Keiper M D, Grossman R I, Hirsch J A, Bolinger L, Ott I L, Mannon L J, Langlotz C P, Kolson D L
Department of Radiology, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
AJNR Am J Neuroradiol. 1998 Sep;19(8):1489-93.
Although MR spectroscopy and functional MR imaging of the brain have been successful at 4 T, conventional fast spin-echo imaging of the brain at 4 T has not been adequately evaluated. The purpose of this study was to compare the detection of white matter abnormalities in multiple sclerosis (MS) at 1.5 T and 4 T.
Fifteen patients with clinically definite MS were imaged at both 1.5 T and 4 T within a 1-week period. Comparison was made between fast spin-echo long-TR images at both field strengths. Pulse sequences were tailored to maximize resolution and signal-to-noise ratio in clinically relevant imaging times (< 7 min). Four interpreters independently reviewed the images obtained at both field strengths in separate sessions and evaluated them for lesion identification, size, characterization, and subjective resolution. Differences in interpretations at 1.5 T and 4 T were subsequently recorded.
Images obtained at 4 T showed a mean of 88 more lesions as compared with images obtained at 1.5 T. All the lesions measured less than 5 mm and were typically aligned along perivascular spaces. Twenty-five consensually identified lesions on 4-T images were not seen at all on 1.5-T images. Moreover, 4-T images showed 56 additional consensually identified lesions, which were indistinct and seen only in retrospect on 1.5-T images. These lesions were frequently (n = 48) identified in large confluent areas of white matter signal intensity abnormality at 1.5 T. All observers also agreed that 4-T images subjectively enhanced the perception of normal perivascular spaces and small perivascular lesions.
MR imaging at 4 T can depict white matter abnormalities in MS patients not detectable at 1.5 T through higher resolution with comparable signal-to-noise ratio and imaging times.
尽管脑部磁共振波谱成像和功能磁共振成像在4T磁场强度下已取得成功，但4T磁场强度下脑部的传统快速自旋回波成像尚未得到充分评估。本研究的目的是比较1.5T和4T磁场强度下多发性硬化症（MS）患者白质异常的检测情况。
15例临床确诊的MS患者在1周内分别于1.5T和4T磁场强度下进行成像。对两种场强下的快速自旋回波长TR图像进行比较。调整脉冲序列以在临床相关成像时间（<7分钟）内最大化分辨率和信噪比。四名解释者在不同的时间段独立审查两种场强下获得的图像，并对病变的识别、大小、特征和主观分辨率进行评估。随后记录1.5T和4T下解释结果的差异。
与1.5T磁场强度下获得的图像相比，4T磁场强度下获得的图像平均多显示88个病变。所有病变均小于5mm，通常沿血管周围间隙排列。4T图像上经共识确定的25个病变在1.5T图像上根本未被发现。此外，4T图像还显示了另外56个经共识确定的病变，这些病变不清晰，仅在回顾1.5T图像时可见。这些病变在1.5T磁场强度下常出现在白质信号强度异常的大片融合区域（n = 48）。所有观察者还一致认为，4T图像在主观上增强了对正常血管周围间隙和小血管周围病变感知。
4T磁场强度下的磁共振成像能够通过更高的分辨率、可比的信噪比和成像时间，显示出1.5T磁场强度下无法检测到的MS患者白质异常。
