In the conditions of the next wave of Covid, more and more patients are looking for information which test is preferable in diagnosing the condition of the lungs – Computed tomography (Scanner) or X-ray? Within the pre-hospital care, the answer to this question should be given by the sending specialist – GP or pulmonologist. However, based on the accumulated experience, the diagnostic approaches and the motives for choosing one or another test can be outlined.
Dr. Ventsislav Bozhkov about the diagnosis of Covid pneumonia and the subsequent monitoring of lung lesions:
Dr. Bozhkov, in the context of Covid’s lung lesions, which study do you prefer?
Undoubtedly, the scan is much more informative than a plain X-ray. The computed tomograph generates a three-dimensional image based on a large number of slices, which are combined by software. This allows accurate identification of the affected partitions and tracking the development of the process. The detail and precision in this case are unparalleled in the diagnosis of respiratory organs in general.
Apart from the general motives, there are quite pragmatic prerequisites for appointing a CT scan. In the early stages of Covid infection, most often a chest X-ray does not show any changes, while a scan reveals them. This makes it possible to take timely action.
It should be noted that clear symptoms such as shortness of breath and difficulty breathing occur in advanced pneumonia, when it is not possible to talk about preventive measures. Most often, experts recommend that if on the 6th day after the onset of Covid infection, the patient continues to have a fever, even without any other symptoms, then do a lung scan.
Why, then, did computed tomography of the lung not become a mandatory protocol in the treatment and diagnosis of Covid?
The reason is that the scanner has a higher level of radiation. It should be noted here, however, that this restriction applies mainly to older devices. The latest generation of Siemens CT from the SOMATOM go series has been installed at the Center for Imaging Diagnostics MLADOST. The device has a so-called low-dose mode, in which the radiation is reduced by more than 6 times. In this way, levels are achieved as in a normal X-ray of the spine.
This is especially important in the future, as many patients need to have follow-up tests to track lung damage and whether the body is able to overcome it over time. Here we are talking about a cumulative “ray price” and it is important to keep it to a minimum.
Has low-dose computed tomography been developed specifically for Covid’s research?
Not at all. The low-dose scanner is used mainly for the prevention of lung cancer among risk groups – smokers, patients with genetic predisposition, people working in high-risk environments. The logic is that such a reduction in radiation dose during regular screening does not pose a risk to the patient’s health.
Such campaigns are still not carried out in Bulgaria and therefore low-dose computed tomography (CT) is not popular enough. There is a logical explanation for this – only the latest devices have such a mode of examination, and they are not so many in the country, especially in pre-hospital care, where such screenings actually have to be conducted.
In conclusion, what damage does Covid inflict on the respiratory system?
Covid infection affects the lungs in the form of so-called “interstitial pneumonia”. The affected areas have the appearance of “frosted glass”, and subsequently
fibrous changes (adhesions) develop in these areas. This affects the capacity and functioning of the lungs. In other words, it reduces the amount of oxygen that the body effectively absorbs when inhaled, and this leads to a state of fatigue and exhaustion.
Changes in lung tissue remain after the disease, and there is still insufficient data on whether and when lung function will be fully restored.