When changing the collimator from low energy all purpose to high resolution, how does acquisition time change if the same number of counts is acquired?

When changing from a low energy all-purpose collimator to a high-resolution collimator, the acquisition time will indeed increase if the same number of counts is desired. This is because high-resolution collimators have finer septa and holes that are designed to enhance image detail, but they also allow fewer photons to pass through compared to low-energy all-purpose collimators.

Since high-resolution collimators are more restrictive in terms of the amount of gamma radiation that can be detected, the system must collect data for a longer period to gather the same number of counts as would be achieved with the low-energy all-purpose collimator. This means that for a fixed number of detected events (counts), the time required to collect these counts will be longer, necessitating an increase in acquisition time.

In summary, the acquisition time increases due to the reduced efficiency of the high-resolution collimator in capturing the gamma rays compared to the low energy all-purpose collimator, while still aiming to achieve the same amount of data as indicated by the number of counts.