Computed Tomography: Revolutionize COVID-19 Diagnosis with Low-Dose Chest Scans


Computed Tomography image showing diagnosis

Dr. Ana Luisa Mendizábal Méndez.

The COVID-19 pandemic has brought unprecedented challenges to the medical community, bringing resources as computed tomography. One of the biggest challenges is the timely and accurate diagnosis of the disease, which is crucial for effective patient management and infection control. Radiology societies around the world have recognized the importance of imaging in the diagnosis of COVID-19 and have established guidelines for the use of various imaging modalities, including chest CT.

While chest CT is not the recommended initial diagnostic method for COVID-19,it has proven to be a valuable tool, particularly in cases where laboratory tests are negative, as CT findings can appear earlier than a positive RT-PCR test. Understanding the role of chest CT in COVID-19 diagnosis is essential for clinicians to make informed decisions in the management of the disease.

Nevertheless, computed tomography may present a normal appearance in the first two days of infection, which limits its usefulness as a screening method.

There is great variability in the results of studies related to the diagnostic capacity of chest computed tomography  in COVID-19. According to the North American Radiological Society, sensitivity ranges from 60% to 98%, while specificity ranges from 25% to 53%. The positive predictive value is 92%, and the negative predictive value is 42%, which is considered a limitation for its use as a screening test.

Despite the potential risks associated with CT, such as exposure to ionizing radiation and the possible development of cancer, its usefulness in the management of the current health emergency cannot be ignored. Advances in equipment manufacturing technology and progress in the development of low-dose protocols have made computed tomography (CT) a more viable option, especially for patients who may be at a higher risk for complications from COVID-19.

In fact, low-dose CT protocols have been continuously implemented and improved since the late 1990s for the purpose of using chest CT as a screening method for lung cancer. These protocols can be adapted and applied to the diagnosis and management of COVID-19, allowing for a safer and more efficient use of computed tomography in the clinical setting. It is important for clinicians and radiologists to stay up-to-date on these developments and utilize them appropriately in the care of patients with COVID-19.

Currently, the estimated average radiation dose in a low-dose computed tomography (LDCT) is 1.6 to 2.4 mSv, while the dose of a chest CT with “standard” technique is approximately 7 mSv.

It is important to know the parameters that must be modified in the CT equipment to obtain a low-dose study, especially because most cases of COVID-19 in Mexico occur in a young population sector, aged 30 to 34 years.

Recently, the European Radiology journal published a protocol that reduced the estimated radiation dose to 0.203 mSv using a dual-source equipment, without significantly sacrificing signal-to-noise and contrast-to-noise ratios. To learn about other low-dose chest computed tomography (CT) protocols on different equipment, we recommend consulting the guide published by the American Association of Medical Physicists (AAPM), available at the following link.

Overall, while CT is not the recommended initial diagnostic method for COVID-19, it is still useful, especially in cases that are negative to the laboratory test. Low-dose CT protocols have been developed and improved over time, and they should be considered in the management of this health emergency, taking into account the potential risks of ionizing radiation.


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