Dual-Layer Spectral CTA for TAVI Planning Using a Split-Phase Protocol and Low-keV Virtual Monoenergetic Images: Improved Image Quality in Comparison with Single-Phase Conventional CTA

Purpose Adaptation of computed tomography protocols for transcatheter aortic valve implantation (TAVI) planning is required when a first-generation dual-layer spectral CT scanner (DLCT) is used. The purpose of this study was to evaluate the objective image quality of aortic CT angiography (CTA) for TAVI planning using a split-phase technique with reconstruction of 40 keV virtual monoenergetic images (40 keV-VMI) obtained with a DLCT scanner. CT angiography obtained with a single-phase protocol of a conventional single-detector CT (SLCT) was used for comparison. Materials and Methods 75 CTA scans from DLCT were retrospectively compared to 75 CTA scans from SLCT. For DLCT, spiral CTA without ECG-synchronization was performed immediately after a retrospectively ECG-gated acquisition covering the heart and aortic arch. For SLCT, spiral CTA with retrospective ECG-gating was performed to capture the heart and the access route simultaneously in one scan. Objective image quality was compared at different levels of the arterial access route. Results 40 keV virtual monoenergetic images of DLCT showed a significantly higher mean vessel attenuation, SNR, and CNR at all levels of the arterial access route. With 40 keV-VMI of DLCT, the overall mean aortic attenuation of all six measured regions was 589.6 ± 243 HU compared to 492.7 ± 209 HU of SLCT (p < 0.01). A similar trend could be observed for SNR (23.6 ± 18 vs. 18.6 ± 9; p < 0.01) and CNR (21.1 ± 18 vs. 16.4 ± 8; p < 0.01). No deterioration was observed for vascular noise (27.8 ± 9 HU vs. 28.1 ± 8 HU; p = 0.599). Conclusion Using a DLCT scanner with a split-phase protocol and 40 keV-VMI for TAVI planning, higher objective image quality can be obtained compared to a single-phase protocol of a conventional CT scanner. Key Points: Citation Format

Non-ST elevation myocardial infarction (NSTEMI) and complex coronary artery fistula in a fit 57-year-old man and its management

A fit 57-year-old man presented with exertional chest pain to the emergency department and was found to have anterolateral T wave inversion on ECG and blood troponin of 1290. Coronary angiography showed a severe proximal to mid-course lesion in mid left anterior descending (LAD) artery, severe ostial disease in obtuse marginal 1 (OM1) and large coronary artery fistula between proximal LAD and main pulmonary artery (PA). Subsequent cardiac CT multiple gated acquisition scan showed a coronary artery to main PA fistula, fed by small branches of the LAD and right coronary artery (RCA). Cardiac magnetic resonance (CMR) showed preserved left ventricle systolic function, ejection fraction 62% and small left to right shunt. Following multidisciplinary team (MDT) discussion, the patient was offered coronary artery bypass grafting (CABG) and fistula ligation as first option, but percutaneous intervention (PCI) to the LAD would also be feasible. After lengthy discussions the patient declined CABG and opted for PCI and stent insertion.

Phase Analysis for Dyssynchrony by MPI and MUGA

Fourier phase analysis can be used to assess dyssynchrony from nuclear images, such as multi-gated acquisition (MUGA) radionuclide angiography, gated blood-pool SPECT, and gated SPECT myocardial perfusion imaging. This chapter reviews the technical background of Fourier phase analysis with these imaging modalities and demonstrates how it measures ventricular dyssynchrony. The major clinical application of ventricular dyssynchrony assessment is to improve response to cardiac resynchronization (CRT) in patients with heart failure. This chapter introduces the current practice of CRT and the potential factors related to CRT response, and then reviews the clinical studies of the above phase analysis techniques for increasing CRT response.