Perfusional deficit and the dynamics of cerebral edemas in experimental traumatic brain injury using perfusion and diffusion-weighted magnetic resonance imaging.

The aim of this work was to characterize edema dynamics, cerebral blood volume, and flow alterations in an experimental model of brain trauma using quantitative diffusion and perfusion magnetic resonance imaging (MRI). Associated with an influx of water in the intracellular space 1-5 h post-trauma as demonstrated by the 40% reduction in apparent diffusion coefficient, a 70-80% reduction in cerebral blood flow was measured within the lesioned region. Transient hypoperfusion (40-50%) was also observed in the non-traumatized contralateral hemisphere, although there was no evidence of edema formation. After the initial cytotoxic edema, a clear evolution toward extracellular water accumulation was observed, demonstrated by an increase in apparent diffusion coefficient.

Correlations between MR and endothelial hyperplasia in low-grade gliomas.

PURPOSE: To investigate the capacity of multimodal MR to detect endothelial hyperplasia (EH), which has been linked to the aggressiveness of gliomas and which is so far only detected by biopsy, an invasive technique that prevents repeated measurements and early detection. MATERIALS AND METHODS: A total of 26 patients with low-grade gliomas participated in the study. All underwent a histopathological analysis and a multimodal MR examination (spectroscopic, anatomic, diffusion, perfusion, and postcontrast imaging). RESULTS: EH was present (EH+) in 15 patients and absent (EH-) in 11. No differences were observed between EH- and EH+ groups when comparing spectroscopic and diffusion parameters. Perfusion measurements, however, allowed us to distinguish EH+ from EH-: the relative regional cerebral blood flow (rCBF) was found equal to 3.23 +/- 2.05 for EH+ and 1.33 +/- 0.46 for EH- (P = 0.006). CONCLUSION: We have observed a strong correlation between the presence of EH and the increase of rCBF. Compared to conventional imaging, MR perfusion provides additional and complementary information that may be used for biopsy guidance, early detection of tumor aggressiveness, and noninvasive follow-ups.

NOS substrate during cardioplegic arrest and cold storage decreases stunning after heart transplantation in a rat model.

BACKGROUND: In this study, we evaluated how adding L-arginine to Centre de Résonance Magnétique Biologique et Médicale (CRMBM) solution affected myocardial performance during post-ischemic in vivo reperfusion. METHODS: Experiments were conducted using a modified Lewis-Lewis heterotopic heart transplantation model, with a total ischemic time of 3 hours followed by 1 or 24 hours of blood reperfusion. Heart grafts were arrested using intra-aortic injection of CRMBM solution, either supplemented or not supplemented with 2 mmol/liter L-arginine (n = 12 in each group). We measured systolic indexes and simultaneously performed phosphorus magnetic resonance spectroscopy ((31)P MRS). We quantified total endothelial nitric oxide synthase (eNOS) protein using the Western blot test of freeze-clamped hearts. RESULTS: Contractility during early reperfusion was significantly better in grafts arrested with CRMBM solution enriched with L-arginine: mean rate pressure product, 11249 +/- 1548 vs 5637 +/- 1118 mm Hg/min (p = 0.05), and maximal first derivative of the pressure signal (dP/dt(max)), 1721 +/- 177 vs 1214 +/- 321 mm Hg/sec (p = 0.013). Conversely, during late reperfusion, contractility did not relate to the nature of the preservation solution. The presence of L-arginine in the CRMBM solution did not alter time-related variations of high-energy phosphate ratios measured using in vivo (31)P MRS. The eNOS protein level decreased significantly during early compared with late reperfusion, with no effect caused by L-arginine. CONCLUSIONS: During early reperfusion, the limited myocardial stunning observed with CRMBM solution containing L-arginine does not relate to energy metabolism but to better preservation of the NO pathway.

Objective and noninvasive metabolic characterization of donor hearts by phosphorous-31 magnetic resonance spectroscopy.

OBJECTIVE: The authors performed a multi-institutional, prospective, blind study on hearts from local donors to validate the feasibility and accuracy of the metabolic evaluation of human hearts by phosphorus-31 ( P) magnetic resonance spectroscopy (MRS) before transplantation. METHODS: Twenty-one hearts were separated into two groups according to a transplantation score (TS) on the basis of the current clinical and echocardiographic evaluation as follows: TS1 (n=7), grafts for United Network for Organ Sharing (UNOS) 1 patients only; and TS2 (n=14), grafts suitable for UNOS 2 patients. All hearts were cold preserved with Celsior and underwent ex situ P MRS to measure ratios of various high-energy phosphate metabolites and the intracellular pH (pHi). RESULTS: The total duration of the MRS procedure was 32 min, thereby not unacceptably increasing the total ischemic time for the transplanted grafts. Phosphocreatine (PCr) and inorganic phosphate (Pi ) was significantly different between the two groups (0.95+/-0.29 for TS1 and 2.05+/-0.74 for TS2). The difference in pHi was also significant (7.44+/-0.13 for TS1 and 7.64+/-0.19 for TS2). CONCLUSIONS: Determination of PCr-Pi and pHi as markers of ischemic injury before transplantation can be considered as an objective and accurate criterion for the decision to accept or refuse heart grafts for transplantation.