Clinical Trial Details
— Status: Active, not recruiting
Administrative data
NCT number |
NCT05841524 |
Other study ID # |
238649 |
Secondary ID |
|
Status |
Active, not recruiting |
Phase |
|
First received |
|
Last updated |
|
Start date |
April 1, 2023 |
Est. completion date |
January 1, 2025 |
Study information
Verified date |
June 2024 |
Source |
St. Olavs Hospital |
Contact |
n/a |
Is FDA regulated |
No |
Health authority |
|
Study type |
Observational
|
Clinical Trial Summary
The goal of this observational study is to perform an in vivo feasibility study using real
time (3D) ultrasound based vector flow imaging in 10 AAA patients (5 with intraluminal
thrombus and 5 without intraluminal thrombus). Furthermore, the investigators will
investigate the added value of contrast microbubbles in these high framerate, plane wave
ultrasound measurements.
Included patients will undergo ultrasound scanning of their AAA, using multiple ultrasound
sequences. Sequences will be tested with and without the addition of ultrasound contrast
microbubbles.
Description:
Currently a AAA diameter > 5.5 cm is the cut-off for treatment with the rationale that
rupture risk outweighs risk of surgery at that point. Although in large cohorts such
thresholds adequately reflect the repair indication, they fail in case of patient-specific
decision-making. This is reflected by the fact that both small AAA rupture and large AAA's
have been documented to be stable. Moreover, recently introduced biomechanical parameters
show promising results with respect to improved rupture risk prediction. A key parameter is
intraluminal thrombus (ILT) formation at the vessel wall, which is observed in 75% of AAA's.
Recent work has shown ILT to be promoting rupture risk, outweighing its protective effect by
reducing wall stress. An explanation lies in the fact that the vessel wall is primarily
oxygenated due to luminal oxygen diffusion and ILT decreases oxygen supply to the AAA wall by
as much as 95%. This, in turn, leads to hypoxia, inflammation and vessel wall weakening,
promoting AAA rupture. Others have also shown that small AAA's (< 6 cm) that ruptured have a
significantly higher volume percentage of ILT. Biomechanics behind the formation of ILT
indicate that aneurysmal blood flow plays a role, in combination with the complex and
patient-specific AAA geometry, inducing blood flow perturbations, e.g. vortices and
stagnation zones. These local blood flow perturbations facilitate platelet adhesion and ILT
formation in regions of slow and stagnant flow, in turn increasing AAA growth and the
associated rupture risk. This project is a first step to quantify in vivo AAA blood flow,
using high frame rate ultrasound techniques, to perform both better risk stratification and
risk management.
Conventional color Doppler imaging is performed using focused ultrasound beams, which limits
the achievable frame rates to approximately 25 frames per second (fps). Recent developments
in computer hardware and software has enabled a shift towards unfocused imaging, where
anatomical ultrasound images can be made using only a single unfocused ultrasound pulse. With
the new technology, the frame rate limit is suddenly increased by a factor of 500, which
results in increased flexibility when designing imaging sequences. Extremely high frame rates
can now be traded for increased complexity, enabling new information to be obtained.
In this project, the investigators will use continuous, high frame rate, ECG gated, 3D slice
acquisition to quantify blood flow at the inflow of the aneurysm. This will result in a
vector flow imaging dataset, including the through plane component. The received signal is
based on the in vivo scattering properties of blood. However, the technique might benefit
from the addition of ultrasound contrast agents, therefore a second set of measurements will
be obtained after intravenous injection of a contrast agent (SonoVue).
The hypothesis is that high frame rate 3D ultrasound can be used to image aneurysm blood
flow. From these measurements the investigators expect that travel distance analysis shows
different outcomes between AAA patients with and without intraluminal thrombus. In turn this
is another piece of the puzzle to stratify patients having a higher risk of aneurysm rupture.