Single-shot ADC imaging for fMRI.

It has been suggested that apparent diffusion coefficient (ADC) contrast can be sensitive to cerebral blood flow (CBF) changes during brain activation. However, current ADC imaging techniques have an inherently low temporal resolution due to the requirement of multiple acquisitions with different b-factors, as well as potential confounds from cross talk between the deoxyhemoglobin-induced background gradients and the externally applied diffusion-weighting gradients. In this report a new method is proposed and implemented that addresses these two limitations. Specifically, a single-shot pulse sequence that sequentially acquires one gradient-echo (GRE) and two diffusion-weighted spin-echo (SE) images was developed. In addition, the diffusion-weighting gradient waveform was numerically optimized to null the cross terms with the deoxyhemoglobin-induced background gradients to fully isolate the effect of diffusion weighting from that of oxygenation-level changes. The experimental results show that this new single-shot method can acquire ADC maps with sufficient signal-to-noise ratio (SNR), and establish its practical utility in functional MRI (fMRI) to complement the blood oxygenation level-dependent (BOLD) technique and provide differential sensitivity for different vasculatures to better localize neural activity originating from the small vessels.     

一种双道生物信号数据采集系统的设计

为了能够同时得到两个不同的生物信号，作者设计了一种双通道的生物信号数据采集系统，本文介绍了该系统的构成、性能特点和各部分的设计原理。     

多b值磁共振扩散加权成像在前列腺良、恶性结节中的对比研究

目的：通过对前列腺结节多b值的定量分析研究,探讨评价DWI对前列腺良、恶性结节的临床应用价值。方法回顾性分析经手术及病理证实的36例前列腺结节的常规MRI及DWI征象,分别测量在多b值条件下良、恶性结节的表观扩散系数（ADC）,并讨论不同b值的应用价值。结果本组36例患者中,良性结节25例,恶性结节11例。采用b值（200、400、600、800、1000s/mm2）时良性组与恶性组之间ADC值的差异均有统计学意义（P<0.05）。结论前列腺良性结节的ADC值高于恶性结节,在多b值的扩散加权成像中,尤其以b值取800 s/mm2时,鉴别良、恶性结节的效能最高,有助于前列腺结节性质的判断和鉴别,对其术前诊断分期、术后治疗方案的设计制定,都有着十分重要的指导意义。     

正常成人骶髂关节ADC值测量研究

目的:探讨健康成人骶髂关节的DWI特征,测量b值=500s/mm2时骶髂关节ADC值范围,为进一步研究DWI在骶髂关节病变中的应用提供依据。方法:应用Siemens Avanto 1.5T MRI扫描仪对100例随机选取的健康成人志愿者共200个骶髂关节行常规序列及DWI序列扫描。分别测量双侧骶骨面、髂骨面ROI的ADC值,比较同一b值不同部位ADC值的差异。按年龄分为3组(≤30岁;31~50岁;≥51岁),比较不同年龄组骶骨及髂骨ADC值的差异。结果:在b值=500s/mm2时,髂骨和骶骨的ADC值分别为(311.95±55.32)mm2/s、(362.64±72.16)mm2/s;成像条件相同时,骶骨的ADC值大于髂骨的ADC值,差异有统计学意义。不同年龄组骶骨、髂骨ADC值比较,差异有统计学意义。结论:本研究得到了1.5T MRI正常人骶髂关节的ADC值范围,为DWI在骶髂关节相关疾病的研究提供了一定的参考价值。     

磁共振扩散加权成像在不同类型正常乳腺组织中的应用

目的：探讨不同类型正常乳腺组织与其表现扩散系数值(ADC)是否存在相关性。方法选取2008年1月至2013年12月在我院同时行乳腺X线摄影及乳腺MRI检查的78例女性患者,根据美国放射学会制定的乳腺影像报告和数据系统将乳腺分为四型：致密型(9例),多腺体型(27例),少腺体型(26例),脂肪型(16例)。乳腺X线摄片体位为头尾位及内侧斜位片,MRI检查行平扫、动态增强扫描及MR扩散加权成像(DWI)序列,扩散敏感因子b=800/mm2。分别测量各组乳腺的ADC值并做统计。结果各组ADC均值中致密型(1.5±0.0006)×10-3 mm2/s ,多腺体型(1.7±0.0005)×10-3 mm2/s ,少腺体型(1.7±0.0004)×10-3 mm2/s ,脂肪型(1.1±0.0005)×10-3 mm2/s,经单因素方差分析,其差异具有统计学意义(F=6.317,P<0.01);其中致密型与多腺体型间,致密型与少腺体型间,致密型与脂肪型间,以及多腺体与少腺体型间分别两两比较差异均无统计学意义(P>0.05),而多腺体与脂肪型间和少腺体型与脂肪型间两两比较,差异均有统计学意义(P<0.01)。结论不同类型正常乳腺与其组织的ADC值有一定的相关性。     

Whole body MRI: Improved lesion detection and characterization with diffusion weighted techniques

Diffusion‐weighted imaging (DWI) is an established functional imaging technique that interrogates the delicate balance of water movement at the cellular level. Technological advances enable this technique to be applied to whole‐body MRI. Theory, b‐value selection, common artifacts and target to background for optimized viewing will be reviewed for applications in the neck, chest, abdomen, and pelvis. Whole‐body imaging with DWI allows novel applications of MRI to aid in evaluation of conditions such as multiple myeloma, lymphoma, and skeletal metastases, while the quantitative nature of this technique permits evaluation of response to therapy. Persisting signal at high b‐values from restricted hypercellular tissue and viscous fluid also permits applications of DWI beyond oncologic imaging. DWI, when used in conjunction with routine imaging, can assist in detecting hemorrhagic degradation products, infection/abscess, and inflammation in colitis, while aiding with discrimination of free fluid and empyema, while limiting the need for intravenous contrast. DWI in conjunction with routine anatomic images provides a platform to improve lesion detection and characterization with findings rivaling other combined anatomic and functional imaging techniques, with the added benefit of no ionizing radiation. J. Magn. Reson. Imaging 2013;38:253–268. © 2013 Wiley Periodicals, Inc.     

Epidermoid cyst in intrapancreatic accessory spleen: A systematic review

Background/Objectives

Due to its rarity, epidermoid cyst in intrapancreatic accessory spleen (ECIPAS) is still a diagnostic dilemma during clinical practice. The aim of this review was to summarize the epidemiologic features and management of ECIPAS.

Evaluation and evolution of apparent diffusion coefficient (ADC) in image-guided adaptive brachytherapy (IGABT) for cervical cancer

PURPOSEImage-guided adaptive brachytherapy (IGABT) recently has shown excellent clinical outcomes with superior local control and less toxicity. For IGABT, T2W (T2-weighted) MRI is the gold standard. However, studies have shown that target delineation with the same results in uncertainties, poor interobserver variabilities, and low conformity indices for high-risk clinical target volume contours. In this study, we investigate the role of diffusion-weighted imaging–derived apparent diffusion coefficient (ADC) maps to aid in IGABT. We also evaluated ADC from the baseline to brachytherapy.Methods and MaterialsThirty selected patients were enrolled for this study, and two MRIs were taken at diagnosis and before brachytherapy. Patients were divided into two groups, Group 1 being patients with parametrial involvement before external beam radiotherapy and no parametrial involvement before brachytherapy. Group 2 included patients with parametrial involvement before external beam radiotherapy and persistent parametrial involvement before brachytherapy. ADC was measured at the center, edge, and 1 cm from the edge.ResultsThe measured ADC increased from diagnosis to brachytherapy, and this increase was more for the patients in Group 1 than in Group 2. The mean TDadc (diagnosis ADC, center), TEadc (tumor edge ADC diagnosis), and T1cmDadc (1 cm from edge at diagnosis) were 0.884, 1.45, and 1.9 × 10^?3 mm²/s, respectively. The TBadc (ADC at brachytherapy, center), TEBadc (tumor edge ADC at brachytherapy), and TE1cmBadc (1 cm from edge brachytherapy) were 1.2, 1.8, and 2.3 × 10^?3 mm²/s, respectively, p-value <0.00001. No abnormal ADC was present outside the high-risk clinical target volume contours.ConclusionMRI-based IGABT using T2W imaging essentially covers all functionally abnormal zones at brachytherapy. Diffusion-weighted imaging, along with ADC maps, should only be used as a supplement for target delineation.     

Analysis of ischemic cerebral lesions using 3.0-T diffusion-weighted imaging and magnetic resonance angiography after revascularization surgery for ischemic disease

Background

Cerebral revascularization surgery (CRS) is increasingly recognized as an important component in the treatment of complex cerebral vascular disease and tumors. CRS requires that the incidence of perioperative neurological complications should be minimized, because CRS for ischemic disease is often not the goal of treatment, but rather a prophylactic surgery. CRS carries the risk of focal postoperative neurological deficits. Little has been established concerning mechanisms of post-CRS ischemia. We used 3.0-T diffusion-weighted magnetic resonance imaging (DWI) and magnetic resonance angiography (MRA) to analyze the incidence and mechanism of ischemic lesions.

Methods

We studied the anterior circulation territory after 20 CRS procedures involving 33 vascular anastomosis procedures (13 double anastomoses and 7 single anastomoses) in 12 men and 8 women between June 2007 and October 2011. The operations included single or double superficial temporal artery–middle cerebral artery (STA–MCA) anastomosis to treat internal carotid artery/MCA occlusions or severe MCA stenosis. A combined STA–MCA anastomosis and indirect bypass were performed for moyamoya disease. Postoperative DWI and MRA were obtained in all patients between 24 and 96 h after surgery to detect thromboembolism, hypoperfusion, or procedural ischemic complications and vasospasms of the donor STA.

Results

Follow-up DWI and MRA were carried out 1.8 ± 0.6 days after CRS (range, 1–4 days). Temporary occlusion time for anastomoses averaged 18.9 min (range, 16–32 min). Asymptomatic new hyperintensities occurred in the ipsilateral hemisphere of 2 patients on postoperative DWI (10% patients/6.0% anastomoses), and 1 moyamoya patient (5.0% patients/3.0% anastomoses) developed a symptomatic hyperintensity in the ipsilateral occipital lobe in response to the operation. Two abnormal small (<5 mm) cortical DWI lesions were caused by sacrifices of a small branch of the recipient MCA.

Conclusion

This study is the first postoperative 3.0-T DWI study of CRS and related clinical events. The incidence of symptomatic postoperative DWI abnormalities was restricted to 1 moyamoya patient representing 5.0% of total patients and 3.0% anastomoses. Although some postoperative DWI abnormalities occurred, CRS was found to be safe with a low risk of symptomatic ischemia.