On the optimal temporal resolution for phase contrast cardiovascular magnetic resonance imaging: establishment of baseline values

Abstract

Background: The aim of this study is to quantify the frequency content of the blood velocity waveform in different body regions by means of phase contrast (PC) cardiovascular magnetic resonance (CMR) and Doppler ultrasound. The highest frequency component of the spectrum is inversely proportional to the ideal temporal resolution to be used for the acquisition of flow-sensitive imaging (Shannon-Nyquist theorem).

Methods: Ten healthy subjects (median age 33y, range 24-40) were scanned with a high-temporal-resolution PC-CMR and with Doppler ultrasound on three body regions (carotid arteries, aorta and femoral arteries). Furthermore, 111 patients (median age 61y) with mild to moderate arterial hypertension and 58 patients with aortic aregurgitation, atrial septal defect, or repaired tetralogy of Fallot underwent aortic CMR scanning. The frequency power distribution was calculated for each location and the maximum frequency component, fmax, was extracted and expected limits for the general population were inferred.

Results: In the healthy subject cohort, significantly different fmax values were found across the different body locations, but they were nonsignificant across modalities. No significant correlation was found with heart rate. The measured fmax ranged from 7.7 ± 1.1 Hz in the ascending aorta, up to 12.3 ± 5.1 Hz in the femoral artery (considering PC-CMR data). The calculated upper boundary for the general population ranged from 11.0 Hz to 27.5 Hz, corresponding to optimal temporal resolutions of 45 ms and 18 ms, respectively. The patient cohort exhibited similar values for the frequencies in the aorta, with no correlation between blood pressure and frequency content.

Conclusions: The temporal resolution of PC-CMR acquisitions can be adapted based on the scanned body region and in the adult population, should approach approximately 20 ms in the peripheral arteries and 40 ms in the aorta.

Trial registration: This study presents results from a restrospective analysis of the clinical study NCT01870739 (ClinicalTrials.gov).

Keywords: Doppler ultrasound; Frequency content; Phase contrast MRI; Temporal resolution.

Conflict of interest statement

There are no competing interests pertaining this study.

Figures

Fig. 1

Exemplary CMR images at the three locations: common carotid artery (a, d); aorta (b, e); common femoral artery (c, f). The top row represents magnitude images, and the bottom row represents phase contrast images. Arrows point at the vessels of interest

Fig. 2

Spectrum of one waveform acquired at the same location by CMR (solid line) and Doppler (dashed line)

Fig. 3

Velocity waveforms (left) and corresponding power spectra (right) at three different locations (CCA = common carotid artery, AAo = ascending aorta, CFA = common femoral artery) in one healthy subject

Fig. 4

Representative (mean-detrended) velocity waveform in the ascending aorta of a healthy subject reconstructed from a full spectrum (solid black line) and with various percentages of the spectrum retained (99, 95, and 90%)

Fig. 5

Distributions of maximum detected frequencies across the healthy subjects grouped by location and modality (CCA = Common Carotid Artery, AAo = Ascending Aorta, DAo = Descending Aorta, CFA = Common Femoral Artery)

Fig. 6

fmax99 distributions in the ascending aorta (blue) and descending (orange) aorta with respect to patient age (a) and estimated central mean pressure (b)