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Background Active endothelial cell proliferation occurs at the tumor edge, known as the invading-tumor front. This study focused on perfusion analysis of non-small cell lung cancers. Purpose To analyze dual-phase, dual-energy CT perfusion according to the degree of tumor hypoxia. Materials and Methods This prospective study was performed 2016-2017. A two-phase dual-energy CT protocol was obtained for consecutive participants with operable non-small cell lung cancer. The first pass and delayed iodine concentration within the tumor and normalized iodine uptake, corresponding to the iodine concentration within the tumor normalized to iodine concentration within the aorta, were calculated for the entire tumor and within three peripheral layers automatically segmented (ie, 2-mm-thick concentric subvolumes). The expression of the membranous carbonic anhydrase (mCA) IX, a marker of tumor hypoxia, was assessed in tumor specimens. Comparative analyses according to the histologic subtypes, type of resected tumors, and mCA IX expression were performed. Results There were 33 mCA IX-positive tumors and 16 mCA IX-negative tumors. In the entire tumor, the mean normalized iodine uptake was higher on delayed than on first-pass acquisitions (0.35 ± 0.17 vs 0.13 ± 0.15, respectively; P < .001). A single layer, located at the edge of the tumor, showed higher values of the iodine concentration (median, 0.53 mg/mL vs 0.21 mg/mL, respectively; P = .03) and normalized iodine uptake (0.04 vs 0.02, respectively; P = .03) at first pass in mCA IX-positive versus mCA IX-negative tumors. Within this layer, a functional profile of neovascularization was found in 23 of 33 (70%) of mCA IX-positive tumors, and the median mCA IX score of these tumors was higher than in tumors with a nonfunctional profile of neovascularization (median mCA IX score, 20 vs 2, respectively; P = .03). Conclusion A two-phase dual-energy CT examination depicted higher perfusion between the tumor edge and lung parenchyma in hypoxic tumors. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Murphy and Ryan in this issue.

Purpose In the literature on automated phenotyping of chronic obstructive pulmonary disease (COPD), there is a multitude of isolated classical machine learning and deep learning techniques, mostly investigating individual phenotypes, with small study cohorts and heterogeneous meta-parameters, e.g., different scan protocols or segmented regions. The objective is to compare the impact of different experimental setups, i.e., varying meta-parameters related to image formation and data representation, with the impact of the learning technique for subtyping automation for a variety of phenotypes. The identified associations of these parameters with automation performance and their interactions might be a first step towards a determination of optimal meta-parameters, i.e., a meta-strategy. Methods A clinical cohort of 981 patients (53.8 ± 15.1 years, 554 male) was examined. The inspiratory CT images were analyzed to automate the diagnosis of 13 COPD phenotypes given by two radiologists. A benchmark feature set that integrates many quantitative criteria was extracted from the lung and trained a variety of learning algorithms on the first 654 patients (two thirds) and the respective algorithm retrospectively assessed the remaining 327 patients (one third). The automation performance was evaluated by the area under the receiver operating characteristic curve (AUC). 1717 experiments were conducted with varying meta-parameters such as reconstruction kernel, segmented regions and input dimensionality, i.e., number of extracted features. The association of the meta-parameters with the automation performance was analyzed by multivariable general linear model decomposition of the automation performance in the contributions of meta-parameters and the learning technique. Results The automation performance varied strongly for varying meta-parameters. For emphysema-predominant phenotypes, an AUC of 93%-95% could be achieved for the best meta-configuration. The airways-predominant phenotypes led to a lower performance of 65%-85%, while smooth kernel configurations on average were unexpectedly superior to those with sharp kernels. The performance impact of meta-parameters, even that of often neglected ones like the missing-data imputation, was in general larger than that of the learning technique. Advanced learning techniques like 3D deep learning or automated machine learning yielded inferior automation performance for non-optimal meta-configurations in comparison to simple techniques with suitable meta-configurations. The best automation performance was achieved by a combination of modern learning techniques and a suitable meta-configuration. Conclusions Our results indicate that for COPD phenotype automation, study design parameters such as reconstruction kernel and the model input dimensionality should be adapted to the learning technique and may be more important than the technique itself. To achieve optimal automation and prediction results, the interaction between input those meta-parameters and the learning technique should be considered. This might be particularly relevant for the development of specific scan protocols for novel learning algorithms, and towards an understanding of good study design for automated phenotyping.

The radiologic community is rapidly integrating a revolution that has not fully entered daily practice. It necessitates a close collaboration between computer scientists and radiologists to move from concepts to practical applications. This article reviews the current littérature on machine learning and deep neural network applications in the field of pulmonary embolism, chronic thromboembolic pulmonary hypertension, aorta, and chronic obstructive pulmonary disease.

To compare dual-energy (DE) lung perfused blood volume generated by subtraction of virtual monoenergetic images (Lung Mono) with images obtained by three-compartment decomposition (Lung PBV).The study included 58 patients (28 patients with and 30 patients without PE) with reconstruction of Lung PBV images (i.e., the reference standard) and Lung Mono images. The inter-technique comparison was undertaken at a patient and segment level.The distribution of scores of subjective image noise (patient level) significantly differed between the two reconstructions (p0.0001), with mild noise in 58.6% (34/58) of Lung Mono images vs 25.9% (15/58) of Lung PBV images. Detection of perfusion defects (segment level) was concordant in 1104 segments (no defect: n=968; defects present: n=138) and discordant in 2 segments with a PE-related defect only depicted on Lung Mono images. Among the 28 PE patients, the distribution of gradient of attenuation between perfused areas and defects was significantly higher on Lung Mono images compared to Lung PBV (median= 73.5 HU (QI=65.0; Q3=86.0) vs 24.5 HU (22.0; 30.0); p0.0001). In all patients, fissures were precisely identified in 77.6% of patients (45/58) on Lung Mono images while blurred (30/58; 51.7%) or not detectable (28/58; 48.3%) on Lung PBV images.Lung Mono perfusion imaging allows significant improvement in the overall image quality and improved detectability of PE-type perfusion defects.

Background During COVID-19, the main manifestations of the disease are not only pneumonia but also coagulation disorders. The purpose of this study was to evaluate pulmonary vascular abnormalities 3 months after hospitalization for SARS-CoV-2 pneumonia in patients with persistent respiratory symptoms. Methods Among the 320 patients who participated in a systematic follow-up 3 months after hospitalization, 76 patients had residual symptoms justifying a specialized follow-up in the department of pulmonology. Among them, dual-energy CT angiography (DECTA) was obtained in 55 patients. Findings The 55 patients had partial (n = 40; 72.7%) or complete (n = 15; 27.3%) resolution of COVID-19 lung infiltration. DECTA was normal in 52 patients (52/55; 94.6%) and showed endoluminal filling defects in 3 patients (3/55; 5.4%) at the level of one (n = 1) and two (n = 1) segmental arteries of a single lobe and within central and peripheral arteries (n = 1). DECT lung perfusion was rated as non-interpretable (n = 2;3.6%), normal (n = 17; 30.9%) and abnormal (n = 36; 65.5%), the latter group comprising 32 patients with residual COVID-19 opacities (32/36; 89%) and 4 patients with normal lung parenchyma (4/36; 11%). Perfusion abnormalities consisted of (a) patchy defects (30/36; 83%), (b) PE-type defects (6/36; 16.6%) with (n = 1) or without proximal thrombosis (n = 5); and (c) focal areas of hypoperfusion (2/36; 5.5%). Increased perfusion was seen in 15 patients, always matching GGOs, bands and/or vascular tree-in- bud patterns. Interpretation DECT depicted proximal arterial thrombosis in 5.4% of patients and perfusion abnormalities suggestive of widespread microangiopathy in 65.5% of patients. Lung microcirculation was abnormal in 4 patients with normal lung parenchyma.

The goal of radiomics is to convert medical images into a minable data space by extraction of quantitative imaging features for clinically relevant analyses, e.g. survival time prediction of a patient. One problem of radiomics from computed tomography is the impact of technical variation such as reconstruction kernel variation within a study. Additionally, what is often neglected is the impact of inter-patient technical variation, resulting from patient characteristics, even when scan and reconstruction parameters are constant. In our approach, measurements within 3D regions-of-interests (ROI) are calibrated by further ROIs such as air, adipose tissue, liver, etc. that are used as control regions (CR). Our goal is to derive general rules for an automated internal calibration that enhance prediction, based on the analysed features and a set of CRs. We define qualification criteria motivated by status-quo radiomics stability analysis techniques to only collect information from the CRs which is relevant given a respective task. These criteria are used in an optimisation to automatically derive a suitable internal calibration for prediction tasks based on the CRs. Our calibration enhanced the performance for centrilobular emphysema prediction in a COPD study and prediction of patients' one-year-survival in an oncological study.

Rationale and Objectives The noninvasive approach of lung perfusion generated from dual-energy computed tomography acquisitions has entered clinical practice. The purpose of this study was to analyze the regional distribution of iodine within distal portions of the pulmonary arterial bed on dual-source, dual-energy computed tomography examinations in a cohort of subjects without cardiopulmonary pathologies. Materials and Methods The study population included 42 patients without cardiorespiratory disease, enabling quantitative and qualitative analysis of pulmonary blood volume after administration of a 40% contrast agent. Qualitative analysis was based on visual assessment. Quantitative analysis was obtained after semiautomatic division of each lung into 18 areas. Results The iodine concentration did not significantly differ between the right (R) and left (L) lungs (P = .49), with a mean attenuation of 41.35 Hounsfield units (HU) and 41.14 HU, respectively. Three regional gradients of attenuation were observed between: (a) lung bases and apices (P Conclusion Distribution of pulmonary blood volume is influenced by physiological gradients and scanning conditions.

Radiation dose reduction is a primary objective in pediatric populations owing to the well-known risks of radiation-induced cancers. Low-energy photons participate in the radiation dose without significantly contributing to image formation. Their suppression by means of tin filtration should decrease the image noise, anticipating a subsequent application to dose saving. To investigate the level of noise reduction achievable with tin (Sn) filtration at 100 kVp for chest computed tomography (CT) in comparison with a standard scanning mode at 70 kVp with comparable radiation dose. Fifty consecutive children (Group 1) underwent non-contrast chest CT examinations on a third-generation dual-source CT system at tin-filtered 100 kVp and pitch 2. The tube-current time product (mAs) was adjusted to maintain the predicted dose length product (DLP) value at 70 kVp for the respective patient. Each child was then paired by weight and age to a child scanned at 70 kVp on the same CT unit (Group 2); Group 2 patients were consecutive patients, retrospectively selected from our database of children prospectively scanned at 70 kVp. Objective and subjective image quality were compared between the two groups of patients to investigate the overall image quality and level of noise reduction that could be subsequently achievable with tin filtration in clinical practice. The mean image noise was significantly lower in Group 1 compared to Group 2 when measured in the air (P

To evaluate the impact of CT perfusion imaging on the detection of peripheral chronic pulmonary embolisms (CPE). 62 patients underwent a dual-energy chest CT angiographic examination with (a) reconstruction of diagnostic and perfusion images; (b) enabling depiction of vascular features of peripheral CPE on diagnostic images and perfusion defects (20 segments/patient; total: 1240 segments examined). The interpretation of diagnostic images was of two types: (a) standard (i.e., based on cross-sectional images alone) or (b) detailed (i.e., based on cross-sectional images and MIPs). The segment-based analysis showed (a) 1179 segments analyzable on both imaging modalities and 61 segments rated as nonanalyzable on perfusion images; (b) the percentage of diseased segments was increased by 7.2 % when perfusion imaging was compared to the detailed reading of diagnostic images, and by 26.6 % when compared to the standard reading of images. At a patient level, the extent of peripheral CPE was higher on perfusion imaging, with a greater impact when compared to the standard reading of diagnostic images (number of patients with a greater number of diseased segments: n = 45; 72.6 % of the study population). Perfusion imaging allows recognition of a greater extent of peripheral CPE compared to diagnostic imaging. • Dual-energy computed tomography generates standard diagnostic imaging and lung perfusion analysis. • Depiction of CPE on central arteries relies on standard diagnostic imaging. • Detection of peripheral CPE is improved by perfusion imaging.

To investigate the reliability of ungated, high-pitch dual-source CT for coronary artery calcium (CAC) screening. One hundred and eighty-five smokers underwent a dual-source CT examination with acquisition of two sets of images during the same session: (a) ungated, high-pitch and high-temporal resolution acquisition over the entire thorax (i.e., chest CT); (b) prospectively ECG-triggered acquisition over the cardiac cavities (i.e., cardiac CT). Sensitivity and specificity of chest CT for detecting positive CAC scores were 96.4 % and 100 %, respectively. There was excellent inter-technique agreement for determining the quantitative CAC score (ICC = 0.986). The mean difference between the two techniques was 11.27, representing 1.81 % of the average of the two techniques. The inter-technique agreement for categorizing patients into the four ranks of severity was excellent (weighted kappa = 0.95; 95 % CI 0.93–0.98). The inter-technique differences for quantitative CAC scores did not correlate with BMI (r = 0.05, p = 0.575) or heart rate (r = –0.06, p = 0.95); 87.2 % of them were explained by differences at the level of the right coronary artery (RCA: 0.8718; LAD: 0.1008; LCx: 0.0139; LM: 0.0136). Ungated, high-pitch dual-source CT is a reliable imaging mode for CAC screening in the conditions of routine chest CT examinations. • CAC is an independent risk factor for major cardiac events. • ECG-gated techniques are the reference standard for calcium scoring. • Great interest is directed toward calcium scoring on non-gated chest CT examinations. • Reliable calcium scoring can be obtained with dual-source CT in a high-pitch mode.

The purpose of the study was to evaluate the prevalence of compressive lymphadenopathy on pulmonary veins (PV) and left atrium (LA) in patients with sarcoidosis.A total of 101 consecutive patients underwent a chest computed tomography angiographic examination with specific analysis of: (a) 3 nodal stations (ie, 7, 8, and 9 stations) for detection of LA compression; (b) 2 nodal stations (ie, 10 and 11 right and left stations) for detection of PV compression.Lymphadenopathy was present in 64 patients (64/101; 63.4%) with computed tomography features of venoatrial compression in 17 patients (17/101; 16.8%). This subgroup included 10 patients with LA compression alone (10/64; 15.6%), 6 patients with PV compression alone (6/64; 9.4%), and 1 patient with both (1/64; 1.5%). The mean diameter of enlarged lymph nodes compressing the LA and PVs was 3.18 ± 0.73 cm (range: 2.1 to 4.4 cm) and 1.9 ± 0.45 cm (range: 1 to 2.9 cm), respectively. PV compression was depicted in a total of 7 patients (7/101; 6.9%), observed as a unilateral (n = 5) or bilateral (n = 2) finding, with a mean number of 3.0 PVs compressed per patient (range: 1 to 7). A total of 10 venous sections showed features of compression, at the level of a lobar confluence (n = 6) or individual segmental veins (V6; n = 4), with a mean reduction in the venous cross-sectional area of 51.09% ± 12.85% (median: 50.06%). Nonfibrotic lung infiltration associated with sarcoidosis was observed in 88.2% of patients with compressive lymphadenopathy (15/17).The prevalence of venoatrial compression in sarcoidosis is 16.8% in the studied population.

GoalsTo compare the quality of low-dose CT images with sinogram affirmed iterative reconstruction (SAFIRE), and full-dose CT with filtered back projection reconstructions (FBP).Materials and methodsFifty pulmonary CT performed by a dual-source technique (120kVp; 110mAs) with (a) the same energy in both tubes, and (b) the distribution of reference mAs with 40% in tube A (44mAs) and 60% in tube B (66mAs). Each acquisition allowed reconstruction of: (a) full-dose images (with both tubes) with FBP reconstructions (group 1); and (b) low-dose images (from tube A) reconstructed with SAFIRE (group 2).ResultsGroup 2 images presented: (a) a significant objective reduction in noise measured in the trachea on mediastinal (16.04±5.66 vs 17.66±5.84) (P=0.0284) and pulmonary (29.77±6.79 vs 37.96±9.03) (P

To evaluate the impact of iterative reconstruction on the detectability of clots. Fifty-three patients were enrolled in a study comparing reduced-dose and full-dose images, available from the same dual-source data set. From each acquisition, three series of images were generated: (1) full-dose images (from both tubes), reconstructed with filtered back projection (FBP) (group 1; standard of reference), (2) reduced-dose images (from tube A only; 60 % dose reduction) reconstructed with FBP (group 2) and iterative reconstruction (SAFIRE) (group 3). In group 1 (mean DLP: 264.6 mGy.cm), (1) PE was diagnosed in 8 patients (15 %) with 82 clots in the central (n = 5), segmental (n = 39) and subsegmental (n = 38) arteries and (2) mean level of noise was 30.56 ± 5.07. In group 2 (mean DLP: 105.8 mGy.cm), a significant increase in noise (44.56 ± 6.24; p

Background Because of growing body of interest on the association between fibrosing idiopathic interstitial pneumonias (f-IIP) and ischaemic heart disease, we initiated this prospective study to evaluate the prevalence of asymptomatic coronary artery disease (CAD) in patients with f-IIP. Methods Forty-two patients with f-IIP underwent noninvasive screening for CAD that included (a) a chest CT examination enabling calculation of the coronary artery calcium (CAC) score, then depiction of coronary artery stenosis; and (b) stress myocardial perfusion scintigraphy (MPS). Patients with significant coronary abnormalities, defined by a CAC score >400 or coronary artery stenosis >50% at CT and/or perfusion defect >5% at MPS, were referred to the cardiologist. Coronary angiography was indicated in presence of a perfusion defect >10% at MPS or significant left main or proximal left anterior descending stenosis whatever MPS findings. Results Combining CT and MPS, significant abnormalities were detected in 32/42 patients (76%). The cardiologist: (a) did not consider further investigation in 21 patients (CT abnormalities but no ischaemia at MPS: 12/21; false-positive findings at MPS: 3/21; poor respiratory condition: 6/21); (b) proceeded to coronary angiography in 11 patients which confirmed significant stenoses in 5 patients (5/42; 12%). In the worst-case-scenario (i.e., inclusion of 6 patients with significant coronary artery abnormalities who were not investigated due to poor respiratory condition), the prevalence of CAD reached 26% (11/42). Conclusion In the studied population of patients with f-IIP, asymptomatic CAD ranged between 12% and 26%.

The aim of the study was to compare iterative metallic artefact reduction (iMAR) and monochromatic imaging on metal artifact reduction.Follow-up of 29 occluded pulmonary arteriovenous malformations was obtained with dual-energy computed tomography with reconstruction of averaged images using filtered back projection (group 1), iMAR (group 2), and creation of high-energy monoenergetic images (group 3). Two types of coils had been used: (a) nickel only (group A, n = 18) and (b) nickel and platinum (group B, n = 11).Compared with group 1, groups 2 and 3 images showed significant reduction in artifact severity. Compared with group 3, group 2 images showed less artifacts on subjective (artifact severity score: P = 0.0118; score of visibility of surrounding structures: P = 0.0056) and objective (artifact attenuation: P0.0001) analyses. In group A, there was no significant difference in artifact severity between groups 2 and 3 images (P0.05). In group B, metal artifacts were only significantly reduced in group 2 images.Iterative metallic artefact reduction reduces metal artifacts more efficiently than monoenergetic imaging.

Immune checkpoint inhibitors are promising new therapies for advanced cancers. In particular, antibodies against programmed cell death 1 (PD-1), such as nivolumab and pembrolizumab, increase anti-tumour T cell responses by blocking the interaction between PD-1 on T cells and its ligand PD-L1 on cancer cells [1]. Enhanced T-cell responses resulting from checkpoint inhibition can lead to an unusual spectrum of side effects called immune-related adverse events, which involve numerous organs, particularly the skin, liver, and gastrointestinal and endocrine systems [2–11]. Pneumonitis is a potentially lethal side effect of immune checkpoint inhibition, occurring in 1–5% of patients enrolled in trials [2–11]. However, little is known about the clinical and radiological features of checkpoint inhibitor-induced lung disease. Here, we report three cases of pembrolizumab-induced acute interstitial lung disease (ILD). The medical data of the patients presented below were collected in accordance with French regulations, none of which was opposed to their uses., Three cases of pembrolizumab-induced pneumonitis are described, two being consistent with organising pneumonia http://ow.ly/Dvhc308QI39

International audience; no abstract

International audience; no abstract

The increasing absolute number of paediatric CT scans raises concern about the safety and efficacy and the effects of consecutive diagnostic ionising radiation. To demonstrate a method to evaluate the lifetime attributable risk of cancer incidence/mortality due to a single low-dose helical chest CT in a two-year patient cohort. A two-year cohort of 522 paediatric helical chest CT scans acquired using a dedicated low-dose protocol were analysed retrospectively. Patient-specific estimations of radiation doses were modelled using three different mathematical phantoms. Per-organ attributable cancer risk was then estimated using epidemiological models. Additional comparison was provided for naturally occurring risks. Total lifetime attributable risk of cancer incidence remains low for all age and sex categories, being highest in female neonates (0.34%). Summation of all cancer sites analysed raised the relative lifetime attributable risk of organ cancer incidence up to 3.6% in female neonates and 2.1% in male neonates. Using dedicated scan protocols, total lifetime attributable risk of cancer incidence and mortality for chest CT is estimated low for paediatric chest CT, being highest for female neonates.

Purpose The aim of the study was to evaluate left atrial (LA) volume in smokers according to the severity of emphysema, with the objective of providing indirect evidence of reduced pulmonary venous return due to capillary destruction. Materials and methods A total of 121 smokers underwent a high-pitch and high-temporal resolution computed tomography (CT) angiographic examination, enabling quantification of emphysema, total lung volume, and LA volume measurements normalized to body surface area. Results The CT phenotypes were as follows: emphysema predominant (group 1; n=57); airway predominant (group 2; n=30); a mixed pattern of emphysema and airway disease (group 3; n=15); and absence of bronchopulmonary CT abnormalities (group 4; n=19). A negative correlation was found between the indexed LA volume and the percentage of emphysema: (a) in the overall study group (P=0.032; r=-0.19); (b) in group 1 (P=0.0163; r=-0.32); and (c) in groups 1 and 3 when analyzed together (P=0.0492; r=-0.23). A negative correlation was found between the indexed LA volume and the total lung volume in the overall study group (P=0.039; r=-0.19) and in group 1 (P=0.048; r=-0.26), whereas no correlations were found in group 2 (P=0.44; r=-0.15), group 3 (P=0.52; r=-0.17), and groups 1 and 3 analyzed as a whole (P=0.14; r=-0.17). Conclusions The indexed LA volume, impacting left ventricular preload, is correlated to the severity of emphysema.

Before introducing 70-kVp settings in the low-kilovoltage strategies for pediatric examinations, it was mandatory to demonstrate, at similar dose levels, an equivalence of image quality at 70 kVp and 80 kVp. To assess image quality of chest CT examinations acquired at 70 kVp in comparison with standard scanning at 80 kVp. We prospectively evaluated 129 children with a 70-kVp scanning protocol (group 1). All scanning parameters were kept similar to those usually selected for pediatric standard 80-kVp protocols, except the milliamperage increased by a factor of 1.6 to maintain comparable radiation dose. Image quality of group 1 examinations was compared to that of a paired population scanned at 80 kVp (group 2). The noninferiority hypothesis was fixed at 10% of the mean level of image noise. There was no significant difference in the mean dose length product (DLP) and the volume computed tomography dose index (CTDIvol) between the groups (DLP: 20.5 ± 5.8 mGy.cm [group 1] vs. 19.7 ± 7.6 mGy.cm [group 2]; P = 0.06) (CTDIvol: 0.8 ± 0.1 mGy [group 1] vs. 0.8 ± 0.18 mGy [group 2]; P = 0.94). The mean of differences in image noise between group 1 and group 2 examinations was −1.38 (−2.59; −0.18), verifying the noninferiority hypothesis. Subjective image quality did not significantly differ between group 1 and group 2 examinations (P = 0.18). At equivalent radiation dose levels, 70-kVp protocols provide similar image quality to that achievable at 80 kVp.

Initiative that emanated from the French National Reference Centre and the Network of Competence Centres for Rare Lung Diseases; International audience; Idiopathic pulmonary fibrosis (IPF) is the most frequent chronic idiopathic interstitial pneumonia in adults. The management of rare diseases in France has been organised by a national plan for rare diseases, which endorsed a network of expert centres for rare diseases throughout France. This article is an overview of the executive summary of the French guidelines for the management of IPF, an initiative that emanated from the French National Reference Centre and the Network of Regional Competence Centres for Rare Lung Diseases. This review aims at providing pulmonologists with a document that: 1) combines the current available evidence; 2) reviews practical modalities of diagnosis and management of IPF; and 3) is adapted to everyday medical practice. The French practical guidelines result from the combined efforts of a coordination committee, a writing committee and a multidisciplinary review panel, following recommendations from the Haute Autorité de Santé. All recommendations included in this article received at least 90% agreement by the reviewing panel. Herein, we summarise the main conclusions and practical recommendations of the French guidelines.

This article highlights new areas of interest in the management of patients with acute pulmonary embolism, with the objective of alerting radiologists about necessary updates for daily practice.

a Inra, UMR754, IFR 128, centre national de reference des maladies pulmonaires rares, centre de competences de l’hypertension pulmonaire, service de pneumologie, universite de Lyon, universite Claude-Bernard Lyon 1, hospices civils de Lyon, hopital Louis-Pradel, 28, rue du Doyen-Lepine, 69000 Lyon, France b CHU Bichat, centre de competences pour les maladies pulmonaires rares, 46, rue Henri-Huchard, 75877 Paris cedex 18, France

Purpose To evaluate the frequency and severity of cardiac motion artifacts on high-pitch, dual-source computed tomography angiograms of the chest. Materials and methods One hundred consecutive patients underwent a non-electrocardiogram-gated, dual-source chest computed tomography examination with high pitch and high temporal resolution. Results The mean (±SD) duration of data acquisition was 0.9 (±0.07) seconds and the mean (±SD) heart rate was 78.9 (±15.2) bpm. Cardiac motion artifacts were seen at the level of the pulmonary trunk in 2 patients (2%). Among the 7000 pulmonary arteries analyzed (5 central, 5 lobar, 20 segmental, and 40 subsegmental arteries/patient), pseudofilling defects were depicted at the level of 3 arteries (0.042%), always seen with the concurrent presence of a "double contour" appearance of the vessel walls. Twinkling star artifacts beyond the subsegmental level were seen within 76 segments (76/2000; 3.8% of the examined segments), most commonly in the lingula and left lower lobe. A total of 23 patients (23%) showed at least 1 category of motion artifacts, whereas 77 patients (77%) had motion-free imaging of the pulmonary arteries. Conclusions Routine scanning of patients with high pitch and high temporal resolution provides examinations devoid of detrimental cardiac motion artifacts.

Purpose To establish the radiation dose level for single- and dual-source thoracic CT scans in daily practice. Materials and methods The dose levels delivered during 634 consecutive examinations over a period of 2 months were recorded. The CT scans were performed using: (a) a standard protocol (single source, single energy [group 1]: n = 266; dual source, single energy [group 2]: n = 276; (b) with prospective ECG synchronisation [group 3]: n = 13; or (c) with dual energy [group 4]: n = 79. All the acquisitions included kilovoltage selection depending on the weight and automatic milliamperage modulation. Results The mean DLP of the standard protocols was 97.12 mGy cm (group 2; BMI = 23.1 kg/m 2 ) and 211.1 mGy cm (group 1; BMI = 27.3 kg/m 2 ), the choice of protocol depending on the diameter of the thorax relative to the diameter of the field of the second source, and therefore on the patient's morphotype. When imaging included examination of the proximal and middle coronary arteries (group 3), the mean DLP was 105.5 mGy cm. Morphological and functional imaging (group 4) was obtained with a mean DLP of 404.3 mGy cm. Conclusion Depending on the objective of the protocol, the mean DLP varied from 97.12 to 404.3 mGy cm.

To evaluate the tolerance and level of enhancement achievable after inhalation of stable krypton.This study was approved by the institutional review board and the local ethics committee. Written informed consent was obtained from all subjects. The study was planned as a Fleming two-stage design, enabling one to assess the effectiveness of a newer treatment or technique on a small number of patients. At the end of each stage, the results are computed, and the trial can be stopped if the effectiveness is less than a minimum success rate or greater than an expected success rate. After informed consent was obtained, a total of 32 patients (ie, two successive series of 16 patients each) with severe emphysema underwent a dual-source, dual-energy chest computed tomographic (CT) examination after inhalation of a mixture of stable krypton (80%) and oxygen (20%), with reconstruction of diagnostic and ventilation images. For each patient, two regions of interest were selected on a diagnostic image, one in a region of severe emphysema (presumed to be poorly ventilated or not ventilated) and a second one in a region devoid of structural abnormalities (presumed to be normally ventilated), with measurements of attenuation values on the corresponding ventilation image.All examinations were successfully performed, without adverse effects. Differences in attenuation between normal lung and emphysematous areas were found in 28 patients (88%; 95% confidence interval: 71%, 96.5%). The maximal level of attenuation within normal lung was 18.5 HU. Krypton attenuation difference between normal and emphysematous lung was significant, with a median value of 51.8% (P.001).The level of enhancement after inhalation of krypton and its excellent clinical tolerance makes this gas eligible for ventilation CT examinations.

Identifying the role of fungi present in the domestic environment in the development of interstitial pneumonia can be a difficult clinical problem. We report a case of interstitial lung disease case occurring in a 53-year-old patient. He presented with profound hypoxemia (PaO(2) 54mmHg). Chest CT showed diffuse ground glass opacities. Initial blood tests for allergy and autoimmune disease were negative. Faced with a worsening of his clinical status after returning home he was hospitalized several times. At fibreoptic bronchoscopy, multiple white deposits were observed. Bronchoalveolar lavage with differential cell count was performed, revealing a 23% lymphocytosis. Serology for specific household molds showed moderate reaction to various molds found in homes, especially Stachybotrys chartarum. Pulmonary function tests revealed a moderate restrictive pattern with impaired diffusion of carbon monoxide and a bronchiolocentric interstitial pneumonia was found at lung biopsy. After a permanent move to a new residence, clinical parameters, radiological, biological and functional normalized. The final diagnosis was interstitial lung disease related to mycotoxins of S. Chartarum. The diagnosis of hypersensitivity pneumonitis to domestic mold or interstitial lung disease secondary to mycotoxins should be considered in patients presenting with interstitial pneumonia and requires specific investigations to ensure that an environmental cause with an allergic or toxic role is not missed.

Before the advent of fast-scanning multidetector-row computed tomography (CT) technology, thoracic CT studies were exclusively used for the morphologic assessment of thoracic organs, as the concurrent examination of the heart was hampered by image degradation from cardiac motion artifacts. The introduction of fast rotation speed and dedicated cardiac reconstruction algorithms has opened new possibilities for chest imaging, starting with the possibility to integrate cardiac morphologic and functional information into a diagnostic CT scan of the chest. Initiated with 16-slice multidetector-row CT, this concept of integrating morphology and function has been further simplified with 64-slice CT scanners, thus allowing radiologists to provide vital information in the management of patients with a wide variety of acute or chronic respiratory disorders. Because this CT technology offers the possibility of generating high-resolution and motion-free images of the coronary arteries, evaluation of the coronary arteries during CT examinations of the chest should further widen the clinical applications of CT for respiratory patients, keeping in mind that cigarette smoking is a shared risk factor for both impaired lung function and cardiovascular events. The recent advent of high temporal resolution and high pitch modes with dual-source CT simplifies the concept of integrated cardiothoracic imaging, introducing non-electrocardiographic-gated coronary artery imaging. The purpose of this article is to review the successive approaches of these redefined borders of thoracic imaging.

Rationale and Objectives The aim of this study was to evaluate whether the spectral characterization of the iodine content of lung microcirculation could help identify ground-glass opacity (GGO) of vascular origin. Materials and Methods Thirty-five consecutive patients with GGO of bronchioloalveolar (group 1; n = 24) and vascular (group 2; n = 11) origin underwent dual-energy multi-detector computed tomographic angiography of the chest using a standard injection protocol. For each patient, two radiologists evaluated by consensus the presence, location, and extent of GGO on diagnostic computed tomographic scans (ie, contiguous 1-mm-thick averaged images from both tubes) and characteristics of the corresponding areas on perfusion scans. Results A total of 443 segments with GGO were depicted on the diagnostic scans (group 1, n = 231; group 2, n = 212), always intermingled with areas of normal lung attenuation, with a mean of 12.7 segments with GGO per patient. Areas of GGO were located at the level of the upper lobes ( n = 128), middle lobe and/or lingula ( n = 81), and lower ( n = 234) lobes, involving n = 165), 25% to 50% ( n = 103), 50% to 75% ( n = 155), and >75% ( n = 20) of the segmental surface. The overall quality of perfusion scans was rated as interpretable in all patients. Perfusion scans depicted areas of hyperattenuation within segments of GGO with a significantly higher frequency in group 2 (211 of 212 [99.5%]) than in group 1 (27 of 231 [12%]) ( P Conclusion Dual-energy computed tomography can help recognize GGO of vascular origin.

Recent technological advances in multidetector computed tomography (CT) have led to the introduction of dual-source CT, which allows acquisition of CT data at the same energy or at 2 distinct tube voltage settings during a single acquisition. The advantage of the former is improvement of temporal resolution, whereas the latter offers new options for CT imaging, allowing tissue characterization and functional analysis with morphologic evaluation. The most investigated application has been iodine mapping at pulmonary CT angiography. The material decomposition achievable opens up new options for recognizing substances poorly characterized by single-energy CT. Although it is too early to draw definitive conclusions on dual-energy CT applications, this article reviews the results already reported with the first generation of dual-source CT systems.

The aim of the present study was to describe angiographic findings and embolisation results in smokers with haemoptysis. We retrospectively reviewed the clinical data and angiographic findings from 35 patients with smoking-related bronchopulmonary disease and no associated comorbidity, who were referred for embolisation for mild (n = 6), moderate (n = 14) and severe (n = 15) haemoptysis. Spirometric classification subdivided our population into: 16 patients with chronic bronchitis but no airflow limitation; and 19 patients with chronic obstructive pulmonary disease (COPD) (stage I: n = 12; stage II: n = 5; stage III: n = 2). Bronchoscopy depicted focal submucosal vascular abnormalities in three patients and only endobronchial inflammation in 32 (91%) patients. Bronchial artery angiography revealed moderate (n = 18) or severe (n = 10) hypervascularisation in 28 (80%) patients, and normal vascularisation in seven (20%). No statistically significant difference was observed between the angiographic findings and the severity of COPD, tobacco consumption or the amount of bleeding. Cessation of bleeding was obtained by embolisation in 29 out of the 34 technically successful procedures (85%), requiring surgery in three out of five patients with recurrence. Follow-up (mean duration 7 yrs) demonstrated no recurrence of bleeding in 32 (94%) out of 34 patients and excluded late endobronchial malignancy. Smokers with various stages of COPD severity may suffer from haemoptysis that is efficiently treatable by endovascular treatment.

To evaluate, by using electrocardiographically (ECG)-gated multidetector computed tomography (CT), parameters such as right ventricular outflow tract (RVOT) systolic shortening and myocardial thickness and right pulmonary artery (RPA) distensibility, reported to be abnormal at echocardiography and/or magnetic resonance (MR) imaging in patients with pulmonary hypertension (PHT).The institutional review board approved the study and waived informed consent. Forty-five patients, 21 with PHT (group 1; mean pulmonary arterial pressure [PAP], 42 mm Hg) and 24 without (group 2; mean PAP, 16.5 mm Hg), who had undergone thoracic ECG-gated 64-section CT and right heart catheterization as part of their diagnostic work-up were included in this study. Two independent observers measured RPA distensibility and RVOT myocardial thickness, diameter, and cross-sectional area during systole and diastole. Their values were compared in both groups (Mann-Whitney U test). The area under the receiver operating characteristic (ROC) curve and Spearman correlation with mean PAP were also obtained.Interobserver agreement was good for all measurements (R0.8) except for systolic RVOT wall thickness. Median values of RPA distensibility, diastolic RVOT wall thickness, and systolic RVOT diameter and cross-sectional area were significantly different between groups 1 and 2. The largest area under the ROC curve was obtained with RPA distensibility (0.951; 95% confidence interval: 0.89, 1) also showing the closest correlation with mean PAP (r = -0.79; P.0001).Among all parameters evaluated, RPA distensibility shows the best diagnostic value for PHT and could be useful for risk stratification.

Among the various imaging modalities available, CT has remained over time the core imaging technique for the evaluation of respiratory disorders. The recent advent of dual-source CT offers innovative approaches to investigate thoracic diseases, based on the use of one or two tubes as well as single or dual energy to scan the entire thorax. Two major options can be used in clinical practice with promising results. Dual source, single-energy scanning allows scanning of the entire thorax with ultra-high temporal resolution which opens the field of integrated cardiothoracic imaging without ECG gating as well as optimized evaluation of pediatric and adult patients with limited ability to cooperate. Dual-source, dual-energy acquisitions represent another very innovative means of investigating respiratory disorders, adding tissue characterization and functional analysis to morphological evaluation. The purpose of this review article is to provide results on preliminary experiences with the above-mentioned scanning conditions with dual-source CT and to envisage potential forthcoming applications in the field of thoracic imaging.

Rationale and Objectives To investigate the accuracy of dual-energy computed tomography in the depiction of perfusion defects in patients with acute pulmonary embolism (PE). Materials and Methods One hundred seventeen consecutive patients with clinical suspicion of acute PE underwent dual-energy multidetector computed tomographic (CT) angiography of the chest with a standard injection protocol. Two radiologists evaluated, by consensus, the presence of endoluminal clots on ( 1 ) transverse “diagnostic” scans (contiguous 1-mm-thick averaged images from tubes A and B) and ( 2 ) lung perfusion scans. Results Seventeen patients showed CT features of acute PE, with the depiction of 75 clots within the lobar (n = 15), segmental (n = 43) and subsegmental (n = 17) pulmonary arteries. A total of 17 clots were identified as complete filling defects (ie, obstructive clots), located within segmental (12 of 17) and subsegmental (5 of 17) arteries. Fourteen of the 17 obstructive clots were seen with the concurrent presence of corresponding perfusion defects, whereas cardiac motion and/or contrast-induced artifacts precluded the confident recognition of perfusion abnormalities in the remaining two segments and one subsegment. Four subsegmental perfusion defects were depicted without the visualization of endoluminal thrombi within the corresponding arteries. Perfusion defects were identified beyond five nonobstructive clots. Conclusion Simultaneous information on the presence of endoluminal thrombus and lung perfusion impairment can be obtained with dual-energy computed tomography.

Automated lobar quantification of emphysema has not yet been evaluated. Unenhanced 64-slice MDCT was performed in 47 patients evaluated before bronchoscopic lung-volume reduction. CT images reconstructed with a standard (B20) and high-frequency (B50) kernel were analyzed using a dedicated prototype software (MevisPULMO) allowing lobar quantification of emphysema extent. Lobar quantification was obtained following (a) a fully automatic delineation of the lobar limits by the software and (b) a semiautomatic delineation with manual correction of the lobar limits when necessary and was compared with the visual scoring of emphysema severity per lobe. No statistically significant difference existed between automated and semiautomated lobar quantification (p > 0.05 in the five lobes), with differences ranging from 0.4 to 3.9%. The agreement between the two methods (intraclass correlation coefficient, ICC) was excellent for left upper lobe (ICC = 0.94), left lower lobe (ICC = 0.98), and right lower lobe (ICC = 0.80). The agreement was good for right upper lobe (ICC = 0.68) and moderate for middle lobe (IC = 0.53). The Bland and Altman plots confirmed these results. A good agreement was observed between the software and visually assessed lobar predominance of emphysema (kappa 0.78; 95% CI 0.64–0.92). Automated and semiautomated lobar quantifications of emphysema are concordant and show good agreement with visual scoring.

To evaluate the assessibility of coronary arteries in respiratory patients with high heart rates. This study was based on the comparative analysis of two paired populations of 54 patients with a heart rate >70 bpm evaluated with dual-source (group 1) and single-source (group 2) CT. The mean heart rate was 89.1 bpm in group 1 and 86.7 bpm in group 2 (P = 0.26). The mean number of assessable segments per patient was significantly higher in group 1 compared to group 2 (P ≤ 0.0001). The proportions of patients in whom proximal and mid-coronary segments were assessable (i.e., the anatomical level enabling screening for asymptomatic coronary artery disease) were 35.3% for heart rates

International audience; PurposeTo evaluate the effect of iterative reconstruction on the depiction of systemic sclerosis–related interstitial lung disease (ILD) when the radiation dose is reduced by 60%.Materials and MethodsThis study was based on retrospective interpretation of prospectively acquired data over a 12-month period and approved by the institutional review board. The requirement to obtain informed consent was waived. Fifty-five chest computed tomographic (CT) examinations were performed in 38 women and 17 men (mean age, 55.8 years; range, 23–82 years) by using a dual-source CT unit with (a) both tubes set at similar energy (120 kVp) and (b) the total reference milliampere seconds (ie, 110 mAs) split up in a way that 40% was applied to tube A and 60% to tube B. Two series of images were generated simultaneously from the same dataset: (a) standard-dose images (generated from both tubes) reconstructed with filtered back projection (group 1, the reference standard) and (b) reduced-dose images (generated from tube A; 60% dose reduction) reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE) (group 2). In both groups, the analyzed parameters comprised the image noise and the visualization and conspicuity of CT features of ILD. Two readers independently analyzed images from both groups. Results were compared by using the Wilcoxon test for paired samples; the 95% confidence interval was calculated when appropriate.ResultsThe mean level of objective noise in group 2 was significantly lower than that in group 1 (22.02 HU vs 26.23 HU, respectively; P < .0001). The CT features of ILD in group 1 were always depicted in group 2, with subjective conspicuity scores (a) improved in group 2 for ground-glass opacity, reticulation, and bronchiectasis and/or bronchiolectasis and (b) identical in both groups for honeycombing. The interobserver agreement for their depiction was excellent in both groups (κ, 0.84–0.98).ConclusionDespite a 60% dose reduction, images reconstructed with SAFIRE allowed similar detection of systematic sclerosis–related ILD compared with the reference standard.

To evaluate the influence of temporal resolution (TR) on cardiogenic artefacts at the level of bronchial walls. Ninety patients underwent a dual-source, single-energy chest CT examination enabling reconstruction of images with a TR of 75 ms (i.e., optimized TR) (Group 1) and 140 ms (i.e., standard TR) (Group 2). Cardiogenic artefacts were analyzed at the level of eight target bronchi, i.e., right (R) and left (L) B1, B5, B7, and B10 (total number of bronchi examined: n = 720). Cardiogenic artefacts were significantly less frequent and less severe in Group 1 than in Group 2 (p

International audience; Systemic sclerosis-related interstitial lung disease (SSc-ILD) is the leading cause of death in SSc. In this study, we aimed to describe the baseline severity and evolution of forced vital capacity (FVC) and diffusing capacity for carbon monoxide (DLCO) in patients with SSc-ILD and to assess the baseline clinical, biological and high-resolution CT scan (HRCT) predictors of this evolution. Baseline and serial FVC and DLCO were collected in 75 SSc-ILD patients followed during 6.4±4.2 years (n = 557 individual data). FVC and DLCO evolution was modelled using a linear mixed model with random effect. During follow-up, FVC was stable while DLCO significantly decreased (-1.5±0.3%/year (p

To the Editors: A 61-yr-old female was diagnosed with pulmonary embolism. She had a history of poorly differentiated thyroid cancer with follicular cell phenotype, and had first been treated in 2006 by thyroidectomy and radioactive iodine-131. Local relapse (cervical nodes) had occurred within 3 months and required five cycles of chemotherapy, consisting of cisplatin and doxorubicin, followed by cervical radiotherapy and surgical resection of residual nodes. 2 yrs later during follow-up, abnormal 18F-fluorodeoxyglucose (FDG) uptake was described on positron emission tomography (PET)/computed tomography (CT) in the left thoracic hilar regions. CT pulmonary angiography showed a filling defect in the left lower lobe pulmonary artery and at the origin of the lingular artery; no delayed embolism enhancement was observed. It was considered to be a pulmonary embolism, and anticoagulation was initiated. 6 months later, follow-up imaging showed stability of both FDG uptake and CT pulmonary angiography images, and anticoagulation was continued. 10 months later, follow-up showed a right pulmonary upper lobe nodule on CT scan associated with high FDG uptake on PET/CT, and thyroglobulin ascension. This nodule was considered to be a thyroid cancer metastasis and treated by CyberKnife radiotherapy. As FDG uptake and thyroglobulin …

Dual-source CT allows scanning of the chest with high pitch and high temporal resolution, which can improve the detection of proximal coronary arteries in infants and young children when scanned without general anesthesia, sedation or beta-blockade. To compare coronary artery visibility between higher and standard temporal resolution. We analyzed CT images in 93 children who underwent a standard chest CT angiographic examination with reconstruction of images with a temporal resolution of 75 ms (group 1) and 140 ms (group 2). The percentage of detected coronary segments was higher in group 1 than in group 2 when considering all segments (group 1: 27%; group 2: 24%; P = 0.0004) and proximal segments (group 1: 37%; group 2: 32%; P = 0.0006). In both groups, the highest rates of detection were observed for the left main coronary artery (S1) (group 1: 65%; group 2: 58%) and proximal left anterior descending coronary artery (S2) (group 1: 43%; group 2: 42%). Higher rates of detection were seen in group 1 for the left main coronary artery (P = 0.03), proximal right coronary artery (P = 0.01), proximal segments of the left coronary artery (P = 0.02) and proximal segments of the left and right coronary arteries (P = 0.0006). Higher temporal resolution improved the visibility of proximal coronary arteries in pediatric chest CT.

PurposeTo provide quantitative information on emphysema in asymptomatic smokers in correlation with pulmonary function tests (PFT).Patients and methodsThe study population included 75 smokers (current smokers: n=39; ex-smokers: n=36) and 25 nonsmokers who underwent volumetric high-resolution CT of the chest with automated quantification of emphysema and PFTs.ResultsCurrent smokers had a higher percentage of emphysema in the right lung (P=0.041) and right upper lobe (P=0.037). The overall percentage of emphysema did not differ according to the Gold stage (P=0.77). Smokers with emphysema had significantly higher mean values of FRC (P=0.012), RV (0.05). Correlations were found between the percentage of emphysema and (a) cigarette consumption of current (r=0.34215; P=0.0330) and ex-smokers (r=0.44104; P=0.0071); and (b) alterations of TLC, FRC, RV and DLCO of smokers.ConclusionQuantitative CT allows recognition of regional specificities and subclinical functional alterations in smokers with emphysema.

To evaluate the clinical impact of automatic tube voltage selection on chest CT angiography (CTA). Ninety-three patients were prospectively evaluated with a CT protocol aimed at comparing two successive CTAs acquired under similar technical conditions except for the kV selection: (1) the initial CTA was systematically obtained at 120 kVp and 90 ref mAs; (2) the follow-up CTA was obtained with an automatic selection of the kilovoltage (Care KV; Siemens Healthcare) for optimised CTA. At follow-up, 90 patients (97 %) underwent CTA with reduced tube voltage, 100 kV (n = 26; 28 %) and 80 kV (n = 64; 69 %), resulting in a significant dose-length-product reduction (follow-up: 87.27; initial: 141.88 mGy.cm; P

To determine the energy levels that provide optimal imaging of thoracic circulation at dual-energy computed tomographic (CT) angiography with reduced iodine load in comparison with a standard technique.The institutional review board approved the study with waiver of patient consent. Eighty patients underwent a dual-source, dual-energy CT examination after administration of low-concentration contrast material (170 mg of iodine per milliliter), and eight series of images were reconstructed, including the original polychromatic images at 80 and 140 kV and six series of virtual monochromatic spectral images at 50, 60, 70, 80, 90, and 100 keV. For each vascular compartment, the energy level that provided optimal evaluation on virtual monochromatic spectral images was determined, and these series were compared with the polychromatic dual-energy images and with standard chest CT images that were used as controls. Comparisons between groups were performed by using the paired Student t test for continuous variables and the McNemar test for categorical variables. Comparisons between dual-energy and standard CT images were performed by using the unpaired Student t test for continuous variables and the χ(2) test for categorical variables.For the aorta, pulmonary arteries, and veins, the reconstruction at 60 keV provided adequate attenuation without marked beam-hardening artifacts in 90% of patients, with the highest contrast-to-noise and signal-to-noise ratios, the lowest level of subjective noise, and no significant differences with images at 80 kV (mean energy, 54 keV). For the superior vena cava and brachiocephalic veins, the reconstructions at 100 keV enabled artifact-free analysis of the perivascular anatomic zone without a significant difference with images at 140 kV (mean energy, 92 keV). Compared with standard CT images acquired after administration of a 35% iodinated contrast agent, there was a statistically significant reduction in the frequency of artifacts around systemic veins at 100 keV (P.001) and similar overall image quality for central vessels at 60 keV (P.05).An optimal analysis of thoracic circulation can be achieved on virtual monochromatic spectral images at 60 keV and 100 keV and on the original polychromatic images at 80 kV and 140 kV.http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120195/-/DC1.

To evaluate image quality of low-voltage chest computed tomographic (CT) angiography with raw data-based iterative reconstruction (sonogram-affirmed iterative reconstruction) in comparison with image quality of standard-dose standard-voltage filtered back projection (FBP) CT.This prospective study was approved by the institutional review board, and the informed consent requirement was waived. Eighty consecutive patients who were referred for follow-up chest CT angiography underwent reduced-dose CT (hereafter, T2 examination) under technical conditions similar to those of the initial examination (hereafter, T1 examination), except the voltage selection was reduced by 20 kV with adaptation of the tube current to ensure a 50% reduction in CT dose index, and regular FBP was replaced by iterative reconstruction with sonogram-affirmed iterative reconstruction. The two techniques were compared by using paired tests (Student t test, Wilcoxon test, or McNemar test, according to the nature of variables).When compared with standard-dose T1 studies, reduced-dose T2 images showed: (a) significantly less objective noise at the level of the trachea on mediastinal and lung parenchymal images (P.001) and no significant difference in objective noise at the level of the aorta on mediastinal images (P = .507); (b) significantly higher signal-to-noise and contrast-to-noise (P.001) ratios; (c) similar visual perception of noise on mediastinal (P = .132) and lung (P = .366) images, mainly rated as moderate; and (d) similar overall subjective image quality (P = .405).Raw data-based iterative reconstruction yielded equivalent subjective and improved objective image quality of low-voltage half-dose CT angiograms compared with standard-dose FBP CT images for an average dose-length product of less than 80 mGy · cm in this population.http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120414/-/DC1.