Quantitative sodium MR imaging of native versus transplanted kidneys using a dual-tuned proton/sodium (¹H/²³Na) coil: Initial experience

Objectives: To compare sodium (²³Na) characteristics between native and transplanted kidneys using dual-tuned proton (¹H)/sodium MRI. Methods: Six healthy volunteers and six renal transplant patients (3 normal function, 3 acute allograft rejection) were included. Proton/sodium MRI was obtained at 3 T using a dual-tuned coil. Signal to noise ratio (SNR), sodium concentration ([²³Na]) and cortico-medullary sodium gradient (CMSG) were measured. Reproducibility of [²³Na] measurement was also tested. SNR, [²³Na] and CMSG of the native and transplanted kidneys were compared. Results: Proton and sodium images of kidneys were successfully acquired. SNR and [²³Na] measurements of the native kidneys were reproducible at two different sessions. [²³Na] and CMSG of the transplanted kidneys was significantly lower than those of the native kidneys: 153.5±11.9 vs. 192.9±9.6 mM (P =0.002) and 8.9±1.5 vs. 10.5±0.9 mM/mm (P =0.041), respectively. [²³Na] and CMSG of the transplanted kidneys with normal function vs. acute rejection were not statistically different. Conclusions: Sodium quantification of kidneys was reliably performed using proton/sodium MRI. [²³Na] and CMSG of the transplanted kidneys were lower than those of the native kidneys, but without a statistically significant difference between patients with or without renal allograft rejection. Key Points: • Dual-tuned proton/sodium RF coil enables co-registered proton and sodium MRI. • Structural and sodium biochemical property can be acquired by dual-tuned proton/sodium MRI. • Sodium and sodium gradient of kidneys can be measured by dual-tuned MRI. • Sodium concentration was lower in transplanted kidneys than in native kidneys. • Sodium gradient of transplanted kidneys was lower than for native kidneys.