Hepatocellular carcinoma and cavernous hemangioma: differentiation with MR imaging. Efficacy of T2 values at 0.35 and 1.5 T

Seventy-two patients with hepatocellular carcinoma (hepatoma) and 56 with hemangioma were studied with magnetic resonance (MR) imaging at 0.35 or 1.5 T to evaluate the efficacy of T2 values in differential diagnosis. T2 values were calculated with the two-point method. The mean T2 values of hepatoma and hemangioma were 58.9 msec +/- 8.9 and 101.6 msec +/- 25.8 at 0.35 T and 49.1 msec +/- 9.8 and 85.3 msec +/- 21.2 at 1.5 T. The difference in the T2 values for hepatoma and hemangioma was statistically significant (P less than .001) at both 0.35 and 1.5 T. Fifty-three of 56 lesions (94.6%) at 0.35 T and 86 of 102 lesions (84.3%) at 1.5 T were correctly classified when the T2 borderline between hepatoma and hemangioma was set at 80 msec. All misdiagnosed lesions were hemangioma, and all but one were smaller than 2 cm. However, over 90% of lesions smaller than 2 cm were correctly diagnosed when 70 msec at 0.35 T and 60 msec at 1.5 T were used as borderline T2 values. MR imaging with T2 measurement was very useful for differentiating between hepatoma and hemangioma (including small lesions) at 1.5 T as well as at 0.35 T.     

Hepatic tumors: differentiation by transverse relaxation time (T2) of magnetic resonance imaging

Fifty-three patients who had hepatic tumors (24 hepatomas, ten metastases, and 19 cavernous hemangiomas) underwent MR imaging using a 0.35-T superconducting imager. The transverse relaxation time (T2) was calculated from a pair of spin echo images (repetition time [TR] of 1600 msec) with echo delay times (TE) of 35 and 70 msec. The computed T2 value was obtained in a fashion similar to that used to obtain CT numbers with region-of-interest cursors. The mean T2 was 59 +/- 9 msec in hepatomas, 64 +/- 15 msec in metastases, and 100 +/- 30 msec in hemangiomas. The difference between the T2 of hemangioma and that of liver malignancies was statistically significant (P less than .001); however, differentiation between hepatoma and metastases was not possible. The T2 was shorter than 80 msec in all 24 hepatomas and in nine of ten metastases, and was longer than 80 msec in 16 of 19 hemangiomas. Forty-nine of 53 cases (92%) were correctly classified when the borderline of T2 between hemangioma and hepatic malignancies was set at 80 msec. MR with T2 calculation was valuable in differentiating between hemangioma and hepatic malignancies.     

Differentiation between hepatoma and hemangioma by inversion recovery snapshot FLASH MR imaging with variable TIs]

To differentiate hepatoma from hemangioma, MR studies were performed for 18 patients with 21 untreated liver tumors (hepatoma 10, hemangioma 11). We obtained inversion recovery snapshot FLASH images of liver tumors with variable TIs (50, 100, 150, 200, 250, 300, 400, and 500 msec). 8 hemangiomas showed higher intensity than liver parenchyma on the images at 150 msec and less of TI, and lower intensity at 200 msec or more TI. In 7, signal intensity of hepatoma became low at 150 msec or less of TI or remained high with prolonged TI. Inversion recovery snapshot FLASH imaging with variable TIs will be useful for differentiating between hepatoma and hemangioma.     

Quantitative assessment of iron-oxide-enhanced magnetic resonance imaging of the liver: Vessel isointensity is a potential characteristic of liver hemangiomas on late T1-weighted images

PURPOSE: To test whether a new quantitative measure, the tumor-to-vessel ratio, obtained from late post-iron-oxide-enhanced T1-weighted images allows for differentiating hemangiomas from liver metastases or all malignant liver lesions. MATERIAL AND METHODS: Twenty-six patients (mean 57, range 33-79 years) were prospectively studied at 1.5T magnetic resonance imaging (MRI) with a T1-weighted 2D fast low-angle shot (FLASH) sequence (repetition time/echo time/flip angle; 200 ms/4.8 ms/90 degrees ) and a T2-weighted turbo spin-echo sequence (4072 ms/99 ms/180 degrees ). Imaging was carried out before and at intervals up to 18 min after IV injection of Ferucarbotran (Resovist, Schering, Germany). In 19 patients, one representative malignant lesion was analysed. Eleven hemangiomas were evaluated in 7 patients. Two readers performed a consensus reading with a signal intensity measurement in a lesion, normal liver and hepatic veins, from which ratios were computed. RESULTS: On T1-weighted iron-oxide-enhanced MRI of 30 lesions, tumor-to-vessel signal intensity ratios were distinct in hemangiomas (median 1.04, range 0.99-1.10) as opposed to either metastases (0.64, 0.33-0.77; P < 0.05) or all malignant lesions taken together (0.64, 0.33-0.98; P < 0.05), while the tumor-to-liver ratio was not. CONCLUSION: The tumor-to-vessel ratio may help to differentiate between hemangiomas and metastases. A ratio greater than 0.98 allowed differentiating hemangiomas from metastases with a wide safety margin.     

Magnetic resonance imaging of cavernous hemangioma of the liver: tissue-specific characterization

Twenty-one patients with hepatic hemangioma, five with hepatic cysts, and 25 with primary or metastatic cancer involving the liver were studied by magnetic resonance imaging (MRI). Benign lesions (hemangiomas, cysts) were diagnosed noninvasively by CT, radionuclide studies, and/or sonography and confirmed by follow-up examinations more than 1 year later. Malignant lesions were confirmed by liver biopsy in every case. Identical multisection/multiecho techniques were used in all patients to obtain T1-and T2-weighted spin-echo (SE) and inversion-recovery (IR) images. MRI detected more hemangiomas than any other imaging technique. Of 30 hemangiomas, 25 were spherical or ovoid with a homogeneous appearance and smooth, well defined margins. Cancer tended to have a heterogeneous appearance and poorly defined margins. On T2-weighted SE images obtained with 2000 msec TR and 60, 120, or 180 msec TE, hemangiomas had significantly greater contrast-to-noise ratios (C/N) than liver cancer (p less than 0.001). The SE 2000/120 sequence provided the single most useful image for distinguishing hemangiomas from cancers. When morphologic criteria are used in conjunction with measured C/N, MRI correctly distinguished cavernous hemangiomas from liver cancer with 90% sensitivity, 92% specificity, and an overall accuracy of 90%. Cysts had a low signal intensity on SE 500/30 images and could often be distinguished from hemangiomas and cancers that were nearly isointense relative to liver. IR images were sensitive for lesion detection but provided no tissue-specific information. The data indicate that T2-weighted SE imaging may become the procedure of choice for distinguishing cavernous hemangioma from liver cancer.     

Differentiation between hemangiomas and metastases of the liver with ultrafast MR imaging: preliminary results with T2 calculations

We studied the efficacy of T2 measurements at high field strength in distinguishing between liver hemangiomas and hepatic metastases when an ultrafast (single-excitation) MR imaging technique is used. Fourteen patients with known liver tumors were imaged in a 2.0-T prototype ultrafast MR scanner with a spin-echo (infinite TR and TE of 30-340 msec) pulse sequence. Each image was obtained with a total data acquisition time of 20 msec. T2 calculations for hepatic metastases (n = 6) showed a mean of 79.3 +/- 13.5 msec, whereas hemangiomas (n = 8) showed a T2 of 139.8 +/- 18.8 msec (p less than .0001). T2 values of lesions had a smaller relative standard deviation than previously reported, and the range of T2 values of hemangiomas (119-181 msec) and metastases (68-103 msec) did not overlap. Our preliminary results suggest that T2 calculations with ultrafast MR imaging may be useful for differentiating hemangiomas from metastases. We hypothesize that T2 values obtained from ultrafast MR images are more reliable than those obtained from conventional MR images, primarily because of the elimination of T1 information and effects of motion on image signal intensity.     

Differentiation between hemangiomas and cysts of the liver with single-shot fast-spin echo image using short and long TE

PURPOSE: This study was designed to examine whether hepatic hemangioma can be differentiated from cyst by use of single-shot fast spin echo (SSFSE) sequence without contrast material. METHODS: SSFSE images with a short TE (90 msec) and a long TE (600-700 msec) were obtained in 30 patients with cyst (n= 19) or hemangioma (n= 26) on a 1.5-T unit. In short TE, both cysts and hemangiomas showed well-defined hyperintense masses. RESULTS: In long TE, however, cysts showed well-defined hyperintense masses, whereas hemangiomas were poorly defined faint masses with intermediate signal intensity. The contrast-to-noise ratio of hemangiomas and cysts were 3.23 and 52.9 (p < 0.001) in long TE; there was no overlap for the ranges, and the result did not depend on lesion size. All 45 lesions were differentiated correctly with these qualitative criteria. CONCLUSIONS: SSFSE with short and long TE is useful in the evaluation of cyst and hemangioma of the liver.     

Characterization of Focal Liver Lesions with Superparamagnetic Iron Oxide-Enhanced MR Imaging: Value of Distributional Phase T1-Weighted Imaging

Objective

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

Materials and Methods

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas [HCC], 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

Results

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p < .05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

Conclusion

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.     

软组织血管瘤的MRI诊断与鉴别诊断

目的探讨软组织血管瘤的MRI表现及其特征。方法收集有完整MRI资料并经手术病理证实的软组织血管瘤16例,分析其大小、边缘、形态及信号特征。结果16例中,海绵状血管瘤9例,肿瘤直径2.0~5.0cm,边界清楚,T2WI多呈不均匀性高信号。肌肉内血管瘤5例,形态不规则,T2WI表现为高信号为主的混杂信号。蔓状血管瘤2例,血管迂曲扩张和肌肉萎缩是其特征性MRI表现。结论软组织血管瘤MRI表现有一定特征性,结合临床,可做出诊断。     

Addition of gadolinium chelates to heavily T2-weighted MR imaging: limited role in differentiating hepatic hemangiomas from metastases

OBJECTIVE: The purpose of this study was to determine whether the addition of gadolinium-enhanced imaging to heavily T2-weighted MR imaging of the liver is valuable in differentiating hemangiomas from metastases. The T2 relaxation time was also included in our analysis. SUBJECTS AND METHODS: Fifty-one patients with 52 proven liver lesions (24 hemangiomas and 28 metastases) larger than 1 cm underwent MR imaging at 1.5 T with T2-weighted spin-echo (TR/TE, 3000/80, 160) and gadolinium chelate-enhanced dynamic T1-weighted gradient-recalled echo (80/2.6, 80) pulse sequences. Images were reviewed by observers who were unaware of the patients' clinical history; first, only T2-weighted images were reviewed and then T2-weighted plus dynamic images were reviewed together. The T2 relaxation times were calculated for each lesion. Diagnostic accuracy by each method was compared using receiver operating characteristic analysis. RESULTS: Mean T2 relaxation times were 76 +/- 26 msec for metastases and 133 +/- 25 msec for hemangiomas. The addition of dynamic scanning to the T2-weighted sequence made a statistically significant difference for only one observer (p = 0.03). However, it did not make a statistically significant contribution for either observer when compared with the T2 relaxation time. Although addition of the dynamic images resulted in correct diagnosis of six lesions, three lesions were misdiagnosed after having been correctly characterized on the T2-weighted images alone. CONCLUSION: When optimized T2-weighted images are obtained and the T2 relaxation time is calculated, routine use of gadolinium enhancement for differentiation of hemangiomas from metastases is unnecessary although dynamic scanning is valuable in selected cases.     

Hepatic tumors: quantitative tissue characterization with MR imaging

To determine which quantitative methods of image analysis are most suitable for the differential diagnosis of benign and malignant hepatic lesions, the authors analyzed magnetic resonance images obtained at 0.6 T in 42 patients with proved hepatic cavernous hemangioma and 63 patients with various hepatic malignancies. The lesion-liver signal-intensity ratio for images obtained with a repetition time of 2,350 msec and echo time of 180 msec was most helpful in distinguishing hemangiomas from cancer (area under the receiving operator characteristic curve [ROC] = 0.99 +/- 0.005). All 38 lesions with lesion-liver signal-intensity ratios greater than 3.5 were hemangiomas, whereas all 57 hepatic tumors with a ratio less than 2.5 were malignant neoplasms. A specificity of 93% and sensitivity of 89% can be achieved with use of quantitative signal-intensity data only. The authors conclude that in conjunction with heavily T2-weighted pulse sequences, signal-intensity ratios are an important adjunct to morphologic analysis in the differential diagnosis of hepatic neoplasms.     

Transient peritumoral enhancement during dynamic MRI of the liver: cavernous hemangioma versus hepatocellular carcinoma

PURPOSE: The purpose of this work was to compare the incidence and pattern of transient peritumoral parenchymal enhancement for cavernous hemangioma and hepatocellular carcinoma during dynamic MRI of the liver. METHOD: Two hundred seven hemangiomas and 155 hepatocellular carcinomas up to 4 cm in size were retrospectively assessed. The peritumoral enhancement was comparatively analyzed in terms of the shape, extent, signal intensity, and dependence on the size and degree of contrast enhancement of each tumor. RESULTS: For small lesions (<2 cm), hemangiomas (16/141; 11.3%) showed a higher incidence (p = 0.026) of peritumoral enhancement than hepatocellular carcinomas (3/87; 3.5%). For larger lesions (2-4 cm), there was no significant difference (p > 0.05) in the incidence of peritumoral enhancement of hemangiomas (15/66; 22.7%) and hepatocellular carcinomas (15/68; 22.1%). Nineteen (61.3%) of the 31 hemangiomas showed contrast agent filling the entire tumor volume at the phase of peritumoral enhancement. CONCLUSION: In spite of the limited specificity, for a <2 cm small focal lesion with homogeneous contrast enhancement on early phase dynamic MR images in the liver, peritumoral enhancement could suggest a higher possibility of hemangioma rather than hepatocellular carcinoma.     

Differentiation between small hepatic hemangiomas and metastases on MR images: importance of size-specific quantitative criteria

We studied the feasibility of using MR imaging at 0.6 T to differentiate small hepatic hemangiomas from small metastases on the basis of quantitative criteria. Ninety-two liver masses up to 5 cm in diameter, including 51 proved hemangiomas (mean, 1.9 +/- 1.1 cm) and 41 proved metastases (mean, 1.9 +/- 1.2 cm) were analyzed. Lesions were divided into three groups on the basis of size (less than or equal to 1 cm, greater than 1- less than or equal to 2 cm, greater than 2- less than or equal to 5 cm). The ability to distinguish hemangiomas from metastases was examined by using differences in lesion/liver signal-intensity ratio (SIR) and contrast-to-noise ratio (CNR) on T2-weighted images (SE 2350/180). Receiver-operating-characteristic analysis for all lesions grouped together showed that differentiation based on SIR was superior to that based on CNR (p less than .05). The mean SIR of hemangioma and the difference between mean SIRs of hemangioma and metastasis decreased with lesion size (greater than 2- less than or equal to 5 cm: 6.11 +/- 2.61 vs 2.30 +/- 1.22; greater than 1- less than or equal to 2 cm: 4.47 +/- 1.56 vs 2.40 +/- 0.73; less than or equal to 1 cm: 3.59 +/- 0.92 vs 2.01 +/- 0.52). However, in each size group, the difference between the mean SIR of hemangioma and metastasis was statistically significant (p less than .0001). These observations suggest that MR imaging is useful in differentiating small hepatic hemangiomas from small metastases and suggest the need for establishing size-specific quantitative criteria for tissue characterization.     

Temperature measurement using echo-shifted FLASH at low field for interventional MRI

We investigated the feasibility of using echo-shifted fast low-angle shot (FLASH) for temperature-monitored thermo-therapeutic procedures in a 0.2 T interventional magnetic resonance (MR) scanner. Based on the proton resonance frequency shift technique, modified echo-shifted FLASH has sufficiently high signal-to-noise ratio to provide accurate temperature maps with short scan times, i.e., 5 seconds in phantoms (TR = 20.5 msec; effective TE = 30 msec; one echo shift; NSA = 2) and ex vivo experiments (TR = 19.4 msec; effective TE = 28.9 msec; one echo shift; NSA = 2) and 3 seconds (TR = 19.4 msec; effective TE = 28.9 msec, one echo shift; NSA 1) for an in vivo case. The proton resonance frequency shifts with temperature observed in a 0.2 T MR scanner using this sequence were -0.0072 ppm/degrees C (temperature uncertainty = +/-2.5 degrees C) for polyacrylamide phantoins and -0.0086 ppm/degrees C (temperature uncertainty = +/- 1 degrees C) for ex vivo bovine liver. These experiments demonstrated that echo-shifted FLASH is a viable method for low-field temperature monitoring despite the decreased signal and decreased phase sensitivity compared with its counterpart in a 1.5 T MR imaging system. The improved temporal resolution of temperature images, now possible in low-field interventional MR systems using echo-shifted FLASH, will allow clinicians more accurate monitoring of interstitial ablation in MR-guided interventional procedures.     

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。     

Characterization of focal hepatic lesions with ferumoxides-enhanced MR imaging: utility of T1-weighted spoiled gradient recalled echo images using different echo times

PURPOSE: To evaluate the different signal characteristics of focal hepatic lesions on ferumoxides-enhanced MR imaging, including T1-weighted spoiled gradient recalled echo (GRE) images using different echo times (TE) and T2- and T2*-weighted images. MATERIALS AND METHODS: Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients who were referred for evaluation of known or suspected hepatic malignancies. One hundred and seven lesions (42 hepatocellular carcinomas [HCC], 40 metastases, 13 cysts, eight hemangiomas, three focal nodular hyperplasias [FNHs], and one cholangiocarcinoma) were evaluated. Postcontrast MR imaging included 1) T2-weighted FSE; 2) T2*-weighted GRE; 3) T1-weighted spoiled GRE using moderate (TE = 4.2-4.4 msec) TE; and 4) minimum (TE = 1.8-2.1 msec) TE. Signal intensities of the focal lesions were rated by two radiologists in conference as follows: hypointense, isointense or invisible, hyperintense, and markedly hyperintense. Lesion-to-liver contrast-to-noise ratio (C/N) was measured by one radiologist for a quantitative assessment. RESULTS: On ferumoxides-enhanced FSE images, 92% of cysts were "markedly hyperintense" and most of the other lesions were "hyperintense", and the mean C/N of cysts was significantly higher than that of other focal lesions. T2*-weighted GRE images showed most lesions with similar hyperintensities and the mean C/N was not significantly different between any two types of lesion. T1-weighted GRE images using moderate TE showed all FNHsand hemangiomas, 29 (69%) HCCs and eight (20%) metastases as "hyperintense". On T1-weighted GRE images using minimum TE, however, all HCCs and metastasis except one were iso- or hypointense, while all of the FNHs and hemangiomas were hyperintense. Ring enhancement was highly suggestive of malignant lesions, and was more commonly seen on the minimum TE images than on the moderate TE images. CONCLUSION: Addition of T1-weighted GRE images using minimum and moderate TE is helpful for characterizing focal lesions in ferumoxides-enhanced MR imaging.     

Differentiation between hemangiomas and cysts of the liver with nonenhanced MR imaging: Efficacy of T2 values at 1.5 T

The authors studied the utility of non-contrast-agent-enhanced magnetic resonance (MR) imaging for differentiating cysts and cavernous hemangiomas of the liver. Nineteen patients with hemangiomas (51 lesions) and 16 with cysts (30 lesions) were studied with a 1.5-T MR imager. T2 values were calculated with the two-point method to evaluate the efficacy of T2 values in the differentiation between hemangiomas and cysts of the liver. For lesions larger than 1 cm, the mean T2 value of cysts (306 msec ± 156) was significantly longer than that of hemangiomas (113 msec ± 15) (P < .0001); there was no overlap of the ranges for T2 values of hemangiomas and cysts. All cysts larger than 1 cm could be differentiated from hemangiomas by using a threshold T2 value of 140 msec. This study suggests that calculated T2 values permit differentiation between hemangiomas and cysts larger than 1 cm at 1.5 T.     

Dynamic spin-echo imaging with Gd-DTPA: value in the differentiation of hepatic tumors

Thirty patients with hemangiomas (n = 6), benign liver cell tumors (n = 7), and primary or metastatic malignant tumors of the liver (n = 17) underwent dynamic MR imaging with Gd-DTPA to determine the value of the procedure in the differentiation of hepatic tumors. The diagnoses were proved by histology or follow-up. Hemangiomas had a significantly greater mean T2 value (192.1 +/- 34.8 msec) than did both benign liver cell tumors (71.9 +/- 16.9 msec; p less than .01) and primary or metastatic malignant tumors (79.7 +/- 21.2 msec; p less than .01), but the T2 values of benign liver cell tumors and malignant tumors were not significantly different. Both hemangiomas and benign liver cell tumors had a significantly greater mean signal-intensity ratio (1.86 +/- 0.60 and 1.77 +/- 0.26, respectively) than did malignant tumors (1.04 +/- 0.34; p less than .01) in the early phase after Gd-DTPA administration, and hemangiomas had a significantly greater signal-intensity ratio (1.59 +/- 0.21) than did both benign liver cell tumors (1.21 +/- 0.08; p less than .01) and malignant tumors (1.06 +/- 0.26; p less than .01) in the delayed phase. These results suggest that dynamic MR images obtained after administration of Gd-DTPA are useful in differentiating hepatic hemangiomas, benign liver cell tumors, and malignant liver lesions.     

颅内海绵状血管瘤的病理及MR特征

目的:结合颅内海绵状血管瘤的病理特征,分析其MRI影像学表现.方法:搜集颅内海绵状血管瘤共53例,其中脑内型40例,脑外型13例,全部病例均行MRI检查.结果:脑内型海绵状血管瘤MRI大多表现为爆米花样或桑椹状的混杂信号灶,周边围以低信号环;脑外型T1WI表现为均匀低信号,T2WI为高信号,增强扫描明显强化.结论:不同类型的颅内海绵状血管瘤具有不同的病理学特点,导致其MRI表现的不同,其手术方案及预后亦有很大差异.利用MRI检查术前可做出准确诊断,从而指导手术方案的制订.     

Prediction rule for characterization of hepatic lesions revealed on MR imaging: estimation of malignancy

OBJECTIVE: Our aims were to establish factors that are most predictive of hepatic lesion malignancy and to formulate a prediction rule. MATERIALS AND METHODS: A cross-sectional study of 227 abdominal MR imaging examinations revealed 85 lesions in 67 patients (29 men, 38 women; age range, 29-78 years; mean age, 51.4 years) who were being examined for primary malignancy (n = 42) or unknown lesion characterization (n = 25). All were referred for MR imaging after CT or sonography. Patient demographics (age, sex, history of malignancy), lesion size and morphology, quantitative T2 calculation, and pattern of enhancement on gadopentetate dimeglumine administration were evaluated for predictive ability. RESULTS: Thirty-two liver lesions were malignant (eight colon cancer, five breast cancer, four cervical cancer, three renal cancer, three lung cancer, and nine miscellaneous cancers), 53 were benign (37 hemangiomas, 15 cysts, and one focal nodular hyperplasia). Calculated T2 relaxation times (mean +/- standard deviation [SD]) were as follows: malignant tumors (91.72 +/- 21.9 msec), hemangiomas (136.1 +/- 26.3 msec), cysts (284.1 +/- 38.2 msec) (p < 0.001). Logistic regression analysis indicated that lesion size and sex and age of patient were not significant independent predictors (p > 0.05). However, the combination of a history of malignancy, T2 value, and gadopentetate dimeglumine-enhancement pattern allowed generation of a prediction rule with an area under the receiver operating characteristic curve of 0.95. The patient's weight, lesion morphology, and cell type of the primary malignancy did not provide additional predictive information (p > 0.2). CONCLUSION: We recommend using the combination of T2 quantification and patient history of malignancy before deciding to administer gadopentetate dimeglumine for optimal lesion characterization, especially for equivocal lesions with T2 values between 90 and 130 msec. These factors allowed the construction of a prediction rule for lesion characterization.