Search PubMed⌕ Search

Biomedical subjects

J Machi

Publications and source records attributed to J Machi.

At least 37 records · Page 2Linked to original sources
PubMed1996

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.

Biliary Tract Diseases↗
PubMed1995

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.

Adult↗
PubMed1995

Determining the acuteness and stability of deep venous thrombosis by ultrasonic tissue characterization.

PURPOSE: The intent of the study was to determine whether ultrasonic tissue characterization (UTC) could indicate acuteness and stability of deep venous thrombosis (DVT) of the lower extremities. METHODS: Thrombi presenting as filling defects on color Doppler imaging in the common or superficial femoral or popliteal veins in 50 extremities in 45 patients with DVT were studied. Acute DVT was less than 4 days duration, and chronic DVT was greater than 21 days duration. UTC analysis of parameters from the normalized power spectrum of backscattered ultrasound signals from venous filling defects was performed. This spectrum approaches a straight line, and its basic parameters, slope, and Y-intercept are related to scatterer size, concentration, and the square of the scatterer-to-medium acoustic impedances. Ten of the DVT extremities were reexamined at 1 week to assess UTC changes that would indicate thrombus instability. RESULTS: Acute DVT (19 of the 50 extremities) could be distinguished from chronic DVT, mainly on the basis of significantly higher intercept values for the acute group, which were 11.6 relative decibels (dBr) higher than those of the chronic DVT group. Discriminant linear analysis of the two parameters indicated a sensitivity of 94.7% and specificity of 90.3% in correctly diagnosing acute DVT. In a small sample of 10 extremities reexamined at 1 week, acute DVT extremities showed a mean 9.4 dBr decrease in intercept values with no significant change in slope. CONCLUSIONS: UTC distinguished clinically defined acute from chronic DVT. In a small series of extremities, UTC revealed significant instability of acute thrombi in a selected patient population.

Acute Disease↗
PubMed1994

Surgery in Japan.

Explore the source record for details and available documents.

Education, Medical, Graduate↗
PubMed1994

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.

Abdominal Muscles↗
PubMed1994

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.

Humans↗
PubMed1994

Oversaturation of color may obscure small intraluminal partial occlusions in color Doppler imaging.

Color Doppler imaging has been reported to have a low degree of accuracy in diagnosing nonocclusive deep venous thrombosis. In this modality the color saturation while diagnosing deep vein thrombosis depends on the blood flow velocity and the sensitivity setting of the color image. To determine the effect of color saturation on the detection of thrombi, an in vitro experiment was performed using a closed-loop tube circulation system with a simulated small intraluminal partial occlusion. Heparinized blood was circulated at three different velocities (2, 5.5, and 9 cm/sec) and the vessels were scanned longitudinally and transversely with color Doppler imaging at three color sensitivity settings (low, medium, and high sensitivity). In appropriate color sensitivity settings (i.e., the low, medium, and high sensitivity for the velocity of 9,5.5 and 2 cm/sec, respectively), the color was saturated adequately in the tube lumen so that the partial occlusion was delineated as a color filling defect in the color field. In undersaturated color conditions, the partial occlusion was depicted owing to its echogenicity, but not as a color filling defect. In over-saturated color conditions, such as the high color sensitivity at the high velocity, the partial occlusion was obscured by the excessive amount of color. The over saturation of color may be one of the reasons color Doppler imaging fails to detect deep vein thrombosis, particularly small intraluminal thrombi.

Blood Flow Velocity↗
PubMed1993

Effect of perfusion and blood content on ultrasonic backscattering of liver tissue.

The purpose of this study was to determine the effect of blood flow perfusion and red cell content on ultrasonic scattering by liver tissue. Data acquisition for ultrasonic tissue characterization (UTC) employing analysis of the backscattered echoes from the power spectrum was obtained from the same region of pig liver tissue under four conditions: 1) normal perfusion in situ, 2) ischemia in situ in the living pig, 3) ischemia in situ immediately postmortem, and 4) immediately after excision of the liver. Discriminant function analysis was used to evaluate differences in the two basic parameters from the normalized power spectrum: slope and intercept. Normal perfused liver had significantly higher intercept values and lower slope values than liver under the other three conditions. Excised liver showed the lowest intercept and highest slope values (p < 0.01). These experiments indicate that differences in perfusion produce significant differences in ultrasonic scattering by liver tissue (ischemia caused a 3 dB drop in intercept amplitude). Normal or ischemic in vivo and in vitro liver tissue is associated with different patterns of ultrasonic scattering, and scattering data under these various circumstances are not equivalent.

Animals↗
PubMed1993

Operative color Doppler imaging for general surgery.

Operative CDI was performed during 125 general surgical operations (53 hepatic, 25 biliary, 24 pancreatic, 7 esophagogastric, 10 pulmonary, 3 kidney transplant, and 3 soft tissue operations). Operative CDI provided beneficial information in 108 of 125 operations (86.4%). On the basis of operative CDI findings, surgical management was altered in 34 of 125 operations (27.2%), most frequently hepatic and pancreatic operations. Operative CDI demonstrated advantages over B-mode imaging in (1) detection and localization of small blood vessels that are impossible or difficult to identify by B-mode imaging, (2) rapid and definitive distinction of blood vessels from other hypoechoic areas, such as tissue spaces and ducts, (3) determination of the relation of tumors to vascular structures such as vascular invasion of carcinoma, (4) confirmation of blood flow to organs after surgical procedures, and (5) clearer needle localization for guidance of needle placement by color motion marking.

Blood Flow Velocity↗
PubMed1992

Operative color Doppler imaging for vascular surgery.

Operative color Doppler imaging (CDI) was performed during 57 vascular operations (24 carotid, 24 lower extremity, six renal artery, and three other operations), and its benefits were assessed in comparison to B-mode imaging. Pre-reconstruction operative CDI was used selectively in 18 operations, and post-reconstruction operative CDI was used routinely in all operations. In 16 operations (28.6%), post-reconstruction CDI diagnosed vascular defects such as intimal flaps (n = 4), anastomotic stenoses (n = 7), and in situ bypass arteriovenous fistulas (n = 4). Vascular defects at eight operations required immediate repair. Operative CDI had advantages over B-mode imaging in (1) detection of preoperatively unknown vascular abnormalities before reconstruction, (2) faster recognition of vascular defects after reconstruction, (3) unique ability to detect problems (i.e., arteriovenous fistulas) that were unidentifiable by B-mode imaging, and (4) provision of supplemental blood flow information.

Blood Flow Velocity↗
PubMed1992

Intraoperative ultrasonography.

Four major benefits of intraoperative ultrasonography (IOU) were determined after its use in more than 2400 operations. They are the acquisition of new information not otherwise available, complement of or replacement for operative radiography, guidance of surgical procedure, and confirmation of completion of operation. IOU also has the advantages of safety, speed, higher accuracy, acquisition of more information, and wider application over operative radiography. Intraoperative color Doppler imaging, which has been introduced recently, seems to provide additional beneficial information during cardiovascular and general surgery. We believe that IOU should have a wider application and that surgeons and radiologists should develop cooperative working relations similar to those that exist for operative radiography.

Cardiovascular System↗
PubMed1992

The value of operative ultrasonography in diagnosing tumor extension of carcinoma of the stomach.

Operative ultrasonography was performed during operations to improve the accuracy of diagnosing the extent of the spread of carcinoma of the stomach in the following areas: tumor invasion in the gastric wall (31 patients), para-aortic lymph node metastasis (30 patients) and hepatic metastasis (30 patients). The over-all diagnostic accuracy rates of operative ultrasonography were 81 per cent for determining the depth of tumor invasion, 80 per cent for carcinoma of the mucosa, 70 per cent for carcinoma of the submucosa, 83 per cent for carcinoma of the proper muscle, 80 per cent for carcinoma of the subserosa and 100 per cent for carcinoma of the extraserosa. The over-all accuracy of operative ultrasonography in diagnosing para-aortic lymph node metastasis was 93 per cent. In comparison with the results of preoperative studies, the accuracy (sensitivity) of operative ultrasonography was significantly superior in diagnosing metastasis to the lymph nodes. In three of 30 operations, preoperatively unrecognized and nonpalpable (occult) hepatic metastases were identified by operative ultrasonography. Operative ultrasonography provides more accurate information regarding the spread of carcinoma of the stomach, and thus may be helpful in deciding upon the type of surgical procedure or in avoiding unnecessary tissue dissection.

Carcinoma↗
PubMed1991

Escherichia coli bacteremia in children. A review of 91 cases in 10 years.

We reviewed 91 cases of pediatric Escherichia coli bacteremia during a 10-year period. Thirty one patients were afebrile; a significantly greater proportion of these patients were aged less than 1 month, had ampicillin-resistant E coli isolates, or had persistent bacteremia 24 hours after initiating antibiotic therapy. Infection was community acquired in 65 cases; associated urinary tract infection was six times more common in this setting than in nosocomially acquired infections. In 85 cases at least 1 underlying medical condition/focus of infection was identified at the time the positive blood culture was obtained, the most common were immune deficiency states (38 cases), urinary tract infection (29 cases), and lesions of the gastrointestinal tract (27 cases). Polymicrobial bacteremia occurred in five cases. Twelve patients died; significantly associated with death were hypotension requiring pressor therapy, presence of a central venous catheter, and neutropenia.

Adolescent↗
PubMed1991

Technique of ultrasonic detection and mapping of abdominal wall adhesions.

A 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.

Abdominal Muscles↗