Reference Detector Arrangement For Computed Tomography Imaging System
An x-ray CT system includes a gantry with a rotor arranged for rotation. The x-ray CT system includes an x-ray source and an x-ray detector supported on the rotor, with the x-ray source being configured to generate x-rays. The x-ray CT system includes a reference detector assembly for measuring flux of photons generated by the x-ray source. The reference detector assembly includes a tungsten shield defining an aperture, an x-ray sensitive element adjacent to the aperture for generating a reference output in response to x-rays from the x-ray source passing through the aperture, a photodiode adjacent to the x-ray sensitive element for receiving the reference output, and a reference detector controller for generating a reference signal based on the reference output. The x-ray CT system includes a controller for performing tomographic reconstruction of image data received from the x-ray detector and normalized based on the reference signal.
1 . An x-ray CT system, comprising:
a gantry with a rotor arranged for rotation about an axis;
an x-ray source supported on the rotor and configured to generate x-rays;
an x-ray detector supported on the rotor;
a reference detector assembly operatively attached to the x-ray source for measuring flux of photons generated by the x-ray source, the reference detector assembly including:
a tungsten shield defining an aperture,
an x-ray sensitive element supported adjacent to the aperture of the tungsten shield and configured to generate a reference output in response to x-rays generated by the x-ray source passing through the aperture,
a photodiode supported adjacent to the x-ray sensitive element and configured to receive the reference output from the x-ray sensitive element, and
a reference detector controller in communication with the photodiode and configured to generate a reference signal based on the reference output from the x-ray sensitive element; and
a controller including a memory and a processor coupled to the memory and configured with processor-executable instructions to perform tomographic reconstruction of image data received from the x-ray detector and normalized based on the reference signal from the reference detector controller.
2 . The x-ray CT system of claim 1 , wherein the reference detector assembly further includes a shielding enclosure; and
wherein the tungsten shield is operatively attached to the shielding enclosure.
3 . The x-ray CT system of claim 2 , wherein at least a portion of the shielding enclosure is formed from leaded bronze.
4 . The x-ray CT system of claim 2 , wherein at least a portion of the shielding enclosure is formed from tungsten.
5 . The x-ray CT system of claim 2 , wherein at least a portion of the shielding enclosure is formed using an additive manufacturing process; and
wherein the additive manufacturing process comprises selective laser melting or laser sintering.
6 . (canceled)
7 . (canceled)
8 . The x-ray CT system of claim 2 , wherein one of the shielding enclosure and the tungsten shield defines an interior; and
further comprising a reference detector board disposed within the interior and supporting the photodiode.
9 . The x-ray CT system of claim 8 , wherein the x-ray sensitive element is supported within the interior arranged between the tungsten shield and the reference detector board.
10 . The x-ray CT system of claim 9 , wherein the reference detector assembly further includes an insulator supported within the interior adjacent to the reference detector board.
11 . The x-ray CT system of claim 9 , wherein the reference detector assembly further includes a heat transfer pad supported within the interior adjacent to the reference detector board.
12 . The x-ray CT system of claim 9 , wherein the reference detector controller is supported on the reference detector board at a location spaced from the aperture.
13 . The x-ray CT system of claim 8 , further comprising:
a harness coupled to the reference detector board via a connector; and
a retainer assembly to limit relative movement between the harness and the shielding enclosure:
wherein the retainer assembly includes a relief defined in the shielding enclosure and shaped to receive a pair of keepers each shaped to engage and compress against a portion of the harness; and
wherein the pair of keepers each define a notch arranged to abut the harness.
14 . (canceled)
15 . (canceled)
16 . The x-ray CT system of claim 2 , wherein the shielding enclosure includes a first enclosure plate and a second enclosure plate, the first enclosure plate being coupled to the second enclosure plate with the tungsten shield supported between the first enclosure plate and the second enclosure plate.
17 . The x-ray CT system of claim 16 , wherein one of the first enclosure plate and the second enclosure plate defines an interior; and
wherein the reference detector assembly further includes a reference detector board disposed within the interior and supporting the photodiode, with the x-ray sensitive element arranged between the tungsten shield and the reference detector board.
18 . The x-ray CT system of claim 17 , wherein at least one of the first enclosure plate and the second enclosure plate defines a seat shaped to receive the reference detector board within the interior.
19 . The x-ray CT system of claim 17 , wherein one of the first enclosure plate and the second enclosure plate defines a window; and
wherein the reference detector assembly further includes an auxiliary tungsten shield defining an auxiliary aperture, the auxiliary tungsten shield being secured to the window with the auxiliary aperture in alignment with the aperture of the tungsten shield to permit x-rays generated by the x-ray source to pass through the auxiliary aperture and through the aperture towards the x-ray sensitive element.
20 . The x-ray CT system of claim 1 , wherein the reference output generated by the x-ray sensitive element is visible light, and wherein the photodiode is configured to sense the visible light outputted by the x-ray sensitive element; and
wherein the x-ray sensitive element comprises a crystal scintillator.
21 . (canceled)
22 . The x-ray CT system of claim 1 , wherein the x-ray detector comprises an array of x-ray detector modules; and
wherein the x-ray source is further configured to generate a fan beam of x-rays.
23 . The x-ray CT system of claim 1 , further comprising a second a reference detector assembly operatively attached to the x-ray source in spaced relation from the reference detector assembly for measuring flux of photons generated by the x-ray source, the second reference detector assembly including:
a second tungsten shield defining a second aperture,
a second x-ray sensitive element supported adjacent to the second aperture of the second tungsten shield and configured to generate a second reference output in response to x-rays generated by the x-ray source passing through the second aperture,
a second photodiode supported adjacent to the second x-ray sensitive element to receive the second reference output from the x-ray sensitive element, and
a second reference detector controller in communication with the second photodiode to generate a second reference signal based on the second reference output from the second x-ray sensitive element.
24 . The x-ray CT system of claim 23 , wherein the controller is further configured to perform tomographic reconstruction with image data received from the x-ray detector normalized based on one or more of the reference signal from the reference detector controller and the second reference signal from the second reference detector controller.
25 . The x-ray CT system of claim 23 , wherein the x-ray source is configured to generate x-rays based at least partially on one or more of the reference signal from the reference detector controller and the second reference signal from the second reference detector controller.