Sheen-Woo Lee MD, Abstract Co-Author: Nothing to Disclose

Edward E. Graves PhD, Abstract Co-Author: Nothing to Disclose

Tae Joo Jeon MD,PhD, Abstract Co-Author: Nothing to Disclose

Sang Hoon Lee MD, PhD, Abstract Co-Author: Nothing to Disclose

Garry Evan Gold MD, MSEE, Abstract Co-Author: Nothing to Disclose

Sandip Biswal MD, Presenter: Nothing to Disclose

Manganese (Mn)-enhanced MRI is a method to interrogate the central nervous system. Mn can be used as an MR contrast agent as it enters active neuronal cells through voltage-gated calcium channels and is a T1 shortening agent. We aim to validate MEMRI for detection of active areas in the spinal cord related to nociception.

Animal experiments were approved by Stanford IACUC. A model of painful inflammation was created by intradermal injection of 50ul of Complete-Freund’s Adjuvant in the left forepaw of Sprague-Dawley rats. Experimental and control animals were then injected intraperitoneally with manganese chloride (30mM). The spinal cord was scanned with a volume coil in a 3T and 4.7T magnet 24 hours after MnCl2 administration. Gradient echo images (TR/TE/Flip angle 800/15ms/15º, in-plane resolution 234µm2) were taken for anatomical analysis of the spinal cord. T1 was mapped using sagittal T1-weighted FSE IR (TR/TE/TI = 3000/7.4/50, 100, 200, 500, 800, 1200, and 2100 ms, in-plane resolution 391µm2, slice thickness 2mm). CMIR_Image analysis software was used to place ROIs on spinal cord to quantify the degree of Mn enhancement. T1 measurements were adjusted according to administered dose, animal weight and background levels. The Mn2+ content in the harvested cord was measured by inductive coupled plasma (ICP). The data was analyzed with student t-test on Excel spreadsheet (N=8).

Pain group showed increased enhancement in the cervical cord compared to the control. The corrected T1 value of the cervical cord in the pain group was shorter than the control (22.67±4.02 vs 24.11± 2.52 respectively, p<0.05). By ICP, the cervical cord Mn was relatively higher in the pain group than the control (38.6±9.21 vs 24.0±5.30, p<0.05).

Animals with pain and inflammation in the forepaw show increased Mn uptake in the cervical cord on MRI in vivo, which correlates with the measured in vitro Mn content. MEMRI is a promising modality for showing the pain-activated sensorineural pathway in the spinal cord.

Abnormal neuronal pain pathway will be identified in chronic pain patients. Pain sensation will be objectively quantified for adequate therapy.

Lee, S, Graves, E, Jeon, T, Lee, S, Gold, G, Biswal, S, Manganese-enhanced Magnetic Resonance Imaging (MEMRI) Detects Changes in the Spinal Cord Following Painful Stimuli.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5016459.html