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Deputy Director, University of Mississippi School of Medicine

When this happens, a difference may again appear between the cortex and pyramids, the latter becoming once more hypoechoic. This reappearance of hypoechoic areas corresponding to the pyramids must be remembered because it has a likeness to the enhancement pattern seen in most malignant tumors (see below). Cysts, Abscesses, and Infarctions Characteristics Pathology It is important to understand that the established phases of ultrasound contrast enhancement in the liver (1, 2) do not Because structures without perfusion will have no contrast uptake, they will have no brightness in the ultrasound contrast image; they will remain dark with an excellent delineation against surrounding tissues. Simple cysts will thus be unechoic during all the contrast phases even if they Contrast Media, Ultrasound, Applications in Kidney Tumor 533 C Contrast Media, Ultrasound, Applications in Kidney Tumor. Figure 1 Normal renal enhancement after an intravenous bolus of ultrasound contrast agent. The pyramids (arrows) enhance slower but show a complete fill-in after about 60 sec. This is also shown by the quantification graph where regions-of-interest have been placed in a segmental artery, cortex and a pyramid. In this manner, smaller cysts can be detected and, more importantly, cysts containing echoes. New software programs have an excellent sensitivity for detecting even tiny amounts of contrast agents, which makes it possible to detect thin but perfused septae indicative of malignancy rather than simple cysts. Similarly, focal lesions that on native ultrasound contain echoes but have no perfusion, such as abscesses and cortical infarctions, can be detected and distinguished from perfused, possibly malignant lesions. Thus, tumoral vessels can be detected, possibly with the aid of quantification software that can prove an increase in image brightness, assisting the subjective assessment. In addition, small vessels may be depicted in mural nodules, septae, or thickened cyst walls even when they are too small to be detected by Doppler (5). In the same way, biopsies can be guided to viable areas of a suspected lesion, avoiding necrosis and thus improving the diagnostic yield (6). Renal tumors often have a contrast enhancement pattern similar to the normal renal parenchyma in the early stages. However, the vasculature of malignant tumors differs from that of normal tissues, and early experiences indicate that contrast will be washed out of the neovasculature faster than from the renal capillaries, creating a similar but weaker equivalent to the situation in the liver, possibly helping characterization if not detection (8). Thus, malignant tumors tend to be hypoechoic compared with normal parenchyma in the later phases. This could be helpful in evaluating normal variants, such as a prominent column of Bertin (see above). The suspected area must then be followed to the later stages of the contrast enhancement, at least for 1 min. Most often, a clear difference can be detected by 534 Contrast Media, Ultrasound, Applications in Kidney Tumor Contrast Media, Ultrasound, Applications in Kidney Tumor. Contrast Media, Ultrasound, Applications in Transcranial and Intra-Operative Brain Ultrasound 535 analysis software at that stage and seen subjectively shortly thereafter. Necrotic areas of the tumor will remain dark, but because partially necrotic tumors tend to be large, they are easily diagnosed on native ultrasound. The detection of necroses is, therefore, of limited importance except as guidance for biopsies. Tumors, Benign Vessel anatomy may eventually help distinguish malignancies from benign oncocytomas, but at present, there is not enough scientific evidence to allow us to make that distinction. Lesions such as angiomyolipomas have been shown to enhance less than renal cell carcinomas in the arterial phase (9) and tend to retain the contrast better than a malignant tumor in the later phases, presumably due to vessel anatomy. However, knowledge about how a small, highly differentiated malignant tumor would behave is limited, and differentiation in the individual patient remains difficult. Krause J, Nilsson A (2003) Targeted tumor biopsy under contrastenhanced ultrasound guidance.

Associated cardiac malformations are also noted as well as the cardiac position (position of the heart within the chest and the orientation of the cardiac apex). The recurrence risk varies between 3 and 8% and is dependent on the cardiac defect and the gender of the involved parent. This is an autosomal dominant disorder characterized by atrial and ventricular septal defects as wells as upper limb abnormalities. Failure to wean the patient off the ventilator post-operatively may result from the airway compression caused by the vascular structure. This information is useful for surgical management and cannot be provided by any other imaging modality. After surgical intervention, however, the use of ultrasound is often restricted because of scar tissue and thoracic deformations. Biventricular volumes and blood flow can be accurately measured during a single examination, allowing complete evaluation of both right and left ventricular systolic and diastolic function as well as intracardiac and vascular flow. Careful monitoring of functional parameters such as cardiac function and vascular flow will help to allow early detection of the most important postoperative complications and aid in the timing of re-interventions (4). Timely detection of late complications requires adequate assessment of right ventricular size and function as well as quantification of intracardiac blood flow in these patient groups. However, none of the investigated instruments contained properties required for complex cardiovascular interventions, such as (a) fast and reliable detection of the tip; (b) curvature of the shaft and (c) material properties such as tip flexibility, torque and tracking ability, shaft strength and flexibility. In the future, research methods such as use of resonance circuits as fiducial markers should be investigated to provide tip and shaft detection without incorporating the risk of heating effects inherent with active catheter tracking methods. Burn J, Brennan P, Little J et al (1998) Recurrence risks in offspring of adults with major heart defects: results from first cohort of British collaborative study. Synonyms Congenital lesions of the adrenal gland 386 Congenital Malformations, Adrenals Definition Congenital lesions of the adrenal gland arise from disordered embryogenesis, inborn errors of metabolism, or the occurrence of disease processes identified in the fetus or early neonatal period. Histology/Pathology the fetal adrenal cortex develops around 6 intrauterine weeks from coelomic mesodermal tissue and between 8 and 12 weeks it is invaded by ectodermal sympathetic cells of the neural crest to form the adrenal medulla producing catecholamines. The fetal adrenal cortex differentiates into an outer definitive zone and a larger inner fetal zone producing androgenic precursors for the placental synthesis of estriol. The fetal adrenal gland is proportionately very large, but soon after birth the fetal zone involutes disappearing by 1 year. At the same time the definitive zone of the cortex differentiates to form the glomerulosa (15%), lying peripherally and producing aldosterone, and the fasciculata (75%) and the reticularis (10%), lying next to the medulla both producing glucocorticoids and androgens. The glomerulosa becomes fully differentiated around 3 years of age, whereas the reticularis is not fully differentiated until approximately 15 years. Straight adrenal refers to a discoid-shaped adrenal gland that appears elongated and straight on both longitudinal and transverse imaging rather than having the normal Y, Z, or V shape. This anomaly is seen in association with renal agenesis, hypoplasia, or ectopia and is thought to result from the failure of the renal tissue to indent into the adrenal gland during early development. Coexisting anomalies occur frequently including 52% asplenia, 37% neural tube defects, 29% renal anomalies, and in 3% Cornelia de Lange syndrome. Horseshoe adrenal does not occur in association with polysplenia, a differentiating feature from asplenia. Circumrenal adrenal gland is a further anatomical variant describing the finding where there is fusion of two limbs of one gland extending down and around the kidney. These occur when the adrenal gland becomes incorporated within the capsule of the liver or kidney and is thought to be due to the disruption of intervening coelomic epithelium allowing these adjacent organs to fuse. Abnormalities in Embryogenesis A number of developmental abnormalities of the adrenal gland result from disordered embryogenesis. Adrenal agenesis is rare and usually occurs in conjunction with ipsilateral renal agenesis. In these cases, the renal/adrenal agenesis is thought to be due to the failure of the mesonephric ridge to develop, whereas the majority of cases of renal agenesis.

This is primarily an imaging finding that maybe accompanied by clinical symptoms in one third of the patients (1). Pathology the flow reversal in the vertebral artery can be either permanent, the upper extremity being perfused by the ipsilateral vertebral artery (permanent vertebral steal), or induced after exercise or hyperemia of the ipsilateral arm (latent or temporary steal). It has been shown that decreased regional cerebral flow is present in patients with vertebral steal. Other types of vascular steal may be encountered: carotid artery steal in the presence of innominate artery occlusive lesion; or in patients with internal mammary artery to coronary artery by pass graft, the presence of a proximal subclavian occlusion may cause coronary artery steal phenomenon. Square Vertebrae and BarrelShaped Vertebrae Square vertebrae and barrel-shaped vertebrae show straightening or convex bulging of the ventral aspect of the vertebral body, mainly in the thoracolumbar junction and lumbar segments as a result of rheumatic inflammation. They occur in ankylosing spondylitis and are most conspicuous in the lateral view of lumbar spine X-ray images. The stage of a tumour will predict the probable prognosis as well as optimising treatment requirements. Neoplasms, Gastroduodenal Symptoms of this syndrome include those of upper limb ischemia, usually presenting as claudication, vertebrobasilar insufficiency (visual disturbances, dizziness, drop attack, ataxia, vertigo, syncope), and anterior circulation transient ischemic attacks. Patients with prior internal mammary to coronary artery bypass graft and associated subclavian steal may present with angina. Compression of the ipsilateral brachial artery is accompanied with clear change in the direction of the 1740 Steal Syndrome Vertebral Steal Syndrome Vertebral. In patients with the temporary type of vertebral steal syndrome, flow reversal is depicted during exercise or hyperemia of the ipsilateral upper extremity. Several techniques have been used to demonstrate the flow reversal in the vertebral artery. Interventional radiological treatment: Percutaneous angioplasty with or without stent placement has evolved as an alternative to the standard surgical management. Femoral artery approach is more commonly used; but when dealing with complete occlusions, a brachial artery approach may be necessary to cross the obstruction with the guidewire. The reversed flow in the ipsilateral vertebral artery has been shown to provide protection against stroke complication. Pathology and Histopathology Hepatic steatosis is a common condition which represents a non-specific response to many metabolic disorders and toxic insults. In all of these secondary fatty liver diseases, fat accumulation is associated with other abnormalities and is thought to result from liver cell injury. Another type of secondary fatty liver disease is unrelated to other liver diseases, but is due to metabolic disorders. Such causes include certain drugs, some gastrointestinal surgical interventions, malnutrition, parenteral nutrition and metabolic genetic diseases. Simple fatty liver is a benign condition and it occurs due to the accumulation of fat in the liver cells without flogosis or fibrosis. The fat is composed of triglycerides that accumulate in tiny sacs within the liver cells. The inflammatory cells can destroy the hepatocytes leading to necrosis (steatonecrosis). Necrosis is followed by fibrotic phenomena, while the last, irreversible stage is cirrhosis. Hepatic steatosis may present with a diffuse, subtotal, segmental or focal distribution. In non-diffuse steatosis, the fat may have an anatomic distribution (segmental steatosis) or a nonanatomic distribution (focal steatosis). The focal distribution of fat is related to local differences in portal perfusion; areas with lower portal supply tend to accumulate less fat. In other regions of the liver, focal sparing in fatty infiltration may reflect segmental portal vein obstruction (1). Actually, most patients are completely asymptomatic, but they may occasionally have vague Definition Accumulation of fat in tiny sacs within the hepatocytes. The symptoms and signs of liver failure include jaundice, severe weakness, loss of appetite, nausea, vomiting.

Subsequently, orthogonal mammographic views are acquired for documentation purposes. According to the "European Guidelines for Quality Assurance" (pathology), the biopsy samples are microscopically evaluated after rapid embedding (approximately 2 h) and in traditional paraffin cuts (24 h). In cases of discordant findings, repeated intervention or open/excisional biopsy/resection is mandatory. In benign findings, follow-up mammography is performed 6 and 12 months following biopsy. Stereotactic vacuum biopsy can also be carried out in the upright position (seated patient). Appropriate patient positioning makes it possible to visualize lesions adjacent to the chest wall as well. B Results In the current literature, sensitivity and specificity values of up to 100% are reported. Through several fenestrations within those compression pads, biopsy needles or markers can be placed following exact three-dimensional localization. In bore magnet or closed systems, real-time control of interventions is impossible; they must be performed outside of the bore instead. In cases of lesion progression, surgery (for definite clarification) is obligatory. Breast, Cysts Fluid-filled structures derived from the terminal duct lobular unit. Traditionally, mammography has been produced as analog images with screen-film combinations. Digital imaging technology has now been introduced in diagnostic radiology, but for many years no adequate digital technique was available for mammography. It was assumed that digital mammography would require spatial resolution similar to that of Bibliography 1. However, it has been shown that other features of digital systems could compensate for the lower spatial resolution, leading to better detection of microcalcifications. In digital mammography, contrast can be changed in postprocessing by windowing and leveling. The further advantage of digital systems is the high dynamic range and the linear relationship between dose at the detector and signal intensity, as opposed to the sigmoid relationship between optical density and dose in screen-film systems. The main advantage of any digital imaging system is the separation of image acquisition, processing, and display, allowing optimization of each of these steps. In addition, advanced applications such as computer-assisted detection/diagnosis can be easily applied to the digital mammogram. Digital Systems Various equipment manufacturers have adopted different approaches to digital mammography. Photostimulable phosphor computed radiography was the first digital imaging system to be used for mammography. The imaging plate is contained within a cassette, which can be used in a standard mammography machine without modification. After exposure, the cassette containing the imaging plate is inserted into a reader. The emitted light is detected by a photomultiplier system, and the resultant electrical signal is digitized. Other systems combine digital storage phosphor plates with the direct magnification technique and an X-ray tube with a very small focal spot.

Probably, because of the calcifications within thoracic disc herniations, posterior approaches have had poor results with frequent neurological complications leading to a more severe deficit compared to the preoperative status. Because of the low incidence of thoracic disc herniations patients are treated in specialized centers, reducing the risks of surgery. The posterolateral approach employs costotransversectomy, and provides access by removing the proximal rib and transverse process. This classical approach has recently been replaced by a less invasive microscopic approach. Large thoracotomy approaches with division of the diaphragm at the disc level between the 12th thoracic and 1st lumbar vertebrae have nowadays been replaced by thoracoscopic techniques and more recently by mini-open thoracotomies using an incision of less than 4 cm and normal ventilation of both lungs. One in every 1586 Radiculopathy scan may be beneficial when bony compression is suspected or even an ossified posterior longitudinal ligament. The surgical procedure may be altered depending on the presence and location of calcifications. The same holds true for the thoracic spine, where some surgeons also prefer to have spinal angiography performed to localize the Adamkiewicz artery, the major spinal cord feeder, before deciding on the side of a transthoracic approach. Postoperative imaging is done frequently as a routine measure in thoracic and cervical pathology, but after surgery of lumbar disc herniations only when complaints persist or recur. It represents the most assessed method for percutaneous thermal ablation of hepatic malignancies. Radiographic Iodinated Contrast Media A radiographic iodinated contrast medium is an imaging contrast agent in which iodine, bound to organic molecules, provides the increased attenuation to X-rays required for visualization. Brachial Ischemia Radionuclide Cystography Scintigraphic examination with direct or indirect administration of radionuclide for exclusion or detection of vesicoureteral reflux. Contrast Media, Ultrasound, Applications in Vesicoureteral Reflux Receptor Imaging Receptor Studies, Neoplasms Radiotracer A very small mass of the molecule of interest that is radiolabelled to evaluate the behaviour of the compound of interest. It manifests clinically with acute peripheral facial nerve paralysis and vesicular eruptions over the ear, face and neck. Facial Nerve Palsy Receptor imaging; Targeted tumor imaging Definitions Receptors are proteins on the cell membrane, in the cytoplasm, or in the nucleus of the cell that bind ligands such as neurotransmitters, hormones, or others. This interaction between the receptor and its ligand initiates a cellular response. The profile of expressed receptors is different for cells with different functions. In many neoplasms, the cellular production of certain receptors is upregulated, and therefore they are overexpressed. Agonists initiate a cellular response after their binding to the receptor, whereas antagonists occupy the binding site of a receptor without causing a response. Typically the skin discoloration follows a time course with primary paleness, then a livid aspect, and subsequent reddening in the phase of painful hyperemia. Connective Tissue Disorders, Musculoskeletal System 1588 Receptor Studies, Neoplasms Characteristics Nuclear medicine offers the opportunity to visualize receptors by labeling a ligand with a radionuclide suitable for imaging. The radiolabeled ligands used are mainly molecules similar to the natural ligand, often peptides. Beside peptides, other ligands such as antibodies, parts of antibodies, or artificial molecules can be used. These ligands can be from both categories, either receptor agonists or receptor antagonists. Antagonists have the disadvantage that they are mostly not internalized into the cell, which often results in a shorter retention time of the radioactivity in the target. Radiolabeled ligands have to fulfill a number of prerequisites such as metabolic stability, high receptor affinity, favorable toxicity profile, and stable binding of the radionuclide to be useful for in vivo imaging. Not only the radiolabeled ligand but also the receptor must fulfill a number of prerequisites. To visualize a tumor, the target receptor has to be overexpressed on the tumor cells. In addition, an exclusive expression of the target receptor on the tumor is desirable to achieve a higher tumor-to-non-tumor ratio with the radiolabeled ligand. Generally, the higher the expression of the target and the more exclusively the target is expressed on the tumor, the higher the sensitivity for the consecutive imaging procedure. Other important parameters determining the success of tumor receptor imaging are localization of the receptor on the cell and the biological behavior of the receptor after the binding of the ligand. Receptor-Mediated Radionuclide Therapy Apart from receptor imaging, receptor-mediated radionuclide therapy is an emerging field in nuclear medicine for treating malignant, metastatic tumors.