Here is the design of a clinical trial:

Official Title: Carbon-Dioxide Flushing Versus Saline Flushing in Thoracic Endovascular Aortic Repair to Reduce Neurological Injury: A Pilot Randomised Controlled Trial

Included conditions:
- Stroke
- Silent Cerebral Infarction
- Neurocognitive Dysfunction
- Vascular Brain Injury

Study Armgroups:
- {'label': 'carbon-dioxide', 'type': 'EXPERIMENTAL', 'description': 'Flushing of stent-grafts in TEVAR with carbon-dioxide', 'interventionNames': ['Other: CO2 flushing']}
- {'label': 'Saline', 'type': 'ACTIVE_COMPARATOR', 'description': 'Flushing of stent-grafts with saline', 'interventionNames': ['Other: Saline flushing']}

Interventions:
- {'type': 'OTHER', 'name': 'CO2 flushing', 'description': 'As above', 'armGroupLabels': ['carbon-dioxide']}
- {'type': 'OTHER', 'name': 'Saline flushing', 'description': 'As above', 'armGroupLabels': ['Saline']}

Primary Outcomes:
- {'measure': 'Recruitment', 'description': 'The number of patients recruited into the trial will be collected', 'timeFrame': '36 months'}
- {'measure': 'Retention', 'description': 'The proportion of patients undergoing follow-up assessments will be collected', 'timeFrame': '36 months'}
- {'measure': 'Study design for full randomised controlled trial', 'description': 'The proportion of patients who are eligible for the trial will be collected', 'timeFrame': '36 months'}

Please estimate the sample size based on the assumption: 
Significance level and power are not explicitly mentioned. Assumes a 20% MRI dropout rate.
Sample size
        Observational data indicate that the incidence of SCI from TEVAR is 81%.6 Based on our CO2-pilot study that reduced SCI to 25%, a 50% reduction in SCI is possible. Taking a pragmatic and realistic approach to recruitment, we aim for an effect size of 40% reduction in incidence of SCI. Considering a 10% MRI dropout rate from our observational study, a total of 76 (38 per group) would be sufficient to detect an effect size. However, given that randomisation will be by zone of TEVAR, of which there are 5, and we expect a 20% MRI drop-out rate, we are aiming to recruit 120 cases (60 in each arm). This number has been chosen to ensure 10â12 patients in each of five arch landing zones in each of the two intervention groups, to allow us to quantify brain injury by zone between the two interventions in addition to establishing an overall measure of effect between the two interventions.