MRI and conservative treatment of locally advanced breast cancer

AIMS: The objectives of this study were to compare the efficacy of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in assessing the response of primary breast carcinoma to neoadjuvant chemotherapy compared to conventional imaging modalities, and to see how surgical outcome was influenced as a result of these findings. METHODS: Thirty-four patients with locally advanced primary breast cancer underwent conventional imaging and DCE-MRI following six cycles of neoadjuvant chemotherapy prior to surgery. Changes in surgical management based on the post-chemotherapy DCE-MRI findings were recorded. RESULTS: Prior to neoadjuvant chemotherapy, 22 of the 34 patients were assessed as requiring mastectomy and the remaining 12 were considered inoperable. Following chemotherapy two patients were still considered inoperable. In 11 of the 34 patients, the final decision to proceed to either mastectomy or non-surgical management was based primarily on pre-treatment disease status or patient choice. DCE-MRI findings, therefore, contributed to the operative decision in 21 of 34 patients. Two of these 21 patients were spared surgery as DCE-MRI demonstrated complete response to chemotherapy and one declined surgery. The remaining 18 were able to undergo wide local excision, with only two patients subsequently requiring mastectomy for involved margins. CONCLUSIONS: DCE-MRI is able to accurately predict those patients suitable for breast conserving surgery following neoadjuvant chemotherapy and should be the imaging modality of choice in assessing the response of patients with primary breast carcinoma to neoadjuvant chemotherapy.     

Imaging update on soft tissue sarcoma

Soft tissue sarcomas (STS) are rare tumours presenting as soft tissue lumps. Ultrasound is often the primary modality for the initial assessment, with MRI the mainstay for lesion characterisation. PET/CT along with other emerging MRI sequences are used in certain situations as an adjunct and problem solving tool in STS staging and assessment of disease recurrence. Recent advances include the promise of whole body MRI, hybrid PET/MRI, diffusion weighted imaging, dynamic contrast enhanced MRI and advances in artificial intelligence. This article discusses current concepts in extremity STS imaging and highlights recent advances.     

Perfusion and vascular permeability: Basic concepts and measurement in DCE-CT and DCE-MRI

The microvascular network formed by the capillaries supplies the tissues and permits their function. It provides a considerable surface area for exchanges between blood and tissues. All pathological conditions cause changes in the microcirculation. These changes can be used as imaging biomarkers for the diagnosis of lesions and optimisation of treatment. Among the many imaging techniques developed to study the microcirculation, the analysis of the tissue kinetics of intravenously injected contrast agents is the most widely used, either as positive enhancement for CT, T1-weighted MRI and ultrasound – dynamic contrast-enhanced-imaging (DCE-imaging) – or negative enhancement in T2*-weighted brain MRI – dynamic susceptibility contrast-MRI (DSC-MRI) –. Acquisition involves an injection of contrast agent during the acquisition of a dynamic series of images on a zone of interest. These kinetics may be analyzed visually, to define qualitative criteria, or with software using mathematical modelling, to extract quantitative physiological parameters. The results depend on the acquisition conditions (type of imaging device, imaging mode, frequency and total duration of acquisition), the type of contrast agent, the data pre-processing (motion correction, conversion of the signal into concentration) and the data analysis method. Because of these multiple choices it is necessary to understand the physiological processes involved and understand the advantages and limits of each strategy.     

Normalized gradient fields for nonlinear motion correction of DCE-MRI time series

Dynamic MR image recordings (DCE-MRI) of moving organs using bolus injections create two different types of dynamics in the images: (i) spatial motion artifacts due to patient movements, breathing and physiological pulsations that we want to counteract and (ii) signal intensity changes during contrast agent wash-in and wash-out that we want to preserve. Proper image registration is needed to counteract the motion artifacts and for a reliable assessment of physiological parameters. In this work we present a partial differential equation-based method for deformable multimodal image registration using normalized gradients and the Fourier transform to solve the Euler–Lagrange equations in a multilevel hierarchy. This approach is particularly well suited to handle the motion challenges in DCE-MRI time series, being validated on ten DCE-MRI datasets from the moving kidney. We found that both normalized gradients and mutual information work as high-performing cost functionals for motion correction of this type of data. Furthermore, we demonstrated that normalized gradients have improved performance compared to mutual information as assessed by several performance measures. We conclude that normalized gradients can be a viable alternative to mutual information regarding registration accuracy, and with promising clinical applications to DCE-MRI recordings from moving organs.     

Dynamic contrast enhanced MRI of the placenta: A tool for prenatal diagnosis of placenta accreta?

BackgroundUltrasound (US) is the primary imaging modality for the diagnosis of placenta accreta, but it is not sufficiently accurate. MRI morphologic criteria have recently emerged as a useful tool in this setting, but their analysis is too subjective. Recent studies suggest that gadolinium enhancement may help to distinguish between the stretched myometrium and placenta within a scar area. However, objective MRI criteria are still required for prenatal diagnosis of placenta accreta. The purpose of this study was to assess the diagnostic value of dynamic contrast gadolinium enhancement (DCE) MRI patterns for placenta accreta.Materials and methodsMR images were acquired with a 1.5-T unit at 30–35 weeks of gestation in women with a history of Caesarian section, a low-lying anterior placenta, and US features compatible with placenta accreta. Sagittal, axial and coronal SSFP (Steady State Free Precession) sequences were acquired before injection. Then, contrast-enhanced dynamic T1-weighted images were acquired through the entire cross-sectional area of the placenta. Images were obtained sequentially at 10- to 14-s intervals for 2 min, beginning simultaneously with the bolus injection. Functional analysis was performed retrospectively, and tissular relative enhancement parameters were extracted from the recorded images. The suspected area of accreta (SAA) was placed in the region of the previous scar, and a control area (CA) of similar size was placed on the same image plane, as far as possible from the SAA. Semi-quantitative analysis of DCE-MR images was based on the kinetic enhancement curves in these two regions of interest (ROI). Three tissular relative enhancement parameters were compared according to the pregnancy outcomes, namely time to peak, maximal signal intensity, and area under the enhancement curve.ResultsWe studied 9 women (43%) with accreta and 12 women (57%) with a normal placenta. All three tissular relative enhancement parameters differed significantly between the two groups (p < 10⁻³).ConclusionThe use of dynamic contrast-enhanced MRI at 30–35 weeks of gestation in women with a high risk of placenta accreta allows the extraction of tissular enhancement parameters that differ significantly between placenta accreta and normal placenta. It therefore provides objective parameters on which to base the diagnosis and patient management.     

Influence of metabolic syndrome on post-stroke outcome,angiogenesis and vascular function in old rats determined by dynamic contrast enhanced MRI

Stroke affects primarily aged and co-morbid people, aspects not properly considered to date. Since angiogenesis/vasculogenesis are key processes for stroke recovery, we purposed to determine how different co-morbidities affect the outcome and angiogenesis/vasculogenesis, using a rodent model of metabolic syndrome, and by dynamic enhanced-contrast imaging (DCE-MRI) to assess its non-invasive potential to determine these processes. Twenty/twenty-two month-old corpulent (JCR:LA-Cp/Cp), a model of metabolic syndrome and lean rats were used. After inducing the experimental ischemia by transient MCAO, angiogenesis was analyzed by histology, vasculogenesis by determination of endothelial progenitor cells in peripheral blood by flow cytometry and evaluating their pro-angiogenic properties in culture and the vascular function by DCE-MRI at 3, 7 and 28 days after tMCAO. Our results show an increased infarct volume, BBB damage and an impaired outcome in corpulent rats compared with their lean counterparts. Corpulent rats also displayed worse post-stroke angiogenesis/vasculogenesis, outcome that translated in an impaired vascular function determined by DCE-MRI. These data confirm that outcome and angiogenesis/vasculogenesis induced by stroke in old rats are negatively affected by the co-morbidities present in the corpulent genotype and also that DCE-MRI might be a technique useful for the non-invasive evaluation of vascular function and angiogenesis processes.     

动态对比增强磁共振与扩散加权成像对脑胶质瘤分级诊断的比较研究

目的比较动态对比增强磁共振（DCE-MRI）渗透性参数Ktrans值、ve值及扩散加权成像（DWI）的ADC值对脑胶质瘤分级的诊断价值。方法回顾性分析经病理证实的16例高级别脑胶质瘤（HGG）和12例低级别脑胶质瘤（LGG）患者的磁共振资料,所用序列包括常规平扫、DWI和动态对比增强扫描LAVA序列,分别测量肿瘤感兴趣区域（ROI）DCE-MRI的渗透性参数Ktrans值、ve值和DWI的tADC值、rADC值。t检验比较HGG和LGG两组间参数的统计学差异。采用ROC曲线分析Ktrans值、Ve值、tADC值、rADC值的最佳阈值及其敏感度、特异度和AUC。结果HGGKtrans值、ve值均高于LGG,差异均有统计学意义（均P＜0.01）;而HGGtADC值、rADC值均明显低于LGG,差异均有统计学意义（均P＜0.01）。ve值诊断HGG的AUC最大为0.906,取ve值最佳阈值0.142,对诊断HGG的敏感度和特异度分别为87.5%和91.7%。结论DCE-MRI渗透性参数及DWI的ADC值均有助于高级别和低级别脑胶质瘤的分级诊断,但ve值的价值更高。     

Kinetic Modeling of Contrast-Enhanced MRI: An Automated Technique for Assessing Inflammation in the Rheumatoid Arthritis Wrist

In recent years, development of rheumatoid arthritis (RA) drug therapy has been more directly targeted to counteract specific mechanisms of inflammation, and it is now believed that early aggressive treatment with disease modifying drugs is important to inhibit future structural joint damage. The development of these new treatments has increased the need for methodologies to assess disease activity in RA and monitor the effectiveness of drug therapy. Unlike X-ray, which shows only structural bone damage, magnetic resonance imaging (MRI) can depict soft tissue damage and synovitis, the primary pathology of RA. Recent studies have also indicated that MRI is sensitive to pathophysiologic changes that may predate radiographic erosions and may predict future joint damage. In this study, we have developed a computer automated analysis technique for MR wrist images that provides an objective measure of RA synovitis. This method applies a two-compartment pharmacokinetic model to every voxel of a dynamic contrast-enhanced MRI (DCE-MRI) dataset and outputs resulting parametric images. The aim of this technique is to not only objectively quantify the severity of rheumatoid synovitis, but to also locally determine where areas of serious disease activity are situated through kinetic modeling of blood-tissue exchange. Preliminary results show good correlation to early enhancement rate, which has previously been shown to be a useful clinical marker of RA activity. However, the use of tracer kinetic modeling methods potentially provides more specific information regarding underlying RA physiology. This approach could provide a useful new tool in RA patient management and could substantially improve RA therapeutic studies by calculating objective biomarkers of the disease state.     

T2 VISTA联合DWI及DCE-MRI在直肠癌术前局部分期中的临床价值

目的:探讨T2 VISTA联合扩散加权成像(DWI)及动态增强扫描(DCE-MRI)对直肠癌术前局部分期(TN分期)的临床价值。方法:回顾性分析经术后病理证实为直肠癌患者30例的常规序列扫描、T2 VISTA、DWI及DCE-MRI扫描,比较浸润情况的影像学分期与术后病理组织学分期。结果:T2 VISTA结合DWI及DCEMRI较常规序列能更好地显示肠壁的各层解剖结构,能更准确地评估肿瘤对肠壁及其邻近结构的侵犯范围、程度及直肠系膜筋膜内淋巴结转移情况。结论:T2 VISTA结合DWI及DCE-MRI较常规序列能对直肠癌TN分期做更准确的诊断。     

DCE-MRI定量参数在卵巢癌分期诊断及预后评估中的应用研究

目的探究DCE-MRI定量参数在卵巢癌分期诊断及预后评估中的应用研究。方法选择卵巢癌患者61例作为观察组,并同期选择体检的健康女性50例作为对照组,比较两组的DCE-MRI定量参数(速率常数Kep、容量转移常数Ktrans及血管外细胞外间隙容积Ve)及表观扩散系数(ADC),并比较观察组的不同临床分期患者的DCE-MRI定量参数及ADC。随访3年,比较存活组及死亡组卵巢癌患者的DCE-MRI定量参数。结果观察组的Ktrans、Kep、Ve、ADC值水平均高于对照组,差异有统计学意义(P<0.05);不同临床分期卵巢癌患者的Ktrans、Kep、Ve、ADC值水平比较,差异有统计学意义(P<0.05);Ktrans、Kep、Ve水平与卵巢癌分期呈正相关(P<0.05),ADC值水平与卵巢癌分期呈负相关(P<0.05);存活组的Ktrans、Kep、Ve水平均低于死亡组(P<0.05)。结论 DCE-MRI定量参数能够有助临床判断卵巢癌分期,并了解肿瘤微血管状态,从而判断预后。