Monitoring peripheral hemodynamic response to changes in blood pressure via photoacoustic imaging

Abstract

Chronic wounds and amputations are common in chronic kidney disease patients needing hemodialysis (HD). HD is often complicated by drops in blood pressure (BP) called intra-dialytic hypotension. Whether intra-dialytic hypotension is associated with detectable changes in foot perfusion, a risk factor for wound formation and impaired healing remains unknown. Photoacoustic (PA) imaging is ideally suited to study perfusion changes. We scanned the feet of 20 HD and 11 healthy subjects. HD patients were scanned before and after a dialysis session whereas healthy subjects were scanned twice at rest and once after a 10 min exercise period while BP was elevated. Healthy (r=0.70, p<0.0001) and HD subjects (r=0.43, p<0.01) showed a significant correlation between PA intensity and systolic BP. Furthermore, HD cohort showed a significantly reduced PA response to changes in BP compared to the healthy controls (p<0.0001). Hence showing that PA can monitor hemodynamic changes due to changes in BP.

Multispectral optoacoustic tomography for the non-invasive identification of patients with severe anemia in vivo

“…Finally, local quantitative perfusion assessment is another promising potential field of application. Promisingly, previous studies were already able to demonstrate a positive correlation of foot perfusion assessed by general optoacoustic signal intensity in pedal tissue of dialysis patients and healthy controls with systolic blood pressure [37] . Real-time local quantitative perfusion and oxygenation analysis based on quantitative assessment of oxygenated and deoxygenated hemoglobin could prove valuable in numerous settings, including assessing perfusion of a freshly implanted kidney as an addition to pulse doppler sonography on a tissue level, and in support of both preclinical and clinical functional imaging studies in various tissues.…”

Photoacoustic imaging to monitor outcomes during hyperbaric oxygen therapy: Validation in a small cohort and case study in a bilateral chronic ischemic wound

“…(57) But the laser-based systems are significantly more expensive and sometimes operate above the maximum permissible exposure limit set by ANSI. (46, 58)…”

“…The AcousticX uses a 128-element US transducer operating at a central frequency of 7 MHz, 0.38 × 6 cm field of view, and a bandwidth of 80.9%. (46) All scans were done using a hand-held transducer. All participants were scanned twice within 5 min of entering or existing the HBO 2 chamber ( Fig.…”

“…1 ). Beyond oxygenation, PA signal can also correspond to perfusion based on total signal (i.e., more total signal = more total hemoglobin);(46) concurrently, ratiometric signal can be used to quantify oxygenation. (42)…”

Two-step proximal gradient descent algorithm for photoacoustic signal unmixing

“…Optical-resolution photoacoustic microscopy (OR-PAM) is a non-invasive biomedical imaging technique that provides subcellular resolution based on optical-absorption contrast [1] , [2] . Multi-wavelength photoacoustic excitations of the same target can probe various molecules [3] , [4] , [5] , [6] , [7] and quantify hemoglobin concentration [8] , [9] , [10] , [11] , [12] , oxygen saturation (sO 2 ) [13] , [14] , [15] , and blood flow [16] , [17] , [18] . Multiple excitations usually sacrifice the scanning speed, which is unfavorable for acquiring dynamic information and mitigating motion artifacts.…”