Search

We studied 273 premenopausal women recruited from mammography units who had different degrees of density of the breast parenchyma on mammography, in whom we measured height, weight and skinfold thicknesses. Mammograms were digitized to high spatial resolution by a scanning densitometer and images analysed to measure the area of dense tissue and the total area of the breast. Per cent density and the area of non-dense tissue were calculated from these measurements. We found that the mammographic measures had different associations with body size. Weight and the Quetelet index of obesity were strongly and positively associated with the area of non-dense tissue and with the total area of the breast, but less strongly and negatively correlated with the area of dense tissue. We also found a strong inverse relationship between the areas of radiologically dense and non-dense breast tissue. Statistical models containing anthropometric variables explained up to 8% of the variance in dense area, but explained up to 49% of the variance in non-dense area and 43% of variance in total area. These results suggest that aetiological studies in breast cancer that use mammographic density should consider dense and non-dense tissues separately. In addition to per cent density, methods should be examined that combine information from these two tissues.

N Strumas, O Antonyshyn, MJ Yaffe, G Mawdsley, P Cooper. Computed tomography artefacts: An experimental investigation of causative factors. Can J Plast Surg 1998;6(1):23-29.The factors that produce computed tomography (CT) artefacts associated with craniofacial fixation devices were analyzed. The effects of attenuation, motion, partial volume and implant shape were evaluated. By using a CT phantom model with an engine to produce reproducible motion, a vitallium rod, fixation plate and blank were scanned sequentially. for each experimental condition, the degree of artefact produced was quantified by measuring the standard deviation of the CT number at standardized regions of interest, and a comparative analysis was performed. Motion produced the greatest degree of artefact. Both the frequency and direction of motion were important, with high frequency motion in the plane of the CT slice producing the greatest degree of CT artefact. Partial volume artefacts increased as the volume of material in the plane of section increased. The amount of artefact produced was dependent on the volume of material x-rays passed through the object rather than on the geometric configuration. Attenuation effects were evaluated. Results revealed that the amount of artefact was greatest between highly attenuating objects.

Previous investigators have shown that there is a strong association between the fraction of fibroglandular tissue within the breast as determined by X-ray mammography (per cent density) and breast cancer risk. In this study, the quantitative correlation between per cent density and two objective magnetic resonance (MR) parameters of breast tissue, relative water content and mean T2 relaxation time, as investigated for 42 asymptomatic subjects. Using newly developed, rapid techniques MR measurements were performed on a volume-of-interest incorporating equal, representative portions of both breasts. X-ray mammograms of each subject were digitised and analysed semiautomatically to determine per cent density. Relative water content showed a strong positive correlation with per cent density (Pearson correlation coefficient rp = 0.79, P < 0.0001) and mean T2 value showed a strong negative correlation with per cent density (rp = -0.61, P < 0.0001). The MR and X-ray parameters were also associated with sociodemographic and anthropometric risk factors for breast cancer (P < 0.05). The potential use of MR parameters to assess risk of breast cancer and to provide a frequent, non-hazardous monitor of breast parenchyma is discussed.