Quantitative Analysis of the Thermal Image of the Hand Dorsum in the Assessment of Peripheral Circulatory Impariment in Workers Exposed to Hand-Arm Vibration / 日本温泉気候物理医学会雑誌

ABSTRACT

Infrared thermography was performed on 38 forestry workers. The thermograms were analyzed separately for the left and right hands of each subject. Of 75 hands evaluated, vibration-induced white finger was noted in 18 (VWF group), and no symptoms were noted in 57 (non-VWF group). In addition to the above two groups, 42 subjects (84 hands) who had no symptoms of vibration exposure were used as a control group. Based of the thermograms taken after a local warming of the hands for 5min, the temperature distributions of the dorsal aspect of subject's hands were evaluated, and the thermal images of the hand with VWF were categorized into three main patterns. To establish a quantitative evaluation index that incorporates the characteristic thermal image observed in the VWF group, we constructed the representative parameters for each of the three thermogram patterns, and a linear discriminant analysis was performed using the presence or absence of VWF symptoms as the dependent variable and the constructed parameters as the independent variables. A discriminant score derived from this model expression was used as the evaluation index. The accuracy of the index was estimated according to a receiver operating characteristic (ROC) curve, and the area under the curve of 0.942 was obtained (p<0.001). When the cutoff point was set at the maximum point in the Youden index, the sensitivity of the VWF group was 94.4%, and the specificity of the non-VWF group and control group was 84.2% and 89.3%, respectively. These findings suggest that this newly proposed quantitative analysis method, which uses the thermal distributions of the dorsal side of the hand as indicators, may be useful for evaluating peripheral circulatory impairment of HAVS.