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Relation of external surface to internal tumor motion studied with cine CT
Author(s) -
Chi PaiChun Melinda,
Balter Peter,
Luo Dershan,
Mohan Radhe,
Pan Tinsu
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2241993
Subject(s) - respiratory monitoring , reproducibility , nuclear medicine , medicine , imaging phantom , radiation therapy , biomedical engineering , radiology , respiratory system , anatomy , mathematics , statistics
The accuracy of delivering gated‐radiation therapy to lung tumors using an external respiratory surrogate relies on not only interfractional and intrafractional reproducibility, but also a strong correlation between external motion and internal tumor motion. The purpose of this work was to use the cine images acquired by four‐dimensional computed tomography acquisition protocol to study the relation between external surface motion and internal tumor motion. The respiratory phase information of tumor motion and chest wall motion was measured on the cine images using a proposed region‐of‐interest (ROI) method and compared to measurement of an external respiratory monitoring device. On eight lung patient data sets, the phase shifts were measured between (1) the signal of a real‐time positioning‐management (RPM) respiratory monitoring device placed in the abdominal region and four surface locations on the chest wall, (2) the RPM signal in the abdominal region and tumor motions, and (3) chest wall surface motions and tumor motions. Respiratory waveforms measured at different surface locations during the same respiratory cycle often varied and had significant phase shifts. Seven of the 8 patients showed the abdominal motion leading chest wall motion. The best correlation (smallest phase shift) was found between the abdominal motion and the superior‐inferior (S‐I) tumor motion. A wide range of phase shifts was observed between external surface motion and tumor anterior‐posterior (A‐P)/lateral motion. The result supported the placement of the RPM block in the abdominal region and suggested that during a gated therapy utilizing the RPM system, it is necessary to place the RPM block at the same location as it is during treatment simulation in order to reduce potential errors introduced by the position of the RPM block. Correlations between external motions and lateral/A‐P tumor motions were inconclusive due to a combination of patient selection and the limitation of the ROI method.