1. Radiation Protection in Radiotherapy Part 6 Brachytherapy Lecture 2 (cont.): Brachytherapy Techniques IAEA Training Material on Radiation Protection in Radiotherapy

2. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques2 Brachytherapy l Very flexible radiotherapy delivery l Allows a variety of different approaches, creating the opportunity for special and highly customized techniques l Not only used for malignant disease (=cancer)

3. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques3 Special techniques A. Prostate seed implants B. Endovascular brachytherapy C. Ophthalmic applicators D. Other special techniques Both point B and C are examples for the use of brachytherapy for non-oncological purposes

4. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques4 A. 125-I seeds for prostate implants l Relatively new technique l Indicated for localized early stage prostate cancer l Permanent implant l Preferred by many patients as it only requires one day in hospital

5. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques5 Treatment Options for prostate cancer l Seed Implant Monotherapy (about 144Gy) l EBT (45Gy) + Implant Boost n Seed Implant (108Gy) n HDR Implant (16.5Gy/3) l External Beam only (65-84Gy) l Surgery (Radical Prostatectomy) è This all could be combined with hormones and/or chemotherapy

6. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques6 Implant schematic

7. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques7 A typical implant l Deliver 144 Gy to entire prostate gland l Approximately 100 I-125 seeds (25 needles) l Needles are guided by ultrasound and a template grid l Pre-planned needle positions to give even dose but avoid pubic arch l Minimise rectal dose and avoid urethra overdose l CT after 3 weeks for post-planning

8. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques8 l Palladium 103 - 108Gy - Pd -103 n Half Life = 17 days - dose rate about 2.5 times larger than for 125-I n Energy = 22 keV n TVL lead = 0.05mm Isotopes in use l Iodine 125 - 144Gy - I-125 n Half Life = 60 days n Energy = 28 keV n TVL lead = 0.08mm

9. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques9 Prostate Implant Process l Ultrasound Volume Study l Pre-planning: what would be ideal l Ordering I-125 seeds and calibration l Needle loading l Ultrasound guided Implantation l CT post-planning a couple of weeks after: what has been achieved?

10. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques10 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 Rays) Commence treatment

11. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques11 Pre-planning l Several different systems possible l Provides guidance for approach, data on number of sources required and loading of needles l Avoid central column to spare urethra l Cover target laterally l Conform to posterior border (spare rectum)

12. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques12 Preparation of seeds l Ordering planned number of seeds + some spares l Checking seed activity l Sorting and loading seeds into needles Seed alignment tray

13. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques13 Implant needle loaded with seeds and spacers

14. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques14 Implant template

15. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques15 Implant jig

16. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques16 Ultrasound Guided Implant Procedure

17. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques17 X-ray of implanted seed

18. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques18 CT post-planning after 4 weeks Swelling is gone - CT provides true three dimensional information on the implant geometry

19. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques19 Post CT planning = establishing the actual dose distribution

20. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques20 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 Rays) Commence treatment

21. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques21 Quality of Implant l Depends on seed placement l Seeds may migrate with time l If large dose inhomogeneities exist, the critical cold spots can be boosted by either placing more seeds in the prostate or using external beam radiotherapy

22. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques22 Notes on prostate seed implants l A similar technique is available using 103-Pd seeds n 103-Pd has a shorter half life and therefore a higher activity is implanted n Otherwise the rules an considerations are similar to 125-I seed implants

23. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques23 2. Endovascular brachytherapy

24. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques24 The issue: re-stenosis l After opening of a blocked blood vessel there is a high (60%+) likelihood that the vessel is blocked again: Re-stenosis l Radiation is a proven agent to prevent growth of cells l Radiation has been shown to be effective in preventing re-stenosis

25. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques25 Dilation of blood vessels l Mostly for cardiac vessels but also possible in some extremities

26. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques26 Endovascular irradiation l Mostly for cardiac vessels but also possible in some extremities l Many different systems and isotopes in use

27. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques27 Isotopes for endovascular brachytherapy l Gamma sources: 192-Ir n the first source which has been clinically used (Terstein et al. N Eng J Med 1996) l Beta sources: 32-P, 90-Sr/Y, 188-Rh (Rhenium) l Activity around 1Ci Dose calculation

28. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques28 Beta sources l Most commercial systems use them because: n finite range in tissues n less radiation safety issues in the operating theatre n smaller, hand held units possible for use in cardiac theatres l Potential problem: may not reach all cells of interest

29. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques29 The Beta-Cath™ System (Novoste)

30. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques30 Guidant system l Employs centering catheter to ensure source is always in the center of the vessel

31. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques31 Radiation safety in theatre l Application of radiation in theatre: n time is of the essence - planning in situ n shielding would be difficult n physicists must be present

32. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques32 Irradiation of extended lesions l Use “Radiation Source Train” l Stepping source process to cover desired length Longitudinal Dose Distribution 50 % 100 % 0 % L/2L/2

33. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques33 Angiographic Appearance of PDL in Delivery Catheter

34. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques34 Radiation Source Train: Dose Profile at 2mm Radiation Source Train: Dose Profile at 2mm 40mm Radiation Source Train (RST)

35. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques35 Radioactive stents l Stents are used to keep blood vessels open l Can be impregnated with radioactive material (typically 32-P) to help prevention of re- stenosis

36. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques36 C. Ophthalmic applicators l Treatment of pterigiums and corneal vasculations, a non- oncological application of radiotherapy l Use of beta sources - mostly 90-Sr/Y l Typical activity 40 to 200MBq (10-50mCi)

37. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques37 Ophthalmic applicators l Activity covered by thin plated gold or platinum l Curvature to fit the ball of the eye l Diameter 12 to 18mm l Activity may only be applied to parts of the applicator l Typical treatment time for several Gy less than 1min

38. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques38 Decay scheme of 90 Sr / 90 Y 90 Sr 90 Y 90 Zr ß 0.54 MeV, T 1/2 = 28.5 yrs ß 2.25 MeV, T 1/2 = 64 hrs

39. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques39 Dept Dose Curve of 90 Sr in H 2 O Finite treatment depth

40. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques40 Issues with ophthalmic applicators - dosimetry l Dosimetry difficult due to short range of particles l Dose uncertainty > 10% l Short treatment times taken from look- up tables - potential for mistakes l Documentation often less than complete

41. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques41 Other guidance and issues l Never point source at someone - range in tissue 1m!!! l Radiation typically used by non radiotherapy staff (eye specialists, nurses) - training required l Sterilisation/cleaning - must not affect integrity of the cover l Regular check of homogenous distribution of activity required l Wipe tests required

42. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques42 D. Other specialized brachytherapy applications l Intra-operative brachytherapy n Use of radiation in operating theatre n Useful for incomplete surgical removal of cancer n Allows highly topical application of radiation n If surgery is followed by radiotherapy, one is “10Gy ahead” in tumor dose

43. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques43 Intra-operative brachytherapy l In practice not often used because n not always possible to predict if radiation will be needed during the operation n requires radiation oncologist to be available n radiation safety issues sshielded theatre costly spatient must be left alone during irradiation seven if less than 5min this is a risk due to anesthetics

44. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques44 A note on radiation protection l Many specialized brachytherapy applications are performed outside of a conventional radiotherapy department - this requires consideration of: n training n shielding n communication l Excellent planning and documentation is required

45. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques45 Intra-operative brachytherapy l In principle possible l Treatment units (must be HDR) available l Applicators are available

46. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques46 Summary I l Brachytherapy is a highly customized and flexible treatment modality l Quality of treatment depends on operator skills l From a radiation protection point of view remote afterloading is most desirable: A variety of equipment is available to deliver remote afterloading brachytherapy l HDR brachytherapy is the most common delivery mode nowadays.

47. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques47 Summary II l 125-I seed implants are a alternative for radiotherapy of early prostate cancer l Endovascular brachytherapy is one of an increasing number of non-oncological applications of brachytherapy l There may be radiation safety issues if specialized brachytherapy procedures are performed outside of a radiotherapy department as staff not used to working with ionizing radiation is using radioisotopes

48. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques48 References l l Nath et al. Intravascular brachytherapy physics. AAPM TG60 report. Med. Phys. 26 (1999) 119-152 l l Waksman R and Serray P: Handbook of vascular brachytherapy (London: Martin Dunitz) 1998

49. Any questions?

50. Question: Please list some radiation safety issues when using 90-Sr/Y applicators for ophthalmic treatments - you should consider the appendices of BSS to classify them...

51. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques51 Radiation Safety Issues when using 90-Sr/Y applicators l Occupational exposure: n cleaning n sterilization n contamination n handling of sources by non-radiotherapy staff

52. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques52 Radiation Safety Issues when using 90-Sr/Y applicators l Medical exposure: n dosimetry difficult n contamination from damaged applicator n over/under exposure of the eye of the patient n irradiation of other areas of the patient

53. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques53 Radiation Safety Issues when using 90-Sr/Y applicators l Public exposure: n transport of the sources n security of sources n storage and disposal

54. Radiation Protection in RadiotherapyPart 6, lecture 2 (cont.): Brachytherapy techniques54 Acknowledgement l Craig Lewis, London Regional Cancer Centre l Mamoon Haque, RPA Hospital