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- Open Access
Pressure gradient measurement in the coronary artery using phase contrast (PC)-MRI: initial patient results towards noninvasive quantification of fractional flow reserve
© Deng et al. 2016
- Published: 27 January 2016
- Fractional Flow Reserve
- Coronary Stenosis
- Invasive Coronary Angiography
- Significant Lesion
- High Pressure Drop
Fractional flow reserve (FFR) is an invasive procedure evaluating the functional significance of an intermediate coronary stenosis in patients with coronary artery disease (CAD) . Quantification of pressure gradient (ΔP) across a particular stenosis is the key to the determination of FFR. Noninvasive ΔP measurement (ΔPMR) using phase-contrast (PC)-MRI in conjunction with Navier-Stokes (NS) equations has been attempted in various vessels [2-4]. Our previous work has shown the feasibility of deriving ΔPMR at various vessel diameters in a phantom (fig.1a) and excellent correlation between ΔPMR and ΔP measured via a pressure-transducer (fig.1b). This study aimed to investigate the feasibility of deriving ΔPMR in healthy and diseased coronary arteries.
Coronary PC-MRI acquisitions were ECG triggered (mid-diastole) and navigator gated (end-expiration) . Fat-suppression pre-pulses were applied prior to the acquisitions to avoid chemical shift effects and increase vessel contrast . Contiguous slices (4-9) were consecutively collected across the proximal coronary segment (healthy controls) or stenotic lesion (patients). Imaging parameters were: VENC=35-65 cm/s in all 3 directions, FA=15o, cardiac phase=2(~70 ms/phase), in-plane resolution = 0.5-0.6 × 0.5-0.6 mm2, slice thickness=3.2 mm and TA=2-4 min/slice at 3T. Eddy-current correction was done offline followed by NS calculations . Protocol was performed on 11 healthy controls and 6 patients (one with known invasive FFR). Patient inclusion criteria: known/suspected CAD, ≥1 coronary lesion (proximal stenosis ≥30%) detected by CTA and/or invasive coronary angiography (ICA).
A significant (p<0.001) increase in ΔPMR was seen in the patient group (6.40 ± 4.43 mmHg) vs. healthy controls (0.62 ± 0.49 mmHg) (figre 2a). CTA/ICA reports in 5/6 patients showed a range of stenoses of 30-50% (proximal left anterior descending coronary artery (pLAD)), but not significant enough to perform invasive FFR. ICA/FFR was performed in 1/6 patients (diffused, 50% lumen narrowing at pLAD, fig 2b-c) with FFR=0.56, suggesting a functionally significant lesion. The same patient showed a ΔPMR of ~14 mmHg, likewise suggesting a functionally significant lesion (relatively high pressure drop).
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