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Tatusagami et al.
In coronary CTA with prospective ECG
triggering, radiation is administered only
during the end-diastolic phase of the R-R
cycle rather than throughout the entire cardiac
cycle [13]. Combining prospective ECG
triggering for coronary CTA with BMIadapted
scanning parameters allows a substantial
reduction in radiation dose [7, 8].
The mean effective radiation dose in the
present study (2.1 ± 0.7 mSv) was much lower
than in previous reports [5, 6] of retrospective
ECG gating without a BMI-adapted
scanning protocol (9.4–21.4 mSv).
We acknowledge the following limitations.
First, the dose of contrast material was
not adapted to BMI, as suggested in previous
reports [11, 17]. However, use of only a fixed
amount of contrast material enabled us to
evaluate the influence of BMI on image noise
and coronary vessel attenuation. Second,
coronary attenuation and CNR were selectively
evaluated in the proximal RCA and
LMA. Distal segments were not evaluated
because the small diameters of distal segments
do not allow placement of an ROI
without including parts of the vessel wall and
adjacent tissue, thus causing partial volume
effects. Finally, BMI may not be an exact estimation
of body mass at the level of the
heart. The physique differs, for example, in
men and women in the upper and lower parts
of the thorax, which might have been an additional
reason for the lack of correlation between
BMI and image noise in this study.
We conclude that at coronary CTA with
prospective ECG triggering, a BMI-adapted
scanning protocol yields images with similar
noise regardless of BMI. Increased bolus dilution
due to larger blood volume might have
accounted for a decrease in CNR and vessel
attenuation in patients with a higher BMI in
this study because the contrast material bolus
was not adapted.
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