Optical spectroscopy approach for the predictive assessment of kidney functional recovery following ischemic injury

Abstract

Tissue that has undergone significant yet unknown amount of ischemic injury is frequently encountered in organ transplantation and trauma clinics. With no reliable real-time method of assessing the degree of injury incurred in tissue, surgeons generally rely on visual observation which is subjective. In this work, we investigate the use of optical spectroscopy methods as a potentially more reliable approach. Previous work by various groups was strongly suggestive that tissue autofluorescence from NADH obtained under UV excitation is sensitive to metabolic response changes. To test and expand upon this concept, we monitored autofluorescence and light scattering intensities of injured vs. uninjured rat kidneys via multimodal imaging under 355 nm, 325 nm, and 266 nm excitation as well as scattering under 500 nm illumination. 355 nm excitation was used to probe mainly NADH, a metabolite, while 266 nm excitation was used to probe mainly tryptophan to correct for non-metabolic signal artifacts. The ratio of autofluorescence intensities derived under these two excitation wavelengths was calculated and its temporal profile was fit to a relaxation model. Time constants were extracted, and longer time constants were associated with kidney dysfunction. Analysis of both the autofluorescence and light scattering images suggests that changes in microstructure tissue morphology, blood absorption spectral characteristics, and pH contribute to the behavior of the observed signal which may be used to obtain tissue functional information and offer predictive capability.

Enhancing in vivo renal ischemia assessment by high-dynamic-range fluorescence molecular imaging

“…Previous works on enhancing renal ischemia assessment include spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging. [40][41][42][43][44][45] These approaches have improved the assessment of ischemic physiology; however, they have limitations such as interference with imaging process due to hypothermic preservation, 36 altered fluorophore quantum efficiency, 39 phototoxicity, 43 and limited application in clinical settings. 42,43 The fluorescence intensity values and the scene exposure have a nonlinear relationship [ Fig.…”

“…Another strategy adopted multiwavelength approaches including optical spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging [40][41][42][43][44][45] to investigate the renal ischemia physiology. However, these approaches have limitations, including altered fluorophore quantum efficiency, 39 weak or absent correlation between fluorescence and ischemia, 41 phototoxicity under short-wavelength, 43 and restricted clinical application. 42,43 The high-dynamic-range (HDR) method is a widely used method in digital photography that could effectively enhance the dynamic range by combining features of images with different exposures.…”

Enhancing in vivo renal ischemia assessment by high-dynamic-range fluorescence molecular imaging

“…Previous works on enhancing renal ischemia assessment include spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging. [40][41][42][43][44][45] These approaches have improved the assessment of ischemic physiology; however, they have limitations such as interference with imaging process due to hypothermic preservation, 36 altered fluorophore quantum efficiency, 39 phototoxicity, 43 and limited application in clinical settings. 42,43 The fluorescence intensity values and the scene exposure have a nonlinear relationship [ Fig.…”

“…Another strategy adopted multiwavelength approaches including optical spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging [40][41][42][43][44][45] to investigate the renal ischemia physiology. However, these approaches have limitations, including altered fluorophore quantum efficiency, 39 weak or absent correlation between fluorescence and ischemia, 41 phototoxicity under short-wavelength, 43 and restricted clinical application. 42,43 The high-dynamic-range (HDR) method is a widely used method in digital photography that could effectively enhance the dynamic range by combining features of images with different exposures.…”

Predictive assessment of kidney functional recovery following ischemic injury using optical spectroscopy

“…1(a). 12 Three laser sources provided UV excitation at 355 (UVSQAOM355-5, Meshtel), 266 (DTL-382QT, Power Technology), and 325 nm (HeCd Omnichrome, Melles Griot) with average fluences of 0.2, 0.2, and 2 mJ∕cm 2 , respectively. In addition, white LED emission filtered by a 500 AE 20 nm bandpass dielectric filter (Corion) provided visible illumination.…”

“…12 All animal procedures were approved by the University of California, Davis, Animal Use and Care Administrative Advisory Committee (AUCAAC) and Institutional Animal Care and Use Committee (IACUC). Adult male spontaneously hypertensive rats (SHR) were placed under general anesthesia using 2% isoflurane delivered with 1.0 L of air per minute.…”

Enhancing in vivo renal ischemia assessment by high-dynamic-range fluorescence molecular imaging

“…Previous works on enhancing renal ischemia assessment include spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging. [40][41][42][43][44][45] These approaches have improved the assessment of ischemic physiology; however, they have limitations such as interference with imaging process due to hypothermic preservation, 36 altered fluorophore quantum efficiency, 39 phototoxicity, 43 and limited application in clinical settings. 42,43 The fluorescence intensity values and the scene exposure have a nonlinear relationship [ Fig.…”

“…Another strategy adopted multiwavelength approaches including optical spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging [40][41][42][43][44][45] to investigate the renal ischemia physiology. However, these approaches have limitations, including altered fluorophore quantum efficiency, 39 weak or absent correlation between fluorescence and ischemia, 41 phototoxicity under short-wavelength, 43 and restricted clinical application. 42,43 The high-dynamic-range (HDR) method is a widely used method in digital photography that could effectively enhance the dynamic range by combining features of images with different exposures.…”

Predictive assessment of kidney functional recovery following ischemic injury using optical spectroscopy

“…1(a). 12 Three laser sources provided UV excitation at 355 (UVSQAOM355-5, Meshtel), 266 (DTL-382QT, Power Technology), and 325 nm (HeCd Omnichrome, Melles Griot) with average fluences of 0.2, 0.2, and 2 mJ∕cm 2 , respectively. In addition, white LED emission filtered by a 500 AE 20 nm bandpass dielectric filter (Corion) provided visible illumination.…”

“…12 All animal procedures were approved by the University of California, Davis, Animal Use and Care Administrative Advisory Committee (AUCAAC) and Institutional Animal Care and Use Committee (IACUC). Adult male spontaneously hypertensive rats (SHR) were placed under general anesthesia using 2% isoflurane delivered with 1.0 L of air per minute.…”

Enhancing in vivo renal ischemia assessment by high-dynamic-range fluorescence molecular imaging

“…Previous works on enhancing renal ischemia assessment include spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging. [40][41][42][43][44][45] These approaches have improved the assessment of ischemic physiology; however, they have limitations such as interference with imaging process due to hypothermic preservation, 36 altered fluorophore quantum efficiency, 39 phototoxicity, 43 and limited application in clinical settings. 42,43 The fluorescence intensity values and the scene exposure have a nonlinear relationship [ Fig.…”

“…Another strategy adopted multiwavelength approaches including optical spectroscopic imaging 17,[36][37][38][39] and autofluorescence imaging [40][41][42][43][44][45] to investigate the renal ischemia physiology. However, these approaches have limitations, including altered fluorophore quantum efficiency, 39 weak or absent correlation between fluorescence and ischemia, 41 phototoxicity under short-wavelength, 43 and restricted clinical application. 42,43 The high-dynamic-range (HDR) method is a widely used method in digital photography that could effectively enhance the dynamic range by combining features of images with different exposures.…”

Predictive assessment of kidney functional recovery following ischemic injury using optical spectroscopy

“…1(a). 12 Three laser sources provided UV excitation at 355 (UVSQAOM355-5, Meshtel), 266 (DTL-382QT, Power Technology), and 325 nm (HeCd Omnichrome, Melles Griot) with average fluences of 0.2, 0.2, and 2 mJ∕cm 2 , respectively. In addition, white LED emission filtered by a 500 AE 20 nm bandpass dielectric filter (Corion) provided visible illumination.…”

“…12 All animal procedures were approved by the University of California, Davis, Animal Use and Care Administrative Advisory Committee (AUCAAC) and Institutional Animal Care and Use Committee (IACUC). Adult male spontaneously hypertensive rats (SHR) were placed under general anesthesia using 2% isoflurane delivered with 1.0 L of air per minute.…”