Susan M. Weeks

Transcatheter Thrombolytic Therapy for Acute Mesenteric and Portal Vein Thrombosis

PURPOSE The purpose of this study was to evaluate the utility of transcatheter thrombolytic therapy in 20 patients with acute or subacute (symptoms <40 days) portal and/or mesenteric vein thrombosis with severe symptoms, deteriorating clinical condition, and/or persistent symptoms despite anticoagulation. MATERIALS AND METHODS This retrospective study examined 12 male patients and eight female patients seen over a period of 11 years. The average age was 37.6 years. Four of the patients had previously undergone liver transplantation. An anatomic classification system was established to describe the extent of thrombus at the time of diagnosis. Patients were treated with thrombolytic therapy via the transhepatic route, common femoral vein route, and/or superior mesenteric artery route. Improvement in symptoms, avoidance of bowel resection, complications, and radiographic evidence of clot resolution were the main clinical outcomes. RESULTS Fifteen of the 20 patients exhibited some degree of lysis of the thrombus. Three patients had complete resolution, 12 had partial resolution, and five had no resolution. Eighty-five percent of patients (n = 17) had resolution of symptoms. Sixty percent of patients (n = 12) developed a major complication. No patients required bowel resection after thrombolytic therapy. One patient died with gastrointestinal hemorrhage and septic shock 2 weeks after thrombolytic therapy. Other major complications included bleeding and conditions requiring transfusion. No patients developed new portal or mesenteric thromboses. Two of the patients who received transplants eventually required repeat transplantation. CONCLUSIONS Transcatheter thrombolysis was beneficial in avoiding patient death, resolving thrombus, improving symptoms, and avoiding bowel resection. However, there was a high complication rate, indicating that this therapy should be reserved for patients with severe disease. Further evaluation of these techniques and outcomes should continue to be pursued.

Registration and Analysis of Vascular Images

We have developed a method for rigidly aligning images of tubes. This paper presents an evaluation of the consistency of that method for three-dimensional images of human vasculature. Vascular images may contain alignment ambiguities, poorly corresponding vascular networks, and non-rigid deformations, yet the Monte Carlo experiments presented in this paper show that our method registers vascular images with sub-voxel consistency in a matter of seconds. Furthermore, we show that the methods insensitivity to non-rigid deformations enables the localization, quantification, and visualization of those deformations.Our method aligns a source image with a target image by registering a model of the tubes in the source image directly with the target image. Time can be spent to extract an accurate model of the tubes in the source image. Multiple target images can then be registered with that model without additional extractions.Our registration method builds upon the principles of our tubular object segmentation work that combines dynamic-scale central ridge traversal with radius estimation. In particular, our registration methods consistency stems from incorporating multi-scale ridge and radius measures into the model-image match metric. Additionally, the methods speed is due in part to the use of coarse-to-fine optimization strategies that are enabled by measures made during model extraction and by the parameters inherent to the model-image match metric.

Incidence of donor renal fibromuscular dysplasia: does it justify routine angiography?

Background. The use of digital subtraction angiography (DSA) versus helical CT angiography (CTA) or MR angiography (MRA) for live renal donor evaluation is still controversial. Although CTA and MRA can detect some proximal moderate to severe arterial changes caused by fibromuscular dysplasia (FMD), mild and distal moderate FMD are not detected well without angiography. Methods. This is a retrospective chart review of all potential, normotensive live renal donors at our center from July 1995 to June 2001. One hundred fifty-nine patients completed the donor evaluation process and underwent DSA. Results. Seven cases of FMD, an incidence of 4.4%, were discovered. These patients were eliminated from donation. The distribution of renal vessels for our 159 patients was single arteries bilaterally, 64.8%; single left with multiple right, 16.4%; double left with single right, 9.4%; and multiple bilateral arteries, 9.4%. Three of the seven FMD patients had bilateral disease. Two of the seven (28.6%) FMD patients have subsequently required antihypertensive medications, with one requiring angioplasty of a progressive FMD stenotic lesion. Conclusions. We are concerned that CTA or MRA may overlook mild cases of DSA-detectable FMD. All seven FMD patients had single left renal arteries and would have undergone left donor nephrectomy. This would have resulted in their remaining right native kidneys having mild to moderate FMD in six of seven patients and in four donor kidneys having mild to moderate FMD. The need for antihypertensive medications in two of these seven potential donors within 4 years of their evaluation supports previous literature reports.

Primary Gianturco stent placement for inferior vena cava abnormalities following liver transplantation.

PURPOSE To determine the efficacy of primary Gianturco stent placement for patients with inferior vena caval (IVC) abnormalities following liver transplantation. MATERIALS AND METHODS From August 1996 through March 1999, nine adult patients developed significant IVC abnormalities following liver transplantation. Patients were referred for vena cavography on the basis of abnormal clinical findings, laboratory values, liver biopsy results, Doppler findings, or a combination. Those patients demonstrating a significant caval or hepatic venous gradient were treated with primary Gianturco stent placement. Patients were followed clinically (nine patients), with duplex ultrasound (nine patients), vena cavography (four patients), and biopsy (seven patients). RESULTS Original pressure gradients ranged from 3 to 14 mm Hg, with a mean of 9 mm Hg. Gradients were reduced to 3 mm Hg or less in all nine patients; presenting signs and symptoms either resolved or improved in eight of nine patients. The ninth patient required repeated transplantation 2 days later. A second patient died 433 days after stent placement of recurrent hepatitis C. Another initially improved following caval stent placement, but underwent repeated transplantation 7 days later due to hepatic necrosis from hepatic arterial thrombosis. Follow-up for the remaining six patients has averaged 491 days, with no clinical, venographic, or ultrasound evidence for recurrent caval stenosis. CONCLUSIONS Intermediate term results suggest that primary Gianturco stent placement for IVC stenosis, compression, or torsion resulting after liver transplantation is safe and effective.

Intra-operative 3D ultrasound augmentation

We introduce an automated and accurate system for registering pre-operative 3D MR and CT images with intraoperative 3D ultrasound images based on the vessels visible in both. The clinical goal is to guide the radio-frequency ablation (RFA) of liver lesions using percutaneous ultrasound even when the lesions are not directly visible using ultrasound. The lesions locations and desired RFA sites are indicated on pre-operative images, and those markings are made to appear within the intra-operative 3D ultrasound images. We present our current implementation, provide analyses of its components, and demonstrate its performance.

Sonographic Evaluation of Venous Obstruction in Liver Transplants

OBJECTIVE The purpose of our study was to identify specific Doppler criteria for portal vein and outflow vein (hepatic veins and inferior vena cava) obstruction in liver transplants. MATERIALS AND METHODS A retrospective review was performed of Doppler sonographic studies and angiograms in 94 liver transplant cases (72 whole liver, 22 lobar) with suspected vascular obstruction. The angiograms were classified as normal, occluded, or stenosed on the basis of appearance and elevated pressure gradient. Sonography was correlated with angiography. The following Doppler parameters were evaluated: for the portal vein, peak anastomotic velocity and anastomotic-to-preanastomotic velocity ratio; and for the outflow veins, venous pulsatility index. Receiver operating characteristic curves were constructed and optimum thresholds for stenosis were defined. RESULTS There were 16 cases of portal vein obstruction (11 stenosis, five occlusion) and 35 cases of outflow vein obstruction (34 stenoses, one occlusion). Mean peak anastomotic velocity in normal portal veins was 58 cm/s, whereas mean peak anastomotic velocity in stenosed veins was 155 cm/s (p = 0.0007). Peak anastomotic velocity threshold of > 125 cm/s was 73% sensitive and 95% specific for stenosis. Mean anastomotic-to-preanastomotic velocity ratio in normal portal veins was 1.5, and mean anastomotic-to-preanastomotic velocity ratio in stenosed veins was 4.69 (p = 0.001). A 3:1 ratio was 73% sensitive and 100% specific for stenosis. Mean venous pulsatility index for normal outflow veins was 0.75, and mean venous pulsatility index in stenosed veins was 0.39. A venous pulsatility index of < 0.45 was 95.7% specific for stenosis. The areas under the receiver operating characteristic curve were 0.83 for peak anastomotic velocity, 0.86 for anastomotic-to-preanastomotic velocity ratio, and 0.84 for venous pulsatility index, indicating good correlation. CONCLUSION Peak anastomotic velocity, anastomotic-to-preanastomotic velocity ratio, and venous pulsatility index are useful parameters for diagnosing venous stenosis in liver transplants.

Analysis of the Parameter Space of a Metric for Registering 3D Vascular Images

We present a new metric for registering 3D images of vasculature, and we analyze the rigid-body transformation parameter space of that metric and its derivatives. To quantify and direct a source images alignment with a target image, this new vascular-image registration system models the vessels in the source image and makes measurements in the target image at a sparse set of transformed points from the centerlines of those models. The system is fast and effective because the measures made at the transformed centerline points incorporate the general geometric properties of tubes and specific model-quality information calculated during the vessel model generation process. Additionally, by adjusting the sample density or scaling the centerline point measures, coarse-to-fine registration strategies are directly enabled. We present visualizations of the metrica nd its derivatives over a range of mis-registrations given different sample densities and different measure scalings using magnetic resonance angiograms, x-ray computed tomography images, and 3D ultrasound images.

3D stereo interactive medical visualization

Our interactive, 3D stereo display helps guide clinicians during endovascular procedures, such as intraoperative needle insertion and stent placement relative to the target organs. We describe a new method of guiding endovascular procedures using interactive 3D stereo visualizations. We use as an example the transjugular intrahepatic portosystemic shunt (TIPS) procedure. Our goal is to increase the speed and safety of endovascular procedures by providing the interventionalist with 3D information as the operation proceeds. Our goal is to provide 3D image guidance of the TIPS procedure so that the interventionalist can readily adjust the needle position and trajectory to reach the target on the first pass. We propose a 3D stereo display of the interventionalists needle and target vessels. We also add interactivity via head tracking so that the interventionalist gains a better 3D sense of the relationship between the target vessels and the needle during needle advancement.

Correlation of perfusion abnormalities on CTAP and immediate postintravenous gadolinium-enhanced gradient echo MRI.

Abstract.Background: The purpose of this study was to evaluate patients with wedge-shaped perfusion defects seen on spiral CT arterial portography for the presence of transient increased wedge-shaped enhancement on dynamic gadolinium-enhanced gradient echo MR images. Methods: Nineteen patients underwent CTAP and MRI within a 2-week interval. All patients with wedge-shaped perfusion defects on CT arterial portography were evaluated in a separate review session for the presence of transient increased segmental hepatic enhancement on dynamic gadolinium-enhanced spoiled gradient echo (SGE) MR images. Results: Eight patients were identified to have subsegmental, segmental, or lobar wedge-shaped perfusion defects by CT arterial portography. In 8/8 patients, there was transient wedge-shaped increased hepatic enhancement on MR images which corresponded to the perfusion defects identified on CT arterial portography. Transient increased enhancement on MR images was observed on immediate postgadolinium images as high-signal intensity of the involved subsegment, segment, or lobe. This relatively high-signal area faded to near isointensity in all cases on images obtained at 45 s. Conclusion: Wedge-shaped perfusion defects demonstrated by CT arterial portography corresponded to wedge-shaped increased hepatic enhancement following gadolinium administration on SGE MR images.

Balloon tamponade for the treatment of inadvertent subclavian arterial catheter placement.

Abbreviations: CFA common femoral artery, SCA subclavian artery THE routine placement of central venous access devices using bony landmarks is cost-effective and safe. Complications from “blind” subclavian vein access are uncommon, but they can occur and include pneumothorax, accidental puncture of the subclavian artery (SCA) with or without subsequent catheter placement, arteriovenous fistula formation, pseudoaneurysm formation, and “pinch-off syndrome” (1,2). Inadvertent catheterization of the SCA has been classically treated in one of two ways: (i) surgical catheter removal with repair of the arterial injury and (ii) uncontrolled catheter removal with simultaneous external compression. We relate our experience with a simple technique previously described for the controlled removal of inadvertently placed SCA catheters by endovascular balloon tamponade.