Devices, systems and methods for determining depth of interaction in positron emission tomography detectors

A positron emission tomography (PET) detector being configured to identify a depth of a photon gamma interaction, comprising:

• a crystal array including a plurality of crystal elements, the plurality of crystal elements being arranged along a first direction and a second direction so as to define a plurality of crystal groups along the first direction, each of the plurality of crystal groups including at least two crystal elements of the plurality of crystal elements, each of the plurality of crystal elements including a first end and a second end and extending along a third direction from the first end to the second end, and
• a photon-sensor array optically coupled with the crystal array,
• wherein at least one pair of neighboring crystal groups of the plurality of crystal groups include:
• a first optical separator of a first length located between the crystal groups of the at least one pair of neighboring crystal groups, the first length being along the third direction;
• and
• a second optical separator of a second length located between two neighboring crystal elements of a crystal group of the at least one pair of neighboring crystal groups, the second length being along the third direction, wherein the first length of the first optical separator is equal to a length of at least one of the two neighboring crystal elements between which the first optical separator is located, and the second length of the second optical separator is shorter than a length of at least one of the two neighboring crystal elements between which the second optical separator is located.