Low-Dose High-Res CT Protocol for COVID-19

April 20, 2020

Protocol can minimize dose for CT scans when viral testing is less available.

Even though CT scans aren’t recommended for COVID-19 detection, radiologists still need a strategy for using the modality – and minimizing radiation dose exposure – for cases where other detection options aren’t readily available, according to industry experts.

To provide some guidance for imaging patients with suspected COVID-19 infection, a team of experts from the Iranian Society of Radiology, led by Mehran Arab-Ahmadi, M.D., MPH, outlined a strategy in Academic Radiology for imaging when there’s a shortage of the gold standard of testing, reverse transcriptase-polymerase chain reaction (RT-PCR).

“Low dose high-resolution CT might have more advantages than RT-PCR, especially in highly infected societies with low availability of PCR-kits,” the team wrote. “Our primary goal of screening and evaluation is to detect COVID-19 infection in patients with highly suspicious clinical conditions and laboratory findings.”

The Society developed a protocol for use with patients who have a high probability of COVID-19. It was created to work with all CT scanners with four or more detectors, the team said, and it’s defined for each manufacturer and model.

To find ground glass opacities in the typical sub-pleural location, the team made these suggestions:

  • Perform the scan with one breath-hold to reduce thoracic motion.

  • Capture 1 mm-to-3 mm slices.

  • Coronal and sagittal reconstructions are optional.

  • Maximum Intensity Projections used for lung nodules are not necessary.

  • Do not use oral or intravenous contrast agents.

  • Place the patient supine, arms above his or her head, in the middle of the gantry.

  • Capture image throughout the entire thorax

  • Follow these parameters to minimize radiation dose:

               Kvp: 100-120
               mAs: 50-100
               Pitch: 0.8-1.5
               Thickness: 1-3 mm