Comparison of single-spot technique and RGB imaging for erythema index estimation

Abstract

A commercially available point measurement device, the Mexameter(®), and an experimental RGB imaging prototype device were used for erythema index estimation of 50 rosacea patients by analysing the level of skin redness on the forehead, both cheeks and both sides of a nose. Results are compared with Clinician's Erythema Assessment (CEA) values given by two dermatologists. The Mexameter uses 568 nm and 660 nm LEDs and a photodetector for estimation of erythema index, while the used prototype device acquired RGB images at 460 nm, 530 nm and 665 nm LED illumination. Several erythema index estimation algorithms were compared to determine which one gives the best contrast between increased erythema and normal skin. The erythema index estimations and CEA values correlated much better for the RGB imaging data than for those obtained by the conventional Mexameter technique that is widely used by dermatologists and in clinical trials. In result, we propose an erythema index estimation approach that represents increased erythema with higher accuracy than other available methods.

Noninvasive objective skin measurement methods for rosacea assessment: a systematic review

“…For pH, all three studies used pH900 meters, possibly overestimating true pH due to a small electrode area and short stabilization period of only 3 s . For erythema, skin light absorption by components other than haemoglobin (melanin, bilirubin) may influence outcomes and application of variable skin pressure can change haemoglobin level and skin colour . For laser Doppler, absolute values are meaningless without measuring sympathetic flux changes and blood vessel density, which is impossible with noninvasive techniques .…”

“…Placing the device on the same area of interest in follow-up visits is therefore challenging. 64,76,113 Computer-aided image analysis does not impose these problems as whole face erythema is mapped. Moreover, redness values are obtained without performing skin contact.…”

“…Fifteen articles used computer-aided imaging analysis in rosacea diagnosis, severity assessment and therapy monitoring, mainly in ETR (Table S4). 46,48,[57][58][59][60][61][62][63][64][65][66][67][68][69] To measure erythema, five studies used the VISIA â Complexion Analysis system (Canfield Scientific, Parsippany, NJ, U.S.A.), 46,62,63,68,69 a commercially available high-resolution facial imaging system with quantitative imaging-analysis software (RBX â ; Canfield Scientific), which separates red skin-colour components. 70 In all studies, reduction of concentrated facial dark-red areas after treatment (brimonidine, laser, photodynamic therapy) was seen, corresponding to a reduction in erythema.…”

“…70 In all studies, reduction of concentrated facial dark-red areas after treatment (brimonidine, laser, photodynamic therapy) was seen, corresponding to a reduction in erythema. The remaining 10 articles incorporated a variety of spectral imaging methods (L*a*b* colour space, 60,61,67 red-blue difference index, 61 erythema dose, 61 red-green-blue imaging, 57,59,66 emission of visible and infrared light 48 ) to quantify erythema, 57,58,60,61,[64][65][66][67] telangiectasias 57 and skin haemoglobin distribution. 48,59 Other techniques Sonographic imaging and infrared photography are two additional imaging techniques used in rosacea cases.…”

“…[99][100][101][102] Erythema Twenty-two studies assessed monitoring of facial skin erythema by spectrometry. 48,64,68,[78][79][80]82,83,90,96,[103][104][105][106][107][108][109][110][111][112][113][114] Three spectrometric methods were applied; 28 reflectance spectrophotometry, 3,64,68,[78][79][80]82,96,104,[106][107][108]110,111,113 tristimulus colorimetry 83,90,103,109,112 and diffuse reflectance spectroscopy. 105,114 One study used an optical densitometer.…”