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K M Jones

Publications and source records attributed to K M Jones.

At least 37 records · Page 2Linked to original sources
PubMed1994

Fast spin-echo MR in the detection of vertebral metastases: comparison of three sequences.

PURPOSE: To examine the relative capabilities for the detection of vertebral metastases of three available fast spin-echo sequences: T1-weighted fast spin-echo, short tau inversion recovery (STIR) fast spin-echo, and T2-weighted fast spin-echo sequences with chemical shift selective saturation pulse fat suppression. METHODS: Fourteen patients were evaluated prospectively over a 2-month period with T1-weighted fast spin-echo (four echo train, four acquisitions, 1 min 59 sec-2 min 37 sec). STIR fast spin-echo (16 echo train, four acquisitions, 2 min 30 sec-3 min 19 sec), and T2-weighted fast spin-echo (16 echo train, 4 acquisitions, 2 min 27 sec-3 min 16 sec). For all three pulse sequences, measurements were obtained of the signal intensities of normal marrow, abnormal marrow, fat, and noise posterior to the spine. Contrast-to-noise ratios were calculated for metastases in each case. Lesions were evaluated by three observers and rated for size, location, and conspicuity. RESULTS: Signal intensities of fat, normal marrow, and noise were highest for T1-weighted fast spin-echo sequences. STIR fast spin-echo and fat-suppressed T2-weighted fast spin-echo had approximately similar fat-suppression capabilities. Though contrast-to-noise ratios were highest overall for STIR fast spin-echo, the finding was not statistically significant and lesion conspicuity was deemed better with fat-suppressed T2-weighted fast spin-echo and T1-weighted fast spin-echo images. Discrete lesions were well identified on all three pulse sequences. CONCLUSION: Fast spin-echo sequences appear promising for the detection of vertebral metastases. Further work should be directed toward comparison with conventional spin-echo to determine whether fast spin-echo may replace conventional spin-echo sequences for evaluation of vertebral metastases.

Adult↗
PubMed1993

The gdhA1 point mutation in Escherichia coli K12 CLR207 alters a key lysine residue of glutamate dehydrogenase.

gdhA1 is a spontaneous mutant of Escherichia coli that causes complete loss of activity of the NADP-specific glutamate dehydrogenase (GDH) encoded by the gdhA gene. The gdhA1 mutational site has been identified by recombinational mapping, polymerase chain reaction (PCR) amplification and DNA sequencing, as an A to G transition at nucleotide 274 of the gdhA coding sequence, resulting in an amino acid change of lysine 92 to glutamic acid. The mutant enzyme forms hybrid hexamers with a wild-type GDH, providing a useful system for analysis of conformational integrity of mutational variants.

Base Sequence↗
PubMed1993

Imaging of neurologic complications associated with pregnancy.

The occurrence of a neurologic event during pregnancy or the puerperium may have devastating consequences for mother and child. It is imperative that the radiologist be familiar with the entities likely to be encountered in pregnancy so that these patients can be examined rapidly and efficiently. The importance of early and accurate diagnostic imaging is underscored by the fact that most patients are otherwise young and healthy, and prompt institution of appropriate therapy can result in complete recovery. In this report, we illustrate some of the more common neurologic complications that occur during pregnancy and the immediate postpartum period.

Adult↗
PubMed1993

Fast spin-echo imaging of the brain.

Fast spin-echo (FSE) imaging is a recently modified rapid-acquisition relaxation-enhanced technique that affords rapid magnetic resonance (MR) imaging while retaining true spin-echo (SE) contrast features. By manipulating factors such as echo train length, echo spacing, and order of phase encoding, dual-echo brain images currently may be obtained many times faster than with conventional SE techniques. The time advantage of FSE may be used simply to obtain images much more rapidly or to acquire images of much higher contrast or spatial resolution compared with conventional SE images in a comparable period of time. Lesion appearance and conspicuity are usually quite similar to those on conventional SE images, with the important exception of some hemorrhagic blood products, which may appear less conspicuous on FSE images because of reduced magnetic susceptibility effects. Another important difference is the bright appearance of fat on all routine FSE sequences (T1-weighted, proton-density, and T2-weighted), although this may be eliminated easily by using routine fat-suppression techniques. Recent applications of FSE include three-dimensional multislab imaging and high-resolution imaging with large-matrix, small-field of view, thin-slice, and multiple-excitation imaging parameters. FSE techniques appear quite promising for rapid MR imaging of the brain, and they have largely replaced conventional SE technique at some institutions.

Brain↗
PubMed1992

Bone marrow imaging using STIR at 0.5 and 1.5 T.

We retrospectively examined MR images in 82 patients to evaluate the usefulness of short inversion time inversion recovery (STIR) in bone marrow imaging at 0.5 and 1.5 T. The study included 56 patients at 1.5 T and 26 patients at 0.5 T with a variety of pathologic bone marrow lesions (principally oncological), and compared the contrast and image quality of STIR imaging with spin-echo short repetition time/echo time (TR/TE), long TR/TE, and gradient-echo sequences. The pulse sequences were adjusted for optimal image quality, contrast, and fat nulling. STIR appears especially useful for the evaluation of red marrow (e.g., spine), where contrast between normal and infiltrated marrow is greater than with either gradient-echo or T1-weighted images. STIR is also extremely sensitive for evaluation of osteomyelitis, including soft tissue extent. In more peripheral (yellow) marrow, T1-weighted images are usually as sensitive as STIR. Limitations of STIR include artifacts, in particular motion artifact that at high field strength necessitates motion compensation. At 0.5 T, however, motion compensation is usually not necessary. Also, because of extreme sensitivity to water content, STIR may overstate the margins of a marrow lesion. With these limitations in mind, STIR is a very effective pulse sequence at both 0.5 and 1.5 T for evaluation of marrow abnormalities.

Adolescent↗
PubMed1992

Brain hemorrhage: evaluation with fast spin-echo and conventional dual spin-echo images.

Signal intensity of blood products on proton-density- and T2-weighted images obtained with spin-echo (SE) and fast SE (FSE) sequences was evaluated in 15 patients with central nervous system hemorrhage to determine the extent of differences between the two techniques when signal loss from magnetic susceptibility effects in hemorrhagic lesions is considered. Within operator-defined regions of interest, signal intensity of hemorrhage, iron-containing nuclei, white matter, scalp fat, and noise was measured along the phase-encoding direction. Hemosiderin, deoxyhemoglobin, and iron-containing nuclei had slightly higher signal intensity on FSE images than on SE images, but the differences were not statistically significant. Signal intensity of methemoglobin was similar with both sequences, whereas that of scalp fat was higher on FSE images. Signal intensity measurements for most tissues studied were comparable, but the signal-to-noise ratios with FSE imaging were less than those with SE imaging. Although paramagnetic blood products may show slightly higher signal intensity with FSE imaging, contrast with the two sequences was comparable and lesion conspicuity was nearly identical.

Adult↗
PubMed1992

Common carotid artery bifurcation: evaluation with spiral CT. Work in progress.

To determine the utility of spiral computed tomography (CT) in evaluation of carotid artery stenosis, spiral CT images of 20 patients were compared with images obtained with conventional angiography (20 patients), ultrasound (US) (15 patients), and magnetic resonance (MR) angiography (six patients). The category of stenosis was determined for each internal carotid artery on the basis of the percentage of narrowing: mild = less than 30%, moderate = 30%-69%, and severe = 70%-99%. Occlusions were also noted. The degree of carotid stenosis determined with spiral CT correlated with that determined with conventional angiography in 92% of cases, with that determined with US in 97% of cases, and with that determined with MR angiography in 100% of cases. Calcifications and large ulcers were also well delineated. Spiral CT provided an accurate anatomic depiction of the carotid bifurcation, which could be helpful in preoperative evaluation. The major disadvantage of the technique was the need to postprocess data to remove veins, calcifications, and bone structures from the images.

Adult↗
PubMed1992

Hypertensive encephalopathy: findings on CT, MR imaging, and SPECT imaging in 14 cases.

Hypertensive encephalopathy is a syndrome consisting of headache, seizures, visual changes, and other neurologic disturbances in patients with elevated systemic blood pressure. The purpose of this study was to analyze the imaging findings in 14 patients with hypertensive encephalopathy. CT (n = 13), MR (n = 12), and single-photon emission computed tomography (n = 2) examinations performed in these patients before and after resolution of symptoms were reviewed. Eight had the preeclampsia-eclampsia syndrome, and six had hypertensive encephalopathy due to other causes. CT and MR findings in all patients having these examinations were indicative of edema in the cortex and subcortical white matter in the occipital lobes. Two of the 14 patients also had similar findings in the cerebellum and frontal lobes. Single-photon emission computed tomography showed increased vascular perfusion adjacent to areas that appeared abnormal on CT and MR. The findings on the imaging studies resolved on follow-up examinations performed after the hypertension was corrected. Our results suggest that the radiologic findings associated with hypertensive encephalopathy may be useful in establishing the diagnosis in the appropriate clinical setting.

Adolescent↗
PubMed1992

The value of cerebral angiography in predicting cerebral ischemia during carotid endarterectomy.

OBJECTIVE: Temporary occlusion of the carotid artery during endarterectomy can result in ipsilateral cerebral ischemia if collateral blood flow is insufficient. This requires placement of a shunt across the carotid bifurcation, which is associated with increased operative risk. We retrospectively analyzed preoperative cerebral angiograms and intraoperative electroencephalographic recordings to determine if ischemia during carotid endarterectomy could be predicted from angiographic data. MATERIALS AND METHODS: The cerebral angiograms of 30 patients were examined. Collateral blood flow to the hemisphere on the side of surgery was determined to be present if both proximal segments of the anterior cerebral artery and the anterior communicating artery were visualized, or if filling and washout of the ipsilateral posterior cerebral artery could be seen. Collateral flow was determined to be inadequate if the anterior collateral system was incomplete, and if either the ipsilateral posterior communicating artery was absent or the posterior cerebral artery filled without washout. This information was compared with intraoperative electroencephalographic and shunting data. RESULTS: Of 15 patients who had demonstrable collateral blood flow, 14 had stable electroencephalograms and did not require a shunt during surgery. In all 15 patients in whom no collateral flow to the ipsilateral hemisphere could be shown, electroencephalographic changes prompted placement of an intraluminal shunt. CONCLUSION: We found that the angiographic determination of inadequate collateral cerebral circulation correlated strongly with the development of intraoperative ischemia. This implies that routine preoperative cerebral angiograms can be used to alert the surgeon to the potential need for shunt placement during carotid endarterectomy.

Aged↗
PubMed1990

Computer use and education in radiology residency programs.

Computers play an increasingly important role in radiology education and research. We surveyed all U.S. residency programs to assess computer availability, education, and use by residents. Out of 210 questionnaires sent, 132 were returned (63% response). Areas of inquiry included computer equipment and software as well as resident use of facilities. Opinions were also solicited concerning the importance of computer literacy and education. Sixty-nine percent of the respondents have computer facilities (61% within the department). Predominant uses include scientific papers, slides/audiovisual presentations and resume preparation. Popular software includes word processing, spreadsheets, databases and graphics. Of those training programs with computers, 85% provided computer education, and most (70%) felt computer training was very important. Forty-seven percent expected their residents to have at least passing acquaintance with computers. However, in 60% of programs with computers, the computers are used by less than half the residents. Of those programs without a computer, 61% provided no computer training, and only 44% felt computer education was very important. A sizable minority of radiology residency programs are still without computer facilities. Those programs that have computers tend to place a greater emphasis on computer education and literacy for radiology residents. However, even in programs that have computers, it seems they are often underutilized by residents.

Computer User Training↗
PubMed1989

Treatment of mandibular fractures in children.

Thirty-seven mandibular fractures were treated in 25 patients between January 1984 and January 1988. The patients' ages ranged from 4 months to 16 years (6.9 +/- 4.6 years [mean +/- standard deviation]). Nineteen of the patients were male and 6 were female, indicating a significant gender predilection (p less than 0.05). A treatment approach based on the patients' dental maturity and fracture location has evolved that stresses rapid restoration of osseous continuity and preoperative occlusion while striving to minimize risk to unerupted dentition.

Adolescent↗
PubMed1989

Maintenance of airway patency following treatment of choanal atresia.

Airway patency following repair for choanal atresia is effectively maintained utilizing Argyle polyethylene chest tubes as stents. Retrograde placement of the tubes from the mouth into the nasal passage is accomplished so that once secured, the largest diameter of the tubes is wedged against the posterior portion of the nasal ostium. This approach limits anterior migration of the tubes, preserving the columella and nasal rims while ensuring maintenance of airway patency following treatment of choanal atresia.

Airway Obstruction↗
PubMed1988

Metabolism of low-density lipoprotein-proteoglycan complex by macrophages: further evidence for a receptor pathway.

Earlier, we (Vijayagopal, P., et al. (1985) Biochim. Biophys. Acta 837-251) have shown that complexes of plasma low-density lipoproteins (LDL) and arterial chondroitin sulfate-dermatan sulfate proteoglycan aggregate promote LDL degradation and cholesteryl ester accumulation in mouse peritoneal macrophages. Further studies were conducted to determine whether LDL-proteoglycan complex is metabolized by a receptor-mediated process. Native proteoglycan aggregate was isolated from bovine aorta by associative CsCl isopycnic centrifugation. Complex of 125I-labeled LDL and proteoglycan aggregate formed in the presence of 30 mM Ca2+ was incubated with macrophages, and the binding at 4 degrees C and degradation at 37 degrees C of 125I-labeled LDL in the complex was monitored. Both binding and degradation of the complex were specific and saturable, suggesting that the processes are receptor mediated. The Kd for binding was 23 micrograms LDL protein per ml in the complex. Degradation of 125I-labeled LDL-proteoglycan complex was not suppressed by preincubation of macrophages with excess unlabeled complex, suggesting that the receptor for the complex is not subject to down regulation. Both binding and degradation of the complex and the resultant stimulation of cholesteryl ester synthesis were inhibited by limited treatment of cells with low doses of trypsin and pronase, indicating that the binding sites are protein or glycoprotein in nature. Binding was not inhibited by an excess of native LDL and beta-VLDL and exhibited only partial competition by excess unlabeled acetyl-LDL; however, polyinosinic acid, fucoidin and dextran sulfate, known inhibitors of acetyl-LDL binding and degradation in macrophages, did not affect LDL-proteoglycan complex binding and degradation. Similarly, excess unlabeled LDL-proteoglycan complex produced only partial inhibition of the binding and degradation of 125I-labeled acetyl-LDL by macrophages, suggesting that the binding sites for acetyl-LDL and LDL-proteoglycan complex are probably not identical. These studies provide evidence for a receptor-mediated pathway for the metabolism of LDL-proteoglycan complex in macrophages.

Animals↗
PubMed1988

Multiple interactions of lysine-128 of Escherichia coli glutamate dehydrogenase revealed by site-directed mutagenesis studies.

A highly conserved lysine at position 128 of Escherichia coli glutamate dehydrogenase (GDH) has been altered by site-directed mutagenesis of the gdhA gene. Chemical modification studies have previously shown the importance of this residue for catalytic activity. We report the properties of mutants in which lysine-128 has been changed to histidine (K128H) or arginine (K128R). Both mutants have substantially reduced catalytic centre activities and raised pH optima for activity. K128H also has increased relative activity with amino acid substrates other than glutamate, especially L-norvaline. These differences, together with alterations in Km values, Kd values for NADPH and Ki values for D-glutamate, imply that lysine-128 is intimately involved in either direct or indirect interactions with all the substrates and also in catalysis. These multiple interactions of lysine-128 explain the diverse effects of chemical modifications of the corresponding lysine in homologous GHDs. In contrast, lysine-27, another highly reactive residue in bovine GDH, is not conserved in all of the sequenced NADP-specific GDHs and is therefore not likely to be involved in catalysis.

Amino Acid Sequence↗