Search

Photoacoustic imaging is a hybrid modality with advantages of both the ultrasound and optical imaging. This technique with optical spectroscopic contrast and acoustic resolution holds promise in wide range of clinical and preclinical applications. Since photoacoustic imaging also involves ultrasound detection, it is straight forward to implement pointof- care dual mode systems with capability of structural and functional imaging. High signal generated from skin-melanin layer is an important problem in any handheld reflection-mode photoacoustic probes. This problem caused by high light fluence just beneath the ultrasound probe results in reduction of vascular contrast and also causes difficulty in image interpretation. In this work, using our LED-based photoacoustic and ultrasound imaging system (AcousticX), we demonstrate the potential of using ultrasound acquisitions dynamically to suppress high photoacoustic signal from skin surface and qualitatively improve the image contrast and quality. In AcousticX, photoacoustic and conventional pulseecho acquisitions are performed in an intermittent manner resulting in a dual-mode display frame rate of 30 Hz. We make use of the line-by-line/planewave ultrasound acquisitions to automatically delineate the skin surface in quasi realtime and suppress photoacoustic signal from the identified area, resulting in improved image interpretation and contrast without losing temporal resolution. Real-time 2D and 3D (linear scan) imaging experiments were performed on finger and foot dorsum of healthy human volunteers to validate the new skin-signal suppression technique. Results give a direct confirmation that our ultrasound-assisted skin-signal reduction feature holds strong potential in enhancing vascular contrast and visual quality in real-time 2D and 3D LED-based photoacoustic imaging.

Photoacoustic imaging, the fastest growing biomedical imaging modality of the decade holds strong potential in creating a significant impact in the field of medicine. This non-invasive technique with optical spectroscopic contrast and ultrasonic spatial resolution can be a potential tool for diagnosis and treatment monitoring of several devastating diseases like cancer. Even though the growth of this imaging modality in a research setting is exemplary, clinical translation is not happening at an expected pace. In this chapter, after briefly discussing about the technology and its market, we will discuss about important components in a photoacoustic imaging system (light source, ultrasound probes, DAQ etc.) and conclude about the key strategies in this direction and the improvements that may potentially help for fast clinical translation. In the next part, we elaborate about the major steps in the clinical translation process—focusing on key opportunities and challenges to be solved.

Photoacoustic (PA) or optoacoustic imaging can visualize tissue-optical absorbers, especially hemoglobin, with optical contrast and ultrasound (US)-like resolution and imaging depth. Since both PA and US imaging involves US detection, it is straightforward to develop dual-mode imaging systems with unprecedented functional and structural imaging capabilities. Researchers have already demonstrated the potential of utilizing this complementary contrast for several animal imaging experiments and early clinical pilot studies. PA imaging conventionally uses slow, bulky and high-priced lasers as excitation sources. Use of these high-power pulsed lasers is hindering the clinical translation process of this imaging modality with tremendous potential. Advances in solid-state device technology have recently resulted in the development of a new class of high-power light emitting diodes (LEDs) that can be used as fast, robust and affordable pulsed excitation sources for PA imaging. In this paper, we review multiple LED-based PA/US imaging implementations (commercial and lab-made systems) and demonstrate its functional, molecular and structural imaging capabilities using several clinical/preclinical imaging examples. Specific focus will be given to 2D and 3D superficial vasculature and oxygen saturation imaging in multiple in vivo clinical and preclinical studies.

Photoacoustic imaging is a hybrid medical imaging technique that combines the contrast and spectral sensitivity of optical imaging with resolution and tissue penetration of ultrasound. Due to the difference between the optical absorption spectra of deoxygenated and oxygenated hemoglobin, multispectral photoacoustic imaging holds strong potential in noninvasive local blood oxygen saturation imaging. Oxygen saturation imaging is one of the most promising applications of photoacoustic imaging and has been widely explored in studies related to tumor hypoxia, cancer therapy etc. However, clinical translation of this technology has often been limited by bulky and expensive excitation sources. Recently, we introduced a multi-wavelength real-time LED-based photoacoustic/ultrasound imaging system. In this work, potential of this LED-based system in real-time oxygen saturation imaging is demonstrated using an in vivo measurement on a human volunteer. We used ultra-fast switching two-wavelength LED arrays (750nm/850nm) along with a linear-array 7 MHz US probe for the experiments. 2D PA, US, and oxygen saturation imaging were performed on the index finger of a human volunteer. Results demonstrate that LED-based PA imaging system used in this study is promising for generating 2D/3D oxygen saturation maps along with PA and US images in real-time. We believe that these results will have profound impact in non-invasive blood oxygen saturation imaging and subsequent clinical translation of PA-based oximetry.

In order to maintain and promote health among elderly people through the effective use of exercise, an “e-Health Promotion System” is proposed as a network-based health promotion system, to manage health conditions and provide evidence-based exercise prescriptions via the Internet. The personal information such as health conditions and exercise prescriptions need to be securely managed as security threats exist in the Internet medium. The aim of this research is to develop a secure data management server for an e-Health Promotion System. The data management server requires a secure system, a fault tolerance database system and an easy-to-use user interface. In order to establish the server which meets the above-mentioned system requirements, We selected a host computer with a Unix type operating system, which contains a robust security features in its core. Since the database system we adopted here has the features such as a fault-tolerance and high-speed access to the stored data, it can maintain much user information both securely and speedily. Moreover, the web-based user interface allows users to provide secure and easy access to the data server by an access control of authentication. The server can therefore manage the user information with both high security and high reliability, and provide easy user interface for the elderly. As a result of applying this system to field experiments, we confirmed the security and the reliability of the proposed system.

In 1995, a group at Baylor College of Medicine started to develop the NEDO biventricular assist device (BVAD) using two Gyro permanently implantable (PI) centrifugal pumps. This pump consists of a sealless pump housing and an impeller supported with a double pivot bearing. In May 2001, an RPM dynamic suspension system (RPM-DS) for the impeller was developed to improve durability and antithrombogenicity without a complex magnetic suspension system. From March 2000 to March 2002, eight BVAD bovine experimental studies were performed for more than 1 month. Two pumps were implanted in two cases without the RPM-DS (group A) and in six cases with the RPM-DS (group B). In group A, the survival period was 45 and 50 days. The primary reason for termination was an increase in the requiring power, which was related to deposition of white thrombus on the bottom bearing. In group B, the survival period was 37, 48, 51, 60, 80, and 90 days. The reasons for termination were not related to thrombus formation. No thrombus was observed in the pumps except for one right pump. In that experiment, the thrombus formation may have occurred when that pump had a low flow rate at a level of 1 L/min for 6 hr. These studies demonstrate the apparent antithrombogenic effect of RPM-DS. The NEDO BVAD is ready to move into a 3-month preclinical system evaluation.

For safe and effective home healthcare, a network system monitoring one’s vital signs and evaluating one’s health conditions is highly desirable. In our laboratory, we have developed a vital sensing system for home healthcare. The purpose of this study is to design and implement a prototype web-based healthcare management system (WBHMS) to make effective use of the data that are measured by the vital sensing system.

Physiological adaptation of the recipient to a nonpulsatile biventricular assist system (NPBVAS) is not well understood. The aim of this study is to evaluate the physiological adaptation of experimental animals after NPBVAS implantation. Since May 2001, four long-term NPBVAS implant experiments in calves were performed. The blood gas and hemodynamic data were analyzed retrospectively. An additional prospective experiment was performed to confirm retrospective findings. All calves (n = 5) lived longer than 5 weeks without complication. In retrospective analysis, there was not a correlation between the O2 content and total blood flow in the pulmonary artery during the 1st postoperative week, but they began to correlate within the 2nd postoperative week. Then, there was a strong correlation after the 3rd postoperative week (r = 0.753). In the prospective experiment, O2 content related to total pulmonary flow after 2 weeks (r = 0.732) was the same as in the retrospective study. Most of the hemodynamic parameters studied became normalized after 14 days. In addition, easier controllability of the blood pumps was demonstrated after the 2nd postoperative week in all five experiments. Experimental results suggested that the native healthy heart accepted NPBVAS by reducing its cardiac output in 2 weeks. In addition, complicated control of the BPVAS was not necessary after 2 weeks of implantation. These results demonstrate the possibility of physiological adaptation to the NPBVAS being established within 2 postoperative weeks.