MEDICAL IMAGING PRIMER - Home - CAR
MEDICAL IMAGING PRIMERWITH A FOCUS ON X-RAY USAGE AND SAFETY2013
MEDICAL IMAGING PRIMERWITH A FOCUS ON X-RAY USAGE AND SAFETYAuthors:JULIAN DOBRANOWSKI, MD, FRCPCa,bALYAA H. ELZIBAK, MScc,dALEXANDER DOBRANOWSKIeANTHONY FARFUSeCHRISTOPHER ASTILLeABIRAM NAIReANTHONY LEVINSONfYOGESH THAKUR, PhD, MCCPMgMICHAEL D. NOSEWORTHY, Ph.D., P.Eng.d,hThe CAR also gratefully acknowledgesthe external review contribution of:THOR BJARNASON, PhD, MCCPMiabDiagnostic Imaging, St. Joseph’s Healthcare, Hamilton, Ontario, Canada.Associate Clinical Professor, McMaster University, Hamilton, Ontario, Canada.Department of Medical Physics and Applied Radiation Sciences, McMaster University,Hamilton, Ontario, Canada.c deImaging Research Centre, St. Joseph’s Healthcare, Hamilton, Ontario, Canada.The University of Adelaide, MBBS Program - Adelaide, South Australia.John Evans Chair in Educational Research, Associate Professor, McMaster University,Hamilton, Ontario, Canada.f gDepartment of Radiology, Vancouver Coastal Health Authority, Vancouver, BC.Diagnostic Imaging Services, Interior Health Authority, Kelowna, BC Radiology,University of British Columbia, Vancouver, BC.h Radiation Safety and Quality Lead, Diagnostic Imaging Services, Interior HealthAuthority, Kelowna, BC.i
Table of ContentsIntroduction. 21.About Radiation. 33.Ionizing Radiation: Basic Concepts. 72.4.5.6.7.8.9.10.11.12.Radiation in Medical Imaging. 4Ionizing Radiation: Proper Protection.10Ionizing Radiation: The Pregnant Patient .12Alternative Non-Radiation Imaging Modalities.15Ionizing Radiation (X-Rays, γ-Rays) and the Learner – Important Facts.16General Information About Radiation Dose and the Equipment.17X-Ray Protective Measures Implemented by the Radiology Department.17Evidence-Based Approach To Ordering X-Rays.18Appendix 1: Case Scenarios For Evidence-Based Radiology.19Appendix 2: Test of Important Concepts.22References .241
INTRODUCTIONPREFACEOBJECTIVES & AIMSThe aim of this primer is to provide a concentrated andfocused information package as a quick reference guidefor students, pertaining to diagnostic radiation usage andsafety, with a focus on modalities that involve the use ofx-rays. Medical schools throughout the world emphasizeradiological examination interpretation, but through ourcombined experience, we have concluded that little istaught on the science behind these examinations and thepotential harm of exposure to radiation of certain energy.This primer gives a brief overview of ionizing radiation,the dosage associated with various radiological examinations,the precautions that need to be taken with a pregnantpatient and the techniques of basic protection fromradiation exposure as a physician, student or resident.We hope that through this primer, an important gap ofknowledge will be filled that will ultimately result inbetter decisions, with safer patient outcomes. To know how x-rays are formed and the varioussources of ionizing radiation2 To know the biological effects of ionizing radiation To know how to protect oneself when working in areasthat have sources of ionizing radiation To know the management options for pregnant patientsrequiring medical imaging To know the management options for a patient who hashad a medical x-ray examination and was subsequentlyfound to be pregnant To recognize unresolved clinical and scientific questions related to medical imaging To communicate with patients and their families aboutthe risks and benefits of medical imaging
1. ABOUT RADIATIONHumans are constantly being exposed to natural sourcesof radiation, including rays that reach us from outer spaceand rays from the sun. In addition, some foods that weingest contain naturally-occurring radioactive isotopes,such as potassium and carbon. The environment that welive in may also contribute to our exposure to radiation,such as of inhaled radon gas. Not only are we exposedto natural sources of radiation, but manmade sources,including medical equipment, also contribute to ourradiation dose.The radiation that we are exposed to can be ionizing ornon-ionizing, depending on whether or not the radiationhas enough energy to remove an electron from an atomwith which it interacts. Ionizing radiation, by definition,is any type of subatomic particle or high-energy photonthat causes the formation of ions (electrically-chargedatoms or molecules) when interacting with matter.These ions can lead to biologic damage in cells. Cosmicrays, neutrons, alpha particles, x-rays, ultraviolet raysof certain wavelength, and gamma rays are all forms ofionizing radiation. They contain enough energy perphoton to eject electrons from the atoms with which theyinteract. Visible light, infrared waves, most wavelengthsof ultraviolet rays and radiofrequency waves, on the otherhand, are non-ionizing.In order to image the body, various imaging modalitiesare available. Most of these require the use of radiationto obtain a clear de piction of the area being investigated.X-rays, gamma rays and radiofrequency waves are allforms of electromagnetic radiation that are commonlyused in imaging departments. These forms of radiation,and a collection of others (such as cosmic rays, ultraviolet rays, visible light, and infrared rays), all makeup what is known as the electromagnetic spectrum.Each of these types of electromagnetic radiation carriesa certain amount of energy with it. The higher thefrequency of the wave, the larger its associated energy.Thus, infrared, radiofrequency, and visible light haveless energy than x-rays, gamma rays and cosmic rays.Table 1 shows examples of ionizing and non-ionizingsources of radiation.TypeExamples where usedNon-Ionizing RadiationRadio WavesRadio StationInfrared WavesRemote ControlUltraviolet WavesBactericidal LampsMicrowavesRadio StationVisible LightX-raysGamma RaysLight BulbIonizing RadiationMedical X-raysPET ImagingTable 1: Ionizing and non-ionizing sources of radiation.3
2. RADIATION IN MEDICAL IMAGINGBoth ionizing and non-ionizing forms of radiation are usedin diagnostic imaging departments. Imaging techniquesthat involve x-rays (such as plain film radiography, digitalradiography, CT scans, mammography and fluoroscopy)all employ ionizing radiation. Nuclear medicine techniques(PET and SPECT imaging) also utilize ionizing radiation,in the form of gamma rays. MRI uses non-ionizingradiation (radiofrequency waves). Ultrasound usespressure waves (mechanical waves) to image the body.Note that these sound waves are only mentioned here forthe sake of presenting most of the modalities encounteredin an imaging department. They are not classified aselectromagnetic radiation.In all imaging techniques (excluding ultrasound, MRI andnuclear medicine) an external source generates photonsin the form of x-rays that become incident on the body.These x-rays are then absorbed or scattered (changetrajectory and diverge from the beam path) as a resultof interactions within the body. The beam that emergesafter passing through the patient is thus attenuated, orless intense (it has lost some of its photons as it passedthrough the area being imaged, as they were removedthrough scattering or absorption). This attenuatedbeam then reaches a detector and allows for thegeneration of images.In nuclear medicine, on the other hand, the radioactivesource is not external, but internal. The patient isadministered a radionuclide, typically through injectionor inhalation. Initially, the radionuclide (or source) isbound to a molecule that will be metabolized by the bodypart or pathological tissue being investigated (the target).The radionuclide is unstable and is constantly undergoingradioactive decay, releasing gamma radiation (gammarays, γ-rays). As this radionuclide pools in the target,gamma emission from the target will intensify. Anexternal detector measures gamma radiation, whichis used to produce the medical images.X-rays and γ-rays are defined by their origin in thenucleus. X-rays originate from outside the nucleus,while gamma rays originate from inside the nucleus ofa radioactive atom. The production of an x-ray beam ina clinical imaging system is performed by the x-ray tube.4Fig. 1a- A diagram of an x-ray tube. The glass that seals the inside of thetube produces a high vacuum. A large voltage is applied between thecathode and the anode (typically made of tungsten).Inside the x-ray tube, an electron beam isgenerated by liberating electrons from the filament viathermionic emission (heating of the filament). Electronswithin the beam are accelerated towards the anode(usually made of tungsten, molybdenum or rhodium)via tube potential or the tube anode. Once these electronsreach the target, the result of the interaction is a transferof the electron’s kinetic energy (through the accelerationinside the tube caused by the tube potential, or kVp)into heat and x-ray photons (1).The continuous x-ray spectrum that is produced by a beam ofelectrons is referred to as bremsstrahlung (braking) radiation.Fig. 1b- Production of continuous x-rays from an x-ray tube. Heating of afilament liberates electrons that are then accelerated towards the anode.The abrupt stopping of electrons results in the production of x-rays.
beta decay, electron capture and alpha decay. A fulldescription of the transformations is beyond the scopeof this primer and interested readers are encouraged toread any nuclear medicine textbook (2).Fig. 2- Generation of bremsstrahlung or “braking radiation”. Whenthe incident beam of electrons is in the vicinity of the nucleus, itcan experience a sharp deflection that results in energy loss bythe emission of photons.If a sufficient tube voltage is applied, the incident electronsmay eject electrons from the target atom. Electrons fromhigher shells then fill the produced vacancy, resulting inthe emission of characteristic x-rays.Fig. 3a- When the incident beam of electrons has sufficient energy, it caneject electrons from the target (green arrow).Fig. 3b- The produced vacancy is then filled by electrons from highershells (orange arrow), resulting in the emission of characteristic x-rays.The origin of γ-rays is the nucleus of a radioactive atom.When the nucleus is radioactive, it is unstable and mustundergo a radioactive transformation to reach a stablestate. Radioactive transformations consist of beta- decay,When γ-rays are used in imaging, radiation is presentafter the medical procedure. This is because γ-rays areproduced through a radioactive transformation, thusthe source is constantly emitting radiation. The intensityof radiation emitted by the source is governed by thehalf-life. As a result, the patient remains radioactiveuntil the entire injected source has either passed fromthe body (excrement, urination and sweat) or enoughtime has elapsed such that the source has decayed tonatural background radiation levels. A patient exposedto x-rays, on the other hand, is not radioactive after theexamination because x-ray production is terminatedby the x-ray tube.In diagnostic x-ray imaging, images are formed by theinteraction of the x-ray beam, the patient and the detector.As the x-ray beam passes through the patient, the photonsinteract with the tissues of the body and are absorbedby the patient. The degree of absorption is related to thedensity of the material that is in the beam’s path. Denseobjects (such as bone and metal) have a high degree ofphoton absorption, while less dense objects (such as fatand water) absorb less photons. The differential absorptionof photons by different materials in the photons’ path resultsin the beam exiting the patient with different intensities.This is known as the transmittance beam. A detector isused to measure the intensity variation, thus providinginformation on the different densities in the beam’s path.In radiography, the transmittance beam is visualizedusing plain-film detector or with digital detectors. In plain-filmradiography, areas of high intensity (thus low materialabsorption) within the transmittance beam result in blackeningof the film, while areas of low intensity (thus high materialabsorption) will result in less blackening of the film. Thefilm will remain white in areas with no photons.Since the human body is made up of tissues with varyingdensities, the film that results when x-rays are used toimage the body is in grayscale, where black correspondsto tissues with little attenuation (such as air) and whitecorresponds to tissues with a high degree of attenuation(such as bone).5
The simple x-ray can be done in different orientations inorder to view different aspects of the patient’s anatomy. Theorientations most frequently used are the PA (poster o anterior,or back-to-front), AP (anteroposterior, or front-to-back)and lateral (side view). Note that instead of using photographic film, digital radiographs can be produced. Imageformation using digital detectors are beyond the scope ofthis primer and readers interested in this topic are referredto (1). Typical tube voltages range from 50-150 kVp.Mammography is used to identify any calcification (seenin some types of breast cancers), as well as any areas ofhypodensity or hyperdensity that can be seen in othercancers (1; 4). It is employed both as a screening tooland for diagnosis. Mammography also uses x-rays tovisualize the breast and detect any abnormalities inthis organ; however, there are fundamental differencesbetween a mammography system and a diagnostic x-raysystem. Due to the tissue characteristics of the breast andof pathology of interest, mammography systems utilizea lower tube potential than diagnostic x-ray systems(15-35 kVp vs. 50-150 kVp). In addition, two compressionplates are used to decrease breast thickness and minimizemotion, thus resulting in less scatter radiation and betteroverall image quality.Fluoroscopy is a real time x-ray examination, whichutilizes a series of low-dose x-rays obtained over time.It is useful for the assessment of the gastrointestinal tract,the urinary tract, and the musculoskeletal system.Angiography is a specialized fluoroscopic examinationin which a contrast agent is used to highlight vasculaturein the patient. Contrast is a radiopaque (high density)material injected into the blood vessels of the patient.Vessels containing contrast show up dark on the image,while areas without contrast show up bright. Advancedtechniques, such as Digital Subtraction Angiographyand Road-mapping can be utilized to improve vesselvisualization and also guide percutaneous tools.Computed tomography scans (or CT scan), in the simplestsense, utilize thousands of x-rays of the patient, taken atvarious angles around the patient. The most commonCT systems employ an x-ray tube and detector, whichsimultaneously revolve around a ‘slice’ of the patient,while taking x-rays. Through image processing, each6acquisition is used to reconstruct the slice of the patientimaged. This process is then repeated for different areasof the patient, thus resulting in a 2D stack of axial imagesof the patient. Advanced data acquisition techniques andcomputer processing can be employed to produce a varietyof images, including 3D perspectives. CT scanners that arein use today have more than a single row of detector arrays(multi-detector CT, MDCT). Thus, they can simultaneouslycollect more than a single slice. 16-slice and 64-slice MDCTscanners are commonly encountered in imaging departmentsand some institutions have 320-slice scanners (3). Inaddition to this simultaneous technique, helical CT imagingallows for the continuous movement of the CT table duringimaging. If multi-slice imaging is done in conjunction withhelical scanning, reductions in scan time are possible.In Positron Emission Tomography (PET), the radioactivedecay of the administered source (such as Fluorine-18)results in the emission of positrons (electrons that arepositively charged). This particle then annihilates with anearby electron and two gamma rays are emitted that are180 degrees apart. Thus, PET uses a ring of detectors thatsurround the patient to register the emitted photons. Oncephoton pairs have been detected, computers can reconstructan image of the distribution of the radioactive source.Since the source is internal, different tissue compartmentsand the locations of differing tracer (i.e. a pharmaceuticallabeled with a radioisotope) uptake are shown by areasof hyperdensity (hot spots, high uptake of the tracer) orhypodensity (cold spot, low uptake of the tracer) (1; 4).Single photon emission tomography (SPECT) is anothernuclear medicine procedure that is similar to PET imaging.It also requires the injection of a radioactive isotope (such asTechnetium-99m) that is usually attached to a pharmaceutical.However, unlike PET imaging, the radioisotope used inSPECT imaging emits a single γ-ray when it decays.Gamma cameras capture the emitted gamma rays andreconstruction of the resulting image can be done usingdifferent techniques, such as filtered back-projection.SPECT has many clinical applications, including cerebralblood flow imaging and myocardial imaging.
3. IONIZING RADIATION: BASIC CONCEPTS3.1 ACTION OF IONIZING RADIATIONRecall that gamma rays (used in nuclear medicine)and x-rays (used in CT, radiography, fluoroscopy andmammography) are both classified as ionizing radiation(see Section 1). When ionizing radiation interacts withmatter, it deposits some or all of its energy into thematerial, resulting in excitations, ionizations and heatingof the exposed area. Specifically speaking, the interactionof radiation results in the ejection of an electron from thetarget atom. If this electron then interacts with criticaltargets in the cell, such as DNA, and produces ionizations,the radiation is said to have a direct action. Alternatively,the ejected electron can interact with other molecules inthe cell (such as water, H2O) and produce free radicals(OH) that then travel to and interact with the criticaltarget; a process referred to as the indirect action ofradiation. Fig. 4 shows the two possible actions of radiation.Hydrogen bond disruptions, as well as single or doublestrand breaks, may result (1). Once these chemical changesare induced, the cell might respond by activating repairmechanisms and restoring the damage. However, if repairerrors occur, the cell might be eliminated through apoptosis(programmed cell death) or mitotic death (death duringthe next cell division cycle). If the repair errors occur andthe cell does not get removed, then a mutated cell results.When it comes to describing an organ system, if error-freerepair of cells takes place following radiation exposure,then no observable effects will be seen. No effects will alsobe observed if the unstable cells are eliminated, providedthat not many cells are killed. If a large dose is given andtoo many cells are killed, the organ might lose some of itsfunction. However, such high-focused doses are not typicalof medical imaging. Finally, if the mutated cells continue tosurvive, this may result in the formation of cancers orhereditary effects if the mutations occur in somatic orgerm cells, respectively (5). An organ’s response toradiation and its consequent ability to repair the damagecan depend on a number of factors, including the receiveddose, the rate at which the dose was received, the presenceof certain molecules after exposure to radiation, the typeof radiation used, the age of the exposed individual andthe location of the damage within DNA molecules.3.2 REGULATORY AGENCIES ANDRADIATION EFFECTSFig. 4- Action of ionizing radiation. When the radiation ejects an electron(grey in the figure), the electron may interact with water molecules andproduce free radicals (top part of the figure). These radicals can thenbecome incident onto the critical target. This action is referred to as theindirect action of radiation. In the direct action (bottom part of thefigure), the radiation ejects an electron that then interacts with thecritical target and produces biological damage.The action of radiation, whether direct or indirect, resultsin the diffusion of either free radicals or electrons, whichmay then become incident on the DNA in the cell anddamage it by altering its structure in numerous ways.Numerous advisory committees have been establishedto review current scientific findings and print reports toassess the effects of ionizing radiation. These include theInternational Commission on Radiological Protection(ICRP), the National Council on Radiation Protection andmeasurement (NCRP) and the committee on the BiologicalEffects of Ionizing Radiation (BEIR). The recommendationsof the ICRP form the basis for radiological protection inCanada and most countries (6).The ICRP classifies the biological effects of ionizingradiation into two categories: deterministic andstochastic (7). Deterministic effects are those whoseseverity increases with dose and they occur above acertain threshold. Examples of these effects are cataractsand erythema (skin reddening). Stochastic effects are7
those whose probability of occurrence increases withdose. Radiation-induced cancers and genetic effects fallin the stochastic category. The current consensus amongadvisory committees is that stochastic effects follow alinear, non-threshold model (7; 8), which implies that anydose of radiation, regardless of how small it may be, isbelieved to carry an associated risk. It should be notedhere that the use of the linear non-threshold model incancer risk estimates stems from extrapolation of risksfrom high dose and high dose rate exposures, wheremost of the data comes from the atomic bomb survivors.However, there is an ongoing debate regarding the trueeffect of ionizing radiation at low doses, such as thoseused in imaging procedures. Some researchers believein the existence of adaptive repair mechanisms basedon radiobiology studies. Due to the limited scientificknowledge regarding low dose exposures, most agenciesprescribe the ALARA principle (As Low as ReasonablyAchievable), simply put – since we don’t know the extentof damage caused by low levels of radiation, we shouldmitigate risk to future generations by using as lowradiation doses as possible. The reader is directed tothe following for further discussion of the effects of lowdoses of ionizing radiation (8; 9).When a patient is being imaged using ionizing radiation,the health effects that are of most concern are the stochasticeffects. Assuming a linear non-threshold model, anyprocedure that imparts a dose to the patient increases therisk of these effects. The deterministic effects, on the otherhand, are observed with large doses that are not typical ofthe majority of the imaging procedures. Recommendeddose limits have been set by the ICRP for radiation workersand for the public (see Section 4, Table 4). The ICRP doesnot put a limit on medical exposures of patients. It is left3.3 IONIZING RADIATION:QUANTIFICATION, EXPOSUREAND RISKA number of quantities are used to refer to the radiationdose. The term exposure describes the ions (i.e., chargedparticles) produced by a radiation field within a givenvolume of air. If two different materials are exposed to thesame radiation field, the amount of energy that they absorbwill not be the same. Although exposure describes theionization present, it does not explain how the body willrespond to that energy. The term absorbed dose, which ismeasured in Gy (where 1 Gy 1 joule/ kg) is the amountof energy absorbed per unit mass. If the same body part isexposed to two different types of ionizing radiation, thebiological damage produced will not be the same. In addition,the severity of the biological damage depends on the type ofradiation. To reflect the biological effects of radiation, the termeffective dose is used, which is measured in the unit referredto as the sievert (Sv). This is the best measurement whencomparing the radiobiological effects of different types ofmedical procedures (11). Non-SI (International System ofUnits) units and terms such as the rad (radiation absorbeddose), the roentgen and the rem also exist; however, theiruse is now discouraged (11). Readers who need to usethese units can find conversion factors and definitionsreadily available in any older medical physics textbook.Radiation SourceContribution to the Total Effective Dose (%)Natural Background50Consumer Products2Medical RadiationOther (Nuclear Power Plants/Fallout)8up to the physician to decide if the benefits of a medicalexam outweigh the risks from radiation, or whether toproceed with care without the diagnostic information.However, the ICRP emphasizes optimization of radiationprotection measures for procedures using ionizing radiation (10).48 0.1Table 2- The contribution of the common sources of radiation. Data from (13).
ProcedureEffective Radiation Dose(mSv)Natural BackgroundRadiation EquivalentBone Densitometry0.011 dayGalactography0.73 monthsIVP1.66 monthsX-ray (Lower GIT)416 monthsSinus0.62 monthsHead2Chest X-ray0.1Mammography0.7X-ray (Upper GIT)CT scans2Myelography4Cardiac CT for Calcium10 days3 months8 months16 months28 months520 monthsAbdomen103 yearsSpine10ColonographyChest8Body108 months3 years3 years3 yearsTable 3- Radiation dose for various procedures compared to background radiation. Data from (14;15).To put the doses received from medical procedures intoperspective, a reference to natural background radiation ishelpful. In everyday life, humans are exposed to a certainlevel of background radiation from natural sources suchas cosmic rays, atmospheric gas (radon) and the decayof radioisotopes of carbon and potassium present in thebody (see Section 1). The annual effective backgroundradiation dose in Canada is 1.77mSv (12). The naturalbackground dose around the world varies between1-10mSv, with an average effective annual dose of 2.4mSv(8). Besides natural background, the population is exposedto other sources of radiation. Table 2 gives a depiction ofthe sources to which humans are commonly exposed.When radiological procedures are carried out, certaindoses are received, depending on the type of exam and thearea being imaged. The radiation dose that is receivedfrom various imaging procedures is shown in Table 3,along with a comparison to the background radiation thatone would be exposed to from everyday living.Recommended dose limits have been set by the ICRP forradiation workers and for the public (see Section 4, Table 4).The ICRP does not put limits on the dose received by thepatient. Justification of a medical procedure that involvesthe use of ionizing radiation is left to the physician, whoshould weigh the benefits of the procedure against the risks.In addition, the ALARA principle must be adhered to, whereproper measures are taken to avoid unnecessary exposures.9
4. IONIZING RADIATION: PROPER PROTECTIONFor the purpose of radiation protection, recommendeddose limits have been established by the ICRP forradiation workers (individuals exposed to man-maderadiation due to their occupation) and for the remainderof the population. These dose limits are shown in Table 4.Note that these limits do not include doses obtained frommedical procedures or background radiation.As all radiological imaging that uses ionizing radiation iscurrently assumed to be associated with some level ofrisk, the protection of both the patient and staff needs tobe ensured. There are no current specific limits on thelevels of exposure from medical imaging. Accordingly,Type of LimitOccupational ExposurePublicWhole Body1 mSv/yearAnnual Dose in:20 mSv/yearaveraged over periods of 5 yearsLens of the Eye150 mSv15 mSvHands and Feet500 mSv-Skin10an assessment of the benefit of each exposure for thepatient must be weighed against the perceived risks. Inorder to achieve the maximum benefit for the patient, anypossible reduction in the total risk of the procedure mustbe actively pursued. However, a reduction in the risks of aprocedure may not necessarily equate to a reduction in theradiation dose to be received by the patient. For example,image clarity may be compromised in order to reduce theoverall dose of radiation to the patient. However, in somecases, reduction in image clarity would be of a greater risk(in misdiagnosis) to the patient than the potential risk ofradiation exposure.500 mSv50 mSvTable 4- Dose limits recommended by the ICRP for planned exposure situations (7).
There are three principles of radiation safety to reduceoccupational exposure and they are: time, distance andpersonal protective equipment (PPE). Time refers to theamount of time spent in the vicinity of radiatio
in diagnostic imaging departments. Imaging techniques that involve x-rays (such as plain film radiography, digital radiography, CT scans, mammography and fluoroscopy) all employ ionizing radiation. Nuclear medicine techniques (PET and SPECT imaging) also utilize ionizing radiation, in the form of gamma rays. MRI uses non-ionizing
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1. Medical imaging coordinate naming 2. X-ray medical imaging Projected X-ray imaging Computed tomography (CT) with X-rays 3. Nuclear medical imaging 4. Magnetic resonance imaging (MRI) 5. (Ultrasound imaging covered in previous lecture) Slide 3: Medical imaging coordinates The anatomical terms of location Superior / inferior, left .
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Medical X-Ray Medical Imaging N/A N/A 5-100 Tc-99m Medical Imaging (SPECT) 6.02 hours J 140.5 Tl-201 Medical Imaging (SPECT) 73 hours H 135, 167 In-111 Medical Imaging (SPECT) 2.83 days H 171, 245 F-18 Medical Imaging (PET) 1.83 hours E 511 Ga-68 Medical Imaging (PET) 68 minutes E 511 Cs-137 Fission Product 30.17 years E- 662
BIBLIOGRAPHY Physics for Medical Imaging P. Allisy-Roberts, J. Williams – Farr’s Physics for Medical Imaging Radiological Physics P. Dendy, B. Heaton – Physics for Radiologists Medical Imaging J. Bushberg et al – The Essential Physics of Medical Imaging S. Webb – The Physics of Medical Imaging Nuclear Medicine
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Nature of Medical Imaging For this class: Medical Imaging: Non-invasive imaging of internal organs, tissues, bones, etc. Focus on: 1.Macroscopic not microscopic 2.in vivo (in the body) not in vitro ("in glass", in the lab) 3.Primarily human studies 4.Primarily clinical diagnostic applications Alessio - BIO508 Nature of Medical Imaging QUICK .
