NeuraSignal’s NovaGuide Intelligent Ultrasound System Significantly Outperforms Standard of Care for Detecting Stroke-Associated Heart Defects

Data published in Stroke show that NovaGuide was about three times more likely to detect right to left shunt (RLS) and large RLS than transthoracic echocardiography(TTE)

—NovaGuide, a robot-assisted transcranial Doppler (raTCD) system requires no human guidance for data acquisition, potentially allowing more clinicians to access the data they need to detect RLS

—NeuraSignal, Inc. acquires the business of NovaSignal, original developer of NovaGuide


Los Angeles, CA — October 10, 2023 — NeuraSignal, a medical technology and data company specializing in the assessment and management of brain health, today announced the publication of positive results from the BUBL clinical study (#NCT04604015) supporting the safety and superior performance of its NovaGuide Intelligent Ultrasound system in detecting Right to Left Shunt (RLS) — often due to a patent foramen ovale (PFO) — in patients with acute ischemic stroke. The data, published in Stroke, show that the NovaGuide system detected RLS that TTE missed. Importantly, NovaGuide also detected large RLS, which typically require intervention to prevent subsequent ischemic events, that were frequently missed with TTE.

“An accurate assessment for RLS is a critical part of evaluating patients with cryptogenic ischemic stroke. While TTE has long been the most common screening diagnostic for RLS we know from decades of TCD experience that TTE falls short as a screening tool,” said Mark N. Rubin, M.D., Service Chief of Neurology at the Edward Hines, Jr. Veterans Affairs Medical Center and national Principal Investigator of the BUBL study. “These study results clearly show that RLS and large RLS are frequently underdiagnosed with TTE, which potentially puts patients at risk for their doctors unwittingly underestimating both their stroke cause and recurrence. These findings, in conjunction with decades of prior studies, support TCD as the superior initial screening test for RLS compared with TTE. Importantly, they also show that robot assisted TCD can make this superior test more broadly available by eliminating the need for extensive TCD expertise for the type of study conducted, namely aTCD bubble study. TCD expertise is rare, which means most doctors and patients have no idea what TCD is and what it can do for them. The democratization of technique with robotic and software tools has made TCD, finally, as “pushbutton” as I have seen it in my career so far, which I sincerely hope translates into these advanced diagnostic tools helping patients.”

Every 40 seconds someone in the United States has a stroke, and nearly one in four stroke events occur in people who have a previous stroke. Understanding the cause of a particular stroke episode enables more effective intervention, reducing the risk of subsequent strokes. However, up to40% of strokes are cryptogenic. PFO, the most common type of RLS, is a hole between the right and left atria and a known risk factor in stroke because it provides a pathway for blood clots to travel to the brain. This hole is present before birth and usually closes soon after a baby is born.

The standard of care for PFO screening is TTE, an ultrasound-based approach in which the ultrasound transducer is moved across the chest to create an image of the heart. TTE is widely available but has been shown to have only 45% sensitivity in detecting RLS. Transesophageal echocardiography (TEE), in which the ultrasound transducer is placed in the esophagus using an endoscope, is the gold standard for PFO diagnosis but it requires sedation and is invasive, increasing the risk to the patient. In prior studies TCD has been shown to have high sensitivity (96%) and specificity (92%) for detecting PFO, but its success is highly operator-dependent and there is a limited number of healthcare providers with expertise using this approach.

"Our mission is to provide physicians and healthcare providers with the tools they need to excel in an ever-demanding landscape,” said Robert Hamilton, Ph.D., CEO of NeuraSignal, which sponsored the BUBL study. “Through democratizing access to TCD technology, we are leveling the playing field so that more clinicians can obtain the data they need, when and where they need it. Importantly, everything we offer is backed by robust clinical evidence, ensuring that care decisions are well-informed and patient centric. This is more than a new technology; it’s about equipping those on the frontline of treating stroke with the solutions they need to make a tangible difference in patients’ lives."

The NovaGuide Intelligent Ultrasound system was designed to overcome the limitations of existing RLS detection methods. NovaGuide integrates TCD technology with automated robotics and artificial intelligence to enable autonomous acquisition of ultrasound signals and provide insight into subtle changes in blood flow to the brain indicative of a wide range of pathologies including RLS.


About the BUBL Study

The BUBL study was a prospective, single-arm clinical study designed to compare RLS and large RLS detection rates with NovaGuide and TTE in adults who had neurological signs and symptoms of ischemic stroke or transient ischemic attack. Patients in the study were assessed using NovaGuide and TTE with agitated saline contrast bubbles within 30 days of the ischemic event. The research coordinators conducting NovaGuide assessments had no prior TCD experience before being trained to perform standard bubble study technique and to use the NovaGuide system. A total of 129 evaluable subjects were prospectively enrolled in the study at six clinical sites across the United States. The key study findings are:

· For the primary endpoint of RLS detection, NovaGuide detected RLS in 82 (64%) of subjects compared with 26 (20%) of subjects with TTE (absolute difference of 43.4%, p < 0.001).

· For the secondary endpoint of large RLS detection, NovaGuide detected RLS in 35 (27%) of subjects compared with 13 (10%) of subjects with TTE (absolute difference of 17%, p < 0.001). TTE failed to detect approximately two-thirds of the large RLS detected by NovaGuide.

· For the secondary endpoint compared against manual TCD (n=21), NovaGuide detected a RLS in 18 (85.7%) of subjected compared with 12 (57.1%) with manual TCD (absolute difference of 28.6%, p < 0.05)

· There were no serious adverse events, which was the primary safety endpoint of the study.

· Results using NovaGuide suggest that RLS are frequently underdiagnosed.


About NeuraSignal Inc.

In 2023 NeuraSignal, Inc. acquired the business of NovaSignal, the original developer of NovaGuide. NeuraSignal is a medical technology company with a mission to save lives by unlocking the power of cerebral blood flow data. The company’s FDA-cleared NovaGuide Intelligent Ultrasound combines non-invasive ultrasound, robotics, and artificial intelligence to assess cerebral hemodynamics in real time. Using cloud computing and data analytics, NeuraSignal supports physicians in their clinical decision making in several neurological conditions including stroke, traumatic brain injury, and dementia. To learn more, visit

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