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PO-0891: Quality assessment of target volume delineation and dose planning in the Skagen Trial 1
S490 ESTRO 36 _______________________________________________________________________________________________
Conclusion This work presents a methodology to e stimate the parameters of a mechanistic, radiobiological l TCP model based on pre-treatment FMISO and FDG PET scans. The method is able to predict mean and median values of intra-treatment hypoxia for each of the lesions in a validation dataset held out from the analysis. This could potentially be used in the future to, for example, select patients for a de-escalation protocol based on their expected response. More patients will be added to the analysis in order to refine the prediction, find the defining characteristics of the outliers, and consolidate the results. PO-0891 Quality assessment of target volume delineation and dose planning in the Skagen Trial 1 G. Francolini1, M. Thomsen2, E. Yates2, C. Kirkove3, I. Jensen4, E. Blix5, C. Kamby6, M. Nielsen7, M. Krause8, M. Berg9, I. Mjaaland10, A. Schreiber11, U. Kasti12, K. Boye13, B. Offersen14 1 Azienda Ospedaliera Universitaria Careggi, Department of Radiation oncology, Firenze, Italy 2 Aarhus University hospital, Department of Medical physics, Aarhus, Denmark 3 Catholic University of Louvain, Department of Radiation Oncology, Brussels, Belgium 4 Aalborg University Hospital, Department of Medical Physics, Aalborg, Denmark 5 University Hospital of North Norway, Department of Oncology, Tromso, Norway 6 Rigshospitalet, Department of Oncology, Copenhagen, Denmark 7 Odense University Hospital, Department of Oncology, Odense, Denmark 8 University Hospital Carl Gustav Carus, Department of Radiation Oncology, Dresden, Germany 9 Hospital of Vejle, Department of Physics, Vejle, Denmark 10 Stavanger University Hospital, Department of Oncology, Stavanger, Norway 11 Praxis für Strahlentherapie, Department of Radiation oncology, Dresden, Germany 12 Sørlandet Sykehus HF, Department of Oncology, Kristiansand, Norway 13 Zealand University Hospital, Department of Oncology, Naestved, Denmark 14 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark Purpose or Objective Skagen Trial 1 is a multicenter, non-inferiority trial randomising early breast cancer patients to loco-regional irradiation with 50 Gy/25 fractions vs 40 Gy/15fractions. Primary endpoint is arm lymphedema. The protocol has pre-specified criteria for target volume delineation and dose planning, and quality assessment of this is reported. Inter-observer variability in delineation and its impact on dose parameters were assessed. Automated atlas-based segmentation was used in order to streamline assessment procedure.
Material and Methods Treatment CT scans from up to 8 randomly selected patients included in the trial had target volumes auto delineated with MIM Maestro™ software version 6.5 (MIM Software Inc., Cleveland, OH) and manually edited according to ESTRO target volume delineation guidelines. Post editing of contours were verified by an observer (BVO),and considered as a gold standard reference (GS). Dice similarity coefficient (DSC) between original delineation (OD) and GS was calculated. Protocol compliance and dose distribution of delineated volumes (Dmin, Dmax, D2%, D95%, D98% and Homogeneity index (HI) for breast and nodal target volumes) were assessed in OD. HI and D95% were compared between OD and GS delineation of primary (CTVp),CTVn_L2-4- interpectoral (CTVn), internal mammary CTV (CTVn_ IMN) and CTVn_L1.
Results 88 treatment plans from 12 centres in 4 countries were assessed. Delineation of all target volumes and organs at risk was complete in 99% and 96% of the patients,respectively. DSC showed high agreement in contouring, with average values of 0,9 for CTVp and 0,77 for nodal volumes.Complete dosimetric assessment was available in all patients for CTVp, but 1 patient with missing target volume delineation required integration with data extrapolated from GS. No deviations for target dose distribution were found in 76% of the patients, and 82% and 95%of the patients had successful target coverage of CTVp and CTVn, with 95% of volume covered by >95% and >90% of prescribed dose, respectively. Dose comparison for CTVp was performed in all patients, but 17 patients were excluded from CTVn comparison due to incomplete target delineation or exclusion of one or more nodal levels from target volume according to institutional policy. No differences were found for CTVp HI and D95% between OD and GS. CTVn, CTVn_L1 and CTVn_IMN were successfully covered (D95>90% of prescribed dose) in both delineations. Minimal differences were found in D95% and HI for CTVn (p<0,001 for both), CTVn_IMN (p=0,001 for D95%) and CTVn_L1 (p=0,02 for HI andp=0,03 for D95%).
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adjacent contours, 3) conformity index (CI) between adjacent contours, 4) presence of air or bone across the line of the contour, 5) presence of air or bone within 5 mm outside of the contour boundary, and 6) presence of spacing > 20 mm between adjacent contour points. The threshold values for the metrics 1-3 were calculated from the rectum contours drawn by oncology experts on 315 pelvic kVCT scans, where we used 6 mm superiorinferior contour spacing to match the slice spacing of the IG scans. The settings for metrics 4-6 were determined empirically. Our software developed in Python 2.7 analysed the DICOM RTSTRUCT and IG scan data, applied the metrics and recorded the evaluation results in a spreadsheet. A contour was marked as “error” if any of the thresholds defined in the metrics was triggered. Results
Conclusion There was low interobserver variability across all centres. Low rates of protocol deviations ensured high compliance of the participating centres. Targets were adequately and homogeneously covered in the majority of patients. Dose parameters were comparable between OD and GS and confirmed that interobserver variability did not influence treatment outcomes. Poster: Physics track: Images and analyses PO-0892 Automatic quality assurance of rectal contours on image guidance scans M. Romanchikova1, D.I. Johnston1, M.P.F. Sutcliffe2, K. Harrison3, S.J. Thomas1, J.E. Scaife4, N.G. Burnet4 1 Cambridge University Hospitals, Medical Physics and Clinical Engineering, Cambridge, United Kingdom 2 University of Cambridge, Engineering, Cambridge, United Kingdom 3 University of Cambridge, Physics, Cambridge, United Kingdom 4 University of Cambridge, Oncology, Cambridge, United Kingdom Purpose or Objective Assessment of the quality of contours produced by automatic methods is labour-intensive and inherently dependant on the skills of the evaluator. The utilisation of these contours in radiotherapy requires objective quality metrics and efficient tools for contour quality assurance. We present a method to determine the quality of automated rectum contours on daily image guidance scans (IG). Material and Methods We analysed 11519 automatically produced rectum contours on 1062 pelvic IG scans of 33 prostate cancer patients. Each contour was evaluated by 1) a trained clinician and 2) an automated classification software that applied a set of binary and numeric metrics to each contour. The metrics included 1) centre-to-centre contour distances, 2) differences in contour areas between
The automatic evaluation of 11519 contours for 33 patients took 6 minutes on a computer with 8 GB RAM and 1.6 GHz Intel Xeon CPU. The evaluation results were compared to the errors recorded by a human observer, and confusion matrices were calculated. The mean error prevalence in the observer evaluation was 0.29 ± 0.1. Our algorithm achieved a mean sensitivity of 0.84 ± 0.1 (range [0.58 – 1.0]) and a mean specificity of 0.88 ± 0.1 (range [0.51 – 1.0]). One patient data set totalling 339 slices was evaluated with a sensitivity and specificity of 1.0. Conclusion Metric-based evaluation of rectum contours is a feasible alternative to evaluation of contours by a human observer. It provides an unbiased contour classification and detects over 80% of typical errors in the contours. The method can be used to assess the performance of automated contouring tools and to aid the development of improved contouring software. PO-0893 Improving CBCT image quality for daily image guidance of patients with head/neck and prostate cancer I. Chetty1, P. Paysan2, F. Siddiqui1, M. Weihua1, M. Brehm2, P. Messmer2, A. Maslowski3, A. Wang3, D. Seghers2, P. Munro2 1 Henry Ford Health System, Radiation Oncology, Detroit, USA 2 Varian Medical Systems Imaging Laboratory GmbH, Image Enhancement and Reconstruction, Baden-Daettwil, Switzerland 3 Varian Medical Systems- Inc., Oncology Systems, Palo Alto, USA Purpose or Objective Image quality of on-board CBCT imaging in radiation therapy generally falls short of diagnostic CT in particular
Conclusion This work presents a methodology to e stimate the parameters of a mechanistic, radiobiological l TCP model based on pre-treatment FMISO and FDG PET scans. The method is able to predict mean and median values of intra-treatment hypoxia for each of the lesions in a validation dataset held out from the analysis. This could potentially be used in the future to, for example, select patients for a de-escalation protocol based on their expected response. More patients will be added to the analysis in order to refine the prediction, find the defining characteristics of the outliers, and consolidate the results. PO-0891 Quality assessment of target volume delineation and dose planning in the Skagen Trial 1 G. Francolini1, M. Thomsen2, E. Yates2, C. Kirkove3, I. Jensen4, E. Blix5, C. Kamby6, M. Nielsen7, M. Krause8, M. Berg9, I. Mjaaland10, A. Schreiber11, U. Kasti12, K. Boye13, B. Offersen14 1 Azienda Ospedaliera Universitaria Careggi, Department of Radiation oncology, Firenze, Italy 2 Aarhus University hospital, Department of Medical physics, Aarhus, Denmark 3 Catholic University of Louvain, Department of Radiation Oncology, Brussels, Belgium 4 Aalborg University Hospital, Department of Medical Physics, Aalborg, Denmark 5 University Hospital of North Norway, Department of Oncology, Tromso, Norway 6 Rigshospitalet, Department of Oncology, Copenhagen, Denmark 7 Odense University Hospital, Department of Oncology, Odense, Denmark 8 University Hospital Carl Gustav Carus, Department of Radiation Oncology, Dresden, Germany 9 Hospital of Vejle, Department of Physics, Vejle, Denmark 10 Stavanger University Hospital, Department of Oncology, Stavanger, Norway 11 Praxis für Strahlentherapie, Department of Radiation oncology, Dresden, Germany 12 Sørlandet Sykehus HF, Department of Oncology, Kristiansand, Norway 13 Zealand University Hospital, Department of Oncology, Naestved, Denmark 14 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark Purpose or Objective Skagen Trial 1 is a multicenter, non-inferiority trial randomising early breast cancer patients to loco-regional irradiation with 50 Gy/25 fractions vs 40 Gy/15fractions. Primary endpoint is arm lymphedema. The protocol has pre-specified criteria for target volume delineation and dose planning, and quality assessment of this is reported. Inter-observer variability in delineation and its impact on dose parameters were assessed. Automated atlas-based segmentation was used in order to streamline assessment procedure.
Material and Methods Treatment CT scans from up to 8 randomly selected patients included in the trial had target volumes auto delineated with MIM Maestro™ software version 6.5 (MIM Software Inc., Cleveland, OH) and manually edited according to ESTRO target volume delineation guidelines. Post editing of contours were verified by an observer (BVO),and considered as a gold standard reference (GS). Dice similarity coefficient (DSC) between original delineation (OD) and GS was calculated. Protocol compliance and dose distribution of delineated volumes (Dmin, Dmax, D2%, D95%, D98% and Homogeneity index (HI) for breast and nodal target volumes) were assessed in OD. HI and D95% were compared between OD and GS delineation of primary (CTVp),CTVn_L2-4- interpectoral (CTVn), internal mammary CTV (CTVn_ IMN) and CTVn_L1.
Results 88 treatment plans from 12 centres in 4 countries were assessed. Delineation of all target volumes and organs at risk was complete in 99% and 96% of the patients,respectively. DSC showed high agreement in contouring, with average values of 0,9 for CTVp and 0,77 for nodal volumes.Complete dosimetric assessment was available in all patients for CTVp, but 1 patient with missing target volume delineation required integration with data extrapolated from GS. No deviations for target dose distribution were found in 76% of the patients, and 82% and 95%of the patients had successful target coverage of CTVp and CTVn, with 95% of volume covered by >95% and >90% of prescribed dose, respectively. Dose comparison for CTVp was performed in all patients, but 17 patients were excluded from CTVn comparison due to incomplete target delineation or exclusion of one or more nodal levels from target volume according to institutional policy. No differences were found for CTVp HI and D95% between OD and GS. CTVn, CTVn_L1 and CTVn_IMN were successfully covered (D95>90% of prescribed dose) in both delineations. Minimal differences were found in D95% and HI for CTVn (p<0,001 for both), CTVn_IMN (p=0,001 for D95%) and CTVn_L1 (p=0,02 for HI andp=0,03 for D95%).
S491 ESTRO 36 _______________________________________________________________________________________________
adjacent contours, 3) conformity index (CI) between adjacent contours, 4) presence of air or bone across the line of the contour, 5) presence of air or bone within 5 mm outside of the contour boundary, and 6) presence of spacing > 20 mm between adjacent contour points. The threshold values for the metrics 1-3 were calculated from the rectum contours drawn by oncology experts on 315 pelvic kVCT scans, where we used 6 mm superiorinferior contour spacing to match the slice spacing of the IG scans. The settings for metrics 4-6 were determined empirically. Our software developed in Python 2.7 analysed the DICOM RTSTRUCT and IG scan data, applied the metrics and recorded the evaluation results in a spreadsheet. A contour was marked as “error” if any of the thresholds defined in the metrics was triggered. Results
Conclusion There was low interobserver variability across all centres. Low rates of protocol deviations ensured high compliance of the participating centres. Targets were adequately and homogeneously covered in the majority of patients. Dose parameters were comparable between OD and GS and confirmed that interobserver variability did not influence treatment outcomes. Poster: Physics track: Images and analyses PO-0892 Automatic quality assurance of rectal contours on image guidance scans M. Romanchikova1, D.I. Johnston1, M.P.F. Sutcliffe2, K. Harrison3, S.J. Thomas1, J.E. Scaife4, N.G. Burnet4 1 Cambridge University Hospitals, Medical Physics and Clinical Engineering, Cambridge, United Kingdom 2 University of Cambridge, Engineering, Cambridge, United Kingdom 3 University of Cambridge, Physics, Cambridge, United Kingdom 4 University of Cambridge, Oncology, Cambridge, United Kingdom Purpose or Objective Assessment of the quality of contours produced by automatic methods is labour-intensive and inherently dependant on the skills of the evaluator. The utilisation of these contours in radiotherapy requires objective quality metrics and efficient tools for contour quality assurance. We present a method to determine the quality of automated rectum contours on daily image guidance scans (IG). Material and Methods We analysed 11519 automatically produced rectum contours on 1062 pelvic IG scans of 33 prostate cancer patients. Each contour was evaluated by 1) a trained clinician and 2) an automated classification software that applied a set of binary and numeric metrics to each contour. The metrics included 1) centre-to-centre contour distances, 2) differences in contour areas between
The automatic evaluation of 11519 contours for 33 patients took 6 minutes on a computer with 8 GB RAM and 1.6 GHz Intel Xeon CPU. The evaluation results were compared to the errors recorded by a human observer, and confusion matrices were calculated. The mean error prevalence in the observer evaluation was 0.29 ± 0.1. Our algorithm achieved a mean sensitivity of 0.84 ± 0.1 (range [0.58 – 1.0]) and a mean specificity of 0.88 ± 0.1 (range [0.51 – 1.0]). One patient data set totalling 339 slices was evaluated with a sensitivity and specificity of 1.0. Conclusion Metric-based evaluation of rectum contours is a feasible alternative to evaluation of contours by a human observer. It provides an unbiased contour classification and detects over 80% of typical errors in the contours. The method can be used to assess the performance of automated contouring tools and to aid the development of improved contouring software. PO-0893 Improving CBCT image quality for daily image guidance of patients with head/neck and prostate cancer I. Chetty1, P. Paysan2, F. Siddiqui1, M. Weihua1, M. Brehm2, P. Messmer2, A. Maslowski3, A. Wang3, D. Seghers2, P. Munro2 1 Henry Ford Health System, Radiation Oncology, Detroit, USA 2 Varian Medical Systems Imaging Laboratory GmbH, Image Enhancement and Reconstruction, Baden-Daettwil, Switzerland 3 Varian Medical Systems- Inc., Oncology Systems, Palo Alto, USA Purpose or Objective Image quality of on-board CBCT imaging in radiation therapy generally falls short of diagnostic CT in particular