Interfractional variations in patient setup and anatomic change assessed by daily computed tomography.
OBJECTIVE
To analyze the interfractional variations in patient setup and anatomic changes at seven anatomic sites observed in image-guided radiotherapy.


METHODS
A total of 152 patients treated at seven anatomic sites using a Hi-Art helical tomotherapy system were analyzed. Daily tomotherapy megavoltage computed tomography images acquired before each treatment were fused to the planning kilovoltage computed tomography images to determine the daily setup errors and organ motions and deformations. The setup errors were corrected before treatment and were used, along with the organ motions, to determine the clinical target volume/planning target volume margins. The organ motions and deformations for 3 representative patient cases (pancreas, uterus, and soft-tissue sarcoma) and for 14 kidneys of 7 patients are presented.


RESULTS
Interfractional setup errors in the skull, brain, and head and neck are significantly smaller than those in the chest, abdomen, pelvis, and extremities. These site-specific relationships are statistically significant. The margins required to account for these setup errors range from 3 to 8 mm for the seven sites. The margin to account for both setup errors and organ motions for kidney is 16 mm. Substantial interfractional anatomic changes were observed. For example, the pancreas moved up to +/-20 mm and volumes of the uterus and sarcoma varied <or=30% and 100%, respectively.


CONCLUSIONS
The interfractional variations in patient setup and in shapes, sizes, and positions of both targets and normal structures are site specific and may be used to determine the site-specific margins. The data presented in this work dealing with seven anatomic sites may be useful in developing adaptive radiotherapy.
Li
X Allen
XA
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI 53226, USA. ali@radon.mcw.edu
Qi
X Sharon
XS
Pitterle
Marissa
M
Kalakota
Kapila
K
Mueller
Kevin
K
Erickson
Beth A
BA
Wang
Dian
D
Schultz
Christopher J
CJ
Firat
Selim Y
SY
Wilson
J Frank
JF
D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D019583:Dose Fractionation, Radiation; D005121:Extremities / Q000000981:diagnostic imaging; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006801:Humans; D008297:Male; D009068:Movement; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D010386:Pelvic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D050397:Radiotherapy, Intensity-Modulated; D012535:Scalp; D012878:Skin Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D013899:Thoracic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D036542:Tomography, Spiral Computed / Q000379:methods*; D014594:Uterine Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy