Table 1.
The tumor volumes, respiratory-tumor motion, and tumor margins for six cases.
Fig 1.
(a) The GTV volume and location of the six patient cases, (b) Design of a 3D printed lung phantom, (c) Rendering image (left) and fabricated 3D-printed lung phantom (right).
Fig 2.
4D phantom with 3D printed lung phantom.
The inserts are either a 3D printed lung phantom (inhomogeneous) or a homogeneous phantom.
Fig 3.
The lung tissue volume (LTV) of the phantom.
(a) The LTV is filled with 0.3 mm strips with a 2 mm air gap to match the lung density. (b) The green area is the LTV in the phantom.
Fig 4.
Patient-specific respiratory data.
Six patient-specific breathing patterns were acquired from the Varian RPM system during planning CT scan for each patient.
Fig 5.
4D-CT scan of the 4D-lung phantom for case P4.
(a) A respiratory motion device and the 3D-printed lung phantom insert. The EBT3 film could be placed inside phantoms. (b) 4D-CT image set of the lung phantom was sorted in phases. The images listed from left to right correspond to the breathing phases of end-inhale (0%), mid-exhale (30%), end-exhale (50%), and mid-inhale (70%), respectively. The 17.9 mm full motion was reduced to 3.6 mm residual motion in the 30–70% gating window. (c) VMAT plan dose distribution for the lung phantom at the end-exhale (50%) phase.
Fig 6.
Image registration between the patient CT and lung phantom CT.
Both CT image were used in the coronal plane.
Fig 7.
Dosimetric evaluation of the phantoms with lung density reassignment.
(a) Axial and sagittal images of the lung phantom are shown. The phantom lung regions were implemented with a mesh structure with 2 mm spacing. The plan dose of 2 arc VMAT is shown in the coronal plane. (b) The CT number of the phantom LTV was replaced by the average lung CT number in the patient’s image (-813 HU). The dose distributions based on the original and reassigned images were compared in the gamma index map. (c) For the HU reassignment with air (-1000 HU), the GPR was 62.5%.
Table 2.
HU value of GTV and LTV for six cases and the GPRs (3%/0 mm) compared under various material assignments of LTV in the lung phantoms.
Fig 8.
The analysis of the gamma passing rates (2%/1 mm) between the calculated dose and the measured dose comparing VMAT techniques under the static and gating conditions using both homogeneous and inhomogeneous phantom (3D-printed patient-specific moving phantom) in the P2 case.
The treatment planning dose was applied using the AAA or the AXB dose calculation algorithm.
Table 3.
The gamma analysis (2%/1 mm criteria) results of the homogeneous and inhomogeneous phantoms (patient-specific lung phantom) for the six cases.