01 suh brain anatomy, planning and delivery hyderabad 2013 (cancer ci 2013) john h. suh
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This document provides an overview of brain anatomy, advances in radiation therapy treatment planning and delivery for brain tumors, and methods to focus radiation dose on tumors while minimizing dose to healthy brain tissue. It discusses contouring important brain structures, use of imaging like CT and MRI in treatment planning, and the evolution of techniques like intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT). It also reviews stereotactic radiosurgery and different technologies used like Gamma Knife and linear accelerators. The document concludes that understanding brain anatomy and dose constraints is essential for optimizing radiation delivery for brain tumors.
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01 suh brain anatomy, planning and delivery hyderabad 2013 (cancer ci 2013) john h. suh
- 1. Basics of Anatomy, Planning and Treatment Delivery for Brain Tumors John H. Suh, M.D. Professor and Chairman, Dept. of Radiation Oncology Associate Director of the Gamma Knife Center Rose Ella Burkhardt Brain Tumor and Neuro-oncology Center Taussig Cancer Institute
- 2. Conflict of interest • Abbott Oncology Consultant • Varian Travel funds
- 3. Objectives • Provide overview of brain anatomy • Review advances in treatment planning and delivery oncology that have allowed optimization of radiation therapy of brain tumors. • Discuss methods to direct dose to the tumor while minimizing dose to the normal neural tissues. • Review advances in stereotactic radiosurgery.
- 5. Structures that are contoured • Lenses • Eyes (retina) • Optic nerves and chiasm • Brain stem • Spinal cord • Cochlea • Temporal lobes and hippocampus • T2/FLAIR and T1 changes for gliomas
- 6. Cranial Anatomy • Brainstem = midbrain + pons + medulla Cerebral Aqueduct Chiasm Midbrain Pons Medulla C1 Foramen Magnum
- 7. Cranial Anatomy Motor Strip “Omega” Sign Motor Strip
- 8. Cochlea
- 9. Optic Chiasm • Chiasm is always above the sella Chiasm Pituitary
- 10. Visual Cortex Variability of visual cortex fMRI Visually Evoked Potentia
- 11. RTOG Atlas Red: Hippocampus Green: Hippocampal Avoidance Zone Hippocampal 1)Hippocampal Tail 1) Tail 2) Body 3)2) Body Head 3) Head The hippocampus has three anatomic subdivisions: the head, body, and tail; note that the head is inferior or caudad, the body is superoposterior and the tail is most cephalad (superior) and posterior, and an overall “banana” shape emerges on sagittal images, located in the plane of the lateral ventricle. MR Images courtesy of: Holmes CJ, Hoge R, Collins L, et al. "Enhancement of MR Images Using Registration for Signal Averaging" Journal of Computer Assisted Tomography 22, 324-333 (1998)
- 12. Radiation Therapy in 1990s
- 13. Dose distribution for WBRT
- 15. Conventional Radiotherapy Conventional Beam Shaper Desired Actual Dose Dose Distribution Distribution
- 16. CT simulator use in radiation oncology Provides cross sectional anatomical information 1) Target volume delineation 2) Relative geometry of critical structures 3) Beam placement and field shaping 4) Dose distribution calculation and analysis
- 19. Beam’s Eye View (BEV)
- 20. What are the Best Beam Directions?
- 21. Fusion of MRI to CT
- 22. Intensity Modulated Radiotherapy (IMRT) Intensity Transmitted Modulator Beamlets Desired Dose Actual Dose Distribution Distribution
- 23. IMRT using Rotational Arc (Peacock)- 1996
- 24. 3D Multileaf Collimator Photo courtesy of Siemens Medical Solutions
- 26. TransitionRADIATION Guided Radiation to Image ONCOLOGY Therapy Elekta Synergy
- 27. Therapeutic Index 100 Tumor control (%) Control 5 0 Complications 0 Dose (Gy) 95002052-01
- 28. On Board Imager (OBI)– KV/MV-Cone Beam CT Elekta KV-OBI Varian KV-OBI Siemens MV-OBI
- 29. Daily CT Prior to Treatment Tomotherapy Units Siemens CTvision
- 30. Image guided radiation therapy (IGRT) Novalis Shaped Beam Therapy
- 31. Cranial Patient Positioning ExacTrac CBCT
- 32. Glioblastoma of right temporal region
- 33. Sequential Planning Six static IMRT beams were used with 3 non-planar beams. The beam was on for 11 minutes.
- 34. Dose Constraints for RTOG 0825 • Lenses 7 Gy • Retina 50 Gy • Optic nerves 55 Gy • Optic chiasm 56 Gy • Brainstem 60 Gy
- 35. Conventional Dose Painting 63.0 59.4 50.4 45.0 30.0
- 36. Simultaneous Integrated Boost Delivery Four partial arcs are used for the plan. Estimated beam time was about 4 minutes
- 37. Beam arrangement for meningioma
- 39. RTOG 0933 Phase II Trial of Hippocampal Avoidance During Whole Brain Radiotherapy for brain metastases • Fused planning MRI CT image set • Hippocampal avoidance regions will 3D expansion of hippocampal contours by 5 mm.
- 41. Importance of optimizing image performance to achieve fundamental objectives of radiation therapy Dawson LA et al. The Oncologist 15:338-349, 2010
- 42. Stereotactic Radiosurgery “Replace the needle by narrow beams of radiation energy and thereby produce a local destruction of the tissue” Lars Leksell The stereotaxic method and radiosurgery of the brain Acta Chirurgica Scandinavia Vol 102, Fasc 4, 1952
- 43. Early days of Stereotactic Radiosurgery
- 44. Therapeutic Index 100 Tumor control (%) Control 5 0 Complications 0 Dose (Gy) 95002052-01
- 45. Stereotactic radiosurgery • Small, well-defined target < 4 cm diameter • Single fraction • Steep dose gradient • Intersection of multiple beams of radiation at isocenter
- 46. Clinical uses of stereotactic radiosurgery • Vascular malformations • Benign brain tumors • Malignant brain tumors • Functional disorders
- 47. Model B unit
- 49. Plugging helmets to shape dose
- 51. Leksell Gamma Knife® Treatable volume Leksell Gamma Knife C Leksell Gamma Knife PERFEXION
- 52. Collimator system 8-16-8-16- Collimator system 8-16-8- 16-16-16-16 16-8-16-8-16
- 53. Treatment plan with composite shots
- 55. Discordance caused by loose frame
- 56. Artifact caused by dental work
- 59. Micro Multileaf Collimators (mMLC)
- 60. Different linac approaches for brain SRS Dynamic Conformal Arc Conformal Beam Circular Arc IMRT HybridArc
- 61. Frameless Cranial Stereotaxy • Upper palate based immobilization – Good dentition helpful – Must be able to tolerate the mouthpiece • Mask based – More uncertainty • Relocatable – Hypofractionation – Larger lesions – Near dose sensitive structures – Post op cavity – Prior RT – Image guided – Skull is an excellent fiducial marker – Reusable • Not restricted by physical limitations
- 63. Radiation oncology team • Therapists • Nurses and nurse practitioners • Dosimetrists • Medical physicists • Clinical engineers • Schedulers • Secretaries • Radiation oncologists Strong teamwork and q/a program helps ensure proper and safe radiation delivery
- 64. Conclusions • Understanding brain anatomy and dose constraints are essential. • Technical advances in radiation oncology have allowed optimization of radiation delivery for brain tumors. • Dose painting, dose sculpting, and conformal avoidance for brain tumors can be achieved given the advances in technology, imaging and treatment planning.
- 65. Title of Presentation Arial Regular 22pt Single line spacing Up to 3 lines long Date 20pts Author Name 20pts Author Title 20pts
Editor's Notes
- The goal of radiation therapy is to maximize tumor control while minimizing complications. This axes of this graph represent Dose on the X-axis and tumor control or complications to normal tissues on the Y-axis. With respect to tumor control, as dose increases, the chance of tumor control increases. Likewise as dose increases, so does the probability of complication (represented by the red curve). Both these curves are sigmoidal in shape. Initially with low doses, there is little cell kill, and hence little tumor control. At a certain dose, the probability of cell kill increases dramatically, and hence high tumor control. However, beyond a certain dose, the curve again flattens so that increases in dose (while still toxic to tumor), does not increase the probability of further cell killing beyond what a lower dose can achieve. The risk of complication follows this same paradigm. Low dose has little chance of causing complication. However, at certain doses, the complication rate climbs sharply. These curves tend to be parallel, and the goal of radiation oncology is to maximize the potential for tumor killing (or tumor control) while minimizing the potential for normal tissue complications. The white vertical dashed line represents this compromise in therapeutic efficacy to achieve maximal tumor control with minimal normal tissue complication.
- Diagram depicting the importance of optimizing imaging performance based on the fundamental objectives of radiotherapy (outer circle). Trade-offs among geometric integrity, tissue contrast, and spatial resolution must be considered when designing time-efficient image acquisition protocols.
- The goal of radiation therapy is to maximize tumor control while minimizing complications. This axes of this graph represent Dose on the X-axis and tumor control or complications to normal tissues on the Y-axis. With respect to tumor control, as dose increases, the chance of tumor control increases. Likewise as dose increases, so does the probability of complication (represented by the red curve). Both these curves are sigmoidal in shape. Initially with low doses, there is little cell kill, and hence little tumor control. At a certain dose, the probability of cell kill increases dramatically, and hence high tumor control. However, beyond a certain dose, the curve again flattens so that increases in dose (while still toxic to tumor), does not increase the probability of further cell killing beyond what a lower dose can achieve. The risk of complication follows this same paradigm. Low dose has little chance of causing complication. However, at certain doses, the complication rate climbs sharply. These curves tend to be parallel, and the goal of radiation oncology is to maximize the potential for tumor killing (or tumor control) while minimizing the potential for normal tissue complications. The white vertical dashed line represents this compromise in therapeutic efficacy to achieve maximal tumor control with minimal normal tissue complication.
- Due to its complete integration Novalis is the only SRS/SRT machine in the market that can safely deliver Dynamic Shaped Beam Surgery (dynamic arc). Please save the AVI file “mlc 400x300 Cinepak 12fps 300kbs.avi” in the same folder as this powerpoint for animation.
- iPlan RT Dose offers a wide range of tools for treating various indications. Circular arc treatments utilize conical collimators to deliver a spherical dose with a sharp dose fall off, ideal for small spherical mets or functional indications such as trigeminal neuralgia. Conformal beam treatments consist of multiple static beams each with a fixed MLC position based on the shape of the target, ideal for wedged tumors where arcs would hit too many critical structures or for some extracranial targets. Dynamic conformal arcs provide a treatment in which the gantry rotates about the patient and as the gantry rotates, the MLC shapes to the target dynamically. Dynamic arc treatments are used in most cranial treatments with the benefit of normal tissue sparing and increased conformity to the target. IMRT treatments have static beams with dynamically moving MLCs which are used to selectively block dose or deliver dose in particular areas based on the prescription constraints. IMRT is used when you are concerned with sparing adjacent critical structures such as the spinal cord. Finally, our newest delivery technique is HybridArc. HybridArc is an automated blending of enhanced Dynamic Conformal Arcs (modulated arcs) and static IMRT fields.