Simulator verification of the accuracy of patient repositioning after virtual simulation. Is physical simulation still needed?
OBJECTIVE
To evaluate the frequency and amount of displacements after repositioning a patient on the physical simulator following virtual simulation.


METHODS
After laser marking at the CT scanner and virtual simulation, patients were repositioned on the simulator. The isocenter obtained from the calculated table movements was checked by fluoroscopically measuring the distances to standardized anatomic landmarks and comparing them to the treatment plan.


RESULTS
In 86% of patients, displacements were < or = 0.5 cm. There was no significant difference between the supine and prone position, diagnosis categories or CT reconstruction indices. The use of immobilization devices and cranial versus body stem localization did make a significant difference. Rates of exact repositioning were high in brain and head and neck patients and comparatively low in abdominal tumors and breast cancer.


CONCLUSIONS
Immobilization devices play an important role for the precision of radiotherapy. Whenever precise positioning is possible (e. g. with a head mask), virtual simulation alone might be sufficient. Patients with abdominal and breast tumors, were repositioning precision is often suboptimal, might profit from an additional physical simulation.
Schüller
Patrick
P
Hospital and Outpatient Department for Radiotherapy - Radiooncology, University Hospital Münster, Germany. pschuel@uni-muenster.de
Bruns
Frank
F
Hesselmann
Stefan
S
Horn
Kirsten
K
Panke
Joan E
JE
Schuck
Andreas
A
Schäfer
Ulrich
U
Micke
Oliver
O
Willich
Normann
N
D000328:Adult; D000368:Aged; D016477:Artifacts; D002138:Calibration; D003198:Computer Simulation; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000532:radiotherapy*; D016684:Prone Position; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D012984:Software; D016683:Supine Position; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface