Biomedical subjects
Publications and source records attributed to J B Liu.
Flexible fiberoptic bronchoscopy is the procedure of choice for the diagnosis of endobronchial neoplasm. Because of technical limitations of fiberoptic bronchoscopy, the use of ultrasound assistance was initiated and evaluated. This article reviews the technique, study design, and clinical results of ultrasound-assisted fiberoptic bronchoscopy.
During the past 25 years, many attempts have been made to establish effective ultrasound contrast agents for both cardiac and noncardiac applications. The ideal ultrasound contrast agent would be: (a) nontoxic; (b) injectable intravenously; (c) capable of passing through the pulmonary, cardiac and capillary circulations; and (d) stable for recirculation. A variety of potential ultrasound contrast agents have been or are now under development. Present and future ultrasound contrast agents should provide for increased diagnostic capabilities in a variety of normal and abnormal vessels and organs throughout the body. These agents will enhance tumor vascularity, delineate areas of ischemia, as well as improve visualization of vascular stenosis. Future developments with modification of ultrasound equipment should increase the capabilities of these agents to improve imaging as well as Doppler sensitivity.
Endoluminal sonography is a technique well suited to imaging structures beyond the lumen of the hollow viscus. The development of small-diameter (6.2F), catheter-enclosed ultrasound probes has made this technique available for use within the urinary tract. It is capable of defining adjacent vessels, calculi, and masses. Ureteropelvic junction (UPJ) obstruction has been increasingly treated by incisional techniques, either nephroscopic, ureteroscopic, or radiographically controlled, with each incision at risk for causing damage to any adjacent vessel. Endoluminal sonography of the obstructed UPJ was attempted in 46 patients and completed in 45 patients, 41 with primary and 4 with secondary obstruction. Adjacent vessels could be seen in 24 patients. Twelve were located anterior or medial to the UPJ or both. Nine patients had vessels at the UPJ located laterally or anterolaterally, posterolaterally, or medially and laterally. Sonographic localization guided the choice of incision site in all patients and changed therapy in five patients. This technique also allows recognition of high insertion of the ureter into the renal pelvis. Endoluminal sonography of the obstructed UPJ is a valuable technique to determine the location and nature of associated vessels and, therefore, to guide decisions in treatment.
PURPOSE: To demonstrate the value of ultrasound (US) guidance during flexible bronchoscopic procedures in a series of patients with known or suspected pulmonary neoplasms. MATERIALS AND METHODS: US-guided bronchoscopy was carried out as an adjunct to conventional bronchoscopy for the diagnosis of mediastinal, hilar, or parenchymal neoplasms in 25 patients with masses previously detected with chest radiography or computed tomography. Miniature transducer-containing catheters were inserted through the biopsy port of the flexible bronchoscope, and cross-sectional real-time US scans of tumors, lymph nodes, and blood vessels were obtained. RESULTS: Among six cases of peripheral masses and 19 cases of central masses, additional information was provided in 18 cases (72%). This information was used to choose the optimal site for transmural biopsy. CONCLUSION: These preliminary results suggest that this US procedure may become an important diagnostic tool during bronchoscopy, due to the ability to identify structures beyond the lumen of the tracheobronchial tree.
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The ability of a high-frequency miniature ultrasonographic transducer to image the anatomy of the anal sphincter complex was investigated in 20 normal subjects. A 9 Fr catheter containing a 12.5 MHz transducer was inserted into the anal canal. Cross-sectional ultrasonographic images of the canal were acquired as the catheter was advanced through the canal into the distal rectum. Three analog images were digitally stored on a computer system, and measurements of the anal sphincters were made from an eight octant grid by two independent investigators. In all 20 subjects the hypoechoic mucosa, hyperechoic submucosa, and hypoechoic internal anal sphincter (IAS) were identified. The first band of the external anal sphincter (EAS) was imaged in 12 of 20 subjects. The mean width of the IAS was 3.5 +/- 0.5 mm (range, 2.6-4.3 mm). The mean width of the first band of the EAS was 2.3 +/- 0.5 mm (range, 1.6-3.2 mm). High-resolution sonography of the anal canal allows detailed evaluation of anatomic structures that cannot be achieved by conventional imaging technology.
Intravenously injected ultrasonic contrast agents making use of encapsulated gas microbubbles have excellent clinical potential for both color and spectral Doppler studies. However, a number of artifacts are associated with sonographic contrast agent measurements. Three artifacts were identified: (1) color "blooming," (2) increased maximum Doppler shift, and (3) spectral "bubble noise." Experiments have been conducted with Albunex and Levovist. These agents were injected into rabbits and humans to allow the cause of the artifacts to be established. Color blooming occurs soon after the bolus injection and is seen as gray scale pixels changing to color display. This is caused by the increase in flow signal strength. The apparent increase in the maximum Doppler shift frequency is due to the limited dynamic range of the spectral display. Only signals above a certain threshold are visible. As the Doppler signal power is enhanced, the highest frequency visible also increases. Finally, very large excursions can sometimes be seen in the spectral display (bubble noise). These might be due to either the breakdown of microbubbles or individual very large bubbles. The color blooming and bubble noise artifacts are easily identifiable and will not influence diagnostic management. The increase in peak Doppler shifts is more troublesome as it prevents comparison of spectral parameters obtained before and after injection of contrast agent.
This study investigates the ability of endorectal ultrasonography aided by color flow and pulse wave Doppler techniques to identify submucosal arterial plexuses of the normal rectal wall and to detect vessels supplying rectal wall masses. Color flow and pulsed wave Doppler analysis of 62 normal submucosal arterial plexuses and vessels feeding rectal wall masses (one rectal endometriosis and seven rectal cancers) was performed. The color signals from normal submucosal arterial plexuses and the one case of rectal endometriosis were judged to be sparse or decreased in comparison to color signals from rectal cancers. The median and mean P1 values for normal submucosal arterial plexuses were significantly greater than those for the central feeding vessels or small peripheral vessels within rectal masses. Our experience with color and duplex endorectal ultrasonography suggests that different vascular structures exist in normal persons compared to those in rectal wall masses. Pathologically, rectal cancers possess vessels with and without a smooth muscle layer, which may produce the high and low resistance signals identified by pulse Doppler.
Between Sept. 1991 and June 1992, a total of 453 cases with carcinomas of the esophagus or gastric cardia underwent surgical resection of cancer. In all patients, ECG was continuously monitored for at least 3 days after operation. There were 108 cases of postoperative arrhythmias, with an incidence of 23.8%, but 32.9% in patients with abnormal preoperative ECG, higher than that with normal preoperative ECG (21.9%) (P < 0.05). The postoperative arrhythmia appeared more frequently in the gastroesophageal anastomosis above the aortic arch (35.0%) than in that below it (16.3%) (P < 0.01). In 87.0% of arrhythmias appeared within 24 hours after the operation and 72.2% was sinus arrhythmia. The fatal arrhythmia was rarely seen. The common causes of postoperative arrhythmia were operative trauma and stress, respiratory insufficiency, heart failure, hypovolemia and high fever. After treatment in time, arrhythmias disappeared in 4 days. The emphasis is to find and get rid of the causes at first, then is the treatment of arrhythmia.
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A selected area mechanical polishing technique has been developed to improve the precision of cross-sectional TEM sample preparation, based upon the early work of Benedict and colleagues [Benedict et al. (1990) MRS Symp. Proc. Vol. 199, p. 189]. TEM samples were made from a pre-selected section through the middle of a 1 micron wide band of transistors extending laterally for more than 1 mm by precise control over the plane of polish with a corresponding reduction in sample preparation time. To illustrate the application of this technique, a uniformly thin, electron transparent TEM sample of a single, specific, failed transistor is obtained from a 4 mm by 10 mm device array.
The correlative factors of left ventricular hypertrophy (LVH) in 287 end-stage renal disease (ESRD), admitted from 1983 to 1992, were analyzed. 52% of patients had LVH including 54% of patients on hemodialysis, 75% of patients with peritoneal dialysis and 38% of transplanted patients. Single factor analysis indicated that age, blood pressure, serum creatinine and BUN, hemoglobin, serum alkaline phosphatase, aortic valve disease and present DSRD therapy were related to LVH. Multiple logistic regression analysis indicated that the most important factors which independently related to LVH in all patients studied, were management of present ESRD treatment, age, hypertension and high serum alkaline phosphatase. In a subset of patients with severe LVH, high serum alkaline phosphatase level, high systolic blood pressure and age were the predictive factors. In patients on dialysis, the most important variable were age and high serum alkaline phosphatase. Hypertension was the sole predictor of LVH in the transplant group.
BACKGROUND: The aim of this study is to apply high-resolution endoluminal sonography (HRES) to the study of the esophageal disease in systemic sclerosis (SSc). METHODS: An HRES transducer was used to image the esophagus. Autopsy specimens of normal and SSc esophagi were imaged to define a hyperechoic abnormality in the normally hypoechoic muscularis propria. The presence or absence of this hyperechoic abnormality of the esophagus in SSc patients was compared with sonographic findings in normal volunteers. The degree of the hyperechoic abnormality was correlated with the results of functional esophageal studies including esophageal motility, lower esophageal sphincter pressure, and 24-hour pH monitoring in SSc patients. RESULTS: A hyperechoic abnormality in the normally hypoechoic muscularis propria on HRES seemed to correspond with the presence of fibrosis on histological sections from the distal esophagus in SSc autopsy specimens. A significant difference was found in the presence of this hyperechoic abnormality in patients with SSc when compared with normal controls (P < 0.001). Finally, there were strong positive correlations between the degree of this hyperechoic abnormality and esophageal manometric abnormalities (r = 0.89; P < 0.001) and supine (r = 0.74; P < 0.01) and total (r = 0.70; P < 0.02) acid reflux on 24-hour pH monitoring. CONCLUSIONS: HRES is a sensitive new method to determine the presence or absence of hyperechoic abnormalities in the muscularis propria and to predict functional abnormalities of the esophagus in patients with SSc.
Experimental studies in the therapy of intravesically growing bladder tumors in mice have been hampered by an inability to monitor tumor growth before and during treatment. To establish a repeatable, noninvasive method to monitor the intravesical growth of bladder tumors, MB49 murine bladder tumor cells were instilled into the bladders of syngeneic C57BL/6 mice. Following 3 weeks of growth, the bladders of tumor-bearing and control mice were imaged using a 20 mHz, 6.2 F catheter-based ultrasound transducer inserted rectally. Bladders of tumor implanted and control mice were identified by high resolution endoluminal ultrasound after distension with 0.15 ml. of normal saline. When compared with the results of histologic analysis, transrectal ultrasound (TRUS) accurately identified tumor presence, size, and location.
To image esophageal and gastric varices qualitatively and to measure esophageal varices quantitatively, 29 patients with portal hypertension underwent transnasal esophageal and gastric ultrasonography (US). Twenty-three patients underwent standard endoscopy. Endoluminal US demonstrated the varices as anechoic areas with communications in the submucosal, periesophageal, and perigastric regions, as well as ascites visualized through the gastric wall. Interobserver variation between two investigators for measurements of the largest esophageal varix in each patient was r value of .99 for diameter, r value of .99 for cross-sectional surface area, and r value of .98 for circumference. Endoscopy for evaluation of gastric varices had a sensitivity of 48% and a specificity of 50% and for evaluation of esophageal varices had a sensitivity of 94% and a specificity of 17%. Periesophageal and perigastric varices could not be visualized at endoscopy. Transnasal esophageal US, a new imaging technique with which to detect and measure esophageal varices, is a more sensitive modality than endoscopy for the detection of gastric varices.
The authors report their experience with an intraurethral prosthetic stent as an alternative treatment for detrusor-external urethral sphincter dyssynergia (DESD). A sphincter prosthesis was inserted into the membranous urethra of 25 men with spinal cord injuries, DESD, and elevated voiding pressure. Bladder voiding pressure decreased from 87 cm H2O +/- 23 to 27 cm H2O +/- 11 in 12 months (P < .001). There was a significant decrease in residual urine volume 12 months after prosthesis placement, from 122 mL +/- 77 to 33 mL +/- 19 (P < .01); bladder capacity remained relatively unchanged, from 174 mL +/- 84 to 230 mL +/- 92 (P < .57). No deleterious effects were seen in renal or erectile function. Migration of three prostheses occurred 1 day to 6 weeks after insertion. One additional complication, pyelonephritis, occurred in a patient with preexisting vesicoureteral reflux, necessitating reimplantation of bilateral ureters. The intraurethral wire mesh prosthesis, with its simplicity of placement and minimal associated morbidity, offers a potential alternative to external sphincterotomy.
Miniature ultrasound transducers (12.5 MHz) housed in 9 Fr catheters were passed through a laparoscope or mediastinoscope to image a variety of normal and abnormal structures within the peritoneal cavity and mediastinum in 20 patients. These transducers made it possible to visualize the gallbladder and bile ducts and evaluate for the presence of stones, to detect masses and provide guidance for their aspiration or biopsy, and to image the internal structures of the ovary and fallopian tube. In addition, these miniature transducers were used to locate such normal vital structures as blood vessels, thereby allowing the surgeon to decide on the best approach for dissection during mediastinoscopy. During conventional surgery, the surgeon or gynecologist can palpate an area of abnormality not directly visualized. However, during laparoscopy and mediastinoscopy direct palpation is not possible. Therefore, it is important to find another method to determine what structures lie beneath the visualized surface. These miniature ultrasound transducers appear to offer a means for making such determinations.
A 20 MHz ultrasound transducer housed in a 6.2 Fr catheter was used to image human esophageal autopsy specimens from six cadavers. Histologic sections taken from the areas imaged were correlated with cross-sectional sonographic images. Six echo layers were seen in the non-fluid-filled esophagus whereas seven echo layers were seen in the fluid-filled esophagus. These seven layers correspond to the following histologic structures: first hyperechoic layer--mucosa (including squamous epithelium and lamina propria); second thin hypoechoic layer--muscularis mucosae; third very bright hyperechoic layer--submucosa; fourth hypoechoic layer--circular smooth muscle; fifth thin hyperechoic layer--intermuscular connective tissue; sixth hypoechoic layer--longitudinal smooth muscle; seventh hyperechoic layer--adventitia.