Gamma ray detector elements with variable light guide thickness

1. A gamma ray detector module, comprising:

at least one crystal element arranged in a plane;

a plurality of light sensors arranged to cover the at least one crystal element and configured to receive light emitted from the at least one crystal element, the plurality of light sensors including end light sensors arranged at respective ends of the detector module and interior light sensors arranged between the end light sensors; and

a light guide arranged between the at least one crystal element and the plurality of light sensors, the light guide being optically connected to the at least one crystal element,

wherein the light guide positions at least one of the interior light sensors farther away from the plane of the at least one crystal element than at least one of the end light sensors.

2. The gamma ray detector module of claim 1 , wherein the plurality of light sensors include first light sensors each having a first size, and second light sensors, each second light sensor being adjacent to one of the first light sensors and having a second size, so that the first and second light sensors cover different-sized portions of the at least one crystal element, the first size being larger than the second size.

3. The gamma ray detector module of claim 2 , wherein the light guide further includes angled recessed portions that position the second light sensors at an oblique tilt angle with respect to the first light sensors and the plane of the at least one crystal element.

4. The gamma ray detector module of claim 2 , wherein the first light sensors are positioned closer to the plane of the at least one crystal element by a distance d, wherein d is based on a difference in sizes of the first and second light sensors.

5. The gamma ray detector module of claim 2 , wherein the plurality of light sensors are arranged in a two-dimensional array covering the at least one crystal element, and a light sensor of the first size is arranged adjacent to two light sensors of the second size.

6. The gamma ray detector module of claim 1 , wherein the at least one crystal element includes a plurality of optically isolated crystal elements.

7. A gamma ray detector module, comprising:

at least one crystal element arranged in a plane;

a plurality of light sensors arranged to cover the at least one crystal element and configured to receive light emitted from the at least one crystal element, each light sensor including a photocathode having a curved bottom surface facing the at least one crystal element; and

a light guide arranged between the at least one crystal element and the plurality of light sensors, the light guide being optically connected to the at least one crystal element,

wherein the plurality of light sensors include a first light sensor having a first size and a second light sensor adjacent to the first light sensor and having a second size, so that the first and second light sensors cover different-sized portions of the at least one crystal element, the first size being smaller than the second size; and

the light guide positions the first and second light sensors so that a maximum distance of the bottom surface of the photocathode of the first light sensor from the plane of the at least one crystal element is equal to a maximum distance of the bottom surface of the photocathode of the second light sensor from the plane of the at least one crystal element.

8. The gamma ray detector module of claim 7 , wherein the at least one crystal element includes a plurality of optically isolated crystal elements.

9. A gamma ray scanner system, comprising:

a plurality of rectangular detector modules arranged adjacent to one another to form a cylindrical detector ring, wherein each of the detector modules includes

at least one crystal element arranged in a plane;

a plurality of light sensors arranged to cover the at least one crystal element and configured to receive light emitted from the at least one crystal element, each light sensor including a photocathode having a curved bottom surface facing the at least one crystal element; and

a light guide arranged between the at least one crystal element and the plurality of light sensors, the light guide being optically connected to the at least one crystal element,

wherein the plurality of light sensors include a first light sensor having a first size and a second light sensor adjacent to the first light sensor and having a second size, so that the first and second light sensors cover different-sized portions of the at least one crystal element, the first size being smaller than the second size; and

the light guide positions the first and second light sensors so that a maximum distance of the bottom surface of the photocathode of the first light sensor from the plane of the at least one crystal element is equal to a maximum distance of the bottom surface of the photocathode of the second light sensor from the plane of the at least one crystal element.