Tag: covid

Slashing CT Radiation Dose

Posted on by Brian Casey

Cutting CT radiation dose should be the goal of every medical imaging facility. A new paper in European Radiology offers a promising technique that slashed CT dose to one-tenth of conventional CT – and just twice that of a standard chest X-ray.

CT’s wide availability, excellent image quality, and relatively low cost make it an invaluable modality for many clinical applications.

  • CT proved particularly useful during the COVID-19 pandemic for diagnosing lung pathology caused by the virus, and it continues to be used to track cases of long COVID.

But patient monitoring can involve multiple CT scans, leading to cumulative radiation exposure that can be concerning, especially for younger people.

  • Researchers in Austria wanted to see if they could use commercially available tools to produce ultra-low-dose CT scans, and then assess how they compared to conventional CT for tracking patients with long COVID.

Using Siemens Healthineers’ Somatom Drive third-generation dual-source CT scanner, they adjusted the parameters on the system’s CAREDose automated exposure control and ADMIRE iterative reconstruction to drive down dose as much as possible.

  • Other ultra-low-dose CT settings versus conventional CT included fixed tube voltage (100 kVp vs. 110 kVp), tin filtration (enabled vs. disabled), and CAREDose tube current modulation (enabled – weak vs. enabled – normal). 

They then tested the settings in a group of 153 patients with long COVID seen from 2020 to 2021; both ultra-low-dose and conventional CT scans were compared by radiologists, finding … 

  • Mean entrance-dose radiation levels with ultra-low-dose CT were less than one-tenth those of conventional CT in (0.21 mSv vs. 2.24 mSv); a two-view chest X-ray is 0.1 mSv
  • Image quality was rated 40% lower on a five-point scale (3.0 vs. 5.0)
  • But all ultra-low-dose scans were rated as diagnostic quality
  • Intra-reader agreement between the two techniques was “excellent,” at 93%

The findings led the researchers to conclude that ultra-low-dose CT could be a good option for tracking long COVID, such as in younger patients. 

The Takeaway

The study demonstrates that CT radiation dose can be driven down dramatically through existing commercially available tools. While this study covers just one niche clinical application, such tools could be applied to a wider range of uses, ensuring that the benefits of CT will continue to be made available at lower radiation doses than ever.

Imaging and COVID Vaccine Effectiveness

Posted on by Brian Casey

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.

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