Real-time multislice MR-thermometry of the prostate: Assessment of feasibility, accuracy and sources of biases in patients

•Two-dimensional multislice MR-thermometry with an in-plane spatial resolution of 1.5 mm is precise enough for monitoring focal thermotherapy at both 1.5 T and 3 T.•The proportion of noisy voxels (temporal standard deviation of temperature ≥ 2°C) per prostate is not associated with technical and clinical variables.•The proportion of noisy voxels (temporal standard deviation of temperature ≥ 2°C) per prostate is not influenced by the presence of PI-RADS-4 and PI-RADS-5 nodules. The primary purpose of this study was to evaluate the accuracy of an MR-thermometry sequence for monitoring prostate temperature. Secondary purposes were to analyze clinical and technical factors that may affect accuracy and testing the method in a realistic setting, with MR-guided Laser ablation on an ex vivo muscle sample. An ex vivo muscle sample was subjected to Laser ablation while using a two-dimensional multislice segmented echo planar imaging sequence for MR thermometry. The MR thermometry measurements were compared with invasive sensor temperature readings to assess accuracy. Subsequently, 56 men with a median age of 70 years (range: 53–84 years) who underwent prostate MRI examinations at 1.5- (n = 27) or 3 T (n = 24) were prospectively included. For each patient, the proportion of 'noisy voxels' (i.e., those with a temporal standard deviation of temperature [SD(T)] > 2 °C) in the prostate was calculated. The impact of clinical and technical factors on the proportion of noisy voxels was also examined. MR-thermometry showed excellent correlation with invasive sensors during MR-guided Laser ablation on the ex vivo muscle sample. The median proportion of noisy voxels per patient in the entire cohort was 1% (Q1, 0.2; Q3, 4.9; range: 0–90.4). No significant difference in median proportion of noisy voxels was observed between examinations performed at 1.5 T and those at 3 T (P = 0.89 before and after adjustment) No clinical or technical factors significantly influenced the proportion of noisy voxels. Two-dimensional real time multislice MR-thermometry is feasible and accurate for monitoring prostate temperature in patients.