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Biomedical subjects

J R Perry

Publications and source records attributed to J R Perry.

At least 55 records · Page 3Linked to original sources
PubMed1992

Fatal basilar vasculopathy complicating bacterial meningitis.

BACKGROUND: Bacterial meningitis complicated by thrombosis, vasculitis, and aneurysm formation affecting both small and distal branches of cerebral vessels has been well described. Involvement of major cerebral vessels is rare and has only been documented late in the course of disease. CASE DESCRIPTION: We describe the clinical and pathological findings in a young man who presented with pontine infarction as an early manifestation of bacterial meningitis. Streptococcus milleri, an unusual organism in this setting, was cultured. Despite improvement with antibiotic therapy, the patient experienced fatal subarachnoid hemorrhage. A ruptured inflammatory aneurysm of the basilar artery, evidence of residual meningitis and vasculitis, and basilar thrombosis associated with pontine infarction were found. CONCLUSIONS: Bacterial meningitis, which may be associated with severe vasculopathy of the basilar artery and lead to cerebral infarction, aneurysm formation, and subarachnoid hemorrhage, should be considered in the differential diagnosis of these conditions. The role of S. milleri in meningitis and its vascular complications merits further study.

Adult↗
PubMed1992

Simultaneous acquisition of emission and transmission data for improved thallium-201 cardiac SPECT imaging using a technetium-99m transmission source.

Transmission computed tomography (TCT) data provides useful complementary information to single-photon emission computed tomography (SPECT) reconstructions, especially for cardiac studies. In particular, TCT data has been used to correct for nonuniform attenuation in the chest. Typically the transmission data are acquired in a separate acquisition, but simultaneous acquisition is preferable both to save time and to avoid difficulties involved with registration. In this work, we present a technique for simultaneously acquiring 201Tl SPECT and TCT data using a 99mTc sheet source that requires only minor equipment modifications. The use of these isotopes results in cross-contamination of the emission and transmission data. We present a practical technique to compensate for this contamination using post-acquisition image processing. This technique was evaluated by performing phantom and patient studies. The resulting images compare well with data obtained from separate emission and transmission studies.

Heart↗
PubMed1992

The effect of ibuprofen on ethanol concentration and elimination rate.

Pursuant to a recent driving under the influence (DUI) case, a medical study of six subjects was cited reporting that ibuprofen causes a decrease in the maximum rate of elimination of ethanol. Such a drug interaction is of significant forensic science interest and warrants further examination. This study investigates the effect of ibuprofen on ethanol elimination rate and ethanol concentration in nineteen volunteers. Volunteer subjects were randomly assigned to two groups administered either a placebo followed by ethanol or ibuprofen followed by ethanol. Subjects served as their own control. Blood ethanol concentrations were monitored every 30 to 60 min for up to 4 h with Intoximeter 3000 instruments. A blood sample was drawn at the final Intoximeter test and analyzed for ethanol and ibuprofen by gas chromatography and mass spectrometry, respectively. The mean elimination rate (+/- SD) as calculated using Widmark's elimination factor was 0.018 +/- 0.006 g/dL for ethanol and 0.017 +/- 0.007 g/dL/h for ethanol with ibuprofen. Mean ethanol concentrations (g/dL +/- SD) were: 0.095 +/- 0.026 (ethanol) and 0.095 +/- 0.033 (ethanol and ibuprofen) at 30 min; 0.077 +/- 0.026 (ethanol) and 0.075 +/- 0.031 (ethanol and ibuprofen) at 150 min; and 0.089 +/- 0.025 (ethanol) and 0.087 +/- 0.030 (ethanol and ibuprofen) overall. There was no statistically significant affect of ibuprofen on either the peak blood ethanol concentration or the ethanol elimination rate (p less than or equal to 0.001). These results reveal no evidence of a significant ethanol-ibuprofen interaction.

Chromatography, Gas↗
PubMed1992

An evaluation of maximum likelihood-expectation maximization reconstruction for SPECT by ROC analysis.

A ROC study was performed in order to evaluate whether the maximum likelihood expectation maximization (ML-EM) reconstruction algorithm improves diagnostic performance compared to the conventional filtered backprojection method in SPECT. Several implementations of the algorithm were tested including 25 and 50 iteration stopping points, with and without nonuniform attenuation compensation, and with and without Metz filtering. Filtered backprojection was with Metz filter and without attenuation compensation. The test data were computer simulated to model cardiac 201Tl SPECT. The data incorporated the effects of nonuniform attenuation, distance-dependent collimator response, and scatter. Patient CT images provided realistic anatomy and attenuation information for the data simulation. Four observers each viewed 120 images for each of the reconstruction methods. Lesion detectability with ML-EM increased with Metz filtering and decreased with nonuniform attenuation compensation. The best MIL-EM implementation, 50 iterations with Metz filtering and without attenuation compensation, was not statistically better than filtered backprojection.

Algorithms↗
PubMed1991

Isolation and characterization of S. cerevisiae mutants deficient in amino acid-inducible peptide transport.

The transport of small peptides into the yeast Saccharomyces cerevisiae is subject to complex regulatory control. In an effort to determine the number, and to address the function, of the components involved in peptide transport and its regulation, spontaneous mutants resistant to toxic di- and tripeptides were isolated under inducing conditions. Twenty-four mutant strains were characterized in detail and fell into two phenotypic groups; one group deficient in amino acid-inducible peptide uptake, the other with a pleiotropic phenotype including a loss of peptide transport. Complementation analysis of recessive mutations in 12 of these strains defined three groups; ptr1 (nine strains), ptr2 (two strains), and ptr3 (one strain). Isolation and screening of 31 additional N-methyl-N-nitro-N-Nitrosoguanidine (MNNG)-induced, peptide transport-deficient mutants produced one ptr3 and 30 ptr2 strains: no additional complementation groups were detected. Uptake of radiolabeled dileucine was negligible in ptr1 and ptr2 strains and was reduced by 65% and 90% in the two ptr3 mutants, indicating that all strains were defective at the transport step. We conclude that the S. cerevisiae amino acid-inducible peptide transport system recognizes a broad spectrum of peptide substrates and involves at least three components. One gene, PTR3, may play an indirect or regulatory role since mutations in this gene cause a pleiotropic phenotype.

Amino Acids↗
PubMed1991

Radionuclide diuresis pyelography.

Radionuclide diuresis renography continues to be relied upon as a major diagnostic tool to differentiate obstructive and nonobstructive hydronephrosis. Controversy continues to exist with respect to methodology and interpretation of intermediate obstructive patterns. In this study radionuclide diuresis pyelography was performed in 11 renal units with hydronephrosis and a pre-existing percutaneous nephrostomy tube in place. The procedure consisted of the introduction per kidney of 20 muc./kg. 99mtechnetium-diethylenetriaminepentaacetic acid and sterile saline as a bolus into the renal pelvis via a percutaneous nephrostomy tube to produce a volume equal to the capacity of the hydronephrotic system. The kidney was monitored with a gamma camera and computer system. Furosemide (0.3 mg./kg.) was injected intravenously halfway into a 40-minute study. The time/activity curves thus generated were relatively independent of the cortical transport phase. The 2 types of curves were accelerated and constant. Analysis of these pyelogram curves revealed a strong correlation between the presence of an accelerated clearance rate response to furosemide and hydronephrosis without obstruction in 5 of 6 renal units. A constant clearance rate response to furosemide correlated with the presence of obstruction in 4 of 5 units. These observations may indicate that diuretic pyelogram curve dynamics may reflect not only the presence or absence of obstruction but also the ability of the hydronephrotic kidney to respond to the diuretic. More experience must be accumulated to determine the conditions under which diuresis pyelography may become useful clinically.

Child↗
PubMed1990

Comparison of coronary angiography and early oral dipyridamole thallium-201 scintigraphy in patients receiving thrombolytic therapy for acute myocardial infarction.

We evaluated 50 consecutive patients who received thrombolytic therapy for acute myocardial infarction using thallium-201 single photon emission computed tomography in combination with oral dipyridamole (300 mg) to assess the frequency of residual myocardial ischemia. Thallium studies were performed early after myocardial infarction at a mean of 4.6 days (range 3 to 11) in 50 patients. The time from the onset of chest pain to the administration of thrombolytic therapy was 2.6 hours (range 0.5 to 5.5). Q wave myocardial infarction was evident in 46 patients; four patients had a non-Q wave infarction (anterior infarction in 31 patients and inferior infarction in 19 patients). The serum mean peak creatinine kinase was 1503 IU/L (range 127 to 6500). Coronary angiography was performed in all patients at a mean of 3.1 days (range 2 to 10) and revealed the infarct-related vessel to be patent in 36 patients (72%). The ejection fraction was 48% (range 26% to 67%). After dipyridamole administration, 13 patients (26%) developed angina that was easily reversed with the administration of intravenous aminophylline. Systolic blood pressure decreased from 122 to 115 mm Hg (p less than 0.05) and the heart rate increased from 76 to 85 beats/min (p less than 0.05). None of the patients had significant hypotension, arrhythmias, or evidence of infarct extension. Perfusion abnormalities were present on the initial thallium images in 48 patients. Redistribution suggestive of ischemia was present in 36 patients (72%). Ischemia confined to the vascular distribution of the infarct vessel was evident in 22 patients. Seven patients had ischemia in the infarct zone as well as in a remote myocardial segment. Thus 29 patients (58%) had ischemia in the distribution of the infarct vessel. Ischemia in the infarct zone was evident in 19 of 36 patients (53%) with open infarct vessels and in 10 of 14 patients (71%) with occluded infarct vessels. In conclusion, thallium-201 single photon emission computed tomography using oral dipyridamole was safely performed in patients with recent myocardial infarctions who receive thrombolytic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

General practitioners' knowledge about patients and use of medical records in out of hours calls.

The medical record is an established adjunct to good care and this paper describes the extent to which general practitioners use patients' records in out of hours calls and how their previous knowledge of their patients affects the decision to visit. Seven general practitioners from three group practices in Cambridge and Newmarket each operating a separate out of hours rota recorded details of out of hours telephone calls. Of 368 calls recorded, 293 (80%) resulted in a visit. In 51% of calls the patient was known to the doctor but the doctors were just as likely to visit patients they knew as those unknown to them. In 41% of the calls the doctors were able to recall a degree of clinically relevant information about the patient. In 47 of the calls (13%) recalled information concerning the patient was an influence in the decision whether to visit. The patient's record was collected before the visit in 30% of visits to the elderly compared with 17% for all age groups. The most often quoted reasons for not collecting the medical record were that it was likely to be unhelpful and/or it was geographically inconvenient. Although doctors who collected the record found it useful in 84% of cases, obtaining the record either before or after the visit rarely changed the management of the patient. On the occasions when it did affect management it was of importance both clinically and medico-legally.(ABSTRACT TRUNCATED AT 250 WORDS)

England↗
PubMed1989

In vitro NMR evaluation of human thyroid lesions.

In vitro analysis of spin-lattice relaxation times (T1), water self-diffusion coefficients (DH2O), and proton NMR spectroscopy were performed in a study of 88 patients with thyroid lesions in order to determine the usefulness of these parameters in the differentiation of benign and malignant tissues. Thyroid tissue sample proton NMR spectral patterns were examined at 360 MHz. Proton NMR spectra were different for normal thyroid tissues, benign, and cancerous lesions. Significantly prolonged T1 (0.5T) and decreased DH2O were found in cancerous thyroid lesions relative to normal thyroid tissues. Considerable overlap was found, however, in comparing T1 and DH2O values for benign and malignant thyroid lesions. This study suggests that proton NMR spectroscopy may be more useful than T1 and DH2O in differentiating benign and malignant thyroid lesions.

Adenoma↗
PubMed1989

The REV1 gene of Saccharomyces cerevisiae: isolation, sequence, and functional analysis.

The REV1 gene of Saccharomyces cerevisiae is required for normal induction of mutations by physical and chemical agents. We have determined the sequence of a 3,485-base-pair segment of DNA that complements the rev1-1 mutant. Gene disruption was used to confirm that this DNA contained the REV1 gene. The sequenced segment contains a single long open reading frame, which can encode a polypeptide of 985 amino acid residues. The REV1 transcript is 3.1 kilobase pairs in length. Frameshift mutations introduced into the open reading frame yielded a Rev-phenotype. A base substitution, encoding Gly-193 to Arg-193, was found in this open reading frame in rev1-1. Deletion mutants, lacking segments of the 5' region of REV1, had intermediate mutability relative to REV1 and rev1-1; a complete deletion exhibited lower mutability than rev1-1. REV1 is not an essential gene. An in-frame fusion of the 5' end of the REV1 open reading frame to the lacZ gene produced beta-galactosidase activity constitutively. The predicted REV1 protein is hydrophilic, with a predicted pI of 9.82. No homologies to RAD1, RAD2, RAD3, RAD7, or RAD10 proteins were noted. A 152-residue internal segment displayed 25% identity with UMUC protein.

4-Nitroquinoline-1-oxide↗
PubMed1989

Correction of nonuniform attenuation in cardiac SPECT imaging.

Correction for photon attenuation in cardiac SPECT imaging using a measured attenuation distribution with an iterative expectation maximization (EM) algorithm and an iterative Chang algorithm were compared with the conventional filtered backprojection and an iterative EM algorithm without attenuation correction. The attenuation distribution was determined from a transmission computed tomography study that was obtained using an external collimated sheet source. The attenuation of the emitting photons was modeled in the EM algorithm by an attenuated projector-backprojector that used the estimated attenuation distribution to calculate attenuation factors for each pixel along each projection and backprojection ray. Results from a heart-lung phantom study and a 201Tl patient study demonstrated that the iterative EM algorithm with attenuation correction provided improved image quality in terms of reduced streak artifacts and noise, and more accurate quantitative information in terms of improved radioactivity distribution uniformity where uniformity existed, and better anatomic object definition.

Algorithms↗
PubMed1988

Determination of the optimum filter function for SPECT imaging.

An observer study was performed in order to evaluate several filters used in SPECT imaging. The filters were applied to the simulated projection data of a uniform activity density cylinder which contained a cold, spherical lesion, 2 cm in diameter. The data incorporated the effects of the detector and scatter response functions, photon attenuation, and noise. Reconstructed transaxial images were used in 2AFC and ROC observer studies testing lesion detectability. In the 2AFC experiment, the Hanning filter scored lowest and did not show a optimum cutoff frequency. The Butterworth filter performed better and showed a well-defined optimum cutoff frequency at 0.15 cycles/pixel. The Metz filter performed as well as the optimum Butterworth but did not show an optimum power factor. In the ROC study, a high power Metz filter demonstrated an ROC curve of lower Az index and different shape from a lower power Metz filter and the optimum Butterworth filter.

Filtration↗
PubMed1986

Extramedullary hematopoiesis. Demonstration by transmission and emission computed tomography.

Extramedullary hematopoiesis occurring in the thorax is a well-known complication of a number of various blood dyscrasias, and its appearance with planar Tc-99m sulfur colloid marrow scintigraphy and transmission computed tomography (CT) has been described previously. The authors present a case of thoracic extramedullary hematopoiesis evaluated by CT and emission computed tomography (ECT).

Abdomen↗
PubMed1986

Design and clinical utility of a fan beam collimator for SPECT imaging of the head.

A long bore fan beam collimator for imaging the head was designed and constructed for a SPECT system with a rotating scintillation camera. In order to avoid the patient's shoulder during rotation of the camera with a thick camera housing, the long bore design is necessary to allow the collimator to get close to the patient's head for improved spatial resolution. Operating at the minimum radius of rotation, the prototype fan beam collimator provides about the same spatial resolution as the high resolution collimator, while the geometric efficiency is equal to approximately 85% of that of the general purpose and approximately 55% higher than the high resolution collimator. Images from a phantom study demonstrate good image quality and are void of artifacts. Comparative clinical studies on temporomandibular joints (TMJ) between the LEGP and fan beam collimators also confirm the superior image quality obtained with the fan beam collimator.

Equipment Design↗
PubMed1985

Radionuclide diagnosis of infradiaphragmatic total anomalous pulmonary venous drainage.

We hypothesized that infradiaphagmatic total anomalous pulmonary venous drainage (ITAPVD), because of its unique physiology, could be diagnosed with radionuclide angiography. Seven neonates with severe respiratory distress were injected intravenously with 3 mCi technetium-99m pertechnetate. In each of four neonates demonstrated to have ITAPVD by pulmonary angiography, nuclide recirculation through the right atrium occurred 3-6 s after initial passage. In addition, direct visualization of the anomalous common pulmonary trunk with nuclide as a "tail" below the diaphragm was obvious in the third infant studied. This prompted review of the first two infants with ITAPVD; in retrospect the anomalous trunk was also visualized with nuclide in both of these infants. All three were injected via the upper extremity. In the fourth ITAPVD infant, nuclide was injected via the lower extremity. In that infant, preferential streaming of the inferior vena caval flow and nuclide across the foramen ovale into the left heart led to simultaneous opacification of anomalous trunk and descending aorta, obscuring the "tail" sign.

False Negative Reactions↗
PubMed1985

Positive treadmill stress tests post myocardial infarction in patients with single-vessel coronary disease.

To investigate the possibility that patients with single-vessel coronary artery disease (CAD) and recent myocardial infarction (MI) can have ST segment depression on post infarction treadmill testing due to ischemia, we studied 16 such patients who underwent cardiac catheterization and exercise testing after MI. Of the 11 patients with ST segment depression on treadmill testing, 10 failed to increase their ejection fraction and nine had a focal worsening of wall motion during exercise radionuclide ventriculography. Seven of these 11 patients had hypokinesis or normokinesis in the suspected area of infarction. In contrast, four of the five patients without ST segment depression on treadmill stress testing had an increase in ejection fraction with stress which was significantly greater than that seen in patients with ST depression (7.2% vs 0%, p less than 0.05). Short-term follow-up (1.1 years) revealed continued post infarction angina in 10 of the 11 patients with positive treadmill stress tests. Four of these patients underwent either percutaneous transluminal angioplasty or surgery. We conclude that positive post infarction treadmill tests due to exercise-induced ischemia may occur in patients with single-vessel CAD and may be associated with continued angina that requires surgical intervention.

Adult↗
PubMed1985

Radionuclide diagnosis of anomalous origin of the right pulmonary artery from the ascending aorta (so-called hemitruncus).

A 5-week-old infant presented with signs of severe congestive heart failure and pulmonary hypertension. Injection of technetium-99m pertechnetate demonstrated anomalous perfusion of the right lung. Subsequently, anomalous origin of the right pulmonary artery from the ascending aorta was proven at cardiac catheterization and repaired. Repeat injection of radionuclide 1 week postoperatively demonstrated normal flow to the right lung.

Aorta, Thoracic↗