Factors predicting the time-length variability of identically protocoled MRI exams

Abstract

Background: Clinical variability in MRI exam durations can impede efficient MRI utilization. There is a paucity of data regarding the degree of variability of identically protocoled MRI studies and when nontechnological factors contribute to time-length variations in MRI exams.

Purpose: To measure the magnitude of variation in MRI exam duration for identically protocoled MRI exams and to identify potential contributors to variations in MRI exam times.

Study type: Retrospective.

Subjects: 2705 identically protocoled MRI examinations of the cervical spine without contrast, comprehensive stroke exams, and comprehensive brain examinations performed on adult patients from June 30, 2016 through June 30, 2017.

Assessment: MRI exam duration was obtained directly from the image data. Potential predictors for exam length variability were evaluated including patient age, patient gender, performing technologist, patient status (inpatient/outpatient/emergency department), MRI field strength, use of sedation, day of week, and the time of day.

Statistical tests: Linear regression analysis was performed for each individual variable after correcting for the MRI exam type. A multivariate mixed model was generated to assess for independent associations between the predictors and exam duration.

Results: There was substantial variability in the duration of the selected clinical MRI exams, with standard deviations (SDs) ranging between 19% and 29% of the mean exam length for each individual type of exam. The performing technologist was the most significant identified factor contributing to this variation in exam length; SD = 2.645 (P < 0.001). Compared with outpatient exams, inpatient exams required 4.18 minutes longer to complete (P < 0.001), and emergency department studies 1.86 minutes longer (P = 0.005). Male gender was associated with an additional 1.36 minutes of exam time (P < 0.001).

Data conclusion: Nontechnical factors are associated with substantial variation in MRI exam times. These variations can be predicted based on relatively simple clinical and demographic factors, with implications for MRI exam scheduling, protocol design, staff training, and workflow design.

Level of evidence: 4 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2019.