Feasibility of High-Dose Dobutamine Stress SSFP Cine MRI at 3 Tesla with Patient Adaptive Local RF Shimming using Dual-Source RF Transmission: Initial Results

Abstract

Purpose: To investigate the feasibility of high-dose dobutamine stress (HDDS) imaging using SSFP sequences at 3 T employing patient-adaptive local RF-shimming using a dual-source RF transmission system.

Materials and Methods: 13 Patients underwent a HDDS protocol on a 3 T MRI scanner (Achieva 3.0T-TX, Philips Healthcare), equipped with a dual-source RF transmission system. SSFP cine sequences using patient-adaptive local RF-shimming (RF-S) were compared to cine images acquired without additional shimming. Image quality was evaluated on a 4-point grading scale and number of non-diagnostic segments assessed. Contrast (CN) between myocardium (SIM) and blood pool (SIB) was calculated [(SIB-SIM)/(SIB+SIM)].

Results: Image quality both at rest and maximum stress was significantly improved with RF-S (ED:3.56 ± 0.5 vs. 3.23 ± 0.63; ES:3.4 ± 0.5 vs. 3.1 ± 0.7) compared to no RF-S (ED:2.9 ± 0.72 vs. 2.15 ± 0.78; ES:2.64 ± 0.74 vs. 1.95 ± 0.76; p < 0.01). The amount of non-diagnostic segments was significantly reduced when using RF-S at rest and stress (3 vs. 39; 19 vs. 78, p < 0.05). All HDDS studies were diagnostic if performed with RF-S (n = 13/13) in comparison to conventional shimming (n = 5/13). Image contrast was improved for SSFP sequences with RF-S (0.53 ± 0.08) compared to conventional images (0.46 ± 0.09, p = 0.06).

Conclusion: Patient-adaptive local RF-shimming using a dual-source RF transmission system allows for reliable SSFP imaging in a clinical high-dose dobutamine stress protocol at 3 T. RF-S significantly improves image quality and reduces the number of non-diagnostic myocardial segments.

Zusammenfassung

Ziel: Evaluierung von Hochdosis-Dobutamin-Stress(HDDS)-Kardio-MRT mittels B-SSFP-Cine-Sequenzen bei 3 T mit paralleler RF-Sendetechnik und patientenadaptiertem lokalem Shimming des Radiofrequenzfeldes (B1-S).

Material und Methoden: 13 Patienten mit V. a. koronare Herzerkrankung (KHK) wurden an einem mit paralleler RF-Sendetechnik ausgestatteten 3T-MRT-System (Achieva 3T-TX, Philips Healthcare) untersucht. HDDS erfolgte mittels SSFP-Cine-Sequenzen in Ruhe (R) sowie auf jeder Belastungsstufe in der horizontalen (HLA), vertikalen langen (VLA) sowie kurzen Achse (SA) unter Einsatz von B1-S. Zum Vergleich wurden SSFP-Sequenzen mit identischen Parametern, jedoch ohne B1-S, in R und unter maximaler Belastung (Bmax) akquiriert. Die Bildqualität wurde mittels 4-Punkte Skala (4: exzellent; 1: nicht diagnostisch) end-diastolisch (ED) und end-systolisch (ES) bewertet und die Anzahl der nicht diagnostischen Segmente (17-Segment-Modell) ermittelt. Der Kontrast (CN) zwischen interventrikulärem Septum (SIM) und linksventrikulärem Kavum (SIB) wurde berechnet [(SIB-SIM)/(SIB+SIM)].

Ergebnisse: B1-S führte zu einer signifikanten Verbesserung der Bildqualität in Ruhe und unter B_max (ED:3,56 ± 0,5 vs. 3,23 ± 0,63; ES:3,4 ± 0,5 vs. 3,1 ± 0,7) im Vergleich zu Untersuchungen ohne B1-S (ED:2,9 ± 0,72 vs. 2,15 ± 0,78; ES:2,64 ± 0,74 vs. 1,95 ± 0,76; p < 0,01). Die Anzahl der nicht diagnostischen Segmente wurde durch den Einsatz von B1-S sowohl in R (3 vs. 39) als auch unter B_max (19 vs. 78, p < 0.05) signifikant reduziert. Alle HDDS-Untersuchungen mit B1-S waren diagnostisch (n = 13/13) im Vergleich zum herkömmlichen Ansatz (n = 5/13). Der Kontrast zwischen interventrikulärem Septum und linksventrikulärem Kavum mit Einsatz von B1-S (0,53 ± 0,08) war besser als ohne B1-S (0,46 ± 0,09, p = 0,06).

Schlussfolgerung: Parallele RF-Sendetechnik kombiniert mit B1-Shimming erlaubt die Durchführung von Hochdosis-Dobutamin-Stress-Untersuchungen mittels SSFP-Cine-Sequenzen bei 3 T. B1-S verbessert die Bildqualität und reduziert die Anzahl der nicht diagnostischen kardialen Segmente signifikant.

Key words

patient-adaptive local RF-shimming - high-dose dobutamine stress testing - cardiac MRI - 3.0 Tesla - steady state free precession sequences - dual-source RF transmission

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