固体検出器を用いたCTDI 測定法に関する特性評価

抄録

The purpose of this study was to evaluate measurement method for the volume CTDI (CTDI_vol) using a solid-state detector. Methods : The CTDI_vol was measured from dose profiles obtained during continuous translation of a solid-state detector (CT Dose Profiler ; RTI, Sweden) in the head PMMA phantom (16 cm in diameter). Input values of translation speed were 20.8, 41.7 and 83.3 mm/s. The CTDI_vol measurement was performed by using a commercial CT scanner (Aquilion ONE ; Canon, Japan). The CTDI_vol measured with the solid-state detector was compared with two CTDI_vol values, one was measured with the 100 mm pencil ionization chamber (TN30009 ; PTW, Germany) and the other was the CTDI_vol displayed value by the CT scanner. All the CT scan parameters were 120 kV, 200 mA, the beam width of 8 mm and a rotation time of 1.5 s. The CTDI_vol displayed value by the CT scanner and measured value with the ionization chamber were 90.1 and 86.5 mGy, respectively. Measured values with the solid-state detector were 85.7 ± 1.6 mGy, 86.8 ± 2.9 mGy and 83.0 ± 5.4 mGy respectively correspond to 20.8, 41.7 and 83.3 mm/s. Conclusion : A solid-state detector is useful for measuring the CTDI_vol. On the other hands, the translation speed of the solid-state detector can affect measurement accuracy.