Geographic disparities in MRI access and patterns of mobile MRI deployment across Michigan counties

Rural populations face higher risks of poor health outcomes in part due to limited access to diagnostic imaging. Geographical barriers may be exacerbated by longer travel distances, limited public transportation, and structural and policy factors such as Certificate of Need (CON) regulations. Mobile MRI units have been deployed across Michigan; however, it remains unclear whether they are deployed in a manner that meaningfully reduces geographic barriers to MRI access in rural populations.

To examine geographic disparities in access to MRI machines across Michigan counties and evaluate whether current mobile MRI deployment aligns with geographic distance to fixed MRI services in rural communities. Understanding whether mobile MRI unit routes correlate with counties with the greatest geographic distance to fixed MRI services is essential for informing equitable imaging infrastructure planning.

All hospital based, outpatient facility, and mobile MRI units in Michigan were extracted from the 2024 MRI Service Utilization Lists posted by Michigan Health and Human Services. County population centers were retrieved from the U.S Census Bureau and used as travel origins to determine the straight-line distance to the nearest fixed MRI unit in each county using QGIS. Additionally, each county was characterized by MRI access (No MRI, mobile MRI only, fixed MRI, or both) and categorized into long distance (>9.44 miles) and short distance (<9.44 miles) to the nearest fixed MRI based on whether the distance was greater or less than the median distance to a fixed MRI. Association between long and short distance and mobile MRI availability were assessed using chi-square analysis (p < 0.05). Associations between mobile MRI availability and distance to the nearest fixed MRI were assessed using chi-square analysis and univariable logistic regression with distance modeled continuously. A multivariable logistic regression model additionally adjusted for county population density.

Rural counties in northern Michigan and the Upper Peninsula exhibited the longest mean straight-line distance to a fixed MRI. In univariable logistic regression, straight-line distance to the nearest MRI was not significantly associated with mobile MRI availability (OR per 10-mile increase, 1.10; 95% CI, 0.84-1.43; p = 0.50). After adjustment for county population density, greater distance was associated with increased odds of mobile MRI placement (adjusted OR per 10-mile increase, 1.46; 95% CI, 1.03-2.07; p = 0.034), while higher population density per county was also independently associated with mobile MRI availability (adjusted OR per 100 persons/mi², 2.05; 95% CI, 1.21-3.48; p = 0.008). Thirteen counties (15.7%), all rural, lacked fixed or mobile MRI access.

Rural counties in northern Michigan and the upper peninsula experience geographic barriers to MRI access. Although greater distance to fixed MRI services was associated with increased mobile MRI availability after adjusting for population density, 13 rural counties still lacked a mobile or fixed MRI unit. These findings highlight opportunities for more targeted infrastructure planning and policy strategies to improve imaging equity in rural communities.