A study to establish reasonable action limits for patient‐specific quality assurance in intensity‐modulated radiation therapy

Abstract

An effective patient quality assurance (QA) program for intensity‐modulated radiation therapy (IMRT) requires accurate and realistic plan acceptance criteria—that is, action limits. Based on dose measurements performed with a commercially available two‐dimensional (2D) diode array, we analyzed 747 fluence maps resulting from a routine patient QA program for IMRT plans. The fluence maps were calculated by three different commercially available (ADAC, CMS, Eclipse) treatment planning systems (TPSs) and were delivered using 6‐MV X‐ray beams produced by linear accelerators. To establish reasonably achievable and clinically acceptable limits for the dose deviations, the agreement between the measured and calculated fluence maps was evaluated in terms of percent dose error (PDE) for a few points and percent of passing points (PPP) for the isodose distribution. The analysis was conducted for each TPS used in the study (365 ADAC, 162 CMS, 220 Eclipse), for multiple treatment sites (prostate, pelvis, head and neck, spine, rectum, anus, lung, brain), at the normalization point for 3% percentage difference (%Diff) and 3‐mm distance to agreement (DTA) criteria. We investigated the treatment‐site dependency of PPP and PDE. The results show that, at 3% and 3‐mm criteria, a 95% PPP and 3% PDE can be achieved for prostate treatments and a 90% PPP and 5% PDE are attainable for any treatment site.PACS Numbers: 87.53Dq, 87.53Tf, 87.53Xd, 87.56Fc

Per‐beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

“…Finally, it could be argued that the methodology of basing action levels on prior performance achievements [2][3][4][5][6] is not warranted because meeting these criteria does not ensure that clinically acceptable dose errors are within tolerance per patient. The converse is true as well, i.e., not meeting IMRT QA performance goals does not imply that clinically relevant dose differences would be significant.…”

“…[2][3][4][5][6][7] Some of these studies base action levels on retrospective statistical analysis of the performance levels/metrics that have been achieved over many plans and IMRT beams. [2][3][4][5] It has been suggested that meeting such action levels should be a requirement in order to take part in clinical trials. 6 In a recent report of the AAPM Task Group 119 ͑Ref.…”

“…6 In a recent report of the AAPM Task Group 119 ͑Ref. 5͒ and, in fact, the other studies [2][3][4] as well, the "3%/3 mm" criteria is common, employed as either the composite distance-to-agreement ͑DTA͒ metric or the Gamma index. 8 It is not surprising then that the 3% dose difference and 3 mm DTA criteria were reported as those most commonly used by clinicians 1 in per-patient, planar IMRT QA.…”

Investigation of ultrasonic properties of MAGIC gels for pulse-echo gel dosimetry

“…respectively are often used to determine whether the two dose distributions are similar (Nelms and Simon, 2007), although many different criteria have been applied in different clinical situations (for example see James et al, 2008, Both et al, 2007 and the actual criteria that are used should be selected according to the clinical situation.…”

PIXEL-BASED CORRECTION METHOD FOR GAFCHROMIC®EBT FILM DOSIMETRY

“…Less than 3% of error is required in order to use film with an error tolerance of 3% for IMRT plan verification [9,[10][11][12]. Thus, we obtained dose data with ten dose-steps (8.…”