Performance analysis of a film dosimetric quality assurance procedure for IMRT with regard to the employment of quantitative evaluation methods

Winkler, Peter; Zurl, B.; Guss, H.; Kindl, Peter; Stuecklschweiger, Georg

doi:10.1088/0031-9155/50/4/006

Cited by 33 publications

(26 citation statements)

References 26 publications

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“…This is lower than what is typically reported in the conventional IMRT literature, where relative and absolute dose verification measurements are within the 3–4% range for absolute dose measurements (12) and 5% and 3 mm distance to agreement for relative dosimetry (13) . In comparison, our current action levels for an acceptable ion chamber point dose validation from an IMRT hybrid measurement, film dosimetry, and relative dose distribution agreements are given in Table 7.…”

Section: Discussionmentioning

confidence: 60%

Dosimetric verification of micro‐MLC based intensity modulated radiation therapy

Basran¹,

Yeboah²

2008

J Applied Clin Med Phys

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A methodology for the dosimetric verification of micro‐multileaf collimator (mMLC) based intensity modulated radiation therapy (IMRT) plans intended for stereotactic applications is described. The method is similar to that of conventional IMRT patient‐specific quality assurance (QA) with some notable exceptions, particularly, mechanical tests that verify the mMLC positioning with respect to the isocenter and individual leaf calibration prior to use. Relative dosimetry measurements are performed with radiographic film, a commercial film‐scanning system and a dose‐image registration program. Film dosimetry results are within ±3.0% of calculated distributions or within 2.0 mm distance to agreement. Absolute dosimetry measurements are performed with a small volume ion chamber and a commercially available stereotactic phantom. The cumulative dose from all beams is within ±2.0% of the prescribed dose. Large deviations may be observed from individual beams since the smaller IMRT fields tend to have very few high‐dose and low‐gradient regions. An independent program that examines the treatment mMLC file is used to estimate the central axis dose from each beam and provide a dose image that can be assessed alongside the intended fluence distribution prior to treatment. Tolerances for relative and absolute dosimetry of mMLC‐based IMRT treatments are tighter than what is typically reported for conventional MLC‐based IMRT. Also, the time commitment for the IMRT QA is slightly longer than of conventional MLC‐based IMRT due to QA processes that check the mechanical alignment of the mMLC device with the laser and radiation isocenter.PACS Number: 87.53Dq, 87.53Ly, 87.53Tf

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Section: Discussionmentioning

confidence: 60%

Dosimetric verification of micro‐MLC based intensity modulated radiation therapy

Basran¹,

Yeboah²

2008

J Applied Clin Med Phys

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“…Silver halide based radiographic films, often referred to as radiographic films ͑although all dosimetry films are, in fact, radiographic͒, have been widely used for validation of the relative dosimetry of IMRT treatment phantom plans. 56,65,68,90,106,[117][118][119][120][121][122][123][124][125][126][127] In principle, such measurements allow for the verification of the appropriate shape and registration of the IMRT dose distribution in a selected twodimensional plane ͑film plane͒. Appropriate selection of the orientation and locations of the film planes is important to assure that the measured dose is useful for the desired QA function.…”

Section: Iib1 Filmmentioning

confidence: 99%

“…The ␥ tool has been successfully implemented in a number of dose comparison studies, 12,123,133,[165][166][167][168][169][170][171][172][173][174] and some authors have proposed modifications to the tool to provide more efficient calculations and to extend the capabilities of the tool. 162,164,167,[175][176][177][178] One example is shown in Fig.…”

Section: Ivb4a Composite Toolmentioning

confidence: 99%

Dosimetry tools and techniques for IMRT

et al. 2011

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Intensity modulated radiation therapy ͑IMRT͒ poses a number of challenges for properly measuring commissioning data and quality assurance ͑QA͒ radiation dose distributions. This report provides a comprehensive overview of how dosimeters, phantoms, and dose distribution analysis techniques should be used to support the commissioning and quality assurance requirements of an IMRT program. The proper applications of each dosimeter are described along with the limitations of each system. Point detectors, arrays, film, and electronic portal imagers are discussed with respect to their proper use, along with potential applications of 3D dosimetry. Regardless of the IMRT technique utilized, some situations require the use of multiple detectors for the acquisition of accurate commissioning data. The overall goal of this task group report is to provide a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IMRT treatment plans. This report is not intended to provide a comprehensive review of commissioning and QA procedures for IMRT. Instead, this report focuses on the aspects of metrology, particularly the practical aspects of measurements that are unique to IMRT. The metrology of IMRT concerns the application of measurement instruments and their suitability, calibration, and quality control of measurements. Each of the dosimetry measurement tools has limitations that need to be considered when incorporating them into a commissioning process or a comprehensive QA program. For example, routine quality assurance procedures require the use of robust field dosimetry systems. These often exhibit limitations with respect to spatial resolution or energy response and need to themselves be commissioned against more established dosimeters. A chain of dosimeters, from secondary standards to field instruments, is established to assure the quantitative nature of the tests. This report is intended to describe the characteristics of the components of these systems; dosimeters, phantoms, and dose evaluation algorithms. This work is the report of AAPM Task Group 120.

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“…Following sets of dose difference and distance-to-agreement criteria were used for gamma index evaluation: 2 mm and 2%, [23] proposed tolerance levels for static photon-beam calculations of 3% dose difference and 4 mm spatial accuracy respectively. Other authors [12,25] use 3 mm and 5% for calculation of the gamma distribution in clinical evaluations, which is also a criterion accepted for the verification of the entire IMRT plans in our clinic. This criterion incorporates for the dosimetric error caused by the uncertainties of the room laser, phantom positioning, and imprecise image registration [25].…”

Section: Verification Of An Entire Imrt Planmentioning

confidence: 99%

“…Other authors [12,25] use 3 mm and 5% for calculation of the gamma distribution in clinical evaluations, which is also a criterion accepted for the verification of the entire IMRT plans in our clinic. This criterion incorporates for the dosimetric error caused by the uncertainties of the room laser, phantom positioning, and imprecise image registration [25].…”

Section: Verification Of An Entire Imrt Planmentioning

confidence: 99%