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.     

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.     

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.     

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.     

MR imaging and CT of extrahepatic cavernous hemangiomas

Ten extrahepatic cavernous hemangiomas in seven patients were evaluated by MR and CT. MR was done with a 1.0-T superconducting magnet and spin-echo imaging. The lesions occurred in the musculoskeletal system, parotid gland, and spleen. MR and CT features of hemangiomas were compared, and MR findings in hemangiomas were also compared with those in eight musculoskeletal tumors of nonvascular origin. MR detected 10 hemangiomas, while nine were shown by CT. Also, MR was more accurate than CT in three patients in determining the true extent of hemangiomas. At a pulse-repetition interval of 2000 msec and an echo delay time of 90 msec, all hemangiomas were markedly hyperintense compared with skeletal muscle. Quantitatively, at this pulse sequence, intensity ratios of hemangiomas to skeletal muscle were all seven or greater (mean = 9.89), while the ratios for other tumors were usually less than seven (mean = 5.14). These means differed significantly (p less than .001). Small cavernous hemangiomas were homogeneous, well-defined round or oval lesions, while large hemangiomas consisted of dilated, tortuous vascular channels. Other tumors, however, were usually heterogeneous owing to hemorrhage and necrosis and had irregular margins. MR may, therefore, be useful for distinguishing cavernous hemangiomas from other soft-tissue tumors, particularly sarcomas.     

Hepatic hemangiomas vs metastases: MR differentiation at 1.5 T

We retrospectively studied the value of MR imaging at 1.5 T in distinguishing hepatic hemangiomas (n = 15) from metastases (n = 15) by using (1) lesion/liver signal-intensity ratios, (2) contrast/noise ratios, and (3) T2 relaxation time on long TR/TE spin-echo (SE) sequences. Lesion/liver margin sharpness, lesion shape, and overall lesion morphologic pattern were evaluated also. Univariate logistic regression analysis of the quantitative data showed that T2 was the only statistically significant (p less than .02) variable for distinguishing a hemangioma from a metastasis. A receiver-operator-characteristic plot of T2 produced an area of 0.80 (+/- 0.08). T2 values for these lesions still overlapped with those for metastases. Morphologically, hemangiomas were sharply marginated (80%), rounded or oval (93%), homogeneous, hyperintense lesions (73%), whereas metastases were poorly marginated (66%) and inhomogenous (67%) lesions. The marked, hyperintense appearance was present in 27% of metastases. Retrospective, multivariate logistic regression analysis of T2 and the presence of hyperintense morphology did not improve results based on T2 alone. Morphologic criteria are helpful in differentiation, as some metastases have a prolonged T2 and are not homogenous, hyperintense lesions. In cases where T2 or morphology are equivocal, other diagnostic tests may help confirm the MR findings. We currently use a T2 of greater than 88 msec and the presence of hyperintense morphology to diagnose hemangiomas. Despite both quantitative and qualitative analysis, data for these hemangiomas and metastases still overlap.     

Conventional and rapid MR imaging of the liver with Gd-DTPA

Twenty-three patients with malignant hepatic tumors underwent magnetic resonance (MR) imaging before and after intravenous administration of gadolinium-diethylene-triaminepentaacetic acid (DTPA). Two different doses were used, 0.1 mmol/kg and 0.2 mmol/kg. The larger dose proved to be more effective than the smaller dose. The signal-enhancement-to-noise ratio was significantly larger in the tumor than in the liver (2 alpha less than or equal to .05). In a moderately T1-weighted spin echo (SE) sequence (SE 400/30) (repetition time [TR] msec/echo time [TE] msec), the tumor was better defined 6 minutes after administration of Gd-DTPA. More strongly T1-weighted sequences--that is, SE 200/20 and inversion recovery 1,500/35/400 (TR msec/TE msec/inversion time, msec)--showed significantly worse contrast between tumor and liver (signal-difference-to-noise ratio [SD/N]) 10 and 15 minutes after administration (2 alpha less than or equal to .05). On the other hand, the low SD/N in the rapid MR imaging sequence was significantly improved (2 alpha less than or equal to .05). The most important indications for administration of Gd-DTPA in diagnosing hepatic tumors are the presentation of perfusion conditions and contrast optimization in rapid MR images.     

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.     

Diffusion-weighted single-shot echoplanar MR imaging for liver disease.

OBJECTIVE: The aims of this study were to determine apparent diffusion coefficients (ADCs) of the abdominal organs and liver lesions, to determine the effect of the magnitude of b values on the ADCs, and to determine whether measured ADCs of liver tumors help differentiate benign from malignant lesions. SUBJECTS AND METHODS: Six healthy volunteers and 126 patients were examined with diffusion-weighted single-shot echo-planar imaging using multiple b values (maximum, 846 sec/mm2). The ADCs of the liver, spleen, kidney, 49 malignant liver lesions (33 hepatocellular carcinomas, 15 metastatic liver tumors, and one cholangiocellular carcinoma), and 30 benign lesions (17 cysts, 12 hemangiomas, and one angiomyolipoma) were calculated. RESULTS: The ADCs of the abdominal organs and liver lesions showed smaller values when calculated with the greater maximum b values. The ADCs of the benign lesions calculated with all the b values of less than 850 sec/mm2 (2.49+/-1.39 x 10(-3) mm2/sec) were significantly (p = .0024) greater than those of the malignant lesions (1.01+/-0.38 x 10(-3) mm2/sec). When the maximum b value is 846 sec/mm2, use of a threshold ADC of 1.6 x 10(-3) mm2/sec would result in a sensitivity of 98% and a specificity of 80% for differentiation of malignant liver lesions from benign lesions. CONCLUSION. Measurement of ADC has good potential for characterizing liver lesions, but the calculated ADCs could be affected by the magnitude of the maximum b value.     

Salivary gland tumors at in vivo proton MR spectroscopy

PURPOSE: To prospectively evaluate whether proton magnetic resonance (MR) spectroscopy can be used to characterize salivary gland tumors (SGTs). MATERIALS AND METHODS: Ethics committee approval and informed consent were obtained. Hydrogen 1 ((1)H) MR spectroscopy was performed with echo times of 136 and 272 msec at 1.5 T in both SGTs and normal parotid glands. Spectra were analyzed in the time domain by using prior knowledge in the fitting procedure to obtain peak amplitudes of choline (Cho), creatine (Cr), and unsuppressed water. Mean Cho/Cr and Cho/water ratios for each subgroup of SGTs were obtained, and results were compared by using a nonparametric t test. RESULTS: Successful spectra were acquired in 56 patients (35 men, 21 women; mean age, 56 years) with a total of nine malignant tumors and 47 benign SGTs (24 Warthin tumors, 22 pleomorphic adenomas, one oncocytoma). At an echo time of 136 msec, Cho/Cr ratios were obtained in 26 (47%) of 55 spectra, with a mean value (+/- standard deviation) of 1.73 +/- 0.47, 5.49 +/- 1.86, 3.46 +/- 0.84, and 2.45 for malignant tumors, Warthin tumors, pleomorphic adenomas, and oncocytoma, respectively. Differences were significant between Warthin tumors and pleomorphic adenomas (P = .028) and between benign SGTs and malignant tumors (P < .001). At an echo time of 272 msec, Cho/Cr ratios were obtained in 16 (30%) of 53 spectra, with a mean value of 2.27 +/- 0.69, 6.92 +/- 1.47, and 3.67 +/- 1.23 for malignant tumors, Warthin tumors, and pleomorphic adenomas, respectively. Differences were also significant between Warthin tumors and pleomorphic adenomas (P = .041) and benign SGTs and malignant tumors (P = .004). There was a significant difference in mean Cho/water ratio for Warthin tumors versus pleomorphic adenomas at echo times of 136 msec (P = .003) and 272 msec (P = .002) but not for benign SGTs versus malignant tumors. CONCLUSION: (1)H MR spectroscopy may be used to characterize SGTs, but a larger study is required to validate these initial results.     

MR differentiation of hepatocellular carcinoma from cavernous hemangioma: complementary roles of FLASH and T2 values

Forty-two patients with hepatocellular carcinoma (hepatoma) and 18 patients with hemangioma were studied with MR imaging at 1.5 T to evaluate the efficacy of single-slice breath-hold FLASH (fast low-angle shot) images in distinguishing between the lesions and to compare with T2 differentiation using conventional spin-echo images. The difference between mean tumor-to-liver signal ratio on FLASH imaging of hepatocellular carcinoma (1.46 +/- 1.06) and hemangioma (0.86 +/- 0.45) was statistically significant (p less than .01). Fifty-one (82%) of 62 lesions were classified correctly when the borderline of tumor-to-liver signal ratio between hepatoma and hemangioma was set at 0.9. The mean T2 values of hepatomas and hemangiomas were 48 +/- 10 msec and 89 +/- 20 msec, respectively. Fifty-seven (92%) of 62 lesions were correctly diagnosed with the T2 borderline of 80 msec. The five misdiagnosed lesions with the T2 borderline were hemangiomas smaller than 2 cm with tumor-to-liver signal ratios less than 0.9. FLASH images appear promising for differentiating between hepatoma and hemangioma, and they complement T2 values in characterizing small lesions.     

Evaluation of liver diffusion isotropy and characterization of focal hepatic lesions with two single-shot echo-planar MR imaging sequences: prospective study in 66 patients

PURPOSE: To (a) evaluate liver diffusion isotropy, (b) compare two diffusion-weighted magnetic resonance (MR) imaging sequences for the characterization of focal hepatic lesions by using two or four b values, and (c) determine an apparent diffusion coefficient (ADC) threshold value to differentiate benign from malignant lesions. MATERIALS AND METHODS: Sixty-six patients were examined with two single-shot echo-planar diffusion-weighted MR sequences. In the first sequence, liver diffusion isotropy was evaluated by using diffusion gradients in three directions with two b values. In the second sequence, a unidirectional diffusion gradient was used with four b values. ADCs were measured in 43 patients with 52 focal hepatic lesions more than 1 cm in diameter and in 23 patients with 14 normal and nine cirrhotic livers and were compared by using nonparametric tests. RESULTS: Diffusion in the liver parenchyma was isotropic. ADCs of focal hepatic lesions were significantly different between sequences (P <.01). The mean (+/- SD) ADCs in the first sequence were 0.94 x 10(-3) mm(2)/sec +/- 0.60 for metastases, 1.33 x 10(-3) mm(2)/sec +/- 0.13 for HCCs, 1.75 x 10(-3) mm(2)/sec +/- 0.46 for benign hepatocellular lesions, 2.95 x 10(-3) mm(2)/sec +/- 0.67 for hemangiomas, and 3.63 x 10(-3) mm(2)/sec +/- 0.56 for cysts. There was a significant difference between benign (2.45 x 10(-3) mm(2)/sec +/- 0.96, isotropic value) and malignant (1.08 x 10(-3) mm(2)/sec +/- 0.50) lesions (P <.01 for both sequences). CONCLUSION: Diffusion-weighted MR imaging can help differentiate benign from malignant hepatic lesions. The use of two b values in one direction could be sufficient for the design of MR sequences in the liver.     

Differentiation between hepatoma and hemangioma with inversion-recovery snapshot FLASH MRI and Gd-DTPA.

Thirty-eight patients with focal liver tumors (20 hepatomas, 18 hemangiomas) were studied by dynamic sequential inversion recovery (IR) snapshot fast low angle shot (FLASH) MR imaging with Gd-DTPA. Immediately after 0.05 mmol/kg Gd-DTPA was administered intravenously for 2-3 s followed by flushing with normal saline for 4-5 s, 10 images were obtained in the first 20 s (time zero is the end of flush, early phase). Then, one image every 30 s from 1 to 3 min (late phase) and images at 5 min and 7 min (delayed phase) were obtained serially. Hepatomas showed total enhancement in 18 of 20 patients in the early phase, and isointense or low intensity enhancement with respect to the surrounding liver parenchyma in 18 patients in the late to delayed phases. Hemangiomas showed peripheral enhancement in 14 patients in the early phase, but did not show total enhancement (except for two hemangiomas less than 3 cm in size) in the early phase, and showed high intensity enhancement in 15 patients in the late phase. Ninety percent of hepatomas and 82% of hemangiomas showed their characteristic enhancement patterns in the early to delayed phases. We conclude that dynamic sequential IR snapshot FLASH MR images enhanced with Gd-DTPA can facilitate differentiation between hepatomas and hemangiomas.     

Hepatic metastases: randomized, controlled comparison of detection with MR imaging and CT

To determine the accuracy of magnetic resonance (MR) imaging relative to computed tomography (CT) in the diagnosis of liver metastases, a randomized, controlled study was conducted of 135 subjects, including 57 with cancer metastatic to the liver, 27 with benign cysts or hemangiomas, and 51 without focal liver disease. The sensitivity of MR imaging for detecting individual metastatic deposits was 64%, significantly greater than 51% for CT (P less than .001); the difference in sensitivity for identifying patients with one or more hepatic metastases was less (82% for MR imaging vs. 80% for CT). In patients without hepatic metastases, the specificity of MR imaging was 99% versus 94% for CT. Significant differences were found between individual MR pulse sequences in detection of individual lesions. The sensitivity of both T1-weighted spin-echo (SE) (64%) and inversion-recovery (IR) (65%) pulse sequences was significantly (P less than .001) greater than either the TE (echo time) 60 msec (43%) or TE 120 msec (43%) T2-weighted pulse sequences. Overall, the accuracy of a single T1-weighted (10-minute) pulse sequence was superior to that of contrast-enhanced CT.     

Characterization of focal liver lesions with half-Fourier acquisition single-shot turbo-spin-echo (HASTE) and inversion recovery (IR)-HASTE sequences

The half-Fourier acquisition single-shot turbo-spinecho (HASTE) sequence allows for heavily T2-weighted images, and the inversion recovery (IR)-HASTE sequence represents the T1 value of the tissue in a very short time. This study was undertaken to determine whether characterizing focal liver lesions can be made by combination with these very fast sequences. Seventy-four patients (33 cysts, 28 hemangiomas, and 33 malignant solid liver masses [15 metastatic tumors, 14 hepatocellular carcinomas, and 4 cholangiocarcinomasl]) underwent dynamic CT and breath-hold abdominal MRI using turbo-spin-echo (TSE), HASTE, and IR-HASTE sequences with variable TI values on a 1.5-T MR unit. The imaging time for each slice was 2 seconds for HASTE imaging and 2 to 4 seconds for IR-HASTE imaging. Lesion detection and qualitative characterization were evaluated. Quantitative analysis was performed by measuring the contrast-to-noise ratios (CNRs) as well as visual analysis. The inversion time (TI) nulling values were also statistically analyzed. All cystic lesions were detected on both TSE and HASTE imagings. For solid lesions, TSE failed to detect one small solid lesion and HASTE sequence failed to detect three lesions. With HASTE sequences, all cysts and hemangiomas were markedly hyperintense in comparison with malignant solid masses. CNRs of hemangiomas or cysts were significantly higher than those of malignant solid masses (P < .01), and there was no overlap. The TI nulling value was 1,100 ± 100 msec for hemangiomas, 1,900 ± 110 msec for cysts, and 740 ± 140 msec for malignant solid masses. There was no overlap between the TI nulling values of hemangiomas and cysts (P < .01). By combining the CNR from the HASTE sequence and the TI nulling value from the IR-HASTE sequence, complete discrimination among malignant solid masses, hemangiomas, and cysts of the liver could be made. Application of HASTE (representing T2 values) and IR-HASTE (representing T1 values) sequences provided a rapid and reliable imaging method for characterizing focal liver lesions without the use of contrast medium.     

MR evaluation of adrenal masses at 1.5 T

We retrospectively studied the value of MR imaging at 1.5 T to distinguish between nonadenomatous (n = 17) and adenomatous (n = 15) adrenal masses on the basis of (1) signal-intensity ratios on T1- and T2-weighted spin-echo images, (2) T2 relaxation times, and (3) T2 relaxation-time ratios. Univariate and then multivariate logistic regression were applied to these quantitative parameters to determine which of these best discriminated nonadenomas from adenomas, and whether or not more than one of these parameters improved the prediction. The adrenal mass/liver signal-intensity ratio on T2-weighted spin-echo images could not be used to differentiate nonadenomas from adenomas. Adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images, adrenal/liver T2 relaxation-time ratios, and adrenal mass T2 relaxation times were best for distinguishing nonadenomas from adenomas. By using a T2 value of greater than 61 msec, the true-positive ratio/false-positive ratio of differentiating nonadenomas from adenomas was 100%/20%; at greater than 82 msec, it was 64%/0.06%. The adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images and the adrenal/liver T2 relaxation-time ratios showed similar inherent discriminatory capacity. Overlap remains despite the use of these parameters. On the basis of this preliminary information, we conclude that MR has merit for the characterization of adrenal masses at 1.5 T. T2 relaxation time of the adrenal mass shows the greatest promise for discriminating nonadenomas from adenomas.     

Hepatic metastases: liposomal Gd-DTPA-enhanced MR imaging

Liposomal gadolinium diethylenetriaminepentaacetic acid (DTPA) encapsulated within 70- and 400-nm vesicles was tested as a contrast agent for magnetic resonance (MR) imaging of the liver in rats with hepatic metastases. Liposomal Gd-DTPA caused significant improvement in contrast between liver and tumor (P less than .005) on T1-weighted MR images. Smaller 70-nm liposomal Gd-DTPA vesicles caused greater contrast enhancement, reflecting the larger surface-area-to-volume ratio of the smaller vesicles. Liposomal Gd-DTPA-enhanced images permitted significant improvement in metastasis detection by five blinded radiologists (P less than .005). By comparison, free Gd-DTPA without liposomes caused a statistically significant reduction in contrast between tumor and liver and reduced lesion detection (P less than .01). Liposomal Gd-DTPA also resulted in sustained vascular enhancement for 1 hour after administration. The results suggest that paramagnetic liposomes may become a useful MR imaging contrast agent.     

Acute myocardial infarction: MR evaluation in 29 patients

This study evaluated the ability of MR to identify and characterize the region of myocardial infarction in humans. Twenty-nine patients, all with ECG and enzyme rises consistent with an acute myocardial infarction, were studied by MR 3-17 days from the onset of acute chest pain. Four patients were excluded because of inability to acquire adequate MR studies. For comparison, 20 normal subjects were studied who also had gated MR examinations. The site of infarction was visualized in 23 patients as an area of high signal intensity in relation to the normal myocardium, a contrast that increased on the second-echo image. The regions of abnormal signal intensity corresponded to the anatomic site of infarction as defined by the ECG changes. The mean T2 relaxation time of the infarcted myocardium (79 +/- 22 msec) was significantly prolonged in comparison with the mean T2 (43.9 +/- 9 msec) of normal myocardium (p less than .01). The mean percentage of contrast (intensity difference) between normal and infarcted myocardium was much greater on the second-echo images (65.6 +/- 34.0%) than the first-echo images (27.5 +/- 18.7%). In the normal subjects there was no difference in T2 between the anterolateral (40.3 +/- 5.7 msec) and septal (39.5 +/- 7.4 msec) regions, and percentages of contrast between these two regions of myocardium on the first-echo (9.1 +/- 7.4%) and second-echo (15.0 +/- 13.3%) images were similar. Thus, MR can be used to directly visualize acute infarcts. However, it has several pitfalls, including the necessity to differentiate signal from slowly flowing blood in the ventricle, from increased signal from a region of infarction and artifactual variation of signal intensity in the myocardium due to respiratory motion or residual cardiac motion.     

Differential diagnosis between metastatic tumors and nonsolid benign lesions of the liver using ferucarbotran-enhanced MR imaging

Purpose

To evaluate ability of ferucarbotran-enhanced MR imaging (MRI) in differentiating metastases from nonsolid benign lesions of the liver according to signal-intensity characteristics.

Materials and methods

Sixty-six consecutive patients, who had 138 focal hepatic lesions (26 cysts, 11 hemangiomas, and 101 metastases), underwent ferucarbotran-enhanced MRI. The signal-intensity pattern of each kind of lesion relative to the liver parenchyma on ferucarbotran-enhanced T2* and heavily T1-weighted gradient-echo images were assessed and categorized into the following three categories: high-intensity and iso-intensity, respectively (category A), high and low (category B), and iso- and low-intensity (category C). For category B, lesions were subdivided into two groups based on single-shot half-Fourier RARE images: category B1 (not significantly high-intensity) and category B2 (significantly high-intensity).

Results

Category A had 11 hemangiomas and 2 metastatic tumors, category B1 had 97 metastatic tumors, category B2 had 2 metastatic tumors and 9 cysts, and category C had 17 cysts. When a tumor with a signal intensity of category A was considered to be hemangioma, category B1 metastasis, and category B2 and C cyst, the diagnostic accuracy for differentiating these lesions was 97% (134/138).

Conclusion

The combination of signal-intensity pattern on ferucarbotran-enhanced T2*- and heavily T1-weighted gradient-echo MRI has ability to differentiate liver metastases from nonsolid benign lesions. However, T2-weighted single-shot half-Fourier RARE imaging should also be employed to achieve better performance.     

Differentiation of hepatic malignancies from hemangiomas and cysts by T2 relaxation times: early experience with multiply refocused four-echo imaging at 1.5 T

The purpose of this study was to examine hepatic lesions with a sequence designed to yield improved T2 measurements and evaluate the clinical utility of these measurements in distinguishing malignant from benign disease. Using a modified Carr-Purcell sequence incorporating features designed to compensate for imperfections in the imaging system, including a train of refocusing pulses emitted in an MLEV pattern oriented in composite fashion along all three coordinate axes, and a single spatially selective pulse placed immediately before a spiral readout, 14 benign lesions and 13 malignant lesions were evaluated prospectively with a conventional 1.5 T imager. The maximum, minimum, and mean T2 values of malignant lesions, hemangiomas, and cysts exceeded corresponding published values from spin-echo and echoplanar studies. The mean T2 value of the malignant lesions differed significantly (P < 0.0001) from those of hemangiomas and cysts. All malignant lesions and all benign lesions were distinguishable by their T2 values, which had ranges of no greater than 118.6 msec and no less than 134.3 msec, respectively. This early experience suggests that improved T2 measurements can facilitate the differentiation of hepatic malignancies from hemangiomas and cysts.