Biomedical subjects
Publications and source records attributed to J L Barat.
A gamma-camera on-line distortion corrector, based on a fast microprocessor, has been tested on two cameras. The original electronic design and the software algorithm are described. Performance measurements on phantoms and clinical results show an improvement of the pictures.
In a patient with a prior history of cerebral abscess and cerebral ischemia, an unsuccessful perfusion lung scan led to a radionuclide angiocardiogram using an arm vein injection. This showed a total right-to-left (R-L) shunt from the superior vena cava (SVC) to the left atrium. Repeat radionuclide study, through a leg vein, demonstrated a moderate R-L shunt and an interpretable lung scan could be obtained. Catheterization and contrast cineangiogram did not provide the exact diagnosis, the preoperative conclusion being anomalous drainage of the SVC into the left atrium, with atrial septal defect (ASD) and partial anomalous pulmonary venous connection to the SVC. The operative diagnosis was high atrial (sinus venosus) septal defect. This example of major but clinically unsuspected R-L shunt emphasizes the value of performing a perfusion lung scan, preferably in conjunction with radionuclide angiocardiography in patients with a prior history of unexplained cerebral abscess or systemic ischemia. Implications of the site of an ASD on quantitation of L-R shunts by radionuclide methods are also discussed.
Congenitally corrected transposition of the great arteries (CTGA) may constitute a pitfall for interpretation of radionuclide angiocardiography, since the two anatomic discordances cancel each other from a physiologic point of view. However, the unusual shape of the ventricles (due to ventricular discordance) and the relative position of the great arteries (due to transposition) can allow a clear scintigraphic diagnosis, especially for CTGA with mild or absent associated congenital anomalies. Five cases are described. Gated cardiac blood pool imaging is particularly helpful since it permits multiple views, allowing a more detailed study of the scintigraphic signs.
A prospective evaluation of conventional planar scintigraphy (PS), single photon emission computed tomography (SPECT), and transmission computed tomography (TCT) was performed in 98 patients with suspected focal hepatic disease (FHD). The three examinations were performed on the same day. TCT had slightly higher sensitivity (91%) and specificity (96%) than either PS or SPECT. The sensitivity and specificity of TCT was also higher than that of the combination of PS and SPECT, which was more accurate than either radionuclide technique alone, with a sensitivity of 85-87% and a specificity of 90%. These differences were not statistically significant. However, receiver operating characteristic (ROC) analysis showed that the performance of TCT was significantly better. The ROC curves also showed, without statistical significance, that SPECT appears to have better diagnostic accuracy than PS and that it seems desirable to complement SPECT imaging with PS views, to reduce the number of equivocal results.
Radionuclide studies were performed on 12 patients who had had a Fontan operation for cyanotic congenital heart disease, six of whom had undergone a prior palliative Glenn procedure. The patients without prior Glenn anastomoses were studied by radionuclide first-pass angiocardiography, using a right antecubital vein injection of 99mTc pertechnetate. The patients with Glenn anastomoses required two injections, one by femoral vein to study the Fontan procedure, using bolus injection of 99mTc pertechnetate or microspheres, and the second by right antecubital vein to study the Glenn anastomosis and right lung, using a bolus of microspheres. Gated cardiac blood-pool scintigraphy was used to measure right atrial and left ventricular ejection fraction in three patients. In nine patients, contrast angiography confirmed that these techniques allowed recognition of residual right-to-left shunts, right atrial stasis, right atrial outflow obstructions, left ventricular dysfunction, and right lung arteriovenous fistulas. Noninvasive radionuclide methods seem to be dependable in the postoperative evaluation of patients after the Fontan procedure. First-pass angiocardiography is most helpful in evaluating the dynamics and distribution of blood flow, especially the right atrial output, and gated blood-pool scintigraphy offers a better evaluation of right atrial and left ventricular contraction, so both supply complementary information.
We describe a quantitative method that measures segmental motion of the left ventricle, using tomographic slices obtained by gated single photon emission tomography (GSPECT). These slices contain the major axis of the left ventricle and are presumed to show wall motion directed towards a center of contraction. Values of parameters describing segmental wall motion in GSPECT were obtained from 61 patients, who received a left cardiac catheterization 1 hr later. These values were compared with results of similar calculations applied to data from contrast ventriculography. We conclude that GSPECT allows a detailed and quantitative, noninvasive study of wall motion of all left ventricular segments, with high inter- and intraobserver reproducibility.
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Radionuclide quantitation of cerebrospinal fluid (CSF) flow through a ventricular shunt using a Cordis-Hakim valve was performed in 78 adults (138 studies). All remained supine for at least two hours before the study to avoid possible depletion of ventricular CSF. The absolute flow rate distinguished shunt adequacy from patency by defining flow of less than 0.1 ml/min. as abnormal. Measurements were performed with the patient first supine and then erect. When abnormal supine flow was the criterion of malfunction, all obstructions were detected but there were 6 false positives. When abnormal erect flow was considered, there were 5 false negatives. Abnormal flow in both supine and erect positions is a reliable indication of malfunction. The authors conclude that this technique is valuable for neurosurgical management of ventricular shunts.
Radionuclide angiography has diagnosed systemic arterialization of the right lung base in a patient presenting with a basal thoracic bruit. The bruit was due to high flow in the systemic artery and development of arteriovenous fistulas, confirmed by TCT scan and contrast aortography. But the parenchyma of the right lung base appeared normally aerated on the radiographic studies, and Xe-133 ventilation scintigraphy was normal. This case was therefore classified as systemic arterialization of lung without sequestration.
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