Three-dimensional image quality test phantom for planar X-ray imaging

We aimed to produce a simple, inexpensive 3D printed phantom as a prototype for image quality assessment of contrast, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and resolution in planar X-ray imaging systems. The test phantom was designed using SOLIDWORKS software, printed with a polylactic acid material and filled with paraffin wax. Circular aluminium sheets were used as inserts for contrast evaluation. A planar X-ray system was used for imaging and DICOM images were evaluated using ImageJ software. We evaluated spatial resolution, contrast, CNR and SNR. For resolution, full width at half maximum (FWHM) was measured on different grid sizes. For contrast, intensity of grey values and standard deviation were calculated on the different grid sizes. For CNR and SNR, difference in greyscale of investigated tissue and background per standard deviation of noise in the background was calculated. Resolution of the system was evaluated to be 1.57 and 1.80 lp/mm on grids A and B respectively. Contrast showed differential attenuation per variation in thickness. CNR increased from -13.7 for a thickness of 0.00 mm to 24.90 for a thickness of 28 mm. CNR did not change for a thickness greater than 16.0 mm. The SNR of the system fell in the acceptable range of ≥ 5 . The results from the analyses performed indicate that the test phantom has great potential to be a good substitute for the commercially available phantoms on the market, especially for low-resource settings.