Category: Brain Imaging

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).

Teleradiology AI’s Mixed Bag

Posted on by Brian Casey

An AI algorithm that examined teleradiology studies for signs of intracranial hemorrhage had mixed performance in a new study in Radiology: Artificial Intelligence. AI helped detect ICH cases that might have been missed, but false positives slowed radiologists down. 

AI is being touted as a tool that can detect unseen pathology and speed up the workflow of radiologists facing an environment of limited resources and growing image volume.

  • This dynamic is particularly evident at teleradiology practices, which frequently see high volumes during off-hour shifts; indeed, a recent study found that telerad cases had higher rates of patient death and more malpractice claims than cases read by traditional radiology practices.

So teleradiologists could use a bit more help. In the new study, researchers from the VA’s National Teleradiology Program assessed Avicenna.ai’s CINA v1.0 algorithm for detecting ICH on STAT non-contrast head CT studies.

  • AI was used to analyze 58.3k CT exams processed by the teleradiology service from January 2023 to February 2024, with a 2.7% prevalence of ICH.

Results were as follows…

  • AI flagged 5.7k studies as positive for acute ICH and 52.7k as negative
  • Final radiology reports confirmed that 1.2k exams were true positives for a sensitivity of 76% and a positive predictive value of 21%
  • There were 384 false negatives (missed ICH cases), for a specificity of 92% and a negative predictive value of 99.3%
  • The algorithm’s performance at the VA was a bit lower than in previously published literature
  • Cases that the algorithm falsely flagged as positive took over a minute longer to interpret than prior to AI deployment
  • Overall, case interpretation times were slightly lower after AI than before

One issue to note is that the CINA algorithm is not intended for small hemorrhages with volumes < 3 mL; the researchers did not exclude these cases from their analysis, which could have reduced its performance.

  • Also, at 2.7% the VA’s teleradiology program ICH prevalence was lower than the 10% prevalence Avicenna has used to rate its performance.

The Takeaway

The new findings aren’t exactly a slam dunk for AI in the teleradiology setting, but in terms of real-world results they are exactly what’s needed to assess the true value of the technology compared to outcomes in more tightly controlled environments.

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.

Is Head CT Overused in the ED?

Posted on by Brian Casey

A new study suggests that head CT could be overused in the emergency department for patients presenting with conditions like headache and dizziness. Writing in a paper in Internal and Emergency Medicine, researchers looking at CT angiography use at a large medical center found a big increase in CTA utilization – even as the rate of positive findings dropped. 

CTA is a powerful tool that can quickly and efficiently give clinicians information to guide treatment of acute neurovascular conditions like aneurysm and stroke. 

  • As such, many emergency departments have been installing their own CT scanners to enable them to scan emergent patients without transporting them to the radiology department. 

But with great power comes great responsibility, and there is always the temptation to scan first and ask questions later. 

  • To better understand changing CTA use in the emergency setting, researchers from the Harvey L. Neiman Health Policy Institute analyzed CTA exams at a level 1 trauma center that sees about 110k emergency patients a year.

Researchers analyzed 25k ED visits from 2017 to 2021 and correlated them to head and neck CTA exams for headache and/or dizziness, finding …

  • The rate of CTA exams rose 64%, from 7.9% of ED visits to 13%
  • Symptomatic patients were 15% more likely to have a CTA in 2021 versus 2017
  • The rate of positive CTA findings fell 38%, from 17% to 10%
  • Patients with private insurance were more likely to have CTA (OR=1.44)
  • Black patients were less likely to be scanned (OR=0.69)

The researchers said the findings indicate the need for better clinical decision support tools, which they believe can help emergency physicians provide an accurate diagnosis without exposing patients to unnecessary radiation and incurring additional cost. 

The Takeaway

This study further confirms widespread accounts that head and neck CTA is overused and on the rise. As the US government backs off on its attempt to force clinical decision support on referring physicians, it may be up to health systems and providers themselves to ensure more appropriate utilization – in a way that doesn’t rely on heavy-handed tools like prior authorization. 

PET’s Milestone Moment

Posted on by Brian Casey

In a milestone moment for PET, CMS has ended its policy of only paying for PET scans of dementia patients if they are enrolled in a clinical trial. The move paves the way for broader use of PET for conditions like Alzheimer’s disease as new diagnostic and therapeutic agents become available. 

CMS said it was rescinding its coverage with evidence development (CED) requirement for PET payments within Medicare and Medicaid. 

  • Advocates for PET have chafed at the policy since it was established in 2013, claiming that it restricted use of PET to detect buildup of amyloid and tau in the brain – widely considered to be precursors to Alzheimer’s disease. The policy limits PET payments to one scan per lifetime for patients enrolled in clinical trials. 

But the landscape began changing with the arrival of new Alzheimer’s treatments like Leqembi, approved in January 2023. CMS telegraphed its changing position in July, when it announced a review of the CED policy, and followed through with the change on October 13. The new policy…

  • Eliminates the requirement that patients be enrolled in clinical trials
  • Ends the limit of one PET scan per Alzheimer’s patient per lifetime
  • Allows Medicare Administrative Contractors (MACs) to make coverage decisions on Alzheimer’s PET
  • Rejects requests to have the policy applied retroactively, such as to when Leqembi was approved

CMS specifically cited the introduction of new anti-amyloid treatments as one of the reasons behind its change in policy. 

  • The lifetime limit is “outdated” and “not clinically appropriate” given the need for PET for both patient selection and to potentially discontinue treatment if it’s ineffective or if it’s worked to clear amyloid from the brain – a key need for such expensive therapies. 

The news was quickly applauded by groups like SNMMI and MITA, which have long advocated for looser reimbursement rules.

The Takeaway

The CMS decision is great news for the PET community as well as for patients facing a diagnosis of Alzheimer’s disease. The question remains as to what sort of reimbursement rates providers will see from the various MACs around the US, and whether commercial payers will follow suit.

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.

MRI Findings Linked to Psychosis

Posted on by Brian Casey

Over one-quarter of patients presenting with a first episode of psychosis had some kind of abnormality on brain MRI scans, and about 6% of all findings were clinically relevant and required a change in patient management. Writing in JAMA Psychiatry, researchers from the UK and Germany say their study suggests that MRI should be used in the clinical workup of all patients presenting with psychosis. 

Psychosis caused by another medical condition – called secondary psychosis – can have causes that produce brain abnormalities visible on MRI scans. These are findings like white-matter hyperintensities that – while not themselves a form of pathology – are sometimes associated with more serious conditions like cognitive decline. 

MRI scans of people experiencing their first psychotic episode could detect some of these abnormalities before subsequent episodes occur. But at present there is no consensus as to whether MRI should be used in the evaluation of patients presenting with first-episode psychosis. 

In a meta-analysis, researchers wanted to investigate the prevalence of intracranial radiological abnormalities on MRI scans of patients with first-episode psychosis. They reviewed 12 independent studies that covered a total of 1,613 patients. Findings across all the studies included:

  • A prevalence rate of 26.4% for all radiological abnormalities 
  • A prevalence rate of 5.9% for clinically relevant abnormalities 
  • One in 18 patients had a change in management after an MRI scan
  • White-matter hyperintensities were the most common abnormality, with a prevalence of 7.9% for all abnormalities and 0.9% among clinically relevant abnormalities

Given the impact of MRI on patient management, the authors suggested that performing routine scans on people after their first psychotic episode could have both clinical and economic benefits. This could be especially true due to the financial costs of failing to identify a clinically relevant abnormality that could lead to a later episode if not treated.

The Takeaway 

These findings may break the logjam over whether MRI should be routinely used in the evaluation of patients with first-episode psychosis. The authors note that while many of the abnormalities found on MRI in the studies they reviewed did not require a change in patient management, abnormalities could be harbingers of poorer patient outcomes, even if they don’t eventually lead to a diagnosis of secondary psychosis.

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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