Raff Ulrich, Hutchinson Michael, Rojas Gonzalo M, Huete Isidro
Department of Physics, University of Santiago de Chile, Santiago.
Acad Radiol. 2006 Jun;13(6):721-7. doi: 10.1016/j.acra.2006.01.049.
Segmented inversion recovery (IR) ratio imaging (SIRRIM) has been established as a sensitive tool to assess neurodegeneration of the substantia nigra pars compacta (SN(C)) in patients with idiopathic Parkinson disease (IPD). The obtained results suggest the possibility of magnetic resonance imaging (MRI) as a biological marker for IPD. The strength and a parsimonious analysis of the technique are discussed to assess the potential of using MRI as a biological marker for IPD and improve the differential diagnosis of sporadic Parkinson disease. Our hypothesis states that the magnetic resonance SIRRIM technique allows direct visualization and quantitation of neural cell loss in the SN(C) and therefore could become a reliable biological marker for Parkinson disease. To achieve this goal, some key aspects of data acquisition and data analysis need to be addressed. The clinical impact of the SIRRIM technique could be considerable, considering that it might become a viable surrogate to other techniques.
Twelve patients with IPD and 12 age-matched control subjects were imaged by using the SIRRIM technique based on two IR imaging sequences that were designed to suppress white and gray matter to assess loss of neural cells in situ by means of a ratio image (white matter suppressed image to gray matter suppressed image). The radiological index was correlated with the Unified Parkinson Disease Rating Scale (UPDRS) for patients with IPD.
All patients with IPD were identified correctly, and full dichotomization between healthy volunteers and patients was obtained with our database. Our SIRRIM technique shows that it can be used to rule out Parkinson disease from essential tremor and other forms of Parkinsonism, such as progressive supranuclear palsy and multisystem atrophy. In addition, it is sensitive enough to identify patients with early-stage IPD.
The hypothesis of using SIRRIM as a biological marker to assess IPD is supported by excellent correlation with clinical UPDRS scoring and has proved useful for the evaluation and quantitation of neurodegeneration with our SIRRIM technique, showing, in addition, that the differential diagnosis of IPD can be improved. Technical aspects of acquisition and data processing that need to be addressed can be overcome. It ultimately confirms that our objectives can be achieved and allows us to expect assessment of the progressive development of neurodegeneration in longitudinal studies and the putative neuroprotective approaches taken during the evolution of the disease.
分段反转恢复（IR）比率成像（SIRRIM）已被确立为评估特发性帕金森病（IPD）患者黑质致密部（SN(C)）神经退行性变的敏感工具。所得结果提示磁共振成像（MRI）作为IPD生物学标志物的可能性。讨论了该技术的优势及简洁性分析，以评估将MRI用作IPD生物学标志物的潜力，并改善散发性帕金森病的鉴别诊断。我们的假设是，磁共振SIRRIM技术可直接可视化并定量SN(C)中的神经细胞丢失，因此可能成为帕金森病可靠的生物学标志物。为实现这一目标，需要解决数据采集和数据分析的一些关键方面。考虑到SIRRIM技术可能成为其他技术的可行替代方法，其临床影响可能相当大。
12例IPD患者和12例年龄匹配的对照者采用基于两个IR成像序列的SIRRIM技术进行成像，这两个序列旨在抑制白质和灰质，通过比率图像（白质抑制图像与灰质抑制图像）原位评估神经细胞丢失。将放射学指标与IPD患者的统一帕金森病评定量表（UPDRS）进行关联。
所有IPD患者均被正确识别，利用我们的数据库实现了健康志愿者与患者之间的完全二分法。我们的SIRRIM技术表明，它可用于排除特发性震颤和其他形式帕金森综合征（如进行性核上性麻痹和多系统萎缩）中的帕金森病。此外，它足够敏感，能够识别早期IPD患者。
使用SIRRIM作为评估IPD生物学标志物的假设得到了与临床UPDRS评分的良好相关性的支持，并且已证明我们的SIRRIM技术在评估和定量神经退行性变方面是有用的，此外还表明可以改善IPD的鉴别诊断。需要解决的采集和数据处理技术方面的问题是可以克服的。这最终证实了我们的目标能够实现，并使我们有望在纵向研究中评估神经退行性变的进展以及疾病演变过程中采取的假定神经保护方法。
