Tag: CT radiation

CT vs. MRI for Pediatric TBI Surveillance

Posted on by Brian Casey

Sometimes less is more. That may be the case with pediatric CT for surveillance of traumatic brain injury, which should be limited as much as possible due to the radiation it delivers to young patients. Other modalities like MRI should be considered instead for follow-up.

That’s according to a new Viewpoint article in JAMA Pediatrics that proposes a new surveillance protocol relying on rapid MRI scans rather than CT to follow kids who have experienced TBI.

The authors note that the head is the most frequently imaged body region in pediatric CT, with a 2025 study claiming…

  • Cancer risk in scanned kids rose with higher radiation exposure.
  • Just two head CT scans added up to a 1.8X higher risk of hematologic malignancy by age 21.
  • 2-3 scans conferred a 2X higher brain cancer risk.

But regardless of how you interpret those statistics, few imaging specialists would dispute the need to keep pediatric CT radiation dose as low as reasonably achievable.

Instead of CT, the new imaging pathway proposed in JAMA Pediatrics recommends a rapid MRI protocol for surveillance imaging, as follows…

  • Initial TBI diagnosis should continue to be made with index cranial CT to identify hemorrhage. 
  • Stable patients should be referred to MRI using motion-tolerant and blood-sensitive sequences like T2 with gradient-echo or susceptibility-weighted imaging. 
  • Such sequences can be performed without sedation in 5-7 minutes or less.
  • For unstable patients, timely imaging – regardless of modality – and urgent neurosurgery consultation should be prioritized.  

But there are barriers to wider use of MRI, such as the availability of MRI scanners and technologists, especially outside daytime hours.

  • Nor do the authors recommend that children be transferred to other facilities solely to receive MRI scans. 

But in cases where MRI is available, every effort should be made to provide a radiation-free option for tracking children with TBI.

The Takeaway

Radiology has demonstrated impressive progress in reducing overall CT radiation dose in the long term. The new article recommending an MRI-forward pathway for following children with TBI shows that additional progress can be made when it comes to our most vulnerable patients.

Rating CT Image Quality

Posted on by Brian Casey

As radiology strives to reduce CT radiation dose, one of its challenges is maintaining image quality while keeping dose low. A new five-star system for rating images is described in a new paper in EJR and could offer a solution by establishing an easy-to-understand global metric.

The radiology community has been making progress in reducing CT radiation dose, but much work remains to be done.

  • In particular, radiology professionals struggle between the desire for better-looking images – which usually result from higher radiation dose – with low-dose images that may be noisier but are good enough to make a diagnosis.

While there are lots of metrics for measuring radiation dose, image quality doesn’t have a widely recognized scale. 

  • So a team from the IAEA and MGH worked together to develop one, based on the widely recognized five-star paradigm for ranking consumer-facing businesses. 

In an interesting wrinkle, the five-star system acknowledges the dose dilemma, essentially penalizing images in which too much radiation dose was used to produce an image that’s crisper than what’s needed for diagnosis. 

  • On the other hand, the system rewards images that might be noisy due to use of less radiation, but that are still diagnostic.

 The system’s ratings are as follows…

  • Five stars – Acceptable, despite high image noise associated with low-dose CT.
  • Four stars – Acceptable for all parts within the region of interest.
  • Three stars – Acceptable, despite unintended high noise and/or some artifacts.
  • Two stars – Excellent quality with unjustifiably low image noise and no artifacts.
  • One star – Non-diagnostic, due to excessive noise or artifacts, or poor contrast.

To test the rating scale, IAEA and MGH researchers performed a study at six hospitals across five European countries. 

  • CT scans of 2.7k adults were acquired, and three radiologists per hospital were trained in the five-star scale and scored the images to see how reader subjectivity affected the scoring. 

The study found… 

  • Reader concordance was up to 93% at some sites, indicating little variability in scoring.
  • Overall discordance was rare, at 1.6%.
  • The two-star ratings (in which too much radiation was used) were associated with higher radiation dose in nearly all patient weight groups. 

The Takeaway

The new study shows that a five-star system for rating CT image quality is feasible and can reveal cases of unnecessarily high radiation dose. The question is whether the system remains an interesting thought experiment, or if it becomes an integral part of radiology’s effort to better manage radiation.

CT Radiation Dose Drops in Nationwide Survey

Posted on by Brian Casey

Some good news arrived this week in the campaign to reduce CT radiation dose. A new nationwide survey in Radiology found that radiation dose from CT scans has fallen markedly over the past decade in the U.S.

CT has been radiology’s workhorse modality since the 1980s thanks to its winning combination of cost-effectiveness and diagnostic power. 

  • But radiation dose has always been the modality’s Achilles heel. That was highlighted by a controversial 2025 paper claiming that routine CT could cause over 100k cancers in a year in the U.S.

There are plenty of technologies that effectively reduce CT radiation dose, but the trick has always been getting clinicians to use them. 

  • Another problem is standardizing best-practice CT protocols, so there’s less variation in radiation dose between CT scanners in the same health system or institution. The key to standardization is establishing best-practice benchmarks.

A landmark study published almost 10 years ago got the ball rolling by tracking radiation dose in 2014, producing key metrics like diagnostic reference levels (DRLs) and achievable doses (AD) for 1.3M exams at 583 U.S. CT sites.

  • DRLs represent the 75th percentile of dose distribution, while ADs are set at the 50th percentile, and both numbers represent targets for dose optimization efforts that are dynamic and can change over time. 

In the current study, researchers updated the radiation knowledge base with new data from 5.2M CT exams at 592 U.S. facilities, a 4X larger sample than in 2014, finding…

  • Overall radiation dose fell by 22% as measured by volume CT dose index (CTDIvol) and by 20% using dose-length product, another common radiation measure.
  • The largest dose reductions came in chest CT with contrast (-31%) and chest CT without contrast (-27%), while head CT without contrast fell 3.5%. 
  • New levels of achievable dose benchmarks were set for a variety of CT exams, giving CT facilities new targets for radiation dose reduction that are in some cases as much as 19% lower than 2014 targets.

The Takeaway

The new findings on CT radiation dose reduction are a welcome counter to recent studies that have whipped up hysteria around medical radiation. But now is no time to take the foot off the pedal – radiology must continue to drive dose lower through a combination of new technologies and judicious protocol standardization.

New CT Protocols Reduce Radiation Dose

Posted on by Brian Casey

With patient safety top of mind these days, radiology professionals are correct to focus on performing CT scans with less radiation. To that end, three recently published research studies highlight new protocols to do just that.

Radiation safety has been one of the top radiology stories in 2025 following several studies underscoring the links between medical radiation and cancer. 

  • The irony is that patient radiation exposure can be reduced dramatically using protocols that already exist – it’s just a matter of applying them consistently in the real world. 

In the first paper, published in European Journal of Radiology, researchers share their MINDS-CAD protocol for coronary CT angiography. 

  • MINDS-CAD relies on tailoring contrast dose to patient weight and CT scanner tube voltage using a five-step process. 

MINDS-CAD was tested with 112 obese patients getting clinically indicated CCTA with Siemens Healthineers’ Somatom Force dual-source CT scanner and Bayer’s Ultravist 370 contrast agent. Researchers found that compared to a conventional tube voltage-adapted protocol, MINDS-CAD…

  • Achieved superior image quality according to cases rated “good” or “excellent” (86% vs. 75%).
  • Generated fewer poor-quality scans (3.5% vs. 8.8%).
  • Produced sharply lower radiation dose (99 vs. 386 mGy•cm).
  • Saw no link between vascular attenuation and BMI or tube voltage.

In a second EJR paper, researchers from India tested the ability of an AI-based reconstruction algorithm to reduce dose in cerebral CTA exams.

  • They used Philips’ Precise Image AI-based reconstruction protocol, which produces images resembling traditional filtered back projection scans while reducing noise like advanced iterative reconstruction methods.

In tests with 68 patients who got cerebral CTA at 100 kVp, compared to iterative reconstruction, Precise Image…

  • Improved contrast-to-noise ratio 26%, signal-to-noise ratio 22%, and visual noise 16%.
  • Generated higher image quality scores from radiologists.
  • Generated an extremely low median effective dose of 0.785 mSv.

Finally, a third study – this one in Clinical Radiology – used a “double low” technique of low-energy 50 keV images on GE HealthCare’s Revolution Apex dual-energy CT scanner with TrueFidelity deep learning image reconstruction on 60 patients with cirrhotic liver disease. 

  • Compared with a conventional protocol, the double-low technique had 48% lower radiation entrance dose (4.10 vs. 7.88 mSv) and 32% lower contrast dose (67.3 vs. 99.1 mL), while image quality was rated higher.

The Takeaway

Taken together, the new papers show that radiology’s radiation dose challenge is eminently solvable thanks to the ingenuity of clinicians and researchers who are pioneering new ways to scan.

Reducing CT Radiation Dose System-Wide

Posted on by Brian Casey

CT radiation dose has been one of the top radiology headlines this year due to the publication of several studies linking radiation to cancer risk. But new research offers hope that CT radiation dose can be reduced, even across large healthcare systems. 

CT’s link to cancer risk has been controversial, but most established models connect low-level radiation to cancer formation.

There are lots of great technologies for reducing CT radiation dose, from photon-counting CT to adjusting scanner parameters like mA and kVp, while image reconstruction algorithms can upscale noisy low-dose images to look like higher-quality exams.

  • But the problem has always been getting these technologies into the hands of clinicians – and then making sure they use them, especially across large multi-center health systems, where dose can vary even within the same network.  

Taking a crack at the problem were cardiologists from Lee Health Heart Institute in Fort Myers, Florida, in a new paper in JACC: Case Reports. 

  • They specifically looked at radiation dose for coronary CT angiography exams, determining that based on the literature an optimal radiation dose for CCTA should be ≤ 4 mSv – lower than the system’s 6.2 mSv median dose. 

So they implemented several strategies for reducing CCTA dose…

  • Standardizing scanning protocols that emphasized prospective ECG gating, reduced field of view, BMI-tailored tube voltage (kVp), and elimination of redundant imaging phases.
  • Setting parameters for single-source CT at 100 kVp for patients with BMI <30 and 120 kVp for BMI ≥30, with prospective scanning for 60-80% of the cardiac cycle.
  • Using similar kVp settings for dual-source CT scanners, but implementing systolic imaging between 250-450 milliseconds.

How well did it work? After reviewing the program, researchers found…

  • System-wide radiation dose fell 23% (4.8 vs. 6.2 mSv).
  • Diagnostic quality improved as measured by the acceptance rate for FFR-CT exams (93% vs. 91%). 
  • Dose consistency was achieved across locations despite differences in scanner models and practices.

The Takeaway

The new study on CCTA radiation dose shows that dose can be reduced system-wide while maintaining – and even improving – diagnostic image quality. Is it a problem that the research was led by cardiologists and not radiologists? Not if you’re a patient. 

Emergency CT Use Booms

Posted on by Brian Casey

Increased use of CT drove a boom in medical imaging utilization in the emergency department setting over the past 10 years. That’s according to a new study in Radiology that comes amid increased scrutiny over the long-term health effects of CT radiation. 

CT is tailor-made for evaluating patients in the emergency setting. It’s fast, relatively inexpensive, and provides high-quality images that can deliver a diagnosis quickly.

  • For these reasons, emergency departments have been quick to install workhorse CT scanners running at all hours in the hope that faster diagnoses will lead to better patient outcomes. 

But there are also downsides to the growth in CT utilization. It can put strains on radiology departments to read all the new scans – a particular challenge in an era of workforce shortages.

  • Concerns about the link between CT radiation dose and cancer also persist. Two controversial studies were published this year on the subject, one linking CT to future cancers across the U.S. population and the other specifically to pediatric blood cancer. 

The new study offers a useful benchmark for tracking CT’s growth in the ED. Researchers chronicled changes in U.S. emergency imaging use in Medicare from 2013 to 2023, finding that per 100 Medicare beneficiaries…

  • CT use grew 96% (37 vs. 19 encounters).
  • While ultrasound only grew 20% (2.8 vs. 2.3 encounters).
  • And radiography use remained flat at 37 encounters in both years.

In addition, the number of overall ED encounters actually declined 16% (55 vs. 65 encounters), showing that imaging’s growth was due to more imaging per ED encounter rather than overall increased ED visits by beneficiaries. 

  • On a per-encounter basis, CT use grew 134% over the study period compared to 43% for ultrasound and 19% for radiography. 

Researchers believe that the difference in modality growth rates could be due to the use of CT to accelerate patient turnover in the ED.

  • Meanwhile, ultrasound use may have grown more modestly due to the proliferation of point-of-care handheld scanners among non-radiologists.

The Takeaway

The new findings underscore the conundrum behind emergency CT – it’s an incredibly powerful technology that nevertheless requires restraint in order to be used judiciously. Let’s hope emergency physicians take note.

Obesity Drives CT Radiation Dose Higher

Posted on by Brian Casey

The proportion of patients getting CT scans with high radiation doses more than tripled over a five-year period. That’s according to a new study in British Journal of Radiology that found the rate of high-dose CT rising along with growing obesity rates – despite technical advances in CT instrumentation.

CT radiation dose has been closely watched due to its potential to cause cancer.

  • A controversial paper published earlier this year in JAMA Internal Medicine estimated that all the CT scans performed in a year in the U.S. would cause 100k cancers.
  • And another recent paper made a connection between the number of CT scanners installed in a country and the number of patients with high cumulative radiation exposure (over 100 mSv) over five years.

In the new paper, a research team led by radiation safety expert Madan Rehani, PhD, tracked radiation exposure to patients who got CT exams at Massachusetts General Hospital from 2013 to 2022. 

  • They defined high-dose CT exams as those in which individual exam radiation dose exceeded 50 mSv. 

Over a 10-year period, nearly 1.4 million CT exams were performed on 382k patients, revealing that the rate of CT exams with effective doses ≥ 50 mSv…

  • Was less than 1%, but more than tripled from 2017 to 2022 (0.25% to 0.86%).
  • 59% of high-dose exams were multiphase studies (≥ 3 phases).
  • The rate of high-dose CT exams rose 7X faster in overweight and obese patients than in their underweight or normal-weight counterparts in a subset of 5k patients with available BMI data.

There was a close association between obesity and radiation dose, as patients with larger body habitus require more radiation to penetrate deeper for diagnostic-quality images. 

  • Ironically, the introduction of CT scanners with higher table weight capacity and larger gantry diameter may have contributed to the increase by making it possible to scan patients who previously were too large to be imaged.

Researchers also believe the rise in radiation dose starting in 2018 occurred around the same time as MGH’s introduction of more advanced CT scanners with more powerful X-ray tubes.

The Takeaway

The new findings on CT radiation dose illustrate the balancing act that imaging providers face between radiation safety and achieving optimal image quality. With obesity rates steadily rising, it’s a choice that will become increasingly common. 

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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