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O Ratib

Publications and source records attributed to O Ratib.

At least 37 records · Page 2Linked to original sources
PubMed1992

Current views on the functionalities of PACS.

The concept of PACS has evolved from a central storage of medical images to a distributed data and image management system. The trend and evolution of the definition and design of PACS systems is described in this paper. Special emphasis on the concept of distributed and open architecture is given with a discussion of the advantages and disadvantages of each approach. A hospital-wide PACS system designed based on a distributed architecture integrated with a Hospital Information System (HIS) at the University Hospital of Geneva is further described.

Computer Systems↗
PubMed1992

Semiquantitative assessment of myocardial blood flow and viability using polar map displays of cardiac PET images.

Preserved glucose metabolism in ischemically injured, dysfunctional myocardial tissue as demonstrated on PET imaging predicts functional improvement after revascularization. To characterize more precisely the relationship between regional myocardial blood flow, viability and extent and severity of flow and metabolism abnormalities, we developed a PC-based semiquantitative analysis technique using 13N-ammonia and 18F-deoxyglucose polar map displays. A data base for mean values (m) and standard deviations (s.d.) for relative 13N activities reflecting regional myocardial blood flow, relative 18F activities normalized to normal flow regions reflecting regional glucose utilization and the difference of normalized 18F and 13N activities as an index of a flow-metabolism mismatch was established in 11 normals. Parametric polar maps were derived by comparing patient data to a normal range defined as greater than m - 2 s.d. for relative myocardial blood flow and less than m + 2 s.d. for both relative glucose utilization and the difference between normalized 18F and 13N activities. Semiquantitative indices of extent and severity of blood flow defects, of relative increases in glucose utilization and of flow-metabolism mismatch areas are generated for the entire myocardium and the three coronary territories. The approach promises to be clinically useful to confirm presence and absence of flow and metabolic abnormalities and to assess their extent as a potential predictor of functional outcome after therapy.

Adult↗
PubMed1991

Noninvasive detection of functionally significant coronary artery stenoses with exercise and positron emission tomography.

Positron emission tomography has been employed in vivo to assess flow using N-13 (nitrogen-13) ammonia and glucose metabolism, with the glucose analog F-18 (fluorine-18) fluorodeoxyglucose. Flow metabolism mismatches in which glucose metabolism is increased with respect to flow have been used to define ischemic, but viable myocardium. The feasibility of detecting exercise-induced ischemia using this technique was explored. Eleven normal volunteers and 16 patients who had undergone coronary arteriography were studied with N-13 ammonia at rest and with bicycle exercise, and with F-18 fluorodeoxyglucose in the postexercise period. Each image was divided into 16 sectors. Comparison of absolute net extractions of N-13 ammonia at rest and with exercise was not sensitive in detecting functionally significant coronary artery lesions. Myocardial uptakes of F-18 fluorodeoxyglucose and exercise N-13 ammonia were normalized to the sector with the highest N-13 ammonia uptake (corresponding to the highest flow rate). The differences and ratios of these normalized uptakes were successfully used to objectively define flow metabolism mismatches and to identify functionally significant coronary artery disease. Our data suggest that exercise flow and metabolic imaging are superior to rest and exercise flow imaging, particularly in patients with prior myocardial infarctions.

Ammonia↗
PubMed1991

A quantitative index of regional blood flow in canine myocardium derived noninvasively with N-13 ammonia and dynamic positron emission tomography.

To derive a quantitative index of regional myocardial blood flow, the arterial input function of the flow tracer N-13 ammonia and the regional myocardial N-13 activity concentrations were noninvasively determined in 29 experiments in eight dogs. N-13 ammonia was administered intravenously and cross-sectional images were acquired dynamically using an ECAT III positron emission tomograph with an effective in-plane resolution of 13.46 mm full-width half-maximum. Time-activity curves were derived from the serial images by assigning regions of interest to the left ventricular myocardium and left ventricular blood pool. Tracer net extractions were estimated from the myocardial time-activity concentrations at various times after tracer injection and the integral of the arterial input function. Myocardial blood flow was altered by intravenous dipyridamole, morphine, propranolol and partial or complete occlusion of the left anterior descending coronary artery, and ranged from 9 to 860 ml/min per 100 g. Estimates of tracer net extractions were most accurate when determined from the myocardial N-13 activity concentrations at 60 s divided by the integral of the arterial input function to that time. These estimates correlated with regional myocardial blood flows determined independently by the microsphere technique by y = x (1 - 0.64(e-114/x); SEE = 22.9; r = 0.94). First pass extraction fractions of N-13 ammonia determined noninvasively with this approach declined with higher flows in a nonlinear fashion and were similar to those determined invasively by direct intracoronary N-13 ammonia injections. The findings indicate that an accurate index of regional myocardial blood flow can be obtained noninvasively by high temporal sampling of arterial and myocardial tracer activity concentrations with positron emission tomography. They also provide a basis for the in vivo application of tracer kinetic principles to derive quantitatively and noninvasively regional rates of functional processes in human myocardium.

Ammonia↗
PubMed1991

Metabolic and functional recovery of ischemic human myocardium after coronary angioplasty.

Although revascularization of hypoperfused but metabolically active human myocardium improves segmental function, the temporal relations among restoration of blood flow, normalization of tissue metabolism and recovery of segmental function have not been determined. To examine the effects of coronary angioplasty on 13 asynergic vascular territories in 12 patients, positron emission tomography and two-dimensional echocardiography were performed before and within 72 h of revascularization. Ten patients underwent late echocardiography (67 +/- 19 days) and eight underwent a late positron emission tomographic study (68 +/- 19 days). The extent and severity of abnormalities of wall motion, perfusion and glucose metabolism were expressed as wall motion scores, perfusion defect scores and perfusion-metabolism mismatch scores. Angioplasty significantly increased mean stenosis cross-sectional area (from 0.95 +/- 0.9 to 2.7 +/- 1.4 mm2) and mean cross-sectional luminal diameter (from 0.9 +/- 0.6 to 1.9 +/- 0.5 mm) (both p less than 0.001). Perfusion defect scores in dependent vascular territories improved early after angioplasty (from 116 +/- 166 to 31 +/- 51, p less than 0.002) with no further improvement on the late follow-up study. The mean perfusion-metabolism mismatch score decreased from 159 +/- 175 to 65 +/- 117 early after angioplasty (p less than 0.01) and to 26 +/- 29 at late follow-up (p less than 0.001 vs. before angioplasty; p = NS vs. early after angioplasty). However, absolute rates of glucose utilization remained elevated early after revascularization, normalizing only at late follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1991

NMINT--introductory courseware for nuclear medicine: database design.

Computer-Aided Instruction (CAI) provides a dynamic and self-paced learning experience to the medical trainee. Microcomputer based hypermedia systems integrate text, graphics, and image information. We present the design of an introductory CAI course for nuclear medicine called NMINT and elaborate on the underlying relational database that contains clinically relevant information and links to local or remote image storage over high speed networks. The IBM PS/2 Windows system uses Toolbook software augmented by C language modules for image and image-overlay database access. The current implementation stores text, graphical lesson material, and image index information on microcomputer magnetic disk; image data are stored on the attached optical disk. The storage architecture is described in detail. We emphasize its multi-access methods and its expandability into department-wide image networks.

Computer Graphics↗
PubMed1989

Radionuclide evaluation of right ventricular wall motion after surgery in tetralogy of Fallot.

Regional wall motion patterns in tetralogy of Fallot and its postoperative modifications by electrical and hemodynamic factors were assessed by Fourier analysis of gated radionuclide angiograms in 24 studies performed in children after surgical correction of tetralogy of Fallot. The range of right ventricular (RV) phase angles (standard deviation of the peak [SDP] of RV) as well as the difference between RV and LV (delta MPh) were used as indices of the synchronicity of wall motion and were correlated with RV apical electrical activation time determined by endocardial electrical mapping. Postoperative studies were divided into two groups according to apical activation: (a) those involving right bundle branch block (RBBB) (nine patients), and (b) those involving distal RBBB (15 patients). delta MPh was longer in proximal than in distal RBBB. Best discrimination between the two groups was obtained with SDP of RV (proximal = 24 degrees +/- 3 degrees, and distal = 17 degrees +/- 2 degrees; p less than 0.0001). These results showed that the range of ventricular phases measured by the SD of the phase distribution of the right ventricle is a good index for distinguishing between proximal and distal RBBB after cardiac surgery.

Adolescent↗
PubMed1989

Noninvasive quantitation of regional myocardial oxygen consumption in vivo with [1-11C]acetate and dynamic positron emission tomography.

The usefulness of [1-11C]acetate as a tracer of overall myocardial oxidative metabolism for use with positron emission tomography has been investigated in 12 closed-chest dogs. Myocardial 11C activity clearance kinetics after intravenous administration of [1-11C]acetate in dogs have been determined noninvasively by positron emission tomography. Biexponential fitting of regional myocardial 11C time-activity curves was performed to give clearance half-times and fractional distribution. The rate constant k1 for the early rapid phase of 11C activity clearance was found to correlate linearly with myocardial oxygen consumption (y = 0.0156x + 0.039; SEE = 0.023; r = 0.95). k1 was approximately 7% lower in septal sectors compared with the left ventricular free wall, suggesting that regional oxygen consumption in the septum was lower; a concomitant regional attenuation of blood flow in the septum relative to the left ventricular free wall was also observed. In dogs using carbohydrates as the predominant fuel, k1 oxygen consumption was somewhat more than in dogs using predominantly free fatty acids (0.021 +/- 0.002 compared with 0.018 +/- 0.002, p less than 0.01), indicating that increased carbohydrate consumption is associated with a small increase in k1 at constant oxygen consumption. It is concluded that measurement of myocardial [1-11C]acetate kinetics allows noninvasive determination of cardiac oxygen consumption by positron emission tomography and that the technique is relatively insensitive to myocardial fuel selection.

Acetates↗
PubMed1989

13N ammonia myocardial imaging at rest and with exercise in normal volunteers. Quantification of absolute myocardial perfusion with dynamic positron emission tomography.

Positron emission tomography (PET) was applied to the measurement of myocardial perfusion using the perfusion tracer 13N-labeled ammonia. 13N ammonia was delivered intravenously to 13 healthy volunteers both at rest and during supine bicycle exercise. Dynamic PET imaging was obtained in three cross-sectional planes for 10 minutes commencing with each injection. The left ventricle was divided into eight sectors, and a small region of interest was assigned to the left ventricular blood pool to obtain the arterial input function. The net extraction of 13N ammonia was obtained for each sector by dividing the tissue 13N concentration at 10 minutes by the integral of the input function from the time of injection to 10 minutes. With this approach for calculating net extractions, rest and exercise net extractions were not significantly different from each other. To obviate possible overestimation of the true 13N ammonia input function by contamination by 13N-labeled compounds other than 13N ammonia or by spillover from myocardium into blood pool, the net extractions were calculated using only the first 90 seconds of the blood and tissue time-activity curves. This approach for calculating net extractions yielded significant differences between rest and exercise, with an average ratio of exercise to rest of 1.38 +/- 0.34. Nonetheless, the increase was less than predicted from the average 2.7-2.8-fold increase in double product at peak exercise or the 1.7-fold increase in double product at 1 minute after exercise. However, when the first 90 seconds of dynamic data were fit with a two compartment tracer kinetic model, average perfusion rates of 0.75 +/- 0.43 ml/min/g at rest and 1.50 +/- 0.74 ml/min/g with exercise were obtained. This average increase in perfusion of 2.2-fold corresponded to similar average increases in double product. Thus, the noninvasive technique of PET imaging with 13N ammonia shows promise for future applications in determining absolute flows in patients with coronary artery disease.

Adult↗
PubMed1987

[Long-term prognosis of patients with silent ischemia].

To study the long-term evolution in patients with silent ischemia we investigated 242 coronary patients showing ischemic signs on exercise T1-201 scintigraphy. The findings in a group of 106 patients with angina were compared with those in a group of 136 patients without angina during exercise and followed up for an average of 60 months. Multiple comparisons of clinical features, ECG, hemodynamic and angiographic data showed no significant differences between the two groups. However, the extent of ischemia detected by T1-201 was significantly smaller in patients with silent ischemia although their work-load and double product were higher.--During the follow-up cardiac mortality (11% vs 11%), unstable angina (27% vs 20%) and myocardial infarction (23% vs 20%) were found with the same frequency in patients with angina compared with those with silent ischemia. Bypass surgery was performed more frequently (55% vs 37%) in patients with symptomatic ischemia. Long-term evolution in our coronary patients with episodes of silent ischemia was similar to that in patients with ischemia accompanied by angina, and showed numerous complications. Therefore, we should try to treat not only angina but also, and especially, ischemia.

Angina Pectoris↗
PubMed1987

[Two-dimensional exercise echocardiography. Comparison with electrocardiography, myocardial scintigraphy with thallium 201 and coronary angiography].

Biapical two-dimensional echocardiograms were obtained immediately before and after a bicycle exercise test in 54 patients referred for coronary angiography. Images of adequate quality were recorded in 47 cases (87%), 39 of whom had significant coronary artery disease. All patients also underwent a stress electrocardiogram. In 22 subjects echocardiography and bicycle stress test in the supine position were combined. 23 patients underwent scintigraphy with thallium-201. The sensitivity of rest and exercise echocardiography for the diagnosis of coronary artery disease was 90% and the specificity 63%, compared to 82% and 75% respectively for the electrocardiogram. The sensitivity for the detection of jeopardized myocardium, defined by angiographic criteria, was 75% for the exercise echocardiogram and 65% for the exercise electrocardiogram in the 28 patients without myocardial infarction. In 19 patients with infarction echocardiography detected jeopardized myocardium with a sensitivity of 73%, compared to 53% for the electrocardiogram. In the subgroup of 23 patients studied by thallium-201 scintigraphy, sensitivity for identification of multivessel disease (8 patients) was comparable for both rest and exercise scintigraphy (6/8) and echocardiography (7/8). The specificities were 88% and 94% respectively. Jeopardized myocardium was detected in this subgroup with a sensitivity of 82% by echocardiography, 76% by thallium scintigraphy and 65% by electrocardiography. In conclusion, this study demonstrates that two-dimensional echocardiography can be combined with exercise electrocardiography in one stress test. This improves the diagnosis of coronary artery disease, detection of jeopardized myocardium and identification of patients with multivessel disease.

Adult↗
PubMed1987

Left ventricular function at 24 hours, 14 days and 6 months after acute myocardial infarction.

To determine the natural history of left ventricular function at rest and during exercise and to assess the impact of this variable on subsequent mortality, 165 patients were studied with radionuclide angiography within 24 hours of acute myocardial infarction. The ejection fraction of the 19 patients who died during the 6 month follow-up was lower than that of the 146 survivals: 41 +/- 16% vs 50 +/- 13% (P less than 0.001). Before hospital discharge (14 +/- 4 days), 83 patients had a rest and submaximal exercise radionuclide study. The ejection fraction of the 42 patients with anterior infarction was 44 +/- 12% and remained unchanged during exercise, while the 41 patients with posterior infarction had a resting value of 54 +/- 9% which increased to 57 +/- 10% (P less than 0.001) during exercise. The ejection fraction during exercise increased slightly but significantly in 37/61 patients with single vessel disease, while it did not change in the 24/61 patients with multivessel disease. At a mean of 4 +/- 1 months following infarction, 58 patients underwent a symptom-limited exercise radionuclide study. Mean value of resting ejection fraction for the group or anterior-posterior infarction subgroups did not change from initial or predischarge values. The 27 patients with anterior infarction showed no change in ejection fraction during exercise, while the 31 patients with posterior infarction increased their ejection fraction from 53 +/- 11% to 57 +/- 12% (P less than 0.001). Thus, ejection fraction measured by radionuclide angiography 24 hours following acute myocardial infarction provides useful prognostic information.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Effects of bopindolol on left ventricular function during exercise in patients with coronary artery disease.

Bopindolol is a new beta blocker with a long duration of action. We examined the haemodynamic effects of multiple oral doses of 2 mg in 12 male patients, with coronary artery disease. Placebo was given for 7 days followed by bopindolol 2 mg daily for 14 days. Scintigraphic ventriculography combined with an exercise test was carried out at baseline before treatment with bopindolol, and repeated after 7 and 14 days treatment. On day 7 the measurements were made 2 h after therapy (i.e., when plasma levels were maximal) and on day 14 when plasma levels were lowest (24 h after the last dose). The results showed that bopindolol had little effect on blood pressure or heart rate at rest in these normotensive patients but that both parameters measured after exercise were statistically significantly reduced (p less than 0.001). There was little difference between the effect seen 2 h after therapy and the effect seen 24 h after therapy, thus, demonstrating the long duration of action. The mean ejection fraction was not changed by bopindolol either at rest or after exercise but individual patients who responded to exercise with a fall in ejection fraction before treatment did not do so following treatment. These were mainly patients with 2 and 3 artery disease and the failure of the mean ejection fraction to show this protective effect was probably due to the predominance in our patients of those with mild single vessel disease who did not react adversely to exercise. We conclude that bopindolol protects the myocardium against ischaemia and that the effect lasts for at least 24 h when therapy is given once daily.

Adrenergic beta-Antagonists↗
PubMed1985

[Multivessel percutaneous coronary angioplasty].

Between August 1983 and October 1984, 44 patients (39 male and 5 female, mean age 53 years) underwent multivessel percutaneous transluminal coronary angioplasty involving 2 vessels in 37 (84%), 3 vessels in 4 (9%), 4 vessels in 1 (2%) and coronary artery bypass graft plus 1 or 2 vessels in 2 (5%). A mean of 2.2 vessels per patient were attempted. Dilatations of multiple stenoses in the same vessel were not included. Primary success was achieved in 87 of 97 vessels (90%) and in 37 of 44 (84%) patients. Primary success per patient was defined as primary success in all or at least in the strategic lesions associated with clinical improvement of the patient. Complications included one death (2%), emergency coronary artery bypass surgery in one (2%) and myocardial infarction in 2 (4%) patients. Five other patients underwent elective coronary artery bypass surgery. Recurrence of lesion was 14% (5/37 patients) during a follow-up period of 3 to 12 months. Repeat angioplasty was successful in 4 patients (80%) and unsuccessful in 1 patient who underwent elective surgery. It is concluded that, in selected cases, multivessel percutaneous transluminal coronary angioplasty is a feasible alternative to coronary artery bypass surgery, with comparable risks. A satisfactory long-term amelioration without coronary artery surgery can be obtained in 2/3 of patients.

Adult↗
PubMed1985

Recent developments of cardiac digital radiography.

Digitization in cardiovascular radiology is on the verge of its realization. Since its introduction digital subtraction angiography (DSA) is gradually replacing conventional angiography in several areas of the body. The initial tendency to avoid the arterial catheterization by intravenous injection is somewhat reversed in favor of smaller intraarterial amounts of contrast medium injected through smaller catheters at reduced rates. However, left ventriculography by intravenous route has gained widespread acceptance at rest and with exercise: motion artifacts are less crucial for ventriculography than for small arteries, in which the same motion artifacts cause a more important relative deterioration of the image, so that it has to be corrected by pixel shift. DSA is only the first step towards functional imaging, where time and other parameters are condensed in one single color coded picture. Biharmonic Fourier analysis for quantitative analysis of regional left ventricular contraction and relaxation and digital coronary radiography for evaluation of contrast progression in the coronary circulation are two areas of cardiology where parametric imaging can help to detect functional abnormalities, especially in coronary heart disease.

Arteries↗