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Characterization of a multi-axis ion chamber array
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10.1118/1.3505452
/content/aapm/journal/medphys/37/11/10.1118/1.3505452
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/11/10.1118/1.3505452

Figures

Image of FIG. 1.
FIG. 1.

Overlay of the IC PROFILER™ (panel) showing the multiple detector axes.

Image of FIG. 2.
FIG. 2.

The panel’s dose response relative to the Farmer-type chamber’s dose response, see “Dose and Instantaneous dose rate dependence” in the Results and Discussion section for a description of .

Image of FIG. 3.
FIG. 3.

The panel’s instantaneous dose rate response relative to the Farmer-type chamber’s.

Image of FIG. 4.
FIG. 4.

The panel’s PRF response relative to the Farmer-type chamber’s PRF response. The measurement update interval was the default (125 ms) for all measurements expect one, which was set to 500 ms.

Image of FIG. 5.
FIG. 5.

The off-axis PRF response for the -axis detectors relative to the center detector for panel orientations of 0° (black curves) and 180° (blue curves). The panel was operated in pulsed mode for each panel orientation. The data for panel orientation of 180° were rotated to maintain the 0° LINAC coordinate system.

Image of FIG. 6.
FIG. 6.

The difference between the 180° and 0° OA_Response(PRF) values for the panel operated in pulsed mode (black curves) and continuous mode (blue curves). The cause of the spike at the (±) 4 cm positions in pulsed mode (or its absence in continuous mode) is not entirely understood and is under continued investigation by the manufacturer.

Image of FIG. 7.
FIG. 7.

The accuracy of the calibration factors.

Image of FIG. 8.
FIG. 8.

The energy response of the calibration factors.

Image of FIG. 9.
FIG. 9.

The buildup response of the calibration factors for 6 and 18 MV x-rays.

Image of FIG. 10.
FIG. 10.

Off axis backscatter response of the -axis detectors for (a) a 6 MV field and (b) an 18 MV field. Buildup was equivalent to d-max.

Image of FIG. 11.
FIG. 11.

Normalized cross-plane measurements with a CC13™ and the panel. The beam energy was 6 MV and the buildup was .

Image of FIG. 12.
FIG. 12.

Profile agreement (over 80% of the field width) between the panel and CC13™ for 6 MV x-ray (a) cross-plane measurements (black) and in-plane measurements (blue) and 18 MV x-ray (b) cross-plane measurements (black) and in-plane measurements (blue).

Image of FIG. 13.
FIG. 13.

(a). FDDs for a 6 MV field. (b) The energy response of the panel’s center detector presented as a ratio of the panel’s FDD to the CC13’s™ FDD.

Image of FIG. 14.
FIG. 14.

(a) Output factors measured with the panel’s center chamber and three independent detectors for a 6 MV (black curves) and 18 MV (blue curves) x-ray beam. (b) The panel output factors were normalized to each independent detector for the 6 MV (black curves) and 18 MV (blue curves) x-ray beams.

Tables

Generic image for table
TABLE I.

List of the categories: subscripts, variables, and equations.

Generic image for table
TABLE II.

The panel’s short and long-term reproducibilities were evaluated on a teletherapy unit; the short term reproducibility was evaluated over the course of 10 min, while the long term reproducibility was evaluated over 9 months. The reproducibility was expressed as the coefficient of variation (CV) and the maximum deviation of each detectors corrected counts relative to their mean for the specific time frame.

Generic image for table
TABLE III.

The short and long term reproducibilities of the relative detector calibration factors; the short term reproducibility was evaluated over the course of 1 h, while the long term reproducibility was evaluated over 6 months. The reproducibility was expressed as the coefficient of variation (CV) and the maximum deviation of each detectors calibration factors relative to their mean for the specific time frame.

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/content/aapm/journal/medphys/37/11/10.1118/1.3505452
2010-11-01
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Characterization of a multi-axis ion chamber array
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/37/11/10.1118/1.3505452
10.1118/1.3505452
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