Assessment of Myocardial Perfusion with Magnetic Resonance Imaging and an Intravascular Contrast Agent

Sammanfattning: The intravascular contrast agent NC100150 Injection (Clariscan™) was tested for its ability to induce signal intensity changes in myocardium, both in steady state and during first pass, and thereby demarcating non-perfused myocardium from perfused.Steady state: Ex vivo in pigs and when using 4 mg Fe/kg bodyweight (b.w.) of the contrast agent, a T1-weighted inversion recovery fast spin echo (IR/TSE) sequence could demarcate 95% of the volume of non-perfused myocardium when compared with the volume determined from photographs where non-perfused myocardium was demarcated by fluorescein. A T2'-weighted gradient echo sequence resulted in significantly lower volume estimations of non-perfused myocardium. Under similar conditions and when using 5 mg Fe/kg b.w., a T2-weighted fast spin echo (TSE) demarcated 99% of the volume of non-perfused myocardium. We were not able to implement the IR/TSE sequence in vivo, but the T2-weighted TSE resulted in clear visualization of non-perfused myocardium in vivo in animals.First pass: With a single-shot T2-TSE, one slice was acquired every heartbeat during the first pass of the contrast agent. When using this sequence, non-perfused myocardium was demarcated in animals and the induced signal intensity changes in perfused myocardium (74±18% @ 5 mg Fe/kg b.w.) were comparable to those in patients (59±13 @ 3 mg Fe/kg b.w.), when taking differences in doses into account.Linear dose–response was found in porcine myocardium between R1, R2, and R2' versus dose (0 – 12 mg Fe/kg b.w.) ex vivo and for R1 (in myocardium and blood) versus dose (0 – 5 mg Fe/kg b.w.) in vivo. However, R1 determination in vivo and in the box ex vivo indicated that blood loss (<2/3) from the myocardium occured during the excision of the heart and preparation for the box, meaning that the box situation ex vivo actually corresponds to lower doses in vivo. Finally, the in vivo measurements of R1 in myocardium and blood indicated that at R1 values in blood as high as 13 s-1, the water exchange is in the fast regime through the capillary wall.In conclusion, the feasibility of NC100150 Injection, in steady state and during first pass, for demarcation of non-perfused myocardium when using a T2-weighted TSE sequence has been demonstrated.