Background Amyloid positron emission tomography (PET) can measure in-vivo demyelination in patients with multiple sclerosis (MS). However, the value of 18 F-labeled amyloid PET tracer, 18 F-florbetapir in the longitudinal study for monitoring myelin loss and recovery has not been confirmed. Methods From March 2019 to September 2020, twenty-three patients with MS and nine healthy controls (HCs) underwent a hybrid PET/MRI at baseline and expanded disability status scale (EDSS) assessment, and eight of 23 patients further underwent follow-up PET/MRI. The distribution volume ratio (DVR) and standard uptake value ratio (SUVR) of 18 F-florbetapir in damaged white matter (DWM) and normal-appearance white matter (NAWM) were obtained from dynamic and static PET acquisition. Diffusion tensor imaging-derived parameters were also calculated. Data were expressed as mean ± standard deviation with 99% confidence interval (99%CI). Finding The mean DVR (1.08 ± 0.12, 99%CI [1.02 ~ 1.14]) but not the mean SUVR of DWM lesions was lower than that of NAWM in patients with MS (1.25 ± 0.10, 99%CI [1.20 ~ 1.31]) and HCs (1.29 ± 0.08, 99%CI [1.23 ~ 1.36]). A trend toward lower mean fractional anisotropy (374.95 ± 45.30 vs. 419.07 ± 4.83) and higher mean radial diffusivity (0.45 ± 0.05 vs. 0.40 ± 0.01) of NAWM in patients with MS than those in HCs was found. DVR decreased in DWM lesions with higher MD (rho = -0.261, 99%CI [-0.362 ~ -0.144]), higher AD (rho = -0.200, 99%CI [-0.318 ~ -0.070]) and higher RD (rho = -0.198, 99%CI [-0.313 ~ -0.075]). Patients’ EDSS scores were reduced ( B = 0.04, 99%CI [-0.005 ~ 0.084]) with decreased index of global demyelination in the longitudinal study. Interpretation Our exploratory study suggests that dynamic 18 F-florbetapir PET/MRI may be a very promising tool for quantitatively monitoring myelin loss and recovery in patients with MS. Funding Shanghai Pujiang Program, Shanghai Municipal Key Clinical Specialty, Shanghai Shuguang Plan Project, Shanghai Health and Family Planning Commission Research Project, Clinical Research Plan of SHDC, French-Chinese program "Xu Guangqi".

Background: Single photon emission computed tomography (SPECT) images provides functional information in both diagnosis and radiation therapy. This study aimed to evaluate a unified framework of different approaches and find the optimal one in integrating SPECT lung perfusion imaging into radiotherapy to estimate radiation pneumonitis.Methods: Twenty-five patients with thoracic tumors were included in this study. All patients had SPECT perfusion imaging before radiotherapeutic treatment. The SPECT images were registered to the planning computed tomography (CT) via a rigid-body transformation. Then a unified framework was presented to integrate functional information with anatomical information to generate functional dose-volume parameters. The framework contained different mapping approaches using uniform, thresholding, linear or non-linear functions. To compare the different approaches in the unified framework, the ability of predicting lung toxicity outcome was evaluated via the receiver operating characteristic (ROC) curve analysis.Results: Functional dose-volume metrics defined using the linear function achieves the highest value of area under the curve (AUC), compared to those defined with the other three types of mapping functions. With the linear mapping function, significant factors for predicting radiation pneumonia (p < 0.05) includes the functional mean lung dose (fMLD) with the threshold of 50-100% and lung volume receiving more than 30 Gy dose (fV_30) with the threshold of 60-100%, among which fMLD showed the highest prediction accuracy (AUC=0.772, threshold=50-100%). Conclusions: We proposed a framework of functional dose-volume metrics to predict the outcome of radiation pneumonitis. The metrics using the linear function outperform the others.

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