Brachytherapy, Radionuclide Therapy Medical Physics in the Clinic. Raymond K. Wu, PhD Chairman AAPM Exchange Scientist Program

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1 Brachytherapy, Radionuclide Therapy Medical Physics in the Clinic Raymond K. Wu, PhD Chairman AAPM Exchange Scientist Program

2 TG 43 of 1995 New dose calculation formalism for brachytherapy Consensus data for Pd-103 and I-125 seeds Resolution of the 17% discrepancy for some seed types Significant improvements in dosimetry methodologies Med. Phys. 22 (2), February 1995 pp

3 After TG 43 Source Activity or Apparent Activity => Source Strength (unit is U or cgy per hour at 1 cm) S k Milligram Radium Equivalent => U Exposure Rate Constant => Dose Rate Constant Λ Tissue Attenuation Coefficient => Tabulated data Ignoring source construction and design => Radial Dose Function, Anisotropy Factor, Anisotropy Function Table Clinical work not standardized for source design except as a point source => Standardized for radioactive sources of various size, shape, and construction

5 TG 43 U Revised definition of Air Kerma Strength Elimination of Apparent Activity as source strength Elimination of Anisotropy Constant and replaced by Anisotropy Functions 1D and 2D Other minor improvements Med. Phys. 31 3, March 2004, pp

6 S K is Source Strength in U Λ is Dose Rate Constant g L (r) is Radial dose function F(r,θ) is Anisotropy function r 0 is 1 cm, and θ 0 is 90

7 ρ(r ) is density of radioactivity at r r is (x, y, z ) within the integrated volume V

8 It may be shown for a point source, the TG 43 equation becomes F(r,θ) may be simplified as a function of r, which becomes the Anisotropy factor Φ an (r)

9 Example for Cs 131 (IsoRay Medical)

10 Cs 131 (IsoRay Medical) Dose Rate Constant (cgy/h-u) 1.06 Anisotropy Constant Half Life (days) Active Length (cm) 0.40 Physical Length (cm) 0.45 Physical Diameter (cm) 0.08

11 Cs 131 (IsoRay Medical)

12 Cs 131 (IsoRay Medical) Point source approximation

13 Cs 131 (IsoRay Medical) Line source approximation

14 Cs 131 (IsoRay Medical)

15 Prostate Seed implants I-125 seeds Pd-103 seeds LDR Implants Ir-192 ribbons Cs-137 sources HDR Sources Ir-192 Co-60

Symbol Common Radionuclides in Rad Onc Primary Emission Energy (or max energy) kev Half-life 10 half-lives 60 Co gamma 1170-1330 5.26yrs 53 yrs 89 Sr beta Ave 1.463 MeV 50.5 days 1.

16 Symbol Common Radionuclides in Rad Onc Primary Emission Energy (or max energy) kev Half-life 10 half-lives 60 Co gamma yrs 53 yrs 89 Sr beta Ave MeV 50.5 days 1.4 yrs 90 Sr beta/gamma 546 (up to 2.27 MeV) 28.5 yrs 285 yrs 103 Pd gamma days 170 days 125 I gamma days 20 months 131 I gamma 364, days 2.7 months 131 Cs beta/gamma EC days 3.25 months 137 Cs gamma 510, 1180, yrs 300 yrs 192 Ir gamma/beta days 2 yrs 223 Ra alpha 5.78 MeV days 114 days

17 Radionuclide Therapy I 131 Thyroid Ablation

18 I-131 Thyroid Ablation Limit of Removable contamination < 2000 dpm/100cm 2 Washable chair covers Disposable absorbing padding material

19 Liquid form of I-131 In house radiopharmacist Urine storage for decay Decontamination tasks Fume hood Bioassays

20 Inhaled or Ingested Radioactive Material

21 Committed dose equivalent (H T,50 ) The dose equivalent to organs or tissues of reference (T) that will be received from an intake of radioactive material by an individual during the 50- year period following the intake. ACPSEM Summer School 2014 Melbourne

22 Committed effective dose equivalent (H E,50 ) The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to these organs or tissues H E,50 = ΣW T H T.50

25 Historical dose information for Radiation Oncology staff Radiation Oncology staff 2011 maximum 2-month whole body dose was 0.08 msv maximum whole body yearly total was 0.08 msv maximum annual extremity exposure was 0.17 msv Radiation Oncology staff 2012 maximum 2-month whole body dose was msv maximum whole body yearly total was msv maximum annual extremity exposure was msv

26 Other Radiation Oncology Procedures Cyberknife X-sight Lung, X-sight Spine Image Guided RT Cs-131 brain implant Prostate seed implant LDR cervix endometrium implants Zevalin, SIR sphere procedures Xofigo, Metastron procedures

27 Let us focus on HDR High Doserate Remote Afterloader

28 HDR High Doserate Remote-afterloader

29 Nucletron Microselectron Version 2

30 One single source 4 mm long Iridium 192 Emits 350 kv ɤ ray Half Life 73.8 days Max activity allowed 10 Ci Source replacement 3-4 time per year When activity becomes 3-4 Ci

Popular because Drastically reduces exposure to staff Can reduce unnecessary dose to patient Can minimize risk of source inadvertently left in

31 Popular because Drastically reduces exposure to staff Can reduce unnecessary dose to patient Can minimize risk of source inadvertently left in patient Can produce desirable dose distribution Greatly increases throughput-outpatient Allows for adjustment of applicators Computerized documentation

32 The Devil is in the Applicators

33 MammoSite

34 Contura

35 Tandem & Ovoid CT/MR Applicator

36 Esophageal Applicator

37 Multi-purpose Applicator

41 Source Location Simulator

42 Misadministration USNRC Delivering treatment to the wrong patient Using the wrong radioisotope Treating the wrong site Using leaking sources Failing to remove a temporary implant Delivering a radiation dose differing more than 20% from the prescribed dose

43 Risks Very High dose rate affords little time to correct problem Intrinsically complicated system takes longer to learn Radiation biology different from external beam Sharp dose gradient requires better anatomical data High risk to staff if failure of unit occurs

45 PermaDoc by Mick

47 Transfer Tubes

58 Rotte Applicator - Radiochromic film exposed by HDR source and by 6e

59 Dummy Sources

62 Global Threat Reduction Initiative GTRI

63 Security of Radioactive Material GTRI program

64 Security of Radioactive Material GTRI program

65 Men and women are created to take care of the necessity

66 When necessary we may apply the law inconsistently

67 We may overkill if we just want to deliver

68 Pay proper attention No need to be afraid

69 BEIR VII

71 NCRP 116 Public Dose Limits Internal (5%) 0.33 Terrestrial (3%) 0.2mSv 0.25 msv/yr per site Cosmic background (5%) 0.34 msv Indoor Radon (37%) 2.45 msv CT (24%) Annual 1.6 msv background radiation doses in USA Nuclear Medicine (12%) msv / yr Interventional fluoroscopy (7%) 0.47 msv 1 msv Radiography/fluoroscopy (5%) 0.35 msv

8 Annual terrestrial dose in Denver 8 Annual dose natural bkgd: Kerala 15 msv Denver 6 msv 0.08 0.06 0.04 0.

72 Radiation Doses in Perspective BSS annual limit to public 10 msv Modern CAT scan 0.1 msv Transpolar flight Annual dose from building materials 1 msv 0.8 Annual terrestrial dose in Denver 8 Annual dose natural bkgd: Kerala 15 msv Denver 6 msv week dose in US, all sources Chest x-ray Trans-continental flight Extremity x-ray Annual dose from medical exams Internal to body Annual cosmic rays Annual terrestrial dose in Maryland Apollo XVI astronauts US Annual dose from natural background 0 0 0

73 As Low as Reasonably Achievable (ALARA)

74 Radiation Hormesis Case of a Taiwan high rise apartment built with contaminated reinforcement steel, published in apartment units, 10,000 occupied building 40 msv average dose received Cancer death only 3% of natural incidence Congenital malformation only 7% of general public

75 IOMP Policy Statement No. 3 This policy statement addresses predictions of induced cancers and cancer deaths in a population of patients exposed to low doses (<100 msv) of ionizing radiation during medical imaging procedures.

76 Prospective estimates of cancers and cancer deaths induced by medical radiation should include a statement that the estimates are highly speculative because of various random and systematic uncertainties embedded in them. These uncertainties include dosimetric uncertainties; epidemiological and methodological uncertainties; uncertainties from low statistical power and precision in epidemiology studies of radiation risk; uncertainties in modeling radiation risk data; generalization of risk estimates across different populations; and reliance of epidemiological studies on observational rather than experimental data. Such uncertainties cause predictions of radiation-induced cancers and cancer deaths to be susceptible to biases and confounding influences that are unidentifiable.

77 IOMP Policy Statement No. 3 Paragraph A86 of Report 103 of the International Commission on Radiological Protection (ICRP) states that There is, however, general agreement that epidemiological methods used for the estimation of cancer risk do not have the power to directly reveal cancer risks in the dose range up to around 100 msv.

78 IOMP Policy Statement No. 3 Further, UNSCEAR Report A-67-46, approved in May, 2012, states that The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) does not recommend multiplying very low doses by large numbers of individuals to estimate numbers of radiationinduced health effects within a population exposed to incremental doses at levels equivalent to or lower than natural background levels.

79 IOMP Policy Statement No. 3 Paragraph 151 of ICRP Report 103 states: The use of effective dose for assessing the exposure of patients has severe limitations that must be considered when quantifying medical exposure, and The assessment and interpretation of effective dose from medical exposure of patients is very problematic when organs and tissues receive only partial exposure or a very heterogeneous exposure which is the case especially with x-ray diagnostics.

80 IOMP Policy Statement No. 3 Predictions of radiation-induced cancers and cancer deaths from medical imaging procedures should be accompanied by estimates of reductions in patient morbidity, mortality and cost resulting from the same medical imaging procedures

81 IOMP Policy Statement No. 3 If effective dose is used to generate predictions of cancers and cancer deaths, a statement should be included that the ICRP has expressed caution in the use of effective dose for purposes of estimating risks to individuals or populations exposed to ionizing radiation. ACPSEM Summer School 2014 Melbourne

83 The End

Brachytherapy Planning and Quality Assurance

Brachytherapy Planning and Quality Assurance Classical implant systems Most common clinical applications and modern dosimetry methods Quality assurance Classical implant systems Manchester (Paterson-Parker)