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Study On the Verification of the Source Positioning and Dwell Time Based On the Well-Chamber

Qiang Zhao*, Xiangyang Wu

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
To study a dosimetric method based on the well-chamber to verify the accuracy of the source positioning and dwell time for the afterloading machine. And to evaluate the ability of the method. It was hoped to provide a new method for the afterloading machine’s quality control.

Methods:
The principle of the method was explained according to the hardware structure of the holder in the well-chamber. Then two simulation experiments were made to measure the precision of the method. One is made to simulate the positioning variation from -4mm to 5mm for point A, which is at the high slope region of the response-position curve of the well chamber. And another is made to simulate the time variation from -0.5s to 0.5s for point B, which is at the plateau region. And the result was analyzed by data fitting. The feasibility test was done also. And the advantages and disadvantages of the method were discussed by comparing it with the traditional method.

Results:
The precision of the method for detecting the source positioning and dwell time is 0.07mm and 0.09s, respectively. In the feasibility test, the standard deviation of the measured value is below 3%.

Conclusion:
The well chamber method can measure the individual point’s positioning and dwell time accuracy except for the accumulated positioning error. And the method is a relative measurement, it depends on the baseline that measured and adjusted by the traditional golden method. However, the well-chamber method has high precision and is easy to operate just like the measurement of the source activity. Comparing to the traditional method, the well-chamber has these advantages:low costs, simple operation, high accuracy. In general, it can be applied to the rapid verification of the relative accuracy of the source positioning and dwell time.

Download ePoster [PDF]

Keywords

Quality Assurance, Brachytherapy, Dosimetry

Taxonomy

TH- Brachytherapy: Calibration & Quality Assurance

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