Here is the design of a clinical trial:

Official Title: Deep Brain Stimulation of Nucleus Accumbens for Opioid Relapse Prevention:A Multicenter Randomized Double-Blind Sham-stimulation Controlled Clinical Trial

Included conditions:
- Addiction

Study Armgroups:
- {'label': 'Postoperative immediate Deep brain stimulation', 'type': 'EXPERIMENTAL', 'description': 'The addicts undergone the deep brain stimulation while the stimulation (Suzhou Sceneray® DBS System) was turned on 1-2 weeks postoperatively.', 'interventionNames': ['Device: Suzhou Sceneray® DBS System']}
- {'label': 'Postoperative delayed Deep brain stimulation', 'type': 'SHAM_COMPARATOR', 'description': 'The addicts undergone the deep brain stimulation while the stimulation (Suzhou Sceneray® DBS System) was off until 25 months postoperatively, during which the following up was kept, then the the stimulation was turned on 25 months postoperatively.', 'interventionNames': ['Device: Suzhou Sceneray® DBS System']}

Interventions:
- {'type': 'DEVICE', 'name': 'Suzhou Sceneray® DBS System', 'description': 'We plan to use the SceneRay 1242 (SceneRay, SuZhou, China) electrode with a diameter of 1.27 mm and 4 contacts. The SceneRay 1242 electrode combined with the SceneRay 1181 implantable pulse generator has the advantage of adaptive coverage area for the Ventral Capsule/Ventral Striatum, enabling simultaneous implantation in the nucleus accumbens (NAc; 2 ventral contacts) and the anterior limb of the internal capsule (ALIC; 2 dorsal contacts) with independently programmed parameters such as frequency, amplitude, and voltage; and remote and wireless programing, which allows for convenient and prompt adjustments in emergency situations.', 'armGroupLabels': ['Postoperative delayed Deep brain stimulation', 'Postoperative immediate Deep brain stimulation']}

Primary Outcomes:
- {'measure': 'The abstinent rate at 25 weeks after DBS stimulation on （Urine Tests）', 'description': 'If the participants or their families report no less than 2 times of the drug use in each of two consecutive weeks, or the consecutive 2 times of urine tests showed positive, or lost of follow-up, the case was defined as relapse', 'timeFrame': 'At 25 weeks after DBS stimulation on'}

Please estimate the sample size based on the assumption: 
A two-sample test with a two-sided significance level of 5%, statistical power of 80%, and a 15% drop-out rate.
Sample size
        In order that more patients can be allocated to the early stimulation group (receiving âtrueâ but not âshamâ intervention), which make trial representing more ethical considerations and make recruitment more easier (patients were informed that they have more chance to be allocated into the early stimulation group), the statistical experts decided the sample ratio to be 2:1 for treatment group:control group, which has been applied for most previous similar trials. Calculation of the sample size was further done by statistical experts designated by China Food and Drug Administration that was in charge of the quality control and approval for clinical trials, based on the primary outcome of the abstinence rate reported by previous literatures.24 43 Based on retrospective analysis of our previous data, the abstinence rate from baseline to 25 weeks after DBS surgery was 70% in 11 patients with opioid dependence, and previous studies showed that the abstinence rate of patients with opioid dependence who do not receive any treatment is around 30%.4 5 A two-sample test will be used to determine if the mean of the treatment group (Î¼A) is different from that of the control group (Î¼B). The hypotheses are: H0: Î¼AâÎ¼B=0, H1: Î¼AâÎ¼Bâ 0. The sample size will be calculated using the PASS V.11 sample size calculation software (NCSS, USA). Based on tests for two means, with a two-sided significance level of 5% and statistical power at 80%, allowing for a 15% drop-out rate, a sample size of 60 patients will be needed to test the hypothesis with the two-sided test. This will consist of 40 patients for the treatment group and 20 patients for the control group.