Statistical process control for IMRT dosimetric verification

摘要: Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate dosimetric performance over time our IMRT process, we have statistical process control (SPC) concepts analyze from 330 head and neck (H N) treatment plans. The objectives present work to: (i) Review a large series consecutive plans better understand appropriate tolerances; (ii) results with SPC develop action levels for measured discrepancies; (iii) estimates number that required describe in clinical setting; (iv) new beam model planning system. H N cases were planned PINNACLE{sup 3} system versions 6.2b or 7.6c (Philips Medical Systems, Madison, WI) treated on Varian (Palo Alto, CA) Elekta (Crawley, UK) linacs. As part regular quality assurance, recalculated 20-cm-diam cylindrical phantom, ion chamber made high-dose volumes (the PTV highest dose) low-dose (spinal cord organ-at-risk, OR). Differences between doses weremore » recorded as percentage dose. stable time. Measurements linacs showed mean difference 0.6% PTVs (n=149, range, -4.3% 6.6%), while OR larger systematic discrepancy (mean 4.5%, range -4.5% 16.3%) was due well-known limitations MLC earlier version demonstrated 0.2% (n=160, -3.0%, 5.0%) -1.0% ORs (range -5.8% 4.4%). capability index (ratio specification data) 1.3 data, indicating almost all within {+-}5%. We tools produce -0.6% 0.4% ORs, although is smaller (n=25). Analysis this accepted tolerances. These data provide useful information assessing alterations models enhanced by addition traditional procedures.« less