EIT monitors valid and robust regional ventilation distribution in pathologic ventilation states in porcine study using differential DualEnergy-CT (ΔDECT).

It is crucial to precisely monitor ventilation and correctly diagnose ventilation-related pathological states for averting lung collapse and lung failure in Intensive Care Unit (ICU) patients. Although Electrical Impedance Tomography (EIT) may deliver this information continuously and non-invasively at bedside, to date there are no studies that systematically compare EIT and Dual Energy CT (DECT) during inspiration and expiration (ΔDECT) regarding varying physiological and ICU-typical pathological conditions such as atelectasis. This study aims to prove the accuracy of EIT through quantitative identification and monitoring of pathological ventilation conditions on a four-quadrant basis using ΔDECT. In a cohort of 13 pigs, this study investigated systematic changes in tidal volume (TV) and positive end-expiratory pressure (PEEP) under physiological ventilation conditions. Pathological ventilation conditions were established experimentally by single-lung ventilation and pulmonary saline lavage. Spirometric data were compared to voxel-based entire lung ΔDECT, and EIT intensities were compared to ΔDECT of a 12-cm slab of the lung around the EIT belt, the so called ΔDECTBelt. To validate ΔDECT data with spirometry, a Pearson's correlation coefficient of 0.92 was found for 234 ventilation conditions. Comparing EIT intensity with ΔDECT(Belt), the correlation r = 0.84 was found. Normalized cross-correlation function (NCCF) between scaled global impedance (EIT) waveforms and global volume ventilator curves was r = 0.99 ± 0.003. The EIT technique correctly identified the ventilated lung in all cases of single-lung ventilation. In the four-quadrant based evaluation, which assesses the difference between end-expiratory lung volume (ΔEELV) and the corresponding parameter in EIT, i.e. the end-expiratory lung impedance (ΔEELI), the Pearson's correlation coefficient of 0.94 was found. The respective Pearson's correlation coefficients implies good to excellent concurrence between global and regional EIT ventilation data validated by ventilator spirometry and DECT imaging. By providing real-time images of the lung, EIT is a promising, EIT is a promising, clinically robust tool for bedside assessment of regional ventilation distribution and changes of end-expiratory lung volume.

Left Ventricular Structure in Patients With Mild-to-Moderate CKD-a Magnetic Resonance Imaging Study.

INTRODUCTION: The high burden of left ventricular (LV) abnormalities in patients with advanced chronic kidney disease (CKD) is well established. However, less is known about the prevalence, patterns, and determinants of LV abnormalities in patients with early CKD. METHODS: We examined LV structure in 290 patients with a median estimated glomerular filtration rate (eGFR) of 51 ml/min per 1.73 m2 by magnetic resonance imaging (MRI). We explored associations with clinical and hemodynamic parameters, hydration (bioimpedance), endothelial function, inflammation (including C-reactive protein and tumor necrosis factor-α and its soluble receptors) and mineral bone disease (MBD) markers (including vitamin D, parathyroid hormone, α-klotho and fibroblast growth factor-23). RESULTS: Normal geometry was found in 56% of patients, dilation in 4%, concentric remodeling in 10%, and LV hypertrophy in 29%. Linear regression analysis revealed that greater LV mass was independently associated with male sex, greater body mass index (BMI), and higher 24-hour systolic blood pressure (24-hour SBP). Concentric remodeling was independently associated with age, male sex, higher 24-hour SBP, and greater hemoglobin levels. Surprisingly, neither hydration status, nor endothelial function, nor any of the inflammatory or MBD parameters added significantly to these models. CONCLUSION: Abnormal LV structure was found in almost one-half of the patients. Reducing BMI and 24-hour SBP and avoiding high hemoglobin concentrations appear to be the key factors to prevent abnormal LV remodeling in patients with mild-to-moderate CKD.

Leadless Cardiac Pacemaker (LCP) without Diagnostic Relevant Artifacts in DualSource and DualEnergy-CT Examinations in First- to Third-Generation DSCT Scanner.

RATIONALE AND OBJECTIVES: To identify the influence and artifact burden in cardiac CT imaging of a leadless cardiac pacemaker (LCP) performed with all three generations of DualSource CT (DSCT) Scanners. MATERIALS AND METHODS: The LCP was examined in DSCT scanners of the first to third generation using DualEnergy (DECT) and DSCT as well as alterations of the current-time product. For DECT examinations, virtual monoenergetic images were computed manually on a dedicated workstation. Virtual voltage was manually selected by subjective assessment of the lowest artifact burden. Systematic variations of the pacemaker angle to the gantry were assessed, too. The angle was successively increased by 10°, ranging from 0° to 90°. Artifact burden was quantified on a five-point Likert scale (1- no artifacts, 2- few artifacts, 3- moderate artifacts, 4- many artifacts, and 5- massive artifacts). Likert values of 1-3 were considered diagnostic and assessed by two board-certified radiologists in consensus. RESULTS: In total, 200 examinations were analyzed, a mean Likert value of 1.93 ± 0.61 was found overall. None of the images were assessed Likert value >3. The positioning evaluation showed a clear and significant reduction of artifact burden toward lower angles, (0°: 1.4 ± 0.5 vs. 90° 2.55 ± 0.51). At scanner level, second-generation DSCT performed significantly better (1.68 ± 0.47) than both other scanners. Comparison of technique (DECT vs. DSCT) revealed a significantly improved image quality in DSCT examinations. CONCLUSION: LCP can be safely examined in DSCT scanner of the first to third generation with the evaluated protocols and techniques, which are currently in use. Artifact burden can be significantly reduced by aligning or approaching the LCP's longitudinal axis toward the scanner's z-axis.

Blood Pressure Pattern and Target Organ Damage in Patients With Chronic Kidney Disease.

In patients with chronic kidney disease, data on blood pressure (BP) pattern and its association with target organ damage, which indicates elevated cardiovascular risk, are sparse. In 305 treated hypertensive chronic kidney disease patients, we assessed BP pattern, left ventricular mass (magnetic resonance imaging), intima-media thickness (ultrasound), 24-hour-pulse wave velocity and 24-hour-central augmentation index (Mobil-O-Graph). Controlled hypertension (normal office and ambulatory BP) was found in 41% and sustained uncontrolled hypertension (elevated office and ambulatory BP) in 30% of patients. Misclassification of BP status occurred in 29%: white coat uncontrolled hypertension (elevated office but normal ambulatory BP) was detected in 11% and masked uncontrolled hypertension (normal office but elevated ambulatory BP) in 18% of patients. Left ventricular mass was increased in white coat uncontrolled hypertension (+11.2 g), masked uncontrolled hypertension (+9.4 g), and sustained uncontrolled hypertension (+16.6 g) compared with controlled hypertension. Intima-media thickness was similar across all 4 BP groups. Twenty-four hour-pulse wave velocity and 24-hour-central augmentation index were increased in masked uncontrolled hypertension (+0.5 m/sec and +2.5%) and sustained uncontrolled hypertension (+0.5 m/sec and +2.9%) compared with controlled hypertension. In conclusion, based on office BP measurements, misclassification of true BP status occurred in almost one-third of chronic kidney disease patients. Both types of misclassification (white coat uncontrolled hypertension and masked uncontrolled hypertension) were associated with parameters of target organ damage. Ambulatory BP monitoring should be used routinely to identify chronic kidney disease patients at high cardiovascular risk.

Magic Angle in Cardiac CT: Eliminating Clinically Relevant Metal Artifacts in Pacemaker Leads with a Lead-Tip/Gantry Angle of ≤70°.

RATIONALE AND OBJECTIVE: To identify the influence of various parameters for reducing artifacts in computed tomography (CT) of commonly used pacemakers or implantable cardioverter-defibrillator (ICD) lead tips. MATERIALS AND METHODS: This ex vivo phantom study compared two CT techniques (Dual-Energy CT [DECT] vs. Dual-Source CT [DSCT]), as well as the influence of incremental alterations of current-time product and pacemaker lead-tip angle with respect to the gantry plane. Four pacemaker leads and one ICD lead were evaluated. The images were assessed visually on a five-point Likert scale (1 = artifact free to 5 = massive artifacts). Likert values 1-3 represent clinically relevant, diagnostic image quality. RESULTS: 344 of 400 total images were rated with diagnostic image quality. The DECT and dual-source DSCT technique each scored 86% diagnostic image quality. Statistically, DECT images showed significantly improved image quality (P < .05). Concerning the current-time product, no statistically significant change was found. Regarding lead-tip positioning, an angle of ≤70° yielded 100% diagnostic image quality. Pacemaker and ICD leads were assessed to have statistically significant differences. CONCLUSIONS: Surprisingly, the lead-tip angle of 70° has been established as the key angle under which diagnostic image quality is always ensured, regardless of the imaging technique. Thus, we call 70° the "Magic angle" in CT pacemaker imaging.

Low contrast media volume in pre-TAVI CT examinations.

PURPOSE: To evaluate image quality using reduced contrast media (CM) volume in pre-TAVI assessment. METHODS: Forty-seven consecutive patients referred for pre-TAVI examination were evaluated. Patients were divided into two groups: group 1 BMI < 28 kg/m(2) (n = 29); and group 2 BMI > 28 kg/m(2) (n = 18). Patients received a combined scan protocol: retrospective ECG-gated helical CTA of the aortic root (80kVp) followed by a high-pitch spiral CTA (group 1: 70 kV; group 2: 80 kVp) from aortic arch to femoral arteries. All patients received one bolus of CM (300 mgI/ml): group 1: volume = 40 ml; flow rate = 3 ml/s, group 2: volume = 53 ml; flow rate = 4 ml/s. Attenuation values (HU) and contrast-to-noise ratio (CNR) were measured at the levels of the aortic root (helical) and peripheral arteries (high-pitch). Diagnostic image quality was considered sufficient at attenuation values > 250HU and CNR > 10. RESULTS: Diagnostic image quality for TAVI measurements was obtained in 46 patients. Mean attenuation values and CNR (HU ± SD) at the aortic root (helical) were: group 1: 381 ± 65HU and 13 ± 8; group 2: 442 ± 68HU and 10 ± 5. At the peripheral arteries (high-pitch), mean values were: group 1: 430 ± 117HU and 11 ± 6; group 2: 389 ± 102HU and 13 ± 6. CONCLUSION: CM volume can be substantially reduced using low kVp protocols, while maintaining sufficient image quality for the evaluation of aortic root and peripheral access sites. KEY POINTS: • Image quality could be maintained using low kVp scan protocols. • Low kVp protocols reduce contrast media volume by 34-67 %. • Less contrast media volume lowers the risk of contrast-induced nephropathy.

Extracoronary Thoracic and Coronary Artery Calcifications on Chest CT for Lung Cancer Screening: Association with Established Cardiovascular Risk Factors - The "CT-Risk" Trial.

RATIONALE AND OBJECTIVES: To investigate the correlation between prevalence and degree of coronary artery calcification (CAC) and extracoronary calcifications (ECCs), scored quantitatively according to Agatston and semiquantitatively by visual analysis, in chest computed tomography (CT) studies obtained for lung cancer screening in asymptomatic subjects and in patients with known coronary heart disease (CHD), and to compare the association of ECC and CAC to established cardiovascular risk factors. MATERIALS AND METHODS: Prospective study on 501 males (67 ± 8 years) with a history of working dust exposure who underwent nongated low-dose chest CT for lung cancer screening. Of these, 63 (12.6%) had a history of CHD, the remaining 438 subjects (87.4%) were clinically asymptomatic and without a history of CHD. On the day of the CT study, subjects underwent a thorough clinical examination including blood tests and completed a standardized questionnaire to establish a complete medical history. ECC and CAC scores were quantified according to Agatston and, in addition, by visual rating of calcium load of individual vessel territories on a five-point scale from "absent" to "extensive." Results were correlated with the respective subjects' cardiovascular risk factors and with the presence or absence of CHD. RESULTS: ECC scores correlated significantly with CAC scores (two-sided Spearman 0.515; P < .001). ECC scores were associated significantly (P < .001) with cardiovascular risk factors (smoking history, hypertension, diabetes, and hypercholesterolemia) and with subjects' Framingham/prospective cardiovascular münster study scores, whereas CAC scores were associated only with the presence of hypercholesterolemia. CAC scores were strongly associated with CHD than ECC scores (area under the curve, 0.88 vs. 0.66 at receiver operating characteristic analysis). Visual scoring of ECC/CAC load correlated closely with the respective Agatston values (P < .001) and revealed the same association (or lack thereof) with cardiovascular risk factors/CHD. CONCLUSIONS: In nongated low-dose CT for lung cancer screening, CAC and ECC load can be accurately established by visual analysis. ECC and CAC scores correlate closely, but not perfectly. There is a strong association between established cardiovascular risk factors and ECC load, but not CAC load, providing further evidence that ECC scoring may complement CAC scoring for broader risk assessment, for example, regarding prediction of extracoronary vascular events.

Efficacy and safety of transcatheter coil embolization in congenital coronary artery fistulas guided by preinterventional cardiac computed tomography.

OBJECTIVE: Transcatheter coil embolization of coronary artery fistulas (CAFs) has emerged as an alternative to surgical closure despite limited data in the current literature. The aim of this study was to show the efficacy of CAF closure and the benefit of the combined preinterventional use of cardiac computed tomography and coronary angiography to evaluate the feasibility and enhance the safety of this procedure by obtaining precise information about the CAF anatomy. PATIENTS AND METHODS: Five consecutive patients (three men, two women, age 51-68 years) with symptomatic angiographically proven CAFs were screened for transcatheter treatment and underwent preinterventional cardiac multidetector computed tomography (MDCT). RESULTS: On the basis of CAF-associated clinical symptoms, exercise-induced ischemia, coronary angiography, and cardiac MDCT, four of five patients with a CAF draining into the pulmonary artery system were considered eligible for transcatheter coil embolization, whereas in MDCT the fifth patient had multiple draining sites of the CAF and a relevant drainage into the right ventricular myocardium and was thus excluded from the procedure. Coil embolization was successfully performed in the remaining four cases without any complications. There was no residual flow through the CAF after the procedure. Clinical symptoms resolved almost completely in all four patients during a median 15.6-month follow-up. CONCLUSION: Transcatheter coil embolization is a feasible and effective method for the treatment of symptomatic CAFs in selected cases. The adjunctive preinterventional use of cardiac MDCT with conventional angiography can identify vessels that are anatomically applicable for transcatheter closure, defer therapy in morphologically unsuitable complex cases, and thus optimize the safety of the procedure.

Full field image reconstruction is suitable for high-pitch dual-source computed tomography.

OBJECTIVES: The field of view (FOV) in high-pitch dual-source computed tomography (DSCT) is limited by the size of the second detector. The goal of this study was to develop and evaluate a full FOV image reconstruction technique for high-pitch DSCT. MATERIALS AND METHODS: For reconstruction beyond the FOV of the second detector, raw data of the second system were extended to the full dimensions of the first system, using the partly existing data of the first system in combination with a very smooth transition weight function. During the weighted filtered backprojection, the data of the second system were applied with an additional weighting factor. This method was tested for different pitch values from 1.5 to 3.5 on a simulated phantom and on 25 high-pitch DSCT data sets acquired at pitch values of 1.6, 2.0, 2.5, 2.8, and 3.0. Images were reconstructed with FOV sizes of 260 × 260 and 500 × 500 mm. Image quality was assessed by 2 radiologists using a 5-point Likert scale and analyzed with repeated-measure analysis of variance. RESULTS: In phantom and patient data, full FOV image quality depended on pitch. Where complete projection data from both tube-detector systems were available, image quality was unaffected by pitch changes. Full FOV image quality was not compromised at pitch values of 1.6 and remained fully diagnostic up to a pitch of 2.0. At higher pitch values, there was an increasing difference in image quality between limited and full FOV images (P = 0.0097). CONCLUSION: With this new image reconstruction technique, full FOV image reconstruction can be used up to a pitch of 2.0.