Table of Contents
Advertisement
If manual mA is selected, the software does not make the noise level changes or mA
adjustment automatically when ASiR-V is enabled. These changes need to be calculated using
the following tables to make changes to manual mA values. Refer to
guidance in making parameter step adjustments during ASiR-V evaluation process.
Before using ASiR-V, the site physicist, in collaboration with the radiologist, should conduct
image quality evaluations with varying degrees of ASiR-V and different scan techniques, both at
routine dose and decreased dose. This should be done using your site's preferred method and
phantoms. Using this information, an appropriate starting point for ASiR-V level and diagnostic
scanning techniques can be incorporated into your site's protocols.
A general guideline for parameter step adjustment is:
Dose Reduction increments of about 20% ASiR-V level increments of 10%.
Whether ASiR-V is used for dose reduction or image quality improvement, parameter settings
should be made in steps and then reviewed for diagnostic image quality until the desired
clinically appropriate image quality is achieved.
2.2 Dose adjustment Factor - Manual mA method
When using standard reconstruction algorithm, use the following chart to calculate dose
reduction for mA based on the ASiR-V level selected.
The mA Adjustment Factors in
mA protocols. These factors were derived based on calculating the relative difference in
measured noise standard deviation (SD) with Filtered Back Projection (FBP) and ASiR-V on a
20 cm water phantom taken by 0.625 mm thickness and 25 cm DFOV with Large Body SFOV.
Chapter 12 Scan Applications
Illustration 2: Filtered Back Projection compared to 100% ASiR-V
Table 1
are intended to help you enter the mA settings in manual
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
Table 1
and
Table 2
for
309
Advertisement
Table of Contents
Troubleshooting
