超顺磁性氧化铁（SPIO）对比剂肝脾MR成像的比较研究

目的 比较两种超顺磁性氧化铁（superparamagnetic iron oxide,SPIO)对比剂,Ferumoxides及SHU－555A在肝脾MR成像中的效应。材料与方法 36例已知为肝转移癌患者于SPIO造影前后进行T2WI快速自旋回波成像（T2WI TSE）及T1WI梯度回波快去速相位成像（T1WI FLASH）。扫描伪为1．0T MR机。18例患者行Ferumoxides增强后90分钟进行MR成像;另18例行SHU－55A快速团柱增强,注药后即刻、30秒及480秒行T1WI FLASH成像,10分钟行T2WI TSE成像。测量肝脾、肝转移癌SPIO增强前后的信号强度（signal intensity,SI),计算两种SPIO对比剂在肝脾、肝转移癌增强前后SI变化的百分比（percentage signal intensity change,PSIC)及病灶肝脏对比噪声比（lesion-to-liver contrast-to-noise ratio,CNR)及其变化（ΔCNR）。结果 在T2WI TSE图像上,两种SPIO对比剂造成的肝实质SI下降无显著性差异（P＞0．05）。Ferumoxides引的脾信号下降显著大于SHU－555A（P＜0．05）。两种SPIO对比剂均导致肝实转移癌SNR显著增高。T1WI FLASH图像上,两种对比剂均可导致延迟像上肝脏SI的轻度下降及肝转移癌CNR下降,两者肝脏SIC之间无显著性差异。T1WI上两种对比剂均可导致脾脏SI显著升高,两者脾脏PSIC之间无显著性差异（P＞0．05）。结论 两种SPIO在肝脏的TI及T2增强效应相似,而脾脏的T2增强效应,Ferumoxides强于SHU－555A。     

Effects of ami-25 on liver vessels and tumors on T1-weighted turbo-field-echo images: Implications for tumor characterization

This study was devoted to tumor differentiation in liver MR T1-weighted imaging with superparamagnetic iron oxide (SPIO). Twenty-one patients with 40 liver lesions were studied at 1.5 T. Before and at least 45 minutes after SPIO administration, turbo-field-echo (TFE) T1-weighted, TFE T1 × T2*-weighted (MXT), and fat-suppressed turbo-spin-echo T2-weighted images were acquired. A quantitative analysis was performed blindly. On TFE T1-weighted images, the signal enhancement was ?33% ± 12 for the liver, ?24% ± 2 for adenomas and focal nodular hyperplasia, +60% ± 33 for the hemangiomas; metastases and cyst enhancement were not significant. After SPIO on TFE T1-weighted images, the hemangioma-to-liver signal ratio (149% ± 18) was definitely higher than the mean metastasis-to-liver signal ratio (90% ± 16). This T1-related differentiation ability lacked dramatically on TFE MXT images and, in one case, was reduced on post-SPIO TFE T1-weighted images by a long imaging delay after SPIO administration (2 hours).     

Time-to-echo optimization for spin echo magnetic resonance imaging of liver metastasis using superparamagnetic iron oxide particles.

Superparamagnetic iron oxide (SPIO) particles are used as a contrast agent in liver magnetic resonance imaging (MRI). SPIO particles exert their greatest influence on T2-weighted MR signal intensity. The time-to-echo (TE) value that provides optimal contrast has not been systematically studied over the range of clinically relevant field strengths. The purpose of this study was to quantitatively evaluate the TE dependence of the post-SPIO tumor to liver contrast-to-noise ratio (CNR). The hypothesis was that there is a TE that provides an optimal CNR. Subjects having probable metastatic hepatic lesions secondary to colorectal carcinoma were studied. Pre- and post-SPIO images were acquired at TE-effective (TE(eff)) equal to 46, 76, and 106 msec by using a turbo spin echo pulse sequence at 0.2 T and 1.5 T. The CNR for all lesions greater than 1 cm in diameter was determined in pre- and post-SPIO images. A paired statistical design was used to identify TE-related CNR dependencies. The primary findings were as follows. (1) CNR differences attributable to TE(eff) variation over the range of 46-106 msec were less than 34%. For 0.2 T, TE(eff) = 46 msec yielded a statistically significantly greater CNR than did TE(eff) = 76 or 106 msec. The same was true at the higher field strength, but differences were not significant. (2) Signal-to-noise measures suggested that SPIO reduced the lesion signal. (3) Post-SPIO CNR was significantly greater at 1.5 T than at 0.2 T. The observations indicate that over the field strength range of 0.2-1.5 T, CNR differences attributable to the TE(eff) variation, while being statistically significant in some cases, are small relative to those resulting from the SPIO administration.     

Improved focal liver lesion detection: comparison of single-shot spin-echo echo-planar and superparamagnetic iron oxide (SPIO)-enhanced MRI

PURPOSE: To prospectively compare single-shot spin-echo echo-planar imaging (SSSE-EPI) using b = 0, 10, 150, and 400 seconds/mm(2) with standard MRI techniques after intravenous super paramagnetic iron oxide (SPIO) in the detection and characterization of focal liver lesions with focus on small (<10 mm) focal liver lesions. MATERIALS AND METHODS: A total of 25 patients suspected for colorectal liver metastases were included. Number of detected lesions was evaluated. Image quality was compared between SSSE-EPI sequence and post-SPIO (fat-suppressed T1-weighted [T1w] gradient echo [GE], T2-weighted [T2w] turbo spin echo [TSE] and T2* GE) sequences using rank order statistic (RIDIT). Lesion characterization was performed for SSSE-EPI and for all remaining sequences pre- and post-SPIO. Reference standard comprised surgery, biopsy, and/or follow-up. RESULTS: Reference standard demonstrated 25 hemangiomas and 70 metastases. Best lesion detection respectively best image quality (P < 0.05) was achieved with SSSE-EPI (b = 10 seconds/mm(2)) post-SPIO T1w GE and T2w turbo spin echo. Lesion characterization using all sequences pre- and post-SPIO performed best for lesion characterization compared with SSSE-EPI. CONCLUSION: This preliminary study shows the potential of SSSE-EPI as a stand-alone sequence for the detection of liver hemangiomas and metastases when compared with SPIO-enhanced imaging. Sequences pre- and post-SPIO are needed for qualitative lesion characterization.     

Gradient- and spin-echo T2-weighted imaging for SPIO-enhanced detection and characterization of focal liver lesions

PURPOSE: To evaluate superparamagnetic iron oxide (SPIO)-enhanced breathhold T2-weighted GRASE imaging in detection and characterization of focal liver lesions. MATERIALS AND METHODS: In 30 patients (including 20 with cirrhosis) with 39 malignant and 25 benign lesions, gradient- and spin-echo (GRASE) images with two echo times (75 and 90 msec; GRASE75 and GRASE90) were obtained prior to and following administration of SPIO, and compared with respiratory-triggered and breathhold fast spin-echo (RT-FSE and BH-FSE) images. Two readers evaluated image quality and reviewed 240 liver segments for sensitivity and specificity. Signal-to-noise ratio (SNR), and its reduction in liver and spleen after administration of SPIO, and lesion-to-liver contrast-to-noise ratio (CNR) were measured. RESULTS: Compared with RT-FSE and BH-FSE, GRASE reduced scan time by 77% to 82% and 21% to 27%, respectively. The image qualities with BH-FSE and GRASE75 were higher than with BH-FSE and GRASE90. BH-FSE showed higher specificity than RT-FSE and GRASE90, but otherwise there were no significant differences between pulse sequences for sensitivity or specificity. The mean SNR and CNR of the lesions with RT-FSE were significantly higher than with the other methods. SPIO-induced signal reduction of liver SNR was smallest with BH-FSE. CONCLUSION: GRASE is faster and more sensitive to SPIO than FSE, but its sensitivity and specificity were slightly inferior to those of BH-FSE. Image quality is a current limitation.     

Gd- DTPA对肝脏、脾脏及肾脏1.5T MR弥散加权成像的影响

目的:探讨钆喷酸葡胺(Gd-DTPA)在1.5T MR机对正常肝脏、脾脏、肾脏弥散加权成像(DWI)的影响.方法:30例健康体检者在1.5T MR机做上腹部MRI.除常规MR平扫和增强外,在增强前和增强后7min采用b值=500 s/mm2单次激发自旋回波平面成像序列(SE- EPI)分别行DWI扫描.测量增强前后肝脏、脾脏、肾脏在DWI上的信噪比(SNR)、脾脏-肝脏对比噪声比(CNR)、信号强度值和ADC值,并进行统计分析.结果:30例健康体检者检查结果均正常.正常肝脏、脾脏DWI的SNR、CNR、信号强度值、ADC值增强后7min与增强前比较差异无统计学意义(P＞0.05),肾脏DWI SNR、信号强度值、ADC值增强后7min较增强前降低,差异有统计学意义(P＜0.05).结论:Gd-DTPA增强后7min对肝脏、脾脏DWI的图像质量和ADC值无明显影响,而肾脏DWI的图像质量和ADC值降低.     

扩散加权成像对局灶性肝癌血供分析的诊断价值

目的探讨不同b值下,磁共振扩散加权成像(DWI)对局灶性肝癌的血供分析的诊断价值。方法回顾性分析经临床诊断或病理证实的31例原发性肝癌和30例转移性肝癌行MRI动态增强扫描和DWI扫描,按照增强动脉期的表现分为富血供组(42个病灶)和乏血供组(47个病灶);观察b值分别为50、500s/mm2时的DWI图像特征,并测量病灶的ADC值。结果 b值为50s/mm2时,富血供病灶组DWI图像上为均匀稍高或高信号,平均ADC值为(3.56±0.21)×10-3 mm2/s,乏血供病灶组DWI呈均匀稍高信号,平均ADC值为(2.50±0.19)×10-3 mm2/s;同时对12个内部血供不均匀的病灶观察,在DWI图像上病灶内信号呈不均匀改变,b值为50s/mm2时富血供区较乏血供区信号下降更明显。在b=50s/mm2时,富血供病灶与乏血供病灶的ADC值有统计学差异(t=2.37,P<0.05)。结论依据磁共振DWI图像特点和ADC值测量,MRI对肝脏局灶性肝癌的血供分析具有一定的价值。     

Diagnostic accuracy of diffusion-weighted imaging in differentiating benign from malignant ovarian lesions

Purpose

To clarify the diagnostic accuracy of diffusion‐weighted imaging (DWI) in differentiating benign from malignant ovarian lesions.

Materials and Methods

We retrospectively analyzed magnetic resonance images of 123 ovarian lesions in 119 patients. We defined lesions with abnormal signal intensity as malignancy and assessed the location of abnormal intensity within the lesions on DWI. We also assessed the mean and lowest apparent diffusion coefficient (ADC) values of the solid portion for each ovarian lesion.

Results

The majority of malignant ovarian tumors and mature cystic teratomas, and almost half of the endometriomas, showed abnormal signal intensity on DWI, whereas most fibromas and other benign lesions did not. The main locations of abnormal signal intensity were solid portions in malignant ovarian tumors, cystic components suggestive of keratinoid substances and Rokitansky protuberance in mature cystic teratomas, and intracystic clots in endometriomas. On DW imaging, receiver‐operating characteristic analysis yielded mean Az values of 0.703. There was no significant difference in mean and lowest ADC values between malignant and benign lesions.

Conclusion

DWI of ovarian lesions and ADC values of the solid component are not useful for differentiating benign from malignant ovarian lesions. This knowledge is essential in avoiding misinterpretation in the diagnosis of ovarian lesions. J. Magn. Reson. Imaging 2008;28:1149–1156. © 2008 Wiley‐Liss, Inc.     

磁共振扩散加权与T2加权成像对肝脏局灶性病变检出的比较研究

目的比较磁共振扩散加权成像(diffusion-weighted imaging,DWI)与T2加权成像(T2-weighted imaging,T2WI)对肝脏局灶性病变的检出效能。方法选择T2WI与DWI2种序列均进行了检查的57例患者共79个病灶(45个恶性,34个良性)纳入本次研究。2位读片者采用盲法分别阅读T2WI与DWI图像。第3位读片者测量病灶和邻近肝实质在DWI及T2WI上的信号强度,计算病灶/肝信号强度比(contrast ratios,CR)。比较2种序列之间检出率及CR值的差异。结果2种序列对恶性病灶的检出率之间的差异无统计学意义,T2WI对全部病灶和良性病灶的检出率高于DWI(2位读片者P<0.001)。对于恶性病灶,当在一种序列上检出病灶即计为检出时,则T2WI+DWI的检出率高于DWI(读片者1P=0.008,读片者2P<0.001),但与T2WI之间检出率的差异无显著性。共对46个病灶测量了CR。良性病灶的CR值在T2WI高于DWI(P=0.008),恶性病灶和全部病灶的CR值在2种序列之间的差异无统计学意义。结论DWI对恶性病灶的检出效能低于T2WI,对良性病灶的检出效能也不及...     

Evaluation of super paramagnetic iron oxide-enhanced diffusion-weighted PROPELLER T2-fast spin echo magnetic resonance imaging: Preliminary experience

OBJECTIVE: To evaluate the usefulness of super paramagnetic iron oxide-enhanced, diffusion-weighted, periodically rotated overlapping parallel lines with enhanced reconstruction (SPIO DWI PROPELLER) T2-fast spin echo (FSE) magnetic resonance imaging (MRI) for the detection of hepatic metastases. METHODS: Fourteen patients were examined with SPIO-enhanced T2-FSE (SPIO FSE) imaging and SPIO DWI PROPELLER T2-FSE imaging. The b-value of the diffusion-sensitizing gradient was 10 s/mm so as to suppress the signal of the hepatic vessels. Hepatic resections were performed on all patients, and the number of lesions on MRI was compared between the 2 pulse sequences with references from pathologic reports. RESULTS: Nearly all metastases 1 cm or larger, totalling 38 metastases, were detected with both pulse sequences. Among the 30 metastases less than 1 cm, more lesions were detected on SPIO DWI PROPELLER T2-FSE imaging than on SPIO FSE imaging (16 for SPIO FSE imaging and 24 for DWI PROPELLER T2-FSE imaging; P < 0.05, McNemar test). CONCLUSION: Super paramagnetic iron oxide-enhanced DWI PROPELLER T2-FSE is useful for detecting small hepatic metastases.     

经量化的扩散加权成像对肝脏占位性病变的鉴别诊断价值

目的：探讨经量化的扩散加权成像(DWI)在肝脏占位性疾病影像诊断中的价值。方法本组回顾性分析120例肝脏占位性病变患者及对照组12例正常肝脏的影像资料,应用3.0T MR 行常规 MR 及 DWI,120例患者共检出179个病灶(其中53个肝癌、61个转移瘤、32个肝血管瘤及33个肝囊肿),分析其与对照组的 DWI 图及表观扩散系数(ADC)图,并测量 ADC 值,比较其间是否存在统计学差异。结果本组研究 b 值选择800 s/mm2,(1)其中33个肝囊肿呈低信号,51个肝癌、61个肝转移瘤及32个肝血管瘤呈高信号,肝囊肿的 DWI 图像信号与肝癌、肝转移瘤及肝血管瘤有显著性差异(P <0.05);(2)肝癌、肝转移瘤 ADC 伪彩图大体呈冷色系表现,肝囊肿、肝血管瘤 ADC 伪彩图大体呈暖色系表现;(3)肝癌、肝转移瘤、肝血管瘤、肝囊肿平均 ADC 值相互间行两两比较,总体上存在统计学差异(P <0.05),但肝癌与肝转移瘤之间两两比较,无统计学差异(P >0.05),通过结合背景肝,比较肝癌的病灶/背景肝 ADC 值与肝转移瘤的病灶/背景肝 ADC 值,二者差异有显著性(P <0.05)。结论DWI 和 ADC 图分析及ADC 值测量可为肝脏占位性病的诊断及鉴别诊断提供重要的补充信息。     

为什么部分肝脏局灶病变在超顺磁氧化铁增强T1WI上呈现高信号

目的:探讨肝脏病变在SPIO增强扫描T1WI上呈现高信号的机制.方法:肝脏局灶病变39例(56个病灶),其中33个恶性病灶(肝细胞癌10个、转移瘤21个、胆管细胞癌2个)和良性病灶23个(海绵状血管瘤9个,肝囊肿14个).平扫序列包括SE T1WI、FSPGR T1WI及FSE T2WI.SPIO(菲立磁)增强扫描序列包括FSE T2WI、SE T1WI(TE值分别为8 ms、20 ms)和 FSPGR T1WI(TE值分别为1.5 ms、4.2 ms).分析不同序列图像上病灶及肝实质的的信号变化.结果:在SPIO增强T1WI上,随着TE的延长,肝实质信号降低,肝内局灶病变信号相对增高.在SPIO增强长TE T1WI上,大部分恶性病灶及全部血管瘤呈相对高信号.结论:在SPIO增强T1WI上,SPIO对肝实质的T2*效应可能是部分局灶病变呈高信号的主要原因.     

Focal nodular hyperplasia: lesion characteristics on state-of-the-art MRI including dynamic gadolinium-enhanced and superparamagnetic iron-oxide-uptake sequences in a prospective study

PURPOSE: To image a cohort of patients with pathology-proven focal nodular hyperplasia (FNH) to assess which characteristics of state-of-the-art magnetic resonance imaging (MRI) of the liver are the most useful for improving the detection and characterization of FNH. MATERIALS AND METHODS: In 14 patients, pathology-proven FNH (N=33) were prospectively examined using gadolinium (Gd) and superparamagnetic iron-oxide (SPIO) contrast media. All lesions were evaluated for signal intensity (SI), fatty infiltration, central scar, mode of enhancement with Gd, and uptake of SPIO. The percentage of dynamic contrast enhancement in the arterial, portal, and delayed phases was assessed. The contrast-to-noise ratio (CNR) before and after administration of SPIO contrast was calculated. RESULTS: The SI of the lesions was low to isointense on T1-weighted (T1W) images, and intermediate to isointense on T2W images. Fatty infiltration of the lesions was present in 6%. The percentages of enhancement in the liver and lesion were 110%, 115%, and 95%, and 151%, 182%, and 160%, respectively (P<0.0001). All lesions showed uptake of SPIO with improved conspicuity of the central scar and septa. The CNR values precontrast and post-Gd/SPIO were significantly different for T1 in- and opposed-phase and black-blood echo-planar imaging (BBEPI). CONCLUSION: Combining dynamic Gd-enhanced imaging with T1W and T2W sequences after administration of SPIO facilitates comprehensive evaluation of FNH.     

Detection and characterization of focal hepatic lesions: mangafodipir vs. superparamagnetic iron oxide-enhanced magnetic resonance imaging

PURPOSE: To compare the mangafodipir-enhanced magnetic resonance (MR) and superparamagnetic iron oxide (SPIO)-enhanced images for their ability to detect and characterize focal hepatic lesions. MATERIALS AND METHODS: Unenhanced, mangafodipir-enhanced, and SPIO-enhanced hepatic MR images obtained from 64 patients were analyzed. A total of 121 hepatic lesions were included: 66 hepatocellular carcinomas (HCCs), 26 metastases, 14 hemangiomas, 5 cysts, 3 cholangiocarcinomas, 4 focal nodular hyperplasias (FNHs), 2 abscesses, and 1 adenoma. Two radiologists independently reviewed the two sets of images in a random order: 1) the unenhanced and mangafodipir-enhanced images (the mangafodipir set) and 2) the unenhanced and SPIO-enhanced images (the SPIO set). This study compared the accuracy of lesion detection, the ability to distinguish between a benign and malignant lesion, and the ability to distinguish between the hepatocellular and nonhepatocellular origins of the lesions using the areas (Az) under the receiver operating characteristic (ROC) curve. RESULTS: The overall accuracy for detecting focal lesions was significantly higher (P < 0.05) with the SPIO set (Az = 0.846 and 0.871 for readers 1 and 2, respectively) than with the mangafodipir set (Az = 0.716 and 0.766). Most of the lesions detected only with the SPIO-enhanced MR images by the readers were small HCCs. For lesions larger than 15 mm, the sensitivities of the two contrast enhancement techniques were similar for both readers. The accuracy of the mangafodipir and SPIO sets in distinguishing between benign and malignant lesions was comparable. The accuracy for distinguishing between the hepatocellular and nonhepatocellular origins of the lesions was significantly higher (P < 0.05) using the mangafodipir set (Az = 0.897 and 0.946) than using the SPIO set (Az = 0.741 and 0.833). CONCLUSION: SPIO- and mangafodipir-enhanced images were comparable for detection of focal hepatic lesions other than small HCCs, which were better detected on the SPIO-enhanced images. Mangafodipir-enhanced images are likely better than the SPIO-enhanced images for distinguishing between focal liver lesions with a hepatocellular or nonhepatocellular origin.     

扩散加权成像鉴别肺恶性肿瘤与实性良性病变的初步研究

目的探讨扩散加权成像(diffusion-weighted imaging,DWI)对肺恶性肿瘤与实性良性病变的鉴别诊断价值。资料与方法62例肺内恶性肿瘤和实性良性病变(共66个病灶)行常规MRI和DWI检查,b值为500s/mm2,观察病变区DWI信号特点并测量其表观扩散系数(apparent diffusion coefficient,ADC)值。结果不同病变组DWI信号虽有一定特点,但不具特征性。恶性病变组和良性病变组ADC值分别为(1.256±0.320)×10-3mm2/s、(1.648±0.416)×10-3mm2/s,两者差异有统计学意义(t=-3.637,P=0.001),ADC值鉴别肺内良恶性病变的最佳诊断阈值为1.400×10-3mm2/s,敏感性和特异性分别为83.3%和74.1%;小细胞肺癌ADC值为(1.064±0.196)×10-3mm2/s,非小细胞肺癌ADC值为(1.321±0.335)×10-3mm2/s,两者差异亦有统计学意义(t=2.967,P=0.007);原发性肺癌ADC值为(1.255±0.328)×10-3mm2/s,肺转移瘤ADC值为(1.263±0.280)×...     

肝脏占位性病变的磁共振成像研究：超顺磁性氧化铁与钆喷替酸葡甲胺的比较

通过与常用造影剂钆喷替酸葡甲胺（Gd-DTPA）的配对实验来评价新型造影剂超磁性氧化铁（SPIO）对有肝占位的检出率和定性诊断能力。材料和方法：53个病例132个肝占位首日行平扫及Gd-DTPA的动态增强扫描,次日行SPIO增强扫描,对照病理及临床随访证实结果,探讨各种占位SPIO增强扫描的强化特点,比较平扫联合Gd-DTPA动态增强扫描与平扫联合SPIO增强扫描的病灶检出率和定性诊断率。结果：SPIO增强扫描良性肝占位的信号随肝实质降低,而恶性肝占位的信号保持不变。平扫联合SPIO增强扫描的病灶检出率和定性诊断率较平扫联合Gd-DTPA增强扫描的略高,但统计学上相差不显著。结论：SPIO强化的原理、强化方式直至临床应用方法、特点与Gd-DTPA均完全不同,两者可相互补充和印证,当Gd-DTPA动态增强扫描定性诊断困难时应积极行SPIO增强扫描。     

DWI及ADC值在肝脏弥漫性疾病诊断中的应用价值

目的:探讨肝脏常见弥漫性疾病的ADC值及DWI上信号强度与相应血供相关性。方法:共110例(19例肝硬化癌变结节、20例肝转移性肿瘤、35例海绵状血管瘤和36例肝囊肿)弥漫性肝占位进行磁共振扫描并计算感兴趣区ADC值、信号强度及增强率。结果:癌变结节与DN及正常肝组织间ADC值相比明显高于后两者,P<0.05。肝囊肿、海绵状血管瘤、肝硬化癌变结节及转移性肝癌在DWI上均为明显高信号。结论:DWI及ADC值对于鉴别弥漫分布的肝脏恶性实质肿块与肝硬化再生结节及良性富水肿块(血管瘤及囊肿)有重要的诊断价值,尤其是在弥漫分布的肝硬化再生结节中发现癌变结节,有其重大的临床意义。     

Single breath-hold diffusion-weighted imaging of the abdomen

PURPOSE: To generate high quality diffusion-weighted images (DWI) and corresponding isotropic ADC maps of the abdomen with full organ (kidneys) coverage in a single breath-hold. MATERIALS AND METHODS: DWI was performed in 12 healthy subjects with an asymmetric, spin-echo, single-shot EPI readout on a system with high performance gradients (40 mT/minute). The isotropic diffusion coefficient was measured from maps and SNR was determined for both diffusion-weighted and reference images in the liver, spleen, pancreas, and kidneys. In six patients, single-axis diffusion encoding along three orthogonal axes (12 NEX) was employed to assess anisotropic diffusion in kidneys. RESULTS: This technique yielded images of quality and resolution which compares favorably to that of prior work. SNR ranged from 27.0 in liver to 44.1 in kidneys for the diffusion-weighted images, and from 19.6 in liver to 39.0 in kidneys in reference images. ADCs obtained in the renal medulla, renal cortex, liver, spleen, and pancreas were (2091 +/- 55) x 10(-6), (2580 +/- 53) x 10(-6), (1697 +/- 52) x 10(-6), (1047 +/- 82) x 10(-6), and (2605 +/- 168) x 10(-6) mm(2)/second, respectively (mean +/- SE). Apparent diffusion coefficient (ADC) in the renal medulla and cortex were significantly different by paired t-test (P = 4.22 x 10(-10)). Renal medulla and cortex yielded anisotropy indices (AI) of 0.129 and 0.067, respectively. CONCLUSIONS: 1) Single-shot SE EPI DWI in the abdomen with this technique provides high quality images and maps with full organ coverage in a single breath-hold; 2) ADCs obtained in the renal medulla and cortex are significantly different; and 3) diffusion within the renal medulla is moderately anisotropic.     

Focal hepatic lesions: detection and characterization with combination gadolinium- and superparamagnetic iron oxide-enhanced MR imaging

PURPOSE: To compare gadolinium- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for detection and characterization of focal hepatic lesions when different contrast agent administration sequences are used. MATERIALS AND METHODS: Unenhanced, dynamic gadolinium-enhanced, and SPIO-enhanced hepatic MR images were obtained in 134 patients. SPIO-enhanced MR imaging was performed immediately after gadolinium-enhanced dynamic MR imaging in 50 patients, 1 day after gadolinium-enhanced dynamic MR imaging in 40 patients, and before gadolinium-enhanced dynamic MR imaging in 44 patients. Two radiologists independently reviewed the gadolinium image set (unenhanced and gadolinium-enhanced dynamic MR images) and the SPIO image set (unenhanced and SPIO-enhanced MR images) in random order. Lesion detection sensitivity and lesion characterization accuracy were compared by analyzing the area under the receiver operating characteristic curve (Az). RESULTS: Overall lesion detection accuracy for pooled data was significantly higher with the SPIO set (Az = 0.903) than with the gadolinium set (Az = 0.857) (P <.05). When hypovascular lesions were excluded, the detection rate was similar with the two sets. When hepatocellular carcinomas were excluded, the detection rate was significantly higher with the SPIO set (P <.01). Readers were more accurate in differentiating benign from malignant lesions with the gadolinium set (Az = 0.915) than with the SPIO set (Az = 0.847) (P <.01). Detection accuracy tended to be better with the images obtained after the second contrast agent was used. CONCLUSION: Hypovascular lesion detection was better with SPIO-enhanced MR images than with gadolinium-enhanced MR images. Detection and characterization of hypervascular lesions were improved with gadolinium-enhanced MR images.     

Hepatic MRI with SPIO: detection and characterization of focal liver lesions

A variety of parenterally administered iron oxides have been developed for contrast-enhanced MRI of the liver. Two different classes of iron oxides are currently clinically approved or in phase 3 trials: superparamagnetic iron oxides (SPIO) with a high R2/R1 relaxivity ratio and short blood half-life (AMI-25 and SH U 555 A), and ultrasmall paramagnetic iron oxides (USPIO) with a lower R2/R1 relaxivity ratio and longer blood half-life (AMI-227). All iron oxides significantly increase tumor-to-liver contrast and allow detection of more lesions than unenhanced MRI on T2-weighted images at a field strength of 0.2–1.5 T. Malignant lesions without phagocytic cells exhibit constant signal on T2-weighted accumulation phase images with all three iron oxides. All iron oxides cause a signal decrease of benign lesions with either phagocytic cells or a significant blood pool on T2-weighted accumulation phase images. The signal decrease of benign lesions is proportional to the Kupffer cell activity or tumor vascularity and is useful for lesion characterization. Another enhancement feature for the differentiation of benign from malignant lesions is ring enhancement of malignant lesions (metastases) on T1-weighted enhanced images either during the perfusion phase with SH U 555 A or during the accumulation phase with AMI-227, which is attributed to the blood pool effects of the compounds. Differentiation of lesions and vessels is easier on enhanced images with angiographic effects than on unenhanced images. Iron oxides improve the quality of two-dimensional MR angiography techniques of the portal venous system by decreasing background signal (liver tissue with all iron oxides) and increasing intravascular signal (AMI-227). The use of iron oxides for hepatic MRI provides an alternative to the existing multistep diagnosis with CT, CT portography, MRI and biopsy. Received: 24 September 1997; Revision received: 12 November 1997; Accepted: 14 November 1997