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.

Aspects of computer-aided detection (CAD) and volumetry of pulmonary nodules using multislice CT.

With the superb spatial resolution of modern multislice CT scanners and their ability to complete a thoracic scan within one breath-hold, software algorithms for computer-aided detection (CAD) of pulmonary nodules are now reaching high sensitivity levels at moderate false positive rates. A number of pilot studies have shown that CAD modules can successfully find overlooked pulmonary nodules and serve as a powerful tool for diagnostic quality assurance. Equally important are tools for fast and accurate three-dimensional volume measurement of detected nodules. These allow monitoring of nodule growth between follow-up examinations for differential diagnosis and response to oncological therapy. Owing to decreasing partial volume effect, nodule volumetry is more accurate with high resolution CT data. Several studies have shown the feasibility and robustness of automated matching of corresponding nodule pairs between follow-up examinations. Fast and automated growth rate monitoring with only few reader interactions also adds to diagnostic quality assurance.

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.

Pulmonary nodules in spiral volumetric and single slice computed tomography.

Single slice acquisition of conventional CT and volume scanning of spiral volumetric CT are compared in terms of detection and assessment of pulmonary nodules. Spiral CT is supposed to be superior to conventional CT in detecting all lung nodules by scanning the complete lung volume, while conventional CT may miss nodules due to inconsistent levels of inspiration for single slices. Different technical procedures of spiral CT may change the imaging of nodules and other findings. Fifty-two patients with known or suspected lung nodules were examined by conventional CT and spiral CT. Number and size of lung nodules and imaging of other pulmonary findings were registered independently by two radiologists. Spiral CT showed 15 lung nodules not seen on conventional CT, and missed one nodule. Spiral CT imaging of nodules was superior in some cases (characterisation of benign nodules) because complete scanning provided more information than conventional CT. It was worse in some cases (small nodules, fibrosis, small pleural effusion) due to the greater partial volume effect and less mAs. Technically improved spiral CT with longer scanning facilities and a 180-degree algorithm may be able to replace conventional CT for this indication.

[A new method in the determination of individual delay time in bolus application in spiral CT]. / Neues Verfahren zur Bestimmung der individuellen Verzögerungszeit für die Bolusapplikation im Spiral-CT.

Helical-CT examinations, particularly CT angiography, require precise timing between the examination procedure and the individual dynamics of contrast medium distribution in the arteriovenous system of the patient. The necessary delay between contrast medium injection and onset of has usually been either estimated or determined by means of an additional helical CT examination. The present paper introduces a new technique which allows bolus analysis without an additional scan. Prior to a CT angiography with 10 patients, two techniques for bolus analysis (BA) were compared. Prior to diagnostic contrast medium enhanced examination, a native (BA I) and a dynamic (BA II) examination were performed. Ten seconds prior to the start of each examination, a 10 ml test bolus was applied with an injection flow rate of 3 ml/s. Both examinations lasted for 30 s. During BA I, increase in attenuation in the aorta was compared at different sites, during BA II consistently at the same site. Comparison of the individual peak times yielded a coefficient of correlation of r = 0.926. The median value for BA I was 18.4 +/- 5.4 s and 19.2 +/- 4.5 s for BA II. The difference between measurement of peak time was 1.2 +/- 1.16 s. This modified technique for bolus analysis during the primary native scan of the upper abdominal organs permits calculation of the required individual delay time between contrast medium application and scan start: no additional examination is required and the method can be performed with any helical CT unit.

[Virtual cystoscopy based on spiral CT data]. / Virtuelle Zystoskopie aus Spiral-CT-Datensätzen.

Simulation of three-dimensional cystoscopy based on helical CT scan data in real-time in patients with tumours of the urinary bladder. In three patients with histologically confirmed carcinoma of the urinary bladder, a helical CT scan with double detector technology was carried out preoperatively. A native scan was first performed, followed by an examination in the early contrast medium enhanced phase. After adequate contrasting of the urinary bladder (30 minutes latency), further images were acquired. These data were transferred to a separate graphic computer workstation and reconstructed. The results were then compared with the cystoscopic and pathohistological findings. All tumours of the urinary bladder identified at fiberoptic cystoscopy were also visualised by virtual cystoscopy. The best reconstruction results were obtained from data acquired after the 30-minute latency period. Virtual cystoscopy represents an interesting option in helical CT scanning, which is able to visualise polypoid tumours of the urinary bladder. Its clinical relevance, however, must be demonstrated in studies with a larger number of patients examined.

[Evacuation proctography: physiological variability and clinical relevance of the anorectal angle and the position of the pelvic floor]. / Evakuationsproktographie: Physiologische Streubreite und klinische Relevanz des Anorektalwinkels und der Beckenbodenlage.

Evacuation proctography is an important imaging method for the investigation of abnormalities of defecation. For this procedure, the most commonly carried out measurements are the ano-rectal angle and the position of the pelvic floor. The given mean values and the physiologically acceptable deviations vary just as much as the perceived clinical value of these measurements. 173 evacuation proctograms were evaluated in a prospective study; the subjective abnormalities were correlated with clinical findings. No significant correlation between the measurements from the proctograms and the clinical findings could be determined. The clinical relevance of these measurements is, therefore, uncertain.

[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.

Coarctations of descending and abdominal aorta: long-term results of surgical therapy.

PURPOSE: Nonarteriosclerotic and nonarteritic descending and abdominal aortic coarctation (DAAC) is a rare disease with a great variety of morphologic findings. The additional affliction of renal and other splanchnic arteries often affords complex corrective procedures. We report on our single-center long-term experiences with operative treatment of this malformation. METHODS: Over a period of 21 years, 15 patients (10 female and 5 male patients; age range, 8 to 57 years) were operated on for DAAC. Six patients had additional stenoses of eight renal arteries, and three had splanchnic arterial obstructions. At 4 to 25 years after the operation, all surviving patients underwent a clinical and a spiral computed tomography examination. RESULTS: There was one intraoperative death due to exsanguination after the rupture of a poststenotic aneurysm of the infrarenal aorta. Fourteen patients were discharged free of symptoms. During follow-up, four repeated operations were necessary for renal arterial bypass stenoses or aneurysms. One late death occurred as the result of an unrelated disease. CONCLUSIONS: Complete operative correction of DAAC usually can be accomplished as a single-stage procedure with low morbidity and mortality rates. The reconstruction of all renal arteries is essential to cure hypertension. Consequent follow-up is recommended for detection of late postoperative complications.

[Dynamic 3D imaging of peripheral vessels using color-coded Doppler ultrasound]. / Dynamische 3D-Darstellung der peripheren Gefässe mittels farbkodierter Dopplersonographie.

3-D reconstructions are established as post-processive methods in CT and MRI. However, these methods permit assessment of morphological findings only. To uncover functional relations on the basis of ultrasound would also be of paramount interest. For this purpose a specific method was developed for the acquisition and time-coded 3-D reconstruction in the diagnosis of peripheral vessels, in particular of the extracranial carotid artery. An imaging device (Acuson 128 XP) with a 7.5 MHz probe, a PC-controlled stepping motor and an imaging system (Kontron Mipron) was used. Data acquisition was performed scan-by-scan in a transverse plane with a slice thickness of 1 mm along the vessel. In every slice position multiple ECG-trigger delays during the cardiac cycle were used. Data were transferred to the imaging system via videosignal. In preliminary clinical application this dynamic 3-D reconstruction method yielded good spatial resolution of the complex physiological flow phenomena in the carotid bifurcation.

[Possibilities of virtual gastrointestinal endoscopy]. / Möglichkeiten der gastrointestinalen virtuellen Endoskopie.

Beside the technological development of the modalities, secondary image-reconstruction procedures are of increasing interest for diagnostic purposes and preoperative planning. Recently the simulation of endoscopic views--so called virtual endoscopy--has become available for presenting volume datasets. This new technique, usually based on CT and MRT data-sets, leads to new possibilities for examination of gastrointestinal organs and vasculature. Most interest has focussed on colon examinations, depending on a detailed knowledge of the technical procedure of the examination and additional experience of endoscopic techniques of the examiner. The procedures for the different parts of the gastrointestinal tract are explained.

[Atypical aortic coarctations in type I neurofibromatosis]. / Atypische Aortenkoarktationen bei Neurofibromatose Typ I.

From 1971 through 1996, 16 patients were operated on for atypical aortic coarctation. Three of them (two women, 18 and 27 years old, one boy, 13 years old) had typical signs of neurofibromatosis type I (NF1). All had renovascular hypertension due to suprarenal and/or interrenal aortic stenosis. Two had additional bilateral renal artery stenoses, one with a poststenotic aneurysm. In all patients a thoraco-abdominal aorto-aortic bypass was implanted. The renal artery stenoses were bridged by two aorto-renal, a prothesio-renal, and a spleno-renal bypass. Only one kidney had to be explanted 13 years after revascularization for a recurring hilar aneurysm after ex-situ reconstruction was found to be impossible. At their last follow-up examination (at 16, 14, and 9 years) all patients were normotensive without medication and had normal serum-creatinine measurements. Angiography or spiral-CT done in all patients showed normal function of all bypasses. In literature we found another 27 patients with neurofibromatosis operated on for atypical aortic coarctation. In these young and otherwise healthy patients, even complex reconstructions can be performed with a low rate of complications and excellent long-term results. Surgical therapy of all relevant stenoses (at best in a single procedure) is necessary for complete relief of renovascular hypertension. Consequent follow-up is advised for the detection of possible late complications, especially after exclusion of aneurysms.

[Portal computed tomography. Methodology and indications]. / Portale Computertomographie. Methodik und Indikationen.

CT arterioportography (CTAP) requires intra-arterial contrast material via the superior mesenteric (splenic) artery. Malignant hepatic tumors are characterized by arterial vascularization and only minimal portal blood supply. Portal contrast therefore reveals small tumors with a high sensitivity of 68-87%. Sensitivity is higher in metastatic tumors than in hepatocellular carcinomas. CTAP is the method of choice for evaluation of the number, size and location of hepatic tumors prior to surgical intervention. If the findings are unclear, additional magnetic resonance imaging and sonography during the operation are useful.