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R Lebtahi

Publications and source records attributed to R Lebtahi.

33 records · Page 2Linked to original sources
PubMed1997

False-positive somatostatin receptor scintigraphy due to an accessory spleen.

A patient with previous left caudal pancreatectomy and splenectomy presented with Zollinger-Ellison syndrome. Abdominal CT and endoscopic ultrasonography revealed a mass in the splenic area. Somatostatin receptor scintigraphy showed a nodular increase of the uptake corresponding to the lesion detected with conventional imaging. A second laparotomy was performed and the mass was resected. Histological analysis showed that the nodular lesion was an accessory spleen. Since physiologic uptake of 111In-pentetreotide is seen in the spleen, an accessory spleen mimicking a tumor, specially after previous splenectomy, may result in false-positive somatostatin receptor scintigraphy.

False Positive Reactions↗
PubMed1996

[Detection of endocrine tumors of the digestive tract. Value and limitations of scintigraphy of somatostatin receptors].

Most neuroendocrin tumors (excepting insulinomas) carry a high density of somatostatin receptors which readily bind somatostatin analogs, allowing tumor and metastasis imaging with indium-labeled somatostasin analogs. For primary tumors (gastrinomas, carcinoid tumors), detection sensitivity is about 80%. The scintiscan adds complementary information to other imaging techniques including echoendoscopy. By combining indium-scan with echoendoscopy we have been able to detect 90% of the tumors in the upper duodenopancreatic area. In addition, scintigraphy detects tumors in about half of the patients with characteristic laboratory tests but negative imaging with other techniques. Metastases can also be detected; sensibility for liver is > 90%. The indium-scan is also positive in up to 20-30% of the patients after other imaging methods failed to identify metastasis. Finally, tumors found to be receptor-positive would respond better to treatment with somatostatin analogs.

Digestive System Neoplasms↗
PubMed1996

Preoperative detection of duodenal gastrinomas and peripancreatic lymph nodes by somatostatin receptor scintigraphy. Groupe D'etude Du Syndrome De Zollinger-Ellison.

BACKGROUND & AIMS: Duodenal gastrinomas and peripancreatic lymph nodes are difficult to localize. The aim of this study was to evaluate the ability of Octreoscan scintigraphy to detect such tumors. METHODS: Results of Octreoscan scintigraphy in 21 consecutive patients with Zollinger-Ellison syndrome were compared with those of conventional imaging techniques, including endoscopic ultrasonography, and with the surgical findings. RESULTS: Surgical exploration found 27 duodenal and/or lymph node gastrinomas in 19 patients. None had pancreatic gastrinoma. Octreoscan scintigraphy was the only positive preoperative technique in 32% of the patients. The sensitivities of conventional techniques, Octreoscan scintigraphy, and their association were 58%, 58%, and 90%, respectively, for all resected gastrinomas. The smallest duodenal gastrinoma detected by Octreoscan scintigraphy measured 3 mm. Endoscopic ultrasonography detected all the tumors visualized by any other conventional technique and was considered falsely positive, as was Octreoscan scintigraphy, in 1 patient. Follow-up and comparison between the number of resected gastrinomas and the number of preoperative hot spots suggested that surgeons should find at least as many tumors as the number of hot spots. CONCLUSIONS: Octreoscan scintigraphy improved the preoperative detection of extrapancreatic gastrinomas, mainly by endoscopic ultrasonography. Surgeons should find at least as many gastrinomas as the number of hot spots.

Adult↗
PubMed1996

Determination of left ventricular cardiac volume by simultaneous radionuclide angiography and measurement of oxygen consumption at rest and during maximal exercise: a comparison of two non-invasive isotopic procedures.

The investigation of left ventricular contractile reserve usually requires the determination of left ventricular volume, but its measurement with radionuclide angiography is difficult. The aim of this study was to determine left ventricular volume directly during exercise by the simultaneous measurement of peak exercise left ventricular ejection fraction (LVEF) and oxygen consumption (VO2max) and to compare the results with another geometric method. In the absence of lung disease, the systemic arteriovenous oxygen difference (DAVmax) during maximal exercise converges to 0.13-0.14 ml O2 per ml blood. The measurement of VO2max allows maximal cardiac output (COmax) to be calculated as VO2max = COmax. DAVmax. By simultaneously determining LVEFex, exercise end-diastolic volume (EDVex) can then be expressed as a linear function of VO2max, maximal heart rate (HRmax), DAVmax and LVEFex. Then, the relationship between end-diastolic counts and true volume can be derived at rest. The two methods were closely correlated (r = 0.91, P < 0.001), despite the geometric method being less accurate when applied to low counting statistic acquisitions. We conclude that rest and exercise left ventricular volume can be determined non-invasively by the simultaneous measurement of VO2max and LVEFex. Furthermore, this method provides additional prognostic information which is clinically relevant in the staging of patients with heart failure.

Adult↗
PubMed1996

Clinical comparison of three labeled-antibody immunoassays of free triiodothyronine.

Three labeled-antibody immunoassays of free triiodothyronine (FT3) were studied in hyperthyroid patients, patients with nonthyroidal illness, and patients being treated with amiodarone; we also studied sera presenting known interferences (n for all groups = 465). The results were compared with those of a one-step labeled-analog assay. The precision of the two automated assays were similar to that of the manual assays. The three labeled-antibody FT3 assays demonstrated a satisfactory diagnostic performance for confirming hyperthyroidism and robustness to interference; nevertheless, two assays displayed unusual behavior in some patients with nonthyroidal illness, with chronic renal failure, or after amiodarone therapy.

Adolescent↗
PubMed1996

Left ventricular myocardial uptake of a labeled somatostatin analog in carcinoid syndrome.

We report a case of left ventricular (LV) myocardial uptake of a labeled somatostatin analog in a patient with a carcinoid tumor of the small bowel. The patient developed liver metastases and a carcinoid syndrome, including right carcinoid heart disease, without right-to-left shunt on contrast ultrasonography or left ventricular myocardial metastases. The basis for visualization of the LV myocardium is probable somatostatin receptor upregulation.

Aged↗
PubMed1995

Nonlimited exercise test combined with high-dose dipyridamole for thallium-201 myocardial single-photon emission computed tomography in coronary artery disease.

Clinical, electrocardiographic, and thallium-201 single-photon emission computed tomography data were evaluated in 397 consecutive patients divided into 3 groups according to coronary hyperemic stimulation: 186 patients (group I; Ex) had maximal symptom-limited exercise ergometric stress testing, 93 patients (group II; Dip) had intravenous dipyridamole (0.7 to 0.8 mg/kg) stress testing, and 118 patients (group III; Dip+Ex) had dipyridamole (0.7 to 0.8 mg/kg) plus nonlimited (i.e., symptom-limited) exercise stress testing, achieving a maximal workload (mean +/- SD) of 102 +/- 37 W. Clinical tolerance was higher in Ex than in Dip groups (p < 0.01), and tended to be higher in Dip+Ex than in Dip groups (p = NS). Image quality--as judged by signal-to-noise ratios--was superior in Ex and Dip+Ex groups when compared with the Dip group (p < 0.01). Chest pain and electrocardiographic positivity were more frequent in the Dip+Ex group than in the Dip group (p < 0.05), despite more extensive coronary artery disease (CAD) in the Dip group; and reversible scintigraphic defects were more frequent in Dip+Ex versus Dip (p < 0.01) and in Ex versus Dip groups (p < 0.05) in patients with established CAD, as well as for the whole group. We conclude that, in patients unable to achieve 85% of their maximal predicted heart rate, the combination of high-dose dipyridamole plus nonlimited exercise stress testing is superior to dipyridamole stress testing alone, and comparable to maximal exercise testing.

Aged↗
PubMed1995

Comparison using dynamic vectorcardiography and MIBI SPECT of ST-segment changes and myocardial MIBI uptake during percutaneous transluminal coronary angioplasty of the left anterior descending coronary artery.

The quantitative relation between ST-segment changes and the severity and extent of myocardial ischemia during coronary occlusion remains unclear. This study assesses whether ST-segment changes during percutaneous transluminal coronary angioplasty (PTCA) correlate with the amount of myocardium at risk, measured with technetium-99m hexakis 2-methoxyisobutyl isonitrile (MIBI; also called sestamibi) single-photon emission computed tomography (SPECT). Quantitative continuous dynamic vectorcardiography was performed during PTCA of the left anterior descending coronary artery in 11 patients (mean age 64.3 years) without previous myocardial infarction. Change in the magnitude of the ST vector (STc-VM) was continuously recorded. A standardized protocol of balloon inflations was used and technetium-99m MIBI was injected intravenously at the onset of the third inflation. SPECT imaging was performed 60 minutes later and compared to a rest acquisition. SPECT was quantified by bull's-eye analysis using: (1) the change in the pathologic/normal area count ratio (delta P/N) as an index of the severity of ischemia; and (2) planimetered defect size during PTCA as an indicator of the size of the area at risk. The delta P/N from baseline to balloon occlusion (22 +/- 11%) was correlated, albeit loosely, to the maximum value of STc-VM (245 +/- 186 microV, r = 0.62, p < 0.05), but there was no correlation between the size of the scintigraphic defect and STc-VM. Likewise, the sum of ST-segment elevation was correlated to delta P/N (r = 0.72, p < 0.02), but not to the size of the scintigraphic defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

[The diagnosis of primary cerebral lymphoma in AIDS. The contribution of imaging].

Apart from the very frequent HIV encephalitis, which lays the foundation for opportunistic infections, the most common diseases encountered in HIV-infected patients are toxoplasmosis and lymphoma; the percentage of cases of other diseases is very small. It is capital to diagnose cerebral lymphoma at an early stage in these patients who already are in a precarious general and neurological state since this type of lesion usually occurs late in the natural course of AIDS. In the differential diagnosis between toxoplasmosis and lymphoma only stereotaxic biopsy enables a positive diagnosis to be made, but imaging methods, such as CT and MRI, provide data that help guide to a diagnosis which sometimes may be definitive. Suggestive of lymphoma is a single infiltrating lesion wider than 4 cm, which is paraventricular or located in the posterior fossa, has little perilesional alteration and a short tumoral doubling time during the imaging follow-up. Suggestive of toxoplasmosis are multiple, small, annular or nodular lesions with an important perilesional inflammation and usually located in basal ganglia. In addition, in MRI the kinetics of enhancement after contrast injection is intense and occurs early in lymphoma, in contrast with the toxoplasmic abscesses, and this should provide a more specific differential diagnosis. Scintigraphic studies with somatostatin or positron emission tomography, using fluorodeoxyglucose (FDG-PET scintigraphy), also seem to be an interesting mean of making a specific diagnosis of cerebral lesion, according to a principle that is close to dynamic MRI. In lymphoma, capturing of the tracer is about 3 times greater than in infective lesions, notably the toxoplasmic ones. Imaging, therefore, is provided with tools which permit an increasingly specific approach to the primary cerebral lymphoma of AIDS, the definitive diagnosis of which rests on stereotaxic biopsy. This high specificity facilitates a better selection of patients requiring this procedure and shortens the delay in its execution.

AIDS-Related Opportunistic Infections↗
PubMed1994

Somatostatin receptor scintigraphy in forty-eight patients with the Zollinger-Ellison syndrome. GRESZE: Groupe d'Etude du Syndrome de Zollinger-Ellison.

In patients with the Zollinger-Ellison syndrome, which is either sporadic or integrated into multiple endocrine neoplasia type 1, accurate localization of all the tumours is difficult and may have therapeutic implications. In an attempt to improve this localization, somatostatin receptor scintigraphy using [111In-DTPA-D-Phe1]-octreotide was performed prospectively in 48 consecutive patients with the Zollinger-Ellison syndrome. Thirty of them had the sporadic type of this disease. Scintigraphic data were compared with data obtained by conventional imaging methods, and also, in 32 selected patients, with those obtained by endoscopic ultrasonography. Somatostatin receptor scintigraphy showed abnormal tracer uptake in 39 patients (81%), in whom it correctly identified 50 of the 60 tumoral sites (83%) previously localized by the other imaging methods. In 17 patients (35%) somatostatin receptor scintigraphy disclosed abnormal tracer uptake at 18 different tumoral sites: 14 were located in the abdomen, including four in the liver and eight in the duodenopancreatic area, and four outside the abdomen, including two in the mediastinum. Six of the ten tumoral sites which were not correctly identified by somatostatin receptor scintigraphy were located in the duodenopancreatic area. However, in the 20 patients for whom conventional techniques failed to visualize any tumour in the duodenopancreatic area, somatostatin receptor scintigraphy was positive in ten (50%) whereas endoscopic ultrasonography was only positive in five (25%). In our patients with the Zollinger-Ellison syndrome, somatostatin receptor scintigraphy appeared to be a useful new addition to the battery of tests used for tumour detection.

Bone Neoplasms↗
PubMed1994

Functional evaluation of normal and ischemic kidney by means of gadolinium-DOTA enhanced TurboFLASH MR imaging: a preliminary comparison with 99Tc-MAG3 dynamic scintigraphy.

The functional value of TurboFLASH MR imaging in the assessment of dynamic contrast enhancement and renal perfusion anomalies was evaluated in seven patients, who also underwent renal scintigraphy in baseline conditions. The basal renograms obtained from MAG-3 scintigraphy (mercapto acetyl triglycine, MAG3-S) and from Gd-DOTA-enhanced turboFLASH MRI were compared. After hydration, the protocol used consisted in breath-hold coronal turboFLASH acquisitions after IV bolus of Gd-DOTA (4 s every 20 s during 10 min) for MRI, and IV bolus of 370 MBq of 99mTc-MAG3 followed by 60 frames of 1 s and then 120 frames of 10 s for MAG3-S. Relative renal functions were computed for both methods by calculation of the integral of the uptake phase between the first and the second minute. Renograms exhibited 10 normal and 4 ischemic kidneys. There was a close correlation between the contrast enhancement of MRI and isotopic uptake in normal and ischemic kidneys. Global renograms of MRI correlated with MAG3-S (r = .82, p < .001) with similar curve shape and time to peak. Relative renal function of the right and left kidney were closely correlated in all patients (r = .98, p < .001), although there was a tendency for MR to overestimate MAG3-S evaluation in kidneys with severe basal dysfunction. Enhanced turboFLASH provides noninvasive assessment of renal perfusion in patients with renovascular disease. Accurate renograms are obtained with dynamic-enhanced MRI, but the relative renal function seems to be overestimated in low values of ischemic kidneys, and needs further comparative evaluation.

Adult↗
PubMed1992

Diagnosis of malignancy in thyroid nodules by factor analysis of spectral and dynamic structures: a simultaneous dual-isotope dynamic study with thallium-201 and iodine-131.

The aim of this study was to identify malignant thyroid nodules using iodine-123 and thallium-201 simultaneous dynamic acquisition. The image sequences acquired were processed by factor analysis of spectral and dynamic structures (FASDS). Some 49 patients were investigated, and their diagnoses were confirmed by histological examination. Data processing enables the estimation of the spectra of the two isotopes and the evaluation of the kinetics and spatial structures related to each tracer. The superimposition of thallium and iodide sum images allowed us to delineate the nodule accurately. Two groups were defined: 21 patients who had 201Tl uptake in the nodule, and 28 who had none. In the first group, 5 nodules were carcinomas, whereas all nodules in the second group were benign. The results of the 201Tl dynamic study improved the diagnosis of carcinoma as the number of false-positive cases decreased. FASDS succeeds in extracting spectral and kinetic information, proving its usefulness in clinical diagnosis.

Adenoma↗
PubMed1992

Multicentre evaluation of a two-step automated enzyme immunoassay of free thyroxine.

The two-step enzymatic immunoassay of free thyroxine (IMx FT4, Abbott Laboratories, Chicago, IL) was studied in three centres. The assay involved a fluorimetric measurement and took 45 minutes using a completely automated procedure. The results were compared with those from the free thyroxine two-step radioimmunoassay and with the "calculation" of free thyroxine. The analytical precision was found to be excellent if the analyser was correctly set. The IMx FT4 assay seemed unaffected by increased concentrations of albumin and of non-esterified fatty acids (oleic acid) up to 5 mmol/l. The euthyroid reference interval, defined as that including 95% of 194 control subjects, was 12-21 pmol/l. A limited overlap existed between euthyroid and hyperthyroid patients, but a larger one was seen between the euthyroid and hypothyroid population, the latter including subclinical hypothyroidism. IMx FT4 results agreed well when compared with those from two-step radioimmunoassays. The IMx FT4 technique gave rise to a low percentage of elevated results in patients being treated with heparin, but was undisturbed by autoantibodies to thyroxine and triiodothyronine which were present in one hypothyroid patient.

Adolescent↗
PubMedDate not supplied

Cardiac gated equilibrium radionuclide angiography and multiharmonic Fourier phase analysis: optimal acquisition parameters in arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Multiharmonic Fourier phase analysis of radionuclide angiography is a well-established method for the diagnosis of arrhythmogenic right ventricular cardiomyopathy. We sought to determine the optimal acquisition parameters: number of frames per cycle and number of counts per frame, with all other acquisition and processing parameters being fixed. METHODS AND RESULTS: Radionuclide angiography with list mode acquisition was performed in 10 normal subjects (pilot group) and 11 patients with arrhythmogenic right ventricular cardiomyopathy (validation group), allowing the reconstruction of electrocardiography-gated constant phase studies with different parameters: 16, 24, and 32 frames per cycle and 200, 400, 600, and 800 kcounts per frame. Three harmonics Fourier phase analysis was applied, and optimal acquisition parameters (defined as those providing best homogeneous phase distribution histogram in the pilot group) were defined as judged by the H3 right ventricular phase SD and delta 95%. These were 16 frames per cycle and 600 kcounts per frame. Then we verified in the validation group that these optimal acquisition parameters did not induce any significant relative loss of information compared with other acquisition parameters with more temporal resolution (24 and 32 frames per cycle) or more statistics (800 kcounts per frame). This result was realized by the calculation of normalized H3 right ventricular SD, right ventricular delta 95%, and (SD[left ventricle] - SD[right ventricle]). CONCLUSIONS: In practice, 16 frames per cycle and 600 kcounts per frame are optimal for multiharmonic Fourier phase analysis, with all other acquisition and processing variables being fixed as specified.

Adult↗