Medical Imaging

• Is fundamentally based on a difference in absorbance between different materials, based on density

Tomography

• If multiple images are taken from different angles, the shadow cast can be used the calculate the shape of the initial geometry

Subtraction Radiography - Z-contrast

Iodine

• Uses a Z-contrast (Z for the atomic weight)
  • Has a higher atomic weight and therefore a higher density than the surrounding tissue.
• Multiple x-ray images are taken, one in which the iodine will absorb the radiation and one in which it won’t
• The two can then be computed to enhance regions where the iodine is present
  • The iodine is injected, so this will highlight the vascularity

Barium

• The same can be done with barium in a “barium swallow” to give a contrast to a digestive x-ray

Radiotherapy

• The treatment of cancer with the use of targeted radiation

Iodine

• Since iodine is readily absorbed and processed by the thyroid, radioactive iodine can be administered, which will decay within the thyroid, killing off all local cells
• This is a regular treatment of thyroid cancer, as thyroxin can be provided as a supplemental hormone

Copper Chelates

• Copper 64 (radioactive) can be bound within chelates that are bound to antibodies to target a particular cell line
• This provides specificity as to where the copper will bind and destroy

Magnetic Contrasts

• High spin metals within a chelate can be used to provide contrast in magnetic imaging
• Gadolinium is used due to its half filled f orbitals (7 unpaired electrons)
  • It is also not particularly toxic and can be excreted from the body
• The multidentate ligand provides high stability