MOVING BEAM HELICAL CT SCANNING

Images generated with helical scanning are degraded by partial volume artifacts caused by an increased slice thickness when compared to conv entional computed tomography (CT) scanning. The slice thickness for a helical scan is proportional to the sum of the thickness of the fan of radiation and the distance the patient moves during data acquisition. We present a method called moving beam helical scanning (MBHS) which significantly reduces the partial volume artifacts caused by helical s canning. The key element of MBHS is a rotatable collimator that is pla ced between the X-lay source and the patient. As the patient is transl ated, the collimator is used to aim the fan on a fixed position in the patient. Once sufficient data are obtained to reconstruct a slice, th e collimator is quickly reset to scan a target in the next slice. We e xamined the performance of MBHS by scanning wires and phantoms on a mo dified scanner. The full-width-at-tenth-maximum of the slice profile a t iso-center for MBHS is identical to conventional CT versus a 59% inc rease for conventional helical scanning. We conclude that MBHS can be used to obtain the scan rate advantages of helical scanning with image quality comparable to conventional scanning.