Mould

Photos:	Fig. 1 Ytterbium 3
	Fig. 3 Ytterbium source seeds 10	Fig. 2 Ytterbium diagram 4

Relevant Historical Data:	-Ytterbium-169 was developed mainly to improve isodose distribution available with iodine-125 or palladium-103 seeds. With a half-life of 32 days, Ytterbium-169 improves the initial dose rate which is achieved in permanent implants with iodine-125. In this respect, Ytterbium-169 has no advantage over palladium-103, which has a half-life of 17 days. Another reason for the development of Ytterbium-169 was to provide a replacement for iridium-192 as a source for high dose rate (HDR) and low dose rate (LDR) treatments. The reduction in energy with Ytterbium-169 simplifies the design and cost of remote afterloading equipment. There is also a cost savings in the reduced shielding requirements for brachytherapy rooms. 5
Chemical/Radioactive Composition:	Chemical symbol: Yb Atomic number (Z): 70 Mass number (A): 169 -Neutron activation of ytterbium oxide in a nuclear reactor produces Y-169. 9 -Geological specimens are known in which the element has an isotopic composition outside the limits for normal material. 3
Energy Characteristics:	-63-308 KeV 1 -Emits photons with energies ranging from 50 to 308 keV 2 (average energy of 93 keV) (excluding energies less than 10 keV) 2 -Gives off gamma radiation 4
Exposure Rate Constant:	-Analytic calculations based on the primary photon spectrum of 169Yb (excluding energies less than 10 keV) yield an air-kerma rate constant of 0.0427 cGy cm2 h-1 MBq-1, and an exposure rate constant of 1.80 R cm2 mCi-1 h-1 for this radionuclide. 2
Half-life Properties:	-32 days 1
Forms available for use:	-Seeds. 2 -The Yb-169 seed is about 5 mm in length with an outer diameter of 1 mm in diameter and contains 0.5 mm diameter ytterbium oxide spheres encapsulated in a cylindrical titanium shell. 9 -The SENTINELTM range of double encapsulated special form sealed source assemblies caters to most industrial applications using gamma radiography. -A choice of isotopes provides solutions for the widely varying requirements demanded by differ ent materials and site conditions. Sources with outputs ranging from less than one curie up to several hundred are available-all precision con structed to ensure the highest possible specific activities and the smallest focal spot sizes. 10 -Ytterbium-169 sources are available in spherical and right circular cylinder focals, housed in a welded titanium alloy capsule 10
HVL in lead:	-The first half-value layer in lead is 0.2 mm; the first tenth-value layer is 1.6 mm 2
Measurement/Calibrations/QA:	-Standardization of brachytherapy source strength in terms of exposure rate has been performed by the National Institute of Standards and Technology. A seed submitted for calibration is placed at the bottom of the re-entrant tube for measurement of its source strength. Exposure rate at 1meter with a stated overall uncertainty of 2%. 7 -The source strength can be measured directly with an ion chamber or calculated indirectly from the source radioactivity [Bq] with corrections for encapsulation. 14
Used in formula/calculation:	Mean Life (T avg)= 1.44 T1/2 Mean Life= 1.44 x 32 days = 46.08 days Dc= Do x Tavg Dc= 10 cGy/hour x 24 hours/day x 46.08 days= 11,059 cGy 11,059 cGy is the total cumulative dose for a permanent Ytterbium-169 implant with an initial dose rate of 10 cGy/hour.8
Uses in Radiation Oncology:	-Used as a substitute for Cs-137 and Ir-192 for temporary implants due to its relatively lower energy emissions.2 -Has also been considered as a replacement for I-125 and Pd-103 in permanent implants. 6,13 Can possibly provide comparable tumor control in slowly proliferating tumors. 6 -Is a promising new radionuclide for intravascular radiotherapy (IVBT). It has a much better penetrating power through calcified plaques and stents compared with the low-energy source Iodine-125. It also provides easier radiation protection measures for cardiac cathlab personnel than the high-energy source Iridium-192, while preserving a favorable dose distribution in tissues surrounding an arterial vessel. 11
Treatment Planning:	-Monte Carlo simulation is an accurate and powerful tool for dosimetric characterization of brachytherapy sources in this energy range. 12 -In spite of the uncertainties in the parameters necessary for an accurate radiobiological modelling, the linear quadratic model can be useful in the comparative evaluation of the radiotherapeutic merit of similar implants. 13
One other interesting fact:	-Radiation protection is not as easily achieved for permanent implants with 169Yb because of the higher energy emissions 2 -For temporary implants, Ytterbium-169 may prove to be a useful substitute for 192Ir or 137Cs because of its relatively lower energy emissions 2

Links:
1. Gamma Ray Sources. Available at: http://onlineshowcase.tafensw.edu.au/ndt/content/radiographic/task2/accessible.htm. Accessed April 7, 2009.
2. Ytterbium-169 Sources. Available at: http://www.entsys-tech.com/ndt/group1radiographicsystems/ytterbium-169.htm. Accessed April 7, 2009.
3. Ytterbium-169: Calculated physical properties of a new radiation source for brachytherapy. Available at: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=MPHYA6000019000003000695000001&idtype=cvips&gifs=yes. Accessed April 7, 2009.
4. Modern Advances in Prostate Brachytherapy. Available at: http://www.aapm.org/meetings/05SS/program/ProstateAdvances_lief.pdf. Accessed April 7, 2009.

References:

1. Sentinel.thomasnet.com. Ytterbium-169. Available at: http://sentinel.thomasnet.com/item/sources-source-holders/sources/pn-1255?&seo=110. Accessed on March 16, 2009.
2. Pubmed.gov. Ytterbium-169. Available at: http://www.ncbi.nlm.nih.gov/pubmed/1508110. Accessed on March 16, 2009.
3. Radioactive Elements. Available at: http://theodoregray.com/PeriodicTable/Elements/070/data.s7.html. Accessed on March 17, 2009.
4. Ytterbium. Available at: http://www.chemistryexplained.com/elements/T-Z/Ytterbium.html. Accessed on March 17, 2009.
5. Mould, R.F., Battermann, J.J., Martinez, A.A. Brachytherapy from Radium to Optimization. Wageningen,The Netherlands: Veenman Drukkers; 1994. pp. 379-382.
6. IOP.org. Analysis of Radiobiology of Ytterbium-169 and Iodine0125 Permanent Brachytherapy Implants. Available at http://iop.org/EJ/abstract. Accessed on March 18, 2009.
7. Leibel Steven, Phillips Theodore. Textbook of Radiation Oncology. Philadelphia, Pennsylvania: W.B. Saunder Company; 1998.
8. Khan, Faiz M. The Physics of Radiation Therapy. 3rd Edition. Philadelphia: Lippincott Williams & Wilkins; 2003. p. 545.
9. Module 7, Session 9, pp.11-15. Accessed March 26, 2009, Stanford Web-Based Dosimetry Training Tool. Available at: http://www.dosimetrytrainingtool.com.
10. Sentinal.thomasnet.com. Ytterbium 169. Available at: http://sentinel.thomasnet.com/item/sources-source-holders/sources/pn-1255?&seo=110. Accessed on March 27, 2009.
11. Science Direct. Ytterbium-169: A promising new radionuclide for intravascular brachytherapy. Available at: http://www.sciencedirect.com/science?_ob=Article. Accessed on March 30, 2009.
12. Biomed Experts. Dosimetric characteristics, air-kerma strength calibration and verification of Monte Carlo simulation for a new Ytterbium-169 brachytherapy source. Available at: http://www.biomedexperts.com/Abstract.bme/8138449/Dosimetric_characteristics_air-kerma_strength_calibration_and_verification_of_Monte_Carlo_simulation_for_a_new_Ytterbium. Accessed on March 30, 2009.
13. IOP Electronic Journals. Analysis of the radiobiology of ytterbium-169 and iodine-125 permanent brachytherapy implants. Available at: http://www.iop.org/EJ/abstract/0031-9155/42/9/005. Accessed on April 6, 2009.
14. Research Gate Scientific Network. Radioactivity measurements of ytterbium-169 brachytherapy sources. Available at: https://www.researchgate.net/publication/13651733_Radioactivity_measurements_of_ytterbium-169_brachytherapy_sources. Accessed on April 6, 2009.





Color Codes:
Purvi - Orange
Alia - Green
Angie - Blue
Tracey -Red