Novel double contrast MRI technique for intramyocardial detection of percutaneously transplanted autologous cells.

Bone marrow cells (BMC) labeled with iron particles can be injected into the heart and detected with MRI. Improvement in conspicuity of labelled cells would be advantageous. This study examined if double contrast with iron oxide and Gd-DTPA enhances cell MRI after transvascular transplantation in myocardial infarction. Ten pigs with week-old myocardial infarction had transvascular peri-infarct delivery of microspheres alone (Group I, n = 3) or mixed with iron-labeled BMCs (Group II, n = 7). Gradient-echo MRI before and 1 min after systemic Gd-DTPA administration produced regions of interest with hypoenhancement that were compared to contralateral regions for contrast-to-noise (CNR) and signal-to-noise (SNR) ratios. All hearts were harvested for gross and microscopic analysis. Areas of focal hypoenhancement corresponding to the BMCs were detected in the myocardium in Group II. Early after administration of Gd-DTPA CNR increased from 17.58 +/- 8.5 to 27.25 +/- 15.8 (P < 0.05) and SNR from 24.87 +/- 9.6 to 35.08 +/- 15.5 (P < 0.05). There was no hypoenhancement in Group I. Tissue examination confirmed presence of iron-containing cells and microspheres in corresponding segments of the heart. The distribution of microspheres was similar between the groups. Double contrast with cellular iron and Gd-DTPA in surrounding myocardium resulted in improved cell localization by MRI.