12 - HDR Brachytherapy

12 - HDR Brachytherapy - Lecture # 12 (Ch. 22) HDR...

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HDR Brachytherapy Tarun K. Podder, PhD, DABR Department of Radiation Oncology Brody School of Medicine Leo Jenkins Cancer Center East Carolina University February 22, 2011 Lecture # 12 (Ch. 22)
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Brachytherapy Dose Rate (ICRU 38) Low Dose Rate (LDR): ≤ 2 Gy/hr Medium Dose Rate (MDR): 2 – 12 Gy/hr High Dose Rate (HDR): ≥ 12 Gy/hr Pulsed Dose Rate (PDR): ~ 1Gy/hr
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Dose Reference Points Point “A” is the dose reference point Effects of different anatomical sizes
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rectum Rectum and Bladder Ref. Points
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Historical example Surface applicator with irregular distribution of radium on the applicator surface (Murdoch, Brussels 1933)
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Other example Treatment of squamous cell carcinoma of the forehead Catheters for source placement
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Source distance from the skin Determines incident dose Determines dose fall off in skin - the further the sources are from the skin the less influence has dose fall off due to inverse square law Dose homogeneity - the further away the sources are the more homogenous the dose distribution is at the skin
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Simulator films of forehead mould Dummy wires as markers for location
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Surface mould advantages Fast dose fall off in tissues Can conform the activity to any surface Flaps available
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HDR brachytherapy In the past possible using 60-Co pellets Today, virtually all HDR brachytherapy is delivered using a 192-Ir stepping source Source moves step by step through the applicator - the dwell times in different locations determine the dose distribution
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Optimization of dose distribution adjusting the dwell times of the source in an applicator Nucletron
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Afterloading Manual The sources are placed manually usually by a
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12 - HDR Brachytherapy - Lecture # 12 (Ch. 22) HDR...

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