Comparison of harmonic and conventional power Doppler ultrasonography for assessment of slow flow in hyperechoic tissue: experimental study using a Doppler phantom

Variable breast conditions: comparison of conventional and real-time compound ultrasonography

OBJECTIVES

To illustrate and compare the appearances of variable breast conditions by conventional and real-time spatial compound images.

METHODS

Cases illustrative of a broad range of breast conditions were collected. Each image pair consisted of conventional and real-time compound images with a stationary probe to maintain an identical projection.

RESULTS

The various breast conditions, including normal anatomic structures and abnormal lesions, were evaluated and compared by conventional and real-time compound images. The real-time compound images revealed more realistic and clear images with reduced artifacts.

CONCLUSIONS

Real-time compound images are superior to conventional images of normal and abnormal breast conditions. Real-time compound imaging is a good technique for evaluating the breast state.

Contrast-enhanced harmonic gray-scale sonographic-histologic correlation of the therapeutic effects of transcatheter arterial chemoembolization in patients with hepatocellular carcinoma

OBJECTIVE

We evaluated the usefulness of contrast-enhanced harmonic wideband gray-scale sonography in the assessment of the therapeutic effects of transcatheter arterial chemoembolization in patients with hepatocellular carcinoma and compared the performance of this imaging modality with the histologic findings for the patients.

SUBJECTS AND METHODS

Twenty-nine patients with 29 hepatocellular carcinoma lesions were examined. Tumor vascularity was evaluated before and 7 days after transcatheter arterial chemoembolization with contrast-enhanced harmonic wideband gray-scale sonography performed after injection of the contrast agent Levovist. Several biopsy specimens were obtained from the evaluated lesions, and the histologic findings were compared with the results of contrast-enhanced sonography.

RESULTS

Contrast-enhanced harmonic wideband gray-scale sonography performed after transcatheter arterial chemoembolization showed tumor vascularity in 16 of the 29 lesions, but none in the other 13 lesions. At histologic examination, 13 of the 16 lesions with tumor vascularity had residual tumor revealed, and the 13 lesions without tumor vascularity were found to have no histologically evident tumor residue, although three of these lesions showed tumor progression detected on CT during a 9- to 12-month follow-up period. Contrast-enhanced harmonic wideband gray-scale sonographic images were compared with the histologic findings as the gold standard, and the sensitivity and specificity of these images for discerning viable and nonviable hepatocellular carcinoma after transcatheter arterial chemoembolization were 100% and 81%, respectively.

CONCLUSION

Contrast-enhanced harmonic wideband gray-scale sonography is potentially useful for evaluating the therapeutic effects of transcatheter arterial chemoembolization on hepatocellular carcinoma.

Quantitative assessment of fetal bowel echogenicity: comparison of harmonic, compound, and fundamental sonographic images

PURPOSE

The aims of this study were to assess normal fetal bowel echogenicity quantitatively and to compare the levels of bowel echogenicity observed with the use of 3 different sonographic image-processing techniques-harmonic plus compound imaging, harmonic imaging alone, and fundamental imaging-and 2 different broadband transducers.

METHODS

Women with normal singleton second-trimester fetuses underwent sonographic scanning with both a 2-5-MHz and a 4-7-MHz transducer. The use of the 3 imaging techniques and the 2 transducers resulted in 6 types of images: 2-5-HC (harmonic plus compound images), 2-5-H (harmonic images), and 2-5-F (fundamental images), and 4-7-HC, 4-7-H, and 4-7-F images. The relative echogenicities (brightness) of the fetal bowel and iliac bone were measured, and bowel echogenicity ratios (bowel echogenicity/iliac bone echogenicity x 100) were calculated using graphics software. The resulting data were analyzed to evaluate differences in echogenicity ratios between the 6 types of images.

RESULTS

We examined 37 fetuses during the study period. The bowel echogenicity ratios were highest on the images obtained with harmonic and compound-imaging techniques (2-5-HC, 84.7 +/- 23.4%; 4-7-HC, 98.5 +/- 36.4%). The bowel echogenicity ratio for the 2-5-HC images was significantly higher than those for the 2-5-H and the 2-5-F images (p < 0.01 and p < 0.001, respectively), and those for the 4-7-HC and 4-7-H images were higher than that for the 4-7-F images (p < 0.01 for both comparisons).

CONCLUSIONS

A sonographic finding of echogenic fetal bowel should be interpreted cautiously because the use of special image-processing techniques can artificially enhance the apparent level of echogenicity of the bowel. We recommend rescanning without the use of those techniques if the fetal bowel appears to have an increased level of echogenicity.

A straightforward algorithm for the quantification of power Doppler signals

RATIONALE AND OBJECTIVES

To document a simple algorithm that quantifies power Doppler signals by computer-based statistical image analysis.

METHODS

Personal computer-based software was developed. Color pixels representing power Doppler signals were separated from the background gray pixels in power Doppler images converted in BMP format. To avoid misregistration during this segmentation, a threshold value is required to adequately distinguish between gray and color pixels. Equating the intensity of each color pixel to a Power Value (PV), a histogram of Power Values in power Doppler images was obtained.

RESULTS

The software was designed to allow users to adjust two thresholds (Difference Threshold and Intensity Threshold) by observing the segmentation results in real time. The software calculates the following indexes within any region of interest as defined by the operator: mean PV, peak PV, standard deviation of PV, percentage power Doppler area, and integrated PV per unit area.

CONCLUSIONS

Power Doppler signals can be objectively quantified using this straightforward algorithm. This simple and practical method can be applied to comparative or longitudinal studies upon vascularity or blood flow.

Sonographic evaluation of breast nodules: comparison of conventional, real-time compound, and pulse-inversion harmonic images

OBJECTIVE

To compare the use of conventional, real-time compound, and pulse-inversion harmonic imaging in the evaluation of breast nodules.

MATERIALS AND METHODS

Fifty-two breast nodules were included in this study, conducted between May and December 2000, in which conventional, real-time compound, and pulse-inversion harmonic images were obtained in the same plane. Three radiologists, each blinded to the interpretations of the other two, evaluated the findings, characterizing the lesions and ranking the three techniques from grade 1, the worst, to grade 3, the best. Lesion conspicuity was assessed, and lesions were also characterized in terms of their margin, clarity of internal echotexture, and clarity of posterior echo pattern. The three techniques were compared using Friedman's test, and interobserver agreement in image interpretation was assessed by means of the intraclass correlation coefficient.

RESULTS

With regard to lesion conspicuity, margin, and internal echotexture of the nodules, real-time compound imaging was the best technique (p < 0.05); in terms of posterior echo pattern, the best was pulse-inversion harmonic imaging (p < 0.05). Real-time compound and pulse inversion harmonic imaging were better than conventional sonography in all evaluative aspects. Interobserver agreement was greater than moderate.

CONCLUSION

Real-time compound and pulse-inversion harmonic imaging procedures are superior to conventional sonography in terms of both lesion conspicuity and the further characterization of breast nodules. Real-time compound imaging is the best technique for evaluation of the margin and internal echotexture of nodules, while pulse-inversion harmonic imaging is very effective for the evaluation of the posterior echo patterns.

Comparison of contrast-enhanced fundamental imaging, second-harmonic imaging, and pulse-inversion harmonic imaging

RATIONALE AND OBJECTIVES

To investigate the feasibility of recent contrast-specific ultrasound techniques in depicting vascular flow and the effects of changing the output power of the transducer and insonation mode on contrast enhancement, the authors performed an experimental study with a flow phantom.

METHODS

While changing the mechanical index and the sound insonation mode (continuous and intermittent), images were obtained with three contrast-enhanced ultrasound techniques: fundamental, second-harmonic, and pulse-inversion harmonic imaging (PIHI) after a bolus injection of microbubble contrast agent. The images were compared on a time-intensity curve.

RESULTS

In assessing fixed flow (10 cm/s), PIHI showed the best depiction of flow signal. In intermittent scanning, increases in the mechanical index caused stronger flow signals and longer enhancement duration in all techniques. However, continuous scanning revealed poor depiction of flow signal regardless of the technique or changes in the mechanical index because of significant bubble destruction.

CONCLUSIONS

Microbubble-enhanced PIHI with intermittent scanning at a high mechanical index can depict vascular flow highly effectively without shortening the duration of enhancement.

Contribution of power Doppler sonography to the detection of renal allograft rejection in the cynomolgus monkey

RATIONALE AND OBJECTIVES

To evaluate whether a change in the power Doppler (PD) flow signals produced by the renal cortical interlobular vasculature of allografts in cynomolgus monkey transplant models is useful for the detection of cellular rejection and vasculopathies.

METHODS

Seventy-three monkeys with life-supporting allografts (bilateral native kidney nephrectomy) and 20 monkeys with allografts implanted with only unilateral native kidney nephrectomy were examined with ultrasound that included an examination with PD. Each graft received a PD score of 3 (normal cortical blush), 2 (reduced flow, no blush), or 1 (absence of cortical flow), and the results were compared with histology either from ultrasound-guided biopsy or at necropsy.

RESULTS

One hundred seventy-one allograft examinations (histological and PD) were compared. Histologically normal grafts were statistically more likely to have normal PD findings than were those with reduced flow or absent flow. Allografts with reduced flow had statistically more severe cellular rejection than those with normal flow. Also, vasculopathies were present in all three PD groups.

CONCLUSIONS

Reduced renal cortical flow in the cynomolgus monkey renal allograft indicates that more severe degrees of cellular rejection are present compared with allografts with normal flow. Overlap in the histological diagnoses of allografts with normal and reduced flow exists, and the finding of reduced flow with PD may be prognostically important and indicates the need for tissue sampling.

Using contrast-enhanced sonography to assess the effectiveness of transcatheter arterial embolization for hepatocellular carcinoma

OBJECTIVE

We evaluated the usefulness of contrast-enhanced wideband harmonic gray-scale sonography in assessing the therapeutic effects of transcatheter arterial embolization for patients with hepatocellular carcinoma and compared the findings of this imaging modality with those of helical CT.

SUBJECTS AND METHODS

Twenty-nine patients with 39 hepatocellular carcinoma lesions were examined. We scanned lesions before and after therapy using contrast-enhanced wideband harmonic gray-scale sonography after injection of a galactose-palmitic acid contrast agent. All patients held their breath for 20--50 sec after injection while the vascularity of the tumor was observed. We then monitored tumor enhancement between 60 and 180 sec after injection with patients breath-holding for a few seconds. Lesions were considered to exhibit viable tumor residue if hypervascular enhancement was observed in the tumor. We compared this enhancement with helical CT findings.

RESULTS

After therapy, 36 of the 39 lesions showed viable tumor residue on contrast-enhanced wideband harmonic gray-scale sonography, with no artifacts from iodized oil. Helical CT revealed a high-attenuation area in 12 of the 36 lesions, whereas 24 of the 36 lesions could not be evaluated for tumor residue as a result of artifacts from iodized oil accumulation in the tumor. The remaining three lesions showed complete deposition of iodized oil and complete necrosis on contrast-enhanced wideband harmonic gray-scale sonography.

CONCLUSION

Contrast-enhanced wideband harmonic gray-scale sonography is useful in evaluating the therapeutic effects of transcatheter arterial embolization for hepatocellular carcinoma.

Renal multigated spectral Doppler imaging before and after captopril challenge

RATIONALE AND OBJECTIVES

A new method of measurement, simultaneous multigated spectral Doppler imaging (MSDI), was used to quantify the hemodynamic changes in kidneys after administration of captopril.

METHODS

Forty kidneys in 22 hypertensive patients were included in the study. All underwent MSDI and scintigraphy before and after administration of captopril.

RESULTS

With scintigraphy used as the gold standard for diagnosing renal artery stenosis (RAS), three kidneys were found to be positive for RAS. Multigated spectral Doppler imaging detected a decrease in the resistive index after administration of captopril in all patients with RAS and correctly excluded RAS in one patient who was diagnosed as having RAS on scintigraphy. The resistive index was increased after captopril administration in normally functioning kidneys and was unchanged in kidneys with impaired function.

CONCLUSIONS

With further supportive evidence, MSDI may prove to be a powerful tool for the acquisition of resistive index information and may increase the value of the resistive index as a physiological hemodynamic parameter in the evaluation of normal and abnormal conditions.