In vivo quantification of human lumbar disc degeneration using T1ρ-weighted magnetic resonance imaging

Diagnostic methods and biomarkers of early disc degeneration are needed as emerging treatment technologies develop (e.g., nucleus replacement, total disc arthroplasty, cell therapy, growth factor therapy) to serve as an alternative to lumbar spine fusion in treatment of low back pain. We have recently demonstrated in cadaveric human discs an MR imaging and analysis technique, spin-lock T1ρ-weighted MRI, which may provide a quantitative, objective, and non-invasive assessment of disc degeneration. The goal of the present study was to assess the feasibility of using T1ρ MRI in vivo to detect intervertebral disc degeneration. We evaluated ten asymptomatic 40–60-year-old subjects. Each subject was imaged on a 1.5 T whole-body clinical MR scanner. Mean T1ρ values from a circular region of interest in the center of the nucleus pulposus were calculated from maps generated from a series of T1ρ-weighted images. The degenerative grade of each lumbar disc was assessed from conventional T2-weighted images according to the Pfirmann classification system. The T1ρ relaxation correlated significantly with disc degeneration (r=−0.51, P<0.01) and the values were consistent with our previous cadaveric study, in which we demonstrated correlation between T1ρ and proteoglycan content. The technique allows for spatial measurements on a continuous rather than an integer-based scale, minimizes the potential for observer bias, has a greater dynamic range than T2-weighted imaging, and can be implemented on a 1.5 T clinical scanner without significant hardware modifications. Thus, there is a strong potential to use T1ρ in vivo as a non-invasive biomarker of proteoglycan loss and early disc degeneration

THE AMERICAN STATES AND THE SHIFTING LOCUS OF POSITIVE ECONOMIC INTERVENTION

While there has been a turn away from positive government intervention in the economy at the national level, we have witnessed an embrace of this strategy in may of the American states. What impact, if any, have these efforts by state governments had on their economies&quest; The paper focuses on variations in party control, competition, and ideology, the institutional capacities of governors and legislatures, and policy measures, while controlling for a variety of alternative influences on state economies. For the period from 1968-1979 states were dominated by the national economy and other forces over which they had little or no control, and thus had little or no effect on their economies. However, for the 1980-1985 period, party, political capacity, and policy exerted a statistically significant influence on state economic performance. Copyright 1990 by The Policy Studies Organization.