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Optimizing Doppler and Color Flow US: Application to Hepatic Sonography¹

¹ From the Department of Radiology, Beth Israel Deaconess Medical Center, 1 Deaconess Rd, Boston, MA 02215. Recipient of a Certificate of Merit Award for an education exhibit at the 2002 RSNA scientific assembly. Received June 4, 2003; revision requested July 7 and received July 24; accepted July 28. Address correspondence to J.B.K. (e-mail: jkruskal@bidmc.harvard.edu).

View larger version (183K): [in a new window]   Figure 1.  Photograph shows the Doppler panel that appears on the console of many contemporary US imagers. Each parameter can be adjusted to optimize the color or spectral Doppler components of the examination.

View larger version (117K): [in a new window]   Figure 2a.  Clinical photographs show transducer placement for imaging of the hepatic vasculature. Depending on which vessels are being evaluated, the transducer can be placed in a transabdominal (a), subcostal (b), or intercostal (c) location.

View larger version (119K): [in a new window]   Figure 2b.  Clinical photographs show transducer placement for imaging of the hepatic vasculature. Depending on which vessels are being evaluated, the transducer can be placed in a transabdominal (a), subcostal (b), or intercostal (c) location.

View larger version (116K): [in a new window]   Figure 2c.  Clinical photographs show transducer placement for imaging of the hepatic vasculature. Depending on which vessels are being evaluated, the transducer can be placed in a transabdominal (a), subcostal (b), or intercostal (c) location.

View larger version (70K): [in a new window]   Figure 3.  Color baseline. The position of the baseline on the color bar is indicated by a horizontal black line (yellow circles). When the baseline is adjusted, the relative position of this horizontal black line changes. Note that when the position of the baseline is changed, the color velocity range that is displayed on the color bar also changes (in this example, from 15.3 to 46.1 cm/sec above or below the baseline). The range of depicted velocities remains constant, but different flow velocities will be emphasized depending on their relative position on the color bar.

View larger version (114K): [in a new window]   Figure 4.  Aliasing of the spectral waveform. Duplex US image shows aliasing of the spectral waveform with wraparound of the highest flow velocities into the negative part of the graph. Note that the color Doppler flow US image shows normal antegrade portal venous flow with no aliasing. To eliminate or reduce this artifact, spectral Doppler US must be active before different parameters can be modified.

View larger version (98K): [in a new window]   Figure 5a.  Changing the color baseline to avoid aliasing. (a) On a color Doppler flow US image, flow within the portal vein appears green, the color equivalent of aliasing on the selected color bar. The color baseline (arrow) is positioned too high on the color bar. Although the US image helps confirm the presence of flow, the baseline should be lowered to obtain meaningful directional flow data. (b) On a color Doppler flow US image obtained after the baseline was lowered (arrow), accurate directional flow data have been obtained from the main portal vein: Appropriate antegrade portal venous flow toward the transducer appears red.

View larger version (99K): [in a new window]   Figure 5b.  Changing the color baseline to avoid aliasing. (a) On a color Doppler flow US image, flow within the portal vein appears green, the color equivalent of aliasing on the selected color bar. The color baseline (arrow) is positioned too high on the color bar. Although the US image helps confirm the presence of flow, the baseline should be lowered to obtain meaningful directional flow data. (b) On a color Doppler flow US image obtained after the baseline was lowered (arrow), accurate directional flow data have been obtained from the main portal vein: Appropriate antegrade portal venous flow toward the transducer appears red.

View larger version (96K): [in a new window]   Figure 6a.  Changing the spectral baseline to avoid aliasing. (a) Duplex US image demonstrates aliasing of the spectral waveform, which results in the production of inaccurate waveform data and an inability to obtain accurate quantitative flow data. (b) On a duplex US image obtained after the spectral baseline was lowered, the spectral waveform falls within the range of velocities being evaluated, so that accurate quantitative data can be obtained. Note that changing the baseline does not change the velocity scale (PRF = 1,515 Hz), making this adjustment a logical initial change when reducing aliasing.

View larger version (82K): [in a new window]   Figure 6b.  Changing the spectral baseline to avoid aliasing. (a) Duplex US image demonstrates aliasing of the spectral waveform, which results in the production of inaccurate waveform data and an inability to obtain accurate quantitative flow data. (b) On a duplex US image obtained after the spectral baseline was lowered, the spectral waveform falls within the range of velocities being evaluated, so that accurate quantitative data can be obtained. Note that changing the baseline does not change the velocity scale (PRF = 1,515 Hz), making this adjustment a logical initial change when reducing aliasing.

View larger version (70K): [in a new window]   Figure 7a.  Adjusting the spectral scale. (a) Color duplex US image demonstrates that when the spectral scale (or the sampling rate) is set too high (in this example, PRF = 14,286 Hz), flow is more difficult to appreciate and characterize on the scale. (b) On a color duplex US image obtained after the scale was reduced (PRF = 3,731 Hz), the range of depicted velocities is reduced and the appearance of the spectral waveform is improved, providing more visible quantitative and qualitative data. Note that the color Doppler flow US image, color bar, and color scale all remain unchanged because the spectral component is active.

View larger version (77K): [in a new window]   Figure 7b.  Adjusting the spectral scale. (a) Color duplex US image demonstrates that when the spectral scale (or the sampling rate) is set too high (in this example, PRF = 14,286 Hz), flow is more difficult to appreciate and characterize on the scale. (b) On a color duplex US image obtained after the scale was reduced (PRF = 3,731 Hz), the range of depicted velocities is reduced and the appearance of the spectral waveform is improved, providing more visible quantitative and qualitative data. Note that the color Doppler flow US image, color bar, and color scale all remain unchanged because the spectral component is active.

View larger version (39K): [in a new window]   Figure 8a.  Adjusting the color velocity scale. (a) Color Doppler flow US image obtained with the color velocity scale set too high (69.2 cm/sec) demonstrates apparent absence of flow in the portal vein. (b) Color Doppler flow US image obtained after the scale was reduced to 30.7 cm/sec demonstrates normal flow in a widely patent portal vein. (c) Color Doppler flow US image obtained after the scale was set even lower (2.3 cm/sec) shows aliasing of color flow in all branches of the portal vein, which results in meaningless data concerning flow direction. Thus, the color velocity scale should be increased to increase the sampling rate.

View larger version (108K): [in a new window]   Figure 8b.  Adjusting the color velocity scale. (a) Color Doppler flow US image obtained with the color velocity scale set too high (69.2 cm/sec) demonstrates apparent absence of flow in the portal vein. (b) Color Doppler flow US image obtained after the scale was reduced to 30.7 cm/sec demonstrates normal flow in a widely patent portal vein. (c) Color Doppler flow US image obtained after the scale was set even lower (2.3 cm/sec) shows aliasing of color flow in all branches of the portal vein, which results in meaningless data concerning flow direction. Thus, the color velocity scale should be increased to increase the sampling rate.

View larger version (103K): [in a new window]   Figure 8c.  Adjusting the color velocity scale. (a) Color Doppler flow US image obtained with the color velocity scale set too high (69.2 cm/sec) demonstrates apparent absence of flow in the portal vein. (b) Color Doppler flow US image obtained after the scale was reduced to 30.7 cm/sec demonstrates normal flow in a widely patent portal vein. (c) Color Doppler flow US image obtained after the scale was set even lower (2.3 cm/sec) shows aliasing of color flow in all branches of the portal vein, which results in meaningless data concerning flow direction. Thus, the color velocity scale should be increased to increase the sampling rate.

View larger version (75K): [in a new window]   Figure 9a.  Changing the wall filter. (a) Color duplex US image obtained with a high wall filter setting shows loss of the low-velocity-flow component of the spectral waveform immediately above the baseline. Higher-velocity flow is well depicted, and accurate flow quantification can still occur. In the evaluation of the liver vasculature, this is likely to become relevant only when flow velocity is very low and falls within the range of velocities that are filtered out. (b) Color duplex US image demonstrates how the spectral waveform progressively fills in toward the baseline as the wall filter is sequentially reduced from high (left arrow) to medium (middle arrow) to low (right arrow).

View larger version (70K): [in a new window]   Figure 9b.  Changing the wall filter. (a) Color duplex US image obtained with a high wall filter setting shows loss of the low-velocity-flow component of the spectral waveform immediately above the baseline. Higher-velocity flow is well depicted, and accurate flow quantification can still occur. In the evaluation of the liver vasculature, this is likely to become relevant only when flow velocity is very low and falls within the range of velocities that are filtered out. (b) Color duplex US image demonstrates how the spectral waveform progressively fills in toward the baseline as the wall filter is sequentially reduced from high (left arrow) to medium (middle arrow) to low (right arrow).

View larger version (96K): [in a new window]   Figure 10a.  Changing the color Doppler wall filter. (a) Color Doppler flow US image obtained with the highest possible wall filter setting shows how color signal arising from low-velocity flow may be filtered out. (b) Color Doppler flow US image obtained with a low filter setting demonstrates filling in of flow in the hepatic veins (blue), which indicates minimal filtering of color signal. The change in the filter setting appears as a change in the width of the horizontal black line in the center of the color bar.

View larger version (99K): [in a new window]   Figure 10b.  Changing the color Doppler wall filter. (a) Color Doppler flow US image obtained with the highest possible wall filter setting shows how color signal arising from low-velocity flow may be filtered out. (b) Color Doppler flow US image obtained with a low filter setting demonstrates filling in of flow in the hepatic veins (blue), which indicates minimal filtering of color signal. The change in the filter setting appears as a change in the width of the horizontal black line in the center of the color bar.

View larger version (88K): [in a new window]   Figure 11a.  Inversion of color flow. (a) On a color Doppler flow US image obtained with color Doppler flow US as the active scanning mode and inversion of the color bar, portal venous flow appears blue, which falsely suggests reversal of flow (ie, away from the transducer). (b) On a color Doppler flow US image obtained with reversal of this inversion, appropriate directional flow is noted.

View larger version (86K): [in a new window]   Figure 11b.  Inversion of color flow. (a) On a color Doppler flow US image obtained with color Doppler flow US as the active scanning mode and inversion of the color bar, portal venous flow appears blue, which falsely suggests reversal of flow (ie, away from the transducer). (b) On a color Doppler flow US image obtained with reversal of this inversion, appropriate directional flow is noted.

View larger version (82K): [in a new window]   Figure 12a.  Inversion of spectral and color flow falsely suggesting reversal of portal venous flow. (a) On a color duplex US image obtained with spectral Doppler US as the active scanning mode, the spectral waveform is below the baseline, with appropriate color flow. (b) Color duplex US image obtained after the inversion button was reversed demonstrates appropriate directional flow, with the spectral waveform now appearing above the baseline. Note that the color bar does not change when the Doppler spectrum is inverted.

View larger version (80K): [in a new window]   Figure 12b.  Inversion of spectral and color flow falsely suggesting reversal of portal venous flow. (a) On a color duplex US image obtained with spectral Doppler US as the active scanning mode, the spectral waveform is below the baseline, with appropriate color flow. (b) Color duplex US image obtained after the inversion button was reversed demonstrates appropriate directional flow, with the spectral waveform now appearing above the baseline. Note that the color bar does not change when the Doppler spectrum is inverted.

View larger version (81K): [in a new window]   Figure 13a.  Angle correction. (a) Color duplex US image obtained with no angle correction shows how no meaningful velocity data can be obtained from the portal venous waveform because the computer automatically assigns an angle of 0° (cos 0° = 1). Without angle correction, the measured flow velocity is 18.0 cm/sec. (b) Color duplex US image obtained with correct definition of the angle between the transducer and the direction of portal venous flow demonstrates a flow velocity of 29.3 cm/sec.

View larger version (82K): [in a new window]   Figure 13b.  Angle correction. (a) Color duplex US image obtained with no angle correction shows how no meaningful velocity data can be obtained from the portal venous waveform because the computer automatically assigns an angle of 0° (cos 0° = 1). Without angle correction, the measured flow velocity is 18.0 cm/sec. (b) Color duplex US image obtained with correct definition of the angle between the transducer and the direction of portal venous flow demonstrates a flow velocity of 29.3 cm/sec.

View larger version (81K): [in a new window]   Figure 14a.  Angle correction. (a) Color duplex US image obtained with a 30° corrected angle, which is too low, demonstrates a flow velocity of 21.3 cm/sec in the portal vein. This figure represents an underestimation of the true flow velocity. (b) Color duplex US image obtained with a 70° corrected angle, which is too high, demonstrates a flow velocity of 52.8 cm/sec in the portal vein, which represents an overestimation of flow velocity. Note that the measured flow velocity increases as the corrected angle increases.

View larger version (81K): [in a new window]   Figure 14b.  Angle correction. (a) Color duplex US image obtained with a 30° corrected angle, which is too low, demonstrates a flow velocity of 21.3 cm/sec in the portal vein. This figure represents an underestimation of the true flow velocity. (b) Color duplex US image obtained with a 70° corrected angle, which is too high, demonstrates a flow velocity of 52.8 cm/sec in the portal vein, which represents an overestimation of flow velocity. Note that the measured flow velocity increases as the corrected angle increases.

View larger version (79K): [in a new window]   Figure 15a.  Angle of insonation. (a, b) Color duplex US images of the anterior branch of the right portal vein obtained with the transducer positioned in an intercostal (a) and subcostal (b) location depict flow as moving toward and away from the transducer, respectively. (c) On a color duplex US image obtained with the transducer positioned perpendicular to flow (arrow), no color is assigned, yielding a false finding of absent flow. The angle of insonation of the vein depends entirely on the position of the transducer.

View larger version (75K): [in a new window]   Figure 15b.  Angle of insonation. (a, b) Color duplex US images of the anterior branch of the right portal vein obtained with the transducer positioned in an intercostal (a) and subcostal (b) location depict flow as moving toward and away from the transducer, respectively. (c) On a color duplex US image obtained with the transducer positioned perpendicular to flow (arrow), no color is assigned, yielding a false finding of absent flow. The angle of insonation of the vein depends entirely on the position of the transducer.

View larger version (87K): [in a new window]   Figure 15c.  Angle of insonation. (a, b) Color duplex US images of the anterior branch of the right portal vein obtained with the transducer positioned in an intercostal (a) and subcostal (b) location depict flow as moving toward and away from the transducer, respectively. (c) On a color duplex US image obtained with the transducer positioned perpendicular to flow (arrow), no color is assigned, yielding a false finding of absent flow. The angle of insonation of the vein depends entirely on the position of the transducer.

View larger version (61K): [in a new window]   Figure 16a.  Optimization of gain settings. (a) Duplex US image obtained with spectral Doppler US as the active scanning mode and too low a gain setting (0%) falsely suggests absent flow. (b-d) Duplex US images obtained with a gain setting of 38% (b), 77% (c), and 100% (d) demonstrate gradual artificial filling in of the spectral waveform, yielding a false finding of increased flow with little meaningful quantitative flow data. The gain settings function independently of other parameters; therefore, changing the gain setting will not alter any other parameter. Changing the color gain does not alter the spectral gain (and vice versa), and the PRF remains unchanged. Whether the color or spectral component is active, the gain setting should be adjusted to outline the contour of the depicted waveform or color flow depiction.

View larger version (69K): [in a new window]   Figure 16b.  Optimization of gain settings. (a) Duplex US image obtained with spectral Doppler US as the active scanning mode and too low a gain setting (0%) falsely suggests absent flow. (b-d) Duplex US images obtained with a gain setting of 38% (b), 77% (c), and 100% (d) demonstrate gradual artificial filling in of the spectral waveform, yielding a false finding of increased flow with little meaningful quantitative flow data. The gain settings function independently of other parameters; therefore, changing the gain setting will not alter any other parameter. Changing the color gain does not alter the spectral gain (and vice versa), and the PRF remains unchanged. Whether the color or spectral component is active, the gain setting should be adjusted to outline the contour of the depicted waveform or color flow depiction.

View larger version (81K): [in a new window]   Figure 16c.  Optimization of gain settings. (a) Duplex US image obtained with spectral Doppler US as the active scanning mode and too low a gain setting (0%) falsely suggests absent flow. (b-d) Duplex US images obtained with a gain setting of 38% (b), 77% (c), and 100% (d) demonstrate gradual artificial filling in of the spectral waveform, yielding a false finding of increased flow with little meaningful quantitative flow data. The gain settings function independently of other parameters; therefore, changing the gain setting will not alter any other parameter. Changing the color gain does not alter the spectral gain (and vice versa), and the PRF remains unchanged. Whether the color or spectral component is active, the gain setting should be adjusted to outline the contour of the depicted waveform or color flow depiction.

View larger version (99K): [in a new window]   Figure 16d.  Optimization of gain settings. (a) Duplex US image obtained with spectral Doppler US as the active scanning mode and too low a gain setting (0%) falsely suggests absent flow. (b-d) Duplex US images obtained with a gain setting of 38% (b), 77% (c), and 100% (d) demonstrate gradual artificial filling in of the spectral waveform, yielding a false finding of increased flow with little meaningful quantitative flow data. The gain settings function independently of other parameters; therefore, changing the gain setting will not alter any other parameter. Changing the color gain does not alter the spectral gain (and vice versa), and the PRF remains unchanged. Whether the color or spectral component is active, the gain setting should be adjusted to outline the contour of the depicted waveform or color flow depiction.

View larger version (101K): [in a new window]   Figure 17.  Optimizing gate size and position. Color duplex US image obtained with a wide gate placed in a suboptimal location shows sampling of flow in both the portal (above the baseline) and hepatic (below the baseline) veins. Too large a gate size may result in sampling from too large an anatomic region. By reducing the gate size and improving the position for sampling, a normal spectral waveform is obtained.

View larger version (92K): [in a new window]   Figure 18a.  Adjustment of color gain with color flow US as the active scanning mode. (a, b) Color Doppler flow US images obtained with a gain setting of 44% (a) and 100% (b) show underadjustment and overadjustment, respectively. (c) Color Doppler flow US image obtained with an optimal gain setting of 65% demonstrates normal-appearing wall-to-wall flow in the main portal vein. Note that, although the color gain changes, no change occurs in the color velocity scale (23 cm/sec) or sampling rate (PRF = 1,500 Hz).

View larger version (73K): [in a new window]   Figure 18b.  Adjustment of color gain with color flow US as the active scanning mode. (a, b) Color Doppler flow US images obtained with a gain setting of 44% (a) and 100% (b) show underadjustment and overadjustment, respectively. (c) Color Doppler flow US image obtained with an optimal gain setting of 65% demonstrates normal-appearing wall-to-wall flow in the main portal vein. Note that, although the color gain changes, no change occurs in the color velocity scale (23 cm/sec) or sampling rate (PRF = 1,500 Hz).

View larger version (90K): [in a new window]   Figure 18c.  Adjustment of color gain with color flow US as the active scanning mode. (a, b) Color Doppler flow US images obtained with a gain setting of 44% (a) and 100% (b) show underadjustment and overadjustment, respectively. (c) Color Doppler flow US image obtained with an optimal gain setting of 65% demonstrates normal-appearing wall-to-wall flow in the main portal vein. Note that, although the color gain changes, no change occurs in the color velocity scale (23 cm/sec) or sampling rate (PRF = 1,500 Hz).

View larger version (121K): [in a new window]   Figure 19a.  Color box or overlay. (a) Color Doppler flow US image obtained with an oversized color box results in an increased frame rate and the inclusion of extraneous data. (b) Color Doppler flow US image obtained with the box size reduced demonstrates a decreased frame rate and improved image quality.

View larger version (125K): [in a new window]   Figure 19b.  Color box or overlay. (a) Color Doppler flow US image obtained with an oversized color box results in an increased frame rate and the inclusion of extraneous data. (b) Color Doppler flow US image obtained with the box size reduced demonstrates a decreased frame rate and improved image quality.

View larger version (120K): [in a new window]   Figure 20.  Hepatic arterial waveform. Color duplex US image obtained with a small gate placed over the hepatic artery adjacent to the main portal vein shows a normal spectral waveform and a low-resistance profile with systolic velocities ranging from 30 to 40 cm/sec.

View larger version (68K): [in a new window]   Figure 21.  Tardus parvus hepatic arterial waveform. Color duplex US image obtained in a patient who had undergone liver transplantation 24 hours earlier shows slow upslope, broadening of the spectral waveform, and low-peak-velocity flow. This waveform is commonly seen in liver transplant recipients and resolves by 24-48 hours after surgery. When this finding is seen more than 48 hours after the procedure, hepatic artery stenosis or even dissection should be excluded.

View larger version (108K): [in a new window]   Figures 22.  Helical portal venous flow. On a color duplex US image of the main portal vein, the spectral waveform shows phasicity secondary to patient respiration. The color Doppler component shows flow as both blue (away from the transducer) and red (toward the transducer), a finding that is consistent with helical flow.

View larger version (105K): [in a new window]   Figures 23.  Helical portal venous flow in a liver transplant recipient. On a color duplex US image, helical flow in the main portal vein appears both red and blue and is depicted as occurring both above and below the baseline. If a gate is too small and is placed on a single component of portal venous flow, the flow may inadvertently appear reversed.

View larger version (130K): [in a new window]   Figure 24.  Reversal of left portal venous flow in a patient with a TIPS. Color Doppler flow US image shows flow toward the transducer (red) in the left hepatic artery (HA) and reversed flow (blue) in the left portal vein (LPV). These findings are expected when a functioning TIPS bridges the right portal and hepatic veins.

View larger version (109K): [in a new window]   Figure 25.  Normal hepatic venous waveform. On a color duplex US image, the spectral waveform for a normal hepatic vein shows triphasic flow above and below the baseline. The waveform shows periodicity and is triphasic due to transmitted cardiac activity, similar to the waveform for the jugular vein. The component above the baseline corresponds to atrial systole; the components below the baseline correspond to ventricular systole and the filling phase during atrial diastole.