radbiolec2

• Conventional Radiography:

  • Images produced through the use of ionizing radiation (X-ray)
  • Does not utilize imaging contrast like barium & iodine
  • Often termed as plain films
  • Requirements: Source, Record, Process
  • Advantages:
  • Images are relatively easy to produce
  • Cheap cost
  • Can be obtained almost anywhere
  • The most widely obtained imaging studies
• Computed Tomography:

  • First introduced in 1970s
  • Utilizes a gantry with a rotating beam and multiple detectors that are also rotating continuously around the patient
  • Produces 2D slice-like images
  • Composed of pixels
  • Each pixel is assigned a CT-number from -1000 to +1000
  • Measured in HU (Hounsfield unit)
  • Hounsfield Unit for Densities:
  • Air: -1000 (Least Dense)
  • Bone: +400 to +600
  • Fat: -40 to -100
  • Water: 0
  • Tissues: +20 to +100
• Ultrasound:

  • Utilizes acoustic energy/soundwaves above the audible frequency to humans to produce an image
  • Relatively inexpensive compared to CT and MRI
  • Widely available and portable
  • Generally considered to be a very safe imaging modality
  • First choice of imaging modality especially for women and children
• Magnetic Resonance Imaging (MRI):

  • Utilizes the potential energy stored in the body’s hydrogen atoms
  • Atoms are manipulated by very strong magnetic fields and radio frequency pulses to produce 2D or 3D images
  • Does not utilize ionizing radiation and produces higher contrast between different types of soft tissues than CT scan
  • MRI vs CT Scan:
  • MRI:
  • Uses large external fields, RF pulse, and 3 different gradient fields
  • Does not emit ionizing radiation
  • Good resolution and 3D reconstruction
• • Gadolinium contrast is relatively non-toxic (except for pregnant women)
  • Costly
  • Lengthy process and non-availability
  • CT Scan:
  • Uses X-rays for imaging
  • Exposure to ionizing radiation
  • Resolution problem
  • Injection of contrast medium
  • Not as costly compared to MRI
  • Quick process and easily available
• Fluoroscopy:

  • Utilizes ionizing radiation
  • Performs real-time visualization of the body allowing for evaluation of motion
  • Utilizes barium/iodine agents as contrast
  • Fluoroscopic tables are made to tilt and so is the fluoroscopic tube
  • 'Spot films'
• Nuclear Medicine:

  • Radioactive isotope (Radioisotope) is an unstable form of element that emits radiation from its nucleus as it decays
  • Can occur naturally (e.g., uranium & thorium) or be produced artificially
  • Radioisotopes for medicine are produced artificially
• Single Photon Emission Computed Tomography (SPECT):

  • A nuclear medicine study performed with a gamma camera to acquire many 2D images from multiple angles, which are then reconstructed by computer into a 3D data set
  • Can be manipulated to demonstrate thin slices in any projection by rotating the gamma camera around the patient
• Positron Emission Tomography (PET):

  • Operates on a molecular level to produce 3D images depicting the body’s biochemical and metabolic processes
  • Uses a positron-producing radioisotope attached to a targeting pharmaceutical
  • Commonly uses fluorodeoxyglucose (FDG) as the target molecule
  • Often used in the diagnosis and treatment follow-up of cancer to locate hidden metastasis or detect recurrence