A single chest CT scan is equivalent to 400 normal chest X-rays.
Computed tomography (CT aka CAT scans) of the chest uses special x-ray equipment to examine abnormalities found in other imaging tests and to help diagnose the cause of unexplained cough, shortness of breath, chest pain, fever and other chest symptoms.
Because PCR scans have not been reliable for the early diagnosis of the Corona Virus, some doctors have advocated using CT scans as a second or even primary source of information. This is because CT scans are already used in hospitals to diagnose pneumonia.
In one study with patients in China, about 60% tested positive with the PCR, but 88% tested positive with chest CT scan. Of the 60% which were confirmed with the PCR method, it was possible to pick up 97% of cases using chest CT alone. This result supports the claim that PCR fails to pick up about 30% to 40% of positive cases (assuming there are no other causes of pneumonia which is not an accurate assumption).
Even more important, when the PCR test was negative, the positive chest CT scan made it possible to pick up approximately 300 more patients who were very likely to have the infection, and 33% of these were thought to have the Corona virus infection. In all, there were about 900 patients with positive chest CT findings, with an average age of 60 years. Just over 300 of them had positive chest CT findings but negative PCR results. Here is a link to the study: https://pubs.rsna.org/doi/full/10.1148/radiol.2020200642
CT scanning is fast, painless and usually but not always accurate. Unfortunately, CT scans have two major drawbacks. They are very expensive with an average cost of over $2,000. This is just the cost of the test and does not include the other costs of hospitalization.
Also CT scans are very damaging to the cells being targeted because they involve extremely high doses of radiation. A single chest CT scan is equivalent to 400 normal chest X-rays. Sadly, surveys of doctors in the US found that less than 10 percent of them were aware of either the price or the x-ray dosage of CAT scans! https://www.ncbi.nlm.nih.gov/pmc/articles/PMC548232/
Given that the corona virus is not significantly more dangerous than the common flu for most people, the known damage of a CT scan is almost certain to be greater than the unknown damage from the corona virus.
Getting the equivalent radiation of 400 X-rays is going to increase the risk of a person getting cancer 10 to 20 years down the road.
This may not be a major issue for someone who is over 80 years old. But it is certainly an issue for someone under 70 years old.
The corona virus is not and never will be a major cause of death in the US. But cancer is and will continue to be one of the two leading causes of death in the US.
At the very least, before people are given a CT scan, they need to be told that the amount of radiation they are exposed to in this test is very high and could eventually cause them to get cancer.
There is another problem with a CT scan which is lack of accuracy. All the test scan reveals is damage to the lower lungs. This damage may be due to the corona virus. But it can also be due to viral pneumonia or even bacterial pneumonia or even be due to cigarette smoking and or air pollution.
Given the known danger of CT scans, I do not think it is a very useful test for the corona virus.