Organ Dose Measurement Using the Phantom Torso (Torso) - 07.15.15
Organ Dose Measurement Using the Phantom Torso (Torso) measures the amount of radiation that a human received during an extended space flight. The measurements are taken using an anatomical model of a male head and torso that contains different types of radiation sensors. This experiment is important for future human long-duration space exploration. Science Results for Everyone
The Phantom of the ISS – Phantom Torso, that is. This model of a male head and torso contains sensors that measure the radiation supposedly absorbed by the body during extended space flight. The data suggest that organ radiation dose and dose equivalent can be projected to within 25 percent accuracy, an improvement to the current plus-or-minus 500 percent accuracy of cancer risk projections. About 80 percent of radiation energy deposited in human tissues seems to come from galactic cosmic radiation, most likely because the spacecraft effectively deflects the protons trapped in Earth's magnetic field. Many uncertainties about space radiation remain, and more research and analyses are needed. The Phantom may ride again. Experiment Details
Gautam D. Badhwar, Ph.D., Johnson Space Center, Houston, TX, United States
Francis A. Cucinotta, Ph.D., University of Nevada, Las Vegas, NV, United States
NASA Johnson Space Center, Human Research Program, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2001 - August 2001
Previous ISS Missions
- This experiment uses a synthetic human torso, embedded with over 300 strategically placed dosimeters (radiation sensors), to determine the levels of cosmic radiation absorbed by specific organs in the human body during space flight.
Two types of sensors are used:
- passive sensors will quantify the total amount of radiation absorbed in various body parts throughout the entire flight.
- active sensors will give real time data describing how much radiation is absorbed at varying times during ISS orbit.
- Real time data will focus on the brain, thyroid, colon, and stomach.
One of the most critical risks to humans in space is radiation exposure. Outside the protection of Earth's atmosphere, space crews are exposed to a wide range of particles, including neutrons, that are not normally a threat on Earth. Exposure to radiation found in low Earth orbit (LEO) and beyond can cause cataracts, cancer, damage to reproductive organs and the nervous system, and changes in heredity.
The Organ Dose Measurement Using the Phantom Torso (Torso) employed a model human head and torso (Rando phantom), imbedded with over 350 detectors (thermo-luminescent detectors) and five silicon diode detectors, over five depths to measure absorbed dose to specific organs during shuttle flight. A tissue equivalent proportional detector and a charged particle directional spectrometer were placed within 1.5-feet of the torso during these ISS measurements. This was the first NASA experiment to simulate doses at discrete locations within the body.
The tissue equivalent proportional counter (TEPC) consisted of a spectrometer and cylindrical detector with which to measure external radiation doses. The TEPC measured radiation dose and dose equivalent in complex radiation fields (fields containing a mixture of particle types). The charged particle directional spectrometer (CPDS) measures particle energy and direction inside ISS. Both the TEPC and the CPDS remained within 1 - 1.5 feet (30.48 - 45.72 cm) of Torso during its operation on station.
The Torso experiment helps scientists more accurately predict the radiation exposure astronauts will experience inside their bodies, especially to critical blood-forming organs. No previous experiment has had the capacity to measure radiation doses in multiple, discrete locations in the body. By performing this experiment aboard the International Space Station (ISS), scientists also learns how long human beings can remain in space before the body absorbs dangerous levels of radiation. The experiment may lead to protective procedures to safely prolong human exposure to radiation.
This experiment is teaching scientists more about the use of embedded devices for data collection and how to monitor real-time data. This could prove beneficial to radiation monitoring of commercial airline crews and military flight crews.
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The crew was only required to transfer and activate the Torso and equipment, check its status every 7 to 10-days, download data (using the Human Research Facility - 1 laptop) every 7 to-10 days, and to change the battery every 20-days. At the completion of the experiment, the crew disassembled the Torso for its return on STS-105.
The crew set up the Torso in the U.S. Destiny Laboratory and activated all the associated hardware. Once activated, the Torso, CPDS, and TEPC collected data continuously, without crew intervention. Data downloads were sent to the Telescience Center at Johnson Space Center for distribution to the investigators.
Previously, radiation risk to crewmembers has been based mainly on measurements using one type of radiation detectors known as passive thermoluminescent dosimeters or TLDs. This makes accurately relating radiation dose on the skin to organs and deep tissue a complex and difficult task. The first space flight using a fully instrumented phantom torso (with head) reveals the relationship between skin dose to organ dose. Small active dosimeters were developed to provide measurements of absorbed dose rates and damaging factors at five organ locations (brain, thyroid, heart/lung, stomach and colon) inside the phantom. Results show there is about a 30% change in dose as one moves from the front to the back of the phantom body. Other types of detectors were flown next to the phantom torso to provide data on the internal radiation environment of the spacecraft. Using all available dosimeters and detectors, it is now possible to quantify dosage as well as separate different components of space radiation such as trapped-protons and galactic cosmic rays (GCRs). For the conditions experienced in the International Space Station (ISS) orbit during periods near the solar minimum, the ratio of the blood-forming organ dose rate to the skin absorbed dose rate is about 80%, and the total amount of radiation absorbed for organs versus skin is almost the same, i.e. ratio equal to 1. Passive detector measurements on the crewmembers and inside the brain and thyroid of the phantom show the presence of a significant contribution to both the skin and organ doses that is due to free neutrons, generated from GCRs bombardment on materials of the ISS, thus the estimated radiation risk using models not accounting for this effect is actually lower than the real risk. This aspect requires additional study. Nonetheless, these measurements provide a comprehensive data set to map the dose distribution inside a phantom torso, and to assess the accuracy and validity of space radiation effects throughout the human body (Badhwar 2002, Cucinotta 2008).^ back to top
Cucinotta FA, Kim MY, Willingham V, George KA. Physical and Biological Organ Dosimetry Analysis for International Space Station Astronauts. Radiation Research. 2008 July; 170(1): 127-138. DOI: 10.1667/RR1330.1. PMID: 18582161.
Ground Based Results Publications
Edwards AA. RBE of radiations in space and the implications for space travel. Physica Medica: European Journal of Medical Physics. 2001; 17 Suppl 1: 147-152.
Kolomensky AV, Kuznetsov VG, Laiko IA, Bengin V, Shurshakov VA. The model of radiation sheilding of the service module of the International Space Station. Aviakosmicheskaia i Ekologicheskaia Meditsina (Aerospace and Environmental Medicine). 2001; 35(6): 39-43.
Yasuda H. Effective Dose Measured with a Life Size Human Phantom in a Low Earth Orbit Mission. Journal of Radiation Research. 2009.
Berger T, Hajek M, Schoner W, Fugger M, Vana N, Noll M, Ebner R, Akatov YA, Shurshakov VA, Arkhangelsky VV. Measurement of the depth distribution of average LET and absorbed dose inside a water-filled phantom on board space station Mir. Physica Medica: European Journal of Medical Physics. 2001; 17 Suppl 1: 128-130.
Badhwar GD, Atwell W, Badavi FF, Yang TC, Cleghorn TF. Space radiation absorbed dose distribution in a human phantom. Radiation Research. 2002 January; 1571(1): 76-91. PMID: 11754645.
Wilson JW, Shinn JL, Tripathi RK, Singleterry Jr. RC, Clowdsley MS, Thibeault SA, Cheatwood FM, Schimmerling W, Cucinotta FA, Badhwar GD, Noor AK, Kim MY, Badavi FF, Heinbockel JH, Miller J, Zeitlin C, Heilbronn L. Issues in deep space radiation protection. Acta Astronautica. 2001; 49(3-10): 289-312.
Badhwar GD, O'Neill PM. Response of silicon-based linear energy transfer spectrometers: implication for radiation risk assessment in space flights. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2001; 466(3): 464-474.
Badhwar GD. Shuttle radiation dose measurements in the international space station orbits. Radiation Research. 2002; 157(1): 69-75.
Life Sciences Data Archive
Science @ NASA
International Space Station Medical Project
NASA Image: ISS002E5952 - Image of the Torso on ISS during Expedition 2.
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Torso is an anatomical model of a torso and head containing more than 300 radiation sensors. Image courtesy of NASA.
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