Author: Katherine Brown, Will Buchsbaum, Mylinh Dang, Joshua Dean, Sameer Faruquee, Gracie Huff, Claudia Maldonado, Gaby Min, David O'Neill, Gemily Wang, Poonam Yadav 👨🔬
Affiliation: Northwestern University, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Northwestern Medicine 🌍
Purpose:
To establish an abdominal imaging phantom that includes deformable organs including the stomach, duodenum, and pancreas. This phantom will be used in routine calibration of an MRI-LINAC system to ensure the system can visualize and respond to morphological deformations in the abdomen including translation and expansion of organs.
Methods:
The housing of the phantom is 30 x 30 x 15 cm3 and is composed of acrylic. The pancreas was 3D printed out of polylactic acid (PLA) as the pancreas only translates. Hollow stomach and duodenum models were filled with water or air to allow for controlled expansion. Wall thickness variations were used to control for uniform (stomach) or anisotropic (duodenum) expansions. During calibration, the phantom would be imaged on the MRI-LINAC system over a course of 45 minutes during which, the stomach and duodenum would be each expanded by pumping air and water respectively at a rate of 5 ml every 4 minutes to simulate a visible expansion of both organs. Scanner calibration is assessed through the comparison of known deformations at four-minute intervals with the deformations imaged through the scanner.
Results:
Scans indicated that the choice of materials resulted in high quality images from the MRI-LINAC. ImageJ was used to calculate a 29.1% increase in area when the stomach is viewed from the sagittal plane. While the duodenum has not been imaged in the scanner, prior testing shows that the design consistently expands preferentially in the circumferential direction.
Conclusion:
High quality images showing organ deformation in the phantom can be collected and quantified. Ongoing investigation aims to confirm similar imaging results with multiple organs and deformation over a period of time. In conclusion, this concept paves the way for more complex phantoms to be designed in the future.