Purpose/Aim Adaptive radiotherapy requires teams to adjust each patient’s treatment plan daily based on changing anatomy, demanding quick, and high-stakes decisions. After a significant safety event during a gastrointestinal (GI) case on the MR-Linac, incident analysis found that team members often hesitated to speak up and were unsure of how to escalate a concern or what to do if it wasn’t acknowledged. These findings highlighted gaps in psychological safety which is the shared belief that team members can speak up without fear of blame or judgment. The Quality Committee led the development of an Escalation of Concern (EOC) process to close that gap and provide a clear, structured method for voicing and resolving concerns before patient safety was at risk. Methods/Process The MR-Linac was chosen as the pilot site. The EOC process was developed in collaboration with MR-Linac medical radiation therapists (RTTs), medical physicists (MPs), and radiation oncologists (ROs). It adapted the Two-Step Challenge method from high-reliability industries. Staff first completed short online modules covering when to escalate, what language to use (“I am concerned...”), and common barriers. This built a shared foundation for open communication and psychological safety, which were some of the defined learning objectives of the program. Two pilot series were completed, each consisting of six one-hour simulation sessions. Each team member participated in one session within teams modeled after real MR-Linac groups, with ROs, MPs, and MRTs training together as they normally work. This structure made the learning realistic and directly transferable to practice. Sessions were co-developed and delivered with the Sunnybrook Canadian Simulation Centre. Each included structured debriefing and pre/post surveys to evaluate learning outcomes, confidence, and perceptions of psychological safety. The first pilot involved the MR-Linac GI team (seven MRTs, seven ROs, three MPs) to test workflow fit, and the second included three MPs and thirteen ROs to assess multidisciplinary communication and learning outcomes Results or Benefits/Challenges Pre- and post-training surveys demonstrated large educational benefits, with significant improvements in knowledge of the escalation process, standardized language, and the Two-Step Challenge (mean scores increased from 2.9 to 4.7, 2.2 to 4.6, and 2.5 to 4.6, respectively; all p < .05). Confidence in identifying when escalation was appropriate also improved significantly (3.7 to 4.6, p < .05). Psychological safety scores improved modestly. Qualitative feedback described the training as “eye-opening” and indicated that shared language reduced fear of sounding confrontational when speaking up. Challenges included small sample sizes and more limited gains in psychological safety, reflecting the complexity and time required for cultural change. Conclusions/Impact Educational gains translated into observable practice-level changes, with participants reporting more consistent communication and greater willingness to escalate concerns during adaptive treatments. The Escalation of Concern process is now embedded within MR-Linac workflows, is currently being adapted for the Gamma Knife program, and is planned for extension to the Ethos platform. Following the pilot, the program received Continuing Medical Education accreditation, supporting its sustainability as an ongoing professional development intervention. Overall, the initiative strengthened communication, psychological safety, and shared accountability in high-pressure adaptive radiation therapy settings and demonstrates a scalable model for culture change.

PURPOSE Radiotherapy (RT)/cetuximab (C) demonstrated superiority over RT alone for locally advanced squamous head and neck cancer. We tested this in completely resected, intermediate-risk cancer. METHODS Patients had squamous cell carcinoma of the head and neck (SCCHN) of the oral cavity, oropharynx, or larynx, with one or more risk factors warranting postoperative RT. Patients were randomly assigned 1:1 to intensity-modulated RT (60-66 Gy) with once-per-week C or RT alone. The primary hypothesis was that RT + C would improve overall survival (OS) in randomly assigned/eligible patients, with a prespecified secondary plan to test this in the human papillomavirus (HPV)–negative subpopulation. Disease-free survival (DFS) and toxicity were secondary end points. OS and DFS were tested via stratified log-rank test; toxicity was compared via Fisher's exact test. RESULTS We enrolled 702 patients from November 2009 to March 2018; 577 were randomly assigned/eligible. Most (63.6%) had oral cavity cancer and most (84.6%) had high epidermal growth factor receptor expression. There were fewer deaths (184) than expected. OS (median follow up, 7.2 years) was not significantly improved (hazard ratio [HR], 0.81; one-sided P = .0747; 5-year OS 76.5% v 68.7%), but DFS was (HR, 0.75; one-sided P = .0168; 5-year DFS 71.7% v 63.6%). Benefit of RT + C was only seen in the HPV-negative subpopulation (80.2% of patients in the trial). Grade 3-4 acute toxicity rates were 70.3% (RT + C) versus 39.7% (RT; two-sided P < .0001), mostly skin and/or mucosal effects. Late grade ≥3 toxicity rate was 33.2% (RT + C) versus 29.0% (RT; two-sided P = .3101). There were no grade 5 toxicities in either arm. CONCLUSION RT + C significantly improved DFS, but not OS, with no increase in long-term toxicity, compared with RT alone for resected, intermediate-risk SCCHN. RT + C is an appropriate option for carefully selected patients with HPV-negative disease.

Purpose: Magnetic resonance image-guided radiotherapy for intracranial indications is a promising advance; however, uncertainties remain for both target localization after translation-only MR setup and intrafraction motion. This investigation quantified these uncertainties and developed a population-based planning target volume (PTV) model to explore target and organ-at-risk (OAR) volumetric coverage tradeoffs.Methods: Sixty-six patients, 49 with a primary brain tumor and 17 with a post-surgical resection cavity, treated on a 1.5T-based MR-linac across 1329 fractions were included. At each fraction, patients were setup by translation-only fusion of the online T1 MRI to the planning image. Each fusion was independently repeated offline ac-counting for rotations. The six degree-of-freedom difference between fusions was applied to transform the planning CTV at each fraction (CTVfx). A PTV model parameterized by volumetric CTVfx coverage, proportion of fractions, and proportion of patients was developed. Intrafraction motion was quantified in a 412 fraction subset as the fusion difference between post-and pre-irradiation T1 MRIs.Results: For the left-right/anterior-posterior/superior-inferior axes, mean +/- SD of the rotational fusion differ-ences were 0.1 +/- 0.8/0.1 +/- 0.8/-0.2 +/- 0.9 degrees. Covering 98 % of the CTVfx in 95 % of fractions in 95 % of patients required a 3 mm PTV margin. Margin reduction decreased PTV-OAR overlap; for example, the proportion of optic chiasm overlapped by the PTV was reduced up to 23.5 % by margin reduction from 4 mm to 3 mm.Conclusions: An evidence-based PTV model was developed for brain cancer patients treated on the MR-linac. Informed by this model, we have clinically adopted a 3 mm PTV margin for conventionally fractionated intra-cranial patients.

Purpose:Variations in dosimetric outcomes among patients treated with low-dose-rate brachytherapy for prostate cancer exist, even when implants are within dose constraints. Here, we used control charts to investigate reasons for intra-patient dosimetric variability.Material and methods:Univariate and multivariate control charts for prostate V100 (percentage of prostate volume that received 100% of prescribed radiation dose), D90 (radiation dose to 90% of prostate volume), and RV100 (rectal wall volume that received 100% of prescribed radiation dose) were generated for 212 consecutive prostate cancer patients implanted with iodine-125 (125I) radioactive seeds at the Princess Margaret Cancer Centre. Control limits were calculated based on the first fifty implants. Data points that were out of control were identified, and their pre-treatment and post-treatment dosimetric and clinical parameters were compared to data points that were in-control, using Student's t-test.Results:All implants were clinically acceptable. Twelve data points exceeded multivariate control limits. Ten of those points fell below the lower control limit of V100 control chart. Average prostate edema in the 10 out-of-control patients on both multivariate and V100 charts was 8.3%, as compared to 0.4% for in-control patients (p < 0.04). Two patients were observed to be out-of-control on multivariate control chart, but not on V100 control chart, and were found to have a reduction in prostate volume of 19.1% and 20.1% at one month after seed implant, compared to prostate volumes of pre-implantation evaluations.Conclusions:Control charts helped in identifying cases with out-of-control variability in post-plan prostate dosimetry. Post-treatment prostatic edema and contraction are important factors predicting variability in patients treated with 125I permanent seed brachytherapy.

Previous literature has shown that 4D respiratory-gated positron emission tomography (PET) is beneficial for quantitative analysis and defining targets for boosting therapy. However the case for addition of a phase-matched 4D-computed tomography (CT) for attenuation correction (AC) is less clear. We seek to validate the use of 4D-CT for AC and investigate the impact of motion correction for low signal-to-background PET imaging of hypoxia using radiotracers such as FAZA and FMISO. A new insert for the Modus Medicals' QUASAR™ Programmable Respiratory Motion Phantom was developed in which a 3D-printed sphere was placed within the “lung” compartment while an additional compartment is added to simulate muscle/blood compartment required for hypoxia quantification. Experiments are performed at 4:1 or 2:1 signal-to-background ratio consistent with clinical FAZA and FMISO imaging. Motion blur was significant in terms of SUVmax, mean, and peak for motion ≥1 cm and could be significantly reduced (from 20% to 8% at 2-cm motion) for all 4D-PET-gated reconstructions. The effect of attenuation method on precision was significant (σ2 hCT-AC = 5.5%/4.7%/2.7% vs σ2 4D-CT-AC = 0.5%/0.6%/0.7% [max%/peak%/mean% variance]). The simulated hypoxic fraction also significantly decreased under conditions of 2-cm amplitude motion from 55% to 20% and was almost fully recovered (HF = 0.52 for phase-matched 4D-CT) using gated PET. 4D-gated PET is valuable under conditions of low radiotracer uptake found in hypoxia imaging. This work demonstrates the importance of using 4D-CT for AC when performing gated PET based on its significantly improved precision over helical CT.

The risk of cardiac toxicity remains a clinical challenge for left-breast irradiation. Our institution evaluated three different breath hold techniques for cardiac sparing in patients receiving left-sided breast radiation therapy (RT): (1) the Active Breathing Coordinator (ABC); (2) an in-house-developed Visually-Monitored Voluntary Breath Hold (VM-VBH) technique and (3) a surface guided technique using the Align-RT system. The aim of this project was to select a primary breath hold technique option for future left-sided breast treatments.

Introduction The oligometastatic (OM) disease hypothesis of an intermediate metastatic state with limited distant disease deposits amenable for curative therapies remains debatable. Over a third of prostate cancer (PCa) patients treated with radical prostatectomy and postoperative radiotherapy experience disease recurrence; these patients are considered incurable by current standards. Often the recurrence cannot be localised by conventional imaging (CT and bone scan). Combined anatomical imaging with CT and/or MR with positron emission tomography (PET) using a novel second-generation prostate-specific membrane antigen (PSMA) probe, [18F]DCFPyL, is a promising imaging modality to unveil disease deposits in these patients. A new and earlier molecularly defined oligorecurrent (OR) state may be amenable to focal-targeted ablative curative-intent therapies, such as stereotactic ablative radiotherapy (SABR) or surgery, thereby significantly delaying or completely avoiding the need for palliative therapies in men with recurrent PCa after maximal local treatments.Methods and analysis This ongoing single-institution phase II study will enrol up to 75 patients total, to include up to 37 patients with response-evaluable disease, who have rising prostate-specific antigen (range 0.4–3.0 ng/mL) following maximal local therapies with no evidence of disease on conventional imaging. These patients will undergo [18F]DCFPyL PET-MR/CT imaging to detect disease deposits, which will then be treated with SABR or surgery. The primary endpoints are performance of [18F]DCFPyL PET-MR/CT, and treatment response rates following SABR or surgery. Demographics and disease characteristics will be summarised and analysed descriptively. Response rates will be described with waterfall plots and proportions.Ethics and dissemination Ethics approval was obtained from the institutional Research Ethics Board. All patients will provide written informed consent. [18F]DCFPyL has approval from Health Canada. The results of the study will be disseminated by the principal investigator. Patients will not be identifiable as individuals in any publication or presentation of this study.Trial registration numbers NCT03160794

Safety huddles (SHs) are an effective communication tool in healthcare, allowing front line staff the opportunity to raise awareness with issues relating to quality and safety. The purpose of this evaluation was to determine the feasibility of implementing SHs in a large radiotherapy (RT) centre. There was a 3-phase implementation process. Firstly, a working group comprised of leadership and front-line radiation therapists proposed a preliminary design for the SH process, designed a huddle board to facilitate SH discussion, and brainstormed potential challenges. Secondly, 10-minute SHs were piloted in selected clinical areas that represented diverse RT expertise, equipment and tasks (e.g. CT/MR simulation, treatment planning/delivery and specialized work areas such as brachytherapy). SHs were held daily for one week. Frontline staff were mentored and supported by "huddle champions." Thirdly, post-implementation interviews were used to evaluate the huddle process and generate lessons learned prior to widespread departmental implementation. Benefits included: improved team communication through a protected pause in the day; a standard method for identifying, documenting and escalating issues relating to clinical quality, safety, delivery and efficiency; and an organizational commitment to promoting safety culture. Challenges included: logistics of gathering team members from various practice areas; difficulties working with the analog huddle board; staff reluctance to "stop and pause"; reduced frontline capacity; and the need to adjust huddle timing to accommodate patient and team needs. Design of the visual huddle board was validated, logistics of huddle timing and coordination were determined, and staff buy-in for the huddle process was established. This evaluation confirmed that huddles could be implemented across a large RT centre with different practice environments. Future considerations for refinement of the process included development of a method to track, communicate, and resolve issues identified by huddles, with staff favoring a digital solution.

PURPOSE: To describe the incidence and type of brachytherapy patient safety events over 10 years in an academic brachytherapy program. METHODS AND MATERIALS: Brachytherapy patient safety events reported between January 2007 and August 2016 were retrieved from the incident reporting system and reclassified using the recently developed National System for Incident Reporting in Radiation Treatment taxonomy. A multi-incident analysis was conducted to identify common themes and key learning points. RESULTS: During the study period, 3095 patients received 4967 brachytherapy fractions. An additional 179 patients had MR-guided prostate biopsies without treatment as part of an interventional research program. A total of 94 brachytherapy- or biopsy-related safety events (incidents, near misses, or programmatic hazards) were identified, corresponding to a rate of 2.8% of brachytherapy patients, 1.7% of brachytherapy fractions, and 3.4% of patients undergoing MR-guided prostate biopsy. Fifty-one (54%) events were classified as actual incidents, 29 (31%) as near misses, and 14 (15%) as programmatic hazards. Two events were associated with moderate acute medical harm or dosimetric severity, and two were associated with high dosimetric severity. Multi-incident analysis identified five high-risk activities or clinical scenarios as follows: (1) uncommon, low volume or newly implemented brachytherapy procedures, (2) real-time MR-guided brachytherapy or biopsy procedures, (3) use of in-house devices or software, (4) manual data entry, and (5) patient scheduling and handoffs. CONCLUSIONS: Brachytherapy is a safe treatment and associated with a low rate of patient safety events. Effective incident management is a key element of continuous quality improvement and patient safety in brachytherapy. (C) 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Image guidance with cone beam computed tomography in radiotherapy can guarantee the precision and accuracy of patient positioning prior to treatment delivery. During the image guidance process, operators need to take great effort to evaluate the image guidance quality before correcting a patient's position. This work proposes an image registration assessment method based on control chart monitoring to reduce the effort taken by the operator. According to the control chart plotted by daily registration scores of each patient, the proposed method can quickly detect both alignment errors and image quality inconsistency. Therefore, the proposed method can provide a clear guideline for the operators to identify unacceptable image quality and unacceptable image registration with minimal effort. Experimental results demonstrate that by using control charts from a clinical database of 10 patients undergoing prostate radiotherapy, the proposed method can quickly identify out-of-control signals and find special cause of out-of-control registration events.

This chapter describes the configuration and design of the brachytherapy room when it is configured to interface with the magnetic resonance (MR) system. It describes the brachytherapy facility of a larger magnetic resonance imaging (MRI) guidance facility built within the Princess Margaret Cancer Centre. Three-dimensional treatment planning is the modern standard for brachytherapy as computed tomography (CT) imaging has widely replaced projection imaging in brachytherapy practice. When the MR-brachytherapy doors, which provide both radiation and radiofrequency (RF) shielding, are closed, adjacent MR room can be used as a standalone MR simulation suite. The brachytherapy room features sufficient RF shielding so that the space can also be used for MRI when the MR-brachytherapy doors are opened to allow the MR travel into the brachytherapy space. Safety considerations for radiation therapy and MRI are both well developed, with well-known best practices. The MR system is an adaptation of IMRIS Visius Surgical Theatre, which includes an MR scanner and ceiling-mounted MR transport system.

IMPORTANCE The Canadian Cancer Trials Group study HN. 6 is the largest randomized clinical trial to date comparing the concurrent administration of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies with radiotherapy (RT) to standard chemoradiotherapy in locoregionally advanced squamous cell carcinoma of the head and neck (LA-SCCHN).OBJECTIVE To compare progression- free survival (PFS) in patients with LA-SCCHN treated with standard-fractionation RT plus high-dose cisplatin vs accelerated-fractionation RT plus the anti-EGFR antibody panitumumab.DESIGN, SETTING, AND PARTICIPANTS A randomized phase 3 clinical trial in 17 Canadian centers. A total of 320 patients were randomized between December 2008 and November 2011.INTERVENTIONS Patients with TanyN+M0 or T3-4N0M0 LA-SCCHN were randomized 1: 1 to receive standard-fractionation RT (70 Gy/35 over 7 weeks) plus cisplatin at 100mg/m(2) intravenous for 3 doses (arm A) vs accelerated-fractionation RT (70 Gy/35 over 6 weeks) plus panitumumab at 9mg/kg intravenous for 3 doses (arm B).MAIN OUTCOMES AND MEASURES Primary end pointwas PFS. Due to an observed declining event rate, the protocol was amended to a time-based analysis. Secondary end points included overall survival, local and regional PFS, distant metastasis-free survival, quality of life, adverse events, and safety.RESULTS Of 320 patients randomized (268 [84%] male; median age, 56 years), 156 received arm A and 159 arm B. A total of 93 PFS events occurred. By intention-to-treat, 2-year PFS was 73%(95% CI, 65%-79%) in arm A and 76%(95% CI, 68%-82%) in arm B (hazard ratio [HR], 0.95; 95% CI, 0.60-1.50; P =.83). The upper bound of the HR 95% CI exceeded the prespecified noninferiority margin. Two-year overall survival was 85%(95% CI, 78%-90%) in arm A and 88%(95% CI, 82%-92%) in arm B (HR, 0.89; 95% CI, 0.54-1.48; P =.66). Incidence of any grade 3 to 5 nonhematologic adverse event was 88% in arm A and 92% in arm B (P =.25).CONCLUSIONS AND RELEVANCE With a median follow-up of 46 months, the PFS of panitumumab plus accelerated-fractionation RT was not superior to cisplatin plus standard-fractionation RT in LA-SCCHN and noninferiority was not proven. Despite having negative results, HN. 6 has contributed important data regarding disease control and toxic effects of these treatment strategies.

Purpose:Our treatment for choroidal melanoma utilizes the GTC frame. The patient looks at a small LED to stabilize target position. The LED is attached to a metal arm attached to the GTC frame. A camera on the arm allows therapists to monitor patient compliance. To move to mask‐based immobilization we need a new LED/camera attachment mechanism. We used a Hazard‐Risk Analysis (HRA) to guide the design of the new tool.Method:A pre‐clinical model was built with input from therapy and machine shop personnel. It consisted of an aluminum frame placed in aluminum guide posts attached to the couch top. Further development was guided by the Department of Defense Standard Practice ‐ System Safety hazard risk analysis technique.Results:An Orfit mask was selected because it allowed access to indexes on the couch top which assist with setup reproducibility. The first HRA table was created considering mechanical failure modes of the device. Discussions with operators and manufacturers identified other failure modes and solutions. HRA directed the design towards a safe clinical device.Conclusion:A new immobilization tool has been designed using hazard‐risk analysis which resulted in an easier‐to‐use and safer tool compared to the initial design. The remaining risks are all low probability events and not dissimilar from those currently faced with the GTC setup. Given the gains in ease of use for therapists and patients as well as the lower costs for the hospital, we will implement this new tool.

122 Background: The Radiation Treatment Program (RTP) at Cancer Care Ontario (CCO) established several Communities of Practice (CoPs), with the goal of improving radiation treatment (RT) quality and safety. The RTP identifies variation in practice and quality improvement (QI) opportunities in the 14 Regional Cancer Centres (RCCs) and facilitates the development of CoPs to share best practices and standardize care. Methods: Since 2010, the RTP has formed 7 CoPs ( > 185 members in total): 4 intra-disciplinary (Radiation Therapy, Medical Physics, Advanced Practice Radiation Therapy, Radiation Safety) and 3 inter-disciplinary (Head and Neck (HN), Gynecological (GYNE) and Lung Cancer). Members are recruited with the aim of securing engagement from all RCCs to ensure representation of regional diversity and to facilitate adoption of best practices. CoPs are supported with nominal funding and resources provided by CCO, but are led and driven by members, who identify and prioritize key quality issues and select corresponding QI projects to pursue. The RTP performs regular evaluation activities to assess initiative engagement and impact. Results: RTP CoPs have enhanced the quality and safety of RT delivery in Ontario through QI initiatives, advice documents and tools that have enabled: Improved RT safety (use of safety straps in RT delivery); Adoption of best practices (RT plan evaluation guidance); Education and knowledge transfer – (stereotactic body RT implementation and training framework); and Support for infrastructure improvements (recommendation for additional Magnetic Resonance-guided brachytherapy units) ( https://www.cancercare.on.ca/ocs/clinicalprogs/radiationtreatment/ ). Advice documents have improved alignment with recommended practice (40% and 50% absolute increases in two HN initiatives). Evaluation surveys indicate that members believe the CoPs have enhanced inter-regional communication and collaboration (89%), knowledge transfer/exchange (91%), and professional networking between RCCs (92%). Conclusions: CoPs can be a highly effective model for improving quality of care. The establishment of CoPs should be considered for QI in other areas of the healthcare system.

6000 Background: Concurrent administration of anti-EGFR monoclonal antibody with radiotherapy (RT) increases survival compared to RT alone in pts with LA-SCCHN. No prospective data are available comparing bioradiotherapy to standard chemoradiotherapy. Methods: Pts with TanyN+M0 or T3-4N0M0 LA-SCCHN were randomized 1:1 to receive SFX (70Gy/35 over 7 weeks) plus CIS at 100 mg/m2 intravenous (IV) for 3 doses on weeks 1, 4 and 7 (Arm A) versus AFX (70Gy/35 over 6 weeks) plus the anti-EGFR monoclonal antibody PMab at 9 mg/kg IV for 3 doses on weeks -1, 3 and 6 (Arm B). Primary endpoint was progression-free survival (PFS). A total of 320 patients were accrued from 12/2008 to 11/2011 with a median follow-up of 46.4 months (range: 0.1-64.3). Due to an observed declining event rate, the protocol was amended to analyze data with a clinical cut-off date of October 31, 2014. Results: Of 320 pts randomized, 5 did not receive protocol treatment, 156 received Arm A and 159 Arm B. Demographics: median age = 56 (range 35-80); male = 84%; ECOG 0:1 (%) = 71:29; primary site: oropharynx (81%), larynx (11%), hypopharynx (6%), oral cavity (2%); smoking history > 10 pack-years (58%). Of 259 oropharynx pts p16 status was known in 217 (84%), with 176 (81%) positive and 41 (19%) negative. A total of 93 PFS events occurred. By intention-to-treat, 2-year PFS was 73% (95% CI: 65-79%) in Arm A and 76% (95% CI: 68-82%) in Arm B, hazard ratio (HR) = 0.95; 95% CI: 0.6-1.5; p = 0.83. Upper bound of HR’s 95% CI exceeded the pre-specified non-inferiority margin. Two-year OS was 85% (95% CI: 78-90%) in Arm A and 88% (95% CI: 82-92%) in Arm B, HR = 0.89; 95% CI: 0.54-1.48; p = 0.66. By multivariable analysis, anatomic location, ECOG PS, p16 status, and T category were significant predictors of PFS (p < 0.05). Incidence of any > grade 3 non-hematologic adverse event (AE) was 88% in Arm A and 91% in Arm B (p = 0.25). QOL is reported separately. Conclusions: With a median follow-up of 46.4 months, PFS of PMab+AFX was not superior to CIS+SFX in LA-SCCHN and non-inferiority was not proven. Clinical trial information: NCT00820248.

Magnetic resonance (MR) imaging is routinely employed in the design of radiotherapy (RT) treatment plans for many disease sites. It is evident that tighter integration of MR imaging into the RT process would increase confidence in dose placement and facilitate the integration of new MR imaging information (including anatomical and functional imaging) into the therapy process. To this end, a dedicated MR-guided RT (MRgRT) facility has been created that integrates a state-of-the-art linear accelerator delivery system, high-dose rate brachytherapy afterloader, and superconducting MR scanner to allow MR-based online treatment guidance, adaptive replanning, and response monitoring while maintaining the clinical functionality of the existing delivery systems. This system is housed within a dedicated MRgRT suite and operates in a coordinated fashion to assure safe and efficient MRgRT treatments.