Feasibility of MRI based oxygenation imaging for the assessment of acute limb ischemia.

BACKGROUND: Acute limb ischemia (ALI) can lead to death and amputation. Evaluating the severity of ischemia is important but difficult, through current methods of examination. The purpose of this research was to demonstrate the feasibility of magnetic resonance imaging (MRI) susceptibility-based imaging techniques for use in assessing muscle oxygenation alterations in ALI. METHODS: ALI animal models were established in 11 rabbits. Their left iliac arteries were embolized by microspheres. MRI scans were conducted 24 hours before (Pre) and 1 hour (Post 1) and 3 hours (Post 2) after the procedure. A susceptibility model was used to calculate skeletal muscle oxygenation extraction fraction (SMOEF) and relaxation rate (R2'). T2 weighted (T2w) imaging and diffusion-weighted (DW) imaging were performed. RESULTS: The average calf muscle SMOEF in the embolized hindlimbs increased from 0.43±0.02 (Pre) to 0.48±0.02 (Post 1) and 0.50±0.02 (Post 2), both P<0.05. The R2' value increased from 13.01±2.31 s-1 (Pre) to 16.78±2.28 s-1 (Post 1) and 17.90±3.29 s-1 (Post 2), both P<0.05. No significant changes of SMOEF and R2' were found after embolization in the contralateral hindlimbs. Apparent diffusion coefficient (ADC) values derived from DW imaging remained unchanged at different stages compared to before the procedures (all P>0.05). No abnormal signals were observed in the anatomical T2w images at Post 1 and Post 2. CONCLUSIONS: This study demonstrates the feasibility of using SMOEF for the assessment of oxygenation alterations in ALI models. SMOEF is more sensitive than T2w and DW imaging in detecting acute muscle ischemia at an early stage.

A feasibility study of using noninvasive renal oxygenation imaging for the early assessment of ischemic acute kidney injury in an embolization model.

PURPOSE: To investigate the feasibility of using MRI based oxygenation imaging for early assessment of ischemic acute kidney injury (AKI) in an embolization model. METHODS: Ischemic AKI model was induced in 40 rabbits by injection of microspheres into the right renal arteries. Animals were grouped according to the dose of microspheres: Severe AKI group, 2.0 mg (N = 10); Moderate AKI group, 1.0 mg (N = 10); Mild AKI group, 0.5 mg (N = 10); Control group, saline without microspheres (N = 10). A serial MRI examination was performed at intervals of 1 h, 1 day, 1 week and 4 weeks to evaluate the deterioration of renal function. A multi-echo ASE sequence was implemented for renal oxygenation measurement 1 h after surgery. Pathological examinations were performed 4 weeks after the surgery. RESULTS: In renal cortex, renal oxygen extraction fraction (OEF) raised significantly after embolization procedures in all experimental groups (severe AKI: 0.39 ±â€¯0.05, P < 0.05; moderate AKI: 0.36 ±â€¯0.03, P < 0.05; mild AKI: 0.34 ±â€¯0.02, P < 0.05) compared to the control group (0.29 ±â€¯0.02). In outer medulla, significant difference was observed between control group (0.29 ±â€¯0.03) and severe AKI group (0.35 ±â€¯0.03, P < 0.05), and between control group and moderate AKI group (0.34 ±â€¯0.04, P < 0.05). Corresponding lesions were found in pathological examinations 4 weeks after the procedure. CONCLUSION: This study demonstrates the feasibility of using oxygenation imaging to assess the embolization induced ischemic AKI at an early stage.

Plaque distribution in common femoral artery bifurcations, based on multi-slice computed tomography assessment.

PURPOSE: The aim of this study was to observe the exact plaque distribution at the common femoral artery bifurcation by multi-slice computed tomography angiography and to examine the relationship between plaque distribution and carina location. METHODS: Symptomatic outpatients who underwent multi-slice computed tomography angiography between May 2013 and February 2015 were enrolled in this study. The presence and distribution of atherosclerotic plaques were assessed in cross section views of vessel lumen. Each vessel lumen cross section was divided into four equal quadrants for the common femoral, superficial femoral and profunda femoral arteries. The quadrant of the superficial femoral artery in which the carina was located was also recorded. RESULTS: In total, 184 common femoral artery bifurcations in 92 patients were analyzed. Normal arteries were more common in profunda femoral arteries than in common femoral arteries and superficial femoral arteries (both P< 0.001). Plaques were found more medial and posterior quadrants in common femoral arteries. In superficial femoral arteries, plaques were found most frequently in anterior quadrants (78.3%, n=144) and least frequently in posterior quadrants (49.5%, n=91). The carina was located in the posterior quadrant in 160 bifurcations (87.0%) of superficial femoral arteries. Quadrants opposite the carina contained plaque most proportionally (77.2%) and quadrants of carina were affected least proportionally (52.7%) in superficial femoral arteries (P.