Abstract: An automatic exposure control for an x-ray system using a large area solid state x-ray detector (26) includes an exposure control (36, 34) arranged to generate data of interest within the data generated by the detector and to adjust the dosage of x-rays to a predetermined level in response to data of interest so that an x-ray image of a patient is generated using the predetermined level.

Abstract: An MRI system has two sets of gradient coils driven by two corresponding sets of gradient amplifiers. Logical gradient waveforms produced during a pulse sequence are rotated to produce corresponding physical gradient waveforms and these are distributed to drive both sets of coils simultaneously. Each distributed set of physical gradient waveforms is separately compensated for Eddy current errors, and a polarizing field Eddy current compensation signal is produced and used to modulate the RF reference frequency of the system transceiver.

Abstract: Image artifacts produced by residual magnetization in elements of the gradient field amplifier system are reduced by driving the residual magnetization to a preselected value at the end of each imaging pulse sequence. Reset gradient pulses are produced by the gradient field amplifier system after each signal is acquired to drive the residual magnetization to a selected value. A number of different reset gradient waveforms may be used, and they may be produced in a number of different ways.

Abstract: A technique is disclosed for calibrating time delays between RF and gradient frequency pulses in a magnetic resonance imaging system. The calibration procedure includes the formation of calibration images of a phantom positioned in the gradient field system. Calibration images are processed and compared to one another to determine deviation between locations in the gradient field system and the impact of radio frequency-to-gradient waveform time delays on the deviations. Optimal time delays are identified which minimize the deviations between the calibration images. Multiple axes of the system may be calibrated through the use of symmetrical phantoms and similar pulse sequences of each axis. A spectral-spatial pulse sequence is employed bearing the calibration routine.

Abstract: An MRI system automatically performs a calibration procedure to calculate optimal compensation parameter values for all three gradient pre-emphasis filters. A single fixture is employed to measure the errors caused by gradient pulses produced by each of the three gradient systems. The measured errors are used to calculate a gradient error function and the optimal compensation parameter values are calculated for each pre-emphasis filter by finding the minimum in the gradient error function.

Abstract: An MRI system performs a calibration procedure to calculate optimal compensation parameter values for a pre-emphasis filter that alters the shape of gradient waveforms. The gradient field errors are measured using a series of pulse sequences in which different compensation parameter values are sampled. The measured errors are used to calculate a gradient error function and the optimal compensation parameter values are calculated by finding the minimum in the gradient error function.

Abstract: A method is presented for correcting Maxwell term error artifacts produced by an NMR system during the production of either a phase contrast angiogram or a complex difference angiogram. Phase corrections are made to the reconstructed phase image to eliminate the artifacts. Correction coefficients calculated from the flow encoding magnetic gradient waveforms of the phase contrast pulse sequence are used in a polynomial to calculate a set of phase error corrections. These corrections are then used to adjust the phase at each pixel of the angiogram image.

Abstract: Artifacts in NMR images produced by Maxwell terms during non-rectilinear scans, such as spiral scans, are reduced or eliminated. Phase corrections for in-plane and through-plane blurring are used to offset Maxwell terms errors.

Abstract: A method for using a gamma camera having a head including an array of photodetectors that produces a group of input pulses in response to an actual interaction of a radiation stimulus with the camera head, includes the step of repetitiously generating groups of synthetic pulses that resemble groups of input pulses and simulate the occurrence of synthetic interactions of stimuli with the head. These groups of synthetic and input pulses are applied to processing circuitry that produces groups of processed pulses. The coordinates of both actual and synthetic interactions based on said processed pulses are computed; and a representation of the spatial locations of both actual and synthetic interactions based on the computed coordinates is stored.

Abstract: The dead time of a nuclear imaging system is compensated for when recording a representation of a dynamically changing radiation field into an image memory by injecting into the system synthetic pulses which resemble, in terms of amplitude and shape, the pulses produced by the system in response to interaction with stimuli from the radiation field, and by determining the percentage of synthetic pulses which are processed by the system. A correction factor based on such percentage is applied to the representation of the field. The synthetic pulses are injected into the system at a predetermined rate with respect to the rate of pulses processed by the system in response to interactions with stimuli from the radiation field. This predetermined rate is functionally related to the rate at which input signals are processed by the system.