Presentation on theme: "Everything You Need to Know About Radiation Protection"— Presentation transcript:
1 Everything You Need to Know About Radiation Protection Kelli Haynes, MSRS, RT(R)Program Director &Associate Professor
2 Radiation Protection45 questions of the 200 will be radiation protection (22.5%)10 -Biological Aspects of Radiation15-Minimizing Patient Exposure11-Personnel Protection9-Radiation Exposure and Monitoring
4 Cell Radiosensitivity Cells and tissues vary intheir degree of radiosensitivityImmature cells are nonspecialized- rapid cell divisionMature cells are specialized-divide slower if at allDNA-most radiosensitive part of cell1. When radiation damage appears at the whole body level, this is a result of damage to organ systems, which are a consequence of radiation damage to cells of that particular system.2. Cells and tissues vary in their degree of radiosensitivity3. Immature cells are nonspecialized- rapid cell division4. Significantly more radiosensitive than mature cells.5. Mature cells are specialized-divide slower if at all6. DNA-most radiosensitive part of cell
7 Dose Response Relationships Graphic representation of the relationship between the amount of radiation absorbed (dose) and the amount of damage (response)Linear or nonlinearThreshold or nonthresholdGraphic representation of the relationship between the amount of radiation absorbed (dose) and the amount of damage (response) seenBiologic data on humans are available only at doses greater than about 1 Gray. No biologic effects have been observed at doses of a few milligray, which is the dose level usually encountered in diagnostic radiology.3. Classified as Linear or nonlinear4. Threshold or nonthreshold5. Generally, as dose increases, so does the response, but that response may or may not be a straight line and there may be some doses below which no response is seen.6. Linear-there is a proportional relationship between dose and response-a straight line in the graph7. Nonlinear-there is no fixed proportional response between dose and response-curved line8. Threshold-the point a which a response first occurs-below this there is a negligible chance of damage9. Nonthreshold-even the smallest dose can have an effect.
8 Threshold Linear Linear NonThreshold Dose Dose Response Response Ionizing radiation is considered to follow the Linear non-threshold graph, which implies that thebiologic response to ionizing radiation is directly proportional to the doseThe Linear non-threshold curve is used to estimate radiation effects in the diagnostic energy range.The Linear threshold curve means a certain dose is required before a response is seen.ResponseResponse
9 NonLinear Threshold NonLinear Nonthreshold Dose Dose Response Response 1. Nonlinear threshold curve of radiation dose-response relationship is generally employed in radiation therapy to demonstrate high-dose cellular response2. In Nonlinear curves the dose and the response are not directly proportional.ResponseResponse
10 Relative Tissue Radiosensitivities LETRBEOER1. The characteristics of radiation such as charge, mass and energy vary among the different types of radiation.These characteristics can affect the amount of biologic damage and determine the extent to which different radiation modalities transfer energy into biologic tissue.To understand the way ionizing radiation causes injury in biologic tissue, 3 concepts must be studied;Linear energy transfer (LET), Relative biologic effectiveness (RBE) and Oxygen enhancement ratio (OER)
11 Linear Energy Transfer (LET) Photons deposit or transfer energy as they travelThe average energy deposited per unit of path lengthAssesses potential tissue and organ damageThe ability of ionizing radiation to cause biological damage can be determined by a physical factor known as Linear Energy Transfer.Remember that the electrons ejected as a result of photoelectric absorption and Compton scattering move through tissue and deposit, or transfer, energy through ionizations.The rate at which an electron transfers energy to the surrounding tissue is referred to as LET.The average energy deposited per unit of path length can be measuredAssesses potential tissue and organ damage from exposure to ionizing radiation.As the LET of the radiation increases, the biological response increases because more ionizations are created along the path of travel of the electron.
12 LET High-LET Radiation Alpha particles Beta particles Low-LET RadiationGamma raysX-raysDifferent types of radiation have different LET values.As high LET radiation passes through tissue, it deposits large amounts of energy in a short distance.So, high LET has a greater biologic effect but very little penetrating ability because it loses all its energy in a short distance. Alpha and Beta particlesLow-LET Radiation-is very penetrating because it spreads its energy over large distances. There is little chance that a low LET radiation will deposit more than one ionization in any one cell.Current theories suggest that 2 or 3 ionizations in a cell nucleus are required to produce a biologic effect. Because the ionizations from low LET are spread over many cells, this radiation does not usually cause significant damage in any one cell. Gamma rays and X-raysImage: Comparison of high LET and low LET ionization tracks.
13 Relative Biologic Effectiveness Measures biologic effectiveness of radiations having different LET’sInfluenced by radiation type, cell or tissue type, physiologic condition, and biologic result1. Measures biologic effectiveness of radiations having different LET’s2. Defined because identical doses of radiations with different LETs cause different amounts of damage3. Influenced by radiation type, cell or tissue type, physiologic condition, and biologic result4. RBE is the ratio of a dose of test radiation to a standard dose of 250 keV x-ray which produces the same biologic response.5. The constant is the biologic response, not the radiation dose.
14 Oxygen Enhancement Ratio Response to radiation is greater when irradiated in the oxygenated stateRadiation dose required to cause response w/o O2OER= Radiation dose required to cause response w/ O2Oxygen enhances the effects of ionizing radiation on biologic tissue by increasing tissue radiosensitivity.If oxygen is present when a tissue is irradiated, more free radicals are formed in the tissue. This increases the indirect damage potential of the radiation. Free radicals have the ability to attack and damage organic molecules.During diagnostic imaging procedures, fully oxygenated human tissues are exposed to xrays. However, because these procedures are at low doses of radiation, very few cells are killed.The effect of oxygen is measured by the Oxygen Enhancement Ratio, which is the ratio of the radiation dose required to cause a particular biologic response of cells in an oxygen deprived environment to the radiation dose required to cause an identical response under normal oxygenated conditions.This is important in radiation therapy because some cancerous tumors have hypoxic cells.
15 Cell Survival and Recovery LD 50/30Adults-3-4 Gy ( rad)Recovery may occurThe number of cells that survive after being exposed to radiation depends on the radiation dose.2. LD 50/303. Whole body dose of radiation that can be lethal to 50% of the exposed population within 30 days4. Adults-3-4 Gy ( rad) w/o treatment5. With medical support humans have tolerated doses as high as 8.5 Gy (850 rad)6. Because cells contain a repair mechanism, repair and recovery may occur when cells are exposed to sublethal doses of ionizing radiation.7. After irradiation, surviving cells begin to repopulate . This permits an organ to regain some of its functional ability.8. However, the amount of damage sustained determines the organ’s potential for recovery.
16 Somatic EffectsBiologic damage sustained by living organisms as a consequence of exposure to ionizing radiationClassified as either early (acute) or late1. Biologic damage sustained by living organisms as a consequence of exposure to ionizing radiation2. Classified as either early (acute) or late3. Early somatic effects are effects of ionizing radiation that appear within minutes, hours, days, or weeks of the time of exposure.4. Examples would be erythema (redness of skin), epilation (hair loss), or desquamation (shedding the outer layer of skin).5. Late somatic effects are nongenetic effects that appear after a period of months, or years following exposure. May als result from previous whole-body exposure or the product of doses sustained over several years.
17 Short-term vs. Long-term NauseaFatigueRedness of skinLoss of hairIntestinal disordersFeverBlood disordersShedding skinCancerEmbryologic effects (birth defects)Formation of cataracts
18 Carcinogenesis The production or origin of cancer Experiments have shown that radiation induces cancer1. The production or origin of cancer2. Cancer is the most important late somatic effect3. Experiments have shown that radiation induces cancer4. The severity of the disease is not dose related.
19 Cataractogenesis Cataracts-opacity of the eye lens 2 Gy results in partial or complete vision lossThreshold, nonlineardose-responserelationship1. Cataractogenesis is the production or origin of cataracts.2. Cataracts-opacity of the eye lens3. There is a high probability that a single dose of radiation of about 2 gray will induce the formation of cataracts.4. A dose of 2 Gy results in a partial or complete loss of vision5. Radiation-induced cataracts in humans follows a threshold, nonlinear dose-response relationship
20 Sterility Female sterility based on age of the subject-more radiosensitivewhen youngerTemporary sterility-2 Gray (200rad)Permanent sterility-5 Gray (50 rad)Human reproductive cells (germ cells) are relatively radiosensitive.2. Female sterility based on age of the subject-more radiosensitive when younger3. Females and males-Temporary sterility-2 Gray (200rad); can last as long as 12 months4. Permanent sterility-5 Gray (50 rad)
22 Hematopoietic Syndrome Whole-body doses ranging from 1 to 10 Gy (100 to 1000 rad)Reduction of blood cells in circulation results in a loss of the body’s ability to clot blood and fight infection1. Aka Bone Marrow Syndrome2. The hematopoietic system manufactures the corpuscular elements of the blood and is the most radiosensitive vital organ system.3. Whole-body doses ranging from 1 to 10 Gy (100 to 1000 rad)4. Reduction of blood cells in circulation results in a loss of the body’s ability to clot blood and fight infection5. Survival time decreases as the dose increases. Death is a consequence of bone marrow destruction.
23 Gastrointestinal Syndrome Appears at a threshold dose of approx. 6 Gy (600 rad) and peaks after a dose of 10 Gy (1000 rad)Without treatment, a dose of 6-10 Gy may cause death in 3-10 days1. Appears at a threshold dose of approx. 6 Gy (600 rad) and peaks after a dose of 10 GyIn the GI tract, the small intestine is the most affected part.3. Without treatment, a dose of 6-10 Gy may cause death in 3-10 days4. With treatment, die anyway.
24 Cerebrovascular Syndrome Doses of 50 Gray(5000rad)Death within 2 hoursor up to 2 days1. Results from CNS and cardiovascular systems receiving doses of 50 Gray (5000rad)2. Death within 2 hours or up to 2 days3. The final result of damage is failure of the CNS and cardiovascular systems.
25 Embryonic and Fetal Risks Fetus is very sensitiveFetal radiosensitivitydecreases as gestationprogressesThe fetus is very sensitive to radiation because it is made up of rapidly dividing cells.2. The fetus is most sensitive to radiation during the first trimester of pregnancy.3. Fetal radiosensitivity decreases as gestation progresses.4. There appears to be a threshold of about 0.1 Gy or 10 rad for fetal damage. Routine diagnostic procedures never reach this level.
26 Genetic Effects GSD-used to assess the impact of gonadal dose Dose equivalent to thereproductive organsthat would bring geneticinjury to the total populationBiologic effects of ionizing radiation on future generations.2. Genetically Significant Dose-used to assess the impact of a gonadal dose. Germ cells are radiosensitive because they are immature genetic cells.3. Genetically Significant Dose is the dose equivalent to the reproductive organs that, if received by every human, would be expected to bring about gross genetic injury to the total population.4. Effects occur as a result of damage to the DNA in the sperm or ova of an adult.
28 Coherent Scattering Photon of low energy interacts with atom. No net energy has been absorbed by the atom.Low-energy photons,1-50 kVpContributes to fogA photon of low energy interacts with an atom.Because the wavelengths of both incident and scattered waves are the same, no net energy has been absorbed by the atom.The atom absorbs the photon and becomes excited.Atom gives off photon with the same wavelength and energy.Low energy x-rays, 1-50 kVp5. X-ray loses no energy, only changes directionContributes to fog in the form of scatter.The least likely to affect body tissue.
29 Compton Scattering Moderate energy x-rays, 60-90 kVp Interaction with outer shell electronElectron ejected, Atom is ionizedPhoton loses energy and recombines with an atomFog and ScatterVery important in diagnostic radiology.Responsible for most of the scatter produced, side scatter, small angle, or backscatter.3. Moderate energy x-rays, kVp4. An incoming xray photon interacts with a loosely bound outer shell electron of an atom of the irradiated object.5. The freed electron has kinetic energy and can ionize atoms.6. Photon changes direction, loses energy, and recombines with an atom that needs another electron.7. The xray photon that surrendered some of its energy continues on its way but in a new direction.8. It can also emerge from the patient and contribute to fog on the film and/or dose to the technologist.8. Major source of fog on film, patient dose and technologist dose.9. *Source of Most Occupational Exposure*
30 Compton ScatteringPIC 1: Compton scattering is responsible for most of the scattered radiation produces during a radiologic procedure.1. PIC 2: Compton scattering results in all-directional scatter.The scatter created may be directed onward as small-angle scatter, backward as backscatter, and to the side as sidescatter.The intensity of radiation scatter in various directions is a major factor in planning protection for medical imaging personnel during a radiologic examination.FIGURE 2-6 Compton scattering is responsible for most of the scattered radiation produced during a radiologic procedure. (From Radiobiology and radiation protection: Mosby’s radiographic instructional series, St. Louis, 1999, Mosby.)
31 Photoelectric Absorption Most important interaction between x-ray photons and the atoms of the pt’s body for producing useful imagesHigher energy x-rays ( kVp), more likely to penetrate & not interactInteraction b/t photon and inner shell electronX-ray is absorbedElectron ejected
32 Attenuation Process that decreases the intensity of the beam Refers to both absorption and scatter processesThickness of body part (mass density)Type of tissue (atomic number)Attenuation is any process that decreases the intensity of the primary beam that was directed toward a destination.It refers to both absorption and scatter processes that prevent photons from reaching the predefined destination.Attenuation is influenced by mass density and atomic number.A density increase leads to a corresponding increase in absorption.In any given sample of biologic material, both density and atomic number play a role in determining attenuation.For example, if radiography is performed on an equal thickness of bone and soft tissue, the bone, which is approximately twice as dense as the soft tissue, will absorb about nine times as many photons in the diagnostic energy range as will the soft tissue.This is because bone has a higher atomic number than soft tissue.
34 Exposure Factors kVp mAs 1. Selection of appropriate technical factors for each x-ray exam is essential to ensure a diagnostic image with minimal patient dose.2. The technique chosen must:1. Ensure sufficient penetration of the area of clinical interest2. Provide adequate radiographic density (exposure)3. Provide an adequate amount of radiographic contrast between adjacent tissue densities3. Selection of the highest possible kVp consistent with image quality is the best method of using exposure factors to reduce patient dose.4. As we know, kVp controls contrast.5. As we also know, mAs controls density. When mAs is decreased, pt dose is decreased.7. Optimal kVp and lowest mAs should be used to decrease patient dose.
35 Shielding Protects gonads when w/i 5 cm of collimated beam Females receivemore exposure dueto locationof organsThe rationale for shielding is that is decreases the dose to the reproductive organs. In males it is 90-95% and in females it is about 50%.2. Protects gonads when within 5 cm of collimated beam3. Females receive more radiation due to the location of the reproductive organs; 3 times more on a pelvisShould be used on individuals with reasonable reproductive potentialIt is Not used when it compromises the examination
36 Types of Shields Flat contact shields Shadow shields Shaped contact shieldsClear leadFlat contact shields-made of lead strips or lead-impregnated materials. These may be placed directly over the patients reproductive organs.Shadow shields-made of radiopaque material. Suspended above area of interest and cast a shadow in the primary beam over the patients reproductive organs. -must be accurately positioned. Good for sterile fields, such as surgery.Shaped contact shields-contoured to enclose male reproductive organsClear lead gonad and breast shields-made of transparent lead-plastic material impregnated with approximately 30% lead by weight.
37 Beam Restriction Purpose-confine useful beam Reduce scatter Types ConesCollimatorsThe purpose of beam restriction is to confine the useful beam before it enters the area of clinical interest, thereby limiting the quantity of body tissue irradiated.And to Reduce the amount of scatter radiation in tissue, preventing unnecessary exposure to tissues not under examination3. Lets look at some different types of beam restriction.
38 CollimatorsThe most versatile device for defining the size and shape of the radiographic beam.Consists of two sets of adjustable lead shutters mounted within the device at different levels, a light source to illuminate the x-ray field and a mirror to deflect the light beam toward the object to be radiographed.
39 Filtration Effect on skin and organ exposure Effect on beam energy Filtration is the process of eliminating undesirable low-energy x-ray photons by the insertion of absorbing materials into the primary beam. It is sometimes called hardening the beam because it removes the low-energy (soft) photons. The primary reason for filtration is the elimination of photons that would cause increased dose to the patient but wouldn’t do anything to enhance the image.2. Effect on skin and organ exposure-reduces exposure by absorbing most of the lower-energy photons. So it Decreases patient skin dose3. Effect on beam energy- increases the energy or quality of the beam. So it Decreases the overall intensity (quantity or amount) of radiation
40 NCRP Report #102 The useful beam shall be limited to the smallest area practicable and consistentwith the objectives of theradiological or fluoroscopic examination.NCRP Report #102 concerns minimum filtration in useful beam.It states “The useful beam shall be limited to the smallest area practicable and consistent with the objectives of the radiological or fluoroscopic examination.”Above 70 kVp the minimum filtration should be 2.5 mm Al Eq.
41 Exposure Reduction Patient positioning AEC Patient Communication ALARA 1. A repeat radiograph refers to any radiograph that must be performed more than once because of human or mechanical error.2. This additional exposure increases patient dose. The patient receives a “double dose” whenever a repeat occurs. For this reason, repeat radiographs must be minimized.3. The radiographer must correctly position the patient and select the appropriate technical factors that will ensure the production of optimal images, on the first exposure.4. Errors related to the AEC are usually positioning errors, or selecting the wrong photocell.5. Radiographers often overlook the importance of gaining the trust and confidence of the patient. This is accomplished by a professional approach that includes technical competence, empathy for the patient and effective communication skills. When the pt has confidence in the radiographer, there is a high probability that instructions will be followed, which helps to reduce motion and degradation of positioning.
42 Image Receptors Film-screen systems Intensifying screens Digital Image receptorsCR and DRFilm speed1. Film-screen systems are the conventional image receptor. They utilize film and intensifying screens. The use of film-screen systems greatly reduces pt dose by reducing the quantity of x-ray photons needed to create an image.2. Intensifying screens convert x-ray photons to light photons, which expose the film within the cassette. Using screens decreases pt dose as opposed to non-screen procedures.3. Computed Radiography uses an Imaging plate with a Photostimulable phosphor4. Digital Radiography utilizes a matrix, pixels, direct and indirect conversion5. Film speed-using higher speed film results in a decrease in pt dose as opposed to slower speed film--Higher speed less patient dose7. Whenever the screen speed is increased, a significant reduction in mAs or kVp can be achieved while maintaining density.8. With digital image receptors, the speed of the system is selected based on the specific exam being performed and is not as closely linked to patient dose as film/screen receptors are. CR image receptors are generally considered to be about 200 speed, which is slower than basic film-screen which is usually about 400.8. DR is faster than 400, so it uses less technique.9. Technical factors control the exposure to the image receptor. The radiographer should select the kVp based on the desired contrast and adjust mAs to provide the appropriate total exposure to the receptor.
43 Image Receptors Digital CT, CR, DR, DF, NM, MR, & US Photons on a detectorElectronic imageMatrixPatient doseFilmIntensifying screens convert photons and expose filmAnalog imagePatient doseDigital vs. FilmDigital includes Computed tomography (CT), computed radiography (CR), Digital radiography (DR), Digital Fluoroscopy (DF), nuclear medicine imaging (NM), magnetic resonance imaging (MRI), and ultrasound (US)CR utilizes a photostimulable phosphor plateLatent image formed by x-ray photons on a radiation detector. Actually an electronic image.Numerical values of digital image are formed by a matrix.Although the radiographer can manipulate the CR image of the patient’s anatomy of interest to adjust image size, density, and contrast, this is NOT AN EXCUSE TO OVEREXPOSE THE PATIENTS!!!In film screen, the X-rays pass through the patient and forms an invisible or latent image on the film.Intensifying screens convert x-ray photons to light photons, which expose the film within the cassette.Film is chemically processed to make the unseen image visible.Finished radiograph is an “analog image”Patient dose is less than digital imaging
44 Grids As grid ratio increases patient dose increases Increases contrastAbsorbs Compton scatterImproves qualityIncreases patient dose1. Grid is a device made of parallel radiopaque lead strips alternated with low-attenuation strips of aluminum, plastic or wood.2. It is placed between the patient and the image receptor to remove scattered x-ray photons that emerge from the pt before they reach the film or other image receptor.Used when anatomic area is 10 cm or greater3. It is used to improve the contrast of the radiographic image.4. Absorbs Compton scatter5. Improves quality6. As grid ratio increases pt dose increases. Why? Because you have to increase mAs to compensate for the increased lead.
45 Fluoroscopy Pulsed or Intermittent Exposure factors Positioning time1. Fluoroscopic procedures produce the greatest patient radiation exposure rate in diagnostic radiology2. Fluoroscopy demonstrates dynamic, or active motion of selected anatomic structures3. If fluoro is necessary, every precaution should be taken to minimize patient exposure time4. Pulsed, or intermittent, fluoroscopy involves manual automatic periodic activation of the fluoroscopic tube rather than lengthy continuous activation. This significantly decrease patient dose.5. Exposure factors-The technologist must select technical factors that will minimize patient dose. Increases in kVp and filtration reduce pt exposure.6. A peak kVp of produces the correct level of image brightness. Lower kVp increases pt dose because a lesser penetrating x-ray beam necessitates the use of a higher mA to obtain adequate image brightness.7. Source to skin distance is not less than 15” for fixed equipment and not less than 12” for mobile fluoroscopes8. Cumulative timer must be provided and used with each fluoroscopic unit. Timer measures the x-ray beam-on time.9. An audible alarm interrupts the exposure after 5 minutes10. Time must be documented for every procedure
47 Sources of Radiation Exposure (3) Primary x-ray beamSecondary radiation1. Scatter2. LeakagePatient1. Primary x-ray beam-radiation that emerges directly from the x-ray tube collimator and moves without deflection toward a wall, door, viewing window, and so on.2. Secondary radiation-two kinds scatter and leakageScatter radiation results whenever a diagnostic x-ray beam passes through matter. It emerges from the patient and spreads in all directions.Leakage radiation is generated in the x-ray tube and does not exit from the collimator opening but penetrates through the protective tube housing and to some degree, through the sides of the collimator. Leakage radiation is always present in some amount.4. The patient is also a source of radiation exposure to the technologist. Radiographer should stand at 90 to patient when on portables if not able to get at least 6 ft away from the patient.
48 Basic Methods of Protection 1. The Cardinal Principles of Radiation Protection for the Radiographer. Time, Distance and Shielding2. Time: Amount of radiation received is directionally proportional to the length of time that the individual is exposed to ionizing radiation. As length of time increases…radiation dose received increases.3. Distance: The most effective means of protection from ionizing radiation for the radiographer4. Increased distance = decreased dose5. Moving further from the source significantly decreases the dose received. This is stated by theInverse square law-the intensity of radiation is inversely proportional to the square of the distance from the source6. When the distance from x-ray tube target is doubled the radiation intensity is decreased by a factor of 47. Shielding-Protective lead shielding should be worn whenever time and distance are not possible
49 Protective Devices Protective structural shielding Primary Barriers Secondary BarriersLead ShieldsProtective structural shieldingWalls and doors-Medical physicist will determine protection requirements needed for imaging facilitiesPrimary protective barriers-Protect against primary radiation. Prevent direct or unscattered radiation from reaching personnel and general public. Located perpendicular to the undeflected line of x-ray beamSecondary protective barriers-Protects against secondary radiation (leakage and scatter). Any wall or barrier never struck by the primary x-ray beam. Control booth.Clear lead plastic shieldsContain approximately 30% impregnated7 ft tallUsed when radiographer must remain in the room with patient
50 Protective Devices Aprons Gloves Thyroid shields Protective glasses NCRP #102 requires the lead equivalents for the following;Aprons should be .05mm lead equivalent for kvp up to 100Gloves, Thyroid shields, and Protective glasses should be .25mm lead equivalent.
51 Portable (mobile) units Lead apparelExposure cordStand at rightangles to thepatient1. Lead apparel should be worn-apron, gloves, thyroid shield2. Exposure cord allows radiographer to stand at least 6ft from beam3. Radiographer should stand at right angles to the patient; when the protection factors of distance and shielding have been accounted for, this is the place at which the least amount of scattered radiation received.4. This would be next to the patient’s side.5. In the image, where should you stand? Position A.
52 Fluoroscopy Protective curtain Bucky slot cover Cumulative timer 1. The exposure to personnel is caused by scatter from the patient. Therefore, the radiographer should stand as far as possible from the pt.2. Protective curtain-minimum of 0.25 mm lead equivalent4. Bucky slot cover-minimum of 0.25 mm lead equivalent must automatically cover the bucky slot opening in the side of the x-ray table during a standard fluoroscopic exam when the bucky tray is positioned at the foot end of the table. Protects radiologist and radiographer at the gonadal level.5. Cumulative timer-on the control panel. Sounds at 5 minute intervals.
53 Fluoroscopy Exposure Rates Exposure Switch Guidelines NCRP Report #102Fluoroscopy Exposure RatesGeneral Purpose: 10 R per minuteNon-image Intensified: 5 R per minuteHigh Level Control: 20 R per minuteExposure Switch GuidelinesSwitch must be of the dead-man type
55 Units of MeasurementSI stands for International System of Measurements
56 DosimetersThe personnel dosimeter provides an indication of the working habits and working conditions of diagnostic imaging personnel.The monitoring device records only the exposure received in the area where it is worn.Should be worn at the collar to approximate radiation dose to the thyroid, head and neck. When wearing an apron, the dosimeter should be worn outside the apron.There are 4 different kinds of personnel dosimeters, lets look at each one.
57 Film Badge Economical Parts Monitors x and gamma rays Temperature and humidity can cause fogRecord whole-body radiation exposure accumulated at a low rate over a long period of time.Made of 3 parts- a film holder, metal filters and a film packet.3. Monitors x and gamma rays4. Economical, however, Temperature and humidity can cause fog
58 Pocket Ionization Chambers Most sensitiveMust be charged to zeroAccurate from0-200 mRMost sensitive but rarely used, due to expense and inconvenience of reading daily.Contains a small ionization chamber that measures exposureCompact and easy to carry.4. Must be charged to zero and read daily5. Provides immediate reading6. Accurate from mR
59 OSL Dosimeter Aluminum oxide detector Optically stimulated luminosity occurs when struck by laser lightAccurate reading as low as 1mrem1. Optically stimulated luminescence2. When laser light is incident upon the sensing material, it becomes luminescent in proportion to the amount of radiation exposure received.3. Aluminum oxide detector4. Optically stimulated luminosity occurs when struck by laser light5. Accurate reading as low as 1mrem
60 TLD’s Look similar to film badge Lithium fluoride Ionization causes crystal to changeThermoluminescent DosimeterContains a crystalline form of lithium fluorideRadiation causes the lithium fluoride crystals to undergo changes in some of their physical properties.Very accurateCan be worn for extended and the crystal can be reused.
61 NCRP #116 Annual occupational effective dose- 50 mSv (5rem) Public Exposure- 1 mSvEmbryo/fetus exposure-50 mSv/monthDosimetry records1. Annual occupational effective dose- 50 mSv (5rem)2. Public Exposure- 1 mSv/year3. Embryo/fetus exposure-50 mSv/month4. Dosimetry records-Monitors should be worn at the same place each day for a consistent report. RSO is responsible for reviewing these reports and making sure the staff is educated and monitored.
62 NCRP #160Typical effective dose per exam; varies from 0.1 mSv for a chest xray to 1.5 for a lumbar spineInterventional- ~3mSvCT- range from 2mSv for a head to 10 mSv for a spineThe ARRT wants us to be aware of the dose the patient receives.The Typical effective dose per exam for radiography varies from 0.1 mSv for a chest xray to 1.5 for a lumbar spine.Comparison of typical doses by modalityInterventional- ~3mSvCT- range from 2mSv for a head to 10 mSv for a spine
63 www.ARRT.org email@example.com That’s All Folks! Outline can be found at the ARRT website under Content SpecificationsCan contact me.
64 Review Questions What is the most radiosensitive part of the cell? Which is more radiosensitive, immature or mature cells?What is the most radiosensitive part of the cell? DNAWhich is more radiosensitive, immature or mature cells? Immature
65 This is a picture of what? This is a picture of what? Dose Response relationship
66 Review Questions What is LET? What is LD 50/30? What is an example of an early somatic effect?Late somatic effect?What is carcinogenesis?What is LET? Linear Energy Transfer-the average energy deposited per unit of path lengthWhat is LD 50/30? Whole body dose of radiation that can be lethal to 50% of the exposed population within 30 daysWhat is an example of an early somatic effect? Erythema (redness of skin), epilation (hair loss), desquamation (shedding of outer layer of skin)Late somatic effect? Cancer, birth defects, cataractsWhat is carcinogenesis? Production or origin of cancer
67 Review Questions What is the threshold dose for cataracts? What is the threshold dose for temporary sterility?What is the threshold dose for permanent sterility?What is the threshold dose for cerebrovascular syndrome?What is the threshold dose for cataracts? 2 GrayWhat is the threshold dose for temporary sterility? 2 GrayWhat is the threshold dose for permanent sterility? 5 GrayWhat is the threshold dose for cerebrovascular syndrome? 50 Gray
68 Review QuestionsWhat is the threshold dose for hematopoietic syndrome?What is the threshold dose for gastrointestinal syndrome?What are some types of shields?What is filtration?What does NCRP Report # 102 state?What is the threshold dose for hematopoietic syndrome? 1 to 10 GrayWhat is the threshold dose for gastrointestinal syndrome? 6 GrayWhat are some types of shields? Flat contact, shadow, shaped contact, clear leadWhat is filtration? Filtration is the process of eliminating undesirable low-energy x-ray photons by the insertion of absorbing materials into the primary beam.What does NCRP Report # 102 state? “The useful beam shall be limited to the smallest area practicable and consistent with the objectives of the radiological or fluoroscopic examination.”
69 Review Questions Why do we use a grid? What are the 3 sources of radiation exposure?What is the SI unit of measurement for exposure?What is the SI unit of measurement for absorbed dose?Why do we use a grid? It is placed between the patient and the image receptor to remove scattered x-ray photons that emerge from the pt before they reach the film or other image receptor. To improve the contrast of the radiographic image.What are the 3 sources of radiation exposure? Primary, secondary (scatter and leakage), and patientWhat is the SI unit of measurement for exposure? SI coulomb/Kg; Traditional-roentgenWhat is the SI unit of measurement for absorbed dose? SI gray; traditional-rad
70 Review QuestionsWhat is the traditional unit of measurement for dose equivalent?What is the sensing material in an OSL dosimeter?What is the sensing material in a TLD dosimeter?What does NCRP # 116 state?What is the traditional unit of measurement for dose equivalent? SI sievert; Traditional-remWhat is the sensing material in an OSL dosimeter? Aluminum oxideWhat is the sensing material in a TLD dosimeter? Lithium fluorideWhat does NCRP # 116 state? Annual occupational effective dose- 50 mSv (5rem)2. Public Exposure- 1 mSv/year 3. Embryo/fetus exposure-50 mSv/month4. ALARA-all exams should be performed with the ALARA principle in mind.5. Dosimetry records-Monitors should be worn at the same place each day for a consistent report. RSO is responsible for reviewing these reports and making sure the staff is educated and monitored.