Table 4

Conversion Factors Relating Effective Dose to Dose-Length Product, Using Current Definition of Effective Dose

ICRP 103Prospective AxialProspective Axial PaddingProspective HelicalICRP 103Retrospective HelicalRetrospective Helical TCMCalciumAverageCV [%]
Scanner/kVp801001208010012080100120Scanner/kVp8010012080100120120
GE Lightspeed VCT XTe0.02590.02980.02950.02630.02830.0290xxxGE Lightspeed VCT XTe0.02420.02670.02640.02430.02590.02690.03060.02758.0
GE Discovery CT750 HDx0.0302x0.02620.02780.0283xxxGE Discovery CT750 HDx0.02840.0267x0.02680.02690.02850.02774.4
Hitachi Scenaria0.02540.02720.02770.02600.02680.0281xxxHitachi Scenaria0.02580.02720.0281xxx0.02650.02693.5
Philips Brilliance 64xxxxxxxxxPhilips Brilliance 640.02490.02600.02610.02460.02600.02670.02850.02614.9
Philips Brilliance iCT 2560.03010.03140.03160.02790.02950.0303xxxPhilips Brilliance iCT 2560.0242§0.0254§0.0254§0.02310.02480.0249x0.027411.2
Siemens SOMATOM Sensation 640.02640.02680.0266xxxxxxSiemens SOMATOM Sensation 640.02500.02490.02490.02560.02530.0251x0.02563.0
Siemens SOMATOM Definition AS+0.02710.02750.02730.0256x0.0257xxxSiemens SOMATOM Definition AS+0.02430.02510.02460.02440.02520.0250x0.02564.6
Siemens SOMATOM Definition0.02880.02880.0274xxxxxxSiemens SOMATOM Definition0.02590.02860.02620.02710.02870.0281x0.02774.1
Siemens SOMATOM Definition FLASH0.02530.02660.02540.02400.02520.02560.02630.02680.0266Siemens SOMATOM Definition FLASH0.02030.02560.02560.02300.02430.0248x0.02506.7
Toshiba Aquilion 64xxxxxxxxxToshiba Aquilion 64x0.02410.0252x0.02310.02360.03490.026218.8
Toshiba Aquilion Primexxxxxx0.02090.02290.0242Toshiba Aquilion Prime0.02080.02310.02320.02120.02330.02340.02560.02296.7
Toshiba Aquilion ONEx0.02270.02500.02290.02590.0261xxxToshiba Aquilion ONExxxxxx0.02570.02476.2
Average, per protocol type & kV0.02700.02790.02760.02560.02730.02770.02360.02480.0254Average, per protocol type & kV0.02390.02590.02570.02420.02530.02560.0289
CV, %6.89.27.86.15.46.216.010.96.6CV, %8.66.64.97.36.66.010.9
Average, per protocol type, all kV0.02750.02690.0246Average, per protocol type, all kV0.02530.0251
CV, %7.96.69.6CV, %7.36.8
Average, all prospective axial (with and without padding)0.0272Average, all retrospective helical (with and without TCM)0.0252
CV, %7.3CV, %7.0
Average, all protocols (prospective, retrospective, and calcium scoring)0.0262Average, all protocols (prospective, retrospective, and calcium scoring)0.0262
CV, %8.9CV, %8.9

Scanner- and protocol-specific k-factors, in units of mSv·mGy−1cm−1, were calculated for cardiac CT using ICRP Publication 103 definition of effective dose, for 12 scanners and 120 scan protocols with standard tube potentials of 80, 100, and 120 kVp. k-Factors here are summarized in 5 categories of axial and helical CT angiography protocol types, and calcium score. Per-scanner averages of the k-factors across all protocol types and energy levels are displayed along with the CV in the 2 right-most columns. Scan length for all scans is 13.3 to 14.2 cm. Heart rate is 60 beats/min for all scans, except where otherwise noted. A detailed description of each protocol here is also provided in Online Table 1, as are additional k-factors and detailed descriptions for very low (70 kVp) and high (135 or 140 kVp) tube potential protocols for selected scanners.

CV = coefficient of variation (ratio of standard deviation to mean in percentage values); other abbreviations as in Tables 1, 2, and 3 .

  • Tube current modulation.

  • Average of 2 beams with 20- and 40-mm widths.

  • Heart rate = 80 beats/min (all others are 60 beats/min).

  • § Average of high and standard resolution modes.

  • Target mode volume scan.

  • Continuous volume scan with exposure throughout a full cardiac cycle.