Bernard Sigel

Ultrasonography of Blood During Stasis and Coagulation

A series of in vitro and animal experiments were performed to determine ultrasonic features of blood during stasis and coagulation. Liquid whole blood became echogenic within a few seconds to 3 minutes following the onset of stasis. This occurred in citrated human blood allowed to stand and in occluded segments of vena cava and aorta of dogs. Mechanical agitation of the blood in stasis caused a disappearance of echoes. This echogenicity occurred with gray-scale and real-time ultrasonography using 7.5-mHz transducers, but was not observed with 3.5-mHz transducer used in real-time scanning. Whole blood clot was echogenic both with 7.5- and 3.5-mHz scanning. Fibrin clot was sonolucent. Echogenicity with stasis did not occur with plasma, serum, or packed erythrocytes. The development of echogenicity required the presence of fibrinogen or its products plus erythrocytes. The echogenicity of blood during stasis detectable by high-frequency ultrasonography probably was related to physical layering of blood products. The disappearance of reflective echoes following agitation suggested that the layering could be readily disrupted.

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.

Effect of Plasma Proteins and Temperature on Echogenicity of Blood

An explanation is proposed for the echogenicity to ultrasound scanning at 5 mHz and above of unclotted blood under conditions of stasis. In vitro experiments using blood from normal subjects and from patients with myeloma revealed that: 1) lysis of red cells prevented echogenicity, 2) echogenicity increased with increasing hematocrit, fibrinogen and other macromolecules, and temperature, and 3) blood from myeloma patients showed increased echogenicity and rouleau formation, a form of aggregation seen on peripheral smears. From these experiments it was concluded that red cell aggregation is a major cause of echogenicity of unclotted blood, requiring both intact red cells and conditions which are known to enhance red cell aggregation, such as the presence of macromolecules and increased temperature.

Technique of ultrasound examination during laparoscopic cholecystectomy

SummaryIntracorporeal ultrasonography was used as a new method to examine the bile ducts during laparoscopic cholecystectomy. A prototype rigid 7.5-MHz ultrasound probe, 10 mm in diameter and 50 cm in length, was introduced during 25 laparoscopic cholecystectomies. A dual scanning technique was developed for complete examination of the bile duct. This entailed transverse scanning via the subxyphoid trocar and longitudinal scanning via the umbilical trocar. The intrahepatic ducts were also visualized by placing the probe on the liver surface. Color Doppler imaging was useful to quickly distinguish the duct from vascular structures. Laparoscopic ultrasonography clearly delineated the bile ducts in all operations except one. The time required for imaging was significantly shorter for ultrasonography than for cholangiography. Our preliminary experience demonstrates that a complete examination of the bile ducts can be performed with intracorporeal ultrasonography in a relatively short period of time.

Operative ultrasound in general surgery.

BACKGROUND Since the introduction of real-time B-mode ultrasound during surgery almost 20 years ago, the use of operative ultrasound (OUS) has gradually expanded to a variety of surgical fields. METHODS A review of the history, technology, and specific applications of OUS in general surgery is presented with our clinical results of over 2300 operations. RESULTS The benefits provided by OUS are the acquisition of new information not otherwise available, complement to or replacement for operative radiography, confirmation of satisfactory completion of an operation, and guidance of surgical procedures. OUS possesses many advantages as an intraoperative tool, including safety, speed, unique imaging information, wide applicability, high accuracy and procedure guidance capability. CONCLUSION OUS is gaining wider acceptance in hepatobiliary, pancreatic, endocrine, and vascular surgery. Newer OUS modalities-color Doppler imaging and laparoscopic ultrasound-potentially may widen the applications of OUS in general surgery.

The role of imaging ultrasound during pancreatic surgery.

Real-time ultrasound imaging was employed at 122 operations for the complications of pancreatitis, adenocarcinoma, and islet cell tumors. Ultrasound was found to be useful in 69% of the operations for pancreatitis and 66% of the operations for tumor. Assistance was provided in diagnosis or definition of pathology. Help in diagnosis consisted in detecting conditions that were not found on preoperative testing or at exploration and excluding conditions that were suspected on the basis of previous diagnostic studies or findings at operation. Better definition of pathology was provided by precise localization of structures, assessment of their size and surrounding anatomy, and distinction of tissue features that helped to recognize their identity. Ultrasound was usually more helpful in defining pathology than in diagnosis. Ultrasound enabled early orientation to important landmarks, reduced the need for contrast x-ray studies, and yielded unique information about the etiology of abnormalities. Although ultrasound has a slow learning curve, we believe that its use during pancreatic operations can significantly aid the surgeon and we recommend its wider application in surgical practice.

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.

Detection of unrecognized liver metastases from colorectal cancers by routine use of operative ultrasonography

The importance of diagnosis and detection of liver metastases cannot be overemphasized for the treatment and prognosis of colorectal cancers. As a new diagnostic technique, operative ultrasonography has been performed during 33 operations for colorectal cancers including three operations for metachronous liver metastases. Of these, in five patients (15.2 percent) ultrasonography using 5- or 7.5-MHz instruments identified metastatic tumors that had not been diagnosed during preoperative imaging studies or at exploration. Most of these tumors were approximately 1 cm in size and nonpalpable. Cases of these five patients are presented in this report. High-resolution operative ultrasonography is considered to be a valuable method for detection of unrecognized metastatic tumors and for precise localization and spatial assessment of these hepatic lesions. Because it is safe, simple, and highly sensitive, the routine use of operative ultrasound is encouraged during surgery upon colorectal cancers for systematic screening of metastatic liver tumors.

Roles of hematocrit and fibrinogen in red cell aggregation determined by ultrasonic scattering properties

Parameters of the power spectrum of backscattered echoes were applied to quantitatively evaluate red cell aggregation in vitro. Human red cell suspensions were circulated in a closed loop of tubing, and ultrasonic, radiofrequency, echo-signal data were obtained using a 10-MHz transducer. Data acquisition was performed at 30-s to 1-min intervals for 5 min after flow stoppage. Two parameters of the normalized power spectrum of the echo signals, spectral slope and Y-intercept, were computed, and estimates of two scattering properties, the scatterer size and acoustic concentration were calculated from these parameters using equations based on scattering theory. Size and acoustic concentration were observed as they changed over time after the stoppage of flow. The key findings were that hematocrit affected the rate of cell aggregation while fibrinogen controlled aggregate size and acoustic concentration.