CRC critical reviews in clinical radiology and nuclear medicine最新文献

This article will review the qualitative and quantitative methods of radionuclide evaluation of intracardiac shunts. Radionuclide angiocardiography of the cardiopulmonary system has proven adequate, with few exceptions, for qualitative detection of left-to-right and right-to-left intracardiac shunts. Numerous authors have reported on the detection of intracardiac shunts using qualitative methods such as rapid sequential visualization of nuclide angiocardiography using the scintillation camera with Polaroid, 35mm or 70mm film. Recent development of videotape storage systems and computers offers a quantitative technique of permanently recording the nuclide angiocardiogram and thus the capability for replay and analysis of the study. Quantitative analysis of the nuclide angiogram in the form of heart chamber dilution curves or pulmonary dilution curves permits 1) determination of the presence or absence of left-to-right, right-to-left, or bi-directional intracardiac shunts, including shunts which might go undetected using the qualitative techniques, 2) shunt location at the atrial or ventricular level, 3) determination of the functional status of a corrective left-to-right shunt, and 4) shunt quantitation. By quantitative analysis of the isotope dilution curves, it is possible to calculate the size of left-to-right or right-to-left intracardiac shunts (Qp/Qs ratio) to within 10% of the values obtained at cardiac catheterization.

Calcification of the heart and great vessels is secondary to those diseases which cause a significant alteration of tissue matrix. Metabolic derangements can cause microscopic calcification of heart muscle, but this has not been demonstrated conclusively roentgenographically. The deposition of calcium may follow a single event or be the result of a longstanding process. The etiology and roentgen appearance of calcium deposition in the various tissues which comprise the heart and great vessels are reveiwed. The common as well as the rare cases are considered; if possible, each entity is demonstrated roentgenographically. In addition, an attempt is made to reciew various points of view, which at times are conflicting. The prognostic importance of cardiac, aortic, or pulmonary arterial calcification is underscored whenever possible.

Localization of the placenta by radionuclide imaging techniques is useful in assessing the cause of vaginal bleeding late in pregnancy. Placenta previa is the most threatening cause of late gestational bleeding, and the acceptably high accuracy of nuclear placentography in detecting this condition is well-established. Nevertheless, B-mode ultrasonography is a preferable method because it delivers no ionizing radiation and is capable of identifying the cervix in virtually all patients. The latter method will eventually replace nuclear placentography.

Radionuclide imaging with labeled colloids is widely used to evaluate and localize primary and metastatic tumors of the liver. The method is fairly sensitive, but the nonspecificity of focal defects remains a significant limitation. Lesions such as cysts and abscesses appear as space occupying areas that are indistinguishable from neoplastic masses. Utilizing a variety of radiopharmaceuticals, one may obtain additional information concerning such lesions. Hepatic blood flow scintiphotography is performed with the Anger camera following the intravenous injection of a high activity, small volume bolus of 99m-Tc pertechnetate. Vascular lesions such as hepatomas or hemangiomas will show increased activity in the lesion which should easily differentiate them from avascular processes such as abscesses, cirrhotic pseudomasses and most metastatic lesions, all of which remain "cold" on these flow studies. If one does not posses a camera, useful blood pool rectilinear scans of these lesions may be obtained with 131-I or 99m-Tc human serum albumin or ionic 113m-In. Additional information concerning the metabolic activity of focal defects on the colloid study is obtained using 75-Se-selenomethionine or 67-Ga. The former is an indicator of active protein metabolism while the latter attaches to lysozymes of metabolically active cells. With either agent, hepatomas show avid uptake, metastatic lesions show variable uptake, and cysts or chronic pseudotumors of cirrhosis show poor uptake. The two agents differ in abscess detection where 75-Se-selenomethionine uptake is poor while 67-Ga concentration generally is intense. 131-I-Rose Bengal occasionally may prove useful in demonstrating impression by an atypically positioned gallbladder or focal dilatation of the biliary tract as a cause of a defect on the colloid scan. Ultrasound examination may complement the radionuclide studies. It is useful for corroborating the presence of lesions and for evaluating their consistency (cystic vs. solid). The information obtained from this multinuclide approach has made scintigraphy examination of the livermore specific. After the completion of this non-invasive series of studies, one generally may venture an intelligent opinion concerning the etiology of the space occupying disease.