Kindai University develops solid gel pad for ultrasound examinations — No sticky mess, unlike liquid gel

A research team led by Kindai University Faculty of Medicine has developed a new solid gel pad for use in ultrasonography (ultrasound examinations). The pad produces diagnostic images comparable to those obtained using conventional liquid gel applied to the body. As it is not sticky and requires no wiping away, patients report a much higher degree of satisfaction. If the pad can be made hygienically reusable, it has the potential to become an eco-friendly medical product that is kind both to people and to the environment.

In an ultrasound examination, a probe (transducer) that sends and receives ultrasound waves is moved across the surface of the body, and the ultrasound waves reflected back from internal organs are converted into images to check for abnormalities. The method is widely used as a highly reliable diagnostic technique that places minimal physical burden on the patient. Because any air between the probe and the body blocks the ultrasound waves and prevents imaging of internal structures, the probe is typically slid over a layer of liquid gel spread on the patient's body to obtain clear images.

However, when examinations take longer, the liquid gel can dry out, allowing air to enter and degrading image quality. After the examination, patients wipe the gel off, but some find it unpleasant when residue dries and flakes or gets on their clothing. Gelatin-based solid gel pads also exist, but their drawbacks include difficulty maintaining moisture and the complexity of storage.

Professor Hajime Monzen (Medical Physics) from Kindai University Faculty of Medicine and his colleagues turned their attention to "tamarind seed gum" as a new material for solid gel pads to replace gelatin. Tamarind seed gum is a natural polysaccharide found in the seeds of the tamarind tree-an evergreen from the Fabaceae family widely used in South Indian cuisine-and is commonly used as an additive in foods, pharmaceuticals, and other products.

Professor Monzen's team had previously attempted to develop a gel pad for radiation therapy using tamarind seed gum, but the continuous seeping of water had been an obstacle. Realizing that this very property could make the material ideal for ultrasound gel pads-which need to remain moist-the team brought in Lecturer Takuya Uehara (Radiation Oncology) and continued development. This development resulted in the completion of a solid gel pad made primarily of tamarind seed gum, polyhydric alcohol, and water.

Research gel pads (5 mm thick, 50 mm square) were prepared and tested on four healthy volunteers. The tests covered examination of abdominal organs such as the liver and gallbladder (convex probe), examination of the carotid artery-which lies relatively close to the surface-for plaque buildup (linear probe), and examination of the movement of heart valves and other internal structures (sector probe). In terms of image clarity and diagnostic accuracy, there was no significant difference compared with conventional liquid gel. When volunteers were asked to rate their satisfaction on a 5-point scale (higher scores indicating greater satisfaction), the conventional liquid gel generally scored 1-2, while the newly developed solid gel pad scored 4-5.

According to Uehara, the team plans to pursue clinical application by validating the pad's efficacy in large-scale clinical trials and assessing its durability over extended use. The research was conducted in collaboration with Hayakawa Rubber Co., Ltd. (Fukuyama City, Hiroshima Prefecture) and was published on January 12 in the British scientific journal Scientific Reports.