Abstract: An MRI system includes a noise filter which receives each acquired NMR signal during a scan and detects short-duration noise pulses by sensing the signal level in a band of frequencies outside the imaging bandwidth. A blanking circuit suppresses the NMR signal during the time interval each noise pulse is detected to remove the noise pulse prior to image reconstruction.

Abstract: A CT scanner in which the amount of x-ray information acquired per unit time is substantially increased by using a continuous-on x-ray source and a sampled data system with the detector. An analog filter is used in the sampling system for band limiting the detector signal below the highest frequency of interest, but is a practically realizable filter and is therefore non-ideal. A digital filter is applied to the detector data after digitization to compensate for the characteristics of the analog filter, and to provide an overall filter characteristic more nearly like the ideal.

Abstract: Image frames produced consecutively with x-ray beams having different spectral bands or average energy levels are converted to analog video signals and then to digital data. The digital data for an image at one energy is stored in a memory and the ensuing data for the next image is subtracted from the stored data in an alternate or cyclic fashion. The resulting difference data is converted to analog video signals and displayed on a television monitor at standard frame rates. The same system can be used to store a digitized data mask frame and the digital data for ensuing frames can be subtracted from the mask. In some embodiments a buffer is used to allow removal of data from memory without having the data from a preceding frame overwritten by ensuing frames.

Abstract: In dental x-ray apparatus a control is provided for driving the high voltage transformer in the tube head at a frequency far above power line frequency. The transformer is driven with an inverter. A precision d-c voltage regulator that operates in an "add-on" mode and thus only handles a portion of the output current controls the voltage supplied to the inverter. The d-c voltage regulator is supplied a voltage by a transformerless a-c/d-c converter whose output is proportional to the 60 Hz power line voltage that supplies it. The x-ray tube filament transformer is also driven at a frequency above power line frequency. Means are provided to cut off power to the x-ray tube if its current does not reach a certain value within a short time after an exposure is initiated. Means are provided for isolating high voltage power circuits from low voltage control circuits.