:: ctdi tables

ImPACT have CTDI₁₀₀ measurements free in air, and in standard Perspex head and body dosimetry phantoms for most of CT scanners in use today. These measurements are useful for calculation of CTDI_w, CTDI_vol, DLP and other dose parameters.

Most of the data was measured by ImPACT on a consistent set of CTDI phantoms, using the same ionisation chamber, and a consistent technique, so the consistency of the results is good. Some of the measurements, particularly for older equipment, result from the ImPACT CT scanner dose survey. The data is available for download as a zipped 'Excel 97 & 5/95' format spreadsheet.

A range of other resources are available as a result of the dose survey - follow the link above to find them.

You can access this spreadsheet by completing the form below and clicking the download document button. Please complete as many details as you can

Those seeking more recent data, this can be found in the CTDosimetry tool, on the SCANNERS worksheet

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ImPACT has done work on converting from CTDI₁₀₀ to CTDI_FDA. Measurements were carried out on eight scanners, representing a range of beam shaping filters, scan geometries and operating kVs from 110 to 130kV. The summary of results is as follows.

Note that a correction factor has been included in the conversion factor to take account of the different media that the doses are quoted in (dose in air for CTDI₁₀₀ and dose to Perspex for CTDI_FDA).

CTDI₁₀₀ to CTDI_FDA Conversion Factors (Head Phantom)
	Head (Centre)			Head (Periphery)
	Mean	sd*	n**	Mean	sd*	n**
10 mm	0.978	0.006	7	0.928	0.008	6
5 mm	0.774	0.010	6	0.832	0.004	5
3 mm	0.623	0.038	3	0.740	0.012	3
2 mm	0.492	0.031	3	0.669	0.000	2
1.5mm	0.452	-	1	0.636	-	1
1 mm	0.320	-	1	-	-	0

CTDI₁₀₀ to CTDI_FDA Conversion Factors (Body Phantom)
	Body (Centre)			Body (Periphery)
	Mean	sd*	n**	Mean	sd*	n**
10 mm	1.035	0.011	5	0.937	0.004	5
5 mm	0.724	0.015	4	0.824	0.006	3
3 mm	0.521	0.064	2	0.712	0.049	2
2 mm	0.387	0.035	3	0.675	0.000	2
1.5mm	0.344	-	1	0.618	-	1
1 mm	0.258	-	1	-	-	0

*sd = standard deviation of meaurements

**n = number of scanners included in mean value

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