Hitachi EUP-L53 Instruction Manual page 15

The acoustic lens of the probe is manufactured very thin and
delicate to get the high resolution. Therefore, in case of wiping
off the ultrasound jelly or cleaning the surface of the acoustic
lens, please use a soft cloth or tissue paper and handle with care.
(See Fig. 4)
Acoustic lens
Fig. 4
Wiping off the ultrasound jelly or cleaning the
surface of the acoustic lens
CAUTION
Soft cloth or tissue paper
-9- Q1E-EP0348