Magnetic resonance angiography in the mana-gement of patients with portal hypertension

BACKGROUND: In recent years, MR techniques have been widely used for displaying hepatic vessels and measuring its hemodynamics, especially in the management of the patients with portal hypertension. The aim of this study was to eva- luate the role of magnetic resonance angiography (MRA) in the treatment of patients with portal hypertension. METHODS: A series of 38 patients with portal hypertension and 12 control patients were enrolled in this study. Three dimensional dynamic contrast-enhanced (3D-DCE) MRA and two dimensional phase-contrast (2D-PC) MR were used for the study of portal venous anatomy and its hemo- dynamics, which were compared with those of indirect portal-venography (IPVG) and doppler ultrasonography (DUS). RESULTS: The anatomical imaging of the portal venous system could be displayed clearly in 3D-DCE MRA and the imaging quality of MRA was better than that of IPVG. The hemodynamic information from 2D-PC MR was closely re- lated to that from DUS. CONCLUSIONS: As a non-invasive technique, MRA can display the anatomy of the portal venous system clearly and measure its hemodynamics exactly. It is very useful and can be applied if necessary in the management of patients with portal hypertension.

Validation of hyperintense middle cerebral artery sign in acute ischemic stroke Comparison between magnetic resonance imaging and angiography

We performed a retrospective analysis of non-contrast computed tomography （CT） scans, immediately subsequent magnetic resonance imaging （MRI）, and cerebral angiography data from 30 consecutive patients with acute ischemic stroke within 6 hours after symptom onset. Results showed that eleven patients developed subsequent hemorrhagic transformation at follow-up. A hyperintense middle cerebral artery sign on MRI was found in six hemorrhagic patients, all of who had acute thrombosis formation on magnetic resonance angiography and digital subtraction angiography. No patients in the non-hemorrhagic group had hyperintense middle cerebral artery sign on MRI. The sensitivity, specificity, and positive predictive values of the hyperintense middle cerebral artery sign on MRI T1-weighted image for subsequent hemorrhagic transformation were 54.5%, 100%, and 100% respectively. Hyperdense middle cerebral artery sign on non-contrast CT was observed in nine patients, five of who developed hemorrhagic transformation. These data suggest that hyperintense middle cerebral artery sign on MRI T1-weighted image is a highly specific and moderately sensitive indicator of subsequent hemorrhagic transformation in patients after acute ischemic stroke, and its specificity is superior to CT.

Magnetic resonance angiography for the primary diagnosis of pulmonary embolism: A review from the international workshop for pulmonary functional imaging

Pulmonary contrast enhanced magnetic resonance angiography(CE-MRA) is useful for the primary diagnosis of pulmonary embolism(PE). Many sites have chosen not to use CE-MRA as a first line of diagnostic tool for PE because of the speed and higher efficacy of computerized tomographic angiography(CTA). In this review, we discuss the strengths and weaknesses of CEMRA and the appropriate imaging scenarios for the primary diagnosis of PE derived from our unique multiinstitutional experience in this area. The optimal patient for this test has a low to intermediate suspicion for PE based on clinical decision rules. Patients in extremis are not candidates for this test. Younger women(< 35 years of age) and patients with iodinated contrast allergies are best served by using this modality We discuss the history of the use of this test, recent technical innovations, artifacts, direct and indirect findings for PE, ancillary findings, and the effectiveness(patient outcomes) of CE-MRA for the exclusion of PE. Current outcomes data shows that CE-MRA and NM V/Q scans are effective alternative tests to CTA for the primary diagnosis of PE.

Comparison of 16 slice multi-detector computed tomography and breath hold 3D magnetic resonance angiography in the detection of coronary stenosis

Objective To compare 16-slice multi-detector spiral computed tomography (MDCT) and breathhold 3D magnetic resonance (MR) coronary angiography in the visualization of coronary arteries and the accuracy of detecting significant (＞ 50%) coronary stenoses in patients with suspected coronary artery disease. Methods Forty patients were examined by 16-slice CT (GE, Lightspeedl6)and MR (GE,Twinspeed) within 3 days; 31 of them underwent conventional coronary angiography (CAG) within 2 weeks after CT and MR scan. CT was performed with 16× 1.25 mm detector collimation, 0.5 s rotation time and images were reconstructed at 60%-75% of the cardiac cycle. MR was performed with breath hold 3D FIESTA (TR4.0 ms, TE1.7 ms, flip angle 65, slice thickness 3 mm, FOV 280 mm, matrix 256× 192). Mean heart rate was 63 ± 5.8 bpm and β-blocker was used in 24 patients. MR and CT image quality was evaluated in 9 coronary segments (RCA1, RCA2, RCA3, LM, LAD1, LAD2, LAD3, LCX1, LCX2) using a four-point grading scale.Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated for detection of significant stenosis using CAG as the gold standard. Results 16-slice CT showed higher image quality in most coronary segments except RCA2.Forty-three segments were diagnosed as significant stenosis by CAG, 36 and 27 of these were correctly detected by CT and MR respectively. Sensitivity, specificity, positive predictive value, and negative predictive value of 16-slice CT and MR for detecting significant stenosis were 83 %, 84 %, 49 %, 97 % and 63 %, 90 %, 55 %, 93 %, respectively. Conclusion Sixteen-slice CT showed higher image quality in most coronary segments excepted for middle RCA. 16-slice CT had higher sensitivity than MR for detection of coronary significant stenosis, whereas MR had higher specificity than CT. Both CT and MR showed high negative predictive value,which is useful for excluding coronary stenosis in symptomatic patients.

Diagnostic Accuracy of Three-Dimensional Whole-Heart Magnetic Resonance Angiography to Detect Coronary Artery Disease with Invasive Coronary Angiography as a Reference:A Meta-Analysis

Objective:We aimed to evaluate the diagnostic performance of three-dimensional whole-heart magnetic resonance coronary angiography(MRCA)in detecting coronary artery disease(CAD)with invasive coronary angiography as the reference standard.Methods:We searched PubMed and Embase for studies evaluating the diagnostic performance of three-dimensional whole-heart MRCA for the diagnosis of CAD with invasive coronary angiography as the reference standard.The bivariate mixed-effects regression model was applied to synthesize available data.The clinical utility of whole-heart MRCA was calculated by the posttest probability based on Bayes’s theorem.Results:Eighteen studies were included,of which 16 provided data at the artery level.Patient-based analysis revealed a pooled sensitivity of 0.90(95%confi dence interval[CI]0.87–0.93)and specifi city of 0.79(95%CI 0.73–0.84),while the pooled estimates were 0.86(95%CI 0.82–0.89)and 0.89(95%CI 0.84–0.92),respectively,at the artery level.The areas under the summary receiver operating characteristic curve were 0.93(95%CI 0.90–0.95)and 0.92(95%CI 0.90–0.94)at the patient and artery levels,respectively.With a pretest probability of 50%,the patients’posttest probabilities of CAD were 81%for positive results and 11%for negative results.Conclusions:Whole-heart MRCA can be an alternative noninvasive method for diagnosis and assessment of CAD.

Celiomesenteric trunk demonstrated by 3-dimensional contrast-enhanced magnetic resonance angiography

Celiomesenteric trunk is a rare vascular anomaly, which has significant clinical implications. 3-di-mensional contrast-enhanced magnetic resonance angiography (3D CE MRA) is a new imaging modality, non-invasive , fast and easy to perform. We describe a patient with a common celiomesenteric trunk demonstrated by 3D CE MRA. METHODS: A 45-year-old man was subjected to 3D CE MRA before transarterial chemoembolization (TACE) for hepatocellular carcinoma. The examination was performed on a 1.5T MR imager with a body coil. The contrast medium was gadopentetate dimeglumine. Source images from the hepatic arterial phase acquisition were reconstructed into MRA images. Intra-arterial digital subtraction angiography (DSA) during TACE was carried out 3 days after 3D CE MRA. RESULTS:On 3D CE MRA, a common trunk of the celiac and superior mesenteric artery was clearly depicted. The origin and course of the hepatic, splenic and superior mesenteric arteries were also visualized. These findings were confirmed by intra-arterial DSA. CONCLUSIONS: Celiomesenteric trunk can be well delineated by 3D CE MRA. The image is correlated precisely with that from DSA.

Modified magnetic resonance angiography of the liver using sensitivity encoding in comparison with digital subtraction angiography and CT arterial portography

BACKGROUND: Over 355 patients have received ortho- topic liver transplantation ( OLT) at this hospital since 1993. Preoperative imaging studies of both hepatic vessels and parenchyma in these recipients bettered surgical plan- ning or even precluded the necessity of surgery. Here we report our preliminary results of modified magnetic reso- nance angiography ( MRA ) using sensitivity encoding ( SENSE) through comparative study with conventional digital subtraction angiography (DSA) and CT arterial por- tography (CTAP). METHODS: Sixteen patients with suspected liver diseases were included in the study. All of them received both dy- namic MRI of the liver using SENSE and digital DSA with CTAP within a two-week interval. The four-phase MRA was reconstructed from source images of the coronal dy- namic study. The arterial phase of the modified MRA was compared with DSA in the evaluation of hepatic arteries and the portal phase compared with CT portography recon- structed from source images of CTAP. In dynamic study of the liver, a fixed dose (20 ml) of contrast medium and scan timing were used. RESULTS: The main branches and variations of the hepatic arterial system were well shown on the modified MRA, al- though the marginal branches of hepatic arteries were of poor quality. The figures of portal veins on MRA were as clear as or superior to those of CTAP. In addition, the su- prarenal inferior vena cava (IVC) was well demonstrated on MRA and/or non contrast-enhanced coronal balanced fast-field echo (b-FFE) scan sequence in most cases. MRI detected most parenchymal lesions of the liver and hemo- dynamics of these lesions could be evaluated on source ima- ges of the modified MRA. MRI/MRA also serendipitously revealed several extrahepatic disease entities or variations that were not found on DSA/CTAP. CONCLUSIONS: The modified MRA using SENSE is a cost-effective modality of examination for the demonstra- tion of the whole hepatic vascular system. Combined with MRI, it has the potential as a one-stop imaging modality in the preoperative evaluation in fields such as OLT.

Three-dimensional time-of-flight magnetic resonance angiography combined with high resolution T2-weighted imaging in preoperative evaluation of microvascular decompression

BACKGROUND Neurovascular compression(NVC) is the main cause of primary trigeminal neuralgia(TN) and hemifacial spasm(HFS). Microvascular decompression(MVD) is an effective surgical method for the treatment of TN and HFS caused by NVC. The judgement of NVC is a critical step in the preoperative evaluation of MVD, which is related to the effect of MVD treatment. Magnetic resonance imaging(MRI) technology has been used to detect NVC prior to MVD for several years. Among many MRI sequences, three-dimensional time-of-flight magnetic resonance angiography(3D TOF MRA) is the most widely used. However, 3D TOF MRA has some shortcomings in detecting NVC. Therefore, 3D TOF MRA combined with high resolution T2-weighted imaging(HR T2WI) is considered to be a more effective method to detect NVC.AIM To determine the value of 3D TOF MRA combined with HR T2WI in the judgment of NVC, and thus to assess its value in the preoperative evaluation of MVD.METHODS Related studies published from inception to September 2022 based on PubMed, Embase, Web of Science, and the Cochrane Library were retrieved. Studies that investigated 3D TOF MRA combined with HR T2WI to judge NVC in patients with TN or HFS were included according to the inclusion criteria. Studies without complete data or not relevant to the research topics were excluded. The Quality Assessment of Diagnostic Accuracy Studies checklist was used to assess the quality of included studies. The publication bias of the included literature was examined by Deeks’ test. An exact binomial rendition of the bivariate mixed-effects regression model was used to synthesize data. Data analysis was performed using the MIDAS module of statistical software Stata 16.0. Two independent investigators extracted patient and study characteristics, and discrepancies were resolved by consensus. Individual and pooled sensitivities and specificities were calculated. The I_(2) statistic and Q test were used to test heterogeneity. The study was registered on the website of PROSERO(registration No. CRD42022357158).RESULTS Our search identified 595 articles, of which 12(including 855 patients) fulfilled the inclusion criteria. Bivariate analysis showed that the pooled sensitivity and specificity of 3D TOF MRA combined with HR T2WI for detecting NVC were 0.96 [95% confidence interval(CI): 0.92-0.98] and 0.92(95%CI: 0.74-0.98), respectively. The pooled positive likelihood ratio was 12.4(95%CI: 3.2-47.8), pooled negative likelihood ratio was 0.04(95%CI: 0.02-0.09), and pooled diagnostic odds ratio was 283(95%CI: 50-1620). The area under the receiver operating characteristic curve was 0.98(95%CI: 0.97-0.99). The studies showed no substantial heterogeneity(I2 = 0, Q = 0.001 P = 0.50).CONCLUSION Our results suggest that 3D TOF MRA combined with HR T2WI has excellent sensitivity and specificity for judging NVC in patients with TN or HFS. This method can be used as an effective tool for preoperative evaluation of MVD.

Cerebral blood flow volume measurements of the carotid artery and ipsilateral branches using two-dimensional phase-contrast magnetic resonance angiography

The optimal velocity encoding of phase-contrast magnetic resonance angiography （PC MRA） in measuring cerebral blood flow volume （BFV） ranges from 60 to 80 cm/s. To verify the accuracy of two-dimensional （2D） PC MRA, the present study localized the region of interest at blood vessels of the neck using PC MRA based on three-dimensional time-of-flight sequences, and the velocity encoding was set to 80 cm/s. Results of the measurements showed that the error rate was 7.0±6.0% in the estimation of BFV in the internal carotid artery, the external carotid artery and the ipsilateral common carotid artery. There was no significant difference, and a significant correlation in BFV between internal carotid artery ＋ external carotid artery and ipsilateral common carotid artery. In addition, the BFV of the common carotid artery was correlated with that of the ipsilateral internal carotid artery. The main error was attributed to the external carotid artery and its branches. Therefore, after selecting the appropriate scanning parameters and protocols, 2D PC MRA is more accurate in the determination of BFV in the carotid arteries.

Enhancement maximum slope of increase of magnetic resonance angiography in patients with diabetes lower extremity arterial disease and its correlation with endothelial injury and oxidative stress

Objective:To study the enhancement maximum slope of increase of magnetic resonance angiography in patients with diabetes lower extremity arterial disease and its correlation with endothelial injury and oxidative stress.Methods: Patients with diabetes lower extremity arterial disease accepting 3D-CEMRA examination in our hospital between May 2013 and December 2015 were selected as the pathology group, and the enhancement maximum slope of increase was measured;healthy volunteers receiving physical examination in our hospital during the same period were selected as control group, and serum levels of endothelial oxidative stress injury-related molecules of two groups of subjects were determined.Results:The enhancement maximum slope of increase of the lesion-side anterior tibial artery, posterior tibial artery, peroneal artery and dorsalis pedis artery of pathology group were significantly lower than those of the unaffected-side;serum CyPA, ERK1, ERK2, Akt, JAK, HO-1 and CO content of pathology group were significantly higher than those of control group and negatively correlated with the enhancement maximum slope of increase of lower extremity while Prdx6, SOD, CAT, GSH-Px, eNOS and NO content were significantly lower than those of control group and positively correlated with the enhancement maximum slope of increase of lower extremity.Conclusion: The enhancement maximum slope of increase of magnetic resonance angiography significantly reduces in patients with diabetes lower extremity arterial disease and is closely related to oxidative stress-induced endothelial injury as well as eNOS/NO and HO-1/CO system function change.

Contribution of cardiovascular magnetic resonance in the evaluation of coronary arteries

Cardiovascular magnetic resonance(CMR) allows the nonradiating assessment of coronary arteries; to achieve better image quality cardiorespiratory artefacts should be corrected. Coronary MRA(CMRA) at the mo-ment is indicated only for the detection of abnormal coronary origin, coronary artery ectasia and/or aneu-rysms(class Ⅰ indication) and coronary bypass grafts(class Ⅱ indication). CMRA utilisation for coronary ar-tery disease is not yet part of clinical routine. However, the lack of radiation is of special value for the coronary artery evaluation in children and women. CMRA can assess the proximal part of coronary arteries in almost all cases. The best results have been observed in the evaluation of the left anterior descending and the right coronary artery, while the left circumflex, which is lo-cated far away from the coil elements, is frequently im-aged with reduced quality, compared to the other two. Different studies detected an increase in wall thickness of the coronaries in patients with type Ⅰ diabetes and abnormal renal function. Additionally, the non-contrast enhanced T1-weighed images detected the presence of thrombus in acute myocardial infarction. New tech-niques using delayed gadolinium enhanced imaging promise the direct visualization of inflamed plaques in the coronary arteries. The major advantage of CMRis the potential of an integrated protocol offering as-sessment of coronary artery anatomy, cardiac function, inflammation and stress perfusion-fibrosis in the same study, providing an individualized clinical profile of pa-tients with heart disease.

In vivo tracking of human adipose-derived stem cells labeled with ferumoxytol in rats with middle cerebral artery occlusion by magnetic resonance imaging

Ferumoxytol, an iron replacement product, is a new type of superparamagnetic iron oxide ap- proved by the US Food and Drug Administration. Herein, we assessed the feasibility of tracking transplanted human adipose-derived stem cells labeled with ferumoxytol in middle cerebral artery occlusion-injured rats by 3.0 T MRI in vivo. 1 × 104 human adipose-derived stem cells labeled with ferumoxytol-heparin-protamine were transplanted into the brains of rats with middle cerebral artery occlusion. Neurologic impairment was scored at 1, 7, 14, and 28 days after transplantation. T2-weighted imaging and enhanced susceptibility-weighted angiography were used to observe transplanted cells. Results of imaging tests were compared with results of Prussian blue staining. The modified neurologic impairment scores were significantly lower in rats transplanted with cells at all time points except I day post-transplantation compared with rats without transplantation. Regions with hypointense signals on T2-weighted and enhanced susceptibility-weighted angiography images corresponded with areas stained by Prussian blue, suggesting the presence of superparamagnetic iron oxide particles within the engrafted cells. Enhanced susceptibility-weighted angiography image exhibited better sensitivity and contrast in tracing ferumoxytol-heparin-protamine-labeled human adipose-derived stem ceils compared with T2-weighted imaging in routine MRI.

Application of MAGnetic resonance imaging compilation in acute ischemic stroke

BACKGROUND Synthetic magnetic resonance imaging(MRI)MAGnetic resonance imaging compilation(MAGiC)is a new MRI technology.Conventional T1,T2,T2-fluidattenuated inversion recovery(FLAIR)contrast images,quantitative images of T1 and T2 mapping,and MAGiC phase sensitive inversion recovery(PSIR)Vessel cerebrovascular images can be obtained simultaneously through post-processing at the same time after completing a scan.In recent years,studies have reported that MAGiC can be applied to patients with acute ischemic stroke.We hypothesized that the synthetic MRI vascular screening scheme can evaluate the degree of cerebral artery stenosis in patients with acute ischemic stroke.AIM To explore the application value of vascular images obtained by synthetic MRI in diagnosing acute ischemic stroke.METHODS A total of 64 patients with acute ischemic stroke were selected and examined by MRI in the current retrospective cohort study.The scanning sequences included traditional T1,T2,and T2-FLAIR,three-dimensional time-of-flight magnetic resonance angiography(3D TOF MRA),diffusion-weighted imaging(DWI),and synthetic MRI.Conventional contrast images(T1,T2,and T2-FLAIR)and intracranial vessel images(MAGiC PSIR Vessel]were automatically reconstructed using synthetic MRI raw data.The contrast-to-noise ratio(CNR)values of traditional T1,T2,and T2-FLAIR images and MAGiC reconstructed T1,T2,and T2-FLAIR images in DWI diffusion restriction areas were measured and compared.MAGiC PSIR Vessel and TOF MRA images were used to measure and calculate the stenosis degree of bilateral middle cerebral artery stenosis areas.The consistency of MAGiC PSIR Vessel and TOF MRA in displaying the degree of vascular stenosis with computed tomography angiography(CTA)was compared.RESULTS Among the 64 patients with acute ischemic stroke,79 vascular stenosis areas showed that the correlation between MAGiC PSIR Vessel and CTA(r=0.90,P<0.01)was higher than that between TOF MRA and CTA(r=0.84,P<0.01).With a degree of vascular stenosis>50%assessed by CTA as a reference,the area under the receiver operating characteristic(ROC)curve of MAGiC PSIR Vessel[area under the curve(AUC)=0.906,P<0.01]was higher than that of TOF MRA(AUC=0.790,P<0.01).Among the 64 patients with acute ischemic stroke,39 were scanned for traditional T1,T2,and T2-FLAIR images and MAGiC images simultaneously,and CNR values in DWI diffusion restriction areas were measured,which were:Traditional T2=21.2,traditional T1=-6.7,and traditional T2-FLAIR=11.9;and MAGiC T2=7.1,MAGiC T1=-3.9,and MAGiC T2-FLAIR=4.5.CONCLUSION The synthetic MRI vascular screening scheme for patients with acute ischemic stroke can accurately evaluate the degree of bilateral middle cerebral artery stenosis,which is of great significance to early thrombolytic interventional therapy and improving patients’quality of life.

Oleic Acid (OA), A Potential Dual Contrast Agent for Postmortem MR Angiography (PMMRA): A Pilot Study

Summary:Choosing proper perfusates as contrast agents is an important aspect for postmortem magnetic resonance angiography(PMMRA).However,in this emerging field,the number of suitable kinds of liquid is still very limited.The objective of this research is to compare MR images of oleic acid(OA)with paraffin oil(PO)in vitro and in ex situ animal hearts,in order to evaluate the feasibility to use OA as a novel contrast agent for PMMRA.In vitro,OA,PO and water(control)were introduced into three tubes separately and T,weighted-spin echo(Tw SE)and T2w-SE images were acquired on a 1.5T MR scanner.In the second experiment,0A and PO were injected into left coronary artery(LCA)and left ventricle(LV)of ex situ bovine hearts and their Tw-SE,Tzw-SE,Tw-multipoint Dixon(Tjw-mDixon)and 3DT2w-mDixon images were acquired.The overall results indicate that OA may have a potential to be used as a dual(T and T2 based)contrast agent for PMMRA when proper sequence parameters are utilized.However,as the pilot study was based on limited number of animal hearts,more researches using OA in cadavers are needed to validate our findings.

Magnetic resonance venography and liver transplant complications

Hepatic vein stenosis is a rare but serious complication following liver transplantation.Multiple modalities can be utilized to image the hepatic vasculature.Magnetic resonance venography(MRV)provides certain advantages over ultrasound,computed tomography angiography and digital subtraction venography.MRV utilizes the same imaging principles of magnetic resonance angiography in order to image the venous system.Blood pool contrast agents,specifically gadofosveset trisodium,allow for steady state imaging up to 1 h following injection,with improved visualisation of vital venous structures by utilising delayed steady state imaging.Additionally,the inherent physics properties of magnetic resonance imaging also provide excellent soft tissue detail and thus help define the extent of complications that often plague the post-liver transplant patient.This case report describes the use of gadofosveset trisodium in a patient with hepatic venous stenosis following liver transplantation.Initial venography failed to outline the stenoses and thus MRV using a blood pool contrast agent was utilised in order to delineate the anatomy and plan a therapeutic endovascular procedure.

Cardiac magnetic resonance in patients with acute cardiac injury and unobstructed coronary arteries

AIM To define the role of cardiac magnetic resonance(CMR) by analyzing a particular group of patients with suspected acute coronary syndrome(ACS) and normal coronary angiogram. METHODS From January 2009 to December 2015, we examined 220 patients with clinical suspicion of ACS, Troponin elevation [the threshold used to define a positive Troponin T test(TnT) was 0.1 ng/mL ] and no significant coronary disease at angiography(the patients were considered to have significant angiographic disease only a 50% stenosis was detected in any of their coronary arteries). The role of CMR with the late gadolinium enhancement was evaluated.RESULTS CMR was performed to 190 patients(86%) of this group which reveals: Myocarditis in 90 patients(47%); apical ballooning(Tako-Tsubo syndrome) in 32 patients(17%); myocardial infarction(MI) in 40 patients(21%) and no clear diagnosis identified by CMR in 28 patients(15%). A comparison with previous studies was also made. Clinical and echocardiographic follow-ups were performed at 12 ± 2 mo and no major adverse cardiac events were revealed.CONCLUSION There is a group of patients with clinical suspicion of ACS displaying normal coronary angiograms. CMR was demonstrated to be a valuable tool in the differential diagnosis evaluation of myocarditis, apical ballooning and MI.

Magnetic Resonance Imaging of Coronary Arteries:Latest Technical Innovations and Clinical Experiences

Cardiovascular disease(CVD)is the leading cause of death and a major health care challenge globally.Coronary artery disease(CAD)is a primary underlying pathological process in the majority of cardiovascular disease cases.Magnetic resonance imaging(MRI)can play a potentially important role in the management of CAD as a noninvasive imaging modality without ionizing radiation,although its early promise has not been delivered because of several crucial technical limitations.However,recent innovations in MRI have reopened the door,with tremendous opportunities for multiparametric assessment of CAD including luminal stenosis,plaque burden and composition,and disease activities such as infl ammation and hemorrhage.Novel MRI acquisition and reconstruction strategies now offer much increased spatial resolution and image quality and shortened examination times compared with conventional approaches.Recent clinical experiences of coronary MRI indicated the potential to improve the current management of coronary atherosclerosis,such as identifying the patients at the highest risk and evaluating therapeutic responses.In this review we discuss the latest technical advances and clinical insights in coronary MRI.

Cutting edge clinical applications in cardiovascular magnetic resonance

Today, the use of cardiovascular magnetic resonance(CMR) is widespread in clinical practice. The increased need to evaluate of subtle myocardial changes, coronary artery anatomy, and hemodynamic assessment has prompted the development of novel CMR techniques including T1 and T2 mapping, non-contrast angiography and four dimensional(4D) flow. T1 mapping is suitable for diagnosing pathologies affecting extracellular volume such as myocarditis, diffuse myocardial fibrosis and amyloidosis, and is a promising diagnostic tool for patients with iron overload and Fabry disease. T2 mapping is useful in depicting acute myocardial edema and estimating the amount of salvageable myocardium following an ischemic event. Novel angiography techniques, such as the selfnavigated whole-heart or the quiescent-interval singleshot sequence, enable the visualization of the great vessels and coronary artery anatomy without the use of contrast material. The 4D flow technique overcomes the limitations of standard phase-contrast imaging and allows for the assessment of cardiovascular hemodynamics in the great arteries and flow patterns in the cardiac chambers. In conclusion, the future of CMR is heading toward a more reliable quantitative assessment of the myocardium, an improved non-contrast visualization of the coronary artery anatomy, and a more accurate evaluation of the cardiac hemodynamics.

头颈联合3D-TOF-MRA人工智能辅助压缩感知序列的优化

目的通过比较施加不同加速因子(acceleration factors,AF)的并行采集(parallel imaging,PI)、压缩感知(compressed sensing,CS)、人工智能-压缩感知(artificial intelligence compressed sensing,ACS)技术的头颈联合三维时间飞跃法磁共振血管成像(three-dimensional time-of-fight magnetic resonance angiography,3D-TOF-MRA)的图像质量,选取优化序列。材料与方法前瞻性招募24例健康志愿者,以PI的AF为3(PI 3)、CS的AF分别为4和6(CS 4、CS 6)以及ACS的AF分别为4、6、8、10(ACS 4、ACS 6、ACS 8、ACS 10)进行头颈联合3D-TOF-MRA扫描。扫描时间:PI 3=8 min 40 s;CS 4=6 min 38 s;CS 6=4 min 9 s;ACS 4=5 min 24 s;ACS 6=4 min 30 s;ACS 8=4 min 13 s;ACS 10=3 min 24 s。分别在双侧大脑中动脉(middle cerebral artery,MCA)M1段、双侧颈内动脉(internal carotid artery,ICA)C4段、颈动脉分叉处下5个层面的双侧颈总动脉(common carotid artery,CCA)以及MCA及ICA同一层面的颞叶白质,CCA同一层面的胸锁乳突肌作为背景区域勾画感兴趣区(regions of interest,ROI),记录信号强度(signal intensity,SI)及标准差(standard deviation,SD),从而计算信噪比(signal-to-noise ratio,SNR)与对比噪声比(contrast-to-noise ratio,CNR)。采用四分法和五分法分别对整体图像质量以及颅内动脉、颈部大动脉进行评分。以组内相关系数(intra-class correlation coefficient,ICC)比较两名放射医师之间及同一名放射医师内客观评价结果的一致性,Kappa检验比较两名放射医师之间及同一名放射医师内主观评价结果的一致性,若一致性良好,则选取其中一位医师的客观评分及主观评分进行后续统计分析。采用单因素方差分析或Kruskal-Wallis检验对客观评分以及主观评分进行总体差异比较,若差异具有统计学意义则进行两两比较。结果与PI技术比较显示,ACS 4~ACS 8的SNR_(L-MCA),ACS 8、ACS 10的CNR_(L-MCA),ACS 4、ACS 6、ACS 10的CNR_(R-MCA),ACS 4~ACS 10的SNR_(R-MCA)、SNR_(L-CCA)、CNR_(L-CCA),ACS 6~ACS 10的SNR_(R-CCA)、CNR_(R-CCA)均高于PI 3,差异具有统计学意义(P<0.05)。与CS技术比较显示,ACS 4~ACS 10的SNR_(R-MCA)、CNR_(L-MCA)及CNR_(R-MCA),ACS 4~ACS 8的SNR_(L-MCA)、SNR_(L-CCA)、SNR_(R-CCA)、CNR_(L-CCA)、CNR_(R-CCA)与CS 4差异具有统计学意义(P<0.05),ACS 4~ACS 10的SNR_(L-MCA)、SNR_(R-MCA)、CNR_(L-MCA)、CNR_(R-MCA)、SNR_(L-ICA)、SNR_(R-ICA)、CNR_(L-ICA)、SNR_(L-CCA)、SNR_(R-CCA)、CNR_(L-CCA)、CNR_(R-CCA)与CS 6差异具有统计学意义(P<0.05),均优于CS 4、CS 6。ACS技术之间两两比较,ACS 8的SNR_(L-MCA)高于ACS 10(P<0.05),ACS 8、ACS 10的SNR_(R-CCA)、CNR_(R-CCA)均高于ACS 4(P<0.05),其余差异均无统计学意义(P>0.05)。除颈部大动脉图像外,主观评分统计结果均为ACS 4~ACS 10与CS 6差异具有统计学意义(P<0.05),优于CS 6。结论与PI及CS技术相比,ACS技术拥有更短的扫描时间,更好的图像质量。ACS 8为最优序列,扫描时间比PI 3缩短51%。

对比5.0T与3.0T时间飞越法MRA图像质量及其所示脉络膜前动脉

目的比较5.0T与3.0T时间飞越法MR血管成像(TOF-MRA)图像质量及其所示脉络膜前动脉(AChA)。方法回顾性收集接受头部5.0T TOF-MRA(5.0T组,n=40)或3.0T TOF-MRA(3.0T组,n=42)的80例患者(其中2例先后接受2种TOF-MRA),对图像质量进行主观评分及客观评价;将AChA均分为近、中及远段(A1、A2、A3段),记录2种TOF-MRA显示左、右侧AChA数量,并观察其所示左、右侧AChA长度及直径的差异。结果5.0T组图像质量主观评分高于3.0T组[5.0(4.0,5.0)vs.5.0(3.0,5.0),Z=6.417,P=0.029],且图像信噪比(91.01±5.04)及对比度噪声比(72.47±5.14)亦均高于3.0T组[(62.11±4.16)、(48.92±4.62),t=28.339、19.681,P均<0.001]。5.0T组共显示80段AChA-A1、80段AChA-A2及60段AChA-A3,3.0T组TOF-MRA共显示60段AChA-A1、36段AChA-A2及12段AChA-A3。5.0T组所示左、右侧AChA长度分别为(24.01±7.41)mm、(22.72±9.36)mm,左、右侧AChA直径分别为(1.16±0.12)mm、(1.19±0.14)mm,3.0T组长度分别为(18.35±8.67)mm、(16.80±6.94)mm,直径分别为(0.99±0.25)mm、(0.95±0.29)mm;5.0T组各值均大于3.0T组(t=3.242、3.183、4.595、3.846,P均<0.001)。结论相比3.0T TOF-MRA,5.0T TOF-MRA图像质量更佳、显示AChA更为清晰,可为临床诊治AChA相关脑血管病提供依据。