Projective imaging of pulsatile flow with magnetic resonance.

Noninvasive angiography with magnetic resonance is demonstrated. Signal arising in all structures except vessels that carry pulsatile flow is eliminated by means of velocity-dependent phase contrast, electrocardiographic gating, and image subtraction. Background structures become in effect transparent, enabling the three-dimensional vascular tree to be imaged by projection to a two-dimensional image plane. Image acquisition and processing are accomplished with entirely conventional two-dimensional Fourier transform magnetic resonance imaging techniques. When imaged at 0.6 tesla, vessels 1 to 2 millimeters in diameter are routinely detected in a 50-centimeter field of view with data acquisition times less than 15 minutes. Studies of normal and pathologic anatomy are illustrated in human subjects.

Embolization of pulmonary catheter-induced pulmonary artery pseudoaneurysms.

STUDY OBJECTIVES: To determine the outcome of patients with pulmonary catheter-induced pulmonary artery pseudoansurysms (PSAs) treated with embolization. DESIGN: Retrospective outcomes review. SETTING: Large urban tertiary-care hospital. PATIENTS: All patients who presented to diagnostic angiography for ruptured pulmonary artery PSA caused by pulmonary artery catheters (PACs) from November 1990 to September 1995. A total of six patients were examined. INTERVENTIONS: Transcatheter embolotherapy with coils, absorbable gelatin sponges (Gelfoam), and suture material. RESULTS: These procedures were technically successful in all patients, and none had recurrent hemoptysis. Four of the six patients were discharged from the hospital. CONCLUSION: Embolotherapy is a useful alternative to surgery for some patients with PAC-induced pulmonary PSA.

Evaluation of optimized biplane pulmonary cineangiography.

Biplane pulmonary cineangiograms utilizing a short cine pulse width and automatic brightness control were performed in 47 patients during normal respiration. The diagnostic quality of the arteriograms was categorized as good in 33 patients, fair in 12 patients, and poor in two patients. Of the 18 patients in whom pulmonary emboli were identified, cineangiography displayed certain diagnostic features to advantage, including motion of emboli in ten and respiratory scissoring of vessels overcoming vascular superimposition in three. Optimized pulmonary cineangiography is an acceptable alternative to serial film pulmonary angiography for the diagnosis of pulmonary embolism.

The intestinal tract.

In this chapter, we have considered angiographic applications for diagnosis and management of patients with gastrointestinal bleeding and intestinal ischaemia. For patients with upper gastrointestinal bleeding, diagnostic angiography should be performed only when and if endoscopy is not available or non-contributory. For therapeutic purposes, angiography is applied in patients who continue to bleed despite conservative measures and intervention becomes unavoidable. Therapeutic interventions include the intra-arterial infusion of vasopressin and/or transcatheter embolization. In patients with rectal bleeding the addition of radionuclide studies has reduced the number of negative arteriographic examinations. We currently use the radionuclide studies only as a guide to whether active bleeding is present or not. If the radionuclide test is negative, we do not perform angiography. If it is positive we proceed with angiography in order to confirm localization and control bleeding with an intervention. For patients with rapid bleeding who are haemodynamically unstable we bypass nuclear medicine and proceed directly with angiography. In patients with suspected intestinal ischaemia, angiography is the only means of deciding whether ischaemia is of the occlusive or the non-occlusive form. Mesenteric vascular occlusions are treated surgically while low flow states are managed with mesenteric artery infusions of papaverine. Angioplasty has been and can be applied in patients with mesenteric arterial stenoses and symptoms of chronic intestinal ischaemia.

Renal insufficiency: gadopentetate dimeglumine as a radiographic contrast agent during peripheral vascular interventional procedures.

Gadopentetate dimeglumine diluted 1:1 with 0.9% normal saline was used as the radiographic contrast agent in two patients with azotemia who underwent peripheral vascular interventional procedures. The patients had no evidence of contrast material-induced renal failure after the procedures. The radiographic attenuation of the diluted gadopentetate dimeglumine was equivalent to diatrizoate meglumine diluted to 40 mg iodine per milliliter. Gadopentetate dimeglumine is an alternative radiographic contrast material for azotemic patients.

Gadopentetate dimeglumine: a possible alternative contrast agent for CT angiography of the aorta.

We report the use of a gadolinium chelate for limited CT angiography of the aorta in a patient in whom iodinated contrast agent was contraindicated and who had undergone nondiagnostic MRI.

Atherosclerotic occlusive disease of the lower extremity: prospective evaluation with two-dimensional time-of-flight MR angiography.

A prospective, blinded comparison of two-dimensional time-of-flight (TOF) magnetic resonance (MR) angiography and conventional arteriography was performed in 25 patients who underwent routine arteriography for symptomatic atherosclerotic occlusive disease of the lower extremity. MR angiography was performed from the distal abdominal aorta through the popliteal trifurcation. The native arterial tree was divided into nine segments; each segment was assessed for patency (defined as stenosis < 50% of arterial diameter), moderate stenosis (50%-69%), severe stenosis (70%-99%), or occlusion (100%). In all 206 segments examined, the sensitivity of MR angiography in diagnosis of occlusion was 100%; the specificity, 98%. All long occlusions were correctly classified. In specific categories of occlusive disease, the sensitivity and specificity were as follows: in all segments with 70% or greater stenosis, including occlusions, 90% and 97%; in all segments with 50% or greater stenosis, including occlusions, 92% and 88%; in femoropopliteal segments with 50% or greater stenosis, 92% and 93%; and in iliac segments, 93% and 83%. Long occlusions were distinguished from short occlusions and stenoses; hence, MR angiography enabled identification of patients with lesions suitable for angioplasty.

Operator errors during percutaneous placement of vena cava filters.

Operator errors during percutaneous insertion of inferior vena cava (IVC) filters are procedural complications specific to filter placement that cannot be attributed to defects in the device itself. These errors can occur during preplacement imaging of the IVC, selection of the filter, or deployment of the filter. Although technical problems are reported to occur in 5-20% [1] of filter insertions, the precise frequency of operator errors is not known. This pictorial essay reviews the different types of operator errors that can occur during percutaneous insertion of IVC filters.

Long-term outcomes of radiologically placed arm ports.

PURPOSE: To evaluate long-term outcomes of an initial experience with radiologic placement of arm ports. MATERIALS AND METHODS: The follow-up of 46 consecutive arm port placements (44 patients) was reviewed by means of chart review (hospital, office, and clinic) in 41 patients, telephone interview in 20, physical, examination in 15, and venous ultrasound in 14. Data on port complications and function were recorded. Statistical methods were the Fisher Exact Test and Cochran-Mantel-Haenszel Test. RESULTS: Technical success for placement was 100%. Follow-up was obtained in 41 (93%) of the 44 patients (43 ports); mean days of catheter use was 344 days (total, 14,797 days; range, 10-1,104 days; median, 278 days). Rate (per 100 catheter days) of symptomatic central venous thrombosis was 0.054; arm phlebitis, 0.007; confirmed infection, 0.034; and catheter dysfunction, 0.095. Prophylactic anti-coagulants did not affect symptomatic central venous thrombosis (P > .05, Fisher Exact Test). Catheter tip high in the right atrium was marginally associated with better catheter function (P = .041, Fischer Exact Test). CONCLUSION: Good long-term results can be anticipated with radiologic placement of arm ports.

Mesenteric venous thrombosis treated with urokinase via the superior mesenteric artery.

A 77-year-old man with a history of multiple surgically treated malignancies presented with increasing abdominal pain after eating. Computerized tomographic scan showed superior mesenteric vein and portal vein thrombosis. The patient was treated with selective superior mesenteric artery infusion of urokinase resulting in clinical improvement and near complete resolution of the mesenteric venous thrombosis. An underlying gastric malignancy was found and is believed to be the cause of the patient's hypercoagulable state. Direct infusion of urokinase into the superior mesenteric artery for treatment of mesenteric venous thrombosis is an alternative to surgery in selected patients and an alternative to the much more complicated delivery systems presently used.

Gadolinium-based contrast agents as an alternative at vena cavography in patients with renal insufficiency--early experience.

The authors reviewed results of digital subtraction vena cavography with a gadolinium-based contrast agent in 14 patients with serum creatinine levels greater than or equal to 1.5 mg/dL (133 mumol/L). All cavograms were diagnostic. In 11 patients, there was no impairment of renal function. In three patients, a rise in serum creatinine level of greater than or equal to 0.5 mg/dL (44 mumol/L) was attributable to concurrent medical problems. Gadolinium-based contrast agents may be suitable for digital subtraction vena cavography in patients with renal insufficiency.

Current use of low-osmolality contrast agents: results of a survey.

Members of the Society of Cardiovascular and Interventional Radiology and the Society of Uroradiology were surveyed to assess both current practice and determinants of use of low-osmolality contrast agents (LOCA). Of 715 questionnaires mailed, 229 were returned (32%). Many indicated that the responses referred to the practice of a group, rather than to an individual. Two thirds of the responses indicated that the choice of agent was made by the radiologist alone; one third shared the decision with administrators. Approximately 40% of respondents use written guidelines, but this percentage was higher when administrators were involved in the decision. Almost all (99%) obtained written informed consent--one third for all procedures that use contrast material and two thirds for angiographic studies only. Four percent noted the availability of LOCA in obtaining consent. Overall, LOCA were used for most angiographic procedures by 38% and for most IV studies by only 9% of respondents. All used them for at least some angiographic studies, and all but 2% used them for some IV studies. The major indications for use in both angiographic and IV studies were a prior major (but not minor) reaction and renal dysfunction. Anticipated patient discomfort also was important for intraarterial use. LOCA were used most often for peripheral and pulmonary arteriography. When LOCA were used, nonionic agents were preferred to low-osmolality ionic dimeric contrast agents for coronary angiography and venography, but this preference was essentially reversed for peripheral arteriography. This survey suggests that IV use of LOCA is much less frequent than intraarterial use and that use is individualized to certain risk factors and certain examinations. Guidelines for use are often in place, but this is clearly not universal. The importance of informed consent for use of contrast agents and of the appropriate role for LOCA remains unsettled.

Dynamic gadolinium-enhanced three-dimensional abdominal MR arteriography.

The abdominal aorta and renal, visceral, and iliac arteries were evaluated in 16 patients with three-dimensional Fourier transform imaging enhanced with gadopentetate dimeglumine. By imaging dynamically during the arterial phase of a 5-minute injection (0.2 mmol/kg), highly significant (P < .0001) preferential arterial enhancement (signal-to-noise ratio +/- standard deviation, 10 +/- 0.9), with minimal enhancement of the inferior vena cava (5.1 +/- 1.4) or background tissues (fat, 4.3 +/- 0.7; muscle, 2.4 +/- 0.5), was achieved in every patient. In six patients with angiographic and/or surgical correlation, 10 of 10 stenoses and two of two occlusions were correctly identified. No in-plane saturation or pulsatility artifact was identified in any of the 16 patients. In conclusion, dynamic imaging during the injection of gadopentetate dimeglumine is a promising technique for evaluation of the abdominal aorta and branch vessels.

Isolated calf venous thrombosis: diagnosis with compression US.

Compression ultrasound (US) is an excellent means of evaluating the femoral and popliteal veins but is generally regarded as inadequate for the diagnosis of calf vein thrombosis. This prospective study evaluated compression sonography of the calf veins in 45 symptomatic patients with normal femoral and popliteal veins. All patients underwent correlative venography. Compression US enabled identification of 15 of 17 patients with calf vein thrombosis (sensitivity, 88%). The two false-negative results were in patients with small isolated thrombi. Compression US results were true-negative in 26 of 27 patients with normal venograms (specificity, 96%). If these results can be duplicated by other investigators in larger series of patients, compression US will be an adequate screening modality for calf vein thrombosis.

Transfemoral venous catheterization through inferior vena caval filters: results in seven cases.

Use of the transfemoral route for venous catheterization has been considered contraindicated in patients with inferior vena caval (IVC) filters. The transjugular route has been used instead in such patients when subsequent diagnostic or therapeutic procedures are required. Many radiologists, however, are more accustomed to the transfemoral approach, and may not find the transjugular route a desirable alternative. We describe seven patients with previously placed IVC filters in whom the transfemoral route was used to perform pulmonary arteriography (five patients) or to place additional IVC filters (two patients). After venographic confirmation of caval patency, filters were catheterized under fluoroscopic control and the procedures were performed. All procedures were technically successful; no complications occurred. We believe the transfemoral route to be a safe and feasible approach for performing venous procedures in selected patients with IVC filters, obviating the less familiar and potentially more hazardous transjugular approach.

Guide-wire entrapment by inferior vena caval filters: in vitro evaluation.

PURPOSE: To study guide-wire engagement and entrapment by inferior vena caval (IVC) filters. MATERIALS AND METHODS: Patterns of engagement were determined in six IVC filters with four commonly used guide wires in a simulated IVC. Force required to disengage guide wires from filters was measured. RESULTS: Eleven engagement patterns were identified with J-tipped guide wires; straight guide wires never engaged. The Simon-Nitinol filter engaged guide wires with the highest frequency (P < .05). The 15-J wire was engaged most frequently overall (P < .0005) but disengaged with forces not significantly different (P > .05) from those required to open the J. Entrapment occurred with only the Vena-Tech (VT) and 12-F stainless steel Greenfield (12SSG) filters and the 1.5-J and 3-J guide wires. The former guide wire became entrapped regardless of engagement pattern; the latter became entrapped only when engaged in the hole in the apex of the 12SSG and VT filters. CONCLUSION: Guide wires with a J tip 3 mm or less in radius are at risk for entrapment by the 12SSG and VT filters.

MR imaging (including MR angiography) of abdominal aortic aneurysms: comparison with conventional angiography.

OBJECTIVE: The purpose of this report is to compare the results of MR imaging, including MR angiography, with the results of conventional angiography in the imaging of abdominal aortic aneurysms (AAA). SUBJECTS AND METHODS: Twenty seven nonconsecutive patients with known AAA underwent both MR imaging (including MR angiography) and conventional angiography preoperatively. MR imaging was done before angiography according to the following protocol in all patients: sagittal and coronal T1-weighted images of the abdomen, followed by axial MR angiograms obtained with a multiple overlapping thin-slab acquisition (MOTSA) three-dimensional time-of-flight (3D TOF) volume centered on the renal arteries. Last, coronal MR angiograms were obtained with a dynamic contrast-enhanced 3D TOF volume centered on the aorta. Conventional angiography was subsequently performed in all patients. Data from each study were collected prospectively and analyzed in a blinded manner. For the MR studies, all sequences were used to determine the extent of the AAA and the presence of iliac aneurysms; stenotic disease of the celiac, superior mesenteric, renal, and iliac arteries and the number and location of renal arteries were determined from the MR angiograms. For evaluation of the extent of the aneurysm, results from both techniques were compared with surgical results; otherwise MR angiography was compared with conventional angiography. Confidence intervals for sensitivity and specificity were calculated at the 95% level. The McNemar test was used for comparison of proportions. RESULTS: MR angiography had a sensitivity of 100% (4/4) and a specificity of 91% (21/23) for the four stenoses of the celiac artery that were greater than 50%. For detection of renal artery stenoses of greater than 50%, present in nine arteries, the sensitivity was 89% (8/9) and specificity was 98% (49/50). MR angiography showed 100% (54/54) of all main renal arteries and 78% (7/9) of all accessory renal arteries seen on conventional angiograms. The proximal extent of the aneurysm was correctly predicted on the basis of MR findings in 100% (26/26) of patients with surgical correlation, compared with 92% (24/26) when conventional angiograms were used. This difference was not statistically significant (p > .1). MR imaging had a sensitivity of 100% (19/19) for detection of isolated aneurysms of the common iliac artery, and MR angiography had a 100% sensitivity (5/5) and specificity (103/103) for detection of stenosis greater than 50% in the common and external iliac arteries. One circumaortic left renal vein was visualized on MR images. CONCLUSION: These results suggest that MR angiography may be a useful noninvasive method for determining the presence of coexistent celiac, superior mesenteric, renal, and iliac atherosclerotic disease in patients with AAA.

Cost comparison of radiologic versus surgical placement of long-term hemodialysis catheters.

OBJECTIVE: The purpose of this study was to compare the cost of radiologic versus surgical placement of long-term hemodialysis catheters. MATERIALS AND METHODS: Our cost analysis was based on 47 long-term hemodialysis catheters radiologically placed in 45 patients and 25 catheters surgically placed in 25 patients from October 1996 through March 1997. Variable and total costs were calculated using data from the hospital administrative computer system that records the actual costs incurred by the hospital in caring for patients. RESULTS: The average total hospital cost was $926 for each radiologic placement and $1849 for each surgical placement of long-term hemodialysis catheters. The total cost saving for radiologic placement was $923 for each catheter. CONCLUSION: Radiologic placement of long-term hemodialysis catheters resulted in substantial savings over surgical placement.

MR angiography of tibial runoff vessels: imaging with the head coil compared with conventional arteriography.

OBJECTIVE: We compared peripheral vascular MR angiography done with a standard transmit-receive head coil with conventional arteriography for identifying and evaluating runoff vessels below the knee. MATERIALS AND METHODS: We examined 55 legs in 31 symptomatic patients with both conventional contrast angiography and gradient-echo two-dimensional time-of-flight MR angiography. Both legs of patients were placed in a standard transmit-receive head coil for MR angiography and were imaged simultaneously. For evaluation of stenoses, images of vessels were divided into 10 segments, and each segment was graded on a four-point scale. RESULTS: In the 393 native vascular segments evaluated, the sensitivity of MR angiography in identifying normal vessels was 95% and the specificity was 98%. In detecting segmental occlusion, MR angiography was 98% sensitive and 97% specific. Sensitivity and specificity for stenoses greater than 75% were 98% and 96%, respectively, and for stenoses greater than 50%, they were 98% and 95%, respectively. Interpretative discrepancies were found in 35 vessel segments in 18 legs; none was of clinical relevance. Of all vessel segments shown as occluded by conventional angiography, 1% appeared patent on MR angiograms. No vessel segments shown as normal on MR angiograms were found to be occluded on conventional angiograms. CONCLUSION: When performed simultaneously on both legs of symptomatic patients, 2D time-of-flight MR angiography with a standard transmit-receive head coil provides a time-efficient and highly sensitive and specific means of evaluating below-knee runoff.