The role of colour velocity imaging (CVI) in prostate ultrasound

Contrast-ultrasound diffusion imaging for localization of prostate cancer

Prostate cancer is the most prevalent form of cancer in western men. An accurate early localization of prostate cancer, permitting efficient use of modern focal therapies, is currently hampered by a lack of imaging methods. Several methods have aimed at detecting microvascular changes associated with prostate cancer with limited success by quantitative imaging of blood perfusion. Differently, we propose contrast-ultrasound diffusion imaging, based on the hypothesis that the complexity of microvascular changes is better reflected by diffusion than by perfusion characteristics. Quantification of local, intravascular diffusion is performed after transrectal ultrasound imaging of an intravenously injected ultrasound contrast agent bolus. Indicator dilution curves are measured with the ultrasound scanner resolution and fitted by a modified local density random walk model, which, being a solution of the convective diffusion equation, enables the estimation of a local, diffusion-related parameter. Diffusion parametric images obtained from five datasets of four patients were compared with histology data on a pixel basis. The resulting receiver operating characteristic (curve area = 0.91) was superior to that of any perfusion-related parameter proposed in the literature. Contrast-ultrasound diffusion imaging seems therefore to be a promising method for prostate cancer localization, encouraging further research to assess the clinical reliability.

Ultrasound low-velocity flow estimations using cross-correlation and decorrelation: a thread phantom study

In this paper, two time-domain flow velocity measurement methods, cross-correlation and decorrelation, were implemented and compared in measuring low blood-flow velocities, ranging from 0.05 to 5 cm/s, at known beam-vessel angles of 50-90 degrees in a thread phantom. Both methods achieved a significant correlation between the measured and the known velocities (r=0.99; P<0.001) in the thread phantom measurements, at 50-70 degrees beam-vessel angles. Although the cross-correlation method showed a significant correlation (r>0.99; P<0.001), this method caused large errors (>45%) at 80 degrees and 90 degrees , whereas the decorrelation method not only achieved a significant correlation (r>0.99; P<0.001) but also resulted in smaller errors (<19%) at 80 degrees and 90 degrees . This study demonstrates the potential of time-domain decorrelation method for measuring low flow velocity at large beam-vessel angles near perpendicular conditions.

Role of Doppler ultrasound and resistive index in benign prostatic hypertrophy

BACKGROUND

The aim of the present study was to assess the resistive index in patients with benign prostatic hypertrophy (BPH) and the role of power Doppler ultrasonography.

METHODS

From April 1996 to December 1997, a total of 214 men aged 48-86 years with symptoms of BPH were prospectively enrolled to participate in our study. All patients presented to our clinic with lower urinary tract symptoms. Transrectal ultrasonography was used to calculate the total prostate volume (TPV), transition zone (TZ) volume, transition zone index (TZI = TZ volume/TPV) and presumed circle area ratio (PCAR). Power Doppler imaging was used to identify the capsular and urethral arteries of the prostate and measure its resistive index (RI) value.

RESULTS

The RI of capsular arteries significantly correlated with theTPV, TZ volume, TZI (r = 0.470; P < 0.0001) and PCAR (r = 0.334; P < 0.0001). Correlations were found between the RI of capsular arteries and the International Prostatic Symptom Score (IPSS) (r = 0.389; P < 0.0001), peak flow rate of uroflowmetry (r = -0.393; P < 0.0001).

CONCLUSION

We demonstrated that an increase of the RI of capsular arteries correlated with increases in the TZI and PCAR in BPH. The lower IPSS and peak flow rate correlated with the high RI of capsular arteries; however, no correlation between the RI of urethral arteries and prostatic parameters was found. The findings suggested that the RI of capsular arteries may become the index for measuring lower urinary obstruction in the future.

In vivo validation of the time domain velocity measurement technique of blood flow in human fetuses

Time domain ultrasonography is an alternative to Doppler analysis of blood flow direction and velocity. The time domain technique uses timing information between successive echo pulses to measure flow velocities directly through a color display map. This study was undertaken to validate this technique for measuring peak systolic velocity compared to the pulsed-wave Doppler method in human fetuses. Twenty normally developing fetuses were included in the study. The fetal abdominal aorta and the umbilical artery were studied in 12 and eight cases, respectively. We first estimated flow velocity using time domain ultrasonography and immediately after pulsed Doppler was used. The intraclass correlation coefficient was used to assess the agreement between measurements. A close correlation was found (intraclass correlation coefficient = 0.96). Our results show that time domain ultrasonography seems to be a valid technique for imaging fetal vessels and for measuring blood flow velocity.