Anthropomorphic phantom for deformable lung and liver CT and MR imaging for radiotherapy

Abstract

In this study, a functioning and ventilated anthropomorphic phantom was further enhanced for the purpose of CT and MR imaging of the lung and liver. A deformable lung, including respiratory tract was 3D printed. Within the lung's inner structures is a solid region shaped from a patient's lung tumour and six nitro-glycerine capsules as reference landmarks. The full internal mesh was coated, and the tumour filled, with polyorganosiloxane based gel. A moulded liver was created with an external casing of silicon filled with polyorganosiloxane gel and flexible plastic internal structures. The liver, fitted to the inferior portion of the right lung, moves along with the lung's ventilation. In the contralateral side, a cavity is designed to host a dosimeter, whose motion is correlated to the lung pressure. A 4DCT of the phantom was performed along with static and 4D T1 weighted MR images. The CT Hounsfield units (HU) for the flexible 3D printed material were -600 -100HU (lung and liver structures), for the polyorganosiloxane gel 50 -120HU (lung coating and liver filling) and for the silicon 650 -800HU (liver casing). The MR image intensity units were 0 -150, 0 -100 and 80 -110 respectively. The maximum range of motion in the 4D imaging for the superior lung was 1 -3.5mm and 3.5 -8mm in the inferior portion. The liver motion was 5.5 -8.0mm at the tip and 5.7 -10.0mm at the dome. No measurable drift in motion was observed over a two hour session and motion was reproducible over three different sessions for sin 2 (t), sin 4 (t) and a patient-like breathing curve with the interquartile range of amplitudes for all breathing cycles within 0.5mm. The addition of features within the lung and of a deformable liver will allow the phantom to be used for imaging studies such as validation of 4DMRI and pseudo CT methods.

Deep learning based synthetic‐CT generation in radiotherapy and PET: A review

“…It could be pretty interesting to have a phantom to allow regular QA procedures, for example, for CT. 213 This would be relatively straightforward for II; however, in MR-based sCT, phantoms' manufacturing is quite chal-lenging due to the need for contrast in MRI and CT. Recently, the first phantoms have been proposed for such task [214][215][216][217] showing the potential of additive manufacturing.…”

Dosimetric Validation of a System to Treat Moving Tumors Using Scanned Ion Beams That Are Synchronized With Anatomical Motion

“…We also selected methods for assessing dosimetric quality that are standard techniques within ion therapy centers (26,41). Further, the range changes were measured by delivering beams to simple phantoms rather than anthropomorphic phantoms (42)(43)(44), eliminating additional variables, such as range uncertainties associated with variations in tissue density, irregular breathing patterns, and generally more complex range changes that are found in a human anatomy. As a result, the delivery quality more directly reflects the capabilities of the MP4D deliver approach.…”

Design of an anthropomorphic PET phantom with elastic lungs and respiration modeling

“…Besides PET/CT imaging, several anthropomorphic phantoms have been developed specifically for radiation dosimetry and radiotherapy planning 26,27 . In such phantoms lungs are typically inflated using a ventilator that applies positive air pressure 28–30 . However, driving lungs by ventilation is difficult when they are surrounded by an incompressible medium, for example, a radioactive water solution.…”