RADIOLOGY
How CTscan is an effective diagnostic tool for COVID-19 Though RT-PCR is the standard test for diagnosing the disease, patients who are negative on RT PCR, but having contact, signs of the disease, require CT scans to diagnose the COVID-19 lung lesions. Dr M C Balaji Reddy, MD, Focus Diagnostics demonstrates how CT scans are playing a crucial role in diagnosing, grading and staging the lung changes during the COVID-19 pandemic
C
omputed tomography (CT scan) has always been an integral part of diagnosis of diseases, from the time of its invention. Its usage is growing in leaps and bounds and the technology is playing a vital role in early diagnosis and treatment planning. The controversies regarding patient’s exposure to radiation and its harmful effects have always been there and it has been one of the focus areas for the scientists to research ways and means to decrease the harmful effects.
Amidst the ongoing pandemic, CT scan is playing a crucial role in diagnosing, grading and staging the lung changes. Though RT-PCR is the standard test for diagnosing the disease, patients who are negative on RT PCR, but having contact, signs of the disease, require CT scan to diagnose the COVID-19 lung lesions. As current studies show marked variation and are likely to overestimate sensitivity, we will use the lower end of current estimates from systematic reviews, with the approximate numbers of 70% for sensitivity and 95% for specificity for illustrative purposes. (BMJ 2020; 369:m1808 doi: 10.1136/bmj.m1808 (Published 12 May 2020)). It is also playing an important role in prognosticating the disease in proven cases, depending on the lung involvement along with other inflammatory markers.
How do the lung lesions look like?
Ground glass opacities, focal consolidations, focal atelectasis
is graded as given in Table 1 below.
Ground glass opacities (GGO) classically seen in the subpleural or parenchymal regions. The lesions can be of varied shapes. The lesions show prominent coursing vein within septal thickenings. The size of the lesions can vary from few millimeters to involve most of the lung (Check images below).
Staging: What is CT severity score?
Grading: What is CORADS score? The Dutch Radiological Society developed CO-RADS based on other efforts for standardisation. Depending on the appearance of the lung lesions it
TABLE 3
TOTAL CT SEVERITY SCORE - 25 SCORE
CT SEVERITY
The right lung has three lobes and the left lung has two lobes. These five lobes are divided into 20 segments.
(< 8)
Mild
(9-15)
Moderate
(> 15)
Severe
Two types of scoring are followed. If total score is 25: Then each lobe is given a score up 0-5 depending on the area of involvement. (Check Table 2 and Table 3). If total score is 40: 5 lobes have 20 segments, with each segment given a score of 0-2. 0-If no disease,
1 if less than 50 per cent of segment involved 2 if more then 50 per cent segment involved. Higher the severity score with decreased oxygen saturation indicates immediate aggressive medical attention. The CT scan chest adds value to manage the sick patients.
TABLE 1
CO-RADS-1
No
Normal or Non-infectious Abnormalties
CO-RADS-2
Low
Abnormalities consistent with infections other than COVID-19
CO-RADS-3
Indeterminate
Unclear whether COVID-19 is present
CO-RADS-4
High
Abnormalities suspicious for COVID-19
CO-RADS-5
Very high
Typical COVID-19 (ground glass lesions)
CO-RADS-6
PCR +
TABLE 2
(Image 01) Ground glass lesions with prominent vein
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EXPRESS HEALTHCARE
June 2021
(Image 02) Pulmo 3D showing the thrombosed vein
1 point
2 points
3 points
4 points
5 points
LOBE
(< 5%)
(5-25%)
(25-50%)
(50-75%)
(> 75%)
Right upper
--
--
--
--
--
Right middle
--
--
--
--
--
Right lower
--
--
--
--
--
Left upper
--
--
--
--
--
Left lower
--
--
--
--
--
