IAEA Training Material on Radiation Protection in Radiotherapy

  • Slides: 52
Download presentation
IAEA Training Material on Radiation Protection in Radiotherapy Part 6 Brachytherapy Lecture 2 (cont.

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

Brachytherapy l l l Very flexible radiotherapy delivery Allows a variety of different approaches,

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

Special techniques A. Prostate seed implants B. Endovascular brachytherapy C. Ophthalmic applicators D. Other

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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 3

A. 125 -I seeds for prostate implants Relatively new technique l Indicated for localized

A. 125 -I seeds for prostate implants 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 l Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 4

Treatment Options for prostate cancer l l Seed Implant Monotherapy (about 144 Gy) EBT

Treatment Options for prostate cancer l l Seed Implant Monotherapy (about 144 Gy) EBT (45 Gy) + Implant Boost n n l l Seed Implant (108 Gy) HDR Implant (16. 5 Gy/3) External Beam only (65 -84 Gy) Surgery (Radical Prostatectomy) è This all could be combined with hormones and/or chemotherapy Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 5

Implant schematic Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques

Implant schematic Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 6

A typical implant l l l Deliver 144 Gy to entire prostate gland Approximately

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

Isotopes in use l Iodine 125 - 144 Gy - I-125 n Half Life

Isotopes in use l Iodine 125 - 144 Gy - I-125 n Half Life = 60 days n Energy = 28 ke. V n TVL lead = 0. 08 mm l Palladium 103 - 108 Gy - Pd -103 n Half Life = 17 days - dose rate about 2. 5 times larger than for 125 -I n Energy = 22 ke. V n TVL lead = 0. 05 mm Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 8

Prostate Implant Process Ultrasound Volume Study l Pre-planning: what would be ideal l Ordering

Prostate Implant Process 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? l Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 9

Pre-planning l l l Several different systems possible Provides guidance for approach, data on

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

Preparation of seeds l l l Ordering planned number of seeds + some spares

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

Implant needle loaded with seeds and spacers Radiation Protection in Radiotherapy Part 6, lecture

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

Implant template Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques

Implant template Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 14

Implant jig Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques

Implant jig Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 15

Ultrasound Guided Implant Procedure Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ):

Ultrasound Guided Implant Procedure Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 16

X-ray of implanted seed Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ):

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

CT post-planning after 4 weeks Swelling is gone - CT provides true three dimensional

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

Post CT planning = establishing the actual dose distribution Radiation Protection in Radiotherapy Part

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

Quality of Implant Depends on seed placement l Seeds may migrate with time l

Quality of Implant 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 l Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 21

Notes on prostate seed implants l A similar technique is available using 103 -Pd

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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 22

2. Endovascular brachytherapy Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy

2. Endovascular brachytherapy Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 23

The issue: re-stenosis After opening of a blocked blood vessel there is a high

The issue: re-stenosis 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 l Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 24

Dilation of blood vessels l Mostly for cardiac vessels but also possible in some

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

Endovascular irradiation l l Mostly for cardiac vessels but also possible in some extremities

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

Isotopes for endovascular brachytherapy l Gamma sources: 192 -Ir n the first source which

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) Beta sources: 32 -P, 90 -Sr/Y, 188 -Rh (Rhenium) l Activity around 1 Ci l Dose calculation Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 27

Beta sources l Most commercial systems use them because: n finite range in tissues

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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 28

The Beta-Cath™ System (Novoste) Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ):

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

Guidant system l Radiation Protection in Radiotherapy Employs centering catheter to ensure source is

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

Radiation safety in theatre l Application of radiation in theatre: n n n time

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

Irradiation of extended lesions Use “Radiation Source Train” l Stepping source process to cover

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

Angiographic Appearance of PDL in Delivery Catheter Radiation Protection in Radiotherapy Part 6, lecture

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

Radiation Source Train: Dose Profile at 2 mm 40 mm Radiation Source Train (RST)

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

Radioactive stents l l Stents are used to keep blood vessels open Can be

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

C. Ophthalmic applicators l l l Treatment of pterigiums and corneal vasculations, a nononcological

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

Ophthalmic applicators Activity covered by thin plated gold or platinum l Curvature to fit

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

Decay scheme of 90 Sr / 90 Y ß 0. 54 Me. V, T

Decay scheme of 90 Sr / 90 Y ß 0. 54 Me. V, T 1/2 = 28. 5 yrs 90 Y ß 2. 25 Me. V, T 1/2 = 64 hrs 90 Zr Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 38

Dept Dose Curve of 90 Sr in H 2 O Finite treatment depth Radiation

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

Issues with ophthalmic applicators - dosimetry Dosimetry difficult due to short range of particles

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

Other guidance and issues l l l Never point source at someone - range

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

D. Other specialized brachytherapy applications l Intra-operative brachytherapy n Use of radiation in operating

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 “ 10 Gy ahead” in tumor dose Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 42

Intra-operative brachytherapy l In practice not often used because n not always possible to

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 s shielded theatre costly patient must be left alone during irradiation even if less than 5 min this is a risk due to anesthetics Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 43

A note on radiation protection l Many specialized brachytherapy applications are performed outside of

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

Intra-operative brachytherapy l l l In principle possible Treatment units (must be HDR) available

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

Summary I l l Brachytherapy is a highly customized and flexible treatment modality Quality

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

Summary II l l l 125 -I seed implants are a alternative for radiotherapy

Summary II l l l 125 -I seed implants are a alternative for radiotherapy of early prostate cancer Endovascular brachytherapy is one of an increasing number of non-oncological applications of brachytherapy 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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 47

References l l Nath et al. Intravascular brachytherapy physics. AAPM TG 60 report. Med.

References l l Nath et al. Intravascular brachytherapy physics. AAPM TG 60 report. Med. Phys. 26 (1999) 119 -152 Waksman R and Serray P: Handbook of vascular brachytherapy (London: Martin Dunitz) 1998 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 48

Any questions? Part 6, lecture 2 (cont. ): Brachytherapy techniques

Any questions? Part 6, lecture 2 (cont. ): Brachytherapy techniques

Question: Please list some radiation safety issues when using 90 -Sr/Y applicators for ophthalmic

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. . . Part 6, lecture 2 (cont. ): Brachytherapy techniques

Radiation Safety Issues when using 90 -Sr/Y applicators l Occupational exposure: n cleaning n

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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 51

Radiation Safety Issues when using 90 -Sr/Y applicators l Medical exposure: n dosimetry difficult

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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 52

Radiation Safety Issues when using 90 -Sr/Y applicators l Public exposure: n transport of

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 Radiation Protection in Radiotherapy Part 6, lecture 2 (cont. ): Brachytherapy techniques 53

Acknowledgement Craig Lewis, London Regional Cancer Centre l Mamoon Haque, RPA Hospital l Radiation

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