Strigel Roberta M, Moritz Chad H, Haughton Victor M, Badie Behnam, Field Aaron, Wood David, Hartman Michael, Rowley Howard A
Department of Radiology, University of Wisconsin, Madison, 53792-3252, USA.
AJNR Am J Neuroradiol. 2005 Mar;26(3):578-84.
The purpose of this study was to determine the incidence of susceptibility artifacts on functional MR imaging (fMRI) studies and their effect on fMRI readings. We hypothesized that the availability of the signal intensity maps (SIMs) changes the interpretation of fMRI studies in which susceptibility artifacts affected eloquent brain regions.
We reviewed 152 consecutive clinical fMRI studies performed with a SIM. The SIM consisted of the initial echo-planar images (EPI) in each section thresholded to eliminate signal intensity from outside the brain and then overlaid on anatomic images. The cause of the artifact was then determined by examining the images. Cases with a susceptibility artifact in eloquent brain were included in a blinded study read by four readers, first without and then with the SIM. For each reader, the number of times the interpretation changed on viewing the SIM was counted.
Of 152 patients, 44% had signal intensity loss involving cerebral cortex and 18% involving an eloquent brain region. Causes of the artifacts were: surgical site artifact, blood products, dental devices, calcium, basal ganglia calcifications, ICP monitors, embolization materials, and air. When provided with the SIM, readers changed interpretations in 8-38% of patient cases, depending on reader experience and size and location of susceptibility artifact.
Patients referred for clinical fMRI have a high incidence of susceptibility artifacts, whose presence and size can be determined by inspection of the SIM but not anatomic images. The availability of the SIM may affect interpretation of the fMRI.
本研究旨在确定功能磁共振成像（fMRI）研究中磁化率伪影的发生率及其对fMRI读数的影响。我们假设信号强度图（SIM）的可用性会改变对fMRI研究的解读，在这些研究中，磁化率伪影影响了明确的脑区。
我们回顾了152例连续进行的使用SIM的临床fMRI研究。SIM由每个层面的初始回波平面图像（EPI）组成，经过阈值处理以消除脑外的信号强度，然后叠加在解剖图像上。然后通过检查图像确定伪影的原因。在一项盲法研究中，将明确脑区存在磁化率伪影的病例纳入其中，由四名读者进行解读，先不看SIM，然后再看SIM。对于每位读者，统计查看SIM时解读改变的次数。
152例患者中，44%存在涉及大脑皮质的信号强度损失，18%涉及明确的脑区。伪影的原因包括：手术部位伪影、血液制品、牙科器械、钙、基底节钙化、颅内压监测器、栓塞材料和空气。当提供SIM时，根据读者经验以及磁化率伪影的大小和位置，读者在8% - 38%的患者病例中改变了解读。
因临床fMRI就诊的患者磁化率伪影发生率较高，其存在和大小可通过查看SIM而非解剖图像来确定。SIM的可用性可能会影响对fMRI的解读。
