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RADIOPHARMACEUTICALS-CHARACTERISTICS

Physics

RADIOPHARMACEUTICALS-CHARACTERISTICS

The “ideal” radionuclide component:
1. Low radiation dose - most modern scintillation cameras are optimized for photon energies close to 140 keV, which is a compromise among patient attenuation, spatial resolution, and detection efficiency.

2. Emits photons in the energy range 100–200 keV -ideally 140 keV. α and β particles would not form an image.

3. Appropriate physical half life - if it’s too short then more radioactive substance would have to be prepared than is actually injected.

4. Easily attached to a ligand without altering it’s metabolism or disassociation.

5. High specific activity (high activity per unit volume).

The “ideal” pharmaceutical component:
1. Maximum concentration of the radiopharmaceutical in the target tissues of interest while minimizing the uptake in surrounding (non-target) tissues and organs improves contrast and the ability to detect subtle abnormalities in the radiopharmaceutical’s distribution => high Tissue/Background ratio.

2. Safety, Convenience, and Cost-Effectiveness - low chemical toxicity is enhanced by the use of high-specific-activity, carrier-free radionuclides that also facilitate radiopharmaceutical preparation and minimize the required amount of the isotope.


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REFERENCES

1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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