XRay Imaging Gerald R Aben MD FACR Department of Radiology College of Osteopathic Medicine XRays High energy electromagnetic radiation Behaves both like a particle photon and a wave Production of XRays ID: 526047
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Ionizing Radiation – X-Ray Imaging
Gerald R. Aben, MD, FACR
Department of Radiology
College of Osteopathic MedicineSlide2
X-RaysHigh energy electromagnetic radiationBehaves both like a particle (photon) and a waveProduction of X-RaysFree electrons produced at filament of x-ray tube (cathode)
High Speed movement of electrons
Rapid deceleration of electrons at anode
Emission of a x-ray photonSlide3
X-ray Tube Schematic
Cathode
Anode – Tungsten Target
Electron
Beam
Window
X-rays
Envelope
CollimatorSlide4
Production of ImageX-ray pass through tissue to expose detectorPassage depends onTissue characteristicsDensity
Atomic Number
Number of electrons per gram
ThicknessSlide5
Production of ImageDifferential absorption of X-ray as the beam passes through the patientUnabsorbed X-rays expose the detector (i.e. film, CR Plate, solid state detector), creating the image (photographic effect)Differential absorption of X-ray by the tissues is the cardinal feature of image formation
Special terms used on x-ray reports
Radiopaque
, Radiolucent, High attenuation, Low attenuation, Water densitySlide6
Standard X-Ray Machine
X-Ray Tube
X-Ray Tube
Detector
DetectorSlide7
Fluoroscopic Imaging Unit
Detector
X-Ray Tube
X-Ray Tube
DetectorSlide8
Natural DensitiesNatural densities in the bodyBoneSoft tissue and body fluidFatLung and air containing organs
Appearance on the radiographic image
White
Black
Shades of GraySlide9
Image Density X-ray
Radiopaque
– High attenuation
Appears white on film – black on fluoroscopy
X-ray photons don’t reach the detector
Radiolucent – Low attenuation
Appears black on film – white on fluoroscopy
X-ray photons unimpeded traveling to detectorWater densityAppears grey on filmAll soft tissuesSlide10
Natural ContrastDifferential contrast between bone and soft tissuesDifferential contrast between soft tissues and airLittle difference between various tissue types i.e. fat, muscle, solid organs, blood….Slide11
Natural ContrastPathologic processes may cause differences in natural densities that can be visualized on the X-ray; high density tumor in air filled lung- whiteLow density cyst in radio-opaque bone- black
Pathologic processes of almost the same density as adjoining structures are not visible on X-ray.
May need to use additional artificial contrast to visualize a density differenceSlide12
Contrast AgentsContrast material (radio-opaque or radio-lucent) administered to see structures or pathologic processes that would not be seen otherwiseSome useful contrast agentsBarium sulfate in the GI tract
Iodine compounds in the vessels
Carbon dioxide in the vessels or GI tract
Naturally occurring air in the GI tractSlide13
Fluoroscopic Room
Radiosensitive
Screen
Video Camera