Introduction to Radiography & Medical Imaging PDF

Introduction to Radiography & Medical Imaging 7-Basics of radiation protection Slide 1 fchs.ac.ae Basics of radiation protection ALARA Philosophy As-Low-As-Reasonably-Achievable (ALARA) philosophy it is prudent to minimize radiation exposure whenever possible There are three basic protection methods...

Introduction to Radiography & Medical Imaging 7-Basics of radiation protection Slide 1 fchs.ac.ae Basics of radiation protection ALARA Philosophy As-Low-As-Reasonably-Achievable (ALARA) philosophy it is prudent to minimize radiation exposure whenever possible There are three basic protection methods for external sources of radiation: Minimizing exposure time, maximizing distance from the X-ray tube, and the utilization of shielding fchs.ac.ae Minimizing Exposure Time Radiation exposure during fluoroscopy is directly proportional to the length of time the unit is activated Maximize Distance A small increase in the radiation source distance from the patient can significantly reduce the patient exposure dose fchs.ac.ae Inverse square law (Inverse square law) This relationship indicates that doubling the distance from a radiation source decreases the radiation level by a factor of four (I1/I2)2 = d2/d1 (I: Intensity, d: Distance) Meter Distance: The amount of X-rays per unit area is 1/4 the original. The resulting radiation exposure is ¼ less. Please watch the video: Inverse Square Law Slide 4 fchs.ac.ae Use of Radiation Shields Use of radiation shielding is highly effective in intercepting and reducing exposure from scattered radiation. The operator can realize radiation exposure reductions of more than 80-90 percent through the correct use of any of the following shielding options. fchs.ac.ae Benefit of Hanging Shield fchs.ac.ae Use of Personal Protective Equipment Typically at least a 80% reduction in radiation exposure is obtained by wearing a lead apron fchs.ac.ae Thyroid shields provide similar levels of protection to the individual’s neck region Optically clear lead glasses are available that can reduce the operator's eye exposure by 85-90% The latex leaded gloves provide extremely limited protection. Standard (0.5 mm lead equivalent) leaded gloves provide useful protection to the user’s hands fchs.ac.ae Collimate the Primary Beam Collimating the primary beam to view only tissue regions of interest reduces unnecessary tissue exposure and improves the patient’s overall benefit-to-risk ratio fchs.ac.ae Radiation Monitoring-Dosimeter Badges Monitoring of personnel exposed to radiation is performed using a radiation dosimeter or "badge to Monitor the level of occupational exposure fchs.ac.ae fchs.ac.ae Radiation Risk From Diagnostic Imaging fchs.ac.ae Ionizing Radiation Radiation capable of producing ionization in tissues and which can be absorbed Continuously present in our environment – background radiation Average exposure 3-6.2 mSv/year in US, varies widely – Cosmic rays, radon, radiation from rock, natural radionuclides mSv: millisievert, unit for a measure of the absorption of radiation by the human body fchs.ac.ae Ionizing Radiation Used in diagnostic imaging – Radiography, fluoroscopy, angiography, nuclear medicine, CT scanning Medical radiation is the largest source of man-made radiation fchs.ac.ae Radiation from Diagnostic Imaging fchs.ac.ae Estimated Medical Radiation Doses for 5 Year-Old Child Effective Dose (mSV) Equivalent Number of CXRS 3-view ankle.0015 1/14th 2-view chest.02 1 Anteroposterior and lateral abdomen.05 2.5 Tc-99m2 radionuclide cystogram.18 9 Tc-99m radionuclide bone scan 6.2 310 FDG PET3 scan 15.3 765 Upper GI/small bowel follow through 1 50 Head CT 4 200 Chest CT 3 150 Abdomen CT 5 250 Imaging Area fchs.ac.ae Things We Know About Ionizing Radiation High dose radiation (> 100 mSv) is known to increase the risk of cancer Children are at higher risk than adults fchs.ac.ae Radiation Risk for Children Cancer risk increases with decreasing age The smaller the patient the higher the exposure from the same technique fchs.ac.ae What Should We Do? fchs.ac.ae Is it reasonable to believe that ionizing radiation from diagnostic imaging can increase cancer? What is the benefit that justifies this risk? fchs.ac.ae Benefit of Radiation Imaging fchs.ac.ae Risk of Surgery Large number of children undergoing general anesthesia 95% normal or mild systemic disease 1 in 30 risk of a “major event” 1 in 2500 risk of death fchs.ac.ae CT Alters Treatment Children with seizures Adults with stroke Blunt abdominal trauma Appendicitis Spine trauma Diffuse lung disease fchs.ac.ae Maximizing the Benefit/Risk Ratio Consider modalities that do not use ionizing radiation Optimize imaging protocols Decrease unnecessary examinations ALARA Image quality fchs.ac.ae Is Radiation Necessary? Magnetic resonance imaging Ultrasound Non-imaging evaluation Not doing a CT scan reduces the radiation by 100% fchs.ac.ae Maximizing the Benefit/Risk Ratio ALARA (As low as reasonably achievable) technique Designing imaging protocols to reduce radiation exposure Reducing unnecessary imaging fchs.ac.ae Summary Ionizing radiation from diagnostic imaging may cause a very small increase in the risk of cancer For an indicated Radiation Imaging, the likely benefit is far greater than the estimated risk Clinician, technologist and radiologists should work together to make the population exposure ALARA fchs.ac.ae