient setup errors needing correction was observed. Systematic components of error remained more stable. An uptick in both datasets was observed correlating with the COVID-19 pandemic. Process control limits for use in prospective process monitoring were established. Challenges that arose from using SPC techniques in a retrospective study are outlined.

324 - Initial clinical experience using a 6-dimensional (6D) positioning system with surface and thermal guidance for setup and intra-fraction motion management of partial-breast radiotherapy patients

324 - Initial clinical experience using a 6-dimensional (6D) positioning system with surface and thermal guidance for setup and intra-fraction motion management of partial-breast radiotherapy patients

Setup errors analysis in iterative kV CBCT: A clinical study of cervical cancer treated with Volumetric Modulated Arc Therapy.

This study aims to analyze setup errors in pelvic Volumetric Modulated Arc Therapy (VMAT) for patients with non-surgical primary cervical cancer, utilizing the onboard iterative kV cone beam CT (iCBCT) imaging system on the Varian Halcyon 2.0 ring gantry structure accelerator to enhance radiotherapy precision. We selected 132 cervical cancer patients who underwent VMAT with daily iCBCT imaging guidance. Before each treatment session, a registration method based on the bony structure was employed to acquire iCBCT images with the corresponding planning CT images. Following verification and adjustment of image registration results along the three axes (but not rotational), setup errors in the lateral (X-axis), longitudinal (Y-axis), and vertical (Z-axis) directions were recorded for each patient. Subsequently, we analyzed 3642 iCBCT image setup errors. The mean setup errors for the X, Y, and Z axes were 4.50±3.79mm, 6.08±6.30mm, and 1.48±2.23mm, respectively. Before correction with iCBCT, setup margins based on the Van Herk formula for the X, Y, and Z axes were 6.28, 12.52, and 3.26mm, respectively. In individuals aged 60 years and older, setup errors in the X and Y axes were significantly larger than those in the younger group (p<0.05). Additionally, there is no significant linear correlation between setup errors and treatment fraction numbers. Data analysis underscores the importance of precise Y-axis setup for cervical cancer patients undergoing VMAT. Radiotherapy centers without daily iCBCT should appropriately extend the planning target volume (PTV) along the Y-axis for cervical cancer patients receiving pelvic VMAT. Elderly patients exhibit significantly larger setup errors compared to younger counterparts. In conclusion, iCBCT-guided radiotherapy is recommended for cervical cancer patients undergoing VMAT to improve setup precision.

Assessment of cancer predisposition syndromes in children with leukemia and solid tumors: germline-genomic profiling and clinical features in a series of cases

Cancer predisposition syndromes (CPS) are a group of genetic disorders that increase the risk of various cancers. Identifying CPS has a significant impact on the treatment plan, screening and follow-up strategy, and genetic counseling of the family. However, in children, it goes underdiagnosed in most clinical setups, especially in low- and middle-income (LMIC) countries. In the present study, we screened 60 pediatric oncology patients for a possible CPS based on pre-defined selection criteria. Six patients met the criteria, three of whom had hematological malignancy, while the remaining three had sarcoma. Whole exome sequencing was performed in the selected patients to confirm the diagnosis. Germline mutation in CPS-related genes was discovered in five of six cases, including novel mutations discovered in two. An adverse outcome was observed in all five patients with underlying cancer predisposition syndrome, with three having relapsed and two having progressive disease. Our study reflects a prevalence of 10% underlying CPS in a limited cohort of patient based on the phenotype-genotype approach in our cohort. Using pre-defined clinical selection criteria, screening can be directed to a high-risk patient cohort with high-pick up rate for CPS. The selection criteria could be utilized in any LMIC-based clinical setup for pediatric cancer patients who may benefit from modification of treatment as well as genetic counseling.

Assessing Surface Guided Radiation Therapy Benefits for Paediatric Cancer Patients: Dosimetric Implications of Intrafractional Motion - An Institutional Review

&amp;lt;i&amp;gt;Introduction/Background&amp;lt;/i&amp;gt;: SGRT, a real-time imaging technique, offers continuous monitoring and motion control during &amp;lt;i&amp;gt;treatment&amp;lt;/i&amp;gt;. The investigation aims to assess potential dosimetric alterations in target coverage due to intrafractional motion, considering its impact on patient safety and treatment efficiency. &amp;lt;i&amp;gt;Materials and Methods&amp;lt;/i&amp;gt;: A retrospective chart review was conducted to assess intrafractional shifts in 18 paediatric cancer patients. Patient setup employed SGRT using AlignRT (Vision RT Ltd., UK), and the PTV was aligned with CBCT. The study introduced induced shifts of 3 mm, 5 mm, and 7 mm during treatment delivery, assessing their impact on portal dosimetry results for both treatment fields. The gamma index criteria (3%, 3 mm) were employed to evaluate dosimetric accuracy. &amp;lt;i&amp;gt;Results&amp;lt;/i&amp;gt;: A total of 18 patients were included, and induced shifts were analyzed for their impact on the planned gamma index values. Significant differences were observed between the Planned Gamma Index and induced shifts of 3 mm, 5 mm, and 7 mm for both treatment fields, highlighting the dosimetric implications of intrafractional motion in paediatric cases. &amp;lt;i&amp;gt;Conclusion&amp;lt;/i&amp;gt;: Surface Guided Radiation Therapy (SGRT) is concluded to offer a comprehensive array of benefits for paediatric cases. The dosimetric implications of induced shifts underscore the importance of SGRT in ensuring accurate and safe treatment for paediatric cancer patients.

Clinical implementation and evaluation of stereotactic liver radiotherapy in inspiration breath-hold using nasal high flow therapy and surface guidance.

To evaluate two years of clinical experience with markerless breath-hold liver stereotactic radiotherapy (SBRT) using non-invasive nasal high flow therapy (NHFT) for breath-hold prolonging and surface guidance (SGRT) for monitoring. Heated and humidified air was administered via a nasal cannula (40 L/min, 80% oxygen, 34 °C). Patients performed voluntary inspiration breath-holds with visual feedback. After a training session, 4-5 breath-hold CT scans were acquired to delineate an internal target volume (ITV) accounting for inter- and intra-breath-hold variations. Patients were treated in 3-8 fractions (7.5-20 Gy/fraction) using SGRT-controlled beam-hold. Patient setup was performed using SGRT and CBCT imaging. A post-treatment CBCT was acquired for evaluation purposes. Fifteen patients started the training session and received treatment, of whom 10 completed treatment in breath-hold. Half of all 60-second CBCT scans were acquired during a single breath-hold. The average maximum breath-hold duration during treatment ranged from 47-108 s. Breath-hold ITV was on average 6.5 cm³/30% larger (range: 1.1-23.9 cm³/5-95%) than the largest GTV. Free-breathing ITV based on 4DCT scans was on average 16.9 cm³/47% larger (range: -2.3-58.7 cm3/-16-157%) than the breath-hold ITV. The average 3D displacement vector of the area around PTV for the post-treatment CBCT scans was 5.0 mm (range: 0.7-12.9 mm). Liver SBRT in breath-hold using NHFT and SGRT is feasible for the majority of patients. An ITV reduction was observed compared to free-breathing treatments. To further decrease the PTV, internal anatomy-based breath-hold monitoring is desired. Non-invasive NHFT allows for prolonged breath-holding during surface-guided liver SBRT.

Comparative analysis of delivered and planned doses in target volumes for lung stereotactic ablative radiotherapy

BackgroundAdaptive therapy has been enormously improved based on the art of generating adaptive computed tomography (ACT) from planning CT (PCT) and the on-board image used for the patient setup. Exploiting the ACT, this study evaluated the dose delivered to patients with non-small-cell lung cancer (NSCLC) patients treated with stereotactic ablative radiotherapy (SABR) and derived relationship between the delivered dose and the parameters obtained through the evaluation procedure.MethodsSABR treatment records of 72 patients with NSCLC who were prescribed a dose of 60 Gy (Dprescribed) to the 95% volume of the planning target volume (PTV) in four fractions were analysed in this retrospective study; 288 ACTs were generated by rigid and deformable registration of a PCT to a cone-beam computed tomography (CBCT) per fraction. Each ACT was sent to the treatment planning system (TPS) and treated as an individual PCT to calculate the dose. Delivered dose to a patient was estimated by averaging four doses calculated from four ACTs per treatment. Through the process, each ACT provided the geometric parameters, such as mean displacement of the deformed PTV voxels (Warpmean) and Dice similarity coefficient (DSC) from deformation vector field, and dosimetric parameters, e.g. difference of homogeneity index (ΔHI, HI defined as (D2%-D98%)/Dprescribed*100) and mean delivered dose to the PTV (Dmean), obtained from the dose statistics in the TPS. Those parameters were analyzed using multiple linear regression and one-way-ANOVA of SPSS® (version 27).ResultsThe prescribed dose was confirmed to be fully delivered to internal target volume (ITV) within maximum difference of 1%, and the difference between the planned and delivered doses to the PTV was agreed within 6% for more than 95% of the ACT cases. Volume changes of the ITV during the treatment course were observed to be minor in comparison of their standard deviations. Multiple linear regression analysis between the obtained parameters and the dose delivered to 95% volume of the PTV (D95%) revealed four PTV parameters [Warpmean, DSC, ΔHI between the PCT and ACT, Dmean] and the PTV D95% to be significantly related with P-values < 0.05. The ACT cases of high ΔHI were caused by higher values of the Warpmean and DSC from the deformable image registration, resulting in lower PTV D95% delivered. The mean values of PTV D95% and Warpmean showed significant differences depending on the lung lobe where the tumour was located.ConclusionsEvaluation of the dose delivered to patients with NSCLC treated with SABR using ACTs confirmed that the prescribed dose was accurately delivered to the ITV. However, for the PTV, certain ACT cases characterised by high HI deviations from the original plan demonstrated variations in the delivered dose. These variations may potentially arise from factors such as patient setup during treatment, as suggested by the statistical analyses of the parameters obtained from the dose evaluation process.

Deep Inspiration breath Hold facilitates surgical cavity registration on cone beam imaging for Partial breast irradiation

Background and purposeThe quality of the Cone Beam Computed Tomography (CBCT) images used for patient set-up is essential to avoid geographical miss when narrower margins or shorter fractionation are used for example in Accelerated Partial Breast Irradiation (APBI). This study evaluates deep inspiration breath hold (DIBH) with skin guided radiotherapy as a tool for image improvement reducing motion artifacts. Materials and methodsDaily CBCT images of left and right breast cancer patients with well-defined surgical cavity on CT simulation were used for this study. Only left sided CBCT were acquired with DIBH. Trained and experienced radiation therapists were asked to evaluate the image quality using a cavity visualization score (CVS), an image quality Likert score, and to perform registration shifts. Images were anonymized and therapists were blinded to the use of DIBH. ResultsImages from 21 patients, with 15 CBCT each, were evaluated by 6 radiation therapists, generating 4,015 evaluation points. Statistically significant improvements were observed in CVS and image quality (p < 0.001) with DIBH. Also, the rate of surgical cavity identification increased to 76 % with DIBH compared to 56 % without (p < 0.001). DIBH significantly reduced the inter-observer variability in registration shift corrections (p < 0.001) ConclusionUtilizing DIBH for motion control improves both the image quality and the surgical cavity identification. This results in a decrease in registration variability, which is important for APBI accuracy.

Treatment Reproducibility in Brain Stereotactic Radiotherapy Using a Shim Mask Versus a Standard Mask.

Introduction This study aimed to evaluate the setup accuracy of the new shim mask with mouth bite compared to the standard full brain mask in stereotactic radiosurgery (SRS) and radiotherapy (SRT) treatments for brain metastases or tumors. Method A combined retrospective and prospective design was employed, involving 40 patients treated at our center. Patients previously treated using standard head masks formed the retrospective cohort, while those treated with the Shim mask and mouth bite formed the prospective cohort. Daily cone-beam computed tomography (CBCT) scans were obtained before each treatment session to ensure patient setup accuracy. Key metrics included absolute shifts in translational and rotational directions, the number of repeat CBCTs, and the time interval between CBCTs. Results The Shim mask significantly reduced the mean setup errors in the lateral translation (p=0.022) from 0.17 cm (SD=0.10) to 0.10 cm (SD=0.10), and in X-axis rotation (p=0.030) from 0.79° (SD=0.43) to 0.47° (SD=0.47). By considering cutoff points of 1 mm in translational and 1° in rotational directions, the Shim mask was significantly more accurate in the lateral direction (p=0.004). Moreover, while 70% of patients in the standard group required repeat CBCT scans, none in the Shim group did, resulting in an average time saving of 10.4 minutes per patient. Conclusion The Shim mask with mouth bite offers enhanced immobilization accuracy in SRT/SRS treatments, leading to time and potential cost savings by reducing the need for repeat CBCT scans. This underscores the importance of adopting innovative immobilization techniques to optimize patient outcomes.

The Usefulness of a Virtual Environment-Based Patient Setup Training System for Radiation Therapy.

In radiation therapy, patient setup is important for improving treatment accuracy. The six-axis couch semi-automatically adjusts the patient's position; however, adjusting the patient to twist is difficult. In this study, we developed and evaluated a virtual reality setup training tool for medical students to understand and improve their patient setup skills for radiation therapy. First, we set up a simulated patient in a virtual space to reproduce the radiation treatment room. A gyro sensor was attached to the patient phantom in real space, and the twist of the phantom was linked to the patient in the virtual space. Training was conducted for 24 students, and their operation records were analyzed and evaluated. The training's efficacy was also evaluated through questionnaires provided at the end of the training. The total time required for patient setup tests before and after training decreased significantly from 331.9 s to 146.2 s. As a result of the questionnaire regarding the usability of training to the trainee, most were highly evaluated. We found that training significantly improved students' understanding of the patient setup. With the proposed system, trainees can experience a simulated setup that can aid in deepening their understanding of radiation therapy treatments.

Quality assurance and other challenges in paediatric radiotherapy: Accurate delivery of craniospinal radiotherapy.

Cranio-spinal radiotherapy (CSI) is used to treat central nervous system malignancies in paediatric, adolescent/young adult (AYA), and adult patients. Its delivery in the paediatric/AYA population is particularly challenging across different age groups. This study aims to assess the setup variations and dosimetric impact of CSI in paediatric and AYA patients. This retrospective analysis included, 10 paediatric and AYA patients (aged 4-25) who underwent volumetric modulated arc therapy (VMAT) CSI between 2016 and 2022. Patient characteristics, diagnoses, prescribed CSI doses, and fractionation details were assessed. CT simulation and treatment planning followed standard protocols with setup errors were quantified by comparing daily treatment setup images with the planned position. The study evaluated the dosimetric impact on target volumes and organs at risk (OARs). The setup errors were identified, ranging from 0.5 to 6.2 mm in different directions, especially in the cranio-caudal direction. Despite these variations, there was minimal impact observed on the coverage of clinical target volumes (CTV) and doses to OARs (<1% relative change). Ensuring precise setup in paediatric and AYA patients undergoing CSI is essential to maintain adequate CTV coverage. Although occasional substantial setup variations occurred during treatment, they had a limited impact on CTV coverage and OAR doses when infrequent. Appropriate planning target volume (PTV) margins can effectively compensate for occasional shifts. However, systematic errors could compromise treatment quality if undetected. Regular off-line review of patient set-up trends is recommended.

Fully ambulatory robotic single anastomosis duodeno-ileal bypass (SADI): 40 consecutive patients in a single tertiary bariatric center

BackgroundSingle Anastomosis Duodeno-Ileal bypass (SADI) is becoming a key option as a revision procedure after laparoscopic sleeve gastrectomy (LSG). However, its safety as an ambulatory procedure (length of stay < 12 h) has not been widely described.MethodsA prospective bariatric study of 40 patients undergoing SADI robotic surgery after LSG with same day discharge (SDD), was undertaken in April 2021. Strict inclusion and exclusion criteria were applied and the enhanced recovery after bariatric surgery protocol was followed. Anesthesia and robotic procedures were standardized. Early follow-up (30 days) analyzed postoperative (PO) outcomes.ResultsForty patients (37 F/3 M, mean age: 40.3yo), with a mean pre-operative BMI = 40.5 kg/m2 were operated. Median time after LSG was 54 months (21–146). Preoperative comorbidities included: hypertension (n = 3), obstructive sleep apnea (n = 2) and type 2 diabetes (n = 1). Mean total operative time was 128 min (100–180) (mean robotic time: 66 min (42–85)), including patient setup. All patients were discharged home at least 6 h after surgery. There were four minor complications (10%) and two major complications (5%) in the first 30 days postoperative (one intrabdominal abscess PO day-20 (radiological drainage and antibiotic therapy) and one peritonitis due to duodenal leak PO day-1 (treated surgically)). There were six emergency department visits (15%), readmission rate was 5% (n = 2) and reintervention rate was 2.5% (n = 1) There was no mortality and no unplanned overnight hospitalization.ConclusionsRobotic SADI can be safe for SDD, with appropriate patient selection, in a high-volume center.

Multi-institutional investigation into the robustness of intra-cranial multi-target stereotactic radiosurgery plans to patient setup errors

PurposeThis study aimed to analyse correlations between planning factors including plan geometry and plan complexity with robustness to patient setup errors. MethodsMultiple-target brain stereotactic radiosurgery (SRS) plans were obtained through the Trans-Tasman Radiation Oncology Group (TROG) international treatment planning challenge (2018). The challenge dataset consisted of five intra-cranial targets with a 20 Gy prescription. Setup error was simulated using an in-house tool. Dose to targets was assessed via dose covering 99 % (D99 %) of gross tumour volume (GTV) and 98 % of planning target volume (PTV). Dose to organs at risk was assessed using volume of normal brain receiving 12 Gy and maximum dose covering 0.03 cc of brainstem. Plan complexity was assessed via edge metric, modulation complexity score, mean multi-leaf collimator (MLC) gap, mean MLC speed and plan modulation. ResultsEven for small (0.5 mm/°) errors, GTV D99 % was reduced by up to 20 %. The strongest correlation was found between lower complexity plans (larger mean MLC gap and lower edge metric) and higher robustness to setup error. Lower complexity plans had 1 %–20 % fewer targets/scenarios with GTV D99 % falling below the specified tolerance threshold. These complexity metrics correlated with 100 % isodose volume sphericity and dose conformity, though similar conformity was achievable with a range of complexities. ConclusionsA higher level of importance should be directed towards plan complexity when considering plan robustness. It is recommended when planning multi-target SRS, larger MLC gaps and lower MLC aperture irregularity be considered during plan optimisation due to higher robustness should patient positioning errors occur.

Impact of setup and geometric uncertainties on the robustness of free-breathing photon radiotherapy of small lung tumors

Purpose:Respiratory motion and patient setup error both contribute to the dosimetric uncertainty in radiotherapy of lung tumors. Managing these uncertainties for free-breathing treatments is usually done by margin-based approaches or robust optimization. However, breathing motion can be irregular and concerns have been raised for the robustness of the treatment plans. We have previously reported the dosimetric effects of the respiratory motion, without setup uncertainties, in lung tumor photon radiotherapy using free-breathing images. In this study, we include setup uncertainty. Methods:Tumor positions from cine-CT images acquired in free-breathing were combined with per-fraction patient shifts to simulate treatment scenarios. A total of 14 patients with 300 tumor positions were used to evaluate treatment plans based on 4DCT. Four planning methods aiming at delivering 54 Gy as median tumor dose in three fractions were compared. The planning methods were denoted robust 4D (RB4), isodose to the PTV with a central higher dose (ISD), the ISD method normalized to the intended median tumor dose (IRN) and homogeneous fluence to the PTV (FLU). Results:For all planning methods 95% of the intended dose was achieved with at least 90% probability with RB4 and FLU having equal CTV D50% values at this probability. FLU gave the most consistent results in terms of CTV D50% spread and dose homogeneity. Conclusions:Despite the simulated patient shifts and tumor motions being larger than observed in the 4DCTs the dosimetric impact was suggested to be small. RB4 or FLU are recommended for the planning of free-breathing treatments.