Showing papers in "Seminars in Ultrasound Ct and Mri in 1996"

The brachial plexus.

Abstract: The brachial plexus arises from the lower cervical and upper thoracic spinal nerve roots. It courses between the anterior and middle scalene muscles and adjacent to the subclavian artery. The brachial plexus may be visualized by both MRI and CT. Symptoms of a brachial plexopathy commonly are nonlocalizing. Traumatic injuries and involvement by tumors probably account for the majority of etiologies responsible for these plexopathies. Inflammatory processes also involve the brachial plexus. This article reviews the anatomy of the brachial plexus from both surgical and radiographic approaches and also addresses the symptomatology of brachial plexopathy underlying it.

Current status of digital mammography

Abstract: Some inherent limitations to further technical improvement in film-screen mammography exist. Many of these limitations can be overcome effectively with digital mammography, in which image acquisition, display, and storage are performed independently, thus allowing the optimization of each. Presented is a brief background of digital and analog imaging with emphasis on the features and drawbacks of digital mammography systems. Image storage, processing, and display, computer-aided detection and diagnosis, as well as telemammography are also discussed.

Sonography of the placenta with emphasis on pathological correlation

Abstract: The placenta is a most interesting but unfortunately often ignored and misunderstood organ. Included in its many functions are fetal oxygenation and nutrition as well as a myriad of endocrinological contributions and protein synthesis. The sonologist is strongly encouraged to study this amazing structure with ultrasound because significant pathology afflicts the placenta, often before affecting the fetus. Placental abnormalities, therefore, can be an "early warning system" for fetal problems. Recognition of clinically important lesions (abruption, accreta) as well as important anatomical variants (intervillous thrombosis, septal cyst) is crucial for the physician who performs and interprets prenatal ultrasound. This article discusses the common abnormalities of the placenta and highlights some correlative pathological processes, which will serve to enhance the reader's understanding of sonographic findings. A practical approach is presented with respect to assessment of the hypoechoic lesion, placental infarction, thick placenta, placenta previa, abruption, placenta accreta, and placental tumors.

Sonography of the breast.

Abstract: Quality mammography remains the primary modality used to image the breast. Sonography currently is the most useful adjunctive technique to mammography, having roles in differentiating cystic from solid masses and in guiding interventional procedures. This article reviews these and other indications for breast ultrasound studies, including evaluation of palpable masses not visible in radiographically dense breasts, masses not completely evaluable with mammography, young patients especially susceptible to radiation damage, and abscesses. Ultrasound interpretation of cysts and solid masses are discussed, as are the relative disadvantages of ultrasound as a breast cancer screening tool.

Imaging of the thyroid gland

Abstract: The thyroid gland is critical in regulating metabolic functions including cardiac rate and output, lipid catabolism, skeletal growth, and oxygen and heat production. Thus, patients with hormonally active thyroid abnormalities present with wide-ranging symptoms, requiring an understanding of the gland's hormonal functions. Radiological imaging assesses the pathophysiological affects of abnormal thyroid function as well as important morphological features. Nuclear scintigraphy provides functional information about the gland, whereas cross-sectional imaging—including ultrasound, CT, and MR—provide adjunctive anatomic information. These modalities also provide information about related structures in the neck. The embryology, anatomy, and physiology of the thyroid are discussed; congenital, autoimmune, inflammatory, metabolic, and neoplastic diseases are reviewed; and the diagnostic utility of radiological imaging is addressed.

Selected topics in chest trauma

Abstract: Trauma is the leading cause of death of young adults in the United States, and chest trauma is one of the leading causes of trauma-related fatalities. This article presents an approach to the radiological evaluation and diagnosis of pneumothorax, pneumomediastinum, traumatic aortic rupture, and thoracic spine injuries. Also discussed is the radiological assessment of vascular catheters, endotracheal tubes, and thoracostomy tubes.

Imaging of the parathyroid glands.

Abstract: Primary hyperparathyroidism resulting in hypercalcemia is the most common presentation of parathyroid pathology and usually is related to a parathyroid adenoma and, less commonly, to hyperplasia. Imaging of the parathyroid glands focuses on the detection of adenomas in patients with primary hyperparathyroidism. The role of imaging (as well as the modality used) for preoperative localization of the parathyroid glands continues to be controversial. The embryology, anatomy, and physiology of the parathyroid glands are reviewed. The diagnostic utility of radiological imaging-including ultrasonography, CT, MR imaging, and nuclear scintigraphy-are discussed, particularly as it pertains to the evaluation of primary hyperparathyroidism.

CT of abdominal and pelvic trauma

Abstract: CT is the diagnostic study of choice at most institutions in the evaluation of hemodynamically stable, blunt abdominal trauma. It is highly specific and sensitive in the detection and definition of the extent of most intra-abdominal and pelvic injuries. The clinical examination is the most important factor in the decision regarding whether surgery should be undertaken. However, a progressive and steady trend toward the nonoperative management of solid parenchymal injury is occurring, partly because of the ability of CT to define the extent of injury and to follow its healing over time. Clinical management, CT findings, and the utility of these findings are presented and discussed for each organ system injury within the abdomen and pelvis.

The imaging of epilepsy.

Abstract: Based on the experience of a university neurological epilepsy center, the neurological classification and the gradation of neurological evaluation of patients with epilepsy are described. Into this the nature and the significance of the imaging of the brain are interwoven. The object, illustrated by several illustrative patients, is to stress the importance of the MRI and to note that based on the MRI findings and the clinical findings, the battery of sophisticated electroencephalographic evaluation is determined. Epilepsy is an area where imaging and all aspects of the clinical neurological evaluation integrate very well and in which correlation is most important.

Spiral (helical) CT of the renal vasculature

Abstract: The renal arteries are among the most challenging of the major aortic branches to image with spiral CT. Optimization of CT acquisition parameters is critical to creating diagnostic renal CT angiograms. When careful attention is paid to prescribing these examinations, renal CT angiography can be a very useful, noninvasive alternative to conventional angiography for the assessment of renal artery stenosis, screening of potential renal donors, planning repair of ureteropelvic junction stenoses, and identification of relevant renal artery relationships to abdominal aortic lesions. This review outlines important technical considerations for performing renal CT angiography and examines currently published data on the utility of spiral CT in a variety of clinical conditions.

Diagnosis of pancreatic injury after blunt abdominal trauma.

Abstract: Expeditious diagnosis and treatment of pancreatic injury continues to elude the trauma surgeon and radiologist. Missed or underestimated pancreatic injury is responsible for a high level of morbidity and mortality after blunt or penetrating trauma. Unfortunately, inappropriate therapy can lead to devastating consequences such as severe endocrine or exocrine insufficiency. Abdominal CT is currently the imaging method of choice for evaluating patients with blunt trauma. This article reviews the constellation of CT findings that the radiologist must rely on to establish the diagnosis of pancreatic injury.

Thoracolumbar burst fracture: Evaluating stability

Abstract: The burst fracture is an injury characterized by anterior vertebral body height loss and retropulsion of the posterior aspect of the vertebral body into the spinal canal. The vertebral body injury frequently is associated with fractures through the neural arch. Using a three-column concept of spinal stability, the division of these fractures into stable and unstable injuries is difficult. Radiographic signs of instability include widening of the interspinous and interlaminar distance, translation of more than 2mm, kyphosis of more than 20 degrees, dislocation, height loss of more than 50%, and articular process fractures. However, fractures may be unstable in the absence of these signs. Unrecognized supraspinous ligament disruption contributes to this instability. This structure is best evaluated by MR examination. Confirmation of posterior ligamentous disruption occurring in conjunction with the burst fracture leads to reevaluation of the presumed mechanism of injury. This article discusses the many issues surrounding the division of burst fractures into stable and unstable injuries and reexamines the common classification systems of thoracolumbar spine injuries.

Imaging of acute head injury

Abstract: This article reviews the neuroradiological evaluation of acute head injury with an emphasis on CT and MR imaging. Subacute and chronic head injury are not discussed. CT remains the modality of choice in the emergency setting, permitting rapid, comprehensive assessment of the great majority of head injuries. MR is most useful in patients in whom there is a discrepancy between clinical symptoms and CT findings. In addition, MR is the imaging modality of choice in the subacute and chronic setting. The superior contrast resolution of MR permits optimal evaluation of nonhemorrhagic (and hemorrhagic) white matter shearing injuries, and the lack of beam-hardening artifact permits a more thorough evaluation of the brain stem, posterior fossa, and cortical surface.

High-resolution MR imaging of the breast.

Abstract: Investigation into the use of MRI as a breast imaging tool is ongoing. Several studies have shown that MRI is a very accurate imaging method for the identification of implant failure in the symptomatic patient with augmented breasts. In this clinical setting, MRI may be the study of choice. Imaging techniques, and the MRI appearance of normal and abnormal implants, are described. The use of MRI for the detection of breast cancer is not as straightforward. Preliminary results suggest that this technique can be used as an adjunct to mammography for the detection and diagnosis of breast cancer. However, it is premature to draw firm conclusions regarding the role that MRI should play in the management of women with breast disease because of the wide variability of imaging techniques, protocols, and patient populations in the studies reported to date. In this overview, the current state of MR imaging of the breast is discussed. Technical requirements are described, and potential clinical applications—including the differentiation of benign from malignant lesions, breast cancer staging, detection of recurrence after breast conservation therapy, and detection of cancer in patients presenting with positive axillary lymph nodes with an unknown primary—are reviewed. Many of these potential clinical applications will require an accurate MR-guided biopsy system, and the implementation of such a system as well as its inherent limitations are discussed.

MR angiography of the renal arteries

Abstract: MR angiography (MRA) has shown considerable promise as a nonivasive tool in the evaluation of renal vascular morphology. There are two fundamental approaches to MRA of the renal arteries: time of flight and phase contrast imaging. Recently, three-dimensional, gradient-echo, gadolinium-enhanced MRA using breath-hold techniques also has been introduced. These techniques have made MRA of the renal arteries a very promising, noninvasive tool in the detection of main renal artery stenosis, with sensitivities between 90% and 100%. MRA is used most often in the evaluation of renal arteries of patients with abdominal aortic aneurysms or allergies to iodinated contrast media, or when other noninvasive screening examinations have been inconclusive. One of the most helpful and unique applications of MRA is in patients who have accelerating hypertension and accelerating renal insufficiency. These patients often have preexisting unilateral renal artery stenosis with a new contralateral renal artery stenosis. Conventional angiography is risky in these patients because of possible contrast nephropathy. MRA, in such cases, is very helpful for differentiating between bilateral renal artery stenosis and end-stage nephrosclerosis.

Subarachnoid hemorrhage and aneurysms

Abstract: Ruptured intracranial aneurysms are the usual cause of acute subarachnoid hemorrhage (SAH). Noncontrast CT is the primary imaging procedure of choice for establishing the diagnosis of SAH. Conventional contrast angiography is the gold standard for establishing the presence of intracranial aneurysms, but CT and MRI have supplementary roles. The pathogenesis, presentation, and imaging of SAH and intracranial aneurysms are discussed.

CT angiography of the visceral vessels

Abstract: CT angiography (CTA) is a promising new technique for vascular imaging This review focuses first on the technique necessary for successful scanning of the visceral vessels As in many new modalities, there are different protocols for scanning and rendering of images The relative strengths and weaknesses of these different approaches are discussed A discussion of the applications of CTA to depict normal and abnormal anatomy of the visceral vessels follows These applications include celiac stenosis, splenic artery aneurysms, evaluation for hepatic arterial anatomy before liver transplantation, visceral arterial anatomy in pancreaticoduodenal surgery, the superior mesenteric artery in intestinal ischemia, vascular encasement in patients with pancreatic neoplasms, and, finally, the hepatic vessels before hepatic tumor resection

MR angiography of the peripheral vasculature

Abstract: MR angiography (MRA) for the evaluation of peripheral arterial occlusive disease is a rapidly evolving technique. Recent prospective clinical trials have indicated that MRA may play an important role in the evaluation of patients with peripheral arterial disease. This article discusses the pertinent technical aspects and limitations of peripheral MRA as well as some of the clinical data available.

CT in blunt chest trauma: Pulmonary, tracheobronchial, and diaphragmatic injuries

Abstract: Routine use of CT in the initial evaluation of blunt chest trauma is controversial. CT however, has been shown to be useful in the diagnosis of unsuspected chest injuries and in directing therapeutic interventions. This review discusses the CT findings in patients with pulmonary, tracheobronchial, and diaphragmatic injuries after blunt chest trauma.

Spiral CT angiography of the aorta

Abstract: Imaging of the aorta and its branches has benefitted greatly from the development of spiral CT techniques, which are relatively fast and noninvasive. The volumetric acquisition of spatial information has permitted the computer to reformat images for inspection of the vessels by several methods from an infinite number of viewing angles. Most aortic diseases—including congenital anomalies, dissection, aneurysm, trauma, inflammation, infection, and thromboembolic disease—can be depicted with this technology. In selected cases, spiral CT may be the only imaging modality needed for the surgical planning of aortic repair. This report discusses the CT angiography technique, its application to a variety of disease states, its role relative to other imaging modalities, and guidelines for patient selection.

Gadolinium-enhanced three-dimensional MR angiography of the thoracoabdominal aorta.

Abstract: MR angiography (MRA) of the thoracoabdominal aorta is a noninvasive technique that can rapidly acquire a volume of data with the capability of multiplanar reformations (MPR) and "bright blood" maximum intensity projection (MIP) angiographic images. These MIP images can display long tortuous vessels in a single three-dimensional (3D) volume, with excellent delineation of branch vessel disease and without the flow artifacts or long examination times of conventional spin-echo (SE) imaging. Two-dimensional (2D) time-of-flight (TOF) imaging is used most widely because of familiarity and ease of implementation, but this method has limitations in evaluating thoracoabdominal aortic disease. Sequential 2D axial imaging (which maximizes flow-related enhancement) is time consuming, subject to slice-to-slice misregistration, and can be degraded by pulsatile and turbulent flow. Coronal or parasagittal imaging is more time efficient, but image degradation secondary to inplane saturation and stagnant or turbulent flow from aneurysmal disease may lead to nondiagnostic studies. Three-dimensional TOF techniques offer the advantages of higher signal-to-noise ratio, better spatial resolution with near isotropic voxels, and shorter echo times (TEs), which lessen signal loss because of intravoxel phase dispersion. Although these techniques provide excellent image quality in the carotid arteries, they are of limited use in the aorta because of saturation effects. However, the addition of gadolinium chelates shortens the T1 relaxation rate of blood, which obviates the need for flow-related enhancement, allowing for inplane imaging without saturation effects, even in regions of virtually stagnant flow. The enormous signal enhancement of gadolinium chelates enables imaging with high-resolution matrices, providing diagnostic angiograms in as little as 2 minutes. With improved hardware, faster and stronger gradients, and phased-array coils that increase the signal-to-noise ratio, breath-hold gadolinium-enhanced 3D schemes with ultrashort TEs will become the optimal method for imaging the aorta and its branch vessels. Using this technique, the aorta can be imaged in less than 1 minute.

Splenic injuries in children after blunt abdominal trauma.

Abstract: Management of splenic injuries in children has evolved over the past two decades. Splenectomies or splenorrhaphies are now performed infrequently, with the majority of hemodynamically stable children with splenic injuries managed nonoperatively. This article reviews the imaging features of acute splenic injuries in children as well as the appearance of healing splenic injuries. Follow-up evaluation and outcomes in children with splenic injuries also are addressed.

The fetal thorax: Noncardiac chest anomalies

Abstract: Fetal thoracic anomalies often lead to pulmonary hypoplasia with subsequent fetal or neonatal demise. Therefore, in utero sonographic identification of these anomalies is important. Unlike cardiac anomalies, most noncardiac thoracic abnormalities are easily detected with ultrasound. An unusually small thorax is usually obvious to the experienced sonographer, and thoracic masses are commonly observed on the routinely obtained four-chamber view of the heart. This article reviews the many causes of pulmonary hypoplasia with an emphasis placed on thoracic masses. Many examples of pathological fetal thoracic conditions are provided as well as a listing of differential considerations with regard to sonographic appearances of chest masses.

MR angiography of the portal venous system

Abstract: MR angiography (MRA) has become an increasingly important and practical clinical tool for the noninvasive assessment of abdominal vessels. Both two-dimensional time-of-flight and phase contrast techniques allow accurate evaluation of the portal venous system. This article reviews these two MRA techniques and discusses their impact on the diagnosis of vascular abnormalities of the portal venous system.

Stereotaxic breast biopsy

Abstract: Stereotaxically guided core needle biopsy is an important procedure used to decrease the number of surgical breast biopsies, as well as to decrease the expense, inconvenience, and deformity that can result from surgical biopsies. Use of the technique also can decrease the expense of breast cancer screening programs. Stereotaxic core biopsy (SCB) should not be used to biopsy lesions that would otherwise not undergo biopsy. The radiologist who performs this procedure must understand the implications of the resultant histological diagnosis and be certain that the pathological and radiological findings are concordant. The performance of this procedure by a radiologist is important for accurate positioning and needle placement in the breast, allowing accurate diagnosis, and in minimizing the number of exposures required for the procedure, thereby keeping the radiation dose to the patient at a minimum. In addition to understanding the guidance system used in this procedure, the radiologist also should understand the needles and guns used and be able to select the most appropriate method for each patient. Patients undergoing SCB should be told that, in some instances, surgical biopsy may still be necessary. They should know that major complications are rare but possible. Before initiating an SCB program, the radiologist performing SCB should develop a mechanism for surgical referral of woman who have a complication or an SCB diagnosis requiring surgery. This article describes the accuracy, indications, patient selection, equipment, technique, histological preparation and interpretation, shortcomings, and complications of SCB. Special emphasis is placed on SCB procedures and findings at Memorial Sloan-Kettering Cancer Center.

MR angiography of abdominal ischemia.

Abstract: Advances during the past decade in MRI have made this modality increasingly suitable for evaluating abdominal vascular diseases. Preliminary results in canine models and humans suggest that MRI has the potential of becoming a definitive, noninvasive test for the diagnosis of both acute and chronic mesenteric ischemia. MRI can provide both morphological information about the patency or degree of stenosis in mesenteric vessels as well as quantitative functional information such as blood flow and blood oxygen saturation in these vessels. The MR techniques developed for studying the mesenteric circulation also can be used for improving the diagnosis and posttreatment evaluation of vascular diseases in other abdominal organ systems.

The regulation of mammography

Abstract: There has been a long history of public and professional concern about the safety and quality of mammography. Whereas concerns about radiation dose levels dominated the 1970s, the type of equipment used in mammography was the focus of the 1980s. In the early 1990s, there was a lack of confidence in the overall quality of mammography. These problems have stood in the way of the widespread utilization of mammography to reduce mortality from breast cancer. The Mammography Accreditation Program of the American College of Radiology, state regulations, and the Mammography Quality Standards Act of 1992 came about to ensure a minimum level of quality that would encourage women to participate in breast cancer screening programs. Designing regulations that ensure quality mammography for women, without burdening mammography facilities with unnecessary costs and depletion of their resources, is one of the most difficult challenges facing the U.S. Food and Drug Administration.

First-trimester ultrasound: the essentials.

Abstract: A review of first-trimester ultrasound findings is presented. The normal first trimester, including practical embryology and pregnancy dating, is first discussed. Abnormal first-trimester findings, including sonographic evaluation of the failing pregnancy, ectopic pregnancy, gestational trophoblastic disease, and first-trimester cystic hygroma, are then stressed. This report reviews the spectrum of findings encountered by sonographers while evaluating early pregnancy.

Multifocal white matter lesions.

Abstract: There is a long differential diagnosis for multifocal white matter lesions on MR. The most common causes are prominent Virchow-Robin spaces, white matter ischemic change, and multiple sclerosis, but many other causes have been reported. Most of these are related to vascular or other demyelinating etiologies, but infectious/inflammatory disease, trauma, and neoplastic and other unusual causes may also be responsible. Typical imaging features of the more common multifocal white matter disorders are outlined, and the rarer causes are discussed briefly. An approach to imaging differential diagnosis is given, with emphasis on the differences between white matter ischemic lesions and multiple sclerosis.

Imaging of cervical spine trauma

Abstract: The cervical spine, supporting such critical structures as the medulla, spinal cord, and cervical nerve roots, can be very challenging to image propertly because of its complex structural anatomy and superimposition of bony and soft tissue parts. In this article, the use and value of the various modalities that image the cervical spine are discussed. Plain radiography remains the best screening tool in the initial evaluation of the cervical spine after trauma. Additional views, such as swimmer's, pillar and lateral flexion, and extension, often are helpful in certain circumstances.