MRI vs CT for TBI in Children

Written by Clay Smith

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Fast MRI appears to be a feasible and reasonably accurate means of imaging some children with traumatic brain injury (TBI).

Why does this matter?
In light of the small but real risk of ionizing radiation we discussed in yesterday’s post, is there a way to reduce exposure through alternative imaging options? We have been successfully using fast MRI for VP shunt malfunction evaluation for a few years at our institution. How would MRI perform for acute head trauma?

Magnets are an attractive option
This was a prospective cohort of children under 6 years with TBI who had CT imaging ordered. Non-sedated fast MRI was done the same visit for comparison. Fast MRI consisted of, “3T [Tesla] axial and sagittal T2 single-shot turbo spin echo, axial T1 turbo field echo, axial fluid-attenuated inversion recovery, axial gradient echo, and axial diffusion-weighted single-shot turbo spin echo planar imaging.” In total, 299 children had CT ordered; 75% had fast MRI completed. Most of those not completed were because MRI was unavailable overnight. Of the 225 children who attempted MRI, just 2 were unable to complete it (99% success). CT took 59 seconds on average; MRI 365 seconds. With CT as the gold standard, MRI sensitivity was 92.8% (95% CI 86.3-96.8). This was below their pre-specified power calculation of a 95% CI 96.7-100.0%, assuming MRI identified all injuries. Prevalence of TBI on CT was high, with 50% of children having findings on imaging. Injuries missed on MRI were 6 isolated skull fractures and 2 cases of traumatic subarachnoid hemorrhage (SAH). However, there were 5 cases in which fast MRI found injuries missed on CT: 3 SDHs, 2 contusions, and 1 SAH. There were 4 cases of equivocal SDH seen on CT that were definitively excluded with fast MRI. So, although it’s sensitivity compared with the “gold standard” of CT was just 93%, CT was an imperfect gold standard. The best sequences for detecting TBI on MRI were GRE (gradient recall echo) and T2.

Here is my opinion. I think it is worth starting conversations with pediatric radiology to consider this in select pediatric head trauma patients and to develop local protocols to safely implement fast MRI for TBI. It appears feasible and accurate and is worth exploring. Most importantly, it could save some kids a 2.6mSv dose of ionizing radiation and downstream cancer risk.

Source
Feasibility and Accuracy of Fast MRI Versus CT for Traumatic Brain Injury in Young Children. Pediatrics. 2019 Sep 18. pii: e20190419. doi: 10.1542/peds.2019-0419. [Epub ahead of print]

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Reviewed by Thomas Davis

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