Radiation Passport

iPhone / iPod Touch Program estimates Radiation / Cancer Risks from Imaging Exams and Related Procedures

The word “radiation” means many things to different people. In its most basic sense, radiation refers to any process in which energy is transported through space, which will eventually be absorbed by some material (for example – your body, or the Earth).

There are a number of different types of Radiation. One of these types of radiation is called “Electromagnetic Radiation” . Different examples of Electromagnetic radiation, that you encounter or your body absorbs on a daily basis, include Radiowaves (how you listen to your radio), Heat waves, Infrared radiation, Light waves (these are the only types of electromagnetic radiation that you can sense/see with your eyes), Ultraviolet (UV) waves (what gives you a sunburn), X-rays, Gamma-rays.

There are a number of sources of radiation that affect us. These include background radiation, radiation from consumer products, radiation associated with our occupation, and Medically-related radiation.

We are all exposed to some natural/background radiation of 2 primary sources – cosmic, and terrestrial. The biggest contributor to natural background radiation is from radon. Radon is what’s called an ‘alpha-emitter’ – when it breaks down, its products are radioactive. In 2000, it was estimated that the worldwide average annual exposure to background radiation was approximately 2.4 milliSieverts.

In Medicine, radiation can be very useful in many situations – both to treat diseases, particularly cancers (radiation therapy or radiotherapy), and even more importantly, to diagnose diseases. The Medical specialty that uses radiation the most is of course Radiology – X-rays, CAT Scans (CTs), fluoroscopy, mammograms, and Nuclear Medicine exams have led to great advances in the ability of doctors to diagnose and subsequently treat diseases. Numerous other Specialists also use radiation, both to diagnose and treat – for example, Nuclear Medicine Physicians, Interventional Radiologists, Cardiologists, Gastroenterologists, Orthopedic Surgeons, General Surgeons, and Dentists, to name a few.

The type of radiation used in Medicine is generally ‘ionizing’ – that is, its photons carry enough energy to eject an electron from a neutral atom, leaving being a small positively-charged particle called an ion. These positively-charged particles can then go on and cause damage to human tissues. This is how radiation can be harmful to patients.

These ionized particles can lead to mutations in your DNA, which can then lead to others problems, arguably the most important of which is cancer.

It is quite well-accepted today that there are risks associated with medical radiation, be it from Radiology exams such as X-rays or CAT (CT) scans, or treatments such as coronary/cardiac angioplasty. Figuring out how to estimate the risks, though, is very difficult, and there are a number of different models used to do this.

One of the authorities on this topic is the Biological Effects of Ionizing Radiation (BEIR) committee, of the U.S. National Academy of Sciences. In their BEIR VII Report, they assume that the cancer-related risks of radiation follow what they call a ‘linear, non-threshold’ model. In other words, 1) all radiation, regardless of how small it is, has some risk associated with, and 2) if a certain amount of radiation is associated with x% risk, then half that radiation is associated with half the risk. The risks are also assumed to be ‘cumulative’ – if you have a CAT scan in a given year, the risk of you developing cancer because of the associated radiation is increased for years after.

The risk estimates for many common procedures and exams may be higher than many people realize. For example, the estimated risk of developing fatal cancer specifically due to the radiation a young woman is exposed to during a single CAT scan of the abdomen is estimated to be somewhere in the neighborhood of 1/800 to 1/2000, depending on the settings of the CAT Scanner. Older patients, in general, have a decreased risk.

A controversial paper by Dr. Brenner and Dr. Hall published in the New England Journal of Medicine suggested that up to 1.5 to 2% of all cancers in the US may be attributable to radiation from CAT scans, if adjusting for current CAT scan usage rates.

There have also been publications suggested that a substantial number of exams currently performed may not be ‘medically-indicated’, and there are many healthcare professionals, including physicians, who significantly underestimate the risks associated with radiation from Radiology and related exams and procedures.

Recently, I teamed up with my brother to create a program – Radiation Passport - for the iPhone or iPod Touch that allows patients to ‘track’ their radiation exposure from medical exams and procedures. Users enter the type of exam they had, and when, and Radiation Passport will record the exam and date, and assign the estimated radiation exposure associated with it. The radiation exposure is then summed for all exams and procedures entered, and an estimate of the cancer risk due to the radiation exposure is calculated. Patients can also write in notes (for example, reminders to follow-up on a Radiology exam), and figure out the estimated risk of developing cancer for a single Radiology or related exam or procedure they are prescribed to undergo by their physician or dentist.

The purpose of Radiation Passport is to simply increase awareness among patients about the potential risks of medical radiation. Radiology and radiology-related exams and procedures have allowed tremendous advances in the field of Medicine, including both in diagnosing diseases, as well as treating diseases. When these exams and procedures are considered necessary, it is assumed that the potential benefit of the exam or treatment outweighs the potential risk. This Program aims to serve as a reminder to be cognizant that there are assumed risks.

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If a 20-year old woman undergoes a CAT scan of her abdomen and pelvis, what is the estimated risk of her developing fatal cancer caused specifically by the radiation from that single CAT scan? - Dr. Mark Otto Baerlocher