11 - Brachytherapy

11 - Brachytherapy - Lecture # 11 (Ch. 15) Brachytherapy...

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1 Brachytherapy Tarun K. Podder, PhD, DABR Department of Radiation Oncology Brody School of Medicine Leo Jenkins Cancer Center East Carolina University February 17, 2011 Lecture # 11 (Ch. 15)
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2 Brachytherapy The Greek word brachys , meaning "short-distance" Brachytherapy is a form of radiotherapy where a radiation source is placed inside or next to the area requiring treatment. Brachytherapy is commonly used as an effective treatment for cervical, prostate, breast, and skin cancer and can also be used to treat tumors in many other body sites. Brachytherapy can be used alone or in combination with other therapies such as surgery, External Beam Radiotherapy (EBRT) and chemotherapy.
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3 Brachytherapy - History • Brachytherapy has been one of the earliest forms of radiotherapy • After discovery of radium by M Curie, radium was used for brachytherapy already late 19th century • There is a wide range of applications - this versatility has been one of the most important features of brachytherapy
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4 Radium Source Configurations
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5 Source Configuration and Dose Distributions Cs-137 I-125 Ra-226 (3 cm needle, 0.5 pt filter)
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6 Brachytherapy • Very flexible radiotherapy delivery • Source position determines treatment success • Depends on operator skill and experience • In principle the ultimate ‘conformal’ radiotherapy • Highly individualized for each patient
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7 • Typically localized cancer • Often relatively small tumor • Often good performance status (must tolerate the operation) • Sometimes pre-irradiated with external beam radiotherapy (EBRT) • Often treated with combination brachytherapy and EBRT A brachytherapy patient
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8 Patient flow in brachytherapy Treatment decision Ideal plan - determines source number and location Implant of sources or applicators in theatre Treatment plan Localization of sources or applicators (typically using X-ray, CT) Commence treatment
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9 Commonly used Radioisotopes
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10 Dose Rate Low Dose Rate (LDR): ≤ 2 Gy/hr Medium Dose Rate (MDR): 2 – 12 Gy/hr High Dose Rate (HDR): ≥ 12 Gy/hr Pulse Dose Rate (PDR): short pulses of radiation, typically once an hour, to simulate the overall rate and effectiveness of LDR treatment
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11 Duration of dose delivery Temporary brachytherapy involves placement of radiation sources for a set duration (usually minutes to hours) before being withdrawn. Permanent brachytherapy , also known as seed implantation, involves placing small LDR radioactive seeds in the tumor or treatment site and leaving them there permanently to gradually decay.
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12 Alpha ( α ) ex: Ra-226 Beta ( β ) ex: P-32, Sr-90 Gamma ( γ ) and Characteristic X-rays: ex: Cs-137, Ir-192, I-125 Type of Radiation
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13 Half Life (T 1/2 ): Time required for half of the atoms to decay (ie. The time required to reduce its activity to half of its original
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11 - Brachytherapy - Lecture # 11 (Ch. 15) Brachytherapy...

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