Thin-MWCNTs and thick-MWCNTs under evaluation were intravenously administered using the most current and advanced technology for dispersion, including the use of dispersion liquid and ultrasonic dispersion machine.30 This study is the first to report the organ accumulation of highly-dispersed MWCNTs in the circulatory system and the use of a transgenic mouse model to assess carcinogenicity under the severest of conditions.