PSMA-positive prostatic volume prediction with deep learning based on T2-weighted MRI

PURPOSE

High PSMA expression might be correlated with structural characteristics such as growth patterns on histopathology, not recognized by the human eye on MRI images. Deep structural image analysis might be able to detect such differences and therefore predict if a lesion would be PSMA positive. Therefore, we aimed to train a neural network based on PSMA PET/MRI scans to predict increased prostatic PSMA uptake based on the axial T2-weighted sequence alone.

MATERIAL AND METHODS

All patients undergoing simultaneous PSMA PET/MRI for PCa staging or biopsy guidance between April 2016 and December 2020 at our institution were selected. To increase the specificity of our model, the prostatic beds on PSMA PET scans were dichotomized in positive and negative regions using an SUV threshold greater than 4 to generate a PSMA PET map. Then, a C-ENet was trained on the T2 images of the training cohort to generate a predictive prostatic PSMA PET map.

RESULTS

One hundred and fifty-four PSMA PET/MRI scans were available (133 [68Ga]Ga-PSMA-11 and 21 [18F]PSMA-1007). Significant cancer was present in 127 of them. The whole dataset was divided into a training cohort (n = 124) and a test cohort (n = 30). The C-ENet was able to predict the PSMA PET map with a dice similarity coefficient of 69.5 ± 15.6%.

CONCLUSION

Increased prostatic PSMA uptake on PET might be estimated based on T2 MRI alone. Further investigation with larger cohorts and external validation is needed to assess whether PSMA uptake can be predicted accurately enough to help in the interpretation of mpMRI.

Fully automated computational measurement of noise in positron emission tomography

OBJECTIVES

To introduce an automated computational algorithm that estimates the global noise level across the whole imaging volume of PET datasets.

METHODS

[18F]FDG PET images of 38 patients were reconstructed with simulated decreasing acquisition times (15-120 s) resulting in increasing noise levels, and with block sequential regularized expectation maximization with beta values of 450 and 600 (Q.Clear 450 and 600). One reader performed manual volume-of-interest (VOI) based noise measurements in liver and lung parenchyma and two readers graded subjective image quality as sufficient or insufficient. An automated computational noise measurement algorithm was developed and deployed on the whole imaging volume of each reconstruction, delivering a single value representing the global image noise (Global Noise Index, GNI). Manual noise measurement values and subjective image quality gradings were compared with the GNI.

RESULTS

Irrespective of the absolute noise values, there was no significant difference between the GNI and manual liver measurements in terms of the distribution of noise values (p = 0.84 for Q.Clear 450, and p = 0.51 for Q.Clear 600). The GNI showed a fair to moderately strong correlation with manual noise measurements in liver parenchyma (r = 0.6 in Q.Clear 450, r = 0.54 in Q.Clear 600, all p < 0.001), and a fair correlation with manual noise measurements in lung parenchyma (r = 0.52 in Q.Clear 450, r = 0.33 in Q.Clear 600, all p < 0.001). Classification performance of the GNI for subjective image quality was AUC 0.898 for Q.Clear 450 and 0.919 for Q.Clear 600.

CONCLUSION

An algorithm provides an accurate and meaningful estimation of the global noise level encountered in clinical PET imaging datasets.

CLINICAL RELEVANCE STATEMENT

An automated computational approach that measures the global noise level of PET imaging datasets may facilitate quality standardization and benchmarking of clinical PET imaging within and across institutions.

KEY POINTS

• Noise is an important quantitative marker that strongly impacts image quality of PET images. • An automated computational noise measurement algorithm provides an accurate and meaningful estimation of the global noise level encountered in clinical PET imaging datasets. • An automated computational approach that measures the global noise level of PET imaging datasets may facilitate quality standardization and benchmarking as well as protocol harmonization.

Evolution of CT radiation dose in pediatric patients undergoing hybrid 2-[18F]FDG PET/CT between 2007 and 2021

OBJECTIVES

To evaluate the evolution of CT radiation dose in pediatric patients undergoing hybrid 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG) PET/CT between 2007 and 2021.

METHODS AND MATERIALS

Data from all pediatric patients aged 0-18 years who underwent hybrid 2-[18F]FDG PET/CT of the body between January 2007 and May 2021 were reviewed. Demographic and imaging parameters were collected. A board-certified radiologist reviewed all CT scans and measured image noise in the brain, liver, and adductor muscles.

RESULTS

294 scans from 167 children (72 females (43%); median age: 14 (IQR 10-15) years; BMI: median 17.5 (IQR 15-20.4) kg/m2) were included. CT dose index-volume (CTDIvol) and dose length product (DLP) both decreased significantly from 2007 to 2021 (both p < 0.001, Spearman's rho coefficients -0.46 and -0.35, respectively). Specifically, from 2007 to 2009 to 2019-2021 CTDIvol and DLP decreased from 2.94 (2.14-2.99) mGy and 309 (230-371) mGy*cm, respectively, to 0.855 (0.568-1.11) mGy and 108 (65.6-207) mGy*cm, respectively. From 2007 to 2021, image noise in the brain and liver remained constant (p = 0.26 and p = 0.06), while it decreased in the adductor muscles (p = 0.007). Peak tube voltage selection (in kilovolt, kV) of CT scans shifted from high kV imaging (140 or 120kVp) to low kV imaging (100 or 80kVp) (p < 0.001) from 2007 to 2021.

CONCLUSION

CT radiation dose in pediatric patients undergoing hybrid 2-[18F]FDG PET/CT has decreased in recent years equaling approximately one-third of the initial amount.

ADVANCES IN KNOWLEDGE

Over the past 15 years, CT radiation dose decreased considerably in pediatric patients undergoing hybrid imaging, while objective image quality may not have been compromised.

Characterization of hypermetabolic lymph nodes after SARS-CoV-2 vaccination using PET-CT derived node-RADS, in patients with melanoma

This study aimed to evaluate the diagnostic accuracy of Node Reporting and Data System (Node-RADS) in discriminating between normal, reactive, and metastatic axillary LNs in patients with melanoma who underwent SARS-CoV-2 vaccination. Patients with proven melanoma who underwent a 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (2-[18F]-FDG PET/CT) between February and April 2021 were included in this retrospective study. Primary melanoma site, vaccination status, injection site, and 2-[18F]-FDG PET/CT were used to classify axillary LNs into normal, inflammatory, and metastatic (combined classification). An adapted Node-RADS classification (A-Node-RADS) was generated based on LN anatomical characteristics on low-dose CT images and compared to the combined classification. 108 patients were included in the study (54 vaccinated). HALNs were detected in 42 patients (32.8%), of whom 97.6% were vaccinated. 172 LNs were classified as normal, 30 as inflammatory, and 14 as metastatic using the combined classification. 152, 22, 29, 12, and 1 LNs were classified A-Node-RADS 1, 2, 3, 4, and 5, respectively. Hence, 174, 29, and 13 LNs were deemed benign, equivocal, and metastatic. The concordance between the classifications was very good (Cohen's k: 0.91, CI 0.86-0.95; p-value < 0.0001). A-Node-RADS can assist the classification of axillary LNs in melanoma patients who underwent 2-[18F]-FDG PET/CT and SARS-CoV-2 vaccination.

A third of the radiotracer dose: two decades of progress in pediatric [18F]fluorodeoxyglucose PET/CT and PET/MR imaging

OBJECTIVES

To assess the evolution of administered radiotracer activity for F-18-fluorodeoxyglucose (18F-FDG) PET/CT or PET/MR in pediatric patients (0-16 years) between years 2000 and 2021.

METHODS

Pediatric patients (≤ 16 years) referred for 18F-FDG PET/CT or PET/MR imaging of the body during 2000 and 2021 were retrospectively included. The amount of administered radiotracer activity in megabecquerel (MBq) was recorded, and signal-to-noise ratio (SNR) was measured in the right liver lobe with a 4 cm3 volume of interest as an indicator for objective image quality. Descriptive statistics were computed.

RESULTS

Two hundred forty-three children and adolescents underwent a total of 466 examinations. The median injected 18F-FDG activity in MBq decreased significantly from 296 MBq in 2000-2005 to 100 MBq in 2016-2021 (p < 0.001), equaling approximately one-third of the initial amount. The median SNR ratio was stable during all years with 11.7 (interquartile range [IQR] 10.7-12.9, p = 0.133).

CONCLUSIONS

Children have benefited from a massive reduction in the administered 18F-FDG dose over the past 20 years without compromising objective image quality.

CLINICAL RELEVANCE STATEMENT

Radiotracer dose was reduced considerably over the past two decades of pediatric F-18-fluorodeoxyglucose PET/CT and PET/MR imaging highlighting the success of technical innovations in pediatric PET imaging.

KEY POINTS

• The evolution of administered radiotracer activity for F-18-fluorodeoxyglucose (18F-FDG) PET/CT or PET/MR in pediatric patients (0-16 years) between 2000 and 2021 was assessed. • The injected tracer activity decreased by 66% during the study period from 296 megabecquerel (MBq) to 100 MBq (p < 0.001). • The continuous implementation of technical innovations in pediatric hybrid 18F-FDG PET has led to a steady decrease in the amount of applied radiotracer, which is particularly beneficial for children who are more sensitive to radiation.

Automated F18-FDG PET/CT image quality assessment using deep neural networks on a latest 6-ring digital detector system

To evaluate whether a machine learning classifier can evaluate image quality of maximum intensity projection (MIP) images from F18-FDG-PET scans. A total of 400 MIP images from F18-FDG-PET with simulated decreasing acquisition time (120 s, 90 s, 60 s, 30 s and 15 s per bed-position) using block sequential regularized expectation maximization (BSREM) with a beta-value of 450 and 600 were created. A machine learning classifier was fed with 283 images rated "sufficient image quality" and 117 images rated "insufficient image quality". The classification performance of the machine learning classifier was assessed by calculating sensitivity, specificity, and area under the receiver operating characteristics curve (AUC) using reader-based classification as the target. Classification performance of the machine learning classifier was AUC 0.978 for BSREM beta 450 and 0.967 for BSREM beta 600. The algorithm showed a sensitivity of 89% and 94% and a specificity of 94% and 94% for the reconstruction BSREM 450 and 600, respectively. Automated assessment of image quality from F18-FDG-PET images using a machine learning classifier provides equivalent performance to manual assessment by experienced radiologists.

Opportunistic deep learning powered calcium scoring in oncologic patients with very high coronary artery calcium (≥ 1000) undergoing 18F-FDG PET/CT

Our aim was to identify and quantify high coronary artery calcium (CAC) with deep learning (DL)-powered CAC scoring (CACS) in oncological patients with known very high CAC (≥ 1000) undergoing 18F-FDG-PET/CT for re-/staging. 100 patients were enrolled: 50 patients with Agatston scores ≥ 1000 (high CACS group), 50 patients with Agatston scores < 1000 (negative control group). All patients underwent oncological 18F-FDG-PET/CT and cardiac SPECT myocardial perfusion imaging (MPI) by 99mTc-tetrofosmin within 6 months. CACS was manually performed on dedicated non-contrast ECG-gated CT scans obtained from SPECT-MPI (reference standard). Additionally, CACS was performed fully automatically with a user-independent DL-CACS tool on non-contrast, free-breathing, non-gated CT scans from 18F-FDG-PET/CT examinations. Image quality and noise of CT scans was assessed. Agatston scores obtained by manual CACS and DL tool were compared. The high CACS group had Agatston scores of 2200 ± 1620 (reference standard) and 1300 ± 1011 (DL tool, average underestimation of 38.6 ± 26%) with an intraclass correlation of 0.714 (95% CI 0.546, 0.827). Sufficient image quality significantly improved the DL tool's capability of correctly assigning Agatston scores ≥ 1000 (p = 0.01). In the control group, the DL tool correctly assigned Agatston scores < 1000 in all cases. In conclusion, DL-based CACS performed on non-contrast free-breathing, non-gated CT scans from 18F-FDG-PET/CT examinations of patients with known very high (≥ 1000) CAC underestimates CAC load, but correctly assigns an Agatston scores ≥ 1000 in over 70% of cases, provided sufficient CT image quality. Subgroup analyses of the control group showed that the DL tool does not generate false-positives.

Diagnostic Value of Fully Automated Artificial Intelligence Powered Coronary Artery Calcium Scoring from 18F-FDG PET/CT

Objectives: The objective of this study was to assess the feasibility and accuracy of a fully automated artificial intelligence (AI) powered coronary artery calcium scoring (CACS) method on ungated CT in oncologic patients undergoing 18F-FDG PET/CT. Methods: A total of 100 oncologic patients examined between 2007 and 2015 were retrospectively included. All patients underwent 18F-FDG PET/CT and cardiac SPECT myocardial perfusion imaging (MPI) by 99mTc-tetrofosmin within 6 months. CACS was manually performed on non-contrast ECG-gated CT scans obtained from SPECT-MPI (i.e., reference standard). Additionally, CACS was performed using a cloud-based, user-independent tool (AI-CACS) on ungated CT scans from 18F-FDG-PET/CT examinations. Agatston scores from the manual CACS and AI-CACS were compared. Results: On a per-patient basis, the AI-CACS tool achieved a sensitivity and specificity of 85% and 90% for the detection of CAC. Interscore agreement of CACS between manual CACS and AI-CACS was 0.88 (95% CI: 0.827, 0.918). Interclass agreement of risk categories was 0.8 in weighted Kappa analysis, with a reclassification rate of 44% and an underestimation of one risk category by AI-CACS in 39% of cases. On a per-vessel basis, interscore agreement of CAC scores ranged from 0.716 for the circumflex artery to 0.863 for the left anterior descending artery. Conclusions: Fully automated AI-CACS as performed on non-contrast free-breathing, ungated CT scans from 18F-FDG-PET/CT examinations is feasible and provides an acceptable to good estimation of CAC burden. CAC load on ungated CT is, however, generally underestimated by AI-CACS, which should be taken into account when interpreting imaging findings.

Impact of Adaptive Statistical Iterative Reconstruction-V on Coronary Artery Calcium Scores Obtained From Low-Tube-Voltage Computed Tomography - A Patient Study

OBJECTIVE

To evaluate the impact of adaptive statistical iterative reconstruction-V (ASIR-V) on the accuracy of ultra-low-dose coronary artery calcium (CAC) scoring.

MATERIALS AND METHOD

One-hundred-and-three patients who underwent computed tomography (CT) for CAC scoring were prospectively included. All underwent standard scanning with 120-kilovolt-peak (kVp) and with 80- and 70-kVp tube voltage. ASiR-V was applied to the 80- and 70-kVp scans at different levels. The 120-kVp scans reconstructed with filtered back projection served as the standard of reference. Recently published novel kVp-adapted thresholds were used for calculation of CAC scores from 80- and 70-kVp scans and the resulting CAC scores were compared against the standard of reference. Patients were stratified into six CAC score risk categories: 0, 1-10, 11-100, 101-400, 401-1000, and >1000.

RESULTS

Increasing levels of ASIR-V led to an increasing underestimation of CAC scores with bias ranging from -128 to -118 and from -205 to -198 for the 80- and 70-kVp scans, respectively, when compared with the standard of reference. Reconstruction with 20% and 40% ASIR-V for the 80- and 70-kVp scans, respectively, yielded noise levels comparable to the standard of reference. Nevertheless, a change in risk-class was observed in 29 (28.6%) and 46 (44.7%) patients, exclusively to a lower risk-class, when CAC scores were derived from these reconstructions.

CONCLUSION

ASIR-V leads to noise reduction in CT scans acquired with low tube-voltages. However, ASIR-V introduces substantial inaccuracies and marked underestimation of ultra-low-dose CAC scoring as compared with standard-dose CAC scoring despite normalization of noise.

Assessment of Artificial Intelligence in Echocardiography Diagnostics in Differentiating Takotsubo Syndrome From Myocardial Infarction

Importance

Machine learning algorithms enable the automatic classification of cardiovascular diseases based on raw cardiac ultrasound imaging data. However, the utility of machine learning in distinguishing between takotsubo syndrome (TTS) and acute myocardial infarction (AMI) has not been studied.

Objectives

To assess the utility of machine learning systems for automatic discrimination of TTS and AMI.

Design, Settings, and Participants

This cohort study included clinical data and transthoracic echocardiogram results of patients with AMI from the Zurich Acute Coronary Syndrome Registry and patients with TTS obtained from 7 cardiovascular centers in the International Takotsubo Registry. Data from the validation cohort were obtained from April 2011 to February 2017. Data from the training cohort were obtained from March 2017 to May 2019. Data were analyzed from September 2019 to June 2021.

Exposure

Transthoracic echocardiograms of 224 patients with TTS and 224 patients with AMI were analyzed.

Main Outcomes and Measures

Area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity of the machine learning system evaluated on an independent data set and 4 practicing cardiologists for comparison. Echocardiography videos of 228 patients were used in the development and training of a deep learning model. The performance of the automated echocardiogram video analysis method was evaluated on an independent data set consisting of 220 patients. Data were matched according to age, sex, and ST-segment elevation/non-ST-segment elevation (1 patient with AMI for each patient with TTS). Predictions were compared with echocardiographic-based interpretations from 4 practicing cardiologists in terms of sensitivity, specificity, and AUC calculated from confidence scores concerning their binary diagnosis.

Results

In this cohort study, apical 2-chamber and 4-chamber echocardiographic views of 110 patients with TTS (mean [SD] age, 68.4 [12.1] years; 103 [90.4%] were female) and 110 patients with AMI (mean [SD] age, 69.1 [12.2] years; 103 [90.4%] were female) from an independent data set were evaluated. This approach achieved a mean (SD) AUC of 0.79 (0.01) with an overall accuracy of 74.8 (0.7%). In comparison, cardiologists achieved a mean (SD) AUC of 0.71 (0.03) and accuracy of 64.4 (3.5%) on the same data set. In a subanalysis based on 61 patients with apical TTS and 56 patients with AMI due to occlusion of the left anterior descending coronary artery, the model achieved a mean (SD) AUC score of 0.84 (0.01) and an accuracy of 78.6 (1.6%), outperforming the 4 practicing cardiologists (mean [SD] AUC, 0.72 [0.02]) and accuracy of 66.9 (2.8%).

Conclusions and Relevance

In this cohort study, a real-time system for fully automated interpretation of echocardiogram videos was established and trained to differentiate TTS from AMI. While this system was more accurate than cardiologists in echocardiography-based disease classification, further studies are warranted for clinical application.

Comparison of detection of trauma-related injuries using combined "all-in-one" fused images and conventionally reconstructed images in acute trauma CT

OBJECTIVES

To compare the accuracy of lesion detection of trauma-related injuries using combined "all-in-one" fused (AIO) and conventionally reconstructed images (CR) in acute trauma CT.

METHODS

In this retrospective study, trauma CT of 66 patients (median age 47 years, range 18-96 years; 20 female (30.3%)) were read using AIO and CR. Images were independently reviewed by 4 blinded radiologists (two residents and two consultants) for trauma-related injuries in 22 regions. Sub-analyses were performed to analyze the influence of experience (residents vs. consultants) and body region (chest, abdomen, skeletal structures) on lesion detection. Paired t-test was used to compare the accuracy of lesion detection. The effect size was calculated (Cohen's d). Linear mixed-effects model with patients as the fixed effect and random forest models were used to investigate the effect of experience, reconstruction/image processing, and body region on lesion detection.

RESULTS

Reading time of residents was significantly faster using AIO (AIO: 266 ± 72 s, CR: 318 ± 113 s; p < 0.001; d = 0.46) while no significant difference was observed in the accuracy of lesion detection (AIO: 93.5 ± 6.0%, CR: 94.6 ± 6.0% p = 0.092; d =  - 0.21). Reading time of consultants showed no significant difference (AIO: 283 ± 82 s, CR: 274 ± 95 s; p = 0.067; d = 0.16). Accuracy was significantly higher using CR; however, the difference and effect size were very small (AIO 95.1 ± 4.9%, CR: 97.3 ± 3.7%, p = 0.002; d =  - 0.39). The linear mixed-effects model showed only minor effect of image processing/reconstruction for lesion detection.

CONCLUSIONS

Residents at the emergency department might benefit from faster reading time without sacrificing lesion detection rate using AIO for trauma CT.

KEY POINTS

• Image fusion techniques decrease the reading time of acute trauma CT without sacrificing diagnostic accuracy.

Impact of dose reduction and iterative reconstruction algorithm on the detectability of pulmonary nodules by artificial intelligence

PURPOSE

The purpose of this study was to assess whether the performances of an automated software for lung nodule detection with computed tomography (CT) are affected by radiation dose and the use of iterative reconstruction algorithm.

MATERIALS AND METHODS

A chest phantom (Multipurpose Chest Phantom N1; Kyoto Kagaku Co. Ltd, Kyoto, Japan) with 15 pulmonary nodules was scanned with a total of five CT protocol settings with up to 20-fold dose reduction. All CT examinations were reconstructed with iterative reconstruction algorithms ADMIRE 3 and ADMIRE 5 and were then analyzed for the presence of pulmonary nodules with a fully automated computer aided detection software system (InferRead^TM CT Lung, Infervision), which is based on deep neural networks.

RESULTS

The sensitivity of fully automated pulmonary nodule detection for ground-glass nodules at standard dose CT was greater (70.0%; 14/20; 95% CI: 51.6-88.4%) than at 10-fold and 20-fold dose reduction (30.0%; 6/20; 95% CI: 0.0%-62.5%). There were less false positive findings when ADMIRE 5 reconstruction was used (4.0 ± 2.8 [SD]; range: 2-6) instead of ADMIRE 3 reconstruction (25.0 ± 15.6 [SD]; range: 14-36). There was no difference in the sensitivity of detection of solid and subsolid nodules between standard dose (100%; 95% CI: 100-100%) and 10- and 20-fold reduced dose CT (92.5%; 95% CI: 83.8-100.0%). Image noise was significantly greater with ADMIRE 3 (81 ± 2 [SD] [range: 79-84]; 104 ± 3 [SD] [range: 101-107]; 114 ± 5 [SD] [range: 110-119]; 193 ± 10 [SD] [range: 183-203]; 220 ± 16 [SD] [range: 210-238]) compared to ADMIRE 5 (44 ± 2 [SD] [range: 42-46]; 60 ± 2 [SD] [range: 57-61]; 66 ± 1 [SD] [range: 65-67]; 103 ± 4 [SD] [range: 98-106]; 110 ± 1 [SD] [range: 109-111]), respectively in each of the five CT protocols.

CONCLUSION

This phantom study suggests that dose reduction and iterative reconstruction settings have an impact on detectability of pulmonary nodules by artificial intelligence software and we therefore encourage adaption of dose levels and reconstruction methods prior to widespread implementation of fully automatic nodule detection software for lung cancer screening purposes.

Pneumonia Detection in Chest X-Ray Dose-Equivalent CT: Impact of Dose Reduction on Detectability by Artificial Intelligence

RATIONALE AND OBJECTIVES

There has been a significant increase of immunocompromised patients in recent years due to new treatment modalities for previously fatal diseases. This comes at the cost of an elevated risk for infectious diseases, most notably pathogens affecting the respiratory tract. Because early diagnosis and treatment of pneumonia can help reducing morbidity and mortality, we assessed the performance of a deep neural network in the detection of pulmonary infection in chest X-ray dose-equivalent computed tomography (CT).

MATERIALS AND METHODS

The 100 patients included in this retrospective study were referred to our department for suspicion of pulmonary infection and/or follow-up of known pulmonary nodules. Every patient was scanned with a standard dose (1.43 ± 0.54 mSv) and a 20 times dose-reduced (0.07 ± 0.03 mSv) CT protocol. We trained a deep neural network to perform binary classification (pulmonary consolidation present or not) and assessed diagnostic performance on both standard dose and reduced dose CT images.

RESULTS

The areas under the curve of the deep learning algorithm for the standard dose CT was 0.923 (confidence interval [CI] 95%: 0.905-0.941) and significantly higher than the areas under the curve (0.881, CI 95%: 0.859-0.903) of the reduced dose CT (p = 0.001). Sensitivity and specificity of the standard dose CT was 82.9% and 93.8%, and of the reduced dose CT 71.0% and 93.3%.

CONCLUSION

Pneumonia detection with X-ray dose-equivalent CT using artificial intelligence is feasible and may contribute to a more robust and reproducible diagnostic performance. Dose reduction lowered the performance of the deep neural network, which calls for optimization and adaption of CT protocols when using AI algorithms at reduced doses.

Splenic switch-off as a predictor for coronary adenosine response: validation against 13N-ammonia during co-injection myocardial perfusion imaging on a hybrid PET/CMR scanner

BACKGROUND

Inadequate coronary adenosine response is a potential cause for false negative ischemia testing. Recently, the splenic switch-off (SSO) sign has been identified as a promising tool to ascertain the efficacy of adenosine during vasodilator stress cardiovascular magnetic resonance imaging (CMR). We assessed the value of SSO to predict adenosine response, defined as an increase in myocardial blood flow (MBF) during quantitative stress myocardial perfusion 13 N-ammonia positron emission tomography (PET).

METHODS

We prospectively enrolled 64 patients who underwent simultaneous CMR and PET myocardial perfusion imaging on a hybrid PET/CMR scanner with co-injection of gadolinium based contrast agent (GBCA) and 13N-ammonia during rest and adenosine-induced stress. A myocardial flow reserve (MFR) of  > 1.5 or ischemia as assessed by PET were defined as markers for adequate coronary adenosine response. The presence or absence of SSO was visually assessed. The stress-to-rest intensity ratio (SIR) was calculated as the ratio of stress over rest peak signal intensity for splenic tissue. Additionally, the spleen-to-myocardium ratio, defined as the relative change of spleen to myocardial signal, was calculated for stress (SMRstress) and rest.

RESULTS

Sixty-one (95%) patients were coronary adenosine responders, but SSO was absent in 18 (28%) patients. SIR and SMRstress were significantly lower in patients with SSO (SIR: 0.56 ± 0.13 vs. 0.93 ± 0.23; p < 0.001 and SMRstress: 1.09 ± 0.47 vs. 1.68 ± 0.62; p < 0.001). Mean hyperemic and rest MBF were 2.12 ± 0.68 ml/min/g and 0.78 ± 0.26 ml/min/g, respectively. MFR was significantly higher in patients with vs. patients without presence of SSO (3.07 ± 1.03 vs. 2.48 ± 0.96; p = 0.038), but there was only a weak inverse correlation between SMRstress and MFR (R = -0.378; p = 0.02) as well as between SIR and MFR (R = -0.356; p = 0.004).

CONCLUSIONS

The presence of SSO implies adequate coronary adenosine-induced MBF response. Its absence, however, is not a reliable indicator for failed adenosine-induced coronary vasodilatation.

Artificial intelligence in echocardiography diagnostics – detection of takotsubo syndrome

Background

Machine learning allows classifying diseases based only on raw echocardiographic imaging data and is therefore a landmark in the development of computer-assisted decision support systems in echocardiography.

Purpose

The present study sought to determine the value of deep (machine) learning systems for automatic discrimination of takotsubo syndrome and acute myocardial infarction.

Methods

Apical 2- and 4-chamber echocardiographic views of 110 patients with takotsubo syndrome and 110 patients with acute myocardial infarction were used in the development, training and validation of a deep learning approach, i.e. a convolutional autoencoder (CAE) for feature extraction followed by classical machine learning models for classification of the diseases.

Results

The deep learning model achieved an area under the receiver operating curve (AUC) of 0.801 with an overall accuracy of 74.5% for 5-fold cross validation evaluated on a clinically relevant dataset. In comparison, experienced cardiologists achieved AUCs in the range 0.678–0.740 and an average accuracy of 64.5% on the same dataset.

Conclusions

A real-time system for fully automated interpretation of echocardiographic videos was established and trained to differentiate takotsubo syndrome from acute myocardial infarction. The framework provides insight into the algorithms' decision process for physicians and yields new and valuable information on the manifestation of disease patterns in echocardiographic data. While our system was superior to cardiologists in echocardiography-based disease classification, further studies should be conducted in a larger patient population to prove its clinical application.

Funding Acknowledgement

Type of funding source: None

"Apical thinning": Relations between myocardial wall thickness and apical left ventricular tracer uptake as assessed with positron emission tomography myocardial perfusion imaging

BACKGROUND

A reduction in left ventricular apical tracer uptake (apical thinning) is frequently observed in myocardial perfusion imaging (MPI), yet its cause remains a matter of debate, particularly in perfusion emission tomography (PET). This analysis sought to determine whether apical thinning in PET-MPI is attributable to true anatomical thinning of the left ventricular apical myocardium.

METHODS AND RESULTS

We retrospectively analyzed 57 patients without any history or signs of apical myocardial infarction who underwent rest PET-MPI with 13N-ammonia and contrast-enhanced cardiac computed tomography (CT). Semi-quantitative normalized percent apical 13N-ammonia uptake at rest, myocardial blood flow (MBF), and k2 wash-out rate constants were compared to apical myocardial wall thickness measurements derived from CT and base-to-apex gradients were calculated. Apical thinning was found in 93% of patients and in 74% when analysis of normalized apical tracer uptake was confined to end-systole. No significant correlation was found between apical myocardial thickness and apical tracer uptake (r = - 0.080, P = .553), MBF (r = - 0.211, P = .115), or k2 wash-out rate (r = - 0.023, P = .872), nor between apical myocardial thickness and any gradients. A statistically significant but small difference in apical myocardial thickness was observed in patients with moderately to severely reduced apical tracer uptake vs patients with normal to mildly reduced uptake (4.3 ± 0.7 mm vs 4.7 ± 0.7 mm; P = .043).

CONCLUSIONS

Apical thinning is a highly prevalent finding during 13N-ammonia PET-MPI that is not solely attributable to true anatomical apical wall thickness or the partial volume effect. Other factors that yet need to be identified seem to have a more prominent impact.

Sex and age differences in the association of heart rate responses to adenosine and myocardial ischemia in patients undergoing myocardial perfusion imaging

BACKGROUND

In light of growing cardiovascular mortality rates observed in young women, sexual dimorphism in cardiac autonomic nervous control is gaining increasing attention. Heart rate responses to adenosine mirror autonomic activity and may carry important prognostic information.

METHODS AND RESULTS

Hemodynamic changes during adenosine stress were retrospectively analysed in a propensity-matched cohort of 1932 consecutive patients undergoing myocardial perfusion single-photon-emission computed tomography (MPI-SPECT). Heart rate (HR) and systolic blood pressure (SBP) increased during adenosine infusion (P < 0.001). The increase in SBP and HR (heart rate reserve, HRR), was significantly more pronounced in women compared with men (P < 0.05). Patients ≤ 55 years had a higher HRR compared with patients > 55 years (46.8% vs 37.5%, P = 0.015). Women ≤ 55 years with a reversible perfusion defect on MPI-SPECT exhibited the highest HRR (89.2%), while age-matched men showed a blunted HR response to adenosine (26.4%, P = 0.01). Accordingly, age and an interaction term of female sex and increased HRR were identified as significant predictors of myocardial ischemia in a multiple regression analysis (OR 1.4, 95% CI 1.02-1.9, P = 0.038).

CONCLUSION

HRR during adenosine infusion is influenced by age and sex. Our data suggest a stronger, sympathetic-driven, hemodynamic response to adenosine in younger women with myocardial ischemia.

Ultra-low-dose computed tomography for attenuation correction of cadmium-zinc-telluride single photon emission computed tomography myocardial perfusion imaging

BACKGROUND

The applicability of ultra-low-dose computed tomography (CT) for attenuation correction (AC) of single-photon-emission computed tomography myocardial perfusion imaging (SPECT-MPI) remains elusive.

METHODS AND RESULTS

One-hundred patients underwent one-day 99mTc-tetrofosmin stress-rest MPI and non-contrast enhanced cardiac CT with 120, 80, and 70 kilovolt peak (kVp) tube voltage and tube current of 200 milliamperes for creation of AC maps. Normalized percent myocardial uptake from SPECT-MPI using 80 kVp scans for AC showed excellent correlation vs AC from 120 kVp scans for stress [intraclass correlation (ICC) = 0.988, 95% CI = 0.986-0.989, P < .001] and rest (ICC = 0.985, 95% CI = 0.983-0.987, P < .001) with narrow Bland-Altman limits of agreement (BA-LA) (- 5.3% to 4.5% and - 5.4% to 4.4%, respectively) and minimal bias (- 0.4% and - 0.5%, respectively). Correlation of AC SPECT-MPI based on 70 vs 120 kVp scans was excellent for stress (ICC = 0.988, 95% CI = 0.986-0.989, P < .001) and rest (ICC = 0.986, 95% CI = 0.984-0.987, P < .001) with narrow BA-LA (- 5.3% to 4.4% and - 5.2% to 4.5%, respectively) and small bias (- 0.4% and - 0.3%, respectively). Mean effective radiation dose for the 120, 80 and 70 kVp scans were 0.58 ± 0.07, 0.19 ± 0.02, and 0.12 ± 0.01 mSv, respectively.

CONCLUSIONS

Attenuation maps for MPI obtained from ultra-low radiation dose CT scans are interchangeable with attenuation maps from standard-dose CT while offering a substantial reduction in radiation dose exposure.

Artificial intelligence for detecting small FDG-positive lung nodules in digital PET/CT: impact of image reconstructions on diagnostic performance

OBJECTIVES

To evaluate the diagnostic performance of a deep learning algorithm for automated detection of small ¹⁸F-FDG-avid pulmonary nodules in PET scans, and to assess whether novel block sequential regularized expectation maximization (BSREM) reconstruction affects detection accuracy as compared to ordered subset expectation maximization (OSEM) reconstruction.

METHODS

Fifty-seven patients with 92 ¹⁸F-FDG-avid pulmonary nodules (all ≤ 2 cm) undergoing PET/CT for oncological (re-)staging were retrospectively included and a total of 8824 PET images of the lungs were extracted using OSEM and BSREM reconstruction. Per-slice and per-nodule sensitivity of a deep learning algorithm was assessed, with an expert readout by a radiologist/nuclear medicine physician serving as standard of reference. Receiver-operator characteristic (ROC) curve of OSEM and BSREM were assessed and the areas under the ROC curve (AUC) were compared. A maximum standardized uptake value (SUV_max)-based sensitivity analysis and a size-based sensitivity analysis with subgroups defined by nodule size was performed.

RESULTS

The AUC of the deep learning algorithm for nodule detection using OSEM reconstruction was 0.796 (CI 95%; 0.772-0.869), and 0.848 (CI 95%; 0.828-0.869) using BSREM reconstruction. The AUC was significantly higher for BSREM compared to OSEM (p = 0.001). On a per-slice analysis, sensitivity and specificity were 66.7% and 79.0% for OSEM, and 69.2% and 84.5% for BSREM. On a per-nodule analysis, the overall sensitivity of OSEM was 81.5% compared to 87.0% for BSREM.

CONCLUSIONS

Our results suggest that machine learning algorithms may aid detection of small ¹⁸F-FDG-avid pulmonary nodules in clinical PET/CT. AI performed significantly better on images with BSREM than OSEM.

KEY POINTS

• The diagnostic value of deep learning for detecting small lung nodules (≤ 2 cm) in PET images using BSREM and OSEM reconstruction was assessed. • BSREM yields higher SUV_maxof small pulmonary nodules as compared to OSEM reconstruction. • The use of BSREM translates into a higher detectability of small pulmonary nodules in PET images as assessed with artificial intelligence.

Association between beta-adrenoceptor antagonist-induced sympathicolysis and severity of coronary artery disease as assessed by coronary computed tomography angiography (CCTA)

Enhanced sympathetic nervous system activity is associated with increased mortality in many cardiac conditions including heart failure and coronary artery disease (CAD). To ensure adequate image quality of coronary CT angiography (CCTA), pre-scan β-adrenergic blockers (BB) are routinely administered. It is currently unknown whether sensitivity to sympathicolytic compounds is associated with severity of CAD. A total of 2633 consecutive patients (1733 [65.8%] men and 900 [34.2%] women, mean age 56.7 ± 11.5 years) undergoing CCTA for exclusion of significant CAD at our department between 06/2013 and 12/2016 were evaluated. Acute heart rate (HR) responses to BB administration were recorded in all patients. Coronary plaque burden as indicated by segment severity score (SSS), segment involvement score (SIS), and significant CAD (i.e. > 50% luminal narrowing) was higher in weak responders to BB as compared to strong responders to BB (p = 0.001 for SSS and SIS, and p = 0.021 for significant CAD). Accordingly, in a multiple linear regression model adjusted for known risk factors of CAD such as smoking, hypertension, diabetes and dyslipidaemia, as well as age, sex, body mass index (BMI), glomerular filtration rate, and HR during CCTA scan, a strong response to BB was selected as a significant independent negative predictor of coronary plaque burden (beta coefficient - 0.08, p = 0.001). We demonstrate that individuals with a weak acute response to BB administration encounter an increased risk of severe CAD. Taking into account sensitivity to sympatho-inhibition may add complementary information in patients undergoing CCTA for evaluation of CAD.

Clinical Features and Outcomes of Takotsubo (Stress) Cardiomyopathy

BACKGROUND

The natural history, management, and outcome of takotsubo (stress) cardiomyopathy are incompletely understood.

METHODS

The International Takotsubo Registry, a consortium of 26 centers in Europe and the United States, was established to investigate clinical features, prognostic predictors, and outcome of takotsubo cardiomyopathy. Patients were compared with age- and sex-matched patients who had an acute coronary syndrome.

RESULTS

Of 1750 patients with takotsubo cardiomyopathy, 89.8% were women (mean age, 66.8 years). Emotional triggers were not as common as physical triggers (27.7% vs. 36.0%), and 28.5% of patients had no evident trigger. Among patients with takotsubo cardiomyopathy, as compared with an acute coronary syndrome, rates of neurologic or psychiatric disorders were higher (55.8% vs. 25.7%) and the mean left ventricular ejection fraction was markedly lower (40.7±11.2% vs. 51.5±12.3%) (P<0.001 for both comparisons). Rates of severe in-hospital complications including shock and death were similar in the two groups (P=0.93). Physical triggers, acute neurologic or psychiatric diseases, high troponin levels, and a low ejection fraction on admission were independent predictors for in-hospital complications. During long-term follow-up, the rate of major adverse cardiac and cerebrovascular events was 9.9% per patient-year, and the rate of death was 5.6% per patient-year.

CONCLUSIONS

Patients with takotsubo cardiomyopathy had a higher prevalence of neurologic or psychiatric disorders than did those with an acute coronary syndrome. This condition represents an acute heart failure syndrome with substantial morbidity and mortality. (Funded by the Mach-Gaensslen Foundation and others; ClinicalTrials.gov number, NCT01947621.).

Search for physical interaction between BICP0 of bovine herpesvirus-1 and p53 tumor suppressor protein

The immediate-early (IE) protein BICP0 of bovine herpesvirus-1 (BHV-1) may have other functions besides transactivation of viral promoters. Recently, we observed that BICP0, delivered to cultured cells by a helpervirus-free amplicon system, forms spherical or doughnut-like structures in which the tumor suppressor protein p53 is sequestered. The objective was to determine whether BICP0 and p53 interact physically, we used both yeast and mammalian two-hybrid systems. As a bait plasmid, pVA3 which encodes a hybrid protein consisting of the Gal4 DNA binding domain fused to murine p53 was used. The BICP0 gene or its truncated versions were inserted into the prey plasmid pGAD424. Bait and prey plasmids were cotransformed into yeast strain Y153, which has LacZ and HIS3 reporter genes under the control of Gal4 upstream activating sequence. After 4-6 days, colonies were stained for beta-galactosidase activity. In the mammalian two-hybrid system, pM-53 was used as a bait where truncated p53 fused to Gal4 DNA binding domain is expressed. The BICP0 gene was cloned into prey plasmid pVP16. The interaction between p53 and SV40 T-antigen was evaluated as a positive control in both systems. Neither full-length BICP0 nor its truncated derivatives induced beta-galactosidase activity in yeast whereas the positive control turned blue under the same conditions. The mammalian two-hybrid system, in which chloramphenicol acetyltransferase (CAT) activity was used as a reporter, also failed to show an interaction between these two proteins. Co-localization of p53 with BICP0 in spherical structures is unlikely to result from a direct physical interaction between these two proteins. Mediation by additional cellular proteins may be required.

Transduction of Vero cells and bovine monocytes with a herpes simplex virus-1 based amplicon carrying the gene for the bovine herpesvirus-1 Circ protein

Herpes simplex virus-1 (HSV-1) based amplicon vectors are promising gene delivery vehicles because they have a large transgene capacity and can efficiently transduce many different cell types, including non-dividing cells, of various animal species. The Circ protein of bovine herpesvirus-1 (BHV-1) is a myristylated virion component of unknown function. Preliminary experiments with a circ gene deletion mutant indicated that Circ may influence the host's immune response by downregulating MHC-II expression in bovine monocytes. To get more insight into the function of Circ, amplicon vectors were constructed with various open reading frames (ORFs) under the control of the HSV-1 IE4/5 promoter: (i) the Circ ORF alone, (ii) a fusion ORF encoding an N-terminal Circ fused to the enhanced green fluorescent protein (eGFP), (iii) the eGFP ORF alone, and (iv) the Circ ORF in the inverted orientation. Upon helpervirus-free packaging into HSV-1 amplicon particles and transduction of Vero cells, both Circ alone and the Circ-eGFP fusion protein produced a punctate pattern within the cytoplasm, suggesting membrane association of the myristylated protein. In contrast, eGFP alone was evenly distributed over the cytoplasm of transduced cells. Upon infection of bovine buffy-coat cells, it was observed that cells of the monocyte lineage but not lymphocytes were transduced. Transgene expression reached a peak around 20h after transduction and lasted for at least 90h. Transduced monocytes underwent specific morphological changes, which may be attributed to Circ synthesis.

Immediate-early protein BICP22 of bovine herpesvirus 1 trans-represses viral promoters of different kinetic classes and is itself regulated by BICP0 at transcriptional and posttranscriptional levels

Bovine herpesvirus 1 (BHV-1) encodes four immediate-early (IE) proteins. The transactivators BICP0 and BICP4 are key regulatory elements in viral replication, and circ is a myristylated virion component, whereas BICP22--originating from a spliced 1.7-kb transcript synthesized with dual IE and late kinetics--has not yet been characterized as a protein. In this study, Western blot and immunofluorescence analysis using antisera against a C-terminal oligopeptide revealed major 50-kDa and minor 35-kDa species of BICP22, predominantly located in the nuclei of BHV-1 infected cells. In transient expression assays, BICP22 acted as transrepressor protein on viral promoters of different kinetic classes, e.g. the IE promoter of the BICP4/BICP0 gene, early promoter of the BICP0 gene, and late promoter of the gC gene. The BICP22 gene promoter itself was not repressed by BICP22; it could be dissected into a proximal region stimulated by BICP0 and a distal region stimulated by BHV-1 alpha-transinducing factor. Replacement of the BICP22 promoter by cytomegalovirus IE promoter revealed an additional posttranscriptional level of regulation whereby more BICP22 accumulated in cells when functional BICP0 was present. Interplay of BICP22 and BICP0 might involve the recently described nuclear domains (ND10) and ubiquitin-dependent pathway.

Sequence analysis of the bovine herpesvirus type 1 genes homologous to the DNA polymerase (UL30), the major DNA-binding protein (UL29) and ICP18.5 assembly protein (UL28) genes of herpes simplex virus

The nucleotide sequence of a 10.5 kb region (map position 0.332 to 0.410) of bovine herpesvirus type 1 (BHV-1) was determined. This region contained three open reading frames (ORFs) homologous to herpes simplex virus DNA polymerase catalytic subunit (DNApol, UL30), major DNA-binding protein (MDBP, UL29) and ICP18.5 assembly protein (ICP18.5, UL28). The BHV-1 DNApol. MDBP and ICP18.5 ORFs were 1246, 1203 and 826 amino acids long with a calculated molecular mass of 134.2 kDa, 124.4 kDa and 86.9 kDa, respectively. They showed a high homology with alphaherpesvirus homologs despite large differences in the G + C content of the UL30-UL28 segment ranging from 44.4% for varicella zoster virus to 71.5% for BHV-1. Particularly well conserved among Alphaherpesvirinae are the putative functional domains of the DNApol and MDBP proteins which are discussed. Phylogenetic analysis revealed that BHV-1 clustered in the Varicellovirus genus with the animal D-type viruses. In this group, the BHV-1 position was shown to vary according to the investigated genes. Indeed, pseudorabies virus clustered with BHV-1 in the DNApol tree but with equine herpesvirus 1 in the ICP18.5 tree.

Recombinant bovine herpesvirus-1 (BHV-1) lacking transactivator protein BICPO entails lack of glycoprotein C and severely reduced infectivity

The immediate-early transactivator protein BICPO is a key regulatory element of bovine herpesvirus 1 (BHV-1) replication based on transient expression assays. To examine BICPO function in the context of the viral genome, we created recombinant BHV-1 expressing beta-galactosidase instead of BICPO. To complement the defect, a neomycin resistant MDBK cell line (M164) expressing BICPO was established, permitting selection of a blue-staining BHV-1 recombinant (A2G2). Southern blot and PCR analysis confirmed that the BICPO gene was interrupted by the beta-galactosidase gene and that wt progeny was absent. Compared with wt BHV-1, A2G2 reached lower titers in M164 cells but replicated with similar kinetics. Once isolated, A2G2 also grew in MDBK cells although the titer was reduced a further 10-fold and the virus remained strongly cell-associated. Thus, BICPO is not absolutely required for replication in cell culture. Gene expression of A2G2 was investigated by Western blots and immunofluorescence. Surprisingly, not only was BICPO absent, but glycoprotein C (gC) was also missing. Other viral genes were expressed normally. Semiquantitative PCR showed that A2G2 produced similar amounts of viral DNA as wt but a much smaller number of infectious particles. Cotransfection of A2G2 DNA and a plasmid containing the BICPO gene yielded revertant virus with fully restored wt properties. We conclude that BICPO is required for gC expression, and that the missing gC partly accounts for the reduced A2G2 infectivity.

Molecular virology of ruminant herpesviruses

Molecular virology has served to establish bovine herpesvirus 1 (BHV-1) as the prototype member of ruminant herpesviruses. Based on the genomic sequence of the virus, we aim to identify and characterize virus-specified components, to explain their concerted action, and to predict how the chain of events during the lytic and latent phases of the viral life cycle may be interrupted. The nucleotide sequence of the BHV-1 genome (136 kb) has just been completed by international cooperation (July 1995; except for a small gap in UL36). It comprises 67 unique genes and 2 genes, both duplicated, in the inverted repeats. In general, these genes exhibit strong homology at the amino acid sequence level to those of other alphaherpesviruses (HSV-1, VZV, EHV-1) and are arranged in similar order. A few genes are peculiar to only one or two herpesviruses, e.g. in BHV-1 the circ, UL0.5, UL3.5 and US1.5 genes. Not long ago, the repertoire of BHV-1 proteins under study was restricted to the three major glycoproteins (gB, gC, and gD) and thymidine kinase. The repertoire is now growing rapidly and includes 7 additional glycoproteins (gE, gI, gH, gL, gG, gK and gM), a number of enzymes (e.g. ribonucleotide reductase, DNA Polymerase, dUTPase), and a group of regulatory proteins (BICPO, 4, 22, and 27, alpha TIF). Investigations into the functions of these proteins and comparison with their counterparts in other herpesviruses should reveal which are useful targets for diagnosis, prevention or antiviral treatment. Recombinant viruses containing deletions or replacements of individual genes are being created, aiming at vaccine development and insights into pathogenesis, notably latency, neurotropism, and interference with host functions. Molecular analysis of other ruminant herpesviruses is much less advanced. Over a dozen virus species have been described; most share basic properties with BHV-1 and may be classified as alphaherpesviruses. The gammaherpesviruses are represented by the proposed agent of malignant catarrhal fever, alcelaphine herpesvirus 1, and by bovine herpesvirus 4, whose partial sequences exhibit similarity to herpesvirus saimiri.

Gene contents in a 31-kb segment at the left genome end of bovine herpesvirus-1

We report the nucleotide sequence of a 31-kb segment at the left genome end of bovine herpesvirus-1 (BHV-1) and show that it comprises 19 different open reading frames (ORFs), including seven which have been described previously (circ, dUTPase, UL49.5, alpha TIF, VP8, glycoprotein C, and ribonucleotide reductase small subunit). The new sequence resulted in a correction at the C-terminus of glycoprotein C. All 19 ORFs exhibited strong amino acid sequence homology to the gene products of other alphaherpesviruses. The BHV-1 ORFs were arranged colinearly with the prototype sequence of herpes simplex virus 1 (HSV-1) in the range of the UL54 to UL37 genes. No BHV-1 homologs of the HSV-1 UL56, UL55, and UL45 genes were identified. The BHV-1 circ gene was the only gene without a HSV-1 counterpart. The additional ORFs 1 and 2 found at the left genome end of equine herpesvirus-1 (EHV-1) were absent in BHV-1. Among the newly sequenced BHV-1 ORFs are homologs of ICP27 (UL54), glycoprotein K (UL53), helicase-primase (UL52), DNA polymerase accessory protein (UL42), ribonucleotide reductase large subunit (UL39), and several virion proteins (UL49, UL46, UL43, UL41, UL38, UL37), most of which are strongly conserved in all herpesviruses. The possible functions of the proteins encoded within the sequenced region are assessed and features found are discussed.

Identification and characterization of BICP27, an early protein of bovine herpesvirus 1 which may stimulate mRNA 3' processing

Sequence analysis of the left genomic terminus of bovine herpesvirus 1 (BHV-1) revealed two convergently transcribed genes with 3' ends about 300 bp apart. The gene on the left is the previously described circ gene; that on the right was found to encode a protein of 400 amino acids which was designated BICP27 because of its homology to ICP27 (Vmw63) of herpes simplex virus 1 (HSV-1) and related proteins from other alpha- beta- and gammaherpesviruses. Rabbit antisera raised against a synthetic oligopeptide representing the amino terminus of the predicted polypeptide demonstrated the presence of BICP27 in the nuclei of infected cells by in situ immunoadsorbent assays. In Western immunoblots, BICP27 was detected as a 50 kDa BHV-1 specific protein expressed with early kinetics, in contrast to HSV-1 ICP27 which is an immediate early (IE) protein. A DNA fragment containing BICP27 coding sequences was inserted into a baculovirus genome. The recombinant BICP27 protein, identified by its reactivity with the antipeptide sera, exhibited the same electrophoretic mobility as BICP27 specified by BHV-1. Transient expression assays using target genes differing only in their poly(A) sites showed that BICP27, like its HSV-1 counterpart, may be involved in 3' processing of mRNA.

Diagnosis of fetal infection with porcine parvovirus by in situ hybridization

In situ hybridization (ISH) for the diagnosis of fetal infection with porcine parvovirus (PPV) was compared with immune electron microscopy (IEM) and serology by immunofluorescence (IF) for its sensitivity and its applicability in a routine diagnostic laboratory. The technique was applied to the examination of sections of formalin-fixed paraffin-embedded tissues from 68 fetuses. Fifty-three of these fetuses were diagnosed serologically since they had a crown rump length of more than 17 cm, i.e. they were mature enough to mount a humoral immune response; 38 were positive and 15 negative. Eleven out of 15 smaller fetuses examined for the presence of viral antigen by immune electron microscopy (IEM) were positive and 4 were negative. Heart and lung were found to be the most suitable organs for in situ hybridization. In situ hybridization yielded a positive result in 8 of the 11 IEM positive fetuses and in 33 of the 38 serologically positive fetuses. No signal was detected in any of the 4 IEM or the 13 serologically negative fetuses. Expenses for IEM were estimated to be 179% of the expenses for ISH. Expenses for serology by IF on the other hand were 67% of the expenses for ISH. From this it was concluded that the most efficient way to diagnose a fetal infection with PPV was serology by IF, if possible with samples from several fetuses and that the other techniques, IEM or ISH, ought to be reserved for those cases where no immunocompetent fetuses were available for diagnosis.

Sequence analysis of the UL39, UL38, and UL37 homologues of bovine herpesvirus 1 and expression studies of UL40 and UL39, the subunits of ribonucleotide reductase

We sequenced the region of the bovine herpesvirus type 1 (BHV-1) genome corresponding to map units 0.172-0.230 (7964 bp), representing the UL39, UL38, and UL37 homologues of herpes simplex virus which encode the large subunit of ribonucleotide reductase (RR) and components of the viral capsid and the tegument, respectively. To discriminate between two potential initiator AUGs of the UL39 gene, the 5' end of the mRNA was mapped by S1 nuclease protection assays. Comparison of the amino acid sequences of the three BHV-1 proteins with analogous polypeptides from several other herpesviruses revealed significant levels of homology. We also compared the expression kinetics of the large (R1, UL39) versus the small (R2, UL40) RR subunits during the course of in vitro BHV-1 infection by Western blotting using specifically developed and calibrated antisera. Our results show that the R1 protein was synthesized earlier than its R2 counterpart. Moreover, the R1 protein accumulated to a higher level than the R2 protein even though the R2 transcript was in greater abundance than the R1 mRNA. This is discussed with regard to the translational efficiency of their transcripts.

Nucleotide sequence analysis of a 30-kb region of the bovine herpesvirus 1 genome which exhibits a colinear gene arrangement with the UL21 to UL4 genes of herpes simplex virus

We report the nucleotide sequence of the 19-kb HindIII fragment B of bovine herpesvirus 1 (BHV-1) DNA and adjacent parts of the HindIII A and L fragments, which together span a still completely uncharted 30-kb region located between the glycoprotein H gene and the right end of the unique long segment. The analysis revealed 17 complete open reading frames (ORFs) and 2 ORFs that were interrupted by potential splice donor and acceptor sites. All of these ORFs exhibited strong amino acid sequence homology to the gene products of other alphaherpesviruses. The BHV-1 ORFs were arranged colinearly with the prototype sequence of herpes simplex virus 1 in the range of the UL21 to UL4 genes. Colinearity was also observed with the genes of betaherpesviruses and gamma herpesviruses, although not all ORFs exhibited clear sequence homology. The possible functions of the proteins encoded within the sequenced region are assessed and features found are discussed. Unexpected findings include the following: high amino acid sequence conservation among alphaherpesviruses despite large differences in G + C content, ranging from 45% for varicella zoster virus to 72% for BHV-1; high similarity with other UL20 proteins at the predicted structural level in spite of relatively low amino acid homology; and a 2-kb open reading frame overlapping UL19 in the opposite sense and exhibiting high amino acid similarity to the same area of pseudorabies virus.

Identification of the bovine herpesvirus 1 circ protein, a myristylated and virion-associated polypeptide which is not essential for virus replication in cell culture

We have recently reported immediate-early (IE) transcription over covalently joined genome ends of bovine herpesvirus 1 (BHV-1). A spliced 1.5-kb IE RNA (IER1.5) is coterminal with an unspliced 1.1-kb late RNA (LR1.1) which is transcribed from the left end of the genome. Sequence analysis reveals an open reading frame common to IER1.5 and LR1.1 predicted to encode the 247-amino-acid circ polypeptide. This paper reports on the identification of circ as a protein. Using a rabbit antiserum raised against a synthetic oligopeptide representing the carboxy terminus of the predicted circ polypeptide for Western blot (immunoblot) analyses and immunofluorescence assays, we identified a 34-kDa virion-associated protein which accumulated in the cytoplasm of infected cells. To confirm that LR1.1 indeed encoded the 34-kDa polypeptide, we inserted a DNA fragment containing circ coding sequences into the Autographa californica baculovirus genome. A group of recombinant polypeptides with sizes of 32, 34, and 35 kDa were identified by their reactivity with the antipeptide serum. Chicken egg yolk antibodies raised against total proteins of insect cells infected with the recombinant baculovirus identified the 34-kDa circ protein specified by BHV-1. The recombinant circ polypeptides and the circ protein specified by BHV-1 were both myristylated, as determined by radiolabeling with [3H]myristic acid. It was noted that the circ gene could be deleted from the BHV-1 genome without impairing virus replication in cell culture.

BICP22 of bovine herpesvirus 1 is encoded by a spliced 1.7 kb RNA which exhibits immediate early and late transcription kinetics

Kinetic analysis of the two divergent immediate early (IE) transcription units of bovine herpesvirus 1 (BHV-1) revealed an unexpected behaviour. The IE1.7 promoter was not turned off at the end of the IE period but acted as a late promoter, unlike the adjacent IE4.2/2.9 promoter which was active only under IE conditions. The genome region specifying the IE1.7 gene was sequenced (0.814 to 0.839 map units). The IE1.7 promoter was found to overlap with duplicated sequence elements bearing close similarity to herpesvirus origins of replication, which may explain the biphasic transcription kinetics. Exons 1 and 2 of the spliced IE1.7 transcript were non-coding. Exon 3 was found to contain a single open reading frame encoding a protein of 300 amino acids that was designated BICP22 because of its homology to ICP22 (Vmw68) of herpes simplex virus type 1 and related proteins from other herpesviruses. The protein probably represents IEP-55, the most abundant BHV-1 phosphoprotein observed under IE conditions.

Identification and zinc dependence of the bovine herpesvirus 1 transactivator protein BICP0

Bovine herpesvirus 1 (BHV-1) specifies and unspliced early 2.6-kb RNA (ER2.6) which is 3' coterminal with exon 2 of the 2.9-kb immediate-early (IE) RNA. The two transcripts have a common open reading frame (676 codons). The predicted protein, designated BHV-1 infected cell protein 0 (BICP0), contains a zinc finger domain with homology to ICP0 of herpes simplex virus type 1 and protein 61 of varicella-zoster virus, and depending on the promoter, it acts as a strong activator or as a repressor in transient expression assays. In situ immunoadsorbent assays using antisera against synthetic oligopeptides demonstrated that BICP0 accumulates in nuclei of BHV-1-infected cells, as expected for an IE gene product involved in gene regulation. Western blots (immunoblots) revealed a BHV-1-specific 97-kDa protein which was detectable during the IE phase and also at later periods of infection, indicating that the kinetics of BICP0 synthesis is consistent with the switch from IER2.9 to ER2.6. To confirm that ER2.6 encoded the 97-kDa BICP0 protein, a DNA fragment containing BICP0-coding sequences was inserted into the Autographa californica baculovirus genome. A recombinant protein, identified by its reactivity with antipeptide sera, exhibited the same electrophoretic mobility as BICP0 specified by BHV-1. We microinjected Xenopus oocytes with a BICP0 effector plasmid and a promoter-chloramphenicol acetyltransferase plasmid. BICP0-induced stimulation of this promoter was strongly reduced when intracellular zinc was chelated by thionein, indicating that the effect of BICP0 is zinc dependent.

Promoter, spliced leader, and coding sequence for BICP4, the largest of the immediate-early proteins of bovine herpesvirus 1

We report the complete nucleotide sequence of the bovine herpesvirus 1 (BHV-1) immediate-early gene encoding BICP4, the homolog of the ICP4 protein of herpes simplex virus. Combined with previous mapping studies, the sequence analysis revealed that the transcript for BICP4 consisted of a noncoding leader RNA (exon 1; 0.35 kb) separated by an intron (0.46 kb) from the main body (exon 2; 4.1 kb). The open reading frame for BICP4 (1343 amino acid residues) started 27 nt after the splice site and extended across exon 2 for most of its length, BICP4 contained two domains of high homology (regions 2 and 4), which had been recognized earlier to be most conserved in the ICP4 homologs of alpha-herpesviruses and to be functionally important. These domains were flanked by three regions of lower but still discernible homology. Unique features of BICP4 were two large clusters of glutamic acid residues near the end of region 3, and the displacement of a polyserine tract to region 5, which in all other ICP4 homologs residues near the end of region 1. Transient expression assays showed that BICP4 repressed its own promoter and activated other herpes-virus genes. The 8.1-kb sequence summarized here completes analysis of the inverted repeats of the BHV-1 genome; it includes a segment (2.5 kb) upstream of the BICP4 gene apparently devoid of coding sequences but containing numerous scattered transcription signals.

Immediate-early transcription over covalently joined genome ends of bovine herpesvirus 1: the circ gene

Herpesvirus genomes are linear molecules in virions. Prior to replication in host cells, they form circular templates by unknown mechanisms. Examining lytic infection with bovine herpesvirus 1, we observed immediate-early transcription over joined genome ends, which suggested that circles are present at the initial stage of infection. Among the transcripts was a spliced immediate-early RNA (1.5 kb) sharing exon 1 with previously described major immediate-early transcripts from the right genome end and exon 2 with a late transcript located near the left genome end. Exon 2 encodes a putative circ-encoded protein with homology to the varicella-zoster virus open reading frame 2 and equine herpesvirus 1 open reading frame 3 products. The novel features reported here for bovine herpesvirus 1 may constitute a more general property of herpesviruses.

Immediate-early RNA 2.9 and early RNA 2.6 of bovine herpesvirus 1 are 3' coterminal and encode a putative zinc finger transactivator protein

Bovine herpesvirus 1 (BHV-1) contains three major immediate-early (IE) genes involved in regulation of the productive cycle of replication. Two spliced IE RNAs, IER4.2 (4.2 kb) and IER2.9 (2.9 kb), are under the control of a single promoter; IER1.7 (1.7 kb) is transcribed from a different promoter in the opposite direction. Examining the kinetics of transcription, we found that the IER4.2/2.9 promoter was turned off at the end of the IE period. An alternative promoter became active, directing synthesis of an unspliced early RNA, ER2.6 (2.6 kb), which was colinear with the second exon of IER2.9 except for its 5' end in the intron about 10 bases upstream of the splice site. Sequence analysis revealed a single open reading frame common to IER2.9 and ER2.6 with a coding potential of 676 amino acids. The putative protein, named p135, contained a cysteine-rich zinc finger domain near the N terminus with homology to ICP0 of herpes simplex virus type 1, to protein 61 of varicella-zoster virus, to early protein 0 of pseudorabies virus, and to other viral and cellular proteins. The remaining parts of p135 exhibited only limited homology, mainly with pseudorabies virus protein 0, but the entire sequence was highly conserved between two strains of BHV-1 (K22 and Jura). The latency-related antisense transcript covered a large portion of ER2.6 excluding the zinc finger coding region. In transient expression assays, p135 activated a variety of promoters, including that for ER2.6, but repressed the IER1.7 promoter. Thus, p135 combines functional characteristics of ICP0, a strong transactivator, and of protein 61, a repressor. BHV-1 seems to have evolved a subtle mechanism to ensure the continued synthesis of p135 while turning off IER4.2, which encodes p180, the herpes simplex virus type 1 ICP4 homolog.

The three major immediate-early transcripts of bovine herpesvirus 1 arise from two divergent and spliced transcription units

Among 54 transcripts expressed in a temporal cascade during lytic infection with bovine herpesvirus 1, we have previously identified three major immediate-early (IE) RNAs, IER4.2 (4.2 kb), IER2.9 (2.9 kb), and IER1.7 (1.6 to 1.8 kb depending on the virus strain) transcribed from the HindIII C genome region (U. V. Wirth, K. Gunkel, M. Engels, and M. Schwyzer, J. Virol. 63:4882-4889, 1989). Northern (RNA) blot, S1 nuclease protection, and primer extension analysis used in the present study demonstrated that all three IE transcripts were spliced and originated from two divergent transcription units with start sites located in the inverted repeat. Transcription unit 1 encoded two alternative spliced transcripts, IER4.2 and IER2.9, with a common exon 1 located at 0.797 to 0.795 map units (m.u.) and an exon 2 for IER4.2 (0.792 to 0.762 m.u.) in the inverted repeat; exon 2 for IER2.9 (0.754 to 0.738 m.u.) was located in the unique long sequence and transcribed in antisense orientation to latency-related RNA. Transcription unit 2 (0.818 to 0.836 m.u.), further characterized by cDNA cloning, encoded the spliced IER1.7 with three exons in the inverted repeat. Additional minor IE transcripts were interpreted as unspliced precursors and splicing variants. With regard to the number and layout of IE genes, bovine herpesvirus 1 occupies an intermediate position between pseudorabies virus and equine herpesvirus 1 on the one hand and varicella-zoster virus and herpes simplex virus type 1 on the other.

Pseudorabies virus immediate-early gene overlaps with an oppositely oriented open reading frame: characterization of their promoter and enhancer regions

The immediate-early (IE) gene of pseudorabies virus (PRV) has recently been sequenced for two virus strains. To investigate IE gene regulation and to examine the genome segment reported to encode latency-related transcripts in opposite polarity to the IE gene, sequence analysis has been extended by 5 kb from each end of the IE gene. The IE promoter (P1) was found to be more complex than previously recognized: it consisted of nine imperfect repeats, each containing five to six different consensus elements for transcription factor binding. A second promoter (P2) was discovered downstream of the IE gene. It contained numerous octamer consensus sequences (ATGCAAAT) and recognition sites for transcription factor Sp1; specific binding of nuclear proteins to four Sp1 sites was detected. An open reading frame (ORF3) bordering on P2 was identified, oriented antiparallel to the IE gene. Potential enhancer elements (E3 and E4) were isolated by the enhancer trap technique. Linked to P1 and a CAT indicator gene, E3 acted as an enhancer and E4 as a silencer. The PRV IE gene product repressed transcription from its own promoter and activated the SV40 early promoter. The transactivating virion protein Vmw65 of HSV1 had an opposite effect on these promoters.

Update and comparison of the immediate-early gene DNA sequences of two pseudorabies virus isolates

Differences between the immediate-early gene DNA sequences of two pseudorabies virus isolates (Indiana-Funkhauser and Ka) were resolved and confirmed. The deduced amino acid sequences showed that regions 2 and 4 have fewer changes than the rest of the molecules. These two conserved regions may be functionally important.

Spatial and temporal distribution of bovine herpesvirus 1 transcripts

Northern (RNA) blot analysis was used to determine the spatial and temporal distribution of bovine herpesvirus 1 (BHV-1) transcripts. Total RNA was isolated from Madin-Darby bovine kidney cells which had been infected with BHV-1.2b strain K22 or BHV-1.1 strain Jura in the presence or absence of metabolic inhibitors. Cloned restriction fragments representing the entire genome of strain K22 were labeled with 32P and hybridized to immobilized RNA. A total of 54 BHV-1 transcripts were found, ranging in size from 0.4 to larger than 8 kilobases (kb). The inverted repeat regions and an adjacent segment of the unique large part of the BHV-1 genome encoded three major immediate-early (IE) transcripts and one minor IE transcript enriched after cycloheximide treatment of infected cells. Late transcripts were identified by drastically reduced abundance after cytosine arabinoside (araC) treatment. Twelve late transcripts were encoded mainly by the unique long genome region, with a cluster of four transcripts located on HindIII fragment K (map units 0.677 to 0.733). The 21 transcripts unaffected by araC treatment were defined as early; they showed dispersed locations over the whole genome, with a cluster on the unique short sequence. The 17 remaining transcripts could not be classified unambiguously as early or late by these techniques. The IE transcript with a size of 4.2 kb exhibited homology with the single IE gene of pseudorabies virus, and the IE transcript with a size of 2.9 kb was encoded in part by the genome region known to be transcriptionally active during latency.

Nucleotide sequence of the pseudorabies virus immediate early gene, encoding a strong transactivator protein

We report the complete DNA sequence of teh pseudorabies virus (PRV) immediate early (IE) gene and its flanking nucleotide sequences, together comprising 5091 base pairs. An open reading frame starts with an ATG codon in position 263 from the transcription-initiation site and ends with a TGA codon in position 4601, thus encoding a predicted protein of 1446 amino acids (150 kD). The PRV IE protein exhibits significant homology with the functionally related transactivator proteins, ICP4 of herpes simplex virus-1 (HSV-1) and p140 of varicella zoster virus (VZV). The extent of homology varies widely along the three sequences: Two regions of the PRV IE protein extending from amino acids 482 to 659 and 959 to 1350 exhibit 50% to 60% identity with the cognate sequences, whereas the remaining sequence reveals little homology apart from a common polyserine stretch. The base composition of the PRV IE coding region is 80% G + C, compared with 81.5% for HSV-1 and 64.1% for VZV. Yet the PRV IE protein appears to be as closely related to VZV p140 as to HSV-1 ICP4. The regions of strong homology are also apparent in plots predicting secondary structure.

Murine glia cells in culture can be stimulated to generate reactive oxygen

Induction of luminol-enhanced chemiluminescence (CL) indicative of reactive oxygen formation was studied in glia cell cultures from newborn mice. A burst of CL could be induced by phorbol myristate acetate, zymosan, and antibody-coated bovine red blood cells, whereas Sendai virus and several other agents known to induce CL in myeloid cells were ineffective. Sodium azide failed to inhibit CL, indicating a myeloperoxidase-independent mechanism of light emission. In parallel experiments we identified the cells binding antibody-coated erythrocytes as macrophages characterized by the reduction of nitroblue tetrazolium and phagocytosis of zymosan and latex particles. Brain macrophages may use reactive oxygen intermediates (ROI) as a mechanism of antimicrobial defence; and, on the other hand, ROI formed by these cells may contribute to immuno-pathology in the brain.

Inactivation of animal viruses during sewage sludge treatment

Using a previously developed filter adsorption technique, the inactivation of a human rotavirus, a coxsackievirus B5, and a bovine parvovirus was monitored during sludge treatment processes. During conventional anaerobic mesophilic digestion at 35 to 36 degrees C, only minor inactivation of all three viruses occurred. The k' values measured were 0.314 log10 unit/day for rotavirus, 0.475 log10 unit/day for coxsackievirus B5, and 0.944 log10 unit/day for parvovirus. However, anaerobic thermophilic digestion at 54 to 56 degrees C led to rapid inactivation of rotavirus (k' greater than 8.5 log10 units/h) and of coxsackievirus B5 (k' greater than 0.93 log10 unit/min). Similarly, aerobic thermophilic fermentation at 60 to 61 degrees C rapidly inactivated rotavirus (k' = 0.75 log10 unit/min) and coxsackievirus B5 (k' greater than 1.67 log10 units/min). Infectivity of parvovirus, however, was only reduced by 0.213 log10 unit/h during anaerobic thermophilic digestion and by 0.353 log10 unit/h during aerobic thermophilic fermentation. Furthermore, pasteurization at 70 degrees C for 30 min inactivated the parvovirus by 0.72 log10 unit/30 min. In all experiments the contribution of temperature to the total inactivation was determined separately and was found to be predominant at process temperatures above 54 degrees C. In conclusion, the most favorable treatment to render sludge hygienically safe from the virological point of view would be a thermal treatment (60 degrees C) to inactivate thermolabile viruses, followed by an anaerobic mesophilic digestion to eliminate thermostable viruses that are more sensitive to chemical and microbial inactivations.