Magnetic Resonance Elastography as Surrogate Marker of Interstitial Fibrosis in Kidney Transplantation: A Prospective Study.

Background: Fibrosis progression is a major prognosis factor in kidney transplantation. Its assessment requires an allograft biopsy, which remains an invasive procedure at risk of complications. Methods: We assessed renal stiffness by magnetic resonance elastography (MRE) as a surrogate marker of fibrosis in a prospective cohort of kidney transplant recipients compared with the histologic gold standard. Interstitial fibrosis was evaluated by three methods: the semi-quantitative Banff ci score, a visual quantitative evaluation by a pathologist, and a computer-assisted quantitative evaluation. MRE-derived stiffness was assessed at the superior, median, and inferior poles of the allograft. Results: We initially enrolled 73 patients, but only 55 had measurements of their allograft stiffness by MRE before an allograft biopsy. There was no significant correlation between MRE-derived stiffness at the biopsy site and the ci score (ρ=-0.25, P=0.06) or with the two quantitative assessments (pathologist: ρ=-0.25, P=0.07; computer assisted: ρ=-0.21, P=0.12). We observed negative correlations between the stiffness of both the biopsy site and the whole allograft, with either the glomerulosclerosis percentage (ρ=-0.32, P=0.02 and ρ=-0.31, P=0.02, respectively) and the overall nephron fibrosis percentage, defined as the mean of the percentages of glomerulosclerosis and interstitial fibrosis (ρ=-0.30, P=0.02 and ρ=-0.28, P=0.04, respectively). At patient level, mean MRE-derived stiffness was similar across the three poles of the allograft (±0.25 kPa). However, a high variability of mean stiffness was found between patients, suggesting a strong influence of confounding factors. Finally, no significant correlation was found between mean MRE-derived stiffness and the slope of eGFR (P=0.08). Conclusions: MRE-derived stiffness does not directly reflect the extent of fibrosis in kidney transplantation.

Magnetic resonance texture parameters are associated with ablation efficiency in MR-guided high-intensity focussed ultrasound treatment of uterine fibroids.

OBJECTIVES: The objective of this study is to assess the association between texture parameter analysis derived from T2-weighted images and efficiency of magnetic resonance-guided focussed ultrasound (MRgFUS) ablation for the treatment of uterine fibroids. MATERIALS AND METHODS: Fifty-five women treated by MRgFUS were included in this retrospective analysis. Texture parameters were calculated using three 2D regions of interest placed on three consecutive slices on the same sagittal 3D T2-weighted images obtained at the beginning of MRgFUS ablation. Using uni- and multi-variate linear regression, texture parameters, fibroids/muscular T2W ratio (T2Wr), Funaki type, and fibroid depth were correlated with ablation efficiency, defined as the ratio of non-perfused volume (NPV) on post-treatment contrast-enhanced MRI by total volume of treatment-cell sizes used. Inter-rater reproducibility for texture analysis was assessed using variation coefficients. RESULTS: The mean total treatment cell volume was 49.5 (±30) ml, corresponding to a mean NPV of 57.2 (±57) ml (28%). The mean ablation efficiency was 1.14 (±0.7), with a range of 0.03-3.6. In addition to fibroid/muscular T2Wr, seven of the 14 texture parameters were significantly correlated with ablation efficiency: mean signal intensity (p = .047); Skewness (p = .03); Kurtosis (p = .015); mean uniformity (p = .052); mean sum of square (p = .045); mean sum entropy (p = .021) and mean entropy (p = .051). In multivariate linear regression, fibroid/muscular T2Wr and sum of entropy were associated with ablation efficiency. The inter-rater coefficient of variation for sum entropy was 2.6%. CONCLUSIONS: Uterine fibroid texture parameters provide complementary information to T2Wr, and are associated with MRgFUS efficiency. Key points Mean sum entropy is negatively correlated with MRgFUS efficiency (ρ = -0.307, p = .021). Fibroids/muscular T2-weighted ratio and entropy are associated with MRgFUS efficiency. Texture parameters are better predictors of MRgFUS efficiency than Funaki type. Fibroid MR texture analysis can improve patient selection for MRgFUS.

Magnetic resonance-guided high-intensity focused ultrasound for uterine fibroids: Mid-term outcomes of 36 patients treated with the Sonalleve system.

OBJECTIVES: This study sought to assess the mid-term efficacy of magnetic resonance-guided high-intensity focused ultrasound (MRgFUS) (Sonalleve system) for uterine fibroids. METHODS: We retrospectively included patients treated by MRgFUS controlled by real-time MR-thermometry. Clinical efficacy was defined as the minimum reduction of ten points in the Transformed Symptom Severity Score (tSSS) without additional treatment. Fibroid volumes were assessed at 6 months, and patients were contacted to assess mid-term efficacy using tSSS. RESULTS: Thirty-six patients were included; 22 patients (61.1%) exhibited clinical efficacy with a mean follow-up duration of 21.4 (95%CI: 16.3-26.5) months. In addition, the tSSS mean decreased significantly from 42.8 ± 16 to 25.4 ± 18 (p < 0.0001). MRgFUS exhibited a preferential effect on menorrhagia (p = 0.001) and symptoms related to pelvic heaviness and swelling (p = 0.004). The volume reduction was 27% (p < 0.001) and was correlated with the non-perfused volume (NPV) after treatment (r = 0.373; p = 0.028). Cumulative re-intervention rates (surgery or uterine artery embolisation) at 12 months, 18 months and 24 months were 2.8%, 8.5% and 21.6%, respectively. No serious adverse events were reported. Two pregnancies occurred during the follow-up period. CONCLUSIONS: Treatment of uterine fibroids by MRgFUS is efficient and results in low morbidity and satisfactory clinical efficacy with a mean follow-up of 21.4 months.