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D P Flamig

Publications and source records attributed to D P Flamig.

27 records · Page 2Linked to original sources
PubMed1989

New method for fast MR imaging of the knee.

Thirty-five patients with suspected internal derangements of the knee were examined with conventional two-dimensional (2D) spin-echo magnetic resonance (MR) imaging techniques and a new rapid three-dimensional (3D) method called 3D FASTER (field echo acquisition with a short repetition time and echo reduction). A 9-minute 3D FASTER data acquisition achieves nearly isotropic voxels for the calculation of any desired image plane without a significant loss in image quality. Image contrast is optimized for visualization of knee anatomy in a single sequence. An image-processing workstation is used to speed the multiplanar image calculation and display for more efficient analysis of the complex 3D data set. The 3D FASTER images were superior or equal to 2D images (which took three times longer to acquire) in demonstrating meniscal tears, ligament tears, bone marrow disease, and osteochondral defects. The combined advantages of improved imaging capability and efficiency could make 3D FASTER imaging a routine MR method for knee imaging.

Adolescent↗
PubMed1988

In vivo localized proton spectroscopic studies of human gastrocnemius muscle.

In vivo proton magnetic resonance spectroscopy studies of gastrocnemius muscle were performed in six normal volunteers. Both spatially resolved spectroscopy (SPARS) and stimulated echo acquisition mode (STEAM) sequences were used for volume localization. A number of water suppression sequences have been combined with these localization schemes. Among the various techniques investigated in these studies, STEAM with an inversion pulse (T1-discriminated spectrum) seems to have the best potential for in vivo localized high-resolution proton spectroscopy studies of human muscle.

Adult↗
PubMed1983

Kinetic comparison of normal and thyrotoxic bovine cardiac myosin subfragment-1.

A comparison of the transient kinetics of cardiac ventricular normal and hyperthyroid modified myosin subfragment-1 reveals substantial similarities between the two proteins. The nucleotide-binding kinetics are nonexponential for both proteins, but the large tryptophan fluorescence changes, 34% for ATP binding and 12% for ADP binding which are comparable to those of rabbit skeletal myosin subfragment-1, permit the kinetic data to be resolved into a sum of two exponentials. Both the fast and slow forms of the proteins reach limiting rate constants at high nucleotide concentration. The fast forms of normal and thyrotoxic cardiac subfragment-1 are kinetically identical for nucleotide binding at 20 degrees C and pH 7 and the slow forms differ by less than a factor of 2. The kinetic data for ADP release and the single turnover of ATP could neither be fit by a single exponential nor resolved into two components, which indicates a difference in the rate constants by a factor of 2 or less. The largest difference found was in the steady state turnover of ATP for which thyrotoxic subfragment-1 had a 2.5 times faster turnover as compared to normal subfragment-1. The fractions of fast and slow forms of the two proteins are dependent on the nucleotide concentration and the fractions as well as the rate constants are a function of the protein concentration. This is consistent with the kinetic heterogeneity of cardiac myosin subfragment-1 resulting from aggregation. The differences in the rate constant for the steady state turnover of ATP and in aggregation properties between normal and hyperthyroid cardiac subfragment-1 are consistent with the induction of a myosin isozyme by thyroxine treatment. Moreover, the increase in the steady state turnover of ATP is consistent with the increase in contractility of the muscle in the hyperthyroid state.

Adenosine Diphosphate↗
PubMed1981

Aggregation-linked kinetic heterogeneity in bovine cardiac myosin subfragment 1.

Studies of the cardiac myosin fragment 1 concentration dependence of the rate constants for adenosine 5'-triphosphate (ATP) binding and steady-state hydrolysis reveal that the observed rate constants are remarkably dependent on the protein concentration. The kinetics for ATP binding are biphasic, and both the fast- and slow-phase rate constants and the respective fractions of fast and slow material vary as a function of protein concentration. Two different types of kinetic experiments were conducted, one in which the ATP concentration was fixed but the subfragment 1 concentration was varied and another for which the ATP/subfragment 1 ratio was fixed but both concentrations were varied. The results of these two experiments on cardiac subfragment 1 are consistent with an ATP-dependent reversible aggregation. Light-scattering experiments confirm the presence of this aggregation and the ATP dependence. Similar studies on rabbit skeletal subfragment 1 give monophasic, protein-independent kinetics consistent with a monomeric species in solution. a simple monomer--dimer mechanism can account for the cardiac subfragment 1 kinetic results when changes in tryptophan fluorescence are used. However, the light-scattering results show that cardiac myosin subfragment 1 undergoes multiple reversible molecular weight changes in solution and may be tetrameric at high concentrations.

Adenosine Triphosphate↗
PubMed1977

Kinetics of the alkaline tetramer leads to dimer dissociation in liganded human hemoglobin: a laser light-scattering stopped-flow study.

The first-order dissociation of tetrameric HbCO to the dimer has been studied overthe pH range 10.30-11.57 in a light-scattering stopped-flow apparatus using argon-ion laser excitation. The first-order dissociation rate constant varies from 0.25 sec-1 to 24.0 sec-1over this pH interval. A semilogarithmic plot of k versus pH has a slope of 2.56 at pH 11.07, the midpoint. The pH dependence of the dissociation of the tetramer is consistent with progressive titration of alpha1-alpha2 and beta1-beta2 salt bridges. At pH 10.66, the dissociation rates of HbO2, HbCO, methemoglobin, and HbCN vary less than 20% from their mean value. A study of the dissociation kinetics as a function of protein concentration allows one to obtain both association and dissociation rate constants, and hence equilibrium constants, for the tetramer in equilibrium dimer reaction. In this manner, equilibrium constants were obtained on protein solutions with less than 15 sec of exposure to dissociating conditions.

Carboxyhemoglobin↗
PubMedDate not supplied

MR imaging of the breast.

The current strategy for breast cancer treatment involves early detection of the neoplasm before it has metastasized outside the breast, and surgical treatment of the lesion that minimizes deformity. Conventional methods of diagnostic imaging of the breast, including mammography, sonography, and galactography, do not adequately address clinical needs with regard to lesion characterization and staging. Magnetic resonance (MR) imaging has been proposed as a modality that may address these needs. The potential clinical uses of MR imaging are defined in terms of clinical needs and technologic requirements. Applications of MR imaging in detection of breast lesions can be divided into two major approaches based on the clinical questions to be answered: (a) improved specificity and (b) improved sensitivity. These approaches are defined by specific sets of clinical needs and have substantially different technologic requirements. The specificity approach is used to reduce the number of biopsies performed to confirm false-positive mammographic findings. The MR imaging device that is used to improve specificity must visualize only the lesions that are seen mammographically. The sensitivity approach requires the visualization of lesions not identified at mammography, so that breast disease can be more effectively staged for treatment. The technologic requirements for the sensitivity approach are considerably more rigorous because all lesions must be identified. The advantages and disadvantages of each of these approaches and the potential clinical ramifications are described.

Breast↗
PubMedDate not supplied

Breast MRI.

Explore the source record for details and available documents.

Adult↗
PubMedDate not supplied

Silicone-suppressed 3D MRI of the breast using rotating delivery of off-resonance excitation.

OBJECTIVE: A new silicone-suppressed MR technique was developed, and its efficacy in identifying free silicone and differentiating it from other breast tissues was investigated. MATERIALS AND METHODS: Silicone-suppressed MRI was performed using the RODEO (rotating delivery of excitation off-resonance) pulse sequence, which selectively eliminated signal from the narrow range of (CH3)4Si resonance. Ninety breasts in 61 patients were evaluated with both a fat-suppressed 3D MR sequence and a silicone-suppressed 3D MR sequence. RESULTS: Extracapsular free silicone and silicone injections demonstrated a unique appearance compared with normal breast tissue in all cases. Magnetic resonance identified free silicone in 26 breasts, 10 of which were confirmed pathologically or from a history of previous silicone injections. No free silicone was present on MR in 64 breasts; 8 of these were confirmed by biopsy or mastectomy as showing no evidence of free silicone. This technique was useful in evaluation of prosthesis integrity, free silicone, focal palpable or mammographic lesions, and the breast with silicone injections. CONCLUSION: Silicone-suppressed RODEO MRI of the breast can accurately identify free and intracapsular silicone and can distinguish silicone from other tissues. This provides unique information about the breast in a number of specific applications.

Adult↗