Three-Dimensional Pseudo-Continuous Arterial Spin Labeling for Cerebral Blood Flow Monitoring Before and After Carotid Endarterectomy: A Prospective Cohort Study

The brain is a relentless consumer of energy, requiring a steady, high-volume supply of oxygen-rich blood to function. When the large arteries in the neck that deliver this fuel become narrowed by hardened plaque, the brain's blood flow can drop to dangerous levels, setting the stage for a stroke. To prevent this, surgeons often perform a procedure called carotid endarterectomy, where they physically open the artery and remove the blockage. However, this surgery carries a delicate paradox: once the blockage is gone, blood rushes back into the brain with renewed force. If the pressure rises too high too quickly, it can cause bleeding; if it remains too low, the brain tissue may still starve. For decades, doctors have struggled to see exactly how blood flow changes inside the brain during this critical window, often relying on imaging techniques that require injecting a dye into the patient's veins, which cannot be repeated frequently without risk.

A team of researchers in China recently set out to solve this monitoring problem using a different approach. They studied sixty-five patients who were about to undergo surgery for narrowed neck arteries. Instead of using dye, the team employed a specialized magnetic resonance imaging technique that uses the patient's own blood as a tracer. By magnetically tagging the water in the blood and watching how it moves through the brain, the researchers could measure blood flow without any injections. They performed these scans before the surgery and again shortly after, looking specifically at how blood reached different parts of the brain, including the front and sides of the brain, the areas between major blood vessels, and the deep central structures.

The results revealed a clear picture of what happens when the blockage is removed. Before the surgery, the side of the brain affected by the narrowed artery showed significantly reduced blood flow. After the surgery, the scans showed a distinct and measurable improvement in blood flow to that same side. The researchers found that this new imaging method was sensitive enough to detect these changes even when standard dye-based scans failed to show a significant change in relative blood flow volume. However, the dye-based scans did reveal significant improvements in other critical metrics, such as blood volume and the speed at which blood traveled through the brain, confirming that the surgery successfully restored circulation.

Beyond simply confirming that the surgery worked, the scans provided a vital safety net for the patients in the days following the operation. The researchers discovered that the imaging could spot two specific, opposing problems that require different treatments. In a small number of patients, the scans showed that blood flow remained dangerously low even after the surgery, suggesting that the blood vessels were still constricted or blocked by tiny clots. For these individuals, the medical team was able to safely raise the patients' blood pressure to force more blood through the narrow pathways. In a few other cases, the scans showed blood flow had surged too high, a condition that risks causing bleeding in the brain. For these patients, the team immediately lowered the blood pressure to protect the delicate tissue. By catching these issues early, the team was able to adjust care in real time, ensuring that every patient in the study recovered without suffering a stroke or a fatal bleed.

The study followed these patients for three months after their surgery, and the outcome was uniformly positive. Every single patient achieved a favorable recovery with no lasting disability or death. The researchers concluded that this non-invasive imaging technique offers a powerful, repeatable way to watch the brain's blood flow before and after surgery. It allows doctors to move beyond guesswork, providing a clear, contrast-free view of whether the brain is getting too little or too much blood, and guiding precise medical decisions to keep patients safe during their most vulnerable hours.