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Abstract
The machine log files recorded by a scanning control unit in proton beam therapy system have been studied to be used as a quality assurance method of scanning beam deliveries. The accuracy of the data in the log files have been evaluated with a standard calibration beam scan pattern. The proton beam scan pattern has been delivered on a gafchromic film located at the isocenter plane of the proton beam treatment nozzle and found to agree within ±1.0 mm. The machine data accumulated for the scanning beam proton therapy of five different cases have been analyzed using a statistical method to estimate any systematic error in the data. The high-precision scanning beam log files in line scanning proton therapy system have been validated to be used for off-line scanning beam monitoring and thus as a patient-specific quality assurance method. The use of the machine log files for patient-specific quality assurance would simplify the quality assurance procedure with accurate scanning beam data.
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REFERENCES
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 | Fig. 1.A scanned EBT3 film irradiated with the standard scan pattern composed of 5x5 points (230 MeV). |
 | Fig. 2.An example of scanning beam information recorded in the scanning control unit (Top left: x-position in time, top right: y-position in time, bottom left: monitor count in time, bottom right: x-position vs. y-position. Raw data without pedestal/noise reduction). |
 | Fig. 3.A scanning beam information recorded in the scanning control unit (one sample layer of a patient beam delivery plan). |
Table 1.
The summary of pre-treatment QA log file analysis. The “ds” stands for the displacement of the recorded position from the planned position. For a given field (case), the entire energy layers (number of layers) have been analyzed.
| Cases | Number of layers | Average of ds | Standard deviation |
|---|---|---|---|
| [mm] | of ds [mm] | ||
| Case 1 | 15 | 0.09 | 0.09 |
| Case 2 | 17 | 0.11 | 0.10 |
| Case 3 | 23 | 0.15 | 0.07 |
| Case 4 | 18 | 0.10 | 0.11 |
| Case 5 | 11 | 0.06 | 0.14 |
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