Objective      To evaluate the feasibility of extracorporeal ablation of adrenal glands by magnetic resonance imaging (MRI)-guided high-intensity focused ultrasound (HIFU).       Methods      Sixteen healthy mongrel dogs weighing 9-13 kg were randomly divided into a control group

a l

ow-dose HIFU ablation group (acoustic power 200 W) and a high-dose HIFU ablation group (acoustic power 400 W)

respectively. All the dogs underwent MRI-guided extracorporeal HIFU ablation of their left adrenal glands. After the ablation

enhanced MRI was used to evaluate the damage to the adrenal glands and adjacent organs and tissues. The levels of aldosterone and cortisol were monitored every day. All the dogs were sacrificed after 5 d

and the destruction of the left adrenal glands and adjacent organs and tissues were observed. The ablation of the adrenal glands was assessed by hematoxylin and eosin (HE) staining. The difference of the ablation ratio between the low-dose HIFU ablation group and the high-dose HIFU ablation group was evaluated.       Results      After ablation

the vital signs of all the dogs were stable. Enhanced MRI showed a significant signal decrease in the ablation regions of the adrenal glands and no obvious abnormal signal in adjacent organs and tissues. The ablation lesions in the head and tail of the left adrenal glands could be seen clearly. HE staining showed the ablation lesions of adrenal glands had pathological necrosis and a clear demarcation to the surrounding tissues. The number of the ablation lesions of the high-dose HIFU ablation group was significantly greater than that of the low-dose HIFU ablation group. The average ablation area of the low-dose HIFU ablation group was 1.8±0.3 cm

2

with an average ablation ratio of （40.3±18.1）%. The average ablation area of the high-dose HIFU ablation group was 2.7±0.6 cm

2

with an average ablation ratio of （60.3±23.3）%. The ablation area and ablation ratio of the high-dose HIFU ablation group were significantly higher than those of the low-dose HIFU ablation group (P0.05).  Compared with the control group

the levels of aldosterone and cortisol of the low-dose HIFU ablation group and the high-dose HIFU ablation group both showed transient increases at the first day

and then a decrease trend from the second day. From

the third day

they both tended to be stable but were still lower than those of the control group (P0.05).        Conclusion      MRI-guided HIFU is a safe and effective method to achieve controllable ablation of adrenal glands

and HIFU may have potential application in minimally invasive treatment of adrenal diseases.