Calculation of dose and contrast for two mammographic grids.

To aid in selecting optimal conditions for screening mammography practice in Sweden, the performance of two mammographic grids (one moving and one stationary) has been investigated. Monte Carlo techniques were used to simulate photon transport in the breast. Transport through the breast support, grid covers, grid and image receptor (33.9 mg cm-2 Gd2O2S) was treated analytically. The contrast of a 100 microns calcification has been evaluated for three tissue compositions (adipose, glandular, 50:50 fractions by weight of adipose and glandular tissue) as a function of breast thickness (2-8 cm) and potential difference (25-30 kV, Mo anode). Contrast for a 5 cm 'average' breast at 28 kV was improved by 40% using the moving grid and by 30% using the stationary one; the corresponding increases in breast absorbed dose, keeping the energy imparted to the image receptor constant, were 90% and 150%, respectively. The superior properties of the moving grid were due to (i) equal scatter rejection ability and higher transmission of primary photons yielding lower scatter-to-primary ratios behind the grid, and (ii) less attenuation and filtering of the primary photons in the interspace material yielding lower degradation of primary contrast.

[1]  J Persliden,et al.  A Monte Carlo program for photon transport using analogue sampling of scattering angle in coherent and incoherent scattering processes. , 1983, Computer programs in biomedicine.

[2]  D D Dershaw,et al.  Mammography using an ultrahigh-strip-density, stationary, focused grid. , 1985, Radiology.

[3]  D R Dance,et al.  The Monte Carlo calculation of integral radiation dose in xeromammography , 1980, Physics in medicine and biology.

[4]  L. Morin.  Molecular Form Factors and Photon Coherent Scattering Cross Sections of Water , 1982 .

[5]  Haus Ag.  Recent advances in screen-film mammography. , 1987 .

[6]  G. Fagerberg,et al.  Image Quality in Mammography with Special Reference to Anti-Scatter Grids and the Magnification Technique , 1986, Acta radiologica: diagnosis.

[7]  J. H. Hubbell,et al.  Relativistic atomic form factors and photon coherent scattering cross sections , 1979 .

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

[9]  R E Hendrick,et al.  Standardization of image quality and radiation dose in mammography. , 1990, Radiology.

[10]  P P Fatouros,et al.  The effect of breast composition on absorbed dose and image contrast. , 1989, Medical physics.

[11]  J Persliden,et al.  Calculation of the small-angle distribution of scattered photons in diagnostic radiology using a Monte Carlo collision density estimator. , 1986, Medical physics.

[12]  A G Haus.  Technologic improvements in screen-film mammography. , 1990, Radiology.

[13]  P Sprawls,et al.  Grids in mammography. , 1983, Radiology.

[14]  J. S. Laughlin,et al.  Absorbed radiation dose in mammography. , 1979, Radiology.

[15]  Y Higashida,et al.  Ultra-high-strip-density radiographic grids: a new antiscatter technique for mammography. , 1985, Radiology.

[16]  Lellery Storm,et al.  Photon cross sections from 1 keV to 100 MeV for elements Z=1 to Z=100 , 1970 .

[17]  D R Dance,et al.  Quantitative measurement of small-angle gamma ray scattering from water, nylon, and Lucite. , 1989, Medical physics.

[18]  G. A. Carlsson,et al.  Generalised use of contrast degradation and contrast improvement factors in diagnostic radiology. Application to vanishing contrast. , 1986, Physics in medicine and biology.

[19]  L. Tabár.  Control of breast cancer through screening mammography. , 1990, Radiology.

[20]  D R Dance,et al.  X-ray transmission formula for antiscatter grids. , 1983, Physics in medicine and biology.

[21]  J. H. Hubbell,et al.  Atomic form factors, incoherent scattering functions, and photon scattering cross sections , 1975 .