Investigation of the dose characteristics of an n-NIPAM gel dosimeter with computed tomography

Chang, Kou-Hwa; Shih, Tian Yu; Hsieh, Bor‐Tsung; Chang, Shou-Yi; Liu, Yan Lin; Wu, Tung Hsin; Wu, Jen-Ming

doi:10.1016/j.nima.2010.09.099

Cited by 17 publications

(8 citation statements)

References 8 publications

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“…The possible reasons are the chemical characteristics of polymer gel dosimeters. According to the previous study [ 3 ], the NIPAM based gel dosimeters have a linear dose response of 2−15 Gy and a minor dose rate dependence of approximately 30%. In the penumbra region of small fields, the dose distribution has a steep slope because of the low scattering compared to one in the central axis.…”

Section: Resultsmentioning

confidence: 99%

“…The low-toxicity N -isopropylacrylamide (NIPAM) polymer gel dosimeter proposed by Senden et al [ 1 ] has been intensively researched for the optimization of its formula [ 2 ] and its readout systems. The results showed that the NIPAM gel dosimeter had a high linear dose response ranging from 2–15 Gy [ 3 ], and can be read out by various scanning tools [ 4 , 5 ]. During gel reading, the changes of proton groups in gels can be measured using magnetic resonance imaging (MRI), and the T2 results can be correlated with the 3D dose distribution [ 6 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

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Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

Shih

et al. 2016

PLoS ONE

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With advances in therapeutic instruments and techniques, three-dimensional dose delivery has been widely used in radiotherapy. The verification of dose distribution in a small field becomes critical because of the obvious dose gradient within the field. The study investigates the dose distributions of various field sizes by using NIPAM polymer gel dosimeter. The dosimeter consists of 5% gelatin, 5% monomers, 3% cross linkers, and 5 mM THPC. After irradiation, a 24 to 96 hour delay was applied, and the gel dosimeters were read by a cone beam optical computed tomography (optical CT) scanner. The dose distributions measured by the NIPAM gel dosimeter were compared to the outputs of the treatment planning system using gamma evaluation. For the criteria of 3%/3 mm, the pass rates for 5 × 5, 3 × 3, 2 × 2, 1 × 1, and 0.5 × 0.5 cm2 were as high as 91.7%, 90.7%, 88.2%, 74.8%, and 37.3%, respectively. For the criteria of 5%/5 mm, the gamma pass rates of the 5 × 5, 3 × 3, and 2 × 2 cm2 fields were over 99%. The NIPAM gel dosimeter provides high chemical stability. With cone-beam optical CT readouts, the NIPAM polymer gel dosimeter has potential for clinical dose verification of small-field irradiation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

Shih

et al. 2016

PLoS ONE

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“…For the NIPAM-BIS system for example, Huang et al (Huang et al, 2013) reported a decrease of 33% in the dose sensitivity with an increase in the dose rate from 200 cGy/min to 600 cGy/min. On the other hand, Chang et al (Chang et al, 2011a) observed the oposite effect, an increase of almost 33% in the sensititvty when the dose rate was varied from 100 cGy/min to 500 cGy/min, in both cases the experimentes were carried out under 6 MV X-ray energy. Also Senden et al (Senden et al, 2006) …”

Section: Effects Of Dose Ratementioning

confidence: 97%

Polymer gel dosimeter based on itaconic acid

Mattea

Chacón

Vedelago

et al. 2015

Applied Radiation and Isotopes

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A new polymeric dosimeter based on itaconic acid and N, N'-methylenebisacrylamide was studied. The preparation method, compositions of monomer and crosslinking agent and the presence of oxygen in the dosimetric system were analyzed. The resulting materials were irradiated with an X-ray tube at 158cGy/min, 226cGymin and 298cGy/min with doses up to 1000Gy. The dosimeters presented a linear response in the dose range 75-1000Gy, sensitivities of 0.037 1/Gyat 298cGy/min and an increase in the sensitivity with lower dose rates. One of the most relevant outcomes in this study was obtaining different monomer to crosslinker inclusion in the formed gel for the dosimeters where oxygen was purged during the preparation method. This effect has not been reported in other typical dosimeters and could be attributed to the large differences in the reactivity among these species.

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“…9826, Pyrex, USA) which were subsequently wrapped with tinfoil to prevent ambient lighting and solidified at 4°C for 2 h before use. The n-NIPAM gel has been proven to achieve high linearity and sensitivity under a dose range of 0–20 Gy by CT readouts [31].…”

Section: Methodsmentioning

confidence: 99%

“…One vial of each batch was excluded from irradiation to serve as 0 Gy. After dose delivery, the vials were stored in a 4°C refrigerator for 48 h for polymerization to cease completely [31]. The gel vials were further moved to a −20°C liquid-nitrogen-cooled refrigerator for another 24 h of freeze drying before the gels were cut into 5-mm thin slices alone the long axis for SEM imaging.…”

Section: Methodsmentioning

confidence: 99%

A Novel Method of Estimating Dose Responses for Polymer Gels Using Texture Analysis of Scanning Electron Microscopy Images

et al. 2013

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Polymer gels are regarded as a potential dosimeter for independent validation of absorbed doses in clinical radiotherapy. Several imaging modalities have been used to convert radiation-induced polymerization to absorbed doses from a macro-scale viewpoint. This study developed a novel dose conversion mechanism by texture analysis of scanning electron microscopy (SEM) images. The modified N-isopropyl-acrylamide (NIPAM) gels were prepared under normoxic conditions, and were administered radiation doses from 5 to 20 Gy. After freeze drying, the gel samples were sliced for SEM scanning with 50×, 500×, and 3500× magnifications. Four texture indices were calculated based on the gray level co-occurrence matrix (GLCM). The results showed that entropy and homogeneity were more suitable than contrast and energy as dose indices for higher linearity and sensitivity of the dose response curves. After parameter optimization, an R 2 value of 0.993 can be achieved for homogeneity using 500× magnified SEM images with 27 pixel offsets and no outlier exclusion. For dose verification, the percentage errors between the prescribed dose and the measured dose for 5, 10, 15, and 20 Gy were −7.60%, 5.80%, 2.53%, and −0.95%, respectively. We conclude that texture analysis can be applied to the SEM images of gel dosimeters to accurately convert micro-scale structural features to absorbed doses. The proposed method may extend the feasibility of applying gel dosimeters in the fields of diagnostic radiology and radiation protection.

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Investigation of the dose characteristics of an n-NIPAM gel dosimeter with computed tomography

Cited by 17 publications

References 8 publications

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography

Polymer gel dosimeter based on itaconic acid

A Novel Method of Estimating Dose Responses for Polymer Gels Using Texture Analysis of Scanning Electron Microscopy Images

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