Faster MRI Scans Could Slash Anesthetic Doses in Children, Study Finds

Every year, hundreds of thousands of children around the world undergo magnetic resonance imaging, and a large fraction of them cannot simply lie still long enough for the scanner to do its work. For infants, toddlers, and many school-aged children, the solution is sedation or anesthesia, most commonly with the intravenous drug propofol. A new retrospective study from Massachusetts General Hospital, published in Pediatric Radiology, has now quantified something that radiologists and anesthesiologists have long suspected but rarely measured with precision: the operational choices made when designing an MRI protocol directly determine how long a child stays under, and therefore how much anesthetic drug that child receives.

The research team, led by Sergio Valencia and Michael S. Gee, analyzed 2,149 pediatric MRI examinations performed under propofol anesthesia between January 2020 and May 2025. The children had a median age of just five years, and roughly six in ten were female. By linking scanner-level operational variables — magnetic field strength, the use of gadolinium-based contrast agents, and whether the protocol covered a single body region or multiple regions — to total examination time and cumulative propofol dose in milligrams per kilogram of body weight, the investigators were able to disentangle which factors genuinely drive anesthetic burden and which are merely correlated with it.

The headline finding is stark. Multi-region MRI protocols, in which the scanner images several anatomical areas in a single session, lengthened examination time by 45.4 percent compared with single-region protocols, with a 95 percent confidence interval of 40.2 to 50.7 percent. Contrast-enhanced examinations, which require the injection of a gadolinium contrast agent and additional imaging sequences, added 18.6 percent to scan duration. Both associations were highly statistically significant, with p-values below 0.001. In practical terms, a child scheduled for a multi-region, contrast-enhanced study could spend well over an hour on the table — and under anesthesia — where a streamlined single-region scan might have taken half as long.

Not every operational factor pushed in the same direction, however. Imaging at 3 Tesla, the higher field strength now standard in many pediatric radiology departments, was actually associated with a 3.9 percent reduction in MRI duration compared with 1.5 Tesla. That modest but statistically significant advantage — the confidence interval ranged from minus 6.8 to minus 0.9 percent, with a p-value of 0.011 — likely reflects the higher signal-to-noise ratio available at 3 T, which allows faster sequences and shorter acquisition times for a given image quality target. The finding is a useful counterweight to the perception that stronger magnets necessarily complicate pediatric workflows; when protocols are designed to exploit the speed advantage, higher field strength can shorten the anesthetic window.

The most consequential number in the study may be the simplest one. Each additional ten minutes of MRI duration was associated with an increase of 0.71 milligrams per kilogram in total propofol exposure, with a 95 percent confidence interval of 0.59 to 0.84 and a p-value below 0.001. Propofol is typically administered as a bolus for induction followed by a continuous infusion, so the cumulative dose scales almost linearly with time under sedation. That linear relationship means every minute trimmed from a protocol translates directly into less drug delivered to a developing brain — a relationship that holds regardless of why the scan took longer.

Critically, when the researchers adjusted their statistical models for MRI duration, the associations between the protocol-related operational factors and propofol exposure were substantially attenuated. This pattern tells a coherent causal story: multi-region protocols and contrast administration do not independently increase anesthetic dose through some pharmacological mechanism of their own; rather, they increase anesthetic exposure because they make the examination longer. Duration, in other words, is the mediator — the pipeline through which operational decisions flow into anesthetic burden. That insight matters for quality improvement, because it identifies a single, modifiable lever: if departments can shorten scans, they can reduce drug exposure without changing anything about how anesthesia itself is delivered.

Why does reducing propofol exposure matter? Propofol is widely regarded as one of the safest and most controllable sedative agents in pediatric practice, and large registry studies have documented its general safety for procedural sedation in children. Yet no anesthetic is entirely free of risk. Sedation and general anesthesia for MRI carry well-documented risks of airway events, respiratory depression, and hemodynamic changes, and large multicenter analyses from the Pediatric Sedation Research Consortium have shown that adverse events, while uncommon, are a persistent feature of out-of-operating-room sedation. Shorter exposure means a narrower window in which such events can occur, fewer drug-related side effects, and faster recovery times in the post-anesthesia care unit.

There is also the unresolved question of neurotoxicity. Preclinical studies have raised concerns that prolonged exposure to general anesthetics during critical periods of brain development can affect neuronal function, prompting a series of large clinical trials. The GAS trial and the Mayo Anesthesia Safety in Kids study, along with a landmark JAMA analysis of a single early anesthetic exposure, have largely been reassuring for brief, single exposures in infancy. But the question of whether cumulative or prolonged exposure carries risk — particularly in children who require repeated anesthetics, such as those undergoing serial imaging for cancer — remains an active area of research. A recent Children’s Oncology Group study examined the impact of propofol exposure on neurocognitive outcomes in children with high-risk acute lymphoblastic leukemia, underscoring that the concern is not theoretical. In that context, minimizing anesthetic time is a prudent default even in the absence of definitive harm data.

The economic argument points in the same direction. Anesthetic-related adverse events impose a measurable financial burden on health systems, and every minute of scanner time occupied by a sedated child is a minute unavailable for other patients. Pediatric MRI demand has grown steadily, and studies of MRI utilization in pediatric accountable care organizations have highlighted sedation and anesthesia as a major operational bottleneck. Faster protocols therefore offer a rare win-win-win: lower anesthetic exposure for the child, reduced risk and cost for the institution, and increased throughput for the waiting list. Previous work by some of the same investigators, including studies of accelerated and abbreviated imaging protocols and of MRI techniques to decrease imaging times in children, has already demonstrated that substantial time savings are technically feasible without compromising diagnostic quality.

The authors are careful to note the limitations inherent in a single-center retrospective design, and the study’s associations — however well-adjusted — cannot fully exclude residual confounding by case complexity. Still, the central message is difficult to escape. The anesthetic burden of pediatric MRI is not an fixed cost of the technology; it is, to a meaningful degree, a design choice embedded in the protocol. When radiologists decide whether to image two regions or five, whether to add contrast, and which field strength to use, they are also, implicitly, deciding how long a five-year-old will lie anesthetized inside a magnet. The new data give that decision a number: roughly 0.71 milligrams per kilogram of propofol for every ten minutes of scan time. As machine learning reconstruction, compressed sensing, and other acceleration techniques continue to compress acquisition times, the operational levers identified in this study suggest that the safest anesthetic for a child’s MRI may be the one that simply ends sooner.

Subject of Research: The association between MRI protocol-related operational factors, examination duration, and propofol anesthetic exposure in pediatric imaging

Article Title: Associations between protocol-related operational factors, MRI duration, and propofol exposure in pediatric MRI

Article References: Valencia, S., Fazio Ferracioli, S., Nichols, J. H., Jaimes, C., & Gee, M. S. (2026). Associations between protocol-related operational factors, MRI duration, and propofol exposure in pediatric MRI. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06766-0

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06766-0

Keywords: pediatric MRI, propofol, anesthesia, sedation, MRI duration, scan protocols, 3 Tesla, contrast-enhanced MRI, radiology, patient safety, neurotoxicity, workflow efficiency