References
Hyperspectral imaging of tissue perfusion and oxygenation in wounds: assessing the impact of a micro capillary dressing
Abstract
Objective:
Experimental tests of non-invasive multi- or hyperspectral imaging (HSI) systems reveal the high potential of support for medical diagnostic purposes and scientific biomedical analysis. Until now the use of HSI technologies for medical applications was limited by complex and overly sophisticated systems. We present a new and compact HSI-camera that could be used in normal clinical practice.
Method:
We assessed the use of the HSI system on the hands of 10 healthy volunteers, looking at control parameters, and those following venous occlusion, arterial occlusion and reperfusion, including tissue oxygenation, tissue haemoglobin index, perfusion in 4–6mm depth=near infrared spectroscopy (NIR), and tissue water index. Pseudo colours used ranged from 0% (blue) to 100% (red). We also assessed differences in the wounds of three patients.
Results:
The results show good potential in all parameters in the healthy volunteers, which had high conformity with validated reference oximetry measurements. In three wounds, different levels of oxygenation were identified in the wound area, although interpretation of these results is complex. In Cases 2 and 3, following the application of a micro capillary dressing, improvements were seen in perfusion and reduction of the tissue water index (TWI).
Conclusion:
The camera system proved to be quick, flexible and yielded data with high spatial and spectral resolution. These data will be used to perform a power analysis for a randomised controlled study.
Non-invasive hyperspectral imaging (HSI), in the visible and near infrared spectral range, has been shown to provide information on the physiological parameters in different medical areas, such as diabetic foot syndrome and skin ulcers,1,2,3,4,5,6 including tissue perfusion measurements,7,8,9 wound analysis10,11,12,13 and flap monitoring.14,15,16,17 The benefit of this methodology is the contact-free measurement without the need for contrast agents or other invasive procedures.12,13 Irradiated light is scattered and absorbed by structures and components of the skin, wound or tissue. The spectrally modified remitted light intensity transports information about the structure (structure analysis) and the composition of the tissue (chemical analysis). Due to the small penetration depth, mainly caused by high haemoglobin absorption, the remission spectroscopic measurement in the visible range (450–650nm) gains information about the more superficial parts of the tissue. Lower absorption coefficients in the near infrared spectroscopy (NIR)-range (650–1000nm) enable greater depth penetration of the light. This spectral region includes information on the deeper layers of tissue. The NIR range also includes distinct overtone and combination vibration absorption bands of active molecular bonds enabling the detection of, for example, water, fat and other chemical tissue components. An important benefit of HSI is that the spectroscopic measurement is performed over a larger area, so that spatial structures of the measured area can be evaluated in connection with the local spectral information using segmentation procedures, for instance.
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