VT ablations could benefit from Dynamic 3D (4D) left ventricle (LV) visualization as road-map for anatomy-guided procedures. We developed a registration-based method that combines information of several cardiac phases to filter out noise and artifacts in low-dose 3D Rotational Angiography (3DRA) images. This also enables generation of accurate multi-phase surface models by semi-automatic segmentation (SAS). The method uses B-spline non-rigid inter-phase registration (IPR) and subsequent averaging of the registered 3DRA images of 4 cardiac phases, acquired with a slow atrial pacing protocol, and was validated on data from 5 porcine experiments. IPR parameter settings were optimized against manual delineations of the LVs using a composed similarity score (Q), dependent on DICE-coefficient, RMSDistance, Hausdorff (HD) and the percentage of inter-surface distances ≤3mm and ≤4mm. The latter are clinically acceptable error cut-off values. Validation was performed after SAS for varying voxel intensity thresholds (ISO), by comparison between models with and without prior use of IPR. Distances to the manual delineations at optimal ISO were reduced to ≤3mm for 95.6±2.7% and to ≤4mm for 97.1±2.0% of model surfaces. Improved quality was proven by significant mean Q-increase irrespective of ISO (7.6% at optimal ISO (95%CI 4.6-10.5,p<0.0001)). Quality improvement was more important at suboptimal ISO values. Significant (p<0.0001) differences were also noted in HD (-20.5%;95%CI -12.1%-- 29.0%), RMSD (-28.3%;95%CI -21.7%--35.0%) and DICE (1.7%;95%CI 0.9%-2.6%). Generating 4D LV models proved feasible, with sufficient accuracy for clinical applications, opening the perspective of more accurate overlay and guidance during ablation in locations with high degrees of movement.
Cardiac rotational angiography (RA) is well suited for 3-D cardiac imaging during catheter based interventions
but remained limited to static images or was characterized by high dose patient radiation dose. We present a
new prospective imaging technique that is capable of imaging the dynamics of the cardiac cavities in a single
C-arm run during the intervention with a relatively low dose.
By combining slow atrial pacing to obtain a stable heart rhythm and a single C-arm rotation with imaging
at a regular imaging interval, a prospective 4DRA is established. Pacing interval and imaging framerate can be
adapted such that a single cardiac phase is imaged multiple times and a motion free state is imaged from different
equiangular positions. A practical implementation of this technique was realized in which the cardiac cavities
are imaged while pacing at 105 bpm (574 msec) and imaging at approximately 15 fps. A number of animal
experiments were conducted in which the technique was applied and MR imaging was performed subsequently.
Quantitative comparison was made by manual contouring of the left ventricle in the RA and MR images of both
end-systolic and end-diastolic phases.
Reconstructed images of the individual cardiac phases showed all four chambers and important vessels in
spite of substantial image noise. 4DRA and MR absolute surface distance errors amounted to 2:8 ± 0:7 mm,
which is acceptable. Further, no systematic difference could be identified. Finally, it is expected that the effective
dose of a clinical protocol with 381 images will be lower than the current retrospective gated RA protocols.