ABSTRACT
Within the physical-technical quality assurance of the German breast cancer screening program all digital mammography systems have to perform the contrast resolution test and the determination of the average glandular dose based on the European guidelines for quality assurance in breast cancer screening and diagnosis (4th Edition). Since 1.1.2009 this applies to digital systems outside the screening program too. To accomplish uniform measurements in all federal states of Germany, the physical board of the reference centers developed together a special guideline for these test position. This Guideline describes the determination of the average glandular dose for different types of mammography systems, the CDMAM image acquisition and the CDMAM image evaluation as well. This guideline was verified by the German task group "Röntgenverordnung".
Subject(s)
Breast Neoplasms/diagnostic imaging , Breast/radiation effects , European Union , Image Enhancement/standards , Image Processing, Computer-Assisted/standards , Mammography/standards , Mass Screening/standards , Quality Assurance, Health Care/standards , Contrast Media , Europe , Female , Germany , Humans , Image Enhancement/instrumentation , Image Processing, Computer-Assisted/instrumentation , Mammography/instrumentation , Phantoms, Imaging/standards , Radiation Dosage , Reference StandardsABSTRACT
Insulin lowers basal levels of tyrosinase activity and inhibits the MSH-induced increase in tyrosinase in Cloudman S-91 mouse melanoma cell cultures. Insulin exerts its inhibitory effects in a typical dose-response manner, with maximal inhibition of enzyme activity occurring at 10-7 M. At maximal inhibition, tyrosinase activity is reduced to approximately 50% of the control levels. This inhibition precedes the observed inhibitory effect on cellular proliferation. Insulin not only lowers cell responsiveness to MSH, but also inhibits the tyrosinase stimulation produced by either theophylline or (Bu)2cAMP. Neither control levels nor MSH-mediated elevated cellular levels of cAMP were altered by insulin (10-7 M). These findings suggest that insulin exerts its inhibitory effects at a site distal to cAMP production. The inhibitory effect of insulin on tyrosinase activity could not be mimicked by either (Bu)2cGMP or 8-bromo-cGMP, suggesting that insulin does not exert its effects by altering cellular levels of this nucleotide. Insulin reduces the rate of incorporation of [3H]leucine into trichloroacetic acid-precipitable material by 50%, a finding which suggests that insulin may exert its inhibitory effects on tyrosinase activity and perhaps on cellular proliferation by causing a general reduction in protein synthetic rates.
