Research Spotlight: Dr. Tshea Dowers studies the pros and cons of lowering contrast in neurological scans

This past June, Medical Imaging celebrated PGY5 residents’ successful completion of their residency as well as their accomplishments in research with a graduation and Research Day awards ceremony. This year’s Research Day winner was Dr. Tshea Dowers, who won Best Oral Presentation for her research into the benefits and drawbacks of lowering contrast dye in neurological imaging.

Working with her clinical supervisor, Dr. Alcaide Leon, Neuroradiologist, JDMI, Dr. Dowers began her study to assess the dose levels of contrast used in meningioma imaging in December of 2021.

“Meningiomas are indolent, slow-growing tumors of the central nervous system that don’t always require surgical resection but do require consistent surveillance through follow-up brain imaging given their capacity for significant growth,” Dr. Dowers explains. “Contrast-enhanced MRI with gadolinium is the gold standard technique for meningioma detection and characterization as it allows for accurate assessment of tumor location and the surrounding intracranial tissues.”

Due to the frequency of MRIs needed by patients with intracranial meningiomas, Dr. Dowers set out to assess the benefits and risks of lowering gadolinium doses used in follow-up MRIs of meningiomas as a way to mitigate the adverse health effects on patients from repeat exposure to gadolinium, as well as increased imaging costs and time.

At University Health Network (UHN), the institutional approach to imaging meningiomas has changed over the years with varying doses of gadolinium being administered to patients. As a result, Dr. Dowers had a unique opportunity to study the existing brain scans of patients with meningiomas who had already been given varying doses of contrast.

 “Working with this group of patients, we had the opportunity to assess the efficacy of different doses as a way to provide context for different dosing regimens to help radiologists make informed decisions,” she says.

After studying the scans of numerous patients with varying doses of contrast, Dr. Dowers was able to determine whether a lower dose of contrast could yield comparable imaging outcomes to the standard dose. To qualify her findings, Dr. Dowers grouped the patients into 3 groups - those who received a standard dose of contrast, a lower dose, and a micro dose. What she found was that while the standard dose of contrast – the currently accepted dose of 0.1 mg/kg –produced the best quality scans, a low dose of gadolinium (0.04-0.085 mg/kg) yields produced only marginally inferior imaging outcomes compared to the standard dose.

“When comparing the standard dose to the lower dose scans, we found that about two per cent of patients would fall beneath the optimal threshold for characterizing meningiomas when using a lower dose of contrast, however for a majority of scans, we were still able to identify even smaller tumors.” says Dr. Dowers. “We also see the benefits of reducing the dose on patients’ overall health, as the contrast comes with its own set of risks, especially for patients who need long-term imaging.”

Since the study was completed, UHN has begun using a lower dose of contrast as opposed to the standard or micro dose, finding a happy medium that balances both costs for the institution and health risks with gadolinium administration for patients. Dr. Dowers says more research is still needed, but with these new insights, hospitals and healthcare settings can make their own cost-benefit analysis to determine their best practices.

Going forward, Dr. Dowers would like to see more research done, however she explains that standardizing doses across the board is unlikely, as the study results aren’t perfect, and a small subset of patients would be sub-optimally characterized. She’s since been busy wrapping up the study, including identifying limitations within the study and how to improve results with further research.

As for Dr. Dowers’ next steps, she plans to complete a Neuroradiology fellowship at University of Toronto in July 2024.

Congratulations on your successful study and award for Best Oral Presentation, Dr. Dowers!