Effects of skin on bias and reproducibility of near-infrared spectroscopy measurement of cerebral oxygenation changes in porcine brain.
ABSTRACT The influence of skin on the bias and reproducibility of regional cerebral oxygenation measurements is investigated using cw near-infrared spectroscopy (NIRS). Receiving optodes are placed over the left and right hemispheres of a piglet (C3, C4 EEG placement code) and one transmitting optode centrally (Cz position). Optical densities (OD) are measured during stable normo, mild, and deep hypoxemia. This is done for skin condition 1: all optodes on the skin; skin condition 2: transmitting optode on the skin and one receiving optode on the skull; and skin condition 3: all optodes on the skull. Absolute changes of oxy- (cO2Hb), deoxyhemoglobin (cHHb), and total hemoglobin (ctHb) concentrations [micromolL] are calculated from the ODs. These absolute changes are calculated for each skin condition with respect to normoxic condition. Additionally, for skin condition 2, the difference of concentration changes between receiver 1 (skull) and receiver 2 (skin) is calculated. The effect of skin removal is an average increase of attenuation changes by a factor of 1.66 (=0.51 OD) and of the concentration changes due to the arterial oxygen saturation steps by 23%. We conclude that skin significantly influences regional oxygenation measurements. Nevertheless, it is hypothesized that the estimated concentration changes are dominated by changes of the oxygenation in the brain.
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ABSTRACT: Antegrade cerebral perfusion is widely used in neonatal heart surgery, yet commonly used flow rates have never been standardized. The objective of this study was to determine the antegrade cerebral perfusion flow rate that most closely matches standard cardiopulmonary bypass conditions. Nine neonatal piglets underwent deep hypothermic cardiopulmonary bypass at a total body flow of 100 mL/kg/min (baseline). Antegrade cerebral perfusion was conducted via innominate artery cannulation at perfusion rates of 10, 30, and 50 mL/kg/min in random order. Cerebral blood flow was measured using fluorescent microspheres. Regional oxygen saturation and cerebral oxygen extraction were monitored. Cerebral blood flow was as follows: baseline, 60 +/- 17 mL/100 g/min; antegrade cerebral perfusion at 50 mL/kg/min, 56 +/- 17 mL/100 g/min; antegrade cerebral perfusion at 30 mL/kg/min, 36 +/- 9 mL/100 g/min; and antegrade cerebral perfusion at 10 mL/kg/min, 13 +/- 6 mL/100 g/min. At an antegrade cerebral perfusion rate of 50 mL/kg/min, cerebral blood flow matched baseline (P = .87), as did regional oxygen saturation (P = .13). Antegrade cerebral perfusion at 30 mL/kg/min provided approximately 60% of baseline cerebral blood flow (P < .002); however, regional oxygen saturation was equal to baseline (P = .93). Antegrade cerebral perfusion at 10 mL/kg/min provided 20% of baseline cerebral blood flow (P < .001) and a lower regional oxygen saturation than baseline (P = .011). Cerebral oxygen extraction at antegrade cerebral perfusion rates of 30 and 50 mL/kg/min was equal to baseline (P = .53, .48) but greater than baseline (P < .0001) at an antegrade cerebral perfusion rate of 10 mL/kg/min. The distributions of cerebral blood flow and regional oxygen saturation were equal in each brain hemisphere at all antegrade cerebral perfusion rates. Cerebral blood flow increased with antegrade cerebral perfusion rate. At an antegrade cerebral perfusion rate of 50 mL/kg/min, cerebral blood flow was equal to baseline, but regional oxygen saturation and cerebral oxygen extraction trends suggested more oxygenation than baseline. An antegrade cerebral perfusion rate of 30 mL/kg/min provided only 60% of baseline cerebral blood flow, but cerebral oxygen extraction and regional oxygen saturation were equal to baseline. An antegrade cerebral perfusion rate that closely matches standard cardiopulmonary bypass conditions is between 30 and 50 mL/kg/min.The Journal of thoracic and cardiovascular surgery 03/2010; 139(3):530-5; discussion 535. · 3.41 Impact Factor
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ABSTRACT: During clinical interventions objective and quantitative information of the tissue perfusion, oxygenation or temperature can be useful for the surgical strategy. Local (point) measurements give limited information and affected areas can easily be missed, therefore imaging large areas is required. In this study a LED based multispectral imaging system (MSI, 17 different wavelengths 370nm-880nm) and a thermo camera were applied during clinical interventions: tissue flap transplantations (ENT), local anesthetic block and during open brain surgery (epileptic seizure). The images covered an area of 20x20 cm, when doing measurements in an (operating) room, they turned out to be more complicated than laboratory experiments due to light fluctuations, movement of the patient and limited angle of view. By constantly measuring the background light and the use of a white reference, light fluctuations and movement were corrected. Oxygenation concentration images could be calculated and combined with the thermal images. The effectively of local anesthesia of a hand could be predicted in an early stage using the thermal camera and the reperfusion of transplanted skin flap could be imaged. During brain surgery, a temporary hyper-perfused area was witnessed which was probably related to an epileptic attack. A LED based multispectral imaging system combined with thermal imaging provide complementary information on perfusion and oxygenation changes and are promising techniques for real-time diagnostics during clinical interventions.SPIE Proceedings Vol. 8572. 03/2013;
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ABSTRACT: This study describes noninvasive noncontact methods to acquire and analyze functional information from the skin. Multispectral images at several selected wavelengths in the visible and near infrared region are collected and used in mathematical methods to calculate concentrations of different chromophores in the dermis of the skin. The method is based on the continuous wave Near Infrared Spectroscopy. Concentration changes of hemoglobin (dO2Hb, dHHb and dtHb) can be calculated from light attenuations using the modified Lambert Beer equation. We applied this technique on multi-spectral images taken from the skin surface using different algorithms for calculating changes in O2Hb, HHb and tHb. In clinical settings, the imaging of local oxygenation variations and/or blood perfusion in the skin can be useful for e.g. detection of skin cancer, detection of early inflammation, checking the level of peripheral nerve block anesthesia, study of wound healing and tissue viability by skin flap transplantations. Images from the skin are obtained with a multi-spectral imaging system consisting of a CCD camera in combination with a Liquid Crystal Tunable Filter (420 - 730 nm). The skin is illuminated with either a broad band light source or a tunable multi wavelength LED light source. The algorithms were validated during skin oxygen saturation changes induced by temporary arm clamping and applied to some clinical examples. The initial results with the multispectral skin imaging system show good results for detecting dynamic changes in oxygen concentration. However, the optimal algorithm needs to be determined. KeywordsSpectroscopy-Near Infrared-Skin-Methods-Oxygenation01/2010: pages 725-728;