RT Journal Article
SR Electronic
T1 A novel 4D-phantom using rapid prototyping of anatomically realistic tumor models for evaluation of PET/CT and PET-guided radiotherapy
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1938
OP 1938
VO 57
IS supplement 2
A1 Jens Kurth
A1 Christian Gocke
A1 Ingo Jonuchies
A1 Guido Hildebrandt
A1 Bernd Joachim Krause
YR 2016
UL http://jnm.snmjournals.org/content/57/supplement_2/1938.abstract
AB 1938Objectives An important source of image degradation in PET/CT is caused by organ movement, mainly due to cardiac and respiratory motion. This affects quantitative accuracy for diagnostic purposes, the ability to define accurate target volume and position and as well the optimization of deliverable PET-based radiotherapy dose distributions in radiation oncology. Phantom studies help to estimate the intensity of these uncertainties relative to representative ground truth images, RT plans, and delivery probes, which is unavailable in patient data. There-fore the main objectives of the presented projects are: - Design of a 4D-phantom that is suitable for both PET/CT and also radio therapy - Usage of F-18 labeled tumor models, which have no inactive walls (avoiding errors due to cold wall effect [1]) and are based on realistic tumor geometries - Movement of these models with highly reproducible 3D-trajectories.Methods Tumor models: From CT data sets tumor geometries are segmented. Based on these data different reusable negative casting molds are made by solid freeform fabrication. These molds are filled with a specially tailored alginate mixture with desired concentration of F-18. Further on we developed an effector system made of plastics for the positioning of the tumor model, driven by watertight pneumatic cylinders. This allows the im-plementation into a water filled NEMA-PET-phantom. Based on the work by Seppenwoolde et al [2] we derived a mathematical model for the description of the 3-dimensional motion of the tumor model. A control-oriented model was designed that describes the robot kinematics as well as the dynamics of the individual cylinders and a cascaded flatness-based control approach is implemented on a real time system. 4D PET/CT scans of the new phantom with different respiratory motion patterns were acquired and end-to-end test were performed; from PET/CT scanning to transferring data to the planning system, target volume delinea-tion and test of 4D-plans.Results The reproducible production of the tumor models using the negative molds can be easily performed and the handling of the models is easy. The designed mechanics has a working range of up to 6 cm for all three direc-tions in space, which allows the realization of complex 3D movements. The absolute position errors for the desired trajectories of the tumor model are almost below 1 mm, which allows the exact replication of trajecto-ries during imaging and treatment validation.Conclusions The novel 4D-phantom mimics the complex movement of tumors due to respiratory motion. Obtained 4D PET/CT scans are suitable for test of segmentation algorithms and the validation of treatment planning and delivery both for 3D and 4D plans.