Biological response and radiation safety practices. X-ray interactions in the patient Radiation exposures Radiation measurement units Methods of detecting radiation Biological effects of radiation exposure Acute Radiation Syndrome Sub-syndromes- hemopoietic , GI, CNS Radiation Protection
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X-ray interactions in the patient Radiation exposures Radiation measurement units Methods of detecting radiation Biological effects of radiation exposure Acute Radiation Syndrome Sub-syndromes-hemopoietic, GI, CNS Radiation Protection ALARA Biological response and radiation safety practices
NCRP • R, roentgen, coulombs/kg • rad • rem • Gray • Sievert • Curie, Becquerel • Effective does • Quality factor • Threshold • ALARA • OSL • Film badge • TLD • Pocket dosimeter • Field survey instruments • Geiger-Müller counter • Cutie pie • Somatic effect • Genetic effect • Acute Radiation Syndrome(ARS) Terminology
Exposure Measurements Methods of Measuring • Units of measure • International units • British Units • Unit conversions • Film badge • OSL • TLD • Pocket dosimeter • Field Survey Instruments Radiation Exposure
Patient Interactions Classical (Coherent) Scattering • Excitation of the total complement of atomic electrons occurs as a result of interaction with the incident photon • No ionization takes place • Electrons in shells “vibrate” • Small heat is released • The photon is scattered in different directions • Energies below 10kV
Patient Interactions Compton scattering • COMPTON SCATTERING • Outer shell electron in body • Interacts with x-ray photon from the tube • 3. Moderate energy electron
Patient Interactions Photoelectric effect photoelectron Incoming photon interacts with inner shell electron. The “knocked-out” electron is called a photoelectron. The energy of the incoming photon is absorbed.
Patient Interactions Pair Production
Patient Interactions Photodisintegration
X-rays interact with Patient’s body to cause changes in cells. • Interaction in the body begin at the atomic level
No interaction: X-ray passes completely and get to image receptor Complete absorption: no x-rays get to image receptor Partial absorption with scatter-some x-rays get to image receptor but some get scattered Patient Interactions:Interactions of X-rays with matter
Patient Interactions X-ray photons can change cells
Radiation Exposures • To Keep Ourselves Safe: • Measure exposure • Determine levels at which damage occurs
Measuring Exposure • Units of Measure • International Units • C/kg3 • Gray • Sieverts • Becquerel • British Units • Roentgen • Rad • Rem • Curie
rads Grays Patient absorbed dose rems Sieverts Employee (technologists) = RADS REMS In diagnostic radiology: 1 roentgen = 1 rad = 1 rem
Comparison of Units In diagnostic radiology: 1 roentgen = 1 rad = 1 rem
Unit Conversions: A normal chest x-ray exposes the patient to approximately 15mR. How many roentgens is that? A CT examination results in a patient dose of 4000 mrad. How many gray is that? Annual exposure dose for a technologist is 5 rems. What is that in Sieverts? mSv? You Receive ~620 millirem per year. According to stats from the US Nuclear Regulatory Commission average yearly exposure is roughly 620 millirem--half of which comes from natural sources (cosmic radiation, from the soil, radon, etc) and half comes from manmade sources. Note that geography can play a big part in that. In Colorado, for example, natural radiation exposure can be 1000 mrem per year due to higher altitude. What is your exposure in mSv? What is your exposure in mSv if you live in Colorado? A patient left a head of lettuce in the x-ray exam room. The lettuce received a dose of 10mrad. How many Gr is that?
Permissible Occupational Dose Annual dose : • 5 Rem/year 50mSv/year • 5000mrem Cumulative Dose • 1 rem x age or 10mSv x age
PUBLIC EXPOSURENON MEDICAL EXPOSURE • 10 % of Occupational exposure • 0.5 rad or 500 mrad or 5mGray • Under age 18 and Students • 0.1 rem
Pregnancy & Embryo Mother occupationalworker • 5 rem Baby • .5 rem/ year • .05 rem/month
Exam 2 Next Week: ALARA- As Low As Reasonably Achievable