The alterations of magnetic resonance relaxation parameters in excised myocardial tissue during NMR spectroscopy: The effects of time, environmental exposure and TTC staining

Abstract

To investigate the potential impact of air exposure, time delay and vital tissue staining on the MR relaxation parameters in normal and pathological heart tissues, myocardial samples from a canine model of myocardial infarction were subject to (a) air exposure for up to 20 hours or (b) wrapping in Parafilm for up to 20 hours; immersion in (c) full strength pathological stain consisting of triphenyl tetrazolium chloride (TTC), or (d) half strength TTC, or (e) normal saline for 30 minutes. We found that (a) exposure to air produced rapid changes in both T 1 and T 2 such that there is a reduction of T 1 by 12.2% and T 2 by 14.4% ( p < 0.001) in one hour; (b) airtight wrapping attenuated dramatically these changes, but T 1 still was reduced by 2.9% and T 2 by 4.8% in one hour ( p < 0.01). These changes followed similar but non-linear changes of tissue water content. T 1 did not change significantly after exposure to full strength TTC, but did increase significantly after exposure to half strength TTC, and increased even further after exposure to saline. T 2 on the other hand increased significantly with all of these test solutions. We conclude that the in vitro processing of excised myocardial tissues should be done by wrapping in an airtight container with T 1 and T 2 parameters measured within one hour, if possible. All tissue processing, including stains and saline exposure, should be done after spectrometer measurements.