Role of "the frame cycle time" in portal dose imaging using an aS500-II EPID.
Phys Med
; 25(3): 148-53, 2009 Sep.
Article
em En
| MEDLINE
| ID: mdl-19231267
ABSTRACT
INTRODUCTION:
This paper evaluates the role of an acquisition parameter, the frame cycle time "FCT", in the performance of an aS500-II EPID. MATERIALS ANDMETHODS:
The work presented rests on the study of the Varian EPID aS500-II and the image acquisition system 3 (IAS3). We are interested in integrated acquisition using asynchronous mode. For better understanding the image acquisition operation, we investigated the influence of the "frame cycle time" on the speed of acquisition, the pixel value of the averaged gray-scale frame and the noise, using 6 and 15MV X-ray beams and dose rates of 1-6Gy/min on 2100 C/D Linacs.RESULTS:
In the integrated mode not synchronized to beam pulses, only one parameter the frame cycle time "FCT" influences the pixel value. The pixel value of the averaged gray-scale frame is proportional to this parameter. When the FCT <55ms (speed of acquisition V(f/s)>18 frames/s), the speed of acquisition becomes unstable and leads to a fluctuation of the portal dose response. A timing instability and saturation are detected when the dose per frame exceeds 1.53MU/frame. Rules were deduced to avoid saturation and to optimize this dosimetric mode.CONCLUSION:
The choice of the acquisition parameter is essential for the accurate portal dose imaging.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Radiometria
/
Ecrans Intensificadores para Raios X
/
Tomografia Computadorizada por Raios X
Tipo de estudo:
Diagnostic_studies
Idioma:
En
Revista:
Phys Med
Assunto da revista:
BIOFISICA
/
BIOLOGIA
/
MEDICINA
Ano de publicação:
2009
Tipo de documento:
Article
País de afiliação:
França