Diagnosis and treatment of atherosclerosis necessitates the detection and differentiation of rupture prone plaques. In
principle, intravascular photoacoustic (IVPA) imaging has the ability to simultaneously visualize the structure and
composition of atherosclerotic plaques by utilizing the difference in optical absorption. Extensive studies are required to
validate the utility of IVPA imaging in detecting vulnerable plaques and address issues associated with the clinical
implementation of the technique. In this work, we performed ex vivo imaging studies using a rabbit model of
atherosclerosis. The intravascular photoacoustic (IVPA) and ultrasound (IVUS) images of the normal aorta and aorta
with plaque were obtained and compared with histological slices of the tissue. The results indicate that IVPA imaging is
capable of detecting plaques and showed potential in determining the composition. Furthermore, we initially addressed
several aspects of clinical implementation of the IVPA imaging. Specifically, the configuration of combined IVPA and
IVUS catheter was investigated and the effect of the optical absorption of the luminal blood on the IVPA image quality
was evaluated. Overall, this study suggests that IVPA imaging can become a unique and important clinical tool.
In many clinical and research applications including cancer diagnosis, tumor response to therapy, reconstructive
surgery, monitoring of transplanted tissues and organs, and quantitative evaluation of angiogenesis, sequential and
quantitative assessment of microcirculation in tissue is required. In this paper we present an imaging technique capable
of spatial and temporal measurements of blood perfusion through microcirculation. To demonstrate the developed
imaging technique, studies were conducted using phantoms with modeled small blood vessels of various diameters
positioned at different depths. A change in the magnitude of the photoacoustic signal was observed during vessel
constriction and subsequent displacement of optically absorbing liquid present in the vessels. The results of the study
suggest that photoacoustic, ultrasound and strain imaging could be used to sequentially monitor and qualitatively assess
blood perfusion through microcirculation.
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.
Combination of three complementary imaging technologies - ultrasound imaging, elastography, and optoacoustic imaging - is suggested for detection and diagnostics of tissue pathology including cancer. The fusion of these ultrasound-based techniques results in a novel imaging system capable of simultaneous imaging of the anatomy (ultrasound imaging), cancer-induced angiogenesis (optoacoustic imaging) and changes in mechanical properties (elasticity imaging) of tissue to uniquely identify and differentiate pathology at various stages. To evaluate our approach, analytical and numerical studies were performed using heterogeneous phantoms where ultrasonic, optical and viscoelastic properties of the materials were chosen to closely mimic soft tissue. The results of this study suggest that combined ultrasound-based imaging is possible and can provide more accurate, reliable and earlier detection and diagnosis of tissue pathology. In addition, monitoring of cancer treatment and guidance of tissue biopsy are possible with a combined imaging system.