Measurement of the efficiency of tissue removal with the Cavitron Ultrasonic Surgical Aspirator and the comparison with a new motor-driven probe.
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Animals↗
Biomedical subjects
K K Chan
Publications and source records attributed to K K Chan.
Radiological image compression using full-frame cosine transform with adaptive bit-allocation.
We report a new bit-allocation scheme based on the full-frame cosine transform for radiological image compression. The new technique differs from a previously reported method in its use of a two-dimensional bit-allocation table to encode the compression data. This allows for an improved treatment of high frequency components in the transform domain. Consequently, it has the capability of faithfully reproducing limited numbers of high-contrast sharp edges in the image. Previously reported artifacts, induced in the reconstructed image by sharp edges in the original, have been eliminated. Experiments with 10 radiological chest images show almost no perceivable degradation in the reconstructed image at compression ratios below 10:1. Image quality at a fixed compression ratio is, in every case, comparable or superior to results using the old method. Furthermore, the new algorithm lends itself to hardware implementations that are both simple and fast.
Algorithms↗
Systems integration for PACS.
A successful PACS (Picture Archiving and Communications System) implementation requires an eclectic integration of a number of key technologies. Among these are equipment interfaces, communications, storage, and display. Coincident with this, the software architecture must support a distributed system of heterogeneous structures, provide for protocol and format conversions to a unified system standard, be scalable to accommodate expansion, and provide a measure of fault tolerance. In this paper we survey the current state of the UCLA PACS components and architecture.
Computer Systems↗
Modification of tonic-clonic convulsions by atracurium in multiple-monitored electroconvulsive therapy.
STUDY OBJECTIVE: To determine the effect of two different doses of atracurium on the modification of tonic-clonic convulsions in multiple-monitored electroconvulsive therapy (MMECT). To compare recovery time and adverse reactions of these doses. DESIGN: Clinical study. Anesthesiologist was blinded in the evaluation of post-electroconvulsive therapy (ECT) myalgia and other side effects. SETTING: University-affiliated veterans general hospital. PATIENTS: Two groups of twelve psychiatric inpatients who suffered from major depression or catatonic-type schizophrenia that failed to respond to tricyclic antidepressant therapy. INTERVENTIONS: Under single-channel, prefrontal electroencephalographic (EEG) monitoring, patients were given either 0.3 mg/kg or 0.5 mg/kg of atracurium intravenously (IV) after anesthetic induction with methohexital 1 mg/kg i.v. MEASUREMENTS AND MAIN RESULTS: Evoked electromyographic responses of the adductor pollicis muscle was obtained by train-of-four stimulation of the ulnar nerve at the wrist every 20 seconds. The first twitch depression (T1) of neuromuscular blockade was maintained within 11% to 25% (atracurium 0.3 mg/kg) or 0% to 10% (atracurium 0.5 mg/kg) of control during the entire session of MMECT. Patients pretreated with atracurium 0.5 mg/kg had significantly fewer ECT-induced moderate and vigorous convulsions when compared with patients receiving atracurium 0.3 mg/kg (16.7% vs. 78.4%, moderate; 0% vs. 8.3%, vigorous). However, patients pretreated with atracurium 0.5 mg/kg took a longer time to attain a T4 ratio of 0.5 than did patients receiving atracurium 0.3 mg/kg (9.2 +/- 0.8 minutes vs. 4.3 +/- 0.4 minutes). There was no significant difference between the two groups with respect to cumulative seizure duration or frequency of bradycardia, sialorrhea, postseizure myalgia, nausea, headache, or confusion. No patient in either group recalled any event concerning electroconvulsive shock. CONCLUSIONS: Whereas full neuromuscular blockade by atracurium 0.5 mg/kg i.v. is very effective in the modification of tonic-clonic convulsions induced by ECT, we suggest that a lower dose of atracurium (0.3 mg/kg i.v.) be used if one needs to ascertain the occurrence of ECT-induced seizures as indicated by minimum peripheral muscle activity at the time of EEG recording during MMECT.
Adolescent↗
Multidisciplinary team working: is it both holistic and effective?
Multidisciplinary team (MDT) working has been endorsed as the main mechanism to ensure truly holistic care for patients and a seamless service for patients throughout their disease trajectory and across the boundaries of primary, secondary, and tertiary care. However the effectiveness of each team needs to be continually evaluated to ensure that all the relevant disciplines are able to participate in the clinical management of patients. This article describes the work of the Cancer Services Collaborative at the Birmingham Women's hospital in the UK in promoting the development of a holistic MDT in parallel with the medical model.
Continuity of Patient Care↗
A clinical study of 130 patients with biliary tract cancers and periampullary tumors.
A retrospective review of 130 patients with peripheral-type cholangiocarcinomas (PTCC), hilar-type cholangiocarcinomas (HTCC), extrahepatic cholangiocarcinomas (EHCC), gallbladder cancers (GBCA), and periampullary cancers (PACA), seen at National Cheng Kung University Hospital and Tainan Municipal Hospital from June 1987 to July 1993 was performed. There were 47 (36%) HTCC, 32 (25%) PACA, 24 (19%) PTCC, 17 (13%) GBCA, and 10 (8%) EHCC patients. The distribution is completely different from that reported in western countries. These cancers mainly occur in elderly patients. HTCC and GBCA were predominantly noted in female patients. Biliary cancers in Taiwan were not related to liver fluke infestation, inflammatory bowel disease or hepatitis B virus infection. However, a close association with biliary lithiasis was found. The incidence of gallstones was 67, 39, 20, 29 and 19% for PTCC, HTCC, EHCC, GBCA and PACA, respectively. The most common presentation for PTCC and GBCA was abdominal pain, or jaundice for HTCC, EHCC and PACA. These symptoms correlate well with the location of the tumors. Among serum tumor markers, the elevation of CA19-9 was most frequent, occurring in 86% of the patients while CA125 and CEA occurred in 47% and 30% of the patients, respectively. During the course of disease, infection developed in 61% of the patients and was the main cause of death in 25%. Biliary tract infection and sepsis were the two leading manifestations and occurred in 49% and 32% of the patients, respectively. Overall survival was poor except in patients whose tumor could be completely resected.
Adult↗
Pharmacokinetics of 4-hydroxycyclophosphamide and metabolites in the rat.
Pharmacokinetics of 4-hydroxycyclophosphamide (4-OHCP), the major active microsomal metabolite of cyclophosphamide (CP), were investigated in the Sprague-Dawley rat following separate iv bolus administrations of CP, synthetic 4-OHCP, and their combination. CP, 4-OHCP, and other metabolites such as phosphoramide mustard, alcophosphamide, and 3-(2-chloroethyl)-1,3-oxazolidin-2-one in rat plasma were simultaneously analyzed using GC/MS and stable isotope dilution techniques. Following iv administrations of 4-OHCP to rats at doses of 10 mg/kg, 20 mg/kg, and 40 mg/kg, phosphoramide mustard was found to be the major circulating metabolite followed by alcophosphamide and 3-(2-chloroethyl)-1,3-oxazolidin-2-one. No appreciable amount of nor-nitrogen mustard was detected in circulation. The mean excretion of unchanged 4-OHCP in two rats was 4.1 +/- 0.2% of the administered dose in 24-hr urine. Plasma concentration-time profiles of 4-OHCP declined monoexponentially with a mean half-life and total plasma clearance values of 8.1 min and 81.2 ml/min.kg, respectively. No dose-dependent kinetics were apparent between the 10 and 40 mg/kg doses used. The short half-life of 4-OHCP may be due partly to its degradation in plasma, which was found to be a first-order process in vitro with a half-life of 5.2 min. On the other hand, when CP was administrated to eight separate rats at 20 mg/kg each, the mean apparent elimination half-life for the derived 4-OHCP was 55.4 min as compared to 58.2 min, the mean elimination half-life for the parent drug.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Enzymatic detoxification of phosphoramide mustard by soluble fractions from rat organ tissues.
Enzymatic degradation of phosphoramide mustard (PM), the ultimate cytotoxic metabolite of cyclophosphamide (CP), by the cleavage of the phosphorous-nitrogen (P-N) bond was investigated in vitro using 65,000g-soluble fractions from rat organ tissues. In the presence of physiologic bicarbonate in vivo, the P-N bond cleavage of PM was previously found to form 3-(2-chloroethyl)-1,3-oxazolidin-2-one (CNM), which is devoid of antitumor activity. This product was thus quantitated in the present studies using GC/MS and a deuterium-labeled analog (CNM-d8) as the internal standard. Under the experimental conditions, CNM was found to be enzymatically produced from PM in soluble fractions of rat liver, kidney, spleen, and intestine. Mean KM and Vmax values in soluble fractions of rat liver at pH 6.7 and 37 degrees C were determined to be 1.65 +/- 0.536 mM (N = 7) and 6.38 +/- 1.37 microM/min (N = 6), respectively. The enzymic activity of the rat liver soluble fraction was significantly reduced following boiling at 100 degrees C for 5 min. No CNM production was detected from PM incubated in plasma. The P-N bond cleavage for CP and for two other metabolites, 4-ketocyclophosphamide and alcophosphamide, was also investigated using soluble fractions from rat liver similar to that for PM. None of these compounds has been found to form CNM, however, indicating enzyme specificity for the P-N bond in PM. This enzyme probably resembles the previously described phosphamidases.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Tissue concentrations of doxorubicin in animal models with engrafted intraocular tumours.
The role of chemotherapy in the management of retinoblastoma remains unclear. In order to evaluate the responsiveness to conventional or experimental agents, a xenograft model had been developed, where human retinoblastoma is heterotransplanted to the anterior chambers of nude mouse eyes. Because doxorubicin had been found to be ineffective in therapeutic studies utilizing the model, experiments were conducted to evaluate the concentration of the drug in tissues, including intraocular engrafted tumour. The presence of doxorubicin was demonstrated in xenograft containing mouse eyes as well as in tumours of a comparable rabbit model. Distribution in extraocular tissues was consistent with previously published data. It is concluded that failure of response to doxorubicin in the xenograft model is not explained by lack of tumour penetration by the drug.
Animals↗
A simple integrated method for drug and derived metabolite kinetics. An application of the statistical moment theory.
A simple integrated method for the calculation of elimination rate constants of a drug and its derived metabolite has been developed. This method is based on the statistical moment theory and requires only simple calculations of the area under the curve and area under the moment curve of the parent drug and its derived metabolite. The application to a drug following a one-compartmental model is theoretically well justified and this method may also be applicable to drugs following higher kinetic models under certain conditions. The application of this method to several experimental cases is also presented.
Acecainide↗
Differential sensitivity of human nonpregnant and pregnant myometrium to calcitonin gene-related peptide.
OBJECTIVES: Calcitonin gene-related peptide (CGRP) is a smooth muscle relaxant with potent vasodilating properties. To investigate its inhibitory effects on human myometrial contractions, we obtained excised human myometria from term pregnant, with and without spontaneous labor, and nonpregnant patients. METHODS: Myometrial strips were mounted in tissue baths in which contractile activity was recorded. Spontaneously contracting tissues in vitro were exposed to increasing concentrations of CGRP (10(-11)-10(-7) mol/L). Tissues without spontaneous contractions were induced to contract with either oxytocin or KCl before being exposed to CGRP. The IC25 (CGRP concentration required to inhibit contractility by 25%) was used as comparison between groups. RESULTS: Tissues with spontaneous or oxytocin-induced in vitro contractions responded equally to CGRP relaxation. Tissues induced to contract with KCl in vitro required approximately 2000 times more CGRP for equal relaxation. In tissues with spontaneous or oxytocin-induced in vitro contractions, those from pregnant unlabored patients were 60 times more sensitive to CGRP than those from pregnant labored or nonpregnant patients. The letter two groups responded equally to CGRP. CONCLUSIONS: The sensitivity of myometrial tissues to CGRP relaxation in vitro is increased from the nonpregnant to the pregnant term state. This increased sensitivity is lost once patients develop spontaneous term labor. The relative ineffectiveness of CGRP in relaxing KCl-induced in vitro contractions probably reflects its known mechanism of action, namely the hyperpolarization of cell membrane potentials via activation of membrane potassium channels.
Adult↗