Analysis of chromosome translocation frequency after a single CT scan in adults

Abstract

We recently reported an increase in dicentric chromosome (DIC) formation after a single computed tomography (CT) scan (5.78–60.27 mSv: mean 24.24 mSv) and we recommended analysis of 2000 metaphase cells stained with Giemsa and centromere-FISH for dicentric chromosome assay (DCA) in cases of low-dose radiation exposure. In the present study, we analyzed the frequency of chromosome translocations using stored Carnoy's-fixed lymphocyte specimens from the previous study; these specimens were from 12 patients who were subject to chromosome painting of Chromosomes 1, 2 and 4. Chromosomes 1, 2 and 4 were analyzed in ∼5000 cells, which is equivalent to the whole-genome analysis of almost 2000 cells. The frequency of chromosome translocation was higher than the number of DICs formed, both before and after CT scanning. The frequency of chromosome translocations tended to be higher, but not significantly higher, in patients with a treatment history compared with patients without such a history. However, in contrast to the results for DIC formation, the frequency of translocations detected before and after the CT scan did not differ significantly. Therefore, analysis of chromosome translocation may not be a suitable assay for detecting chromosome aberrations in cases of low-dose radiation exposure from a CT scan. A significant increase in the frequency of chromosome translocations was not likely to be detected due to the high baseline before the CT scan; the high and variable frequency of translocations was probably due to multiple confounding factors in adults.

Automated scoring of dicentric chromosomes differentiates increased radiation sensitivity of young children after low dose CT exposure in vitro

“…The advantage of symmetrical translocations is the higher stability over time because they can pass cell division. However, compared to the results gained with dicentric chromosomes, no statistical significant differences between symmetrical translocations before and after CT scan was detected in in vivo studies because of the higher baseline frequencies which are related to different confounding factors (Abe et al 2016) not characteristic for ionising radiation. New approaches investigating global gene expression with DNA microarrays are currently performed and improve the understanding in different cellular responses to low and high doses of X-rays.…”

Dose–response curves for analyzing of dicentric chromosomes and chromosome translocations following doses of 1000 mGy or less, based on irradiated peripheral blood samples from five healthy individuals

“…Centromere-FISH staining was achieved using Poseidon probe (KRATECH, Amsterdam, the Netherlands) according to the manufacturer’s protocol, with slight modifications described previously [ 24 ]. Chromosome painting was achieved using a Customized XCP-Mix probe (Mix-#1R-#2G-#4RG; MetaSystems, Altlussheim, Germany) according to the manufacturer’s protocol, as in our previous study [ 25 ]. Briefly, nuclear DNA was denatured by incubating the slides on a hot plate at 75°C for 2 min, followed by incubation overnight at 37°C in a humidified chamber to allow for hybridization.…”

“…Metaphases with fewer than 45 centromeres were omitted from analysis. For translocation analysis, more than 5000 metaphases were scored on each slide [ 25 ]. Based on a previous report [ 26 ], we included apparent one-way translocations in the two-way translocation counts.…”

Effects of acute exposure to low-dose radiation on the characteristics of human bone marrow mesenchymal stromal/stem cells

“…The stochastic effects of irradiation on the risk of cancers including hematological malignancies are well established [ 4 ]. Diagnostic X-rays can increase the risk of cancer [ 21 ], and chromosome translocation induced by a single CT scan has been demonstrated at the cellular level [ 22 ]. On the other hand, 0.1 Gy is the threshold of the deterministic effects of irradiation, and low-dose irradiation of equal to or less than 0.1 Gy is considered to have no influence on the risk of diseases apart from malignancies.…”