Clinical Validity of the MoSeSS RARE-Sequence at CSF Flow Disturbances

Abstract

The development of non-invasive diagnostic methods is a matter of great importance. This paper describes Motion Sensitized Single Shot RARE Sequences (MoSeSS) as a new, non-invasive diagnostic method in CSF-flow disturbances. The range of applications and clinical validity are examined.The strongly T2-weighted RARE-sequence displays selectively unbound water. The addition of flowencoding gradients shows moving spins flow-dependently as a signal reduction. ECG-triggering enables the registration of present flow phases, and the CSF-flow can be observed as cine-mode in quasi real-time. Thirty healthy subjects and 137 patients from subcollectives with diverse CSF-flow disturbances were investigated.The MoSeSS RARE-sequence provides reliable information in occlusion or stenoses of the inner CSF-spaces and in ventriculocisternostomies. Indirect signs of shunt dysfunction are CSF turbulences which correlate in degree with the increase in CSF pressure. Determination of localization and degree of dural impairment in traumatic or postoperative pseudomeningoceles is dependent on the activity of the CSF-flow at the leak. Depending on the stage of NPH, a variably marked active flow oscillation in the aqueduct and in the third ventricle is shown. Liquorrhoea has no definable flow detectable with the MoSeSS RARE-sequence. Vascular pulsation can make differentiation of the CSF-flow from artefacts difficult near larger vessels.The MoSeSS-RARE-Sequence is a fast, non-invasive and radiation-free method, which yields valid clinical information on circulation disturbances in the inner CSF-spaces. With the cine-mode technique, CSF movements can be observed in quasi real-time. Positive enhancement of the CSF is necessary in assessing processes with an undefined, non-detectable flow. Ricevuto il 29.08.2002 Clinical Validity of the MoSeSS RARE-Sequence at CSF Flow Disturbances M. Orszagh 662The basic principle of the RARE sequence was presented by Hennig as the "MR-Myelography" method in 1986 and has since been further developed 7,8 . The flow-sensitive sequence used here is a fast and non invasive method which displays the pulsatile CSF-movements in the cranial and spinal CSF-spaces.The aim of our study was to determine the possible use of the RARE sequence and the clinical validity of the information obtained about disturbances of CSF-circulation.The flow-sensitive, ECG-triggered single-shot RARE Sequence is a combination of a flow-sensitive preparation-experiment with a RARE-Sequence as the acquisition part. The contrast reaction of the sequence can be influenced by the choice of the position of the phase-encoding zeropoint. A strong T2-weighting can thus be realized, selectively displaying unbound water. Figure 1 shows projection-images of the cranial CSF-spaces with the conventional strongly T2-weighted RARE-sequence as an example.Originally introduced as a fast MR localizationmethod and as an efficient procedure to depict lesions with a long T2, a much wider field for use of RARE is now recognized. In many hospitals, it is a stand...