Mailable TLD system for photon and electron therapy beams

Kirby, Thomas H.; Hanson, W. F.; Gastorf, Robert J.; Chu, Connel; Shalek, Robert J.

doi:10.1016/0360-3016(86)90107-0

Cited by 51 publications

(37 citation statements)

References 8 publications

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“…11,12 The RPC evaluates each batch of TLD-100 powder for dose response, energy dependence, dose linearity, and fading. The TLDs are used to evaluate the absolute dose delivered to the phantom where each TLD is located and to normalize the film dose distributions.…”

Section: Methodsmentioning

confidence: 99%

Credentialing results from IMRT irradiations of an anthropomorphic head and neck phantom

et al. 2013

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Purpose: This study was performed to report and analyze the results of the Radiological Physics Center's head and neck intensity-modulated radiation therapy (IMRT) phantom irradiations done by institutions seeking to be credentialed for participation in clinical trials using intensity modulated radiation therapy. Methods: The Radiological Physics Center's anthropomorphic head and neck phantom was sent to institutions seeking to participate in multi-institutional clinical trials. The phantom contained two planning target volume (PTV) structures and an organ at risk (OAR). Thermoluminescent dosimeters (TLD) and film dosimeters were imbedded in the PTV. Institutions were asked to image, plan, and treat the phantom as they would treat a patient. The treatment plan should cover at least 95% of the primary PTV with 6.6 Gy and at least 95% of the secondary PTV with 5.4 Gy. The plan should limit the dose to the OAR to less than 4.5 Gy. The passing criteria were ±7% for the TLD in the PTVs and a distance to agreement of 4 mm in the high dose gradient area between the PTV and the OAR. Pass rates for different delivery types, treatment planning systems (TPS), linear accelerators, and linear accelerator-planning system combinations were compared. Results: The phantom was irradiated 1139 times by 763 institutions from 2001 through 2011. 929 (81.6%) of the irradiations passed the criteria. 156 (13.7%) irradiations failed only the TLD criteria, 21 (1.8%) failed only the film criteria, and 33 (2.9%) failed both sets of criteria. Only 69% of the irradiations passed a narrowed TLD criterion of ±5%. Varian-Elipse and TomoTherapy-HiArt combinations had the highest pass rates, ranging from 90% to 93%. Varian-Pinnacle 3 , Varian-XiO, Siemens-Pinnacle 3 , and Elekta-Pinnacle 3 combinations had pass rates that ranged from 66% to 81%. Conclusions: The head and neck phantom is a useful credentialing tool for multi-institutional IMRT clinical trials. The most commonly represented linear accelerator-planning system combinations can all pass the phantom, though some combinations had higher passing percentages than others. Tightening the criteria would significantly reduce the number of institutions passing the credentialing criteria. Causes for failures include incorrect data entered into the TPS, inexact beam modeling, and software and hardware failures.

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Section: Methodsmentioning

confidence: 99%

Credentialing results from IMRT irradiations of an anthropomorphic head and neck phantom

et al. 2013

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“…( 17 , 18 ) For this study, standards were irradiated with a Co‐60 unit in order to obtain the system calibration factor ( C D,w ). In addition to the standard energy response correction factor that accounts for the difference in TLD response to a 6 MV spectrum relative to Co‐60 photons (

k_{E}

), an additional energy correction factor was used to account for the softer beam spectra observed outside of the treatment field (

k_{N R}

); these nonreference (out‐of‐field) energy correction factors were taken from Scarboro et al ( 19 ) Thus, the TLD absorbed dose was determined by Eq.…”

Section: Methodsmentioning

confidence: 99%

Accuracy and sources of error of out‐of field dose calculations by a commercial treatment planning system for intensity‐modulated radiation therapy treatments

Huang

Followill

Wang

et al. 2013

J Applied Clin Med Phys

112

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Although treatment planning systems are generally thought to have poor accuracy for out‐of‐field dose calculations, little work has been done to quantify this dose calculation inaccuracy for modern treatment techniques, such as intensity‐ modulated radiation therapy (IMRT), or to understand the sources of this inaccuracy. The aim of this work is to evaluate the accuracy of out‐of‐field dose calculations by a commercial treatment planning system (TPS), Pinnacle3 v.9.0, for IMRT treatment plans. Three IMRT plans were delivered to anthropomorphic phantoms, and out‐of‐field doses were measured using thermoluminescent detectors (TLDs). The TLD‐measured dose was then compared to the TPS‐calculated dose to quantify the accuracy of TPS calculations at various distances from the field edge and out‐of‐field anatomical locations of interest (i.e., radiosensitive organs). The individual components of out‐of‐field dose (patient scatter, collimator scatter, and head leakage) were also calculated in Pinnacle and compared to Monte Carlo simulations for a 10×10 cm2 field. Our results show that the treatment planning system generally underestimated the out‐of‐field dose and that this underestimation worsened (accuracy decreased) for increasing distances from the field edge. For the three IMRT treatment plans investigated, the TPS underestimated the dose by an average of 50%. Our results also showed that collimator scatter was underestimated by the TPS near the treatment field, while all components of out‐of‐field dose were severely underestimated at greater distances from the field edge. This study highlights the limitations of commercial treatment planning systems in calculating out‐of‐field dose and provides data about the level of accuracy, or rather inaccuracy, that can be expected for modern IMRT treatments. Based on our results, use of the TPS‐reported dose could lead to an underestimation of secondary cancer induction risk, as well as poor clinical decision‐making for pregnant patients or patients with implantable cardiac pacemakers and defibrillators.PACS numbers: 87.53.Bn; 7.55.D‐

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“…The test protocol was derived from their electron beam mailable TLD assay system. 28,29 It uses six TLD capsules, three at each of two depths, measuring two points in the SOBP. The TLDs are placed at the positions within a 9 ϫ 9 ϫ 9 cm 3 phantom.…”

Section: Iib2 Absolute Dosimetrymentioning

confidence: 99%

Clinical characterization of a proton beam continuous uniform scanning system with dose layer stacking

et al. 2008

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A proton beam delivery system on a gantry with continuous uniform scanning and dose layer stacking at the Midwest Proton Radiotherapy Institute has been commissioned and accepted for clinical use. This paper was motivated by a lack of guidance on the testing and characterization for clinical uniform scanning systems. As such, it describes how these tasks were performed with a uniform scanning beam delivery system. This paper reports the methods used and important dosimetric characteristics of radiation fields produced by the system. The commissioning data include the transverse and longitudinal dose distributions, penumbra, and absolute dose values. Using a 208 MeV cyclotron's proton beam, the system provides field sizes up to 20 and 30 cm in diameter for proton ranges in water up to 27 and 20 cm, respectively. The dose layer stacking method allows for the flexible construction of spread-out Bragg peaks with uniform modulation of up to 15 cm in water, at typical dose rates of 1 -3 Gy/ min. For measuring relative dose distributions, multielement ion chamber arrays, small-volume ion chambers, and radiographic films were employed. Measurements during the clinical commissioning of the system have shown that the lateral and longitudinal dose uniformity of 2.5% or better can be achieved for all clinically important field sizes and ranges. The measured transverse penumbra widths offer a slight improvement in comparison to those achieved with a double scattering beam spreading technique at the facility. Absolute dose measurements were done using calibrated ion chambers, thermoluminescent and alanine detectors. Dose intercomparisons conducted using various types of detectors traceable to a national standards laboratory indicate that the measured dosimetry data agree with each other within 5%.

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Mailable TLD system for photon and electron therapy beams

Cited by 51 publications

References 8 publications

Credentialing results from IMRT irradiations of an anthropomorphic head and neck phantom

Credentialing results from IMRT irradiations of an anthropomorphic head and neck phantom

Accuracy and sources of error of out‐of field dose calculations by a commercial treatment planning system for intensity‐modulated radiation therapy treatments

Clinical characterization of a proton beam continuous uniform scanning system with dose layer stacking

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