In recent years, the fabrication of patient organ replicas using 3D printers has been attracting a great deal of attention in
medical fields. However, the cost of these organ replicas is very high as it is necessary to employ very expensive 3D
printers and printing materials. Here we present a new gel organ replica, of human kidney, fabricated with a conventional
molding technique, using a particle-double network hydrogel (P-DN gel). The replica is transparent and has the feel of a
real kidney. It is expected that gel organ replicas produced this way will be a useful tool for the education of trainee
surgeons and clinical ultrasonography technologists. In addition to developing a gel organ replica, the internal structure
of the P-DN gel used is also discussed. Because the P-DN gel has a complex structure comprised of two different types
of network, it has not been possible to investigate them internally in detail. Gels have an inhomogeneous network
structure. If it is able to get a more uniform structure, it is considered that this would lead to higher strength in the gel. In
the present study we investigate the structure of P-DN gel, using the gel organ replica. We investigated the internal
structure of P-DN gel using Scanning Microscopic Light Scattering (SMILS), a non-contacting and non-destructive.
Nano-structure of soft and wet materials are making important roles in radiation therapy, as a three-dimensional (3D) gel dosimeter. In the last decades, radiation therapy instruments have had a large progressive of the accuracy, therefore more precise measurements have became important. We study new materials and apparatus, which measure three dimensional absorbed dose distributions. New materials are double network (DN<sup>2</sup>) gel and improved PAGAT (yDAGAT) gel, the former has several good points, high transparency, high water content, high mechanical strength, and toughness, the later has similar properties of PAGAT gel but will be more tractable. The new type of optical-CT machine is Scanning Microscopic Light Scattering System (SMILS). Usual optical-CT uses the opacity, which is measured by the intensity, however SMILS also uses dynamic light scattering (DLS) theory with original ensemble average method. By using the intensity and DLS information, more accurate information are expected. We have established one-dimensional measurement by SMILS using irradiated DN gel. Additionally, yDAGAT is successfully composed. In the future, we are planning to develop three-dimensional radiation measurement apparatus by 3D printable gel and 3D SMILS.