We investigate the effectiveness of a targeted rapid pediatric knee MRI exam with total exam time of about 10 minutes. We aim to enable same-day MRI access, accommodating the abbreviated protocol between other scheduled patients. The protocol is based on T2 Shuffling, a four-dimensional acquisition that permits volumetric reconstruction of images with variable T2-contrast. Preliminary data for ten subjects referred for the targeted knee MRI exam is presented. Mean time from registration to exam completion averaged 48.5 minutes, with one outlier of 269 minutes due to technologist error in documentation.
Although a rapid MRI may have high value, the realization of that value only occurs if the scan can be accommodated into a clinical schedule to yield incremental volume without expanding operating hours. Thus, this work presents the full integration of a fast imaging approach into a clinical workflow.
A four-dimensional fast spin-echo (FSE) acquisition that encodes the knee anatomy in volumetric fashion and also permits reconstruction of images with variable T2-contrast was implemented$$$^1$$$, termed T2 Shuffling (T2sh). The total protocol consisted of a localizer (1 minute), T2sh (7 minute), and a Coronal FSE T1 (3 minute). The scan parameters are summarized in Figure 1.
The overall methodology for the T2sh acquisition and reconstruction method is presented in Figure 2. The acquisition used a randomized view ordering to acquire phase encode samples during the spin-echo train. A compressed sensing-based reconstruction was implemented to resolve volumetric images at varying T2 contrasts.
Insurance plans were reviewed to subselect those plans with high likelihood waived authorization, rapid authorization, or retroactive insurance authorization. Patients with indications of anterior knee pain, or suspicion of osteochondral lesions, anterior cruciate ligament tears, or meniscal pathology covered by subselected insurance plans were eligible for rapid protocol knee MRI exams. A mechanism of communication between orthopedic clinic and an adjacent MRI scanner was established. Over a three month period, time from exam request to exam completion was recorded, along with time from patient registration to exam completion. Indications and clinical findings were also recorded.
1. Tamir JI, Uecker M, Chen W, Lai P, Alley MT, Vasanawala SS, Lustig M. T2 Shuffling: Sharp, Multicontrast, Volumetric Fast Spin-echo Imaging. Magnetic resonance in medicine (2016). doi:10.1002/mrm.26102. [Epub ahead of print].
2. Bao S, Tamir JI, Young JL, Tariq U, Uecker M, Lai P, Chen W, Lustig M, Vasanawala SS. Fast comprehensive single-sequence four-dimensional pediatric knee MRI with T2 shuffling. Journal of magnetic imaging (2016). doi: 10.1002/jmri.25508. [Epub ahead of print].