Identification of pulmonary embolism: diagnostic accuracy of venous-phase dual-energy CT in comparison to pulmonary arteries CT angiography

Nonrigid temporal registration of multiphase CT pulmonary angiography using low-kV and low contrast: a feasibility study with dual-source CT

AIM

This study aimed to compare the nonrigid temporal registration of multiphase computed tomography pulmonary angiography (CTPA) with single-phase CTPA in terms of radiation dose, contrast agent usage, objective and subjective image quality.

MATERIALS AND METHODS

Consecutive patients suspected of acute pulmonary embolism were prospectively included in this study, and randomly received multiphase or single-phase CTPA. Regarding the contrast media, 15 mL was applied in the multiphase CTPA in comparison with 40 mL applied in the single-phase CTPA. Temporal registration was performed for multiphase CTPA during post-processing. Two experienced radiologists independently evaluated the image quality (IQ) based on objective measurements, subjective impression and diagnostic confidence. Patient demographics, scan parameters and image quality were compared between the two groups.

RESULTS

A total of 72 patients were analysed (37 multiphase CTPA and 35 single-phase CTPA). Positive pulmonary embolism was confirmed in five and seven patients, respectively. The two patient groups had similar demographics besides older age in those who underwent single-phase CTPA. Radiation dose and the contrast-to-noise ratio (CNR) were also similar between groups except for the CNR in the right main pulmonary artery. Both readers rated the multiphase CTPA with a statistically superior subjective IQ over the single-phase CTPA. The diagnostics confidence of the two CTPA protocols was similarly rated by one reader and slightly different according to the second reader.

CONCLUSION

The nonrigid temporal registration of multiphase CT pulmonary angiography could offer similar or even better image quality than the single-phase protocol and significantly reduce the amount of contrast usage.

Evolved size-specific dose estimates for patient-specific organ doses from chest CT scans based on hybrid patient size vectors

This study aims to develop a neural network-based method for predicting patient-specific organ doses from chest CT scans, utilizing hybrid patient size vectors for enhanced computational efficiency, accuracy, and generality. A dataset of 705 chest CT scans was retrospectively analyzed to construct predictive models for organ dose estimation. The proposed approach employs high dimensional hybrid vectors to represent patient size, combining muti-slice parameters regarding lateral dimension, anteroposterior dimension, and water-equivalent diameter (Dw). These vectors are used to train fully-connected neural networks, which are designed to correlate high-dimensional patient size features with reference organ doses obtained from Monte Carlo simulations. The performance of the neural networks was evaluated using separate test cohorts, with metrics such as mean absolute percentage error (MAPE) and coefficient of determination (R²) to evaluate predictive accuracy and generality. For the left lung, right lung, heart, and spinal cord, the trained neural networks respectively achieve MAPE values of 2.94%, 2.79%, 7.04%, and 6.76%, and R² values of 0.98, 0.99, 0.93, and 0.91. The maximal discrepancy between reference and predicted values is less than 10% for the left and right lungs, and less than 20% for the heart and spinal cord. With 5-fold cross-validation, the maximal perturbation does not exceed 1% in MAPE and 0.05 in R². By incorporating hybrid patient size vectors, the neural network models achieve superior accuracy in organ dose estimation compared with traditional size specific dose estimates, paving the way for online swift organ dose screening in clinical practice.

Photon-counting CT in Thoracic Imaging: Early Clinical Evidence and Incorporation Into Clinical Practice

Photon-counting CT (PCCT) is an emerging advanced CT technology that differs from conventional CT in its ability to directly convert incident x-ray photon energies into electrical signals. The detector design also permits substantial improvements in spatial resolution and radiation dose efficiency and allows for concurrent high-pitch and high-temporal-resolution multienergy imaging. This review summarizes (a) key differences in PCCT image acquisition and image reconstruction compared with conventional CT; (b) early evidence for the clinical benefit of PCCT for high-spatial-resolution diagnostic tasks in thoracic imaging, such as assessment of airway and parenchymal diseases, as well as benefits of high-pitch and multienergy scanning; (c) anticipated radiation dose reduction, depending on the diagnostic task, and increased utility for routine low-dose thoracic CT imaging; (d) adaptations for thoracic imaging in children; (e) potential for further quantitation of thoracic diseases; and (f) limitations and trade-offs. Moreover, important points for conducting and interpreting clinical studies examining the benefit of PCCT relative to conventional CT and integration of PCCT systems into multivendor, multispecialty radiology practices are discussed.

Dual-Energy CT in Oncologic Imaging

Dual-energy CT (DECT) is an innovative technology that is increasingly widespread in clinical practice. DECT allows for tissue characterization beyond that of conventional CT as imaging is performed using different energy spectra that can help differentiate tissues based on their specific attenuation properties at different X-ray energies. The most employed post-processing applications of DECT include virtual monoenergetic images (VMIs), iodine density maps, virtual non-contrast images (VNC), and virtual non-calcium (VNCa) for bone marrow edema (BME) detection. The diverse array of images obtained through DECT acquisitions offers numerous benefits, including enhanced lesion detection and characterization, precise determination of material composition, decreased iodine dose, and reduced artifacts. These versatile applications play an increasingly significant role in tumor assessment and oncologic imaging, encompassing the diagnosis of primary tumors, local and metastatic staging, post-therapy evaluation, and complication management. This article provides a comprehensive review of the principal applications and post-processing techniques of DECT, with a specific focus on its utility in managing oncologic patients.

Quantitative Assessment of Lung Volumes and Enhancement in Patients with COVID-19: Role of Dual-Energy CT

Dual-energy computed tomography (DECT) has been used for detecting pulmonary embolism, but the role of lung perfusion DECT as a predictor of prognosis of coronavirus disease 2019 (COVID-19) has not been defined yet. The aim of our study was to explore whether the enhancement pattern in COVID-19+ patients relates to the disease outcome. A secondary aim was to compare the lung volumes in two subgroups of patients. In this observational study, we considered all consecutive COVID-19+ patients who presented to the emergency room between January 2021 and December 2021 with respiratory symptoms (with mild to absent lung consolidation) and were studied by chest contrast-enhanced DECT to be eligible. Two experienced radiologists post-processed the images using the "lung-analysis" software (SyngoVia). Absolute and relative enhancement lung volumes were assessed. Patients were stratified in two subgroups depending on clinical outcome at 30 days: (i) good outcome (i.e., discharge, absence of clinical or imaging signs of disease); (ii) bad outcome (i.e., hospitalization, death). Patient sub-groups were compared using chi-square test or Fisher test for qualitative parameters, chi-square test or Spearman's Rho test for quantitative parameters, Students' t-test for parametric variables and Wilcoxon test for non-parametric variables. We enrolled 78 patients (45M), of whom, 16.7% had good outcomes. We did not observe any significant differences between the two groups, both in terms of the total enhancement evaluation (p = 0.679) and of the relative enhancement (p = 0.918). In contrast, the average lung volume of good outcome patients (mean value of 4262 mL) was significantly larger than that of bad outcome patients (mean value of 3577.8 mL), p = 0.0116. All COVID-19+ patients, with either good or bad outcomes, presented similar enhancement parameters and relative enhancements, underlining no differences in lung perfusion. Conversely, a significant drop in lung volume was identified in the bad outcome subgroup eligible compared to the good outcome subgroup.

Diagnosis of an Acute Anterior Wall Infarction in Dual-Energy CT

Due to its high morbidity and mortality, myocardial infarction is the leading cause of death worldwide. Against this background, rapid diagnosis is of immense importance. Especially in case of an atypical course, the correct diagnosis may be delayed and thus lead to increased mortality rates. In this report, we present a complex case of acute coronary syndrome. A triple-rule-out CT examination was performed in dual-energy CT (DECT) mode. While pulmonary artery embolism and aortic dissection could be ruled out with conventional CT series, the presence of anterior wall infarction was only detectable on DECT reconstructions. Subsequently, adequate and rapid therapy was then initiated leading to survival of the patient.

Systemic-pulmonary collateral supply associated with clinical severity of chronic thromboembolic pulmonary hypertension: a study using intra-aortic computed tomography angiography

OBJECTIVES

To assess whether systemic-pulmonary collaterals are associated with clinical severity and extent of pulmonary perfusion defects in chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

This prospective study was approved by a local ethics committee. Twenty-four patients diagnosed with inoperable CTEPH were enrolled between July 2014 and February 2017. Systemic-pulmonary collaterals were detected using pulmonary vascular enhancement on intra-aortic computed tomography (CT) angiography. The pulmonary enhancement parameters were calculated, including (1) Hounsfield unit differences (HUdiff) between pulmonary trunks and pulmonary arteries (PAs) or veins (PVs), namely HUdiff-PA and HUdiff-PV, on the segmental base; (2) the mean HUdiff-PA, mean HUdiff-PV, numbers of significantly enhanced PAs and PVs, on the patient base. Pulmonary perfusion defects were recorded and scored using the lung perfused blood volume (PBV) based on intravenous dual-energy CT (DECT) angiography. Pearson's or Spearman's correlation coefficients were used to evaluate correlations between the following: (1) segment-based intra-aortic CT and intravenous DECT parameters (2) patient-based intra-aortic CT parameters and clinical severity parameters or lung PBV scores. Statistical significance was set at p < 0.05.

RESULTS

Segmental HUdiff-PV was correlated with the segmental perfusion defect score (r = 0.45, p < 0.01). The mean HUdiff-PV was correlated with the mean pulmonary arterial pressure (PAP) (r = 0.52, p < 0.01), cardiac output (rho = - 0.41, p = 0.05), and lung PBV score (rho = 0.43, p = 0.04). And the number of significantly enhanced PVs was correlated with the mean PAP (r = 0.54, p < 0.01), pulmonary vascular resistance (r = 0.54, p < 0.01), and lung PBV score (rho = 0.50, p = 0.01).

CONCLUSIONS

PV enhancement measured by intra-aortic CT angiography reflects clinical severity and pulmonary perfusion defects in CTEPH.

KEY POINTS

• Intra-aortic CT angiography demonstrated heterogeneous enhancement within the pulmonary vasculature, showing collaterals from the systemic arteries to the pulmonary circulation in CTEPH. • The degree of systemic-pulmonary collateral development was significantly correlated with the clinical severity of CTEPH and may be used to evaluate disease progression. • The distribution of systemic-pulmonary collaterals is positively correlated with perfusion defects in the lung segments in CTEPH.

Optimising CT-chest protocols and the added value of venous-phase contrast timing; Observational case-control

INTRODUCTION

To optimize CT chest protocol by comparing venous contrast timing with arterial timing for contrast opacification in vessels, qualitative image quality and radiologists' satisfaction and diagnostic confidence in assessing for potential nodal, pleural and pulmonary disease in general oncology outpatients.

METHOD

Matched case-control study performed following CT protocol update. 92 patients with a range of primary malignancies with 2 CT chests in a 2-year period, one with an arterial phase protocol and the second in the 60 second venous phase, were included. Contrast attenuation in aorta, pulmonary artery and liver were measured. Subjective measurements assessed perivenous artefact, confidence in nodal pleural and pulmonary assessment and presence of pulmonary emboli. Statistical analysis was performed using paired and unpaired t-tests.

RESULTS

Venous-phase CT demonstrated more consistent enhancement of the vessels, with higher attenuation of the nodes, pulmonary and pleural lesions. There was a significant reduction in perivenous beam hardening artefact on venous-phase CT (P < 0.001). Diagnostic confidence was significantly higher for nodal assessment and pleural abnormality visibility (P < 0.001) and pleural assessment (P < 0.05). There was no significant difference in pulmonary mass visibility. There was adequate enhancement to diagnose significant pulmonary emboli (PE) with 4 incidental PEs detected on the venous phase, extending to segmental vessels.

CONCLUSION

Venous-phase CT chest performs better than arterial-phase on all fronts, without compromising assessment of incidental pulmonary emboli. When intravenous contrast is indicated in a routine chest CT (excluding a CT-angiogram), the default timing should be a venous or 60s phase.

Identification of bone marrow edema of the knee: diagnostic accuracy of dual-energy CT in comparison with MRI

BACKGROUND

To assess the diagnostic accuracy of dual-energy computed tomography (DECT) in diagnosing bone marrow edema (BME) of the knee in traumatic and non-traumatic patients.

METHODS

This prospective IRB approved study included 33 consecutive patients (20 males, 13 females; mean age of 52.2 years) evaluated with DECT (80 and 150 kV) and MRI within 6 days. Two experienced radiologists qualitatively and quantitatively evaluated DECT images. The accuracy values were calculated by using receiver operator curves (ROC) and area under the curve (AUC), using MRI as the reference standard. Inter-observer and intra-observer agreement were calculated with k-statistics. A p < 0.05 was considered statistically significant.

RESULTS

MRI depicted BME in 25/33 patients (75.7%). The sensitivity, specificity, PPV, NPV, and accuracy of per-partition qualitative analysis were 92.9, 92.9, 78.2, 97.9, and 92.9%, for reader 1, and 88.2, 93.9, 79.8, 96.6, and 92.6%, for reader 2, respectively. The inter-observer agreement was substantial (k = 0.793) and the intra-observer agreement was near-perfect (k = 0.844). At the quantitative analysis, a significant difference (p < 0.001) was depicted between the density values of positive (mean 3.6 ± 25.3 HU) and negative cases (mean - 72.2 ± 45.1 HU). By using - 15 HU cutoff to identify BME, sensitivity, specificity, PPV, NPV, and accuracy of DECT were 84.7, 93.6, 78.2, 95.7, and 91.6%, respectively.

CONCLUSION

DECT can accurately identify BME of the knee.