Narrow stereotactic beam profile measurements using<b><i>N</i></b>-vinylpyrrolidone based polymer gels and magnetic resonance imaging

Pappas, E.; Seimenis, Ioannis; Angelopoulos, A.; Georgolopoulou, P.; Kamariotaki-Paparigopoulou, M; Maris, Thomas G.; Sakelliou, L.; Sandilos, P.; Vlachos, L.

doi:10.1088/0031-9155/46/3/313

Cited by 60 publications

(60 citation statements)

References 34 publications

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“…In this study, Vinylpyrrolidone‐based polymer gels were used. A detailed description of Vinylpyrrolidone‐(VIPAR) based polymer gels, the manufacturing process, and their dosimetric characteristics can be found in the literature 17 , 18 , 19 , 20 . Polymer‐gel MRI dosimetry is based on the radiation‐induced polymerization of the gel monomers and cross‐linkers.…”

Section: Methodsmentioning

confidence: 99%

Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

Liu

Pappas

et al. 2016

J Applied Clin Med Phys

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An automatic brain‐metastases planning (ABMP) software has been installed in our institution. It is dedicated for treating multiple brain metastases with radiosurgery on linear accelerators (linacs) using a single‐setup isocenter with noncoplanar dynamic conformal arcs. This study is to validate the calculated absolute dose and dose distribution of ABMP. Three types of measurements were performed to validate the planning software: 1, dual micro ion chambers were used with an acrylic phantom to measure the absolute dose; 2, a 3D cylindrical phantom with dual diode array was used to evaluate 2D dose distribution and point dose for smaller targets; and 3, a 3D pseudo‐in vivo patient‐specific phantom filled with polymer gels was used to evaluate the accuracy of 3D dose distribution and radiation delivery. Micro chamber measurement of two targets (volumes of 1.2 cc and 0.9 cc, respectively) showed that the percentage differences of the absolute dose at both targets were less than 1%. Averaged GI passing rate of five different plans measured with the diode array phantom was above 98%, using criteria of 3% dose difference, 1 mm distance to agreement (DTA), and 10% low‐dose threshold. 3D gel phantom measurement results demonstrated a 3D displacement of nine targets of 0.7±0.4 mm (range 0.2 ~ 1.1 mm). The averaged two‐dimensional (2D) GI passing rate for several region of interests (ROI) on axial slices that encompass each one of the nine targets was above 98% (5% dose difference, 2 mm DTA, and 10% low‐dose threshold). Measured normalD95, the minimum dose that covers 95% of the target volume, of the nine targets was 0.7% less than the calculated normalD95. Three different types of dosimetric verification methods were used and proved the dose calculation of the new automatic brain metastases planning (ABMP) software was clinical acceptable. The 3D pseudo‐in vivo patient‐specific gel phantom test also served as an end‐to‐end test for validating not only the dose calculation, but the treatment delivery accuracy as well.PACS number(s): 87.53.Lv, 87.55.km, 87.55.Qr

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Section: Methodsmentioning

confidence: 99%

Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

Liu

Pappas

et al. 2016

J Applied Clin Med Phys

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“…The principles of the polymer gel dosimeter [25][26][27][28]30] as well as its application in clinical dosimetry have been described previously [23,24,29,[31][32][33][34].…”

Section: Determination Of the Relative Dose Distributionmentioning

confidence: 99%

Evaluation of Geometric and Dosimetric Inaccuracies of Stereotactic Irradiation in the Rat Brain

Novotný

Spěváček²,

Dvořák³

et al. 2002

Stereotact Funct Neurosurg

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Objective: To evaluate geometric and dosimetric inaccuracies in the irradiation of the rat brain with the Leksell Gamma Knife. Materials and Methods: Altogether three types of dosimeters were employed for these measurements: (a) a thermoluminescent dosimeter, (b) a semiconductor detector and (c) a polymer gel dosimeter. The thermoluminescent dosimeter and the semiconductor detector were calibrated using an ion chamber and then implanted in the brain of a rat cadaver and used for absolute dose determination. A special glass phantom mimicking exactly the shape of the rat body filled with the polymer gel was used for measurements of the relative dose distribution and evaluation of geometric inaccuracies during the stereotactic irradiation in the rat brain. Results: Both thermoluminescent and semiconductor detectors, due to their size, measured mean doses. The observed results demonstrated that the Leksell GammaPlan can be employed for the calculation of absorbed doses in irradiation of experimental animals. In our case, it was necessary to apply a correction factor of 1.078 for the absolute absorbed dose to obtain reliable results. A comparison of calculated dose profiles using the treatment planning system in all three axes with those measured by the polymer gel dosimeter demonstrated a very good geometric agreement with the mean deviation in profile position of 0.5 mm. Conclusion: The results indicate that this technique can effectively check the geometric and dosimetric accuracy of stereotactic irradiation in the rat brain. The Leksell GammaPlan can be employed for the calculation of absorbed doses, but the correction factor of 1.078 had to be applied for the absolute dose calculations in our irradiation geometry.

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“…A range of detectors broadly categorized into active (ionization chambers, solid state detectors, and plastic scintillator) and passive (TLD microcubes, gafchromic film, alanine pallets, radio photoluminescent dosimeter, and gel dosimeter) detectors have been investigated by numerous authors for small field measurements. [9101112131415161718192021222324]…”

Section: Introductionmentioning

confidence: 99%

“…[10111213] In addition, plastic scintillator detector, gel dosimeter, and radio photoluminescent dosimeter are found to be very good choice for output factor and profile measurements even for very small fields. [14151617181920]…”

Section: Introductionmentioning

confidence: 99%

Investigating the electronic portal imaging device for small radiation field measurements

et al. 2017

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Purpose:With the advent of state-of-the-art treatment technologies, the use of small fields has increased, and dosimetry in small fields is highly challenging. In this study, the potential use of Varian electronic portal imaging device (EPID) for small field measurements was explored for 6 and 15 MV photon beams.Materials and Methods:The output factors and profiles were measured for a range of jaw-collimated square field sizes starting from 0.8 cm × 0.8 cm to 10 cm × 10 cm using EPID. For evaluation purpose, reference data were acquired using Exradin A16 microionization chamber (0.007 cc) for output factors and stereotactic field diode for profile measurements in a radiation field analyzer.Results:The output factors of EPID were in agreement with the reference data for field sizes down to 2 cm × 2 cm and for 2 cm × 2 cm; the difference in output factors was +2.06% for 6 MV and +1.56% for 15 MV. For the lowest field size studied (0.8 cm × 0.8 cm), the differences were maximum; +16% for 6 MV and +23% for 15 MV photon beam. EPID profiles of both energies were closely matching with reference profiles for field sizes down to 2 cm × 2 cm; however, penumbra and measured field size of EPID profiles were slightly lower compared to its counterpart.Conclusions:EPID is a viable option for profile and output factor measurements for field sizes down to 2 cm × 2 cm in the absence of appropriate small field dosimeters.

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Narrow stereotactic beam profile measurements usingN-vinylpyrrolidone based polymer gels and magnetic resonance imaging

Cited by 60 publications

References 34 publications

Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

Evaluation of Geometric and Dosimetric Inaccuracies of Stereotactic Irradiation in the Rat Brain

Investigating the electronic portal imaging device for small radiation field measurements

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