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Introduction: In this study, we aimed to investigate the feasibility of gadoxetate low-temporal resolution (LTR) DCE-MRI for voxel-based hepatic extraction fraction (HEF) quantification for liver sparing radiotherapy using a deconvolution analysis (DA) method. Methods: The accuracy and consistency of the deconvolution implementation in estimating liver function was first assessed using simulation data. Then, the method was applied to DCE-MRI data collected retrospectively from 64 patients (25 normal liver function and 39 cirrhotic patients) to generate HEF maps. The normal liver function patient data were used to measure the variability of liver function quantification. Next, a correlation between HEF and ALBI score (a new model for assessing the severity of liver dysfunction) was assessed using Pearson's correlation. Differences in HEF between Child-Pugh score classifications were assessed for significance using the Kruskal-Wallis test for all patient groups and Mann-Whitney U-test for inter-groups. A statistical significance was considered at a P-value <0.05 in all tests. Results: The results showed that the implemented method accurately reproduced simulated liver function; root-mean-square error between estimated and simulated liver response functions was 0.003, and the coefficient-of-variance of HEF was <20%. HEF correlation with ALBI score was r = -0.517, P < 0.0001, and HEF was significantly decreased in the cirrhotic patients compared to normal patients (P < 0.0001). Also, HEF in Child-Pugh B/C was significantly lower than in Child-Pugh A (P = 0.024). Conclusion: The study demonstrated the feasibility of gadoxetate LTR-DCE MRI for voxelbased liver function quantification using DA. HEF could distinguish between different grades of liver function impairment and could potentially be used for functional guidance in radiotherapy. [ABSTRACT FROM AUTHOR]

Introduction: Tumour recurrences after treatment of head and neck squamous cell carcinoma (HNSCC) are more likely to originate from regions of high‐baseline FDG‐PET uptake. Mid‐treatment functional imaging can potentially predict for higher risk of tumour recurrence. The aim of this study is to correlate the location of locoregional tumour recurrence with baseline FDG‐PET metabolic volumes and mid‐treatment FDG‐PET metabolic volumes in patients with HNSCC following definitive radiotherapy. Methods: A total of 23 patients with 26 local and/or regional recurrences underwent baseline (W0‐PET) and mid‐treatment (W3‐PET) 18F‐FDG PET scans as part of their radiotherapy. FDG‐PET‐based metabolic volumes (MTV20%, MTV40%, MTV60%, MTV80%, SUV2.5, SUVpeak and PET_EDGE) were delineated onto the FDG‐PET scans. The recurrence nidus was identified on FDG‐PET at the time of recurrence (REC‐PET). DIR‐based fusion was performed for REC‐PET to W0‐PET, and REC‐PET to W3‐PET. The location of the recurrence nidus was correlated with the FDG‐PET volumes. Further analysis included a comparison of the recurrence density to FDG‐PET metabolic volumes. Results: Most recurrences occurred within the MTV20%, MTV40% and SUV 2.5 volumes. Sixty‐nine per cent of recurrences (18 of 26) occurred within both the W0 MTV40% and W3 MTV40% volumes. A higher recurrence density was seen for iso‐SUV contours closer to the maximum SUV for both W0 and W3. For a number of the FDG‐PET volumes, including MTV20%, MTV40% and SUV2.5, the recurrence density was improved for W3 compared to W0, however, this improvement was small in magnitude. The average volume of MTV40% contours was considerably smaller than MTV20% and SUV2.5 contours. Conclusion: The metabolic parameters of SUV2.5, MTV20% and MTV40% delineated on the baseline and mid‐treatment FDG‐PET scans encompassed the majority of recurrences. The MTV40% is significantly smaller, hence, we prefer this volume for future dose escalation studies. [ABSTRACT FROM AUTHOR]