Exposure Time in ms Attribute
| Tag | (0018,9328) |
|---|---|
| Type | Conditionally Required (1C) |
| Keyword | ExposureTimeInms |
| Value Multiplicity | 1 |
| Value Representation | Double (FD) |
Duration of exposure for this frame in milliseconds. If Acquisition Type (0018,9302) equals SPIRAL the duration of the exposure time for this frame shall be Revolution Time (0018,9305) divided by the Spiral Pitch Factor (0018,9311). See Section C.8.15.3.8.1.
Required if Frame Type (0008,9007) Value 1 of this frame is ORIGINAL, or if Image Type (0008,0008) Value 1 is ORIGINAL and Multi-energy CT Acquisition (0018,9361) is YES. May be present otherwise.
Section C.8.15.3.8.1
C.8.15.3.8.1 Exposure Time in ms Attribute (Informative)
An example of how the value of Exposure Time in ms (0018,9328) can be calculated:
The Exposure Time Texposuretime of a volume shall be the time of the X-Ray radiation in position with this volume. It depends on the travel speed and the total collimation width.
Texposuretime of the volume represented by a distinguished frame of a Spiral Scan can be calculated as follows:
Texposuretime = N x S / Vtravelspeed
CTpitchfactor = DD / N x S
Vtravelspeed = DD / Trevolutiontime
From this the exposure time can be derived:
Texposuretime = N x S x Trevolutiontime / DD = Trevolutiontime / CTpitchfactor
Legend:
DD = Table Feed per Rotation (0018,9310) in mm distance moved by the patient support in the z direction per 360° revolution in Spiral scanning
S = collimation of a single slice in mm
N = number slices
N x S = Total Collimation Width (0018,9307) in mm
Vtravelspeed = Table Speed (0018,9309) in mm/second, travel speed of the patient table
Trevolutiontime = Revolution time (0018,9305) in seconds
CTpitchfactor = Spiral Pitch Factor (0018,9311)