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Dose error from deviation of dwell time and source position for high dose-rate 192Ir in remote afterloading system
Hiroyuki Okamoto1, Ako Aikawa1, Akihisa Wakita1
1Department of Radiation Oncology, National Cancer Center Hospital, 104-0045, Tokyo, Japan.
Journal of Radiation Research
|February 26, 2014
Summary
Investigating deviations in dwell times and source positions for Iridium-192 high-dose-rate (HDR) brachytherapy revealed that multiple interstitial needles are most susceptible to dose errors, reaching up to 2%. Other techniques showed less than 1% error.
Area of Science:
- Medical Physics
- Radiation Oncology
- Radiotherapy Physics
Background:
- High-dose-rate (HDR) brachytherapy utilizes Iridium-192 ((192)Ir) sources for precise radiation delivery.
- Deviations in dwell time and source positioning can lead to significant dose errors in brachytherapy procedures.
- Accurate dose delivery is critical for effective cancer treatment and minimizing side effects.
Purpose of the Study:
- To investigate the influence of dwell time and source position deviations for (192)Ir HDR brachytherapy.
- To evaluate potential dose errors across various brachytherapy techniques and applicators.
- To determine the susceptibility of different brachytherapy methods to positioning and timing inaccuracies.
Main Methods:
- Dwell time deviations (ΔT) were measured using a well-type ionization chamber.
- Source position deviations (ΔP) were measured using a check ruler and radiographic film analysis.
- Composite dose errors were calculated using Gaussian distribution, incorporating measured ΔT and ΔP values.
Main Results:
- Measured deviations were ΔT = 32 ms and ΔP = 0.12 mm (ruler) / 0.11 mm (film).
- Dose errors were found to be dependent on dwell time and distance from the point of interest to the dwell position.
- Multiple interstitial needle techniques exhibited the highest dose error (2%), while other applicators (cylinder, tandem-ovoid) showed errors <1%.
Conclusions:
- Potential dose errors in (192)Ir HDR brachytherapy are influenced by both dwell time and source position deviations.
- The susceptibility to dose errors varies significantly among different brachytherapy techniques.
- Multiple interstitial needle brachytherapy is the most sensitive technique to these deviations, necessitating careful quality assurance.
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