A method for the inter-calibration of a matrix of sensors

Donetti, M.; Garelli, E.; Marchetto, F.; Attanasio, Roberto; Bourhaleb, F.; Cirio, R.; Cornelius, Iwan; Giordanengo, S.; Rosa, A. La; Nastasi, U.; Peroni, C.

doi:10.1088/0031-9155/51/3/002

Cited by 10 publications

(12 citation statements)

References 3 publications

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“…For larger array sizes, the calibration approach should be improved. Donetti et al 36 described array calibration for a matrix of ion chambers. For a given dose, the detector-to-detector variations in total light output were relatively large ͑14% standard deviation͒ as expected with the large variability in the quality of the couplings in the making of a scintillation detector.…”

Section: Dosimeter Array Prototypementioning

confidence: 99%

Water‐equivalent dosimeter array for small‐field external beam radiotherapy

et al. 2007

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With the increasing complexity of dose patterns external beam radiotherapy, there is a great need for new types of dosimeters. We studied the first prototype of a new dosimeter array consisting of water-equivalent plastic scintillating fibers for dose measurement in external beam radiotherapy. We found that this array allows precise, rapid dose evaluation of small photon fields. Starting with a dosimeter system constructed with a single scintillating fiber coupled to a clear optical fiber and read using a charge coupled device camera, we looked at the dosimeter's spatial resolution under small radiation fields and angular dependence. Afterward, we analyzed the camera's light collection to determine the maximum array size that could be built. Finally, we developed a prototype made of ten scintillating fiber detectors to study the behavior and precision of this system in simple dosimetric situations. The scintillation detector showed no measurable angular dependence. Comparison of the scintillation detector and a small-volume ion chamber showed agreement except for 1 x 1 and 0.5 x 5.0 cm (2) fields where the output factor measured by the scintillator was higher. The actual field of view of the camera could accept more than 4000 scintillating fiber detectors simultaneously. Evaluation of the dose profile and depth dose curve using a prototype with ten scintillating fiber detectors showed precise, rapid dose evaluation even with placement of more than 75 optical fibers in the field to simulate what would happen in a larger array. We concluded that this scintillating fiber dosimeter array is a valuable tool for dose measurement in external beam radiotherapy. It possesses the qualities necessary to evaluate small and irregular fields with various incident angles such as those encountered in intensity-modulated radiotherapy, radiosurgery, and tomotherapy.

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Section: Dosimeter Array Prototypementioning

confidence: 99%

Water‐equivalent dosimeter array for small‐field external beam radiotherapy

et al. 2007

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“…This method is, by far, the most sophisticated iterative method in the array calibration with propagation error analysis and reduction. Donetti et al (6) proposed a similar approach, but it is limited to a square array calibration.…”

Section: Introductionmentioning

confidence: 99%

Calibration of a detector array through beam profile reconstruction with error‐locking

Wang

Chao

et al. 2014

J Applied Clin Med Phys

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An iterative method is proposed to calibrate radiation sensitivities of an arbitrary two‐dimensional (2D) array of detectors. The array is irradiated with a wide open‐field beam at the central position, as well as at laterally and longitudinal shifted positions; the 2D beam profile of the wide field is reconstructed iteratively from the ratios of shifted images to the central image. The propagation errors due to output variation and inaccurate array positioning are estimated and removed from the reconstructed beam profile by an error‐locking scheme with narrow open‐field irradiations. The beam profile is interpolated when necessary and then compared to raw detector responses to determine sensitivities. Two additional methods were implemented for comparison: 1) the commercial iterative calibration method for MapCHECK2 with translation and rotation operations; 2) a labor‐intensive noniterative method without the issue of error propagation. A MapCHECK2 2D detector array was used to validate the proposed method with the 6 MV photon beam from a Varian iX linear accelerator. All calibration methods were repeated three times. A total of 5, 9, and 29 irradiations were required to implement the commercial method, the proposed method and the noniterative method respectively. Moreover, a 5 mm positioning error was intentionally introduced into the calibration procedures of the commercial and the proposed method to test their robustness. Under the normal operation condition of the linear accelerator and with careful alignment of the MapCHECK2, the deviations of the calibrated sensitivities of the proposed method and commercial method with respect to the noniterative method were 0.30%±0.29% and 0.92%±0.63% respectively; when the 5 mm positioning error was presented, these two methods resulted in deviations of 0.40%±0.36% and 3.58%±1.94%, respectively. A patient study suggested that, due to this 5 mm positioning error, the mean DTA (dose to agreement) passing rate by the commercial method was 2.7% lower than that by the noniterative method, whereas the proposed method led to a comparable passing rate. It is evident from this study that the proposed iterative method leads to within 1% mean calibration results to established methods. It requires much fewer number of measurements than noniterative method and is more robust against the positioning error than the commercial iterative method. The method also eliminates the need of rotation operations and, therefore, is applicable to inline detector arrays without rotation function, such as electronic portal imager device (EPID).PACS number: 87.56.Fc

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“…9 One such device is the MatriXX ͑IBA Dosimetry GmbH, Schwarzenbruck, Germany͒, a 2D ion chamber array that has been employed in radiation oncology clinics for routine patient spe-cific IMRT/volumetric modulated arc therapy ͑VMAT͒ QA and for other dose verification tasks. The design and construction of MatriXX were described by Amerio et al 5 Donetti et al 7 described a method for interchamber calibration. Some of the dosimetric properties were investigated by Amerio et al 5 and Herzen et al, 8 where MatriXX showed good dose linearity and energy independence for megavoltage photon beams.…”

Section: Introductionmentioning

confidence: 99%

“…Two-dimensional ͑2D͒ arrays of ion chambers or diodes have recently been characterized and used for intensity modulated radiation therapy quality assurance ͑IMRT QA͒. [1][2][3][4][5][6][7][8][9][10][11] Due to their capability of real-time measurement of 2D dose distribution, these arrays are preferred to conventional film dosimetry for IMRT plan verification in many clinics. 9 One such device is the MatriXX ͑IBA Dosimetry GmbH, Schwarzenbruck, Germany͒, a 2D ion chamber array that has been employed in radiation oncology clinics for routine patient spe-cific IMRT/volumetric modulated arc therapy ͑VMAT͒ QA and for other dose verification tasks.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of MatriXX for IMRT and VMAT dose verifications in peripheral dose regions

Han

Bhagwat

et al. 2010

Medical Physics

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The performance of MatriXX has been systematically evaluated in the peripheral dose regions. Major sources of error associated with MatriXX are identified and a correction method is suggested. This method has been successfully tested using both experimental and clinical plans. In all cases, good agreements between MatriXX and an ion chamber are achieved after corrections. The authors conclude that with proper corrections, MatriXX can be reliably used for peripheral dose measurements within the ranges studied.

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A method for the inter-calibration of a matrix of sensors

Cited by 10 publications

References 3 publications

Water‐equivalent dosimeter array for small‐field external beam radiotherapy

Water‐equivalent dosimeter array for small‐field external beam radiotherapy

Calibration of a detector array through beam profile reconstruction with error‐locking

Evaluation of MatriXX for IMRT and VMAT dose verifications in peripheral dose regions

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