Nunzia Tacelli

Spectral Optimization of Chest CT Angiography with Reduced Iodine Load: Experience in 80 Patients Evaluated with Dual-Source, Dual-Energy CT

PURPOSE 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. MATERIALS AND METHODS 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. RESULTS 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). CONCLUSION 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. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120195/-/DC1.

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.

Assessment of Non–Small Cell Lung Cancer Perfusion: Pathologic-CT Correlation in 15 Patients

PURPOSE To assess tumor perfusion with multi-detector row computed tomography (CT) in patients with non-small cell lung carcinoma and to correlate CT findings with pathologic results. MATERIALS AND METHODS This study was approved by the local Ethics Committee, and all patients provided written informed consent, which included information on the radiation exposure at the CT examinations. Fifteen consecutive patients (mean age, 60.5 years ± 7.7 [standard deviation]), including 14 men (mean age, 59.9 years ± 7.5) and one woman (age, 70 years) with histologically proved non-small cell lung carcinoma were prospectively enrolled. Overall, pathologic-CT correlations were examined in 31 focal tumoral zones. Comparative analysis was performed by using the χ(2) or the Fisher exact test for categoric data. For numeric data, group comparisons were performed by using the Mann-Whitney test. RESULTS Whole-tumor coverage (mean height, 4.3 cm ± 2.1) was possible in all patients with generation of colored parametric maps of volume transfer constant (K(trans)) and blood volume (BV) by using Patlak analysis. Of the 12 areas that showed high BV, 10 (83%) had a high K(trans); in all 12 cases, the vascular score was high, confirming the presence of numerous tumoral vessels. Nineteen areas showed low BV; when observed concurrently with a high K(trans) (seven of 19), the mean vessel number per area was significantly higher than that seen in areas with low BV and low K(trans) (12 of 19) (P = .038), suggestive of tumoral vessels associated with high interstitial pressure. CONCLUSION Whole-tumor perfusion analysis is technically feasible with 64-detector row CT, with two patterns suggestive of high tumoral vascularity. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100181/-/DC1.

Thoracic applications of dual-source CT technology

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.

Dual-energy CT angiography of chronic thromboembolic disease: can it help recognize links between the severity of pulmonary arterial obstruction and perfusion defects?

PURPOSE To evaluate whether dual-energy CT angiography (DE-CTA) could identify links between morphologic and functional abnormalities in chronic pulmonary thromboembolism (CPTE). MATERIALS AND METHODS Seventeen consecutive patients with CPTE without underlying cardio-respiratory disease were investigated with DE-CTA. Two series of images were generated: (a) transverse diagnostic scans (i.e., contiguous 1-mm thick averaged images from both tubes), and (b) perfusion scans (i.e., images of the iodine content within the microcirculation; 4-mm thick MIPs). Two radiologists evaluated by consensus the presence of: (a) pulmonary vascular features of CPTE and abnormally dilated systemic arteries on diagnostic CT scans, and (b) perfusion defects of embolic type on perfusion scans. RESULTS Diagnostic examinations showed a total of 166 pulmonary arteries (166/833; 19.9%) with features of CPTE, more frequent at the level of peripheral than central arteries (8.94 vs 0.82; p<0.0001), including severe stenosis with partial (97/166; 58.4%) or complete (20/166; 12.0%) obstruction, webs and bands (37/166; 22.3%), partial filling defects without stenosis (7/166; 4.2%), focal stenosis (4/166; 2.4%) and abrupt vessel narrowing (1/166; 0.6%). Perfusion examinations showed 39 perfusion defects in 8 patients (median number: 4.9; range: 1-11). The most severe pulmonary arterial features of CPTE were seen with a significantly higher frequency in segments with perfusion defects than in segments with normal perfusion (p<0.0001). Enlarged systemic arteries were observed with a significantly higher frequency ipsilateral to lungs with perfusion defects (9/12; 75%) compared with lungs without perfusion defects (5/22; 22.7%) (p=0.004). CONCLUSION Dual-energy CTA demonstrates links between the severity of pulmonary arterial obstruction and perfusion impairment, influenced by the degree of development of the systemic collateral supply.

Evaluation of peripheral pulmonary arteries at 80 kV and at 140 kV: dual-energy computed tomography assessment in 51 patients.

Purpose: To compare peripheral pulmonary artery image quality at 80 kVp and 140 kVp in the same patients. Materials and Methods: Image quality of third-, fourth- and fifth-order arteries was assessed at 80 kV and 140 kV on 1-mm-thick transverse scans, generated from dual-source computed tomography (CT) acquisitions. Results: The mean level of enhancement was significantly higher at 80 kV compared with 140 kV for the third-, fourth-, and fifth-order arteries (P < 0.0001). Despite a higher noise level at 80 kV (P < 0.0001), the signal-to-noise ratio and contrast-to-noise ratio were significantly higher at 80 kV than at 140 kV at the level of third-, fourth-, and fifth-order arteries (P < 0.0001). The mean vascular attenuation, mean signal-to-noise ratio and contrast-to-noise ratio for peripheral arteries were significantly superior at 80 kV in the 3 body mass index categories (P < 0.005). Conclusions: Eighty-kilovolt protocols significantly improve the image quality of peripheral pulmonary arteries on CT angiograms of the chest.

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.

Dual-source chest CT angiography with high temporal resolution and high pitch modes: evaluation of image quality in 140 patients

ObjectiveTo evaluate image quality of dual-source computed tomography (CT) angiograms acquired with high temporal resolution and high pitch modes.MethodsTwo groups of 70 consecutive patients underwent chest CT angiography with dual-source, single-energy CT, with an 83-ms temporal resolution and a pitch of 2 (group 1) or a pitch of 3 (group 2). Subjective and objective image quality and the diagnostic value were assessed by two radiologists in consensus. The radiation dose was recorded.ResultsThe image quality was always diagnostic in both groups, rated as excellent in 97% of group 1 (68/70) and 98.5% of group 2 (69/70) examinations. Although no statistically significant difference in subjective image noise was found between the two groups (p = 0.3055), objective noise was found to be statistically higher in group 2 (p < 0.0001). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were found to be significantly higher in group 1 than in group 2 (p = 0.0014). The acquisition time was significantly shorter in group 2 than in group 1 (p < 0.0001). The dose-length product was significantly lower in group 2 than in group 1 (p < 0.0001).ConclusionHigh temporal resolution and high pitch modes provided standard CT angiographic examinations of excellent quality for thoracic applications in routine clinical practice.

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.

Imaging Tumor Response and Tumoral Heterogeneity in Non-Small Cell Lung Cancer Treated With Antiangiogenic Therapy: Comparison of the Prognostic Ability of RECIST 1.1, an Alternate Method (Crabb), and Image Heterogeneity Analysis.

Purpose: We aimed to assess computed tomography (CT) intratumoral heterogeneity changes, and compared the prognostic ability of the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, an alternate response method (Crabb), and CT heterogeneity in non–small cell lung cancer treated with chemotherapy with and without bevacizumab. Materials and Methods: Forty patients treated with chemotherapy (group C) or chemotherapy and bevacizumab (group BC) underwent contrast-enhanced CT at baseline and after 1, 3, and 6 cycles of chemotherapy. Radiologic response was assessed using RECIST 1.1 and an alternate method. CT heterogeneity analysis generating global and locoregional parameters depicting tumor image spatial intensity characteristics was performed. Heterogeneity parameters between the 2 groups were compared using the Mann-Whitney U test. Associations between heterogeneity parameters and radiologic response with overall survival were assessed using Cox regression. Results: Global and locoregional heterogeneity parameters changed with treatment, with increased tumor heterogeneity in group BC. Entropy [group C: median −0.2% (interquartile range −2.2, 1.7) vs. group BC: 0.7% (−0.7, 3.5), P=0.10] and busyness [−27.7% (−62.2, −5.0) vs. −11.5% (−29.1, 92.4), P=0.10] showed a greater reduction in group C, whereas uniformity [1.9% (−8.0, 9.8) vs. −5.0% (−13.9, 5.6), P=0.10] showed a relative increase after 1 cycle but did not reach statistical significance. Two (9%) and 1 (6%) additional responders were identified using the alternate method compared with RECIST in group C and group BC, respectively. Heterogeneity parameters were not significant prognostic factors. Conclusions: The alternate response method described by Crabb identified more responders compared with RECIST. However, both criteria and baseline imaging heterogeneity parameters were not prognostic of survival.