Relaxivity-Iron Calibration in Hepatic Iron Overload: Probing Underlying Biophysical Mechanisms Using a Monte Carlo Model
Relaxivity-Iron Calibration in Hepatic Iron Overload: Probing Underlying Biophysical Mechanisms Using a Monte Carlo Model
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DOI：
10.1002/mrm.22657
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发表时间：
2011-03-01
影响因子：
3.3
通讯作者：
Wood, John C.
中科院分区：
文献类型：
--
作者：
Ghugre, Nilesh R.;Wood, John C.
铁过载是β地中海贫血、输血依赖性镰状细胞性贫血和遗传性铁代谢紊乱患者的严重病症。MRI在无创定量组织铁方面变得越来越重要，克服了传统技术（肝活检）的缺点。在人肝中，有效横向弛豫率（1/有效横向弛豫时间）随铁的增加而线性增加，而横向弛豫率（1/T-2）则呈曲线关系。虽然最近的工作已经证明了人类肝脏铁的临床有效估计，校准随着MRI序列，场强，铁螯合治疗和器官成像而变化，迫使患者重新校准。为了理解和纠正这些局限性，彻底理解潜在的生物物理学至关重要。为此，使用人肝脏作为“模型”组织系统的基于Monte Carlo的方法用于确定颗粒尺寸和分布对MRI信号弛豫的贡献。测定肝铁浓度范围为0.5至40毫克铁/克干组织重量的弛豫率。模型预测捕获的线性和曲线关系的有效横向弛豫率和横向弛豫率与肝铁浓度，分别在体内的置信范围内，接触或化学交换机制是没有必要的。一个经过验证和优化的模型将有助于理解和量化铁介导的弛豫在组织活检是不可行的（心脏和脾脏）。Magn Reson Med 65：837-847，2011. (c)2010 Wiley-Liss，Inc.
Iron overload is a serious condition for patients with beta-thalassemia, transfusion-dependent sickle cell anemia, and inherited disorders of iron metabolism. MRI is becoming increasingly important in noninvasive quantification of tissue iron, overcoming the drawbacks of traditional techniques (liver biopsy). Effective transverse relaxation rate (1/effective transverse relaxation time) rises linearly with iron while transverse relaxation rate (1/T-2) has a curvilinear relationship in human liver. Although recent work has demonstrated clinically valid estimates of human liver iron, the calibration varies with MRI sequence, field strength, iron chelation therapy, and organ imaged, forcing recalibration in patients. To understand and correct these limitations, a thorough understanding of the underlying biophysics is of critical importance. Toward this end, a Monte Carlo-based approach, using human liver as a "model'' tissue system, was used to determine the contribution of particle size and distribution on MRI signal relaxation. Relaxivities were determined for hepatic iron concentrations ranging from 0.5 to 40 mg iron per gram dry tissue weight. Model predictions captured the linear and curvilinear relationship of effective transverse relaxation rate and transverse relaxation rate with hepatic iron concentrations, respectively, and were within in vivo confidence bounds; contact or chemical exchange mechanisms were not necessary. A validated and optimized model will aid understanding and quantification of iron-mediated relaxivity in tissues where biopsy is not feasible (heart and spleen). Magn Reson Med 65:837-847, 2011. (c) 2010 Wiley-Liss, Inc.