Percutaneous Large-Bore Pulmonary Thrombectomy with the FlowTriever Device: Initial Experience in Intermediate-High and High-Risk Patients.

OBJECTIVES: This retrospective cohort study investigates outcomes of patients with intermediate-high and high-risk pulmonary embolism (PE) who were treated with transfemoral mechanical thrombectomy (MT) using the large-bore Inari FlowTriever aspiration catheter system. MATERIAL AND METHODS: Twenty-seven patients (mean age 56.1 ± 15.3 years) treated with MT for PE between 04/2021 and 11/2021 were reviewed. Risk stratification was performed according to European Society of Cardiology (ESC) guidelines. Clinical and hemodynamic characteristics before and after the procedure were compared with the paired Student's t test, and duration of hospital stay was analyzed with the Kaplan-Meier estimator. Procedure-related adverse advents were assessed. RESULTS: Of 27 patients treated, 18 were classified as high risk. Mean right-to-left ventricular ratio on baseline CT was 1.7 ± 0.6. After MT, a statistically significant reduction in mean pulmonary artery pressures from 35.9 ± 9.6 to 26.1 ± 9.0 mmHg (p = 0.002) and heart rates from 109.4 ± 22.5 to 82.8 ± 13.8 beats per minute (p < 0.001) was achieved. Two patients died of prolonged cardiogenic shock. Three patients died of post-interventional complications of which a paradoxical embolism can be considered related to MT. One patient needed short cardiopulmonary resuscitation during the procedure due to clot displacement. Patients with PE as primary driver of clinical instability had a median intensive care unit (ICU) stay of 2 days (0.5-3.5 days). Patients who developed PE as a complication of an underlying medical condition spent 11 days (9.5-12.5 days) in the ICU. CONCLUSION: In this small study population of predominantly high-risk PE patients, large-bore MT without adjunctive thrombolysis was feasible with an acceptable procedure-related complication rate.

Molecular coronary MR imaging of human thrombi using EP-2104R, a fibrin-targeted contrast agent: experimental study in a swine model.

PURPOSE: The aim of this study was to investigate the use of a fibrin-specific contrast agent (EP-2104R, EPIX Pharmaceuticals, Lexington, Massachusetts, USA) for targeted molecular magnetic resonance (MR) imaging of human clot material removed from patients in a model of coronary thrombosis in swine. MATERIALS AND METHODS: Freshly ex vivo engineered clots from human blood and human in situ developed clots removed from patients were delivered into the coronary arteries of nine domestic swine. For MR imaging a navigator-gated, free-breathing, cardiac-triggered 3D inversion recovery black-blood gradient echo sequence was performed prior to clot delivery (baseline), after clot delivery but prior to contrast media administration, and two hours after systemic (i.v.) injection of 4 micromol/kg EP-2104R. MR images were analyzed by two investigators and the contrast-to-noise ratio and Gadolinium (Gd) concentration in the clots were assessed. RESULTS: On baseline images and prior to contrast media application no thrombi were visible. Post contrast administration all 10 coronary emboli (five ex vivo engineered clots and five human clots removed from patients) were selectively visualized as white spots with a mean contrast-to-noise ratio to the blood pool and the surrounding tissue of >12 and a mean Gd concentration of >100 microM. CONCLUSION: Molecular MR imaging using the fibrin-targeted contrast agent EP-2104R allows selective visualization of human clot material in a model of coronary thrombosis in swine.

[Imaging of the abdominal wall: combination of tissue-harmonic-imaging and extended field-of-view sonography]. / Ultraschall der Bauchdecke: Kombination von Tissue-Harmonic-Imaging und Panorama-Ultraschall.

PURPOSE: To evaluate the combined use of extended field-of-view sonography and tissue harmonic imaging (THI) for assessment of the abdominal wall. MATERIALS AND METHODS: In 32 patients (25 patients without and 7 patients with abdominal wall pathologies) extended field-of-view sonography of the abdominal wall was performed with and without THI using a 7.5 MHz ultrasound transducer. Images with a scan length of 60 cm were acquired above and below the arcuate line. The images were independently assessed by two observers regarding visibility of the anatomic structures and delineation of pathological changes using a 4-point grading scale. Furthermore, the influence of the extent of the subcutaneous fat on the image quality was assessed. For statistical analysis, kappa coefficients, Fisher"s exact test and a repeated measurement analysis of variance (ANOVA) were applied. RESULTS: In all patients, delineation of the abdominal wall was possible with diagnostic image quality. Abdominal wall pathologies were concurrently diagnosed for extended field-of-view sonography with and without utilization of THI. Image quality was rated better with THI when compared to extended field-of-view B-Mode sonography. In comparison to extended field-of-view B-Mode sonography, the agreement between both readers regarding image quality was markedly improved using extended field-of-view sonography in combination with THI. With increasing thickness of the subcutaneous fat layer, image quality was rated significantly better using THI than B-Mode ultrasound. CONCLUSION: Combined use of extended field-of-view sonography and THI improves image quality and documentation of ultrasound examinations. Especially in obese patients, the use of THI is advantageous. Therefore, abdominal wall ultrasound gains additional value in the preoperative planning.

Improved in-stent magnetic resonance angiography with high flip angle excitation.

RATIONALE AND OBJECTIVES: To optimize the intraluminal signal intensity of a nitinol stent by performing contrast-enhanced three-dimensional magnetic resonance angiography (CE-MRA) with varying flip angles (FAs). METHODS: Contrast-enhanced magnetic resonance angiography at 1.5 T and FAs of 30 degrees, 100 degrees, and 150 degrees was performed on five sheep with 10 iliac nitinol stents (Memotherm-FLEXX). Maximum-intensity projections (MIPs) and composite images of MIPs were performed and compared. RESULTS: Reconstructed MIPs at an FA of 150 degrees showed a slightly disturbed lumen visibility inside the stent accompanied by low-grade lumen visibility outside the stent and vice versa for an FA of 30 degrees. Composite images of a 30 degrees MIP added to a 150 degrees MIP resulted in improved image quality compared with the standard MIP of a single FA. CONCLUSIONS: Signal loss due to radiofrequency shielding inside nitinol stents imaged by CE-MRA can be reduced by applying high FAs. Composite MIP images allow simultaneous visualization of the lumen inside as well as outside the stent.

MR-guided percutaneous drainage of abdominal fluid collections in combination with X-ray fluoroscopy: initial clinical experience.

The aim of this study was to examine the feasibility of a hybrid interventional MR system, which combines a closed bore magnet with a C-arm fluoroscopy unit for percutaneous drainage of abdominal fluid collections. During the past 2 years, we have performed four drainage procedures in four patients (mean age 47 years). Three patients had abscesses (psoas muscle, kidney, subphrenic location) and the fourth patient had a recurrent splenic cyst. All procedures were performed on an interventional MR system consisting of a 1.5-T ACS-NT scanner combined with a specially shielded C-arm. The drainages were guided by T1-weighted fast gradient-echo images, T2-weighted single-shot turbo spin-echo images or both. A standard 18 G (1.2 mm) nonferromagnetic stainless steel needle with a Teflon sheath was used for the punctures following which a 0.89 mm nitinol guidewire was inserted into the fluid collection. Thereafter, the patient was positioned in the immediate adjacent fluoroscopy unit and a drainage catheter was placed under fluoroscopic control. All drainage catheters were successfully placed into the fluid collections, as proven by fluid aspiration and resolution of the collection. The mean time needed for the entire drainage procedure (MR and fluoroscopy) was 110 min. No procedure-related complications occurred. It is feasible to perform drainage procedures on a closed-bore MR scanner. The multiplanar imaging capabilities of MR are particularly helpful for fluid collections in the subphrenic location.

Diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration of the vertebral body.

OBJECTIVE: The aim of this study was to investigate diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration with and without accompanying fracture. SUBJECTS AND METHODS: In 10 volunteers, diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences were optimized on a clinical 1.5-T scanner. In 34 patients, MR imaging with and without diffusion-sensitizing gradients (b = 598 sec/mm(2) in spin-echo and fat-suppressed spin-echo, b = 360 sec/mm(2) in stimulated-echo) was performed. Thirty-five lesions were analyzed, with 18 caused by acute (< or =10 days old) osteoporotic or traumatic fractures and 17 caused by untreated malignant vertebral infiltration including nine fractures. Signal attenuation in diffusion-weighted images and contrast-to-noise ratio were calculated. The diffusion-weighted images were analyzed by two radiologists. RESULTS: Images from three of 34 patients were excluded because of motion artifact. In osteoporotic and traumatic fractures, a strong signal attenuation of bone marrow edema was seen. In contrast to this, malignant-tumor infiltration caused only minor signal attenuation (p < 0.05), independent of accompanying pathologic fracture. All sequences showed identical changes of signal intensities. In four patients, initial diagnosis was changed by the findings in the diffusion-weighted images. CONCLUSION: Diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences are equally suitable for imaging of the spine. Calculation of signal attenuation and observation of signal characteristics allowed differentiation of benign fracture edema and tumor infiltration and provided excellent distinction between benign and malignant vertebral fractures in our series.

Dosimetry of a 188rhenium-labeled self-expanding stent for endovascular brachytherapy in peripheral arteries.

PURPOSE: Radioactive stents have been proposed as endovascular irradiation device to prevent in-stent restenosis by inhibiting neointimal proliferation. 32P-stents have been used in several studies so far, but require large-scale labeling procedures and endovascular barotrauma for stent expansion supporting the development of edge restenosis. Purpose of this study was to establish dosimetry of a self-expanding nitinol stent for peripheral vascular disease, which was radiolabeled with 188rhenium (188Re) by a dip coating technique. METHODS AND MATERIALS: The surface of nitinol Memotherm FLEXX stents was polymer-coated providing functional NH(2) groups for diethylenetriaminepentaacetic acid (DTPA) binding, providing the ligand for the complexation of 188Re onto the stent surface. Stability of radiolabeling was tested over 48 h using an in vitro blood circulation (Chandler Loop). Radial and longitudinal dose distributions of a radiolabeled stent were obtained with a plastic scintillator dosimetry system. RESULTS: Stents with a length of 30 mm and a diameter of 8 mm were labeled with up to 33 MBq 188Re. A total of 69+/-4% of the labeled 188Re remained stable on the stent surface after 48 h. Ninety-five percent of the infinitely accumulated dose was supplied to the target tissue within 72 h. Including correction for radioactivity washout from the stent, the infinitely accumulated dose at 1 mm radial distance from the stent surface was 1.85+/-0.19 Gy/MBq 188Re/cm stent length. CONCLUSIONS: We developed a technique for radiolabeling of self-expanding nitinol stents with 188Re by dip coating and formation of 188Re chelate complexes. We provide dosimetry data useful for application of this beta-emitting stent for endovascular brachytherapy in peripheral vascular occlusive disease.

Real-time MR fluoroscopy for MR-guided iliac artery stent placement.

The purpose of this study was to test the feasibility of real-time magnetic resonance (MR) guidance of iliac artery stent placement. Radial scanning together with the sliding window reconstruction technique was implemented on a 1.5 T magnet, yielding a frame rate of 20 images per second. Seven prototype nitinol ZA stents were deployed in iliac arteries of living pigs under MR control. All stents were well visualized on the radial MR images, allowing depiction of the mounted stents as well as stent deployment without anatomy-obscuring artifacts. Stent placement was sucessful in all cases and took 6 minutes on average. The position of the stents was correctly visualized by real-time radial MR scanning, as proved by digital subtraction X-ray angiography. Combined radial scanning and the sliding window reconstruction technique allow real-time MR-guided stent placement in iliac arteries.

MR evaluation of stent patency: in vitro test of 22 metallic stents and the possibility of determining their patency by MR angiography.

RATIONALE AND OBJECTIVES: To determine the extent to which visualization of intrastent anatomy in stents of different composition and design is possible by using contrast-enhanced MR angiography. METHODS: Twenty-two MR-compatible stents, most of which had a diameter of 8 mm, were positioned in a phantom filled with aqueous gadolinium solution. Coronal and axial spoiled three-dimensional gradient-echo sequences were performed. Images were acquired with stents positioned at varying angulations to the main magnetic field B0. Profiles orthogonal to the stent axis allowed measurement of artifact sizes independent of window width and center. RESULTS: Oriented along B0, the Cragg, Corvita, Passager, Wallstent, Strecker, Impag, Perflex, and ZA stents allowed visualization of more than 48% of the lumen. The Memotherm, Smart, and Jostent SelfX stents showed a prominent reduction of the inner lumen to below 41%. The lumina of the covered Jostent, Palmaz, Sinus, and Symphony stents were completely obscured. The Impag, Perflex, and Strecker tantalum stents showed growing artifact sizes and a lumen reduction of at least 40% with increasing angulation to B0. CONCLUSIONS. Evaluation of the inner stent lumen by applying contrast-enhanced, three-dimensional gradient-echo sequences is not possible for the majority of stents because of their large artifacts. These depend on the stent type and orientation to B0. Even stents made of nitinol and cobalt alloys only allow qualitative patency assessment but no quantification of stenosis.

Circular spirit level guidance system for CT- and MR-guided punctures.

A circular spirit level guidance system was tested for control of CT- and MR-guided punctures. The device consists of a needle holder fixed to a ground plate and two protractors. This allows adjustment of the fixed needle according to the angulation of the supposed puncture path as measured on tomographic images. A circular spirit level is fixed to the needle and leveled. Now the needle can be removed from the needle holder; by leveling the circular spirit level during the puncture, the formerly adjusted angulation is achieved. The system was tested in vitro and in vivo (22 patients) under CT and MR guidance. The average needle deviation was measured to be 1.96 degrees in vitro and 2.51 degrees in vivo. This simple device allows accurate puncture under CT and MR guidance.

Treatment of hemodialysis-related central venous stenosis or occlusion: results of primary Wallstent placement and follow-up in 50 patients.

PURPOSE: To analyze the effectiveness of stent placement as the primary treatment for central venous obstruction in patients undergoing hemodialysis. MATERIAL AND METHODS: Fifty-seven Wallstents were placed in 50 patients with symptomatic shunt dysfunction and arm swelling due to central venous obstruction. Technical success, complication, and patency rates were evaluated. RESULTS: Stent deployment was successful in all patients, and early rethrombosis (within 1 week) was noted in one patient (2%). Seventy-three episodes of reobstruction occurred and were treated percutaneously with angioplasty alone in 54 cases (74%). Nineteen cases (26%) necessitated additional stent placement. The 3-, 6-, 12-, and 24-month primary patency rates were 92%, 84%, 56%, and 28%, respectively. Cumulative overall stent patency was 97% after 6 and 12 months, 89% after 24 months, and 81% after 36 and 48 months. CONCLUSION: In the treatment of brachiocephalic and subclavian venous obstruction, stent placement shows excellent technical results and helps preserve vascular access for a substantial period. Multiple repeat interventions are, however, frequently required to maintain patency.

MR-guided biopsy using a T2-weighted single-shot zoom imaging sequence (Local Look technique).

The purpose of this study was to demonstrate the utility of a T2-weighted single shot turbo spin-echo technique--the so-called "Local Look" (LoLo) and more recently renamed "Zoom Imaging" technique--for MR-guided percutaneous interventions. We performed 28 procedures on 22 patients using a 1.5-T system for MR guidance. All procedures were controlled with the LoLo technique, which acquires T2-weighted images in 600 msec. This is achieved by using a small field of view (250 x 125 mm) along with a maximum echo train length, the so-called "single shot method." To prevent backfolding artifacts, the 90 degrees and 180 degrees pulses were oriented orthogonally to each other. Because signal is created only in the region in which the pulses overlap, no backfolding can occur from outside this area. Half of the biopsies were additionally monitored using a fast gradient-echo sequence, which was compared with the LoLo technique. All of the procedures were technically successful, and there were no procedural complications. The LoLo technique produced images that had good contrast between the lesion and the needle artifact, and the artifact size was smaller than that produced by the gradient-echo technique. Subjective judgment of the ability to accurately delineate the needle tip indicated that the LoLo technique was either superior to (73%) or equal to (27%) the gradient-echo sequence in all cases. The LoLo technique is an accurate and effective method for MR guidance of percutaneous procedures, because it shows good lesion contrast and small needle artifacts. The additional use of a gradient-echo sequence during the procedure planning stage is advisable in more difficult cases, particularly when adjacent blood vessels are a concern. Monitoring of the needle tip is best performed with the LoLo technique.

MRI-guided biopsy of bone in a hybrid system.

This is a report of our experience with percutaneous, MRI-guided biopsies in 25 patients with skeletal lesions using a 1.5-T MR hybrid system. Twenty-five consecutive patients with skeletal lesions were referred for MRI-guided biopsy. Biopsies were performed with a 1.5-T Philips Gyroscan (Philips Medical Systems, Best, The Netherlands) combined with a c-arm fluoroscopy. Specimens were obtained percutaneously either with a 14- or 18-gauge "side-slit" type of biopsy needle (n = 10 skeletal lesions that had penetrated through the cortex), or using a prototype coaxial drill system powered either by hand or an optional motor (n = 15 skeletal lesions still covered with cortical bone). All but two biopsies could be completed within the MR unit. For one patient, who required a transpedicular approach to a lumbar vertebra, and for one child, who required general anesthesia, we decided to switch to CT guidance. In 19 of the 25 cases (17 of the 23 cases performed in MR), the sample was sufficient and the histopathologic diagnosis was confirmed. Three patients had an inadequate sample, and three others had adequate samples but inaccurate results. No procedural complications occurred. Percutaneous biopsy of skeletal lesions performed under MRI-guidance was found to be safe and reasonably accurate. There were no procedural complications in our small series. MRI may be used as an alternative to CT, but its role vis-à-vis CT has yet to be ascertained.

In vitro evaluation of a rheolytic thrombectomy system for clot removal from five different temporary vena cava filters.

PURPOSE: To evaluate the feasibility of thrombus removal from temporary vena cava filters using a rheolytic thrombectomy device and to assess the embolization rate of this procedure. METHODS: Five temporary vena cava filters together with porcine thrombi were placed in a vena cava flow model (semitranslucent silicone tube of 23 mm diameter, pulsatile flow at a mean flow rate of 4 L/min). A rheolytic thrombectomy system (Hydrolyser) was used with a 9 Fr guiding catheter to remove the clots. The effluent was passed through filters of different size and the amount of embolized particles as well as the remaining thrombus were measured. RESULTS: Thrombus removal rates ranged from 85% to 100%. Embolization rates between 47% and 60% were calculated for the different filters. CONCLUSION: The Hydrolyser is able to remove sufficiently high amounts of thrombus from temporary vena cava filters. However, the amount of embolized particles makes it impossible to utilize this method without special precautions against embolization.

Stent placement on fresh venous thrombosis.

PURPOSE: To report on the efficacy of fixing fresh venous thrombus to the venous wall by stent placement. METHODS: Seven patients underwent stenting to treat acute venous thrombosis. In two patients, the hemodialysis fistula was thrombosed with the thrombus extending into the brachial veins. In three patients, the hemodialysis fistula was patent but massive swelling of the ipsilateral arm was caused by proximal venous thrombosis. Two patients presented with iliac venous thrombosis within stented pelvic veins. Stent placement was preceded by other mechanical thrombectomy methods in all cases. RESULTS: Attachment of thrombus to the venous wall was successful in all cases treated. Acute rethrombosis did not occur. Follow-up patency in dialysis patients was 7.2 +/- 2.1 months. One patient had rethrombosis of the dialysis graft 3 months after primary treatment. Three patients developed restenosis within a mean period of 7.7 months. One shunt remained patent for 10 months with no event of reobstruction during follow-up. In both patients with iliac stent placement, the vein remained patent over a follow-up period of 8 and 12 months respectively. CONCLUSION: Stenting fresh venous thrombus can achieve immediate venous patency. It may be used as an alternative approach when all other percutaneous methods fail. Frequent restenosis within stented veins limits its use to very selected cases.

Successful closure and embolization of a fistula between the pancreatic duct and a pseudocyst using ethibloc.

We successfully achieved complete regression of a pancreatic pseudocyst after Ethibloc embolization of a fistula between the cyst and the pancreatic duct. Previous treatment by percutaneous drainage over 6 weeks had failed. Treatment with a somatostatin analog had not been undertaken.

Esophageal perforation: comparison of use of aqueous and barium-containing contrast media.

PURPOSE: To assess the need for follow-up esophagography with barium-containing contrast medium after examination with a water-soluble contrast medium in the detection of esophageal perforation. MATERIALS AND METHODS: Sixty-seven patients suspected of having esophageal perforation were examined prospectively with use of an aqueous contrast medium during a 1-year period. The examinations were performed with a digital fluoroscopy unit. Eighteen patients without proved extravasation at esophagography performed with aqueous contrast medium and without other contraindications underwent esophagography with barium-containing contrast medium. RESULTS: In four of 18 patients (22%) with unremarkable findings at esophagography performed with a water-soluble contrast medium, a perforation was detected subsequently with use of a barium-containing contrast medium. No complications related to barium extravasation occurred. CONCLUSION: Patients suspected of having esophageal perforation and who have unremarkable findings at esophagography with water-soluble contrast media need to undergo follow-up esophagography with a barium-containing contrast medium. The use of a digital fluoroscopy unit does not obviate the follow-up examination.

Hemodialysis fistulas and grafts: use of cutting balloons to dilate venous stenoses.

To evaluate percutaneous transluminal angioplasty (PTA) with a cutting balloon performed in stenosed hemodialysis fistulas and grafts, 19 venous lesions in 15 patients were treated with a cutting balloon with an inflated diameter of 3-6 mm. The grade of stenosis ranged from 40% to 90% (mean, 65% +/- 15 [standard deviation]). Cutting PTA was performed before conventional PTA in seven patients and was followed with conventional PTA with larger balloons in seven patients. The balloon expanded completely in all patients, and no balloon waist remained. The mean grade of stenosis decreased to 14% +/- 9. Cutting PTA increased the technical success of balloon dilation of hemodialysis fistulas and grafts.

Iliocaval stenosis and iliac venous thrombosis in retroperitoneal fibrosis: percutaneous treatment by use of hydrodynamic thrombectomy and stenting.

A case of bilateral iliac stenosis and caval stenosis due to retroperitoneal fibrosis was treated by caval stenting and iliac balloon angioplasty, but was complicated by subsequent iliac thrombosis. Venous thrombectomy was successfully achieved by hydrodynamic thrombectomy, and iliac patency was stabilized by bilateral stent insertion.

Late reobstruction in iliac arterial stents: percutaneous treatment.

PURPOSE: To retrospectively analyze in a nonrandomized fashion the efficacy of percutaneous reintervention in obstructed iliac stents. MATERIALS AND METHODS: In 21 symptomatic patients with iliac lesions, 26 reinterventions (16 for stent occlusion and 10 for stent stenosis) were performed. Restenoses were treated with balloon dilation and either atherectomy or stent placement. Reocclusions were treated with atherectomy or aspiration thrombectomy and then recanalization with balloon dilation and selective stent placement. RESULTS: Balloon angioplasty for stent stenosis was effective in all but one patient. Recanalization was successful in 14 of 16 patients with stent occlusion. The mean period of patency after reintervention was 18 months +/- 15. Cumulative stent stenosis patency after reintervention was 87% after 1 year. Stent occlusion patency was 57%. Recurrent stent obstruction occurred in eight of 24 (33%) patients with successful primary interventions. CONCLUSION: Percutaneous reintervention for both stent stenosis and occlusion is feasible with a moderate complication rate and may be attempted before surgery.