MR Imaging of Lymph Nodes using Gadofluorine M: Feasibility in a Swine Model at 1.5 and 3T

Zusammenfassung

Ziel: Untersuchung von Gadofluorine M für die MR-Bildgebung von Lymphknoten (LK) in einem Großtiermodel bei 1,5 und 3 T. Material und Methoden: Es wurden sowohl die pelvinen als auch die zervikalen Lymphknotenstationen in einem Schweinemodell vor als auch 24 h nach intravenöser Gabe von 50 µmol/kgKG des Kontrastmittels Gadofluorine M (experimentelles Kontrastmittel) untersucht. Als MR-Sequenzen dienten klinisch einsetzbare T 1-gewichtete Sequenzen, welche sowohl bei 1,5 als auch bei 3 T eingesetzt wurden. Das Signal-zu-Rauschen-Verhältnis und das Kontrast-zu-Rauschen-Verhältnis im Vergleich zum umliegenden Gewebe wurden bestimmt und mit dem Stundents-t-Test verglichen. Post mortem wurde in 43 explantierten Lymphknoten die Gd-Konzentration bestimmt. Ergebnisse: Nach Gabe von Gadofluorine M zeigten alle Lymphknoten eine deutlich gesteigerte Signalintensität mit hohem Kontrast zum umliegenden Gewebe (SNRpelvineLKs post vs. pre: 46 ± 7 vs. 14 ± 3, SNRcervicaleLKs post vs. pre: 105 ± 64 vs. 32 ± 21; CNRpelvineLKs vs. Muskel post vs. pre 28 ± 5 vs. 0.2 ± 0.5, CNRcervicaleLKs vs. Muskel post vs. pre 76 ± 53 vs. 11 ± 15, p < 0,05 für alle Vergleiche). SNR und CNR der pelvinen LKs war bei 3 T höher im Vergleich zu 1,5 T (SNR LKs 3 T vs. 1,5 T 84 ± 6 vs. 46 ± 7, CNR LKs vs. Muskel 3 T vs. 1,5 T 53 ± 9 vs. 28 ± 5; p < 0,05). In allen Lymphknoten wurde eine hohe Akkumulation von Gd nachgewiesen (149 ± 25 µmol Gd/L). Schlussfolgerung: Gadofluorine M akkumuliert in Lymphknoten. Dieses erlaubt die selektive Darstellung von Lymphknoten mit hohem Kontrast in einem Großtiermodell, wobei klinisch verwendbare MR-Sequenzen eingesetzt werden können. 3 T verbessert sowohl das SNR als auch das CNR im Vergleich zu 1,5 T.

Abstract

Purpose: To investigate the potential of Gadofluorine M for targeted lymph node imaging in a human size animal model and on a clinical MR scanner at 1.5 and 3 T. Materials and Methods: Pelvic and cervical lymph nodes in a swine model were investigated prior to and 24 hours after intravenous administration of 50 µmol/kg body weight Gadofluorine M, an experimental contrast agent. MR imaging was carried out on clinical 1.5 T and 3 T whole-body MR systems using clinically available coils and T 1-weighted sequences. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) with respect to the surrounding tissue were assessed and compared using the Student’s t-test. The Gd concentration in the lymph nodes (n = 43) was measured post mortem by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Results: Gadofluorine M allowed for high signal and high contrast visualization of lymph nodes in all stations on post-contrast images with a significantly increased SNR and CNR (SNR pelvic lymph nodes post vs. pre: 46 ± 7 vs.14 ± 3, SNR cervical lymph nodes post vs. pre: 105 ± 64 vs. 32 ± 21; CNR pelvic lymph node vs. muscle post vs. pre 28 ± 5 vs. 0.2 ± 0.5, CNR cervical lymph node vs. muscle post vs. pre 76 ± 53 vs. 11 ± 15, p < 0.05 for all comparisons). The SNR and CNR in the pelvis were further improved using 3 T compared to 1.5 T scanners (SNR lymph nodes 3 T vs. 1.5 T 84 ± 6 vs. 46 ± 7, CNR lymph node vs. muscle 3 T vs. 1.5 T 53 ± 9 vs. 28 ± 5 respectively, p < 0.05). A high concentration of Gd in the lymph nodes was found (149 ± 25 mmol Gd/L). Conclusion: Gadofluorine M accumulates in the lymph nodes and allows for selective targeted high contrast MR imaging of lymph node tissue in a large animal model using clinically available MR imaging techniques. 3 T further improves SNR and CNR compared to 1.5 T.

Key words

lymphatic - lymphography - MR imaging - animal investigations - contrast agents - molecular imaging

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