Mean CT Values Research Articles

Head-to-Head Comparison of Nasopharyngeal, Oropharyngeal and Nasal Swabs for SARS-CoV-2 Molecular Testing.

Nasopharyngeal swabs (NPS) are considered the gold standard for SARS-CoV-2 testing but are technically challenging to perform and associated with discomfort. Alternative specimens for viral testing, such as oropharyngeal swabs (OPS) and nasal swabs, may be preferable, but strong evidence regarding their diagnostic sensitivity for SARS-CoV-2 testing is still missing. We conducted a head-to-head prospective study to compare the sensitivity of NPS, OPS and nasal swabs specimens for SARS-CoV-2 molecular testing. Adults with an initial positive SARS-CoV-2 test were invited to participate. All participants had OPS, NPS and nasal swab performed by an otorhinolaryngologist. We included 51 confirmed SARS-CoV-2-positive participants in the study. The sensitivity was highest for OPS at 94.1% (95% CI, 87 to 100%) compared to NPS at 92.5% (95% CI, 85 to 99%) (p = 1.00) and lowest for nasal swabs at 82.4% (95% CI, 72 to 93%) (p = 0.07). Combined OPS/NPS was detected in 100% of cases, while the combined OPS/nasal swab increased the sensitivity significantly to 96.1% (95% CI, 90 to 100%) compared to that of the nasal swab alone (p = 0.03). The mean Ct value for NPS was 24.98 compared to 26.63 for OPS (p = 0.084) and 30.60 for nasal swab (p = 0.002). OPS achieved a sensitivity comparable to NPS and should be considered an equivalent alternative for SARS-CoV-2 testing.

Time series analysis revealed prognostic value of continuous nasopharyngeal SARS-CoV-2 nucleic acid quantification for COVID-19: A retrospective study of >3000 COVID-19 patients from 2 centers

BackgroundEarly stratification of disease progression remains one of the major challenges towards the post-coronavirus disease 2019 (COVID-19) era. The clinical relevance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid load is debated due to the heterogeneity in patients’ underlying health conditions. We determined the prognostic value of nasopharyngeal viral load dynamic conversion for COVID-19. MethodsThe cycling threshold (Ct) values of 28,937 nasopharyngeal SARS-CoV-2 RT-PCRs were retrospectively collected from 3,364 COVID-19 patients during hospitalization and coordinated to the onset of disease progression. The ROC curve was utilized to determine the predictive performance of the rate of Ct value alteration between two consecutive RT-PCR runs within 48 h (ΔCt%) for disease transformation across patients with different COVID-19 severity and immune backgrounds, and further validated with 1,860 SARS-CoV-2 RT-PCR results from an independent validation cohort of 262 patients. For the 67 patients with severe COVID-19, Kaplan-Meier analysis was performed to evaluate the difference in survival between patients stratified by the magnitude of Ct value alteration between the late and early stages of hospitalization. ResultsThe kinetics of viral nucleic acid conversion diversified across COVID-19 patients with different clinical characteristics and disease severities. The ΔCt% is a clinical characteristic- and host immune status-independent indicator for COVID-19 progression prediction (AUC = 0.79, 95 % CI = 0.76 to 0.81), which outperformed the canonical blood test markers, including c-reactive protein (AUC = 0.57, 95 % CI = 0.53 to 0.61), serum amyloid A (AUC = 0.61, 95 % CI = 0.54 to 0.68), lactate dehydrogenase (AUC = 0.61, 95 % CI = 0.56 to 0.67), d-dimer (AUC = 0.56, 95 % CI = 0.46 to 0.66), and lymphocyte count (AUC = 0.62, 95 % CI = 0.58 to 0.66). Patients with persistent high SARS-CoV-2 viral load (an increase of mean Ct value < 50 %) during the first 3 days of hospitalization demonstrated a significantly unfavorable survival (HR = 0.16, 95 % CI = 0.04 to 0.65, P = 2.41 × 10–3). ConclusionsViral nucleic acid dynamics of SARS-CoV-2 eliminates the inter-patient variance of basic health conditions and therefore, can serve as a prognostic marker for COVID-19.

Value of MDCT data of mandibular condyle cancellous bone to osteoporosis screening

The purpose of this study was application of age- and gender-related differences in mandibular condyle CT values on multidetector-row computed tomography imaging to osteoporosis screening. The mandibular CT images of 327 patients were analyzed retrospectively. The ovoid-shaped region of interest contouring was manually performed on both sides of the mandibular condyle on axial images to determine the mean CT value. The Klemetti index (KI) for each patient was categorized into C1, C2 and C3 based on coronal CT images. The mean CT values of the mandibular condyle were decreased with age in both males and females. The mean CT values of the mandibular condyle also decreased as the KI progressed. Our result suggested that the mean CT values of the mandibular condyle may be a new predictor for screening osteoporosis on multidetector-row computed tomography images.

Cytobrush and cotton swab as sampling tools for molecular diagnosis of female genital schistosomiasis in the uterine cervix

Female genital schistosomiasis (FGS) caused by Schistosoma haematobium is a neglected chronic parasitic disease. Diagnosis relies mainly on a colposcopy, which reveals non-specific lesions. This study aimed to assess the performance of two sampling methods for the molecular diagnosis of FGS in the uterine cervix. We conducted a descriptive cross-sectional study in women of reproductive age in Saint Louis, Senegal, who presented for cervical cancer screening. Cotton swab and cytobrush samples were collected from the cervix and examined by real-time PCR. The PCR results obtained using the cotton swabs were compared with those obtained using cytobrush. Of the 189 women recruited, 56 (30%) were found to be positive for S. haematobium infection via real-time PCR. Women aged 40–54 years were predominantly infected (45%) followed by those aged 25–39 years (36%). Numerically more PCR-positive specimens were identified using cytobrush sampling. Of the 89 women who underwent both cytobrush and cotton swab sampling, 27 were PCR-positive in the cytobrush sampling vs 4 in the swab sampling. The mean Ct-value was 31.0 ± 3.8 for cytobrush-based PCR vs 30.0 ± 4.4 for swab-based PCR. The results confirm that real-time PCR can detect Schistosoma haematobium DNA in the uterine cervix. The next step will be to compare PCR with the other diagnostic methods of FGS.

Pooling Strategy for Detection of SARS-CoV-2 RNA by Real-Time RT-PCR: Comparison of Pooling 5 and 10 Samples.

We evaluated whether it was appropriate to screen SARS-CoV-2 in sample pools of 5 and 10. This study was aimed to evaluate whether the pooling strategy would be an appropriate strategy for SARS-CoV-2 screening. In the study, 5 and 10 sample pools were formed using 720 nasopharyngeal swab samples, of which 72 were positive, and 648 were negative. The samples were analyzed in three groups according to their Ct values as high, medium, and low viral load. SARS-CoV-2 RNA in nasopharyngeal swab samples was detected by the real-time PCR method on the Bio-Rad platform. The sensitivity of 5-sample pooling was 77.8%, and the sensitivity of 10-sample pooling was 75%. The false-negative rate was 22.2% in 5 sample poolings and 25% in 10 sample poolings. Out of the samples with medium and high viral loads, none of the positive samples were lost in either pool. In pools containing both 5 samples and 10 samples, the individual mean Ct values of the samples detected as false-negative were significantly higher (low viral load) than those of the other samples (p < 0.001). In this study, 5 and 10 pooling seems useful in detecting patients with medium and high viral loads. Pooling strategies that allow mass screening of SARS-CoV-2 can contribute to early detection of patients at high risk of SARS-CoV-2 transmission in low prevalence areas, as well as timely public health interventions.

Enhanced detection of Taylorella equigenitalis by qPCR using 'Dry' swabs.

Detection of Taylorella equigenitalis (CEMO) in the horse uses genital swabs. These swabs traditionally have been put in Amies charcoal transport medium for detection by culture but are also used for PCR. We determined the suitability of swabs without transport medium (Dry swabs) for CEMO PCR compared to swabs in Amies charcoal transport medium. The experiment was a factorial design using swab type and dilution of organism in culture suspensions, done in two parts. Simulated genital swabs were prepared in the laboratory by dipping in pairs into culture suspensions containing T. equigenitalis with or without other organisms, and then inserting them into a sleeve either with or without transport medium. In study 1, the difference in Ct value for the two swab types was compared. In study 2 genital swab material was then also added to culture suspensions and the swab types again compared. The swabs were tested by a validated quantitative PCR method. The Ct value of the PCR test was used as the measure for comparison, and the effect of variables assessed with linear regression. There was an 7.7% (6.5-8.9) higher mean Ct value of TM versus Dry swabs (P<0.001) overall. The Ct difference was more marked at higher dilutions. Addition of genital swab material had no effect on the Ct value. Dry swabs perform at least as well for PCR as swabs in Amies charcoal transport medium, especially when relatively low numbers of organism are present, and are advantageous for routine sampling when culture is not being used.

Association of Actinomyces Israelii with Pyogenic Granuloma - A RT-QPCR Study

Background Pyogenic granuloma is a benign vascular non-neoplastic inflammatory lesion that may be re-active to trauma hormonal changes and chronic local irritation. Occasionally they occur as a result of the invasion of microorganisms secondary to minor trauma. Actinomyces species are one of the normal habitants of the oral cavity that tend to penetrate submucosal tissues when there is a disruption in the mucosal barrier and cause pathology. Actinomyces israelii a gram-positive rod-shaped bacterium is an opportunistic pathogen that is difficult to culture. Molecular analyses a polymerase chain reaction and DNA sequencing will identify bacterial species and strains that are difficult or impossible to grow in artificial culture media.Methodology A total of 15 paraffin-embedded pyogenic granuloma samples were taken. All samples were subjected to molecular analysis using real-time polymerase chain reaction with forward and reverse primers of Actinomyces israelii.Result Out of 15 samples 13 samples 86.7 had expressed Actinomyces israelii gene sequence with good mean CT value suggesting that Actinomyces israelii have an association with pyogenic granuloma. There was a weak negative correlation r - 0.022 between age and CT value and the correlation was found to be statistically insignificant p0.943.Conclusion The anterior region of the oral cavity is more prone to trauma and thereby might act as a source for breaking the mucosal barrier which can be a route for microorganisms to establish their association with pyogenic granuloma. These microorganisms may play a role in recurrence. Identification of the causative organisms of irritation could serve as a tool for the radical treatment of pyogenic granulomas.

Which modality is better to diagnose high-grade transformation in retroperitoneal liposarcoma? Comparison of computed tomography, positron emission tomography, and magnetic resonance imaging.

Survival in patients with retroperitoneal liposarcoma (RPLS) depends on the surgical management of the dedifferentiated foci. The present study investigated the diagnostic yield of contrast-enhanced CT, 18F-fluorodeoxyglucose positron emission tomography (PET), and diffusion-weighted MRI in terms of dedifferentiated foci within the RPLS. Patients treated with primary or recurrent RPLS who underwent the above imaging between January 2010 and December 2021 were retrospectively reviewed. The diagnostic accuracy of the three modalities for histologic subtype of dedifferentiated liposarcoma (DDLS) and French Federation of Cancer Center (FNCLCC) grade 2/3 were compared using receiver operating characteristic curves and areas under the curves (AUCs). The cohort involved 32 patients with 53 tumors; 30 of which exhibited DDLS and 31 of which did FNCLCC grades 2/3. The optimal thresholds for predicting DDLS were mean CT value of 31 Hounsfield Unit (HU) (AUC = 0.880, 95% CI 0.775-0.984; p < 0.001), maximum standardized uptake value (SUVmax) of 2.9 (AUC = 0.865 95% CI 0.792-0.980; p < 0.001), while MRI failed to differentiate DDLS. The cutoff values for distinguishing FNCLCC grades 1 and 2/3 were a mean CT value of 24 HU (AUC = 0.858, 95% CI 0.731-0.985; p < 0.001) and SUVmax of 2.9 (AUC = 0.885, 95% CI 0.792-0.978; p < 0.001). MRI had no sufficient power to separate these grades. Contrast-enhanced CT and PET were useful for predicting DDLS and FNCLCC grade 2/3, while MRI was inferior to these two modalities.

Comparison of CT values in traditional trajectory, traditional cortical bone trajectory, and modified cortical bone trajectory

BackgroundTo compare the CT values and length of the screw tracks of traditional trajectory (TT), cortical bone trajectory (CBT), and modified cortical bone trajectory (MCBT) screws and investigate the effects on the biomechanics of lumbar fixation. MethodsCT scan data of 60 L4 and L5 lumbar spine were retrieved and divided into 4 groups (10 male and 10 female cases in the 20–30 years old group and 20 male and 20 female cases in the 30–40 years old group). 3-dimentional (3D) model were established using Mimics 19.0 for each group and the placement of three techniques was simulated on the L4 and L5, and the part of the bone occupied by the screw track was set as the region of interest (ROI). The mean CT value and the actual length of the screw track were measured by Mimics 19.0.ResultsThe CT values of ROI for the three techniques were significantly different between the same gander in each age group (P < 0.05). The difference of screw track lengths for CBT and MCBT in the male and female is significant (P < 0.05). ConclusionsAccording to the CT values of the three screw tracks: MCBT > CBT > TT, the MCBT screw track has greater bone-screw surface strength and longer screw tracks than CBT, which is easier to reach the anterior column of the vertebral body contributing to superior biomechanical properties.

Difference in CT RT-PCR Value of SARS-COV-2 on VTM Non-inactivated with VTM Inavtivated

Nasopharyngeal swab collection for SARS-CoV-2 examination by RT-PCR requires Viral Transport Medium (VTM) using VTM non-activated and inactivated. This study determined the difference in CT values for SARS CoV-2 RT-PCR examination in non-activated VTM and inactivated VTM. This study is a comparative analytical study with a cross-sectional method using 20 confirmed positive samples for SARS-CoV-2 at RSU. Dr. Suyoto was analyzed by the T-Independent test (N gene) and Mann-Whitney test (ORF1ab gene) using SPSS with α=0.05. The results showed that VTM non-inactivated had a mean CT value of the N gene 33.56 ± 1.39 and the ORF1ab gene 35.4 ± 1.94, while VTM inactivated had an average CT value of 32.24 ± 1.44 for the N and ORF1ab gene 33.93 ± 3.22. Statistical analysis was tested by the T-independent test (N gene), and the Mann Whitney test (ORF1ab gene) between the use of VTM non-inactivated and VTM inactivated in the SARS CoV-2 RT-PCR examination, obtained p-value 0.05 with a mean difference the results of Ct gene n (p=0.006) and gene ORF1ab (p=0.028). This indicated a difference in the mean C CT value of the SARS CoV-2 RT-PCR examination in non-activated VTM and inactivated VTM.

Difference in CT RT-PCR Value of SARS-COV-2 on VTM Non-inactivated with VTM Inavtivated

Nasopharyngeal swab collection for SARS-CoV-2 examination by RT-PCR requires Viral Transport Medium (VTM) using VTM non-activated and inactivated. This study determined the difference in CT values for SARS CoV-2 RT-PCR examination in non-activated VTM and inactivated VTM. This study is a comparative analytical study with a cross-sectional method using 20 confirmed positive samples for SARS-CoV-2 at RSU. Dr. Suyoto was analyzed by the T-Independent test (N gene) and Mann-Whitney test (ORF1ab gene) using SPSS with α=0.05. The results showed that VTM non-inactivated had a mean CT value of the N gene 33.56 ± 1.39 and the ORF1ab gene 35.4 ± 1.94, while VTM inactivated had an average CT value of 32.24 ± 1.44 for the N and ORF1ab gene 33.93 ± 3.22. Statistical analysis was tested by the T-independent test (N gene), and the Mann Whitney test (ORF1ab gene) between the use of VTM non-inactivated and VTM inactivated in the SARS CoV-2 RT-PCR examination, obtained p-value 0.05 with a mean difference the results of Ct gene n (p=0.006) and gene ORF1ab (p=0.028). This indicated a difference in the mean C CT value of the SARS CoV-2 RT-PCR examination in non-activated VTM and inactivated VTM.

Comparing feasibility of different tube voltages and different concentrations of contrast medium in coronary CT angiography of overweight patients.

To compare image quality, radiation dose, and iodine intake of coronary computed tomography angiography (CCTA) acquired by wide-detector using different tube voltages and different concentrations of contrast medium (CM) for overweight patients. A total of 150 overweight patients (body mass index≥25 kg/m2) who underwent CCTA are enrolled and divided into three groups according to scan protocols namely, group A (120 kVp, 370 mgI/ml CM); group B (100 kVp, 350 mgI/ml CM); and group C (80 kVp, 320 mgI/ml CM). The CT values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure-of-merit (FOM) of all images are calculated. Images are subjectively assessed using a 5-point scale. In addition, the CT dose index volume (CTDIvol) and dose length product (DLP) of each patient are recorded. The effective radiation dose (ED) is also calculated. Above data are then statistically analyzed. The mean CT values, SNR, CNR, and subjective image quality of group A are significantly lower than those of groups B and C (P < 0.001), but there is no significant difference between groups B and C (P > 0.05). FOMs show a significantly increase trend from group A to C (P < 0.001). The ED values and total iodine intake in groups B and C are 30.34% and 68.53% and 10.22% and 16.85% lower than those in group A, respectively (P < 0.001). The lower tube voltage and lower concentration of CM based on wide-detector allows for significant reduction in iodine load and radiation dose in CCTA for overweight patients comparing to routine scan protocols. It also enhances signal intensity of CCTA and maintains image quality.

The value of CT radiomics features to predict visceral pleural invasion in ≤3 cm peripheral type early non-small cell lung cancer.

To investigate predictive value of CT-based radiomics features on visceral pleural invasion (VPI) in ≤3.0 cm peripheral type early non-small cell lung cancer (NSCLC). A total of 221 NSCLC cases were collected. Among them, 115 are VPI-positive and 106 are VPI-negative. Using a stratified random sampling method, 70% cases were assigned to training dataset (n = 155) and 30% cases (n = 66) were assigned to validation dataset. First, CT findings, imaging features, clinical data and pathological findings were retrospectively analyzed, the size, location and density characteristics of nodules and lymph node status, the relationship between lesions and pleura (RAP) were assessed, and their mean CT value and the shortest distance between lesions and pleura (DLP) were measured. Next, the minimum redundancy-maximum relevance (mRMR) and least absolute shrinkage and selection operator (LASSO) features were extracted from the imaging features. Then, CT imaging prediction model, texture feature prediction model and joint prediction model were built using multifactorial logistic regression analysis method, and the area under the ROC curve (AUC) was applied to evaluate model performance in predicting VPI. Mean diameter, density, fractal relationship with pleura, and presence of lymph node metastasis were all independent predictors of VPI. When applying to the validation dataset, the CT imaging model, texture feature model, and joint prediction model yielded AUC = 0.882, 0.824 and 0.894, respectively, indicating that AUC of the joint prediction model was the highest (p < 0.05). The study demonstrates that the joint prediction model containing CT morphological features and texture features enables to predict the presence of VPI in early NSCLC preoperatively at the highest level.

Omicron Subvariants: Clinical, Laboratory, and Cell Culture Characterization.

The variant of concern Omicron has become the sole circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant for the past several months. Omicron subvariants BA.1, BA.2, BA.3, BA.4, and BA.5 evolved over the time, with BA.1 causing the largest wave of infections globally in December 2021-January 2022. This study compared the clinical outcomes in patients infected with different Omicron subvariants and the relative viral loads and recovery of infectious virus from upper respiratory specimens. SARS-CoV-2-positive remnant clinical specimens, diagnosed at the Johns Hopkins Microbiology Laboratory between December 2021 and July 2022, were used for whole-genome sequencing. The clinical outcomes of infections with Omicron subvariants were compared with infections with BA.1. Cycle threshold (Ct) values and the recovery of infectious virus on the VeroTMPRSS2 cell line from clinical specimens were compared. BA.1 was associated with the largest increase in SARS-CoV-2 positivity rate and coronavirus disease 2019 (COVID-19)-related hospitalizations at the Johns Hopkins system. After a peak in January, cases decreased in the spring, but the emergence of BA.2.12.1 followed by BA.5 in May 2022 led to an increase in case positivity and admissions. BA.1 infections had a lower mean Ct value when compared with other Omicron subvariants. BA.5 samples had a greater likelihood of having infectious virus at Ct values <20. Omicron subvariants continue to be associated with a relatively high rate of polymerase chain reaction (PCR) positivity and hospital admissions. The BA.5 infections are more while BA.2 infections are less likely to have infectious virus, suggesting potential differences in infectibility during the Omicron waves.

Abstract 15601: Optimal Virtual Monoenergetic Settings for Spectral Ct With a Dual-Layer Detector: A Breakthrough in Evaluating the Patency of the Coronary Arterial Lumen With a Metallic Stent in a Real-World Study

Introduction: Evaluation of the patency of a metallic stent in coronary arteries using CT is difficult because the metallic stent causes a blooming artifact. The CT values of metallic stents are influenced by tube kilovoltage (kV). Recent spectral CT with a dual-layer detector can generate CT images at any kiloelectron voltage (keV) (range: 40-200) after ordinary acquisition using virtual monoenergetic settings (VMS). Hypothesis: Using a new spectral CT, we can determine the optimal VMS for evaluating the patency of stents in coronary arteries. Methods: We performed enhanced 128 slice Spectral CT 7500 scans with a dual-layer detector in 35 patients with CAC who underwent implantation of a metallic stent in coronary arteries (tube voltage: 120 kV). After scanning, VMS images at various keV values were created from the spectral-based images. We measured the mean CT values of the metallic stent, coronary artery calcification (CAC), lumen in the left coronary artery (LCA), and fat tissue around the coronary arteries in the axial images at each keV in the early phase with contrast. Results: Lower keV values were associated with markedly increased mean CT values of the metallic stent and CAC. The CT values of the lumen in the LCA were moderately increased. Conversely, the CT values of fat tissue were slightly decreased. The greatest differences in mean CT values between the metallic stent and lumen in the LCA were observed at 40-50 keV, however, those between the metallic stent and CAC were observed at 110-180 keV. The optimal keV for achieving the best contrast between the CT values of the metallic stent, CAC, and the lumen in the LMA at each patient was influenced by age, male sex. Conclusions: The metallic stent, CAC, lumen of the LCA, and fat tissue exhibit unique characteristics. When conventional rather than spectral CT is used to evaluate the patency of a metallic stent in coronary arteries, it is necessary to determine the optimal tube voltage based on the age and male sex of the patient.

Abstract 15552: Optimal Virtual Monoenergetic Settings in Spectral Ct With a Dual Layer Detector: Breakthrough in Achieving Best Contrast Between Non Calcified and Calcified Plaques and Lumen in Coronary Arteries

Introduction: Non calcified plaque (NCP) in coronary arteries on CT is correlated with occurrence of acute coronary syndromes and coronary artery calcification (CAC) may occasionally be co-existed. CAC induces a blooming artifact, which magnifies the calcification versus its actual size. The CT values of NCP and CAC are influenced by tube kilovoltage (kV). Recent spectral CT with a dual-layer detector can generate CT images at any kiloelectron voltage (keV) (range: 40-200) after ordinary acquisition using virtual monoenergetic settings (VMS). Hypothesis: Using a new spectral CT, we can determine the optimal VMS settings for achieving best contrast between NCP, CAC and the lumen in coronary arteries. Methods: We performed enhanced 128 slice Spectral CT 7500 scans using a dual-layer detector in 42 patients with NCP and CAC on CT (tube voltage: 120 kV). After scanning, VMS images at various keV values were created from the spectral-based images. We measured the mean CT values of NCP and CAC, lumen in left main artery (LMA), and fat tissue around coronary arteries within a 1.0 mm2 circle in the axial images at each keV in early phase with a contrast. Results: Lower keV values were linked to only slightly increased mean CT values of NCP, but markedly increased mean CT values of CAC. The CT values of the lumen in the LMA were markedly increased. Conversely, the CT values of fat tissue were slightly decreased. The greatest differences in mean CT values between NCP and the LMA were observed at 40 keV. However, considering blooming artifact of CAC at 40 keV, the optimal keV for achieving the best contrast between the CT values of NCP and the lumen in the LMA was influenced by age, male sex. Conclusions: The NCP in coronary arteries, CAC, lumen of the LMA, and fat tissue exhibit unique characteristics. When conventional CT rather than spectral CT is used to evaluate the occurrence of NCP, it is necessary to determine the optimal tube voltage based on the age and male sex of the patient, CAC, and lumen of the LMA.

Abstract 15060: New Diagnostic Method Using Latest Spectral Computed Tomography With Dual-Layer Detector to Diagnose Pulmonary Thromboembolism and Pulmonary Infarcted Tissue Changes

Introduction: Spectral CT with a dual-layer detector generates CT images at any keV (range: 40-200) after ordinary acquisition using virtual monoenergetic settings (VMS). An appropriate keV improves the contrast of a pulmonary artery (PA) thrombus (PAT). On iodine no water (INW) display, areas with decreased PA blood flow are visualized. With effective atomic number display (Z effective), infarcted and normal lung tissues are distinguished. Hypothesis: Spectral CT improves the detection of PAT, areas with decreased PA blood flow, and infarcted lung tissue, increasing diagnostic accuracy. Methods: We performed enhanced 128 slice Spectral CT 7500 (Philips) scans with a dual-layer detector in 23 patients (11 males, 61±13 years) with clinically suspected PAT. VMS images at various keV values were created from spectral-based images. We developed an INW display to detect decrements in PA blood flow and also made Z effective displays to distinguish infarcted from normal lung tissue. We measured patent PA lumens, PAT, lung areas with decrements in PA flow and infarcted lung tissue. Results: 19 patients had PAT. Of the remaining 4 patients, two revealed decrements in PA flow on INW display and lung tissue changes on Z effective display. On a spectral profile analysis using images in the early phases using contrast, lower keV values were associated with markedly and slightly increased mean CT values for the patent PA lumen and PAT, respectively. Lower keV values were associated with markedly increased mean CT values for normal lung tissue, however, mean CT values were constant at various keV values for an area related to decrements in PA blood flow by INW display and also infarcted lung tissue by Z profile, simultaneously, respectively (Figure). Conclusions: A small PAT may be missed in enhanced CT. However, spectral CT can detect PAT, an area corresponding to decrements in PA blood flow on INW display, and also distinguish infarcted from normal lung tissue on a Z profile, simultaneously.

Abstract 15175: Differentiation Between Intramural Hematoma and Thrombosed False Lumen in Aortic Dissection Using Latest Spectral Computed Tomography With Dual-Layer Detector

Introduction: Differentiating intramural hematoma (IH) from a thrombosed false lumen (FL) in aortic dissection (AD) is difficult by CT since both are regarded as AD without a tear. IH may be caused by vasa vasorum rupture, and therefore differentiation should be by histology. Spectral CT with a dual layer detector can generate CT images at any keV after ordinary acquisition using virtual monoenergetic settings (VMS). Hypothesis: Using spectral CT (range 40-200 keV), and a spectral distribution of CT values for aortic true lumen (TL) and FL, we can differentiate IH from thrombosed FL in AD in early and late-phase enhanced CT values. Methods: We performed enhanced 128-slice spectral CT 7500 (Philips) scans with a dual-layer detector in 8 patients (5 males, 71±14 years), with suspected IH or thrombosed FL in AD in the ascending aorta (Group 1), and 6 patients (4 males, 67±12 years) with thrombosed FL in AD in the descending aorta (Group 2). VMS images at various keV values were created from spectral-based images. We measured TL, FL or IH lumens in axial images at each keV in early and late phases using contrast. Results: On spectral profile analysis, in Group 1, lower keV values were associated with almost no and slightly increased mean CT values for FL or IH, in early and late phases using contrast. In Group 2, lower keV values were associated with slightly and moderately increased mean CT values for FL, in early and late phases using contrast. The degree of increments in CT values in lower keV images in late phase with contrast was significantly smaller for FL or IH in ascending aortas (n=8) than for FL in descending aortas (n=6) (P&lt;0.05). Conclusions: On CT, TL, FL, and IH lumens, in early and late phases using contrast are unique. IH may be caused by vasa vasorum rupture and thrombosed FL in AD spreading contrast in late phase. This may cause a difference in the degree of increments in CT values in lower keV images in late phase using contrast for FL or IH in the ascending aorta and for FL in the descending aorta.

107. Development of novel RT-PCR assay for detection of COVID-19 in the Post-Omicron Era

Background We are facing a new era of the COVID-19 pandemic by omicron variant. This raises concern about the accuracy of conventional RTqPCR assays. There is a need for a new RTqPCR assay appropriate for the omicron variant with multiple mutations. Materials and Methods We herein have developed 2 types of new RTqPCR assays which detect G142D/del143-145, 452 and 478 of S, 69/70 of S or N, and internal control (IC) to make a new single tube, quadplex RTqPCR assay of COVID-19 ('GG COVID-19 Omicron and Delta kit'). Analytical performance was analyzed with Twist/BEI controls. Clinical performance analysis was done as a multi-center study in South Korea with specimens from New Jersey, collected between October 2021 and January 2022. Result 400 left over nasopharyngeal swabs including 149 SARS-CoV-2 positive samples were collected and tested on January 2022 out of which 148 were due to omicron variant and 1 delta variant, respectively. S142-145 assay was superior to conventional RT-PCR(sensitivity 100% vs 00.0 to 00.0%, mean Ct value 25.0 vs 30.4 to 31.3). 330 samples including 125 SARS-CoV-2 positive samples from October 2021 and also tested, out of which 78 were due to delta and confirmed by sequencing. Conclusion GG COVID-19 Omicron and Delta kit showed higher sensitivity than conventional RTqPCR (100% vs 95.4%) and 100% specificity in detecting SARSCoV-2 and could differentiate all of omicron variants. These results indicate that our GG COVID-19 Omicron and Delta kit may be more sensitive than conventional PCR assays in detecting Omicron and Delta SARS-CoV-2. We are facing a new era of the COVID-19 pandemic by omicron variant. This raises concern about the accuracy of conventional RTqPCR assays. There is a need for a new RTqPCR assay appropriate for the omicron variant with multiple mutations. We herein have developed 2 types of new RTqPCR assays which detect G142D/del143-145, 452 and 478 of S, 69/70 of S or N, and internal control (IC) to make a new single tube, quadplex RTqPCR assay of COVID-19 ('GG COVID-19 Omicron and Delta kit'). Analytical performance was analyzed with Twist/BEI controls. Clinical performance analysis was done as a multi-center study in South Korea with specimens from New Jersey, collected between October 2021 and January 2022. 400 left over nasopharyngeal swabs including 149 SARS-CoV-2 positive samples were collected and tested on January 2022 out of which 148 were due to omicron variant and 1 delta variant, respectively. S142-145 assay was superior to conventional RT-PCR(sensitivity 100% vs 00.0 to 00.0%, mean Ct value 25.0 vs 30.4 to 31.3). 330 samples including 125 SARS-CoV-2 positive samples from October 2021 and also tested, out of which 78 were due to delta and confirmed by sequencing. GG COVID-19 Omicron and Delta kit showed higher sensitivity than conventional RTqPCR (100% vs 95.4%) and 100% specificity in detecting SARSCoV-2 and could differentiate all of omicron variants. These results indicate that our GG COVID-19 Omicron and Delta kit may be more sensitive than conventional PCR assays in detecting Omicron and Delta SARS-CoV-2.

Self-collected gargle fluids and nasopharyngeal swabs as a strategy for molecular diagnostics of respiratory viruses

Diagnosis of respiratory viruses traditionally relies on deep oropharynx or nasopharynx swabs collected by healthcare workers (HCW). However, outpatients must make an appointment, and the procedure can cause discomfort in patients. Self-collecting has the potential as a strategy to improve participants’ willingness to participate in diagnostics, surveillance, or studies.We compared self-collected gargle fluids and nasopharyngeal swabs as a strategy for molecular diagnostics of respiratory viruses and compared the average cycle threshold (Ct)-values with those of samples collected by HCW. The study was conducted among technicians of the Laboratory of Clinical Microbiology and Infectious Diseases, Zwolle, the Netherlands, and their family members, between April 2019 and March 2020. It included a questionnaire regarding the severity and date of first symptoms and an assessment of the sampling experience. The primary outcome was the mean Ct of positive PCRs. Similar mean Ct values were obtained using self- or HCW-collected swabs. In addition, gargle fluids and self-swabbed specimens had comparable detection rates of respiratory viruses. Notably, most participants preferred gargling over self-swabbing. Interestingly, but not surprisingly, the time between the onset of symptoms and sampling was shorter in PCR-positive compared to PCR-negative participants.Though this study was abrogated by the SARS-CoV-2 pandemic, the results indicate that both self-swabs and gargle fluids are acceptable for diagnosing common respiratory viruses in the outpatient population, including influenza virus, rhinovirus, adenovirus, SARS-CoV-2 and endemic human coronaviruses. Gargling could be considered an alternative sampling strategy and may enhance willingness to participate in screenings or diagnostics for respiratory viruses.