Jeffrey R. Justin

Technique of ultrasonic detection and mapping of abdominal wall adhesions

SummaryA technique for noninvasive ultrasound examination to detect and map abdominal wall adhesions is described. The examination is based on the demonstration of movement of abdominal viscera during real-time imaging. This movement is called viscera slide and either occurs spontaneously as a result of respiratory movement or may be induced by manual compression. Abdominal wall adhesions produce a restriction of viscera slide. Ultrasonic demonstration of restricted viscera slide has been used for the precise localization and mapping of abdominal wall adhesions prior to abdominal surgery. The technique may be particularly useful in providing safe initial access in patients undergoing laparoscopy who are at increased risk for trocar injury of viscera due to abdominal wall adhesions resulting from previous surgery or peritonitis.

Differentiation of breast tumors by ultrasonic tissue characterization.

The ability of ultrasonic tissue characterization to differentiate and classify benign and malignant breast tissues in vivo in patients with palpable breast masses and in vitro in excised breast tissue was evaluated. One‐hundred and twenty‐four in vivo and 89 in vitro studies were performed using a technique of UTC based on parameters from the power spectrum of backscattered echoes. Sensitivities and specificities for diagnosing carcinoma were 86 and 84% for in vivo studies and 94 and 92% for in vitro studies. These UTC parameters provided threshold values for color‐coding breast lesion images. The results of this preliminary investigation suggest that UTC provides a basis for assessing more accurately lesions suspected of being malignant prior to biopsy and possibly for evaluating breast lesions noninvasively.

Accuracy of viscera slide detection of abdominal wall adhesions by ultrasound.

Viscera slide is the normal, longitudinal movement of the intraabdominal viscera caused by respiratory excursions of the diaphragm. By detecting areas of restricted viscera slide, ultrasonic imaging was used to identify anterior abdominal wall adhesions prior to laparotomy or laparoscopy. Transcutaneous ultrasound examination was performed on 110 patients. A prediction of adhesions was made for each patient and then compared to the findings during subsequent laparotomy or laparoscopy. Only patients with previous abdominal surgery or history of peritonitis demonstrated adhesions. Sensitivity and specificity of viscera slide ultrasound in predicting adhesions were 90% and 92%. Nine out of 10 false results involved misinterpretation of ultrasound images of the lower one-third of the abdomen. Ultrasonic imaging of viscera slide is highly accurate in detecting abdominal wall adhesions. This technique is most useful in guiding the insertion of trocar in laparoscopic surgery, and as a noninvasive method in studying the formation of adhesions.

Experimental assessment of spectrum analysis of ultrasonic echoes as a method for estimating scatterer properties

In vitro experiments using weak scatterers ranging in size from mean longest diameter of 26.9 to 83.0 microns were performed to test the validity of theoretical predictions for scatterer size and concentration derived from normalized power spectrum parameters of ultrasonic backscatterer echoes. Scatterers consisting of cell clusters were suspended in collagen gel and scanned by a 10 MHz transducer system. Optical measurements validated theoretical predictions that (1) slope value is a function solely of scatterer size; (2) intercept value is a function of scatterer size and concentration; and (3) midband fit value increases as scatterer concentration increases, and, to a lesser extent, as size increases. These results were obtained under relatively ideal conditions of minimal attenuation and scatterer spacing (not closer than two scatterer diameters) and were consistent with the assumptions underlying the scattering theory.

Motion marking in color Doppler ultrasound needle and catheter visualization

Fine-gauge needles and plastic catheters may not be well visualized by real-time ultrasonic imaging under certain circumstances. u This has prompted the use of various techniques to improve ultrasonic visualization, such as roughening the surface of needles or guide wires and using contrast material. In particular, these methods have been used to improve the visualization of the shaft of a fine _needle during ultra~nic visualization. We have discovered recently that improved visualization of needles and catheters can be achieved during operative ultrasonography using color Doppler imaging. We have been using color Doppler imaging during operations for soft tissue sarcomas (Fig. 1) and pancreatic carcinomas in order to facilitate the localization of blood vessels within and near the tumors. During the course of some of these operations, needle biopsy under color Doppler image control was performed and we noted that the passage of biopsy needles or their guide wires was distinctly evident on the color Doppler images as the needle or guide wire was being moved. The identification of the needle was provided by a color image that corresponded to the shaft of the needle. In order to evaluate the potential use of this observation for ultrasonic needle guidance, we conducted in vitro and in vivo experiments to better define the ability of color Doppler imaging to detect needles of various calibers. Color Doppler needle and catheter detection was studied on the basis of motion marking produced by manipulations usually employed in needle passage.

Ultrasonic Detection of Platelet Aggregation at Variable Shear Rates

We have observed that high-resolution ultrasonic imaging can be used to detect and measure the size and sedimentation of large human platelet aggregates formed in vitro. At progressively lower shear rates, individual platelet aggregates grew in cross-sectional area from the limit of ultrasonic detectability of less than 1 mm2 at moderate shear rates to an approximate mean area of 25 mm2 at zero shear. Platelet aggregates tended to sediment at mean shear rates higher than zero shear. At a shear rate of 5.5 s-1, 70% of platelet aggregates had settled, and at 1.6 s-1, 90% had settled to the dependent half of horizontal tubes in less than 15 s. Ultrasonic aggregometry of platelets may be a valuable technique for investigation of platelet dynamics under controlled flow conditions in vitro.

Experimental assessment of imaging variables associated with operative ultrasonic and radiographic cholangiography.

The comparative accuracies of operative ultrasonic and radiographic cholangiography to detect biliary calculi 1 mm in diameter inside tubes of different calibers were assessed. One hundred eighty tubes were prepared to provide ten tubes each for the following variables: three sizes of tubes (6, 13, 20 mm), three concentrations of contrast material (15, 30, 60 per cent), and presence or absence of calculi. Real‐time B‐mode ultrasound scans with a single gain and time gain compensation (TGC) setting were performed and contrast radiographs were also made at a single optimal exposure. Sixty ultrasonic and 180 radiographic examinations were studied. All ultrasonic interpretations were correct regardless of size of tube. Under optimal conditions, radiographic interpretations were also correct. However, whereas a single gain and TGC setting was applicable for all ultrasound examinations, variable contrast concentrations were required for the best radiographic imaging. Optimal radiographic contrast concentrations differed with tube diameters. The authors conclude that both ultrasonic and radiographic contrast imaging are highly accurate for the detection of small biliary calculi. However, contrast radiography requires stricter optimization of variables needed to provide the high accuracy. Thus, operative ultrasonography may be a more practical and reliable diagnostic procedure because of high sensitivity and greater ease of performance and interpretation.

The effects of temperature on blood flow ultrasonic echogenicity in vitro.

An explanation of the mechanism of ultrasonic echogenicity in flowing blood is proposed based upon an in vitro study that indicates a causal relation between red cell aggregation and these echoes. Echogenicity was measured in vitro at 37 degrees, 24 degrees, and 0 degree C as blood flow shear rates were varied. Echogenicity increased at higher temperatures and lower shear rates. The directions of changes in blood echogenicity exactly paralleled previously known changes in red cell aggregation resulting from changes in temperature. The authors consider this to be further evidence that red cell aggregation is an important cause of low‐intensity echoes observed in clinical ultrasonography of the heart and circulation.