Low cost multifunctional 3D printed image quality and dose verification phantom for an image-guided radiotherapy system

Abstract

Purpose: Image-guided radiation therapy (IGRT) is used to precisely deliver radiation to a tumour to reduce the possible damage to the surrounding normal tissues. Clinics use various quality assurance (QA) equipment to ensure that the performance of the IGRT system meets the international standards set for the system. The objective of this study was to develop a low-cost and multipurpose module for evaluating image quality and dose.

Methods: A multipurpose phantom was designed to meet the clinical requirements of high accuracy, easy setup, and calibration. The outer shell of the phantom was fabricated using acrylic. Three dimensional (3D) printing technology was used to fabricate inner slabs with the characteristics of high spatial resolution, low-contrast detectability, a 3D grid, and liquid-filled uniformity. All materials were compatible with magnetic resonance (MR). Computed tomography (CT) simulator and linear accelerator (LINAC) modules were developed and validated.

Results: The uniformity slab filled with water is ideal for the assessment of Hounsfield units, whereas that filled with wax is suitable for consistency checks. The high-spatial-resolution slab enables measurements with a resolution up to 5 lp/cm. The low-contrast detectability slab contains rods of 5 different sizes that can be clearly visualised. These components meet the American College of Radiology (ACR) standards for QA of CT simulators and LINACs.

Conclusions: The multifunctional phantom module meets the ACR recommended QA guidelines and is suitable for both LINACs and CT-sim. Further measurements in an MR simulator and an MR linear accelerator (MR-LINAC) will be arranged in the future.

Fig 1. High-spatial-resolution slab printed using a three-dimensional (3D) printer.

Fig 2. Low-contrast detectability slab.

Fig 3. Slab with a 3D grid with equal spacing.

Fig 4

Computed tomography (CT) simulator module: A. high-spatial-resolution slab; B. low-contrast detectability slab; C. water-filled uniformity slab.

Fig 5. Magnetic resonance imaging module connected to a piezoelectric motor.

Fig 6. Inserting the ion chamber in the centre cavity for dose verification.

Fig 7. Image quality module.

Fig 8. CT image of the high-spatial-resolution slab.

Fig 9. CT image of the low-contrast detectability slab.

Fig 10. CT image of the water-filled uniformity slab.

Fig 11. CT image of the wax-filled uniformity slab.

Fig 12. CT image of the silicone-filled uniformity slab.

Fig 13. Cone-beam computed tomography (CBCT) images of the water-filled uniformity slab.

Fig 14. CBCT images of the high-spatial-resolution slab.

Fig 15. CBCT images of the low-contrast detectability slab.