Parallel Hole Collimators

Low energy all-purpose collimators have holes with a large diameter. This increases the sensitivity but decreases the resolution. This means that LEAP collimators have a relatively high sensitivity with a moderate resolution. The average sensitivity of a LEAP is approx. 500,000 cpm for a 1-uCi source, and the resolution is 1cm at 10cm from the patient side of the collimator.

Low energy high-resolution collimators have holes with a smaller diameter. The holes of LEHR collimators are also deeper than those of LEAP collimators. These smaller and deeper holes cause LEHR collimators to have a higher sensitivity than LEAP collimators. The sensitivity is approx. 185,000 cpm for 1-uCi source, and the resolution is higher with 0.65cm at 10cm from the patient side of the collimator. LEAP and LEHR collimators are mainly used with Technetium-99m.

Medium energy collimators are used for imaging with medium energy photons of nuclides such as Gallium-67, Indium-111 and Krypton-81. The septal thickness of medium energy collimators has been increased to reduce septal penetration caused by the higher energy photons. High energy collimators have even thicker septas and are mainly used for imaging with Iodine-131 and 18F-FDG.

• - Low energy all-purpose collimator (LEAP)
• - Low energy high-resolution collimator (LEHR)
• - Medium energy collimator
• - High energy collimator