When an aneurysm occurs, which is essentially a bulge in a blood vessel, the size of the cross section of an artery more than doubles. This considerably increases artery wall tension and therefore the risk of rupture. An aneurysm in the brain leads to life-threatening hemorrhaging, requiring immediate emergency surgery. "10 % of patients with a burst aneurysm die on the way to hospital", says Enseñat. “Aneurysms are an extremely complex disease with a high mortality rate, 46 % during the first 30 days after treatment. Three quarters of the patients who survive will never fully regain their ability to work." To avoid blood vessel enlargement and rupture, cerebral aneurysms are treated by a procedure where the bulge in the blood vessel is separated from the blood flow with a clip.
Fast, reliable checking of blood flow
A successful outcome of such neurovascular surgery depends on cutting off blood flow to the aneurysm while maintaining blood flow in the neighboring functional blood vessels. However, a purely visual evaluation of the surgical site is inadequate, as it is extremely difficult to inspect vascular circulation. “Postoperative evaluation shows that between 4 and 8 % of deformities are not completely clipped and 8 to 12 % of neighboring functional blood vessels are closed by mistake,” says Enseñat. For the first time, fluorescence-aided videoangiography with the Leica FL800 fluorescence module enables neurosurgeons to watch blood flow in the brain during surgery via the surgical microscope, without additional measuring apparatus.
The patient is injected intravenously with ICG (IndoCyanineGreen) dye, which is well tolerated and spreads through the bloodstream quickly. Excited by light in the 800 nanometer wavelength range, the ICG fluoresces and emits light at a wavelength of 835 nanometers. This infrared light, which is invisible to the human eye, is filtered out by means of the microscope optics and then transformed into a black-and-white image by a near infrared NIR CCD camera. Within seconds after the ICG injection, the surgeon can examine blood flow in the vascular structures in real time on a connected monitor.
Intraoperative monitoring of blood vessels offers more safety for the patient
"Videoangiography with the Leica FL800 is a fast, easy method of checking whether the aneurysm has been perfectly clipped and whether blood is properly flowing through the bypass", says Enseñat. "We can then predict with more certainty that the patient will not suffer from complications. When we see the contrast medium in the branch that supplies blood to the arms, we know that this part of the brain has not been damaged and the patient can move his or her arms."
Gaining valuable time
"Unlike intraoperative arteriography, videoangiography does not require extra staff or space in the operating room. Whereas surgery has to be stopped for 20 to 40 minutes for arteriography, the Leica FL800 can be used to check blood vessels with minimal interruption. The surgeon presses a single key to switch from white light to infrared mode and then watches the blood flow in real time. “Our study showed an almost 100 % match between the results of postoperative arteriography and fluorescence-aided video angiography", comments Enseñat. "Arteriography will still be important; due to digital subtraction we are able to see hidden blood vessels, too. But videoangiography with the Leica FL800 fluorescence module is an innovative, simple, and above all, extremely fast method – and that is one of the main criteria in cerebral aneurysm surgery."
Leica FL800 for Real-time Vascular Fluorescence
The Leica FL800 intraoperative videoangiography module is used in conjunction with ICG (IndoCyanineGreen) fluorescent agent to visualize blood flow in cerebral vessels. Surgeons can watch a patient’s blood flow in the brain during surgery directly through the microscope or on a monitor. The patient is injected intravenously with ICG, which is well tolerated. Excited by light in the 800 nanometer wavelength range, the ICG fluoresces. A near infrared NIR CCD camera captures the fluorescence signal and transforms it into a black-and-white image. The surgeon can then examine the blood flow in the vascular structures within seconds after the ICG injection. “Using the Leica FL800, the ICG can be visualized quickly, conveniently, and most importantly, directly through the surgical microscope,” says Senior Product Manager Roger Spink from Leica Microsystems. The Leica FL800 can be integrated with the Leica M530 OH6, Leica M720 OH5, and Leica M525 OH4 surgical microscopes.