Document Detail

Development of a phantom to evaluate the positioning accuracy of patient immobilization systems using thermoplastic mask and polyurethane cradle.
MedLine Citation:
PMID:  22830755     Owner:  NLM     Status:  In-Data-Review    
Purpose: The purpose of this study was to develop a new phantom to evaluate the positioning accuracy of patient immobilization systems.Methods: The phantom was made of papers formed into a human shape, paper clay, and filling rigid polyester. Acrylonitrile butadiene styrene (ABS) pipes were inserted at anterior-posterior (A-P) and right-left (R-L) directions in the phantom to give static load by pulling ropes through the pipes. First, the positioning precision of the phantom utilizing a target locating system (TLS) was evaluated by moving the phantom on a couch along inferior-superior (I-S), A-P, and R-L directions in a range from -5 mm to +5 mm. The phantom's positions detected with the TLS were compared with values measured by a vernier caliper. Second, the phantom movements in a tensile test were chosen from patient movements determined from 15 patients treated for intracranial lesions and immobilized with a thermoplastic mask and polyurethane cradle. The phantom movement was given by minimum or maximum values of patient movements in each direction. Finally, the relationship between phantom movements and the static load in the tensile test was characterized from measurements using the new phantom and the TLS.Results: The differences in all positions between the vernier caliper measurement and the TLS detected values were within 0.2 mm with frequencies of 100%, 95%, and 90% in I-S, A-P, and R-L directions, respectively. The phantom movements according to patient movements in clinical application in I-S, A-P, and R-L directions were within 0.58 mm, 0.94 mm, and 0.93 mm from the mean value plus standard deviation, respectively. The regression lines between the phantom movements and static load were given by y = 0.359x, y = 0.241x, and y = 0.451x in I-S, A-P, and R-L directions, respectively, where x is the phantom movement (mm) and y is the static load (kgf). The relationship between the phantom movements and static load may represent the performance of inhibiting patient movements, so the accuracy of the immobilization system in the intracranial lesion will be estimated in advance by basic tensile test on the new phantom.Conclusions: The newly developed phantom was useful to evaluate the accuracy of immobilization systems for a Cyberknife system for intracranial lesions.
Hiroki Inata; Takatoshi Semba; Yoshihiro Itoh; Yuta Kuribayashi; Suetoshi Murayama; Osamu Nishizaki; Fujio Araki
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  39     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-07-26     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4219-27     Citation Subset:  IM    
Department of Radiology, Saiseikai Imabari Hospital, 7-1-6 Kitamura, Imabari, Ehime 799-1592, Japan.
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