Department of Radiology, Mackay Memorial Hospital, Taitung, Taiwan.
Acad Radiol. 2010 May;17(5):624-7. doi: 10.1016/j.acra.2009.12.014.
The aim of this study was to design a pulse sequence that suppresses methemoglobin and is applicable in a 0.3-T permanent magnet.
Blood samples were collected from six healthy volunteers. Magnetic resonance imaging was performed with a 0.3-T scanner until the typical signal intensities of methemoglobin were obtained. Each blood sample was then scanned using repetition times of 300, 600, 900, 1200, 1500, and 1800 ms and a constant echo time of 20 ms. All other parameters (field of view, slice thickness, matrix, and number of signal averages) were kept constant for all six sequences. Signal intensities and repetition time data were used to calculate the T1 relaxation time of extracellular methemoglobin. T1 was determined by ordinary least square regression according to the equation S =k(1 - e(-repetition time/T1)), where S is signal intensity and k is the proportional constant. A short tau inversion recovery sequence with an inversion time calculated from the T1 value of methemoglobin was used on fat, water, and methemoglobin blood samples and in 11 patients diagnosed with subacute brain hemorrhages. The inversion time was calculated as ln2 T1 (tissue), where T1 is the relaxation time of extracellular methemoglobin to be suppressed.
The T1 relaxation time of extracellular methemoglobin was determined to be 231.24 +/- 9.068 ms, and inversion time was calculated to be 160 +/- 6.67 msec. Application of an inversion time of 160 ms showed complete suppression on extracellular methemoglobin blood samples and all of the 11 subjects.
A methemoglobin suppression technique using an inversion time of 160 +/- 6.67 ms is applicable in a 0.3-T permanent magnet.
本研究旨在设计一种能够抑制正铁血红蛋白且适用于 0.3T 永磁体的脉冲序列。
采集六位健康志愿者的血液样本。使用 0.3T 扫描仪进行磁共振成像，直到获得正铁血红蛋白的典型信号强度。然后，对每个血液样本进行重复时间为 300、600、900、1200、1500 和 1800ms，以及固定回波时间为 20ms 的扫描。所有六个序列的其他参数（视野、切片厚度、矩阵和信号平均次数）保持不变。使用信号强度和重复时间数据计算细胞外正铁血红蛋白的 T1 弛豫时间。根据 S=k(1-e(-重复时间/T1))方程，通过普通最小二乘法回归确定 T1，其中 S 是信号强度，k 是比例常数。在脂肪、水和正铁血红蛋白血液样本以及 11 名诊断为亚急性脑出血的患者中，使用反转时间根据正铁血红蛋白 T1 值计算的短τ反转恢复序列。反转时间计算为 ln2T1（组织），其中 T1 是要抑制的细胞外正铁血红蛋白的弛豫时间。
细胞外正铁血红蛋白的 T1 弛豫时间确定为 231.24 +/- 9.068ms，反转时间计算为 160 +/- 6.67msec。应用 160ms 的反转时间可完全抑制细胞外正铁血红蛋白血液样本和 11 名受试者中的所有样本。
适用于 0.3T 永磁体的正铁血红蛋白抑制技术采用 160 +/- 6.67ms 的反转时间。
