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Contrast-enhanced US (CEUS) has an important role as a supplement to CT or MRI in clinical practice. The main established utilizations are in the liver and the kidney. The primary advantages of CEUS compared with contrast-enhanced CT or MRI relate to its superior contrast resolution, real-time continuous scanning, pure intravascular nature, portability, and safety-especially in patients with renal impairment or CT or MRI contrast agent allergy. This article focuses on the use of CEUS in the liver and kidney.

Accurate characterization of cirrhotic nodules and early diagnosis of hepatocellular carcinoma (HCC) are of vital importance. Currently, computed tomography (CT) and magnetic resonance (MR) imaging are standard modalities for the investigation of new nodules found at surveillance ultrasonography (US). This article describes the successful integration of contrast material-enhanced US into a multimodality approach for diagnosis of HCC and its benefits in this population. The application of contrast-enhanced US immediately following surveillance US allows for prompt dynamic contrast-enhanced evaluation, removing the need for further imaging of benign lesions. Contrast-enhanced US also provides dynamic real-time assessment of tumor vascularity so that contrast enhancement can be identified regardless of its timing or duration, allowing for detection of arterial hypervascularity and portal venous washout. The purely intravascular nature of US contrast agents is valuable as the rapid washout of nonhepatocyte malignancies is highly contributory to their differentiation from HCC. The authors believe contrast-enhanced US provides complementary information to CT and MR imaging in the characterization of nodules in high-risk patients.

To compare the low-contrast detectability and image quality of computed tomography (CT) at different radiation dose levels reconstructed with iterative reconstruction (IR) and filtered back projection (FBP).A custom liver phantom with 12 simulated hypoattenuating tumors (diameters of 5, 10, 15, and 20 mm; tumor-to-liver contrast values of -10, -20, and -40 HU) was designed. The phantom was scanned with a standard abdominal CT protocol with a volume CT dose index of 21.6 mGy (equivalent 100% dose) and four low-dose protocols (20%, 40%, 60%, and 80% of the standard protocol dose). CT data sets were reconstructed with IR and FBP. Image noise was measured, and the tumors' contrast-to-noise ratios (CNRs) were calculated. Tumor detection was independently assessed by three radiologists who were blinded to the CT technique used. A total of 840 simulated tumors were presented to the radiologists. Statistical analyses included analysis of variance.IR yielded an image noise reduction of 43.9%-63.9% and a CNR increase of 74.1%-180% compared with FBP at the same dose level (P.001). The overall sensitivity for tumor detection was 64.7%-85.3% for IR and 66.3%-85.7% for FBP at the 20%-100% doses, respectively. There was no significant difference in the sensitivity for tumor detection between IR and FBP at the same dose level (P = .99). The sensitivity of the protocol at the 20% dose with FBP and IR was significantly lower than that of the protocol at the 100% dose with FBP and IR (P = .019).As the radiation dose at CT decreases, the IR algorithm does not preserve the low-contrast detectability.http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122349/-/DC1.

To retrospectively compare the arterial and portal venous phase enhancement patterns of hepatocellular carcinoma (HCC) at contrast material-enhanced ultrasonography (US) with the degree of HCC histologic differentiation.This study was approved by the research ethics board, and informed consent was obtained. The study population included 112 consecutive patients (91 men, 21 women; aged 25-86 years) with 112 histologically proved HCCs: 23 well differentiated, 77 moderately differentiated, and 12 poorly differentiated. All underwent continuous real-time low-mechanical-index contrast-enhanced US from wash-in of contrast material to 300 seconds by using a blood-pool microbubble agent. Initial image interpretation included arterial enhancement, dysmorphic intratumor arteries, and presence and time of negative enhancement (washout). Enhancement patterns were compared with histologic differentiation by using the Fisher exact test.In the arterial phase, 97 of 112 (87%) HCCs showed hypervascularity, with a significantly higher proportion in moderately differentiated HCCs (74 of 77, 96%) when compared with well- (14 of 23, 61%; P.001) and poorly differentiated HCC (nine of 12, 75%; P.004). Eight of 112 (7%) were isovascular and seven (6%) were hypovascular. Dysmorphic arteries were seen in 81 (72%) HCCs. Of 97 hypervascular tumors, only 42 (43%) showed typical washout by 90 seconds. Late washout appeared in 25 (26%) HCCs in the 91-180 seconds phase and in 21 (22%) in the 181-300 seconds phase. The remaining nine showed no washout up to 300 seconds and seven (78%) were well-differentiated HCCs.Moderately differentiated HCC generally shows classic enhancement features, while well- and poorly differentiated tumors account for most atypical variations. Extended observation in the portal phase is important as late washout occurs with slightly more frequency than washout in the conventionally defined portal venous phase.

To determine the importance of the finding of segmental wall thickening in the colonic loop distal to colonic carcinoma at computed tomography (CT) by means of histopathologic correlation.Thirteen consecutive patients whose helical CT scans showed segmental wall thickening (1 cm in maximal width,5 cm in length) in the colonic loop distal to colonic carcinoma were included. The thickness and length of an involved segment, location, morphologic tumor type, CT patterns of wall thickening, and pericolic changes were evaluated. Surgical pathologic findings in all 13 patients were correlated with CT findings.The involved segment distal to the colonic carcinoma showed circumferential wall thickening with a preserved wall layer pattern at CT. Pericolic changes of varying degrees were seen in 10 patients. Histopathologic examination revealed submucosal and subserosal edema (n = 6), chronic inflammation and fibrosis (n = 5), or both (n = 1), and no histopathologic alteration (n = 1). The tumors were mostly fungating (n = 11), larger than 5 cm in the greatest dimension (n = 12), located in the ascending colon (n = 10), and extended to pericolic adipose tissue (n = 11).Colonic carcinoma, especially a large fungating type involving the ascending colon with pericolic infiltration, can produce segmental wall thickening in the distal segment at CT, which represents edema or colitis at histopathologic examination.

To determine if a tiny enhancing dot is characteristic of small hemangiomas with low attenuation during the hepatic arterial phase (HAP) and portal venous phase (PVP) of two-phase spiral computed tomography (CT).Among 249 consecutive patients with 377 hemangiomas who underwent two-phase spiral CT (performed 30 and 65 seconds after the start of injection), 34 hemangiomas in 20 patients were less than 2 cm in diameter, had low attenuation during the HAP and PVP, and showed characteristic findings on dynamic contrast material-enhanced magnetic resonance (MR) images. The CT scans were retrospectively reviewed for tiny enhancing dots and correlated with the MR images.Tiny enhancing dots were found in 26 of 34 hemangiomas (76%). The dots were seen during the HAP and PVP in 15 lesions (58%) and during the PVP alone in 11 lesions (42%). The lesions showed a tendency toward slow fill-in at MR imaging (only four lesions completely filled with contrast material within 5 minutes). The dots seen at CT corresponded to the initial enhancing area at MR imaging.Small hemangiomas with persistent low attenuation at two-phase spiral CT can be diagnosed with the "bright dot" sign.

To determine characteristic features of peripheral cholangiocarcinoma on two-phase spiral computed tomographic (CT) scans.Thirty-four patients with peripheral cholangiocarcinoma underwent two-phase spiral CT. Hepatic arterial phase and portal venous phase images were obtained 30 and 65 seconds, respectively, after the start of contrast material infusion.Thin, mild, incomplete rimlike contrast enhancement at the tumor periphery was seen on CT scans from both phases in 23 patients. Thick, continuous rimlike contrast enhancement and marked homogeneous contrast enhancement were present on scans in four patients and one patient, respectively. No definite contrast enhancement pattern was seen on scans in six patients. Other findings included increased lobar or segmental hepatic attenuation in adjacent normal liver during the arterial phase (n = 10), markedly low attenuation with amorphous areas of slightly high attenuation in the tumor during both phases (n = 33), internal septumlike linear structures (n = 8), narrowing or obstruction of the portal vein as it traversed the tumor (n = 16), and a patent hepatic vein (n = 4).Thin, mild, incomplete rimlike contrast enhancement at the tumor periphery and markedly low intratumoral attenuation with amorphous areas of slightly high attenuation during both scanning phases are typical findings of peripheral cholangiocarcinoma.

To assess an early thin-section computed tomographic (CT) finding of the localized formation of bronchioloalveolar carcinoma (BAC).From October 1994 to September 1995, four consecutive patients with biopsy-proved BAC were studied. Thin-section CT (n=4), radiographic (n=4), pathologic (n=4), and positron emission tomographic (n=2) findings were analyzed.Chest radiographs showed focal areas of poorly defined nodules (n=2) and poorly defined opacity (n=2). At thin-section CT, lesions appeared as isolated areas of ground-glass attenuation (n=2) and mixed areas of ground-glass attenuation and consolidation (n=2). The areas of ground-glass attenuation were 1.8-11 cm in longest diameter. A focal, isolated area of ground-glass attenuation changed into mixed areas with consolidation at serial CT in one patient. Mucinous and nonmucinous BACs were observed in two patients each. Positron emission tomography showed false-negative results for malignancy.Focal areas of ground-glass attenuation at CT could be an early sign of localized BAC.

To retrospectively identify magnetic resonance (MR) imaging findings that are associated with hepatocellular carcinoma (HCC) in 1-2-cm nodules detected at surveillance ultrasonography (US) and to propose newer MR imaging diagnostic criteria.Institutional research ethics board approval was obtained, and informed patient consent was waived. Among 145 consecutive patients who had 1-2-cm nodules that were newly detected at surveillance US, 108 patients underwent gadobenate dimeglumine-enhanced MR imaging. After excluding hemangiomas and unconfirmed nodules, the study sample comprised 96 patients with 116 nodules, including 43 HCCs and 73 benign nodules. MR imaging findings were assessed for signal intensity at each sequence. On the basis of the results of univariate and multivariable logistic regression analyses, several diagnostic criteria were developed by using combinations of MR imaging findings, which were then compared with the American Association for the Study of Liver Diseases (AASLD) practice guideline.Univariate analysis revealed four imaging findings associated with HCC, including arterial phase hyperintensity, portal or delayed phase hypointensity (washout), hyperintensity on T2-weighted images, and hepatobiliary phase hypointensity (P.001 for each). In the multivariable analysis, arterial phase hyperintensity (adjusted odds ratio [OR], 17.1; P = .003) and washout (adjusted OR, 11.7; P = .007) were associated with HCC. Of the developed criteria, the criteria including nodules fitting the AASLD practice guideline (arterial phase hyperintensity and washout) or nodules having three or more findings were considered most reasonable, showing improved sensitivity (77% [33 of 43] versus 67% [29 of 43], P = .048) and comparable specificity (95% [69 of 73] versus 99% [72 of 73], P = .09), as compared with AASLD practice guideline.Alternative MR imaging criteria for diagnosing HCC in 1-2-cm nodules detected at surveillance US that can improve sensitivity compared with the AASLD practice guideline were proposed. A larger study is needed to verify the preliminary criteria in this study.http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101549/-/DC1.

To evaluate the usefulness of power Doppler ultrasonography (US) with a microbubble contrast agent in assessing the therapeutic response of hepatocellular carcinomas (HCCs) treated with percutaneous radio-frequency (RF) ablation.Forty patients with 45 nodular HCC lesions 1.0-3.8 cm in diameter underwent power Doppler US before and after intravenous injection of a microbubble contrast agent. The same procedures were repeated after US-guided percutaneous RF ablation. The results of these studies were compared with those of three-phase helical computed tomography (CT) performed immediately after RF ablation.Before RF ablation, nonenhanced power Doppler US demonstrated flow signals within tumor in 33 of 45 HCCs. After contrast agent administration, flow signals increased or newly appeared in all cases. After RF ablation, none of the ablated tumors showed intratumoral flow signals at nonenhanced power Doppler US, whereas six showed marginal intratumoral flow signals at contrast agent-enhanced power Doppler US. These six tumors were found to have small enhancing foci, suggestive of viable tumor, in corresponding areas at immediate follow-up CT. Additional RF ablation or transcatheter arterial chemoembolization was performed in these tumors.The results of power Doppler US with a microbubble contrast agent in HCCs treated with RF ablation correlated well with those of contrast-enhanced CT. Preliminary data suggest that contrast-enhanced power Doppler US can be a promising noninvasive technique for assessing therapeutic response.