System design options for a high-resolution, conventional scintillator detector.

It is commonly believed that energy integrating detector (EID) CT has limited spatial resolution because of reflective septa placed around each pixel. Reducing the pixel size would increase the proportion of detector area lost. We point out that this can be avoided if the detector is tilted, because then rays would penetrate reflective septa and reach buried scintillator. But how should this be accomplished? We consider three options for system design: (1) with the false focal spot geometry, the detector is focused at a "false" point about 5 cm from the true focal spot. The anti-scatter grid (ASG) must still point towards the true focal spot. (2) With tilted detector modules, each detector tile is tilted by a few degrees. Slight discontinuities are created at boundaries between tiles, which could cause artifacts if not appropriately handled. The anti-scatter grid would have to float above some pixels. (3) With tilted cuts, the scintillator is structured with angled cuts rather than vertical cuts before the cuts are infilled with reflective septa. This minimizes changes to reconstruction and the ASG. All three options would improve fill factor. Using ray tracing simulations and assuming a reflective septa width of 0.1 mm, we estimate that the effective fill factor is increased from 81% for a conventional, 1 mm pitch detector to 91% with a high-resolution, 0.5 mm pitch detector that is tilted. These concepts open up a pathway for high-resolution CT without requiring photon counting technology.