Behavior of tip-steerable needles in ex vivo and in vivo tissue.

Robotic needle steering is a promising technique to improve the effectiveness of needle-based clinical procedures, such as biopsies and ablation, by computer-controlled, curved insertions of needles within solid organs. In this paper, we explore the capabilities, challenges, and clinical relevance of asymmetric-tip needle steering through experiments in ex vivo and in vivo tissue. We evaluate the repeatability of needle insertion in inhomogeneous biological tissue and compare ex vivo and in vivo needle curvature and insertion forces.

Impact of dynamic computed tomographic angiography on endograft sizing for endovascular aneurysm repair.

Purpose: To quantify dynamic changes in aortoiliac dimensions using dynamic electrocardiographically (ECG)-gated computed tomographic angiography (CTA) and to investigate any potential impact on preoperative endograft sizing in relation to observer variability.

Methods: Dynamic ECG-gated CTA was performed in 18 patients with abdominal aortic aneurysms. Postprocessing resulted in 11 datasets per patient: 1 static CTA and 10 dynamic CTA series.

In-vivo imaging of changes in abdominal aortic aneurysm thrombus volume during the cardiac cycle.

Purpose: To evaluate in-vivo thrombus compressibility in abdominal aortic aneurysms (AAAs) to hopefully shed light on the biomechanical importance of intraluminal thrombus.

Methods: Dynamic electrocardiographically-gated computed tomographic angiography was performed in 17 AAA patients (15 men; mean age 73 years, range 69-76): 11 scheduled for surgical repair and 6 under routine surveillance. The volumes of intraluminal thrombus, the lumen, and the total aneurysm were quantified for each phase of the cardiac cycle.

Phase 3, randomized, double-blind study of plasma-derived human thrombin versus bovine thrombin in achieving hemostasis in patients undergoing surgery.

Objective: To compare the effectiveness of plasma-derived human thrombin and bovine thrombin for achieving hemostasis during surgery.

Methods: Adults (N = 305) with > or = 1 mild or moderate bleeding site not manageable by conventional modalities during elective cardiovascular, neurologic, or general surgical procedures at multiple study centers were randomized to human (n = 153) or bovine (n = 152) thrombin, applied topically with an absorbable gelatin sponge. Bleeding was assessed 3, 6, and 10 min post-application.

Prototypical metal/polymer hybrid cerebral aneurysm clip: in vitro testing for closing force, slippage, and computed tomography artifact. Laboratory investigation.

Object: The aim of this study was to explore the possibility that a hybrid aneurysm clip with polymeric jaws bonded to a metal spring could provide mechanical properties comparable to those of an all-metal clip as well as diminished artifacts on computed tomography (CT) scanning.

Methods: Three clips were created, and Clips I and 2 were tested for mechanical properties. Clip 1 consisted of an Elgiloy spring (a cobalt-chromium-nickel alloy) bonded to carbon fiber limbs; Clip 2 consisted of an Elgiloy spring with polymethylmethacrylate (PMMA) jaws; and Clip 3 consisted of PMMA limbs identical to those in Clip 2 but bonded to a titanium spring.

Pulse doppler and M-mode to assess viability of cardiac allografts using heterotopic femoral heart transplantation in rats.

Noninvasive assessment of heterotopic heart transplants using Doppler echocardiography was first described in two patients by Allen at Stanford in 1981. Since then, numerous experiments studying heterotopic heart transplantation in humans and large animals have confirmed its utility by employing either an intra-abdominal or cervical model. In rats, however, prior research investigating intra-abdominal heterotopic hearts has showed echocardiography to be ineffective.

A new modified technique for heterotopic femoral heart transplantation in rats.

Background: Abbott developed the first experimental accessory heart transplant rat model in 1964. This intra-abdominal model required a labor-intensive aortic anastomosis. In 1971, Heron modified the operation by using sutureless cervical vessel anastomoses.

Elastic and rupture properties of porcine aortic tissue measured using inflation testing.

A new inflation test device was developed to study the mechanical properties of aortic tissue. The device was used to measure failure (rupture) strength and to determine the nonlinear, anisotropic elastic properties of porcine thoracic aorta. The tester was designed to stretch initially flat, circular tissue specimens to rupture under uniform biaxial loading.

Elemental composition, morphology and mechanical properties of calcified deposits obtained from abdominal aortic aneurysms.

Calcified deposits exist in almost all abdominal aortic aneurysms (AAAs). The significant difference in stiffness between these hard deposits and the compliant arterial wall may result in local stress concentrations and increase the risk of aneurysm rupture. Calcium deposits may also complicate AAA repair by hindering the attachment of a graft or stent-graft to the arterial wall or cause vessel wall injury at the site of balloon dilation or vascular clamp placement.

North American multicenter experience with the On-X prosthetic heart valve.

Background And Aim Of The Study: This ongoing, longitudinal, multi-center, North American study was designed to evaluate the safety and effectiveness of the On-X valve.

Methods: The On-X valve was implanted in isolated aortic (AVR) and mitral (MVR) valve replacement patients at nine North American centers. Follow up was 98.

Automated methodology for determination of stress distribution in human abdominal aortic aneurysm.

Knowledge of impending abdominal aortic aneurysm (AAA) rupture can help in surgical planning. Typically, aneurysm diameter is used as the indicator of rupture, but recent studies have hypothesized that pressure-induced biomechanical stress may be a better predictor Verification of this hypothesis on a large study population with ruptured and unruptured AAA is vital if stress is to be reliably used as a clinical prognosticator for AAA rupture risk. We have developed an automated algorithm to calculate the peak stress in patient-specific AAA models.

Adjunctive transmyocardial revascularization: five-year follow-up of a prospective, randomized trial.

Background: In a prospective, randomized trial involving 263 patients who would be incompletely revascularized by coronary artery bypass grafting (CABG) alone, CABG plus transmyocardial revascularization (CABG/TMR) provided an early mortality benefit with similar angina relief compared with CABG alone at 1 year. We evaluated the long-term outcome of patients randomized to CABG/TMR or CABG alone.

Methods: Thirteen centers that enrolled 83% (218/263) of the patients in the original trial participated in this longitudinal study.

Prediction of rupture risk in abdominal aortic aneurysm during observation: wall stress versus diameter.

Objectives: We previously showed that peak abdominal aortic aneurysm (AAA) wall stress calculated for aneurysms in vivo is higher at rupture than at elective repair. The purpose of this study was to analyze rupture risk over time in patients under observation.

Methods: Computed tomography (CT) scans were analyzed for patients with AAA when observation was planned for at least 6 months.

In vivo analysis of mechanical wall stress and abdominal aortic aneurysm rupture risk.

Objective: The purpose of this study was to calculate abdominal aortic aneurysm (AAA) wall stresses in vivo for ruptured, symptomatic, and electively repaired AAAs with three-dimensional computer modeling techniques, computed tomographic scan data, and blood pressure and to compare wall stress with current clinical indices related to rupture risk.

Methods: CT scans were analyzed for 48 patients with AAAs: 18 AAAs that ruptured (n = 10) or were urgently repaired for symptoms (n = 8) and 30 AAAs large enough to merit elective repair within 12 weeks of the CT scan. Three-dimensional computer models of AAAs were reconstructed from CT scan data.