Establishing a framework to implement 4D XCAT phantom for 4D radiotherapy research.
OBJECTIVE
To establish a framework to implement the 4D integrated extended cardiac torso (XCAT) digital phantom for 4D radiotherapy (RT) research.


METHODS
A computer program was developed to facilitate the characterization and implementation of the 4D XCAT phantom. The program can (1) generate 4D XCAT images with customized parameter files; (2) review 4D XCAT images; (3) generate composite images from 4D XCAT images; (4) track motion of selected region-of-interested (ROI); (5) convert XCAT raw binary images into DICOM format; (6) analyse clinically acquired 4DCT images and real-time position management (RPM) respiratory signal. Motion tracking algorithm was validated by comparing with manual method. Major characteristics of the 4D XCAT phantom were studied.


RESULTS
The comparison between motion tracking and manual measurements of lesion motion trajectory showed a small difference between them (mean difference in motion amplitude: 1.2 mm). The maximum lesion motion decreased nearly linearly (R 2 = 0.97) as its distance to the diaphragm (DD) increased. At any given DD, lesion motion amplitude increased nearly linearly (R 2 range: 0.89 to 0.95) as the inputted diaphragm motion increased. For a given diaphragm motion, the lesion motion is independent of the lesion size at any given DD. The 4D XCAT phantom can closely reproduce irregular breathing profile. The end-to-end test showed that clinically comparable treatment plans can be generated successfully based on 4D XCAT images.


CONCLUSIONS
An integrated computer program has been developed to generate, review, analyse, process, and export the 4D XCAT images. A framework has been established to implement the 4D XCAT phantom for 4D RT research.
Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA.
Raj K
RK
Panta
Paul
P
Segars
Fang-Fang
FF
Yin
Jing
J
Cai
D035843:Biomedical Research; D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D012984:Software