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Doppler angle correction in the measurement of intrarenal parameters.

Gao J, Hentel K, Zhu Q, Ma T, Shih G, Mennitt K, Min R - Int J Nephrol Renovasc Dis (2011)

Bottom Line: There were statistical differences in PSV and EDV at the interlobar artery in the upper, mid, and lower poles of the kidney between Group 1 and Group 2 (all P < 0.001).PSV and EDV in Group 1 were significantly lower than in Group 2.RI in Group 1 was the same as that in Group 2 in the upper, mid, and lower poles of the kidneys.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, New York Presbyterian Hospital, Weill Cornell Medical College, NY, USA;

ABSTRACT

Background: The aim of this study was to assess differences in intrarenal artery Doppler parameters measured without and with Doppler angle correction.

Methods: We retrospectively reviewed color duplex sonography in 30 normally functioning kidneys (20 native kidneys in 10 subjects and 10 transplanted kidneys in 10 subjects) performed between January 26, 2010 and July 26, 2010. There were 10 age-matched men and 10 age-matched women (mean 39.8 ± 12.2, range 21-60 years) in this study. Depending on whether the Doppler angle was corrected in the spectral Doppler measurement, Doppler parameters including peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) measured at the interlobar artery of the kidney were divided into two groups, ie, initial Doppler parameters measured without Doppler angle correction (Group 1) and remeasured Doppler parameters with Doppler angle correction (Group 2). Values for PSV, EDV, and RI measured without Doppler angle correction were compared with those measured with Doppler angle correction, and were analyzed statistically with a paired-samples t-test.

Results: There were statistical differences in PSV and EDV at the interlobar artery in the upper, mid, and lower poles of the kidney between Group 1 and Group 2 (all P < 0.001). PSV and EDV in Group 1 were significantly lower than in Group 2. RI in Group 1 was the same as that in Group 2 in the upper, mid, and lower poles of the kidneys.

Conclusion: Doppler angle correction plays an important role in the accurate measurement of intrarenal blood flow velocity. The true flow velocity converted from the maximum Doppler velocity shift is produced only when the Doppler angle is 0°, so that the emission sound beam is parallel to the direction of blood flow at the sampled artery. Therefore, the Doppler angle correction should be routinely applied and displayed on renal color duplex sonography.

No MeSH data available.


This illustration shows Doppler angle at the mid to lower pole of the kidney is not corrected. Yellow dotted arrow shows the ultrasound beam emitted from the transducer. The red solid arrow indicates the blood flow direction of the interlobar artery. The white Θ is the angle between the emission sound beam from the transducer and the flow direction at sampled artery in the mid to lower pole of the kidney.
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f2b-ijnrd-4-049: This illustration shows Doppler angle at the mid to lower pole of the kidney is not corrected. Yellow dotted arrow shows the ultrasound beam emitted from the transducer. The red solid arrow indicates the blood flow direction of the interlobar artery. The white Θ is the angle between the emission sound beam from the transducer and the flow direction at sampled artery in the mid to lower pole of the kidney.

Mentions: The second explanation lies in how Doppler angle correction works on currently commercially available ultrasound scanners. The Doppler circuitry determines the change in frequency, and this may only be translated into a blood velocity if the Doppler angle is recorded and included in the calculation. Nevertheless, all the newer scanners report blood velocity assuming that the Doppler angle is zero. Given our cases, when Doppler angle correction was not displayed (Figure 1), the Doppler angle would be considered the same as the emission sound beam, ie, the line containing the Doppler gate from the transducer is parallel to the flow direction at the interlobar artery (Figure 2). However, this is more often incorrect than correct, and we are in fact dealing with frequency information unless angle correction has been performed.19 Hence, the flow velocity at the interlobar artery of the kidney measured without Doppler angle correction would be inaccurate. This may eventually result in technical error for spectral Doppler sampling if the operator mistakenly assumes the emission sound beam from the transducer is nearly parallel to the blood flow direction without displaying and adjusting the Doppler angle correction. As shown in Table 2, blood flow velocity at the interlobar artery would be underestimated, and blood flow velocity converted from Doppler frequency shift measured without Doppler angle correction (Figure 2A) tends to be lower than that measured with Doppler angle correction (Figure 3A). Without Doppler angle correction, the angle between the flow direction at the interlobar artery to the transducer beam would be 45–60° in the upper and the lower pole, and 15–30° in the mid pole (Figure 2B). Because the Doppler angle and flow velocity are directly proportional, the PSV and EDV in Group 1 were significantly lower than that in Group 2 (P < 0.001). This was confirmed by the increased values for PSV and EDV in Group 2 when the Doppler angle was manually corrected from approximately 30° earlier in the mid to lower pole in Group 1 (Figure 2B) to near 0° in Group 2 (Figure 3B).


Doppler angle correction in the measurement of intrarenal parameters.

Gao J, Hentel K, Zhu Q, Ma T, Shih G, Mennitt K, Min R - Int J Nephrol Renovasc Dis (2011)

This illustration shows Doppler angle at the mid to lower pole of the kidney is not corrected. Yellow dotted arrow shows the ultrasound beam emitted from the transducer. The red solid arrow indicates the blood flow direction of the interlobar artery. The white Θ is the angle between the emission sound beam from the transducer and the flow direction at sampled artery in the mid to lower pole of the kidney.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3108792&req=5

f2b-ijnrd-4-049: This illustration shows Doppler angle at the mid to lower pole of the kidney is not corrected. Yellow dotted arrow shows the ultrasound beam emitted from the transducer. The red solid arrow indicates the blood flow direction of the interlobar artery. The white Θ is the angle between the emission sound beam from the transducer and the flow direction at sampled artery in the mid to lower pole of the kidney.
Mentions: The second explanation lies in how Doppler angle correction works on currently commercially available ultrasound scanners. The Doppler circuitry determines the change in frequency, and this may only be translated into a blood velocity if the Doppler angle is recorded and included in the calculation. Nevertheless, all the newer scanners report blood velocity assuming that the Doppler angle is zero. Given our cases, when Doppler angle correction was not displayed (Figure 1), the Doppler angle would be considered the same as the emission sound beam, ie, the line containing the Doppler gate from the transducer is parallel to the flow direction at the interlobar artery (Figure 2). However, this is more often incorrect than correct, and we are in fact dealing with frequency information unless angle correction has been performed.19 Hence, the flow velocity at the interlobar artery of the kidney measured without Doppler angle correction would be inaccurate. This may eventually result in technical error for spectral Doppler sampling if the operator mistakenly assumes the emission sound beam from the transducer is nearly parallel to the blood flow direction without displaying and adjusting the Doppler angle correction. As shown in Table 2, blood flow velocity at the interlobar artery would be underestimated, and blood flow velocity converted from Doppler frequency shift measured without Doppler angle correction (Figure 2A) tends to be lower than that measured with Doppler angle correction (Figure 3A). Without Doppler angle correction, the angle between the flow direction at the interlobar artery to the transducer beam would be 45–60° in the upper and the lower pole, and 15–30° in the mid pole (Figure 2B). Because the Doppler angle and flow velocity are directly proportional, the PSV and EDV in Group 1 were significantly lower than that in Group 2 (P < 0.001). This was confirmed by the increased values for PSV and EDV in Group 2 when the Doppler angle was manually corrected from approximately 30° earlier in the mid to lower pole in Group 1 (Figure 2B) to near 0° in Group 2 (Figure 3B).

Bottom Line: There were statistical differences in PSV and EDV at the interlobar artery in the upper, mid, and lower poles of the kidney between Group 1 and Group 2 (all P < 0.001).PSV and EDV in Group 1 were significantly lower than in Group 2.RI in Group 1 was the same as that in Group 2 in the upper, mid, and lower poles of the kidneys.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, New York Presbyterian Hospital, Weill Cornell Medical College, NY, USA;

ABSTRACT

Background: The aim of this study was to assess differences in intrarenal artery Doppler parameters measured without and with Doppler angle correction.

Methods: We retrospectively reviewed color duplex sonography in 30 normally functioning kidneys (20 native kidneys in 10 subjects and 10 transplanted kidneys in 10 subjects) performed between January 26, 2010 and July 26, 2010. There were 10 age-matched men and 10 age-matched women (mean 39.8 ± 12.2, range 21-60 years) in this study. Depending on whether the Doppler angle was corrected in the spectral Doppler measurement, Doppler parameters including peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) measured at the interlobar artery of the kidney were divided into two groups, ie, initial Doppler parameters measured without Doppler angle correction (Group 1) and remeasured Doppler parameters with Doppler angle correction (Group 2). Values for PSV, EDV, and RI measured without Doppler angle correction were compared with those measured with Doppler angle correction, and were analyzed statistically with a paired-samples t-test.

Results: There were statistical differences in PSV and EDV at the interlobar artery in the upper, mid, and lower poles of the kidney between Group 1 and Group 2 (all P < 0.001). PSV and EDV in Group 1 were significantly lower than in Group 2. RI in Group 1 was the same as that in Group 2 in the upper, mid, and lower poles of the kidneys.

Conclusion: Doppler angle correction plays an important role in the accurate measurement of intrarenal blood flow velocity. The true flow velocity converted from the maximum Doppler velocity shift is produced only when the Doppler angle is 0°, so that the emission sound beam is parallel to the direction of blood flow at the sampled artery. Therefore, the Doppler angle correction should be routinely applied and displayed on renal color duplex sonography.

No MeSH data available.