Differentiation of myocardial scar from potential pitfalls and artefacts in delayed enhancement MRI

Delayed enhancement cardiac magnetic resonance (DE-CMR) imaging is used increasingly to identify and quantify focal myocardial scar. Our objective is to describe factors used in the interpretation of DE-CMR images and to highlight potential pitfalls and artefacts that mimic myocardial scar. Inversion recovery gradient recalled echo sequence is commonly accepted as the standard of reference for DE-CMR. There are also alternative sequences that can be performed in a single breath-hold or with free breathing. Radiologists need to be aware of factors affecting image quality, and potential pitfalls and artefacts that may generate focal hyperintense areas that mimic myocardial scar.Delayed enhancement cardiac magnetic resonance (DE-CMR) imaging can identify the presence, location and extent of myocardial scar (dense myocardial fibrosis) due to ischaemic and non-ischaemic heart diseases. This technique is also called late gadolinium-enhanced MRI (LGE-MRI), myocardial delayed enhanced (MDE) MRI and delayed hyperenhanced MRI (DHE-MRI) in the literature. DE-CMR has been shown to be more sensitive than other imaging methods in detecting small subendocardial infarctions [1] and has recently been used in population-based studies to assess the presence of myocardial scar [2,3]. The technique is relatively straightforward to implement, and images can be interpreted visually for the presence of myocardial scar (hyperenhanced region) without the need for post-processing.This article is intended to describe quality control procedures, factors affecting image quality, assessment of myocardial scar, and potential pitfalls and artefacts causing focal hyperintensities that mimic myocardial scar in delayed enhancement imaging.     

Pulmonary Arteriovenous Malformations: How Do I Embolize?

Pulmonary arteriovenous malformations (PAVM) are high-flow, low-pressure shunts, consisting of a single feeding artery connecting via an aneurysmal sac to a draining vein. The aneurysmal connection is referred to as an aneurysmal sac. The "filter capacity" of the pulmonary capillaries is lost and results in predisposition to brain abscess, stroke, and transient ischemic attack and, when multiple, dyspnea, because of right-to-left shunting and hypoxemia. PAVM are markers of hereditary hemorrhagic telangiectasia (HHT). Up to 30% of patients with HHT have PAVM complicating their disorder. Left untreated, 50% of patients with PAVM will develop disabling or fatal complications. In addition to stroke and transient ischemic attack syndromes due to passage of paradoxical emboli through the PAVM, rupture of the aneurysmal sac, particularly in the third trimester of pregnancy, can lead to fatal hemoptysis or hemothorax. Finally, brain abscess or more obscure musculoskeletal or spinal infections may be secondary to PAVM. Since detachable silicone balloons are no longer available, we have developed precise techniques for closing pulmonary malformations using pushable fibered coils. It is not the coil that is so important, but it is the use of coaxial or triaxial catheters that allow for precise placement of the coil. Cross-sectional occlusion is essential for embolization of PAVM and this is achieved using the "anchor" or "scaffold" technique. Our recent results indicate permanent involution of treated malformations with a 3% recurrence rate. All patients should be assessed for other manifestations of HHT before treatment and they are best followed in one of the 20 HHT Centers worldwide (www.hht.org).     

Quantitative assessment of myocardial scar in delayed enhancement magnetic resonance imaging

PURPOSE: To characterize the extent and distribution of left ventricular myocardial scar in delayed enhancement magnetic resonance imaging (MRI). MATERIALS AND METHODS: Delayed enhancement images from 18 patients were categorized into three groups based on myocardial scar appearance: discrete myocardial infarction (N = 10), diffuse fibrosis (N = 4), and circumferential endocardial scarring (N = 4). Images were segmented manually by two observers (twice by one observer) to identify nonviable myocardium. Scar was characterized by the following morphologic parameters: the relative area of nonviable myocardium (Percent Scar); a measure of scar cohesion (Patchiness); and the extent to which scar traversed the ventricle wall (Trans>50). RESULTS: The three scar parameters successfully discriminated between patient groups, although no one parameter was able to differentiate between all groups. The average bias between readers was approximately 3% for each parameter, and the average bias between repeated measurements was 1%. In addition, five patients exhibited regions of nonhyperenhanced nonviable myocardium that were expected to show hyperenhancement based upon their location within the infarct zone and appearance on cine images. CONCLUSION: Quantitative characterization of myocardial scar showed good interobserver and intraobserver agreement. However, the appearance of nonhyperenhanced scar in chronic ischemia is problematic for segmentation of delayed enhancement images.     

封闭负压引流技术在乳房脓肿治疗中的应用

目的 探讨封闭负压引流技术（VSD）在乳房脓肿切开引流中的临床意义.方法 将48例患者分为封闭负压引流组（VSD组）和凡士林纱布填塞组（对照组）,对两组患者的愈合后瘢痕长度、换药次数、愈合时间及患者满意度进行对比分析.结果 与对照组相比,VSD组愈合后瘢痕长度明显缩短,换药次数减少8次,愈合时间缩短1 w,患者满意率高.结论 VSD用于治疗乳房脓肿疗效可靠、有效,能明显缩短愈合时间,并能保证乳房的完整、美观,同时能明显减轻医师的工作量.     

Indium-111 leukocyte scintigraphic detection of myocardial abscess formation in patients with endocarditis

Myocardial abscess formation in patients with bacterial endocarditis in most clinical settings, especially in patients with prosthetic valves, is a primary indicator for surgical valve replacement. We report the detection of myocardial abscesses using 111In leukocyte scintigraphy in three patients with prosthetic or native valve endocarditis and nondiagnostic echocardiograms. Leukocyte scintigraphy may allow identification of myocardial abscess formation earlier than other imaging modalities.     

Cardiac Magnetic Resonance Scar Imaging for Sudden Cardiac Death Risk Stratification in Patients with Non-Ischemic Cardiomyopathy

In patients with non-ischemic cardiomyopathy (NICM), risk stratification for sudden cardiac death (SCD) and selection of patients who would benefit from prophylactic implantable cardioverter-defibrillators remains challenging. We aim to discuss the evidence of cardiac magnetic resonance (CMR)-derived myocardial scar for the prediction of adverse cardiovascular outcomes in NICM. From the 15 studies analyzed, with a total of 2747 patients, the average prevalence of myocardial scar was 41%. In patients with myocardial scar, the risk for adverse cardiac events was more than 3-fold higher, and risk for arrhythmic events 5-fold higher, as compared to patients without scar. Based on the available observational, single center studies, CMR scar assessment may be a promising new tool for SCD risk stratification, which merits further investigation.     

MRI三维技术在冠心病左心室瘢痕评估中的应用价值

目的 评价自由呼吸膈肌导航三维相位敏感反转恢复( PSIR)磁矩预准备快速小角度激发( Turbo-FLASH)序列在心脏MRI评估冠心病左心室瘢痕中的应用价值.方法 23例临床有明确心肌梗死的患者,静脉注射钆对比剂,10～15 min后,先行二维PSIR Turbo-FLASH序列成像.随后,立即行三维PSIR Turbo-FLASH序列自由呼吸下成像.由2名医师独立对MRI总体质量进行等级评分.再按照美国心脏学会17节段法,对左心室钆对比剂延迟强化(LGE)的面积和类型进行半定量分析,对LGE的体积进行定量评估.两种方法变量间的比较采用配对t检验或秩和检验,Pearson相关和线性回归模型评价两者之间的相关性和依存关系.结果 23例心肌梗死患者的二维和三维图像,总体质量分别为(2.57±0.59)和(2.39±0.66)分(Z=-0.93,P=0.35);瘢痕的面积积分分别为(24.48±10.83)和(29.00±11.56)分(Z=- 1.41,P=0.16);类型分别为(16.78 ±6.51)和( 18.87 ±6.76)分(Z=-1.17,P=0.24);差异均无统计学意义.三维比二维LGE体积定量更大:二维和三维分别为(23.46±10.61)和(31.65±13.86) cm3(t=-2.25,P=0.03).进一步分析显示延迟强化体积定量二维和三维之间呈现出良好的相关性(r =0.940,P＜0.01)和依存性(y=2.851+1.228x,R2=0.883).结论 自由呼吸下三维PSIR Turbo-FLASH序列对比剂延迟增强成像比常规二维序列能够更准确地显示心肌梗死后瘢痕,是更加有效检测心肌活性的新技术.     

烧伤创疡再生医疗技术联合超声清创治疗肛周脓肿术后创面疗效观察

目的观察肛周脓肿术后创面应用烧伤创疡再生医疗技术联合超声清创治疗的临床疗效方法对2016年3月至2018年12月中铁十二局集团有限公司中心医院创面修复科收治的63例肛周脓肿患者行手术治疗后采用烧伤创疡再生医疗技术联合超声清创治疗术后创面,观察创面愈合时间及疼痛、感染与瘢痕形成情况。结果经烧伤创疡再生医疗技术联合超声清创治疗5 d后,63例患者中无痛52例、轻微疼痛9例、中度疼痛2例;治疗过程中,所有患者创面均未发生感染;最终除1例患者创面未愈出院外,其余62例患者创面均完全愈合,创面愈合时间为16~34d,平均24 d,痊愈率为98.41%;出院后随访3~30个月,所有患者愈后皮肤及黏膜均无明显瘢痕增生。结论烧伤创疡再生医疗技术联合超声清创治疗肛周脓肿术后创面,可有效缓解创面疼痛,抑制创面感染,促进创面无瘢痕愈合,疗效显著,值得临床推广应用。     

Cardiac MRI to investigate myocardial scar and coronary venous anatomy using a slow infusion of dimeglumine gadobenate in patients undergoing assessment for cardiac resynchronization therapy

Purpose

To evaluate a cardiac MR (CMR) examination with slow infusion of a high‐relaxivity contrast agent to visualize coronary venous anatomy (CVA) and myocardial scar in heart failure patients awaiting cardiac resynchronization therapy (CRT).

Materials and Methods

Fourteen patients awaiting CRT (seven ischemic cardiomyopathy (ICM) and seven non‐ICM) and two with normal LV function underwent CMR on a 1.5 Tesla (T) MR scanner. Dimeglumine‐gadobenate was slowly infused. Bolus arrival in the LV was measured by a dynamic electrocardiogram (ECG) ‐triggered inversion recovery (IR) scan subsequent to starting an ECG‐triggered respiratory‐navigated three‐dimensional (3D) SSFP MR scan with IR preparation to acquire systolic whole‐heart anatomy for vein visualization. Delayed contrast‐enhanced MR scan was performed to assess myocardial scar. CVA obtained by CMR was compared with X‐ray venography in 11 patients. CVA and scar were segmented and registered for visual inspection.

Results

For all subjects, there was excellent visualization of the CVA. All ICM and one non‐ICM patient showed scar. There was excellent correlation between veins seen by CMR and venography.

Conclusion

We have demonstrated that slow infusion protocol of dimeglumine‐gadobenate can be used to assess both CVA and myocardial scar in a single MR examination. Furthermore, an image overlay technique has been used to show the relationship of scar to the CVA. J. Magn. Reson. Imaging 2011;33:87–95. © 2010 Wiley‐Liss, Inc.     

Percutaneous Ethibloc injection in aneurysmal bone cysts

Objective. To investigate whether the injection of Ethibloc into aneurysmal bone cysts can be an effective treatment modality. Design and patients.Ethibloc is an alcoholic solution of zein (corn protein) which has thrombogenic and fibrogenic properties. Ten patients with aneurysmal bone cysts were treated with CT-guided percutaneous injection of Ethibloc into the cyst cavity. Ethibloc injection was the primary treatment in five patients. Four patients had recurrence following previous curettage and bone grafting and one patient had not responded to injection into the lesion of autologous iliac crest bone marrow aspirate. Three patients needed a second injection. The median follow-up was 27 (6–60) months. Results and conclusion.Symptoms were relieved in all patients. At imaging, seven patients had resolution of the lesion and three had partial response at the most recent follow-up. Complications consisted of a local transitory inflammatory reaction in two patients and an aseptic abscess in one patient. This relatively simple, minimally invasive procedure makes an operation unnecessary by stopping the expansion of the cyst and inducing endosteal new bone formation. This technique may be used as the primary management of aneurysmal bone cysts excluding spinal lesions. Received: 19 July 1999 Revision requested: 20 September 1999 Revision received: 9 November 1999 Accepted: 6 December 1999     

Optimized cardiac magnetic resonance imaging inversion recovery sequence for metal artifact reduction and accurate myocardial scar assessment in patients with cardiac implantable electronic devices

Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) is the gold standard for imaging myocardial viability. An important application of LGE CMR is the assessment of the location and extent of the myocardial scar in patients with ventricular tachycardia (VT), which allows for more accurate identification of the ablation targets. However, a large percentage of patients with VT have cardiac implantable electronic devices (CIEDs), which is a relative contraindication for cardiac magnetic resonance imaging due to safety and image artifact concerns. Previous studies showed that these patients can be safely scanned on 1.5 T scanners provided that an adequate imaging protocol is adopted. Nevertheless, imaging patients with a CIED result in metal artifacts due to the strong frequency off-resonance effects near the device; therefore, the spins in the surrounding myocardium are not completely inverted, and thus give rise to hyperintensity artifacts. These artifacts obscure the myocardial scar tissue and limit the ability to study the correlation between the myocardial scar structure and the electro-anatomical map during catheter ablation. In this study, we developed a modified inversion recovery technique to alleviate the CIED-induced metal artifacts and improve the diagnostic image quality of LGE images in patients with CIEDs without increasing scan time or requiring additional hardware. The developed technique was tested in phantom experiments and in vivo scans, which showed its capability for suppressing the hyperintensity artifacts without compromising myocardium nulling in the resulting LGE images.     

MEBO纱条脓腔引流联合远红外线照射治疗乳房脓肿的临床研究

目的评价湿润烧伤膏（MEBO）纱条脓腔引流联合远红外线照射治疗乳房脓肿的疗效。方法对收治的80例乳房脓肿患者,随机分为治疗组40例和对照组40例,治疗组行脓肿切开术后用MEBO纱条填塞脓腔引流联合远红外线照射治疗;对照组行脓肿切开术后用凡士林纱条填塞脓腔引流联合远红外线照射治疗。结果治疗组创面愈合快,疼痛反应轻,愈合后瘢痕小,无乳瘘发生,两组比较P〈0．05,差异有统计学意义。结论MEBO纱条脓腔引流联合远红外线照射治疗乳房脓肿,能很快控制局部炎症,明显缩短愈合时间,减少疼痛及乳瘘发生,且愈后瘢痕小,临床疗效显著。     

Pharmacokinetic modeling of delayed gadolinium enhancement in the myocardium

Delayed contrast‐enhanced magnetic resonance imaging (DCE‐MRI) provides prognostic information by delineating regions of myocardial scar. The mechanism of this delayed enhancement in myocardial infarctions (MIs) is hypothesized to result from altered kinetics and changes in the volumes of distribution in the myocardium. Pharmacokinetic models with two and three compartments were fitted to the concentration‐time curves of dynamic contrast‐enhanced MRI data obtained from five patients with known MI. Furthermore, the parameter stability was investigated in simulations for the two different models. The transfer constants and volumes of distribution showed a good correlation with imaging findings on early and delayed contrast‐enhanced MRI. The two compartment model showed higher parameter stability. The three compartment model allows a more in‐depth quantification of myocardial scarring. These models have the potential to improve the diagnosis of myocardial pathologies involving scar, with differing kinetics and volumes of distribution such as infarction or cardiomyopathy. Magn Reson Med 60:1524–1530, 2008. © 2008 Wiley‐Liss, Inc.     

Spinal epidural abscess with gadolinium-enhanced MRI: serial follow-up studies and clinical correlations

We reviewed serial MRI with and without gadolinium-DTPA in eight patients with spinal epidural abscess and correlated the findings and the clinical manifestations. In four patients, diffuse abscesses spanned four vertebral bodies or more; the others had focal abscesses associated with osteomyelitis and/or diskitis. In three of the four patients with diffuse abscesses, MRI (NCMRI) showed diffuse encasement of the subarachnoid space. Contrast-enhanced MRI (CEMRI) demonstrated linear enhancement surrounding unenhanced pus. In the four patients with focal abscesses, CEMR delineated the inflammatory process more clearly than NCMR. On follow-up studies, decrease in abscess size and better visualization of the subarachnoid space correlated with clinical improvement in both diffuse and focal abscesses. Despite clinical improvement, contrast enhancement persisted in the disk or epidural space of three patients, and was thought to represent chronic granulomatous change or postsurgical scar. CEMR is very valvable for the initial diagnosis of an epidural abscess, particularly if it involves lengthy segments. During follow-up, CEMR can document responses to therapy, and provide information for determining appropriate treatment.     

The etiology and implications of dense cavitary "photopenia" on myocardial perfusion scintigraphy

Dense cavitary "photopenia" was observed on 21 of 200 consecutive stress perfusion scintigrams. A prominent finding in many cases, it sometimes occupied only a portion of the region overlying the ventricular cavity, was often seen in some projections and not others, and was frequently adjacent to myocardial perfusion defects. To distinguish an etiology among reduced cavitary radioactivity, relatively increased background radioactivity, or reduced radioactivity in overlying myocardium, quantitative analysis of cavitary, lung and myocardial radioactivity was performed in patients with dense cavitary "photopenia," with and without lung uptake, and compared with results from studies showing increased lung uptake without cavitary photopenia and with normal studies. The results showed that dense cavitary photopenia was related to reduced radioactivity in overlying myocardium. Correlative imaging studies performed with echocardiography and contrast ventriculography confirmed this relationship to myocardial scar in 15 of 21 patients in whom associated akinesis or dyskinesis was seen. Hence, dense cavitary photopenia on stress perfusion scintigraphy is due to a dense myocardial perfusion abnormality, and is often indicative of related scar and an associated severe contraction abnormality.     

The influence of myocardial blood flow and volume of distribution on late Gd-DTPA kinetics in ischemic heart failure

PURPOSE: To determine the mechanism of enhancement of contrast-enhanced MRI (ceMRI) in chronic ischemic myocardium. While ceMRI can identify scar tissue in chronic ischemic myocardium, the mechanism of enhancement is not completely understood. MATERIALS AND METHODS: A total of 11 patients with ischemic heart failure (ejection fraction [EF] 28 +/- 9%) were imaged with ceMRI and positron emission tomography (PET) to measure myocardial blood flow (MBF). Longitudinal relaxation rate (T1) of blood, normal tissue, and scar tissue defined by ceMRI was determined before and two to 50 minutes after contrast (Look Locker technique), and the partition coefficient (lambda) and volume of distribution (VD) were calculated. RESULTS: In scar and viable tissue, T1 was significantly different over the whole period after contrast, but not before contrast. However, T1 of scar and blood were similar five to 15 minutes post contrast, making the detection of subendocardial defects difficult. lambda reached an initial steady state in viable tissue, but was delayed (20 minutes) in scar tissue. VD in scar was double that of viable tissue (0.54 +/- 0.01 vs. 0.29 +/- 0.02, respectively) indicating an increased interstitial space. Contrast wash-in kinetics correlated moderately with MBF (r = -0.36), but well with the combination of MBF and VD (r = 0.59). CONCLUSION: Late myocardial contrast kinetics depend on both MBF and VD; however the increased VD seems to be the main mechanism for the late enhancement effect.     

An adult case of the left coronary artery anomalously originating from the pulmonary artery (BWG syndrome), demonstrating remarkable improvement in postoperative thallium-201 myocardial imaging

Stress thallium-201 myocardial scintigraphy were performed in a 44-year-old female with BWG syndrome before and after aorto-coronary bypass surgery. Preoperative stress thallium-201 studies demonstrated anterior reversible perfusion defect and posterior persistent defect. But postoperative studies demonstrated no defects in both areas. These data suggest that preoperative anterior defect was due to transient myocardial ischemia, but the finding of posterior persistent defect wasn't due to infarction or scarring. Thus, stress thallium-201 myocardial imaging provided useful informations to clarify the myocardial perfusion patterns pre- and postoperatively.     

Cine delayed-enhancement MR imaging of the heart: initial experience

This study was performed by using an institutional review board-approved protocol, with waived informed consent and HIPAA compliance. The purpose of this study was to preliminarily evaluate a cine delayed-enhancement (DE) pulse sequence for depiction of wall motion and myocardial scar extent during a single acquisition. The technique is based on inversion-recovery single-shot balanced steady-state free precession magnetic resonance imaging. Cine DE images were acquired in 26 patients (18 men, eight women; age range, 25-84 years; mean age, 61 years+/-13 [standard deviation]). Image contrast was consistent throughout each series. Overall (ie, with both readers' scores averaged), the cine DE imaging-depicted wall motion was scored correctly in 71% of myocardial segments. Scar extent was scored correctly in 76% of segments; in no patient was scarring missed. Cine DE imaging is a promising technique for simultaneous visualization of wall motion and myocardial scar extent.     

Detection of a false left ventricular aneurysm by first-pass radionuclide ventriculography

A false left ventricular aneurysm complicating an inferior myocardial infarction was successfully identified by computerized first-pass radionuclide ventriculography using a multicrystal gamma camera. The aneurysmal chamber exhibited paradoxical systolic expansion, a pattern of contraction confirmed by contrast cineangiography. Because of the propensity of false aneurysms to rupture, early noninvasive firm diagnosis is desirable and may be accomplished by first-pass radionuclide angiography.     

Euglycemic hyperinsulinemic clamp and oral glucose load in stimulating myocardial glucose utilization during positron emission tomography.

To enable assessment of myocardial viability, myocardial glucose utilization has commonly been stimulated by oral glucose loading. To compare the effects of glucose loading and insulin and glucose infusion (insulin clamp) on PET fluorodeoxyglucose ([18F]FDG) myocardial scan image quality and regional myocardial glucose utilization rate (rMGU), eight patients with angiographically documented coronary artery disease and previous myocardial Q-wave infarction were studied twice, once during insulin clamp and once 1 hr after oral glucose loading. The rMGU rates were derived by graphic Patlak analysis in 33 normal, 10 scar and 6 "hot spot" myocardial segments. Infusion of insulin and glucose gave stable plasma-glucose and serum-insulin levels during imaging. In contrast, glucose loading caused marked changes in plasma-glucose and insulin concentrations. The image quality was clearly superior and the fractional utilization rates of [18F]FDG were twice as high during insulin clamp than after glucose loading (p less than 0.0001). Due to the higher plasma-glucose levels after glucose loading, the calculated rMGU in normal, scar and hot spot myocardial segments was comparable between the two protocols. The insulin clamp technique makes it possible to adjust and maintain a metabolic steady state during the PET study. It does not alter [18F]FDG uptake patterns in different myocardial areas when compared to the standard glucose loading protocol, but this technique results in superior image quality and permits the use of smaller [18F] FDG patient doses.