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This paper describes the development of an early detection method for probing pathological tissue variations. The method could be used for classifying various tissue alteration namely tumors tissue or skin disorders. The used approach is based on light scattering and absorption spectroscopy. Spectral content of the scattered light provides diagnostic information about the tissue contents. The importance of this method is using a safe light that has less power than the used in the imaging methods that will enable the frequent examination of tissue, while the exiting modalities have drawbacks like ionization, high cost, time-consuming, and agents' usage. A modality for mapping the oxygen saturation distribution in tissues noninvasively is new in this area of research, since this study focuses on the oxygen molecule in the tissue which supposed to be homogenously distributed through the tissues. Cancers may cause greater vascularization and greater oxygen consumption than in normal tissue. Therefore, oxygen existence and homogeneity will be alternated depending on the tissue state. In the proposed system, the signal was extracted after illuminating the tissue by light emitting diodes (LED's) that emits light in two wavelengths, red (660 nm) and infrared (880 nm). The absorption in these wavelengths is mainly due to oxyhemoglobin (HbO 2 ) and deoxyhemoglobin (Hb) while other blood and tissue contents nearly have low effect on the signal. The backscattered signal which is received by a photodiodes array (128 PDs) was measured and processed using LabVIEW. Photoplethysmogram (PPG) signals have been measured at different locations. These signals will be used to differentiate between the normal and the pathological tissues. Variations in hemoglobin concentration and blood perfusion will also be used as an important indication feature for this purpose.

Till now, there is no available device which can measure the total hemoglobin (THb) concentration and the fractional oxygen saturation (SaO2) noninvasively. Finger, earlobe, nose bridge clamp and forehead sensors have been already used to monitor the functional oxygen saturation of the hemoglobin. Earlobe sensor has a lot of advantages that make it attractive for measuring the hemoglobin concentration and the SaO2. The structure of earlobe enables the application of the theoretical discipline with smaller errors. This may enable the calculation of other blood constituents like glucose. Less disturbance of the patient is achieved for monitoring. In cases of low perfusion, the pulse wave velocity will be affected and the time delay problem will be appeared. But the time delay for the earlobe sensor will be stay smaller than the finger sensor. For motion artifact effect in ambulance overcoming, an adaptive filter is used for reliable measurements. The effect of the motion artifact on the earlobe sensor will be also smaller than on the finger sensor. For long time monitoring and for home use the earlobe sensor consumes less power than the finger sensor. Available reformed light emitting diodes (LEDs) with different wavelengths and especially in the infrared region, where the light absorption of tissue is too high, can be applied by the earlobe clip. The noninvasive measurements are based on the Photoplethysmography (PPG) signal which will be studied for the earlobe and the finger sensors under various conditions using Lambert Beer Law (LBL). The difficulties related to the calculations will be also discussed. The study reported that the earlobe sensor can be a suitable sensor under various conditions to calculate the THb concentration and SaO2.

In addition to the perilous pitfall of pulse oximeter which is its disability to detect carboxyhemoglobin (COHb) and methemoglobin (metHb) concentrations, other shortcomings of pulse oximetry are also cumbersome or even dangerous. A finger probe for example will not be able to show a result at very low perfusion of tissues. This case is available when the patient is under shock or has a low blood pressure. Finger sensor, ear clip, nose bridge clamp and forehead sensor are used by monitoring oxygen saturation of hemoglobin. Some of the pitfalls of the standard pulse oximetry can be avoided using the appropriate sensor for the case under consideration. After an introduction in pulse oximetry we will show in this article the differences between these sensors mainly used by this valuable technique. Plethysmogram signal, which is an important measured variable by this in-vivo method, will be studied from three sensors under various conditions. Also the time delay which is a vital parameter by detection of oxygen saturation will be considered. The difficulties by the calculations of fractional hemoglobin concentrations using the different sensors will be discussed before the advantages and shortcomings of each sensor and the possible enhancement will be shown. At the end a decision will be taken to choose the suitable sensor for the calculation of hemoglobin concentration and its fractional oxygen saturation by our used method.

A hazardous pitfall among the deficiencies of currently used pulse oximeter is that carboxyhemoglobin (COHb) and methemoglobin (metHb) concentrations can not be detected. This leads to erroneous measurement of oxygen saturation in case of carbon monoxide poisoning and methemoglobinemia. Also the total hemoglobin concentration - which can only be measured in-vitro up to now - will not be considered. Another pitfall of transmission pulse oximetry is that it will not be able to give any result for low perfusion of tissue. To overcome these shortcomings a new non-invasive reflectance pulse hemometer is designed to measure the hemoglobin concentration and the actual oxygen saturation (SaO2) considering the concentrations of COHb and metHb. Light emitting sources with different wavelengths and a photodiode (PD) as a light detector are used. We will show in this article the signal processing of the reflected light detected by the photodiode using a modified Lambert-Beer law. A brief comparison with other possible methods like photon diffusion theory will also be given. The sensor has to be applied primarily at forehead or at other better perfused locations of the body. First measurements with this sensor have shown promising results for this non-invasive method to detect hypoxia “whatever its causes” and anemia even in case of low tissue perfusion.

Deficiencies of the currently used pulse oximeter are discussed in diverse literature. A hazardous pitfalls of this method is that the pulse oximeter will not detect carboxyhemoglobin (COHb) and methemoglobin (metHb) concentrations. This leads to incorrect measurement of oxygen saturation by carbon monoxide poisoning and methemoglobinemia. Also the total hemoglobin concentration w ill not be considered and can only be measured in-vitro up to now. A second pitfall of the standard pulse oximetry is that it will not be able to show a result by low perfusion of tissues. This case is available inter alia when the patient is under shock or has a low blood pressure. The new non-invasive system we designed measures the actual (fractional) oxygen saturation and hemoglobin concentration. It will enable us also to measure COHb and me tHb. The measurement can be applied at better perfused central parts of the body. Four or more light emitting diodes (LEDs) or laser diodes (LDs) and five photodiodes (PDs) are used. The reflected light signal detected by photodiodes is processed using a modified Lambert-Beer law (I I