Here is the design of a clinical trial:

Official Title: A Study of 18F-FLT Positron Emission Tomography/Computed Tomography (PET/CT) Imaging in Cases of Prefibrotic/Early Primary Myelofibrosis (PMF) and Essential Thrombocythemia (ET)

Included conditions:
- Essential Thrombocythemia
- Primary Myelofibrosis, Fibrotic Stage
- Primary Myelofibrosis, Prefibrotic Stage

Study Armgroups:
- {'label': 'Diagnostic (18F-FLT PET/CT)', 'type': 'EXPERIMENTAL', 'description': 'Patients undergo 18F-FLT (3\'-18Fluoro-3\'-deoxy-L-thymidine) PET/CT (Positron Emission Tomography/Computed Tomography) at baseline. No specific dietary restrictions or hydration are required for FLT-PET scans, however, patients will be urged to drink plenty of water before and after the PET studies. \\[18F\\] FLT will be prepared by the cyclotron core facility and assessed for quality control following "good manufacturing practice" criteria. The radiopharmaceutical will immediately be brought to the Molecular Imaging and Therapy Service Radiopharmacy for dispensation in the PET suite. For each scan, patients will receive approximately up to 370 MBq (target of 10 mCi) \\[18F\\] FLT by intravenous infusion.', 'interventionNames': ['Device: Diagnostic (18F-FLT PET/CT)']}

Interventions:
- {'type': 'DEVICE', 'name': 'Diagnostic (18F-FLT PET/CT)', 'description': "The tracer compound \\[F-18\\] FLT will be injected into the patient's veins in a small volume of normal saline solution. The PET scan data collection is started immediately and is continued for 2 hours.", 'armGroupLabels': ['Diagnostic (18F-FLT PET/CT)'], 'otherNames': ['18F-FLT PET/CT', "3'-Deoxy-3'-(18F) Fluorothymidine", "3'-deoxy-3'-[18F]fluorothymidine", 'Fluorothymidine F 18']}

Primary Outcomes:
- {'measure': 'Number of patients with 50% or more uptake of FLT-PET in patients with Prefibrotic/Early Primary Myelofibrosis (PMF) and Essential Thrombocythemia (ET) 12 months from the baseline', 'description': "Evaluate the uptake of 3'-deoxy-3'-\\[18F\\] fluorothymidine (FLT) positron emission tomography/computed tomography (PET) imaging and it is value in assessing the malignant hematopoiesis in patients with Prefibrotic/Early Primary Myelofibrosis (PMF) and Essential Thrombocythemia (ET).", 'timeFrame': '12 Months'}

Please estimate the sample size based on the assumption: 
Not specified
5.3
        Sample size and recruitment
        All patients will undergo static whole-body FLT PET/CT imaging at baseline in a cohort of 21 patients.