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Radiosurgery Revised

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Radiosurgery Revised

  1. 1. Radiosurgery: Overview R. Rick Bhasin, MD Department of Neurosurgery University of Florida
  2. 2. Outline <ul><li>History </li></ul><ul><li>How does radiation work </li></ul><ul><li>Types of radiosurgery </li></ul><ul><li>Current available systems </li></ul><ul><li>Planning and Treatment </li></ul><ul><li>Targets </li></ul><ul><li>Dose Selection </li></ul><ul><li>Outcomes </li></ul>
  3. 3. Definitions <ul><li>Stereotactic radiosurgery (SRS) treats brain disorders with a precise delivery of a single, high dose of radiation in a one-day session. </li></ul><ul><li>Fractionated stereotactic radiation therapy—which are received over a period of days or weeks—may be administered to the body with the assistance of removable masks and frames that achieve a lesser degree of immobilization. </li></ul>
  4. 4. History <ul><li>1895, first use of radiation therapy in cancer </li></ul><ul><li>1946, Robert Wilson first proposed the clinical use of charged particle beams </li></ul><ul><li>1949, Lars Leksell, Professor of Neurosurgery in Lund, Sweden & later Karolinska Institute in Stockholm, developed a stereotactic apparatus based on the Cartesian coordinate system </li></ul>
  5. 5. More History <ul><li>1951, Lars Leksell and Borje Larsson, a radiobiologist, realized that an x-ray tube could be the surgical tool placed on a stereotactic arc. They started with an x-ray tube and later applied proton beam therapy to human subjects at the Uppsala University. He called this therapy “stralkniven” (ray knives) </li></ul>
  6. 6. How does radiation work? <ul><li>The fundamental principle of radiosurgery is that of selective ionization. Ionization is the production of ions and free radicals in tissue from water, which causes irreversible DNA damage. </li></ul><ul><li>The cells lose their ability to reproduce and retain fluids. The tumor reduction occurs at the rate of normal growth for the specific tumor cell. </li></ul><ul><li>In lesions such as AVMs radiosurgery causes the blood vessels to thicken and close off. The shrinking of a tumor or closing off of a vessel occurs over a period of time. For benign tumors and vessels, this will usually be 36 months. For malignant or metastatic tumors, results may be seen in a few months, because these cells are very fast-growing. </li></ul>
  7. 8. <ul><li>There are six types of irradiation available in radiation therapy: </li></ul><ul><ul><li>1. Gamma rays - high energy photons produced by fixed sources of radioactive cobalt (cobalt-60) </li></ul></ul><ul><ul><li>2. X-rays - high energy photons produced by accelerating electrons and colliding them with a metal target, called Bremsstrahlung </li></ul></ul><ul><ul><li>3. Electrons - very similar characteristics to x-rays </li></ul></ul><ul><ul><li>4. Protons - protons are produced by a cyclotron </li></ul></ul><ul><ul><ul><li>“ Bragg Peak Effect” </li></ul></ul></ul><ul><ul><li>5. Neutrons - Boron neutron capture therapy depends on the interactions of slow neutrons with boron-10 to produce alpha particles, another type of radiation. Neutrons are produced by a nuclear reactor or by colliding protons with a Lithium target </li></ul></ul><ul><ul><li>6. Carbon ions </li></ul></ul>
  8. 9. Proton Therapy
  9. 10. Proton Therapy <ul><li>Proton therapy, like all forms of radiotherapy, works by aiming, energetic ionizing particles (protons) onto the target </li></ul><ul><li>All protons of a given energy have a certain range; no proton penetrates beyond that distance. Furthermore, the dosage to tissue is maximum just over the last few millimeters of the particle’s range, this maximum is called the Bragg Peak. This depth depends on the energy to which the particles were accelerated by the accelerator. It is therefore possible to focus the cell damage due to the proton beam at the very depth in the tissues where the tumor is situated; tissues situated before the Bragg peak receive some reduced dose, and tissues situated after the peak receive none. </li></ul>
  10. 11. Bragg Peak Effect While rapidly traveling through tissue, high-energy proton beams lose energy. As this energy is lost, the likelihood of the particle interacting with the tissue increases. This leads to deposition of most of the energy within a discrete band of spatial depth measuring roughly 12-20 mm.
  11. 12. Proton Beam Centers in the USA <ul><li>The Northeast Proton Therapy Center at Massachusetts General Hospital </li></ul><ul><li>Loma Linda University Medical Center in Loma Linda, California (LLUMC) </li></ul><ul><li>UC Davis Proton Facility </li></ul><ul><li>Midwest Proton Radiotherapy Institute at Indiana University </li></ul><ul><li>M. D. Anderson Cancer Treatment Center, Houston, Texas </li></ul><ul><li>Florida Proton Therapy Institute at the University of Florida Shands Medical Center, Jacksonville, Florida </li></ul>
  12. 13. Proton Therapy
  13. 14. Proton Therapy <ul><li>Current clinical applications of proton therapy include: </li></ul><ul><ul><li>Choroidal melanoma - ocular tumors </li></ul></ul><ul><ul><li>Chondrosarcoma </li></ul></ul><ul><ul><li>Chordoma </li></ul></ul><ul><ul><li>Prostate cancer </li></ul></ul><ul><ul><li>Nasopharyngeal tumors </li></ul></ul><ul><ul><li>Pediatric tumors </li></ul></ul>
  14. 15. The Gamma Knife
  15. 16. Development of the Gamma Knife <ul><li>In 1968, Lars Leksell and Bjorn Larsson, developed a device which consisted of radioactive Cobalt-60 placed around a helmet with central channels for irradiation. </li></ul><ul><li>In order to achieve a high degree of precision, the patients head was placed in a stereotactic frame. </li></ul><ul><li>The first patient treated with the Gamma Knife was in 1967 for a craniopharyngioma at the Studsvik nuclear plant. </li></ul><ul><li>In 1968 the first patient treated at the Karolinska Institute was for intractable cancer pain. </li></ul>
  16. 17. Development of the Gamma Knife <ul><li>The first Gamma Knife was designed to create small lesions used in functional neurosurgery, acoustic neuromas, pituitary adenomas, craniopharngiomas, and AVMs. </li></ul><ul><li>The first AVM treated by Lars Leksell and Ladislau Steiner in 1970 resulted in obliteration of the AVM two years later. </li></ul><ul><li>The first USA installation was at the University of Pittsburgh in 1987 (under Dade Lunsford) </li></ul><ul><li>Over the years there have been modifications of the gamma knife several times (models U, B, & C). The current model is the Eleckta Leksell Gamma Knife C </li></ul><ul><li>(201 beams) </li></ul>
  17. 19. Linear Accelerator Radiosurgery
  18. 20. History of LINAC Radiosurgery <ul><li>Linear accelerators are the standard machine used to deliver radiation therapy treatments </li></ul><ul><li>Linear accelerators convert electricity into radiation </li></ul><ul><li>Terms: gantry, couch, collimator (multileaf or cone) </li></ul><ul><li>Linear accelerators were available during Leksell’s time, however they lacked accuracy </li></ul>
  19. 21. History of LINAC Radiosurgery <ul><li>Betti, Derechinsky, and Colombo were the first to apply linear accelerator technology to radiosurgery in 1984 </li></ul><ul><li>Winston and Lutz modified their LINAC in 1987 to treat neurosurgical patients (Boston) </li></ul><ul><ul><li>Initial problem with this technique was a high degree of error in targeting, complicated dose planning and dose delivery </li></ul></ul><ul><ul><li>1986-1987: University of Florida developed a system to improve LINAC radiosurgery accuracy to 0.2 mm, which included a new floorstand, dose planning software & detailed phantom testing </li></ul></ul><ul><li>UF Radiosurgery system licensed to Philips and Sofamor Danek (Zmed). The system is now incorporated by Varian as the Trilogy System </li></ul>
  20. 22. How LINAC Radiosurgery Works <ul><li>University of Florida System </li></ul>Reduced error to within 2/10 mm
  21. 23. How LINAC Radiosurgery Works <ul><li>5 Arcs per Isocenter, with 100 degrees of arc </li></ul>
  22. 24. How LINAC Radiosurgery Works <ul><li>The gantry of the LINAC rotates around the patient, producing an arc of radiation focused on the target. The couch in which the patient rests is then rotated in the horizontal plane, and another arc is performed. In this manner, multiple noncoplanar arcs of radiation intersect at the target volume and produce a high target dose, resulting in minimal radiation affecting the surrounding brain. This dose concentration method is exactly analogous to the multiple intersecting beams of cobalt radiation in the Gamma Knife. </li></ul>
  23. 25. How LINAC Radiosurgery Works
  24. 26. <ul><li>Online Video </li></ul>
  25. 27. <ul><li>Stand mount versus couch mount </li></ul>Frame-based intracranial positioning
  26. 28. Frameless intracranial positioning Used for fractionated radiotherapy
  27. 29. <ul><li>Current devices using linear accelerator sources include: </li></ul><ul><ul><li>Novalis (BrainLab, Helmstetten, Germany) </li></ul></ul><ul><ul><li>Peacock (Nomos, Cranberry, PA) </li></ul></ul><ul><ul><li>X-Knife (Radionics, Burlington, MA) </li></ul></ul><ul><ul><li>Trilogy (Varian Medical Systems, Palo Alto, CA) </li></ul></ul><ul><ul><li>CyberKnife (Accuray, Sunnyvale, CA) </li></ul></ul>
  28. 30. Trilogy <ul><li>The Trilogy incorporates: </li></ul><ul><li>Image guidance technology - Locates tumor precisely with sub-millimeter accuracy, using on-board imaging that verifies positioning at each session. </li></ul><ul><li>Respiratory gating - Synchronizes dose delivery with the patient's breathing cycle to ensure accuracy and reduce radiation to healthy tissue. </li></ul><ul><li>Imaging adaptability - Offers adaptable modes of operation, including radiographic, cone beam CT and fluoroscopic for maximum flexibility. </li></ul><ul><li>Intensity-modulated beam delivery - Calculates dose distributions that conform to the three-dimensional shape of the target, including concave and complex shapes. </li></ul><ul><li>Stereotactic radiosurgery - Treats tumor with surgical precision, both cranially and extracranially. </li></ul><ul><li>Operates at least 60 percent faster than conventional accelerators </li></ul>
  29. 31. Intensity Modulated Radiotherapy (IMRT) <ul><li>Intensity-modulated radiation therapy (IMRT) is an advanced form of three dimensional conformal radiotherapy (3DCRT). It uses sophisticated software and hardware (multileaf collimator) to vary the shape and intensity of radiation delivered to different parts of the treatment area </li></ul><ul><li>IMRT dose gradient not as steep as standard sphere packing </li></ul>
  30. 32. UF Radiosurgery Treatment Paradigm <ul><li>1. Patient obtains volumetric MRI scan </li></ul><ul><li>2. Patient seen in clinic by both Neurosurgeon and Radiation Oncologist </li></ul><ul><li>3. Dose pre-planning performed day before treatment </li></ul><ul><li>4. Placement of stereotactic head ring followed by volumetric CT scan </li></ul><ul><li>5. Fusion of two sets of images </li></ul><ul><li>6. Dose Planning (with Neurosurgeon and Radiation Oncologist) </li></ul><ul><li>7. Dose Delivery (physicist): 15 minutes/isocenter </li></ul>
  31. 33. How to place a headring <ul><li>See online video on resident website </li></ul><ul><li>Key points </li></ul><ul><ul><li>Review films to locate tumor </li></ul></ul><ul><ul><li>Two people required </li></ul></ul><ul><ul><li>No prepping, local anesthetic </li></ul></ul><ul><ul><li>Generally, short pins in front & </li></ul></ul><ul><ul><ul><li>long in back </li></ul></ul></ul><ul><ul><li>Place ring below EAC </li></ul></ul><ul><ul><li>Check with localizer </li></ul></ul>
  32. 34. Dose Planning <ul><li>Concepts in Planning </li></ul><ul><ul><li>Conformality </li></ul></ul><ul><ul><ul><li>Maximum dose to target, minimum dose to surrounding tissues </li></ul></ul></ul><ul><ul><ul><li>Achieved by multiple isocenters, arc weighting, single arcing, arc spacing and collimator size </li></ul></ul></ul><ul><ul><ul><li>Sphere packing </li></ul></ul></ul><ul><ul><ul><li>Minimum collimator 5 mm </li></ul></ul></ul><ul><ul><li>Treat to the 80% isodose line to maximize dose fall off </li></ul></ul><ul><ul><li>When multiple isocenters used treat to the 70% isodose line to avoid hotspots </li></ul></ul>
  33. 35. Dose Falloff Curve
  34. 36. What do we treat with radiosurgery? <ul><li>Brain metastases (up to 4 usually) </li></ul><ul><li>AVM </li></ul><ul><li>Vestibular Schwannoma </li></ul><ul><li>Meningioma </li></ul><ul><li>Recurrent GBM </li></ul><ul><li>Trigeminal Neuralgia </li></ul><ul><li>Spinal Radiosurgery </li></ul><ul><li>Others: Pituitary adenoma, Hemangioblastoma, Nasopharyngeal carcinoma </li></ul>
  35. 37. Radiation Doses Prescribed <ul><li>Dose is selected to maximize dose, while minimizing complications </li></ul><ul><ul><li>Mets: 15-20 Gy </li></ul></ul><ul><ul><li>AVM: 17.5-20 Gy </li></ul></ul><ul><ul><li>Meningioma: 12.5-15 Gy </li></ul></ul><ul><ul><li>Vestibular Schwannoma: 12.5 Gy </li></ul></ul><ul><ul><li>Trigeminal Neuralgia: 70-90 Gy </li></ul></ul><ul><ul><li>(need to keep max dose at visual apparatus less than 800 cGy) </li></ul></ul><ul><ul><li>Compare to WBRT, 30 Gy in 10 fractions </li></ul></ul>
  36. 38. Brain Metastasis <ul><li>UF 12 year experience from 1989 - 2001 </li></ul><ul><li>393 patients </li></ul><ul><li>Types by frequency: lung, melanoma, breast, renal, GI </li></ul><ul><li>Actuarial 1 year local control rate was 75% </li></ul><ul><li>Median actuarial survival was 9 months </li></ul>Ulm et al, Neurosurgery 55: 1076-1085, 2004
  37. 40. AVM <ul><li>UF experience with AVM from 1989-1999 </li></ul><ul><ul><li>269 patients reviewed </li></ul></ul><ul><ul><li>For lesions less than <1 cc, 87.9 % radiological success </li></ul></ul><ul><li>Submitted, UF experience with large volume AVMs from 1989 - 2005 </li></ul><ul><ul><li>90 patients reviewed </li></ul></ul><ul><ul><li>70% success rate with repeat radiosurgery </li></ul></ul>Bradshaw et al, Neurosurgery 52:296-308,2003
  38. 42. Vestibular Schwannoma <ul><li>UF experience from 1988 to 1998 </li></ul><ul><li>149 patients treated </li></ul><ul><li>Overall radiological tumor control rate was 93% </li></ul><ul><li>Median followup 36 months </li></ul><ul><li>5 year actuarial control rate was 87% </li></ul><ul><li>At lower doses (12.5 Gy) the incidence of facial and trigeminal neuropathies fell from 29% to 5 and 2%, respectively </li></ul>Foote et al, J Neurosurg 95:440-449, 2001
  39. 44. Meningioma <ul><li>UF experience from 1989-2001 </li></ul><ul><li>201 patients treated </li></ul><ul><li>Actuarial local control for benign tumors </li></ul><ul><ul><li>100 % at 1 and 2 years, 96% at 5 years </li></ul></ul><ul><li>Actuarial local control for atypical tumors </li></ul><ul><ul><li>100% at 1 year, 92% at 2 years, 77% at 5 years </li></ul></ul><ul><li>6.2% temporary complication rate, 2.3% permanent complication rate </li></ul>Friedman et al, J Neurosrg 103:206-209, 2005
  40. 45. Glioblastoma Multiforme <ul><li>RTOG-9305: Prospective randomized trial designed to evaluate upfront SRS followed by RT with BCNU compared to RT with BCNU </li></ul><ul><li>186 patients enrolled </li></ul><ul><li>Median survival for the two arms was 14.1 and 13.7 months </li></ul><ul><li>No difference in survival with upfront radiosurgery </li></ul>
  41. 46. Glioblastoma Multiforme <ul><li>UF 12 year experience from 1989-2002 </li></ul><ul><li>100 patients </li></ul><ul><li>Decreased survival for Class I/II, </li></ul><ul><li>Similar survival for Class III/IV </li></ul><ul><li>Increased survival for Class V </li></ul><ul><li>Some role for radiosurgery in recurrent GBM </li></ul>Ulm et al, Neurosurgery 57:512-517, 2005
  42. 48. Spinal Radiosurgery <ul><li>Initial treatments with Cyberknife </li></ul><ul><li>Patient immobilized on the couch, implantation of fiducials, followed by localizing orthogonal xrays </li></ul><ul><ul><li>University of Pittsburgh experience, 2004 </li></ul></ul><ul><ul><ul><li>125 patients treated </li></ul></ul></ul>
  43. 51. Cyberknife Outcomes <ul><ul><li>Intradural extramedullary lesions (schwannomas, neurofibromas, meningiomas) </li></ul></ul><ul><ul><ul><li>Stanford experience 1999 - 2004: 51 patients treated </li></ul></ul></ul><ul><ul><ul><li>3/51 required surgery within one year because of worsening symptoms </li></ul></ul></ul><ul><ul><ul><li>28/51 have at least 24 months followup, 61% are stable in size, 39% are smaller in size </li></ul></ul></ul><ul><ul><ul><li>Dodd et al, Neurosurgery 58:674-85,2006 </li></ul></ul></ul>
  44. 52. Spinal Radiosurgery with Trilogy <ul><li>On board CT scanner to localize target with MRI (or CT) fusion </li></ul><ul><li>We will begin at UF in the fall </li></ul>
  45. 53. Trigeminal Neuralgia <ul><li>University of Wisconsin LINAC Experience </li></ul><ul><ul><li>28 patients treated with single fraction of 80 Gy to the trigeminal nerve root (treatment time 55 minutes) </li></ul></ul><ul><ul><li>57% had complete pain relief, 75% had some reduction in pain to 3 or less (out of 10) </li></ul></ul><ul><ul><li>Median time to pain relief was one month </li></ul></ul>Mehta et al, Neurosurgery: 57:1193-2000, 2005 .

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