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Methods for improvement of velocity measurement for carotid artery stenosis estimation
Abstracts
s40
Summary - Study was carried out to assess the diagnostic value of intravenous contrast agent Levovist applied in colour Doppler evaluation of breast vascularity. The study included 28 women with solid breast masses. In that number: 12 carcinomas and 16 benign lesions. During baseline ultrasound examination authors estimated vascular pattern of the lesion by means of colour as well as Power Doppler ultrasound. The same evaluation was performed after intravenous contrast agent infusion. An increase in intensity of colour Doppler signal, duration of the enhancement, number of vessels within the lesion was subjectively estimated. After Levovist administration authors noticed stronger and longer Doppler signal enhancement, larger number of additional vessels in malignant lesions in comparison to benign ones. The conclusion is that ultrasound contrast agent such as Levovist can play significant role in differentiation of the character of breast located tumour in the future.
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Methods for Improvement of Velocity Measurement for Carotid Artery Stenosis Estimation
P.R. Hoskins PR. Department of Medical Physics, Royal Infmaty,
Edinburgh, UK
Errors in carotid artery velocity estimation made using Doppler systems have important implications for categorisation of patients for endarterectomy. There is an angle dependent error in velocity caused by geometric spectral broadening (errors of lo-60 %). Also the true beam-velocity vector angle is not equal to the beamvessel angle (errors of 5-25”). This study explores the dependence on beam-vessel angle of the velocity estimated using several techniques. A flow phantom is used with vessels containing stenoses from 35 to 80% area reduction. Images were required using Acuson and Diasonics scanners with linear arrays, for beam vessel angles from 50 to 80”. The variability in velocity for stenoses from 60 to 80% area reduction was averaged, and is summarised in the table. (1) Conventional (Acuson). Measurements were taken using conventional angle correction. (2) Spectral broadening correction (Acuson). Using a string phantom the velocity error as a function of beam-string angle was measured and an angle dependant correction factor derived. This was applied to the flow phantom velocity measurements. (3) Angle correction from the
end of the array (Diasonics).Angle correction was performed from the edge of the linear array. (4) Spectral vector Doppler (Acuson). Spectral data from 2 different directions was acquired and combined vectorially. This procedure automatically calculated the true velocity magnitude and beam-vector angle.
Procedure
Variability (50-70”)
Variability (SO-SO”)
1. Conventional Doppler 2. SB correction factor 3. Edge of array angle correction 4. Spectral vector Doppler
14%
30%
9%
14%
7%
-
5%
8%
All alternative methods are better than the conventional method. Correction for geometric spectral broadening occurs for procedure 2 and 3, however only procedure 3 measures the true beam-vector angle; this probably explains why it has the lowest variability.
?? P8
Comparison of Power Doppler with conventional colour flow imaging
P.R. Hoskins. Dept. of Medical Physics, Royal Infimaly, Edinburgh EH3 9yct: UK Power Doppler supposed angle compared with gates this using
has been widely accepted because of its independence and increased sensitivity colour flow imaging. This study investia tissue equivalent flow phantom. Angle independence. A latex tube was scanned using a sector proble, producing beam-vessel angles from 60”-90”. The power Doppler colouration was mostly uniform. Near to 90” no colour was displayed, due to low Doppler frequencies falling below the clutter filter. This emphasises that the power Doppler technique is not fully angle independent. Stenosis Model. A stenosis was embedded within a latex tube. The power Doppler image colouration was uniform except in the region of recirculation behind the stenosis, where no colour was seen. This is due to the low Doppler frequencies falling below the level of the clutter filter. This emphasises that gaps in the power Doppler image are not necessarily diagnostic of thrombosis. Penetration depth. A 1 mm vessel within a tissue equivalent agar phatom was used. With no persistence there
s40
Summary - Study was carried out to assess the diagnostic value of intravenous contrast agent Levovist applied in colour Doppler evaluation of breast vascularity. The study included 28 women with solid breast masses. In that number: 12 carcinomas and 16 benign lesions. During baseline ultrasound examination authors estimated vascular pattern of the lesion by means of colour as well as Power Doppler ultrasound. The same evaluation was performed after intravenous contrast agent infusion. An increase in intensity of colour Doppler signal, duration of the enhancement, number of vessels within the lesion was subjectively estimated. After Levovist administration authors noticed stronger and longer Doppler signal enhancement, larger number of additional vessels in malignant lesions in comparison to benign ones. The conclusion is that ultrasound contrast agent such as Levovist can play significant role in differentiation of the character of breast located tumour in the future.
w 0
Methods for Improvement of Velocity Measurement for Carotid Artery Stenosis Estimation
P.R. Hoskins PR. Department of Medical Physics, Royal Infmaty,
Edinburgh, UK
Errors in carotid artery velocity estimation made using Doppler systems have important implications for categorisation of patients for endarterectomy. There is an angle dependent error in velocity caused by geometric spectral broadening (errors of lo-60 %). Also the true beam-velocity vector angle is not equal to the beamvessel angle (errors of 5-25”). This study explores the dependence on beam-vessel angle of the velocity estimated using several techniques. A flow phantom is used with vessels containing stenoses from 35 to 80% area reduction. Images were required using Acuson and Diasonics scanners with linear arrays, for beam vessel angles from 50 to 80”. The variability in velocity for stenoses from 60 to 80% area reduction was averaged, and is summarised in the table. (1) Conventional (Acuson). Measurements were taken using conventional angle correction. (2) Spectral broadening correction (Acuson). Using a string phantom the velocity error as a function of beam-string angle was measured and an angle dependant correction factor derived. This was applied to the flow phantom velocity measurements. (3) Angle correction from the
end of the array (Diasonics).Angle correction was performed from the edge of the linear array. (4) Spectral vector Doppler (Acuson). Spectral data from 2 different directions was acquired and combined vectorially. This procedure automatically calculated the true velocity magnitude and beam-vector angle.
Procedure
Variability (50-70”)
Variability (SO-SO”)
1. Conventional Doppler 2. SB correction factor 3. Edge of array angle correction 4. Spectral vector Doppler
14%
30%
9%
14%
7%
-
5%
8%
All alternative methods are better than the conventional method. Correction for geometric spectral broadening occurs for procedure 2 and 3, however only procedure 3 measures the true beam-vector angle; this probably explains why it has the lowest variability.
?? P8
Comparison of Power Doppler with conventional colour flow imaging
P.R. Hoskins. Dept. of Medical Physics, Royal Infimaly, Edinburgh EH3 9yct: UK Power Doppler supposed angle compared with gates this using
has been widely accepted because of its independence and increased sensitivity colour flow imaging. This study investia tissue equivalent flow phantom. Angle independence. A latex tube was scanned using a sector proble, producing beam-vessel angles from 60”-90”. The power Doppler colouration was mostly uniform. Near to 90” no colour was displayed, due to low Doppler frequencies falling below the clutter filter. This emphasises that the power Doppler technique is not fully angle independent. Stenosis Model. A stenosis was embedded within a latex tube. The power Doppler image colouration was uniform except in the region of recirculation behind the stenosis, where no colour was seen. This is due to the low Doppler frequencies falling below the level of the clutter filter. This emphasises that gaps in the power Doppler image are not necessarily diagnostic of thrombosis. Penetration depth. A 1 mm vessel within a tissue equivalent agar phatom was used. With no persistence there