Relative Contributions of Hemoglobin and Myoglobin to Near-Infrared Spectroscopic Images of Cardiac Tissue

Abstract

Near-infrared (NIR) spectroscopic imaging is emerging as a unique tool for intra-operative assessment of myocardial oxygenation, but quantitative interpretation of the images is not straightforward. One confounding factor specific to muscle tissue (both skeletal and cardiac) is that the visible/NIR absorbance spectrum of myoglobin (Mb), an intracellular O(2) storage protein, is virtually identical to that of hemoglobin (Hb). As a consequence, the relative contributions of Mb and Hb to the NIR spectra measured in vivo for blood perfused muscle tissue cannot be determined from the measured spectra alone. To estimate the relative contributions of Mb and Hb to NIR spectra and spectroscopic images, isolated pig hearts were perfused first with a Hb-free blood substitute (Krebs-Henseleit buffer; KHB) and then with a 50/50 KHB/blood mixture, with spectroscopic images acquired at each step. Tissue Mb levels were estimated directly from the measurements during KHB perfusion, and total (Mb+Hb) levels were estimated from the images acquired during 50/50 blood/KHB perfusion. Myoglobin accounted for 63 +/- 11% of the total heme content during perfusion with the 50/50 mixture (implying that Mb would contribute 46% of the combined (Mb+Hb) NIR profile during whole blood perfusion), confirming that Mb contributes substantially to near-infrared absorbance spectra of blood perfused cardiac tissue.

Direct Measurement of Tissue Oxygenation in Neonates via Resonance Raman Spectroscopy: A Pilot Study

“…While some NIRS sensors, designed to measure cerebral, renal, and splanchnic tissue oxygenation, are convenient, others are cumbersome when applied to a neonate, making prolonged monitoring challenging [7,8,9,10]. Additionally, the NIRS spectra of myoglobin are indistinguishable from that of oxy- and deoxyhemoglobin, which might account for the majority of the NIRS signal based on proton magnetic resonance data [11,12,13]. Additional optical methods used to assess peripheral perfusion include perfusion index, laser Doppler flowmetry, orthogonal polarization spectroscopy, and resonance Raman spectroscopy (RRS).…”

Near‐Infrared In Vivo Spectroscopic Imaging: Biomedical Research and Clinical Applications

“…To address this question, near-IR spectroscopic images were acquired for eight hearts that were perfused initially with blood-free KHB perfusate [38]. During KHB perfusion, only myoglobin contributed to the heme protein absorption profile.…”

Mapping the myoglobin concentration, oxygenation, and optical pathlength in heart ex vivo using near-infrared imaging

“…The mapping of subepicardial hemoglobin (Hb) 1 + myoglobin (Mb) oxygenation in pig hearts has been reported using a near-infrared (NIR) spectroscopic imaging technique that, however, does not provide absolute concentrations and is limited to the oxygen saturation parameter (OSP) only [1], [2], [3], [4] and [5]. In spite of these limitations, the efficiency of this approach in cardiac research has been shown to be significant [6], [7] and [8].…”

“…The camera allows imaging with a frame readout time of 536.8 ms in the wavelength range of 200 to 1100 nm. The LCTF works as an electronically activated tunable interference filter in the range of 650 to 1100 nm with a bandwidth of 7 nm and a response time of 150 ms. LCTF-based spectral imaging principles have been reviewed previously [1], [2], [3] and [18].…”

“…In the spectral imaging studies, i changed from 1 to n = 86, which corresponds to the wavelength range from 700 to 1040 nm with an increment of 4 nm. A null hypothesis y i = f i is considered to be true if (3) Here a critical is given for n > 30 [27] and [28]. At a significance level of = 0.05, we have z 2 = 1.6 and = 106.6 at n = 86.…”