a solid , multipurpose , flexible , ultrasonic biomedical couplant hydrogel in sheet form is applied to the skin of a patient to facilitate the transfer of ultrasound energy between a standard ultrasound instrument and the body . the couplant sheet has broad upper and lower surfaces and a narrow peripheral edge which is usually circular , square or rectangular but can have other shapes such as the shape of the part of the body being monitored . during use , the lower surface of the sheet is applied to the skin of a patient and remain in place throughout use . the ultrasound instrument is then passed back and forth , usually in contact with the exposed upper surface of the hydrogel sheet while ultrasound energy is transmitted through the hydrogel which serves as a transmission path for the sonic energy passing to and from the body of the patient . the hydrogel sheet of the present invention is a flexible , self - supporting solid sheet which holds its form during storage and when placed on the body . the sheet contains water and a humectant such as triethylene glycol or glycerin and a network of long hydrophilic polymer molecules that hold the liquid in place and give solidity to the hydrogel sheet the polymer can comprise polyacrylamide , karaya gum or a modified starch .