Abstract
BACKGROUND: Pathophysiological changes affect tissue cell composition and density. For example, neurodegenerative disorders and brain tumors are associated with cell loss and abnormal accumulation, respectively. In these scenarios, if monitored and tracked, tissue cellularity might be used to inform clinical diagnosis and management. PURPOSE: To propose and evaluate a new marker of tissue cellularity, called susceptibility-Derived Cellularity Index (χDCI), that would be readily available for clinical applications with fast acquisition and at high resolution. STUDY TYPE: Retrospective study. POPULATION/SUBJECTS: 24 healthy subjects (7/17 M/F, 70 ± 11 years) and 21 patients with IDH-wild type glioblastoma (16/5 M/F, 65 ± 8 years). FIELD STRENGTH/SEQUENCE: 3 T MRI sequences including 3D T1w pre- and post-contrast agent injection, 3D T2w, 3D FLAIR, 3D multi-echo gradient recalled echo, 2D diffusion weighted imaging. ASSESSMENT: χDCI was computed based on parameters estimated with DECOMPOSE-QSM. The Neurite Density Index (NDI) was estimated with the NODDI model. T1w images were used for region of interest (ROIs) segmentations with FreeSurfer (i.e., cortical gray matter, white matter, thalamus, caudate, putamen, pallidum, hippocampus and amygdala). For the patients with glioblastoma, regions of contrast enhancement, necrosis, and edema were also included in the analysis. STATISTICAL TESTS: Pearson's correlation analysis between mean χDCI and NDI values in the ROIs was carried out separately for the two cohorts of participants (significance level = 0.05, after correction for multiple comparisons). RESULTS: Significant correlations were observed between χDCI and NDI in white matter (r = 0.56) and putamen (r = 0.69) for the healthy participants. Significant positive correlations were also found in white matter (r = 0.6), pallidum (r = 0.48), putamen (r = 0.79), thalamus (r = 0.64) and edema (r = 0.69) for the patient cohort. DATA CONCLUSION: χDCI is proposed as a marker of tissue cellularity. The significant associations between χDCI and NDI in several regions investigated in the present study support the potential of χDCI as a proxy of intracellular volume fraction. TECHNICAL EFFICACY: Stage 1.