Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5

Standardized Weight and Heart Rate based Acquisition Protocol for coronary CT angiography (WRAP-Protocol)
S. Hoepffner1, M. Eckstein2, S. Smolka1, D. Bittner1, F. Ammon1, M. Moshage1, S. Achenbach1, M. Marwan1
1Med. Klinik 2 - Kardiologie, Angiologie, Universitätsklinikum Erlangen, Erlangen; 2Pathologisches Institut, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen;

Introduction: 
We assessed the feasibility and performance of a standardized acquisition protocol for coronary CT angiography.


Methods: 
630 consecutive patients referred for CT coronary angiography due to suspected CAD were screened for inclusion in this retrospective analysis of a standardized acquisition protocol at the cardiac CT department of the university hospital Erlangen. All CT data sets were acquired using a third-generation dual source system. Based on weight, patients were stratified in 3 arms: <90 kg, 90-100 kg, > 100 kg with acquisition using 90 kV/600 mAs, 100 kV/600 mAs and 120 kV/500 mAs, respectively for tube output and tube current. Furthermore, depending on heart rate after breath hold, patients were stratified in 3 arms as follows: HR< 65 bpm, HR 66-70 bpm and HR > 70 bpm with acquisition using prospective axial trigger at 70% of the peak R-wave to R-wave, at 60-70% or prospectively triggered axial acquisition using absolute delay at 250-350 ms following R-wave, respectively.   Coronary assessment was performed using the 18-coronary segment model recommended by the SCCT with standard multiplanar reconstruction and maximum intensity projection. Data sets were evaluated for image quality on a 4-point-scale (excellent, minor artifacts, major artifacts and non-diagnostic). Protocol deviations were documented. Patients with previous revascularization (Stents/CABG), patients with ectopic beats defined as presence of ectopic beats within 30 seconds before acquisition, severe coronary calcification >2000 Agatston units were excluded from this protocol.


Results: 

Out of 630 patients, 215 were excluded from the protocol. Furthermore 30 patients were documented as protocol deviation. 381 patients (mean age 59 ± 10 years, 56% males, mean heart rate 60±10 bpm, mean weight 82±16 kg) were included in this analysis. Acquisition was performed using prospective axial trigger at 70% of the peak R-wave to R-wave, prospective axial trigger at 60-70% or prospective axial acquisition using absolute delay at 250-350 ms following R-wave, in 298 (median heart rate 57 bpm), 40 (median 68 bpm) and 43 patients (median 78 bpm), respectively with acquisition parameters set at 90kV/600 mAs in the majority of patients (267 patients). Using a conversion factor of 0.017, the median estimated effective radiation dose for the 3 arms 90kV/600 mAs, 100 kV/600 mAs and 120 kV/500 mAs was (2/2.9/3.2 mSv, 2.8/4.5/4.2 mSv and 4.1/7.1/6 mSv for the arms 60%/60-70%/250-350 ms, respectively, p< 0.05 for all). In 26 patients (7%), repeat CT angiography was necessary due to artifacts and was most common in the arm with axial acquisition at only 70% of the peak R-wave to-R-wave (17 patients compared to 7 patients for 60-70% and 2 patients for 250-350 ms p< 0.05). In 18 patients (4%), at least one coronary segment was deemed as non-assessable (stratified according to the arms 70%/60-70%/250-350 ms 8, 3 and 7 patients respectively). Using cumulative frequency assessment, coronary segments with major artifacts or deemed non-assessable were most frequently reported in patients with heart rate > 70 bpm or patients with weight > 100 kg.


Conclusion: 
Using a standard weight and heart rate-based protocol for coronary CT angiography acquisition is feasible and is associated with low effective radiation exposure. Major-artifacts and non-assessable segments are most frequently found in patients with higher heart rate and body weight.


https://dgk.org/kongress_programme/jt2022/aP1228.html