Biomedical subjects

J B Liu

Publications and source records attributed to J B Liu.

At least 73 records · Page 4Linked to original sources

PubMed1996

Comparison of high-resolution endoluminal sonography to video endoscopy in the detection and evaluation of esophageal varices.

High-resolution endoluminal sonography (HRES) was used to image and measure esophageal varices in control subjects and patients with portal hypertension and compared with endoscopic findings. Nine control patients and 68 patients with known cirrhosis or noncirrhotic portal hypertension underwent videotaped HRES and videotaped esophagoscopy (EGD). Two blinded investigators reviewed the videotapes to determine the presence and size of the largest esophageal varix in each patient. The largest varix by HRES was measured with the esophagus at rest at a point where the varix appeared most circular. The largest varix seen on EGD was graded on a 5-point scale. All nine of the control patients were correctly identified by both EGD and HRES as grade I (no varices). Eight of the 10 patients with no varices seen on EGD had varices identified by HRES. The interobserver correlation for HRES was r = .88 and for EGD was r = .79. The correlation between EGD and HRES was r = .50. High resolution endoluminal sonography allows quantitative measurement of variceal size, is a more sensitive and reproducible imaging modality than esophagoscopy for the detection and sizing of esophageal varices. There is poor correlation between monographic measurement and endoscopic grading of esophageal varices. Assessment of esophageal variceal presence and the measurement of variceal size by high resolution endoluminal sonography is an accurate, reproducible method of determining the size of esophageal varices.

Adult↗

PubMed1996

Use of high-resolution endoluminal sonography to measure the radius and wall thickness of esophageal varices.

BACKGROUND: Measurement of variceal wall tension theoretically provides the most accurate method of predicting future variceal bleeding. Using high-resolution endoluminal sonography in 45 patients with known portal hypertension, we measured and correlated the two previously unmeasured variables involved in the calculation of variceal wall tension (radius and wall thickness) by the Laplace equation. METHODS: A 20 MHz 6.2F ultrasound transducer was used to image esophageal varices during standard esophagoscopy. All images were captured on videotape and later reviewed by two blinded investigators. Outer and inner variceal wall circumferences were measured at a cross section of each varix. The radius of each varix and the variceal wall thickness were calculated. The radius of each varix was then correlated with its wall thickness. The interobserver and intraobserver variabilities were measured. RESULTS: The mean variceal radius was .86 +/- .34 cm for the inner radius and 1.48 +/- .41 cm for the outer radius; mean variceal wall thickness was .099 +/- 0.037 cm. Intraobserver and interobserver correlation for the radius was r = .98 and r = .97, respectively. The intraobserver and interobserver correlations for the wall thickness were r = .92 and r = .91, respectively. Variceal radius did not correlate with the wall thickness of the varix. CONCLUSIONS: High-resolution endoluminal sonography provides a method for the accurate measurement of esophageal variceal radius and wall thickness. Variceal radius does not correlate with variceal wall thickness, implying that variceal wall tension cannot be accurately estimated by measurement of variceal size alone. Combining these data with measurements of variceal pressure should allow for the direct determination of wall tension and, subsequently, identification of patients at risk for variceal bleeding.

Adult↗

PubMed1996

Endoluminal sonographic imaging of the ureteropelvic junction.

Endoluminal ultrasound imaging of the ureter can demonstrate the periureteral anatomy. Ultrasound probes are available as catheters from 3.5F to 6.2F. The transducer is available as a 12.5 or 20 MHz design and gives a cross-sectional image with penetration of 1.5 to 2 cm. Endoureteral ultrasonography has demonstrated blood vessels associated with the obstructed ureteropelvic junction (UPJ) in more than 50% of patients. These vessels have been located at all sites adjacent to the UPJ. The anteromedial location is the most common site. In comparison, only 8 significant crossing vessels were found in 44 patients with a normal UPJ. Inspection of the UPJ with a high insertion of the ureter demonstrates a characteristic sonographic image with a septum between the ureteral and renal pelvic lumen. Endoluminal ultrasonography of the obstructed UPJ can be used to guide the site of endopyelotomy to avoid damage to adjacent vessels. The presence of such vessels may also be related to the success of the procedure. An ultrasound-guided cutting device has been developed for preclinical studies.

Humans↗

PubMed1996

Device for intraluminal incision guided by endoluminal ultrasonography.

Intraluminal incision is often used for the treatment of strictures of both the upper and the lower urinary tracts. The depth of the stricture and the location of surrounding structures such as blood vessels are important factors in guiding the incision. Endoluminal ultrasonography has been shown to be effective in defining periureteral anatomy accurately. A new device is described that combines an endoluminal ultrasound transducer and cutting device (electrocautery or laser fiber) in 9F catheter. This catheter was evaluated in two live anesthetized pigs (four kidneys) and four ex-vivo kidneys. Incisions were made at the ureteropelvic junction and middle and distal ureter. The ability to image the periureteral structures and to direct the location and the adequacy of the incision were assessed. Endoluminal ultrasound imaging was excellent, and the electrocautery wire was well seen. Well-defined, limited, full-thickness incisions were made using this device and could be directed accurately toward or away from periureteral vessels. This study demonstrates the potential for endoluminal ultrasound guidance of intraluminal incisions.

Animals↗

PubMed1996

Fecal incontinence: transvaginal US evaluation of anatomic causes.

PURPOSE: To evaluate transvaginal ultrasonography (US) as an alternative to transanal US for determining the anatomic cause of fetal incontinence in women. MATERIALS AND METHODS: Transvaginal US of the anal canal was performed in 28 women (aged 27-74 years) with fecal incontinence. A side-fire endorectal probe was inserted into the vagina and directed toward the posterior vaginal wall. RESULTS: The internal anal sphincter (IAS) and external anal sphincter muscles were imaged as independent bands in all 28 patients. The calculated mean thickness of the IAS in patients aged younger than 55 years was not significantly different from that in patients aged older than 55 years (P=.31). Posttraumatic anterior muscle disruptions were detected in 16 women; three also had rectovaginal fistulas. A rectal fistula with abscess was detected in one of 12 patients with intact muscles. All muscle disruptions, fistulas, and abscesses were surgically confirmed. CONCLUSION: Transvaginal US enables determination of the anatomic cause of fecal incontinence, allowing the surgeon to select patients who would benefit form surgical repair.

Age Factors↗

PubMed1996

Value of sonohysterography in the diagnosis and management of abnormal uterine bleeding.

PURPOSE: To assess the value of sonohysterography in the diagnosis and management of abnormal uterine bleeding. MATERIALS AND METHODS: Sonohysterography was performed in 28 women (aged 29-55 years) in whom transvaginal sonography (TVS) suggested an abnormal endometrial echo (n = 14) or fibroids (n = 14). Its effect on diagnosis and treatment was studied. RESULTS: In the patients with an abnormal endometrial echo, sonohysterography depicted endometrial polyps (n = 9), intracavitary fibroids (n = 3), placental polyp (n = 1), and a normal cavity (n = 1). Hysteroscopic resection resolved the bleeding in 11 of 14 patients; surgery was obviated in one. In the group with fibroids, sonohysterography depicted small submucous fibroids amenable to hysteroscopic myomectomy (n = 5), a small mural fibroid with a normal cavity, which obviated surgical intervention (n = 4), and endometrial polyps, which altered the treatment plan (n = 1). Sonohysterography suggested the need for an abdominal myomectomy (n = 4) and alerted the surgeon to explore the uterine cavity in three patients. CONCLUSION: By helping elucidate the cause of bleeding, sonohysterography assisted in determining the therapeutic approach and often reduced the level of surgical intervention or obviated it altogether.

Adult↗

PubMed1996

On the feasibility of real-time, in vivo harmonic imaging with proteinaceous microspheres.

Harmonic imaging is a new contrast-specific imaging modality, which utilizes the nonlinear properties of microbubble-based sonographic contrast agents by transmitting at the fundamental frequency but receiving at the second harmonic frequency. The feasibility of improving the detection of slow, small-volume blood flow using real-time harmonic imaging has been investigated in vivo. Proteinaceous microspheres (FS069) were administrated to four dogs, two woodchucks (with multiple hepatomas), and one rabbit. Three different scanners were used to obtain real-time images of kidneys and liver (including vessels) in harmonic and conventional gray scale and color flow modes. The duration of contrast enhancement lasted significantly longer in harmonic than in conventional modes (on average 87 s; P = 0.008). Harmonic images were less susceptible to artifacts, such as acoustic shadowing, and a clear increase in the (flow) signal-to-noise ratio was observed. These preliminary in vivo results demonstrate the feasibility of performing real-time, contrast-enhanced harmonic imaging, but further studies are required to establish clinical efficacy.

Animals↗

PubMed1996

Color amplitude imaging: preliminary results using vascular sonographic contrast agents.

Conventional (mean Doppler frequency shift) color Doppler imaging and a new method of displaying blood flow in color that uses the amplitude of the Doppler signal were utilized to evaluate three vascular sonographic contrast agents. To compare the two color flow detection modalities, a total of 20 pairs of contrast agent injections were performed while imaging a variety of abdominal organs and tumors in experimental animal models. The 20 paired injections were scored independently to indicate whether color amplitude imaging better demonstrated the effects of contrast enhancement (n = 14), both techniques were equivalent in demonstrating the effects of contrast enhancement (n = 4), or color Doppler imaging better demonstrated the effects of contrast enhancement (n = 2). These results indicate that compared to color Doppler imaging, color amplitude imaging improved visualization of both normal and abnormal blood flow in 70% of these cases (P < 0.0001). Specifically, with contrast enhancement of the Doppler signals, organ vascularity and regional differences in parenchymal blood flow were better demonstrated with color amplitude imaging than with color Doppler imaging. In addition, since color amplitude imaging is nondirectional and less angle dependent than color Doppler imaging, it was possible to visualize vessel continuity more completely and to demonstrate vessel branching more clearly with this modality. However, owing to the lack of directivity and poor temporal resolution, information obtained with color amplitude imaging appears to be complementary to that of color Doppler imaging. In conclusion, color amplitude imaging is a reliable method of determining the effectiveness of vascular sonographic contrast agents and should be considered one of the primary flow imaging modalities used for the assessment of these agents.

Animals↗

PubMed1996

Laparoscopic liver sonography: preliminary experience in liver metastases compared with CT portography.

This study evaluated the ability of laparoscopic ultrasonography to detect, localize, and characterize focal liver masses. Laparoscopic ultrasonography and CT portography of the liver were performed in 13 patients with known or suspected malignancy. Laparoscopic ultrasonography directly influenced surgical management in four (31%) cases; three by detection of small focal masses and one by exclusion of masses suspected on CT portography. Laparoscopic ultrasonography provided guidance for biopsy or added important anatomic information in three cases. Laparoscopic ultrasonography was complementary to CT portography but added no additional information in three cases, and it failed to provide any information in two cases. Laparoscopic ultrasonography was falsely negative in one case. In this preliminary series, laparoscopic ultrasonography assisted surgeons in critical decision-making by either providing important new information, clarifying questionable areas, or complementing CT portography.

Adult↗

PubMed1995

Correlation of high-frequency esophageal ultrasonography and manometry in the study of esophageal motility.

BACKGROUND & AIMS: No studies correlate manometric measurements with morphological changes during the esophageal peristaltic sequence. The aim of this study was to develop and use a system for sonographically imaging the esophageal wall while simultaneously recording esophageal pressure changes. METHODS: An ultrasonography transducer attached to a manometric probe was used to evaluate the esophagus. RESULTS: Four sonographic phases of an esophageal peristaltic sequence were identified. The esophageal lumen was not open at rest in phase 1 (resting), increased to a maximum mean circumference of 4.90 +/- 0.57 cm in phase 2 (passive distention), and returned to a closed position in phases 3 (contraction) and 4 (relaxation). The muscle layers of the esophageal wall were baseline resting width in phase 1, decreased in width during phase 2, increased and reached maximum mean widths during phase 3, and returned to baseline widths during phase 4. The measurement of esophageal intraluminal pressure remained at a baseline resting level during phases 1 and 2, increased to a maximum mean peak of 67.95 +/- 9.18 mm Hg during phase 3, and returned to baseline during phase 4. CONCLUSIONS: A combined ultrasonography transducer/manometry probe was used to dynamically and simultaneously evaluate esophageal wall motion, muscle thickness, and esophageal pressure changes during peristalsis.

Adult↗

PubMed1995

Volume flow estimation using time domain correlation and ultrasonic flowmetry.

A comparison of two volumetric blood flow measurement techniques, CVI-Q (based on time domain correlation) and ultrasonic flowmetry, has been performed in vitro and in vivo. A pulsatile flowpump was used to simulate carotid and femoral type waveforms which were measured simultaneously using the two methods. Five dogs had their common carotid and femoral arteries exposed, and the instantaneous maximum volume flow and the mean flow were measured. Each vessel was partially occluded halfway through the experiment, simulating a 90% stenosis. In vitro, both techniques achieved absolute errors below +/- 5% for flow rates over 100 mL/min, but ultrasonic flowmetry had statistically significant larger errors for slower flow rates. In vivo correlation coefficients ranging from 0.73 to 0.95 were obtained with regression line slopes close to unity. The two techniques were in reasonable agreement, but with standard deviations of 20% to 28%. These studies indicate that noninvasive CVI-Q measurements of blood flow in the carotid and femoral arteries are linear and accurate compared to invasive ultrasonic flowmetry.

Algorithms↗

PubMed1995

High-resolution endoluminal sonography in achalasia.

BACKGROUND: Imaging of the lower esophageal sphincter in patients with achalasia using 7.5 and 12 MHz ultrasound transducers has shown variable results. METHODS: A 20 MHz radial ultrasound transducer was used to quantitatively compare the lower esophageal sphincter in patients with achalasia to that of normal volunteers. The transducer, housed in a 6.2F catheter, was placed at the level of the lower esophageal sphincter in 29 patients with achalasia and 19 normal subjects. Videotaped images from the lower esophageal sphincter were digitized and the width of the circular smooth muscle, longitudinal smooth muscle, and total muscularis propria were measured. A mean width for each muscle layer was calculated. RESULTS: All muscle layers were found to be significantly thickened at the lower esophageal sphincter in patients with achalasia when compared with those in normal subjects: circular smooth muscle (0.206 cm +/- 0.137 cm vs 0.124 cm +/- 0.038 cm, p < 0.017); longitudinal smooth muscle (0.128 cm +/- 0.077 cm vs 0.088 cm +/- 0.028 cm, p < .041); and total muscle thickness (0.317 +/- 0.180 cm vs 0.224 cm +/- 0.049 cm, p < 0.033). CONCLUSION: Although high-resolution endoluminal sonography cannot be used to differentiate patients with achalasia from normal controls, this study quantitatively demonstrates that both the mean longitudinal and mean circular smooth muscle layers at the lower esophageal sphincter are wider in patients with achalasia than in a group of normal subjects.

Adult↗

PubMed1995

Submucosal calculi: endoscopic and intraluminal sonographic diagnosis and treatment options.

After shock wave lithotripsy and endoscopic lithotripsy, occasionally a patient has persistent ureteral fragments associated with ureteral obstruction. After lithotripsy, stone fragments may be embedded in the ureteral mucosa, and they may become completely submucosal and associated with obstruction. Others may be hidden in iatrogenic ureteral outpouchings, while still others may be extruded from the ureter entirely. We present 20 patients who were referred after previous treatment failed to clear fragments or who had residual obstruction. The majority of patients had failed endoscopic fragment retrieval or shock wave lithotripsy and were referred with ureteral obstruction. All patients were reevaluated by repeated upper tract endoscopy with small diameter endoscopes. As an adjunct to ureteral endoscopy, a 6F, 20 MHz. ultrasound probe was placed transureterally to determine the depth and location of stones. A total of 15 patients in this series had hyperechoic foci with shadowing consistent with submucosal or periureteral stone fragments. A decision for treatment was based upon the location as noted by sonographic and fluoroscopic visualization of intramucosal and submucosal fragments. Calculi more than 4 mm. from the lumen were not removed without evidence of obstruction. Multiple, small (speckled) fragments embedded in the mucosa were often associated with subsequent stricture. Solitary fragments within the wall of the ureter could be removed with relief of obstruction. The risk of embedding calculi submucosally during lithotripsy should be recognized. Submucosal fragments causing obstruction should be removed endoscopically. Totally extruded calculi may be left in situ safely.

Adolescent↗

PubMed1995

Endopyelotomy: importance of crossing vessels demonstrated by endoluminal ultrasonography.

Endoscopic incision has become a common treatment for ureteropelvic junction (UPJ) obstruction. Recent reports have indicated the importance of crossing vessels in the success of endopyelotomy. Endoluminal ultrasound can define the location and size of adjacent vessels, and the effect of these vessels and their location on the success of endopyelotomy can be determined. A group of 28 patients found to have UPJ obstruction on excretory urography, retrograde ureteropyelography, radiographic nuclear scan, and clinical presentation were evaluated by endoluminal ultrasound at the time of endopyelotomy, which was performed by percutaneous nephroscopy or retrograde ureteroscopy. All patients had an indwelling ureteral stent postoperatively. Follow-up evaluation included renal ultrasound and nuclear scans. Excretory urography was performed in several patients. In this preliminary study, the success rate was lower in patients with vessels in a lateral position at the UPJ. The endoscopic approach did not alter the success rate. These factors should be considered in treating primary UPJ obstruction with endoluminal incision.

Adolescent↗

PubMed1995

Intraoperative endo-luminal ultrasound evaluation of urethral diverticula.

The imaging accuracy of a catheter-based endo-luminal ultrasound system was compared to traditional imaging techniques for surgical treatment of urethral diverticula in 7 women and 1 man. At surgical repair the urethra was catheterized directly with a 6.2F or 9F (12.5 or 20 MHz.) catheter-based ultrasound transducer, generating a 360-degree transaxial real-time image. The endo-luminal ultrasound images were compared with preoperative voiding cystourethrography (7 patients), transvaginal ultrasound examinations (3) and double balloon urethrograms (2). Surgical diverticulectomy was then done with endo-luminal ultrasound monitoring. Intraoperatively, all diverticula were well visualized by endo-luminal ultrasound, which demonstrated improved identification of the size and orientation of urethral diverticula, sludge within the diverticula, the extent of periurethral inflammation, diverticular wall thickness, and the distance between the diverticular wall and urethral lumen. In 3 patients the urethral connections of the diverticula were exceptionally well visualized. Comparison with traditional imaging revealed 2 false-negative and 1 false-positive voiding cystourethrograms, 1 false-negative transvaginal ultrasound study and 1 false-negative double balloon urethrogram. Intraoperative monitoring of the urethra enabled precise anatomical dissection, eliminated all diverticular components, and prevented inadvertent urethral and bladder neck injury. Urethral endo-luminal ultrasound is a valuable new adjunct in the evaluation of a variety of urethral abnormalities. This new ultrasound application permits visualization of the precise size, location, orientation and characteristics of urethral diverticula and surrounding tissues. Through enhanced imaging, surgical repair is facilitated. Further application of this technique should increase the diagnostic accuracy of urethral imaging beyond radiographic techniques currently available.

Catheterization↗

PubMed1995

Laparoscopic gray-scale and color Doppler US: preliminary animal and clinical studies.

PURPOSE: To evaluate a semiflexible ultrasound (US) transducer inserted through a laparoscopic port to image abdominal structures. MATERIALS AND METHODS: Laparoscopic US with a 9.6-mm-diameter, 5.0-7.5-MHz semiflexible transducer with gray-scale, color, and spectral Doppler capabilities was performed in three miniature swine and in 25 patients with a variety of abdominal abnormalities. RESULTS: This miniature US probe was used to locate normal structures such as blood vessels, allowing the surgeon to decide the best approach for dissection. Color and spectral Doppler US proved especially useful in differentiating vascular from nonvascular structures. The presence or absence of stones in the gallbladder and common bile duct was readily determined. It was possible to detect masses and to provide guidance for their aspiration or biopsy within abdominal organs. In 10 cases (40%), laparoscopic US helped the surgeon make the decision for clinical management and altered the surgical procedures. CONCLUSION: Laparoscopic US was useful in assisting laparoscopic evaluation of abnormalities in the abdomen.

Abdomen↗

PubMed1995

Endoluminal vascular and nonvascular sonography: past, present, and future.

Almost since the beginnings of medical sonography, investigators have attempted to place miniature sonographic transducers into vascular and nonvascular lumina to image abnormalities. The primary goal of intravascular imaging has been the evaluation of atherosclerotic lesions and the monitoring of interventional therapies in peripheral and coronary arteries. Endoluminal catheter-based sonography has also been used for the evaluation of the genitourinary and gastrointestinal tracts as well as the bronchotracheal tree to image a variety of abnormalities. Intravascular sonography has been widely investigated, and efficacy has been established in some areas. Preliminary reports have shown that endoluminal sonography has the potential to successfully evaluate anatomic and pathologic structures in a variety of nonvascular lumina.

Catheterization↗

PubMed1995

Parenchymal enhancement and tumor visualization using a new sonographic contrast agent.

The purpose of this study was to assess the ability of a sonographic contrast agent to increase parenchymal echogenicity and improve tumor visibility. The agent is an emulsion that changes at body temperature from nonechogenic submicrometer liquid droplets to echogenic 1 to 5 microns microbubbles, capable of transversing the pulmonary and capillary circulations. Peripheral venous injections (dosages of 0.05 to 0.8 ml/kg) were administered to five woodchucks (three with multiple hepatomas), 12 rabbits (with renal VX-2 tumors), and four dogs. Ultrasonograms were acquired from kidney, liver, tumors (including tumor vessels) and normal vessels. Uptake and washout curves were generated via videodensitometry. Finally, Doppler shifts from a cuff transducer around the celiac trunk were analyzed to provide an in vivo dose-response curve. Vascular enhancement, including hepatoma and VX-2 tumor vessels, was seen for 2 to 3 min. Maximum enhancement was 18.7 dB for a 0.6 ml/kg dose. Enhancement of normal liver and kidney parenchyma was observed in all three species for up to 20 min. Small hepatomas became more echogenic centrally, but larger tumors showed no increase in central echogenicity. In conclusion, improved tumor visibility and parenchymal enhancement was demonstrated in animals.

Animals↗