Dosimetric and geometric characteristics of a small animal image‐guided irradiator using 3D dosimetry/optical <scp>CT</scp> scanner

Na, Yong Hum; Wang, Yifang; Black, Paul; Velten, Christian; Qian, X.; Lin, Shih‐Chi; Adamovics, J

doi:10.1002/mp.12955

Cited by 10 publications

(9 citation statements)

References 21 publications

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“…The excellent agreement between the measurements acquired from PRESAGE and the manufacturer’s Monte‐Carlo based values indicates that PRESAGE is a suitable dosimeter for 3D dosimetry and for clinical research. It is important to mention that small discrepancies were observed between EBT3 film and PRESAGE measurement for low energy applications and small field dosimetry . The main advantages of using PRESAGE over other types of dosimeters include its linear response to the absorbed dose over a wide dose range, its tissue‐equivalency over a wide energy range, and its capability to provide 3D dose distribution with high resolution.…”

Section: Introductionmentioning

confidence: 99%

“…The dosimetric characteristic of PRESAGE polyurethane dosimeters (Heuris Inc., Skillman, New Jersey, NJ, USA), formulated with a halogenated hydrocarbon free radical initiator and leuco dye has been thoroughly investigated and is well-characterized. [1][2][3][4][5][6][7] A 2009 Radiologic Physics Center phantom study investigating the 3D dosimetric applications of PRESAGE showed good agreement (98% pass rate with gamma criteria of 4%, 3 mm) of PRESAGE measurement with EBT radiochromic film (Ashland Inc., Wilmington, DE, USA) measurement for a Head and Neck Intensity Modulated Radiation Therapy (IMRT) plan. 4 Additionally, PRESAGE was used to measure Gamma Knife Perfexion output factors in 2014.…”

Section: Introductionmentioning

confidence: 99%

“…It is important to mention that small discrepancies were observed between EBT3 film and PRESAGE measurement for low energy applications and small field dosimetry. 7 The main advantages of using PRESAGE over other types of dosimeters include its linear response to the absorbed dose over a wide dose range, its tissue-equivalency over a wide energy range, and its capability to provide 3D dose distribution with high resolution. Additionally, the dosimeter can be fabricated to any size or shape for customized clinical and research purposes.…”

Section: Introductionmentioning

confidence: 99%

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Dosimetric characterization of a body‐conforming radiochromic sheet

Wang

Dona

Liu

et al. 2020

J Applied Clin Med Phys

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Purpose A novel radiochromic PRESAGE sheet (Heuris Inc.) with 3 mm thickness has been developed as a measurement tool for 2D dosimetry. Its inherent ability to conform to irregular surfaces makes this dosimeter advantageous for patient surface dosimetry. This study is a comprehensive investigation into the PRESAGE sheet’s dosimetric characteristic, accuracy and its potential use as a dosimeter for clinical applications. Methods The characterization of the dosimeter included evaluation of the temporal stability of the dose linearity, reproducibility, measurement uncertainties, dose rate, energy, temperature and angular dependence, lateral response artifacts, percent depth dose curve, and 2D dose measurement. Dose distribution measurements were acquired for regular square fields on a flat and irregular surface and an irregular modulated field on the smooth surface. All measurements were performed using an Epson 11000XL high‐resolution scanner. Results The examined dosimeters exhibit stable linear response, standard error of repeated measurements within 2%, negligible dose rate, energy, and angular dependence. The same linear dose response was measured while the dosimeter was in contact with a heated water surface. Gamma test and histogram analysis of the dose difference between PRESAGE and EBT3 film, PRESAGE and the treatment planning system (TPS) were used to evaluate the measured dose distributions. The PRESAGE sheet dose distributions showed good agreement with EBT3 film and TPS. A discrepancy smaller than the statistical error of the two dosimeters was reported. Conclusions This study established a full dosimetric characterization of the PRESAGE sheets with the purpose of laying the foundation for future clinical uses. The results presented here for the comparison of this novel dosimeter with those currently in use reinforce the possibility of using this dosimeter as an alternative for irregular surface dose measurements.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dosimetric characterization of a body‐conforming radiochromic sheet

Wang

Dona

Liu

et al. 2020

J Applied Clin Med Phys

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“…Although efforts have been made to ensure high geometric accuracy with SA‐IGRT systems, the main challenge with these approaches is that they cover only limited aspects. For example, several investigators have quantified the accuracy of mechanical or rotational isocenters in novel small animal IGRT, X‐RAD, and SARRP systems. The isocentricity of the stage rotation was determined for the SARRP system .…”

Section: Introductionmentioning

confidence: 99%

“…For example, several investigators have quantified the accuracy of mechanical or rotational isocenters in novel small animal IGRT, X‐RAD, and SARRP systems. The isocentricity of the stage rotation was determined for the SARRP system . The congruence of imaging and delivery isocenters was characterized on the Stanford modified micro‐CT system, X‐RAD, and SARRP systems.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive geometric quality assurance framework for preclinical microirradiators

2019

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Purpose: The mechanical and geometric accuracy of small animal image-guided radiotherapy (SA-IGRT) systems is critical and is affected by a number of system-related factors. Because of the small dimensions involved in preclinical radiotherapy research, such factors can individually and/or cumulatively contribute to significant errors in the small animal radiation research. In this study, we developed and implemented a comprehensive quality assurance (QA) framework for characterizing the mechanical and geometric constancy and accuracy of the small animal radiation research platform (SARRP) system. Methods: We quantified the accuracy of gantry and stage rotation isocentricity and positional stage translations. We determined the accuracy and symmetry of field sizes formed by collimators. We evaluated collimator assembly system performance by characterization of collimator axis alignment along the beam axis during gantry rotation. Furthermore, we quantified the end-to-end precision and accuracy of image-guided delivery by examining the congruence of intended (e.g., imaging) and actual delivery (measured during experiment) isocenters. Results: The fine and broad beams showed different central axes. The center of the beam was offset toward the cathode (0.22 AE 0.05 mm) when switching the beam from a fine to a broad focus. Larger (custom-made) collimators were more symmetrically centered than smaller (standard) collimators. The field formed by a 1-mm circular collimator was found to deviate from the circular shape, measuring 1.55 mm and 1.25 mm in the X and Y directions, respectively. The 40-mm collimator showed a field that was 1.65 (4.13%) and 1.3 (3.25%) mm smaller than nominal values in the X and Y directions, respectively, and the 30-mm collimator field was smaller by 0.75 mm (2.5%) in the X direction. Results showed that fields formed by other collimators were accurate in both directions and had ≤2% error. The size of the gantry rotation isocenter was 1.45 AE 0.15 mm. While the gantry rotated, lateral and longitudinal isocenter displacements ranged from 0 to À0.34 and À0.44 to 0.33 mm, respectively. Maximum lateral and longitudinal displacements were found at obliques gantry angles of À135°and 45°, respectively. The stage translational accuracies were 0.015, 0.010, and 0 mm in the X, Y, and Z directions, respectively. The size of the stage rotation runout was 2.73 AE 0.3 mm. Maximum displacements of the stage rotational axis were À0.38 (X direction) and À0.26 (Y direction) mm at stage angles of À45°and À135°, respectively. We found that displacements of intended and actual delivery isocenters were 0.24 AE 0.10, 0.12 AE 0.62, and 0.12 AE 0.42 mm in the X, Y, and Z directions, respectively. Conclusion: We used the SARRP built-in electronic portal imaging device (EPID) to perform most of the geometric QA tests, demonstrating the utility of the EPID for characterizing the geometric accuracy and precision of the SA-IGRT system. However, in principle, the methodology and tests developed here are applicable to any digita...

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3D isocentricity analysis for clinical linear accelerators

2020

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Purpose: To perform a three-dimensional (3D) concurrent isocentricity measurement of a clinical linear accelerator's (linac) using a single 3D dosimeter, PRESAGE. Methods: A 3D dosimeter, PRESAGE, set up on the treatment couch of a Varian TrueBeam LINAC using the setup lasers, was irradiated under gantry angles of 0 , 50 , 160 , and 270 with the couch fixed at 0 and subsequently, under couch angles of 10 , 330 , 300 , and 265 with the gantry fixed at 270 . The 1 cm 2 (at 100 cm SAD) square fields were delivered at 6 MV with 800 MU/field. After irradiation, the dosimeter was scanned using a single-beam optical scanner and images were reconstructed with submillimeter resolution using filtered back-projection. Postprocessing was used to extract views parallel to the star-shot planes from which beam trajectories and the smallest circles enclosing these were drawn and extracted. These circles and information from the view orthogonal to both star-shots were used to represent the rotational centers as spheroids. The linac isocenter was defined by the distribution of midpoints between any, randomly selected, points lying inside the center spheroids defined by the table and gantry rotations; isocenter location and size were defined by the average midpoint and the distribution's semi-axes. Collimator rotations were not included in this study. Results: Relative to the setup center defined by lasers, the table and gantry rotation center coordinates (lat., long., vert.) were measured in units of millimeters, to be (À0.24, 0.18, À0.52) and (0.10, 0.53, À0.52), respectively. Displacements from the setup center were 0.60 and 0.75 mm for the table and gantry centers, while the distance between them measured 0.49 mm. The linac's radiation isocenter was calculated to be at (À0.07, À0.17, 0.51) relative to the setup lasers and its size was found to be most easily described by a spheroid prolate in vertical direction with semi-axis lengths of 0.13 and 0.23 mm for the lateral-longitudinal and vertical directions, respectively. Conclusions: This study demonstrates how to measure the location and sizes of rotational centers in 3D with one setup. The proposed method provides a more comprehensive view on the isocentricity of LINAC than the conventional two-dimensional film measurements. Additionally, a new definition of isocenter and its size was proposed.

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Dosimetric and geometric characteristics of a small animal image‐guided irradiator using 3D dosimetry/optical CT scanner

Cited by 10 publications

References 21 publications

Dosimetric characterization of a body‐conforming radiochromic sheet

Dosimetric characterization of a body‐conforming radiochromic sheet

A comprehensive geometric quality assurance framework for preclinical microirradiators

3D isocentricity analysis for clinical linear accelerators

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