Search PubMed⌕ Search

Biomedical subjects

J Machi

Publications and source records attributed to J Machi.

At least 91 records · Page 5Linked to original sources
PubMed1985

Operative ultrasonography in the biliary tract during pregnancy.

Operative roentgenographic cholangiography entails problems during pregnancy because of the hazard of radiation to the fetus and mother. In 450 biliary tract operations in which real-time B-mode operative ultrasonography was performed, five were for diseases of the biliary tract during pregnancy. Operative ultrasound correctly revealed non-palpable stones in the gallbladder in one patient and in the common bile duct in three patients. Furthermore, operative ultrasound provided anatomic information, such as dilation or stenosis of the common bile duct. Of seven possible occasions in which roentgenography would customarily be expected to be performed, operative cholangiography was used only once. Thus, ultrasound significantly reduced the number of operative roentgenographic studies. Operative ultrasonography was not associated with any complications and significant time delays. It is concluded that operative ultrasonography can replace operative roentgenographic cholangiography as a screening procedure for gallbladder and common duct calculi at biliary tract operations during pregnancy.

Adult↗
PubMed1984

Role of red cells in preventing the growth of platelet aggregation.

Using high-resolution real-time two-dimensional ultrasound, we have investigated the role of red cells in the growth of already established platelet aggregates under controlled flow conditions. Platelet rich plasma (PRP) was circulated in vitro in horizontally and vertically arranged tubing at mean shear rate ranging from 60 to 0 sec-1, and adenosine diphosphate (ADP) was used to induce platelet aggregation. ADP-induced platelet aggregates grew in size and tended to sediment as shear rate decreased, in particular, below 10 sec-1. At 0 sec-1 (stasis), large clusters of platelet aggregates formed. The addition of washed red cells to produce a hematocrit of only 2% significantly interfered with the growth and sedimentation of platelet aggregates as shear rate was reduced. Formaldehyde-hardened erythrocytes had a similar effect in preventing the growth of platelet aggregates, suggesting that mechanical collision of red cells with platelet aggregates may be the cause of growth inhibition. Therefore, the thrombotic process may be enhanced in red cell poor zones in circulation resulting from flow disturbances associated with vascular stenosis or within artificial organs and extracorporeal systems. The present study also suggested that red cell free PRP should be carefully administered therapeutically.

Adenosine Diphosphate↗
PubMed1984

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.

Abscess↗
PubMed1984

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.

Adult↗
PubMed1984

Criteria for using imaging ultrasound during brain and spinal cord surgery.

Imaging ultrasonography was performed during 23 brain and five spinal cord operations with real-time B-mode instruments. Criteria for the utilization of ultrasound at neurosurgical procedures were identified in terms of assistance in the diagnosis or better definition of lesions. The diagnosis criteria were detection and exclusion. Because of the accuracy of preoperative imaging, usually little further help was provided by operative ultrasonography in detecting previously totally unknown abnormalities or excluding lesions found on positive studies. The definition criteria were localization, distinction of tissue features, and assessment of spatial relations. Operative ultrasonography was most useful when applied on the basis of these definition criteria. Operative ultrasonography was considered to be useful in 22 of 28 operations (79 per cent) in which it assisted in exposing, accessing, and extirpating disease.

Adult↗
PubMed1984

[Operative ultrasonography of the brain and spinal cord pathology].

B-mode real-time ultrasound using 5 or 7.5 MHz transducer has been employed during 21 operations for brain pathology and spinal cord lesions. Ultrasonic scanning was performed at the following operations: 10 brain tumors (4 glioblastomas multiforme, 2 astrocytomas, 1 medulloblastoma, 2 metastatic tumors), 2 brain cysts (arachnoid, epidermoid), 1 tuberculous abscess, 3 cerebral hematomas: 2 spinal cord tumors (malignant melanoma, glioma), 2 syringomyelias, 1 posterior longitudinal ligament thickening. Operative ultrasound was useful prior to dural incisions and particularly for subcortical lesions. In addition, ultrasound provided assistance at spinal cord surgery. Our experience has been reviewed and summarized in this report in terms of specific usefulness of assistance of this method which has proven helpful to the neurosurgeons. The types of assistance provided by operative ultrasonography include: Location of dural incision. Localization of brain and spinal cord lesions prior to biopsy. Diagnosis which has not been made preoperatively (e.g. necrosis or cystic area in tumor). Consistency of each lesion (e.g. solid or cystic, necrosis, loculation). Size, extent and depth of brain tumor, cyst, abscess and hematoma. Presence and extent of spinal cord syrinx. Relation of tumor to spinal cord and dura. Access route for biopsy and drainage (avoiding critical areas such as motor strip). Exclusion of bleeding or hematoma following biopsy. Confirmation of the effectiveness of drainage or resection of lesions. Relationship between pathology and surrounding anatomic structures. A number of important assistance by the utilization of ultrasound during neurological surgery have been identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Relation of in vivo blood flow to ultrasound echogenicity.

The mechanism of echogenicity of flowing blood during real-time ultrasonography was investigated experimentally in vivo by scanning venous and arterial blood and venous blood subjected to varying degrees of obstruction. Luminal echoes were more intense in flowing blood of the vena cava than in aortic blood of dogs. Vena cava and portal echoes increased in intensity as flow was decreased progressively by obstruction. We believe that an important cause of echogenicity of flowing blood is red cell aggregation which is greatest at low shear rates (low flow velocity). Echogenicity decreases with increase in shear rate (higher flow velocity) which causes red cell disaggregation.

Animals↗
PubMed1983

Critical factors in the image clarity of operative cholangiography.

To evaluate image clarity in operative cholangiography with changing radiographic variables, in vitro experiments were performed in which 1-mm radiographically nonopaque biliary calculi in tubes were examined. Variables changed in these studies were tube caliber (6, 13 and 20 mm), contrast concentration (15, 30, and 60%), X-ray exposures (1, 2, 4, 8, 16, 32, 64, and 128 mAs) and location of calculi (central or peripheral). Sensitivity for the detection of calculi and the clarity of contrast radiographic images depended upon these variables. Reduced contrast concentration or increased radiographic exposure were needed for large caliber tubes. Central small calculi required more exposure than peripheral calculi. Practical inferences from these studies can be summarized as guidelines for performing operative cholangiography: (1) Surgeons should become aware of exposure settings used on the radiographic equipment in the operating room. In particular, the milliampere-seconds-setting is an important variable. (2) Normal size and slightly enlarged ducts should be injected with 30% radiographic contrast. (3) Ducts which are 20 mm or more in diameter should be injected with 15% contrast. (4) Variable radiographic exposures may be necessary to demonstrate centrally and peripherally located calculi, especially for small calculi in large ducts.

Bile Duct Diseases↗
PubMed1983

Red cell aggregation as a cause of blood-flow echogenicity.

The role of red cell aggregation as a cause of ultrasonic echogenicity in flowing blood was evaluated by in vitro experiments using fresh human blood. Blood was circulated in tubes of varying diameter (12 mm to 6 mm). In all experiments, echogenicity increased as blood approached static conditions. Echogenicity was greater in tubes with a larger diameter over the same range of blood velocity. However, echogenicity in tubes of various diameters was the same when evaluated in terms of shear rate. Thus, shear rate and not velocity is the flow condition that determines echogenicity. Since shear rate determines the degree of red cell aggregation, while other conditions affecting red cell aggregation (hematocrit, erythrocyte membrane conditions, and plasma macromolecules) are held constant, we conclude that these results provide additional evidence that red cell aggregation is a cause of echogenicity in flowing blood. Furthermore, a red cell aggregation mechanism for blood-flow echogenicity would explain the increased prominence of internal echoes in lower shear rate venous blood flow compared with those of higher shear rate arterial blood flow.

Cardiovascular Physiological Phenomena↗
PubMed1983

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.

Adult↗
PubMed1983

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.

Cholangiography↗
PubMed1983

Imaging ultrasound in the intraoperative diagnosis of vascular defects.

High-resolution real-time ultrasonography was employed during 267 vascular operations in order to diagnose vascular defects such as intimal flaps, strictures, and thrombi. These defects occur at operative areas (e.g., anastomoses, endarterectomized segments, and sites of placement of occlusive clamps) and can lead to serious thrombotic complications in the early post-operative period. Ultrasound detected vascular defects in 83 patients (31.1 per cent). The defects in 59 patients were considered clinically insignificant because of their sizes and locations, and were not re-explored. Early post-operative results of these patients were comparable to those of the patients without demonstrated defects. In 24 patients (9.0 per cent of all patients examined), ultrasonography revealed clinically significant defects which prompted re-exploration. In 20 of these 24 patients, these vascular defects were confirmed and corrected. No defect was found at re-exploration in four patients, but two of them developed early postoperative thrombosis. Ultrasonography and arteriography were compared at 100 operative sites. The two imaging methods were equal in terms of sensitivity, specificity, efficiency, and predictability of a negative test. Predictability of a positive test was 77.8 per cent for ultrasonography and 59.1 per cent for arteriography. This indicates that fewer needless re-explorations would occur following a decision based on ultrasonography. Operative ultrasonography is a simple, safe and accurate technique that should be applied to reconstructive vascular surgery for diagnosis of vascular defects.

Diagnostic Techniques, Surgical↗