23- Organ Motion Management

23- Organ Motion Management - Lecture # 23 Organ Motion...

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Organ Motion Management Tarun K. Podder, PhD, DABR Department of Radiation Oncology Brody School of Medicine Leo Jenkins Cancer Center East Carolina University March 12, 2011 Lecture # 23
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Read TG-76
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Why geometric errors appear? Inter- and intra-observer variations in GTV delineation Motion artifacts on the CT images used to delineate targets and surrounding structures Motion during dose delivery due to respiration and cardiac functions Variations caused by changing organ volumes, tumor growth or shrinkage, edema, etc. Patient setup error
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Internal organs that known to move 1. Lung 2. Esophagus 3. Liver 4. Pancreas 5. Breast 6. Prostate 7. Kidney Power frequency spectrum analysis Low-frequency component – respiratory cycle (0.3Hz) High-frequency component – cardiac cycle (1.05Hz) Respiratory cycle Organ Motion responsible for tumor motion
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Tumor Motion
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Tumor Motion
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Tumor Motion
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Problems of Target/ tissue Motion during RT • Image-acquisition limitations Motion artifacts Target/structure delineation error Dose-calculation error • Treatment-planning limitations Large PTV margin (motion + setup) Tumor motion may vary intra- and inter-fractionally • Radiation-delivery limitations Blurring of static dose distribution Exacerbate in IMRT
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CT with free breathing Respiratory gated CT scan GTV PTV Problems of Target/ tissue Motion during RT
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Effects of Tumor Motion CTV_exh CTV_inh CTV_norm Range of tumor motion PTV Tissue sparing PTV_norm PTV_inh PTV_exh Tissue sparing CTV CTV CTV
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Respiratory gating methods Breath-hold methods Forced shallow breathing with abdominal compression Real-time tumor-tracking methods Tumor Motion Compensating Techniques
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Real-time tumor-tracking methods 1) Determining the tumor position Direct tumor imaging Tumor location using implanted fiducial markers Tumor position prediction based on surrogate breathing signals Nonradiographic tumor tracking 2) Compensating for time delays in the beam-positioning response 4) Correcting the dosimetry for breathing effects 5) Implementation of real-time tracking response to respiratory
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23- Organ Motion Management - Lecture # 23 Organ Motion...

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