Tag: neurology

Real-World Stroke AI Implementation

Posted on by Brian Casey

Time is brain. That simple saying encapsulates the urgency in diagnosing and treating stroke, when just a few hours can mean a huge difference in a patient’s recovery. A new study in Clinical Radiology shows the potential for Nicolab’s StrokeViewer AI software to improve stroke diagnosis, but also underscores the challenges of real-world AI implementation.

Early stroke research recommended that patients receive treatment – such as with mechanical thrombectomy – within 6-8 hours of stroke onset. 

  • CT is a favored modality to diagnose patients, and the time element is so crucial that some health networks have implemented mobile stroke units with ambulances outfitted with on-board CT scanners. 

AI is another technology that can help speed time to diagnosis. 

  • AI analysis of CT angiography scans can help identify cases of acute ischemic stroke missed by radiologists, in particular cases of large vessel occlusion, for which one study found a 20% miss rate. 

The U.K.’s National Health Service has been looking closely at AI to provide 24/7 LVO detection and improve accuracy in an era of workforce shortages.

  • StrokeView is a cloud-based AI solution that analyzes non-contrast CT, CT angiography, and CT perfusion scans and notifies clinicians when a suspected LVO is detected. Reports can be viewed via PACS or with a smartphone.  

In the study, NHS researchers shared their experiences with StrokeView, which included difficulties with its initial implementation but ultimately improved performance after tweaks to the software.  

  • For example, researchers encountered what they called “technical failures” in the first phase of implementation, mostly related to issues like different protocol names radiographers used for CTA scans that weren’t recognized by the software. 

Nicolab was notified of the issue, and the company performed training sessions with radiographers. A second implementation took place, and researchers found that across 125 suspected stroke cases  … 

  • Sensitivity was 93% in both phases of the study.
  • Specificity rose from the first to second implementation (91% to 94%).
  • The technical failure rate dropped (25% to 17%).
  • Only two cases of technical failure occurred in the last month of the study.

The Takeaway

The new study is a warts-and-all description of a real-world AI implementation. It shows the potential of AI to improve clinical care for a debilitating condition, but also that success may require additional work on the part of both clinicians and AI developers.

MRI Predicts Cognitive Decline

Posted on by Brian Casey

Early detection of cognitive decline is becoming increasingly important as new therapies become available for conditions like Alzheimer’s disease. A new 20-year study in JAMA Network Open shows that MRI can detect structural brain changes indicating future cognitive decline – years before symptoms occur. 

Longitudinal research has shown that subtle changes in body structure – be they in the heart, brain, or other organs – can predict future disease risk, in some cases decades in advance.

  • That enables the possibility of targeted treatments or behavioral interventions to reduce risk before sick patients experience a cascade of expensive and invasive therapies. 

Mild cognitive impairment is an excellent example. MCI can be a transition to more serious diseases like Alzheimer’s, and previous research has connected it to vascular risk factors that are signs of brain atrophy. 

  • In the current paper, researchers analyzed MRI scans acquired as part of the BIOCARD cohort, a longitudinal study started in 1995 in which cognitively normal participants got baseline brain MRI scans and follow-up exams. 

In a group of 185 BIOCARD participants, researchers tracked how many transitioned to MCI over a mean follow-up period of 20 years, then compared structural brain changes on MRI, finding …

  • 60 participants (32%) progressed to MCI, eight of whom later developed dementia (4.3%).
  • Those with white-matter atrophy on MRI had an 86% higher chance of progression to MCI, the highest rate of any variable studied.
  • Participants with enlargement of the ventricles on MRI had 71% higher risk.
  • Other variables like diabetes and amyloid pathology also had higher risk, but not at the rate of the MRI-detected variables. 

The findings indicate that white-matter volume is closely associated with cognitive function in aging, and that people with higher rates of change are more likely to develop MCI. 

  • The association of diabetes with MCI was not a shock, but researchers said they were surprised there was no association from risk factors like hypertension, dyslipidemia, and smoking.

The Takeaway

The new findings demonstrate the power of MRI to predict pathology years in advance – the question is how and whether to put this knowledge into clinical practice. One could almost see structural brain scans incorporated into whole-body MRI screening exams (if anyone’s listening).

Next-Generation Brain PET

Posted on by Brian Casey

A new paper in JNM includes the first human images acquired with a next-generation dedicated brain PET/CT scanner that could create a new standard for neurological research. United Imaging’s NeuroEXPLORER scanner has sensitivity and spatial resolution “an order of magnitude” better than existing technology. 

In addition to its value as a clinical tool, PET has carved out a research role for investigating some of the most fundamental questions about brain function and pathology. 

  • Commercial whole-body scanners can be used for research, but dedicated brain systems like the High Resolution Research Tomograph (HRRT) offer even higher resolution for imaging tiny structures in the brain. 

NeuroEXPLORER was developed by a consortium that includes United Imaging, UC Davis, and Yale University to adapt for dedicated brain imaging the long-axis PET technology found in United’s uEXPLORER total-body PET/CT system. 

  • NeuroEXPLORER was a highlight at the recent SNMMI 2024 conference, and images acquired with the system won the show’s coveted Image of the Year honors.

In the new study, researchers go into more detail about NeuroEXPLORER’s specifications, which include … 

  • An extended axial field of view (FOV) of 49.5cm for higher sensitivity
  • Transverse spatial resolution ranging from 1.64-2.51mm at full-width half-maximum
  • Average time-of-flight resolution of 236 picoseconds
  • NEMA sensitivities of 46.0 and 47.6 kcps/MBq at center and 10cm offset, and absolute sensitivity of 11.8% at the center of the FOV

Such high sensitivity and spatial resolution enables tasks “previously considered difficult or impossible,” like imaging focal tracer uptake of small subcortical regions or low-density binding sites like cortical dopamine receptors. 

  • What’s more, NeuroEXPLORER’s long axial length enables high-quality imaging of the spinal cord and carotid arteries.

Now for the disclaimer: United Imaging notes that NeuroEXPLORER has not been submitted to the FDA for clearance and at present is only for research use; the company’s uEXPLORER scanner does have clearance and is in operation at several commercial sites. 

The Takeaway

Publication in a journal of the first human images from NeuroEXPLORER are an exciting development and underscore the potential of dedicated brain PET to advance research into neurological function and pathology. Whether the scanner develops into a clinical tool remains to be seen.

CT Changes Headache Workup

Posted on by Brian Casey

Recent studies have raised concerns about whether CT is overused in the emergency setting for patients with symptoms like headache, but a new study in JAMA Network Open suggests that higher CT utilization could be contributing to a decline in more invasive procedures like lumbar puncture. 

Earlier this month, we covered a study documenting the rapid rise of emergency head CT for patients presenting with acute-onset headache – which could be an indication of subarachnoid hemorrhage or other serious issues. 

  • Researchers theorized that higher CTA utilization could be a sign of overuse because the rate of positive findings over time fell 38%.

But the new study suggests that the growth in cerebral CTA use could have beneficial effects, by reducing the use of more invasive procedures and by detecting unruptured intracranial aneurysm. 

  • Some 5% of acute-onset headaches in emergency patients are caused by subarachnoid hemorrhage; these cases have a 50% risk of death or serious disability at one year, making accurate detection and workup a serious issue.

Researchers from Kaiser Permanente in Northern California analyzed 198k encounters for patients with headache at 21 community EDs from 2015 to 2021. 

  • They compared multiple workup protocols, ranging from CT only to others in which CT was used first, with nondiagnostic cases sent to either lumbar puncture or cerebral CTA. 

Dramatic changes occurred in headache workup over the study period, including … 

  • Overall use of CT grew at an average annual percent change of 5.4%
  • Cerebral CTA use grew 19% annually
  • Lumbar puncture use fell 11% annually
  • Detection of unruptured intracranial aneurysms grew 33%
  • The ratio of unruptured aneurysms to subarachnoid hemorrhage grew

The authors noted that the findings show clinicians are shifting away from a headache workup protocol that includes lumbar puncture to one that relies more on cerebral CTA.

  • The researchers were equivocal on the increase in detection of unruptured aneurysms; on the one hand, the absolute risk of rupture is low, but on the other, the consequences of rupture are severe.  

The Takeaway

The new study offers a more nuanced – and perhaps more positive – view of growing cerebral CTA use in the ED. In the end, it’s possible that two conflicting statements can be true: CT indeed may be overused in the emergency department, but its growing use is also having a beneficial impact on patient care.

CMS May Shake Up PET Payments

Posted on by Brian Casey

In a major victory for PET advocates, CMS this week said it was opening a review of its reimbursement policy on PET scans for Alzheimer’s disease. The review could lead to more generous Medicare and Medicaid payments for PET to detect amyloid buildup in the brain, long known as a link to the debilitating – and inevitably fatal – disease. 

Medicare’s current policy on PET for Alzheimer’s has been in place since 2013 and is based on its coverage with evidence (CED) framework; it restricts reimbursement to a single scan per lifetime for patients who must be participating in clinical trials. The CED policy reflects not only CMS’ cautious approach to new technology, but also the fact that for years there have been no effective treatments for Alzheimer’s disease. 

That’s all changed within the last year. A new class of drugs that target amyloid buildup in the brain has begun to receive FDA approval, the most recent being Leqembi from Esai/Biogen in January 2023. And this week, Eli Lilly reported positive results for its amyloid-targeting treatment donanemab (see below), with approval expected by the end of 2023. 

The new drugs have changed the game when it comes to diagnosis and treatment of Alzheimer’s disease: 

  • PET can now be used to identify eligible patients and monitor their treatment
  • Thanks to PET, patients won’t continue to be given expensive drugs after amyloid buildup has been eliminated
  • Expanded PET reimbursement could boost the use of PET diagnostic tracers for identifying amyloid buildup 

CMS is taking comments on its proposal through August 16. If the agency eliminates the CED policy in favor of a national coverage decision, then decisions on PET reimbursement will be made by local Medicare Administrative Contractors (MACs). 

This week’s news could be a Pyrrhic victory if PET reimbursement levels are set too low. One positive sign is that CMS has said it also plans to review its policy that bundles radiotracer payments together with scan payments, which tends to depress reimbursement.

The Takeaway

The nuclear medicine and molecular imaging community has chafed for years under CMS’ restrictive policies on PET for Alzheimer’s disease, with groups like SNMMI lobbying for the change. This week’s news should have wide-ranging benefits not only for the PET business sector, but also for patients who are facing the scourge of Alzheimer’s disease.

When TIA Imaging Is Incomplete

Posted on by Brian Casey

A new study in AJR calculates the cost to patients when imaging evaluation is incomplete, finding that people with transient ischemic attack (TIA) who didn’t get full imaging workups were 30% more likely to have a new stroke diagnosis within the next 90 days.

Some 240,000 people experience TIA annually in the US. While TIAs typically last only a few minutes and don’t cause lasting neurological damage, they can be a warning sign of future neurological events to come.

Medical imaging – typically CT and MRI – are key in the neurological workup of TIA patients, and TIA can be treated with antithrombotic therapy, which reduces the likelihood of a stroke 90 days later. Therefore, guidelines call for prompt neuroimaging of the brain and neck in TIA patients, typically within 48 hours, with MRI the primary and CT the secondary options.

But what happens if TIA patients don’t get complete imaging as part of their workup? To answer this question, researchers from Colorado and California analyzed a database of 111,417 people seen at 4,253 hospitals who presented to the ED with TIA symptoms from 2016 to 2017. 

They tracked which patients received complete neurovascular imaging within 48 hours as part of their workup, then followed how many received a primary diagnosis of stroke within 90 days of the initial TIA encounter. Findings included:

  • 62.7% of patients received brain imaging and complete neurovascular imaging (both head and neck) within 48 hours
  • 37.3% received brain imaging but incomplete neurovascular imaging 
  • There was a higher rate of stroke at 90 days in TIA patients with incomplete imaging workup (7.0% vs. 4.4%)
  • Patients with incomplete neurovascular imaging also had a greater chance of stroke at 90 days (OR=1.3)

The Takeaway 

While the benefits of neuroimaging for stroke have been demonstrated in the literature, imaging’s value for TIA has been less certain – until now. The AJR study shows that neuroimaging is just as vital for TIA workup, and it supports guidelines calling for cross-sectional imaging of the head and neck within 48 hours of TIA.

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