YTTERBIUM SOURCES FOR BRACHYTHERAPY Sergey Akulinichev and Vasily - - PowerPoint PPT Presentation

YTTERBIUM SOURCES FOR BRACHYTHERAPY

Sergey Akulinichev and Vasily Derzhiev Institute for nuclear research of RAS (INR), Moscow and Troitsk, Russia

Preliminary schedule of the talk:

• 1. Medical applications of ytterbium sources
• 2. Source production using laser technology
• 3. Conclusions

Medical applications of ytterbium sources

• In HDR Brachytherapy only 1 source of 6-20 Ci is short-

time inserted via several (or one) catheters .

• Usual isotopes: Co-60, Ir-192 or Yb-169.
• Main localizations: prostate, breast, lung (possibly-

vascular system).

Why ytterbium?

• Soft spectrum compared to Co-60 and Ir-192 ( ~ 92 KeV ),
• Reduced dose to normal tissue and easier shielding,
• High radioactivity - up to 6 Ci / mg for pure Yb-169

(only 0.6 Ci/ mg for Ir-192),

• Half-life 32 days.

easy shielding:

• 2. Source production using laser technology

3 steps:

1) Enrichment of initial isotope Yb-168 (AVLIS : Atomic Vapor Laser Isotope Separation), 2) Production of inner and outer capsules, 3) Activation by thermal neutrons Yb-168 → Yb-169,

AVLIS production of initial

isotope Yb-168

Design of AVLIS facility:

ais

|3> = 4f13(2F7/2)6s26p(7/2,3/2)2

|1> = 4f136s2 1S0 |2> = 4f136s6p3P1

λ = 555.648 nm λ = 581.067 nm λ = 582.79 nm

copper vapor lasers 120W

3 Dye laser system

Vacuum Chamber With extractor

ms

Control system

cooling system 3-step cascade of photo-ionization of Yb-168 (ais-auto ionization state)

The vacuum chamber with evaporator and extractor

(the unique and most complicated part of the facility)

a

diaphragm collector Vapor source Symmetry

axis

Zone of selective ionization gap

y x

Some methods of isotope enrichment

laser photo-ionization AVLIS (the present technology) centrifuges

3 Li H 1 Na 11 K 19 Rb 37 Cs 55 Fr 87 Mg 12 20 Ca 38 Sr 56 Ba 88 Ra Sc 21 Y 39 La 57 Ac 89 22 Ti 40 Zr 72 Hf 104 Rf 58 90 Ce Th 23 V 41 Nb 73 Ta 105 59 Pr 91 Pa 24 Cr 42 Mo 74 W 106 60 Nd 92 U 25 Mn 43 Tc 75 Re 107 61 Pm 93 Np 26 Fe 44 Ru 76 Os 108 62 Sm 94 Pu 27 Co 45 Rh 77 I r 109 63 Eu 95 Am Ni 28 Pd 46 Pt 78 64 Gd 96 Cm 29 Cu 47 Ag 79 Au 65 Tb 97 Bk 30 Zn 48 Cd 80 Hg 66 Dy 98 Cf 31 Ga 49 I n 81 Tl 67 Ho 99 Es 32 Ge 50 Sn 82 Pb 68 Er 100 Fm 33 As 51 Sb 83 Bi 69 Tm 101 Md 34 Se 52 Te 84 Po 70 Yb 102 No 35 Br 53 I 85 At 71 Lu 103 Lr 2 He 10 Ne 18 Ar 36 Kr 54 Xe 86 Rn 9 F 17 Cl 8 O 16 S 7 N 15 P 6 C 14 Si 5 B 13 Al I A I I A I I I B I V B V B VI B VI I B I I I A I V A V A VI A VI I A I B I I B VI I I VI I I B 4 Be Lanthanide series Actinide series

Pumping: power 120 – 130W, λ = 510nm, f = 10kHz, τ = 20ns.

Output of the system: 3 g/ year Final isotope content:

• Yb – 168 – 20.21% (only 0.14 % in natural Yb)
• Yb – 170 – 2.36%
• Yb – 171 – 18.38%
• Yb – 172 – 15.45%
• Yb – 173 – 12.1%
• Yb – 175 – 22.38%
• Yb – 176 – 9.12%

Channel Wavelength, nm Dye Power, W Spectr.band, MHz Pulse width, ns 1 555 R110 5 500 15 2 581 R6G 5 500 15 3 582 R6G 20 3·104 20

Parameters of 3 Parameters of 3-

• Channel Dye

Channel Dye -

• Laser System

Laser System for AVLIS of Ytterbium for AVLIS of Ytterbium

Experimental source of Yb-169 produced on our facility, the measured activity 7 Ci (designed by Implant Sciences, USA)

inner capsule

Nano-granules of ytterbium

The inner capsule irradiation by secondary neutrons

• n INR proton linac

Measured Ytterbium Spectrum

50000 100000 150000 200000 250000 300000 350000 400000 450000 10 47 85 122 160 197 234 272 309 347 384 Energy, keV N u m b e r o f P h

• to

n s

Spectrum of inner capsule (our result) Standard spectrum of Yb-169 Neutron irradiation facility RADEX 1- protons; 2 – vacuum channel 3 – tungsten target; 4 - moderator; 5 – irradiation channel; 6- loading channel; 7 – iron shielding.

• 3. Conclusions
• Titanium inner shell is unimportant for the source spectrum.
• Our laser technology can provide for HDRB low cost

ytterbium sources (electricity consumption is 8 times less compared to standard EM technology of Yb-168 extraction).

• The sources with Yb-169 are less expensive than sources with

Ir-192 and do not require a heavy shielding.

• The HDRB with ytterbium can be carried out in any hospital.
• The sources with ytterbium have additional clinical benefits

(reduced dose to neighbor organs and normal tissue ).

• Light mobile afterloaders designed for ytterbium sources are

going to appear.

• 2-3 facilities (as the one described above) can cover the needs
• f HDR brachytherapy in whole Russia.