Dual-Energy CT in Hemorrhagic Progression of Cerebral Contusion: Overestimation of Hematoma Volumes on Standard 120-kV Images and Rectification with Virtual High-Energy Monochromatic Images after Contrast-Enhanced Whole-Body Imaging.

BACKGROUND AND PURPOSE: In patients with hemorrhagic contusions, hematoma volumes are overestimated on follow-up standard 120-kV images obtained after contrast-enhanced whole-body CT. We aimed to retrospectively determine hemorrhagic progression of contusion rates on 120-kV and 190-keV images derived from dual-energy CT and the magnitude of hematoma volume overestimation. MATERIALS AND METHODS: We retrospectively analyzed admission and follow-up CT studies in 40 patients with hemorrhagic contusions. After annotating the contusions, we measured volumes from admission and follow-up 120-kV and 190-keV images using semiautomated 3D segmentation. Bland-Altman analysis was used for hematoma volume comparison. RESULTS: On 120-kV images, hemorrhagic progression of contusions was detected in 24 of the 40 patients, while only 17 patients had hemorrhagic progression of contusions on 190-keV images (P = .008). Hematoma volumes were systematically overestimated on follow-up 120-kV images (9.68 versus 8 mm3; mean difference, 1.68 mm3; standard error, 0.37; P < .001) compared with 190-keV images. There was no significant difference in volumes between admission 120-kV and 190-keV images. Mean and median percentages of overestimation were 29% (95% CI, 18-39) and 22% (quartile 3 - quartile 1 = 36.8), respectively. CONCLUSIONS: The 120-kV images, which are comparable with single-energy CT images, significantly overestimated the hematoma volumes, hence the rate of hemorrhagic progression of contusions, after contrast-enhanced whole-body CT. Hence, follow-up of hemorrhagic contusions should be performed on dual-energy CT, and 190-keV images should be used for the assessment of hematoma volumes.

Dual-Energy CT in Enhancing Subdural Effusions that Masquerade as Subdural Hematomas: Diagnosis with Virtual High-Monochromatic (190-keV) Images.

BACKGROUND AND PURPOSE: Extravasation of iodinated contrast into subdural space following contrast-enhanced radiographic studies results in hyperdense subdural effusions, which can be mistaken as acute subdural hematomas on follow-up noncontrast head CTs. Our aim was to identify the factors associated with contrast-enhancing subdural effusion, characterize diffusion and washout kinetics of iodine in enhancing subdural effusion, and assess the utility of dual-energy CT in differentiating enhancing subdural effusion from subdural hematoma. MATERIALS AND METHODS: We retrospectively analyzed follow-up head dual-energy CT studies in 423 patients with polytrauma who had undergone contrast-enhanced whole-body CT. Twenty-four patients with enhancing subdural effusion composed the study group, and 24 randomly selected patients with subdural hematoma were enrolled in the comparison group. Postprocessing with syngo.via was performed to determine the diffusion and washout kinetics of iodine. The sensitivity and specificity of dual-energy CT for the diagnosis of enhancing subdural effusion were determined with 120-kV, virtual monochromatic energy (190-keV) and virtual noncontrast images. RESULTS: Patients with enhancing subdural effusion were significantly older (mean, 69 years; 95% CI, 60-78 years; P < .001) and had a higher incidence of intracranial hemorrhage (P = .001). Peak iodine concentration in enhancing subdural effusions was reached within the first 8 hours of contrast administration with a mean of 0.98 mg/mL (95% CI, 0.81-1.13 mg/mL), and complete washout was achieved at 38 hours. For the presence of a hyperdense subdural collection on 120-kV images with a loss of hyperattenuation on 190-keV and virtual noncontrast images, when considered as a true-positive for enhancing subdural effusion, the sensitivity was 100% (95% CI, 85.75%-100%) and the specificity was 91.67% (95% CI, 73%-99%). CONCLUSIONS: Dual-energy CT has a high sensitivity and specificity in differentiating enhancing subdural effusion from subdural hematoma. Hence, dual-energy CT has a potential to obviate follow-up studies.

Effect of iodine concentration of contrast media on contrast enhancement in multislice CT of the pancreas.

The purpose of this study was to determine the influence of two different iodine concentrations of the non-ionic contrast agent, Iomeprol, on contrast enhancement in multislice CT (MSCT) of the pancreas. To achieve this MSCT of the pancreas was performed in 50 patients (mean age 57+/-14 years) with suspected or known pancreatic tumours. The patients were randomly assigned to group A (n=25 patients) or group B (n=25 patients). There were no statistically significant differences in age, height or weight between the patients of the two groups. The contrast agent, Iomeprol, was injected with iodine concentrations of 300 mg ml(-1) in group A (130 ml, injection rate 5 ml s(-1)) and 400 mg ml(-1) in group B (98 ml, injection rate 5 ml s(-1)). Arterial and portal venous phase contrast enhancement (HU) of the vessels, organs, and pancreatic masses were measured and a qualitative image assessment was performed by two independent readers. In the arterial phase, Iomeprol 400 led to a significantly greater enhancement in the aorta, superior mesenteric artery, coeliac trunk, pancreas, pancreatic carcinomas, kidneys, spleen and wall of the small intestine than Iomeprol 300. Portal venous phase enhancement was significantly greater in the pancreas, pancreatic carcinomas, wall of the small intestine and portal vein with Iomeprol 400. The two independent readers considered Iomeprol 400 superior over Iomeprol 300 concerning technical quality, contribution of the contrast agent to the diagnostic value, and evaluability of vessels in the arterial phase. No differences were found for tumour delineation and evaluability of infiltration of organs adjacent to the pancreas between the two iodine concentrations. In conclusion the higher iodine concentration leads to a higher arterial phase contrast enhancement of large and small arteries in MSCT of the pancreas and therefore improves the evaluability of vessels in the arterial phase.

Virtual cystoscopy based on helical CT scan datasets: perspectives and limitations.

The purpose of the study was to simulate cystoscopy based on three-dimensional helical CT scan datasets in real-time in patients with tumours of the urinary bladder. A helical CT scan with double detector technology was carried out pre-operatively in 11 patients with histologically confirmed carcinoma of the urinary bladder and one patient with chronic cystitis. A non-enhanced scan was first performed, followed by an examination in the early phase of contrast medium enhancement. Further images were acquired after adequate filling of the bladder with contrast medium, approximately 30 min after injection. These data were transferred to a separate graphic computer workstation and reconstructed. The results were then compared with the cystoscopic and histopathological findings. All tumours of the urinary bladder identified at fibreoptic cystoscopy were shown on virtual cystoscopy. The best reconstruction results were obtained from data acquired 30 min after injection of contrast medium. The ureteric orifices were not visualized at virtual cystoscopy. These data lead us to conclude that, at present, virtual cystoscopy has not reached the quality of fibreoptic examination and remains restricted to use in specific cases, for example patients with urethral strictures.

[ECG-triggered MDR-CT for the detection of pulmonary metastases]. / EKG-getriggerte Mehrzeilen-Spiral-CT des Thorax zur Erkennung intrapulmonaler Metastasen.

PURPOSE: Comparison of multidetector-row CT (MDR-CT) of the chest with and without ECG triggering for the detection of pulmonary metastases. MATERIALS AND METHODS: Fifty patients with malignant tumors underwent CT of the chest. The unenhanced phase was performed with ECG-triggered MDR-CT and the contrast-enhanced phase with helical MDR-CT. The ECG-triggered and standard helical scans were interpreted in separate sessions, with the analysis determining the number and demarcation of the intrapulmonary nodules and the delineation of the mediastinal structure (rated 1 = excellent to 5 = poor). RESULTS: ECG-MDR-CT images detected 38 % more pulmonary nodules than MDR-CT. The detection rate for tumors < 5 mm was 64 % higher in ECG-triggered scans. The median demarcation rating of all pulmonary findings was 2 for ECG-MDR-CT and 3 for MDR-CT. The median demarcation rating of tumors < 5 mm was 3 for ECG-MDR-CT and 4 for MDR-CT. Mediastinal structures were better delineated by ECG-triggering. The median demarcation rating of the vessels and left bronchus was 2 for ECG-MDR-CT and 4 for MDR-CT. Detection rate and demarcation rating of pulmonary tumors and the delineation of mediastinal structures were not significant different for either CT technique. CONCLUSION: Our study indicates superiority for ECG-MDR-CT.

[Non-invasive, multi detector row (MDR) CT based computational fluid dynamics (CFD) analysis of hemodynamics in infrarenal abdominal aortic aneurysm (AAA) before and after endovascular repair]. / Blutflusssimulation mittels Computational-Fluid-Dynamics an aus CT-Daten rekonstruierten Aortenaneurysmata vor und nach Stent-Graft Implantation.

PURPOSE: Simulation, description and analysis of dynamic pressure in infrarenal abdominal aortic aneurysms (AAA) before and after endovascular repair. MATERIALS AND METHODS: During March 1996 and May 2001, 13 patients with AAA underwent endovascular treatment. The MDR-CT scans of these patients were used for the non-invasive analysis of the hemodynamics in the aorta with CFD software before and after endovascular repair. One pre-interventional and three post-interventional CT scans were analyzed for each patient. RESULTS: Compared to the pre-interventional simulation, endovascular treatment led to an average dynamic pressure decrease of 1057 Pa in 10 of 13 patients. During the subsequent course, the median of the dynamic pressure decreased in 8 of 13 patients. Vulnerable regions initially identified as high-pressure regions, like the docking area or the second stent limb, adapted to the pressure in the surrounding tissue in the course of time. CONCLUSION: CFD-based blood flow simulation offers the opportunity to analyze dynamic pressure in AAA before and after endovascular repair and allows a prognostic statement as to the possible homogenization of the pressure in abdominal stent-grafts.

Numerical simulation of air temperature and airflow patterns in the human nose during expiration.

Recovery of heat and water during expiration is an important but not yet fully understood function of the nose. The presented study investigated cooling of the expiratory air for heat recovery within the human nose applying numerical simulation. A numerical simulation in a bilateral three-dimensional model of the human nose based on computed tomography was employed. Temperature distribution and airflow patterns during expiration were displayed. Cooling of the expiratory air primarily takes place in the areas of inferior and middle turbinate. Areas of the highest decrease in temperature are characterized by turbulent airflow with vortices of low velocity. Numerical results showed good concordance with experimental in vivo temperature measurements. Heating of inspired air not only depends on inspiration but also on expiration. Cooling the warm expiratory air may be regarded as an important factor for heat recovery. Furthermore, the results demonstrate the close relation between heat exchange and airflow patterns.