Tag: CT radiation

CT Use Linked to Higher Radiation Exposure

Posted on by Brian Casey

A new study revisits the debate over CT radiation risk, finding a link between greater use of CT scanning in a country and the percentage of patients getting higher cumulative doses of radiation over time.

Managing medical radiation has been a priority for decades, but the issue gained new prominence in April with the publication of a controversial paper linking CT use to future cancers. 

  • Critics accused study authors of sensationalizing the radiation dose issue, but researchers pointed out that they used existing models for radiation dose and cancer risk.

Enter the new study, in which a team led by international radiation safety expert Madan Rehani, PhD, calculated the number of patients getting over 100 mSv of cumulative radiation dose over five years across 27 countries, mostly in Europe. 

  • Radiation at such levels is concerning due to the established dose-response nature of current radiation theory – that is, higher doses are believed to lead to higher cancer risk.

Radiation dose exposure rates for CT, fluoroscopy-guided interventions, and PET were analyzed for 2022 for 513M people from Austria to the U.K., with a particular focus on patients getting over 100 mSv in a five-year period. 

  • For point of reference, a chest X-ray PA view is typically 0.02 mSv, a CT scan 1-10 mSv, and the average for a year of background radiation is about 3 mSv.

Researchers found … 

  • In all, 0.27% of the population received cumulative radiation exposure over 100 mSv.
  • The countries with the highest rates of patients per 1k getting over 100 mSv included Belgium (4.52), Portugal (4.48), Luxembourg (4.19), and France (4.15).
  • These same countries also tended to have the highest use rates of CT exams per 1k population, led by Portugal (285), Luxembourg (249), Belgium (226), and France (224).
  • Countries with the lowest exposure rates over 100 mSv included Finland (1.09), Romania (1.1), Norway (1.64), and Bulgaria (1.76), and all had CT use rates below 100 exams per 1k population.

While the U.S. was not included in the study, other research shows it might fall at the upper end of the scale – if not at the top. 

The Takeaway

The new study offers a sobering take on the radiation dose issue. While reasonable people can debate the exact link between low-level radiation exposure and cancer risk, it’s harder to justify such wide variation in CT use and cumulative radiation exposure between countries, especially those at similar levels of economic development.

CT Cancer Risk Study Raises Questions

Posted on by Brian Casey

The radiology world was turned on its head this week with the publication of a new paper in JAMA Internal Medicine on CT radiation risk. Researchers estimated that all the CT scans performed in the U.S. in a single year would cause more than 100k cancers over the lives of the patients who got them. 

Radiation risk has always been the Achilles heel of CT, radiology’s workhorse modality for advanced imaging. 

  • But CT is plagued by dose variation and a lack of reporting on exactly how much dose patients are getting – especially when it exceeds guidelines.

In the new study, researchers led by radiation safety expert Rebecca Smith-Bindman, MD, of UCSF used existing estimates of low-level radiation risk to calculate how many cancers would result from the 93M CT scans performed in the U.S. in 2023, finding …

  • CT radiation dose would cause 103k future cancers over the lifetimes of the patients.
  • At the current rate, “CT-associated cancer” would account for 5% of all cancers – about the same number caused by alcohol. 
  • The study’s projection of CT-linked cancers is 3X-4X higher than previous estimates, mostly due to the growth in CT utilization. 

The paper generated pushback from sources including the ACR and AAPM, who questioned whether it really reveals any new information about the risks of CT radiation. 

  • They reiterated the medical value of CT scans, noting that the research was based on statistical models and that there are no published studies directly linking CT scans to cancer.

Another thing the paper doesn’t touch on are the dramatic reductions in CT radiation dose that have occurred in recent years. 

  • CT protocol optimization and AI-based data reconstruction – as well as technologies like photon-counting CT – have enabled imaging professionals to reduce doses to levels previously thought impossible, such as under 1 mSv for a routine chest exam. 

To help providers manage dose, CMS this year launched new dose reporting quality measures, CMS1074v2, designed to reward radiology practices for tracking and reporting radiation dose. 

  • Smith-Bindman is a co-founder of Alara Imaging, which provides software to help radiology providers comply with the new CMS measures. ACR also offers a variety of dose optimization and monitoring tools.

The Takeaway

So what to make of the new study? On the one hand, the sensational headlines it generated could scare many patients away from getting medically necessary CT scans. On the other, any attention toward radiation dose reduction and appropriate imaging is a good thing, and if it spurs new efforts toward more judicious and consistent use of CT at lower radiation levels, so much the better. 

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.

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