Three-dimensional surface imaging for detection of intra-fraction setup variations during radiotherapy of pelvic tumors.
OBJECTIVE
Surface-based image guided radiotherapy (IGRT) allows positioning and/or monitoring patients in 3 dimensions (3D), without the use of ionizing radiation. In this study, we report on intra-fraction motion measured by acquisition of multiple images of 3D body surfaces.


METHODS
Twenty-nine patients treated for pelvic tumors were enrolled. Setup variations (SV) through three consecutive body surfaces acquired by the optical IGRT system Align-RT (Vision-RT, London, UK) were analyzed before, during and at the end of treatment delivery. Displacements along the main axes (X, Y and Z) from initial (I) to mid-treatment (MT) and final (F) acquisitions were recorded. Time and direction of SV were assessed.


RESULTS
A total of 6272 images from 792 fractions of 29 patients were available. The main source of misalignment was between I and MT acquisition (p < 0.001). The dominant SV direction was the vertical one (Z axis), with mean SV of -1.20 ± 0.06 mm and -1.55 ± 0.06 mm for I-MT and I-F acquisitions, respectively. The Y mean components of SV were, respectively, -0.95 ± 0.10 mm and -1.0 ± 0.10 for I-MT and I-F acquisitions, while the X deviations were 0.07 ± 0.08 mm for I-MT and 0.26 ± 0.08 mm I-F.


CONCLUSIONS
Three-D surface imaging for patient setup monitoring highlighted remarkable mobility of patients during RT session, especially in the anterior-posterior direction (Z axis). The largest magnitude in patient movements occurred during the first part of delivery. These findings suggest that the initial setup control cannot not to be sufficient to guarantee treatment reproducibility, especially for long-lasting RT treatments.
Division of Radiotherapy, University Hospital "Maggiore della Carità", Novara, Italy.
Giuseppina
G
Apicella
Medical Physics, University Hospital "Maggiore della Carità", Novara, Italy.
Gianfranco
G
Loi
Division of Radiotherapy, University Hospital "Maggiore della Carità", Novara, Italy.
Sara
S
Torrente
Division of Radiotherapy, University Hospital "Maggiore della Carità", Novara, Italy.
Silvia
S
Crespi
Division of Radiotherapy, University Hospital "Maggiore della Carità", Novara, Italy.
Debora
D
Beldì
Medical Physics, University Hospital "Maggiore della Carità", Novara, Italy.
Marco
M
Brambilla
Division of Radiotherapy, University Hospital "Maggiore della Carità", Novara, Italy. krengli@med.unipmn.it.|Department of Translational Medicine, University of "Piemonte Orientale", Novara, Italy. krengli@med.unipmn.it.
Marco
M
Krengli
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005833:Genital Neoplasms, Female / Q000532:radiotherapy*; D005834:Genital Neoplasms, Male / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D011785:Quality Assurance, Health Care; D061106:Radiotherapy Setup Errors / Q000517:prevention & control*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results
IGRT; Intra-fraction; Organ motion; Radiotherapy; Setup; Surface imaging