Is and in to a was not you i of it the be he his but for are this that by on at they with which she or from had we will have an what been one if would who has her. Keywords for The Engines of Our Ingenuity If you use Netscape or Microsoft Internet Explorer, pull down the Edit menu and use the Find function to search this file. Ab-przedrostek do ozn.
Urologic Imaging Without X- rays - Ultrasonography, MRI, and Nuclear Medicine: Urologic Ultrasound, Prostascintigraphy, Magnetic Resonance Imaging. Ultrasonography was initially developed as a military tool and was adopted by the medical world after World War II. In 1. 96. 1, Schlegel et al first reported the usefulness of sonography in urology, for the detection of renal calculi. Ultrasonography is mainly performed by radiologists. However, nonradiologist clinicians commonly perform and interpret specific types of ultrasound (eg, obstetricians, fetal ultrasound; urologists, transrectal ultrasound . Therefore, physicians should observe ultrasound studies during the examination. For excellent patient education resources, visit e.
Clinical Practice Guidelines for Clostridium difficile Infection in Adults: 2010 Update by the Society for Healthcare Epidemiology of America (SHEA) and the. Get the latest international news and world events from Asia, Europe, the Middle East, and more. See world news photos and videos at ABCNews.com. Artisti/Bändi-Cetjussa jo olevat nimet TARKISTETAAN tästä koosteesta + parasta aikaa auki olevasta säikeestä. Artisti/Bändi-Cetjua JATKETAAN viimeksi avatussa.
Medicine. Health's Cancer Center. Also, see e. Medicine. Health's patient education articles Magnetic Resonance Imaging (MRI) and Bladder Cancer.
Ultrasound Equipment and Physics. An ultrasound probe is a housing structure for an ultrasound transducer and the associated wiring for connection to a console with a computer.
The probe is shaped for the desired application, eg, cylindrical for endorectal use. The transducer generates high- frequency sound waves (typically 5- 1. MHz) and directs them through body tissues via a probe held against the skin.
Various probes and transducers are available for examination of different organs and body parts. The probe also contains a receiver to detect sound waves (called echoes) reflected from tissues. The electrical energy is processed by the computer in the ultrasound console to generate an image of minute white dots (pixels) corresponding to the returning signals. Displayed on a black background, the white pixels produce an image of assorted shades of gray.
When the sound waves travel easily through uniform substances (eg, water, oil, urine), no echoes are generated. The ultrasound image seen on the screen is therefore black; no echoes are present. When the sound waves encounter tissues of different densities, the sound waves are absorbed, reflected back to the probe, or transmitted through the tissue at different velocities. When this happens, the ultrasound image is white or gray depending on the intensity of the reflection. Unlike radiography or CT scans, ultrasound does not reveal tissue density. Rather, it shows sonotransmission (the passage or reflection of sound).
Highly dense tissues, such as bone or kidney stones, readily reflect echoes and, therefore, appear bright white on an ultrasound image. Air, such as in the bowel, also readily reflects echoes, so the edge of the bowel appears white on an ultrasound image. Thus, substances with widely differing densities (eg, air, bone) may appear bright white on an ultrasound image. The range of gray shades generated lends this imaging technique the alternative label . In order to produce a recognizable image, the transducer must be swept across the area of interest, producing multiple bands that are combined to form an image. The system for moving the transducer is called the scanner. As the speed at which the scanner sweeps across the imaged area decreases, resolution increases.
Coupling medium. The acoustic properties of soft tissue are very similar to those of water, but air is distinctly different; the presence of air between the probe and the tissue of interest can distort or obscure the image. For this reason, a water- density substance, termed a coupling medium, is used for transmission of the ultrasound image. This coupling medium is usually a sonographic jelly or lubricant and should be placed between the probe and the skin surface. Artifacts. The computer within the ultrasound console is designed with the assumption that ultrasound signals propagate through tissue at a constant velocity and reflect back to the transducer in a narrow, straight line. In fact, the velocity and angle of ultrasound wave propagation is affected by different tissue density, the rate of change in these tissue densities (abrupt vs gradual), and the dimensions and configuration of the transducer.
Such variations can lead to deviation of the ultrasound signals from the assumed direction of propagation, creating artifacts. Kossoff cautions that a feature should not be considered by the examiner to be real simply because it is displayed sonographically until it is appropriately evaluated from various angles. Conversely, a feature that is not displayed is not necessarily absent. This signal is ricocheted back and forth between the transducer and the reflector. An image representing the echogenic structure is accurately produced on the monitor, but each subsequent reflection of the sound wave back and forth, which takes twice as long to reach the transducer as the prior reflection, is interpreted by the transducer as another structure. This results in artifactual images, equally spaced, distal to the original reflector, and of decreasing intensity. In TRUS imaging, this effect is usually produced by the rectal wall and condom covering the probe and results in multiple hyperechoic arches evenly spaced between the rectal wall and the anterior aspect of the image.
Such an effect can be minimized by using copious amounts of coupling medium and ensuring that no air is between the probe and the rectum. Phase cancellation of the ultrasound signal can occur when the signal laterally strikes a curved structure, reflecting the signal laterally away from the transducer. The transducer interprets this absence of signal as an absence of tissue, which results in a lack of echoes on the image. In TRUS imaging, this artifact is often encountered during transverse sector scanning of large prostates. The sound waves striking the curve of the posterolateral margin of the prostate are scattered, resulting in a hypoechoic shadow extending anteriorly and laterally from this edge of the prostate. Similar shadows can also be generated by the posterolateral margin of the transition zone (TZ), resulting in additional shadows.
These shadows can be minimized by centering the probe under the lateral portions of the gland when inspecting this area of the prostate. Lateral and anterior refraction, also called dispersion or scatter, of the ultrasound signals is spread in a fanlike configuration away from the central portion of the image. Anterior refraction is not a significant problem in TRUS imaging of the prostate because the gland is relatively close to the transducer. Lateral refraction during sector scanning results in elongation of the lateral aspect of the image, creating a more bean- shaped image of the prostate than the actual spherical configuration of the gland. Renal Ultrasound. Normal appearance. The cortex (the periphery of the kidney tissue) is seen as gray with some darker circles spaced uniformly around the edge.
These darker circles correspond to the renal pyramids. A dromedary hump, the incidental finding of an extra mass of normal renal cortex tissue only on the lateral portion of the left kidney, is a normal variant. Relative to the liver parenchyma, the kidney is isoechoic (the same shade of gray) or slightly hypoechoic (a darker shade of gray). The liver is superior to the kidney and superficial (towards the top of the image). It is rather homogeneous (with a fairly regular gray pattern).
The kidney is not as homogeneous. These 2 organs can be compared to determine if renal medical disease is present. The center, or hilum, of the kidney contains multiple structures, such as the renal pelvis, blood vessels, nerves, fat, and lymphatics. The fat of the renal sinus is particularly echogenic (bright white). These structures transmit sound differently, and, as the sound waves hit these interfaces between 2 such structures, an echo is generated. Because of this, the renal hilum has increased echogenicity. A prominent column of Bertin is partial hypertrophy of the renal cortex protruding into the renal sinus, and this is another normal variant.
The upper pole of the kidney, particularly on the left, can sometimes be hidden behind rib shadows. This fact makes it very important for the sonographer to use breathing techniques and multiple windows to visualize the entire kidney. Doppler ultrasound examination is a useful adjunct to renal sonography. Color Doppler imaging can reveal whether blood flow to an area of tissue is increased, decreased, or normal, narrowing the differential diagnosis. In addition to the presence of blood flow, a waveform tracing can be generated to show the nature of the flow throughout the cardiac cycle. Normally, a renal waveform tracing shows a rapid rise to a peak during systole and a slow fall to a plateau during diastole. The tracing remains above the baseline throughout, indicating flow throughout systole and diastole.
The resistive index is a ratio and is essentially a measure of the end- diastolic flow in the arterial system (resistive index = . Typical resistive index is 7. The higher the resistive index, the higher the downstream resistance. A resistive index higher than 9. A high resistive index can also indicate ureteral obstruction and may serve as an indirect sign for a ureteral stone. Power Doppler is significantly more sensitive to flow than standard color Doppler and can demonstrate blood flow on the arteriolar level.
Obstruction. Ultrasound is the initial imaging modality of choice in any patient with an unexplained elevation of the creatinine level or recent onset of renal dysfunction. In most instances, the screening ultrasound images in the setting of acute renal failure are normal. Certain risk factors, such as prior obstruction, recent surgery, and pelvic neoplasms, can increase the likelihood of finding an obstructed kidney. The crucial finding of obstruction in renal ultrasound is renal pelvis and calyceal dilation characterized by effacement of the renal sinus fat by an anechoic- branched structure with posterior enhancement and through- transmission. This dilation involving the calyces and renal pelvis is termed hydronephrosis or pelvocaliectasis.