螺轉 CT 和傳統 CT 輻射劑量的比較 - rsroc.org.tw

1 Chin J Radiol 2007; 32: 121-129 121 Computed Tomography CT CT CT 10 cm CT CT CT CT CT CTdosimetry CT CT 16 CT 4 CT CT 3 CT CT CT CT 1970 computed tomogra-phy CT United National Scientific Committee on the Effects of Atomic Radiation UNSCEAR [1] Mettler Shrimpton [2, 3] 67% 40% kVp mAs International Atomic Energy Agency IAEA multiple scan average dose MSAD [4] International Electrotechnical Commission IEC US Food and Drug Administration European Communities computed tomography dose index CTDI [5, 6, 7]

2 CTDI MSAD pitch 1 1 1 CT CT 1 1 2 2 2 1 1 2 112 155 CT 122 CT CT CT RTI Electronics AB WDCT 10 CT PMMA phantom Imaging Performance Assessment CT scanning ImPACT CTdosimetry 1917 Radon reconstruction 1972 Hounsfield X [8]

3 X rotate-translate 1 180 X X 300 700 360 X X XY XY Z X X X Z detector row X X Somatom plus 4 Light Speed Qx/i series Sensation 16 Somatom plus 4 CT X X CT fan angle beam shaping filter slice thickness CT Shope 1981 CT CTDI [9] CTDI 1 CT Z D1(z) z T CTDI () =dzzDTCTDI11.

4 (1) CTDI CT 1 Z CTDIair CT scanner CTDI CTDI CT dose profile T () =nTnTairdzzDnTCTDI212111 ..(2) (2) D1(z)dz 1 Z n CT inter-slice space MSAD 1 CTDI CT 123 MSAD=nTdCTDI ..(3) T n n=1 CT n 1 CT d d=T 1 MSAD=CTDI 2a d>T 1 MSAD>CTDI 2b FDA CT CTDI 7 CTDIFDA() =TTdzzDT771 ..(4) CT CTDIFDA FDA polymethylmethacrylate PMMA 16 cm 32 cm probe 10 cm 1 cm pencil shaped CTDI in absolute terms - to + Leight [10] CTDI CTDI100() =50501dzzDT.

5 (5) CTDI100 mm CT CT nCTDIw CT nCTDIw += ,10032311 ..(6) (6) nCTDIw mGy/mAs A mA CTDI100,c CTDI100,p 1 cm 1991 ICRP dose constrain ICRP-60 X X CT CTDIw Working Group of the Commission of the European Communities CEC CT CT dosimetry phantom CTDIw CTDI100() =50501dzzDT ..(7) CTDIw X 2 a.

6 7 b. d T CT 124 CT CT A mA CT CEC CT dose-length product DLP DLP =wnXNTCTDI(mGy cm) ..(8) (8) i CT T cm N X mAs CT DLP DLP =iwntATCTDI (mGy cm) ..(9) (9) i CT heli-cal sequences T cm A mA t s CT DLP CT PMMA PMMA RTI Electronics AB WDCT 10 cm 10 cm cm3 RTI Electronics AB Solidose 400 PMMA 15 cm 16 32 cm CTDI100,c 1 cm CTDI100.

7 P insert part CTdosimetry NRPB SR-250 MIRD 5 MIRD 5 3 NRPB 208 cm nCTDIw SR-250 Imaging Performance Assessment CT scanning CTdosimetry X 360 CTdosimetry 4 4 a kVp .. b mA s .. c equivalent dose HT WT HT effective dose TTTHW ICRP60 (d) remainder organ 3 CTdosimetry CT 125 X kVp mAs CT collimation.

8 1 Somatom plus 4 Light Speed Qx/i series Sensation 16 nCTDIw CTdosimetry 2 1 kVpmAspitchCollimator (mm) Sensation 16120120120320120160111121824 Light Speed Qx/i plus 41401201203092002401115510 Light Speed Qx/i series 2 CT nCTDIw DLP nCTDIw (mGy/100mAs)DLP (mGy cm) Sensation Speed Qx/i plus 4 CTdosimetry CT Sensation16 a b c d a. b.

9 X CT collimation pitch CTDI c. equivalent dose HT WT HT effective dose TTTHW d. remainder organ CTDIw DLP CT 126nCTDIw mGy/mAs DLP mGy cm Sensation 16 nCTDIw DLP Light Speed Qx/i series Somatom plus 4 3 4 5 CT Sensation 16 48 mSv Somatom plus 4 50 mSv mSv CT CT Sensation 16 Light Speed Qx/i series Somatom plus 4 CT mSv mSv 6 CTdosimetry effective dose Sensation 16 Light

10 Speed Qx/i series Somatom plus 4 CT CT CT CTdosimetry CTdosimetry 4 mSv CT Sensation 16 Light Speed Qx/i seriesSomatom plus 4 HTWT HTHTWT HTHTWT HT 3 mSv CT Sensation 16 Somatom plus 4 HTWT HTHTWT HT Light Speed Qx/i series CT 127 CT CT CT 3 2 mSv CT Richard 5 20 [11] CT 64 CT X CT 1.