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An Evaluation of Two Approaches to Skin Bolus Design for Radiotherapy Planning of Head & Neck Cancers
question arises whether new staffing practice models in the Radiation Therapy departments should be implemented in order to manage and adapt to this change. A study was conducted to collect the opinions of Radiation Therapists at a large academic Canadian Cancer Centre on specialized versus generalized practice models of staffing. Understanding staff perceptions can indicate weaknesses and strengths of different practice models. This can lead to innovations in practice models for the Radiation Therapy departments for the better patient care and staff satisfaction. Methods and Materials: A literature review conducted summarized staffing model types used in major cancer centres. Concentrating the major themes of the literature review results, a survey was created and administered to analyze the perceptions of Radiation Therapists (N¼48) and Radiation Therapy students (N¼10) on a generalized versus specialized practice model of care in a Radiation Therapy department. Results: Staff wanted to work in areas with more advancing technology and displayed an interest to work in areas of the department that encouraged participation in inter-professional team dynamics. Job rotation within the department is consistently favoured by participants. Job satisfaction was another key theme arising from data analysis. Conclusion: Radiation therapy is dynamically evolving and pushing technological boundaries. Innovation in staffing practice models is paramount to the delivery of care. There is not one customary practice model that suits every agency the same. It is important to get a sense of the perceptions of the Radiation Therapy population from a larger, developed cancer centre. It will provide supportive information on preferred practice models that can be referred to by individuals in the future considering implementing a change within a department.
Characterization of the Accuracy of the Dose Delivery for Pelvic Adaptive Radiotherapy Using Cone-Beam CT for Post Planning Presenting author: D. Ribeiro Radiation Therapy student, Mohawk-McMaster University Medical Radiation Sciences Program, Juravinski Cancer Centre, Canada. E-mail: [email protected] Other author: J. Juhasz Purpose: Characterization of the feasibility of post-planning on Cone-Beam Computed Tomography (CBCT) images for pelvic adaptive radiotherapy. Methods and Materials: Previously, a commercially available phantom (CIRS 062) was modified to mimic the pelvis anatomy and to allow for full scatter conditions in a CBCT radiation field. Calibrated CBCT Hounsfield unit numbers were converted to electron density numbers. Afterwards, calibration curves were generated for dose calculation purposes to examine and compare dose distributions between treatment plans generated on CT-Simulator and CBCT images. In the Pinnacle Treatment Planning software, beams, points, and regions of interest (ROIs) were transferred from the original CT plan images to the CBCT images acquired on the treatment unit. Dose distributions were re-computed using the previous calibration curve and the new CBCT calibration curve specifically derived for this study. The generated treatment plans were cross-compared and analyzed. Results: Examination of Dose Volume Histograms (DVHs) and dose distribution analysis using an image processing software (Image J) confirmed the acceptable accuracy of the CBCT calibration curve. The results inferred that 3 of 4 patients received exceptional treatment accuracy using CBCT post-planning (within 3% difference). However, the comparison was based on image registration and not on the actual couch adjustment parameters before the treatment. Additional accuracy must be maintained, such as exact treatment setup parameters, and region of interest or contour adjustments on the CBCT images. Conclusions: The methodology established provides an insightful method in determining the accuracy in pelvic adaptive radiotherapy. Through the process of post-planning on CBCT scans, a valuable platform for pelvic adaptive therapy could possibly be made available and implemented in the treatment routine.
POSTER PRESENTATIONS An Evaluation of Two Approaches to Skin Bolus Design for Radiotherapy Planning of Head & Neck Cancers Presenting author: A. Luu Radiation Therapy student, Mohawk-McMaster University Medical Radiation Sciences Program, Juravinski Cancer Centre, Canada. E-mail: [email protected] Purpose: To compare our practice of placing bolus prior to CT simulation to an alternative where bolus is placed based on post-CT evaluation on the basis of target dose coverage and normal skin sparing. Methods and materials: Twelve previously planned head and neck patients requiring bolus were identified. The skin layers under the bolus but external to the CTV (normal skin) as well as the CTV layer within 5 mm of the bolus (superficial CTV) were delineated. The dose to these regions due to the original plan was compared to the dose resulting from the same plan, but with the original bolus region replaced (using density overrides) with a 1 cm thick custom bolus region overlaying the superficial CTV. The two configurations were compared on the basis of: bolus area and minimum dose to superficial CTV. Results: Out of 12 plans, 9 required a decrease in bolus area, while 3 required an increase. A Wilcoxon one-tail signed rank test at a 95% confidence interval determined that using the CT images to design bolus improves dose coverage compared to bolus made prior to the CT simulation. Post-CT designed bolus increased the minimum dose to superficial CTV by between 2.1% and 57.3%, roughly in proportion to the area under bolus. Similar statistical analysis indicated that the difference in bolus area between the two approaches was significant. Conclusion: Using the CT simulation image set to design bolus significantly improves dose coverage of the superficial CTV and significantly influences the area under bolus needed to ensure adequate target coverage and optimal sparing of normal skin.To determine if the minimum dose to a bolused CTV is affected when bolus is altered. Secondarily, this experiment attempts to determine if there is a noticeable difference in skin dose in the case of a difference in area of coverage from the pre-CT bolus to the treatment planning bolus.
Simple Figure of Merit to Assess Intraluminal Brachytherapy Plans Presenting author: T. Finnie Radiation Therapy student, Mohawk-McMaster University Medical Radiation Sciences Program, Juravinski Cancer Centre, Canada. E-mail: [email protected] Other authors: R. Hunter and T. Farrell Purpose: To design a simple figure of merit that can be used to assess the accuracy and optimization of intraluminal High Dose Rate (HDR) brachytherapy plans. Materials and Methods: Research was conducted in three phases, the first of which consisted of designing 15 multiline and 40 single line ’standard’ intraluminal HDR brachytherapy plans with visibly uniform and optimal dose distributions. The second phase involved the creation and assessment of 8 multiline plans and 10 single line plans that would be considered ‘‘unacceptable’’ for patient treatment based on their dose distributions. The final phase investigated plans that have been created and implemented as treatment for previous patients and have therefore already been considered ’acceptable’. The data collected from the standard plans assessed in phase I was graphed using various combinations of the three variables: irradiated volume (cm3), length of catheter (cm) and workload (curie seconds). Data collected in phases II and III were then compared with these graphs so see whether or not the unacceptable and acceptable plans would deviate from the expected standard graphs. Results: An algorithm designed from the data comparing the volume receiving 150% of the prescribed dose vs. the workload (curie seconds) identified the unacceptable single line plans with 100% accuracy and acceptable plans with 60% accuracy. There was no such algorithm that could be devised to effectively assess multi-line plans based on these three variables. Conclusion: More research is needed to design an accurate tool for the assessment of multi-line plans. Other factors are currently being implemented and
Abstracts/Journal of Medical Imaging and Radiation Sciences 44 (2013) 157-162
159
Characterization of the Accuracy of the Dose Delivery for Pelvic Adaptive Radiotherapy Using Cone-Beam CT for Post Planning Presenting author: D. Ribeiro Radiation Therapy student, Mohawk-McMaster University Medical Radiation Sciences Program, Juravinski Cancer Centre, Canada. E-mail: [email protected] Other author: J. Juhasz Purpose: Characterization of the feasibility of post-planning on Cone-Beam Computed Tomography (CBCT) images for pelvic adaptive radiotherapy. Methods and Materials: Previously, a commercially available phantom (CIRS 062) was modified to mimic the pelvis anatomy and to allow for full scatter conditions in a CBCT radiation field. Calibrated CBCT Hounsfield unit numbers were converted to electron density numbers. Afterwards, calibration curves were generated for dose calculation purposes to examine and compare dose distributions between treatment plans generated on CT-Simulator and CBCT images. In the Pinnacle Treatment Planning software, beams, points, and regions of interest (ROIs) were transferred from the original CT plan images to the CBCT images acquired on the treatment unit. Dose distributions were re-computed using the previous calibration curve and the new CBCT calibration curve specifically derived for this study. The generated treatment plans were cross-compared and analyzed. Results: Examination of Dose Volume Histograms (DVHs) and dose distribution analysis using an image processing software (Image J) confirmed the acceptable accuracy of the CBCT calibration curve. The results inferred that 3 of 4 patients received exceptional treatment accuracy using CBCT post-planning (within 3% difference). However, the comparison was based on image registration and not on the actual couch adjustment parameters before the treatment. Additional accuracy must be maintained, such as exact treatment setup parameters, and region of interest or contour adjustments on the CBCT images. Conclusions: The methodology established provides an insightful method in determining the accuracy in pelvic adaptive radiotherapy. Through the process of post-planning on CBCT scans, a valuable platform for pelvic adaptive therapy could possibly be made available and implemented in the treatment routine.
POSTER PRESENTATIONS An Evaluation of Two Approaches to Skin Bolus Design for Radiotherapy Planning of Head & Neck Cancers Presenting author: A. Luu Radiation Therapy student, Mohawk-McMaster University Medical Radiation Sciences Program, Juravinski Cancer Centre, Canada. E-mail: [email protected] Purpose: To compare our practice of placing bolus prior to CT simulation to an alternative where bolus is placed based on post-CT evaluation on the basis of target dose coverage and normal skin sparing. Methods and materials: Twelve previously planned head and neck patients requiring bolus were identified. The skin layers under the bolus but external to the CTV (normal skin) as well as the CTV layer within 5 mm of the bolus (superficial CTV) were delineated. The dose to these regions due to the original plan was compared to the dose resulting from the same plan, but with the original bolus region replaced (using density overrides) with a 1 cm thick custom bolus region overlaying the superficial CTV. The two configurations were compared on the basis of: bolus area and minimum dose to superficial CTV. Results: Out of 12 plans, 9 required a decrease in bolus area, while 3 required an increase. A Wilcoxon one-tail signed rank test at a 95% confidence interval determined that using the CT images to design bolus improves dose coverage compared to bolus made prior to the CT simulation. Post-CT designed bolus increased the minimum dose to superficial CTV by between 2.1% and 57.3%, roughly in proportion to the area under bolus. Similar statistical analysis indicated that the difference in bolus area between the two approaches was significant. Conclusion: Using the CT simulation image set to design bolus significantly improves dose coverage of the superficial CTV and significantly influences the area under bolus needed to ensure adequate target coverage and optimal sparing of normal skin.To determine if the minimum dose to a bolused CTV is affected when bolus is altered. Secondarily, this experiment attempts to determine if there is a noticeable difference in skin dose in the case of a difference in area of coverage from the pre-CT bolus to the treatment planning bolus.
Simple Figure of Merit to Assess Intraluminal Brachytherapy Plans Presenting author: T. Finnie Radiation Therapy student, Mohawk-McMaster University Medical Radiation Sciences Program, Juravinski Cancer Centre, Canada. E-mail: [email protected] Other authors: R. Hunter and T. Farrell Purpose: To design a simple figure of merit that can be used to assess the accuracy and optimization of intraluminal High Dose Rate (HDR) brachytherapy plans. Materials and Methods: Research was conducted in three phases, the first of which consisted of designing 15 multiline and 40 single line ’standard’ intraluminal HDR brachytherapy plans with visibly uniform and optimal dose distributions. The second phase involved the creation and assessment of 8 multiline plans and 10 single line plans that would be considered ‘‘unacceptable’’ for patient treatment based on their dose distributions. The final phase investigated plans that have been created and implemented as treatment for previous patients and have therefore already been considered ’acceptable’. The data collected from the standard plans assessed in phase I was graphed using various combinations of the three variables: irradiated volume (cm3), length of catheter (cm) and workload (curie seconds). Data collected in phases II and III were then compared with these graphs so see whether or not the unacceptable and acceptable plans would deviate from the expected standard graphs. Results: An algorithm designed from the data comparing the volume receiving 150% of the prescribed dose vs. the workload (curie seconds) identified the unacceptable single line plans with 100% accuracy and acceptable plans with 60% accuracy. There was no such algorithm that could be devised to effectively assess multi-line plans based on these three variables. Conclusion: More research is needed to design an accurate tool for the assessment of multi-line plans. Other factors are currently being implemented and
Abstracts/Journal of Medical Imaging and Radiation Sciences 44 (2013) 157-162
159