Essig M, Deimling M, Schoenberg S O, Debus J, Knopp M V, van Kaick G
Forschungsschwerpunkt Radiologische Diagnostik und Therapie, Deutsches Krebsforschungszentrum, Heidelberg.
Radiologe. 2000 Dec;40(12):1163-71. doi: 10.1007/s001170050901.
The HIRE sequence utilizes the very long T2 value of CSF to suppress its high signal contribution in T2-weighted imaging by an image subtraction technique.
To assess the diagnostic potential of a new dark fluid sequence HIRE (High Intensity REduction) in the diagnostic work-up, 20 patients with histologically confirmed cerebral gliomas were examined with T2-weighted FSE, T1-weighted SE, fast FLAIR and HIRE using identical scan parameters. In patients with enhancing lesions fast FLAIR and HIRE were added to the contrast-enhanced T1-weighted SE images. Images were analyzed in a qualitative and quantitative evaluation. In the qualitative lesion analysis, lesion delineation and differentiation between enhancing and non enhancing tumor tissue were by two readers. For the quantitative analysis lesion-to-background and lesion-to-CSF contrast and contrast to noise ratios were determined in an region of interest analysis.
HIRE achieved a significant reduction of the CSF signal without loosing the high gray-to-white matter contrast of T2 weighted sequences. In the quantitative analysis, the contrast ratios of the HIRE were lower compared to the FLAIR images due to a relative high background and CSF signal. After the application of contrast media HIRE images revealed a significant signal increase in enhancing lesions, which subsequently increased the contrast and contrast-to-noise ratios. In the qualitative analysis, both readers found all tumors clearly delineated on HIRE imaging. Compared to T2-weighted FSE the tumor delineation with HIRE was better in nine patients, equal in four patients and less in one patient. Compared to the FLAIR images HIRE was rated superior in three patients, equal in nine patients and inferior in another three patients. Delineation of the enhancing tumor parts was possible with HIRE in all patients. HIRE images present significant less image artifacts than FLAIR images due to reduced inflow effects.
The presented T2 based HIRE sequence is an alternative to the T1 based FLAIR sequence with the advantage of a better gray to white matter contrast and shorter measurement time. Due to the subtraction technique signal intensities from tissues with T2 relaxation times in the range between white matter and CSF are also partially affected depending on their T2 values. With respect to this undesired effect, an improvement in HIRE imaging will be expected by a self-weighted subtraction algorithm.
HIRE序列利用脑脊液极长的T2值，通过图像减法技术抑制其在T2加权成像中的高信号贡献。
为评估一种新的暗流体序列HIRE（高强度降低）在诊断检查中的诊断潜力，对20例经组织学证实的脑胶质瘤患者采用相同扫描参数进行T2加权FSE、T1加权SE、快速FLAIR和HIRE序列检查。对于有强化病变的患者，在增强T1加权SE图像上增加快速FLAIR和HIRE序列。对图像进行定性和定量评估。在定性病变分析中，由两位阅片者对病变进行勾勒，并区分强化和非强化肿瘤组织。在定量分析中，通过感兴趣区分析确定病变与背景、病变与脑脊液的对比度以及对比噪声比。
HIRE序列显著降低了脑脊液信号，同时未丧失T2加权序列的高灰白质对比度。在定量分析中，由于相对较高的背景和脑脊液信号，HIRE序列的对比度比值低于FLAIR图像。应用对比剂后，HIRE图像显示强化病变有显著信号增加，随后提高了对比度和对比噪声比。在定性分析中，两位阅片者均发现所有肿瘤在HIRE成像上清晰可辨。与T2加权FSE相比，HIRE对肿瘤的勾勒在9例患者中更好，4例患者相同，1例患者较差。与FLAIR图像相比，HIRE在3例患者中被评为更优，9例患者相同，3例患者较差。所有患者均可通过HIRE序列勾勒出强化肿瘤部分。由于流入效应降低，HIRE图像的图像伪影明显少于FLAIR图像。
所提出的基于T2的HIRE序列是基于T1的FLAIR序列的替代方法，具有更好的灰白质对比度和更短测量时间的优点。由于减法技术，白质和脑脊液之间T2弛豫时间范围内组织的信号强度也会根据其T2值受到部分影响。针对这种不良影响，有望通过自加权减法算法改善HIRE成像。
