Buerk Bruce M, Pulido Jose S, Chiong Ignacio, Folberg Robert, Edward Deepak P, Duffy Mark T, Thulborn Keith R
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.
Trans Am Ophthalmol Soc. 2004;102:209-15; discussion 215-7.
Because signal-to-noise performance improves with increased magnetic field strength, the quality of magnetic resonance images is greater at 3.0 tesla (T) than at 1.5 T. Because of the longer T1 values at higher field strength, intravenously administered magnetic resonance contrast agents provide improved T1 enhancement at 3.0 T. We have used these factors to obtain high-quality contrast-enhanced imaging of small intraocular lesions using a standard head radiofrequency volume coil. Specifically, we have examined lesion size and magnitude of maximum contrast enhancement in a series of intraocular melanomas before and during therapy.
Eighteen patients with intraocular masses were examined by 3.0 T magnetic resonance imaging (MRI) including intravenous contrast enhancement. Precontrast images were acquired through the orbits followed by sequential postcontrast images at 1-minute intervals for 5 minutes. The magnitude of contrast enhancement of the lesion, extraocular muscles, and brain parenchyma was measured as a percentage increase in magnetic resonance signal over the preenhancement signal intensity.
Lesions demonstrated different levels of enhancement ranging up to 130%. Three patterns of enhancement--0% to 20%, 20% to 50%, and >50%-were identified. Brain parenchyma, benign lesions, and responsive tumors following brachytherapy with 125I demonstrated enhancement of less than 20%. Four choroidal melanomas showed intermediate (20% to 50%) levels of enhancement. Four malignant lesions (three melanomas, one metastatic tumor), as well as the extraocular muscles, showed strong, rapid enhancement (>50%). Four patients who had MRI studies before and following plaque brachytherapy ultimately demonstrated a decline in the contrast enhancement following treatment.
Contrast enhancement of intraocular lesions measured by 3.0 T MRI demonstrates different patterns of enhancement that may be useful for indicating the degree of malignancy and in monitoring response to therapy.
由于信噪比性能会随着磁场强度的增加而提高，所以3.0特斯拉（T）磁共振成像的质量要高于1.5T。由于在更高场强下T1值更长，静脉注射的磁共振造影剂在3.0T时能提供更好的T1增强效果。我们利用这些因素，使用标准的头部射频容积线圈，对眼内小病变进行高质量的对比增强成像。具体而言，我们在一系列眼内黑色素瘤治疗前和治疗期间，研究了病变大小和最大对比增强幅度。
对18例眼内肿物患者进行3.0T磁共振成像（MRI）检查，包括静脉注射对比剂增强扫描。先通过眼眶获取平扫图像，然后以1分钟的间隔顺序采集5分钟的增强后图像。病变、眼外肌和脑实质的对比增强幅度以磁共振信号相对于增强前信号强度的百分比增加来衡量。
病变显示出不同程度的增强，增强幅度高达130%。确定了三种增强模式——0%至20%、20%至50%以及>50%。脑实质、良性病变以及接受125I近距离放疗后的反应性肿瘤增强幅度小于20%。4例脉络膜黑色素瘤显示出中等（20%至50%）水平的增强。4例恶性病变（3例黑色素瘤、1例转移瘤）以及眼外肌显示出强烈、快速的增强（>50%）。4例在敷贴近距离放疗前后进行MRI检查的患者最终显示治疗后对比增强有所下降。
通过3.0T MRI测量的眼内病变对比增强显示出不同的增强模式，这可能有助于指示恶性程度以及监测治疗反应。
