Integration of resting state functional MRI into clinical practice - A large single institution experience

Abstract

Functional magnetic resonance imaging (fMRI) is an important tool for pre-surgical evaluation of eloquent cortex. Classic task-based paradigms require patient participation and individual imaging sequence acquisitions for each functional domain that is being assessed. Resting state fMRI (rs-fMRI), however, enables functional localization without patient participation and can evaluate numerous functional domains with a single imaging session. To date, post-processing of this resting state data has been resource intensive, which limits its widespread application for routine clinical use. Through a novel automated algorithm and advanced imaging IT structure, we report the clinical application and the large-scale integration of rs-fMRI into routine neurosurgical practice. One hundred and ninety one consecutive patients underwent a 3T rs-fMRI, 83 of whom also underwent both motor and language task-based fMRI. Data were processed using a novel, automated, multi-layer perceptron algorithm and integrated into stereotactic navigation using a streamlined IT imaging pipeline. One hundred eighty-five studies were performed for intracranial neoplasm, 14 for refractory epilepsy and 33 for vascular malformations or other neurological disorders. Failure rate of rs-fMRI of 13% was significantly better than that for task-based fMRI (38.5%,) (p <0.001). In conclusion, at Washington University in St. Louis, rs-fMRI has become an integral part of standard imaging for neurosurgical planning. Resting state fMRI can be used in all patients, and due to its lower failure rate than task-based fMRI, it is useful for patients who are unable to cooperate with task-based studies.

Fig 1. Resting state processing workflow.

The Translational Imaging Portal (TIP) provides informatics capabilities to (1) retrieve MRI exams from the hospital clinical information system (PACS), (2) run the automated rsfMRI processing pipeline via the multi-layer perceptron analytic on a HIPAA-compliant computing cluster, (3) review quality control metrics generated by the pipeline, and (4) submit MLP maps for exams that pass QC to the PACS.

Fig 2. Resting state networks shown in stealth navigation software.

After acquisition of rs-fMRI and processing of the data through the MLP analytic, the images are uploaded to the Medtronic Stealth Station. The workflow was streamlined to facilitate acquisition of the rs-fMRI data and rapidly transfer data before and after processing using a system referred to as the Translational Imaging Portal (TIP). The seven RSN were as follows: Default Mode network (DMN), Sensorimotor network (SMN), Visual network (VIS), Language network (LAN), Dorsal and Ventral Attention network (DAN, VAN), Fronto-Parietal Control network (FPC).

Fig 3. Comparable localization between task and resting-state fMRI.

Single patient comparison for language for both MLP rsfMRI (A) and task (B). Both demonstrate similar regions of topographic localization of function. Imaging threshold for MLP rsfMRI was 97% probability. Threshold for task was above threshold as defined by clinical imaging software package.

Fig 4. Successful rsfMRI mapping in the setting of failed task-based fMRI.

Single patient comparison for motor and language for both task and MLP rsfMRI. While both modalities are successful for motor which is distant from the tumor (A), task-based imaging does not show localization in the frontal lobe, while MLP-resting state fMRI does show good localization (B). Imaging threshold for MLP rsfMRI was 97% probability. Threshold for task was above threshold as defined by clinical imaging software package.

Fig 5. Resting state MRI mapping of speech networks in an aphasic patient.

A. Forty year old patient with left temporal tumor. B. rs-fMRI mapping of speech when speech was intact. C. rs-fMRI mapping of speech when patient globally aphasic due to prolonged seizure. Imaging threshold for MLP rsfMRI was 97% probability.

Fig 6. Resting state MRI mapping of eloquent cortex in a sedated pediatric patient.

Three and half year old patient with brain stem tumor imaged while under propofol sedation. A. Tumor. B. rs-fMRI mapping of speech. C. rs-fMRI mapping of motor. Imaging threshold for MLP rsfMRI was 97% probability.