Jacques Remy

Chest computed tomography using iterative reconstruction vs filtered back projection (Part 2): image quality of low-dose CT examinations in 80 patients

PurposeTo evaluate the image quality of an iterative reconstruction algorithm (IRIS) in low-dose chest CT in comparison with standard-dose filtered back projection (FBP) CT.Materials and methodsEighty consecutive patients referred for a follow-up chest CT examination of the chest, underwent a low-dose CT examination (Group 2) in similar technical conditions to those of the initial examination, (Group 1) except for the milliamperage selection and the replacement of regular FBP reconstruction by iterative reconstructions using three (Group 2a) and five iterations (Group 2b).ResultsDespite a mean decrease of 35.5% in the dose-length-product, there was no statistically significant difference between Group 2a and Group 1 in the objective noise, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios and distribution of the overall image quality scores. Compared to Group 1, objective image noise in Group 2b was significantly reduced with increased SNR and CNR and a trend towards improved image quality.ConclusionIterative reconstructions using three iterations provide similar image quality compared with the conventionally used FBP reconstruction at 35% less dose, thus enabling dose reduction without loss of diagnostic information. According to our preliminary results, even higher dose reductions than 35% may be feasible by using more than three iterations.

Chest computed tomography using iterative reconstruction vs filtered back projection (Part 1): evaluation of image noise reduction in 32 patients

ObjectiveTo assess noise reduction achievable with an iterative reconstruction algorithm.Methods32 consecutive chest CT angiograms were reconstructed with regular filtered back projection (FBP) (Group 1) and an iterative reconstruction technique (IRIS) with 3 (Group 2a) and 5 (Group 2b) iterations.ResultsObjective image noise was significantly reduced in Group 2a and Group 2b compared with FBP (p < 0.0001). There was a significant reduction in the level of subjective image noise in Group 2a compared with Group 1 images (p < 0.003), further reinforced on Group 2b images (Group 2b vs Group 1; p < 0.0001) (Group 2b vs Group 2a; p = 0.0006). The overall image quality scores significantly improved on Group 2a images compared with Group 1 images (p = 0.0081) and on Group 2b images compared with Group 2a images (p < 0.0001). Comparative analysis of individual CT features of mild lung infiltration showed improved conspicuity of ground glass attenuation (p < 0.0001), ill-defined micronodules (p = 0.0351) and emphysematous lesions (p < 0.0001) on Group 2a images, further improved on Group 2b images for ground glass attenuation (p < 0.0001), and emphysematous lesions (p = 0.0087).ConclusionCompared with regular FBP, iterative reconstructions enable significant reduction of image noise without loss of diagnostic information, thus having the potential to decrease radiation dose during chest CT examinations.

Thoracic Applications of Dual Energy

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.

Automated lobar quantification of emphysema in patients with severe COPD

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.

Thoracic applications of dual energy.

Computed tomography (CT) is the core imaging modality for the evaluation of thoracic disorders. With the recently developed dual-energy CT (DECT) technique, the clinical utility of CT in the management of pulmonary diseases can be expanded. The most actively investigated principle of dual energy is material decomposition based on attenuation differences at different energy levels. This technique provides two key insights into lung physiology, that is, regional perfusion and ventilation. This functional information is obtained in addition to morphologic information because high-resolution thoracic anatomy is entirely preserved on dual-energy thoracic CT. The second major possibility offered by DECT is virtual monochromatic imaging that represents a new option for standard chest CT in daily routine. In this review, imaging principles and clinical applications of dual-energy thoracic CT are described. Knowledge of the applications of DECT may lead to wider use of this technique in the field of respiratory disorders.

Automated 3D Rendering of Ribs in 110 Polytrauma Patients: Strengths and Limitations

RATIONALE AND OBJECTIVES To evaluate the strengths and limitations of a rib-unfolding software in a polytrauma context. MATERIALS AND METHODS Chest computed tomography (CT) examinations of 110 patients were reviewed for specific detection of rib fractures using: (1) transverse CT sections ±  multiplanar reformattings (ie, the standard of reference), and (2) unfolded rib images reconstructed by the CT Bone Reading software with the possibility of rib analysis along their long axis and creation of standard orthogonal views in different orientations of any area suspected of fracture. RESULTS The software provided complete reconstruction of the whole rib cage in 94 patients (85.5%) and partially incomplete reconstruction in 16 patients (14.5%). The percentage of ribs inadequately reconstructed was 1.5% (40 of 2640 ribs), mainly related to unfused epiphyses (13 of 40), costal hypoplasia (8 of 40), and vertebral fracture (6 of 40). The sensitivity and specificity in detecting rib fractures at a per-patient, per-rib, and per-costal arc level ranged from 0.73 to 0.84 and 0.99 to 1, respectively. At a costal arc level, the readers misinterpretations accounted for 67% (4 of 6) of false-positive and 24% (20/84) of false-negative results, and interpretive difficulties were encountered for single-cortex fractures or fractures at the extremities of the costal shaft. CONCLUSIONS An accurate diagnosis of rib fracture was achieved with the reading of unfolded rib images. In a polytrauma context, the evaluated system could facilitate rib analysis.

Prevalence of asymptomatic coronary disease in fibrosing idiopathic interstitial pneumonias

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%.

New Insights in Thromboembolic Disease

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.

CT features of primary systemic pulmonary amyloidosis mimicking pulmonary sarcoidosis

ita sp ed s) t X an computed tomography (CT) angiography of the chest was performed after pneumothorax resolution (Somatom Definition, Siemens, Germany) which revealed multiple well-defined micronodules with a perilymphatic pattern, i.e. distributed along the interlobular septa and bronchovascular bundles, as well as beneath the visceral pleura and two small-sized intraparenchymal and thin walled cystic lesions (figure 2A and B). All of these abnomalities were particularly marked in the upper lobes of the lungs. No fibrotic changes and no tracheal abnormalities were found. Moderate lymph node enlargement was present in right paratracheal and subcarinal sites (figure 2C). The diagnosis of pulmonary sarcoidosis was suggested. Further laboratory workup revealed normal lymphocyte count, normal serum angiotensin-converting enzyme level (14 UI/L) as well as low gammaglobulin level (IgG:5 g/L). Pulmonary function tests results showed a normal value of total lung capacity (TLC; 7.701 L, i.e. 103% of predicted value), but a reduction of the other parameters including slow vital capacity (SVC; 3.541 L, i.e. 76% of predicted value), forced expiratory dicted ), and (DLCO) alue). ation reveal count . Four pneubiopsy deposlveoli, ). The ons of d stain hich is largeg lung; sarcoïdose pulmonaire en tomodensitomé