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

• Published in: PloS one Vol. 11; no. 3; p. e0151300
• Main Authors: Shih, Tian-Yu, Wu, Jay, Shih, Cheng-Ting, Lee, Yao-Ting, Wu, Shin-Hua, Yao, Chun-Hsu, Hsieh, Bor-Tsung
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.03.2016; Public Library of Science (PLoS)
• Subjects: Acrylic Resins; Biology and Life Sciences; CAT scans; Computation; Computed tomography; Criteria; Dose-Response Relationship, Radiation; Dosimeters; Dosimetry; Engineering and Technology; Gelatin; Health aspects; Irradiation; Light; Measurement; Medical imaging; Medicine and Health Sciences; Monomers; NMR; Nuclear magnetic resonance; Physical Sciences; Physiological aspects; Polymers; Polymers - chemistry; Properties; Radiation dosage; Radiation therapy; Radiometry - methods; Research and Analysis Methods; Science; Studies; Tomography, Optical - methods; Tomography, X-Ray Computed - methods; Taiwan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0151300

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.