A Simple and Inexpensive Method for Determining the Proton Energy of a Medical Cyclotron

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• A Simple and Inexpensive Method for Determining
  the Proton Energy of a Medical Cyclotron

July 31, 2007 TRIUMF Student Symposium Katie
Gagnon Supervisor Tom Ruth
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Outline

• PET/Medical Cyclotrons
• Proton Energy from Production Yields
• The Simple and Inexpensive Method
• Results
• Conclusions

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PET A Review

• Utilizes Coincidence Detection of Positron Decay

• Cyclotron Produced Positron Emitters

Z
Others 18O(p,n)18F 16O(p,a)13N 15N(p,n)15O
Example 14N(p,a)11C
University of Washington, 1999 University of
Pennsylvania, 2000 KAERI, 2000
N
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Medical Cyclotron
To Consider Production Cross Section
Why is an On-Site Cyclotron Preferred?

• IAEA Cyclotron Summary

Question
How is the proton energy verified?
IAEA-DCRP/2006 Directory of Cyclotrons Used for
Radionuclide Production in Member States
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Energy (Direct) Method 1

• Production Yields

A Activity n Number of target nuclei per
cm2 I Proton flux s Cross section ? Decay
constant t Irradiation time

• Drawbacks

Beam flux is not constant s ? A is not one-to-one
Diagnostic Radioisotopes and Monitor Reactions,
IAEATECDOC1211, 2001
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Energy (Ratio) Method 2

• Method 1

• Method 2

• Benefits

Eliminates dependence on beam current

• Drawbacks

Expensive
Diagnostic Radioisotopes and Monitor Reactions,
IAEATECDOC1211, 2001
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Method 2 made less expensive?

• Make us of an ionization chamber
• A tool already located in many hospitals!
• Current measurement ? Activity
• Measures ALL isotopes (non-specific)
• Must correct for isotope dependence

New Korea Industrial Co. LTD.,www.nekoind.co.kr
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Choosing a Target Material

• For ratio method, must choose target material
  carefully
• Goal Determine EOB A1 and A2 activities

• Category I
• Only two short-lived isotopes
• Long lived contaminants OK

• Category II
• Only one short-lived isotope
• Only one long-lived isotope

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Target Material Choice natCu

• Cross Sections

• natCu(p,x) Products

IAEATECDOC1211, 2001 Meadows, J, PR, 91,
885, 1953 Ghoshal, J, PR, 80, 939, 1950
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Results TR-13 (TRIUMF)
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Conclusions

• Need for medical cyclotrons on-site is important
• Characterization of proton energy guides
  understanding of yields
• Ionization chamber ratio method consistent with
  HPGe measurements
• Careful choice of target material necessary

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Acknowledgements

• Edmonton PET Center
• John Wilson
• Miguel Avila-Rodriguez
• Steve Mcquarrie

• TRIUMF
• Tom Ruth
• Suzy Lapi
• Ken Buckley
• Wade English
• PET Members

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• Questions?

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Correction Factors

• Isotope dependence of ionization chamber

• Copper Foil

• Finite foil size
• Utilize TRIM (Transport and Range of Ions in
  Matter)

t 25µm
20 MeV
19.64 MeV
10 MeV
9.38 MeV
1.29 MeV
3 MeV
SRIM (Stopping Ranges of Ions in Matter), 2006
www.srim.org
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Results TR-13 (TRIUMF)
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Results TR-19 (Edmonton)
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BNL Threshold Surpassed