A preliminary study on the design, fabrication and application of a 3D-printed paediatric bladder phantom for optimisation of nuclear medicine procedures

Abstract

Background: Ectopic kidneys often deviate from their normal position, affecting accurate differential renal function measurements in conventional renograms. Misdiagnosis is common with a single posterior detector. Existing literature recommends using two detectors, one anterior and one posterior to the patient, to obtain the geometric mean. Literature also states that reliable dosimetry in medical physics requires measurements on anthropomorphic phantoms with known activity concentration. This can be done using 3D printing techniques to create tissue-mimicking phantoms. Objectives: This research study investigates the application and feasibility of 3D printing in Nuclear Medicine, specifically focusing on the development and evaluation of a patient specific anthropomorphic paediatric phantom. This study also explores the differential renal function measurements in the presence of a pelvic kidney as well as the effect the bladder has on this kidney. Research Methodology: This research was conducted by designing and fabricating the anthropomorphic phantom, injecting it with Technetium-99m, and scanning using a gamma camera having two detectors, one anterior and the other posterior to the phantom. Results: The results obtained from the gamma scans were evaluated using specialised software and surprisingly, contrary to what was reviewed in the literature, no significant differences in differential renal function measurements were observed between normal and pelvic kidneys. Nonetheless, according to this study, the close proximity of the bladder to the pelvic kidney does influence the detected gamma counts. Conclusions: This study demonstrated the feasibility of injecting radioisotopes into 3Dprinted phantoms, without posing any risks, thereby showcasing their potential for use in Nuclear Medicine. The absence of significant differences in the differential renal function between normal kidneys and kidneys with a pelvic kidney could potentially be attributed to the thinness of the paediatric pelvic bone. The thinner pelvic bone found in children might have contributed to the preservation of accurate renal measurements. Recommendations: It is suggested that the study should be repeated with an adult phantom to compare the findings with the paediatric population. With the introduction of 3D printed phantoms, Medical Physicists need to establish Quality Assurance tests for such phantoms ensuring they are up to standards according to the current European protocols.