CEST MRI quantification procedures for breast cancer treatment‐related lymphedema therapy evaluation.

Purpose: To quantify chemical exchange saturation transfer contrast in upper extremities of participants with lymphedema before and after standardized lymphatic mobilization therapy using correction procedures for B0 and B1 heterogeneity, and T1 relaxation. Methods: Females with (n = 12) and without (n = 17) breast cancer treatment‐related lymphedema (BCRL) matched for age and body mass index were scanned at 3.0T MRI. B1 efficiency and T1 were calculated in series with chemical exchange saturation transfer in bilateral axilla (B1 amplitude = 2µT, Δω = ±5.5 ppm, slices = 9, spatial resolution = 1.8 × 1.47 × 5.5 mm3). B1 dispersion measurements (B1 = 1‐3 µT; increment = 0.5 µT) were performed in controls (n = 6 arms in 3 subjects). BCRL participants were scanned pre‐ and post‐manual lymphatic drainage (MLD) therapy. Chemical exchange saturation transfer amide proton transfer (APT) and nuclear Overhauser effect (NOE) metrics corrected for B1 efficiency were calculated, including proton transfer ratio (PTR'), magnetization transfer ratio asymmetry (MTRasymmetry′), and apparent exchange‐dependent relaxation (AREX'). Nonparametric tests were used to evaluate relationships between metrics in BCRL participants pre‐ versus post‐MLD (two‐sided P < 0.05 required for significance). Results: B1 dispersion experiments showed nonlinear dependence of Z‐values on B1 efficiency in the upper extremities; PTR' showed < 1% mean fractional difference between subject‐specific and group‐level correction procedures. PTR'APT significantly correlated with T1 (Spearman's rho = 0.57, P < 0.001) and body mass index (Spearman's rho = −0.37, P = 0.029) in controls and with lymphedema stage (Spearman's rho = 0.48, P = 0.017) in BCRL participants. Following MLD therapy, PTR'APT significantly increased in the affected arm of BCRL participants (pre‐ vs. post‐MLD: 0.41 ± 0.05 vs. 0.43 ± 0.03, P = 0.02), consistent with treatment effects from mobilized lymphatic fluid. Conclusion: Chemical exchange saturation transfer metrics, following appropriate correction procedures, respond to lymphatic mobilization therapies and may have potential for evaluating treatments in participants with secondary lymphedema. [ABSTRACT FROM AUTHOR]

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