Visualization of flow patterns from stents and stent-grafts in an in vitro flow-model.

RATIONALE AND OBJECTIVES: The authors determine flow characteristics and pressure gradients of different stents and stent grafts in an in vitro flow-model. METHODS: Five vascular stents (Memotherm, Cragg, two Palmaz P308, Strecker, and Wall) and one stent graft (Cragg EndoPro System 1), equal in length (60 mm) and diameter (10 mm), were deployed in a closed flow-model. The inner diameter of the tube measured 9 mm. Flow at 1.5 L/min, 6 L/min, and 10 L/min was simulated. Flow patterns were visualized by anionic particles illuminated with two Helium-Neon lasers. Laminary flow characteristics and pre-/poststent pressure gradients were determined in either expanded stent, 25% stenosis, or 50% stenosis. RESULTS: Stent implantation induced a decrease of laminary flow compared with an unstented tube with and without concentric 25% stenosis (P < 0.01) at all flow rates and an increase of pressure gradients compared with an unstented tube for flow rates greater than 1.5 L/min (P < 0.01) (except for Cragg EndoPro System 1 stent, which revealed an increase of the pressure gradient at a flow rate of 1.5 L/min [P < 0.01]). Memotherm stent permitted maximum of laminary flow at all flow rates and stenoses (expanded: 79.50% at 1.5 L/min to 69.90% at 10 L/min; P < 0.01). Memotherm and Palmaz permitted lowest pressure gradients (P < 0.01). All of the endoprostheses demonstrated laminary flow at 50% stenosis. CONCLUSIONS: The investigated stents and stent grafts showed different severity of flow disturbances and pressure gradients at different graded stenoses. Inadequate stent depolyment bears the risk of creating less laminary flow and pathologic pressure gradients. Because flow disturbances and pressure gradients may influence neointimal hyperplasia, stent design and completeness of stent unfolding are important regarding the appearance of postinterventional restenoses.

Pulmonary Wegener's granulomatosis: correlation between high-resolution CT findings and clinical scoring of disease activity.

STUDY OBJECTIVE: To evaluate the usefulness of high-resolution CT (HRCT) for monitoring pulmonary disease activity in Wegener's granulomatosis (WG). DESIGN: Prospective study of CT and clinical data. SETTING: Main referral hospital for rheumatic diseases and department of diagnostic radiology of collaborating university hospital. PATIENTS: Seventy-three patients with WG underwent 98 staging examinations using HRCT. The status of pulmonary disease activity at the time of examination was scored according to clinical, bronchoscopic, BAL, and radiographic findings as follows: activity (n=25, group 1), past activity (n=45, group 2) and lack of any pulmonary disease (n=28, group 3). HRCT findings were correlated with the clinical scoring of pulmonary disease activity. RESULTS: Of 98 staging examinations 78 (79.6%) revealed abnormal CT scans showing the following main abnormalities: (a) nodules or masses (group 1: 16 [60.4%], group 2: 9 [20%]); (b) parenchymal bands (group 1: 12 [48%], group 2: 27 [60%], group 3: 6 [21.5%]); (c) septal thickening (group 1: 8 [32%], group 2: 6 [13.3%]); (d) parenchymal opacification (group 1: 7 [28%], group 2: 4 [8.9%]); and (e) pleural irregularity (group 1: 14 [56%], group 2: 22 [49%], group 3: 9 [32%]). Nodules/masses and areas of parenchymal opacification were significantly associated with florid disease activity of the lungs. Parenchymal bands and septal thickening were observed in both groups with pulmonary involvement, but statistical analysis revealed no significant difference. Pleural irregularities were nonspecific. CONCLUSION: HRCT may be a useful adjunct to clinical scoring of pulmonary disease activity in patients with WG and suspected lung involvement.

[Ultra-rapid T2-weighted MR imaging during suspended respiration for the examination of focal lesions of the liver: a comparison of TSE, HASTE and HASTE-STIR sequences using a CP body array coil]. / Ultraschnelle T2-gewichtete MR-Bildgebung in Atemstillstand zur Untersuchung fokaler Leberläsionen: Ein Vergleich von TSE-, HASTE- und HASTE-STIR-Sequenzen unter Verwendung einer CP-Körper-Arrayspule.

PURPOSE: A comparison of ultra rapid T2-weighted HASTE and HASTE-STIR sequences during suspended respiration for the detection of focal lesions of the liver. MATERIAL AND METHODS: Twenty-one patients (59 +/- 12 years) with a total of 33 focal lesions (7 < or = 1 cm, 19 < or = 3 cm; 17 cystic liquid and 16 solid lesions) were examined with a 1.5 T MR apparatus. Sequences: T2 weighted HASTE (TEeff = 64 ms, 90 ms), HASTE-STIR (TEeff = 64 ms, 81 ms) TSE (TE = 132 ms) and T1-weighted FLASH 2D. RESULTS: The T2-weighted TSE and both HASTE sequences showed all the lesions. Two out of the 33 lesions were not demonstrated by the other sequences. Best image quality without movement artefacts and the best resolution of the lesions in the T2-weighted sequences, with the most favourable contrast/noise ratio (36.6 +/- 33.1) and signal/noise ratio (20.8 +/- 10.5) resulted from the HASTE 90, followed by the HASTE 64 sequence (27.5 +/- 24.2; 24.6 +/- 9.1). Both these techniques were superior to the TSE sequence (23.9 +/- 29.4; 13.9 +/- 7.4), which resulted in movement artifacts. With the HASTE-STIR sequences it was possible to show 31 and 32 of the 33 lesions respectively, with very good resolution but poor signal/noise ratio. CONCLUSION: HASTE sequences have the potential of improving the diagnosis of focal liver lesions.

Restenosis of peripheral stents and stent grafts as revealed by intravascular sonography: in vivo comparison with angiography.

OBJECTIVE: Our objective was to compare intravascular sonography with digital subtraction angiography (DSA) in the assessment of luminal dimension and morphologic features of endovascular stents and stent grafts. MATERIALS AND METHODS: Thirty-seven pelvic and 24 femoral stents (12 Wall-stents; 27 covered and 22 uncovered nitinol stents) in 50 patients were evaluated 15 +/- 10 months after implantation by DSA and intravascular sonography. The degree of maximum instent restenosis as revealed by DSA and intravascular sonography was compared for each location. Morphologic features of the stents and stenoses were also assessed. RESULTS: Intravascular sonography and DSA correlated well (R2 = .96) in determining in-stent restenosis. In-stent restenosis was underestimated by 13% +/- 6% by DSA compared with intravascular sonography. Differences in determining in-stent restenosis with intravascular sonography and DSA were not associated with severity of stenosis or type of stent. Intravascular sonography revealed incomplete expansion of stents in 21 cases, whereas DSA revealed incomplete expansion of stents in seven cases. The intra- and interobserver variabilities in our study were 4% and 5%, respectively. CONCLUSION: In-stent restenoses are underestimated with DSA. Intravascular sonography is superior to DSA for detection of incomplete stent expansion.

Biomechanical aspects of the subarachnoid space and cervical cord in healthy individuals examined with kinematic magnetic resonance imaging.

STUDY DESIGN: In vivo flexion-extension magnetic resonance imaging studies of the cervical spine were performed inside a positioning device. OBJECTIVE: To determine the functional changes of the cervical cord and the subarachnoid space that occur during flexion and extension of the cervical spine in healthy individuals. SUMMARY OF BACKGROUND DATA: As an addition to static magnetic resonance imaging examinations, kinematic magnetic resonance imaging studies of the cervical spine were performed to obtain detailed information about functional aspects of the cervical cord and the subarachnoid space. The results were compared with published data of functional flexion-extension myelograms of the cervical spine. METHODS: The cervical spines of 40 healthy individuals were examined in a whole-body magnetic resonance scanner from 50 degrees of flexion to 30 degrees of extension, using a positioning device. At nine different angle positions, sagittal T1-weighted spin-echo sequences were obtained. The images were analyzed with respect to the segmental motion, the diameter of the subarachnoid space, and the diameter of the cervical cord. RESULTS: The segmental motion between flexion and extension was 11 degrees at C2-C3, 12 degrees at C3-C4, 15 degrees at C4-C5, 19 degrees at C5-C6, and 20 degrees at C6-C7. At flexion, a narrowing of the ventral subarachnoid space of up to 43% and a widening of the dorsal subarachnoid space of up to 89% (compared with the neutral position, 0 degrees) were observed. At extension, an increase in the diameter of the ventral subarachnoid space of up to 9% was observed, whereas the dorsal subarachnoid space was reduced to 17%. At flexion, there was a reduction in the sagittal diameter of the cervical cord of up to 14%, and, at extension, there was an increase of up to 15%, compared with the neutral position (0 degrees; these values varied depending on the cervical segment. Statistically significant differences (P < 0.05) were found between flexion and extension in the diameter of the ventral and dorsal subarachnoid space and in the diameter of the cervical cord. CONCLUSIONS: Compared with the results of previous studies using functional cervical myelograms, kinematic magnetic resonance imaging provides additional noninvasive data concerning the physiologic changes of the cervical subarachnoid space and the cervical cord during flexion and extension in healthy individuals.

Kinematic MR imaging of the ankle--initial results with ultra-fast sequence imaging.

PURPOSE: In order to evaluate the advantages of ultra-fast MR sequences, kinematic MR imaging studies were performed in 4 patients with osteochondritis dissecans of the talus and in 12 healthy volunteers. MATERIAL AND METHODS: The patients and volunteers were placed inside a custom-made positioning device. Sagittal ultra-fast T2-weighted turbo gradient-echo sequences and HASTE sequences were obtained during active joint motion from dorsiflexion to plantar flexion. Eight sagittal slices were scanned separately to cover this ankle motion. In each slice, 8 to 10 images were obtained in 12-s or 18-s periods. RESULTS: Adequate image quality for analyzing the normal kinematics of the ankle was obtained in all subjects. At surgery, the osteochondral fragment was found to be mobile in 3 of the 4 of the patients. In none of these cases was fragment mobility observed on kinematic MR imaging. No motion of the fragments was observed in the fourth patient, neither at surgery nor on kinematic MR imaging. CONCLUSION: Ultra-fast MR imaging sequences made it possible to produce kinematic MR imaging studies of active joint motion. The positioning device was useful for guiding joint motion in patients and for obtaining adequate image quality.

[3D-CT angiography and duplex sonography compared to arteriography in carotid stenoses]. / 3D-CT-Angiographie und Duplexsonographie im Vergleich zur Arteriographie bei Karotisstenosen.

PURPOSE: To determine the value of 3D-CT angiography, duplex sonography in comparison to selective digital subtraction angiography for evaluation of carotid artery stenoses. METHODS: 30 patients with 51 stenoses of carotid artery underwent 3D-CT angiography, duplex sonography and angiography. Quantification of stenosis was determined according to the NASCET study and categorized into mild (0-29%), moderate (30-69%), severe (70-99%) and occluded (100%). RESULTS: The agreement of 3D-CT angiography with intraarterial digital subtraction angiography (DSA) was 62% (r = 0.89; p < 0.0001) and of duplex sonography with DSA was 77% (r = 0.94; p < 0.0001). Both modalities underestimated one occlusion as stenosed. In the evaluation of moderate and severe stenoses 3D-CT angiography showed an agreement with DSA in 50% (duplex: 88%) and 55% (duplex: 89%) respectively and was inferior to duplex sonography. CONCLUSION: 3D-CT angiography is inferior to duplex sonography in the evaluation of carotid stenosis and not useful as a screening or reference examination.

[CT morphology of fractured thoraco-lumbar vertebrae after transpedicular spongiosaplasty and use of internal fixator]. / CT-Morphologie frakturierter thorakolumbaler Wirbelkörper nach transpedikulärer Spongiosaplastik und Fixateur-interne-Anlage.

PURPOSE: An analysis of the CT morphology of fractured thoraco-lumbar vertebrae after treatment with internal fixation and transpedicular spongiosaplasty (SP). MATERIAL AND METHOD: 30 patients were examined following trauma and surgery after about 12 and 30 months by means of CT. The following were evaluated: width of the spinal canal; height of the vertebra and intervertebral space; degree of kyphosis; position, size and appearance of the SP and of the vertebral body. RESULTS: The width of the spinal canal was reconstituted in 91%; in 83% the anterior vertebral margin and in 35% the intervertebral space was reduced. A kyphosis of 8.9 degree was found on the followup examination. The SP showed a reduction in size (18/30) or could no longer be defined (6/30). Hypodense areas (28/30) with cavitation (12/30) were found in the vertebral body and the SP could be identified by a sclerotic margin (22/30). CONCLUSION: Treatment by this form of therapy was successful, reaction of the vertebral body against the spongiosaplasty could be identified.

[Comparison of T2-weighted turbo spin-echo and ultrafast HASTE sequence in the diagnosis of cervical myelopathies and spinal stenoses and static and kinematic MRT of the spine]. / Vergleich von T2-gewichteter Turbo-Spin-Echo- und ultraschneller HASTE-Sequenz in der Diagnostik von zervikalen Myelopathien und Spinalstenosen mit der statischen und kinematischen MRT der Halswirbelsäule.

PURPOSE: The purpose of this study was to compare HASTE-sequence with T2-weighted TSE-sequence in the detection of cervical myelopathy and cervical spinal stenosis in kinematic MRI. METHODS: 24 patients with degenerative disease of the cervical spine were studied. Images were evaluated according to the following criteria: artifacts, delineation of the vertebra, disks and degenerative changes, grade of spinal stenosis (grade 0-3) and evaluation of the cervical spinal cord. RESULTS: Due to image blurring and artifacts, evaluation and delineation of the cervical spine was possible in all cases in the T2-weighted TSE-sequence, but only in 23 of 24 patients using HASTE-sequence. Differentiation between osteophytes and disks was obtained in most cases (23/24) in the T2-weighted TSE-sequence but none in the HASTE-sequence. Cervical myelopathy was observed in 4 patients in T2-weighted TSE images but only in two cases using HASTE-sequence. Compared to T2-weighted TSE-sequence spinal canal stenosis was underestimated using HASTE-sequence. CONCLUSION: T2-TSE-sequence is superior to HASTE-sequence in the delineation of anatomical structures of the cervical spine, the grading of cervical spinal stenosis and the evaluation of cervical myelopathy.

[Comparison of CT arterioportography and spiral CT arterioportography in malignant lesions of the liver]. / Vergleich von CT-Arterioporto-graphie und Spiral-CT-Arterioportographie bei malignen Läsionen der Leber.

PURPOSE: To determine the value of spiral CT during arterial portography (SCTAP) in detecting and localising focal liver lesions we compared the SCTAP findings to those gained by conventional CT during arterial portography (CTAP). MATERIAL AND METHODS: We evaluated a total of CT scans of 128 patients with 162 malignant lesions of the liver. 45 patients underwent SCTAP and 83 patients CTAP. Results of radiological studies were compared with surgical and pathological findings. RESULTS: The overall sensitivity of SCTAP was 93% with a sensitivity of 80% for lesions of less than 1 cm diameter. For CTAP the overall sensitivity was 88%, but the sensitivity for lesions smaller than 1 cm was only 53%. Although with SCTAP examination of hepatic vasculature and liver parenchyma was continuous, we found no advantage in the localisation of lesions to the liver segments compared to CTAP, and the sensitivity of localisation did not correlate with the size of lesions. CONCLUSION: In our study SCTAP turned out to be a reliable radiological method in the preoperative detection of focal liver lesions, with a high overall sensitivity. SCTAP showed improved sensitivity in the detection of small malignant lesions (< 1 cm) in comparison to CTAP.

Spiral CT angiography for preoperative planning in patients with epigastric tumors: comparison with arteriography.

PURPOSE: Spiral CT angiography (CTA) was performed on 22 patients for the preoperative assessment of epigastric tumors in comparison with intraarterial angiography. METHODS: One hundred fifty milliliters of contrast material was administered with a flow of 4 ml/s. After a delay of 30 s, a spiral CT examination of the epigastrium was performed (slice thickness 3 mm, table feed 6 mm/s). Axial images were reconstructed at 2 mm increments. Postprocessing was performed with a maximum intensity projection and shaded surface display imaging program. Plain film arteriography was performed via a catheter inserted transfemorally and placed into the epigastric arteries. The following parameters were evaluated: visualization of the arteries and the portal vein and involvement of these vessels by disease. RESULTS: The vessels (22/22 = 100%) and variations (1/22 = 4.5%) were clearly identified with both techniques. Involvement was diagnosed by angiography 15 times compared with 22 findings by CTA. CONCLUSION: Concerning vessel anatomy, the correlation between both techniques was excellent and vessel involvement showed good correlation, especially when using the axial slices additionally. CTA has the potential to become a minimally invasive diagnostic tool for preoperative planning in epigastric tumors.

[Spiral CT angiography versus DSA in detection of carotid stenoses]. / Spiral-CT-Angiographie versus DSA beim Nachweis von Carotisstenosen.

PURPOSE: To determine the value of spiral CT angiography for evaluation of internal carotid artery stenosis. METHODS: Spiral CT angiography was compared with selective intraarterial DSA in 40 patients with 72 internal carotid artery stenoses. Quantification of stenoses was performed according to the NASCET-study and categorized in mild (0-29%), moderate (30-69%), severe (70-99%) and occlusion (100%). RESULTS: The total agreement of spiral CT angiography with DSA in all stenoses was 78% (r = 0.933; p < 0.0001). In the mild stenoses group there was an agreement of 56% (r = 0.598; p = 138), in the moderate stenosis group there was an agreement of 59% (0.623; p = 0.0128) and in the group with severe stenosis the agreement was 97% (0.944; p < 0.0001). All occlusions were correctly interpreted by spiral CT angiography (r = 1; p = 0.0082). CONCLUSION: The agreement of spiral CT angiography with DSA is good. Especially SCTA allows a good correlation in the severe stenosis group and in the occlusion group. DSA remains the standard of reference, because of its ability to demonstrate tandem lesions and collateral flow.

[Spiral CT angiography after the application of an iliac artery stent]. / Spiral-CT-Angiographie nach arterieller iliakaler Stentapplikation.

PURPOSE: To evaluate the diagnostic and clinical value of CT-A performing MIP- and SSD-reformations after intraarterial iliac stent application. METHODS: In a prospective study 32 patients underwent CT-A after stent placement in the iliac arteries. The vascular morphology was analyzed regarding neointimal hyperplasia and calcification pattern. The results were compared with those of clinical findings (walking distance), Doppler ultrasound (ankle-brachial index) and DSA. RESULTS: All 47 stents were visible and patent (100%). One misplacement was identified. A good correlation was found between an improved ankle-brachial index and CT-A (88.5%) and extension of the walking distance and CT-A (92.3%). Concerning location, number and grade of stenoses the results between CT-A and DSA matched in 42.1%. An exact mapping of calcified plaques was possible in all cases. CONCLUSIONS: CT-A as MIP is shown to be superior than DSA with regard to calcifications. Complementary to the indirect methods of the ankle-brachial index and walking distance, CT-A is useful for therapy control after vascular stent placement.

[CT angiographic imaging of atypical arterial blood supply to the liver by the superior mesenteric artery]. / CT-angiographische Darstellung einer atypischen arteriellen Versorgung der Leber über die Arteria mesenterica superior.

Variations of the celiac trunk are seen in 25-35% of all patients. In 10-12% the right hepatitic artery arises from the superior mesenteric artery, the left hepatic artery in 4-5%. An aberrant origin of the common hepatic artery is seen in about 2.5%. We report about a patient with liver cell adenoma, in whom we diagnosed preoperatively the atypical origin of the common hepatic artery by performing CT angiography in the MIP technique (MIP = Maximum Intensity Projection). Conventional angiography as well as intraoperative findings confirmed the diagnosis.