Imaging with @-kV/@-mAs instead of @-kV/@-mAs was associated with @ % lower radiation dose ( mean dose-length product , @ vs @ mGy -LSB- Symbol : see text -RSB- cm ; P < @ ) with no significant difference in CNR ( @ vs @ ; P = @ ) or MBF in non-ischaemic myocardium ( @ vs @ ml/min/g ; P = @ ) .