Which of the following is the most common transmission source used in PET imaging?

In PET imaging, the most common transmission source is germanium-68 (68-Ge). This radioisotope is frequently used because it emits gamma photons that are well-suited for transmission imaging, which plays a crucial role in attenuation correction during PET scans. The ability of 68-Ge to provide a consistent and reliable source of gamma radiation helps improve the accuracy of the resulting images by correcting for tissue attenuation effects.

Transmission sources are integral to ensuring that PET images accurately reflect the distribution of the radiotracer used in the study. 68-Ge's half-life of approximately 271 days allows it to be practical for clinical use, ensuring that it remains effective over a reasonable period and making it a preferred choice in many facilities.

Using other options, like cobalt-60 (60-Co), iodine-131 (131-I), and cesium-137 (137-Cs), is less common in the context of PET. While these isotopes can emit gamma rays suitable for imaging applications, they do not provide the same level of effectiveness in terms of energy peaks and dose delivery for routine clinical PET scans as 68-Ge does. Therefore, 68-Ge stands out as the most common transmission source in PET imaging.