Acoustical Imaging and Processing of Blood Vessel and the Related Materials Using Ultrasound Doppler Effect

Pre-clinical assessment of a prototype non-invasive diagnostic device to detect aortic aneurysms

We have developed a non-invasive diagnostic device for treating thoracic aortic aneurysm that can be applied at a peripheral artery. This study aimed to examine how configuration and size of an aneurysm as well as endoluminal pressure affect our diagnostic device's ability to detect an aneurysm, using a pulsatile mock circulation. We created three different-sized (12, 16, and 20 mm) saccular and fusiform aneurysm models using silicone and incorporated them in a pulsatile perfusion circuit to evaluate vertical vessel wall velocity wave form at a location apart from the aneurysm. We also varied the pressure condition to evaluate the changes in the detected wave forms. In both fusiform and saccular aneurysm models, biphasic wave forms indicating the presence of aneurysm within the circuit were observed. Regarding aneurysm diameter, biphasic wave forms were observed in all aneurysm models. However, in the 12-mm model, which is relevant to the minimum diameter of clinical diagnostic criteria for an aneurysm relative to normal size, no biphasic waveform was detected when the endoluminal pressure was relatively low. In the 16- and 20-mm models, biphasic waveform was detected without being affected by the configuration and endoluminal pressure. The detectability of aneurysms within a pulsatile mock circulation using our non-invasive diagnostic device was not affected by the clinically relevant configuration and size of the aneurysm under slightly hypertensive endoluminal pressure condition. Low endoluminal pressure may lower the diagnostic sensitivity for relatively small saccular aneurysm.

Frequency and chaotic analysis of pulsatile motion of blood vessel wall related to aneurysm

BACKGROUND/OBJECTIVE

In this research, using our proposed method, clinical measurements on the pulsatile velocity of blood vessel wall were conducted for cases with aneurysm. Furthermore, detailed analyses of frequency and attracter of trajectories of velocity of blood vessel wall were conducted. On the basis of these analyses, we tried to conduct unified clarification of the change and disturbance of frequency and wave form of pulsatile velocity of blood vessel wall caused by blood vessel diseases such as aneurysm.

RESULTS

In the pulsation motion of blood vessel wall, vasomotion, which is a regular long periodic fluctuation of amplitude of the pulsatile velocity of blood vessel wall, was found to exist. Furthermore, the shift of its frequency into low frequency region was found to correspond well with an increase in I∗, an indicator of progressive degree of visco elasticity of blood vessel wall and it reflects the mechanical deterioration of blood vessel wall. This long periodic fluctuation of amplitude of the pulsatile velocity of blood vessel wall exists in the low frequency region that composes the frequency of the pulsatile velocity of blood vessel wall. On the other hand, wave forms in high frequency region that compose the frequency of pulsatile velocity of blood vessel wall were found to correspond well with each pulsatile velocity wave form of blood vessel wall itself and their disturbances caused by the existence of aneurysm was typically reflected in these wave forms.

CONCLUSION

By dividing frequencies that compose the frequency of the pulsatile velocity of blood vessel wall into low and high frequency regions and conducting analyses at each region, the possibility of accurate selective detection of blood vessel diseases such as mechanical deterioration of blood vessel wall (low frequency region) and morphological change of blood vessel wall that is aneurysm (high frequency region) was indicated.

The analysis and diagnosis of unstable behavior of the blood vessel wall with an aneurysm based on noise science

Previously, one of the authors developed a noninvasive measurement method of acceleration and deceleration during the expansion process of the blood vessel wall under pulsatile pressure flow by measuring the strain rate of the blood vessel wall using a supersonic Doppler effect sensor aided by computer analysis (DPC method). In this paper, on the basis of the analysis of chaos theory, that is, the complexity of science, the unstable behavior of the blood vessel wall with an aneurysm was investigated by identifying the characteristic DPC wave forms induced by the onset and progression of aneurysm. These results showed that unstable dynamic behavior of the blood vessel wall occurs due to the progression of the aneurysm. Furthermore, using the theoretical analysis of chaos, this unstable behavior of the blood vessel wall was quantified and the fundamental principle of a noninvasive diagnostic method of the progressive degree of aneurysm was proposed.