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Evaluation of Accuracy and Performance of a Fast Monte Carlo Code for Dose Calculation in Proton Therapy
S40
Abstracts / Clinical Oncology 23 (2011) S1eS58
Aim: To commission our 6 MV Monte Carlo beam model in MonacoÒ v2.03 into clinical use for IMRT. Method: A structured programme for commissioning was followed, progressing through different levels of complexity, comparing measurements with Monte Carlo calculated results. Baseline commissioning was carried out for percentage depth doses, output factors and profiles for a range of geometries. Upon satisfactory completion of baseline comparisons with measured data, commissioning progressed onto irregular fields and heterogeneities in reference geometries. Finally, absolute dose comparisons between planned and measured data were carried out using ion chambers and various detector arrays for both simple field combinations and complex IMRT plans. Results: All results fall within acceptable levels of tolerances set and are summarised as follows: Percentage depth doses within 2% deviation from measurements (global maximum): B Build-up data verified against parallel plate chamber data were found to agree within 2% beyond 5 mm depth. Output factors at reference depth and SSD within 1.2%. Profiles within 2% (local deviation) in the flattened portion of the field: B Distance to agreement in penumbra for small fields within 1.2 mm; B Outside the field calculations within 2% of measured data (global maximum). Off-axis ratios within 2% of measurements for a range of geometries. Heterogeneities: Monte Carlo calculated results within 2% of measurements for oblique geometry low density heterogeneity. IMRT plans: ion chamber measurements within 0.5% at isocentre. Gamma analysis: >90% pass at 3%/3 mm.
P45 Evaluation of Accuracy and Performance of a Fast Monte Carlo Code for Dose Calculation in Proton Therapy K. Jabbari *, M. Roayaei y, A. Saeedi y * Department of Medical Physics and Engineering, Isfahan University of Medical Sciences, Isfahan, Iran y Department of Radiation Oncology, Isfahan University of Medical Sciences, Isfahan, Iran Introduction: Accurate treatment planning is a substantial step in radiation therapy. Monte Carlo techniques, as the most accurate dose calculation method, attracted a growing interest in treatment planning. In this study, we evaluated a fast Monte Carlo treatment planning, and compared it to other algorithms. Methods: Early versions of dose calculation algorithms used simple and fast methods like the pencil beam and analytical methods that simulate the particles as a group. Monte Carlo methods simulate and transport each particle individually. We used pre-calculated data, generated by a general purpose Monte Carlo code (MCNPX). A set of data including the track of the particle was produced in each particular material (water, air, lung, bone, tissues). This code is able to transport photons and electrons, as well as protons in a wide range of energies (up to 200 MeV for protons). Results: The validity of the fast Monte Carlo code is evaluated with data of the patients' CT scans. Although analytical pencil beam algorithm transport shows great errors (up to 10%) near small high density heterogeneities, there was less than 2% deviation of experimental results in our dose calculation and isodose distribution. In terms of speed, the code runs 200 times faster than MCNPX. Conclusion: Transition from Monte Carlo to fast Monte Carlo codes can solve the slow calculation speed without missing the accuracy. At this time, it takes the system less than 2 min to calculate the dose for each patient; thus it is suitable for practical use in treatment planning.
Conclusions: Our results indicate that agreement between MonacoÒ Monte Carlo calculated results and measurements is within acceptable tolerances to proceed to clinical implementation for IMRT.
P44 Factors Affecting Job Satisfaction of Band 5 and 6 Therapy Radiographers D. Hutton *, A. Eddy y * Clatterbridge Centre for Oncology, Bebington, Wirral, UK y Sheffield Hallam University, Sheffield, UK
HR = 0.28, p = 0.096 95% CI 0.062, 1.255
Aims: To obtain a detailed understanding of the current professional experiences of band 5 and 6 therapy radiographers. To identify how and why certain factors influence perceptions of job satisfaction. To inform the development of future strategies that can be employed in departments to increase the level of job satisfaction for this group of practitioners. Method: A qualitative study using a case study approach was employed to explore the experiences of band 5 and 6 therapy radiographers, in two radiotherapy departments, totalling 40 participants (four focus groups). A thematic analysis was undertaken and emergent themes identified through the iterative process of reading, coding and revisiting the data. Results: Job satisfaction is multifaceted, dependant on the individual, and is influenced by the context of their working environment. Key factors include: patients, team, development, rotations, perceived fairness, encourage, support and recognition. Conclusions: Poor job satisfaction is a precursor to turnover. Attrition or significant turnover at any level of an organisation's structure impacts negatively on the trust's ability to deliver a high quality, patient centred service. Preceptorship programmes incorporating structured rotations and systematic personal development reviews, may assist individuals in achieving their profession goals, a key element of satisfaction. Teams and peers have the potential to significantly influence job satisfaction. It is important that radiographers feel aligned with the organisation's values and vision. It is essential to retain and develop this group of staff, employing appropriate support strategies for them. This is especially important if government and national workforce targets are to be met. We currently do not fully understand the nature or factors influencing job satisfaction and consequently attrition and turnover. This work will inform the development of a phase II study comprising a national questionnaire to band 5 and 6 therapy radiographers, to further investigate the relationship.
P46 The Role of Radiotherapy in Extensive Stage Small Cell Lung Cancer (ED SCLC): Prophylactic Cranial Irradiation (PCI) and Consolidation Thoracic Radiotherapy P. Jain *, M. McKay y, H. Wong y, F. Alam *, J.A. H.L. Littler *, J. Maguire *, Z. Malik *, V. Ramani *, P. Schofield *, K. Whitmarsh * * Clinical Oncology, Clatterbridge Centre for Oncology, Bebington, Wirral, UK y Clinical Effectiveness Team, Clatterbridge Centre for Oncology, Bebington, Wirral, UK Introduction: ED SCLC has a poor prognosis with a median survival of 9 months. PCI can double 1 year overall survival and should be standard practice in patients who respond to first line chemotherapy. The role of consolidation thoracic radiotherapy is less well defined. Methods: Retrospective case note audit of ED SCLC patients who responded to first line chemotherapy and had PCI (25 Gy/10 fractions), thorax or both from January 2008 to December 2009. Data on irradiated site, dose fractionation
Abstracts / Clinical Oncology 23 (2011) S1eS58
Aim: To commission our 6 MV Monte Carlo beam model in MonacoÒ v2.03 into clinical use for IMRT. Method: A structured programme for commissioning was followed, progressing through different levels of complexity, comparing measurements with Monte Carlo calculated results. Baseline commissioning was carried out for percentage depth doses, output factors and profiles for a range of geometries. Upon satisfactory completion of baseline comparisons with measured data, commissioning progressed onto irregular fields and heterogeneities in reference geometries. Finally, absolute dose comparisons between planned and measured data were carried out using ion chambers and various detector arrays for both simple field combinations and complex IMRT plans. Results: All results fall within acceptable levels of tolerances set and are summarised as follows: Percentage depth doses within 2% deviation from measurements (global maximum): B Build-up data verified against parallel plate chamber data were found to agree within 2% beyond 5 mm depth. Output factors at reference depth and SSD within 1.2%. Profiles within 2% (local deviation) in the flattened portion of the field: B Distance to agreement in penumbra for small fields within 1.2 mm; B Outside the field calculations within 2% of measured data (global maximum). Off-axis ratios within 2% of measurements for a range of geometries. Heterogeneities: Monte Carlo calculated results within 2% of measurements for oblique geometry low density heterogeneity. IMRT plans: ion chamber measurements within 0.5% at isocentre. Gamma analysis: >90% pass at 3%/3 mm.
P45 Evaluation of Accuracy and Performance of a Fast Monte Carlo Code for Dose Calculation in Proton Therapy K. Jabbari *, M. Roayaei y, A. Saeedi y * Department of Medical Physics and Engineering, Isfahan University of Medical Sciences, Isfahan, Iran y Department of Radiation Oncology, Isfahan University of Medical Sciences, Isfahan, Iran Introduction: Accurate treatment planning is a substantial step in radiation therapy. Monte Carlo techniques, as the most accurate dose calculation method, attracted a growing interest in treatment planning. In this study, we evaluated a fast Monte Carlo treatment planning, and compared it to other algorithms. Methods: Early versions of dose calculation algorithms used simple and fast methods like the pencil beam and analytical methods that simulate the particles as a group. Monte Carlo methods simulate and transport each particle individually. We used pre-calculated data, generated by a general purpose Monte Carlo code (MCNPX). A set of data including the track of the particle was produced in each particular material (water, air, lung, bone, tissues). This code is able to transport photons and electrons, as well as protons in a wide range of energies (up to 200 MeV for protons). Results: The validity of the fast Monte Carlo code is evaluated with data of the patients' CT scans. Although analytical pencil beam algorithm transport shows great errors (up to 10%) near small high density heterogeneities, there was less than 2% deviation of experimental results in our dose calculation and isodose distribution. In terms of speed, the code runs 200 times faster than MCNPX. Conclusion: Transition from Monte Carlo to fast Monte Carlo codes can solve the slow calculation speed without missing the accuracy. At this time, it takes the system less than 2 min to calculate the dose for each patient; thus it is suitable for practical use in treatment planning.
Conclusions: Our results indicate that agreement between MonacoÒ Monte Carlo calculated results and measurements is within acceptable tolerances to proceed to clinical implementation for IMRT.
P44 Factors Affecting Job Satisfaction of Band 5 and 6 Therapy Radiographers D. Hutton *, A. Eddy y * Clatterbridge Centre for Oncology, Bebington, Wirral, UK y Sheffield Hallam University, Sheffield, UK
HR = 0.28, p = 0.096 95% CI 0.062, 1.255
Aims: To obtain a detailed understanding of the current professional experiences of band 5 and 6 therapy radiographers. To identify how and why certain factors influence perceptions of job satisfaction. To inform the development of future strategies that can be employed in departments to increase the level of job satisfaction for this group of practitioners. Method: A qualitative study using a case study approach was employed to explore the experiences of band 5 and 6 therapy radiographers, in two radiotherapy departments, totalling 40 participants (four focus groups). A thematic analysis was undertaken and emergent themes identified through the iterative process of reading, coding and revisiting the data. Results: Job satisfaction is multifaceted, dependant on the individual, and is influenced by the context of their working environment. Key factors include: patients, team, development, rotations, perceived fairness, encourage, support and recognition. Conclusions: Poor job satisfaction is a precursor to turnover. Attrition or significant turnover at any level of an organisation's structure impacts negatively on the trust's ability to deliver a high quality, patient centred service. Preceptorship programmes incorporating structured rotations and systematic personal development reviews, may assist individuals in achieving their profession goals, a key element of satisfaction. Teams and peers have the potential to significantly influence job satisfaction. It is important that radiographers feel aligned with the organisation's values and vision. It is essential to retain and develop this group of staff, employing appropriate support strategies for them. This is especially important if government and national workforce targets are to be met. We currently do not fully understand the nature or factors influencing job satisfaction and consequently attrition and turnover. This work will inform the development of a phase II study comprising a national questionnaire to band 5 and 6 therapy radiographers, to further investigate the relationship.
P46 The Role of Radiotherapy in Extensive Stage Small Cell Lung Cancer (ED SCLC): Prophylactic Cranial Irradiation (PCI) and Consolidation Thoracic Radiotherapy P. Jain *, M. McKay y, H. Wong y, F. Alam *, J.A. H.L. Littler *, J. Maguire *, Z. Malik *, V. Ramani *, P. Schofield *, K. Whitmarsh * * Clinical Oncology, Clatterbridge Centre for Oncology, Bebington, Wirral, UK y Clinical Effectiveness Team, Clatterbridge Centre for Oncology, Bebington, Wirral, UK Introduction: ED SCLC has a poor prognosis with a median survival of 9 months. PCI can double 1 year overall survival and should be standard practice in patients who respond to first line chemotherapy. The role of consolidation thoracic radiotherapy is less well defined. Methods: Retrospective case note audit of ED SCLC patients who responded to first line chemotherapy and had PCI (25 Gy/10 fractions), thorax or both from January 2008 to December 2009. Data on irradiated site, dose fractionation