Fabrication of two-dimensional x-ray antiscatter grids for mammography

Anti-scatter grids are used in mammography to improve the contrast and signal-to-noise ratio by minimizing scattered x- rays. Most commercially available mammographic anti-scatter grids are one-dimensional, focused arrays of lead lamellae, sandwiched between more x-ray transparent spacer materials such as fiber or wood. Two-dimensional (2D), air-core, focused, anti-scatter grids are expected to be able to significantly reduce scatter-to-primary ratio and increase primary transmission in mammography. Two prototype unfocused, 2D, air-core nickel (Ni) anti-scatter grids were fabricated. The fabrication method uses x-ray lithography and electroplating, LIGA, which allows the fabrication of high aspect ratio metal parts. The metal parts are released from substrate. The grids have 20 micrometer thick walls and 300 micrometer period. This geometry permits 87.1% transmission of primary radiation. Each layer of the grid is assembled from nine smaller grid pieces. The assembly technique allows construction of larger grids. Grids of a desired grid height are obtained by stacking the appropriate number of layers, each layer approximately 250 - 350 micrometer thick. The first prototype is 1.48 cm X 1.48 cm and 2.00 mm high and the second prototype is 1.32 cm X 1.44 cm and 1.78 mm high. Electroplating with lead/tin will also be reported.

[1]  B. Chaudhuri,et al.  Design and fabrication of one millimeter high structures , 1998 .

[2]  P. McNally,et al.  A comparative study of Pd/Sn/Au, Au/Ge/Au/Ni/Au, Au-Ge/Ni and Ni/Au-Ge/Ni ohmic contacts to n-GaAs , 1998 .

[3]  Henry Guckel,et al.  Deep x-ray lithography for micromechanics , 1995, Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components.

[4]  M J Yaffe,et al.  Recommended specifications for new mammography equipment: report of the ACR-CDC Focus Group on mammography equipment. , 1995, Radiology.

[5]  H Bernstein,et al.  A detailed experimental and theoretical comparison of the angular and energy dependencies of grid transmission. , 1983, Medical physics.

[6]  Henry Guckel,et al.  Photoresist application for the LIGA process , 1998 .

[7]  H Bernstein,et al.  On the significance of very small angle scattered radiation to radiographic imaging at low energies. , 1983, Medical physics.

[8]  D R Dance,et al.  The computation of scatter in mammography by Monte Carlo methods. , 1984, Physics in medicine and biology.

[9]  H Bernstein,et al.  Experimental and theoretical energy and angular dependencies of scattered radiation in the mammography energy range. , 1983, Medical physics.

[10]  H Bernstein,et al.  Experimental verification of a technique for predicting scattered radiation transfer: application to low photon energies. , 1986, Medical physics.

[11]  Dev P. Chakraborty.  Effect of the antiscatter grid and target/filters in full-field digital mammography , 1999, Medical Imaging.

[12]  K. Fischer,et al.  Long throw linear magnetic actuators stackable to one millimeter of structural height , 1998 .

[13]  Cha-Mei Tang,et al.  Anti-scattering X-ray grid , 1998 .

[14]  R Fahrig,et al.  Performance of glass fiber antiscatter devices at mammographic energies. , 1994, Medical physics.

[15]  Rebecca Fahrig,et al.  Experimental and simulation results of two-dimensional prototype anti-scatter grids for mammography , 2000, Proceedings of the 22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (Cat. No.00CH37143).

[16]  Zhong Min Lin,et al.  Grids and digital grids: the improvement of contrast and SNR in digital radiography , 1999, Medical Imaging.

[17]  D R Dance,et al.  Calculation of dose and contrast for two mammographic grids. , 1992, Physics in medicine and biology.