Abstract
Excess risk of leukemia and brain tumors after CT scans in children has been reported. We performed dicentric chromosome assay (DCAs) before and after CT scan to assess effects of low-dose ionizing radiation on chromosomes. Peripheral blood (PB) lymphocytes were collected from 10 patients before and after a CT scan. DCA was performed by analyzing either 1,000 or 2,000 metaphases using both Giemsa staining and centromere-fluorescence in situ hybridization (Centromere-FISH). The increment of DIC formation was compared with effective radiation dose calculated using the computational dosimetry system, WAZA-ARI and dose length product (DLP) in a CT scan. Dicentric chromosome (DIC) formation increased significantly after a single CT scan, and increased DIC formation was found in all patients. A good correlation between the increment of DIC formation determined by analysis of 2,000 metaphases using Giemsa staining and those by 2,000 metaphases using Centromere-FISH was observed. However, no correlation was observed between the increment of DIC formation and the effective radiation dose. Therefore, these results suggest that chromosome cleavage may be induced by one CT scan, and we recommend 2,000 or more metaphases be analyzed in Giemsa staining or Centromere-FISH for DCAs in cases of low-dose radiation exposure.
Highlights
With respect to radiation exposure resulting from computed tomography (CT) scanning, only lymphocytes localized in the tissues being scanned are exposed to the ionizing radiation, and they are diluted by the non-irradiated cells in the blood circulation afterwards, especially, when a small volume is irradiated by CT scanning, and distributed throughout the body
It is believed that the number of dicentric chromosome (DIC) formed in peripheral blood (PB) lymphocytes is lower than the true number induced by the exposure to ionizing radiation[10,18]
Löbrich et al reported that the number of DNA double-strand breaks (DSBs) induced by CT scan showed linear dose response curve[19]
Summary
There are some reports of DCAs conducted in patients who received a CT scan[12,13] in which the radiation dose was less 100 mSv. the detection of chromosomal aberrations using Giemsa staining is a conventional method for DCA, it requires a well-trained and skilled observer. Because the increment of DIC formation in patient 4, 7, and 8 in analyses using Giemsa staining and in patient 2, 4, 8, and 10 in analyses using Centromere-FISH were lower than the number of DICs formed in the background of the standard dose-response curve, the estimated dose in those patients were not available.
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