Diffusion weighted whole body imaging with background body signal suppression (DWIBS): technical improvement using free breathing, STIR and high resolution 3D display

PURPOSE: To examine a new way of body diffusion weighted imaging (DWI) using the short TI inversion recovery-echo planar imaging (STIR-EPI) sequence and free breathing scanning (diffusion weighted whole body imaging with background body signal suppression; DWIBS) to obtain three-dimensional displays. MATERIALS AND METHODS: 1) Apparent contrast-to-noise ratios (AppCNR) between lymph nodes and surrounding fat tissue were compared in three types of DWI with and without breath-holding, with variable lengths of scan time and slice thickness. 2) The STIR-EPI sequence and spin echo-echo planar imaging (SE-EPI) sequence with chemical shift selective (CHESS) pulse were compared in terms of their degree of fat suppression. 3) Eleven patients with neck, chest, and abdominal malignancy were scanned with DWIBS for evaluation of feasibility. Whole body imaging was done in a later stage of the study using the peripheral vascular coil. RESULTS: The AppCNR of 8 mm slice thickness images reconstructed from 4 mm slice thickness source images obtained in a free breathing scan of 430 sec were much better than 9 mm slice thickness breath-hold scans obtained in 25 sec. High resolution multi-planar reformat (MPR) and maximum intensity projection (MIP) images could be made from the data set of 4 mm slice thickness images. Fat suppression was much better in the STIR-EPI sequence than SE-EPI with CHESS pulse. The feasibility of DWIBS was showed in clinical scans of 11 patients. Whole body images were successfully obtained with adequate fat suppression. CONCLUSION: Three-dimensional DWIBS can be obtained with this technique, which may allow us to screen for malignancies in the whole body.     

MR背景抑制扩散加权成像在乳腺癌的应用

目的 探讨MR扩散加权成像(DWI)结合短时间反转恢复回波成像(STIR-EPI)背景抑制(BS)技术在乳腺癌成像的技术参数及其可行性.方法 回顾性分析26例乳腺癌的MR DWIBS测得各组织的表观扩散系数(ADC),利用三维最大强度投影(3D-MIP)重组及黑白反转技术,观察病变显示效果.观察乳腺痛DWI及DWIBS两种方法的显示率.对乳腺各组织的ADC值进行随机区组设计的方差分析,在乳腺癌与良性病变ADC值的比较中,采用t检验.对两种成像方法乳腺癌的显示率进行配对资料X2检验.结果 在扩散敏感因子(b)=800 mm2/s的图像中,乳腺癌多表现为高信号,其ADC值分别为:肿瘤实质(0.93±0.25)×10-3 mm2/s、瘤内坏死灶(2.06±0.17)×10-3 mm2/s、正常腺体(1.92±0.23)×10-3 mm2/s、转移性淋巴结(1.10 ± 0.14)×10-3mm2/s,各种组织间两两比较,差异具有统计学意义(P值均＜0.01).DWIBS经MIP重组及黑白反转技术,病变周围组织信号被抑制,得到类正电子发射体层成像(PET)图像.在乳腺癌中,DWIBS对肿瘤实质(92.3/)及转移性淋巴结(88.4/)的显示率要高于DWI序列(分别为57.6/和42.3/),差异有统计学意义(x2值分别为8.307、12.235,P均＜0.05).乳腺癌与良性病变ADC值分别为(1.092±0·17)×10-3和(2.154±0.53)×10-3mm2/s,差异有统计学意义(t=8.626,P＜0.05).结论 MRDWIBS在显示病灶方面有一定优势,应用DWI结合ADC值对乳腺癌的诊断具有临床应用前景.     

肺部疾病背景抑制磁共振扩散成像的参数优化

目的：通过比较不同扫描参数的图像质量，探讨肺部疾病背景抑制磁共振扩散成像（DWIBS）的最佳扫描技术。材料和方法：20例患者接受了DWIBS成像，通过ADC值、质量指数、sNR及APPCNR来评价不同扫描技术：屏气扫描和自由呼吸扫描；不同b值的选择，分别采用0、250s／mm^2、500s／mm^2、800s／mm^2进行扫描；SE—EPISPIR与STIR—EPI的比较；采用4mm及9mm层厚观察薄层DWI的可行性。最后评价高分辨率MPR及MIP图像的可行性。结果：自由呼吸扫描的质量指数、SNR及AppCNR高于屏气扫描（P〈0．01）；图像质量指数及AppCNR以b=500s／mm^2最高（P=0．000）；STIR—EPI质量指数较高（P〈0．05）；STIR的A矿pCNR优于SPIR（P〈0．05）。自由呼吸4mm的质量指数优于自由呼吸9mm质量指数（P〈0．05），SNR与AppCNR无明显统计学差别（P〉0．05）。TR值6000ms、8000ms的APPCNR高于TR值4000ms（P〈0．05），图像质量指数与SNR以及病灶的ADC值变化均很小（P〉0．05）。结论：采用自由呼吸，b：500s／mm^2，层厚4mm，STIR脂肪抑制技术以及TR值6000ms以上可以获得高质量的DWIBS图像。     

肺部疾病MR背景抑制扩散成像应用初探

目的 初步评价MR背景抑制扩散成像(DWIBS)最大密度投影(MIP)图像及表观扩散系数(ADC)值的定量测量在肺部疾病中的应用价值.方法 61例患者接受了肺部DWIBS,其中肺癌38例,肺部炎性病变23例,分析肺部疾病三维(3D)MIP重组图像表现,确定肺部病变的ADC值范围,评价DWIBS对肺部疾病的诊断价值.结果 DWIBS上肺癌及炎性病变表现为不同形态的信号强度密集区域.DWIBS上中央型肺癌平均ADC值为(1.05±0.23)×10-3 mm2/s,周围型肺癌平均ADC值为(1.10±0.17)×10-3 mm2/s,各种炎性病变平均ADC值为(1.69±0.29)×10-3 mm2/s,周围型肺癌与炎性病变的平均ADC值差异有统计学意义(P＜0.05).3.0 T MRI+DWIBS对肺部疾病诊断的敏感性、特异性及准确性(分别为86.84%、82.60%和85.24%)高于单纯MRI诊断(分别为78.94%、78.26%和78.68%).结论 DWIBS能够立体、直观地显示病灶,实现了肺部病变ADC值的定量测量,有望成为肺部疾病鉴别诊断的方法之一.     

扩散加权成像在卵巢肿瘤中的应用

扩散加权成像(DWI)是目前唯一能够检测生物组织内水分子扩散运动的无创方法 ,该种扩散运动可以通过表观扩散系数(ADC)来量化分析。扩散峰度成像(DKI)、体素内不相干运动(IVIM)成像、背景抑制扩散加权全身成像(DWIBS)等DWI新技术用于卵巢肿瘤的评估提高了卵巢肿瘤影像诊断的准确性。综述DWI及其新技术在卵巢肿瘤定性诊断、分期、疗效评估、预后判断中的作用及其潜在缺陷。     

MR背景信号抑制弥散加权成像对肠道肿瘤的诊断价值

目的 评价MR背景信号抑制弥散加权成像(DWIBS)对肠道肿瘤及肿瘤转移的诊断价值.方法 15例肠道肿瘤均行常规MRI扫描及MR背景信号抑制扩散加权成像(DWIBS),4例行CT扫描.结果 15例肠道肿瘤在常规MRI及DWIBS像上均显示了原发肿瘤,DWIBS显示4例肿瘤侵犯浆膜层,5例腹腔种植转移,5例淋巴结转移;MRI显示10例肿瘤侵犯浆膜层,8例脂肪侵犯,3例腹腔种植转移,3例淋巴结转移.结论 DWIBS对原发肿瘤、腹膜种植转移、淋巴结转移的显示方面优于常规MRI及CT,对浆膜及周围脂肪侵犯显示方面较常规MRI及CT差.     

Inherent correction of motion-induced phase errors in multishot spiral diffusion-weighted imaging

Multishot spiral imaging is a promising alternative to echo‐planar imaging for high‐resolution diffusion‐weighted imaging and diffusion tensor imaging. However, subject motion in the presence of diffusion‐weighting gradients causes phase inconsistencies among different shots, resulting in signal loss and aliasing artifacts in the reconstructed images. Such artifacts can be reduced using a variable‐density spiral trajectory or a navigator echo, however at the cost of a longer scan time. Here, a novel iterative phase correction method is proposed to inherently correct for the motion‐induced phase errors without requiring any additional scan time. In this initial study, numerical simulations and in vivo experiments are performed to demonstrate that the proposed method can effectively and efficiently correct for spatially linear phase errors caused by rigid‐body motion in multishot spiral diffusion‐weighted imaging of the human brain. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Endometrial cancer: Utility of diffusion‐weighted magnetic resonance imaging with background body signal suppression at 3T

Purpose:

To prospectively assess the usefulness of diffusion‐weighted magnetic resonance imaging (MRI) with background body signal suppression (DWIBS) at 3T for the preoperative evaluation of endometrial cancer.

Materials and Methods:

Fifty‐two consecutive patients with biopsy‐proven endometrial cancer were examined with a 3T MR scanner, followed by a hysterectomy. MR examinations included T2‐weighted (T2WI), DWIBS, and dynamic contrast‐enhanced T1‐weighted imaging (DCEI). The apparent diffusion coefficient (ADC) was calculated in the tumor and normal myometrium. According to tumor grade, the mean ADC of the tumor was analyzed. The depth of myometrial invasion was independently assessed by two radiologists for three MRI datasets on a five‐point scale.

Results:

The mean ADC of the tumors was significantly lower than that of normal myometrium (P < 0.001). The mean ADC of grades 2 or 3 was significantly lower than grade 1 (P < 0.01). For predicting myometrial invasion, the specificity, accuracy, and area under the curve of combined T2WI and DWIBS in both readers were similar to DCEI (P > 0.05). Interreader agreement in all MRI datasets was excellent.

Conclusion:

DWIBS at 3T has potential for being an effective method for the preoperative evaluation of endometrial cancer. J. Magn. Reson. Imaging 2013;37:1151–1159. © 2012 Wiley Periodicals, Inc.     

MR背景信号抑制弥散加权成像对宫颈癌的诊断与分期价值研究

目的:评价MR背景信号抑制弥散加权成像(DWIBS)对宫颈癌的诊断与分期价值。方法:收集病理诊断为宫颈癌的患者17例,常规MRI检查后,行DWIBS成像,并对DWIBS原始图像进行薄层及厚层最大密度(MIP)多平面重建。结果:DWIBS像上15例显示肿瘤,肿瘤在类PET像上较周围正常结构呈明显低(黑)信号,常规MRI有13例显示肿瘤;7例DWIBS显示肿瘤的周围侵犯或阴道受侵,4例显示盆腔淋巴结转移。结论:DWIBS成像较常规MRI更容易显示宫颈癌及其周围侵犯和盆腔淋巴结转移。     

Diffusion-weighted whole-body MRI with background body signal suppression: technical improvements at 3.0 T

Purpose:

To improve image quality of diffusion‐weighted body magnetic resonance imaging (MRI) with background body signal suppression (DWIBS) at 3.0 T.

Materials and Methods:

In 30 patients and eight volunteers, a diffusion‐weighted spin‐echo echo‐planar imaging sequence with short TI inversion recovery (STIR) fat suppression was applied and repeated using slice‐selective gradient reversal (SSGR) and/or dual‐source parallel radiofrequency (RF) transmission (TX). The quality of diffusion‐weighted images and gray scale inverted maximum intensity projections (MIP) were visually assessed by intraindividual comparison with respect to the level of fat suppression and signal homogeneity. Moreover, the contrast between lesions/lymph nodes and background (C_lb) was analyzed in the MIP reconstructions.

Results:

By combining STIR with SSGR, fat suppression was significantly improved (P < 0.001) and C_lb was increased two times. The use of TX allowed the reduction of acquisition time and improved image quality with regard to signal homogeneity (P < 0.001) and fat suppression (P = 0.005).

Conclusion:

DWIBS at 3.0 T can be improved by using SSGR and TX. J. Magn. Reson. Imaging 2012;456‐461. © 2011 Wiley Periodicals, Inc.     

磁共振背景抑制弥散成像在肿瘤诊断中的价值

磁共振背景抑制弥散成像(DWIBS)技术已广泛应用于肿瘤筛查、良恶性肿块的初步鉴别以及评估肿瘤的治疗效果.目前国内外有许多关于DWIBS的研究,普遍认为DWIBS在评估恶性肿瘤及其转移方面有一定的价值,但亦存在一定的不足.该文综述了DWIBS在肿瘤诊断中的研究现状、应用前景及不足之处.     

背景抑制扩散加权成像(DWIBS)在宫颈癌诊断与分期中的价值

目的：探讨背景抑制扩散加权成像（DWIBS）在宫颈癌术前诊断与分期中的价值。方法：39例宫颈癌患者术前行常规MRI与背景抑制扩散加权成像（DWIBS）检查,所得图像经最大强度投影（MIP）重建,并反相显示。结果：宫颈癌、宫颈周围浸润灶及盆腔转移灶呈明显高信号。MRI常规序列检出宫颈癌38例,DWIBS检出39例;MRI常规序列检出24枚盆腔转移性淋巴结,DWIBS检出32枚。MRI常规序列宫颈癌分期符合率87.2%（34/39例）,MRI常规序列结合DWIBS符合率97.4%（38/39例）。结论：背景抑制扩散加权成像（DWIBS）能直观、敏感地显示宫颈癌及其转移灶,结合MRI常规序列有利于肿瘤分期,应作为宫颈癌重要辅助检查序列。     

Automated monitoring of diaphragm end-expiratory position for real-time navigator echo MR coronary angiography

Real-time navigator echo (NE)-gated magnetic resonance coronary angiography (MRCA) during free respiration is now possible. However, the mean diaphragm end-expiratory position (DEEP) drifts over time, and this results in a reduction in scanning efficiency and increased artifacts due to the acquisition of data during periods of high diaphragm velocity. To address these problems, a diaphragm monitoring program that follows the mean DEEP over time has been developed. Fifteen subjects with ischemic heart disease underwent continuous NE monitoring of their diaphragm for 30 minutes. Using these diaphragm traces, theoretical MRCA scans were performed. Several diaphragm monitoring algorithms were developed and compared with the simplest case (a stationary 5 mm NE acceptance window placed around the mean DEEP, as measured by NE monitoring at the outset of the scan). An overall scan efficiency was calculated, and the number of completed scans where the mean DEEP lay within the NE acceptance window was recorded. Of the six algorithms considered, the most effective one monitored the mean DEEP and prospectively placed the upper limit of the NE acceptance window on this position for the subsequent acquisition. Using this algorithm in comparison with the simplest stationary scenario, both scan efficiency (47.9% vs. 38.5%, P = 0.01) and the number of completed scans where the mean DEEP lay within the NE acceptance window (71.2 vs. 30.3, P < 0.001) were improved. The implementation of such a monitoring algorithm, in combination with adaptive motion correction techniques, should improve overall scan efficiency while maintaining the end-expiratory position at the top end of the NE acceptance window, to reduce image artifacts.     

Diffusion imaging with prospective motion correction and reacquisition

A major source of artifacts in diffusion‐weighted imaging is subject motion. Slow bulk subject motion causes misalignment of data when more than one average or diffusion gradient direction is acquired. Fast bulk subject motion can cause signal dropout artifacts in diffusion‐weighted images and results in erroneous derived maps, e.g., fractional anisotropy maps. To address both types of artifacts, a fully automatic method is presented that combines prospective motion correction with a reacquisition scheme. Motion correction is based on the prospective acquisition correction method modified to work with diffusion‐weighted data. The images to reacquire are determined automatically during the acquisition from the imaging data, i.e., no extra reference scan, navigators, or external devices are necessary. The number of reacquired images, i.e., the additional scan duration can be adjusted freely. Diffusion‐weighted prospective acquisition correction corrects slow bulk motion well and reduces misalignment artifacts like image blurring. Mean absolute residual values for translation and rotation were <0.6 mm and 0.5°. Reacquisition of images affected by signal dropout artifacts results in diffusion maps and fiber tracking free of artifacts. The presented method allows the reduction of two types of common motion related artifacts at the cost of slightly increased acquisition time. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

多b值DWI在儿童脑肿瘤中的初步研究

目的:探讨多b值DWI在儿童脑肿瘤中的应用价值。方法:对31例脑肿瘤患儿行EPI-DWI扫描,采用0～4000s/mm2之间的12个b值。按照单指数模型计算低b值ADC(ADClow)(b≤200s/mm2)、高b值ADC(ADChigh,200s/mm2相似文献   

A comparative study: diffusion weighted whole body imaging with background body signal suppression and hybrid Positron Emission Computed Tomography on detecting lesions in oncologic clinics

Objective

To compare diffusion weighted whole body imaging with background body signal suppression (DWIBS) with hybrid Positron Emission Computed Tomography (HPET/CT) on clinical value in oncology.

Methods

43 patients with oncological diseases were enrolled in our hospital from October, 2008 to April, 2010. All the cases underwent DWIBS and HPET/CT within 14 days. Combined with other imagings, lesions detected by both modalities were evaluated. Lesions were confirmed by pathology, cytology or clinical diagnosis (needed no less than 6 months and three times follow-up).

Results

The overall detection rate of the DWIBS and HPET/CT were 90.3% (261/289), 86.6% (251/289), concordant ratio of the two modalities was 88.2% (255/289). There was no statistical difference between DWIBS and HPET/CT on detecting lesions (P > 0.05). HPET/CT was significantly more sensitive in detecting lesions in lung (P < 0.05), whereas DWIBS was more sensitive in identifying lesions in brain and bone (P < 0.05). With regard to finding lesions in liver and lymph node, the two procedures had no significant difference (P > 0.05).

Conclusion

DWIBS and HPET/CT have a certain degree of consistency in terms of identifying lesions. However, they have advantages and disadvantages in some organs or tissues, which should be taken into full consideration in clinical practice.     

DWIBS和全脊柱MR成像对脊柱恶性肿瘤的诊断研究

目的 探讨磁共振背景抑制弥散加权成像(DWIBS)在脊柱恶性肿瘤早期诊断中临床应用价值.方法 60例临床证实为恶性肿瘤患者行全身弥散加权成像检查,并于同一时间对可疑部位行常规磁共振成像检查,必要时增强扫描,诊断结果与临床综合评价结果进行比较,分别比较DWIBS和常规磁共振成像所显示的病例数.结果 60例患者中55例经临床综合评价为脊柱转移瘤.常规MRI联合DWIBS检查的敏感性、特异性、阳性预测值、阴性预测值分别为98.8％、99.4％、95.4％、99.8％.与常规MRI及DWIBS比较,P＜0.05有统计学意义.结论 DWIBS在恶性肿瘤脊柱转移瘤早期诊断中具有一定的应用价值,结合常规MRI检查可进一步明确诊断.     

Respiratory motion compensated MR cholangiopancreatography at 3.0 Tesla

Purpose:

To reduce irregular respiratory motion‐induced artifacts in free‐breathing prospective navigator‐triggered three‐dimensional (3D) MR cholangiopancreatography (MRCP).

Materials and Methods:

A reference respiration model was estimated from the first‐five respiration periods during the initial navigator scan. With the navigator information acquired before and after triggering, the un‐acquired diaphragm position during the actual imaging was interpolated using the amplitude‐scaled reference model. Craniocaudal translational motion during imaging was retrospectively corrected using the estimated diaphragm position. T2‐weighted 3D MRCP data were acquired from 17 healthy volunteers. For quantitative analysis, contrast‐to‐noise ratio (CNR) and relative contrast (RC) of the biliary tree and gallbladder were compared using the paired t‐test.

Results:

The CNR and RC of the biliary tree and gallbladder were significantly higher (P < 0.05) in the maximum intensity projection images after motion compensation.

Conclusion:

The proposed algorithm can be an effective tool to reduce the irregular respiratory motion‐induced artifacts in 3D MRCP imaging. J. Magn. Reson. Imaging 2010;32:726–732. © 2010 Wiley‐Liss, Inc.     

3D steady‐state diffusion‐weighted imaging with trajectory using radially batched internal navigator echoes (TURBINE)

While most diffusion‐weighted imaging (DWI) is acquired using single‐shot diffusion‐weighted spin‐echo echo‐planar imaging, steady‐state DWI is an alternative method with the potential to achieve higher‐resolution images with less distortion. Steady‐state DWI is, however, best suited to a segmented three‐dimensional acquisition and thus requires three‐dimensional navigation to fully correct for motion artifacts. In this paper, a method for three‐dimensional motion‐corrected steady‐state DWI is presented. The method uses a unique acquisition and reconstruction scheme named trajectory using radially batched internal navigator echoes (TURBINE). Steady‐state DWI with TURBINE uses slab‐selection and a short echo‐planar imaging (EPI) readout each pulse repetition time. Successive EPI readouts are rotated about the phase‐encode axis. For image reconstruction, batches of cardiac‐synchronized readouts are used to form three‐dimensional navigators from a fully sampled central k‐space cylinder. In vivo steady‐state DWI with TURBINE is demonstrated in human brain. Motion artifacts are corrected using refocusing reconstruction and TURBINE images prove less distorted compared to two‐dimensional single‐shot diffusion‐weighted‐spin‐EPI. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.     

磁共振扩散加权成像在诊断肝脏占位性病变中的应用进展

随着磁共振扩散加权成像（DWI）的表面扩散系数（ADC）值的变化规律及扩散成像的量化分析、背景抑制磁共振弥散加权成像（DWIBS）等技术开发应用,肝占位性病变的准确诊断与鉴别诊断已成为可能。