Intraarterial gadolinium-enhanced MR angiography in humans for the detection of infrainguinal arterial stenoses before and after percutaneous angioplasty

OBJECTIVE: The objectives of this study were to show the feasibility of intraarterial MR angiography of the infrainguinal arteries and to compare the accuracy of intraarterial MR angiography with selective intraarterial digital subtraction angiography for the detection of stenoses before and after percutaneous balloon angioplasty. SUBJECTS AND METHODS: Fifteen patients underwent digital subtraction angiography and intraarterial MR angiography before and after balloon angioplasty. For intraarterial MR angiography, 30 mL of diluted contrast agent (5 mL of gadodiamide diluted in 55 mL of 0.9% saline solution) was injected through a sheath in the superficial femoral artery using a flow rate of 2.5 mL/sec. A 3D gradient-echo sequence was performed. Four independent blinded observers assessed differences in the quantitative measurement of stenoses and localization of lesions between digital subtraction angiography and intraarterial MR angiography. The overall impression of the intraarterial MR angiography images was documented on a 4-point scale (1 = excellent, 4 = poor). Interobserver variability was calculated. RESULTS: Intraarterial MR angiography from the upper leg to the trifurcation was feasible in all 30 examinations with a mean overall impression of all segments of 1.3 (SD, 0.68). For the detection of significant stenoses (> or = 50% stenosis), the overall sensitivity and specificity for the femoropopliteal and crural vessels were 92.4% and 91.7% and 91.9% and 87.8%, respectively. For the complete leg, sensitivity and specificity were 92.2% and 88.6%, respectively. Interobserver variability for intraarterial MR angiography of the crural vessels exceeded that of the femoropopliteal arteries. CONCLUSION: Intraarterial MR angiography of the infrainguinal arteries is feasible in humans using injections of diluted contrast agent at concentrations as low as 8%. It has a high sensitivity for detecting stenoses and an acceptable interobserver variability.     

Laser catheter thermal angioplasty: technique and early results in 34 patients

The laser catheter is a nylon vascular catheter with a metal tip that has an end hole as well as side holes. The metal tip is heated by laser energy delivered through an optical fiber embedded in the catheter wall. The catheter may be advanced over a guidewire for use as an adjunct to balloon angioplasty or for use in smaller vessels as the exclusive method of recanalization. We used the catheter to treat 34 patients with 54 discrete vascular lesions in 35 extremities. Twenty patients were treated for clinically significant claudication and 14 for ischemic changes. Laser catheter-assisted balloon angioplasty was used to treat six iliac artery occlusions, two iliac artery stenoses, 10 superficial femoral artery occlusions, 12 superficial femoral stenoses, four popliteal artery occlusions, and three popliteal stenoses. Initial technical and clinical success in these patients, with follow-up periods of 3-6 months, was equivalent to the results of previous reports of laser probe-assisted balloon angioplasty. In 11 patients, 15 of 17 popliteal or tibial-peroneal lesions were treated with the laser catheter without subsequent balloon angioplasty. The treatment was successful in eight of these patients, with follow-ups for up to 6 months. Our results suggest that the laser catheter is a useful device for the treatment of vascular stenosis or occlusion when used either as an adjunct to balloon angioplasty or in smaller vessels as the exclusive method for angioplasty.     

MR angiography of lower-extremity arterial disease: preliminary experience.

Nineteen patients underwent magnetic resonance (MR) angiography for evaluation of lower-extremity arterial disease. The underlying conditions included atherosclerotic occlusive disease in 12 patients, femoral or popliteal aneurysms in four, and bypass graft stenoses or occlusion in four. In the patients with occlusive disease, the iliac and femoropopliteal vessels were classified as patent, moderately stenotic, severely stenotic, or occluded. Fifteen of 16 occlusions (accuracy = 94%) were correctly classified. In the one missed case, there was a long delay between MR angiography and x-ray angiography and it is likely that the occlusion occurred during the interval. Three of five severe stenoses were correctly classified with MR angiography. In two cases of iliac artery stenosis, there was a signal void at the point of maximal stenosis, which on the basis of anatomic features could be recognized as severe stenosis rather than an occlusion. Three of four moderate stenoses were correctly classified. Correlation with x-ray angiography or surgery demonstrated the ability of MR angiography to accurately depict the status of runoff vessels.     

Popliteal and tibioperoneal arteries: feasibility of two-dimensional time-of-flight MR angiography and phase velocity mapping.

To assess the feasibility of using magnetic resonance (MR) angiography and velocity-encoded cine MR imaging to evaluate morphology and function in the popliteal and tibioperoneal arteries, the profiles of blood flow velocity measured with velocity-encoded cine MR were compared with those measured with color-coded sonography. Two-dimensional time-of-flight MR angiography was performed in the popliteal and tibioperoneal arteries of 10 healthy subjects; velocity-encoded cine MR and color-coded sonography were performed above and below the trifurcation. The velocity waveforms acquired with velocity-encoded cine MR and color-coded sonography correlated well and showed a typical triphasic pattern. At peak systole in the popliteal artery, spatial maximum and spatial mean velocities measured with velocity-encoded cine MR were 42.29 cm/sec +/- 9.55 (standard deviation) and 27.7 cm/sec +/- 5.8, respectively; the peak velocity measured with color-coded sonography was 44.2 cm/sec +/- 12.3. It is concluded that use of both MR angiography and velocity-encoded cine MR should be considered for identification of arterial stenoses and assessment of the hemodynamic importance of peripheral vascular stenoses.     

Recanalization of long segment occlusion of superficial femoral artery by percutaneous transluminal laser angioplasty--report of a case

Percutaneous Transluminal Laser Angioplasty (PTLA) for 46 cm complete occlusion of right superficial femoral and popliteal artery was successfully carried out. Intravenous digital subtraction angiography five months after the procedure showed almost complete recanalization of the arteries, and good flow of the contrast medium through the femoral and popliteal artery. Only Percutaneous Transluminal Angioplasty (PTA) was previously done for the stenosis of right popliteal artery, but restenosis of the artery took place. On this occasion PTLA was carried out to treat stenosis of the popliteal artery as well as the femoral artery lesions. It is speculated that one of the major causes of reocclusion of the femoral and popliteal artery is due to recurrence of a few portions of severe stenosis of superficial femoral and popliteal arteries. This case will illustrate the long term effect of PTLA, because stenotic segments treated only with balloon dilatation recurred, but those stenoses treated with laser did not recur.     

Quickscan: Doppler ultrasound emulation of angiography--its value prior to arteriography in peripheral vascular disease

The prevalence of peripheral vascular disease demands a quick, reliable, non-invasive technique for initial assessment. We have devised a new method which combines the two physical principles that (1) Doppler shift is proportional to blood velocity and (2) blood velocity is inversely proportional to arterial cross-section with the ability to track probe position using a non-contacting method. An image of the probe track and any arterial narrowing is shown superimposed on an outline of the patient. Pressure measurement, scan and graphics with final report take about 20 minutes. The accuracy of this system in peripheral vascular disease was evaluated. Thirty-one patients underwent quickscan (QS) and arteriography within an average time of 7 days. Abdominal aorta, common iliac-common femoral, superficial femoral and popliteal artery segments were graded independently as normal, significant stenosis (greater than 50% of diameter) or occluded by both techniques. Of 197 segments, QS correctly assessed 106 normal, 22 stenosed and 28 occluded segments. Four equivocal angiographic stenoses were normal on QS and three severe stenoses were graded occlusion. Fifteen segments on angiography and five on QS were not assessed. For the iliac and superficial femoral artery segments, sensitivity and specificity averaged 77% and 86%, respectively, for all grades. Aortic statistics were invalid (only one significant lesion). Six out of eight popliteal occlusions were correctly diagnosed by QS, but no popliteal stenoses were detected out of six shown on arteriography. Low numbers may contribute to this discrepancy but an improved popliteal scanning method may be necessary. We find initial QS an invaluable aid to direct percutaneous angiography and to indicate potential sites for angioplasty.     

Multicenter phase-II trial of safety and efficacy of NC100150 for steady-state contrast-enhanced peripheral magnetic resonance angiography

The aim of this study was to test the safety and efficacy of NC100150 injection for steady-state contrast-enhanced peripheral MR angiography in a multicentre phase-II trial. Thirty-three patients underwent steady-state NC100150 enhanced MR angiography (5 mg Fe/kg body weight) of the aortoiliac and femoropopliteal arteries. Safety assessment consisted of pre- and post-injection (2, 24 and 72 h) monitoring of vital signs, physical examination as well as laboratory and electrocardiographic parameters. To determine sensitivity and specificity for detection of haemodynamically significant stenoses (HSS; >50% reduction of luminal diameter) MR angiograms were compared with intra-arterial digital subtraction angiography (IA DSA), which was considered the standard of reference. In 33 patients a mean of 12.8 ml NC100150 was injected. Eleven patients reported 13 mild and 2 moderate adverse events. Five mild and one moderate adverse event were considered due to NC100150 injection. There were no significant changes in vital signs, laboratory or electrocardiographic parameters. Sensitivity and specificity (in percent) for detection of HSS were 87 and 64, 56 and 76, and 75 and 84, for iliac, femoral and popliteal arteries, respectively. NC100150 high-resolution steady-state MR angiography can be performed safely and is feasible for the detection of peripheral arterial HSS, but is as yet not a clinically useful alternative to conventional gadolinium-enhanced MR angiography.     

Decreased venous contamination on 3D gadolinium-enhanced bolus chase peripheral mr angiography using thigh compression

OBJECTIVE: We evaluated the potential for improving bolus chase peripheral MR angiography in patients with fast arterial flow using thigh compression to prevent venous contamination. SUBJECTS AND METHODS: We performed bolus chase peripheral MR angiography in 32 consecutive patients in whom the travel time for a contrast agent to reach the popliteal artery trifurcation was less than 25 sec. Thigh compression was applied by a tourniquet (n = 13) or blood pressure cuff inflated to 60 mm Hg (n = 19). We compared the results with those of 36 consecutive patients who underwent angiography without thigh compression. The effect of thigh compression on arterial flow and tissue enhancement was assessed in patients with symmetric travel time in both legs by applying compression to one leg during the time-resolved 2D-projection MR angiography with 6 mL of gadolinium. On 3D bolus chase MR angiography, thigh compression was applied bilaterally. Venous contamination on the 3D images of the calf was graded as 0, none; 1, trace; 2, mild; 3, moderate; and 4, severe. Signal-to-noise ratio was measured in the popliteal artery. RESULTS: Thigh compression slowed the arterial travel time by a mean +/- SD of 4.7 +/- 2 sec (p < 0.001) with a blood pressure cuff and 3.1 +/- 1 sec (p < 0.001) with a tourniquet. Blood pressure cuffs reduced the score of venous contamination on the calf station from 1.9 to 0.4 (p < 0.05) for intermediate flow (contrast travel time, 20-25 sec) and from 2.5 to 0.9 (p < 0.05) for fast flow (< 20 sec). Thigh compression increased the popliteal artery signal-to-noise ratio (81 vs 52, p < 0.001). CONCLUSION: Thigh compression with blood pressure cuffs inflated to 60 mm Hg slows down arterial flow, increases arterial signal-to-noise ratio, and reduces venous contamination on 3D gadolinium-enhanced bolus chase peripheral MR angiography.     

MR imaging and MR angiography in popliteal artery entrapment syndrome

Popliteal artery entrapment (PAE) syndrome is an uncommon congenital anomaly seen in young adults causing ischemic symptoms in the lower extremities. It is the result of various types of anomalous relationships between the popliteal artery and the neighboring muscular structures. The purpose of this study was to define the role of MR imaging combined with MR angiography in the diagnosis of PAE cases. Four cases with segmental occlusion and medial displacement of popliteal artery in digital subtraction angiography (DSA) examinations were diagnosed as PAE syndrome by MR imaging and MR angiography. The DSA and MRA images are compared. All of the cases showed various degrees of abnormal intercondylar insertion of the medial head of the gastrocnemius muscle. The MR images showed detailed anatomy of the region revealing the cause of the arterial entrapment. Subclassification of the cases were done and fat tissue filling the normal localization of the muscle was evaluated. The DSA and MRA images demonstrated the length and localization of the occluded segment and collateral vascular developments equally. It is concluded that angiographic evaluation alone in PAE syndrome might result in overlooking the underlying cause of the arterial occlusion, which in turn leads to unsuccessful therapy procedures such as balloon angioplasty. Magnetic resonance imaging combined with MR angiography demonstrates both the vascular anatomy and the variations in the muscular structures in the popliteal fossa successfully, and this combination seems to be the most effective way of evaluating young adults with ischemic symptoms suggesting PAE syndrome. Received 7 April 1997; Revision received 15 July 1997; Accepted 13 November 1997     

MR imaging-guided stent placement in iliac arterial stenoses: a feasibility study

PURPOSE: To assess the feasibility of magnetic resonance (MR) imaging-guided stent placement in iliac arterial stenoses. MATERIALS AND METHODS: Thirteen patients with 14 iliac arterial stenoses were examined prospectively. Angioplasty was performed through a femoral sheath by using a conventional 1.5-T MR imaging system. Stents and catheters were visualized on the basis of their artifacts. Nitinol stents were placed with gradient-echo MR imaging guidance. Angioplasty balloons were inflated with gadolinium-based contrast material. Results were evaluated clinically and with both digital subtraction angiography (DSA) and contrast material-enhanced MR angiography. RESULTS: Ten of 13 patients were treated with technical success by using MR imaging-guided intervention alone. Three patients were treated with additional fluoroscopic guidance, because complications (ie, panic attack, subintimal recanalization, and stent misplacement) occurred with MR guidance. The quality of the postinterventional contrast-enhanced MR angiograms of three of 12 lesions with stents was limited owing to stent-induced signal loss of the lumen. The mean stenosis degree after stent placement was significantly higher at contrast-enhanced MR angiography than at DSA (24.6% vs 6.2%). The mean MR imaging-guided procedure time was 74 minutes. CONCLUSION: MR imaging-guided stent placement in iliac arteries is feasible in select patients. The presented technique has limitations-that is, long procedure times, lack of real-time monitoring, and stent artifacts-that necessitate further modifications before it can be recommended for clinical use.     

Contrast-enhanced subtraction MR angiography in occlusive disease of the pelvic and lower limb arteries: results of a prospective intraindividual comparative study with digital subtraction angiography in 76 patients.

PURPOSE: The purpose of this work was to evaluate the feasibility and clinical use of MR angiography (MRA) for examining the pelvic and lower limb arteries in patients with arterial occlusive disease. METHOD: Seventy-six patients with clinical signs of peripheral arterial occlusive disease were included in the study. MRA was performed using a fast contrast-enhanced high-resolution 3D technique that covered the area from the distal abdominal aorta to the distal lower limbs in two examination steps. RESULTS: In all patients, diagnostic images comparable with those of conventional intraarterial digital subtraction angiography (DSA) could be obtained. No false-negative findings were seen in the iliac, femoral, or popliteal arteries. Ten to 16% of the mild stenoses and 6-14% of the severe stenoses, mainly in the crural vessels, were overgraded compared with intraarterial DSA. Particularly in patients with proximal severe obstructions or occlusions, the crural segments could be depicted more clearly due to decreased arterial runoff in conventional angiography. CONCLUSION: The consistency of the excellent depiction of the vascular territories of the distal aorta and the pelvic and lower limb arteries in a standardized setting suggests great potential for the use of MRA in the primary diagnosis of peripheral arterial occlusive disease.     

Infrarenal aortic and lower-extremity arterial disease: diagnostic performance of multi-detector row CT angiography

PURPOSE: To compare multi-detector row spiral computed tomographic (CT) angiography with digital subtraction angiography (DSA) in evaluation of the infrarenal aorta and lower-extremity arterial system. MATERIALS AND METHODS: Fifty patients with peripheral arterial occlusive disease were evaluated with multi-detector row CT angiography and DSA. Arteries depicted at CT angiography and DSA were graded separately for degree of stenosis as 23 anatomic segments (infrarenal aorta, right and left common iliac artery, internal iliac artery, external iliac artery, common femoral artery, superficial femoral artery, deep femoral artery, popliteal artery, anterior tibial artery, tibioperoneal trunk, posterior tibial artery, and peroneal artery). Grades included the following: 1, normal patency; 2, moderate (< or =50%) stenosis; 3, focal severe (>50%) stenosis; 4, multiple severe stenoses; and 5, occlusion. Three readers independently interpreted the images, and statistical analysis was performed. The results of image interpretation were evaluated for strength of agreement by using Cohen kappa statistics. On the basis of consensus readings, sensitivity, specificity, and accuracy for detection of stenotic lesions were calculated, with findings at DSA used as the reference standard. RESULTS: Substantial to almost perfect interobserver agreement was achieved in all cases. At DSA, 349 diseased segments were found among the 1,137 segments evaluated. Sensitivity, specificity, and accuracy, based on a consensus reading of multi-detector row CT angiograms, were 96%, 93%, and 94%, respectively. A statistically significant difference (P <.05) between DSA and multi-detector row CT angiography was present only in arteries graded 1 or 2. Interobserver agreement was almost perfect among the three readers for treatment recommendations based on findings at CT angiography and DSA. CONCLUSION: Multi-detector row CT angiography appears consistent and accurate in the assessment of patients with peripheral arterial occlusive disease.     

Coronary artery imaging with real-time navigator three-dimensional turbo-field-echo MR coronary angiography: initial experience

PURPOSE: To examine the value of a commercially available three-dimensional (3D) real-time navigator magnetic resonance (MR) coronary angiographic examination for detection of significant coronary artery stenoses, with conventional coronary angiography as the standard of reference. MATERIALS AND METHODS: Twenty-one patients underwent 3D navigator MR coronary angiography immediately before catheterization. Two observers independently graded image quality on a scale from 1 (unreadable) to 5 (excellent), quantified coronary artery visualization, and evaluated the presence of significant (ie, >50% narrowing) stenoses. kappa statistics were used to assess interobserver agreement, and receiver operating characteristic (ROC) analysis was used to assess stenosis detection. RESULTS: For two of 21 patients, MR coronary angiogram quality was insufficient for analysis (mean score < 2). For the remaining 19 patients, the mean image quality scores assigned by observers 1 and 2 were 3.3 +/- 1.0 (SD) and 3.2 +/- 0.9, respectively. A mean of 71% of all coronary artery segments were visible at MR coronary angiography, and there was 91% agreement between the observers (kappa = 0.78). Observers 1 and 2 detected significant stenoses (n = 29) at MR coronary angiography with sensitivities of 44.4% and 55.5%, respectively; specificities of 95.1% and 83.7%, respectively; and 80% agreement (kappa = 0.35). Areas under the ROC curve were 0.817 and 0.795 for observers 1 and 2, respectively. CONCLUSION: Large portions of the coronary arteries can be visualized with MR coronary angiography. Imaging results are not consistently reliable, however. The examination is premature for routine clinical assessment of significant coronary artery stenosis owing to low sensitivity and large observer variability.     

X线导向下逆行腘动脉穿刺植入支架治疗股浅动脉闭塞症九例

目的 探讨X线导向下逆行腘动脉穿刺在股浅动脉闭塞介入治疗中的应用价值.方法 对9例股浅动脉长段闭塞患者采用经股动脉入路顺行开通受阻,改用X线导向下逆行腘动脉穿刺技术成功建立通路后,对闭塞段行球囊扩张及支架植入治疗.结果 9例患者腘动脉穿刺技术均获成功,闭塞段股动脉均获开通,间歇性跛行症状消失,未出现相邻神经、血管损伤...     

Use of abciximab during infrainguinal peripheral vascular interventions: initial experience

PURPOSE: To investigate the use of abciximab as an adjunct during infrainguinal angioplasty. MATERIALS AND METHODS: Abciximab was used in conjunction with recanalization techniques and angioplasty to treat stenoses or occlusions in 16 patients: 10 patients had high-grade stenoses or occlusions longer than 5 cm in the superficial femoral artery and popliteal artery, and six patients had stenoses or occlusions below the popliteal artery. All patients received a bolus of heparin after arterial access was achieved. Abciximab was administered by means of a weight-base nomogram that consisted of an initial bolus followed by an overnight infusion. Technical success was defined as a less than 30% residual stenosis after angioplasty. Patients were carefully followed up for possible postprocedural complications. Platelet counts were monitored for 24 hours. RESULTS: Technical success was achieved in 15 (94%) of 16 patients. One occlusion of the superficial femoral artery could not be crossed. There was a mean postprocedural increase of 0.23 in the ankle-brachial index. There was no significant effect on platelet count. Two minor complications occurred. One major complication occurred; this was a groin hematoma, which required a blood transfusion. CONCLUSION: The use of abciximab as an adjunct during complex infrainguinal arterial interventions appears promising, on the basis of initial experience.     

Renal arterial stenosis: prospective comparison of color Doppler US and breath-hold, three-dimensional, dynamic, gadolinium-enhanced MR angiography

PURPOSE: To compare color Doppler ultrasonography (US) with fast, breath-hold, three-dimensional, gadolinium-enhanced magnetic resonance (MR) angiography in detecting renal arterial stenosis. MATERIALS AND METHODS: Forty-five patients with clinical suspicion of renovascular disease were prospectively examined with intra- and extrarenal color Doppler US and breath-hold, gadolinium-enhanced MR angiography. Digital subtraction arteriography (DSA) was the standard of reference in all patients for the number of renal arteries and degree of stenosis. RESULTS: DSA depicted 103 arteries and 52 stenoses. Color Doppler US was nondiagnostic in two examinations. Significantly more of 13 accessory renal arteries were detected with MR angiography (n = 12) than with color Doppler US (n = 3; P <.05). For assessing all stenoses, the sensitivity and accuracy were 94% and 91%, respectively, for MR angiography and 71% and 76%, respectively, for US (P <.05). The sensitivity was higher for MR angiography (100%) than for US (79%; P <.05) in diagnosing stenoses with at least 50% narrowing. The specificity, accuracy, and negative predictive value in diagnosing stenoses of at least 50% narrowing were 93%, 95%, and 100% for MR angiography and 93%, 89%, and 90% for US. CONCLUSION: Breath-hold, gadolinium-enhanced MR angiography is superior to color Doppler US in accessory renal artery detection. Although the specificity of MR angiography is similar to that of color Doppler US, MR angiography has a better sensitivity and negative predictive value in depicting renal arterial stenoses.     

A polymer-based MR-compatible guidewire: a study to explore new prospects for interventional peripheral magnetic resonance angiography (ipMRA)

PURPOSE: To introduce a newly developed polymer-based and magnetic resonance (MR)-compatible guidewire and to explore its capabilities with respect to interventional peripheral magnetic resonance angiography (ipMRA) in a flow phantom. MATERIALS AND METHODS: The guidewire is based on a polyetheretherketone (PEEK) polymer core, and small iron particles are embedded in its coating. A passive device tracking technique was designed utilizing a susceptibility artifact induced by the wire in images acquired with a balanced steady-state free precession (b-SSFP) sequence using small flip angles. The position of the guidewire tip was determined from image intensity maxima and overlayed onto a roadmap in near real-time. Guidewire tracking and balloon angioplasty of an artificial stenosis were attempted in two configurations of a flow phantom. RESULTS: Successful passive guidewire tracking was performed for all phantom configurations. Robustness and accuracy of the tracking technique were sufficient for phantom studies. A balloon catheter was placed into the stenosis using the guidewire under complete MR guidance, and subsequent balloon angioplasty yielded improved flow conditions. CONCLUSION: The new guidewire is well-suited for clinical application due to an absence of the risk of core fracture and its atraumatic flexible tip. It opens novel prospects for the realization of ipMRA in humans that need to be explored in further studies.     

Simultaneous real-time visualization of the catheter tip and vascular anatomy for MR-guided PTA of iliac arteries in an animal model

PURPOSE: To examine the feasibility of simultaneous MR real-time active tip tracking and near real-time depiction of the vascular anatomy for percutaneous angioplasty of iliac arteries under MR guidance. MATERIALS AND METHODS: Nine surgically created stenoses of external iliac arteries in pigs were dilated with MR-compatible balloon catheters (Cordis, Roden, The Netherlands). These catheters were equipped with a microcoil for active tracking of the catheter tip with an in-plane update rate of 10 positions per second. The procedures were performed on an interventional 1.5 T Gyroscan ACS-NT scanner (Philips, Best, The Netherlands). Real-time calculation of images acquired by radial k-space filling was performed on a specially designed backprojector exploiting the sliding window reconstruction technique (Philips Research Laboratories, Hamburg, Germany). The image update rate was 20 frames per second using a radial gradient-echo technique (TR = 12 msec, TE = 3.3 msec, 300 radials). MR angiography and X-ray digital subtraction angiography on the X-ray system positioned in-line next to the interventional MR system served as control for the angioplasty results. RESULTS: Real-time guidance and positioning of the balloon catheters was possible. The actual position of the catheter tip was indicated in the MR images without any time delay for the reconstruction of the anatomical MR images, which were updated with a rate of 20 frames per second. This yielded a combination of a roadmap and fluoroscopy image, in which the catheter position and the anatomical background image both were continuously updated in real time. Six out of nine stenoses were successfully dilated. The effects of the angioplasty could be visualized by the real-time MR technique, as was proven by X-ray digital subtraction angiography. CONCLUSION: Active tip tracking simultaneous with MRI of the vascular anatomy-both in real time-is possible with the applied technique, enabling MR-guided percutaneous dilatation (PTA) of iliac arteries.     

The Outback Catheter: A New Device for True Lumen Re-entry After Dissection During Recanalization of Arterial Occlusions

To report the initial experience with a new catheter system (The Outback catheter) designed to allow fluoroscopically controlled re-entry of the true arterial lumen after subintimal guidewire passage during recanalization procedures of arterial occlusions. The catheter was used in 10 patients with intermittent claudication caused by chronic segmental occlusions of the superficial femoral or popliteal arteries. In all patients, conventional guidewire recanalization had failed. In 8 patients, successful true lumen re-entry was achieved with the Outback catheter. Percutaneous transluminal angioplasty was successfully performed in these patients without complications. Two technical failures occurred in heavily calcified arteries. The Outback catheter was safe and effective when used in complicated recanalization procedures in the superficial femoral and popliteal artery and the tibial trunk.     

Brachiocephalic artery dilation by percutaneous transluminal angioplasty

Percutaneous transluminal angioplasty (PTA) was used to dilate stenotic lesions in 38 brachiocephalic arteries in 36 patient. Complete evaluation of the central nervous system blood supply is a prerequisite for the brachiocephalic PTA when cerebral symptoms are present. The femoral artery is the best vascular entry site; use of digital subtraction angiography equipment for arterial mapping is helpful. Balloon diameter should be the same as or slightly wider than the diameter of the normal artery adjacent to the stenotic segment. Spasm was successfully treated with intraarterial injection of nitroglycerin. The only drug therapy consistently used with PTA was aspirin. Complete dilation of the stenosis is the best prevention of thrombotic or embolic complications. In properly selected cases, proximal subclavian artery stenoses can be safely dilated, and the balloon can eventually be placed across the origin of the vertebral artery. Because of potential complications associated with brachiocephalic PTA, indications must be well established, and interventions should not be performed on marginal or asymptomatic stenoses.