Performance of ICE and IVUS
In our study, ICE performed better than IVUS with regards to quality of
imaging provided and to inter-observer reproducibility of measurements
obtained. These findings are likely due to the lower ultrasound
frequency used by ICE, which was advantageous in terms of acoustic
penetration without a significant loss in spatial resolution. When using
ICE, the outer vessel circumference was well-defined in most or all
image quadrants, as well as inner structures such as lumen circumference
and wall.
We observed no significant differences between the two technologies in
terms of trackability: similar additional procedural times were needed
for ICE and for IVUS imaging and no procedural complications occurred as
result of imaging.
Both lumen and vessel diameters and areas were consistently larger in
the ICE-imaged PVs compared to the IVUS-imaged PVs. Moreover, although
both imaging techniques showed an elliptical shape of the PV
cross-sections, in keeping with previous CT and MRI
studies17,18, lumen and vessel sphericity indexes were
lower in the ICE-imaged PVs, which is indicative of a more elliptical
shape of the PV cross-sections. Our PV measurements determined by IVUS
are in line with previously reported PV measurements, obtained from both
IVUS images and histological sections15. Taken
together, these data might suggest that ICE overestimated the PVs sizes
due to non-coaxial cross-sectioning, as indicated by the lower
sphericity index when compared to the IVUS images. ICE catheters are not
advanced or pulled back over a wire and this different design might have
reduced the chance of a coaxial position of the probe within the PV
lumen. Despite different lumen and vessel diameters and absolute areas,
pre- and post-ablation WTI% were comparable between PV cross-sections
imaged either ICE or IVUS, thus suggesting that both imaging modalities
can provide similar accuracy in depicting acute changes in tissue
thickness after ablation.