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Updated: May 4, 2026
In vivo Macrophage Imaging Using MR Targeted Contrast Agent for Longitudinal Evaluation of Septic Arthritis
Published on: October 20, 2013
Systematic protocol for assessment of the validity of BOLD MRI in a rabbit model of inflammatory arthritis at
Michael W Chan1, George Nathanael, Antonella Kis
1Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Ave., Toronto, Canada, M5G 1X8.
Background:
Blood-oxygen-level-dependent (BOLD) MRI has the potential to identify regions of early hypoxic and vascular joint changes in inflammatory arthritis. There is no standard protocol for analysis of BOLD MRI measurements in musculoskeletal disorders.
Objective:
To optimize the following BOLD MRI reading parameters: (1) statistical threshold values (low, r > 0.01 versus high, r > 0.2); (2) summary measures of BOLD contrast (percentage of activated voxels [PT%] versus percentage signal difference between on-and-off signal intensities [diff_on_off]); and (3) direction of BOLD response (positive, negative and positive + negative).
Materials And Methods:
Using BOLD MRI protocols at 1.5 T, arthritic (n = 21) and contralateral (n = 21) knees of 21 juvenile rabbits were imaged at baseline and on days 1, 14 and 28 after a unilateral intra-articular injection of carrageenan. Nine non-injected rabbits served as external control knees (n = 18). By comparing arthritic to contralateral knees, receiver operating characteristic curves were used to determine diagnostic accuracy.
Results:
Using diff_on_off and positive + negative responses, a threshold of r > 0.01 was more accurate than r > 0.2 (P = 0.03 at day 28). Comparison of summary measures yielded no statistically significant difference (P > 0.05). Although positive + negative (AUC = 0.86 at day 28) and negative responses (AUC = 0.90 at day 28) for PT% were the most diagnostically accurate, positive + negative responses for diff_on_off (AUC = 0.78 at day 28) also had acceptable accuracy.
Conclusions:
The most clinically relevant reading parameters included a lower threshold of r > 0.01 and a positive + negative BOLD response. We propose that diff_on_off is a more clinically relevant summary measure of BOLD MRI, while PT% can be used as an ancillary measure.
Insights
Optimizing blood-oxygen-level-dependent (BOLD) MRI parameters for inflammatory arthritis in rabbits showed a lower threshold (r > 0.01) and positive + negative responses were most accurate. This improves diagnostic potential for joint changes.
Area of Science:
- Biomedical Imaging
- Radiology
- Musculoskeletal Imaging
Background:
- Blood-oxygen-level-dependent (BOLD) MRI shows promise for detecting early hypoxic and vascular changes in inflammatory arthritis.
- A standardized protocol for BOLD MRI analysis in musculoskeletal disorders is currently lacking.
Purpose of the Study:
- To optimize BOLD MRI reading parameters for inflammatory arthritis.
- Parameters evaluated include statistical thresholds, summary measures of BOLD contrast, and direction of BOLD response.
Main Methods:
- BOLD MRI was performed on arthritic and contralateral knees of juvenile rabbits following carrageenan injection.
- Receiver operating characteristic curves were used to assess diagnostic accuracy by comparing arthritic to contralateral knees.
Main Results:
- A lower statistical threshold (r > 0.01) combined with positive + negative BOLD responses demonstrated higher accuracy than a higher threshold (r > 0.2).
- The percentage signal difference between on-and-off signal intensities (diff_on_off) was proposed as a clinically relevant summary measure.
- Percentage of activated voxels (PT%) with negative or positive + negative responses showed high diagnostic accuracy.
Conclusions:
- The optimal BOLD MRI parameters for inflammatory arthritis include a low threshold (r > 0.01) and a positive + negative response.
- Percentage signal difference (diff_on_off) is recommended as the primary summary measure, with percentage of activated voxels (PT%) serving as a secondary measure.
