Integrated catheter for intravascular ultrasound and photoacoustic imaging Andrei B. Karpiouk, Bo Wang, Stanislav Y. Emelianov * Department of Biomedical Engineering University of Texas at Austin emelian@mail.utexas.edu ABSTRACT The vulnerability of atherosclerotic plaques that are formed in the arterial walls due to atherosclerosis depends on both their distribution and composition. The distribution of the plaques can be imaged using an intravascular ultrasound (IVUS) imaging which is a clinically approved minimally-invasive method. The recently introduced intravascular photoacoustic (IVPA) imaging may be used to obtain the necessary information about the composition of the plaques. Previous studies using excised rabbit arteries have demonstrated that the combined IVUS/IVPA imaging may simultaneously provide the morphology and functional information of plaques. However, for in-vivo IVUS/IVPA imaging, an integrated IVUS/IVPA imaging catheter capable both of delivering light into a vessel lumen with consequent detection of photoacoustic transients and of probing the arterial walls in pulse-echo mode is required. In the current study, an advanced prototype of the integrated IVUS/IVPA imaging catheter based on a 40-MHz single-element ultrasound transducer and a 600-μm-core single optical fiber is introduced. Unlike previously reported prototypes, the current integrated IVUS/IVPA imaging catheter is capable of cross-sectional imaging of vessel walls via mechanical rotation of the catheter. The performance of the integrated IVUS/IVPA catheter was evaluated in tissue-mimicking phantoms with and without the presence of blood in a lumen. The results of our study suggest that the approach used to develop integrated IVUS/IVPA imaging catheter can be successfully translated to the clinical environment for in-vivo combined IVUS/IVPA imaging. Keywords: Intravascular imaging, imaging catheter, intravascular photoacoustic imaging, intravascular ultrasound imaging, atherosclerotic plaques, vulnerability of the plaques. 1. INTRODUCTION Atherosclerosis is a complex disease related to serious problems with arteries and characterized by different types of plaques which develop within arterial walls. The estimated incidence of the atherosclerotic plaques is more than one million per year in the United States alone. 1 Vulnerable plaques exhibit a rapid progression that depends on both distribution and composition. 2 Therefore, reliable information about both distribution and composition of plaques may help to determine how vulnerable the plaques are and what the appropriate treatment is. Among the number of imaging methods that are suitable to obtain the distribution of the atherosclerotic plaques, intravascular ultrasound (IVUS) imaging has demonstrated great potential to monitor the distribution of the plaques in the arterial walls and along the arteries. 3 Compared to non-invasive imaging techniques such as angiography, computational tomography and magnetic resonance imaging, 4 the clinically approved, minimally invasive IVUS imaging is real-time, inexpensive, and high resolution imaging method that does not use an ionizing radiation. Compared to optical coherence tomography, the IVUS imaging is characterized by a significantly greater penetration depth. 5 IVUS imaging can identify atherosclerotic plaques, yet the information about the composition of the plaques provided in IVUS images is very limited. However, the composition of the plaques can be obtained using the recently introduced intravascular photoacoustic (IVPA) imaging. 6-9 While the weak contrast in IVUS imaging is dictated by modest * emelian@mail.utexas.edu ; phone 1-512-471-1733; fax 1-512-471-0616; http://ultrasound.bme.utexas.edu/ Photons Plus Ultrasound: Imaging and Sensing 2010, edited by Alexander A. Oraevsky, Lihong V. Wang, Proc. of SPIE Vol. 7564, 756408 · © 2010 SPIE · CCC code: 1605-7422/10/$18 · doi: 10.1117/12.842984 Proc. of SPIE Vol. 7564 756408-1 Downloaded from SPIE Digital Library on 25 Feb 2010 to 128.83.154.17. Terms of Use: http://spiedl.org/terms