Search PubMed⌕ Search

Biomedical subjects

O Ratib

Publications and source records attributed to O Ratib.

At least 55 records · Page 3Linked to original sources
PubMed1984

[Global ventricular function and synchronism of contraction during and after exertion].

Phase analysis and ejection fraction (EF) of the left ventricle were obtained by radionuclide angiography in 53 patients at rest, during submaximal exercise and 3-8 minutes after exercise. The standard deviation of the peak of the histogram of phases (SDP) was used as an index of the synchronicity of regional contraction. The material comprised 13 sportsmen and 40 patients who underwent coronarography, 12 of whom had normal coronaries and 28 significant lesions. EF, while comparable in the three groups at rest, increased significantly on effort in normals and did not change in patients with coronary disease. At rest SDP was higher in coronary patients than in normals (p less than 0.01), and during exercise, it increased, but decreased in normals (p less than 0.01). After exercise, mean EF decreased in comparison with exercise in normals (p less than 0.01), while the opposite was the case in coronary patients. Normals had lower SDP values in the post-exercise period than at rest; on the other hand, SDP of coronary patients was significantly higher in the post-exercise period than at rest (p less than 0.001). Phase analysis during, and particularly after, exercise was found to be superior to EF in detecting ischemic left-ventricular dysfunction, and should be used in conjunction with EF to evaluate patients suspect for coronary disease.

Adult↗
PubMed1984

Limitations of quantitative phase analysis of radionuclide angiograms for detecting coronary artery disease in patients with impaired left ventricular function.

Phase analysis of radionuclide ventriculograms is used for identifying ischemic wall motion abnormalities. Myocardial segments with an abnormal phase, that is, delayed onset of wall motion, can be localized on a phase distribution image, and the synchronicity of left ventricular (LV) wall motion can be assessed from a histogram of LV phase distribution. The standard deviation of the LV peak on this histogram (SDP-LV) describes the width of the peak and is used as an index of the synchronicity of wall motion. We examined in this study the sensitivity of SDP-LV for identifying coronary artery disease (CAD) and its specificity in patients with normal and various degrees of LV impairment. A total of 84 patients were studied. Forty-five patients had CAD and 39 had congestive cardiomyopathy or valvular heart disease. Patients were grouped according to their LV ejection fraction (EF). In group I (37 patients) resting LVEF was equal to or greater than 50%, in group II (24 patients) it ranged from 35% to 50%, and in group III (23 patients) it was less than 25%. SDP-LV was highly specific in groups I and II for CAD with sensitivities of 48% and 89% at rest that increased with exercise to 88% and 100%. In group III patients, SDP-LV remained highly sensitive but was no longer specific for CAD. Therefore, in severe LV impairment, phase analysis does not aid in distinguishing CAD from other causes of ventricular dysfunction. By contrast, phase analysis is highly sensitive and specific for CAD in patients with normal or moderately depressed LV function.

Blood Pressure↗
PubMed1984

Left ventricular stroke volume determinations from radionuclide ventriculograms: the effects of photon attenuation.

To improve the accuracy of scintigraphic ventricular volume determination, which is limited by photon attenuation between the heart and the gamma camera, a method was developed for directly measuring the photon attenuation of radioactivity delivered as a bolus through a Swan-Ganz catheter into the right atrium. Comparison of the count rate recovered from this bolus with the total ex vivo measured activity determined by imaging an aliquot of the administered activity allowed calculation of the attenuation factor. Left ventricular stroke volumes determined scintigraphically by the count method in gated blood pool studies and then corrected with this attenuation factor correlated well with stroke volumes determined from thermodilution cardiac output and heart rate (r = 0.92; SEE, 6.1 ml). The agreement between the two measurements was markedly less when an average attenuation factor was employed for correction of scintigraphic volumes (r = 0.52; SEE, 14.8 ml). The results indicate that correction for photon attenuation is needed for accurate measurement of left ventricular volumes. Correction of left ventricular counts based on body weight or body surface area improves the accuracy of volume estimates.

Adult↗
PubMed1983

[Evaluation of a method for ambulatory and automatic measurement of nyctohemeral arterial pressure].

This study was designed to evaluate a method of automatic non-invasive ambulatory blood pressure monitoring. Using a Del Mar Avionics Pressurometer II, we tested 12 normal subjects at rest and during exercise in our laboratory, and 12 patients with borderline hypertension during 24 hours of normal activity. At rest correlation coefficient of sequential measurements between pressurometer and a standard mercury sphygmomanometer were 0.96 for individual systolic measurements, 0.65 for individual diastolic measurements, and 0.99 for sequentially coupled diastolic or systolic measurements. The same correlation coefficients were found during a low level exercise test on cycloergometer (50 watts); at a higher level (75 watts), the correlation coefficient for systolic measurements is still high (0.93), whereas for diastolic measurements the correlation coefficient is low (0.45) in our experimental conditions. Fifty-eight non-invasive ambulatory recordings were obtained during normal daily activities. About 10% of the measurements were eliminated because of artefacts. We conclude that the nycthemeral fluctuations of the blood pressure can be reasonably estimated by the Del Mar Avionics Pressurometer II, but that such results can be obtained only if special attention is given to the positioning of the pressurometer on a motivated patient.

Adult↗
PubMed1983

Measurements of regional tissue and blood-pool radiotracer concentrations from serial tomographic images of the heart.

Quantification of myocardial tissue kinetics from serial tomographic images is limited because of bidirectional cross-contamination of recorded counts between myocardium and blood for metabolic tracers with relative slow blood clearance. We have developed and validated a new deconvolution technique that permits calculation of spillover fractions derived from geometric measurements of the imaged cross section (wall thickness, chamber diameter) and the intrinsic resolution of the tomograph. Serial gated positron-emission computerized imaging (PCT) and a-v blood sampling across the heart were performed in five dogs for 45 min after i.v. C-11 palmitate (CPA) and in five dogs for 3 hr after i.v. F-18 deoxyglucose (FDG). Tracer concentrations in myocardial tissue and arterial blood were also measured in vitro. Uncorrected PCT tissue and blood concentrations correlated poorly with in vitro measurements. After correction for count crossover, the correlation for FDG in tissue was r = 0.99, for FDG in blood r = 0.97, and for CPA in blood r = 0.99. Deconvolution techniques applied to serial PCT images provide accurate noninvasive measurement of myocardial tracer concentrations and direct determination of the arterial input function required for measurements of myocardial metabolism.

Animals↗
PubMed1982

Assessment of regurgitant fraction and right and left ventricular function at rest and during exercise: a new technique for determination of right ventricular stroke counts from gated equilibrium blood pool studies.

Calculation of accurate stroke count ratios for the assessment of valvular regurgitation from equilibrium blood pool images has been difficult and did not permit computation of regurgitant fractions (RF) because of contamination of right ventricular (RV) stroke counts by right atrial activity. We describe a new approach to correct for this contamination by subtracting one half of the right atrial counts from the RV counts, assuming that in the standard or "modified" left anterior oblique projection commonly used about one half of the right atrial activity is superimposed to the RV. This new method was tested in 20 patients without valvular disease or shunts. Left ventricular (LV) to RV stroke count ratio approached unity (1.01 +/- 0.14). RV ejection fractions (EF) derived by this technique agreed well with those obtained by gated first-pass studies recorded in the right anterior oblique projection. In 9 normals and 17 patients with moderate severe or severe aortic (12 patients or mitral (7 patients) regurgitation, LVEF, RVEF, and RF were determined at rest and maximum exercise. In patients at rest, LVEF (56.0 +/- 6.4%) and RVEF (49.0 +/- 7.3%) did not differ significantly from LVEF (59.6 +/- 4.2%) and RVEF (52.5 +/- 6.4%) in normals. The calculated RF was negligible in normals (1.9 +/- 8.6%), but averaged 51.8 +/- 9.8% in patients with valvular disease. During exercise, LVEF fell significantly (p less than 0.001) to 44.1 +/- 7.2% in patients but increased to 70.5 +/- 3.8% in normals. RVEF increased in aortic regurgitation to 64.5 +/- 9.8% (NS to normals) but fell in mitral regurgitation to 36.6 +/- 5.9% (p greater than 0.001). In both patient subsets RF decreased with exercise to 25.4 +/- 15.0% in aortic and 39.1 +/- 12.7% in mitral regurgitation. The results indicate that this new approach permits assessment of RVEF and RF from gated equilibrium blood pool studies and is suitable to evaluate the hemodynamic response to physiologic and therapeutic interventions in patients with valvular regurgitation.

Adult↗
PubMed1982

Phase analysis of radionuclide ventriculograms for the detection of coronary artery disease.

The value of phase analysis of multiple gated acquisition blood pool images for identifying wall motion abnormalities due to stress-induced ischemia was examined. Myocardial segments with an abnormal phase, i.e., delayed onset of wall motion, were localized on a phase distribution image of the LV and the synchrony of LV systolic wall motion was assessed from histograms of the LV phase distribution, i.e., the standard deviation (SD) from the mean of this peak, which was defined as SDP, its upper limits of normal at rest and exercise were established in seven normals as the mean +2 SD and were 12 degrees at rest and 10 degrees at maximum exercise. Of the 56 patients, 37 had coronary artery disease (CAD), 11 had valvular disease but normal coronary arteries, and eight had normal coronary arteries, no valvular disease, but had either cardiomyopathy or typical angina. In the CAD patients, SDP was abnormal in 95% during exercise while only 86% had an abnormal ejection fraction (EF) response and/Or exercise-induced wall motion abnormalities by visual interpretation. By contrast, in the 11 valvular heart disease patients, SDP was abnormal in only two despite exercise-induced wall motion abnormalities in five and an abnormal EF response in all 11. Thus, although an abnormal EF response to exercise is a sensitive indicator of cardiac disease, it is, however, like exercise-induced wall motion abnormalities, not specific for CAD. By contrast, phase analysis not only permitted separation of wall motion abnormalities induced by ischemia from those associated with valvular disease, but was also an objective, highly sensitive, and specific indicator of regional myocardial ischemia.

Adolescent↗
PubMed1982

Performance of the rotating slant-hole collimator for the detection of myocardial perfusion abnormalities.

To determine the usefulness of the rotating slant-hole (RSH) collimator, a new imaging device for tomographic myocardial imaging, we evaluated its performance in phantom studies. Perfusion defects of variable size, location, and tracer concentration were simulated and imaging was performed with a conventional parallel-hole collimator and the RSH collimator. Planar and depth resolutions assessed with a line source compared favorably with those reported previously for the seven-pinhole collimator. The results also showed RSH tomography to be more sensitive than planar imaging in detecting simulated myocardial defects but indicated some limitations, especially the occurrence of artifactual defects that may reduce the specificity of the imaging device for the detection of perfusion abnormalities.

Coronary Disease↗
PubMed1982

Positron tomography with deoxyglucose for estimating local myocardial glucose metabolism.

The deoxyglucose method originally developed for measurements of the local cerebral metabolic rate for glucose has been investigated in terms of its application to cardiac studies with positron computed tomography (PCT) and fluorodeoxyglucose (FDG). Studies were performed in dogs to measure the tissue kinetics of FDG with PCT and by arterial and venous sampling. The operational equation developed in our laboratory as an extension of the Sokoloff model was used to analyze the data. Error propagation, primarily from corrections applied to remove spillover of activity from the myocardial blood pool to tissue and from partial-volume effects in the PCT images, limited accuracy in the estimation of the individual rate constants for transport, phosphorylation, and dephosphorylation. However, a constant representing the combination of transport and phosphorylation was accurately determined and yielded measured values of the myocardial metabolic rate for glucose (MMRGlc) that were in good agreement with direct determinations using the Fick method over a wide range of glucose metabolic rates (from 1.7 to 21.1 mg/min-100 g). The lumped constant (0.67 +/- 0.10) was also found accurate and stable over this range of metabolism. The FDG method accurately predicted the true MMRGlc even when the glucose metabolic rate was normal but myocardial blood flow (MBF) was five times the control value, or when metabolism was reduced to 10% of normal and MBF increased to five times normal. Improvements of PCT resolution are required to improve the accuracy of the estimates of the rate constant and the MMRGlc.

Animals↗
PubMedDate not supplied

Update on digital image management and PACS.

Information technology is becoming a vital component of all health care enterprises, from managed care services to large hospital networks, that provides the basis of electronic patient records and hospital-wide information. The rationale behind such systems is deceptively simple: physicians want to sit down at a single workstation and call up all information, both clinical data and medical images, concerning a given patient. Picture archiving and communication systems (PACS) are responsible for solving the problem of acquiring, transmitting, and displaying radiologic images. The major benefit of PACS resides in its ability to communicate images and reports to referring physicians in a timely and reliable fashion. With the changes in economics and the shift toward managed and capitated care, the teleradiology component of PACS is rapidly gaining momentum. In allowing remote coverage of multiple sites by the same radiologists and remote consultations and expert opinion, teleradiology is in many instances the only option to maintain economically viable radiologic settings. The technical evolution toward more integrated systems and the shift toward Web-based technology is rapidly merging the two concepts of PACS and teleradiology in global image management and communication systems.

Costs and Cost Analysis↗
PubMedDate not supplied

PACS workstation design.

This paper covers some of the recent concepts in designing a digital imaging workstation in a multimodality Picture Archiving and Communications Systems (PACS) network. A workstation in a multimodality PACS network must access, display, and analyze digital images from different imaging modalities with very different formats. The user interface should allow clinicians with minimal or no computer manipulation skills to use complex analysis tools. General guidelines of a graphics oriented user interface, based on windows and icons, are proposed. Instantaneous (real-time) response in the primary display and processing functions is vital for user acceptance. The hardware architectural concepts to achieve such a performance speed are described. Finally, a workstation environment conducive to comfortable viewing by the radiologists is discussed.

Computer Graphics↗
PubMedDate not supplied

From multimodality digital imaging to multimedia patient record.

The constant improvement in computer power and performance nowadays offers convenient and efficient means of manipulating images, graphics, and movies on off-the-shelf workstations. With this improvement the trend toward integration of multimodality clinical documents from patient records comes naturally. Images and graphs are certainly the most important part of the complementary information that must accompany the text and numerical data. It is, however, possible to include sounds and voice messages together with all the other modalities. In medicine that could certainly help conveying hart murmur or sounds, but could also offer a convenient way of including vocal messages and comments. These new possibilities will certainly change the way physicians use workstations for direct communication. The computer industry will soon offer means of interactive communication between remote users through computer workstations. That alone will open a completely new era in cooperative computing and remote consultation scenarios in medicine. More than the technology itself, a complete change in behavior and work habits can be expected in the medical community.

Computer Communication Networks↗
PubMedDate not supplied

Digital image management and communication in medicine.

With the rapid development of digital imaging modalities in medicine, there is an increasing need for an efficient management and archival of medical images in digital form. Picture Archiving and Communication Systems (PACS) are becoming an essential component of medical imaging equipment, allowing for medical images to be accessed and stored directly in digital form. This paper describes a hospital-wide PACS currently under development at the University Hospital of Geneva, based on an open architecture, regrouping equipment from different vendors in a distributed topology. The image archival is organized in multiple locations geographically distributed in the hospital. The PACS database is fully integrated with the concurrent Radiology Information System (RIS) and Hospital Information System (HIS). A standard image storage format called the PAPYRUS format was developed for the storage of medical images from a variety of imaging modalities. To provide a more uniform user interface on a variety of different workstations, a common platform for image display and manipulation called OSIRIS was developed.

Computer Communication Networks↗
PubMedDate not supplied

Image analysis and computer vision in medicine.

Multimedia lives with images; medical images are born from digital imaging. A physician's multimedia workstation cannot exist without tools for manipulating images, performing measurements and, generally speaking, extracting and collecting pieces of information from the available data. Image analysis and computer vision constitute a wide and rapidly evolving field. This paper is intended as an introductory document for medical imaging researchers and practitioners wishing an overview of recent developments and trends. The major lines of activities in the domain are presented, under the common framework of a processing pipeline. After a presentation of the various stages of this pipeline, current subjects of research are indicated.

Computer Graphics↗
PubMedDate not supplied

Object-oriented design of medical imaging software.

A special software package for interactive display and manipulation of medical images was developed at the University Hospital of Geneva, as part of a hospital wide Picture Archiving and Communication System (PACS). This software package, called Osiris, was especially designed to be easily usable and adaptable to the needs of noncomputer-oriented physicians. The Osiris software has been developed to allow the visualization of medical images obtained from any imaging modality. It provides generic manipulation tools, processing tools, and analysis tools more specific to clinical applications. This software, based on an object-oriented paradigm, is portable and extensible. Osiris is available on two different operating systems: the Unix X-11/OSF-Motif based workstations, and the Macintosh family.

Computer Communication Networks↗
PubMedDate not supplied

Multimedia image and data navigation workstation.

World Wide Web (WWW) standards have been established for the transmission of and remote consultation on medical information and records, including medical images, extracted from an existing hospital information system. A software package called Osiris is being used for the display and manipulation of medical images in a hospital-based picture archiving and communication system. Recent extensions of Osiris, through the integration of WWW navigational tools, allow easy access to a variety of clinical data from patient records. A special interface allows access to radiologic images, laboratory results, and related textual information through public-domain software programs. These technologic advances offer medical professionals the convenience and ease of use that have made WWW and Internet navigation so popular in the academic community.

Computer Communication Networks↗