End-to-end delivery quality assurance of computed tomography–based high-dose-rate brachytherapy using a gel dosimeter

Tachibana, Hideki; Watanabe, Yusuke; Mizukami, Shinya; Maeyama, Takashige; Terazaki, Tsuyoshi; Uehara, Ryuzo; Akimoto, Tetsuo

doi:10.1016/j.brachy.2020.02.002

Cited by 24 publications

(9 citation statements)

References 33 publications

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“…Various studies have analyzed the MRI response of polymer gels for possible application in radiotherapy dose mapping ( [58,63] and references therein). In particular, polymer gels have been investigated for dosimetry in conformal therapy, IMRT, IMAT, IGRT, VMAT and tomotherapy [55,70,83,88,102,, small photon fields [136][137][138], stereotactic radiosurgery [55,[139][140][141][142], 60-cobalt source [143,144], brachytherapy [55,85,92,[145][146][147][148][149], cyberknife [150], gamma-knife [151], low-energy X-rays [152,153], high-LET and proton therapy [55,154,155], boron capture neutron therapy [55,[156][157][158][159], for interface dosimetry in the presence of tissue inhomogeneities [55,160,161], for X-ray tubes [162] and for diagnostic nuclear medicine [163]. Recently, polyacrilamide gels were proposed for dosimetry and end-to-end test for MRI-linac apparatus [164]…”

Section: Characterization and Performancementioning

confidence: 99%

Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry

Marrale

D’Errico

2021

Gels

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Radiation-sensitive gels are among the most recent and promising developments for radiation therapy (RT) dosimetry. RT dosimetry has the twofold goal of ensuring the quality of the treatment and the radiation protection of the patient. Benchmark dosimetry for acceptance testing and commissioning of RT systems is still based on ionization chambers. However, even the smallest chambers cannot resolve the steep dose gradients of up to 30–50% per mm generated with the most advanced techniques. While a multitude of systems based, e.g., on luminescence, silicon diodes and radiochromic materials have been developed, they do not allow the truly continuous 3D dose measurements offered by radiation-sensitive gels. The gels are tissue equivalent, so they also serve as phantoms, and their response is largely independent of radiation quality and dose rate. Some of them are infused with ferrous sulfate and rely on the radiation-induced oxidation of ferrous ions to ferric ions (Fricke-gels). Other formulations consist of monomers dispersed in a gelatinous medium (Polyacrylamide gels) and rely on radiation-induced polymerization, which creates a stable polymer structure. In both gel types, irradiation causes changes in proton relaxation rates that are proportional to locally absorbed dose and can be imaged using magnetic resonance imaging (MRI). Changes in color and/or opacification of the gels also occur upon irradiation, allowing the use of optical tomography techniques. In this work, we review both Fricke and polyacrylamide gels with emphasis on their chemical and physical properties and on their applications for radiation dosimetry.

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Section: Characterization and Performancementioning

confidence: 99%

Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry

Marrale

D’Errico

2021

Gels

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“…Polymer gels have an electron density that is like tissue-equivalent material [ 12 , 13 , 14 ]. It contains monomers that polymerize during ionizing radiation [ 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

Improved Dose Response of N-(hydroxymethyl)acrylamide Gel Dosimeter with Calcium Chloride for Radiotherapy

Rabaeh

Al-Tarawneh

Eyadeh

et al. 2022

Gels

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The impact of calcium chloride (CaCl2) on the performance of N-(hydroxymethyl)acrylamide (NHMA) polymer gel dosimeter is studied in this article. The dosimeter was exposed to doses of up to 10 Gy with radiation beam-energy of 10 MV and dose-rates of 300 cGy/min. The relaxation rate (R2) parameter was utilized to explore the performance of irradiated NHMAGAT gels. The dose response in terms of R2 increased from 0.29 to 0.63 Gy−1·s−1 with increasing calcium chloride concentration from 0 to 1000 mM. The results show no substantial impact of dose-rates as well as radiation energies on NHMAGAT samples. For the steadiness of irradiated NHMAGAT dosimeters, it was found that there is no apparent variation in R2 (less than ±3%; standard deviation) up to 3 days. The overall uncertainty of the gel dosimeter with calcium chloride is 4.96% (double standard deviation, 95% confidence level).

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“…Recently, it has been reported that three‐dimensional (3D) dosimetry using a polymer gel dosimeter is an effective method for directly measuring the dose distribution 21,22 . This method is used as a quality assurance tool in radiation therapy, 23 and to measure slice thickness and CT dose index (CTDI) in CT scans 24–26 . However, since polymer gel dosimeters require MRI for reading, magnetic field inhomogeneities and temperature rise due to radiofrequency pulses may lead to uncertainty 27,28 .…”

Section: Introductionmentioning

confidence: 99%

Head CT dose reduction with organ‐based tube current modulation

et al. 2022

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Background A helical head CT examination uses a pitch factor (PF) of <1.0, resulting in a part of the slice being directly irradiated twice. This raises the possibility of double irradiation, which may increase the amount of radiation to the lens. Organ‐based tube current modulation (OBTCM) is an effective method for reducing lens exposure because it reduces the dose to the anterior aspect of the patient. However, it is challenging to visualize the complex dose distribution when factoring in double irradiation. Purpose To visualize twice‐irradiated areas in helical head CT in three dimensions and to clarify the exposure reduction effect of OBTCM. Material and methods A leuco crystal violet (LCV) dosimeter was placed into an empty polyethylene terephthalate bottle 16.5 cm in diameter. Helical scans were performed without and with OBTCM using the following parameters: tube voltage 120 kV, tube current 600 mA, pitch factor 0.637, rotation time 0.5 s, 80 (detector rows) × 0.5 mm (detector collimation), and ten scans. Exposed areas were visualized using an optical computed tomography (OCT) system designed by our group. The dose reduction rate of OBTCM was defined as the ratio of the average values of the histogram with the dose value on the x‐axis and the frequency on the y‐axis without and with OBTCM at 90° to the anterior midline. Results The LCV dosimeter visualized the spiral‐shaped twice‐irradiated areas. Double irradiation resulted in a dose of 2.19/1.90 and 1.38/1.19 Gy (15.0% and 15.9% increase) without and with OBTCM, respectively. The dose reduction using OBTCM was 29.6% at 90° anterolateral. Conclusion The LCV dosimeter visualized the complex three‐dimensional irradiated areas and enabled dose measurement in twice‐irradiated areas. Increased exposure from double irradiation was attenuated by OBTCM.

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End-to-end delivery quality assurance of computed tomography–based high-dose-rate brachytherapy using a gel dosimeter

Cited by 24 publications

References 33 publications

Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry

Hydrogels for Three-Dimensional Ionizing-Radiation Dosimetry

Improved Dose Response of N-(hydroxymethyl)acrylamide Gel Dosimeter with Calcium Chloride for Radiotherapy

Head CT dose reduction with organ‐based tube current modulation

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