Up to 60% of chest CTs could involve over-scanning

Up to 60 percent of chest CTs could involve over-scanning, increasing effective and organ radiation doses and threatening patients whose treatment plans call for imaging exams, researchers  reported online in the European Journal of Radiology this month.

A team led by Fides Schwartz and colleagues in Biel, Switzerland, found that, at multiple practice locations in Europe, incidence of over-scanning in chest CTs could be as low as 7 percent and as high as 60 percent, with varying increases in radiation dose. And, though CT use is accepted and encouraged for diagnostic purposes, its increasing prevalence on the global stage means the population’s overall exposure to ionizing radiation is also rising.

Things like adaptive collimation, automatic tube current modulation, automatic tube voltage selection and iterative reconstruction algorithms have all helped decrease radiation doses in these cases, Schwartz et al. said, but those technologies aren’t useful if clinicians fail to apply the simple principles—like proper scan ranges—to their work.

“Former studies have shown that the importance of a proper scan range in the context of radiation exposure is underestimated in clinical practice,” the authors wrote. “However, these studies were limited to results from single institutions. To date, no data is available which compares the incidence of over-scanning among different hospitals.”

Typically, CT technologists rely on scouts, ideally a pair of them, to define cranial and caudal scan borders in an imaging system. But, Schwartz and co-authors said, many times hospitals will perform only a coronal scout, ignoring the patient’s sagittal plane and risking an inappropriate scan range that could lead to under- or over-scanning.

The researchers retrospectively examined scout images of 600 chest CT scans from six hospitals using a radiation dose tracking software. They determined optimal scan range for each image, comparing those specs to the images’ actual scan ranges.

Caudal over-scanning was the most common mistake, according to the study—the authors marked its presence in 147 of 600 scans, and the over-scanning resulted in increased organ effective doses in the upper abdomen by up to 14 percent. Cranial over-scanning was an issue in 45 cases, with organ effective doses increasing by 0.35 mSv in the thyroid gland, and simultaneous cranial and caudal over-scanning was present in 29 instances, with an effective radiation dose increase of 0.29 mSv.

The incidence of over-scanning varied, Schwartz and colleagues wrote, and differed significantly between hospitals. Academic centers had the greatest success rates, while community-centered hospitals struggled the most with over-scanning.

“This emphasizes the importance of providing continuous training to CT technologists and radiologists to ensure an increased awareness and prevention of over-scanning in clinical practice,” the authors wrote.

Schwartz and co-authors said rates of radiation exposure and over-scanning could be reduced with the consistent use of two imaging scouts and the addition of dose-tracking software that could be used as a quality-control and training tool for technologists.

“Substantial differences in the incidence of over-scanning in chest CT exist among different hospitals,” they wrote. “These differences result in excessive effective radiation dose and increased individual organ effective doses in patients.”