Responsiveness of Bold MRI to Short-Term Temperature Changes in Rabbit Knees with Inflammatory Arthritis

Andrea S Doria

doi:10.4172/2161-1149.s2-003

Abstract

Objectives: Tissue signal change caused by temperature-dependent alterations in the affinity of oxygen for hemoglobin contributes to BOLD contrast. Our goals were to test whether BOLD MRI contrast changes with short-term variations in joint temperature (internal responsiveness) and to determine whether an association exists between BOLD MRI and intraarticular pO2 and blood flow [reference standards] upon joint temperature changes (external responsiveness). Methods: Seven juvenile rabbits had the carrageenin (antigen)-injected knee imaged, 10 had the contralateral knee imaged and 11 had one of non-injection knees imaged. Assigned knees underwent experimentally forced increased (37°-42°C) or decreased (37°- 30°C) local temperature for 15-minute periods using heating/cooling pads and were subsequently imaged. Intra-articular pO2 and blood flow were measured in vivo during MRI scanning by polarographic probes. Results: Relative BOLD MRI measurements showed moderate (≤0.8 and >0.5) or large (>0.8) Standardized Response Mean (SRM) changes upon increased local temperature in contralateral knees. Significant substantial correlations were obtained between absolute BOLD MRI measurements and intraarticular pO2 measurements in contralateral knees (r = 0.71, P = 0.048) upon increased local temperature and high correlations were obtained in arthritic knees (r = 0.92, P = 0.004) upon decreased local temperature. Conclusions: BOLD MRI was responsive to short-term joint temperature changes. Imaging contralateral joints in addition to arthritic joints with BOLD MRI may help maximize identification of minimal early changes in subjects with arthritis if findings of this study are confirmed in larger sample size experiments.

Highlights

Juvenile idiopathic arthritis (JIA) is the most common connective tissue disease in the pediatric population with a prevalence of approximately 1 in 10,000 children in North America [1]
The objectives of this study were two-fold: (1) to test whether Blood Oxygen Level Dependent (BOLD) MRI values change with increased (37-42°C) and decreased local joint temperatures (37-30°C) in relation to corresponding baseline values over a short period of time (15 minutes) [internal responsiveness]; and (2) to determine whether an association exists between BOLD MRI values and results of intraarticular pO2 and blood flow (BPU) [reference standard measures] with increased and decreased local joint temperatures over a short period of time (15 minutes) [external responsiveness]
Because we were interested in evaluating the responsiveness of BOLD MRI to short-term variations in joint temperature both related and not related to early synovitis we used an animal model of acute arthritis as well as control animals

Summary

Introduction

Juvenile idiopathic arthritis (JIA) is the most common connective tissue disease in the pediatric population with a prevalence of approximately 1 in 10,000 children in North America [1]. This chronic disease is associated with inflammation of the synovium which is a highly vascularized membrane that overlies the articular cartilage of the joints. Later on during the disease course this highly vascular synovium can undermine the articular cartilage and erode bone at the osteochondral junction resulting in joint deformity and severe functional impairment if the disease is not treated in its early stage [2]

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Conclusion