Experiences at the Paul Scherrer Institute with a remote patient positioning procedure for high-throughput proton radiation therapy.
OBJECTIVE
To describe a remote positioning system for accurate and efficient proton radiotherapy treatments.


METHODS
To minimize positioning time in the treatment room (and thereby maximize beam utility), we have adopted a method for remote patient positioning, with patients positioned and imaged outside the treatment room. Using a CT scanner, positioning is performed using orthogonal topograms with the measured differences to the reference images being used to define daily corrections to the patient table in the treatment room. Possible patient movements during transport and irradiation were analyzed through periodic acquisition of posttreatment topograms. Systematic and random errors were calculated for this daily positioning protocol and for two off-line protocols. The potential time advantage of remote positioning was assessed by computer simulation.


RESULTS
Applying the daily correction protocol, systematic errors calculated over all patients (n = 94) were below 0.6 mm, whereas random errors were below 1.5 mm and 2.5 mm, respectively, for bite-block and for mask immobilization. Differences between pre- and posttreatment images were below 2.8 mm (SD) in abdominal/pelvic region, and below 2.4 mm (SD) in the head. Retrospective data analysis for a subset of patients revealed that off-line protocols would be significantly less accurate. Computer simulations showed that remote positioning can increase patient throughput up to 30%.


CONCLUSIONS
The use of a daily imaging and correction protocol based on a "remote" CT could reduce positioning errors to below 2.5 mm and increase beam utility in the treatment room. Patient motion between imaging and treatment were not significant.
Bolsi
Alessandra
A
Center for Proton Radiation Therapy, Paul Scherrer Institute, Villigen PSI, Switzerland. alessandra.bolsi@psi.ch
Lomax
Antony J
AJ
Pedroni
Eros
E
Goitein
Gudrun
G
Hug
Eugen
E
D003951:Diagnostic Errors; D004526:Efficiency; D005160:Facility Design and Construction; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006801:Humans; D009010:Monte Carlo Method; D009068:Movement; D061766:Proton Therapy; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D013679:Technology, Radiologic / Q000379:methods; D019112:Teleradiology / Q000379:methods; D013997:Time Factors; D011522:Protons
D011522:Protons