BRAIN IMAGING - REDUCED SENSITIVITY OF RARE-DERIVED TECHNIQUES TO SUSCEPTIBILITY EFFECTS

Objective: Our goal was to evaluate the decreased sensitivity of RARE- derived pulse sequences to susceptibility effects. Materials and Metho ds: A variety of RARE-derived T2-weighted fast SE echo (FSE) sequences with echo trains from 6 to 16 were compared with conventional SE (CSE ) sequences by means of MRI in phantoms (iron oxides), volunteers (n = 10), and patients (n = 13) with old hemorrhagic brain lesions. All ex periments were performed on a 1.5 T clinical MR system (Magnetom SP 40 00; Siemens AG, Erlangen, Germany) with constant imaging parameters. C ontrast-to-noise ratios (CNRs) of tubes doped with iron oxides at diff erent concentrations and brain areas with physiological iron depositio n (red nucleus, substantia nigra) were calculated for CSE and FSE puls e sequences. Areas of old brain hemorrhage were analyzed for lesion co nspicuity by blinded analysis with CSE as an internal standard. Result s: CNR of iron oxide tubes (TE 90 ms, CSE 45.0 +/- 3.5, FSE 16 echo tr ains 28.5 +/- 3.1; p less than or equal to 0.01) and iron-containing b rain areas decreased with increasing echo trains of FSE sequences. A s ignificantly lower number of old hemorrhagic brain lesions was visible in patients scanned with FSE sequences (6 echo trains: n = 28; 16 ech o trains: n = 26) than CSE (n = 40). Conclusion: Our results demonstra te that the sensitivity of RARE-derived techniques to susceptibility e ffects is significantly decreased compared with CSE. CSE sequences or GE sequences should still be preferred in patients with a history of s eizures or intracranial hemorrhage.