Biomedical subjects

J B Liu

Publications and source records attributed to J B Liu.

At least 19 recordsLinked to original sources

PubMed1997

Improved staging of liver tumors using laparoscopic intraoperative ultrasound.

BACKGROUND: Intraoperative ultrasound has been shown to provide significant assistance in operative staging and management of patients with liver tumors during open surgery. The availability of the 5.0-7.5 Mhz semiflexible ultrasound transducer with gray-scale, color and spectral Doppler capabilities can provide similar information laparoscopically. METHODS: Twenty-four consecutive patients with liver tumors (18 metastatic and six primary), in technically resectable locations determined by a variety of conventional imaging studies, were brought to the operating room. There was no known extrahepatic disease, and there was no recurrence at the primary site in the metastatic subgroup. These patients were evaluated intraoperatively with laparoscopy and intraoperative laparoscopic ultrasound to assess resectability prior to performing a major laparotomy. Laparoscopy was successful in 23 of the patients and in 19 of 23, laparoscopic ultrasound was also employed, using the 5.0-7.5 MHz semiflexible transducer. The use of the open entry technique, selection of alternate entry sites, coupled with expertise in laparoscopic lysis of adhesions, has allowed safe laparoscopic tumor staging. RESULTS: The laparoscopic evaluation was aborted only once due to dense adhesions, despite the fact that 67% of the patients had undergone previous abdominal surgery. There was only one complication: bleeding from a liver biopsy in an unresectable cirrhotic patient, necessitating laparotomy. Laparoscopy and ultrasound together predicted nonresectability in six of eight unresectable patients, all of whom were spared an unnecessary laparotomy. CONCLUSIONS: Laparoscopic ultrasonographic evaluation for the staging of liver tumors should be a prerequisite to definitive laparotomy, with the objective of avoiding unnecessary surgery.

Adult↗

PubMed1997

High-resolution endoluminal sonography is a sensitive modality for the identification of Barrett's metaplasia.

BACKGROUND: The "gold standard" and only accurate method for diagnosing Barrett's esophagus is by esophagogastroduodenoscopy with biopsy. We evaluated the ability of high-resolution endoluminal sonography (HRES) to detect the mucosal changes in Barrett's esophagus. METHODS: Seventeen patients with documented Barrett's and 12 normal controls underwent endoscopy with HRES examination using a 20 MHz ultrasound transducer to evaluate for mucosal changes. HRES examinations were videotaped then reviewed by an unblinded investigator to identify criteria possibly diagnostic of Barrett's and then by a blinded investigator to test the validity of these criteria. Barrett's was diagnosed by HRES if the second hypoechoic layer appeared thicker than the first hyperechoic layer of the mucosa. Normal mucosa was defined as having a pencil-thin second hypoechoic layer on HRES. Measurements of the second hypoechoic layer were made using a computer and compared in patients with Barrett's and patients with normal esophagus. RESULTS: All 17 patients with Barrett's were correctly identified by HRES (sensitivity 100%). Ten of 12 controls were correctly identified as normal (specificity 86%). There was good correlation between HRES and pathologic diagnoses (r 0.86). The second hypoechoic layer was significantly thicker in Barrett's patients than in normal controls (p < .001). CONCLUSIONS: HRES is a sensitive new method for identifying Barrett's esophagus. However, dysplasia could not be identified by HRES in this study.

Barrett Esophagus↗

PubMed1997

Image-guided localization for video-assisted thoracic surgery.

Video-assisted thoracic surgery (VATS) has become a useful diagnostic and therapeutic tool in the management of lung, pleural, and mediatstinal disease. Preoperative image-guided localization is performed to aid the surgeon in the thoracoscopic resection of small lung lesions that would otherwise be difficult to resect. This article describes the techniques of localization and reviews our experience with this procedure. While the majority of localization procedures are performed during an immediately preoperative computed tomography (CT), the use of intraoperative lesion localization using an endosonographic probe has been reported. The need for localization before resection is dependent on the skill and experience of the thoracoscopist and the characteristics of the lung lesions.

Endoscopy↗

PubMed1997

Sonographic guidance for the localization of peripheral pulmonary nodules during thoracoscopy.

OBJECTIVE: The value of sonographic guidance during video-assisted thoracoscopic surgery (VATS) was studied in 13 patients with one or more peripheral pulmonary nodules who later underwent wedge resection. SUBJECTS AND METHODS: After a review of the chest radiographs and CT scans of each patient, sonographic guidance for VATS was requested by the attending surgeon when the nodule or nodules in question were determined to be too small or too deep in the lung parenchyma from the pleural surface for location by VATS. A multifrequency (5.0-, 6.5-, or 7.5-MHz) sonographic probe was introduced through a thoracoscopic port during VATS. The nodule or nodules in question were located by intraoperative sonography or determined by inspection and confirmed by sonography before wedge resection. The size and location of each lesion and the time needed for sonographic guidance were recorded. RESULTS: Sonography revealed a peripheral pulmonary nodule in 12 of the 13 patients. Of these, it confirmed the suspected location of the pulmonary nodule in six. In the remaining six patients, the surgeon was unable to locate the nodule without the use of sonography. The additional operative time required for sonographic guidance during VATS averaged 7.5 min. However, the time commitment of radiology personnel during surgery varied and was sometimes lengthy (maximum, 150 min). CONCLUSION: Sonographic guidance during thoracoscopy helped to locate lesions and determine their size and proximity to pleural surfaces. Sonographic guidance can be done safely and can be completed expeditiously. Unlike percutaneous hookwire techniques, sonographic guidance does not require an additional invasive procedure to locate the peripheral pulmonary nodule.

Aged↗

PubMed1997

Endoluminal sonographic evaluation of ureteral and renal pelvic neoplasms.

The objective of this study was to demonstrate the feasibility of endoluminal ultrasonography as an adjunct to endoscopy for the evaluation of urothelial neoplasms. An endoluminal ultrasound system using a 12.5 or 20 MHz transducer housed in a 6.2 French catheter was used intraureterally in 38 patients being evaluated endoscopically for suspected tumors in the renal pelvis or ureter. The ultrasonographic, endoscopic, and pathologic findings were evaluated. The location, size, and sonographic characteristics of the tumors in the upper urinary tract were well demonstrated. The information obtained by this technique can be used to guide endoscopic biopsy and laser ablation of the tumor. Endoluminal ultrasonography also has proved helpful in defining the location of a tumor relative to an adjacent vessel and in identifying crossing vessels that cause extrinsic filling defects in the ureter. In a few pathologically correlated cases, endoluminal ultrasonography was accurate in assessing invasion. We have evaluated successfully a variety of non-neoplastic filling defects in relatively few cases. Determination of the eventual usefulness of this technique awaits greater clinical experience and large clinical trials.

Adolescent↗

PubMed1996

Endosonographic and color Doppler flow imaging alterations observed within irradiate rectal cancer.

PURPOSE: To correlate the endosonographic and color Doppler flow imaging alterations observed in irradiated rectal cancers with the pathologic features of radiation response, and to evaluate the potential impact of altered blood flow on the integrity of the surgical anastomosis. METHODS AND MATERIALS: Endosonography with color and pulsed wave Doppler was performed on 20 rectal cancer masses before and after high dose preoperative radiation (XRT). Pre- and post-XRT observations included comparing alterations in tumor size, sonographic echotexture, color Doppler flow, and pulsatility indices. Comparisons were made with pathologic findings in the irradiated specimens and with the incidence of anastomotic failure. RESULTS: Compared to pre-XRT observations, irradiated rectal cancers decreased in size and became either mixed in echogenicity with less apparent color Doppler flow (16 of 20) or unchanged in color Doppler flow and echotexture (4 of 20). Those with less flow (16 of 20) were imaged later (mean = 90.2 +/- 12.1 days) than those without change in color Doppler flow (mean = 21.7 +/- 2.7 days). Pathologically, the group of four without change in color Doppler signal had features of acute inflammation which were not observed in 16 of 20 imaged later. Based on pulsatility index measurements, both high and low resistance vessels were detected and confirmed by immunohistochemical staining, and features of postradiation obliterative vasculitis were observed. Only one primary anastomosis in 14 patients with decreased flow failed. CONCLUSIONS: The sonographic and color Doppler flow imaging alterations observed within irradiated rectal cancer correlated with changes of postradiation obliterative vasculitis. The apparent diminished local blood flow within high and low resistance vessels post-XRT did not result in an increased incidence of anastomotic failures.

Aged↗

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↗