TWO-DIMENSIONAL X-RAY COLLIMATION GRID BY ION BEAM ETCHING

THE STATE-OF-THE-ART X-RAY IMAGE ENHANCING DEVICE IS THE BUCKY GRID WHICH ALLOWS PRIMARY RADIATION TO PASS THROUGH UNIMPEDED WHILE STOPPING THE PASSAGE OF SCATTERED RADIATION FROM REACHING THE X-RAY FILM AND FOGGING THE IMAGE. GRIDS CONSIST OF A SYSTEM OF VERTICAL LAMELLAE MADE OF ALTERNATING RADIOPAQUE AND TRANSPARENT LAYERS. THE BUCKY GRID IS LIMITED IN MEETING THE CURRENT DEMANDS OF RADIOLOGY, PARTICULARLY MAMMOGRAPHY WHERE SPOTS LESS THAN A MILLIMETER MUST BE DETECTED. THE PROBLEM WITH THE CURRENT DESIGN IS THAT THE FILTER ONLY ATTENUATES SCATTERED RADIATION IN ONE DIMENSION, THE LAMELLAE (TYPICALLY 0.5 MM WIDE) ARE TOO THICK TO OFFER HIGH RESOLUTION IMAGING, AND THE THICK ATTENUATING LAYERS STOP A SIGNIFICANT PORTION OF THE NON-SCATTERED SIGNAL. THIS LOW TRANSPARENCY TO THE DESIRED NON-SCATTERED X-RAYS REQUIRES THAT THE PATIENT BE EXPOSED TO HIGHER DOSES OF X-RAYS IN ORDER TO PROVIDE A DISCERNABLE IMAGE. ANTIQUATED GRID MANUFACTURING TECHNOLOGY IS PRIMARILY RESPONSIBLE FOR THESE CURRENT LIMITATIONS. ION BEAM ETCHING AND PHOTOLITHOGRAPHY ARE BEING USED TO CREATE HIGH-DEFINITION, HIGH-TRANSMISSION GRIDS WITH LINE WIDTHS REACHING LESS THAN 0.1 MM. THE UNIQUE ADVANTAGE OF THIS TECHNIQUE LIES IN THE OPTICAL DIVERGENCE OF THE ION BEAM SOURCE USED FOR ETCHING THE HIGH-DEFINITION GRIDS WHICH CAN BE CONFIGURED TO EMULATE THE EMISSION GEOMETRY FROM AN X-RAY SOURCE.