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

The numerous general and special techniques for examination of the cervical spine, with particular reference to the demonstration of occult traumatic lesions will be presented and evaluated. The advantages and limitations of each technique will be presented. Optimal procedures will be suggested for the examination of the acutely injured patient, with injuries of unknown severity, as well as for the longer term followups and minor injuries. The mechanisms of the production of cervical spine traumatic lesions and the long term abnormalities to be anticipated will be related, together with the types of radiographic findings associated with them. These will be presented in the context of the anatomy, function and dynamic physiology of the cervical spine. The dynamic interrelationship between segments of the cervical spine and the cervical spine as a whole, as well as the interrelation of the cervical spine with the skull and the remainder of the spine will be considered. The clinical data available in the literature will be collected and correlated with the radiographic findings. The results will be used to evaluate the clinical significance of these occult traumatic lesions, and the efficacy of therapy.

The focus of this review will be on the current role of imaging studies in the clinical evaluation of patients with acute and chronic renal failure. We will stress the application of these studies in specific clinical settings in an effort to indicate the current value, and also to suggest fruitful areas for future clinical investigation. It is clear that imaging studies are an essential component in the evaluation of acute and chronic renal failure. Physicians who manage such patients must choose appropriately from a variety of available studies to obtain a maximal information with the least risk to their patients. This selection is influenced by local conditions, the most important among these being the experience and technical skill of those involved. Attention to detail is particularly important and it is critical that the studies be done at the appropriate time in the evaluation. There will be emphasis on the evolving role of imaging studies in evaluating these patients.

The findings from both animal and human studies on the radiation risk at low doses and low dose rates are far from conclusive, primarily due to statistical limitations. However, to arrive at some estimate of radiation risk, a conservative approach has been taken, and a linear extrapolation of radiation effects from high doses to low doses has been made. Thus, it is assumed that any exposure to radiation carries some risk of somatic or genetic damage and that there is no threshold or safe dose. In medical practice, diagnostic radiological procedures should be performed only if useful clinical information will be derived. In addition, this information should be obtained at the least possible risk to the patient. For mass chest X-rays, mammography, and lung scans, a quantitative determination of benefit to risk is developed. This approach, though possible desirable, is exceedingly difficult to establish for most diagnostic radiological procedures. Thus, good clinical judgement should be employed in radiological practice, just as it should be employed in all aspects of medical practice.

The observation by Subramanian and his co-workers that a 99mTc-labeled polyphosphate had excellent affinity for bone has led to widespread use of 99mTc-labeled phosphates as bone scanning agents. Initially, only polyphosphate was employed, but because of somewhat inconstant results and difficulty in preparation of this product, other phosphate compounds were sought. We soon discovered that an inorganic compound, pyrophosphate, appeared to have certain advantages over polyphosphate. Other workers formulated diphosphonates (organic phosphates) which also demonstrated advantages over polyphosphates. Comparison studies in rabbits utilizing 85Sr, 87mSr, 18F, and several phosphates (inorganic and organic) proved the 99mTc-labeled phosphates to be clearly superior in delineating normal skeletal anatomy. Studies in humans confirmed that excellent visualization of bone was obtained with 99mTc-labeled phosphates using either a gamma camera or a rectilinear scanner. What was not known, however, was just how reliable this class of agents would prove to be in detecting bone disease when compared to bone-seeking radiopharmaceuticals such as 85Sr, 87mSr, and 18F. Further comparative analyses have clearly demonstrated that both inorganic and organic 99mTc phosphate complexes are extremely sensitive in revealing more bone disease than the older bone scanning agents.

This paper represents a review of the recent literature on techniques to measure myocardial blood flow in man. A short discussion on flow meters in followed by a more detailed discussion of the radionuclide techniques used to measure myocardial blood flow. The radionuclide techniques are discussed in two groups: (1) qualitative measurement of blood flow using static images; and (2) quantitative measurements of blood flow using diffusible substances that actively enter the cell, radioactive labeled particles, and radioactive diffusible gases.

Soft tissue damage is an integral part of trauma. This basic fact is commonly ignored in the evaluation of roentgenograms obtained because of trauma. The soft tissue component of the traumatic lesion may produce the most obvious roentgen sing of injury and is, in these instances, fundamental to the correct roentgen diagnosis. In many instances, the soft tissue lesion is frequently of greater clinical significance that the more obvious skeletal injury. An awareness of the roentgen signs that signal soft tissue injury, and of those skeletal lesions that are commonly associated with radiographically silent, but clinically more significant, soft tissue damage, leads to prompt institution of appropriate additional diagnostic studies or therapeutic measures. Thus, the soft tissue injury in the roentgen diagnosis of trauma has both diagnostic and therapeutic significance. Each will be discussed in this article.

Within a month after Roentgen's discovery of the X-ray, the first cadaveric peripheral arteriogram was performed. It was not until 28 years later that the initial in vivo femoral arteriogram was reported. Arteriographic growth and development since that time have been punctuated with such names as Seldinger, Steinberg, Viamonte, Abrams, Sones, and many more. Keeping pace with their technical and diagnostic achievements has been the cause for a whole new industrial field - that of angiographic equipment and technology. New X-ray tubes, generators, film, etc. have been developed. Angiographic tables are available which have been designed to do highly subspecialized studies. The spectrum of catheter curves and materials available allows visualization of vessels down to the order of 0.1 mm when combined with magnification. Chemoangiography for treatment and subselective venous sampling for hormonal assays are commonplace. Although "the beginnings" for all angiography lie in the evaluation of peripheral vasculature, equipment sophistication for this basic study has often lagged behind that of the more glamorous organal examinations. The development of the biphasic ijection technique hopefully represents an anwer to both multiple injections and X-ray exposures. It allows single injection and single exposure visualization of the vascular tree from distal aorta to the pedal vessels.

This review covers conventional radiographic tomography, radioisotopic tomography, and a review of computerized transaxial tomography. Simple, reproducible radiographic tomographic methods are increasing in use, and despite their complexity, the diagnostic results are superior to conventional radiographs. There are many different motions of the X-ray tube and the film which can be employed to create a tomogram. The perfect tomographic motion is partly determined by the geometric shape of the object to be imaged and the thickness of the plane of interest. The undirectional tomographic method blurs a point in a linear fashion; the pleuridirectional method blurs a point over a wider surface. Among the most popular directions used are linear, circular, elliptical, and hypocycloidal. The numerous applications of tomography described in this review are an encouraging, broad-based foundation from which the most clinically useful and economically feasible devices will emerge.