Volumetric perfusion fraction change in MR angiography for monitoring sclerotherapy-related changes in peripheral venous malformations.

Background In venous malformations (VMs), postprocedural edema on T2-weighted (T2w) MRI can obscure true post-treatment changes, making reliable posttherapeutic imaging-based monitoring challenging. Current MRI evaluation is often qualitative and center-dependent, underscoring the need for standardized quantitative parameters.Methods We retrospectively analyzed patients with VMs treated at our hospital between 2018 and 2022 who underwent MRI with MR angiography (MRA) before and after ethanol sclerotherapy. VM volume was calculated from diameters measured in two orthogonal planes on T2w and MRA images. A new parameter, volumetric perfusion fraction (VPF), was calculated as the ratio of perfused MRA volume to total T2w volume. Parameters were compared using comparative tests and receiver operating characteristic (ROC) analysis reflecting each parameter's ability to distinguish baseline from post-sclerotherapy images.Results Thirty-six patients with VMs were included (median age 21 years; 7 - 59 years; 24 female; 66.7 %). Total malformation volume on T2w images decreased by 9.0 % (45.4 mL; 0.6 - 801.9 mL vs 30.9 mL; 0.1 - 802.4 mL; p = 0.056) after therapy, whereas perfused MRA volume decreased by 87.4 % (26.1 mL; 0.5 - 643.6 mL vs 4.5 mL; 0.0 - 352.4 mL; p < 0.001). VPF decreased by 68.1 % (74.0 %; 10.1 - 131.7 % vs 18.2 %; 0.0 - 85.3 %; p < 0.001) despite considerable interindividual variability. ROC analysis showed the strongest effect for VPF, with an area under the curve (AUC) of 0.91 (p < 0.001), followed by MRA-derived diameter and volume (AUC 0.75 and 0.79; both p < 0.001). T2w MRI parameters showed the lowest effect (AUC 0.57; p = 0.30).Conclusion VPF showed the strongest discrimination of treatment effects compared with MRA and T2w measures. It may serve as a robust and objective MRI parameter for monitoring therapy-related changes in clinical routine and future trials.