This document summarizes intensity modulated radiotherapy (IMRT) and its advantages over conventional radiotherapy. IMRT allows for superior dose distribution and better sparing of normal tissues by modulating the radiation beam intensity inside each treatment field. It provides more conformal dose coverage of irregularly shaped tumor targets while further reducing dose to nearby healthy tissues and critical organs. IMRT planning requires defining treatment goals and optimizing dose constraints using computer algorithms to determine the optimal intensity patterns delivered via multileaf collimators.

1. State of the Art CRT: IMRT Intensity Modulated Radiotherapy James C. Li M.D. Chung Shan Medical and Dental College Medical Center Department of Radiation Oncology

6. Superior Dose Distribution IMRT plan for Prostate Cancer

7. Superior Dose Distribution Prostate IMRT plan

8. Superior Dose Distribution

9. Superior Dose Distribution

10. Nasopharynx 50 70 Levels in % 100 110 PTV Cord, Brainstem IMRT of

11. Resultant Radiation Distributions

12. NPC Recurrent Disease

13. Dose Volume Histograms

14. IMRT for Brain Tumor

15. IMRT for Frontal Sinus Tumor

16. IMRT for Recurrent Endometrial Ca

17. IMRT for Lung Cancer

18. Lung, IMRT Lung, Conventional

22. IMRT Plan Design Process Localization and Image Transfer Contouring Beam Definition Dose Calculation Plan Evaluation Pre-Optimization Calculations Optimization- Std. Constraint Temp. Leaf Motion Files (DVA) Independent MU check

29. State of the Art Computer Driven Linear Accelerator, with MLC Let’s take a closer look of a “ Multi-leaf collimator (MLC)”

30. Shaping of Radiation fields with a MLC have been the primary use of MLC for many years. Computer-controlled Multileaf Collimator

31. But, MLCs can be used to modulate radiation beam intensity in addition to the classical use of MLCs as radiation field shaping devices. Computer-controlled Multileaf Collimator

33. How’s IMRT Done? Sliding Windows technique

35. IMRT QA and Treatment MLC Controller TPS Leaf Motion Treatment Machine Record and Verify Log File Indep. MU Calc. DMLC Port Film/ DRR Comparison Film/Ion Chamber Verification ?

36. Graphics illustration of a Radiation beam intensity being modulated field width field length Beam-let

37. Example (6-field head/neck RX): gantry 0 gantry 30 gantry 60 sup sup sup gantry 270 gantry 330 gantry 135 sup sup sup

38. For example: RX fields with IMRT in a 6-field ABD treatment. gantry 15 gantry 320 gantry 270 gantry 220 gantry 180 gantry 70

41. Biological Target Volume? PET ; F-miso Hypoxia PTV PTV MRI ; choline/citrate Tumor burden PET ; IUDR Tumor growth Biological Eye View BTV

46. Limited Experience at CSMDC Medical Center Department of Radiation Oncology (Aug,2000~now)