A compilation of microdosimetry for uniformly distributed Auger emitters used in medicine

Abstract

Purpose: To provide a compilation of microdosimetric characteristics for 12 Auger emitters commonly used in medicine.

Materials and methods: Monte Carlo electron track structure simulations are performed for 12 Auger emitters. They are ⁵⁵Fe, ⁶⁷Ga, ^99mTc, ¹¹¹In, ^113mIn, ^115mIn, ¹²³I, ¹²⁵I, ^193mPt, ^195mPt, ²⁰¹Tl, and ²⁰³Pb. Proximity functions of 12 Auger emitters are calculated from the simulated track structures and compared with that of gamma rays from ⁶⁰Co.

Results: Some of those Auger emitters are highly radiotoxic compared to hard gamma rays from ⁶⁰Co. The more electrons per decay and the lower electron energies, the more effective an Auger emitter could be.

Conclusions: The high radiotoxicity of Auger emitters is due to correlations of low-energy electrons released from decay processes. If these correlations were disregarded, Auger emitters would not differ significantly from other low linear energy transfer (LET) radiation sources. Even in the case of uniform distribution, some of those Auger emitters are highly radiotoxic compared to hard gamma rays. For Auger emitters to bond to radiosensitive sites in cell nucleus, much higher radiation effectiveness could be expected.

Keywords:

• Auger emitter
• microdosimetry
• proximity function
• relative biological effectiveness