To improve the precision in radiation therapy and optimize treatment strategies during the radiotherapy, in vivo radiation dosimetry monitoring which measures the actual dose received in and around target region during treatment becomes necessary. Given the fact that X-ray induced acoustic amplitude is proportionally correlating to X-ray absorption, we propose applying X-ray acoustic computed tomography (XACT) to monitor X-ray dosimetry during radiotherapy. A prototype X-ray acoustic (XA) detection system with single immersion ultrasound transducer, which was positioned by a motor controlled rotation stage, was synchronized with a medical linear accelerator to acquire the XA signal at each rotating position. A porcine gel phantom, which is embedded with equally spaced lard made cylindrical indicators, was shot by different X-ray beams modulated by physical wedge filters (with wedge angles of 15°, 30°, 45° and 60°). The reconstructed 2D XACT images not only showed the positions of the indicators but also displayed the different intensity profiles for each indicator, which had good correlations with the corresponding dose distributions captured in radiochromic film tests. A dose difference as small as 3.6% can be determined. Moreover, a phantom imitating complex scenario of body, which has lard made indicators covered by different materials (bone, muscle and air-gap), was shot by uniform beam. The variances of dose delivered to target regions suffering different attenuations were successfully presented in XACT images. The results of phantom experiments have proved that XACT can be a promising technique in monitoring the 2D dosimetry during radiotherapy with high sensitivity and good accuracy.
Hao Lei, Wei Zhang, Ibrahim Oraiqat, Issam El Naqa, and Xueding Wang, "2D x-ray dosimetry monitoring during radiotherapy using x-ray acoustic computed tomography (Conference Presentation)," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 104940F (Presented at SPIE BiOS: January 28, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2289113.5752213044001.
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