环形图默认高亮显示最大值echarts 饼配置项内容和展示

”动环”所属部分图像怎么默认高亮凸显？

      var labelTop = {
normal : {
    label : {
        show : true,
        position : 'center',
        formatter : '{b}',
        textStyle: {
            baseline : 'bottom',
            fontSize:30
        }
    },
    labelLine : {
        show : false
    }
}
};
option = {
tooltip: {
    trigger: 'item',
    show:'true',
    formatter: "{a} <br/>{b} : {c} ({d}%)"
    	
},
color:['#DB4D4B','#EC13A6','#ffdf33','#654FC0','#00A2E8','#DE9B32','#84B059'],
legend: {
    orient: 'vertical',
    y: '20%',
    x: 'content',
    textStyle: {
        fontWeight: 'normal', 
        color: '#ABE3FE', 
        fontSize:12
     },
     icon : 'pin',
     data: ['CPU', '内存', '磁盘','通道','进程','网线断开','动环']
},
calculable: true,
series: [
    {
        type: 'pie',
        radius: ['50%', '70%'],
        avoidLabelOverlap: false,
        label: {
            normal: {
                show: false,
                position: 'center',
            },
            emphasis: {
                show: true,
                textStyle: {
                    fontSize: '30',
                    fontWeight: 'bold'
                }
            }
        },
        labelLine: {
            normal: {
                show: false
            }
        },
        data: [
            {value: 30, name: 'CPU'},
            {value: 30, name: '内存'},
            {value: 30, name: '磁盘'},
            {value: 40, name: '通道'},
            {value: 40, name: '进程'},
            {value: 50, name: '网线'},
            {value: 80, name: '动环',itemStyle:labelTop} 
        ]
    }
]
}