Answer to Question #202 Submitted to "Ask the Experts"

Q

What is the risk assessment for the following x-ray procedures done since age 18: (four) lower spine (only two film on last procedure); (two) nasal; (one) skull; (one) upper GI; (one) upper & lower GI w/fluoroscopy. I'd also appreciate the approximate dose for each procedure. I'm a 45-year-old male. Thank you.

A

We are going to answer your second question (about doses) first because that is the first step in an assessment. You do not specify the dose you are interested in--dose to a particular organ of interest, dose to organs in the primary beam, or the "effective dose" (the average uniform whole-body dose that is estimated to represent the same risk as the actual nonuniform irradiation). To calculate dose from a particular diagnostic procedure, it is necessary to know specific information for each exam. This would include the kVp (energy of x rays) and x-ray beam half-value layer, the mAs (the product of the x-ray tube current and the time of the exposure in seconds), the radiation field size, the projection (such as lateral, anterior/posterior, or posterior/anterior), the SID (distance between the x-ray tube and film), total fluoroscopy time, and the approximate size of the patient (body diameter). While an individualized dose assessment requires this specific information, you can get an idea of the magnitude of doses to various organs from the typical doses shown below for some of the exams you listed: Skull Examination: Thyroid dose = 222 mrad Active bone marrow dose = 31 mrad Lung dose = 2.0 mrad Testes dose = <0.01 mrad Upper GI Examination: Thyroid dose =7 mrad Active bone marrow dose =117 mrad Lung dose =532 mrad Testes dose =0.4 mrad Lumbosacaral Spine Examination: Thyroid dose =0.05 mrad Active bone marrow dose =224 mrad Lung dose =35 mrad Testes dose =43 mrad Doses for the individual organs are taken from >CRC Handbook of Radiation Doses in Nuclear Medicine and Diagnostic X-Ray by J.G. Kereiakes, and M. Rosenstein (Boca Raton, FL: CRC Press, Inc.; 1980). The risk from a diagnostic x-ray procedure will depend upon the body part of concern and the dose delivered to that part of the body from the particular procedure. For example, if you are concerned about gonadal dose, the risk would be minimal for the skull and sinus x rays on your list. However, the risk would be higher for the lower spine x rays on your list. If you are concerned about thyroid dose, the skull exam on your list (particularly an anterior/posterior projection) would be the biggest contributor. Keep in mind that the generalized risks from medical exposures are much lower than the individual benefits gained by using such radiation. A reference you may find useful is Radiation Risks in Medical Imaging by Joseph Whalen and Stephen Balter (Chicago, IL: Year Book Medical Publishers, Inc.; 1984). Carmine Plott, Ph.D., CHP