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Compact Systems for Effective and Precise Brachytherapy

IB-2114 and IB-1793

PROTON BRACHYTHERAPY DEVICE

APPLICATIONS OF TECHNOLOGY:

  • Direct proton irradiation of breast, prostrate, and other tumors between 5 and 10 mm in diameter

ADVANTAGES:

   
 
DIAGRAM OF THE BERKELEY LAB PROTON BRACHTHERAPY DEVICE
 
   
  • Compact and portable: ~ 4 cm in diameter x 13 cm long
  • Delivers 15 MeV protons at 6 x 107 H+/second without a radioactive source
  • Designed to localize the radiation dose to minimize healthy tissue damage
  • Expected to be effective at treating low energy gamma-radiation resistant tumors

DESCRIPTION:

Ka-Ngo Leung, Sami Hahto and Tak Lou from Berkeley Lab have developed a miniature proton brachytherapy system designed to precisely deliver short range, high energy (15 MeV) proton radiation directly to the site of a small tumor with minimal damage to healthy tissue.Proton brachytherapy is preferable to neutron brachytherapy for treating small tumors because protons don’t travel as far in the body as neutrons. Proton brachytherapy offers the highest tumor-dose to heavy-tissue-dose ratio of any brachytherapy method.

Until now, proton brachytherapy has only been performed using large proton accelerators that produce ~ 200 MeV protons for external radiation therapy. External proton therapy can deliver radiation precisely to a tumor site but healthy tissue is also damaged by the high energy protons. The tumor typically has to be irradiated from several angles to reduce healthy tissue dose.

The Berkeley Lab device is designed to produce 3He ions in a plasma chamber and then extract a 3He ion beam. It accelerates the beam down a thin hollow tube to hit a deuteron-bearing target. 15 MeV protons are produced and escape isotropically, reaching cells within a 2.5 mm radius around the generator target.

STATUS:

REFERENCE NUMBER: IB- 2114

 



MINI NEUTRON GENERATOR

APPLICATIONS OF TECHNOLOGY:

  • Fast neutron brachytherapy for breast, prostrate and other tumors between 1 and 5 cm in diameter

ADVANTAGES:

  • Compact and portable: ~ 4 cm in diameter x 13 cm long
  • Radiation dose to healthy tissue is expected to be much less than with external sources
  • Expected to be more effective than gamma radiation in treating radioresistant tumors
  • Doesn’t require radiation shielding or a remotely activated HDR system
  • Delivers ~ 106 n/s with 2.5 MeV D-D reactions and ~ 108 n/s with 14 MeV D-T reactions

DESCRIPTION:

Ka-Ngo Leung and colleagues at Berkeley Lab have designed a compact deuterium-deuterium (D-D) or deuterium-tritium (D-T) neutron generator for fast neutron brachytherapy treatment of tumors ~ 1 to 5 cm in diameter. The Berkeley Lab neutron source could be inserted directly into a tumor, minimizing damage to healthy tissue while delivering a potent dose of radiation to the tumor.

Currently, brachytherapy neutron sources in the United States are manually afterloaded low-dose-rate (LDR) 252Cf sources. Because the spontaneous fission of 252Cf cannot be turned off, high-dose-rate (HDR) sources require expensive shielding and loading devices to protect clinical personnel and patients. An accelerator based neutron source such as the Berkeley Lab D-D or D-T neutron generator has the advantage of being switchable, eliminating the need for shielding and a remotely afterloaded HDR system.

The generator is composed of a 2 cm x 2.5 cm plasma source from which deuterium or tritium ions are extracted and then accelerated. The accelerated ion beam is then directed down a 10 cm long needle-like tube (diameter ~ 3 mm) with a titanium target at the end where neutrons are produced. The primary cell killing mechanism of fast neutrons is the elastic collision of neutrons with hydrogen atoms in tissue. Because heavy charge particles have a short range and high linear energy transfer (LET), the recoiled protons leave a track with a large number of free radicals in a small volume. These free radicals will react with cancerous cells and can cause the death of these cells.

STATUS:

REFERENCE NUMBER: IB- 1793

 

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