Inversion Prepared Coronary MR Angiography: Direct Visualization of Coronary Blood Flow[*]

Zusammenfassung

Ziel: Implementierung einer Bright-Blood MR-Koronarangiographie-Sequenz in Kombination mit einem schichtselektiven Inversionspuls zur Darstellung des koronaren Blutflusses. Material: Bei acht gesunden Probanden wurde das rechte Koronargefäßsystem mit einem 1,5-Tesla MR-Tomographen (Gyroscan ACS-NT, Philips Medical Systems, Best, NL) mittels einer navigatorgesteuerten EKG-getriggerten 3D-Steady-State Free-Frecession (SSFP)-Sequenz mit radialer k-Raum-Abtastung untersucht. Die gleiche Sequenz wurde mit und ohne schichtselektiven Inversionspuls durchgeführt, der entlang der Koronararterie, jedoch orthogonal zur Bildebene und unter Ausschluss der Aorta geplant wurde. Bei beiden Sequenzen wurden das Signal (SRV)- und Kontrast-zu-Rausch-Verhältnis (KRV) aus Signalintensitätsmessungen im Gefäßlumen, epikardialen Fettgewebe, Blut im rechten Ventrikel und in der extrakorporalen Luft ermittelt. Ferner wurden die dargestellte Gefäßlänge und die Kantenschärfe gemessen. Ergebnisse: Die Verwendung eines selektiven Inversionspulses ermöglicht eine direkte Darstellung des koronaren Blutflusses. Dabei wird exakt die Länge des Gefäßes dargestellt, die das Blut während eines Herzzyklus zurücklegt. Die SSFP-Sequenz mit selektivem Inversionspuls ergab ein höheres KRV zwischen koronarem und rechtsventrikulärem Blut und eine bessere Darstellung der Gefäßkanten. Das SRV der Koronararterien und KRV zwischen Koronararterie und epikardialem Fettgewebe war in beiden Sequenzen vergleichbar. Schlussfolgerung: Die Kombination einer 3D SSFP-Sequenz mit einem schichtselektiven Inversionspuls ermöglicht die direkte Darstellung des koronaren Blutflusses und verstärkt den Kontrast zwischen den Koronararterien und dem Blut im rechten Ventrikel.

Abstract

Purpose: Visualization of coronary blood flow by means of a slice-selective inversion pre-pulse in concert with bright-blood coronary MRA. Materials and Methods: Coronary magnetic resonance angiography (MRA) of the right coronary artery (RCA) was performed in eight healthy adult subjects on a 1.5 Tesla MR system (Gyroscan ACS-NT, Philips Medical Systems, Best, NL) using a free-breathing navigator-gated and cardiac-triggered 3D steady-state free-precession (SSFP) sequence with radial k-space sampling. Imaging was performed with and without a slice-selective inversion pre-pulse, which was positioned along the main axis of the coronary artery but perpendicular to the imaging volume. Objective image quality parameters such as SNR, CNR, maximal visible vessel length, and vessel border definition were analyzed. Results: In contrast to conventional bright-blood 3D coronary MRA, the selective inversion pre-pulse provided a direct measure of coronary blood flow. In addition, CNR between the RCA and right ventricular blood pool was increased and the vessels had a tendency towards better delineation. Blood SNR and CNR between right coronary blood and epicardial fat were comparable in both sequences. Conclusion: The combination of a free-breathing navigator-gated and cardiac-triggered 3D SSFP sequence with a slice-selective inversion pre-pulse allows for direct and directional visualization of coronary blood flow with the additional benefit of improved contrast between coronary and right ventricular blood pool.

Coronary MRA - steady-state free-precession (SSFP) - radial k-space sampling - slice-selective inversion - coronary blood flow

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1 This work is supported in part by a Biomedical Engineering Grant from the Whitaker Foundation (RG-02-0745), a grant from the Donald W. Reynolds Foundation and by the National Institutes of Health (HL61912).

1 Dr. Stuber is compensated as a consultant by Philips Medical Systems NL, the manufacturer of equipment described in this presentation. The terms of this arrangement have been approved by the Johns Hopkins University in accordance with its conflict of interest policies.