1 / 41

INTRODUCTION to Radiology

INTRODUCTION to Radiology. Carol P. Becker, M.D. Acknowledgements: N.E. Diethelm, M.D., E.Blaudeau,M.D. Diagnostic Radiology. Radiographs – X-rays, plain films, XR Fluoroscopy – “Fluoro” Tomography – “Tomo” (planar, helical) Urography - IVP Ultrasound - US Computed Tomography - CT

amyg
Télécharger la présentation

INTRODUCTION to Radiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. INTRODUCTION to Radiology Carol P. Becker, M.D. Acknowledgements: N.E. Diethelm, M.D., E.Blaudeau,M.D..

  2. Diagnostic Radiology • Radiographs – X-rays, plain films, XR • Fluoroscopy – “Fluoro” • Tomography – “Tomo” (planar, helical) • Urography - IVP • Ultrasound - US • Computed Tomography - CT • Magnetic Resonance Imaging - MRI • Nuclear Medicine – NM • Breast Imaging - Mammography, US, MRI

  3. More photons strike the film => film appears blacker Fewer photons strike the film => film appears whiter www.med.harvard.edu/JPNM/TF03_04/Sept2/CXR.jpg

  4. 1895: Roentgen discovers X-rays (XRAYs wife’s handby accident)

  5. Ionization • An atom which loses an electron is ionized • Photons having  15electron volts can produce ionization in atoms and molecules • X-Rays, Gamma Rays, and certain types of UV Radiation are Ionizing Radiation

  6. Ionizing Radiation in Radiology • Patients undergoing these types of studies are exposed to Ionizing Radiation: • Radiographs • Fluoroscopy/Conventional Angiography • CT • Nuclear Medicine

  7. IONIZING RADIATION • Ionizing Radiation can be carcinogenic and, to the fetus, mutagenic or even lethal

  8. Goals of Radiation Safety • Eliminate deterministic effects • Reduce incidence of stochastic effects

  9. Exposure to Ionizing Radiationcauses two types of effects • Deterministic Effects: A minimum threshold dose must be attained for the effect to occur. Examples include cataract formation, skin reddening (erythema), and sterility. Also referred to as “non-stochastic” effects • Stochastic Effects: The effect may (potentially) occur following any amount of exposure – there is no threshold. Examples include cancer and genetic defects.

  10. RADIATION SAFETY • PLEASE REVIEW RADIATION SAFETY MATERIAL IN THE SYLLABUS ON WEBSITE (ON YOUR OWN). • INCLUDES RADIATION GUIDELINES FOR PREGNANT PATIENT

  11. What is an X-ray? • X-rays are very short wavelength electromagnetic radiation. Shorter wavelength, greater energy/greater the ability to penetrate matter • X-rays are described as packets of energy called Quanta or Photons • Photons travel at the speed of light • Photon energy measured in Electron Volts

  12. Effects of varying types of tissue and varying thickness same tissue www.med.harvard.edu/JPNM/TF03_04/Sept2/CXR.jpg

  13. X-ray beamabsorption and attenuation • X-Rays passing through matter becomeATTENUATEDvia absorption and scatter. • With increasing atomic number comes increasing attenuation by the material

  14. X-ray beamabsorption and attenuation • X-Rays passing through matter become ATTENUATED via absorption and scatter. • For a given thickness, the greater the physical density (gm/cc) of a material, the greater its ability to absorb or scatter X-Rays. Lead >Aluminum

  15. Attenuation and Hounsfield unitsversus window and level settings for image display Gas -1,000 HU Soft tissue +20 to +100 HU Fat -100 HU Bone +1,000 HU Water 0 HU 1 2 3

  16. LIMITING YOUR EXPOSURE:You do the math! • Doubling your distance from the X-ray tube reduces your exposure by a factor of four • Tripling your distance from the X-ray tube reduces your exposure by a factor of nine!

  17. Lumbar spine, lateral view Fluoroscopy : intervertebral disc space http://www.orthoassociates.com/images/Image_discogram.jpg

  18. Clinical Medical Specialtiesthat rely on radiation Diagnostic and Interventional Radiology • Imaging (CT, XRAY) • Nuclear Medicine • Interventional procedures Radiation Oncology: The therapeutic use of radiation.

  19. RADIOGRAPH History:weight loss. Diagnosis: Mets or Multiple myeloma

  20. Radiographic Densities • Metal Very White • Bone White • Water Gray • Fat Gray-Black • Air Black • Metal is most Radiodenseor Radiopaque. • Air is most Radiolucent.

  21. Nuclear Medicine • Most imaging modalities detect changes in gross anatomy • However, most NM exams rely on changes in physiology to detect disease. • Radionuclides • Produce ionizing radiation • Administered I.V., orally, SubQ

  22. Normal bone scan mets Posterior Anterior Anterior Posterior Diethelm MD Lisa

  23. Nuclear Medicine • Photonsemitted by radioisotopes are detected by Sodium Iodide crystals. Brightness of light emitted depends on the energy of the photon • Photodetectors convert the light into an electronic signal, which a computer converts to diagnostic images………

  24. PET – CT Fusion Scanner • Combines Positron Emission Tomography (PET) and Helical CT • PET detects area of increased metabolic activity as indicated by uptake of radioactive glucose ( by tumor, infection) • PET data is then “fused” with CT data to produce an image showing increased glucose uptake superimposed upon exquisite anatomic detail of helical CT

  25. Multi-Detector(Helical) CTmultiple planes of detectors in the gantry • Technical innovation allows • faster scanning • over a much longer range • with even better image quality • Radiation exposure greater than single-detector CT • “Total body” CT in trauma pts

  26. HOUNSFIELD UNIT SCALE • Compares attenuation of each tissuethrough which the x-ray beam passes with the attenuation of WATER.

  27. Hounsfield Unit Scale (CT Attenuation) • Gas (Air) -1,000 HU • Fat -100 HU • Water 0 HU • Soft tissue +20 to +100 HU • Bone +1,000 HU

  28. CT • Contrast resolution far superior to plain radiographs, but spatial resolution inferior to XR • Thinly collimated x-ray beam passes through a “slice” of the patient’s body while the x-ray tube moves in an arc around the patient • Electronic detectors, placed opposite the x-ray tube, convert the attenuated x-ray beam into electrical pulses.Computers convert this data to a gray-scale image

  29. MAIN ADVANTAGES OF CT OVER MRI • Rapid scan acquisition • Visualization of cortical boneand soft tissue calcifications

  30. MRI: Main Disadvantages • Poor visualization of cortical bone and soft tissue calcifications (vs. CT, x ray) • Long imaging times (in general) • Limited spatial resolution • Patient cooperation is needed • Some medical devices prohibitive

  31. MRI • Nuclei with odd #’s of nucleons (protons and neutrons) align themselves with external Magnetic Field • A Radio Frequency pulse perturbs this nuclear alignment, resulting in release of radio frequency energy from the nucleus • The scanner converts this released radio frequency into diagnostic images • Tissues that contain the most hydrogen (water, fat) generally have the strongest signal

  32. CONTRAINDICATIONS for MRI SCANNING: • Pacemakers, pacing wires (RF current can induce cardiac arrhythmias, burns) • Cerebral aneurysm clips (movement, burns, induced electrical currents) • Implants (insulin pumps, cochlear implants, neurostimulator, drug infusion pumps, penile and dental implants) • Intra-orbital metallic fragments (may deflect in magnetic field, causing injury/blindness), XRay orbits if unsure

  33. Ultrasound • Exploits differences in acoustic properties of adjacent organs to produce images Ultrasound and MRI are Non- Ionizing

  34. Ultrasound • Nonionizing • Multiplanar • Applications include OB/GYN, Cardiac, Abdominal, Non-Invasive Vascular, Intraoperative, and Neonatal Brain imaging • Limited in skeletal imaging, but can be useful in muscle and tendon imaging

  35. ULTRASOUND1794: Lazzaro Spallanzani figures out that flying bats avoid obstacles in the dark by using reflected echoes of high frequency sound inaudible to humans

  36. Contrast Media • Most viscera are of water-density or close to it • Contrast media are materials we introduce to better define anatomy and pathologic changes

  37. Barium enema www.philips.com/ Main/products/xray/ Assets/images/dose Wise/urf2_large.jpg

  38. Common Indications for IV Contrast in CT • To visualize blood vessels (Aortic injury, Abdominal Aortic Aneurysm, Pulmonary Embolus) • To evaluate for primary or metastatic tumor • To evaluate for infections or inflammatory processes • To evaluate for traumatic injury

  39. Iodinated Contrast Reactions Mild Warmth, metallic taste, N/V, HA, Dizziness, Tachycardia, sneezing, coughing, erythema, Moderate Agitation, bradycardia, hypotension, wheezing, urticaria (“hives”), itching Severe Pulm edema, shock, CHF, cardiac arrest, laryngospasm, laryngeal edema, apnea, seizure, coma

  40. MRI Contrast Media • Gadolinium • Paramagnetic (radiopaque) • IV • NSF/ check GFR=renal function

  41. PACS Training • PictureArchiving and CommunicationSystem • Digital system for storage, retrieval, and display of imaging studies • MCLNO has gone completely filmless =PACS is your only access to your patients’ images • Therefore, you are encouraged to learn to use PACS

More Related