三维表面光学系统在亚洲人种肤色上的参数设置

Parameter setting of 3D surface image system in Asian skin color

目的验证三维表面光学系统在亚洲人种皮肤颜色上参数的设置。方法选用从等级Ⅰ到Ⅳ的4种颜色(非常浅、浅、中间色、褐色)。通过调节增益(Gain)和整合时间(IT),以获得清晰的表面图像。所获得的图像可分为3种类型,没有图像a类(不能显示出表面图像)、模糊图像b类(能够部分显示表面图像,但图像存在缺损,轮廓不全)、清晰图像c类(显示清晰的表面轮廓)。记录每种颜色不同类型时的Gain与IT的数值。结果膜体Ⅰ级肤色,很低的Gain和IT(Gain超过100%,IT超过2 800μs)就能获得c类图像,随着Gain的增高,获得c类图像的IT所需的值慢慢降低。过高的IT就会出现b类图像。膜体Ⅱ级肤色和膜体Ⅰ级肤色相差不多,只是c类图像出现和消失的阈值有所变化。膜体Ⅲ级肤色,Gain为100%、IT大于5 600μs时才能获得c类图像;Gain为400%,IT也要大于3 200μs才会获得c类图像;当Gain为400%时和IT大于6 600μs、Gain为500%时和IT大于6 200μs、Gain为600%时和IT大于5 800μs时,都会出现b类图像。膜体Ⅳ级肤色,只有在很高的Gain和IT时,才能看到c类图像,且范围很小。结论三维表面光学图像引导系统能够降低患者的额外剂量,能够有效地降低患者的摆位误差。对于亚洲人中肤色可以选择IT在5 000μs及Gain范围为300%左右可以在相对广谱的扫描条件下获得较好的图像质量。

Objective To set up the parameters of Asian skin color on 3D surface optical system and verify its accuracy.Methods Four colors from grade Ⅰ to Ⅳ were selected, and the surface images were obtained by the adjustment of gain（Gain） and integration time（IT） to get the clear surface images. The obtained images were divided into 3 types, type a（without image, no image was observed）, type b（fuzzy image, part of surface image was defected with incomplete outline）, and type c（clear image, clear surface outline could be observed）. The value of Gain and IT of each color and type was recorded. Results The image quality in different colors depended on Gain and IT. For lighter color（grade Ⅰ）, type c image could be obtained at lower Gain range and IT. When Gain range and IT exceeded the certain threshold, the type b image was obtained due to the excessive exposure of object surface. For darker color（grade Ⅱ）, only type b image was obtained on lower Gain range and IT,and type c image could be obtained as Gain range and IT increased. Excessive exposure appeared in continuously increased range of Gain and IT. For grade Ⅲ color, c class image was obtained when the Gain was 100 % and IT was greater than 5 600 μs,or the Gain was 400 % and IT was greater than 3 200 μs. When Gain was 400 % and IT was greater than 6 600 μs, the Gain500 % and IT greater than 6 200 μs or Gain 600 % and IT was greater than 5 800 μs, only b class image could be obtained.Only when the Gain and IT were very high, could the c class images be seen for type IV color skin, and the range of the image was very small. Conclusion The 3D surface optical image guidance system could reduce extra radiation dose and effectively reduce the set-up error. For Asians, better quality image can be obtained in a relatively wide range of scanning spectrum when IT is set at 5 000 μs and Gain range about 300 %.