基于定量磁敏感成像的正常青年人脑磁化率分析

目的 采用定量磁敏感成像（QSM）技术探讨正常青年人不同侧别及性别的脑磁化率。方法 对41名健康右利手青年人行常规头颅MRI和QSM扫描,通过后处理软件对图像处理获得磁敏感图,然后手工勾画双侧额叶灰质（FGM）、额叶白质（FWM）、尾状核（CA）、苍白球（GP）、壳核（PU）、丘脑（TH）、黑质（SN）、红核（RN）、齿状核（DN）、桥脑（PO）、胼胝体（CC）的ROI并获得磁化率。对各ROI的磁化率采用Mann-Whitney秩和检验比较不同侧别和性别磁化率的差异。结果 双侧ROI磁化率GP最高,SN次之,FWM最低;双侧FGM、FWM、CA、GP、PU、TH、SN、RN、DN、PO、CC的ROI磁化率差异均无统计学意义（P均>0.05）。不同性别CA的磁化率差异有统计学意义（P<0.05）。结论 通过QSM测定脑磁化率,可评估脑铁含量。     

The future of susceptibility contrast for assessment of anatomy and function

The magnetic properties of tissues affect MR images and differences in magnetic susceptibility can be utilized to provide impressive image contrast. Specifically, phase images acquired with gradient echo MRI provide unique and superb contrast which reflects variations in the underlying tissue composition. There is great interest in extracting tissue susceptibility from image data since magnetic susceptibility is an intrinsic tissue property that reflects tissue composition much more closely than MRI phase. Still, this major tissue contrast mechanism is largely unexplored in magnetic resonance imaging because non-conventional reconstruction and dipole deconvolution are required to quantitatively map tissue susceptibility properly. This short review summarizes the current state of susceptibility contrast and susceptibility mapping and aims to identify future directions.     

基于定量磁敏感成像的急性缺血性脑卒中磁化率分析

目的 采用定量磁敏感成像（QSM）分析急性缺血性脑卒中（ACI）的磁化率变化。方法 对符合纳入标准的23例ACI患者行常规头颅MR和QSM扫描,通过工作站QSM软件行图像后处理,根据有无脑微出血灶（CMBs）,将ACI分为CMBs组和无CMBs组。以DWI图为参考,于磁敏感图病灶处手工勾画ROI,包括皮层灰质（CGM）、皮层下白质（SWM）、尾状核（CA）、苍白球（GP）、壳核（PU）、丘脑（TH）、黑质（SN）、齿状核（DN）、桥脑（PO）,获得病灶磁化率,并通过镜像方式获得对侧镜像区磁化率。对不同组别和ROIs分别与对侧镜像区的磁化率进行统计学分析。结果 CMBs组和无CMBs组病灶磁化率差异有统计学意义（Z=-3.297,P=0.001）。CMBs组病灶侧与对侧的磁化率差异有统计意义（Z=-3.296,P=0.001）,无CMBs组病灶侧与对侧的磁化率差异无统计学意义（Z=-0.157,P=0.875）。根据ROI的位置,仅PO和CGM磁化率与对侧的差异有统计学意义（Z=-2.023、-3.130,P=0.043、0.002）。结论 QSM可定量分析ACI磁化率,发现CMBs,有助于指导治疗。     

定量磁化率成像的基本原理及方法概述

定量磁化率成像(quantitative susceptibility mapping,QSM)是磁共振成像(magnetic resonance imaging,MRI)中一项新兴的用于定量测量组织磁化特性的技术。利用定量磁化率成像,可以对组织的铁含量、钙化、血氧饱和度等进行有效的定量分析,对脑出血、多发性硬化症及帕金森综合症等脑神经疾病的研究和诊断也具有重要意义。定量磁化率图像的重建是一个复杂的过程,包括几个不同的步骤,因此其准确性受到很多因素的影响。本文主要概述定量磁化率成像的基本原理和重建流程,并对重建过程中每个步骤的主要方法进行介绍。同时,也将对当前定量磁化率成像的几种主要临床应用进行介绍。     

MRI estimates of brain iron concentration in normal aging using quantitative susceptibility mapping

Quantifying tissue iron concentration in vivo is instrumental for understanding the role of iron in physiology and in neurological diseases associated with abnormal iron distribution. Herein, we use recently-developed Quantitative Susceptibility Mapping (QSM) methodology to estimate the tissue magnetic susceptibility based on MRI signal phase. To investigate the effect of different regularization choices, we implement and compare ?₁ and ?₂ norm regularized QSM algorithms. These regularized approaches solve for the underlying magnetic susceptibility distribution, a sensitive measure of the tissue iron concentration, that gives rise to the observed signal phase. Regularized QSM methodology also involves a pre-processing step that removes, by dipole fitting, unwanted background phase effects due to bulk susceptibility variations between air and tissue and requires data acquisition only at a single field strength. For validation, performances of the two QSM methods were measured against published estimates of regional brain iron from postmortem and in vivo data. The in vivo comparison was based on data previously acquired using Field-Dependent Relaxation Rate Increase (FDRI), an estimate of MRI relaxivity enhancement due to increased main magnetic field strength, requiring data acquired at two different field strengths. The QSM analysis was based on susceptibility-weighted images acquired at 1.5 T, whereas FDRI analysis used Multi-Shot Echo-Planar Spin Echo images collected at 1.5 T and 3.0 T. Both datasets were collected in the same healthy young and elderly adults. The in vivo estimates of regional iron concentration comported well with published postmortem measurements; both QSM approaches yielded the same rank ordering of iron concentration by brain structure, with the lowest in white matter and the highest in globus pallidus. Further validation was provided by comparison of the in vivo measurements, ?₁-regularized QSM versus FDRI and ?₂-regularized QSM versus FDRI, which again yielded perfect rank ordering of iron by brain structure. The final means of validation was to assess how well each in vivo method detected known age-related differences in regional iron concentrations measured in the same young and elderly healthy adults. Both QSM methods and FDRI were consistent in identifying higher iron concentrations in striatal and brain stem ROIs (i.e., caudate nucleus, putamen, globus pallidus, red nucleus, and substantia nigra) in the older than in the young group. The two QSM methods appeared more sensitive in detecting age differences in brain stem structures as they revealed differences of much higher statistical significance between the young and elderly groups than did FDRI. However, QSM values are influenced by factors such as the myelin content, whereas FDRI is a more specific indicator of iron content. Hence, FDRI demonstrated higher specificity to iron yet yielded noisier data despite longer scan times and lower spatial resolution than QSM. The robustness, practicality, and demonstrated ability of predicting the change in iron deposition in adult aging suggest that regularized QSM algorithms using single-field-strength data are possible alternatives to tissue iron estimation requiring two field strengths.     

Unsupervised resolution-agnostic quantitative susceptibility mapping using adaptive instance normalization

Quantitative susceptibility mapping (QSM) is a useful magnetic resonance imaging (MRI) technique that provides the spatial distribution of magnetic susceptibility values of tissues. QSMs can be obtained by deconvolving the dipole kernel from phase images, but the spectral nulls in the dipole kernel make the inversion ill-posed. In recent years, deep learning approaches have shown a comparable QSM reconstruction performance to the classic approaches, in addition to the fast reconstruction time. Most of the existing deep learning methods are, however, based on supervised learning, so matched pairs of input phase images and ground-truth maps are needed. Moreover, it was reported that the deep learning-based methods fail to reconstruct QSM when the resolution of test data is different from the trained resolution. To address this, here we propose an unsupervised resolution-agnostic QSM deep learning method. The proposed method does not require QSM labels for training and reconstructs QSM with various resolutions by using adaptive instance normalization. Experimental results and clinical validation confirm that the proposed method provides accurate QSM with various resolutions compared to other deep learning approaches, and shows competitive performance to the best classical approaches in addition to the ultra-fast reconstruction.     

定量磁敏感加权成像在急性缺血性脑卒中中的应用

磁敏感加权成像(susceptibility weighted imaging,SWI)是一种利用组织磁敏感性不同而成像的技术,对缺氧缺血及颅内矿物质沉积非常敏感,已被广泛应用于急性缺血性脑卒中的诊断,但SWI不能对磁化率进行定量测定,随着定量磁敏感图(quantitative susceptibility mapping,QSM)的发展,这一缺陷逐步被弥补。QSM是基于梯度回波磁共振相位数据的一种新型的可以非侵入性地评估体内磁性组织之间磁敏感性差异的技术,它通过测量磁性物质的磁化率值来实现对体内磁性物质的定量,目前它在量化体内铁含量、钙化及静脉氧饱和度变化等方面已有了多种多样的应用。本文将就定量磁敏感加权成像的基本原理及其在急性缺血性脑卒中中的应用进行概述。     

Quantitative susceptibility mapping of human brain reflects spatial variation in tissue composition

Image phase from gradient echo MRI provides a unique contrast that reflects brain tissue composition variations, such as iron and myelin distribution. Phase imaging is emerging as a powerful tool for the investigation of functional brain anatomy and disease diagnosis. However, the quantitative value of phase is compromised by its nonlocal and orientation dependent properties. There is an increasing need for reliable quantification of magnetic susceptibility, the intrinsic property of tissue. In this study, we developed a novel and accurate susceptibility mapping method that is also phase-wrap insensitive. The proposed susceptibility mapping method utilized two complementary equations: (1) the Fourier relationship of phase and magnetic susceptibility; and (2) the first-order partial derivative of the first equation in the spatial frequency domain. In numerical simulation, this method reconstructed the susceptibility map almost free of streaking artifact. Further, the iterative implementation of this method allowed for high quality reconstruction of susceptibility maps of human brain in vivo. The reconstructed susceptibility map provided excellent contrast of iron-rich deep nuclei and white matter bundles from surrounding tissues. Further, it also revealed anisotropic magnetic susceptibility in brain white matter. Hence, the proposed susceptibility mapping method may provide a powerful tool for the study of brain physiology and pathophysiology. Further elucidation of anisotropic magnetic susceptibility in vivo may allow us to gain more insight into the white matter micro-architectures.     

Quantitative susceptibility mapping for investigating subtle susceptibility variations in the human brain

Quantitative susceptibility mapping (QSM) is a novel magnetic resonance-based technique that determines tissue magnetic susceptibility from measurements of the magnetic field perturbation. Due to the ill-posed nature of this problem, regularization strategies are generally required to reduce streaking artifacts on the computed maps. The present study introduces a new algorithm for calculating the susceptibility distribution utilizing a priori information on its regional homogeneity derived from gradient echo phase images and analyzes the impact of erroneous a priori information on susceptibility map fidelity. The algorithm, Homogeneity Enabled Incremental Dipole Inversion (HEIDI), was investigated with a special focus on the reconstruction of subtle susceptibility variations in a numerical model and in volunteer data and was compared with two recently published approaches, Thresholded K-space Division (TKD) and Morphology Enabled Dipole Inversion (MEDI). HEIDI resulted in susceptibility maps without streaking artifacts and excellent depiction of subtle susceptibility variations in most regions. By investigating HEIDI susceptibility maps acquired with the volunteers' heads in different orientations, it was demonstrated that the apparent magnetic susceptibility distribution of human brain tissue considerably depends on the direction of the main magnetic field.     

Stimulus-induced Rotary Saturation (SIRS): a potential method for the detection of neuronal currents with MRI

Neuronal currents produce local transient and oscillatory magnetic fields that can be readily detected by MEG. Previous work attempting to detect these magnetic fields with MR focused on detecting local phase shifts and dephasing in T₂ or T₂-weighted images. For temporally biphasic and multi-phasic local currents the sensitivity of these methods can be reduced through the cancellation of the accrued phase induced by positive and negative episodes of the neuronal current. The magnitude of the phase shift is also dependent on the distribution of the current within the voxel. Since spins on one side of a current source develop an opposite phase shift relative to those on the other side, there is likely to be significant cancellation within the voxel.We introduce a potential method for detecting neuronal currents though their resonant T_1ρ saturation during a spin-lock preparation period. The method is insensitive to the temporal and spatial cancellation effects since it utilizes the multi-phasic nature of the neuronal currents and thus is not sensitive to the sign of the local field. To produce a T_1ρ reduction, the Larmor frequency in the rotating frame, which is set by γB_1lock (typically 20 Hz–5 kHz), must match the major frequency components of the stimulus-induced neuronal currents. We validate the method in MRI phantom studies. The rotary saturation spectra showed a sharp resonance when a current dipole within the phantom was driven at the Larmor frequency in the rotating frame. A 7 min block-design experiment was found to be sensitive to a current dipole strength of 56 nAm, an approximate magnetic field of 1 nT at 1.5 mm from the dipole. This dipole moment is similar to that seen using the phase shift method in a similar experimental setup by Konn et al. [Konn, D., Gowland, P., Bowtell, R., 2003. MRI detection of weak magnetic fields due to an extended current dipole in a conducting sphere: a model for direct detection of neuronal currents in the brain. Magn. Reson. Med. 50, 40–49], but is potentially less encumbered by temporal and spatial cancellation effects.     

基于磁化率成像Brainnetome Atlas脑网络组图谱定量分析脑铁的可行性

目的 探讨基于定量磁化率成像（QSM）脑网络组图谱定量分析脑铁的可行性。方法 将43名右利手健康成年志愿者的QSM图像通过Matlab软件配准及滑处理对应到标准脑，在Brainnetome Atlas脑网络组图谱上选择双侧苍白球、壳核、尾状核、海马、丘脑、额叶、顶叶及枕叶皮质ROI，以Matlab软件测量磁化率值，并对上述脑区手工勾画ROI，测量磁化率值。对软件及手工所测磁化率值与尸检脑组织染色所得铁浓度结果进行相关分析，观察其与年龄的相关性，比较不同性别、侧别间磁敏感值差异。结果 Matlab软件和手工测量磁化率值均以苍白球最高，壳核次之，海马最低；2种方法所测磁化率值均与尸检铁浓度结果呈正相关（r=0.920、0.856，P=0.003、0.014）。Matlab法测得男性额叶皮质磁化率值高于女性（P<0.05），其余部位无显著性别差异（P均>0.05）；2种方法所测磁化率值均无显著侧别差异（P均>0.05）。结论 基于QSM成像Brainnetome Atlas脑网络组图谱脑铁定量方法测量脑铁含量具有较高准确性及可行性；脑铁含量随年龄而增加，额叶皮质铁含量存在性别差异。     

Quantitative susceptibility mapping (QSM) as a means to measure brain iron? A post mortem validation study

Quantitative susceptibility mapping (QSM) is a novel technique which allows determining the bulk magnetic susceptibility distribution of tissue in vivo from gradient echo magnetic resonance phase images. It is commonly assumed that paramagnetic iron is the predominant source of susceptibility variations in gray matter as many studies have reported a reasonable correlation of magnetic susceptibility with brain iron concentrations in vivo. Instead of performing direct comparisons, however, all these studies used the putative iron concentrations reported in the hallmark study by Hallgren and Sourander (1958) for their analysis. Consequently, the extent to which QSM can serve to reliably assess brain iron levels is not yet fully clear. To provide such information we investigated the relation between bulk tissue magnetic susceptibility and brain iron concentration in unfixed (in situ) post mortem brains of 13 subjects using MRI and inductively coupled plasma mass spectrometry. A strong linear correlation between chemically determined iron concentration and bulk magnetic susceptibility was found in gray matter structures (r=0.84, p<0.001), whereas the correlation coefficient was much lower in white matter (r=0.27, p<0.001). The slope of the overall linear correlation was consistent with theoretical considerations of the magnetism of ferritin supporting that most of the iron in the brain is bound to ferritin proteins. In conclusion, iron is the dominant source of magnetic susceptibility in deep gray matter and can be assessed with QSM. In white matter regions the estimation of iron concentrations by QSM is less accurate and more complex because the counteracting contribution from diamagnetic myelinated neuronal fibers confounds the interpretation.     

基于定量磁化率成像人脑深层灰质核团概率性图谱的构建

目的基于定量磁化率成像(quantitative susceptibility mapping,QSM)技术制作可用于自动分割大脑深层灰质核团的概率图谱。材料与方法 15名健康受试者参与研究,所有受试者扫描均在3.0 T磁共振成像设备系统上完成。在随机选取的10名受试者得到的标准空间QSM图上,手动勾画出六个双侧脑深部灰质核团,之后采用相应的图谱评价方法选择最优概率阈值的图谱作为最终的概率图谱。在其余5名受试者得到的标准空间QSM图上,分别使用三种图谱(概率图谱、AAL图谱和Johns Hopkins图谱)自动分割和由2名研究者手动勾画出六个双侧脑深部灰质核团感兴趣区,并分别计算自动分割与手动勾画得到的区域的相似度Dice系数和磁化率值,以评价概率图谱的准确性。结果在基底节区域,概率图谱分割结果的Dice系数明显高于AAL图谱,但和Johns Hopkins图谱区别不大;在颅底和小脑区域,概率图谱分割结果的Dice系数明显高于Johns Hopkins图谱。与其他两种图谱相比,概率图谱自动分割深部核团后测量得到的磁化率值,更接近于手动勾画核团测量得到的磁化率值,其差别更小。结论基于多名受试者QSM图像构建的脑深部灰质核团概率图谱,对大脑灰质核团分割效果更加可靠,可有效提高图像分析工作的效率。     

USPIO enhanced lymph node MRI using 3D multi‐echo GRE in a rabbit model

Ultrasmallsuperparamagnetic iron oxide (USPIO) has been suggested to be a negative MR contrast agent to detect metastatic lymph nodes. Previously reported studies have evaluated the diagnostic performance of USPIO‐enhanced MR lymph node imaging based on signal intensity. In this study, we investigate the specific performance of three different parametric approaches (normalized signal intensity, R₂* and susceptibility) using 3D multi‐echo gradient echo to quantify the USPIO particles in lymph nodes. Nine rabbits with VX2 tumor implants were scanned before and after USPIO injection. From 3D multi‐echo GRE magnitude and phase data, we generated multi‐echo combined T₂*‐weighted images, an R₂* map, and a quantitative susceptibility map. Eighteen lymph nodes (nine reactive and nine metastatic) were evaluated and showed remarkable signal drops in the area of USPIO accumulation. On parametric analysis, the R₂* difference before and after USPIO injection was significantly different (p < 0.05) between reactive and metastatic lymph nodes; in contrast, the normalized signal intensity and susceptibility were not significantly different between the nodes. Our study showed the potential utility of USPIO‐enhanced MRI using R2* mapping from 3D multi‐echo GRE for the detection of lymph node metastasis and parametric analysis of lymph node status in a rabbit model. Copyright © 2016 John Wiley & Sons, Ltd.     

定量磁化率成像用于帕金森病研究进展

帕金森病(PD)是以黑质多巴胺能神经元损伤及铁沉积为病理特征的神经退行性疾病。定量磁化率成像(QSM)是根据相位信息定量评估组织中铁含量的MR技术，对铁沉积较传统梯度回波成像更为敏感。本文就QSM用于PD的研究进展进行综述。     

常规MRI信号改变与定量磁敏感加权图像评估高胆红素血症的足月新生儿潜在脑损伤

目的  探究常规MRI信号改变及定量磁敏感加权图像（QSM）定量评估足月新生儿高胆红素血症患儿潜在脑损伤的价值。 方法  回顾性分析2019年1月~2020年12月我院收治的临床综合诊断为高胆红素血症的足月新生儿50例（Ⅰ组）,另选48例胆红素不高的无脑相关疾病的足月新生儿作为对照组（Ⅱ组）。再根据血清总胆红素水平将Ⅰ组分为轻中度升高组和重度及极重度升高组。所有患儿均行治疗前MR平扫、扩散加权成像扫描,其中38例患儿行QSM检查,对比不同组别患儿MR信号强度之间差异及其与血清总胆红素水平的相关性;比较胆红素升高患儿与对照组患儿不同核团磁化率之间的差异,及其与血清总胆红素水平之间的相关性。 结果  胆红素升高患儿更容易出现苍白球（GP）T1WI高信号表现（36/12 vs 13/37,P < 0.001）;3组之间GP的T1WI信号强度（SI1）/T2WI信号强度（SI2）比值的差异有统计学意义（P=0.034）,但SI1GP、SI2GP、SI1P、SI2P、SI1FWM、SI2FWM、SI1FGM、SI2FGM、SI1GP/SI1P、SI1GP/SI1FWM、SI1GP/SI1FGM、△SI1（GP-P）、△SI1（GP-FGM）、△SI1（GP-P）/SI1GP、△SI1（GP-P）/△SI1（GP-FGM）、△SI1（GP-P）/△SI1（GP-FWM）的差异均无统计学意义（P > 0.05）;SI1 GP/SI2GP与血清总胆红素水平呈极弱相关关系（r=0.261,P=0.009）,当日龄与出生体质量控制时,SI1 GP/SI2GP、△SI1（GP-P）/△SI1（GP-FGM）与血清总胆红素仍呈极弱相关（r=0.230,P=0.014;r=-0.184,P=0.014）。胆红素升高组与对照组之间苍白球、壳核、丘脑底核及脑干的磁化率之间的差异均有统计学意义（P < 0.05）;且壳核及丘脑底核与血清总胆红素水平呈轻度相关（r=-0.419,P= 0.011;r=-0.391,P=0.018）,而苍白球及脑干与血清胆红素呈中度相关（r=-0.620,P < 0.001;r=-0.630,P < 0.001）。 结论  高胆红素血症新生儿单纯评价苍白球T1WI高信号有一定的诊断意义,但是常规MR信号强度与血清胆红素是否升高没有明确相关性;而苍白球、壳核、丘脑底核及脑干QSM测定的磁化率可能可以更早的发现高胆红素血症新生儿潜在脑损伤。     

The contribution of myelin to magnetic susceptibility-weighted contrasts in high-field MRI of the brain

T₂*-weighted gradient-echo MRI images at high field (≥ 7 T) have shown rich image contrast within and between brain regions. The source for these contrast variations has been primarily attributed to tissue magnetic susceptibility differences. In this study, the contribution of myelin to both T₂* and frequency contrasts is investigated using a mouse model of demyelination based on a cuprizone diet. The demyelinated brains showed significantly increased T₂* in white matter and a substantial reduction in gray-white matter frequency contrast, suggesting that myelin is a primary source for these contrasts. Comparison of in-vivo and in-vitro data showed that, although tissue T₂* values were reduced by formalin fixation, gray-white matter frequency contrast was relatively unaffected and fixation had a negligible effect on cuprizone-induced changes in T₂* and frequency contrasts.     

MRI 梯度回波T2 加权序列对脑内海绵状血管瘤的诊断价值

目的　通过分析比较自旋回波 (SE)序列和梯度回波T2 WI(准T2 序列T 2 )序列对脑内海绵状血管瘤 (CA)的显示能力 ,以探讨T 2 技术对CA的诊断价值。方法　对 18例CA病人采用SE和T 2 序列进行MRI检查 ,观察两者对CA病灶的检测能力。结果　SE序列共检出 2 3个CA病灶。而T 2 序列则比前者多发现 2 0个CA病灶。T 2 序列能更准确识别邻近蛛网膜下腔的皮层下和缺血灶附近的小CA病灶。结论　CA病人MRI检查时 ,常规SE序列与T 2 相结合 ,能更全面准确地提供诊断信息。     

High‐throughput screening of chemical exchange saturation transfer MR contrast agents

A new high‐throughput MRI method for screening chemical exchange saturation transfer (CEST) agents is demonstrated, allowing simultaneous testing of multiple samples with minimal attention to sample configuration and shimming of the main magnetic field (B₀). This approach, which is applicable to diamagnetic, paramagnetic and liposome CEST agents, employs a set of inexpensive glass or plastic capillary tubes containing CEST agents put together in a cheap plastic tube holder, without the need for liquid between the tubes to reduce magnetic susceptibility effects. In this setup, a reference image of direct water saturation spectra is acquired in order to map the absolute water frequency for each volume element (voxel) in the sample image, followed by an image of saturation transfer spectra to determine the CEST properties. Even though the field over the total sample is very inhomogeneous due to air–tube interfaces, the shape of the direct saturation spectra is not affected, allowing removal of susceptibility shift effects from the CEST data by using the absolute water frequencies from the reference map. As a result, quantitative information such as the mean CEST intensity for each sample can be extracted for multiple CEST agents at once. As an initial application, we demonstrate rapid screening of a library of 16 polypeptides for their CEST properties, but in principle the number of tubes is limited only by the available signal‐noise‐ratio, field of view and gradient strength for imaging. Copyright © 2010 John Wiley & Sons, Ltd.     

Image reconstruction of compressed sensing MRI using graph-based redundant wavelet transform

Compressed sensing magnetic resonance imaging has shown great capacity for accelerating magnetic resonance imaging if an image can be sparsely represented. How the image is sparsified seriously affects its reconstruction quality. In the present study, a graph-based redundant wavelet transform is introduced to sparsely represent magnetic resonance images in iterative image reconstructions. With this transform, image patches is viewed as vertices and their differences as edges, and the shortest path on the graph minimizes the total difference of all image patches. Using the l₁ norm regularized formulation of the problem solved by an alternating-direction minimization with continuation algorithm, the experimental results demonstrate that the proposed method outperforms several state-of-the-art reconstruction methods in removing artifacts and achieves fewer reconstruction errors on the tested datasets.