Assessment of cerebral gliomas by a new dark fluid sequence, high intensity REduction (HIRE): A preliminary study

The purpose of this study was to assess the diagnostic potential of a new d ark. fluid sequence, high intensity reduction (HIRE) in the diagnostic work up of patients with cerebral gliomas, The HIRE sequence utilizes a very lon g T-2 value of the cerebrospinal fluid (CSF) to suppress its high signal co ntribution in T-2-weighted imaging by a image subtraction technique. Fiftee n patients with histologically confirmed cerebral gliomas were examined wit h T-2-weighted fast spin-echo (FSE), T-1-weighted SE, fast fluid-attenuated inversion recovery (FLAIR), and HIRE imaging using identical scan paramete rs. In patients with enhancing lesions, fast FLAIR and HIRE were added to t he contrast-enhanced T-1-weighted SE images. Images were analyzed in a qual itative and quantitative evaluation. In the qualitative analysis, lesion de tection, lesion delineation, and differentiation between enhancing and non- enhancing tumor tissue were assessed in a two-reader study. For the quantit ative analysis, lesion-to-background and lesion-to-CSF contrast and contras t-to-noise ratios were determined in a region of interest analysis. HIRE ac hieved a significant reduction of the CSF signal without losing the high gr ay-to-white matter contrast of T-2-weighted sequences. In the quantitative analysis, the contrast ratios of the HIRE images were lower compared with t he FLAIR images due to a relatively high background and CSF signal. After a dministration of contrast media, HIRE images presented a significant signal increase in enhancing lesions, which subsequently increased the contrast a nd contrast-to-noise ratios, In the qualitative analysis, both readers foun d all tumors clearly delineated on HIRE imaging, Compared with T-2-weighted FSE, the tumor delineation with HIRE was better in nine patients, equal in four patients, and less in one patient, Compared with the FLAIR images, HI RE was rated superior in three patients, equal in nine patients, and inferi or in another three patients. Delineation of the enhancing tumor parts was possible with HIRE in all patients. HIRE images had significantly fewer ima ge artifacts than FLAIR images due to reduced inflow effects. The T-2-based HIRE sequence presented is an alternative to the T-1-based FLAIR sequence, with the advantage of better gray-to-white matter contrast and shorter mea surement time. Due to the subtraction technique, signal intensities from ti ssues with relaxation times in the range T-2 (WM) < < T-2 < T-2 (CSF) are a lso gradually affected, corresponding to their T-2 values. With respect to this unwanted effect, an improvement in HIRE imaging will be possible by us ing a self-weighted subtraction algorithm, In a forthcoming study this conc ept will first be tested on appropriate phantom-fluids. (C) 2000 Wiley-Liss , Inc.