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Biomedical subjects

D M DeLong

Publications and source records attributed to D M DeLong.

53 records · Page 3Linked to original sources
PubMed1996

Doppler sonography in the diagnosis of antepartum pyelonephritis: value of intrarenal resistive index measurements.

This study aims to define the effects of pyelonephritis on intrarenal resistive indices and to determine the role of Doppler sonography in the diagnosis of pyelonephritis in pregnant patients. Twenty pregnant women with pyelonephritis underwent renal Doppler sonography with calculation of intrarenal resistive indices. The resistive index was calculated for the upper, lower, and interpolar areas of each kidney in the patients with pyelonephritis (40 kidneys) and was compared to the resistive indices for a control group of 153 normal asymptomatic pregnant women (306 kidneys). Doppler findings were correlated with the location (sidedness) of flank pain in the pyelonephritis group. The mean resistive index values of patients with pyelonephritis were 0.04 higher than in the controls, and this difference was statistically significant (P < 0.001). Four patients with pyelonephritis had a mean resistive index > or = 0.70, whereas the remaining 16 patients had resistive indices within the normal range of < or = 0.70. In patients with confirmed pyelonephritis and unilateral pain, the average resistive index in the kidney on the side of pain was 0.03 greater than that on the asymptomatic side (P = < 0.01). The mean renal resistive index is significantly greater in pregnant patients with pyelonephritis than in pregnant women without pyelonephritis. Even so, the magnitude of the differences in resistive index is too small and the overlap between the groups too large for this parameter to be of discriminating clinical value.

Diagnosis, Differential↗
PubMed1995

Spontaneously changing gravid cervix: clinical implications and prognostic features.

PURPOSE: To assess the implications of spontaneous changes in the length and configuration of the gravid cervix during a single ultrasound (US) examination and to correlate specific cervical dimensions with pregnancy outcome. MATERIALS AND METHODS: Sonograms in 27 pregnant patients with a spontaneously changing cervix were studied prospectively. The length and width of cervical funneling and the length of intact cervix caudal to the funneling were measured when the cervical dimensions were most normal and most abnormal. Sonographic measurements were correlated with clinical and delivery data. RESULTS: Twenty patients delivered preterm, although only six delivered within a week of the US examination. Wider funneling of the internal os and a shorter segment of intact cervix caudal to the funneling both correlated with an increased likelihood of preterm delivery. CONCLUSION: Most patients with a spontaneously changing cervix deliver preterm. Measurements obtained when the cervix appears most abnormal are most predictive of early delivery.

Adolescent↗
PubMed1995

Optimum scanning protocol for FDG-PET evaluation of pulmonary malignancy.

UNLABELLED: FDG-PET can differentiate benign from malignant focal pulmonary opacities. We performed dynamic FDG-PET studies to determine the optimum time for emission data acquisition. METHODS: Patients with focal pulmonary abnormalities demonstrated by biopsy to be malignant (n = 10) or benign (n = 4) were evaluated with dynamic FDG-PET. Dynamic PET data were acquired as sequential 5-min images for 2.5 hr. Radioactivity concentration measurements of the focal abnormality, a similar area in the opposite lung, and both lungs in the field of view were made throughout the period of acquisition. Standardized uptake ratios (SUR) of the lesions were calculated. SUR data and lesion-to-background ratios were plotted. The time that the SUR provided the maximum separation between benign and malignant masses after FDG administration was determined. RESULTS: The SUR values provided the greatest separation between benign and malignant abnormalities beginning at 50 min and no advantage was identified in imaging later. Achievement of a 4:1 lesion-to-background ratio occurred by 50 min in malignant lesions. CONCLUSION: The acquisition of the emission data used in the evaluation of pulmonary malignancy should begin approximately 50 min after FDG administration.

Deoxyglucose↗
PubMed1995

Evaluation of SPECT quantification of radiopharmaceutical distribution in canine myocardium.

UNLABELLED: This study evaluates the quantitative accuracy of SPECT for in vivo distributions of 99mTc radiopharmaceuticals using fanbeam (FB) and parallel-beam (PB) collimators and compares uniform and nonuniform attenuation correction methods in terms of quantitative accuracy. METHODS: SPECT quantification of canine myocardial radioactivity was performed followed by well counter measurements of extracted myocardial tissue samples. Transmission scans using a line source and an FB collimator were performed to generate nonuniform attenuation maps of the canine thorax. Emission scans with two energy windows were acquired. Images were reconstructed using a filtered backprojection algorithm, with a dual-window scatter subtraction combined with either no attenuation compensation or single iteration Chang attenuation compensation based on an uniform attenuation map (mu = 0.152 cm-1) or the nonuniform transmission map. RESULTS: The measured mean counts from the SPECT images were converted to radionuclide concentrations (MBq/g) using a standard source calibration and were compared with those obtained using the well counter. CONCLUSION: The experimental results demonstrate that, compared with well counter values, the in vivo distributions of 99mTc were most accurately determined in FB and PB SPECT reconstructions with nonuniform attenuation compensation, under-estimated without attenuation compensation and overestimated with uniform attenuation compensation.

Animals↗
PubMed1995

Detection of pulmonary embolism: comparison of contrast-enhanced spiral CT and time-of-flight MR techniques.

We compared the conspicuity of acute pulmonary emboli with contrast-enhanced spiral computed tomography (CT) and two- and three-dimensional time-of-flight magnetic resonance (MR) techniques. Seven dogs who received experimental pulmonary emboli and one control were imaged with spiral CT and with 2-D (FMPVAS and FASTCARD) and 3-D time-of-flight MR. Blinded, independent, prospective evaluations of the CT and MR images by two MR radiologists and two chest radiologists were then compared to the location of the emboli as determined by subsequent pathologic evaluation of the excised lungs. Embolus/blood contrast-to-noise ratios (CNRs) were calculated on both MR and CT images for pulmonary emboli that could be identified. Fifty emboli ranging from 1.0 to 5.5 mm (mean, 2.7, +/- 0.14 SEM) in diameter and from 3.0 to 60 mm (mean, 28.1 +/- 1.9 SEM) in length were found in the seven embolized dogs on pathologic examination. Three of the four radiologists identified more thrombi on CT images than they did on their best MR pulse sequence (FASTCARD) and with greater confidence. The fourth radiologist identified an equal percentage of clot on CT and FASTCARD images with confidence slightly greater on FASTCARD MR than on spiral CT. Mean CNR for the best MR technique was 43.4 (+/- 3.9 SEM) and for CT was 20.7 (+/- 1.3 SEM). In general, pulmonary emboli were detected more accurately on contrast-enhanced spiral CT than on MR. This occurred although the embolus/blood CNR was higher on MR than on CT. Better pulmonary embolus conspicuity on CT images was attributed to better spatial resolution and fewer artifacts on CT than on MR. One MR radiologist performed equally well with both spiral CT and FASTCARD techniques, suggesting that experience may be a factor in performance.

Animals↗
PubMed1994

Evaluation of revised criteria for ventilation-perfusion scintigraphy in patients with suspected pulmonary embolism.

PURPOSE: To evaluate the accuracy of the revised PIOPED (Prospective Investigation of Pulmonary Embolism Diagnosis) criteria for categorization of ventilation-perfusion lung scans and to compare the diagnostic accuracy of the revised criteria with that of the original PIOPED criteria and subjective probability estimates. MATERIALS AND METHODS: The ventilation-perfusion scans of 104 consecutive patients with suspected pulmonary embolism were reviewed. All patients had also undergone pulmonary angiography. The scans were categorized according to the original and revised PIOPED criteria, and a "gestalt" percent probability estimate was made. In addition, the official clinical interpretation (made with the original PIOPED criteria) was recorded. RESULTS: The gestalt percent probability estimate was the most accurate for assessing the likelihood of pulmonary embolism (area under the receiver operating characteristic [ROC] curve = 0.836). The revised PIOPED criteria (area under the ROC curve = 0.753) were more accurate than the original PIOPED criteria. CONCLUSION: The revised PIOPED criteria are more accurate than the original PIOPED criteria. Experienced readers of lung scans can achieve higher accuracy after applying formal criteria by using their experience and subjective judgment.

Evaluation Studies as Topic↗
PubMed1994

Doppler evaluation of renal artery stenosis: interobserver agreement in the interpretation of waveform morphology.

OBJECTIVE: Analysis of Doppler waveform morphology for features of the tardus-parvus phenomenon has been promoted as a useful and accurate means for detecting renal artery stenosis. The purpose of this study was to examine and quantify the interobserver agreement of such an analysis and to determine if interobserver differences limit the value of this approach for predicting renal artery stenosis. SUBJECTS AND METHODS: Four observers independently categorized renal artery waveforms of 47 patients (94 kidneys) clinically selected for renovascular hypertension. Waveforms were classified into five categories based on the presence and severity of tardus-parvus changes in the systolic upstroke and early systolic peak. This categorization was then compared with angiographic findings, and the results were analyzed with receiver-operating-characteristic curves. Kappa statistics and agreement tables were computed to evaluate interobserver agreement. RESULTS: Interobserver agreement in the waveform analysis for the four interpreters was statistically significant (p < 0.001). The receiver-operating-characteristic areas produced by the observers indicated, however, that such waveform classification was not strongly predictive of renal artery stenosis. CONCLUSION: We conclude that substantial agreement in the interpretation of waveform morphology can be obtained between independent observers, and that such differences that do exist do not preclude the use of the pattern-recognition approach to waveform analysis. Even so, the specific application of this strategy to the waveform contours of early systole was not successful in predicting the presence or severity of renal artery stenosis.

Humans↗
PubMed1994

Semiquantitative and visual analysis of FDG-PET images in pulmonary abnormalities.

UNLABELLED: FDG PET images of the thorax can be analyzed semiquantitatively using standardized uptake ratios (SUR) or activity ratios between abnormal and normal tissue, or qualitatively by visual comparison of the abnormality to normal structures. Standardized uptake ratio evaluation of FDG PET images has been shown to accurately differentiate benign from malignant focal pulmonary abnormalities. The accuracy of activity ratios and visual analysis have not been evaluated. We therefore prospectively analyzed FDG PET images in patients with pulmonary abnormalities to evaluate differences in analytic schemes. METHODS: We evaluated 107 patients with an indeterminate focal abnormality on chest radiograph or CT with FDG PET between November 1991 and March 1993. The PET studies were evaluated using SUR, activity ratios and visual analysis. Activity ratios of maximum activity/cc and average activity/cc between regions of interest (ROIs) in abnormalities and normal lung on the contralateral side were calculated. Visual interpretations were graded on a five-point scale of two observers' confidence of malignancy. FDG uptake in the abnormality was also visually graded in comparison to mediastinal activity. Receiver-operating characteristic (ROC) curve areas were generated for the SUR data, activity ratios and visual analysis. RESULTS: Of 88 patients in which a conclusive diagnosis was made, 61 (69%) patients had malignancy and 27 (31%) patients had a benign process. SUR, maximum activity ratio, average activity ratio and visual interpretation ROC curve areas were 0.96, 0.95, 0.92 and 0.96, respectively. CONCLUSIONS: SUR, activity ratios and visual evaluation are each equally accurate methods of FDG PET data analysis in differentiating malignant from benign focal pulmonary abnormalities.

Deoxyglucose↗
PubMed1988

Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach.

Methods of evaluating and comparing the performance of diagnostic tests are of increasing importance as new tests are developed and marketed. When a test is based on an observed variable that lies on a continuous or graded scale, an assessment of the overall value of the test can be made through the use of a receiver operating characteristic (ROC) curve. The curve is constructed by varying the cutpoint used to determine which values of the observed variable will be considered abnormal and then plotting the resulting sensitivities against the corresponding false positive rates. When two or more empirical curves are constructed based on tests performed on the same individuals, statistical analysis on differences between curves must take into account the correlated nature of the data. This paper presents a nonparametric approach to the analysis of areas under correlated ROC curves, by using the theory on generalized U-statistics to generate an estimated covariance matrix.

Algorithms↗
PubMed1986

A comparison of methods for the estimation of plasma low- and very low-density lipoprotein cholesterol. The Lipid Research Clinics Prevalence Study.

Using data from over 10 000 men, women, and children who participated in the Lipid Research Clinics prevalence studies, we have examined the formula adopted by Friedewald et al for estimating plasma or serum concentrations of low-density lipoprotein cholesterol (LDL-C) when (for economy, or in the absence of an ultracentrifuge) only fasting total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) concentrations are measured in milligrams per liter, ie, LDL-C = TC-(HDL-C + 0.20 X TG). Values for LDL-C obtained by use of the Friedewald formula were compared with values derived from the Lipid Research Clinics ultracentrifugal procedure for LDL-C, which was used as a reference. Participants who were pregnant, who had not fasted, or whose plasma contained chylomicrons or floating beta-lipoproteins were excluded. We concluded that a better estimator for LDL-C was provided by the equation LDL-C = TC-(HDL-C + 0.16 X TG), since it produced an error (relative to the reference method) of lesser magnitude than the previous formula. The expression 0.16 X TG (0.37 X TG when measurements are reported in millimoles per liter) also produced a more accurate estimate of very low-density lipoprotein cholesterol relative to values obtained by the standard Lipid Research Clinics procedure for this component. The proposed formula is more precise for plasmas or sera with a TG concentration within the normal range.

Adolescent↗
PubMed1977

The failure of aerosolized superoxide dismutase to modify pulmonary oxygen toxicity.

Superoxide (O2-.) is a highly toxic free radical that may be an important component of pulmonary O2 toxicity. The primary defense against this free radical is superoxide dismutase. Rats were exposed to aerosolized superoxide dismutase, and it failed to modify either the time course or the cumulative toxicity of 100 per cent O2. Because the aerosolized enzyme can be expected to be delivered only to the extracellular space of the lung, it is suggested that the primary site of production and of damage due to O2-induced free radicals must be within the intracellular space.

Aerosols↗
PubMedDate not supplied

Sonographic estimates of vein size in the lower extremities: subjective assessment compared with direct measurement.

PURPOSE: We studied whether subjective impression of vein size is a valid means of assessment during sonographic evaluation for deep vein thrombosis. METHODS: Diameter was assessed at 5 predetermined venous segments on 975 legs of 721 patients referred for evaluation for lower extremity deep vein thrombosis. The sonographer recorded a subjective assessment of whether the venous segment was enlarged, normal, or narrowed based on a visual impression of sonographic images obtained without compression. This subjective impression was then compared with the absolute measurements of vein diameter and vein diameter:artery diameter ratio at each segment. RESULTS: A significant correlation was found between the subjective characterization of vein size as enlarged, normal, and narrowed and both the absolute vein diameter and the vein:artery ratio at all 5 segments. CONCLUSIONS: Vein size can be reliably categorized by the subjective impression of experienced sonographers. Therefore, actual measurement of the vein diameter is not necessary in the evaluation for deep vein thrombosis in the majority of patients.

Analysis of Variance↗
PubMedDate not supplied

Detection of deep venous thrombosis: prospective comparison of MR imaging and sonography.

Seventy-five patients (41 women and 34 men, 20-85 years old) with clinically suspected deep venous thrombosis (DVT) were examined with MR imaging and sonography. In 26 patients, the final diagnosis was acute femoropopliteal DVT. The sensitivity of MR imaging for detecting this disease was 100% with a 95% confidence interval (CI) of 87-100%; the specificity was 100% with a CI of 92-100%; and the accuracy was 96% with a CI of 89-99%. The correspond-ing sensitivity of sonography was 77% with a CI of 53-92%; the specificity was 98% with a CI of 89-100%; and the accuracy was 83% with a CI of 72-90%. In four of the 75 patients, MR images revealed thrombus of the pelvis (n = 1) or calf (n = 3) without femoropopliteal involvement. The estimated prevalence of isolated calf and/or pelvic DVT was 5% with a CI of 1-13%. MR imaging is significantly more sensitive (P = .02) and accurate (P < .01) than sonography in the detection of lower extremity DVT, but there was no difference in the specificity of MR imaging and that of sonography (P = .31).

Adult↗
PubMedDate not supplied

Optimizing fast spin echo acquisitions for hepatic imaging in normal subjects.

The purpose of this study was to determine which implementations of a T2-weighted fast spin-echo sequence of the liver resulted in observer preference in normal subjects. Five volunteers were scanned with a series of fast spin-echo sequences modified to allow for flow compensation, respiratory triggering (RT), ECG triggering, randomized phase encoding (RPE), breath-holding, and echo train length (ETL). Images were compared with conventional 2500/40/80 msec spin-echo images using flow compensation and spatial presaturation by two observers blinded to the specific sequence parameters. All FSE sequences were completed in less than the 12 minutes necessary to perform a conventional spin-echo sequence. The most preferred fast spin-echo sequence employed flow compensation, RT, and used an 8 ETL. Analysis of image preference, signal to noise, and contrast to noise showed that RT was the single most important variable in determining each image response (P < .01, P < .02, P < .01, respectively). There was some evidence that images obtained with an 8 ETL were preferred over those using a 16 ETL (P = .07). No other variables approached statistical significance although one reader preferred images with flow compensation in the frequency direction to those either not flow compensated or flow compensated in the slice direction. Respiratory triggered fast spin-echo images combined with flow compensation in the frequency direction and using ETL = 8 can provide image quality equal to conventional spin-echo sequences with significant time savings.

Electrocardiography↗
PubMedDate not supplied

Prospective comparison of helical CT and MR imaging in clinically suspected acute pulmonary embolism.

The purpose of this study is to compare sensitivity and specificity of helical CT and MR imaging for detecting acute pulmonary embolism(PE). Patients who were suspected clinically of having PE were randomly assigned to undergo either helical contrast-enhanced CT or gradient-echo MR (if one modality was contraindicated, the patient was assigned to the other.) Patients were considered to have PE if they had: 1) high-probability V-Q scan and low clinical probability of PE; 2) pulmonary angiogram positive for PE. Patients were considered not to have PE if they had either:1)normal V-Q scan; 2) low probability V-Q scan and low clinical probability of PE; or 3) pulmonary angiogram negative for PE. The CT and MR images were read randomly and independently by five radiologists with varying levels of CT and MR experience. Twenty eight patients underwent CT and 25 MR. A total of 21 patients underwent pulmonary angiography (6 had PE, 15 did not have PE). Of the other 32 patients, 15 had high probability scan/high clinical probability and 17 had low probability scan/low clinical probability. For the five observers, the average sensitivity of CT was 75% and of MR 46%; the average specificity of CT was 89% and of MR 90%. Experience with vascular MR and enhanced CT influenced diagnostic accuracy. For the two vascular MR experts, average sensitivity and specificity of MR were 71% and 97%, and of CT 73% and 97%. In this pilot study, when CT and MR were interpreted with comparable expertise, they had similar accuracy for detecting pulmonary embolism.

Adult↗
PubMedDate not supplied

Analysis of cardiac arrhythmias during dobutamine pharmacologic stress testing in nuclear cardiology as related to the presence or absence of baseline arrhythmias.

BACKGROUND: Intravenous dobutamine is an acceptable pharmacologic stress agent for evaluation of myocardial ischemia, but it has the undesirable side effect of precipitating cardiac arrhythmias. All patients are susceptible to the arrhythmogenic potential of dobutamine. However, the presence of a baseline arrhythmia creates additional concern about proceeding with a pharmacologic dobutamine stress test. The purpose of this study was to evaluate cardiac arrhythmias during dobutamine stress as they relate to the presence or absence of baseline arrhythmias in patients undergoing radionuclide myocardial perfusion imaging. METHODS AND RESULTS: Data from 486 consecutive dobutamine stress tests in nuclear cardiology were reviewed retrospectively. Baseline and stress electrocardiographic monitoring and 12-lead electrocardiograms were used for classification of arrhythmias. For patients without baseline arrhythmias, the estimated probability of having nonsustained ventricular tachycardia with dobutamine stress was 4.0% (16 of 403), as compared with 15.7% (13 of 83) for patients with baseline arrhythmias (p < 0.001). Three of the 403 patients (0.7%) and 2 of the 83 patients (2.4%) had their study terminated because of ventricular tachycardia (p > 0.05). CONCLUSIONS: The probability of having nonsustained ventricular tachycardia with dobutamine stress testing was significantly greater in patients who had baseline arrhythmias than in those who had no arrhythmias at baseline. Although termination of the study because of ventricular tachycardia was not statistically significant between these two groups, patients with baseline cardiac arrhythmias should be considered at higher risk for the development of nonsustained ventricular tachycardia during dobutamine stress testing than patients who have no baseline arrhythmia.

Adult↗