Dr. Veljko Radeka is developing two tools to aid radiation research – a heavy ion microbeam and a micron resolution detector based on a new concept. These devices will enable researchers to study radiation damage by single heavy ions at the cellular level.
Overview
Heavy Ion Microbeam and Micron Resolution Detector
Principal Investigator:
Veljko Radeka, Ph.D.
Organization:
Brookhaven National Laboratory
Technical Summary
The use of microbeam provides a unique way to control the number of particles traversing individual cells and localizing the dose within the cell. High-energy, heavy- charged particles transfer their energy to biological organisms through high-density ionization and excitation along the particle track even by uniform irradiation. This characteristic microscopically non-uniform dose delivery is expected to induce complex DNA damage and mutagenesis, in contrast to relatively uniform dose delivery in gamma-rays or electron beam irradiation. To investigate the distinct biological effects of heavy ions, especially to determine the effects of occupational and environmental exposure of very low doses of heavy charged particles for example, since virtually no cells receive more than one traversal of cosmic ray HZE particle in its lifetime in a spaceflight environment, one approach is to select cells with the desired exposures from a randomly irradiated population.
Using conventional track segment irradiation methods and sophisticated ion-track detecting techniques, the position of the target cells and the ion tracks can be measured together. However, this conventional approach is not practical because all responses of many cells, which do not contribute to the aim of the irradiation experiment, must be measured. The alternative is to control each ion hit so that irradiation experiment is not a random Poisson process. A heavy ion microbeam can be used to selectively irradiate individual cells, which can be analyzed afterward, to determine what changes have occurred to that cell and to its un-irradiated neighboring cells. A heavy-ion microbeam can also be used to look for pathways other than DNA damage to the cell membrane or cytoplasm.
We want to design and test a high-energy microbeam apparatus and a micron-resolution solid-state detector for space radiobiology studies. In addition, we will develop in vitro models relevant to radiation risk using a microbeam capable of delivering individual charged particles to individual cells in situ. The system will allow us to critically determine the response of human cells to the single-particle traversals typically en-countered in space environmental exposures. During long-term space flight mission, it is estimated that virtually no cell receives more than one Fe ion traversal in a 3-year Mars mission scenario. Thus, the use of the microbeam will aim to produce data for direct input into the analysis of human health risks during long-term space flight exposures involving exposure to low fluences of charged particles.
A single-ion microbeam facility comprises a number of elements arranged to deliver reliably counted numbers of ions to a chosen biological target. The elements are:
- a source of ions of the appropriate energy,
- a means of limiting the location of the ions to an area less than the area of the target,
- a means of locating and moving the biological targets to the beam position,
- a means of detecting each ion as it traverses the target, and
- a means of shutting off the beam after the arrival of the chosen number of ions.
A principal objective of this project is to develop and demonstrate a high resolution silicon detector, which will be able to determine the position of impact of energetic heavy ions in single cell radiation-effects studies to within ~1 micron. An additional objective is a conceptual design of a heavy-ion microbeam in the energy range up to 3 GeV. The beam will be collimated to ~10-20 microns to a region of one or very few cells. The microbeam will be implemented in a separate project at the NASA Space Radiation Laboratory (NSRL) in BNL, previously known as Booster Accelerator Facility (BAF).
These developments will significantly advance the state of the art of high-energy heavy-ion microbeams and of high-resolution heavy-ion detectors. For the cell studies employing these tools, the necessary infrastructure will include a micropositioning stage with a microscope and auxiliary detectors.
Implications
The micron resolution detector, together with the microbeam, will be able to localize the position of an ion impact within a particular region of the cell. This is essential for studies in space radiobiology.
Earth Applications
The ability to place discrete numbers of particles in defined cellular and extracellular locations is now possible by using microbeam irradiation facilities. Such a facility permits heavy-ion radiobiology to address specifically the impact of signal transduction between cellular compartments as well as issues related to intercellular communication on limiting low fluences where not all the cells in a population have been traversed by even a single particle. Moreover, a high-energy heavy-ion microbeam will permit to address an important unanswered question: whether neurons that survive traversal by HZE particles develop changes as a late consequence of the damage they incurred. Therefore, these low-fluence studies promise to aid in our understanding of the consequences of exposure to high-LET radiation such as encountered in the space radiation environment.
This project's funding ended in 2004