Daily on-line set-up correction in 3D-conformal radiotherapy: is it feasible?
OBJECTIVE
The aim of this report was to investigate the feasibility in terms of treatment time prolongation of an on-line no-action level correction protocol, based on daily electronic portal image verification.


METHODS
The occupation of a linear accelerator (LINAC) delivering 3-D conformal treatments was monitored for two weeks (from Monday to Friday, 10 working days). An electronic portal image device I-View (Elekta, UK) was used for setup verification. Single-exposure portal images were acquired daily using the initial 8 monitor units delivered for each treatment field. Translational deviations of isocenter position larger than 5 mm or 7 mm, for radical or palliative treatments, respectively, were immediately corrected. In order to estimate the extra workload involved with the on-line protocol, the time required for isocenter check and table correction was specifically monitored.


RESULTS
Forty-eight patients were treated. In all, 482 fractions had electronic portal images taken. Two hundred and forty-five setup corrections were made (50.8% of all fractions). The occupation of the LINAC lasted 106 h on the whole. Twelve h and 25 min (11.7% of LINAC occupation time) were spent for portal image verification and setup correction. On the average, 4.3 fractions per hour were carried out.


CONCLUSIONS
When used by trained therapists, ideally, portal imaging may be carried out before each fraction, requiring approximately 10% of LINAC occupation time.
Radiotherapy Unit, Department of Oncology, Fondazione di Ricerca e Cura Giovanni Paolo II, UniversitàCattolica, Campobasso, Italy.
Francesco
F
Deodato
Savino
S
Cilla
Mariangela
M
Massaccesi
Gabriella
G
Macchia
Edy
E
Ippolito
Luciana
L
Caravatta
Vincenzo
V
Picardi
Michele
M
Romanella
Carlo
C
Di Falco
Alessandra
A
Bartollino
Vincenzo
V
Valentini
Numa
N
Cellini
Marco
M
De Spirito
Angelo
A
Piermattei
Alessio G
AG
Morganti
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D010315:Particle Accelerators; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D013997:Time Factors; D016896:Treatment Outcome