796 and rapid assessment of brain functioning and cerebral tissue lesions [1]. The MRI is now utilized as the primary imaging modality in major stroke centres to detect and measure cerebral tissue lesions as well as changes in the vascular structure [2]. Moreover, it becomes an accepted feature of clinical trials in a variety of neurological disorders, and particularly in stroke. New MRI markers of cerebrovascular diseases (microbleeds, diffusion) have been recently evalu- ated offering reliable parameters of assessment of clinical outcome [3, 4]. There are few longitudinal neuro-radiolog- ical data assessed in large stroke trials, which mostly are based on the clinical evaluation. In this context the PER- FORM (Prevention of Cerebrovascular and Cardiovascular Events of Ischemic Origin with Terutroban in Patients with a History of Ischemic Stroke or Transient Ischemic Attack) MRI project was designed to depict by MRI structural and functional information on the evolution of cerebral athero- thrombotic processes after a recent ischemic stroke. The aim of this major sub study is to provide a longitudinal assess- ment of multiple MRI parameters in a large subgroup of a post stroke population with a follow-up of 2 years. The rationale and design of the PERFORM study, which includes 19,119 patients randomly allocated either to terutroban, a speciﬁc thromboxane prostaglandin (TP) receptor antagonist [5], 30 mg/day, or to aspirin 100 mg/day, have been described elsewhere, together with the characteristics of the whole population at baseline [6, 7]. Herein we report the design, framework and conduct for this complex interna- tional multi-centre longitudinal study. In particular, the MRI methodology chosen and the data that can be obtained in such a large MRI study are presented. Design Subjects The patients included in the study were aged C55 years, had a cerebral or retinal infarction in the last 3 months preceding inclusion or TIA in the last 8 days, and were stable at inclusion. They did not have any MRI contraindication such as known risk for exposure to high magnetic ﬁelds (e.g., pacemakers, implanted ferromagnetic devices, metallic implants, metal fragments, cochlear implants, brain and spinal cord stimulators), severe claustrophobia and difﬁculty lying in supine position. MRI quality check performed at M1 was validated by the imaging core lab of BioClinica. Study scheme 123 The trial proﬁle of the PERFORM MRI project is shown in Fig. 1. Two MRIs were planned to be performed in each patient included in the study: the ﬁrst at month 1 (M1), Randomization J Neurol (2011) 258:795–803 Terutroban 30 mg/day Aspirin 100 M24 X Qualifying event M0 M1 MRI examinations X Fig. 1 The trial proﬁle of the PERFORM MRI project 1–4 months after the qualifying clinical event and the second at month 24 (M24). Participants were fully informed and written consent was obtained according to local regulatory requirements. MRI acquisition Before the initiation of the study, a total of 48 MRI sites from 16 countries (11 from Europe, and one each from Australia, Canada, Brazil, Singapore and Taiwan) were selected. MRI scans were performed on 1.5 Tesla scanners in 42 sites and on 3T scanners in six sites. The MRI protocol was implemented at each site fol- lowing imaging parameter suggestions to ensure stan- dardization across sites and different MRI systems, and to maximize consistency and comparability between data from different manufacturers. Numbers, vendors, models and ﬁeld strengths of all MRI machines used are listed in Table 1. Each site was qualiﬁed using ACR phantom scans [8], to monitor image quality, in particular for geometrical distortions and adherence to the study protocol. The phantom scans were to be repeated yearly and after each signiﬁcant software and hardware upgrade. Ten machines had a major hardware upgrade including system change in six cases, but due to phantom validation we could mini- mize as much as possible the effect of such changes that affected a relatively small number of patients. All scans included transverse ﬂuid attenuated inversion recovery (FLAIR), gradient-echo T2*-weighted (T2*-weighted), diffusion weighted imaging (DWI) (three directions), 3D time-of-ﬂight (TOF) MR angiography and high-resolution sagittal 3DT1 sequences. For sites with diffusion tensor imaging, transverse DTI (six directions) data were also performed. The total acquisition time was kept reasonably low (from 30 to 45 min, according to the MRI system) to minimize patient’s discomfort. Two-dimensional sequen- ces were made of 5-mm thick contiguous slices with a 240 mm FOV and at least a 192 9 256 matrix (128 9 128