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

Abstract

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.

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

“…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 ].…”

Enrichment of Lactoferrin by a Simple Process Based on Solid Phase Extraction

“…Entropy values were calculated from different random sections of the micrographs (71x71 pixels), and this parameter allowed evaluating the homogeneity of the particle phases (Shih et al 2013).…”

A two-stage classification method for borehole-wall images with support vector machine

“…Borehole-wall images can be classified into different categories based on their texture similarity [ 14 ]. Gray level co-occurrence matrix (GLCM) is probably the most popular method for texture analysis [ 15 ]. However, due to the similarity of horizontal crack images and intact rock mass images, a single statistical method of extracting the texture feature may not be sufficient for the classification task.…”