Huizhi Cao, Presenter: Nothing to Disclose

Fajin Lv MD, Abstract Co-Author: Nothing to Disclose

Isao Tanaka, Abstract Co-Author: Nothing to Disclose

Jingmin Liao, Abstract Co-Author: Employee, General Electric Company

Eiko Ueno MD, Abstract Co-Author: Nothing to Disclose

Yun Shen PhD, Abstract Co-Author: Employee, General Electric Company

The synchronous subtraction CTA is a useful technique for displaying cerebral and carotid artery without bony structure with two helical scans (contrast enhanced scan and non contrast scan), but the two scans will be increase DOSE than single CTA. The purpose of this paper is to investigate DOSE reduction technique with different mA of two for synchronous helical subtraction CTA.

A skull flow phantom underwent helical subtraction examinations with 64-row MDCT (GE LightSpeed VCT) divide two group: one group (Group 1) use same mA (100mA/120kV) for two scan, another group (group 2) using low mA (10, 25, 50, 65, 75 and 85mA) for non contrast scan. The scan protocol was: rotation speed 0.4s, 120kV, 100mA for second scan, 64×0.625mm and pitch 0.531:1. Each examination included two scans at the same region, which represented non-enhanced and contrast-enhanced scan in actual CTA. For each group, the difference of tube start angle between two scans was recorded. The Artifact Index of subtraction image was calculated using standard deviation (SD) of subtraction image (the 2nd scan subtracts the 1st scan) and statistical test was performed to compare the subtraction image quality between two groups.

For group 1 and group 2, the average Artifact Index were 10.12+/-3.36 and 12.96+/-2.58, the differences for two group was no significant statistical difference (p>0.05). Also from SD of Artifact Index, we can confirm different mA of first scan (non contrast scan) don’t effect image quality of synchronous helical subtraction CTA. And this means we can expect to use 1/10 mA of second (contrast enhanced scan) scan to get high image quality synchronous helical subtraction CTA. Also, this low DOSE technique was confirmed from clinical cases.

We concluded low mA of non contrast scan can reduce DOSE of synchronous helical subtraction CTA without image quality risk.

Synchronous helical subtraction CTA has the potential in displaying cerebral and carotid artery. And the result of this study is useful to reduce DOSE for synchronous helical subtraction CTA.

Cao, H, Lv, F, Tanaka, I, Liao, J, Ueno, E, Shen, Y, Basic Study on the Low-Dose Synchronous Helical Subtraction 64-Row MDCT Angiography: Skull Flow Phantom Experiment.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8010496.html