Remove outer dial outline from meter chart

pauljin

Hi
I was wondering whether it is possible to modify default appearance of meter chart by removing the outer semicircle out line of meter chart . I have to have the meter chart in 150px Height and 250 px width . But the chart consumes a lot of while spaces to show the graph. In turn meter chart looks odd in this context . I would like to remove the outer outline and maximize the chart to the area .....Please need your valuable help

thanks in advance