Robustness to source displacement in dual air kerma strength planning for focal low-dose-rate brachytherapy of prostate cancer.

To describe the use of dual source strength implants for focal low-dose-rate brachytherapy.

An interneedle dual source strength planning strategy is described for focal low-dose-rate brachytherapy of the prostate. The implanted treatment plans were designed using peripheral (except near the rectum) needles loaded with high strength (0.9 U) sources and central needles loaded with low strength (0.4 U) sources ("interneedle" dual strength planning). This approach has been applied for focally treating 3 patients. In this article, we compare the characteristics and robustness to source motion of interneedle dual strength planning with four alternative planning strategies (single strength high, low, and intermediate, and intraneedle dual strength) on 50 simulated cases.

Interneedle dual source strength planning results in greater robustness to source motion and overall lower seed and needle density compared to the standard low source strength planning currently used in our centre. This planning approach is also significantly superior to single strength high, single strength intermediate and intraneedle dual strength planning strategies in terms of high dose to the urethral avoidance structure.

The use of interneedle dual source strength treatment plans for focal low-dose-rate brachytherapy is possibly the practical solution for limiting the density of sources required to deliver the prescribed dose while limiting proximity of high strength sources to organs at risk.

Brachytherapy. 2016 Jun 01 [Epub ahead of print]

S Sara Mahdavi, Ingrid T Spadinger, Nicholas T Chng, W James Morris

Department of Radiation Oncology, Vancouver Centre, British Columbia Cancer Agency, Vancouver, BC, Canada. Electronic address: ., Department of Medical Physics, Vancouver Centre, British Columbia Cancer Agency, Vancouver, BC, Canada., Department of Medical Physics, Centre for the North, British Columbia Cancer Agency, Prince George, BC, Canada., Department of Radiation Oncology, Vancouver Centre, British Columbia Cancer Agency, Vancouver, BC, Canada.

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