Keywords:
Vascular, Arteries / Aorta, Extremities, CT-Angiography, Radiation safety
Authors:
E. Kondratyev, G. Karmazanovsky; Moscow/RU
DOI:
10.1594/ecr2013/B-0250
Conclusion
Some reports have investigated the feasibility of MDCT for the assessment of patients with PAOD,
authors reported high degree of accuracy in the evaluation of the site and degree of stenosis,
with results comparable with those of DSA. Some studies revealed that diagnostic quality of images can be achieved with a lower radiation dose.
They showed high sensitivity,
specificity,
accuracy,
PPV and NPV for detecting of significant stenosis using low-dose protocols [2,3].
Our results shows average radiation dose reduction up to 70% achieved using “80kV” and 77% using “50mAs” protocol providing sufficient image quality.
A significant change of image quality was observed in both low-dose protocols,
especially in the aorto-iliac segment.
Most of patients with BMI more than 30 kg\m2 in the second group had fair image quality.
Decreasing of visual scores in the third group was observed mainly in patients with BMI > 28 kg\m2,
while in the second group visual scores mainly decreased in patients with BMI > 24 kg\m2.
However the quality of images was sufficient for assessment of stenosis.
In the second group 30% of patients with normal BMI (18-25 kg\m2),
62% of overweight patients (BMI 26-29 kg\m2) and 78%(22% had poor quality) of obese patients (BMI≥30 kg\m2) had fair visual scores of aorto-iliac segment.
In third group 14%,
55%,
70% studies had fair quality on the level of aorto-iliac segment,
respectively.
There was no statistically significant difference in visual scores between two low dose protocols (p=0,533),
as well as comparing BMI subgroups (p=0,554,
0,845,
0,779 for subgroups with normal weight,
overweight and obese patients,
respectively).
But we should take into account that the mean radiation dose was significantly (p<0,0001) higher in the second group than in the third group (8,1±1,8mZv and 6,4±1,02mZv,
respectively).
There was a tendency of decreasing of visual scores in the second group compared to the third group.
It is associated with significantly higher values of intraarterial attenuation and noise in the second group.
Application of the low-dose protocols in obese patients (BMI>30) is limited,
especially in evaluation of aorto-iliac segment due to higher noise and attenuation levels,
that strongly reduce spatial resolution.
Both low dose protocols can be applied to patients with normal BMI and to overweight patients.
However,
studies performed with the use of 80kV protocol had a strong tendency to reduce the quality in patients with a BMI> 24kg\m2.
While at 50mAs protocol such limitation is observed in patients with BMI>28 kg\m2 .
This allows us to recommend it as the preferred protocol for low-dose runoff CTA in the absence of special reconstruction algorithms.