The scientific unit of measurement for radiation dose, commonly referred to as effective dose, is the millisievert (mSv). Other radiation dose measurement units include rad, rem, roentgen, and sievert.
Because different tissues and organs have varying sensitivity to radiation exposure, the actual dose to different parts of the body from an x-ray procedure varies. The term effective dose is used when referring to the dose averaged over the entire body.
The effective dose accounts for the relative sensitivities of the different tissues exposed. More importantly, it allows for quantification of risk and comparison to more familiar sources of exposure that range from natural background radiation to radiographic medical procedures.
We are exposed to radiation from natural sources all the time. The average person in the U.S. receives an effective dose of about 3 mSv per year from naturally occurring radioactive materials and cosmic radiation from outer space. These natural "background" doses vary throughout the country.
People living in the plateaus of Colorado or New Mexico receive about 1.5 mSv more per year than those living near sea level. The added dose from cosmic rays during a coast-to-coast round trip flight in a commercial airplane is about 0.03 mSv. Altitude plays a big role, but the largest source of background radiation comes from radon gas in our homes (about 2 mSv per year). Like other sources of background radiation, exposure to radon varies widely from one part of the country to another.
To explain it in simple terms, we can compare the radiation exposure from one chest x-ray as equivalent to the amount of radiation exposure one experiences from our natural surroundings in 10 days.
| Radiography-Chest | 0.1 mSv |
http://www.radiologyinfo.org/content/safety/xray_safety.htm#measuring_dosage
The problem I encountered is that each article uses a different scientific unit of measurement to measure the radiation. Here is the explaination of each measurement:
millisievert is defined as "the average accumulated background radiation dose to an individual for 1 year, exclusive of radon, in the United States." 1 mSv is the dose produced by exposure to 1 mGy (milligray) of radiation. In terms of historical measures of radiation dose, exposure to 1 roentgen (R) of X-rays results in absorption of 1 rad , which had the effect of 1 rem: this is equivalent to exposure to 0.1 mGy producing a dose of 0.1 mSv.
rad
The rad represents a certain dose of energy absorbed by 1 gram of tissue. It is a unit of concentration. So if we could uniformly expose the entire body to radiation, the number of rads received would be the same whether we were speaking of a single cell, an organ (e.g., an ovary) or the entire body (just as the concentration of salt in sea water is the same whether we consider a cupful or an entire ocean).
Some forms of radiation are more efficient than others transferring their energy to the cell. To have a level playing field, it is convenient to multiply the dose in rads by a quality factor (Q) for each type of radiation. The resulting unit is the rem ("roentgen-equivalent man"). Thus, rem = rad x Q. X rays and gamma rays have a Q about 1, so the absorbed dose in rads is the same number in rems. Neutrons have a Q of about 5 and alpha particles have a Q of about 20. An absorbed dose of, say, 1 rad of these is equivalent to 5 rem and 20 rem respectively.
The sievert (Sv) and gray (Gy)
Despite the years of high-quality research reported in rems and millirems (mrem, 10-3 rem), the International Commission on Radiation Units and Measurements wants us to give up the rad in favor of the gray (Gy), a unit 100 times larger. Similarly, the rem is to be replaced by the sievert (Sv), again so that 100 rem = 1 Sv. Unfortunately, the rad and rem were already a little large to work with (why the table below is expressed in millirems) and converting to grays and sieverts makes the problem worse. Happily, many workers continue to use the rad and rem, and so shall we. In fact, I will try to express all radiation doses in a single unit, the millirem.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Radiation.html
The amount of energy absorbed per unit weight of the organ or tissue is called absorbed dose and is expressed in units of gray (Gy). One gray dose is equivalent to one joule radiation energy absorbed per kilogram of organ or tissue weight. Rad is the old and still used unit of absorbed dose. One gray is equivalent to 100 rads.
1 Gy = 100 rads
http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html
Interesting Info on Effects of Radiation:
http://www.jlab.org/div_dept/train/rad_guide/effects.html
I hope you have been able to follow this radiology lesson-I am having a hard time doing so! I never realized how complicated they have made it! Too confusing for me! ![]()
It would be much easier if I found something that compared the x-ray radiation used in rads, but that is too simple for scientists![]()
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I asked my mother, who is a physics teacher, to do the math and it looks like you had 56 Gy, which would be equal to 56,000 mSv, which would definitely be a lifetime radiation dose. Have you spoken with your radiation oncologist?
I learned some interesting information. I learned that an abdomen CT is 400x (10 mSv) the amount of radiation of a chest x-ray (I think I am going to avoid the abdomen CT, now). My advice is to stick with MRIs and ultrasounds. I also learned that when I lived in NM, I was exposed to more radiation (not just from visting Trinity Site (where the first atomic bomb was tested)). Very interesting. Thank you for my radiology lesson![]()
of the day.
Hava great day!
Take care.
Meri
