title: A new assessment model for tumor heterogeneity analysis with [18]F-FDG PET images.
abstract: It has been shown that the intratumor heterogeneity can be characterized with quantitative analysis of the [18]F-FDG PET image data. The existing models employ multiple parameters for feature extraction which makes it difficult to implement in clinical settings for the quantitative characterization. This article reports an easy-to-use and differential SUV based model for quantitative assessment of the intratumor heterogeneity from 3D [18]F-FDG PET image data. An H index is defined to assess tumor heterogeneity by summing voxel-wise distribution of differential SUV from the [18]F-FDG PET image data. The summation is weighted by the distance of SUV difference among neighboring voxels from the center of the tumor and can thus yield increased values for tumors with peripheral sub-regions of high SUV that often serves as an indicator of augmented malignancy. Furthermore, the sign of H index is used to differentiate the rate of change for volume averaged SUV from its center to periphery. The new model with the H index has been compared with a widely-used model of gray level co-occurrence matrix (GLCM) for image texture characterization with phantoms of different configurations and the [18]F-FDG PET image data of 6 lung cancer patients to evaluate its effectiveness and feasibility for clinical uses. The comparison of the H index and GLCM parameters with the phantoms demonstrate that the H index can characterize the SUV heterogeneity in all of 6 2D phantoms while only 1 GLCM parameter can do for 1 and fail to differentiate for other 2D phantoms. For the 8 3D phantoms, the H index can clearly differentiate all of them while the 4 GLCM parameters provide complicated patterns in the characterization. Feasibility study with the PET image data from 6 lung cancer patients show that the H index provides an effective single-parameter metric to characterize tumor heterogeneity in terms of the local SUV variation, and it has higher correlation with tumor volume change after radiotherapy (R(2) = 0.83) than the 4 GLCM parameters (R(2) = 0.63, 0.73, 0.59 and 0.75 for Energy, Contrast, Local Homogeneity and Entropy respectively). The new model of the H index has the capacity to characterize the intratumor heterogeneity feature from 3D [18]F-FDG PET image data. As a single parameter with an intuitive definition, the H index offers potential for clinical applications.
authors.affiliation: Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, Tianjin, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Molecular Imaging and Nuclear Medicine, Tianjin Medical University Cancer Institute and Hospital, Tianjin, China.
authors.forename: Wengui
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, Tianjin, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, Tianjin, China; Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Chengwen
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Sa
authors.affiliation: Department of Biomedical Engineering, Tianjin University, Tianjin, China; Department of Physics, East Carolina University, Greenville, NC.
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: Hu
authors.affiliation: Department of Radiation Oncology, Tianjin Medical University Cancer Institute and Hospital, Tianjin, China; Department of Biomedical Engineering, Tianjin University, Tianjin, China.
authors.forename: Yuanming
authors.initials: Y
authors.lastname: Feng
keywords: [18]F-FDG PET image; gray level co-occurrence matrix; intratumor heterogeneity; standard uptake value