Inpatient CT and MRI utilization: trends in the academic hospital setting

The aim of this study was to determine trends in the utilization of inpatient CT and MRI at academic medical centers.

Surveys requesting inpatient CT volumes, inpatient MRI volumes, discharges excluding newborns, and case-adjusted mix index from 2002 to 2007 were e-mailed to all 123 members of the Society of Chairmen of Academic Radiology Departments. CT and MRI studies per discharge were adjusted using the case mix index (CMI) provided by each hospital to adjust for the differences in patient mix at participating institutions. Trends in adjusted inpatient imaging utilization were compared over time and across responding institutions.

Twenty-two of 123 chairs (17.9%) of academic radiology departments, representing all geographic regions and a wide variability in National Institutes of Health research funding ranking, provided responses to our survey. Between 2002 and 2007, there was an increase in median CMI-adjusted CT studies per discharge of 28.0% and an increase in median CMI-adjusted MRI studies per discharge of 19.8%. The largest annual percentage increase in CT utilization (20.2%) occurred from 2003 to 2004, and there was negative growth between 2006 and 2007 of -3.74%. The largest annual percentage increase in MRI utilization (13.9%) occurred from 2006 to 2007, with 3 years of negative growth from 2002 to 2003, 2004 to 2005, and 2005 to 2006. In 2007, there was a wide range in CMI-adjusted CT studies per discharge between institutions from 0.16 to 0.75, with a mean of 0.40 ± 0.18, with a corresponding wide range in CMI-adjusted MRI studies per discharge of 0.04 to 0.16, with a mean of 0.09 ± 0.03.

There has been large growth in inpatient CT and MRI utilization at academic medical centers. This growth is variable over time and between institutions. Practice leaders can use this information to compare themselves with their peers and to monitor the impact of programmatic improvements on inpatient imaging utilization and in discussions with health system leaders who would like to improve system profitability by decreasing costly inpatient imaging procedures.