Verification of IMRT: Techniques and Problems

Bogner, Ludwig; Scherer, Josef; Treutwein, Marius; Hartmann, Matthias; Gum, F.; Amediek, Axel

doi:10.1007/s00066-004-1219-0

Cited by 48 publications

(44 citation statements)

References 25 publications

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“…Additionally, the highlighted region in the figure marks the range for the MC dose calculation results. Table 1 Regarding film dosimetry, there are several challenges in obtaining high-quality dosimetric results, namely, the dependence of optical density on photon energy, field size, depth, film batch sensitivity differences, film orientation, processing conditions, and scanner performance [7,12]. Based on film measurement results obtained in this study, an aimed confidence limit of 3 % dose deviation (with respect to the prescribed dose) or 6 cGy, as suggested in Ref.…”

Section: Verification Proceduresmentioning

confidence: 93%

“…Such a phantom is easily accessible to dosimetry by radiographic films and point measurements [7]. It is possible to mark the coordinate system onto the films with a guided needle for data correlation and evaluation with IMRT software (PTW-VeriSoft Except for two film verification measurements, the mean dose deviations remain within a confidence limit of 5 % proposed for treatment plan acceptance [24].…”

Section: Verification Proceduresmentioning

confidence: 99%

“…Mainly a comparison of two-dimensional calculated and measured data is performed. As a two-dimensional integrating dosimetry medium, radiographic films (an EDR-2 in particular) [6,7] or less commonly, radiochromic films [8] are nearly ideal for such measurements due to their very good resolution.…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo simulations to replace film dosimetry in IMRT verification

Goetzfried

Rickhey

Treutwein³

et al. 2011

Zeitschrift für Medizinische Physik

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Patient-specific verification of intensity-modulated radiation therapy (IMRT) plans can be done by dosimetric measurements or by independent dose or monitor unit calculations. The aim of this study was the clinical evaluation of IMRT verification based on a fast Monte Carlo (MC) program with regard to possible benefits compared to commonly used film dosimetry.25 head-and-neck IMRT plans were recalculated by a pencil beam based treatment planning system (TPS) using an appropriate quality assurance (QA) phantom. All plans were verified both by film and diode dosimetry and compared to MC simulations. The irradiated films, the results of diode measurements and the computed dose distributions were evaluated, and the data were compared on the basis of gamma maps and dose-difference histograms.Average deviations in the high-dose region between diode measurements and point dose calculations performed with the TPS and MC program were 0.7 ± 2.7 % and Preprint submitted to Elsevier 11 February 20101.2 ± 3.1 %, respectively. For film measurements, the mean gamma values with 3 % dose difference and 3 mm distance-to-agreement were 0.74 ± 0.28 (TPS as reference) with dose deviations up to 10 %. Corresponding values were significantly reduced to 0.34 ± 0.09 for MC dose calculation. The total time needed for both verification procedures is comparable, however, by far less labor intensive in the case of MC simulations.The presented study showed that independent dose calculation verification of IMRT plans with a fast MC program has the potential to eclipse film dosimetry more and more in the near future. Thus, the linac-specific QA part will necessarily become more important. In combination with MC simulations and due to the simple set-up, point-dose measurements for dosimetric plausibility checks are recommended at least in the IMRT introduction phase.

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Section: Verification Proceduresmentioning

confidence: 93%

Section: Verification Proceduresmentioning

confidence: 99%

See 1 more Smart Citation

Monte Carlo simulations to replace film dosimetry in IMRT verification

Goetzfried

Rickhey

Treutwein³

et al. 2011

Zeitschrift für Medizinische Physik

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“…Since the introduction of intensity‐modulated radiotherapy (IMRT), the physical measurements and patient‐specific QA procedures to validate each IMRT plan before treatment have been considered an integral component of this delivery technique 1 , 2 . The comprehensive QA is essential for IMRT due to the complex nature of treatment planning and multitude of interfaces between the treatment planning system (TPS) and treatment delivery.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the efficiency and effectiveness of independent dose calculation followed by machine log file analysis against conventional measurement based IMRT QA

Sun

Rangaraj

Boddu

et al. 2012

J Applied Clin Med Phys

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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

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“…Intensity-modulated radiotherapy (IMRT) has significantly changed the planning, delivery and quality assurance in radiotherapy [1,2,4,21]. Its potential is relatively easy to demonstrate in planning exercises and the enthusiasm leads to a continuously increasing number of centers implementing IMRT [6,9,12,13,17,18,24].…”

Section: Introductionmentioning

confidence: 99%