Paired comparison of vascular wall reactions to Palmaz stents, Strecker tantalum stents, and Wallstents in canine iliac and femoral arteries.

BACKGROUND: Palmaz stents, Strecker stents, and Wallstents, all used clinically, differ substantially in their physical characteristics, yet how differently the vascular wall reacts to them has not been demonstrated conclusively. We therefore undertook a side-by-side comparison. METHODS AND RESULTS: One stent was implanted into each canine external iliac and/or the flexing portion of the proximal femoral artery. In 9 dogs, Palmaz stents were placed vis-à-vis Strecker stents, with follow-up of 2 and 4 months. In 7 dogs, Palmaz stents were placed vis-à-vis Wallstents, with 4 months of follow-up. Angiographic midstent luminal diameters immediately after placement and at follow-up as well as midstent cross-sectional areas of neointima were compared for significant differences. In addition, neointimal maturation, medial atrophy, and stent-related trauma were assessed. Angiographically, all arteries remained open. The degree of luminal narrowing by recoil and neointima never reached 50% and was modest for Palmaz stents and Wallstents (P = .33) but significantly higher for Strecker stents (P < .0001 compared with Palmaz stents). This corresponded histologically to a significantly thicker neointima (P = .003) over Strecker than over Palmaz stents but not between Palmaz stents and Wallstents (P = .18). Neointimal buildup was generally more pronounced in the femoral artery segments than in the iliac segments. Maturation of the neointima over Palmaz stents was much further advanced than over Strecker stents and slightly more advanced than over Wallstents. Pressure-related atrophy of the tunica media was least for Strecker stents and more pronounced but similar for Wallstents and Palmaz stents. Wallstent wire ends caused some wall trauma; several femoral Palmaz stent struts protruded through the media. CONCLUSIONS: The lower-hoop-strength, higher-profile tantalum Strecker stent is affected by vascular wall recoil and evokes a greater degree of neointima formation than the lower-profile, higher-hoop-strength Palmaz stent and Wallstent. Medial atrophy is pronounced outside the latter two stents. The rigid Palmaz stent can penetrate through the vascular wall in flexing arteries.

A modification of standard percutaneous nephrolithotripsy technique for the morbidly obese patient.

OBJECTIVES: Urolithiasis in the morbidly obese patient presents several unique challenges to the urologist, and its treatment often requires creativity and innovation. We present a new modification of standard percutaneous nephrolithotripsy (PNL) technique, which is very helpful in overcoming some of the problems that are encountered when performing PNL in this group of patients. METHODS: We present 5 patients in whom this new technique has been used. Each had either failed prior extracorporeal shock-wave lithotripsy (ESWL) therapy or their size and abdominal girth precluded use of ESWL technology. All 5 patients underwent PNL. The radiographically measured skin-to-stone distances (determined by computed tomography or ultrasonography or both) exceeded the lengths of the standard percutaneous access sheaths and the 26 F rigid nephroscope. Thus larger and longer Amplatz access sheaths and a 30 F gynecologic laparoscope were used to reach the stones. Standard ultrasonic lithotripsy was then performed, and extralong bronchoscopic grasping forceps were used to remove stone fragments. RESULTS: All 5 patients were rendered stone-free using this technique. There was no significant perioperative morbidity. CONCLUSIONS: For this very challenging group of patients, the use of larger and longer access sheaths and the gynecologic laparoscope have been very effective additions to the urologists' armamentarium in the treatment of urolithiasis.

Outcome of patients with advanced neoplastic disease receiving vena caval filters.

PURPOSE: The authors examined the appropriateness and outcome of inferior vena caval (IVC) filter placements in patients with advanced malignancies and limited expected survival. PATIENTS AND METHODS: Over a 35-month period, 35 IVC filters were inserted in 34 adult patients with advanced neoplasms. Follow-up was as long as 28 months (mean, 5.2 months). Filter effectiveness, complications, recurrent pulmonary emboli, patient survival, and hospital discharge status were recorded. RESULTS: Twenty-eight patients (82%) were discharged home (n = 21) or to nursing facilities (n = 7) between 1 and 193 days (mean, 23 days) after filter insertion. Six patient (18%) died during hospitalization 1-95 days after filter insertion. The overall mean survival was 6.6 months; for patients with stage III and IV tumors mean survival was 8.0 and 5.5 months, respectively. Even among patients with stage IV disease, 59% survived longer than 3 months. There were no complications related to filter insertion and no clinical evidence of recurrent pulmonary emboli. In 14% of patients, filters enabled invasive therapeutic and palliative procedures to be performed. CONCLUSION: The presence of advanced neoplastic disease by itself should not be a deterrent to insertion of IVC filters, as most patients survived well beyond initial hospitalization.

A low-cost CD-ROM--based image archival system.

Many radiologists have large collections of original or copied radiographs, as well as 35-mm slides of radiographs that require conventional carousel-type projectors for display. These images cannot be digitally manipulated or displayed in other formats. The authors used compact disk, read-only memory (CD-ROM) technology as a low-cost method of digitally storing these images. The CD-ROM disks were created from slide images optically scanned and digitally transferred to a disk. The images may be incorporated into any type of computer application, used on multiple computer platforms, and are easily transportable. The process is a low-cost, high-quality method of transferring images to digital media and is currently available to anyone with a conventional 35-mm camera, a CD-ROM reader, and a computer.

Comparison of mechanical deformation properties of metallic stents with use of stress-strain analysis.

PURPOSE: Elastic and plastic deformation properties of the Wallstent, Palmaz stent, and Strecker stent were evaluated quantitatively with an in vitro model simulating forces exerted by an eccentric lesion. MATERIALS AND METHODS: A miniaturized compression testing device was constructed. Stress-strain graphs were obtained for each stent, and the elastic moduli and yield points were calculated. RESULTS: There is a 21-fold range in the elastic modulus among the Wallstent, Palmaz stent, and Strecker stents. The Palmaz stent was the only device to exhibit permanent plastic deformation. The 10-mm Palmaz stent will undergo 15% focal eccentric narrowing at 0.75 atm of pressure; the "standard braid" and "less shortening braid" 10-mm Wallstents at 0.55 and 0.25 atm, respectively; and the 10-mm tantalum Strecker stent at 0.08 atm. Overlapping of stents doubles the stiffness of the Wallstent and the Strecker stent and doubles the yield point of the Palmaz stent. The 4-9 mm Palmaz stent is 30% more resistant to deformation than the larger 8-12-mm version when expanded to identical 8-mm diameters. CONCLUSIONS: The "standard braid" version of the 10-mm Wallstent provides 2.3-fold additional strength for resistant stenoses compared with the "less shortening braid." Overlapping or nesting of stents may permit full expansion should there be incomplete expansion or recoil of a single stent. The 4-9-mm Palmaz stent is preferable from the standpoint of allowing the use of a smaller (7-F instead of 9-F) introducer sheath and also for providing superior resistance to deformation. A purely elastic stent such as the Wallstent is preferable in locations where permanent plastic deformation may occur, such as the thoracic outlet.

Insertion of Groshong central venous catheters utilizing fluoroscopic techniques.

Groshong central line indwelling catheters are extensively used in gynecologic oncology patients for administration of chemotherapy, intravenous fluids, and pain medications. They are easy to maintain and have a good safety record. We report on the placement of these central venous catheters under direct fluoroscopic visualization as a method which is safe, inexpensive, and efficacious in high-risk patients. Fluoroscopic visualization during insertion provides several advantages: visualization of bony landmarks, placement of the guidewire into the subclavian vein and superior vena cava under direct visualization, and confirmation of appropriate distal placement of the Groshong catheter. Patient advantages include the following: (1) avoidance of unnecessary punctures to access the subclavian vein; (2) verification of guidewire placement to avoid cephalic placement; (3) passage of the guidewire only as far as the right atrium to avoid potential dysrrhythmias secondary to right ventricular irritation; and (4) a savings of approximately 60% over insertion in the general operating room. Thirty patients had placement under fluoroscopic visualization in the angiography suite of Georgetown University Hospital. The average age of the patients was 58 years (42-78). Sixteen patients had ovarian cancer, 6 had endometrial cancer, 5 had cervical cancer, and 3 had other gynecologic malignancies. Fifteen patients had catheters placed for chemotherapy, 14 for hydration, and 1 for pain control. Ten patients had had previous central venous catheters: 6 had been removed for infection, 2 for thrombus, 1 for completion of chemotherapy, and 1 for catheter kinkage. All 10 with previous catheters had successful placement of catheters in the angiography suite. Complications from insertion were minimal with one asymptomatic pneumothorax and one proximal port in an extravascular position. We present the technique of fluoroscopic insertion of Groshong catheters which is an effective method of placement in high-risk patients.

Evaluation of a prototype steerable angioscopic laser catheter in a canine model: a feasibility study.

To overcome some of the persisting technical problems related to laser angioplasty, a new catheter was designed and investigated in a canine model. This 5F catheter contained a deflectable tip for steerability, an angioscope, and a laser fiber. Catheter steerability, angioscopic function, and the effects of a 480 nm flash lamp pumped pulsed dye laser on normal canine vessel walls were evaluated. Steering, angioscopic guidance, and application of laser energy were easy and fast to perform in a bloodless vessel segment. Maintaining a condition of bloodlessness at the target site, critical to angioscopic guidance, proved to be the most difficult part in this prototype evaluation. It was noted that the 480 nm pulsed dye laser did not cause macroscopic alterations or perforations to the normal vessel wall. We conclude that a relatively simple deflection mechanism of a small-caliber angioscope provides the kind of aiming ability requisite for precise endovascular therapy. Complete bloodlessness of the area is necessary for both viewing and laser ablation at 480 nm.

Injection characteristics and downstream contrast material distribution of flush aortography catheters: in vitro study.

Performance of 11 commercially available 4- and 5-F aortic flush catheters was evaluated with respect to the extent of upstream injection, catheter motion, and downstream homogeneity of a 10-, 15-, and 20-mL/sec bolus of 76% meglumine sodium diatrizoate at room temperature. Tests were made in a pulsatile aortic flow model containing circulating fluid isoviscous to blood. The injection process was recorded on videotape. Homogeneity of the contrast material bolus was determined spectrophotometrically from samples collected from the center and each of the four quadrants of the vessel lumen. Upstream contrast material injection between 1.5 and 7 cm in length emerged from all catheters; it was lowest with one of the "tennis racket" designs from one and a new spiral end-loop design (Halo) from another manufacturer. All catheters, except the most rigid and largest-caliber catheter (5.8 F) showed considerable shaft motion at the higher injection rates. Downstream contrast material mixing homogeneity was always best at the highest injection rate but altogether was better for the Halo catheter than for any other catheter tested. It is concluded that all tested 4- and 5-F aortic flush catheters show some undesirable features, but certain design modifications improve performance and comparative testing is helpful to distinguish such features.

Gadolinium-enhanced magnitude contrast MR angiography of popliteal and tibial arteries.

To evaluate the efficacy of gadopentetate dimeglumine in MR angiography of the lower extremities, a flow phantom, seven healthy volunteers, and seven patients with peripheral vascular disease were studied with a magnitude contrast (MC) technique. The combination of an MC rephase-dephase gradient-refocused-echo pulse sequence, a 40-cm-long transmit-receive coil, and intravenous administration of a bolus of gadopentetate dimeglumine improved MR angiographic quality in the phantom, volunteers, and patients. Gadolinium enhancement decreased deleterious saturation effects and improved images of the popliteal and tibioperoneal arteries in the volunteers and patients. However, in some cases, venous overlap, imaging artifacts, and suboptimal visualization of subtle lesions limited interpretation. The authors conclude that gadolinium enhancement combined with an MC subtraction pulse sequence appreciably improves MR angiography of lower extremity arteries.

Spontaneous rupture of an adventitial cyst of the popliteal artery: confirmation with MR imaging.

A case of spontaneous rupture of an adventitial cyst in the popliteal artery is reported. Axial magnetic resonance (MR) images demonstrated the decompressed cyst, and MR angiography was a useful noninvasive technique for confirming vascular patency after cyst rupture.

Embolotherapy for small bowel hemorrhage from metastatic renal cell carcinoma: case report.

Embolization for control of hemorrhage in the small bowel carries a significant risk of bowel infarction. A case is presented where severe gastrointestinal hemorrhage from a hypervascular renal cell carcinoma metastasis to the jejunum was effectively controlled by superselective embolization of mesenteric tumor supply arteries with Gelfoam particles. Adjacent normal mesenteric arteries remained open. It is concluded that in specific instances where direct mesenteric feeders to a tumor can be catheterized, such embolization can be performed safely.

An extended-length coil design for peripheral MR angiography.

Magnetic resonance angiography of the peripheral vascular system has been hampered by the limited view provided by available imaging coils. We have constructed an extended-length, split-saddle design radiofrequency (rf) coil for peripheral angiography. The two coil halves are inductively coupled, to each other and to the rf source. Details regarding the construction of the coil and comparison of the performance with the knee coil are described here. This coil provides the benefit of a larger field of view but with image quality comparable to that of a commercial knee coil.

Renal artery stenosis in patients with aortic dissection: increased prevalence.

The authors retrospectively analyzed the prevalence of renal artery stenosis in 63 consecutive patients with aortic dissection who underwent thoracic and abdominal aortography. Ten patients (16%) had renal artery stenosis, five with atherosclerosis and five with fibromuscular lesions. Risk factors for aortic dissection were Marfan disease in nine patients, bicuspid aortic valve in one, and hypertension in 54 (including seven patients with Marfan syndrome). If the patients with Marfan syndrome and the patient with the bicuspid aortic valve are excluded, renal artery stenosis was present in 10 of 53 patients (19%) when the cause of dissection was presumably hypertension. This finding suggests that renovascular hypertension is a greater risk factor for aortic dissection than is essential hypertension. The success of angiotensin converting enzyme inhibitors and percutaneous transluminal renal angioplasty (PTRA) in controlling renovascular hypertension has been proved. In this series, emergent PTRA successfully controlled the hypertension in one patient with a type B dissection, resulting in an excellent clinical outcome. Angiography should be routinely performed on patients with aortic dissections to evaluate for renal artery stenosis.

Computerized literature reference system: use of an optical scanner and optical character recognition software.

A computerized reference system for radiology journal articles was developed by using an IBM-compatible personal computer with a hand-held optical scanner and optical character recognition software. This allows direct entry of scanned text from printed material into word processing or data-base files. Additionally, line diagrams and photographs of radiographs can be incorporated into these files. A text search and retrieval software program enables rapid searching for keywords in scanned documents. The hand scanner and software programs are commercially available, relatively inexpensive, and easily used. This permits construction of a personalized radiology literature file of readily accessible text and images requiring minimal typing or keystroke entry.