Characterization Of Focal Hepatic Lesions Research Articles

T2-weighted MR imaging for focal hepatic lesion detection: supplementary value of breath-hold imaging with half-Fourier single-shot fast spin-echo and multishot spin-echo echoplanar sequences.

The purpose of our study was to evaluate the supplementary value of breath-hold fat-suppressed T2-weighted magnetic resonance (MR) imaging with half-Fourier single-shot fast spin-echo (SE) or multishot SE echoplanar (EP) sequences combined with respiratory-triggered fat-suppressed fast SE T2-weighted MR imaging for detection and characterization of focal hepatic lesions. MR images in 42 patients with 82 solid, malignant and 77 nonsolid, benign lesions were analyzed. Image review was conducted on a segment-by-segment basis; in all, 333 liver segments were reviewed separately for solid and nonsolid lesions by three independent radiologists. For solid lesions, observer performance with receiver-operating-characteristic (ROC) analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. For nonsolid lesions, observer performance with ROC analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. Combining breath-hold half-Fourier single-shot fast SE imaging with respiratory-triggered fast SE imaging may be recommended for improved detection and characterization of focal hepatic lesions. J. Magn. Reson. Imaging 2000;12:444-452.

Characterization of focal hepatic lesions with ferumoxides-enhanced T2-weighted MR imaging.

The purpose of this study was to evaluate whether ferumoxides-enhanced MR imaging of focal hepatic lesions provides distinctive signal intensity and lesion-to-liver contrast changes for benign and malignant lesions, helping to further characterize and differentiate these lesions. Data analysis was performed on 70 patients, with previously identified focal hepatic lesions, who underwent MR imaging of the liver before and after IV administration of ferumoxides (10 micromol Fe/kg). Lesions analyzed with pathologically proven diagnoses included metastases (n = 40), hepatocellular carcinoma (n = 11), cholangiocarcinoma (n = 6), hemangioma (n = 4), focal nodular hyperplasia (n = 6), and hepatocellular adenoma (n = 3). Response variables measured and statistically compared included the percentage of signal-intensity change and lesion-to-liver contrast. Focal nodular hyperplasia showed significant signal intensity loss on ferumoxides-enhanced T2-weighted images (mean, -43%+/-6.7%, p < 0.01). All other lesion groups showed no statistically significant change in signal intensity on ferumoxides-enhanced T2-weighted images, although signal intensity loss was seen in some individual hepatocellular adenomas (mean, -6.6%+/-24.0%) and hepatocellular carcinomas (mean, -3.3%+/-10.3%). All lesions, with the exception of hepatocellular carcinoma, had a marked increase in lesion-to-liver contrast on ferumoxides-enhanced T2-weighted images, which was statistically significant for metastases and hemangioma (p < 0.02). Focal nodular hyperplasia shows significant decrease in signal intensity on ferumoxides-enhanced T2-weighted images, which may aid in the differentiation of focal nodular hyperplasia from other focal hepatic lesions. Other lesions, namely, hepatocellular adenoma and carcinoma, can have reticuloendothelial uptake, but usually to a lesser degree than that of focal nodular hyperplasia.

A prospective assessment of breath-hold fast spin echo and inversion recovery fast spin echo techniques for detection and characterization of focal hepatic lesions

The purpose of this study was to prospectively assess two breath-hold T 2-weighted fast spin-echo sequences and two breath-hold inversion recovery fast spin-echo sequences to determine their relative ability to detect and characterize focal hepatic lesions. Fourteen patients with a total of nineteen proven focal hepatic lesions were imaged with two breath-hold T 2-weighted (T2W) fast spin echo sequences (HASTE TE = 66 and HASTE TE = 120), two breath-hold inversion recovery fast spin echo sequences (IRFSE TE = 64 and IRFSE TE = 95), and a nonbreath-hold T 2-weighted fast-spin echo sequence (FSE TE = 96–120). Contrast-to-noise ratios (CNRs) were measured for all proven lesions on all sequences. Both IRFSE sequences and the HASTE sequence with TE = 66 showed an improvement in lesion-liver and liver-spleen CNRs compared to the nonbreath-hold T2W sequence. The mean difference in CNR between benign and malignant lesions was largest for the HASTE TE = 120 sequence. These preliminary results suggest that a breath-hold IRFSE sequence (TE = 64 or 95) has an equal ability to detect focal hepatic lesions as a nonbreath-hold T2W FSE sequence (TE = 96–120). The HASTE TE = 120 showed the greatest ability to discriminate between benign and malignant lesions.

T2-weighted MR imaging for focal hepatic lesion detection: Supplementary value of breath-hold imaging with half-fourier single-shot fast spin-echo and multishot spin-echo echoplanar sequences

The purpose of our study was to evaluate the supplementary value of breath-hold fat-suppressed T2-weighted magnetic resonance (MR) imaging with half-Fourier single-shot fast spin-echo (SE) or multishot SE echoplanar (EP) sequences combined with respiratory-triggered fat-suppressed fast SE T2-weighted MR imaging for detection and characterization of focal hepatic lesions. MR images in 42 patients with 82 solid, malignant and 77 nonsolid, benign lesions were analyzed. Image review was conducted on a segment-by-segment basis; in all, 333 liver segments were reviewed separately for solid and nonsolid lesions by three independent radiologists. For solid lesions, observer performance with receiver-operating-characteristic (ROC) analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. For nonsolid lesions, observer performance with ROC analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. Combining breath-hold half-Fourier single-shot fast SE imaging with respiratory-triggered fast SE imaging may be recommended for improved detection and characterization of focal hepatic lesions. J. Magn. Reson. Imaging 2000;12:444-452.

Test-bolus injection for optimization of arterial phase imaging during contrast-enhanced hepatic MR imaging.

Contrast enhancement during the dynamic MR imaging is important for the detection and characterization of focal liver lesions. The purpose of this study was to determine whether or not a timing examination with a injection of a 1.0-mL bolus of gadopentetate dimeglumine into the antecubital vein followed by rapid dynamic scanning and measurement of signal intensity of the aorta could help to obtain proper arterial-dominant phase images for the characterization of focal hepatic lesions during subsequent multiphase dynamic MR imaging. The imaging delay to acquisition of the first gadolinium-enhanced image for multiphase dynamic MR imaging was set to equal the time to peak aortic enhancement during the test examination. The first contrast-enhanced images of 80 patients with 160 focal liver lesions (hepatocellular carcinoma, n = 79; cavernous hemangioma, n = 51; metastatic tumor, n = 30) were then retrospectively reviewed. Peak aortic enhancement occurred between 10 and 28 seconds (mean, 16.5 seconds +/- 3.1) after starting the infusion of contrast material in 80 patients during the test-examination. Depending on the findings of intrahepatic vascular enhancement on the full-scale dynamic images, hepatic arterial phase (n = 11, 14%) or sinusoid phase (n = 65, 81%) imaging was obtained during the first gadolinium-enhanced acquisition in 76 (95%) of 80 patients. Three different lesions were well characterized and easily distinguished from each other (p < .0001) on the first-phase images depending on their enhancement pattern. In the majority of patients, timing examination with test-bolus injection was helpful in obtaining qualified images for the characterization of various focal lesions.

Advances in imaging techniques for the diagnosis of focal hepatic lesions.

In the past few years, tremendous advances have been made in the fields of ultrasound, computed tomography, magnetic resonance imaging and contrast agent development. The purpose of this article is to highlight the important developments in imaging techniques that can be used for detection and characterization of focal hepatic lesions.

MRI with superparamagnetic iron oxide: efficacy in the detection and characterization of focal hepatic lesions

The purpose of this study was to evaluate the potential of superparamagnetic iron oxide particles (SPIO) as tissue specific contrast agent in magnetic resonance (MR) imaging in detection and characterization of focal hepatic lesions. We investigated 45 patients with focal hepatic lesions. T 1-weighted SE (TR 650/TE 15 ms) and T 2-weighted SE (TR 2015–2030/TE 45 and 90 ms) unenhanced images were obtained. After SPIO application we performed T 1-weighted images with and T 2-weighted images with and without fat suppression using the same image parameters. Liver signal intensity decreased by 74% (min 47%, max 83%) on T 2-weighted images after application of the contrast agent. Benign lesions (FNH, adenoma) showed an average signal drop of 40% (min 20%, max 47%) whereas malignant lesions showed no significant change of signal intensity on post-contrast images. The mean tumor-to-liver contrast-to-noise ratio (C/N) was improved in all post-contrast sequences irrespective of the lesion type. An additional increase of tumor-to-liver contrast by use of fat suppression technique could be established in the slightly T 2-weighted sequence (TE 45 ms). In metastases, divided in different size groups, we could determine a significant size relation of tumor-to-liver C/N. After SPIO application the number of detected lesions increased distinctly, especially small foci are more easily demonstrated. SPIO particles are a efficacious contrast agent for MR examinations of the liver. For tumor characterization T 1- and T 2-weighted pre- and post-contrast images are necessary. The T 1-weighted sequences are helpful to differentiate benign lesions such as cysts and hemangiomas from malignant lesions. Detection and differential diagnoses of hepatic lesions are improved by use of the SPIO-particles.

A retrospective analysis of the accuracy of T2-weighted images and dynamic gadolinium-enhanced sequences in the detection and characterization of focal hepatic lesions.

The aim of this study was to determine the relative ability of T2-weighted and dynamic gadolinium-enhanced T1-weighted gradient-echo sequences to detect and characterize focal hepatic lesions. We retrospectively studied 37 patients with proven focal hepatic lesions using the following sequences: a T1-weighted spin-echo sequence (T1), a T2-weighted sequence (T2), and a series of breath-hold dynamic gadolinium-enhanced T1-weighted gradient-echo sequences (Gd). Two observers were asked to determine retrospectively the number and type of focal hepatic lesions present using images from three combinations of sequences (T1+T2, T1+Gd, T1+T2+Gd). Proof of the number and diagnosis of focal lesions in each patient was established using a consensus read. Both readers detected more focal lesions when both the T2-weighted sequences and the gadolinium-enhanced sequences were available than on either sequence alone, although this improvement reached statistical significance (P<0.05) only for one of the readers. There was no significant difference (P<0.05) in the ability to characterize lesions between any of the sets of sequences. The combination of dynamic gadolinium-enhanced images and T2-weighted images was shown to assess focal hepatic lesions better than either of these sequences alone.

Diffusion-weighted MR imaging with a single-shot echoplanar sequence: detection and characterization of focal hepatic lesions.

The purpose of this study was to determine the usefulness of diffusion-weighted MR imaging with single-shot echoplanar imaging in characterizing focal hepatic lesions by apparent diffusion coefficient (ADC) and contrast-to-noise ratio (CNR) measurements. Diffusion-weighted imaging on a 1.5-T MR unit was performed in 46 patients with 74 known focal hepatic lesions (11 hemangiomas, 15 metastases, and 48 hepatocellular carcinomas [HCCs]). Mean values for ADCs and CNRs of all lesions were calculated. Mean values for CNRs with diffusion-weighted imaging were also compared with those for breath-hold T2-weighted fast spin-echo images. The mean values for ADCs were different for each type of tumor (5.39 x 10(-3) mm2/sec +/- 1.23 in hemangiomas, 2.85 x 10(-3) mm2/sec +/- 0.59 in metastases, and 3.84 x 10(-3) mm2/sec +/- 0.92 in HCCs), and each of them was significantly greater than the mean values for ADCs of the normal liver (2.28 x 10(-3) mm2/sec +/- 1.23 in normal liver [p < .05] except metastasis versus normal liver [p < .1]). Also, the mean values for ADCs were based on differences of ADC values. Only four (6%) of 63 malignant tumors (three HCCs and one metastasis) could not be differentiated from hemangiomas. The mean value for CNRs with diffusion-weighted images (14.4 +/- 8.54 in HCC and 29.0 +/- 6.79 in metastasis) was significantly higher than the mean values for CNRs obtained with T2-weighted fast spin-echo images in both metastases and HCCs (p < .05), whereas no significant difference was seen for hemangiomas. Mean values for ADCs differed for the three types of the hepatic lesions and were higher than ADCs of the normal liver. We suggest that diffusion-weighted imaging may be useful for increased detection of HCCs and metastases and in distinguishing these entities from hemangiomas.

Contrast agents for MR imaging of the liver: a clinical overview.

Different contrast agents have been clinically used in MR imaging of the liver including extracellular gadolinium chelates, contrast agents targeted to the macrophage-monocytic phagocytic system (MMPS), hepatobiliary contrast agents, and blood-pool contrast agents. Extracellular gadolinium chelates are optimally used for characterization of focal hepatic lesions, whereas hepatobiliary and MMPS-targeted contrast agents are optimally used for detection and preoperative evaluation. The present review portrays these contrast agents and discusses their advantages and shortcomings.

Iodized-oil retention within hepatic hemangioma: characteristics on iodized-oil CT.

The purpose of this study was to describe the characteristic computed tomographic (CT) appearance of iodized-oil retention in hepatic hemangioma and to evaluate the duration of the retention of iodized oil on follow-up CT. Seventeen hepatic hemangiomas of 14 patients were studied with CT performed 1-3 weeks after injection of 2-9 ml of iodized oil (iodized-oil CT) for the characterization of focal hepatic lesions, which needed differential diagnosis with hepatocellular carcinoma in 10 patients, for therapy in two patients, and for chemoembolization therapy of accompanying hepatocellular carcinomas in two. Twelve patients had 1-7 follow-up CT scans within an interval of 1-38 months. In all cases, iodized-oil CT showed iodized-oil retention within the tumor, regardless of tumor size, shape, location, and amount of injected iodized oil. The distribution was incomplete and predominantly peripheral in all cases. Central retention was also seen in seven cases, in which a relatively large amount of iodized oil was injected, but retention of iodized oil in the tumor was incomplete even in two cases in which a large amount of iodized oil was injected to relieve symptoms and in three cases in which prominent uptake of surrounding liver parenchyma was seen. Patterns of retention were predominantly spotty in five, predominantly nodular in four, and mixed in eight patients. Retention materials slowly washed out but persisted for at least 3 months and up to 38 months (mean = 18.1 months), and complete washout was not seen in any cases at follow-up CT. In all cases of hepatic hemangiomas, iodized oil was retained, and retention persisted over several months. Distribution and patterns of retention were characteristically peripheral, spotty, and nodular at iodized-oil CT. Knowledge of the iodized-oil CT appearance of hepatic hemangioma would be helpful to interpret follow-up CT studies of patients who have undergone iodized-oil chemoembolization procedures.

Blood-pool MR contrast material for detection and characterization of focal hepatic lesions: initial clinical experience with ultrasmall superparamagnetic iron oxide (AMI-227).

AMI-227 is an ultrasmall superparamagnetic iron oxide colloid known to enhance tissue T1 and T2 relaxation rates. Animal studies show that AMI-227 has an estimated blood half-life of more than 200 min. In this study, we evaluated the clinical utility of AMI-227 as an MR contrast agent for detection and characterization of focal hepatic lesions, with MR imaging done while the contrast agent is in the intravascular space (blood-pool phase). Twenty-two patients with known or suspected focal hepatic masses underwent T1- and T2-weighted MR imaging of the liver at 1.5 T before and immediately after drip infusion of AMI-227 at doses of 0.8, 1.1, or 1.7 mg Fe/kg. Unenhanced and contrast-enhanced images were analyzed qualitatively (lesion detection and tissue characterization) and quantitatively (lesion-liver contrast-to-noise ratio). AMI-227 enhanced signal in normal liver and blood vessels on T1-weighted images and decreased signal in these tissues on T2-weighted images. Qualitatively and quantitatively, lesion-liver contrast was increased for solid tumors (non-cyst and nonhemangioma) at all three doses (p < .02) on both T1- and T2-weighted images. Differentiation between blood vessels and small lesions was easier on contrast-enhanced images, which allowed increased confidence in excluding lesions. Unique enhancement patterns were noted for hemangiomas, solid tumors, and cysts. Initial clinical experience suggests that AMI-227 is a useful contrast agent for detection and characterization of focal hepatic lesions.

Characterization of focal hepatic lesions with duplex sonography: findings in 198 patients.

The purpose of this study was to determine the value of duplex Doppler sonography in the characterization of focal hepatic lesions. Duplex Doppler sonography with a 3-MHz transducer was performed prospectively on 198 patients with focal hepatic lesions. One hundred thirty-two patients had pathologically proved diagnoses, confirming 46 hepatomas and 86 metastatic lesions. Twenty-three hemangiomas were confirmed either with tissue, tagged RBC study, MR imaging, or hemangioma CT protocol. Forty-three patients with no history of cancer had benign lesions that were established on the basis of follow-up imaging and at least a 2-year clinical history with no evidence of cancer. Thirty-two hepatomas and four metastatic lesions had Doppler shifts of 4.5 kHz or more, giving a 70% sensitivity, 95% specificity, and 89% positive predictive value in distinguishing hepatomas from metastatic lesions. Forty-three hepatomas, 47 metastatic lesions, one hemangioma, and three benign lesions had Doppler shifts of 1.75 kHz or more, giving a 68% sensitivity, 94% specificity, and 96% positive predictive value in distinguishing malignant from benign lesions. Doppler shifts (mean +/- SD) were as follows: hepatomas, 4.72 +/- 1.72 kHz; metastases, 1.99 +/- 1.63 kHz; and hemangiomas, 0.53 +/- 0.75 kHz. These differences in mean Doppler shifts were statistically significant (p < .0001). Duplex Doppler sonography aids in distinguishing hepatomas from metastases and malignant from benign hepatic lesions with a high degree of specificity but low sensitivity.

Value of T1 and T2 relaxation times from echoplanar MR imaging in the characterization of focal hepatic lesions.

The purpose of this study was to determine the value of echoplanar imaging in characterizing focal hepatic lesions on the basis of image-derived T1 and T2 relaxation times. Forty-six proven hepatic lesions were analyzed: 24 solid (21 metastases, three primary liver tumors) and 22 nonsolid (11 hemangiomas and 11 cysts). Mean lesion size (maximal length) was 4.0 (+/- 3.2) cm, and 16 of 46 lesions were less than 2.0 cm. A commercially available 1.5-T echoplanar-equipped MR scanner was used to obtain fat-suppressed, single-excitation (TR essentially infinite) axial images with a slice thickness of 10 mm. T1-weighted inversion recovery images (TE = 25 msec; TI = 100, 380, 600, or 800 msec) were acquired for 28 of 46 lesions, and T2-weighted spin-echo images (TE = 25, 50, 100, 75 or 150 msec) were acquired for 45 of 46 lesions. For each acquisition (i.e., each different TI or TE), the entire liver was imaged in a single breath-hold of 12 sec or less. The mean T1 was 1004 (+/- 234) msec for solid lesions, 1337 (+/- 216) msec for hemangiomas, and 3143 (+/- 1392) msec for cysts. Although the mean T1 of solid and nonsolid lesions differed (p < .004), overlap precluded the use of T1 as a discriminatory index. Mean T2 times were 80 (+/- 18) msec for solid lesions, 178 (+/- 40) msec for hemangiomas, and 517 (+/- 429) msec for cysts. The mean T2 for hemangiomas is the longest reported to date. A T2 cutoff of 116 msec was 100% accurate for classifying lesions as solid or nonsolid and 93% accurate for characterizing them as benign or malignant. Our study suggests that echoplanar-derived T2 times (but not T1 times) are useful for characterizing focal hepatic lesions. An important use may be to characterize small lesions measuring less than 2.0 cm. The main advantages of echoplanar imaging are the absence of motion-induced volume averaging and phase artifacts, the ability to acquire purely T2-weighted images, and the use of multiple data points to calculate relaxation times.

Color flow Doppler characterization of focal hepatic lesions.

The purpose of this study was to determine the sensitivity and specificity of color flow Doppler sonography for the specific diagnosis of focal hepatic lesions. Color flow Doppler images of 118 focal hepatic lesions in 108 patients were analyzed prospectively. In most patients, liver disease was suspected or known to be present before the Doppler images were obtained. Experienced sonologists obtained and interpreted all sonograms. The lesions were classified, according to their color flow pattern, into two main categories: lesions with internal vascularity and lesions with no internal vascularity. The color flow Doppler pattern of each lesion was correlated with the diagnosis of the lesion on a lesion-by-lesion basis. One hundred two lesions were proved by biopsy and 16 lesions were confirmed by evaluation with other imaging techniques. Lesions included 29 hepatocellular carcinomas, 64 metastases, one cholangiocarcinoma, and 24 benign lesions. The sensitivity and specificity of vascularity as shown by color Doppler imaging in the diagnosis of hepatocellular carcinoma were determined. The majority of hepatocellular carcinoma lesions (76%) had internal vascularity. Most of the metastases (67%) and benign lesions (75%) had no internal vascularity. When the presence of internal vascularity was used as the discriminating criterion, the sensitivity of color flow Doppler findings for the diagnosis of hepatocellular carcinoma was 0.76. The specificity of internal vascularity for the diagnosis of hepatocellular carcinoma vs other focal lesions was 0.69; for hepatocellular carcinoma vs metastases it was 0.67. Although most hepatocellular carcinomas have internal vascularity on color flow Doppler images, a significant number of metastases also have internal vascularity. This overlap limits the usefulness of color flow Doppler imaging for distinguishing hepatocellular carcinoma from metastatic tumors.

MR Characterization of Hepatic Lesions by t-Null Inversion Recovery Sequence

Tissue characterization of focal hepatic lesions was performed employing an inversion recovery sequence with short repetition time and short inversion time (TI) values. Different and specific TI values, correlated to the in vivo measured T1 relaxation times, were used to null the signal intensity of each type of lesion. In 40 patients studied, we observed the nulling effect of normal liver in 10 of 10 cases with a TI of 136 ms, of metastases in 7 of 8 cases with a TI of 175 ms, of hemangiomas in 15 of 16 cases with a TI of 200 ms, and of cysts in 6 of 7 cases with a TI of 235 ms. A quantitative analysis of the nulled signal was performed by measuring the signal/noise values. A further qualitative and quantitative characterization was carried out by evaluating the signal intensity of hepatic lesions at the null point of normal liver. The method provided the possibility of discriminating different focal lesions with specificity values of 83-94%, according to the type of lesion.