A rapid T₁ mapping method for assessment of murine kidney viability using dynamic manganese-enhanced magnetic resonance imaging

Purpose: Dynamic manganese-enhanced MRI (MEMRI) allows assessment of tissue viability by tracing manganese uptake. We aimed to develop a rapid T₁ mapping method for dynamic MEMRI to facilitate assessments of murine kidney viability. Methods: A multi-slice saturation recovery fast spin echo (MSRFSE) was developed, validated, and subsequently applied in dynamic MEMRI at 16.4T on ischemic mouse kidneys after 4 weeks of unilateral renal artery stenosis (RAS). Baseline T₁ values and post-contrast R₁ (1/T₁) changes were measured in cortex (CO), outer (OSOM), inner (ISOM) strips of outer medulla, and inner medulla (IM). Results: Validation studies showed strong agreement between MSRFSE and an established saturation recovery Look-Locker method. Baseline T₁ (s) increased in the stenotic kidney CO (2.10 [1.95–2.56] vs. 1.88 [1.81–2.00], P = 0.0317) and OSOM (2.17 [2.05–2.33] vs. 1.96 [1.87–2.00], P = 0.0075) but remained unchanged in ISOM and IM. This method allowed a temporal resolution of 1.43 min in dynamic MEMRI. Mn²⁺ uptake and retention decreased in stenotic kidneys, particularly in the OSOM (ΔR₁: 0.48 [0.38–0.56] vs. 0.64 [0.61–0.69] s⁻¹, P < 0.0001). Conclusion: Dynamic MEMRI by MSRFSE detected decreased cellular viability and discerned the regional responses to RAS. This technique may provide a valuable tool for noninvasive evaluation of renal viability. Magn Reson Med 80:190–199, 2018.