Figure 2.

Laser source positioning calibration devices are used to determine the shift between the laser source position inside the ET tube and the tip of the stainless steel rod. The device is composed of 4 poles positioned at equal distances (5 cm) from the central pole, which holds an isotropic detector. Light fluence rate was measured at these 4 positions plus another 4 positions when the 4-cm ET tube filled with 0.1% intralipid was in contact with the detector at front, back, right, left positions.