Experimental methods are commonly used for patient‐specific IMRT delivery verification. There are a variety of IMRT QA techniques which have been proposed and clinically used with a common understanding that not one single method can detect all possible errors. The aim of this work was to compare the efficiency and effectiveness of independent dose calculation followed by machine log file analysis to conventional measurement‐based methods in detecting errors in IMRT delivery. Sixteen IMRT treatment plans (5 head‐and‐neck, 3 rectum, 3 breast, and 5 prostate plans) created with a commercial treatment planning system (TPS) were recalculated on a QA phantom. All treatment plans underwent ion chamber (IC) and 2D diode array measurements. The same set of plans was also recomputed with another commercial treatment planning system and the two sets of calculations were compared. The deviations between dosimetric measurements and independent dose calculation were evaluated. The comparisons included evaluations of DVHs and point doses calculated by the two TPS systems. Machine log files were captured during pretreatment composite point dose measurements and analyzed to verify data transfer and performance of the delivery machine. Average deviation between IC measurements and point dose calculations with the two TPSs for head‐and‐neck plans were 1.2±1.3% and 1.4±1.6%, respectively. For 2D diode array measurements, the mean gamma value with 3% dose difference and 3 mm distance‐to‐agreement was within 1.5% for 13 of 16 plans. The mean 3D dose differences calculated from two TPSs were within 3% for head‐and‐neck cases and within 2% for other plans. The machine log file analysis showed that the gantry angle, jaw position, collimator angle, and MUs were consistent as planned, and maximal MLC position error was less than 0.5 mm. The independent dose calculation followed by the machine log analysis takes an average 47±6 minutes, while the experimental approach (using IC and 2D diode array measurements) takes an average about 2 hours in our clinic. Independent dose calculation followed by machine log file analysis can be a reliable tool to verify IMRT treatments. Additionally, independent dose calculations have the potential to identify several problems (heterogeneity calculations, data corruptions, system failures) with the primary TPS, which generally are not identifiable with a measurement‐based approach. Additionally, machine log file analysis can identify many problems (gantry, collimator, jaw setting) which also may not be detected with a measurement‐based approach. Machine log file analysis could also detect performance problems for individual MLC leaves which could be masked in the analysis of a measured fluence.PACS numbers: 87.53.Bn, 87.55.Qr, 87.55.km, 87.57.Uq
Purpose: Experimental methods are commonly used for patient‐specific IMRT verification. The aim of this work is to investigate the possibility of substituting the time and labor intensive IMRT QA with calculation based dose verification and log file analysis. Method: 11 IMRT plans (5 head and neck plans, 3 rectum plans, 3 breast plans and 5 prostate plans) made using Pinnacle were recalculated using a QA phantom. All the plans were verified by ICs and 2D MapCheck measurements and compared to the independent dose calculation using Eclipse. The deviations between dosimetric measurements and independent dose calculation in a QA phantom were evaluated. The plans with patient anatomy were imported to Eclipse for 3D dose calculations. The DVHs and point doses calculated by Pinnacle and Eclipse are evaluated for PTV and critical structures. To verify data transfer and performance of the delivery unit dynalog file analysis was performed. Results: Average deviation between IC measurements and point dose calculations with Pinnalce and Eclipse for Head and Neck were 1.1±1.3% and 1.4±1.6%, respectively. For MapCheck measurement, the mean gamma value with 3% dose difference and 3 mm distance‐to‐agreement were within 1.5% for most plans. The mean 3D dose differences calculated from two different treatment systems are with 3 % for Head‐and‐Neck cases and are within 2% for other plans. The dynalog analysis shows that the gantry angle, jaw position, collimator angle and MLC positions have the passing rate of above 97%. The independent dose calculation with the dynalog analysis takes only 37 minutes, while experimental approach, which takes up to 3 hours. Conclusion: Independent dose calculation followed by dynalog file analysis is a reliable tool to verify the IMRT treatment. With the IMRT QA program becoming more mature, independent dose calculations and dynalog analysis may be used to replace experimental based verification methods.
Purpose: To implement Toyota Production System (TPS) lean tools and techniques in the Department of Radiation Oncology to maximize the individual productivity, process efficiency, deliver high level of quality and safe patient treatments. Methods: To continuously and relentlessly improve the performance of individuals and processes to an acceptable level of operation we have categorized the departmental operations into safety, quality, deliverability, cost and morale. We had issues with all aspects of the radiation therapy process that affect the quality and deliverability of treatment to our patients. To address these areas we adopted TPS lean principles and tools with existing resources such as gemba walk, visual controls and daily huddle where therapists, dosimeterists, physicists and physicians participate towards the lean management of the processes until the requested resources are available. These issues are addressed with clear communication through simple tools and with individuals in the department. To make this process and progress transparent, we have placed a huddle boards consisting of daily update of issues, actions needed to address the issues, and progress in safety, quality, deliverability, cost and morale, and effects of these progressions to the department. Results: With the implementation of simple, direct and effective TPS lean techniques in the department and hard stop policy of postponing IMRT patients not ready by the noon of the day before the first treatment, the work flow has become more streamlined and has helped in timely start of the patient treatments. With the availability of an assigned physicist to answer questions during the clinical hours, physicians, dosimeterists, and therapists concerns were also addressed in timely and orderly fashion and boosted the morale among the departmentConclusion: TPS lean techniques have been effective in decreasing the patient delays while increasing quality and safety to the patients with same cost and improved staff morale.
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