Biomedical subjects

J B Liu

Publications and source records attributed to J B Liu.

At least 55 records · Page 3Linked to original sources

PubMed1999

Examining the obstructed ureter with intraluminal sonography.

PURPOSE: Intraluminal sonography was used to define, differentiate and direct better treatment of obstructing ureteral lesions. MATERIALS AND METHODS: A total of 63 patients with a history of ureteral obstruction and suspected stricture were accrued for evaluation. All patients underwent retrograde contrast imaging, ureteroscopy and intraluminal sonography as part of a diagnostic algorithm. Specific sonographic criteria to differentiate lesions and stricture types were developed. Associated complicating variables defined on sonography included foreign bodies, submucosal stone fragments, ureteral wall fibrosis, mass lesions and adjacent vasculature. Endoscopic treatment was then performed with ultrasound guidance if technically feasible. RESULTS: A total of 63 ureters were evaluated with the preoperative diagnosis of ureteral stricture disease. All ureters were narrowed on contrast imaging in the segment where a stricture was suspected. On sonography 24 ureters (36%) had wall fibrosis with normal periureteral tissues. In general these strictures did well with endoscopic incision. Of the 67 ureters 13 (19%) were thickened or had edematous walls with normal architecture and without fibrosis. These patients all did well with expectant therapy. In contrast, 7 ureters (10%) were obstructed by segmental retroperitoneal fibrosis which did not respond to minimally invasive therapies. In addition, 8 ureters (12%) were obstructed by ureteral wall scarring and periureteral fibrosis, and required open surgical intervention. Ten ureteral strictures had adjacent vasculature, and endoscopic incisions under ultrasound guidance were directed safely away from these structures without associated morbidity. Calculi, stone fragments and foreign bodies embedded in the ureteral wall with associated inflammation were defined with sonography and responded to endoscopic therapies. The intraluminal sonographic diagnosis of ureteral endometriosis was made in 6 patients with a range of lesions from bright, hyperechoic blood filled cysts to an inhomogeneous fluid filled scar involving the wall and periureteral tissues. Primary ureteral carcinoma was also demonstrated in 2 patients after other diagnostic techniques failed. In 1 of these patients intraluminal sonography directed biopsies diagnosed submucosal tumor. Finally, 1 patient had a small periureteral urinoma on intraluminal sonography which was missed on other imaging studies. CONCLUSIONS: Intraluminal sonography is useful in patients with ureteral obstruction of unclear etiology as well as for selecting patients who may benefit from minimally invasive therapies and safely directing these treatments.

Adolescent↗

PubMed1998

Ureteroscopic treatment of ureteropelvic junction obstruction.

PURPOSE: Endopyelotomy has increasingly become well accepted as the optimal management for primary and secondary ureteropelvic junction obstruction. We report our experience with ureteroscopic endopyelotomy guided by endoluminal ultrasound. MATERIALS AND METHODS: Ureteroscopic endopyelotomy was attempted in 27 patients with primary and 10 with secondary ureteropelvic junction obstruction. Retrograde pyelogram and endoluminal ultrasound were performed at the start of the procedure in all patients. Based on sonographic findings 5 patients were not considered candidates for the procedure. The remaining 13 men and 19 women were treated ureteroscopically with a rigid ureteroscope in 5 (15.6%), flexible in 20 (62.5%), and rigid and flexible in 7 (21.9%) patients. Stents were placed postoperatively for 6 to 10 weeks. The patients were followed for a mean duration of 10 months. RESULTS: The procedure was completed in all patients. Average operating time was 95 minutes including the time for imaging. Sonographic localization guided the site of incision in all patients and changed therapy in 5. It identified crossing vessels in 10 patients (31%), septum denoting high insertion in 5 (15.5%) and both in 7 (22%). Preoperative stenting was not required in any patient. Morbidity was low with no patients requiring transfusion and no evidence of ureteral strictures. Success, defined as pain-free with resolution of obstruction on diuretic renal scan, was achieved in 28 of the 32 patients (87.5%). CONCLUSIONS: Ureteroscopic endopyelotomy is a safe and effective treatment for most cases of ureteropelvic junction obstruction. Endoluminal ultrasonography of the obstructed ureteropelvic junction has gained a major role in defining which patient to treat and in directing endoluminal incisions to minimize the risk of injury to adjacent vessels. There is a higher failure rate when vessels are present.

Adolescent↗

PubMed1998

Clinical applications of ultrasound contrast agents.

Within the last decade safe and practical ultrasound contrast agents have been introduced. Most of these are based on gas-filled microbubbles, which markedly enhance Doppler signals and, in some cases, also gray-scale images. The clinical improvements expected from ultrasound contrast is reviewed. Tissue-specific contrast agents constitute another area of potential clinical significance. One particular agent is taken up by the reticulo-endothelial system and produces so-called acoustic emission signals when imaged. An introduction to the unique clinical applications of acoustic emission is given. Harmonic imaging is a new contrast-specific imaging modality, which utilizes the nonlinear properties of some agents in an attempt to alleviate current limitations of ultrasound contrast studies. Examples of harmonic images are presented.

Acoustics↗

PubMed1998

Endoureteral sonography to define the anatomy of the obstructed ureteropelvic junction.

Endoluminal ultrasound of the obstructed ureteropelvic junction (UPJ) provides accurate anatomic information not available through other studies. Endoluminal ultrasonography in the evaluation of the obstructed UPJ can be extremely valuable and its use can be expected to expand with increasing experience with the techniques. The anatomy demonstrated through the fine resolution of this technique may ultimately provide the key to the selection of optimal therapy for the obstructed UPJ.

Animals↗

PubMed1998

Conventional and hypobaric activation of an ultrasound contrast agent.

Hypobaric activation is a new injection technique for use with the contrast agent EchoGen and, in this study, the agent's ability to produce parenchymal enhancement in vivo, with and without prior hypobaric activation, was investigated. Injections, ranging in dose from 0.05 to 0.5 mL/kg, were administrated through a peripheral vein to eight woodchucks with multiple hepatomas. At the 0.10 mL/kg dose level, seven of eight injections following hypobaric activation (88%) resulted in definite parenchymal enhancement. Conversely, dosages of 0.10 mL/kg without prior hypobaric activation produced no grey-scale changes. Only at the 0.4 and 0.5 mL/kg dosage level did the conventional administration technique obtain similar results (4 of 5 injections increased the echogenicity for a 0.4 mL/kg dose). These differences were statistically significant (p = 0.031). In vitro experiments were conducted to establish the physical mechanisms behind hypobaric activation. Relative measurements of contrast microbubble sizes were performed with a phase Doppler particle analyzer after hypobaric and after conventional (bolus) activation. Hypobaric activation produced approximately 20 times more microbubbles per unit volume than the conventional method. In conclusion, this investigation has demonstrated the benefits of prior hypobaric activation when performing in vivo contrast studies with EchoGen and determined the physical mechanisms behind this new injection technique. Hypobaric activation of EchoGen increases contrast enhancement and reduces dose size.

Animals↗

PubMed1998

Simultaneous endoluminal sonography and manometry to assess anal sphincter complex in normal subjects.

The purpose of this study was to use simultaneous anal manometry and high-frequency endoluminal ultrasonography (EUS) to determine the relationship between resting anal pressure and cross-sectional area of the internal and external anal sphincters. Eleven normal subjects underwent simultaneous anal EUS and manometry using catheters containing both pressure ports and ultrasound transducers. Resting pressure and cross-sectional area of the sphincters were made throughout the anal sphincter complex. The length of the internal anal sphincter (IAS) by sonography (27+/-5 mm) was significantly less than the length of the high pressure zone (HPZ) by manometry (44+/-8 mm; P < 0.001). Maximum IAS cross-sectional area (CSA) occurred 10+/-6 mm proximal to the peak resting pressure. The resting anal pressure correlated with external anal sphincter (EAS) CSA (r = 0.77), but not with IAS CSA (r = -0.17). The sum of EAS CSA and IAS CSA correlated strongly with resting pressure (r = 0.85). In conclusion, the IAS is shorter than the HPZ, with a significant distance separating maximum IAS CSA from peak resting pressure. The sum of the IAS and EAS CSAs, but not that of the IAS alone, correlated with resting pressure. Thus, this study suggests that the EAS, in addition to the IAS, contributes to resting anal pressure.

Adult↗

PubMed1998

Three-dimensional endoluminal ultrasonography of the ureter.

Endoluminal ultrasonography has been useful in demonstrating the ureteral and periureteral anatomy. Devices now available give cross-sectional images. A computer program is available to reconstruct these images into three-dimensional (3D) representations. Endoureteral sonography was performed using 6.2F endoluminal ultrasound catheters connected to a dedicated ultrasound unit giving cross-sectional images. The images along the segment in the study were collected by advancing the catheter to the most proximal portion and pulling it in antegrade fashion through the segment with a step-pulling device. The images were collected on videotape and reconstructed into 3D representations using a dedicated 3D computer system (Lis 6000-A). Anatomic features studied included ureteral strictures, obstructed ureteropelvic junction, ureteral neoplasms, and the ureterovesical junction. In each case, additional information and appreciation of the structure could be obtained with the 3D reconstruction. Endoluminal ultrasonography has provided an additional dimension to imaging of the ureter. Three-dimensional reconstruction of these images can give additional information regarding the longitudinal appearance of ureteral segments without the need for development of new ultrasound transducers. It can offer appreciation of anatomic features not evident with two-dimensional imaging alone.

Adult↗

PubMed1998

In vivo comparison of esophageal varices at and above the diaphragmatic high pressure zone using high resolution endoluminal sonography.

Our objective in this study was to use high resolution endoluminal sonography to compare the size of esophageal varices within 5 cm of and at the esophageal high pressure zone. We carried out the study in 36 patients with endoscopically proven esophageal varices. A 20-MHz 6.2F ultrasound catheter was passed through a 34F endoscope and used to image esophageal varices as it was slowly withdrawn through the high pressure zone (the level at which the diaphragm was imaged) and into the body of the esophagus approximately 5 cm above the high pressure zone. All images were captured on videotape and reviewed by one of the investigators. The mean, total, and percent cross-sectional surface areas occupied by varices were calculated and then compared within 5 cm and at the esophageal high pressure zone. Six of 36 (17%) patients had no varices imaged at the high pressure zone but did have varices imaged in the distal esophagus. The mean cross-sectional surface area per varix at the high pressure zone (0.036+/-0.006 cm2) was significantly less (p < or = 0.0001) than the mean cross-sectional area per varix 5 cm above the high pressure zone (0.142+/-0.018 cm2). The average total cross-sectional surface area occupied by varices at the high pressure zone (0.137+/-0.034 cm2) was significantly less (p < 0.0001) than the average cross-sectional surface area occupied by varices 5 cm above the high pressure zone (0.672+/-0.080 cm2). The mean percent esophageal wall cross-sectional surface area occupied by varices at the high pressure zone (16%) was significantly less (p < or = 0.0001) than 5 cm above the high pressure zone (49%). We conclude that the mean, total, and percent cross-sectional surface areas of esophageal varices at the high pressure zone are significantly less than those 5 cm above the high pressure zone.

Endosonography↗

PubMed1998

Differential north to south gastric cancer-duodenal ulcer gradient in China. China Ulcer Study Group.

There are suggestions that duodenal ulcer protects individuals from gastric cancer and that rice is ulcerogenic while wheat is gastro-protective. We aimed to examine the relationship of gastric cancer, duodenal and gastric ulcers in different geographical regions in China and identified dietary risk factors for duodenal ulcer and gastric cancer. The prevalence of peptic ulcer and gastric cancer among symptomatic patients in eight major cities, four each from the north and the south representing all the six defined regions of China were studied. Endoscopy and case records over a 10 year period were reviewed and cases of confirmed duodenal and gastric ulcer and gastric cancer, together with the total number of endoscopies performed per year, were recorded. Rates were expressed as cases/1000 endoscopies. Results were compared to another epidemiological study on diet and mortality in the same regions in China conducted at the same time. Duodenal ulcer rates were 2.4-fold higher in southern China than northern China, whereas gastric cancer rates were 1.6-fold higher in the north than in the south. Correlation studies showed for the first time an inverse linear relationship between the gastric cancer rates and the duodenal ulcer rates (r=-0.8076, P=0.015), as well as the duodenal ulcer: gastric ulcer ratios (r=-0.9133, P=0.002). Gastric ulcer rates were higher in southern China but did not correlate with the gastric cancer rates (r=0.1455, P=0.731). Duodenal ulcer rates were found to be related to daily rice intake (r=0.8554, P=0.029) and inversely related to daily wheat flour intake (r=-0.8472, P=0.033). Gastric cancer rates were not related to any dietary risk factors tested. We concluded there was an inverse relationship between gastric cancer rates and duodenal ulcer rates. Although duodenal ulceration and gastric cancer are both linked to Helicobacter pylori infection, the findings of this study indicate independent additional aetiological factors for the pathogenesis of these conditions. Dietary factors such as rice or wheat intake may play a role.

Adult↗

PubMed1998

Evaluation of bleeding sites with a tissue-specific sonographic contrast agent: preliminary experiences in an animal model.

The purpose of this study was to determine the feasibility and usefulness of using an ultrasonographic contrast agent to enhance the sonographic detection of bleeding sites in a canine model. SH U 563, an ultrasound contrast agent that elicits acoustic emission (i.e., random transient Doppler shifts produced by contrast particle rupture) even when stationary, was used. Acoustic emission is identified as a mosaic pattern on color Doppler imaging. A total of 13 active bleeding sites were created within intraabdominal organs (kidney and spleen, n = 3), the urinary tract (n = 3), and the gastrointestinal tract (n = 7) in three canine models. Gray scale and color Doppler imaging studies were performed prior to and after each of 13 individual intravenous contrast agent administrations. Imaging results were compared to gross pathologic findings. After contrast agent administration, pooling of contrast medium-containing blood in the regions adjacent to bleeding sites could be detected with color Doppler imaging as regions with the characteristic acoustic emission color display. After injection gray scale imaging failed to demonstrate the location or extent of hemorrhaging adequately. A linear relationship existed between the blood loss due to gastrointestinal tract bleeding and the amount of acoustic emission detected (r2 = 0.81). SH U 563 combined with color Doppler imaging improves the detection of bleeding sites in a variety of locations throughout the body.

Animals↗

PubMed1998

Hemodynamic factors affecting uterine artery Doppler waveform pulsatility in sheep.

Quantitative analysis of vascular resistance from the Doppler time-velocity waveform relies on measuring arterial pulsatility. However, input pressure waveform pulsatility, impedance, and resistance have all been found to effect artery flow waveform pulsatility in circulatory mathematic models and in umbilical sheep preparations in vivo. The present study used an in vivo sheep preparation to determine that embolization of the uteroplacental circulation and maternal angiotensin II administration caused changes in the uterine Doppler time-velocity waveform pulsatility that were dependent on input pressure waveform pulsatility, fundamental impedance, and resistance changes. Uteroplacental vascular embolization increased vascular resistance and the uterine artery Doppler waveform resistive index; the mean component of flow (mean pressure/resistance) decreased. Decreased uterine artery Doppler resistive index occurred despite angiotensin II-induced vasoconstriction and increased vascular resistance because the pulse component of flow (pulse pressure/impedance) decreased.

Angiotensin II↗

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↗

PubMed1997

[Clinical and experimental studies of supplemented sini san in treating chronic brucellosis].

OBJECTIVE: To observe the effect of supplemented Sini San (SSNS) in treating chronic Brucellosis (CB). METHODS: One hundred and twenty-seven patients were randomly divided into two groups, 76 cases in the treatment group were treated with SSNS and 51 cases in the control group treated with Dioscorea Nipponica Power. The effect of SSNS on mice model of CB was also observed simultaneously. RESULTS: The short-term effects were that the total effective rate and markedly effective rate of the treatment were 98.7% and 92.1%, which were better than those of the control group (82.4% and 41.2%) respectively, P < 0.01. The long-term follow-up result of the treatment group also showed its superiority to the control group, the total effective rates of the two groups were 98.7% and 51.0%, and the markedly effective rates were 90.8% and 21.6% respectively (P < 0.01). Animal experiments indicated SSNS has obvious effect of antibiotics and immunomodulation. CONCLUSION: SSNS was effective in treating CB, including the long-term follow-up result.

Adult↗

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↗