P0-2 Spectroscopic Intravascular Photoacoustic Imaging
James Amirian2007, 2007 IEEE Ultrasonics Symposium Proceedings
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Abstract
Intravascular photoacoustic (IVPA) imaging has the potential to detect atherosclerotic plaques. Previously, we obtained IVPA images using a 532 nm pulsed laser and a 40 MHz intravascular ultrasound (IVUS) imaging catheter. The optical absorption of light by the plaque components was used as a contrast mechanism helpful in detecting the plaque. However, plaque differentiation requires a method to remotely assess plaque composition. We hypothesized that plaque characterization can be performed by monitoring the changes in photoacoustic response with the change in laser excitation wavelength. In this preliminary study, we performed spectroscopic IVPA imaging to analyze the change in the photoacoustic response of the aortic tissue (a rabbit aorta with plaque and a control aorta) using different laser excitation wavelengths. Specifically, we perform IVPA imaging at multiple wavelengths within 680-900 nm range. The slope of the spectral change in photoacoustic response was computed between selected wavelengths to produce a spectroscopic IVPA image. The results of our study suggest the ability of the multi-wavelength IVPA imaging to identify and differentiate the fibrous, lipid and blood components of the atherosclerotic plaque.
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The potential of intravascular photoacoustic (IVPA) imaging to detect atherosclerosis was previously demonstrated using a 532 nm nanosecond pulsed laser and an intravascular ultrasound (IVUS) imaging catheter. However, to differentiate vulnerable plaques, the composition of plaques needs to be imaged. Therefore, we introduce a multi-wavelength photoacoustic imaging method to distinguish various types of plaques. Multi-spectral IVPA imaging of ex vivo samples of normal and atherosclerotic rabbit aorta was performed at several wavelengths within 680-900 nm range. The spectral variation of photoacoustic response was extracted and a spectroscopic analysis was performed. The results of our preliminary study suggest that the spectroscopic intravascular photoacoustic imaging technique can be used to differentiate fibrous and lipid components of the atherosclerotic plaques.
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Proceedings of SPIE - The International Society for Optical Engineering, 2006
Intravascular ultrasound (IVUS) imaging has emerged as an imaging technique to evaluate coronary artery diseases including vulnerable plaques. However, in addition to the morphological characteristics provided by IVUS imaging, there is a need for functional imaging capability that could identify the composition of vulnerable plaques. Intravascular photoacoustic (IVPA) imaging, in conjunction with clinically available IVUS imaging, may be such a technique allowing vulnerable plaque characterization and differentiation. We have developed an integrated intravascular ultrasound and photoacoustic imaging system to visualize clinically relevant structural and functional properties of the coronary arteries. The performance of the combined IVUS and IVPA imaging system was evaluated through images of arterial phantoms. Experiments were performed using high frequency IVUS imaging catheters operating at 20 MHz, 30 MHz and 40 MHz. The IVPA imaging was successful in highlighting inclusions based on differential optical absorption while these lesions did not have sufficient contrast in the IVUS images. Finally, initial IVUS and IVPA imaging studies were performed on ex vivo samples of a rabbit artery using the 40 MHz IVUS imaging catheter. Results of the above studies demonstrate the feasibility of combining intravascular ultrasound and photoacoustic imaging and suggest clinical utility of the developed imaging system in interventional cardiology.
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