可以与DRT4搭配
    专为深部组织、骨骼（股骨头）的血流量监测而设计
    功率为20mW 785NM 
    典型应用：
    术中骨膜血流灌注量监测（如股骨头）
    经皮肌肉组织血流灌注量监测
    The IRLD20? infra-red laser diode light source is a separate mains powered accessory for the DRT4? which allows measurements to be made using a higher power laser than that used in the standard DRT4?.
    The IRLD20? allows measurements to be taken specifically from deeper tissues where measurements are impractical using the lower power of the standard DRT4? and the narrower fibre separation of standard probes. The typical output power from the IRLD20? probe tip is approximately 20 mW at 785nm.
    Typical applications include measurements from bone at surgery (e.g. assessment of flow in the femoral head), or non invasive measurements of muscle flow through lean skin.