Analysis of left ventricular function, left ventricular outflow tract and aortic valve area using computed tomography: Influence of reconstruction parameters on measurement accuracy.

OBJECTIVES: Computed tomography (CT) allows reproducible assessment of left ventricular (LV) function, left ventricular outflow tract area (LVOTarea) and aortic valve area (AVA). We evaluated the influence of image reconstruction parameters on these measurements. METHODS: We analyzed 45 contrast-enhanced, retrospectively ECG-gated CT datasets acquired on a third-generation dual source system. A standard filtered-back-projection data set (20 cardiac phases (5% steps, 0-95%), 0.6-mm-slice thickness, 512 × 512 matrix) and eight reconstructions with modified slice thickness (1-8 mm), number of cardiac phases (5, 10), matrix size (256×256) and an iterative reconstruction (IR) algorithm were obtained. LV parameters (ejection fraction (EF), stroke volume (SV), end-diastolic (EDV), end-systolic volumes (ESV)), LVOTarea and AVA were assessed. RESULTS: Differences in LV parameters, LVOTarea and AVA, were only minimal between standard reconstructions and those with modified matrix size, IR algorithm and ≤2 mm slice thickness, while reconstructions with 8-mm slice thickness significantly overestimated SV (p < 0.001) and EDV (p = 0.016). AVA planimetry in reconstructions with ≥5 mm slice thickness was not feasible in 56% of patients. A decrease in the number of reconstructed phases (10 or 5) underestimated EF, SV, EDV, LVOTarea and AVA and overestimated ESV. CONCLUSIONS: Modifications of reconstruction parameters (except a slice thickness ≤2 mm) have only a marginal effect on LV, LVOTarea and AVA assessment. However, a reduced number of reconstructions per cardiac cycle may significantly influence measurements. ADVANCES IN KNOWLEDGE: Substantial modifications in number of reconstructions per cardiac cycle significantly affect the assessment of LV function, LVOTarea and AVA also in modern CT scanners.

Robotically assisted coronary artery bypass surgery with the ZEUS telemanipulator system.

Our goal of minimally invasive coronary bypass surgery is a completely endoscopic operation and anastomosis. Minimally invasive procedures reduce the invasiveness of the operation and therefore the morbidity and length of hospitalization of the patients. A possible solution to the technical problems that accompany manually performed endoscopic anastomoses is telemanipulation, which provides surgeons with the necessary equipment to accomplish totally endoscopic coronary anastomoses. Robotic telemetric systems together with 3-D visualization provide the necessary platform. This article summarizes the current worldwide experience with the ZEUS(TM) system in cardiac surgery and describes the steps from preclinical to endoscopic operation, focusing on the potential limitations of the procedure and the system.

Incorporating robotics into an open-heart program.

The above described clinical series show that after a careful and thorough training program and stepwise introduction of surgical telemanipulation systems, application of telemanipulations is safe and shows acceptable results. Still, OR times are longer than for conventional procedures, and the operation is demanding, and expensive. The main shortcoming is that the procedure is only suitable for a highly selected patient population. However, despite all the clinical experience gathered in various centers, this technique is still evolving and in its beginning. There are some very promising developments that will improve the benefit of telemanipulators. For the first time, the separation of the surgeon from the surgical field facilitates training of surgeons on simulators. This might lead to a higher standard of surgical performance. Progress in sensor technology will make tactile-force feedback available, and new 3 D-visualization systems are designed to provide a better depth perception and higher resolution of the endoscopic image. Virtual stabilizing systems will enable robotic systems to operate on a virtual arrested heart without the need for CPB or mechanical stabilizers. These and other research topics summarized under the term augmented reality will enhance the natural senses and abilities of the surgeon. More and more, automatization will find its way into the OR. Preoperatively collected data about the patient's anatomy will be used to create safety margins, the robotic system will allow for the surgeon's movements, and instruments will be able to find their way to the surgical site without remote control. Because a stepwise approach has led to the clinical results that we and others have now achieved, it is the basis for further step-by-step development of the application of telemanipulation systems in coronary artery bypass grafting, and possibly other endoscopic procedures in cardiac surgery.