References - GE Revolution CT User Manual

In SmartmA scans, if none of the kV stations meet all of the user requirements and system
capabilities, kV Assist will revert to the baseline kV. The user interface will indicate whether or
not the desired image quality can be achieved with these baseline scan parameters.
What if the dose reduction results from kV Assist are not as large as I would like?
If the image quality away from the reference technique is better than required and the dose
reduction is lower than desired, you can move to a clinical task that is intended for higher
contrast.
How are mA limits for SmartmA adjusted with kV Assist?
kV Assist will scale the mA limits at each kV in order to achieve the same minimum / maximum
scanner radiation output as at the baseline kV (up to the system limits). Because of the
interaction of tube voltage and tube current, this will result in higher mA limits at lower kV
stations and lower mA limits at higher kV stations.
How do mA limits affect kV Assist selection of kV?
If a SmartmA scan prescription for a given patient would result in mA values falling below the
minimum mA limit, the mA values are adjusted to always fall above the minimum limit (i.e.
clipped). The kV may still be selected by kV Assist (with the dose calculation determined by the
clipped mA values). If a scan prescription for a given patient would result in mA values
exceeding the maximum mA limit, the mA values are adjusted to always fall below the maximum
limit. In this case, kV Assist would not recommend this kV since the resulting image quality
could be suboptimal. In this case, you can still select Manual kV Mode to select the kV and
perform the scan if deemed appropriate.
What if I want to limit kV choices (e.g., I do not want to view head images at 70 kV)?
In addition to the impact of kV Assist Clinical Task on kV selection, there may be clinical
situations in which you wish to lock out a kV or range of kV stations. The range of kVs used for
kV optimization are determined by user selected kVs set in protocol management.

2.7.5 References

1 W Huda, EM Scalzetti and G Levin, "Technique Factors and Image Quality as Functions of
Patient Weight at Abdominal CT." Radiology (2000), 217(2): 430-435.
JM Boone, EM Geraghty, JA Seibert and SL Wooten-Gorges, "Dose Reduction in Pediatric
2
CT: A Rational Approach." Radiology (2003), 228(2): 352-360.
L Yu, H Li, JG Fletcher and CH McCollough, "Automatic Selection of Tube Potential for
3
Radiation Dose Reduction in CT: A General Strategy." Medical Physics (2010), 37(1): 234-243.
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Revolution CT User Manual
Direction 5480385-1EN, Revision 1
2 Scan Theory