Did Malpractice Risk Kill V/Q Exams?

CT perfusion angiography exams have largely replaced nuclear medicine-based ventilation/perfusion (V/Q) studies for detecting pulmonary embolism. But a new article in Academic Radiology suggests that CT’s rise wasn’t entirely based on clinical efficacy – fears of malpractice risk may have played a role. 

V/Q studies can help diagnose PE by enabling clinicians to visualize lung perfusion, showing defects such as blockages in pulmonary vessels. The scans are typically performed in three phases … 

  1. An albumin injection to show pulmonary vasculature.
  2. A radiopharmaceutical that’s inhaled and imaged with a gamma camera.
  3. A chest radiograph to correlate findings. 

The scans dominated PE imaging in the 1980s, but the rise of CT saw radiology facilities begin to shift.

  • CTPA was seen as having higher spatial resolution and was easier to perform than nuclear medicine exams. 

But the new article suggests that there were other forces at work as well – in particular, fear of malpractice risk from PEs that weren’t adequately followed after inconclusive V/Q exams.

  • The problem originated with clinical guidelines for V/Q reporting that classified some 20% of V/Q studies as “low probability” for PE when they probably would have better been classified as “inconclusive” or “non-diagnostic.”

As a result, a number of “low probability” patients weren’t followed up adequately, with tragic results that later figured into medical malpractice cases …

  • A patient who was diagnosed with pneumonia after an inconclusive V/Q exam, sent home, and died one day later of a “massive” PE.
  • A patient with leg and chest pain who was given heparin after a negative V/Q scan and later suffered internal hemorrhage; fortunately she survived.
  • A patient with “vague symptoms” who had an inconclusive V/Q scan and later died of an undiagnosed PE that some claimed would have been detected on CTPA.

Indeed, the theme of PE malpractice cases began to shift over time, from failure to diagnose V/Q scans to failure to order CTPA exams – which were soon seen as the clinical gold standard.

The Takeaway

Given the fast pace of development in radiology, it’s inevitable that some technologies that were once clinical staples fall by the wayside. But the new article offers a fascinating look at how clinical language can lead to medico-legal concerns that influence physician behavior – often in ways that are impossible to detect as they happen.

Combo CT Screening Detects More Disease

A CT lung cancer screening program that also offered abdominal non-contrast CT scans detected a large number of abnormalities outside the lung in a population of people with smoking histories. The combined approach could offer a more efficient way to detect multiple pathologies in a single patient visit. 

CT lung cancer screening is gaining momentum globally, but clinicians and researchers continue to look for ways to make it more valuable. 

  • That’s a good thing, because smoking is a risk factor not just for lung cancer, but also other pathologies like abdominal aortic aneurysm (AAA) – so why not screen for those at the same time?

In a paper in European Urology, U.K. researchers describe their Yorkshire Kidney Screening Trial (YKST), which sought to detect kidney cancer by piggybacking on the county’s existing CT lung cancer screening program. 

  • Abdominal non-contrast CT exams were offered at the same time as thoracic CT lung screening scans to high-risk people who met the lung program’s screening criteria, namely aged 50-85 and more than 30 pack-years of smoking history. 

In all, 4k people accepted the offer to get additional abdominal CT scans, which had the following findings …

  • 64% of patients had normal findings, while another 20% had images that required additional review but no further action.
  • 5.3% had a new serious finding.
  • Serious findings were broken down as follows: renal stones ≥ 5 mm (3%), AAA (1.5%), renal mass/complex cysts (0.62%), kidney cancers (0.25%), and other cancers (0.25%).
  • It took 13 minutes of additional time to perform the abdominal CT scan.

Researchers said the prevalence of additional disease in YKST was within the range of other U.K. screening programs, such as for colorectal cancer (0.16-0.61%) and breast cancer (0.92%). 

  • The high prevalence of AAA was “unexpected,” especially since many AAA cases were found in people who aren’t covered by existing AAA screening programs. 

The Takeaway

As with recent research combining CT lung screening with coronary artery calcium (CAC) scoring, the new study shows that lung screening offers an opportunity to screen for more than just lung cancer. By detecting additional disease, combo screening has the potential to flip the script when it comes to screening’s cost-benefit ratio. 

Lung Screening Narrows Disparities

New research confirms that not only does low-dose CT screening reduce lung cancer mortality, it can also narrow health disparities. Researchers found that screening’s beneficial impact was greater at lower socioeconomic levels in a new study published in Lancet Regional Health – Europe.

As we mentioned in our last issue, CT lung cancer screening is gaining momentum globally; at the same time, researchers have documented greater mortality and morbidity for a variety of diseases among racial minorities and at lower socioeconomic levels.

  • This difference can be especially profound when it comes to lung disease, given higher smoking rates among some minority groups and economically disadvantaged populations.

In the original UK Lung Cancer Screening Trial (UKLS) in 2021, researchers found that a single CT screening round produced a 16% lung cancer mortality reduction. 

  • The new study is a secondary analysis of UKLS to investigate whether CT lung screening’s impact differed by socioeconomic status, which is important given that smoking occurs in England at higher rates in the most deprived neighborhoods compared to wealthier ones (24% vs. 6.8%).

UKLS researchers compared lung cancer mortality rates in 4k individuals in different groups classified by a widely used socioeconomic barometer. They found that … 

  • CT lung screening had the same lung cancer mortality benefit in both low and high socioeconomic groups (-19% vs. -20%)
  • But there was a bigger reduction in death from COPD in lower socioeconomic groups (-34% vs. +4%)
  • And fewer deaths from other lung diseases (-32% vs. +10%)
  • While cardiovascular mortality was also lower (-30% vs. -13%)
  • All-cause mortality was lower in lower socioeconomic groups – a benefit not seen at higher levels

Lung screening’s reduction in all-cause mortality is particularly intriguing, as this is an accomplishment that has eluded most other cancer screening tests – a point that has been repeatedly hammered home by screening skeptics.

The Takeaway

The new findings highlight how – to a greater degree than other major cancer screening tests – CT lung screening has the potential to address ongoing racial and socioeconomic healthcare disparities. It’s yet another reason to press for broader adoption of lung screening.

Imaging and COVID Vaccine Effectiveness

In the debate over how long the protection from COVID-19 vaccines last, radiology has now entered the chat. A new study in Radiology shows that people with COVID who got vaccinated more than eight months before COVID diagnosis had more severe clinical findings on imaging exams. 

The rapid development of COVID vaccines and their rollout worldwide has been one of the biggest public health success stories of the last 100 years. 

  • Still, even the most effective vaccines lose their potency over time, and COVID vaccines are no different. 

The question is, how long does the COVID vaccine’s protection last? 

  • Previous research documented a decline during the Delta and Omicron waves in vaccine effectiveness against hospitalization, from 92% to 79% after 224-251 days, and a drop in efficacy against death from 91% to 86% after 168-195 days in those with severe COVID.

To shed more light on the issue, researchers in South Korea performed imaging exams on 4.2k patients with COVID from June 2021 to December 2022. 

  • They correlated the severity of clinical outcomes like pneumonia visible on imaging exams to the length of time between patient diagnosis and when they had been vaccinated. 

Compared to those vaccinated in the last 90 days before COVID diagnosis, people vaccinated more than 240 days …

  • Had almost twice odds of severe outcomes (OR = 1.94)
  • Had higher odds of severe pneumonia on chest radiographs (OR = 1.65)
  • But there was no difference in the odds of severe outcome between those vaccinated in the last 90 days and those vaccinated 91-240 days before diagnosis

In an interesting wrinkle to the study, the researchers found no statistically significant difference in odds of severe pneumonia visible on chest CT scans between those vaccinated more than 90 days before diagnosis and those vaccinated within 90 days.

  • The authors proposed that the low use of CT for pneumonia assessment in their study population (20%) and its use primarily for critically ill patients could have introduced bias into the results. 

The Takeaway

The new findings shed light on the declining potency of COVID vaccines over time and could inform public debate over the length of time between boosters. The research also dovetails with other studies showing that the vaccine’s effectiveness does indeed begin to wane at six months.

Developing the Eighth Modality

Radiology has adopted seven mainstream modalities over its 127 years, and 4DMedical is determined to create the eighth imaging modality with its new XV Scanner.

The XV Scanner would be the first dedicated lung imaging system, giving radiologists four-dimensional and color-coded visibility into patients’ lung airflow and blood flow, and potentially a new way to assess lung diseases. 

  • The XV Scanner integrates fluoroscopy with advanced analytics software, producing qualitative and quantitative 4D lung function metrics 
  • It simultaneously acquires images from different angles, then measures lung tissue motion, and calculates ventilation at each breathing stage and every lung location
  • XV scans take 5 seconds to perform and deliver less radiation than a typical chest X-ray

4DMedical’s XV technology is also backed by a growing number of positive clinical studies, solid post-IPO funding, and an impressive expansion across Australian imaging giant I-Med Radiology’s 250 locations.

Although the XV Scanner hardware is still forthcoming, 4DMedical will initially launch XV software that can be installed on existing fluoroscopy systems (FDA cleared for ventilation, later adding perfusion) and will also support existing CTs in the future. 

  • Software-only might prove to be a logical starting point, providing 4DMedical with a low-friction way to demonstrate XV’s impact on patient care and test whether this impact is great enough to entice imaging departments to add a whole new scanner to their fleets.

The Takeaway

Creating medical imaging’s eighth mainstream modality might be among the most ambitious goals you’ll hear at RSNA 2022, but if the XV Scanner proves to be much better than existing lung imaging techniques, radiology might have to make room for one more.

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