Methods for quantifying ultrasound backscatter and two-dimensional video intensity: implications for contrast-enhanced sonography

Myocardial ultrasonic tissue characterization in patients with thyroid dysfunction

Background

Structural myocardial abnormalities have been extensively documented in hypothyroidism. Experimental studies in animal models have also shown involvement of thyroid hormones in gene expression of myocardial collagen. This study was planned to investigate the ability of ultrasonic tissue characterization, as evaluated by integrated backscatter (IBS), to early identify myocardial involvement in thyroid dysfunction.

Patients and Methods

We studied 15 patients with hyperthyroidism (HYPER), 8 patients with hypothyroidism (HYPO), 14 patients with subclinical hypothyroidism (SCH) and 19 normal (N) subjects, who had normal LV systolic function. After treatment, 10 HYPER, 6 HYPO, and 8 SCH patients were reevaluated. IBS images were obtained and analyzed in parasternal short axis (papillary muscle level) view, at left ventricular (LV) posterior wall. The following IBS variables were analyzed: 1) the corrected coefficient (CC) of IBS, obtained by dividing IBS intensity by IBS intensity measured in a rubber phantom, using the same equipment adjustments, at the same depth; 2) cardiac cyclic variation (CV) of IBS - peak-to-peak difference between maximal and minimal values of IBS during cardiac cycle; 3) cardiac cyclic variation index (CVI) of IBS - percentual relationship between the cyclic variation (CV) and the mean value of IBS intensity.

Results

CC of IBS was significantly larger (p < 0.05) in HYPER (1.57 ± 0.6) and HYPO (1.53 ± 0.3) as compared to SCH (1.32 ± 0.3) or N (1.15 ± 0.27). The CV (dB) (HYPO: 7.5 ± 2.4; SCH: 8.2 ± 3.1; HYPER: 8.2 ± 2.0) and the CVI (HYPO: 35.6 ± 19.7%; SCH: 34.7 ± 17.5%; HYPER: 37.8 ± 11.6%) were not significantly different in patients with thyroid dysfunction as compared to N (7.0 ± 2.0 and 44.5 ± 15.1%).

Conclusions

CC of IBS was able to differentiate cardiac involvement in patients with overt HYPO and HYPER who had normal LV systolic function. These early myocardial structural abnormalities were partially reversed by drug therapy in HYPER group. On the other hand, although mean IBS intensity tended to be slightly larger in patients with SCH as compared to N, this difference was not statistical significant.

Contrast Sonography, Video Densitometry and Intervillous Blood Flow: A Pilot Project

PURPOSE

To examine the feasibility of constructing time-intensity (TI) curves from the intervillous space with an intravascular ultrasound contrast agent and computer assisted video densitometry.

STUDY DESIGN

We sedated nine pregnant baboons, optimized the grey scale and color Doppler images of their placentas, and then fixed the transducers in place. For each injection of contrast, we recorded images on videotape without changing the ultrasound image processing functions. Video images were captured using a Macintosh personal computer equipped with a video-capture board using image analysis software (Image 1.4, W Rasband, NIH). For each injection, we sampled digitized images of a fixed region of interest at regular intervals. After computing the mean video density of each image, we used the sampling frequency to construct TI curves depicting any change over time as the contrast agents washed into and out of the intervillous space.

RESULTS

Three of four agents tested produced changes in the video density of the placenta. TI curves were established using both grey scale and color Doppler signal augmentation. As expected, intra-arterial agents produced rapid accumulation and decay. Intravenous agents produced more protracted effects secondary to bolus dilution and transit through the right heart and pulmonary vascular bed.

CONCLUSION

TI curves may be generated from the intervillous space with the use of a transpulmonary ultrasound contrast agent and video densitometry. If validated by further study, this may allow investigators to apply ultrasound and indicator-dilution theory to intervillous blood flow.

Establishment of experimental hepatic steatosis model in rabbits and non-invasive quantitative ultrasonic diagnosis of fatty liver disease

AIM: To explore the non-invasive, quantitative ultrasonic diagnostic criteria of fatty liver diseases by establishing a rabbit model of hepatic steatosis and measuring ultrasonic integrated backscatter (IBS) and gray scale (GS).

METHODS: Forty healthy New Zealand rabbits were randomly divided into normal control and three experimental groups. Hepatic steatosis was induced by high fat and sugar diet plus drinking water containing five percent of ethanol. Seven patients with mild or severe hepatic steatosis were also recruited in the study. The steatosis, inflammation, and fibrosis of the rabbits' and patients' liver were evaluated by several histological staining methods including Sudan IV, H&E, and Masson's Trichrome staining. Hepatic steatosis was graded as simple steatosis, steatohepatitis, fibrosis and cirrhosis. Liver IBS including average image intensity (AII) and peak-peak intensity, and GS were measured using HP Sonos 5500 image system. The data were analyzed with one-way ANOVA.

RESULTS: Hepatic AII was associated with the aggravated hepatic steatosis in near areas of the rabbit liver, i.e., normal control < mild fatty liver < moderate fatty liver < severe fatty liver (P < 0.0001). Significant differences were observed between AII of steatohepatitis and simple hepatic steatosis. In the patients, IBS was more accurate in the reflection the severity of the liver pathology than routine ultrosonic examination (85.7% vs 57.1%, P < 0.05), and significant differences of AII were observed between mild and severe hepatic steatosis (P < 0.0001, 0.001 or 0.05). The liver GS were markedly increased in the moderate and severe fatty liver as compared with that in normal control and mild fatty liver. Correlation analysis showed that GS and AII were consistently increased as the disease aggravated in the near area of the left and right liver lobes of the animals (r₁ = 0.442 21, P₁ = 0.0012; r₂ = 0.335 73, P₂ = 0.0160).

CONCLUSION: Rabbit fatty liver models can be developed in a short time by high fat and sugar diet plus alcohol. Hepatic IBS and GS intensity can reflect the grades of hepatic steatosis, inflammation and fibrosis, so they may serve as reliable non-invasive tools for the quantitative diagnosis of fatty liver disease.

Ultrasonic tissue characterization for patients with Chagas' disease

This study was undertaken to test the hypothesis that ultrasonic tissue characterization, as evaluated by intensity and cardiac cyclic variation of integrated backscatter (IBS), could identify early myocardial involvement in Chagas' disease. We evaluated 69 participants, age 15 to 73 years (mean +/- SD: 49 +/- 12 years), who were divided as following: 19 control subjects; 13 patients with the indeterminate form of Chagas' disease; 7 patients with the digestive form; and 30 patients with the cardiac form. IBS images were obtained in parasternal short-axis (basal, papillary muscle, apical) view and analyzed in 12 left ventricular (LV) segments (anterior, lateral, posterior, and septal). The following IBS variables were evaluated: (1) the corrected coefficient (CC) of IBS, obtained by dividing IBS intensity, in each cardiac segment, by IBS intensity measured in a rubber phantom using the same equipment adjustments at the same depth; and (2) magnitude of cardiac cyclic variation (MCV) of IBS, as measured by the peak-to-peak difference between maximal and minimal values of IBS in cardiac cycle. The CC of IBS was increased (P <.05) for patients with the cardiac form who had LV segments with normal wall motion as compared with control subjects, in 4 of 12 segments evaluated (basal anterior, midposterior and midseptal, anterior apical), whereas the remaining chagasic groups were comparable with controls subjects. The CC of IBS tended to increase with worsening of LV segmental wall motion. MCV showed a large individual variability and had a large mean value (P <.05) in just 1 of 12 segments evaluated, when patients with the cardiac form were compared with control subjects. No correlation was observed between the magnitude of LV dysfunction and MCV of IBS.

IN CONCLUSION

(1) the CC of IBS was able to provide early differentiation of cardiac involvement for patients with Chagas' disease who had LV segments with normal wall motion; (2) increase of CC of IBS with worsening of LV segmental wall motion suggests a relationship between the acoustic properties of myocardial tissue and grading of myocardial fibrosis; (3) MCV was not able to differentiate patients with Chagas' disease from control subjects; and (4) patients with the indeterminate form of Chagas' disease were not differentiated from control subjects by any of the IBS techniques evaluated in this study.

Quantitative microbubble enhanced transrectal ultrasound as a tool for monitoring hormonal treatment of prostate carcinoma

BACKGROUND

We quantified changes in prostate carcinoma vascularity treated with anti-androgens using color Doppler and power transrectal ultrasound in combination with microbubble contrast agent Levovist.

METHODS

Thirty-six men with prostate carcinoma were studied at baseline and at intervals during treatment. At each attendance, Levovist((R)) (10 ml, 300 mg/ml) was given as an iv bolus. Using quantitative analysis, we calculated the pre-enhancement scores, arrival time, time to peak, peak value, and area under the time-enhancement curve (AUC). These were compared to pre-treatment values and serial PSA measurements.

RESULTS

The pre-enhancement, peak value, and AUC each showed a marked response with reductions within one week. The average AUC declined to 68% +/- 9% (mean +/- standard error) by week 1, 56% +/- 9% by week 3, and 20% +/- 4% by week 6. A strong correlation with changes in the mean PSA (r = 0.95, P < 0.001) was also measured. In four patients, Doppler indices did not fall with PSA: two patients with the most marked discrepancy relapsed at 6 months.

CONCLUSION

The vascular enhancement declined with therapy, similar to PSA. Microbubble enhanced ultrasound can show early response to treatment.

Sonographic investigation of flow patterns in the perfused human placenta and their modulation by vasoactive agents with enhanced visualization by the ultrasound contrast agent Albunex

PURPOSE

Our objective was to demonstrate sonographically the flow distribution in the circulation of human placentae as well as the sensitivity of the human fetal capillary bed to vasoconstriction and dilatation.

METHODS

Five human full-term placental lobules were maintained in vitro with fetal and maternal flow. Commercial ultrasound scanners were used for imaging. Albunex (1 ml bolus) was administered to the fetal "artery" to monitor patterns of flow. U46619 (1 ml, 10(-6) M; a thromboxane agonist and potent vasoconstrictor) and/or nitroglycerin (a potent vasodilator) were added to the fetal artery.

RESULTS

Following the addition of U46619, mean "fetal pressures" rapidly rose from 23.2 +/- 0.8 to 118 +/- 2. 9 mm Hg (mean +/- standard error of mean; p < 0.001); venous flow rates decreased. As demonstrated by color Doppler imaging, flow markedly changed from a pattern of general distribution throughout the lobule to flow only near the chorionic plate. Color persistence was 94.4 +/- 6.5 seconds with Albunex after nitroglycerin and 39.8 +/- 3.4 seconds with Albunex after injection of U46619 (p < 0.001). Nitroglycerin had no effect when injected by itself but returned "constricted" flow to a "normal" pattern when injected after U46619.

CONCLUSIONS

The contrast medium Albunex improved visualization of the fetal circulation throughout the lobule. Flow in the human placental capillary bed can be regionally manipulated throughout the placental lobule by vasomodulators and monitored by Albunex-enhanced sonographic examination.