Average arterial input function for quantitative dynamic contrast enhanced magnetic resonance imaging of neck nodal metastases

Background

We evaluated the repeatability of the calculation of myocardial blood flow (MBF) at rest and pharmacological stress, and calculated the coronary flow reserve (CFR) utilizing ⁸²Rb PET imaging. The aim of the research was to prove high repeatability for global MBF and CFR values and good repeatability for regional MBF and CFR values. The results will have significant impact on cardiac PET imaging in terms of making it more affordable and increasing its use.

Methods

12 normal volunteers were imaged at rest and during pharmacological stress, with 2220 MBq of ⁸²Rb each. A GE Advance PET system was used to acquire dynamic 50-frame studies. MBF was calculated with a 2-compartmental model using a modified PMOD program (PMOD; University Hospital Zurich, Zurich, Switzerland). Two differential equations, describing a 2-compartmental model, were solved by numerical integration and using Levenberg-Marquardt's method for fitting data. The PMOD program defines 16 standard segments and calculates myocardial flow for each segment, as well as average septal, anterior, lateral, inferior and global flow. Repeatability was evaluated according to the method of Bland and Altman.

Results

Global rest and stress MBF, as well as global CFR, showed very good repeatability. No significant differences were found between the paired resting global MBF (0.63 ± 0.13 vs. 0.64 ± 0.13 mL/min/g; mean difference, -1.0% ± 2.6%) and the stress global MBF (1.37 ± 0.23 vs. 1.37 ± 0.24; mean difference, 0.1% ± 2.3%). Global CFR was highly reproducible (2.25 ± 0.56 vs. 2.22 ± 0.54, P = not statistically significant; mean difference, 1.3% ± 14.3%). Repeatability coefficients for global rest MBF were 0.033 (5.2%) and stress MBF 0.062 (4.5%) mL/min/g. Regional rest and stress MBF and CFR have shown good reproducibility. The average per sector repeatability coefficients for rest MBF were 0.056 (8.5%) and stress MBF 0.089 (6.3%) mL/min/g, and average repeatability coefficient for CFR was 0.25 (10.6%).

Conclusion

The results of the study show that software calculation of MBF and CFR with ⁸²Rb myocardial PET imaging is highly repeatable for global values and has good repeatability for regional values.     

In vivo magnetic resonance spectroscopy and dynamic contrast enhanced imaging of the prostate gland

The quantitation of in vivo 1H MR spectroscopy and dynamic contrast enhanced MR imaging is described for patients with histologically confirmed prostate adenocarcinoma and benign prostatic hypertrophy (BPH). Results are presented which suggest that combined use of these techniques may be helpful in improving the characterization of prostate pathologies and ultimately increase the staging accuracy of magnetic resonance.     

Characterization of an NbTaWZr alloy designed for magnetic resonance angiography compatible stents

The majority of stent materials are not fully compatible with magnetic resonance imaging due to their ferromagnetic or paramagnetic compositions. This leads to image artifact which can obscure clinical data in the vicinity of the stent. An Nb-28Ta-3.5W-1.3Zr alloy has been developed specifically to provide reduced magnetic susceptibility and therefore reduce image artifact. This study reports on initial surface characterization, corrosion behaviour, endothelial cell response and MR image performance. Surface analysis confirms the presence of a niobium oxide with some tantalum oxide also present. Electrochemical corrosion testing demonstrates the oxide to be stable with no evidence of film breakdown. Leaching of metallic ions during a 60-day immersion test shows low levels of release, comparable to cobalt-chromium L605. A short term endothelial cell adhesion study shows that the Nb-28Ta-3.5W-1.3Zr may be similar to stainless steel for supporting cell growth. The MR artifact assessment shows that the material has significantly reduced artifact compared to stainless steel. In summary, results from this initial study show that the Nb-28Ta-3.5W-1.3Zr meets many on the criteria expected of a stent material and that improved MR imaging behaviour is also obtained.     

Improved contrast in multispectral phase images derived from magnetic resonance exams of multiple sclerosis patients

We describe a method to extract data from multispectral MR exams of patients with Multiple Sclerosis (MS). The technique produces images of "spectral phase" (SP) relative to a reference tissue. SP images allow retrospective suppression of signal in the reference tissue, while maintaining high spatial resolution. Image quality in SP images was determined from MR exams of 5 MS patients selected at random from a clinical trial underway at our institute. Exams consisting of proton density weighted (PDw), T2 weighted (T2w), T1 weighted (T1w), and gadolinium-DTPA enhanced T1w (GAD) images were acquired from each patient. The MR exams were corrected for intensity nonuniformity, then filtered with an algorithm based upon anisotropic diffusion, to reduce noise. Principal component (PC) images and SP images relative to cerebrospinal fluid (SP(CSF)), normal appearing white matter (SP(NAWM)), gray matter (SP(GM)), and temporalis muscle (SP(MUS)) were then calculated. Contrast between tissues and MS lesions in the MR and derived images was then determined by measuring the signal-difference-to-noise ratio (dSNR) between tissues. Our new SP images provided better tissue contrast than the original MR, filtered MR, and PC images. Contrast improved between CSF and NAWM (from 19.5 to 56), CSF and GM (from 15 to 36), GM and NAWM (from 8 to 14), MS lesions and CSF (from 16 to 35), and between MS lesions and NAWM (from 24 to 47). (Maximum contrast in the original MR images compared to maximum contrast in the SP images.) The additional contrast in SP images may aid the quantification and analysis of lesion activity in MR exams of MS patients.     

Information in magnetic resonance images: evaluation of signal, noise and contrast

The assessment of diagnostic image quality for MRI is considered. The assessment of three key image quality determinants is addressed: signal, noise and contrast. There is a distinction between random noise evaluation, for the calculation of the SNR, and structured noise evaluation for the assessment of image artefacts. Specific methods used are correlation techniques and the Wiener spectrum. Contrast is assessed by comparison of experimental data and theoretical predictions. For each assessment, the theory and method of the evaluation strategy are discussed. The discussion is illustrated with analysis results from commercial MR systems. The choice of analysis method and the subsequent derivation of quality indices are shown to be critical in respect of robustness and accuracy.     

动态增强MRI定量与半定量分析在直肠癌术前T、N分期中的应用价值

目的 评估动态增强MRI(DCE-MRI)定量、半定量分析在直肠癌术前T、N分期诊断中的应用价值。方法 回顾性分析山西省肿瘤医院MR室2014年7月—2014年11月经肠镜病理证实的27 例直肠癌患者影像资料。其中男18例,女9例,年龄45～73岁,此前均未经任何治疗。均于术前行DCE-MRI,用Omni-Kinetics专用灌注软件进行后处理,同时获得容量转移常数(K^trans)、速率常数(K_ep)、细胞外血管外间隙容积比(V_e)等定量参数,以及达峰时间(TTP)、曲线下面积(AUC)、最大浓度(Max Conc)、最大斜率(Max Slope)等半定量参数。对正常肠壁与病变段肠壁的定量、半定量参数行独立样本t检验;采用秩和检验比较各定量、半定量参数在直肠癌术后病理T、N分期的差异,判断各参数的诊断价值。应用ROC曲线分析定量参数在T、N分期中的最佳诊断界点及敏感性、特异性。根据TNM对患者进行分期。结果 正常肠壁与病变段肠壁的K^trans值[(0.28±0.14)min^-1 vs (1.33±0.86)min^-1]、K_ep值[(1.41±0.67)min^-1 vs (3.56±0.72)min^-1]、Max Conc(0.17±0.02 vs 0.29±0.09)、AUC(0.11±0.07 vs 0.23±0.11)比较,差异均具有统计学意义(t=-6.270、-11.359、-2.487、-2.803,P值均＜0.05)。在T分期为T1～2的早期组与T3～4的晚期组间K^trans值[0.66(0.12～1.35)min^-1 vs 2.15(0.84～2.96) min^-1]、K_ep值[2.51(0.12～5.65)min^-1 vs 4.05(3.18～6.68) min^-1]比较,差异均有统计学意义(Z值分别为-4.077、-2.281,P值均＜0.05)。N分期中,淋巴结无转移组的K^trans值(1.01±0.73)、V_e值(0.29±0.18)、TPP(0.93±0.35)均低于转移组(1.75±0.84、0.54±0.29、1.14±0.15,差异均有统计学意义(Z值分别为-2.433、-2.832、-2.496,P值均＜0.05)。结论 DCE-MRI定量及半定量参数在判断正常肠壁与病变段肠壁、直肠癌的术前T、N分期方面和病理有较高的相关性,对诊断有一定参考价值。定量参数K^trans值、V_e值最佳诊断界点为直肠癌T、N分期提供了较高的敏感性与特异性。     

Application of magnetic resonance imaging and magnetic resonance angiography as diagnostic measures for the first attack of suspected cerebrovascular diseases in Korea

Purpose

No precise data are available showing how magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) can be applied to diagnosis for the first attack of a suspected cerebrovascular disease in Korea. The purpose of this study was to evaluate the application level of MRI and MRA as diagnostic tools and the related factors to the use of these techniques.

Materials and Methods

This study used the health benefit claim data of 89,890 patients who were hospitalized for the first time due to suspected cerebrovascular disease in 2007 without having visited medical institutions as an outpatient or inpatient from 2003 to 2006.

Results

Of the 89,890 cases, 28.4% took both MRI and MRA, 10.7% took only MRI and 6.9% took only MRA. The related factors identified in the multivariate logistic regression analysis were gender, type of insurance, type of medical institution, type of department, duration of hospitalization, and type of disease.

Conclusion

This study showed that the application level of MRI and MRA as diagnostic measures for the first attack of a suspected cerebrovascular diseases varied depending on several factors. It is necessary to study more accurate levels of computerized tomography (CT), computerized tomography angiography (CTA), MRI or MRA as measures to diagnose a first attack of suspected cerebrovascular disease.     

Diagnostic performance of contrast-enhanced ultrasound and enhanced magnetic resonance for breast nodules

In the current study, we sought to evaluate the diagnostic efficacies of conventional ultrasound (US), contrastenhanced US (CEUS), combined US and CEUS and magnetic resonance imaging (MRI) in detecting focal solid breast lesions. Totally 117 patients with 120 BI-RADS category 4A-5 breast lesions were evaluated by conventional US and CEUS, and MRI, respectively. SonoVue was used as contrast agent in CEUS and injected as an intravenous bolus; nodule scan was performed 4 minutes after bolus injection. A specific sonographic quantification software was used to obtain color-coded maps of perfusion parameters for the investigated lesion, namely the time-intensity curve. The pattern of contrast enhancement and related indexes regarding the time-intensity curve were used to describe the lesions, comparatively with pathological results. Histopathologic examination revealed 46 benign and 74 malignant lesions. Sensitivity, specificity, and accuracy of US in detecting malignant breast lesions were 90.14%, 95.92%, and 92.52%, respectively. Meanwhile, CE-MRI showed sensitivity, specificity, and accuracy of 88.73%, 95.92%, and 91.67%, respectively. The area under the ROC curve for combined US and CEUS in discriminating benign from malignant breast lesions was 0.936, while that of MRI was 0.923, with no significant difference between them, as well as among groups. The time-intensity curve of malignant hypervascular fibroadenoma and papillary lesions mostly showed a fast-in/fast-out pattern, with no good correlation between them (kappa < 0.20). In conclusion, the combined use of conventional US and CEUS displays good agreement with MRI in differentiating benign from malignant breast lesions.     

超低对比剂剂量和流率在头颈部CT血管造影中的应用

目的:探讨双层探测器光谱CT在对比剂低耐受度患者头颈部CT血管造影（CTA）检查中应用超低对比剂剂量和流率扫描的优势。方法:收集对比剂低耐受度患者40例（观察组）,对比剂用量20 mL,流率2 mL/s,所得图像行40 keV单能谱重建;选取同期普通患者40例（对照组）,对比剂用量50 mL,流率5 mL/s;两组患者体质量均在70 kg以下。比较两组患者图像的主观评分、CT值、信号噪声比（SNR）、对比噪声比（CNR）和辐射剂量。结果:两组动脉显影图像主观评分比较差异无统计学意义（P>0.05）;在主动脉弓水平,观察组图像CT值、SNR和CNR均显著高于对照组（P<0.05）;在双侧颈总动脉分叉处及双侧大脑中动脉M1段,两组图像CT值比较差异无统计学意义（P>0.05）,但观察组图像SNR和CNR值均显著高于对照组（P<0.05）;观察组和对照组间容积CT剂量指数、剂量长度乘积、有效辐射剂量比较差异均无统计学意义（P>0.05）。结论:双层探测器光谱CT在低耐受度患者头颈CTA检查中应用超低对比剂剂量和流率的扫描方案可以满足诊断需求,降低了对比剂肾病、对比剂外渗等副作用风险,且未增加辐射剂量。     

Demineralized bone matrix-induced ectopic bone formation in rats: in vivo study with follow-up by magnetic resonance imaging, magnetic resonance angiography, and dual-energy X-ray absorptiometry

The aim of this study was to further explore the use of magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and dual-energy X-ray absorptiometry (DEXA) to assess bone formation and blood circulation in a pedicled bone graft substitute. In 14 Wistar rats, initially 10 weeks old, heterogeneous demineralized femur bone matrix implants were wrapped in pedicled adductor thigh muscle flaps. One rat died after surgery. Subsequently, bone formation and maintenance of blood vessel functionality were evaluated in six rats 6 weeks postimplantation by means of in vivo MRI/MRA and postmortem histomorphometry. The other seven rats were left for 12 weeks, whereafter bone formation was evaluated by in vivo DEXA and postmortem histomorphometry. The results demonstrated that after 6 weeks bone formation was present in four of six animals, quantified as 42 (+/-35)% and 25 (+/-19)% by means of MRI and histomorphometry, respectively. MRA was able to show patency of the pedicles of these four rats only, which suggests that the lack of blood supply in the other two rats is the cause of the failure to form bone. In the 12-week group, histology showed increased bone formation without signs of osteolysis, which was quantified histomorphometrically to be as high as 48 (+/-15)%. DEXA failed to show bone formation. It is concluded that in vivo MRI proved to be a reliable method for monitoring ectopic bone formation in a rat model, whereas in vivo DEXA was unable to detect the implants. Furthermore, in vivo MRA proved to be a useful technique for studying the circulation of muscle flaps in this animal model.     

Comparison of velocity patterns in an AComA aneurysm measured with 2D phase contrast MRI and simulated with CFD.

OBJECTIVE: Computational Fluid Dynamic (CFD) is increasingly being used for modeling hemodynamics in intracranial aneurysms. While CFD techniques are well established, need for validation of the results remains. By quantifying features in velocity patterns measured with 2D phase contrast magnetic resonance (pcMRI) in vivo and simulated with CFD, the role of pcMRI for providing reference data for the CFD simulation is explored. METHODS: Unsteady CFD simulations were performed with inflow boundary conditions obtained from 2D pcMRI measurements of an aneurysm of the anterior communication artery. Intra-aneurysmal velocity profiles were recorded with 2D pcMRI and calculated with CFD. Relative areas of positive and negative velocity were calculated in these profiles for maximum and minimum inflow. RESULTS: Areas of positive and of negative velocity similar in shape were found in the velocity profiles obtained with both methods. Relative difference in size of the relative areas for the whole cardiac cycle ranged from 1%-25% (average 12%). CONCLUSION: 2D pcMRI is able to record velocity profiles in an aneurysm of the anterior commuting artery in vivo. These velocity profiles can serve as reference data for validation of CFD simulations. Further studies are needed to explore the role of pcMRI in the context of CFD simulations.     

Combining optical coherence tomography with magnetic resonance angiography and Doppler ultrasonography for clinical detection of scleroderma

Scleroderma (SD) is a rare and agnogenic autoimmune disease whose progression can be modified by medical or surgical intervention if detected early. Multimodality imaging makes early detection of SD possible based on the structural and functional findings from different imaging methods. Combining optical coherence tomography (OCT) with magnetic resonance angiography (MRA) and Doppler ultrasonography (DUS) to identify the typical structural and functional features that can exhibit significant differences between SD patients and healthy controls. In this study, six participants (three healthy volunteers and three SD patients) were recruited and clinically examined by a rheumatologist. Participants’ fingers were scanned by MRA, DUS, and OCT, respectively. MRA and DSU imaging results showed that SD patients exhibited thicker finger skin, a loss of blood vessels, and lower blood flow, whereas OCT captured the high-resolution morphology changes of the skin, epidermal, dermis, and subcutaneous layers, demonstrating a distinct loss of the dermo-epidermal junction in SD patients. Multimodal imaging techniques offer a more comprehensive characterization of the morphological and functional information of biological tissues, which can assist physicians to achieve a more accurate SD diagnosis.     

Inversion recovery measurements in the presence of radiation damping and implications for evaluating contrast agents in magnetic resonance

Relaxation measurements performed at high magnetic field in magnetic resonance (MR) may be adversely affected by the influence of radiation damping in concentrated samples such as water. We consider how the measured value of T1 is affected by this phenomenon for a gadolinium-doped water sample and for an undoped water sample and consider the implications for evaluating contrast agents. A simple method involving the application of a pulsed field gradient to de-phase residual transverse components of the magnetization is shown to be an effective method for suppressing this effect. Given the central role that measurement of the T1 of water plays in the assessment of contrast agents as well as a host of other MR applications, care should always be employed when measuring and interpreting T1 measurements at high magnetic fields.     

Phenomenological universalities: a novel tool for the analysis of dynamic contrast enhancement in magnetic resonance imaging

Dynamic contrast enhancement in magnetic resonance imaging (DCE-MRI) is a promising tool for the clinical diagnosis of tumors, whose implementation may be improved through the use of suitable hemodynamic models. If one prefers to avoid assumptions about the tumor physiology, empirical fitting functions may be adopted. For this purpose, in this paper we discuss the exploitation of a recently proposed phenomenological universalities (PUN) formalism. In fact, we show that a novel PUN class may be used to describe the time-signal intensity curves in both healthy and tumoral tissues, discriminating between the two cases and thus potentially providing a convenient diagnostic tool. The proposed approach is applied to analysis of the DCE-MRI data relative to a study group composed of ten patients with spine tumors.     

Not only manganese,but fruit component effects dictate the efficiency of fruit juice as an oral magnetic resonance imaging contrast agent

Several fruit juices are used as oral contrast agents to improve the quality of images in magnetic resonance cholangiopancreatography. They are often preferred to conventional synthetic contrast agents because of their very low cost, natural origin, intrinsic safety, and comparable image qualities. Pineapple and blueberry juices are the most employed in clinical practice due to their higher content of manganese(II) ions. The interest of pharmaceutical companies in these products is testified by the appearance in the market of fruit juice derivatives with improved contrast efficacy. Here, we investigate the origin of the contrast of blueberry juice, analyze the parameters that can effect it, and elucidate the differences with pineapple juice and manganese(II) solutions. It appears that, although manganese(II) is the paramagnetic ion responsible for the contrast, it is the interaction of manganese(II) with other juice components that modulates the efficiency of the juice as a magnetic resonance contrast agent. On these grounds, we conclude that blueberry juice concentrated to the same manganese concentration of pineapple juice would prove a more efficient contrast agent than pineapple juice.     

幼龄兔及成年兔桡骨骨缺损模型中骨缺损大小的对比研究

目的 探讨不同月龄新西兰兔建立桡骨骨缺损模型时骨缺损大小的选择。方法 选取3月龄(幼龄兔)及6月龄(成年兔)健康雄性新西兰兔各20只,根据兔龄分为A组(3月龄)和B组(6月龄),每组兔前肢采用数字表法随机分为2亚组制备桡骨骨缺损模型,每组20侧。其中A1组、B1组桡骨骨缺损长度为15 mm,A2组、B2组骨缺损长度为20 mm。分别于模型制备术后第4、8、12周行X线检查,并应用X线Lane-Sandhu评分标准评估骨愈合情况。术后12周处死所有实验动物,取桡骨标本进行大体及组织学观察,分析骨愈合情况。结果 制备骨缺损模型术后,所有实验兔均存活。X线检查显示:术后第8周A1组骨缺损基本愈合,至第12周新生骨塑形完全,与正常桡骨形态类似;其余3组至第12周骨缺损均未完全修复,断端及邻近尺侧有少量新骨生成,髓腔封闭。术后各时间点X线Lane-Sandhu评分结果示:组内比较,A1组评分均高于A2组,差异均有统计学意义(P值均<0.05);B1组与B2组评分比较,差异均无统计学意义(P值均>0.05)。组间缺损尺寸相同的亚组间比较:A1组、A2组评分分别高于B1组、B2组,差异均有统计学意义(P值均<0.05)。术后12周标本大体观察显示:A1组断端形成骨性桥接,新生骨塑形良好,其余3组断端髓腔封闭,缺损区由纤维组织填充。组织学结果示A1组修复完全,新生骨骨板排列规则;其余3组缺损空腔可见纤维组织填充。结论 兔龄和骨缺损大小对于术后骨缺损愈合情况有重要影响,在构建兔桡骨骨缺损模型的动物实验中,幼龄兔(3月龄)骨缺损长度宜选择20 mm,成年兔(6月龄)宜选择15 mm。     

Noninvasive mapping of endothelial dysfunction in myocardial ischemia by magnetic resonance imaging using an albumin‐based contrast agent

Noninvasive preclinical methods for the characterization of myocardial vascular function are crucial to an understanding of the dynamics of ischemic cardiac disease. Ischemic heart disease is associated with myocardial endothelial dysfunction, resulting in leakage of plasma albumin into the extravascular space. These features can be harnessed in a novel noninvasive three‐dimensional magnetic resonance imaging method to measure fractional blood volume (fBV) and vascular permeability (permeability–surface area product, PS) using labeled albumin as a blood pool contrast agent. C57BL/6 mice were imaged before and 3 days after myocardial infarction (MI). Following the quantification of endogenous myocardial R₁, the dynamics of intravenously injected albumin‐based contrast agent, extravasating from permeable myocardial blood vessels, were tracked on short‐axis magnetic resonance images of the entire heart. This study successfully discriminated between infarcted and remote regions at 3 days post‐infarct, based on a reduced fBV and increased PS in the infarcted region. These findings were confirmed using ex vivo fluorescence imaging and histology. We have demonstrated a novel method to quantify blood volume and permeability in the infarcted myocardium, providing an imaging biomarker for the assessment of endothelial dysfunction. This method has the potential to three‐dimensionally visualize subtle changes in myocardial permeability and to track endothelial function for longitudinal cardiac studies determining pathophysiological processes during infarct healing.     

Changes in systemic and pulmonary blood flow distribution in normal adult volunteers in response to posture and exercise: a phase contrast magnetic resonance imaging study

Hemodynamics are usually evaluated in the supine position at rest. This is only a snapshot of an individual’s daily activities. This study describes circulatory adaptation, as assessed by magnetic resonance imaging, to changes in position and exercise. Phase contrast magnetic resonance imaging of blood flow within systemic and pulmonary arteries and veins was performed in 24 healthy volunteers at rest in the prone and supine position and with bicycle exercise in the supine position. No change was seen in systemic blood flow when moving from prone to supine. Exercise resulted in an increased percentage of cardiac output towards the lower body. Changes in position resulted in a redistribution of blood flow within the left lung—supine positioning resulted in decreased blood flow to the left lower pulmonary vein. With exercise, both the right and left lower lobes received increased blood flow, while the upper lobes received less.