X-ray CT apparatus, radiation detecting apparatus, and data processing method for x-ray CT apparatus
According to one embodiment, X-ray CT apparatus includes an X-ray tube, an energy integrating type detector, a time data generation circuit, and a projection data generation unit. The X-ray tube emits X-rays. The energy integrating type detector has a plurality of detector units arrayed in a channel direction that accumulate electric charges corresponding to X-rays transmitted through an object. The time data generation circuit generates time data at a timing when the electric charges accumulated in the detector reach a predetermined threshold. The projection data generation unit generates projection data using the time data and energy corresponding to the threshold.
1 . An X-ray CT apparatus, comprising:
an X-ray tube emitting X-rays;
an energy integrating type detector having a plurality of detector units arrayed in a channel direction that accumulate electric charges corresponding to X-rays transmitted through an object;
a time data generation circuit configured to generate time data at a timing when the electric charges accumulated in the detector reach a predetermined threshold; and
a projection data generation circuitry configured to generate projection data using the time data and energy corresponding to the threshold, wherein
the time data generation circuit is further configured to generate the time data for each of the plurality of the detector units; and
the projection data generation circuitry includes an event generation circuit configured to generate event data, which is associated with an event indicating that the electric charges accumulated in a detector unit of the detector units reaches the predetermined threshold, and is associated with the time data indicating a time when the event occurred and identification information of the detector unit in which the event occurred.
2 . The X-ray CT apparatus according to claim 1 , wherein the time data generated by the time data generation circuit is associated with a rotation angle of the X-ray tube and the detector.
3 . The X-ray CT apparatus according to claim 1 , wherein the projection data generation circuitry is further configured to generate projection data with different view rates according to a position in a field of view (FOV) of the object.
4 . The X-ray CT apparatus according to claim 1 , wherein the time data generation circuit includes:
a comparator that generates a trigger signal to reset the electric charges stored in the detector when the electric charge stored in the detector exceeds said threshold; and
a TDC (Time to Digital Converter) that is input with the trigger signal generated by the comparator and generates the time data at the timing when the trigger signal is input.
5 . The X-ray CT apparatus according to claim 1 , wherein the projection data generation unit further includes:
processing circuitry configured to identify, while the X-ray tube and the detector rotate, a first path in which the X-ray emitted from the X-ray tube passes through a determined region set in a field of view (FOV) of the object and is incident on the detector, and a second path in which the X-ray to is incident on the detector without passing through the determined region; and
a transmission data generation circuit configured to
a generate first event data such that a frequency of occurrence of the event is maintained at a first view rate for event data corresponding to the first path,
aggregate occurrence of the events and generates second event data such that a frequency of occurrence of events after aggregation is at a second view rate lower than the first view rate for event data corresponding to the second path, and
combine the first event data with the second event data to generate event data for transmission.
6 . The X-ray CT apparatus according to claim 5 , wherein:
the first view rate of the first event data is a view rate having a resolution corresponding to a minute angle in which a predetermined view interval is divided into multiple views; and
the second view rate of the second event data is a view rate that is reduced from the first view rate by accumulating, view by view, a number of events in the event data corresponding to the second path.
7 . The X-ray CT apparatus according to claim 6 , wherein the processing circuitry of the projection data generation unit is further configured to:
with respect to the first event data, by dividing an energy corresponding to the threshold by an interval between time data corresponding to the occurrence times of two adjacent events, generate first projection data by upsampling the projection data that corresponds to the first path through the determined region to the first view rate corresponding to the minute angle; and
with respect to the second event data, generate second projection data having the second view rate corresponding to the view interval, based on accumulated number of events.
8 . The X-ray CT apparatus according to claim 7 , further comprising a rotating frame and a fixed frame, wherein
the transmission data generation circuit is housed in the rotating frame and the processing circuitry is housed in the fixed frame, and
the event data for transmission is transmitted via a transmission path between the rotating frame and said fixed frame.
9 . The X-ray CT apparatus according to claim 7 , wherein the processing circuitry is further configured to generate a tomographic image by reconstruction processing using the first projection data and the second projection data.
10 . The X-ray CT apparatus according to claim 5 , wherein the determined region set within the FOV is at least one of
(a) a peripheral region of the FOV,
(b) a region with microstructure that is determined, based on a preliminary imaging image of the object, to be prone to partial volume effects, and
(c) a region in a vicinity of dense material that is determined, based on a preliminary imaging image of the object, to be prone to artifacts.
11 . A radiation detecting apparatus, comprising:
an energy integrating type detector having a plurality of detector units arrayed in a channel direction that accumulate electric charges corresponding to radiation transmitted through an object; and
a time data generation circuit generating time data at a timing when the electric charges accumulated in the detector reach a predetermined threshold, wherein
the time data generation circuit generates the time data for each of the plurality of the detector units.
12 . A data processing method for an X-ray CT apparatus including at least an X-ray tube emitting X-rays and an energy integrating type detector having a plurality of detector units arrayed in a channel direction that accumulate electric charges corresponding to X-rays transmitted through an object, the method comprising:
generating time data at a timing when the electric charges accumulated in the detector reach a predetermined threshold;
generating projection data using the time data and energy corresponding to the threshold;
generating the time data for each of the plurality of the detector units; and
generating event data, which is associated with an event indicating that the electric charges accumulated in a detector unit of the detector units reaches the predetermined threshold, and is associated with the time data indicating a time when the event occurred and identification information of the detector unit in which the event occurred.