Construction and validation of a low cost paediatric pelvis phantom

Abstract

PURPOSE: Imaging phantoms can be cost prohibitive, therefore a need exists to produce low cost alternatives which are fit for purpose. This paper describes the development and validation of a low cost paediatric pelvis phantom based on the anatomy of a 5-year-old child. METHODS: Tissue equivalent materials representing paediatric bone (Plaster of Paris; PoP) and soft tissue (Poly methyl methacrylate; PMMA) were used. PMMA was machined to match the bony anatomy identified from a CT scan of a 5-year-old child and cavities were created for infusing the PoP. Phantom validation comprised physical and visual measures. Physical included CT density comparison between a CT scan of a 5-year old child and the phantom and Signal to Noise Ratio (SNR) comparative analysis of anteroposterior phantom X-ray images against a commercial anthropomorphic phantom. Visual analysis using a psychometric image quality scale (face validity). RESULTS: CT density, the percentage difference between cortical bone, soft tissue and their equivalent tissue substitutes were-4.7 to-4.1% and-23.4%, respectively. For SNR, (mAs response) there was a strong positive correlation between the two phantoms (r>0.95 for all kVps). For kVp response, there was a strong positive correlation between 1 and 8 mAs (r=0.85), this then decreased as mAs increased (r=-0.21 at 20 mAs). Psychometric scale results produced a Cronbach's Alpha of almost 0.8. CONCLUSIONS: Physical and visual measures suggest our low-cost phantom has suitable anatomical characteristics for X-ray imaging. Our phantom could have utility in dose and image quality optimisation studies.

Dose optimisation in paediatric radiography – Using regression models to investigate the relative impact of acquisition factors on image quality and radiation dose

“…There was a number of radiolucencies present in the phantom X-ray images, which resulted from a failure to completely fill the PMMA voids with Plaster of Paris. Such radiolucencies are an accepted part of the phantom manufacturing process and have been reported previously in the literature [22]. However, for the method in this study, the visual and physical IQ analyses avoided the radiolucent areas by ensuring the ROIs were placed outside of them and observer evaluations were conducted away from them too.…”

“…The phantom was 15 cm thick and contained radiological tissue substitutes for bone (Plaster of Paris) and soft-tissue (PMMA), which simulated a 10-year-old child's pelvis. Phantom validation utilised computed tomography (CT) data from a 10-year-old child, using a method described in literature [22]. There was a number of radiolucencies present in the phantom X-ray images, which resulted from a failure to completely fill the PMMA voids with Plaster of Paris.…”

Tissue mimicking materials for imaging and therapy phantoms: a review

“…Materials with particular soft tissue properties have been widely investigated for CT, motivated by the increasing number of investigations into deformable and multi-modality phantoms. Solids such as Polymethyl methacrylate (PMMA) and resins (Perrin et al 2017, Mohammed Ali et al 2018, and 3D printed materials (Filippou andTsoumpas 2018, Tino et al 2019b) can be used to mimic soft tissue although printed shells filled with liquids or polymers, as shown in figure 3, have become more prevalent with the increasing requirement for MR-CT visualization (section 5.1) and deformation. Liquids mixed with varying concentrations of contrast agents have allowed the development of liquid phantoms with similar imaging contrast properties to a variety of organs and tissues (Niebuhr et al 2016, Fitzgerald et al 2017, Abdullah et al 2018.…”

“…However, acrylonitrile butadiene styrene (ABS) pellets doped with barium sulphate are showing promise (Hamedani et al 2018) as are other materials (Perrin et al 2017 although their properties were not described. Gypsum is a dense material that has been widely used for cortical bone (Niebuhr et al 2016, Hazelaar et al 2018, Mohammed Ali et al 2018. Many other materials have been used for inner bone including Vaseline doped with dipotassium hydrogen phosphate (Niebuhr et al 2016(Niebuhr et al , 2019, urethane based materials (Cunningham et al 2019, Kobe et al 2019, modified resins (He et al 2019b) and Teflon ® (Hernandez-Giron et al 2019).…”

Proposal of a Lab Bench for the Unobtrusive Monitoring of the Bladder Fullness with Bioimpedance Measurements

“…Most of the anthropomorphic pelvic phantoms presented in the literature have been fabricated for radiation therapy dosimetry [22][23][24][25][26][27][28][29]. Hence, the phantom materials used were selected for their radiological properties, such as Hounsfield unit (HU) [22,30], rather than their electrical properties. As a result, their structures mainly consist of non-electrically conductive materials, such as polymethylmethacrylate (PMMA) [22,31].…”