The chromosomal radiosensitivity of breast cancer patients with a known or putative genetic predisposition was investigated and compared to a group of healthy women. The chromosomal radiosensitivity was assessed with the G2 and the G0-micronucleus assay. For the G2 assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy 60 Co g-rays after 71 h incubation, and chromatid breaks were scored in 50 metaphases. For the micronucleus assay lymphocytes were exposed in vitro to 3.5 Gy 60 Co g-rays at a high dose rate or low dose rate. 70 h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. The results demonstrated that the group of breast cancer patients with a known or putative genetic predisposition was on the average more radiosensitive than a population of healthy women, and this with the G2 as well as with the high dose rate and low dose rate micronucleus assay. With the G2 assay 43% of the patients were found to be radiosensitive. A higher proportion of the patients were radiosensitive with the micronucleus assay (45% with high dose rate and 61% with low dose rate). No correlation was found between the G2 and the G0-micronucleus chromosomal radiosensitivity. Out of the different subgroups considered, the group of the young breast cancer patients without family history showed the highest percentage of radiosensitive cases in the G2 (50%) as well as in the micronucleus assay (75 -78%).

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The results support the value of contrast-detail phantom analysis for evaluating clinical image quality in chest radiography.

The introduction of digital flat-panel radiography systems based on amorphous silicon and cesium iodide is an important step forward in chest imaging that offers improved image quality combined with a significant reduction in the patient radiation dose.

of peripheral blood lymphocytes (Fenech and Morley, 1985) is a valuable and less laborious alternative for large scale L.De Ridder 1 studies . Fluorescence in situ hybridiza- Scoring of micronuclei with and without centromeres has A cytogenetic study was performed in lymphocytes of increased the sensitivity of the technique substantially for hospital workers occupationally exposed to X-and γ-rays monitoring of radiation workers (Vral et al., 1997). According using the micronucleus centromere assay. A comparison of to Streffer et al. (1998), the micronucleus centromere assay is the data for the exposed group and an age-matched group able to detect the effects of chronic exposure in uranium of non-exposed hospital workers showed a significant (P < miners a long time after exposure. 0.05) increase in centromere-positive micronuclei for theUsing the micronucleus centromere assay we performed a radiation workers, while no effect on centromere-negative large scale cytogenetic study of hospital workers occupationally micronuclei was present. The observed systematic increase exposed to X-rays or to radiation from radioactive sources. in micronucleus frequency with age was mainly due to An age-matched population of doctors and nursing staff of increased chromosome loss, reflected in the centromeredepartments such as pediatrics, where exposure to ionizing positivity of the micronuclei. The micronucleus frequencies radiation is neglegible, served as a control group. Apart from were 40% higher in females than in males, which can again a direct comparison between the occupationally exposed and be attributed to higher chromosome loss. Two exposed control groups, the effect of donor age, gender and smoking individuals showed exceptionally high micronucleus yields, on micronucleus frequencies with and without centromeres was 90% of which were centromere-positive. In situ hybridizainvestigated. This study was performed within the framework of tion with a centromeric probe for chromosome X shows the Programme of Scientific Support to the Protection of that X chromosome loss is responsible for these high Workers in the Area of Health of the Services of the Prime micronucleus yields. In the studied population, smokingMinister Science Policy Office of the Belgian Government. had no significant effect on the micronucleus yields. The results obtained indicate that in contrast to the predomiMaterials and methods nantly clastogenic action of acute exposure to ionizing Subjects radiation, the aneugenic properties of radiation may beThe population under study, exposed occupationally to ionizing radiation, important after long-term chronic low dose exposure.

Of all investigated techniques, Veo shows to be most promising, with a significant improvement of both the clinical and physical-technical image quality without adversely affecting contrast detail. MARs reconstruction in CT images of the oral cavity to reduce dental hardware metallic artifacts is not sufficient and may even adversely influence the image quality.

As enhanced chromosomal radiosensitivity (CRS) results from non- or misrepaired double strand breaks (DSBs) and is a hallmark for breast cancer and single nucleotide polymorphisms (SNPs) in DSB repair genes, such as non homologous end-joining (NHEJ) genes, could be involved in CRS and genetic predisposition to breast cancer. In this study, we investigated the association of five SNPs in three different NHEJ genes with breast cancer in a population-based case-control setting. The total patient population composed of a selected group of patients with a family history of the disease and an unselected group, consisting mainly of sporadic cases. SNP analysis showed that the c.2099-2408G>A SNP (XRCC5Ku80) [corrected] has a significant, positive odds ratio (OR) of 2.81 (95% confidence interval (CI): 1.30-6.05) for the heterozygous (He) and homozygous variant (HV) genotypes in the selected patient group. For the c.-1310 C>G SNP (XRCC6Ku70)[corrected] a significant OR of 1.85 (95%CI: 1.01-3.41) was found for the He genotype in the unselected patient group. On the contrary, the HV genotype of c.1781G>T (XRCC6Ku70) [corrected] displays a significant, negative OR of 0.43 (95%CI: 0.18-0.99) in the total patient population. The He+HV genotypes of the c.2099-2408G>A SNP (XRCC5Ku80) [corrected] also showed high and significant ORs in the group of "radiosensitive," familial breast cancer patients. In conclusion, our results provide preliminary evidence that the variant allele of c.-1310C>G (XRCC6Ku70) [corrected]and c.2099-2408G>A (XRCC5Ku80) [corrected] are risk alleles for breast cancer as well as CRS. The HV genotype of c.1781G>T (XRCC6Ku70) [corrected] on the contrary, seems to protect against breast cancer and ionizing radiation induced micronuclei.