Exploring New Characteristics: Using Deep Learning and 3D Reconstruction to Compare the Original COVID-19 and Its Delta Variant Based on Chest CT

Abstract

Purpose: Computer-aided diagnostic methods were used to compare the characteristics of the Original COVID-19 and its Delta Variant.Methods: This was a retrospective study. A deep learning segmentation model was applied to segment lungs and infections in CT. Three-dimensional (3D) reconstruction was used to create 3D models of the patient’s lungs and infections. A stereoscopic segmentation method was proposed, which can subdivide the 3D lung into five lobes and 18 segments. An expert-based CT scoring system was improved and artificial intelligence was used to automatically score instead of visual score. Non-linear regression and quantitative analysis were used to analyze the dynamic changes in the percentages of infection (POI).Results: The POI in the five lung lobes of all patients were calculated and converted into CT scores. The CT scores of Original COVID-19 patients and Delta Variant patients since the onset of initial symptoms were fitted over time, respectively. The peak was found to occur on day 11 in Original COVID-19 patients and on day 15 in Delta Variant patients. The time course of lung changes in CT of Delta Variant patients was redetermined as early stage (0–3 days), progressive and peak stage (4–16 days), and absorption stage (17–42 days). The first RT-PCR negative time in Original COVID-19 patients appeared earlier than in Delta Variant patients (22 [17–30] vs. 39 [31–44], p < 0.001). Delta Variant patients had more re-detectable positive RT-PCR test results than Original COVID-19 patients after the first negative RT-PCR time (30.5% vs. 17.1%). In the early stage, CT scores in the right lower lobe were significantly different (Delta Variant vs. Original COVID-19, 0.8 ± 0.6 vs. 1.3 ± 0.6, p = 0.039). In the absorption stage, CT scores of the right middle lobes were significantly different (Delta Variant vs. Original COVID-19, 0.6 ± 0.7 vs. 0.3 ± 0.4, p = 0.012). The left and the right lower lobes contributed most to lung involvement at any given time.Conclusion: Compared with the Original COVID-19, the Delta Variant has a longer lung change duration, more re-detectable positive RT-PCR test results, different locations of pneumonia, and more lesions in the early stage, and the peak of infection occurred later.

The differences in virus shedding time between the Delta variant and original SARS-CoV-2 infected patients

“…However, patients with the Delta variant showed higher neurological symptoms ( 21 ). A recent retrospective research of 107 patients revealed that the peak of pneumonia occurred later in the Delta variant than those with the Original COVID-19 ( 22 ), whereas our data on chest CT scans were collected upon admission. Notably, patients infected with the Delta variant had a significantly prolonged virus shedding time, which could lead to persistent medical deterioration.…”

Six-month follow-up after recovery of COVID-19 Delta variant survivors via CT-based deep learning

“…Their initial goal was generally to save radiologists' time in reviewing medical images and to improve the accuracy of lesions identification. With computer-aided diagnosis methods, physicians can accurately obtain inflammation annotation in CT slices and accurately calculate the percentage of inflammation (POI) and its inflammatory density for each lung lobe or lung segment in a short time ( 2 ).…”

“…The major pathogen of COVID-19 has been identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), yet new variants kept appearing, leading to ongoing worldwide outbreaks of COVID-19 at different magnitudes. SARS-CoV-2 Delta variant (also known as lineage B.1.617.2), a variant of concern identified by the World Health Organization (WHO), became the primary strain of the COVID-19 pandemic in 2021 ( 2 ), affecting more than 75% of countries worldwide. In March 2022, a new variant named Deltacron with Delta variant as the main stem was confirmed to exist by WHO, which will exacerbate the plague of COVID-19 to humans.…”

“…Since first detected in Wuhan, China, Coronavirus disease 2019 (COVID-19) has swept the world, threatening the world with public health concerns and social instability. As of 3rd November 2022, the cumulative number of confirmed COVID-19 cases worldwide reached 631,324,387, with more than 6,594,803 cumulative deaths (1). The major pathogen of COVID-19 has been identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), yet new variants kept appearing, leading to ongoing worldwide outbreaks of COVID-19 at different magnitudes.…”