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Blood Flow Patterns in Focal Liver Lesions at Microbubble-enhanced US¹

¹ From the Department of Medical Imaging, University of Toronto, Toronto General Hospital, University Health Network, 585 University Ave, Toronto, Ontario, Canada M5G 2N2 (M.B., S.R.W.); and the Department of Medical Biophysics, University of Toronto, Imaging Research, Sunnybrook and Women’s College Health Sciences Centre, Toronto, Ontario, Canada (P.N.B.). Presented as an education exhibit at the 2002 RSNA    scientific assembly. Received July 1, 2003; revision requested July 30 and received September 24; accepted October 28. Supported by grants from   the Canadian Institutes of Health Research and the Terry Fox Program of the National Cancer Institute of Canada. Clinical studies were also supported by Bristol-Myers Squibb Medical Imaging, Berlex Canada, and Mallinckrodt Medical Inc. Address correspondence to S.R.W. (e-mail: stephanie.wilson@uhn.on.ca).

View larger version (157K): [in a new window]   Figure 1a.  Focal liver mass: characterization with microbubble contrast material. (a) Baseline conventional US image obtained with a high mechanical index (MI) of 1.2 (the MI is the ratio of the peak rarefactional pressure to the square root of the frequency and is related to the tendency of the sound to induce bubble motion [1]) shows a large, highly echogenic focal mass with a hypoechoic rim. The echogenicity of the lesion is related to its tissue properties. (b) Pulse inversion US image (MI = 0.1) shows suppression of the tissue echoes. The entire image now appears black. (c) On an arterial phase US image obtained moments after a small (0.1-mL) bolus injection of a suspension of microbubbles into a peripheral vein, the lesion enhances far more than the adjacent liver, a finding that is consistent with a hypervascular mass. The microbubbles within the vasculature now account for the echogenicity of the lesion. (d) Portal venous phase US image shows enhancement of the liver parenchyma. The lesion is less echogenic than the liver (ie, has "washed out"), a finding that is consistent with a hypervascular malignancy. Hepatocellular carcinoma (HCC) was confirmed at biopsy.

View larger version (137K): [in a new window]   Figure 1b.  Focal liver mass: characterization with microbubble contrast material. (a) Baseline conventional US image obtained with a high mechanical index (MI) of 1.2 (the MI is the ratio of the peak rarefactional pressure to the square root of the frequency and is related to the tendency of the sound to induce bubble motion [1]) shows a large, highly echogenic focal mass with a hypoechoic rim. The echogenicity of the lesion is related to its tissue properties. (b) Pulse inversion US image (MI = 0.1) shows suppression of the tissue echoes. The entire image now appears black. (c) On an arterial phase US image obtained moments after a small (0.1-mL) bolus injection of a suspension of microbubbles into a peripheral vein, the lesion enhances far more than the adjacent liver, a finding that is consistent with a hypervascular mass. The microbubbles within the vasculature now account for the echogenicity of the lesion. (d) Portal venous phase US image shows enhancement of the liver parenchyma. The lesion is less echogenic than the liver (ie, has "washed out"), a finding that is consistent with a hypervascular malignancy. Hepatocellular carcinoma (HCC) was confirmed at biopsy.

View larger version (173K): [in a new window]   Figure 1c.  Focal liver mass: characterization with microbubble contrast material. (a) Baseline conventional US image obtained with a high mechanical index (MI) of 1.2 (the MI is the ratio of the peak rarefactional pressure to the square root of the frequency and is related to the tendency of the sound to induce bubble motion [1]) shows a large, highly echogenic focal mass with a hypoechoic rim. The echogenicity of the lesion is related to its tissue properties. (b) Pulse inversion US image (MI = 0.1) shows suppression of the tissue echoes. The entire image now appears black. (c) On an arterial phase US image obtained moments after a small (0.1-mL) bolus injection of a suspension of microbubbles into a peripheral vein, the lesion enhances far more than the adjacent liver, a finding that is consistent with a hypervascular mass. The microbubbles within the vasculature now account for the echogenicity of the lesion. (d) Portal venous phase US image shows enhancement of the liver parenchyma. The lesion is less echogenic than the liver (ie, has "washed out"), a finding that is consistent with a hypervascular malignancy. Hepatocellular carcinoma (HCC) was confirmed at biopsy.

View larger version (154K): [in a new window]   Figure 1d.  Focal liver mass: characterization with microbubble contrast material. (a) Baseline conventional US image obtained with a high mechanical index (MI) of 1.2 (the MI is the ratio of the peak rarefactional pressure to the square root of the frequency and is related to the tendency of the sound to induce bubble motion [1]) shows a large, highly echogenic focal mass with a hypoechoic rim. The echogenicity of the lesion is related to its tissue properties. (b) Pulse inversion US image (MI = 0.1) shows suppression of the tissue echoes. The entire image now appears black. (c) On an arterial phase US image obtained moments after a small (0.1-mL) bolus injection of a suspension of microbubbles into a peripheral vein, the lesion enhances far more than the adjacent liver, a finding that is consistent with a hypervascular mass. The microbubbles within the vasculature now account for the echogenicity of the lesion. (d) Portal venous phase US image shows enhancement of the liver parenchyma. The lesion is less echogenic than the liver (ie, has "washed out"), a finding that is consistent with a hypervascular malignancy. Hepatocellular carcinoma (HCC) was confirmed at biopsy.

View larger version (25K): [in a new window]   Figure 2.  Graph illustrates microbubble behavior in an acoustic field. Bubbles respond asymmetrically to high-intensity sound waves, stiffening when compressed and yielding when expanded, a nonlinear response that produces harmonics in the scattered wave. (Reprinted, with permission, from reference 4.)

View larger version (29K): [in a new window]   Figure 3.  Graphs illustrate the principle of pulse inversion. A pulse of sound is transmitted into the body, and echoes are received from the contrast agent and tissue. A second pulse, an inverted version of the first, is then transmitted in the same direction, and the two echoes are summed. Linear echoes from tissue cancel each other. Nonlinear components of the microbubble echoes are reinforced when summed, producing a strong harmonic signal. (Reprinted, with permission, from reference 4.)

View larger version (191K): [in a new window]   Figure 4a.  Discriminatory features of vessel morphology. (a) Arterial phase image obtained with galactose-palmitic acid shows FNH with classic stellate vascularity. (Reprinted, with permission, from reference 10.) (b, c) Arterial phase images show HCC with heterogeneous dysmorphic vessels (b) and hemangioma with peripheral puddles and pools of contrast material (c). All three images were obtained with continuous low-MI pulse inversion; none shows linear lesion vessels.

View larger version (151K): [in a new window]   Figure 4b.  Discriminatory features of vessel morphology. (a) Arterial phase image obtained with galactose-palmitic acid shows FNH with classic stellate vascularity. (Reprinted, with permission, from reference 10.) (b, c) Arterial phase images show HCC with heterogeneous dysmorphic vessels (b) and hemangioma with peripheral puddles and pools of contrast material (c). All three images were obtained with continuous low-MI pulse inversion; none shows linear lesion vessels.

View larger version (197K): [in a new window]   Figure 4c.  Discriminatory features of vessel morphology. (a) Arterial phase image obtained with galactose-palmitic acid shows FNH with classic stellate vascularity. (Reprinted, with permission, from reference 10.) (b, c) Arterial phase images show HCC with heterogeneous dysmorphic vessels (b) and hemangioma with peripheral puddles and pools of contrast material (c). All three images were obtained with continuous low-MI pulse inversion; none shows linear lesion vessels.

View larger version (150K): [in a new window]   Figure 5a.  Arterial phase enhancement. Assessments are made by comparing the echogenicity of the lesion with that of the adjacent liver during the arterial phase. (a, b) Baseline conventional US image (a) and corresponding arterial phase US image (b) demonstrate FNH as a hypervascular mass. (c, d) Baseline conventional US image (c) and corresponding arterial phase US image (d) obtained in a different patient show hypovascular masses from metastatic colon cancer. In both cases, the lesions are very subtle on the baseline images, whereas the contrast-enhanced images show the lesions clearly.

View larger version (126K): [in a new window]   Figure 5b.  Arterial phase enhancement. Assessments are made by comparing the echogenicity of the lesion with that of the adjacent liver during the arterial phase. (a, b) Baseline conventional US image (a) and corresponding arterial phase US image (b) demonstrate FNH as a hypervascular mass. (c, d) Baseline conventional US image (c) and corresponding arterial phase US image (d) obtained in a different patient show hypovascular masses from metastatic colon cancer. In both cases, the lesions are very subtle on the baseline images, whereas the contrast-enhanced images show the lesions clearly.

View larger version (148K): [in a new window]   Figure 5c.  Arterial phase enhancement. Assessments are made by comparing the echogenicity of the lesion with that of the adjacent liver during the arterial phase. (a, b) Baseline conventional US image (a) and corresponding arterial phase US image (b) demonstrate FNH as a hypervascular mass. (c, d) Baseline conventional US image (c) and corresponding arterial phase US image (d) obtained in a different patient show hypovascular masses from metastatic colon cancer. In both cases, the lesions are very subtle on the baseline images, whereas the contrast-enhanced images show the lesions clearly.

View larger version (125K): [in a new window]   Figure 5d.  Arterial phase enhancement. Assessments are made by comparing the echogenicity of the lesion with that of the adjacent liver during the arterial phase. (a, b) Baseline conventional US image (a) and corresponding arterial phase US image (b) demonstrate FNH as a hypervascular mass. (c, d) Baseline conventional US image (c) and corresponding arterial phase US image (d) obtained in a different patient show hypovascular masses from metastatic colon cancer. In both cases, the lesions are very subtle on the baseline images, whereas the contrast-enhanced images show the lesions clearly.

View larger version (149K): [in a new window]   Figure 6a.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (169K): [in a new window]   Figure 6b.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (140K): [in a new window]   Figure 6c.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (151K): [in a new window]   Figure 6d.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (135K): [in a new window]   Figure 6e.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (150K): [in a new window]   Figure 6f.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (167K): [in a new window]   Figure 6g.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (159K): [in a new window]   Figure 6h.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (150K): [in a new window]   Figure 6i.  Portal venous phase enhancement. (a-c) Baseline conventional US image (a), arterial phase image (b), and portal venous phase image (c) show HCC as a hypervascular mass with washout during the portal venous phase. (d-f) Baseline conventional US image (d), arterial phase image (e), and portal venous phase image (f) obtained in a different patient show FNH as a hypervascular mass, with "sustained enhancement" during the portal venous phase. (g-i) Baseline conventional US image (g), arterial phase image (h), and portal venous phase image (i) obtained in a third patient show hemangioma with peripheral nodular enhancement during the arterial phase and sustained enhancement during the portal venous phase.

View larger version (145K): [in a new window]   Figure 7a.  HCC. (a) Arterial phase US image shows a lesion whose echogenicity exceeds that of the liver, a finding that is consistent with a hypervascular mass. There is a central nonenhancing area that suggests scar or necrosis. (b) On a portal venous phase US image, the lesion is washed out, appearing less echogenic than the adjacent liver. (c, d) Arterial phase (c) and portal venous phase (d) CT scans show the hypervascular mass with necrosis and with washout on the portal venous phase image.

View larger version (134K): [in a new window]   Figure 7b.  HCC. (a) Arterial phase US image shows a lesion whose echogenicity exceeds that of the liver, a finding that is consistent with a hypervascular mass. There is a central nonenhancing area that suggests scar or necrosis. (b) On a portal venous phase US image, the lesion is washed out, appearing less echogenic than the adjacent liver. (c, d) Arterial phase (c) and portal venous phase (d) CT scans show the hypervascular mass with necrosis and with washout on the portal venous phase image.

View larger version (160K): [in a new window]   Figure 7c.  HCC. (a) Arterial phase US image shows a lesion whose echogenicity exceeds that of the liver, a finding that is consistent with a hypervascular mass. There is a central nonenhancing area that suggests scar or necrosis. (b) On a portal venous phase US image, the lesion is washed out, appearing less echogenic than the adjacent liver. (c, d) Arterial phase (c) and portal venous phase (d) CT scans show the hypervascular mass with necrosis and with washout on the portal venous phase image.

View larger version (161K): [in a new window]   Figure 7d.  HCC. (a) Arterial phase US image shows a lesion whose echogenicity exceeds that of the liver, a finding that is consistent with a hypervascular mass. There is a central nonenhancing area that suggests scar or necrosis. (b) On a portal venous phase US image, the lesion is washed out, appearing less echogenic than the adjacent liver. (c, d) Arterial phase (c) and portal venous phase (d) CT scans show the hypervascular mass with necrosis and with washout on the portal venous phase image.

View larger version (137K): [in a new window]   Figure 8a.  Small HCC. A baseline conventional US image (not shown) revealed a small, subtle, hypoechoic mass. (a) Arterial phase US image shows a hypervascular lesion with avid enhancement. (b) On a portal venous phase US image, the lesion is hypoechoic relative to the enhanced background liver. This washout is strongly suggestive of the malignant nature of the mass.

View larger version (163K): [in a new window]   Figure 8b.  Small HCC. A baseline conventional US image (not shown) revealed a small, subtle, hypoechoic mass. (a) Arterial phase US image shows a hypervascular lesion with avid enhancement. (b) On a portal venous phase US image, the lesion is hypoechoic relative to the enhanced background liver. This washout is strongly suggestive of the malignant nature of the mass.

View larger version (142K): [in a new window]   Figure 9a.  Metastasis from primary carcinoma of the anal canal with rim enhancement. (a, b) Baseline US (a) and CT (b) images show an expansive mass in the left lobe of the liver. (c, d) Arterial phase US (c) and CT (d) images demonstrate the mass with rim enhancement. (e) On a portal venous phase US image, the lesion is completely washed out and appears black. (f) Portal venous phase CT scan shows continued rim enhancement of the tumor, a finding that probably represents interstitial contrast material.

View larger version (138K): [in a new window]   Figure 9b.  Metastasis from primary carcinoma of the anal canal with rim enhancement. (a, b) Baseline US (a) and CT (b) images show an expansive mass in the left lobe of the liver. (c, d) Arterial phase US (c) and CT (d) images demonstrate the mass with rim enhancement. (e) On a portal venous phase US image, the lesion is completely washed out and appears black. (f) Portal venous phase CT scan shows continued rim enhancement of the tumor, a finding that probably represents interstitial contrast material.

View larger version (133K): [in a new window]   Figure 9c.  Metastasis from primary carcinoma of the anal canal with rim enhancement. (a, b) Baseline US (a) and CT (b) images show an expansive mass in the left lobe of the liver. (c, d) Arterial phase US (c) and CT (d) images demonstrate the mass with rim enhancement. (e) On a portal venous phase US image, the lesion is completely washed out and appears black. (f) Portal venous phase CT scan shows continued rim enhancement of the tumor, a finding that probably represents interstitial contrast material.

View larger version (147K): [in a new window]   Figure 9d.  Metastasis from primary carcinoma of the anal canal with rim enhancement. (a, b) Baseline US (a) and CT (b) images show an expansive mass in the left lobe of the liver. (c, d) Arterial phase US (c) and CT (d) images demonstrate the mass with rim enhancement. (e) On a portal venous phase US image, the lesion is completely washed out and appears black. (f) Portal venous phase CT scan shows continued rim enhancement of the tumor, a finding that probably represents interstitial contrast material.

View larger version (120K): [in a new window]   Figure 9e.  Metastasis from primary carcinoma of the anal canal with rim enhancement. (a, b) Baseline US (a) and CT (b) images show an expansive mass in the left lobe of the liver. (c, d) Arterial phase US (c) and CT (d) images demonstrate the mass with rim enhancement. (e) On a portal venous phase US image, the lesion is completely washed out and appears black. (f) Portal venous phase CT scan shows continued rim enhancement of the tumor, a finding that probably represents interstitial contrast material.

View larger version (148K): [in a new window]   Figure 9f.  Metastasis from primary carcinoma of the anal canal with rim enhancement. (a, b) Baseline US (a) and CT (b) images show an expansive mass in the left lobe of the liver. (c, d) Arterial phase US (c) and CT (d) images demonstrate the mass with rim enhancement. (e) On a portal venous phase US image, the lesion is completely washed out and appears black. (f) Portal venous phase CT scan shows continued rim enhancement of the tumor, a finding that probably represents interstitial contrast material.

View larger version (137K): [in a new window]   Figure 10a.  Hypervascular metastases from carcinoid tumor. (a) Baseline US image shows the liver with high fat content and hypoechoic lesions. (b) On an arterial phase US image, the lesions enhance avidly, appearing more echogenic than the adjacent liver. (c) On a portal venous phase US image, the liver remains brightly enhanced, and the lesions have washed out and appear hypoechoic. The patient was allergic to iodinated contrast material. (Fig 10 reprinted, with permission, from reference 8.)

View larger version (145K): [in a new window]   Figure 10b.  Hypervascular metastases from carcinoid tumor. (a) Baseline US image shows the liver with high fat content and hypoechoic lesions. (b) On an arterial phase US image, the lesions enhance avidly, appearing more echogenic than the adjacent liver. (c) On a portal venous phase US image, the liver remains brightly enhanced, and the lesions have washed out and appear hypoechoic. The patient was allergic to iodinated contrast material. (Fig 10 reprinted, with permission, from reference 8.)

View larger version (146K): [in a new window]   Figure 10c.  Hypervascular metastases from carcinoid tumor. (a) Baseline US image shows the liver with high fat content and hypoechoic lesions. (b) On an arterial phase US image, the lesions enhance avidly, appearing more echogenic than the adjacent liver. (c) On a portal venous phase US image, the liver remains brightly enhanced, and the lesions have washed out and appear hypoechoic. The patient was allergic to iodinated contrast material. (Fig 10 reprinted, with permission, from reference 8.)

View larger version (144K): [in a new window]   Figure 11a.  Hemangioma. (a) Baseline conventional US image shows a heterogeneous, bulbous, slightly exophytic lesion that extends from the posterior right lobe. (b) Early arterial phase vascular US image shows no linear vessels. There is peripheral nodular enhancement. (c) Late arterial phase US image shows centripetal progression of the enhancement. (d) On a portal venous phase US image, the lesion appears uniformly enhanced and brighter than the background liver. This sustained enhancement is consistent with a benign condition.

View larger version (140K): [in a new window]   Figure 11b.  Hemangioma. (a) Baseline conventional US image shows a heterogeneous, bulbous, slightly exophytic lesion that extends from the posterior right lobe. (b) Early arterial phase vascular US image shows no linear vessels. There is peripheral nodular enhancement. (c) Late arterial phase US image shows centripetal progression of the enhancement. (d) On a portal venous phase US image, the lesion appears uniformly enhanced and brighter than the background liver. This sustained enhancement is consistent with a benign condition.

View larger version (158K): [in a new window]   Figure 11c.  Hemangioma. (a) Baseline conventional US image shows a heterogeneous, bulbous, slightly exophytic lesion that extends from the posterior right lobe. (b) Early arterial phase vascular US image shows no linear vessels. There is peripheral nodular enhancement. (c) Late arterial phase US image shows centripetal progression of the enhancement. (d) On a portal venous phase US image, the lesion appears uniformly enhanced and brighter than the background liver. This sustained enhancement is consistent with a benign condition.

View larger version (168K): [in a new window]   Figure 11d.  Hemangioma. (a) Baseline conventional US image shows a heterogeneous, bulbous, slightly exophytic lesion that extends from the posterior right lobe. (b) Early arterial phase vascular US image shows no linear vessels. There is peripheral nodular enhancement. (c) Late arterial phase US image shows centripetal progression of the enhancement. (d) On a portal venous phase US image, the lesion appears uniformly enhanced and brighter than the background liver. This sustained enhancement is consistent with a benign condition.

View larger version (94K): [in a new window]   Figure 12a.  Rapidly enhancing hemangioma in a patient with known neuroendocrine tumor. Baseline US failed to show a mass that had been detected previously at CT performed as part of a metastasis survey. (a-c) Sequential arterial phase US images obtained over a 2-second interval show a thin rim of marginal enhancement (a), peripheral nodular enhancement (b), and centripetal progression of enhancement to complete fill in the lesion (c). (d) Arterial phase CT scan shows a brightly enhancing mass. The images in c and d are analogous, both showing a hypervascular mass. The peripheral nodular enhancement and the centripetal progression of enhancement are appreciated only on the US images.

View larger version (97K): [in a new window]   Figure 12b.  Rapidly enhancing hemangioma in a patient with known neuroendocrine tumor. Baseline US failed to show a mass that had been detected previously at CT performed as part of a metastasis survey. (a-c) Sequential arterial phase US images obtained over a 2-second interval show a thin rim of marginal enhancement (a), peripheral nodular enhancement (b), and centripetal progression of enhancement to complete fill in the lesion (c). (d) Arterial phase CT scan shows a brightly enhancing mass. The images in c and d are analogous, both showing a hypervascular mass. The peripheral nodular enhancement and the centripetal progression of enhancement are appreciated only on the US images.

View larger version (123K): [in a new window]   Figure 12c.  Rapidly enhancing hemangioma in a patient with known neuroendocrine tumor. Baseline US failed to show a mass that had been detected previously at CT performed as part of a metastasis survey. (a-c) Sequential arterial phase US images obtained over a 2-second interval show a thin rim of marginal enhancement (a), peripheral nodular enhancement (b), and centripetal progression of enhancement to complete fill in the lesion (c). (d) Arterial phase CT scan shows a brightly enhancing mass. The images in c and d are analogous, both showing a hypervascular mass. The peripheral nodular enhancement and the centripetal progression of enhancement are appreciated only on the US images.

View larger version (183K): [in a new window]   Figure 12d.  Rapidly enhancing hemangioma in a patient with known neuroendocrine tumor. Baseline US failed to show a mass that had been detected previously at CT performed as part of a metastasis survey. (a-c) Sequential arterial phase US images obtained over a 2-second interval show a thin rim of marginal enhancement (a), peripheral nodular enhancement (b), and centripetal progression of enhancement to complete fill in the lesion (c). (d) Arterial phase CT scan shows a brightly enhancing mass. The images in c and d are analogous, both showing a hypervascular mass. The peripheral nodular enhancement and the centripetal progression of enhancement are appreciated only on the US images.

View larger version (156K): [in a new window]   Figure 13a.  Hemangioma. Arterial phase US image (a) and CT scan (b) show classic features of hemangioma, with bright peripheral nodules and a typical bridge across the lesion with pools of contrast material along its margins.

View larger version (164K): [in a new window]   Figure 13b.  Hemangioma. Arterial phase US image (a) and CT scan (b) show classic features of hemangioma, with bright peripheral nodules and a typical bridge across the lesion with pools of contrast material along its margins.

View larger version (151K): [in a new window]   Figure 14a.  FNH. (a) Sagittal conventional US image shows a fatty liver with an expansive hypoechoic mass in the caudate lobe. (b) Arterial phase US image shows a hypervascular mass with a stellate vascular pattern. (c) On a portal venous phase US image, the lesion remains equal in enhancement to the liver and contains a central nonenhancing scar. (d) Confirmatory portal venous phase CT scan also demonstrates sustained enhancement of the lesion and the nonenhancing scar.

View larger version (158K): [in a new window]   Figure 14b.  FNH. (a) Sagittal conventional US image shows a fatty liver with an expansive hypoechoic mass in the caudate lobe. (b) Arterial phase US image shows a hypervascular mass with a stellate vascular pattern. (c) On a portal venous phase US image, the lesion remains equal in enhancement to the liver and contains a central nonenhancing scar. (d) Confirmatory portal venous phase CT scan also demonstrates sustained enhancement of the lesion and the nonenhancing scar.

View larger version (158K): [in a new window]   Figure 14c.  FNH. (a) Sagittal conventional US image shows a fatty liver with an expansive hypoechoic mass in the caudate lobe. (b) Arterial phase US image shows a hypervascular mass with a stellate vascular pattern. (c) On a portal venous phase US image, the lesion remains equal in enhancement to the liver and contains a central nonenhancing scar. (d) Confirmatory portal venous phase CT scan also demonstrates sustained enhancement of the lesion and the nonenhancing scar.

View larger version (173K): [in a new window]   Figure 14d.  FNH. (a) Sagittal conventional US image shows a fatty liver with an expansive hypoechoic mass in the caudate lobe. (b) Arterial phase US image shows a hypervascular mass with a stellate vascular pattern. (c) On a portal venous phase US image, the lesion remains equal in enhancement to the liver and contains a central nonenhancing scar. (d) Confirmatory portal venous phase CT scan also demonstrates sustained enhancement of the lesion and the nonenhancing scar.

View larger version (148K): [in a new window]   Figure 15a.  FNH. (a) Baseline conventional US image of the right lobe shows a subtle echogenic mass. (b) Arterial phase US image shows a hypervascular mass with some stellate vascularity, a small nonenhancing scar (arrow), and a typical tortuous feeding artery. (c) Confirmatory arterial phase CT scan also demonstrates the hypervascular mass and nonenhancing scar (arrow).

View larger version (152K): [in a new window]   Figure 15b.  FNH. (a) Baseline conventional US image of the right lobe shows a subtle echogenic mass. (b) Arterial phase US image shows a hypervascular mass with some stellate vascularity, a small nonenhancing scar (arrow), and a typical tortuous feeding artery. (c) Confirmatory arterial phase CT scan also demonstrates the hypervascular mass and nonenhancing scar (arrow).

View larger version (146K): [in a new window]   Figure 15c.  FNH. (a) Baseline conventional US image of the right lobe shows a subtle echogenic mass. (b) Arterial phase US image shows a hypervascular mass with some stellate vascularity, a small nonenhancing scar (arrow), and a typical tortuous feeding artery. (c) Confirmatory arterial phase CT scan also demonstrates the hypervascular mass and nonenhancing scar (arrow).