Tilt-table testing as a predictor of + GZ tolerance.

BACKGROUND: G-tolerance assessment is an essential element of both military pilot and pilot candidate evaluation. AIMS: Attempt at prediction of individual relaxed + Gz tolerance on the basis of head-up tilt (HUT) testing. SETTINGS AND DESIGN: In two stages, 20 healthy men at the mean age 21.5 years took part in this study. The first stage, a 45 min, HUT test was performed using the Westminster protocol. During the second stage each underwent a centrifuge evaluation in response to gradual onset rate profiles. METHODS AND MATERIAL: In each subject, heart rate (HR) and blood pressure (BP) before and at 2, 15 and 45 min of the tilt-test were recorded. The gravity-load centrifuge (GOR) studies were carried out [following the standard GOR programme, at 0.1 G%divide;s rate of gravity load increase until the gravity load tolerance limit (loss of peripheral vision) was reached]. STATISTICAL ANALYSIS USED: Relationships between variables were explored using Kendall's tau-B correlation coefficient. The critical P-level was one-tailed 0.05. RESULTS: In four of 20 subjects (20%), vasovagal syncope occurred during the tilt test. G-level tolerance of this group (of +Gz accelerations) lay in the range from +4 to +8.1 Gz, (+5.72 ? 0.86 Gz average) and was comparable to the group without syncope. Loss of consciousness did not occur in any subjects during the centrifuge test. No statistically significant correlation was observed between HR and BP during tilt test and tolerance to +Gz accelerations. CONCLUSIONS: The result of tilt testing, carried out according to the Westminster protocol, was not useful in predicting individual tolerance to +Gz gravity loads.

Magnetic resonance guided localization and biopsy of suspicious breast lesions.

Contrast-enhanced magnetic resonance imaging (MRI) is being used increasingly as a complementary diagnostic modality in breast imaging of preselected patients. The exclusion of multicentricity before surgery and the differentiation between a scar and a carcinoma are well-accepted indications of this method. Problems result when suspicious lesions found with MRI cannot be visualized with mammography or ultrasonography. In these cases, MRI-based guidance systems are needed to guide needle biopsy or allow localization of the lesion before surgery. At our institution, 167 MR-guided interventions (35 percutaneous biopsies and 132 preoperative localizations) have been performed with the use of different types of add-on devices during the past 3 years. Percutaneous biopsy (31 fine needle aspiration and four core biopsies) revealed 24 benign and 8 malignant lesions, 3 biopsies were insufficient. Histologic examination after MR-guided wire localization showed benign findings in 68 lesions (52%) and malignancy in 64 lesions (48%). Technical aspects, experiences, advantages, and disadvantages of our system as well as those of other devices are reported and discussed. MR-compatible equipment for interventions of the breast is demonstrated. In conclusion, we perform MR-guided interventions of the breast routinely in indicated cases at a rate of approximately 3-5% for all patients undergoing diagnostic contrast-enhanced MRI of the breast.

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries.

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30 degrees ) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70 degrees) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0-3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.

3D MR angiography of the entire aorta: modified application of the body-phased array coil for a single-shot technique.

OBJECTIVE: Evaluation of different contrast-enhanced MR angiography imaging protocols for visualization of the entire aorta in breath-hold technique. METHODS AND PATIENTS: Three different CE (0.15 mmol/kg) MRA protocols were evaluated by phantom and patient studies: (1) two separate MRA with conventional application of the body-phased array coil; (2) a single-shot MRA with modified application of the body-phased array coil; (3) a single-shot MRA with the body coil. Duplex sonography, CTA and DSA were used as standard of reference. RESULTS: In all examinations the entire aorta could be visualized. The best SNR was acquired with protocol (1). The SNR of protocol (2) was reduced if the sagittal body diameter of the patient was greater than 20 cm and decreased significantly with diameters over 30 cm. By the use of protocol (3) the SNR was notably poor. The quality scored for the visualization of the entire aorta was 97.5% (protocol 1); 92.5% (protocol 2); and 80.0% (protocol 3). CONCLUSION: In most cases the modified application of the body-phased array coil allows the imaging of the entire aorta as a single-shot 3D CE MRA in diagnostic quality.

[Multislice CT of the abdomen--current indications and future trends]. / Mehrschicht-Spiral-CT des Abdomens - Aktuelle Indikationen und zukünftige Trends.

Multislice CT systems allow the simultaneous acquisition of multiple slices per gantry rotation. In combination with faster gantry rotation times of 0.5 seconds, the abdominal structures can be displayed in higher spatial and temporal resolution. In MS-CT of the liver it is possible to scan the entire organ with an optimal slice thickness of 2 - 3 mm within a defined perfusion phase in less than 10 seconds. This results in an improved detection and characterization of focal liver lesions. A high-quality, 3-dimensional reconstruction of the hepatic arterial and portalvenous system is obtained with the same data set. The diagnostic use of the simultaneously acquired perfusion data will lead to a better characterization of focal liver lesions in the future. The diagnostics of the pancreas also profits from MS-CT, especially for the detection of small tumors and the evaluation of resectability of a pancreatic carcinoma. All abdominal structures can be displayed in a coronal view without loss of image quality because of the almost isotropic voxels obtained. This proves to be beneficial for the preoperative diagnostics of renal cell carcinomas, especially if the tumor extension into adjacent organs (e. g., liver or spleen) in the longitudinal direction has to be evaluated. The multiplanar display and the sophisticated 3-dimensional reconstruction tools have a substantial value for the abdominal CT angiography. It proves to have a major diagnostic impact on acute abdominal aortic and visceral arterial diseases because even large distances in the z-direction can be covered with high spatial resolution.

[Diagnostic imaging in hepatosplenic candidiasis]. / Bildgebende Diagnostik bei hepatolienaler Candidose.

Hepatosplenic candidiasis is a severe complication encountered in immuno-compromised patients. Different imaging techniques can establish the diagnosis. After an introduction to the pathophysiological and clinical principles, the role of plain radiography, radionuclide scans, ultrasound, computed tomography and magnetic resonance imaging is discussed.

[CT-supported virtual intra-arterial endoscopy after stent implantation: phantom studies and the initial clinical results]. / CT-gestützte virtuelle intraarterielle Endoskopie nach Stentimplantation: Phantomstudien und erste klinische Ergebnisse.

PURPOSE: To evaluate the facilities of computed tomographic virtual intraarterial endoscopy (VIE). Imaging of an intravascular stent in a phantom study and clinical assessment in 10 patients. METHODS: The optimal scan parameters for different 3 D reconstructions (MIP, SSD, VIE) were determined in a vessel phantom with intravascular stent. Furthermore, in vitro stenoses were analysed and initial in vivo investigations were performed. RESULTS: The quality of CT-angiography (CTA) depended on the scanning parameters. VIE allowed the reconstruction of the intravascular surface of a stent. CONCLUSION: VIE is a new kind of post-processing CTA reconstruction. It permits the visualisation of the intravascular structure of a stent. In vitro relevant stenoses were correctly detected. First clinical investigations support these results.

[Three-dimensional surface imaging of the larynx and trachea by spiral CT: virtual endoscopy]. / Dreidimensionale Oberflächendarstellung des Larynx und der Trachea mittels Spiral-CT: virtuelle Endoskopie.

A survey presents the technical conditions and facilities of the computed tomographic virtual endoscopy. The inner surface of the upper airway was reconstructed from the data set of a helical CT. The anatomical structures were visualized in over 80 patients. 15 patients with a suspected tracheal stenosis were additional investigated. The virtual endoscopy allowed an identification of the anatomical structures. Pathological endoluminal findings, as stenosis, were investigated successfully. The virtual endoscopy combines the advantages of helical CT and the imaging of the endoluminal surface. Compared with the endoscopic examination the non-invasive technique offers additional indications, especially in high-risk patients or non-passable Stenosis.

[Impact of different iodine concentrations on abdominal enhancement in biphasic multislice helical CT (MS-CT)]. / Der Einfluss verschiedener Jodkonzentrationen auf die Kontrastierung der Oberbauchorgane im biphasischen Mehrschicht-Spiral-CT.

UNLABELLED: Impact of different iodine concentrations on abdominal enhancement in biphasic multislice helical CT (MS-CT). PURPOSE: To evaluate if different iodine concentrations of a contrast material (c.m.) have an impact on abdominal enhancement in MS-CT during the arterial (AP) and portal venous phase (PVP). MATERIALS AND METHODS: 75 patients underwent biphasic CT of the abdomen. They were assigned to three equally sized groups. For all patients a non-ionic c.m. (iopromide, Ultravist, Schering AG, Berlin) with different iodine concentrations and a constant total iodine load of 37 g with an injection flow rate of 4 ml/s was used. The volume of the c.m. differed depending on the iodine concentrations: group 1 (123 ml of 300 mgl/ml); group 2 (112 ml of 335 mgl/ml); group 3 (100 ml of 370 mgl/ml). The scan delay was optimized by using a bolus tracking device. The groups were compared concerning their mean enhancement of aorta, spleen, pancreas, and liver in the AP and PVP. RESULTS: The comparison of the three groups showed an improved enhancement in aorta, spleen, and pancreas during the AP by using the higher c.m. concentrations. In the PVP the c.m. enhancement of aorta, liver, spleen, and pancreas was independent of the administered c.m. concentration. CONCLUSION: Higher iodine concentrations of c.m. have a positive impact on abdominal enhancement during the AP. The concentration has no influence on the enhancement during the PVP of abdominal MS-CT.

[Contrast media-enhanced 3D MR angiography of the peripheral vessels using a "tracking technique": preliminary results]. / Kontrastmittelgestützte 3D-MR-Angiographie der peripheren Gefässe in "Schrittverschiebe-Technik": Erste Ergebnisse.

PURPOSE: A single bolus contrast-enhanced (CE) 3D MR angiography (MRA) of the peripheral vessels was evaluated using a combination of two surface coils with manual incrementation of the patient table. METHODS: Fifteen patients with peripheral arterial occlusive disease were examined using an ultrafast CE 3D MRA (TR/ TE/FA 5 ms/2 ms/30 degrees). For imaging of the vessels from the distal aorta to the arteries of the lower limbs a combination of a body-array coil and a flexible extremity coil was applied. A coil-interface was designed for a connection of the two coils. The examinations were performed after a single bolus of 0.15 mmol Gd-DTPA/kg. The tracking technique included a manual incrementation of the patient table and the coil-interface had to be switched from the body-array coil to the flexible extremity coil. For acquisition delay measurement of the MR sequence the individual transit times of the contrast material were detected by using a test bolus. RESULTS: CE 3D MRA was technically successful in 14/15 cases. In one case two vascular segments were not imaged. The qualitative evaluation of all vascular segments documented a high quality without any significant differences between the proximal and the distal arteries (p < 0.05). All hemodynamically significant stenoses (n = 15) and all vessel occlusions (n = 36) were detected. CONCLUSION: The single bolus CE 3D MRA using a tracking technique is a favourable method in the evaluation of patients with peripheral arterial occlusive disease.

[Multislice CT angiography: optimization of scan parameters in a vascular phantom]. / Mehrschicht Spiral-CT-Angiographie: Optimierung der Untersuchungsparameter an einem Gefässphantom.

PURPOSE: The aim of this study is to determine the optimal scan parameters for the evaluation of experimental vascular stenoses with a multislice-helical CT. MATERIAL AND METHODS: A vascular phantom consisting of four tubes with an inner diameter of 8 mm and with experimental stenoses of 50%, 75% and 90% was scanned in different tube orientations using a multislice-CT scanner (LightSpeed QX/i, GE, Milwaukee, USA). Examinations were performed with increasing collimations (1.25-5 mm), tube currents (100-300 mA) and two different table speeds (0.75 HQ mode and 1.5 HS mode). RESULTS: The most exact measurements were obtained in tubes angulated parallel to the scan direction with a collimation of 2.5 mm in the HQ mode (7.5 mm/rot.). An almost equivalent accuracy was obtained in the HS mode (15 mm/rot.) with a collimation of 2.5 mm when higher tube currents (300 mA) were employed. The degree of stenoses was overestimated when the tube was angulated perpendicular to the z-axis. CONCLUSION: Multislice-CT provides a good detection rate of vascular stenoses especially at 0 degree and also at 45 degrees angulation in the HQ mode. The use of the HS mode with higher tube currents allows scanning of longer distances with almost identical accuracy.

[Spiral CT in arytenoid cartilage dislocation: the optimization of the study parameters with a cadaver phantom and its clinical evaluation]. / Spiral-CT bei Aryknorpel-Dislokation: Optimeirung der Untersuchungsparameter am Leichenphantom und klinische Evaluation.

PURPOSE: To evaluate an optimal scan protocol in a cadaver phantom and its clinical assessment in 40 patients. MATERIALS AND METHODS: In a cadaver larynx phantom helical CT (HiSpeed Advantage; GE, Milwaukee, Wis) was performed with increasing collimation (1-10 mm) and pitch (1.0-3.0). 40 patients with an immobile vocal cord were randomly assigned to undergo CT with a certain protocol. RESULTS: Best resolution was obtained with a collimation of 1 mm and pitch 1. The pitch could be increased up to 2 without losing information. With a collimation of 3 mm and higher, anatomical details were missed. In the patient studies a combination of 1 mm collimation with a pitch of 2.0 showed less motion artifacts than a pitch of 1.0. CONCLUSION: The quality of CT imaging of the arytenoid cartilage depends greatly on the scanning parameters, the compliance of the patients and the mineralisation of the cartilage. For clinical assessment a collimation of 1 mm with a pitch of 2 is recommended. The increase pitch has the advantage of shorter acquisition times and decreased radiation exposure.

[Diagnosis of lung embolism and underlying venous thrombosis in multi-slice spiral CT]. / Diagnostik der Lungenembolie und zugrundeliegender Venenthrombosen in der Mehrzeilen-Spiral-CT.

AIM: To determine the value of multi-slice CT for the diagnosis of acute pulmonary embolism and an underlying venous thrombosis. METHODS: 70 patients with clinically suspected acute pulmonary embolism were examined. Using multi-slice CT a combined examination of the pulmonary arteries and the veins of the lower limb, pelvis and abdomen was performed. Only one single bolus of 150 ml iopromid 300 was injected into a cubital vein with a flow of 4 ml/s. First, the pulmonary arteries were scanned with a slice thickness of 2.5 mm and a pitch of 1.5. On arrival of the contrast medium at the popliteal veins, indicated by bolus trakking, the veins of the lower limbs up to the end of the inferior vena cava were imaged using a slice thickness of 3.75 mm and a pitch of 1.5. The results could be compared with a ventilation-perfusion scan in 48 cases, with a Doppler ultrasound examination in 46 cases, and with a venography in 10 cases. Furthermore, the image quality of all arterial and venous regions was subjectively assessed. RESULTS: In all patients who underwent multi-slice CT the pulmonary arteries as well as the veins of the lower half of the body could be recorded completely. Regarding the pulmonary arteries the image quality showed excellent results for the central and segmental arteries. The region up to the 3rd division in subsegmental branches could be sufficiently judged. More peripherally, a diagnostic assessment was not possible. The image quality of the veins was excellent in all sections, except the calf, where a reliable diagnosis could not be made. The comparison with the other techniques confirmed the superiority of multi-slice CT concerning the central and segmental pulmonary arteries and the veins from the popliteal vein to the inferior vena cava. In contrast, peripheral pulmonary emboli can be detected more certainly in ventilation/perfusion scans. The veins of the calf can be evaluated more reliably with venography. CONCLUSION: Multi-slice CT proved to be an outstanding tool in the diagnosis of acute pulmonary embolism. The clinically suspected disease and a causing venous thrombosis can be detected in a fast and reliable way. At present, multi-slice CT is not suitable for the recognition of peripheral emboli. However, expected technical developments hold promise for future improvements.

[The MR imaging of the vena cava system: a comparison of different technics]. / MR-Bildgebung des Hohlvenensystems: Vergleich unterschiedlicher Techniken.

PURPOSE: To evaluate the feasibility and diagnostic value of there different MR angiographic imaging techniques for the assessment of the central body veins. METHODS: 25 investigations of the central veins were performed with an ECG-triggered black-blood HASTE sequence, a segmented 2D cine FLASH sequence and a contrast-enhanced 3D-FISP angiography. The results of the MR-studies were compared with those of spiral CT or venography. RESULTS: The HASTE sequence was suitable for the assessment of the complete central body vein system also in less cooperative patients. The combination with the 2D cine FLASH sequence enabled the detection of intravascular tumors or thromboses and the graduation of subtotal occlusions. The involvement of the right atrium was proved in 2/2 cases. The attachment at the vessel wall could be assessed. Only contrast-enhanced 3D MRA visualized the renal veins and complex collaterals sufficiently. But this procedure has to be done in a strict breath-hold technique. CONCLUSION: In the present study all thromboses and tumor cones of the central body veins were detected with the combined use of HASTE/Cine FLASH. For the assessment of complex collaterals and the renal vessels the application of contrast-enhanced 3D-MRA techniques is necessary.

[An anatomically adapted variation of the tube current in CT. Studies on radiation dosage reduction and image quality]. / Anatomisch adaptierte Variation des Röhrenstroms bei der CT. Untersuchungen zur Strahlendosisreduktion und Bildqualität.

PURPOSE: To assess the impact of a method for anatomically adapted tube current variation. The resulting CT image quality was evaluated quantitatively and qualitatively. METHODS: CT scans of 100 patients were performed with a constant tube current (Group 1) and another 100 patients with an anatomically adapted tube current (Group 2). The CT tube current was varied during a 360 degrees tube rotation reflecting the measured density values extracted from two perpendicular scout views. The standard deviation of densities of defined regions was measured. The image quality was ranked (1 = non-diagnostic-5 = excellent) by three radiologists. RESULTS: The effective tube current could be reduced by an average of 8.9% (0-20.4%). The mean tube current reduction depended on the body region: pelvis (13.2%), abdomen (8.4%) and thorax (3.3%). The image quality was not significantly reduced in Group 2. CONCLUSION: The method for anatomically adapted tube current variation leads especially in the pelvis to a significant mAs reduction without considerable loss of image quality.

[Signal characteristics of x-ray contrast media and their interaction with gadolinium-DTPA in MRT]. / Signalverhalten von verschiedenen Röntgenkontrastmitteln sowie deren Wechselwirkung mit Gadolinium-DTPA in der MRT.

T1 and T2 weighted signals derived from various radiological contrast media were studied during MRT spin-echo sequences. In addition, the interaction between radiological contrast media and Gadolinium-DTPA concerning T1 signals was evaluated. Ionic (ioxitalaminic acid) and non-ionic radiological contrast media (Iopromid, Iotrolan) were used in diagnostic concentrations. Measurements were carried out with a superconductive magnet of 1.5 Tesla. Radiological contrast media produced significantly higher signals than a physiological sodium chloride solution in T1-weighted spin-echo sequences. Even small amounts (15% of total volume) of radiological contrast media during T1-weighted spin-echo sequences led to a significant reduction (about 25%) of the signal intensity of a 2 mM Gadolinium-DTPA solution. This may lead to diagnostic problems, as was shown in a series of 25 MR arthrograms of the shoulder. It is recommended than an interval of at least 6 hours should elapse between the use of a radiological contrast medium and an MRT examination.

[Results of a contrast-medium supported 3D MR-angiography in respiratory arrest following optimization of contrast medium bolus]. / Ergebnisse einer kontrastmittelgestützten 3D MR-Angiographie in Atemstillstand nach Optimierung des Kontrastmittelbolus.

PURPOSE: Reduction of the contrast material volume by optimised bolus administration during a breath-hold 3D MR angiography and its clinical value. MATERIALS AND METHODS: Breath-hold ultrafast 3D gadolinium-enhanced MR angiography (TR 5 ms, TE 2 ms, FA 20 degrees) of the thoracic and abdominal aorta was performed in 50 patients and correlated with an i.a. DSA. 25 patients (group 1) were examined with a contrast material volume of 40 ml Gd-DTPA and three successive acquisitions at fixed intervals (25, 53 and 81 s) after start of the contrast material injection. Another group of 25 patients (group 2) received only 20 ml Gd-DTPA and the start of the MR acquisition was determined individually by prior evaluation of the contrast material transit times after injection of a test bolus. The signal-to-noise (S/N) and contrast-to-noise (C/N) ratios were compared and a subjective image quality rating (0-3) by three reviewers was achieved in both groups. RESULTS: A total of 37 vascular pathologies were correctly detected by MR angiography compared to i.a. DSA. The grading of stenoses was overestimated in some cases. The S/N and C/N were higher in group 2 (63.2 and 50.1) than in group 1 (58.0 and 38.9). The subjective ratings also showed better results in group 2 (2.76) than in group 1 (2.20). CONCLUSION: The ultrafast gadolinium-enhanced 3D MR angiography allowed a reliable visualisation of the thoracic and abdominal aorta and its branches in a single breath-hold. An optimised examination with a reduced contrast material volume can be achieved by an individual adaptation of the MR acquisition to contrast material administration after measurement of the contrast material transit times.

[Determination of contour clarity in contrast-enhanced MR angiography: definition and clinical evaluation exemplified by ECG-triggered imaging of the thoracic aorta]. / Konturschärfenbestimmung in der kontrastmittelunterstützten MR-Angiographie: Definition und klinische Evaluation am Beispiel der EKG-getriggerten Darstellung der thorakalen Aorta.

PURPOSE: The sharpness of the vessel contour in 3D contrast-enhanced MR angiography is defined by particular measurements of the signal intensity. To evaluate the facilities of an ECG-triggered data acquisition to optimize the MRA image quality of the thoracic aorta. METHOD: In phantom studies the sharpness of the vessel contour was defined as the distance of the extraluminal signal-minimum to the extraluminal maximum. Afterwards 30 examinations of the thoracic aorta with and without the use of an ECG-triggering were evaluated with regard to the sharpness of the vessel outline. RESULTS: The presented definition of the signal intensity is suitable for objective measurements of the vessel outline. At the level of the ascending aorta, ECG-triggered data acquisition increased the image quality significantly. CONCLUSIONS: An easy, practicable definition enables measurements of the sharpness of the vessel outline. ECG-triggered data acquisition is recommended for optimal visualization, especially of the ascending aorta.

[Slice sensitivity profile and image pixel noise of multi-slice spiral CT in comparison with single slice spiral CT]. / Schichtempfindlichkeitsprofile und Bildpunktrauschen einer Mehrschicht Spiral-CT im Vergleich zu einer Einzelschicht Spiral-CT.

PURPOSE: Presentation and evaluation of slice sensitivity profile and pixel noise of multi-slice CT in comparison to single-slice CT. METHODS: Slice sensitivity profiles and pixel noise of a multi-slice CT equipped with a 2D matrix detector array and of a single-slice CT were evaluated in phantom studies. RESULTS: For the single-slice CT the width of the slice sensitivity profiles increased with increasing pitch. In spite of a much higher table speed the slice sensitivity profiles of multi-slice CT were narrower and did not increase with higher pitch. Noise in single-slice CT was independent of pitch. For multi-slice CT noise increased with higher pitch and for the higher pitch decreased slightly with higher detector row collimation. CONCLUSIONS: Multi-slice CT provides superior z-resolution and higher volume coverage speed. These qualities fulfill one of the prerequisites for improvement of 3D postprocessing.

[Incidence and distribution pattern of pulmonary saddle emboli: Diagnosis by electron beam tomography (EBT)]. / Häufigkeit und Verteilungsmuster pulmonalerSattelembolien: Diagnostik mittels Elektronenstrahl-Computertomographie (EBT).

PURPOSE: To determine the incidence of acute pulmonary emboli extending across the bifurcation of the main pulmonary artery, lobar arteries or segmental arteries (interpulmonary, interlobar or intersegmental saddle emboli, respectively). METHODS: 128 patients with clinically suspected acute pulmonary embolism underwent electron beam tomography (EBT). 140 scans were acquired in the continuous volume scanning mode (3 mm slice thickness). 100 ml of contrast material were intravenously administered. Studies were reviewed for the presence of acute pulmonary embolism and the number and location of interpulmonary, interlobar or intersegmental saddle emboli. Saddle emboli were defined as emboli extending across the bifurcation of a vessel into both branches by at least 5 mm each. RESULTS: 30 of 128 (23.4 %) patients (15 men; mean age 59 +/- 17 years) had acute pulmonary embolism. One or more saddle emboli were present in 20 of 30 patients (66.7 %), a total of 77 saddle emboli were detected ranging from 1 to 10 per patient. Distribution of the saddle emboli in the 20 patients was as follows: 5 interpulmonary, 28 interlobar and 44 intersegmental. CONCLUSIONS: Pulmonary saddle emboli are present in the majority of patients with acute pulmonary embolism. They are often multiple and may be found at different levels of the pulmonary arterial vasculature.