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3T 和 1.5T MRI 是临床常用的两种磁场强度，各有其优势和局限性。以下是它们的主要特点对比：
1.5T MRI 的特点 信噪比（SNR）：
信噪比较低，但足以满足大多数临床需求。
图像质量稳定，适合常规检查。
成像速度：
成像速度较慢，但技术成熟，适用于大多数患者。
伪影：
磁敏感伪影较少，尤其在金属植入物或空气-组织界面附近表现更好。
临床应用：
广泛用于常规心脏、神经、骨骼和腹部成像。
特别适合植入心脏起搏器或除颤器的患者（1.5T 对金属伪影的影响较小）。
成本和维护：
设备成本和维护费用较低，普及率高。
3T MRI 的特点 信噪比（SNR）：
信噪比是 1.5T 的 2 倍左右，图像分辨率更高，细节更清晰。
特别适合需要高分辨率的检查（如小结构或早期病变）。
成像速度：
成像速度更快，适合动态成像（如心脏电影 MRI）或功能成像（如灌注成像）。
伪影：
磁敏感伪影更明显，尤其在金属植入物或空气-组织界面附近。
对运动伪影也更敏感。
临床应用：
适合高分辨率成像，如神经成像（脑功能成像、弥散张量成像）、心脏成像（T1 mapping、纤维化评估）和小关节成像。
在科研和高精度诊断中应用广泛。
成本和维护：
设备成本和维护费用较高，对场地和冷却系统要求更严格。
In magnetic resonance imaging, T1, also known as the spin–lattice relaxation time, is an intrinsic magnetic property of a tissue [1]. Each tissue type, including myocardium, exhibits a characteristic range of normal T1 relaxation times at a particular magnetic field strength [2], and deviation from the normal range may be indicative of disease.
Piechnik, S. K., Ferreira, V. M., Lewandowski, A. J., Ntusi, N. A., Banerjee, R., Holloway, C., Hofman, M. B., Sado, D. M., Maestrini, V., White, S. K., Lazdam, M., Karamitsos, T., Moon, J. C., Neubauer, S., Leeson, P., & Robson, M. D. (2013). Normal variation of magnetic resonance T1 relaxation times in the human population at 1.5 T using ShMOLLI. Journal of Cardiovascular Magnetic Resonance, 15(1), 13. https://doi.org/10.1186/1532-429X-15-13
The T1 values of blood have been shown to vary due to a number of factors like hematocrit, sex , age, and oxygen pressure and variations in these factors may influence the interpretation of myocardial T1 values, and obscure the true T1 value of the myocardium
A linear correlation between septal myocardial T1 and blood measurements was assumed. T1 was corrected using the equation, Equation 1: where is the blood measurement of mean R1, and the constant was calculated as the slopes of linear regression between myocardial T1 and the blood measurements.
Correcting native myocardial T1 for R1 and R1* of blood improves the precision of myocardial T1 measurement by ~13%, and could consequently improve disease detection and reduce sample size needs for clinical research.
Nickander, J., Lundin, M., Abdula, G., Sörensson, P., Rosmini, S., Moon, J. C., Kellman, P., Sigfridsson, A., & Ugander, M. (2016). Blood correction reduces variability and gender differences in native myocardial T1 values at 1.5 T cardiovascular magnetic resonance – a derivation/validation approach. Journal of Cardiovascular Magnetic Resonance, 19(1), 41. https://doi.org/10.1186/s12968-017-0353-7
One of the unique aspects of magnetic resonance imaging (MRI) is the sensitivity of the soft tissue image contrast to tissue composition, which can be a reflection of physiology and pathophysiology. The T1 relaxation time, a measure of how fast the nuclear spin magnetization returns to its equilibrium state after a radiofrequency (RF) pulse in the MRI scanner, is a key source of soft tissue contrast in MRI.
T1 mapping without administration of a paramagnetic contrast agent, referred to as “native” T1 mapping, is sensitive to myocardial edema, iron overload, and the presence of myocardial infarcts and scarring.
In patients suspected of having myocardial fibrosis secondary to aortic stenosis (results validated by biopsy findings), native T1 was elevated and correlated with diffuse fibrosis (25) (Figure 4A). Whether the change in native T1, and more specifically an increase in native T1, is a reflection of the myocardial fibrosis burden, or instead a result of other pathological features (e.g., edema) that occur in parallel remains to be ascertained.
Native T1 mapping has been used in the assessment of acute MI on the basis that interstitial edema (37) is increased at the site of infarction
Taylor, A. J., Salerno, M., Dharmakumar, R., & Jerosch-Herold, M. (2016). T1 Mapping. JACC: Cardiovascular Imaging, 9(1), 67–81. https://doi.org/10.1016/j.jcmg.2015.11.005