painless

a. 无痛的,不痛的

An instrument that in a painless and noninvasive manner uses the differential transmission and reflection of ultrasonic waves to create a detailed visual image of the brain.

超声波心动描记器一种用来显示详细的大脑图象的仪器，利用超声波发送和反射的差异来测试并无伤无痛