The influence of time interval between preoperative radiation and surgical resection on the development of wound healing complications in extremity soft tissue sarcoma.

OBJECTIVE: The aim of this study was to determine the relationship of the time interval between completion of preoperative radiation therapy (RT) and surgical resection on wound complications (WCs) in extremity soft tissue sarcoma (STS). METHODS: Overall, 798 extremity STS patients were managed with preoperative RT and surgery from 1989 to 2013. WCs were defined as requiring secondary operations/invasive procedures for wound care, use of vacuum-assisted closure, prolonged dressing changes, or infection within 120 days of surgery. RESULTS: Mean tumor size was 8.8 cm. A total of 743 (93 %) tumors were primary presentations, 565 (71 %) patients had lower extremity tumors, and 238 patients (30 %) had a prior unplanned excision. Of 242 patients (30 %) who developed a WC, 206 (37 %) had lower extremity tumors and 36 (15 %) had upper extremity tumors. Mean time from RT completion to surgery was 41.3 (range 4-470) days; 42.0 (range 4-470) days for upper extremity cases, and 41.1 (range 4-109) days for lower extremity cases. Similarly, mean time interval for patients who developed a WC was 40.9 (range 4-100) days, and 41.5 (range 4-470) days for those who did not develop a WC (p = 0.69). Thirty-nine cases (5 %) had surgery within 3 weeks of RT; 15 (38 %) patients developed WCs versus 227 (30 %) patients who had their tumors excised after 3 weeks (p = 0.28). One hundred and twenty-nine (16 %) patients had surgery within 4 weeks, and 39 (30 %) patients developed WCs versus 203 (30 %) patients who had their tumors excised after 4 weeks (p = 1.0). A trend towards a higher rate of WCs was seen for those patients who had surgery after 6 weeks (28 % prior vs. 34 % after; p = 0.08). There was no difference in WCs with intensity-modulated RT (IMRT) versus non-IMRT cases (p = 0.6). CONCLUSION: The time interval between preoperative RT and surgical excision in extremity STS had minimal influence on the development of WCs. Four- or 5-week intervals showed equivalent complication rates between the two groups, suggesting an optimal interval to reduce potential WCs.

Phase 2 study of preoperative image-guided intensity-modulated radiation therapy to reduce wound and combined modality morbidities in lower extremity soft tissue sarcoma.

BACKGROUND: This study sought to determine if preoperative image-guided intensity-modulated radiotherapy (IG-IMRT) can reduce morbidity, including wound complications, by minimizing dose to uninvolved tissues in adults with lower extremity soft tissue sarcoma. METHODS: The primary endpoint was the development of an acute wound complication (WC). IG-IMRT was used to conform volumes to avoid normal tissues (skin flaps for wound closure, bone, or other uninvolved soft tissues). From July 2005 to June 2009, 70 adults were enrolled; 59 were evaluable for the primary endpoint. Median tumor size was 9.5 cm; 55 tumors (93%) were high-grade and 58 (98%) were deep to fascia. RESULTS: Eighteen (30.5%) patients developed WCs. This was not statistically significantly different from the result of the National Cancer Institute of Canada SR2 trial (P = .2); however, primary closure technique was possible more often (55 of 59 patients [93.2%] versus 50 of 70 patients [71.4%]; P = .002), and secondary operations for WCs were somewhat reduced (6 of 18 patients [33%] versus 13 of 30 patients [43%]; P = .55). Moderate edema, skin, subcutaneous, and joint toxicity was present in 6 (11.1%), 1 (1.9%), 5 (9.3%), and 3 (5.6%) patients, respectively, but there were no bone fractures. Four local recurrences (6.8%, none near the flaps) occurred with median follow-up of 49 months. CONCLUSIONS: The 30.5% incidence of WCs was numerically lower than the 43% risk derived from the National Cancer Institute of Canada SR2 trial, but did not reach statistical significance. Preoperative IG-IMRT significantly diminished the need for tissue transfer. RT chronic morbidities and the need for subsequent secondary operations for WCs were lowered, although not significantly, whereas good limb function was maintained.

The clinical and functional outcome for patients with radiation-induced soft tissue sarcoma.

BACKGROUND: Radiation-induced soft tissue sarcomas (RI-STS) are rare, and it is believed that they are associated with a poor prognosis.The authors of this report compared the clinical and functional outcomes of adults who had extremity RI-STS with the outcomes of adults with sporadic STS. METHODS: Forty-four patients who were diagnosed with RI-STS from 1989 to 2009 were identified from 4 prospectively collected databases. Patient demographics, surgical and adjuvant treatment parameters, and oncologic and functional outcomes were evaluated. RESULTS: The median latent period from irradiation of the primary condition to RI-STS diagnosis was 16 years. The median radiotherapy dose used for the index condition was 45 gray. The median age at RI-STS diagnosis was 56 years. The most common primary diagnoses were breast cancer (36.4%) and lymphoma (34.1%). The most common RI-STS histologies were malignant fibrous histiocytoma (36.4%) and angiosarcoma (18.2%). Forty-two patients underwent surgery, 13 patients received adjuvant radiotherapy, and 8 patients received adjuvant chemotherapy. Systemic metastases occurred in 50% of treated patients (n = 21), and 26% (n = 11) developed local recurrence, the risk of which was lower among patients who received reirradiation (P = .043). The 5-year disease-free interval (DFI) and overall survival (OS) rates for patients with RI-STS who presented without metastasis were 36% and 44%, respectively. Patients who had International Union Against Cancer TNM stage III RI-STS had a significantly worse DFI compared with patients who had stage III sporadic STS (multivariate analysis, P = .051). Eighteen patients with RI-STS underwent functional assessment after surgery, and their results were comparable to those of patients with sporadic STS. CONCLUSIONS: Despite aggressive surgical treatment, patients who have RI-STS remain at greater risk of both local and systemic recurrence compared with patients who have sporadic STS, but they can anticipate similar functional outcomes. Reirradiation can be relatively safe and effective if used properly.

Forecasting Institutional LINAC Utilization in Response to Varying Workload.

ObjectivesPandemics, natural disasters, and other unforeseen circumstances can cause short-term variation in radiotherapy utilization. In this study, we aim to develop a model to forecast linear accelerator (LINAC) utilization during periods of varying workloads. Methods: Using computed tomography (CT)-simulation data and the rate of new LINAC appointment bookings in the preceding week as input parameters, a multiple linear regression model to forecast LINAC utilization over a 15-working day horizon was developed and tested on institutional data. Results: Future LINAC utilization was estimated in our training dataset with a forecasting error of 3.3%, 5.9%, and 7.2% on days 5, 10, and 15, respectively. The model identified significant variations (≥5% absolute differences) in LINAC utilization with an accuracy of 69%, 62%, and 60% on days 5, 10, and 15, respectively. The results were similar in the validation dataset with forecasting errors of 3.4%, 5.3%, and 6.2% and accuracy of 67%, 60%, and 58% on days 5, 10, and 15, respectively. These results compared favorably to moving average and exponential smoothing forecasting techniques. Conclusions: The developed linear regression model was able to accurately forecast future LINAC utilization based on LINAC booking rate and CT simulation data, and has been incorporated into our institutional dashboard for broad distribution. Advances in knowledge: Our proposed linear regression model is a practical and intuitive approach to forecasting short-term LINAC utilization, which can be used for resource planning and allocation during periods with varying LINAC workloads.

Radiological progression of extremity soft tissue sarcoma following pre-operative radiotherapy predicts for poor survival.

OBJECTIVES: To determine if radiological response to pre-operative radiotherapy is related to oncologic outcome in patients with extremity soft tissue sarcomas (STSs). METHODS: 309 patients with extremity STS who underwent pre-operative radiation and wide resection were identified from a prospective database. Pre- and post-radiation MRI scans were retrospectively reviewed. Radiological response was defined by the modified Response Evaluation Criteria in Solid Tumours. Local recurrence-free, metastasis-free (MFS) and overall survival (OS) were compared across response groups. RESULTS: Tumour volume decreased in 106 patients (34.3%; PR - partial responders), remained stable in 97 (31.4%; SD - stable disease), increased in 106 (34.3%; PD - progressive disease). The PD group were older (p = 0.007), had more upper extremity (p = 0.03) and high-grade tumours (p < 0.001). 81% of myxoid liposarcomas showed substantial decrease in size. There was no difference in initial tumour diameter (p = 0.5), type of surgery (p = 0.5), margin status (p = 0.4), or complications (p = 0.8) between the three groups. There were 10 (3.2%) local recurrences with no differences between the three response groups (p = 0.06). 5-year MFS was 52.1% for the PD group vs 73.8 and 78.5% for the PR and SD groups, respectively (p < 0.001). OS was similar (p < 0.001). Following multivariable analysis, worse MFS and OS were associated with higher grade, larger tumour size at diagnosis and tumour growth following pre-operative radiation. Older age was also associated with worse OS. CONCLUSION: STS that enlarge according to Response Evaluation Criteria in Solid Tumour criteria following pre-operative radiotherapy identify a high risk group of patients with worse systemic outcomes but equivalent local control. ADVANCES IN KNOWLEDGE: Post-radiation therapy, STS enlargement may identify patients with potential for worse systemic outcomes but equivalent local control. Therefore, adjunct therapeutic approaches could be considered in these patients.

Impact of Immobilization on Interfractional Errors for Upper Extremity Soft Tissue Sarcoma Radiation Therapy.

INTRODUCTION/BACKGROUND: Owing to the rare nature and presentation of upper extremity soft tissue sarcomas (STSs) and the high mobility of associated anatomy, various patient positioning strategies are used for radiation therapy. The purpose of this study is to measure the interfractional setup errors associated with upper extremity sarcomas using different immobilization methods through cone-beam computed tomography (CBCT) images. METHODS: All patients treated with daily CBCT guidance for upper extremity STSs during 2014-2015 were identified and triaged based on type of immobilization. After defining an optimal region of interest for image registration, daily CBCT images were automatically registered to reference CT images to quantify positional discrepancies. Means and standard deviations were calculated, and one-way analysis of variance was calculated to determine significance of data. RESULTS: Seventeen patients with upper extremity sarcoma met inclusion criteria: 13 were treated to the shoulder/axilla/upper arm and 4 to the arm/elbow/forearm. Three main types of immobilization were identified: vacuum cradle with custom thermoplastic shell, vacuum cradle alone, and no immobilization accessory used. Patient repositioning occurred if translational and rotational displacements were larger than 1 mm and 5°, respectively, as per institutional guidelines. Patient repositioning rates were 18% for vacuum cradle with thermoplastic shells, 15% for vacuum cradles only, and 6% for no immobilization accessories. Mean translational displacements in right/left (R/L), superior/inferior (S/I), and anterior/posterior (A/P) directions were -0.04 ± 0.33 cm, 0.32 ± 0.33 cm, and 0.12 ± 0.25 cm for vacuum cradle with thermoplastic shell; 0.25 ± 0.10 cm, -0.07 ± 0.22 cm, and 0.00 ± 0.17 cm for vacuum cradle alone; and 0.14 ± 0.15 cm, 0.08 ± 0.45 cm, and -0.01 ± 0.24 cm for no immobilization. For all patients, rotational displacements in the pitch, roll, and yaw were 0.15 ± 1.99°, 0.31 ± 2.11°, and -0.21 ± 1.76°, respectively. There were significant (P < .05) differences in systematic error values for all translational and rotational axes between immobilization methods. CONCLUSION: Large interfractional errors, especially in the rotational axes, were observed, regardless of immobilization strategy. Small study population and unequal representation of different parts of the upper extremity are identified limitations. The need for better immobilization techniques for upper extremity STS treatments is clearly demonstrated.

Patterns of practice of adaptive re-planning for anatomic variances during cone-beam CT guided radiotherapy.

PURPOSE: Substantial, unanticipated anatomic variances during cone-beam CT (CBCT)-guided radiotherapy can potentially impact treatment accuracy and clinical outcomes. This study assessed patterns of practice of CBCT variances reported by RTTs and subsequent interventions for multiple-disease sites. METHODS: A chart review was conducted at a large cancer centre for patients treated with daily online CBCT-guided radiotherapy. Patients selected for review were identified via RTT-reported variances that then triggered offline multi-disciplinary assessment. Cases were categorized by the type of anatomic variance observed on CBCT and any further interventions recorded such as un-scheduled adaptive re-planning. RESULTS: Over a 1-year period, 287 variances from 261 patients were identified (6.2% of the 4207 patients treated with daily CBCT-guided radiotherapy), most often occurring within the first 5 fractions of the treatment course. Of these variances, 21% (59/287) were re-planned and 3.5% (10/287) discontinued treatment altogether. Lung was the most frequent disease-site (27% of 287 variances) reported with IGRT-related variances although head and neck and sarcoma were most frequently re-planned (19% of 59 re-plans for each site). Technical or clinical rationales for re-planning were not routinely documented in patient medical records. All disease-sites had numerous categories of variances. Three of the four most frequent categories were for tumor-related changes on CBCT, and the re-planning rate was highest for tumor progression at 25%. Normal tissue variances were the second most frequency category, and re-planned in 14% of those cases. CONCLUSION: RTTs identified a wide range of anatomic variances during CBCT-guided radiotherapy. In a minority of cases, these substantially altered the care plan including ad hoc adaptive re-planning or treatment discontinuation. Improved understanding of the clinical decisions in these cases would aid in developing more routine, systematic adaptive strategies.

Immobilization and image-guidance methods for radiation therapy of limb extremity soft tissue sarcomas: Results of a multi-institutional survey.

Radiation therapy for limb-extremity soft tissue sarcoma (STS) requires accurate, reproducible dose delivery. However, patient positioning is challenging and there is a lack of existing guidelines to assist institutional standardization. Therefore, we conducted a multi-institutional international survey of STS immobilization, image guidance methods, and treatment protocols to investigate current practice. Seventy-three UK radiotherapy centers and 15 hospitals in 7 other countries completed a questionnaire on STS immobilization and image-guidance procedures. Specifically, the survey collated information on the current usage of immobilization equipment, including custom devices, patient setup tolerances, the use of written protocols, the modality and frequency of image guidance, the method of treatment, allocated treatment times, and the application of surgical clips. Multiple combinations of immobilization devices were reported. In the UK, 12%, 40%, 30%, 12%, and 5% use 1, 2, 3, 4, and 5 types of device for lower limb STS. Vacuum bag plus either foot or ankle support was most common (66%). Of 15 international centers, 27%, 60%, 7%, 0%, 7% use 1, 2, 3, 4, 5 devices, with vacuum bags (73%) and thermoplastic (47%) predominant, similar to UK values of 77% and 52%. For image guidance, in the UK, 37% use kV planar, 34% use MV planar, and 16% use cone-beam CT for the first 3 fractions and then weekly. Internationally, daily imaging was more prevalent with 33% using kV planar, 7% MV planar, and 40% cone-beam CT daily. Custom devices plus combinations of devices, along with 5- and 10-mm set-up tolerances, were most commonly reported. Less than half of centers have written treatment protocols. Conventional treatment is most common in the UK, with only 42% using conformal techniques. Treatment is allocated between 10 and 30 minutes. Twenty-six percent of UK centers and 53% of international centers use surgical clips. Across treatment centers, there is no consistent approach to STS immobilization, image-guidance methods, or treatment protocols assessed by this survey. A wide variety of immobilization devices and configurations are utilized, and the frequency and modality of imaging are similarly diverse. In the absence of guidelines, the creation of an online repository of example immobilization techniques could enable centers to compare a diversity of cases. The availability of a forum for viewing and discussing a range of cases could potentially lead to improved patient setup and reduce the time taken to devise an individual immobilization strategy.

Design and evaluation of a safety-centered user interface for radiation therapy.

PURPOSE: As radiation therapy treatment grows more complex over time, treatment delivery has become more susceptible to adverse events and patient safety risks from use error. The radiation therapy monitoring and treatment delivery user interface explored in this study was redesigned using ecological interface design, a human factors engineering method, and evaluated to improve treatment safety. METHODS AND MATERIALS: An initial design concept was created based on previously completed analysis and informally evaluated in focus groups with radiation therapists. Sixteen newly graduated radiation therapists used both the redesigned and current system in a usability test to determine if the redesigned system better supported detection of errors. RESULTS: The redesigned system successfully improved the error detection rate of 2 errors: wrong treatment volume and wrong treatment site (P < .03 and P < .01, respectively). It also improved level 2 and level 3 situation awareness (ie, comprehension of the meaning of the information and the projection of the behavior of the technology: P < .01 and P < .01, respectively) and achieved a higher user satisfaction. CONCLUSIONS: The ecological interface design approach was found to be effective in redesigning a radiation therapy treatment delivery interface. Radiation therapists were able to deliver simulated radiation therapy with a higher rate of error detection and improved higher-level situation awareness, and participants preferred the redesigned interface to the current interface. Overall, the redesigned interface improved the radiation therapists' system understanding and ability to detect errors that affect patient safety.

Evidence-based region of interest matching guidelines for sarcoma volumetric image-guided radiation therapy.

PURPOSE: Region-of-interest (ROI) guidelines for online cone-beam computed tomography (CBCT) radiotherapy may improve matching reproducibility and reduce inter-user variability of soft tissue sarcoma (STS) image guidance. The purpose of this work is to standardize ROI STS CBCT image registration guidelines using the plan-do-study-act (PDSA) cycle for the lower extremity, retroperitoneal, pelvis, and thorax. METHODS: Based on anatomic bony surrogates, initial ROI matching guidelines for STS were developed by a team of radiation therapists, physicists and oncologists (Plan). Retrospective, qualitative evaluation of the guidelines was completed by the designated sarcoma lead therapist to determine clinical feasibility (Do). Validation of the ROI guidelines was performed through independent evaluation by radiation therapy CBCT imaging experts on a cohort of 10 patients per anatomic region (Study). RESULTS: Draft ROI guidelines were evaluated by 2 independent observers who registered weekly CBCT images to test their validity. Each observer assessed 5 patients per anatomic site, testing ROI options for accuracy of image registration and feasibility, while some ROI borders were adjusted based on algorithm matching performance. Validated ROI guidelines were presented to the sarcoma multidisciplinary site group, and an inter-professional committee of imaging experts for approval prior to clinical implementation (Act). CONCLUSION: ROI matching guidelines for STS IGRT were standardized for 4 anatomic sites using the PDSA cycle for change testing and implementation. IGRT guidelines are intended to improve STS image registration reproducibility, and in turn, are expected to improve the confidence of IGRT decision making and workflow efficiencies for a rare disease with diverse presentation.

A review of the Best Practice in Radiation Oncology project from 2008 to 2018.

The European Society of Radiotherapy and Oncology (ESTRO)/International Atomic Energy Agency (IAEA) Best Practice in Radiation Oncology-a project to train RTT trainers has reached its ten year anniversary and will commence its fifth iteration in 2018. This project commenced as a novel way to address the issue of limited RTT education throughout Europe. In many countries the profession of RTT is not officially recognised and there is no formal education programme. RTT education is frequently a very short component of a broader programme such as diagnostic imaging, nursing or a technical discipline. To date, fifty-nine short courses have been delivered, two RTT-specific National societies have been developed, a South East European cooperation with biannual conferences has evolved and significant progress has been made on improving the radiotherapy-specific content of national educational programmes, which will continue with future iterations of this project.

Management of soft-tissue sarcomas; treatment strategies, staging, and outcomes.

Soft-tissue sarcomas (STS) are a rare group of malignant tumors which can affect any age group. For the majority of patients who present with a localized STS, treatment involves a multidisciplinary team decision-making approach ultimately relying on surgical resection with or without adjuvant radiation for successful limb salvage. The goals of treatment are to provide the patient with a functional extremity without local tumor relapse. The purpose of this article is to review the treatment of extremity STS, with a focus on staging, treatment options, and outcomes.

The value of adaptive preoperative radiotherapy in management of soft tissue sarcoma.

PURPOSE: To determine the value of preoperative adaptive radiotherapy (ART) for soft tissue sarcoma patients (STS) by modeling the dosimetric consequences of tumour volume changes (TVC) using different external beam radiotherapy techniques. METHODS AND MATERIALS: A subset of 22 STS patients from a recent trial (NCT00188175) underwent a repeat CT scan (CT2) prompted by TVC>1cm during IMRT; 14 tumours grew, 8 shrank. Conformal and conventional plans were modelled in addition to IMRT replicating original criteria from the initial planning dataset (CT1):95% PTV encompassed by 97% prescribed dose. CT1 RT parameters for all plans were applied to CT2 for dosimetric assessment of TVC. Co-registration of CT1 and CT2 permitted comparison of original and new contours. RESULTS: Mean TVC was 45% for growing and 33% for the shrinking cohort with TVC prompting CT2 at a mean of 13 fractions. For growers, the lack of target coverage on CT2 was statistically significant but was adequate for shrinkers. CONCLUSION: GTV expansion of >1cm during RT may result in target underdosage independent of RT technique. ART applied offline for TV increases >1cm is a practical adaptive strategy to ensure tumour coverage during RT. TV shrinkage may allow for normal tissue sparing, which should be investigated prospectively.

The role of radiotherapy in the management of localized soft tissue sarcomas.

The combination of radiotherapy (RT) and function-preserving surgery is the most usual contemporary approach in the management of soft tissue sarcomas (STS). Pre- and postoperative RT result in similar local control rates, as shown by a landmark trial in extremity STS. In this review, the role of RT in the management of extremity STS will be discussed, but STS in other sites, including retroperitoneal STS, will also be addressed. The focus will consider various aspects of RT including strategies to reduce the volume of tissue being irradiated, dose, scheduling, and the possible of omission of RT in selected cases. Finally, technology advances through the use of intensity-modulated radiotherapy (IMRT), image-guided IMRT, intraoperative radiotherapy (IORT) and particle therapy will also be discussed.

Adjuvant radiation for soft tissue sarcomas.

Over recent decades, limb-preservation surgery in combination with radiotherapy achieves local control rates exceeding 90% for extremity soft tissue sarcoma (STS). Local control is not as successful for retroperitoneal sarcoma (approximately 60%) despite aggressive surgical approaches including en bloc resection of uninvolved adjacent organs combined with intensity modulated radiotherapy (IMRT). This review will discuss the indications for adjuvant radiation therapy (RT) for primary presentation of soft tissue sarcoma: "What," referring to the type and manner of planning and delivery of RT; "When," referring to the timing and scheduling of RT; and "Why," referring to the rationale for the use of RT will be addressed. From a practical stand point, this Educational Chapter on "adjuvant RT" will focus on pre- and postoperative RT in the context of gross total resection for extremity and retroperitoneal soft tissue sarcoma, the two most frequent paradigms for the use of adjuvant RT.

Optically-tracked handheld fluorescence imaging platform for monitoring skin response in the management of soft tissue sarcoma.

Standard clinical management of extremity soft tissue sarcomas includes surgery with radiation therapy. Wound complications (WCs) arising from treatment may occur due to bacterial infection and tissue breakdown. The ability to detect changes in these parameters during treatment may lead to earlier interventions that mitigate WCs. We describe the use of a new system composed of an autofluorescence imaging device and an optical three-dimensional tracking system to detect and coregister the presence of bacteria with radiation doses. The imaging device visualized erythema using white light and detected bacterial autofluorescence using 405-nm excitation light. Its position was tracked relative to the patient using IR reflective spheres and registration to the computed tomography coordinates. Image coregistration software was developed to spatially overlay radiation treatment plans and dose distributions on the white light and autofluorescence images of the surgical site. We describe the technology, its use in the operating room, and standard operating procedures, as well as demonstrate technical feasibility and safety intraoperatively. This new clinical tool may help identify patients at greater risk of developing WCs and investigate correlations between radiation dose, skin response, and changes in bacterial load as biomarkers associated with WCs.

Spatial and volumetric changes of retroperitoneal sarcomas during pre-operative radiotherapy.

PURPOSE: To determine the positional and volumetric changes of retroperitoneal sarcomas (RPS) during pre-operative external beam radiotherapy (PreRT). MATERIAL AND METHODS: After excluding 2 patients who received chemotherapy prior to PreRT and 15 RPS that were larger than the field-of-view of cone-beam CT (CBCT), the positional and volumetric changes of RPS throughout PreRT were characterized in 19 patients treated with IMRT using CBCT image guidance. Analysis was performed on 118 CBCT images representing one image per week of those acquired daily during treatment. Intra-fraction breathing motions of the gross tumor volume (GTV) and kidneys were measured in 22 RPS patients simulated using 4D-CT. Fifteen other patients were excluded whose tumors were incompletely imaged on CBCT or who received pre-RT chemotherapy. RESULTS: A GTV volumetric increase (mean: 6.6%, p=0.035) during the first 2 weeks (CBCT1 vs. CBCT2) of treatment was followed by GTV volumetric decrease (mean: 4%, p=0.009) by completion of radiotherapy (CBCT1 vs. CBCT6). Internal margins of 8.6, 15 and 15 mm in the lateral, anterior/posterior and superior/inferior directions would be required to account for inter-fraction displacements. The extent of GTV respiratory motion was significantly (p<0.0001) correlated with more superiorly positioned tumors. CONCLUSION: Inter-fraction CBCT provides important volumetric and positional information of RPS which may improve PreRT quality and prompt re-planning. Planning target volume may be reduced using online soft-tissue matching to account for interfractional displacements of GTVs. Important breathing motion occurred in superiorly placed RPS supporting the utility of 4D-CT planning.

Displaying 3D radiation dose on endoscopic video for therapeutic assessment and surgical guidance.

We have developed a method to register and display 3D parametric data, in particular radiation dose, on two-dimensional endoscopic images. This registration of radiation dose to endoscopic or optical imaging may be valuable in assessment of normal tissue response to radiation, and visualization of radiated tissues in patients receiving post-radiation surgery. Electromagnetic sensors embedded in a flexible endoscope were used to track the position and orientation of the endoscope allowing registration of 2D endoscopic images to CT volumetric images and radiation doses planned with respect to these images. A surface was rendered from the CT image based on the air/tissue threshold, creating a virtual endoscopic view analogous to the real endoscopic view. Radiation dose at the surface or at known depth below the surface was assigned to each segment of the virtual surface. Dose could be displayed as either a colorwash on this surface or surface isodose lines. By assigning transparency levels to each surface segment based on dose or isoline location, the virtual dose display was overlaid onto the real endoscope image. Spatial accuracy of the dose display was tested using a cylindrical phantom with a treatment plan created for the phantom that matched dose levels with grid lines on the phantom surface. The accuracy of the dose display in these phantoms was 0.8-0.99 mm. To demonstrate clinical feasibility of this approach, the dose display was also tested on clinical data of a patient with laryngeal cancer treated with radiation therapy, with estimated display accuracy of ∼2-3 mm. The utility of the dose display for registration of radiation dose information to the surgical field was further demonstrated in a mock sarcoma case using a leg phantom. With direct overlay of radiation dose on endoscopic imaging, tissue toxicities and tumor response in endoluminal organs can be directly correlated with the actual tissue dose, offering a more nuanced assessment of normal tissue toxicities following radiation therapy and accurate registration of radiation dose to the surgical field.