Finelli D A
Department of Radiology, MetroHealth Medical Center, Case Western University, School of Medicine, Cleveland, Ohio 44109, USA.
AJNR Am J Neuroradiol. 1997 Jan;18(1):147-59.
To develop a simple tissue phantom to study the effects of various imaging parameters and gadolinium concentrations on magnetization transfer (MT) and lesion-to-background ratios.
A commercial egg product was doped with gadolinium in concentrations of 0.0 to 1.0 mmol/L and cooked. The T1 and T2 values were determined for the phantom materials and for the white and gray matter of a healthy volunteer subject. The gadolinium-doped egg phantom and human brain were studied using a short-repetition-time three-dimensional gradient-echo MT sequence with various effective MT powers, frequency offsets, and section-select flip angles. The normalized signal intensities, MT ratios (MTRs), and simulated lesion-to-background normal white matter contrast ratios were determined for a variety of experimental conditions.
The MTR and lesion-to-background contrast ratios for all materials were greatest at the highest effective MT power (270 Hz, root-mean-square of amplitude) and the narrowest MT pulse frequency offset (1000 Hz). There was an inverse relationship between gadolinium concentration and MTR, and a positive relationship between the gadolinium concentration and lesion-to-background contrast. MTR was greatest at low flip angles, where there was little T1 weighting. The simulated lesion-to-background contrast showed a complex, gadolinium concentration-dependent relationship with section excitation flip angle.
The tissue phantom has relaxation properties and MT behavior close to that expected for enhancing brain lesions, allowing a rigorous analysis of simulated lesion-to-background contrast for high MT power, short-repetition-time, three-dimensional gradient-echo sequences.
开发一种简单的组织模型，以研究各种成像参数和钆浓度对磁化传递（MT）以及病变与背景比值的影响。
将市售蛋类产品掺入浓度为0.0至1.0 mmol/L的钆并煮熟。测定了模型材料以及一名健康志愿者的白质和灰质的T1和T2值。使用具有各种有效MT功率、频率偏移和层面选择翻转角的短重复时间三维梯度回波MT序列，对掺钆蛋类模型和人脑进行了研究。针对各种实验条件，测定了归一化信号强度、MT比值（MTR）以及模拟病变与背景正常白质对比度比值。
在最高有效MT功率（270 Hz，振幅均方根）和最窄的MT脉冲频率偏移（1000 Hz）时，所有材料的MTR和病变与背景对比度比值最大。钆浓度与MTR呈负相关，钆浓度与病变与背景对比度呈正相关。在低翻转角（T1加权小）时，MTR最大。模拟病变与背景对比度与层面激发翻转角呈现复杂的、依赖于钆浓度的关系。
该组织模型具有接近增强脑病变预期的弛豫特性和MT行为，能够对高MT功率、短重复时间三维梯度回波序列的模拟病变与背景对比度进行严格分析。
