Patent Number: 060884274
Section: claims

1. An apparatus for radiological examination, comprising: a radiation source;  a holder for receiving radiation from said radiation source;  a grid comprising an assembly of lead strips between said radiation source and said holder, said grid being capable of reciprocating motion;  a motor capable of displacing said grid in reciprocating motion, said grid having an oscillating mass when in motion; and  a counterweight balancing the oscillating mass of said grid.  a radiation source for producing radiation to be directed toward a patient;  a holder for holding a film or plate and receiving radiation from said radiation source that has passed through a patient;  a grid comprising an assembly of lead strips located between said radiation source and said holder, said grid being mounted for reciprocating motion in a direction generally perpendicular to the direction from said radiation source to said holder;  a motor connected to said grid for displacing said grid with reciprocating motion, said grid having an oscillating mass when in motion; and  a counterweight connected so as to dynamically balance the oscillating mass of said grid during reciprocating motion of said grid. 2. The apparatus of claim 1, wherein said motor comprises a stepper motor, a first crank connected to said stepper motor and a connecting rod connected between said first crank and said grid. 3. The apparatus of claim 2, wherein said counterweight is driven by said stepper motor by a second crank connected to said stepper motor and a second connecting rod connected between said crank and said counterweight. 4. The apparatus of claim 3, wherein said first crank and said second crank are pivotally attached to a shaft of said stepper motor so as to be parallel with each other. 5. The apparatus of claim 4, wherein said stepper motor is controlled by an electronic control means for controlling the angular speed of said stepper motor. 6. The apparatus of claim 1, wherein said counterweight is driven by said motor by a crank connected to said motor and a connecting rod connected between said crank and said counterweight. 7. The apparatus of claim 6, wherein said motor is controlled by an electronic control means for controlling the angular speed of said motor. 8. The apparatus of claim 1, wherein said motor is controlled by an electronic control means for controlling the angular speed of said motor. 9. An apparatus for radiological examinations, comprising: 10. The apparatus of claim 9, wherein said grid and said counterweight are connected to a shaft of said motor so as to be 180 degrees out of phase with respect to each other. 11. The apparatus of claim 9, wherein said grid and said counterweight are connected to said motor with respective first and second motion transmission mechanisms. 12. The apparatus of claim 11, wherein said first and second motion transmission mechanisms each comprises a crank and a connecting rod. 13. The apparatus of claim 9, wherein said counterweight is mounted to reciprocate in a direction opposite to a direction of reciprocation of said grid. 14. The apparatus of claim 9, wherein a housing supports said holder, mounts said grid for reciprocating motion, and houses said motor and said counterweight. 15. The apparatus of claim 9, wherein said motor is a stepper motor. 16. The apparatus of claim 15, and further comprising an electronic control means for controlling the angular speed of said stepper motor. 17. The apparatus of claim 16, wherein said electronic control means controls said stepper motor so maintain a constant reciprocating speed of said grid. 18. The apparatus of claim 9, and further comprising an electronic control means for controlling the angular speed of said motor. 19. The apparatus of claim 18, wherein said electronic control means controls said motor so maintain a constant reciprocating speed of said grid.