1.6

• Computed Tomography (CT)


  Uses ionizing radiation to attenuate x-rays and create slices
• CT Equipment


  • X-ray Tube
  • Table
  • Detectors
  • Computer
• Three Dimensional CT


  Body parts rotated in space, easier view of complex anatomy, not easily viewed in hard copy
• Scout image


  Initial image used to plan further imaging
• Volumetric imaging


  Multi-slice scanners, views not limited to axial plane (multiplanar)
• Image Thickness


  0.1mm to 8.0 mm, thicker images may contain more tissues, "voxel" = pixel x slice thickness, if a voxel contains more than one tissue it will average the densities
• Windowing


  Adjusting the brightness and contrast of the image
• Hardening


  Quality degradation in CT imaging
• Artifacts


  Quality degradation in CT imaging, caused by metals or patient motion
• Clinical Uses of CT

  • Subtle or complex fractures
  • Serious/high velocity injury
  • Loose bodies
  • Degenerative changes
  • Identify alignment difficulties
• Advantages of CT


  • Fast image collection, expense < MRI
• Limitations of CT


  • Limited capacity to determine cellular makeup, increased radiation exposure, not as good for detecting bleeding/edema/ischemia, static procedure
• Magnetic Resonance Imaging (MRI)


  "Reflective Imaging", provides soft tissue detail
• MRI Scanner Elements


  • Magnet
  • Gradient coils
  • RF coils
  • Workstation
  • Computer
• Magnet


  Lies in the Gantry, magnetic field strength can be between .3-8 Tesla
• Gradient coils


  3 gradient coils located internal to the magnet
• RF coils


  Transmit pulses that alter alignment of protons
• Computer (workstation)


  Directs the scanning process, selects sequence and slice thickness, converts data from RF coils, reconstructs images
• MRI Principles


  References hydrogen nuclei in water molecules responding to the magnetic field
• MRI Imaging Process


  1. Magnet aligns protons

  2. RF Pulse

  3. Relaxation
• T1 Sequence


  Shorter, faster recovery time, stronger/brighter signal, short TR and TE times
• T2 Sequence


  Long TR and TE times, tissues slow to give up energy
• MRI Viewing Planes


  • Coronal
  • Sagittal
  • Axial
• Signal Intensity of Tissues in MRI

  • Cortical bone
  • Bone marrow
  • Muscle
  • Ligament
  • Tendon
  • Fibrocartilage
  • Articular cartilage
  • Intervertebral disc
  • Nucleus pulposus
  • CSF
  • Fat
• MRI Pathology


  T1 - Anatomy, T2 - Pathology
• MRI has a high powered magnet, contraindicated with ferrous metal, pacemakers
• Coronal


  Plane of section through the body from front to back
• Sagittal


  Plane of section through the body from side to side
• Axial


  Plane of section through the body from top to bottom
• supresses fat


  Reduces the appearance of fat in an image
• Magnetic Resonance Imaging


  Imaging technique that uses strong magnetic fields and radio waves to generate images of the body
• Viewing the Image


  • 3 planes: Coronal, Sagittal, Axial
• Signal Intensity of Tissue in MRI

  • Cortical bone
  • Bone marrow
  • Muscle
  • Ligament
  • Tendon
  • Fibrocartilage
  • Articular cartilage
  • Intervertebral disc
  • Nucleus pulposus
  • CSF
  • Fat
• T1 weighted


  Imaging technique that highlights anatomy
• T2 weighted


  Imaging technique that highlights pathology
• Magnetic Resonance Imaging


  Imaging technique that uses a high powered magnet
• Contraindications for MRI


  • Ferrous metal
  • Pacemakers
  • Orthopedic hardware may cause distorted images
  • Claustrophobia, anxiety
  • Inability to remain motionless
  • Kidney (renal) function tests required for patients requiring gadolinium
• Diagnostic Ultrasound


  Imaging technique that uses high-frequency sound waves to generate images of the body
• Outline


  • Objectives
  • Equipment
  • Viewing the Image
  • Echogenicity
  • Tissue Specific Characteristics
  • Advantages
• Diagnostic Ultrasound Equipment


  • Pulser
  • Transducer
  • Scan converter
  • Monitor
  • Gel