title: Radiomics Analysis on FLT-PET/MRI for Characterization of Early Treatment Response in Renal Cell Carcinoma: A Proof-of-Concept Study.
abstract: Studying early response to cancer treatment is significant for patient treatment stratification and follow-up. Although recent advances in positron emission tomography (PET) and magnetic resonance imaging (MRI) allow for evaluation of tumor response, a quantitative objective assessment of treatment-related effects offers localization and quantification of structural and functional changes in the tumor region. Radiomics, the process of computerized extraction of features from radiographic images, is a new strategy for capturing subtle changes in the tumor region that works by quantifying subvisual patterns which might escape human identification. The goal of this study was to demonstrate feasibility for performing radiomics analysis on integrated PET/MRI to characterize early treatment response in metastatic renal cell carcinoma (RCC) undergoing sunitinib therapy. Two patients with advanced RCC were imaged using an integrated PET/MRI scanner. [18 F] fluorothymidine (FLT) was used as the PET radiotracer, which can measure the degree of cell proliferation. Image acquisitions included test/retest scans before sunitinib treatment and one scan 3 weeks into treatment using [18 F] FLT-PET, T2-weighted (T2w), and diffusion-weighted imaging (DWI) protocols, where DWI yielded an apparent diffusion coefficient (ADC) map. Our framework to quantitatively characterize treatment-related changes involved the following analytic steps: 1) intraacquisition and interacquisition registration of protocols to allow voxel-wise comparison of changes in radiomic features, 2) correction and pseudoquantification of T2w images to remove acquisition artifacts and examine tissue-specific response, 3) characterization of information captured by T2w MRI, FLT-PET, and ADC via radiomics, and 4) combining multiparametric information to create a map of integrated changes from PET/MRI radiomic features. Standardized uptake value (from FLT-PET) and ADC textures ranked highest for reproducibility in a test/retest evaluation as well as for capturing treatment response, in comparison to high variability seen in T2w MRI. The highest-ranked radiomic feature yielded a normalized percentage change of 63% within the RCC region and 17% in a spatially distinct normal region relative to its pretreatment value. By comparison, both the original and postprocessed T2w signal intensity appeared to be markedly less sensitive and specific to changes within the tumor. Our preliminary results thus suggest that radiomics analysis could be a powerful tool for characterizing treatment response in integrated PET/MRI.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Ave, Wickenden 525, Cleveland, OH 44106. Electronic address: jacob.antunes@case.edu.
authors.forename: Jacob
authors.initials: J
authors.lastname: Antunes
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Ave, Wickenden 525, Cleveland, OH 44106.
authors.forename: Satish
authors.initials: S
authors.lastname: Viswanath
authors.affiliation: General Electric Global Research, 1 Research Cir, Niskayuna, NY 12309.
authors.forename: Mirabela
authors.initials: M
authors.lastname: Rusu
authors.affiliation: Department of Radiology, Case Western Reserve University, Case Center for Imaging Research, 11000 Euclid Ave, Cleveland, OH 44106.
authors.forename: Laia
authors.initials: L
authors.lastname: Valls
authors.affiliation: Department of Medicine, University Hospitals Seidman Cancer Center at the Case Comprehensive Cancer Center, 11000 Euclid Ave, Cleveland, OH 44106.
authors.forename: Christopher
authors.initials: C
authors.lastname: Hoimes
authors.affiliation: Department of Medicine, University Hospitals Seidman Cancer Center at the Case Comprehensive Cancer Center, 11000 Euclid Ave, Cleveland, OH 44106.
authors.forename: Norbert
authors.initials: N
authors.lastname: Avril
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Ave, Wickenden 525, Cleveland, OH 44106.
authors.forename: Anant
authors.initials: A
authors.lastname: Madabhushi