3D Printing Gel Phantoms for Dosimetric Verification of Radiotherapy Treatments

In the recently published ‘3D printable inter cross-linking network (ICN) gels for reversible transparency control with water content,’ authors Yosuke Watanabe, Shota Inoue, Azus Saito, Masasu Kawakawami, and Hidemitsu Furukawa explore 3D printing gel phantoms for dosimetric verification before radiotherapy treatments.

Such innovation would lend the opportunity for better treatment for cancer patients, also meaning the possibility for fewer side effects after chemotherapy or surgery, with the goal for delivering maximum amounts of radiation at cancer cells, and as little radiation as possible at normal cells. With dosimetric verification extremely helpful beforehand, phantoms are often used. 3D printing has been investigated, with polymer gels being used as the chosen medium; however, not without the use of molds. Direct 3D printing allows for 3D printed structures that are hollow inside, meaning better performance due to a lighter weight.

The change in appearance of ICN gels (Mold10, Mold23 and Mold46) at each UV exposure time (0, 180, 300, 420 and 600 s)

“It was found that optical 3D printing system utilized to fabricate gel materials could create the microscale objects,” stated the researchers.

During the study, the team was also surprised by ICN gels transforming due to changing water content after fabrication on a customized 3D printer made by D-lightmatter Co., Ltd, with a stage of 300 × 300 × 200 mm and a high resolution along the X and Y axis 500 μm. They made three different ICN phantoms with molds, and all samples turned white, using double network gels having ICN:ICN gel as the gel phantom, offering UV irradiation sensitivity.

Influence of water content on the transparent-opaque transition of ICN gels

“It is noted that the radical from UV initiator in the ICN phantoms initiate the polymerization similar to conventional gel dosimeter,” said the researchers, also noting a reversible switch between transparent and opaque states.

They also reported their ICN network as highly stable with gels that could be 3D printed via SLA printing, using a dispenser ‘up to micro resolution.’ They also submerged the ICN gels in 2^nd gel solution. The researchers noted that the swollen state of the gels was an impressive 3.5 times heavier.

“For the chemical composition specialized in 3D printing process, we considered photo initiators and UV absorbers. The immersion into 2nd gel solution enable us to add sensitivity for UV light to the 3D printed ICN gel. The cross section of swollen 3D printed ICN gel after UV irradiation showed the distribution of UV light after UV irradiation like gel dosimeter,” concluded the researchers.

“We expect that the 3D printer specialized gel materials and ICN gels are feasible for practical fabrication method of 3D gel phantom,” concluded the researchers.

Process of fabrication of ICN gel phantom. a 3D modeling of a right index finger. b 3D printed ICN gel. c 3D printed ICN gel swollen with 2nd gel solution: ICN gel phantom. d ICN gel phantom after UV irradiation. e Cross section of d.

Researchers have been studying the effectiveness of a wide range of medical phantoms, from cardiac phantoms to those created for breast cancer treatment, and those for the kidneys too. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.