Non-enhanced CT Research Articles

The F-18 FDG PET/CT and CT evaluation of pleural plaques.

Pleural plaques have the possibility of bearing malignancy thus investigation of this entity is important and the most important indicator of malignancy in general is fluorodeoxyglucose (FDG) accumulation in radiological appearance. However there is discrepancy between results of previous studies in the literature about this subject. The aim of this study is to analyze the standardized uptake value of pleural plaques and the cut off levels for malignancy in comparison with computed tomography (CT). Seventy one patients were included in the study (27F, 44M; mean: 59.9 ± 13.1 years). Oncologic F-18 FDG positron emission tomography/computed tomography (PET/CT) was performed to all the subjects for a different primary tumor. Pleural plaques were identified in all patients in CT component of PET/CT examination. Contrast enhanced and nonenhanced CT images were evaluated by a Radiology Physician independently according to the gold standard pathology. The diagnostic sensitivity, specificity of CT was; 39%, 79% respectively and if the cut-off SUVmax level was accepted "4.8" the diagnostic sensitivity and specificity of PET was 71%, and 63% respectively. According to the results and ROC curves determined in the study the cut-off level for evaluation of pleural plaques in PET examination was "4.8". The sensitivity and accuracy of PET was higher compared to CT with this cut-off value.

A "one-stop-shop" 4D CTA protocol using 320-row CT for advanced imaging in acute ischemic stroke: a technical note.

This technical note describes a novel CT scan protocol that includes a non-enhanced CT, dynamic CTA, and perfusion of the whole brain and CTA of the carotid arteries using a 320-row area detector CT scanner, with a unique contrast injection and acceptable radiation exposure dose in patients presenting with acute ischemic stroke. The acquisition parameters and reconstruction parameters will be discussed including the use of model-based iterative reconstruction (MBIR), time summing (tMIP), and subtraction techniques to optimize the results of this protocol.Key Points• Scanning on a 320-row area detector CT can achieve both brain perfusion with dynamic angiography and reconstructed arterial and venous CTA, and supra aortic trunk angiography, in a single acquisition. • It provides, in a single exam, a full diagnostic workup, i.e., all the acquisitions that are needed to make a quick decision, with reasonable exposure to ionizing radiation and reduced amount of medium contrast, in case of acute ischemic stroke presentation.

Abstract TP74: Spotty Calcification on Cervicocerebral Computed Tomography Angiography Associates With Increased Risk of Acute Ischemic Stroke

Introduction: Cervicocerebral vascular calcification on cervicocerebral computed tomography angiography is a known sign of advanced atherosclerosis. However, the clinical significance of calcification pattern remains unclear. This study aimed to investigate the potential association between spotty calcium (SC) and acute ischemic stroke. Methods: This study included patients with first-time nonlacunar ischemic stroke (N=50) confirmed by brain MRI or non-enhanced head CT, as well as age and sex-matched control subjects with asymptomatic carotid atherosclerosis (N=43) confirmed by carotid ultrasonography. Subjects in both groups underwent contrast-enhanced cervicocerebral CTA within a week after the initial imaging exam. Spotty calcification was evaluated at eleven arterial segments commonly affected by atherosclerosis along the carotid and vertebrobasilar circulation. Statistical analysis was performed comparing the frequency and spatial pattern of spotty calcification between the two groups. Results: Spotty calcification in the stroke group was markedly more prevalent than that in the control group (total SC count: 8.74±4.96 vs 1.84±1.77, p<0.001). The relative risk for stroke of spotty calcification at bilateral carotid bifurcation, carotid siphon, and all evaluated locations were (95% confidence interval): 2.521 (1.530~4.155), 1.441 (1.073~1.937), and 1.971 (1.434~2.709), respectively. A total number of 3 spotty calcifications was determined as the optimal cutoff threshold for increased risk of stroke. Spotty calcium showed significantly greater area under the receiver-operating characteristics curve (ROC) than that of total calcium irrespective of size (0.88 versus 0.77). Within the stroke group, ipsilateral lateral side showed significantly more spotty calcium than the contralateral side (5.18±3.05 vs. 3.56±2.67, p<0.001). Conclusions: Nonlacunar ischemia stroke was associated with markedly increased incidence of spotty calcification with a distinct spatial pattern on cervicocerebral computed tomography compared with subclinical atherosclerosis, suggesting the potential role of spotty calcification for improving the risk-stratification for ischemic stroke.

Minor Blunt Thoracic Trauma in the Emergency Department: Sensitivity and Specificity of Chest Ultralow-Dose Computed Tomography Compared With Conventional Radiography

To evaluate the diagnostic performance of chest ultralow-dose computed tomography (CT) compared with chest radiograph for minor blunt thoracic trauma. One hundred sixty patients with minor blunt thoracic trauma were evaluated first by chest radiograph and subsequently with a double-acquisition nonenhanced chest CT protocol: reference CT and ultralow-dose CT with iterative reconstruction. Two study radiologists independently assessed injuries with a structured report and subjective image quality and calculated certainty of diagnostic confidence level. Ultralow-dose CT had a sensitivity and specificity of 100% compared with reference CT in the detection of injuries (187 lesions) in 104 patients. Chest radiograph detected abnormalities in 82 patients (79% of the population), with lower sensitivity and specificity compared with ultralow-dose CT (P<.05). Despite an only fair interobserver agreement for ultralow-dose CT image quality (κ=0.26), the diagnostic confidence level was certain for 95.6% of patients (chest radiograph=79.3%). Ultralow-dose CT effective dose (0.203 mSv [SD 0.029 mSv]) was similar (P=.14) to that of chest radiograph (0.175 mSv [SD 0.155 mSv]) and significantly less (P<.001) than that of reference CT (1.193 mSv [SD 0.459 mSv]). Ultralow-dose CT with iterative reconstruction conveyed a radiation dose similar to that of chest radiograph and was more reliable than a radiographic study for minor blunt thoracic trauma assessment. Radiologists, regardless of experience with ultralow-dose CT, were more confident with chest ultralow-dose CT than chest radiograph.

Structural imaging findings on non-enhanced computed tomography are severely underreported in the primary care diagnostic work-up of subjective cognitive decline

PurposeThe purpose of this study was to investigate how structural imaging findings of medial temporal lobe atrophy (MTA), posterior cortical atrophy (PCA), global cortical atrophy (GCA), white matter changes (WMC), and Evans’ index/width of lateral ventricles (EI/WLV) are reported in the primary care diagnostic work-up of patients with subjective cognitive decline or mild cognitive impairment.MethodsWe included 197 patients referred to a non-enhanced computed tomography (NECT) as part of the diagnostic work-up. We compared the frequencies of reported findings in radiology reports written by neuroradiologists and general radiologists with actual pathological findings in a second view done by a single neuroradiologist using the MTA, PCA, GCA, WMC, and EI/WLV visual rating scales. Structural findings were also compared to cognitive tests.ResultsWe found that MTA and PCA were clearly underreported by both neuroradiologists and general radiologists. The presence of GCA and WMC was also underreported among general radiologists. Only MTA showed a clear association with cognitive test results.ConclusionsWe believe that the use of visual rating scales should be put into clinical practice to increase the yield of clinical NECT exams in the investigation of cognitive impairment. Special emphasis should be put on reporting MTA.

Thrombus Enhancement Is a Predictor of Clinical Outcome in Acute Ischemic Stroke after Mechanical Thrombectomy

Background: Ex vivo computed tomography (CT) studies of artificial blood thrombi showed that contrast enhancement (CE) is determined by fibrin-content, while unenhanced density is associated with red blood cells. Thus, the present study investigates patient outcome in association with combined thrombus density measures in native and contrast-enhanced CT (CECT) of acute ischemic stroke patients. Methods: This retrospective study includes 137 patients with M1 occlusions treated by mechanical thrombectomy (MT) between 2010 and 2016. Clinical outcome was determined with modified Rankin Scale (mRS) at 90 days. Differentiation of complete and incomplete large vessel occlusion (CLVO/ILVO) was based on CT and angiography. Two blinded readers classified blood thrombi based on native non-enhanced CT (NECT) as (a) hypo-, (b) iso-, and (c) hyperdense and in CECT angio measurements as (d) not-enhancing, (e) intermediate and (f) enhancing. To make sure that the mean is not represented in any of the maximum/minimum groups, thresholds in both cases were selected in a way that all values within one SD around the mean value form the isodense/intermediate group. In addition, the CE per se was correlated with the outcome. Correlations between imaging and clinical scales were performed with Spearman’s Rho. For the group testing Pearson chi-square test, Mann-Whitney U, as well parametric and nonparametric one-factor ANOVA “Kruskal-Wallis” test including Bonferroni correction for multiple tests ware used. Results: Twenty-three patients with ILVO (16.8%) differed significantly from patients with CLVO in mRS at admission (median 4 vs. 5) and after 90 days (median 1 vs. 4; p < 0.05) and thus were excluded. In the ILVO cohort, the classification according to NECT did not show statistical difference between hypo-, iso- and hyperdense CLVOs in regard to outcome. Classification of CLVOs according to CECT allowed an outcome prediction between the intermediate (median 3) and enhancing group (median 5) and between the enhancing and non-enhancing group (median 3; both p < 0.05) with a correlation of 291 between CE and higher mRS after 90 days (p < 0.005). Conclusions: CE of thrombi – especially in a range from over 18.4 to 40.35 Hounsfield Units – is an independent predictor of poor clinical outcome in patients undergoing MT due to acute middle cerebral artery occlusion.

Degree of Conjugate Gaze Deviation on CT Predicts Proximal Vessel Occlusion and May Expedite Endovascular Therapy

Purpose: Recent trials have demonstrated superior outcomes with combination IV-tPA and endovascular therapy (EVT) within 6 hours of symptom onset in patients with proximal vessel occlusion (ICA, M1, or proximal M1/M2) compared to IV-tPA alone. The current standard of diagnosis for consideration of EVT is CT angiogram (CTA). Unfortunately, not all hospitals are equipped with CTA, and the decision to transfer to tertiary centers is often based on nonenhanced CT. Ipsilateral conjugate gaze deviation (CGD) is associated with worse outcomes and larger infarcts in acute ischemic stroke. We predicted that the more proximal the occlusion, the higher the degree of CGD. Materials and Methods: Over a period of 12 months, 182 consecutive patients with acute ischemic stroke treated at our institution were prospectively analyzed. Stroke locations were categorized based on CTA. Average degree of CGD was measured. Patient demographics, ASPECTS, collateral score, National Institutes of Health Stroke Scale, modified Rankin Scale, TICI score, length-of-stay, and mortality were collected. The median follow-up was 30 days. Results: Out of ninety one of 182 patients with (+) CGD, 82 (90%) patients had ICA or middle cerebral artery (MCA) territory infarcts. The median was 25.0° in those with proximal occlusion and 13.7° in those with distal MCA occlusion (P < .001). A higher degree of CGD is positively correlated with proximity of vessel occlusion (correlation coefficient 0.2; P < .05). A cut-off greater than 20.25° (area under the curve = .76) showed a sensitivity of 64.0% and specificity 84.2%. Conclusions: Measuring degree of CGD may help in early identification of proximal vessel occlusions and expedite transfer for clot retrieval.

Computed tomography imaging-based normative orbital measurement in Indian population.

Purpose:This study aims to evaluate normal orbital structures with nonenhanced computed tomography (NCCT) and determine normative data for the Indian population.Methods:CT images of the orbits of 100 patients were retrospectively reviewed on a work station to record the normative data of the orbits. Clinical details of all patients were reviewed to ensure that they did not have ocular/orbital diseases. Both axial and coronal images were utilized to record the data.Results:The mean age of the population evaluated was 34.07 years, with male to female ratio of 1.77. The average orbital index for the left orbit was 97 and for the right side was 103. The mean thickness of left inferior rectus, lateral rectus, medial rectus, and the superior rectus was 3.36 mm, 3.14 mm, 3.80 mm, and 3.75 mm, respectively. The right inferior rectus, lateral rectus, medial rectus, and the superior rectus measured 3.46 mm, 3.14 mm, 3.83 mm, and 3.78 mm, respectively. The optic nerve sheath complex diameter varied between 3.05 mm and 7.17 mm for the left eye and 3.05 mm and 7.0 mm for the right eye.Conclusion:The study provides normative data on various orbital structures in an Indian population. This data is likely to be useful for diagnosing various orbital pathologies and in planning surgical orbital procedures.

Sex difference in fibrin clot lysability: Association with coronary plaque composition

IntroductionFibrin clot lysability is associated with development of cardiovascular disease (CVD). We evaluated sex-differences in fibrin clot lysability and the association with coronary plaque composition determined by computed tomography angiography (CTA). MethodsMiddle-aged citizens without known CVD were randomly selected from a national registry. A coronary CTA assessed volumes of calcified-, non-calcified-, low-density non-calcified-, and total- plaque using a validated plaque quantification software. A non-enhanced cardiac CT scan assessed the Agatston score. Fibrin structure properties were determined using turbidimetric methods. Plasma concentrations of C-reactive protein and fibrinogen were assessed. Results138 individuals (71 women) participated. Men more frequently had coronary plaques compared to women, P < 0.05. Coronary plaque features were comparable between men and women, P > 0.05. Women with total plaque volume > 0 mm3 had lower fibrin clot lysability compared to women with total plaque volume = 0 mm3, adjusted difference [95% confidence interval] 10.28 [1.42–19.15], P = 0.02, and a fibrinogen-dependent lower fibrin clot lysability compared to men with and without coronary plaques, 6.82 [−2.67–16.31], P = 0.16, and 8.73 [−0.43–17.89], P = 0.06, respectively. Fibrinogen correlated with all the coronary plaque features (correlation coefficient r = 0.42–0.57) only in women with total plaque volume > 0 mm3, all P < 0.01. ConclusionAsymptomatic women with coronary plaques assessed by coronary CTA have reduced fibrin clot lysability compared to both women without coronary plaques and men, suggesting a sex-dependent link between coronary atherosclerosis and fibrin clot lysability.

The imaging features and prognosis of primary central airway salivary gland-type tumor

Objective To analyze the image features and prognosis of primary central airway salivary gland-type tumor (SGT). Methods The clinical and imaging data of 25 cases with SGT confirmed by histopathology were retrospectively analyzed in our hospital from October 2009 to November 2017. Follow up of patients for survival was performed. Among 25 cases of SGT, there were 14 cases of adenoid cystic carcinoma (ACC), ten cases of mucoepidermoid carcinoma (MEC) and one case of mucoepidermoid carcinoma (EMC). All cases had non-enhanced CT scans (among which 20 cases underwent CT scan with contrast). Post-processing were performed to evaluate the location, range, density, degree of enhancement of the lesions and involvement of hilar or mediastinal lymph nodes. Eight cases underwent PET/CT imaging and one underwent MR imaging, respectively. Independent sample t test was used to compare difference in ages between ACC group and MEC group. Nonparametric test was performed to compare difference in tumor′s diameter between ACC group and MEC group. Comparison of genders, history of smoking, tumor-node-metastasis (TNM) stage and CT features between ACC group and MEC group were tested using Fisher′s exact tests. Survival was calculated using the Kaplan-Meier method, and the survival curves were compared by the log-rank test. Results Compared to MEC, patients with ACC were older. There were significant difference between the two groups (t=3.154, P<0.05). ACC tended to involved trachea or main bronchi (13/14) while MEC were mostly located at lobar or segment bronchi (6/10). The shape of ACC tumors were mainly lobulated or presented as circumferential wall thickening (13/14), while MECs were smoothly oval (7/10). On contrast-enhanced CT scans, ACC mainly showed mild or moderate enhancement (9/10), While most of MEC had shown avid enhancement (8/10). CT findings suggestive of airway obstructive disease were seen more with MEC (9/10) than ACC (4/14). There were significant differences of the above CT features between ACC and MEC group (P<0.05). A case of EMC in an 43 years old female presented rounded nodule in tracheal; The SUVmax in 6 of 8 cases of PET/CT exceeded 2.2; Overall survival (OS) was 87.5% in all cases. No significant difference was found between ACC and MEC groups regarding OS (χ2=0, P=1.000). Ages, surgical and nonsurgical patients and TNM stage were found to be related to OS (χ2=13.799, 13.799, 13.171, respectively, P<0.05). Conclusions Primary central airway salivary gland-type tumors are commonly occurred in patients at a low age, with weak invasive feature and good prognosis. The predominant site and CT characteristics between ACC and MEC were significantly different. Key words: Salivary gland neoplasms; Tomography, X-ray computed; Magnetic resonance imaging; Prognosis

The impact of abdominal fat on abdominal aorta calcification measured on non-enhanced CT.

Cardiovascular (CV) morbidity, atherosclerosis, and obesity are all targets of clinical concern and vast research, as is the association between them. Aim of this study is to assess the impact of adipose tissue (including visceral and subcutaneous fat) on abdominal aorta calcification measured on non-enhanced computed tomography (CT). We retrospectively included 492 patients who underwent non-enhanced CT scans during workup for clinically suspected renal colic. All scans were reviewed for abdominal aorta calcification, liver attenuation, and thickness of visceral and subcutaneous fat. Multivariate general linear regression models were used to assess the association between abdominal aorta calcium score and adiposity measures. In the model that included only adiposity measures; visceral fat thickness had statistically significant direct association with abdominal aorta calcium score (B = 67.1, P <.001), whereas subcutaneous pelvic fat thickness had a significant inverse association with abdominal aorta calcium score (B = −22.34, P <.001). Only the association of subcutaneous pelvic fat thickness with abdominal aorta calcium score remained statistically significant when controlling for age, sex, smoking, hypertension, diabetes mellitus, and hyperlipidemia (B = −21.23, P <.001). In this model, the association of visceral fat remained statistically significant in females (B = 84.28, P = .001) but not in males (B = 0.47, P = .973). Visceral fat thickness and subcutaneous pelvic fat thickness were found to have opposing associations with abdominal aorta calcium score. This suggests that while visceral fat may have a lipotoxic effect on aortic atherosclerotic processes, subcutaneous pelvic fat may have a protective role in these processes.

Computed Tomography Findings for Diagnosing Follicular Thyroid Neoplasms.

Since no diagnostic method has been established to distinguish follicular thyroid carcinoma (FTC) from follicular thyroid adenoma (FTA), surgery has been the only way to reach a diagnosis of follicular neoplasm. Here we investigated the computed tomography (CT) features of follicular neoplasms, toward the goal of being able to identify specific CT features allowing the preoperative differentiation of FTC from FTA. We retrospectively analyzed the cases of 205 patients who underwent preoperative CT of the neck and were histopathologically diagnosed with FTC (n=31) or FTA (n=174) after surgery between January 2002 and June 2016 at several hospitals in Japan. In each of these 205 cases, non-enhanced and contrast-enhanced CT images were obtained, and we analyzed the CT features. On univariate analysis, inhomogeneous features of tumor lesions on contrast-enhanced CT were more frequently observed in FTC than in FTA (p=0.0032). A multivariate analysis identified inhomogeneous features of tumor lesions on contrast-enhanced CT images as an independent variable indicative of FTC (p=0.0023). CT thus offers diagnostic assistance in distinguishing FTC from FTA.

Histogram analysis- a useful tool for tissue characterization in brain CT

Introduction: Pixel value in computed tomography (CT) gives the average linear attenuation coefficient of the scanned material in the path of the x-ray beam, being normalized to that of water. It is known that attenuation coefficient or HU value is a function of the chemical characteristic of the material and of the x-ray energy. The CT image shows the HU value by a shade of gray in each pixel. Human eye is often not able to discriminate gray shadows; whose grayness are close to each other. Therefore, when two different tissues have very similar chemical characteristics they may not be distinguishable in the CT image by human eyes. For this reason, in CT image, it is difficult to distinguish between brain tumor and ischemia, in the hypodense area. The aim of this study is to use histogram analysis, based on the frequency distribution of the HU values in brain CT images to evaluate the possibility of distinguishing tumor from ischemia. Materials and Methods: We collected 150 axial slices of brain CT, from known hypodense areas belonging to ischemia and tumor with similar appearance. They contained 75 samples of each type. Minimum, maximum, and mean HU values of ROI inside the lesions were used to make the histogram, cumulative and probability percentage distribution. We used 10 unknown cases, 5 tumors and 5 ischemia, to evaluate our finding. Results: Bar chart and linear diagram histogram show that the minimum, maximum and mean of HU values are higher in ischemia cases. Also, the median of the cumulative distributions of minimum, maximum and mean appear at higher HU values for ischemia. The probability of occurrence of ischemia cases increases with increasing HU values of minimum, maximum and mean while the behavior of the tumor cases is completely reverse. We have done the same data analysis for 10 unknown cases. Our predictions match in 80% of the cases, with the radiologist’s conclusion, who were unaware of our findings. Conclusion: Histogram analysis may be used as an effective tissue characterization tool in non-enhanced brain CT images. This method could distinguish hypodense areas of ischemic lesion from tumor, as is seen, for the first time, in the present study.

A Novel Texture Analysis Method Based on Reverse Biorthogonal Wavelet and Co-Occurrence Matrix Applied for Classification of Hepatocellular Carcinoma and Hepatic Hemangioma

Purpose: To explore the feasibility of classifying hepatocellular carcinoma (HCC) and hepatic hemangioma (HEM) using texture features of non-enhanced computed tomography (CT) images, especially to investigate the effectiveness of a novel texture analysis method based on the combination of wavelet and co-occurrence matrix. Methods: 269 patients were retrospectively analyzed, including 129 HCCs and 140 HEMs. We cropped tumor regions of interest (ROIs) on non-enhanced CT images, and then used four texture analysis methods to extract quantitative data of the ROIs: gray-level histogram (GLH), gray-level co-occurrence matrix (GLCM), reverse biorthogonal wavelet transform (RBWT), and reverse biorthogonal wavelet co-occurrence matrix (RBCM). The RBCM was a novel method proposed in this study that combined wavelet transform and co-occurrence matrix. It discretized wavelet coefficient matrices based on the statistical characteristics of the training set. Thus, four sets of texture features were obtained. We then conducted classification studies using support vector machine on each set of texture features. 10-fold cross training and testing were used in the classifications, and their results were evaluated and compared. In addition, we tested the significant differences in the texture features of the RBCM method and explored the possible relationships between textures and lesion types. Results: The RBCM method achieved the best classification performance: its average accuracy was 82.14%; its average AUC (area under the receiver operating characteristic curve) was 0.8423. In addition, using the methods of GLH, GLCM, and RBWT, their average accuracies were 75.81%, 78.79%, and 78.8%, respectively. Conclusions: It indicates that the developed texture analysis methods are rewarding for computer-aided diagnosis of HCC and HEM based on non-enhanced CT images. Furthermore, the distinguishing ability of the proposed RBCM method is more pronounced.

Development of a radiomics signature to predict Ki-67 expression level in non-small cell lung cancer

To develop a radiomics signature based on CT image features to estimate the expression level of Ki-67 in non-small cell lung cancer (NSCLC). Methods: A total of 108 NSCLC patients, who underwent non-enhanced and contrast-enhanced CT scan in our hospital from January 2014 to November 2017, were retrospectively analyzed. They were confirmed by histopathological examination and undergone Ki-67 expression level test within 2 weeks after CT examination. The non-enhanced and contrast-enhanced CT three-dimensional structural images of the lesions were manually delineated by MaZda software, and the texture features of the region of interest were extracted. Combination of feature selection and classification methods were used to build radiomics signatures, and the classification were assessed using misclassification rates. The MaZda software provides texture feature selection methods including mutual information (MI), Fisher coefficients (Fisher), classification error probability combined with average correlation coefficients (POE+ACC), and Fisher+POE+ACC+MI (FPM), and texture feature analysis including raw data analysis (RDA), principal component analysis (PCA), linear classification analysis (LDA) and nonlinear classification analysis (NDA). Results: Among the 108 patients, 50 cases were at high levels of Ki-67 expression and 58 cases were at low levels of Ki-67 expression, respectively. The differences of gender, age and pathological type between the two groups were statistically significant (P<0.05). The radiomics signature built by FPM feature selection combined with NDA feature analysis based on non-enhanced CT images achieved the best performance for predicting the level of Ki-67 with a misclassification rate of 14.81%. However, radiomics signature based on contrast-enhanced CT images did not reduce the misclassification rate. Conclusion: The radiomics signature based on conventional CT image texture features is helpful to predict the expression of Ki-67 in NSCLC lesions, which can provide a non-invasive technique for assessing the invasiveness and prognosis for NSCLC.

Radiomics for Classification of Lung Cancer Histological Subtypes Based on Nonenhanced Computed Tomography

To evaluate the performance of using radiomics method to classify lung cancer histological subtypes based on nonenhanced computed tomography images. 278 patients with pathologically confirmed lung cancer were collected, including 181 nonsmall cell lung cancer (NSCLC) and 97 small cell lung cancers (SCLC) patients. Among the NSCLC patients, 88 patients were adenocarcinomas (AD) and 93 patients were squamous cell carcinomas (SCC). In total, 1695 quantitative radiomic features (QRF) were calculated from the primary lung cancer tumor in each patient. To build radiomic classification model based on the extracted QRFs, several machine-learning algorithms were applied sequentially. First, unsupervised hierarchical clustering was used to exclude highly correlated QRFs; second, the minimum Redundancy Maximum Relevance feature selection algorithm was employed to select informative and nonredundant QRFs; finally, the Incremental Forward Search and Support Vector Machine classification algorithms were used to combine the selected QRFs and build the model. In our work, to study the phenotypic differences among lung cancer histological subtypes, four classification models were built. They were models of SCLC vs NSCLC, SCLC vs AD, SCLC vs SCC, and AD vs SCC. The performance of the classification models was evaluated by the area under the receiver operating characteristic curve (AUC) estimated by three-fold cross-validation. The AUC (95% confidence interval) for the model of SCLC vs NSCLC was 0.741(0.678, 0.795). For the models of SCLC vs AD and SCLC vs SCC, the AUCs were 0.822(0.755, 0.875) and 0.665(0.583, 0.738), respectively. The AUC for the model of AD vs SCC was 0.655(0.570, 0.731). Several QRFs ("Law_15," "LoG_Uniformity," "GLCM_Contrast," and "Compactness Factor") that characterize tumor heterogeneity and shape were selected as the significant features to build the models. Our results show that phenotypic differences exist among different lung cancer histological subtypes on nonenhanced computed tomography image.

MR Imaging for Differentiating Contrast Staining from Hemorrhagic Transformation after Endovascular Thrombectomy in Acute Ischemic Stroke: Phantom and Patient Study.

Early differentiation of contrast staining from hemorrhagic transformation in patients with acute ischemic stroke who have undergone endovascular treatment is critical in preventing the delayed administration of antiplatelet agents. We aimed to demonstrate the usefulness of an immediate postinterventional DWI protocol including B0 and gradient recalled-echo sequences to discriminate those 2 conditions through phantom and preliminary retrospective patient studies. On 3T MR imaging, the signal intensities of the phantom models consisting of iodinated contrast agents diluted with normal saline and arterial blood were compared using T1WI, T2WI, and gradient recalled-echo sequences. A total 17 patients (8 with hemorrhagic transformation and 9 with contrast staining; 8 men and 9 women; mean age, 72.00 ± 10.91 years; range, 52-90 years) who underwent mechanical thrombectomy for acute ischemic stroke and showed newly appearing hyperdense lesions on immediate (<24 hours) postinterventional nonenhanced CT scans were included in this study. Immediate postinterventional DWI of patients were compared. In the phantom study, iodinated contrast agents diluted with normal saline showed minimal signal drop, while those diluted with arterial blood demonstrated dark signal intensity in the T2WI and gradient recalled-echo sequences. In the patient study, all hemorrhagic transformations and none of the contrast staining demonstrated dark or low signal (<gray matter) intensities similar to those of the vessel in the B0-DWI and gradient recalled-echo images. According to our preliminary results, contrast staining might be differentiated from hemorrhagic transformation using an immediate postinterventional DWI protocol including gradient recalled-echo sequences. It might be possible to expedite establishment of postinterventional medical treatment strategy.

Virtual non-enhanced dual-energy CT reconstruction may replace true non-enhanced CT scans in the setting of suspected active hemorrhage

ObjectiveTo assess virtual non-enhanced dual energy computed tomography (DECT) reconstruction as a potential alternative to true non-enhanced thoracic and abdominal CT scans in patients with suspected active hemorrhage. Methods and MaterialsNinety-seven consecutive patients with suspected active bleeding, who underwent routine triphasic CT with intravenous contrast, were included. All patients underwent single energy non-enhanced (TNE) and arterial phase CT as well as venous DECT. Using commercially available software, venous dual energy images were used to generate virtual non-enhanced images (VNE). TNE and VNE were evaluated regarding subjective image quality and diagnostic confidence on a 5-point-scale. The consistency of interpretation with respect to presence and type of hemorrhage between conventional triphasic CT including TNE and biphasic CT with simulated VNE was assessed by two blinded independent readers. ResultsAmong the included subjects (mean age: 66.3 ± 14.5 years, 63.9% male), 37.1% were diagnosed with acute hemorrhage. VNE yielded significantly lower image quality but superior reduction of artefacts as compared to TNE (p ≤ 0.001). Diagnostic confidence was rated high for both TNE and VNE with a significant superiority of TNE (p = 0.003). Triphasic and biphasic CT datasets yielded perfect intrareader agreement regarding presence and type of hemorrhage. The interrater agreement was almost perfect (K = 0.955). Radiation dose was significantly reduced using biphasic dual energy CT with VNE (p ≤ 0.001). ConclusionVirtual non-enhanced images yield comparable diagnostic confidence and perfect agreement with true non-enhanced images for assessment of acute hemorrhage. This suggests that true non-enhanced images could be replaced by virtual non-enhanced images resulting in a significant reduction of radiation dose.

Does Nonenhanced CT-based Quantification of Abdominal Aortic Calcification Outperform the Framingham Risk Score in Predicting Cardiovascular Events in Asymptomatic Adults?

Purpose To determine if abdominal aortic calcification (AAC) at CT predicts cardiovascular events independent of Framingham risk score (FRS). Materials and Methods For this retrospective study, electronic health records for 829 asymptomatic patients (mean age, 57.9 years; 451 women, 378 men) who underwent nonenhanced CT colonography screening between April 2004 and March 2005 were reviewed for subsequent cardiovascular events; mean follow-up interval was 11.2 years ± 2.8 (standard deviation). Institutional review board approval was obtained. CT-based AAC was retrospectively quantified as a modified Agatston score by using a semiautomated tool. Kaplan-Meier curves and Cox proportional hazards models were used for time-to-event analysis; receiver operating characteristic curves and net reclassification improvement compared predictive abilities of AAC and FRS. Results An index cardiovascular event occurred after CT in 156 (19%) of 829 patients (6.7 years ± 3.5, including heart attack in 39 [5%] and death in 79 [10%]). AAC was higher in the cardiovascular event cohort (mean AAC, 3478 vs 664; P < .001). AAC was a strong predictor of cardiovascular events at both univariable and multivariable Cox modeling, independent of FRS (P < .001). Kaplan-Meier plots showed better separation with AAC over FRS. The area under the receiver operating characteristic curve (AUC) was higher for AAC than FRS at all evaluated time points (eg, AUC of 0.82 vs 0.64 at 2 years; P = .014). By using a cutoff point of 200, AAC improved FRS risk categorization with net reclassification improvement of 35.4%. Conclusion CT-based abdominal aortic calcification was a strong predictor of future cardiovascular events, outperforming the Framingham risk score. This finding suggests a potential opportunistic role in abdominal nonenhanced CT scans performed for other clinical indications. © RSNA, 2018.

Coronary computed tomography angiography (CCTA) quality

Coronary computed tomography angiography (CCTA) is increasingly being utilized for assessment of coronary artery disease. New techniques for CCTA intend to reduce the radiation dose, whereas maintaining the image quality. This research was carried out in order to explore the advantages of assessing the image quality of the non-enhanced CT scan in the pre-determination of the best CCTA gating protocol, which we hypothesized to result in better image quality and lower radiation exposure. A prospective analysis of the 150 non-enhanced CT scans which were performed before 256-slice CCTA to look into the presence of artifacts affecting the coronary arteries, the scan protocol (prospective vs. Prospective with padding or retrospective gating) was selected in the light of these observations. The image quality (four-point scale) and the radiation dose were compared with 150 standard CCTA scans performed without pre-selection of the desired protocol. The median age of the patients was 49 (23–78) years and the average heart rate during the CCTA scan was 62 ± 14 beats per minute. We found that the subjective image quality obtained with the guidance of the pre-selection of the scan protocol is better compared to the standard CCTA scanning, especially when the heart rate is more than 65 per minute (3.5 ± 0.5 vs. 2.8 ± 0.8; p = 0.06) respectively. The overall radiation dose was significantly lower in the pre-selection group compared to the standard CCTA (4.9 ± 1.4 vs. 7.5 ± 1.8 mSv; p <;0.01) respectively, The use of Prospective with padding or retrospective gating was infrequent in the non-enhanced scans based pre-selection of CCTA protocol compared to the standard group (14 out of 150 versus 28 out of 150 scans) respectively. The use of 256-raw CCTA and the determination of the acquisition protocol based on the assessment of the non-enhanced CT scan, prompts better image quality and a significant radiation exposure reduction. We recommend performing this analysis to guide the selection of the CCTA scan protocol.