The Reliability of MR Angiography as the Sole Imaging Method for Non-Invasive Follow-up of Intracranial Aneurysms Treated with Guglielmi Detachable Coils

1137 lar controls of treated subjects, the invasiveness, high cost, repeated exposure to iodinated contrast agent and ionizing radiation relatively hinder its use in iterative follow-up studies. Magnetic resonance angiography (MRA) is an alternative method for imaging of intracranial aneurysms, it does not expose the patient to ionizing radiation or contrast agent, is completely non-invasive and performed entirely on an outpatient basis. Platinum detachable coils used for endovascular treatment of intracranial aneurysms do not pose a risk or contraindication to MR examination. Magnetic resonance angiography can therefore play a valuable role in the non-invasive follow-up of ETIA. Several studies have already reported favourable results concerning the sensitivity and accuracy of MRA in the detection of aneurysmal reperfusion. There is no general agreement yet to which extent MRA can replace DSA in the follow-up of ETIA. The aim of our study was to evaluate the reliability of MRA as a sole imaging method in the follow-up of subjects treated with Guglielmi detachable coils (GDC). Of 72 subjects treated with GDC for an intracranial aneurysm at our institution, 18 subjects with 21 aneurysms remained Endovascular occlusion of intracranial aneurysms gained welldeserved attention within last few years as an alternative and effective method of treating mainly those aneurysms which are difficult for neurosurgical clipping and for the patients in unfavourable clinical conditions. The results of the method are very encouraging so far, with minimal degree of invasiveness being one of its most valuable features. However, the long-term efficacy of the method remains unknown and is dependent on numerous factors such as anatomic configuration of the aneurysm and its neck, its location, size etc. Therefore, regular follow-up of all endovascularly treated intracranial aneurysms (ETIA) is necessary to prevent reperfusion of the aneurysm due to coil compaction or re-growth of the residual aneurysmal neck. With the rapidly growing number of subjects endovascularly treated for cerebral aneurysms there is also a requirement for an accurate, non-invasive, and practical imaging method for the follow-up. Even though the digital subtraction angiography (DSA) still represents the gold standard for the post-treatment follow-up of subjects with ETIA and numerous centers utilize it for reguin the MRA follow-up at our institution within the time frame between April 1999 and March 2002.After the embolization of an aneurysm, the findings on DSA were correlated with the posttreatment MRA which served as a reference. Subsequent follow-up studies were carried out solely by using MRA in these subjects. No regular follow-up DSA examinations were performed. Altogether, 54 MRA follow-up examinations were performed on 1.0 Tesla MR system (Magnetom Expert; Siemens, Erlangen, Germany) using 3D FISP (Fast Imaging with Steady-State Precession) time-offlight MRA sequence (repetition time ms/ echo time msec/flip angle, 37/9.6/ 20) with magnetization transfer (MT) and tilted optimized non-saturating excitation (TONE); the voxel size was 0.8 x 0.7 x 0.4 mm. Paramagnetic contrast agent was not used. The source images (partitions) from the 3D TOF MRA sequence were carefully reviewed for the presence of flow within the parent or branching arteries and the aneurysm itself, they also served for generation of maximum intensity projections (MIP) and targeted MIP. Conventional T1 weighted spin echo and T2 weighted turbo spin echo sequences were emThe Reliability of MR Angiography as the Sole Imaging Method for Non-Invasive Follow-up of Intracranial Aneurysms Treated with Guglielmi Detachable Coils