Correlation between renal vascular resistance, pulse pressure, and the resistive index in isolated perfused rabbit kidneys.

PURPOSE: To assess the effect of acute changes in renal vascular resistance (RVR) and pulse pressure on the resistive index (RI) measured by using Doppler ultrasonography (US). MATERIALS AND METHODS: Rabbit kidneys were perfused by using a pulsatile perfusion system in which RVR, systolic and diastolic pulse pressures, and pulse kinetics were controlled and monitored while simultaneously measuring the RI. RESULTS: When RVR was increased fivefold with phenylephrine hydrochloride, the RI increased only slightly (from 0.45 at baseline up to 0.50). There was a virtually linear relationship between the RI and the pulse pressure index ([systolic pressure-diastolic pressure]/systolic pressure) in the range of 0.30-0.80. The RI was not affected by the pulse rate or fraction of time that systolic pressure was applied during the pulse cycle. CONCLUSION: Contrary to conventional teaching, which is based on theoretic considerations, the RI is not readily affected by acute changes in RVR. This indicates a need to reconsider the conventional explanations used to explain increases in RI that are frequently found in patients with renal disease or ureteral obstruction.

Blood flow in healthy gallbladder walls on color and power Doppler sonography: effect of wall thickness and gallbladder volume.

OBJECTIVE: The purpose of this study was to determine the effect of gallbladder contraction on the conspicuity of flow in the normal gallbladder wall. SUBJECTS AND METHODS: Ten healthy adult volunteers without clinical evidence of gallbladder disease participated in the study. After patients fasted overnight, the gallbladder was scanned using gray-scale, color Doppler, and power Doppler sonography. The subjects were then given a standard meal consisting of 478 ml of a carbohydrate-rich dietary supplement, and the imaging sequence was repeated 20 and 45 min thereafter. Mural flow was graded using a four-step grading scheme. Gallbladder volume, wall thickness, and visibility of mural flow at all three time points were statistically compared. RESULTS: Enhanced mural flow was seen after meal consumption in all but one volunteer. Overall, mural flow was significantly greater 45 min after eating than at baseline or 20 min on color Doppler sonography (p = .004) and power Doppler sonography (p = .008). CONCLUSION: Flow in the gallbladder wall is a normal finding that is seen more easily when the gallbladder is contracted. This fact must be kept in mind when sonography is used with patients in whom acute cholecystitis is suspected, particularly if they do not fast before sonography.

Effect of injection rate of contrast medium on pancreatic and hepatic helical CT.

PURPOSE: To assess the effect of the injection rate of contrast medium on pancreatic and hepatic enhancement at abdominal helical computed tomography (CT). MATERIALS AND METHODS: Sixty-four contrast medium-enhanced abdominal helical CT scans (64 adult patients) were obtained with 150 mL of contrast medium. The injection rate was 2.5 mL/sec for the first 32 scans and 5.0 mL/sec for the remaining 32. Scans were obtained at 5-sec intervals, with an intermediate 8-sec breathing interval. Hepatic and pancreatic enhancement levels were measured and averaged, and time-attenuation curves were plotted for both groups. Differences in weight, age, time to peak pancreatic and hepatic enhancement, and peak enhancement were assessed with the Student t test. RESULTS: Both peak enhancement and time to peak enhancement were significantly different between the two injection rates (P < or = .002), with faster, more intense hepatic and pancreatic enhancement at the higher rate. At 2.5 mL/sec, the pancreas reached a peak attenuation level of 65 HU at 69 sec, and the liver reached a peak of 58 HU at 87 sec. At 5.0 mL/sec, the pancreas reached a peak attenuation of 84 HU at 43 sec, and the liver reached a peak of 75 HU at 63 sec.

Effect of hydration status on renal medulla attenuation on unenhanced CT scans.

OBJECTIVE: The purpose of this study was to assess the effect of hydration status on renal medulla attenuation during unenhanced CT. SUBJECTS AND METHODS: An unenhanced CT scan was obtained in 10 healthy men after 12-18 hr of complete fluid restriction and again after rehydration. CT images were reviewed for the presence and extent of dense renal medulla, defined as greater attenuation than the adjacent cortex. CT findings were correlated with urine-specific gravity and osmolality. RESULTS: Eight of the 10 subjects showed dense renal medulla on a CT scan after dehydration. After rehydration, complete resolution was seen on the CT scan in four of the eight subjects; three of the eight subjects showed a decrease in the extent of dense renal medulla. After rehydration, the eighth subject showed a slight increase in the attenuation of the renal medulla on the CT scan. Dense renal medulla was seen significantly more often on dehydration images (p = .035). CONCLUSION: Increased renal medulla attenuation on an unenhanced CT scan can be a normal finding related to dehydration.

Ultrasound assessment of testicular and paratesticular masses.

This article discusses the role of ultrasound in the workup of patients with suspected or palpable scrotal masses. By characterizing masses as intra- or extratesticular, the differential diagnosis can be narrowed considerably. Neoplasm is the primary concern with intratesticular masses, although non-neoplastic conditions, such as hematoma and focal orchitis, may have a similar appearance. Correlation with the patient's history is essential. The sonographic presentation of extratesticular pathology, including varicocele and masses of epididymal origin, is also described.

Value of selective second-look sonography by radiologists.

PURPOSE: To assess the usefulness of sonography performed by radiologists after a review of the sonographer's findings. MATERIALS AND METHODS: A total of 398 sonograms were obtained in 392 patients. Sonographers presented preliminary images and impressions to radiologists, who performed additional imaging and recorded their conclusions. Radiologists also attempted to predict in which cases their scan was likely to show new findings or to refute the sonographer's findings. Follow-up data were obtained whenever the sonographer's and the radiologist's findings disagreed. RESULTS: In 28 cases, the radiologist made important new findings. Positive initial findings were refuted in 24 cases. Discrepant findings were seen in 22% of cases in which additional scanning was predicted to be beneficial, compared with only 6% of cases in which second-look sonography was predicted not to be of value. This difference was statistically significant (P<.0001). CONCLUSION: Second-look sonography by radiologists provides a valuable check of the sonographer's findings.

Strategies for developing effective computer-assisted instruction: a computer-based teaching module on color Doppler US.

Computer-assisted instruction is an effective method for teaching visually oriented subjects such as ultrasonography. Although many different forms of instructional strategy can be effective, the process of designing a teaching program should follow the same general procedures, regardless of the format. The first step is to consider the subject material and the target audience; this helps to determine the style of the computer-user interaction (eg, whether the program should be more interactive or dissertative in nature). Teaching objectives should be carefully defined and resources for development identified. Before actually writing the program, the authors should carefully define a lesson plan and develop a set of specifications for implementation. Finally, the program should be tested thoroughly before it is put to use, and the effectiveness of the instruction should be evaluated.

Transvaginal sonographic evaluation of endometrial polyps.

The purpose of this study was to correlate the sonographic and histologic findings of focal lesions of the endometrium as depicted by transvaginal sonography. Sixteen focal endometrial masses were encountered during an 8 month period. The transvaginal sonographic appearance was correlated with findings at surgery or hysteroscopy. All uniformly hyperechoic endometrial masses were benign endometrial polyps. Five heterogeneous lesions were complicated endometrial polyps; one of these showed a focus of endometrial carcinoma. Four small and uniformly hypoechoic lesions were all prolapsed submucosal leiomyomata. Our results showed that a well-defined, uniformly hyperechoic mass within the endometrial cavity is most suggestive of a benign endometrial polyp. Larger masses with a heterogeneous appearance are nonspecific and warrant further evaluation and biopsy.

Color Doppler imaging findings in patients with Budd-Chiari syndrome: correlation with venographic findings.

OBJECTIVE: This study was undertaken to evaluate color Doppler imaging findings in patients with Budd-Chiari syndrome and to compare these findings with results of venography. SUBJECTS AND METHODS: In a prospective study, 21 patients with proved Budd-Chiari syndrome had color Doppler imaging. Sonographic evaluations ware performed to detect appropriately directed flow in the hepatic veins, portal vein, and inferior vena cava. Intrahepatic collaterals were characterized when present. Results of color Doppler imaging were compared with those of angiography in 20 patients. Color Doppler images of the hepatic veins were also obtained in a reference group (20 control subjects, 20 patients with hepatomegaly, and 20 patients with cirrhosis). RESULTS: Color Doppler imaging showed abnormalities of anatomy or flow in one or more of the main hepatic veins in all 21 patients with Budd-Chiari syndrome. Commonly observed abnormalities were visualization of a hepatic vein on real-time sonograms that had no flow or retrograde flow on color Doppler sonograms (11 cases) and no visualization of part or all of a hepatic vein on either real-time or color Doppler sonograms (10 cases). When compared with venographic findings (16 patients), findings on color Doppler sonograms could be used to distinguish patent from occluded hepatic veins in all cases. In our reference group, real-time and color Doppler sonograms showed normal hepatic veins in all control subjects. Real-time sonograms clearly showed hepatic veins in 12 of 20 patients with hepatomegaly; color Doppler sonograms showed flow in the hepatic veins in all 20 of these patients. Among 20 patients with cirrhosis, real-time sonograms showed hepatic veins in only seven; color Doppler imaging confirmed patent veins in 17. Intrahepatic collaterals typical of Budd-Chiari syndrome were observed in 10 of 21 patients with the syndrome. The portal vein was assessed by using color Doppler imaging in all 21 patients with Budd-Chiari syndrome; portograms were available for comparison in 10 patients. Findings were consistent in eight; in two cases, the direction of flow was reversed on color Doppler sonograms compared with portograms. For the inferior vena cava, venographic and sonographic findings correlated in 16 of 20 cases. Color Doppler sonograms did not show a caval web in one patient. CONCLUSION: Abnormalities of the hepatic veins, portal veins, and inferior vena cava detected on color Doppler sonograms in patients with Budd-Chiari syndrome correlate well with findings on venograms.(ABSTRACT TRUNCATED AT 400 WORDS)

Sonographic findings after surgical ablation of the endometrium.

OBJECTIVE: Endometrial ablation is a new surgical technique that is an alternative to hysterectomy in women with dysfunctional uterine bleeding. The endometrium is either coagulated or resected in an attempt to render the patient amenorrheic. Because of the newness of the procedure, no report of radiologic findings after endometrial ablation has been published. Accordingly, the sonographic appearance of the uterus after endometrial ablation is described. MATERIALS AND METHODS: Using transvaginal sonography, we examined a select group of 16 women, seven of whom were symptomatic after endometrial ablation. All patients had a preoperative diagnosis of menorrhagia not responsive to conventional hormonal therapy and no evidence of cancer. RESULTS: In the seven symptomatic patients, sonography showed that postoperatively two had hematometra, one had a nonviable intrauterine pregnancy, and four had residual islands of functioning endometrial tissue alone or in combination with hematometra. In nine asymptomatic patients, postoperative sonography showed seven had normal findings except for leiomyomata and two had residual islands of functioning endometrial tissue. CONCLUSION: Sonographic examination of the uterus after endometrial ablation provides a method for evaluating symptomatic patients and for identifying any remaining endometrium that could later become symptomatic.

Color Doppler imaging of the hepatic vasculature.

Duplex sonography added a new dimension to real-time sonographic imaging and can be used to characterize flow dynamics. Unfortunately, duplex sonography also has significant drawbacks, most of which are the result of the limited sampling ability of pulse-gated technology and the inability to provide a global display of Doppler information. Sonographic imaging of intraabdominal vessels has improved markedly with the advent of color Doppler techniques. This article reviews the use of color Doppler sonography in the evaluation of hepatic vessels. The complementary role of Doppler spectral analysis is also considered.

Fetal exposure from endovaginal ultrasound examinations in the first trimester.

Ultrasonic obstetrical examinations during the first trimester are now often performed endovaginally with higher-frequency (5-7.5 MHz) transducers operating closer to the fetus than for transabdominal examinations. To estimate exposure to the fetus, propagation distances were obtained from a retrospective study of 100 normal first-trimester endovaginal B-mode examinations. No significant dependence of attenuation on gestational age was observed. The range of the attenuation estimates was 1.8-10.4 dB. A mean attenuation of 5.0 dB at 5 MHz for an average depth of 2.8 cm resulted in an attenuation coefficient of .36 dB/cm/MHz. Exposure (ISPTA) to the fetus at each gestational week from three ultrasound units was very similar: worst-case values of the 100 cases ranged from 1.2-1.9 mW/cm2, well within the Food and Drug Administration (FDA) guidelines of 94 mW/cm2 for derated focused transducers. Energy density deposited to the anterior surface of the fetus during a typical examination, assuming that the transducer is kept stationary over one area for the entire period of the examination (which is unlikely), ranged from 143-217 mJoules/cm2, within the American Institute of Ultrasound in Medicine (AIUM) recommendations.