Chan Y. Chung

Simplified method of hepatic fibrosis quantification: design of a new morphometric analysis application

Abstract: Introduction: Semiquantitative evaluation of liver specimens is considered the standard method for measuring fibrosis; however, these systems lack the precision of a quantitative technique.

Muscle shortening along the normal esophagus during swallowing.

Longitudinal shortening of the esophagus during peristaltic contraction has been previously analyzed globally using spaced mucosal clips. This method gives a relatively crude measurement. In this study, local longitudinal shortening (LLS) was evaluated using simultaneous high-resolution endoluminal ultrasound (HREUS) and manometry based on basic principles of muscle mechanics. We sought to determine if there are regional differences in LLS of the esophageal muscle during swallow-induced peristaltic contraction and evaluate shortening of the circular smooth muscle (CSM) and longitudinal smooth muscle (LSM) of the esophagus.Twenty normal subjects underwent simultaneous HREUS/manometry at 4 levels (5, 10, 15, and 20 cm above the upper border of the lower esophageal sphincter [LES] high-pressure zone) in the esophagus with 5-mL swallows of water. Ultrasound images were recorded with synchronized manometric pressure data. The images were digitized and the cross-sectional surface area (CSA) of the LSM, CSM, and total muscle (TM) were measured at baseline (at rest) and at peak intraluminal pressure (implying peak CSM contraction) during swallowing. LLS was calculated for the CSM and LSM using the principle of mass conservation, whereby the change in CSA relative to the resting CSA is quantitatively equal to the relative change in length of a local longitudinal muscle segment.CSM, LSM, and TM all shortened longitudinally, with the circular muscle shortening more than the longitudinal muscle, LLS of the CSM and TM layers at 5 cm above the LES was significantly greater than at 20 cm (CSM: 30% difference, P < .001; TM: 18% difference, P < .05). The greater shortening of LSM at 5 versus 20 cm was found not to be statistically significant (11% difference, P > .05). Peak intraluminal pressure strongly correlated with peak muscle thickness of all layers at all levels (r = 0.96–0.98).LLS increases from the proximal to the distal esophagus during bolus transport. CSM and LSM both shorten longitudinally, with CSM shortening more than LSM. The increase in LLS increases the efficiency of peristaltic contraction and likely contributes to the axial displacement of the LES preceding hiatal opening and esophageal emptying.

A new ultrasound-guided esophageal variceal pressure-measuring device.

OBJECTIVE:To develop a noninvasive method and device to determine intravariceal pressure and variceal wall tension by measuring the variables of the Laplace equation and test this device in a model of esophageal varices.METHODS:Two variceal pressure measurement devices were constructed. The first device consists of an Olympus 20 MHz ultrasound transducer placed next to a latex balloon catheter attached to a pressure transducer. The second device was constructed by placing the same ultrasound transducer inside a latex condom balloon attached to a pressure transducer. These pressure measurement devices were tested blindly in varix models with different intravariceal pressures, by inflating the balloon to flatten the varix models. Each variceal pressure was measured 10 times by two separate investigators blinded to the actual pressures. The mean intravariceal pressures were calculated. The variceal models were made of a latex balloon filled with water and coffeemate.RESULTS:The correlation coefficient between the actual and measured varix pressures for both devices was 0.99. The percent error ranged from 0 to 10%. The correlation coefficient between the investigators making the blinded measurements for both devices was 0.98.CONCLUSION:Two pressure-measuring devices were developed to determine intravariceal pressure in a model varix system. These devices demonstrate a low percent error and a high correlation to the actual variceal pressures with low intra- and interobserver variability. These devices have the potential to measure all the variables of the Laplace equation for wall tension. We plan to test these devices in human subjects.

Validation of volume measurements in esophageal pseudotumors using 3D endoluminal ultrasound

The purpose of this study was to validate the accuracy and reliability of volume measurements using three-dimensional (3D) endoluminal ultrasound (ELUS) in canine pseudotumor esophageal specimens in vitro. Pseudotumors were created by injecting various volumes of US gel (0.1-1.0 ml) into canine esophageal specimens. A stepping-motor was used to pull either a 9, 12.5 or 20 MHz transducer through the lumen of the specimen at 1.5 mm/s. Images were downloaded to a LIFE computer system for 3D reconstruction. Volume measurements were made by two investigators and compared to spiral CT images. Averaging across all measurements, the average magnitude of error was 8.7% in individual US determinations and 11. 9% in CT measures. Volumes estimated from images spaced 0.5 and 1.0 mm apart, from images in the original and reconstructed planes, and from different scan frequencies, produced percentage errors that were not statistically significantly different from each other on ELUS. 3D ELUS can be used accurately and reproducibly to measure tumor volumes with a low mean percent in vitro.

Simultaneous Endoluminal Sonography and Manometry to Assess Anal Sphincter Complex in Normal Subjects

The purpose of this study was to usesimultaneous anal manometry and high-frequencyendoluminal ultrasonography (EUS) to determine therelationship between resting anal pressure andcross-sectional area of the internal and external anal sphincters.Eleven normal subjects underwent simultaneous anal EUSand manometry using catheters containing both pressureports and ultrasound transducers. Resting pressure and cross-sectional area of the sphincters weremade throughout the anal sphincter complex. The lengthof 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 IAScross-sectional area (CSA) occurred 10 ± 6 mmproximal to the peak resting pressure. The resting analpressure correlated with external anal sphincter (EAS) CSA (r =0.77), but not with IAS CSA (r = –0.17). The sumof EAS CSA and IAS CSA correlated strongly with restingpressure (r = 0.85). In conclusion, the IAS is shorter than the HPZ, with a significant distanceseparating maximum IAS CSA from peak resting pressure.The sum of the IAS and EAS CSAs, but not that of the IASalone, correlated with resting pressure. Thus, this study suggests that the EAS, in addition to theIAS, contributes to resting anal pressure.

Minimally invasive measurement of esophageal variceal pressure and wall tension (with video)

BACKGROUND There is no simple method to measure intravariceal pressure in patients with esophageal varices. OBJECTIVE Our purpose was to develop a new noninvasive technique to measure resting intravariceal pressure and wall tension. DESIGN A model was developed. A long balloon (varix) was fitted inside an airtight cylinder (esophagus). Fluid ran through the model varices to maintain 5 different constant pressures. An endoscope was placed in the model esophagus, and pressure was increased by air insufflation. The endoscopy and pressure readings from the esophagus and varix were recorded continuously until variceal collapse. SETTING Patient studies were done in an endoscopy suite with the patient under fentanyl and midazolam sedation. PATIENTS Esophageal pressure was measured during air insufflation in patients with varices until the varices collapsed. EUS was used to measure radius and wall thickness to calculate wall tension. RESULTS In the varix model, the mean (SD) intraluminal esophageal pressures at variceal flattening for the model varices at 5, 10, 15, 20, and 25 mm Hg were 5.69 (0.34), 11 (0.32), 15.72 (0.51), 21.55 (0.63), and 25.8 (0.14) mm Hg. The correlation between actual and measured variceal pressure in the model at variceal flattening was r = 0.98. In the patients, a total of 10 varices in 3 patients were evaluated. The mean (SD) for the varices in each subject was 12.16 (2.4), 23.2 (1.3), and 6.5 (2.2) mm Hg for subjects 1, 2, and 3, respectively. CONCLUSION Standard endoscopy with air insufflation and manometry can be used as an accurate, simple, and reproducible method to measure intravariceal pressure.