Rad T 110 Introduction to Radiation Protection and Interaction of X-ray and Matter Sherer Ch 1 and Ch 2

Biologic Effects All radiographic exposures cause biologic effects Consequently, risk versus benefit of receiving an exposure needs to be established This is not your job

ALARA As low as reasonably achievable This is the underlying tenet of modern radiography. The radiography equivalent of, first do no harm.’ Basically, use the lowest exposure possible that will produce a good film.

Patient Education Patients need to understand their exams so that they can actively and accurately participate in them. This is not the same as getting consent Prep, changing clothes, pre-medicating If patients are cooperating then you will have an easier encounter and fewer repeats.

BERT Background radiation equivalent time A great way of expressing exposure in a sensible way to the patient. Based on background exposure of 300 mRem annually.

Electromagnetic Radiation There are numerous types of electromagnetic radiation, i.e. microwaves, visible light, radiowaves, etc. We will focus primarily on x-rays. Due to their energy level, x-rays are a form of ionizing radiation. This is how they cause biologic effects. Not all electromagnetic radiation causes ionization; some forms cause excitation.

Particulate Radiation Nuclear decay can produce both electromagnetic (gamma rays) and particulate radiation. As a rule, particulate radiation is much more dangerous than electromagnetic radiation. Beta, electrons Alpha neutrons

Equivalent Dose This is a means of equalizing the effects of different types of radiation so that total dose can be accurately expressed.

Biologic Damage Photons ionize atoms Cellular damage Organic damage Genetic or somatic manifestations Genetic – your progeny Somatic – to you Can be early, late, or syndromes Organic damage

Sources of Radiation Natural Terrestrial Cosmic Internal Basically, these sources of radiation are unavoidable They combine to form what is referred to as background radiation. In the US background exposure is approximately 360 mRad annually.

From NCRP Report No. 160, “Ionizing Radiation Exposure of the Population of the United States” (2009)

From NCRP Report No. 160, “Ionizing Radiation Exposure of the Population of the United States” (2009)

Significance of X-ray Absorption X-rays are electromagnetic energy As such, they can deposit energy when they interact with tissue This is called absorption and results in the ionization of an atom. The amount of energy absorbed becomes the absorbed dose measured in Rads or Grays.

Primary Radiation Radiation produced in the tube and traveling in the primary beam; generally between the patient and the tube. The beam is polyenergetic( there are a multitude of energies represented in the beam NOT a single energy.)

Attenuation Occurs when the beam interacts with tissue Can occur thru absorption (photoelectric effect) and scatter (compton effect). Photons do three things in tissue Absorb Scatter Pass thru The primary beam after it interacts becomes the exit beam.

Probability of Interaction Absorption (Photoelectric effect) Depends on beam energy, tissue atomic number, thickness, density Scatter (Compton effect) Depends primarily on beam energy. Pair production and photodisintegration do not occur in the diagnostic energy range