Measurement of MV CT dose index for Hi-ART helical tomotherapy unit

VernacularTitle:Hi-ART螺旋断层放疗机MV螺旋CT剂量指数的测量
Author: Yunlai WANG ; Xiongfei LIAO
Publication Type:Journal Article
Keywords: Helical tomotherapy; CT dose index; Dose length product; Imageguided radiotherapy
From: Chinese Journal of Radiological Medicine and Protection 2010;30(1):44-46
CountryChina
Language:Chinese
Abstract: Objective To evaluate the patient dose from Hi-ART MV helical CT imaging in image-guided radiotherapy.Methods Weighted CT dose index (CTDI_W) was measured with PTW TM30009 CT ion chamber in head and body phantoms,respectively,for slice thicknesses of 2,4,6 mm with scanned range of 5 cm and 15 cm.Dose length products (DLP) were subsequently calculated.The CTDI_W and DLP were compared with XVI kV CBCT and ACQSim simulator CT for routine clinical protocols.Results An inverse relationship between CTDI and the slice thickness was found.The dose distribution was inhomogeneous owing to the attenuation of the couch.CTDI and DLP had close relationship with the slice thickness and the scanned range.Patient dose from MVCT was lower than XVI CBCT for head,but larger for body scan.Results CTDI_W can be used to assess the patient dose in MV helical CT due to its simplicity for measurement and reproducibility.Regular measurement should be performed in QA & QC program.Appropriate slice thickness and scan range should be chosen to reduce the patient dose.