RIA: A new Opportunity for Medical Isotope Research and Production

Transcription

1 RIA: A new Opportunity for Medical Isotope Research and Production Jose R. Alonso Fanqing Guo Lawrence Berkeley` National Laboratory J. Alonso 1

2 Outline Accelerator-based medical isotope production today New opportunities presented by RIA Isotope production using light ions Role of RIA in fostering new opportunities for medical isotope production techniques J. Alonso 2

3 Current State of the Art H - cyclotrons have revolutionized high-current applications Stripping extraction provides 100% extraction efficiency Greatly reduces activation Reduces thermal loading on extractors Maximum current 500 µa Vendors claim currents up to 1 ma obtainable Typical top energy 50 MeV Lorentz stripping limits highest energies BUT: Limited to z = 1 beam J. Alonso 3

4 Examples of Current Production 67 Ga Use: Diagnostic imaging via SPECT Halflife: 78 hrs Reaction: 68 Zn (p, 2n) 67 Ga Isotopic abundance of target: 18% Production rate: 4.5 mci/µah Yield 1 Ci/hr 201 Tl Use: Diagnostic imaging, SPECT Halflife: 73 hrs Reaction: 203 Tl (p, 3n) 201 Pb 201 Tl Isotopic abundance of target: 23% Production rate: 1.5 mci/µah Yield 500 mci/hr J. Alonso 4

5 Examples (cont.) 103 Pd Use: Brachytherapy - seeds implanted for prostate cancer treatment Halflife: 17 days Reaction: 103 Rh (p,n) 103 Pd Isotopic abundance of target: 100% Production rate: 0.5 mci/µah Yield 150 mci/hr J. Alonso 5

6 Example: 82 Rb- 82 Sr Generator J. Alonso 6

7 Example: 82 Rb- 82 Sr Generator J. Alonso 7

8 Example: 82 Rb- 82 Sr Generator J. Alonso 8

9 Evaluation PET-generators (for instance Strontium- Rubidium) are too cost-expensive. In Germany only one study was performed. Gustav Hör, Frankfurt, Radiopharmacy-Clinical Reality and Selected Research Demands reported in Regional Workshop, Slowak Academy of Sciences, Nov 2001 Issues affecting cost: 60 MeV is beyond range of most commercial H - cyclotrons Yield for {4n} lower than other reactions J. Alonso 9

10 Proton-based production Very little flexibility available Product must be close to target Z, A Most often requires separated isotope targets May require complex chemistry In marketplace where cost factors are of great importance, this lack of flexibility can be a restricting factor for optimum exploitation of technique J. Alonso 10

11 RIA Driver For first time, currents of light ions approach levels capable of commercial isotope production Driver Linac can be configured to allow diversion of low-energy beams J. Alonso 11

12 Light Ions Provide: Alternatives for currently-popular isotopes Flexibility of ion species Flexibility in target selection Several reactions can produce same isotope Possibility of avoiding separated isotopes Target selection to facilitate chemistry Access to many new isotopes E.g. in transuranic region Kinematic separation of product from target Compound nucleus recoil momentum is appreciable J. Alonso 12

13 Example: 82 Rb- 82 Sr Generator J. Alonso 13

14 Example: 82 Rb- 82 Sr Generator J. Alonso 14

15 Example: 82 Rb- 82 Sr Generator J. Alonso 15

16 75 As ( 11 B, 4n) 82 Rb Calculations using ALICE (Marshall Blann) J. Alonso 16

17 Yield of 82 Sr 75 As Target Thickness 25 mg/cm 2 Excitation function quite clean between 45 and 70 MeV From Northcliffe & Schilling, thickness of As to degrade boron from 70 to mg/cm 2 Average cross section 950 millibarns Production rate.033 mci/µah Assume 100 pµa beam current Activity production of 82 Sr 3 millicuries/hour J. Alonso 17

18 139 La ( 12 C, 6n) 145 Eu 145 Eu: T 1/2 = 5.9 days, possible therapeutic agent Production rate: 0.3 mci/µah Activity production: 30 mci/hr J. Alonso 18

19 232 Th ( 13 C, 5n) 240 Cm 240 Cm: T 1/2 = 26.8 days, pure alpha emitter, excellent potential for therapeutic agent Production rate 2 µci/µahr Activity production: 0.2 mci/hr Note: (6n) 239 chain are short-lived β emitters J. Alonso 19

20 232 Th ( 14 N, 6n) 240 Bk 240 Cm Alternate production channel using 14 N 240 Bk (4.8 m T 1/2 ), no α branching, all β to 240 Cm 239 Bk (1.6 m T 1/2 ), both α and β chains shortlived Almost identical yield to 13 C Perhaps somewhat better purity J. Alonso 20

21 Kinematic Effects Projectile imparts substantial recoil momentum to compound nucleus E recoi l E projectile { m/(m+m)} For 82 Rb, E recoil 9.4 MeV = 0.11 MeV/amu Range of CN in 75 As 1.5 mg/cm 2 EG: If target irradiated is 1.5 mg/cm 2 thick, all products recoil out of target 0.7 mg/cm 2 He stop all recoils Flowing gas transports products to collection area Continuous production no hot-target chemistry J. Alonso 21

22 Composite Target Concept 1.5 mg/cm 2 target 0.7 mg/cm 2 helium 10 targets covers full excitation fcn 60% of maximum production rate 4 mci/hr No hot-target chemistry Continuous production At 8 atm, 0.7 mg/cm 2 He 5 mm J. Alonso 22

23 Comparing H - and Light Ions - Production rates with H - still substantially higher Lower proton de/dx allows thicker targets Initial design for RIA Driver current not optimized for maximum light-ion current + Light ion cross sections x10 higher + Thinner targets may allow more efficient cooling Yield may be determined by max current available, not by target engineering considerations + New isotopes available + More flexibility in target material selection + Kinematic effects may increase overall efficiency J. Alonso 23

24 Why is RIA Needed? Excitation functions, yields, chemistry, initial efficacy studies can all be done with isotopes produced at existing facilities (88, ATLAS, ) RIA is vital for next steps: Economics Development of technology for accelerator Low-risk replication of RIA Driver front end, at known cost Operating cost models Engineering Target development, thermal management Production, handling techniques J. Alonso 24

25 RIA Driver will be a Test Bed Enabling technology for reliable, high-current light-ion accelerator Development of engineering concepts for targets, material handling Validation of economic models for new medical isotope production Will lead to construction of dedicated production facilities J. Alonso 25

26 RIA could usher in a new age of accelerator-based medical isotope production J. Alonso 26