Investigation of Endogenous Renal CEST Contrast and the Influence of Respiratory Motion on a Clinical 3 Tesla MRI: An...

The aim is to evaluate the effectiveness of timed breathing in reducing respiratory motion artifacts in renal chemical exchange saturation transfer (CEST) MRI and to assess potential differences in CEST effects between renal compartments.

An electro-pneumatic phantom with a kidney CEST model simulated variable respiratory motion and sequence-synchronized breathing. Motion-induced deviations from a static reference were quantified using the mean absolute error (MAE). Ten healthy volunteers (six females, four males; 25.2 ± 1.9 years) and one patient (47 years) with ccRCC (3.0 × 2.2 × 2.2) cm³ were examined on a 3 T MRI system using a multi-echo gradient echo sequence with 15 Gaussian-shaped saturation pulses (B₁ = 1.5 μT, t_p = t_ipd = 100 ms). CEST effects in cortex, medulla, and pelvis at 1.0, 2.0, and 3.5 ppm were quantified by MTR_asym analysis under timed and free-breathing conditions.

Timed breathing reduced motion artifacts in both phantom and in vivo data. MTR_asym analysis exhibits visibly distinguishable and significantly different (p < 0.05) CEST effects in renal compartments, with increased MTR_asym values of (0.78% ± 0.41%) at 1.0 ppm in the cortex, (1.43% ± 0.70%) at 2.0 ppm in the medulla, and (-2.02% ± 0.84%) at 3.5 ppm in the pelvis. Significant differences (p < 0.05) in MTR_asym values were observed between the patient and the healthy cohort.

Timed breathing improves renal CEST MRI by reducing motion artifacts and enabling detection of compartment-specific CEST effects, highlighting its potential for biochemical characterization of renal tissue in clinical applications.