Ultrasound is also limited by its inability to image through air pockets lungs, bowel loops or bone. Its use in medical imaging has developed mostly within the last 30 years. The first ultrasound images were static and two-dimensional 2D , but with modern ultrasonography, 3D reconstructions can be observed in real time, effectively becoming "4D". Because ultrasound imaging techniques do not employ ionizing radiation to generate images unlike radiography, and CT scans , they are generally considered safer and are therefore more common in obstetrical imaging.
The progression of pregnancies can be thoroughly evaluated with less concern about damage from the techniques employed, allowing early detection and diagnosis of many fetal anomalies.
Ultrasound of the Gastrointestinal Tract | Giovanni Maconi | Springer
Growth can be assessed over time, important in patients with chronic disease or pregnancy-induced disease, and in multiple pregnancies twins, triplets, etc. Color-flow Doppler ultrasound measures the severity of peripheral vascular disease and is used by cardiologists for dynamic evaluation of the heart, heart valves and major vessels. Stenosis , for example, of the carotid arteries may be a warning sign for an impending stroke. A clot , embedded deep in one of the inner veins of the legs, can be found via ultrasound before it dislodges and travels to the lungs, resulting in a potentially fatal pulmonary embolism.
Ultrasounds is useful as a guide to performing biopsies to minimise damage to surrounding tissues and in drainages such as thoracentesis. Small, portable ultrasound devices now replace peritoneal lavage in trauma wards by non-invasively assessing for the presence of internal bleeding and any internal organ damage. Extensive internal bleeding or injury to the major organs may require surgery and repair. MRI uses strong magnetic fields to align atomic nuclei usually hydrogen protons within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the radio frequency signal generated as the nuclei return to their baseline states.
An advantage of MRI is its ability to produce images in axial , coronal , sagittal and multiple oblique planes with equal ease. MRI scans give the best soft tissue contrast of all the imaging modalities. With advances in scanning speed and spatial resolution, and improvements in computer 3D algorithms and hardware, MRI has become an important tool in musculoskeletal radiology and neuroradiology.
One disadvantage is the patient has to hold still for long periods of time in a noisy, cramped space while the imaging is performed. Recent improvements in magnet design including stronger magnetic fields 3 teslas , shortening exam times, wider, shorter magnet bores and more open magnet designs, have brought some relief for claustrophobic patients. However, for magnets with equivalent field strengths, there is often a trade-off between image quality and open design. MRI has great benefit in imaging the brain, spine, and musculoskeletal system. The use of MRI is currently contraindicated for patients with pacemakers, cochlear implants, some indwelling medication pumps, certain types of cerebral aneurysm clips, metal fragments in the eyes and some metallic hardware due to the powerful magnetic fields and strong fluctuating radio signals to which the body is exposed.
Nuclear medicine imaging involves the administration into the patient of radiopharmaceuticals consisting of substances with affinity for certain body tissues labeled with radioactive tracer. The most commonly used tracers are technetiumm, iodine, iodine, gallium, indium, thallium and fludeoxyglucose 18F 18F-FDG. The heart , lungs , thyroid , liver , brain , gallbladder , and bones are commonly evaluated for particular conditions using these techniques.
While anatomical detail is limited in these studies, nuclear medicine is useful in displaying physiological function. The excretory function of the kidneys, iodine-concentrating ability of the thyroid, blood flow to heart muscle, etc. The principal imaging devices are the gamma camera and the PET Scanner, which detect the radiation emitted by the tracer in the body and display it as an image. With computer processing, the information can be displayed as axial, coronal and sagittal images single-photon emission computed tomography - SPECT or Positron-emission tomography - PET.
Barium X-Rays (Upper and Lower GI)
In the most modern devices, nuclear medicine images can be fused with a CT scan taken quasisimultaneously, so the physiological information can be overlaid or coregistered with the anatomical structures to improve diagnostic accuracy. Positron emission tomography PET scanning deals with positrons instead of gamma rays detected by gamma cameras. The positrons annihilate to produce two opposite traveling gamma rays to be detected coincidentally, thus improving resolution. In PET scanning, a radioactive, biologically active substance, most often 18F-FDG, is injected into a patient and the radiation emitted by the patient is detected to produce multiplanar images of the body.
Metabolically more active tissues, such as cancer, concentrate the active substance more than normal tissues. PET images can be combined or "fused" with anatomic CT imaging, to more accurately localize PET findings and thereby improve diagnostic accuracy. The technology recently blossomed after passing the technical hurdle of altered positron movement in strong magnetic field thus affecting the resolution of PET images and attenuation correction. Interventional radiology IR or sometimes VIR for vascular and interventional radiology is a subspecialty of radiology in which minimally invasive procedures are performed using image guidance.
Some of these procedures are done for purely diagnostic purposes e.
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The basic concept behind interventional radiology is to diagnose or treat pathologies , with the most minimally invasive technique possible. Minimally invasive procedures are currently performed more than ever before. These procedures are often performed with the patient fully awake, with little or no sedation required. Interventional Radiologists and Interventional Radiographers  diagnose and treat several disorders, including peripheral vascular disease , renal artery stenosis , inferior vena cava filter placement, gastrostomy tube placements, biliary stents and hepatic interventions.
Images are used for guidance, and the primary instruments used during the procedure are needles and catheters. The images provide maps that allow the clinician to guide these instruments through the body to the areas containing disease. By minimizing the physical trauma to the patient, peripheral interventions can reduce infection rates and recovery times, as well as hospital stays.
To be a trained interventionalist in the United States, an individual completes a five-year residency in radiology and a one- or two-year fellowship in IR. Teleradiology is the transmission of radiographic images from one location to another for interpretation by an appropriately trained professional, usually a Radiologist or Reporting Radiographer.
- Ultrasound of the Gastrointestinal Tract (Medical Radiology / Diagnostic Imaging).
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It is most often used to allow rapid interpretation of emergency room, ICU and other emergent examinations after hours of usual operation, at night and on weekends. In these cases, the images can be sent across time zones e. However at present, large private teleradiology companies in the U.
Teleradiology can also be used to obtain consultation with an expert or subspecialist about a complicated or puzzling case. In the U.
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Teleradiology requires a sending station, a high-speed internet connection, and a high-quality receiving station. At the transmission station, plain radiographs are passed through a digitizing machine before transmission, while CT, MRI, ultrasound and nuclear medicine scans can be sent directly, as they are already digital data. The computer at the receiving end will need to have a high-quality display screen that has been tested and cleared for clinical purposes.
Reports are then transmitted to the requesting clinician. The major advantage of teleradiology is the ability to use different time zones to provide real-time emergency radiology services around-the-clock. The disadvantages include higher costs, limited contact between the referrer and the reporting Clinician, and the inability to cover for procedures requiring an onsite reporting Clinician.
Laws and regulations concerning the use of teleradiology vary among the states, with some requiring a license to practice medicine in the state sending the radiologic exam. Lastly, the major benefit of teleradiology is that it can be automated with modern machine learning techniques. Radiology is a field in medicine that has expanded rapidly after due to advances in computer technology, which is closely linked to modern imaging techniques. Applying for residency positions in radiology is relatively competitive. Applicants are often near the top of their medical school classes, with high USMLE board examination scores.
The American Board of Radiology ABR administers professional certification in Diagnostic Radiology, Radiation Oncology and Medical Physics as well as subspecialty certification in neuroradiology, nuclear radiology, pediatric radiology and vascular and interventional radiology. The Core Exam is given after 36 months of residency.
What is an Endoscopic Ultrasound?
A , Ileocecal region with mild wall thickening in the terminal ileum arrows shown on a transverse image through the right lower quadrant. B , Enlarged paramesenteric lymph nodes shown on a transverse image through the right lower quadrant. Infantile hypertrophic pyloric stenosis is a common entity and affects 2 to 3 per live births.
Boys are affected 4 times more frequently than girls. A length of the pyloric channel of 14 mm or greater and the thickness of the pyloric muscle of 3 mm or greater are used as sonographic criteria for the diagnosis of infantile hypertrophic pyloric stenosis Figure An increase in diameter to greater than 6 mm in an adult patient with right lower quadrant pain is highly suggestive of acute appendicitis.
Vascularity in the wall may be increased. Sonographic features associated with perforation are loculated pericecal fluid, phlegmon, abscesses, and prominent pericecal fat Figure 13 A—C. Diverticula are multiple and most commonly located in the sigmoid and descending colon. Complications of diverticulitis include macroperforation or microperforation and localized abscess or fistula formation to the bladder, vagina, skin, or other bowel loops.
On sonography, segmental concentric thickening of the colon is seen. Peridiverticular abscess formation is seen as loculated fluid collections in an intramural pericolonic or remote location. Fistulas appear as linear tracts that extend from the involved segments of the gut to the bladder, vagina, or adjacent loops Figure 14 , A and B.
Carcinoma of the stomach: sonographic images showing a localized large mass in the antrum of the fluid filled stomach A , which proved to be a large leiomyoma, and diffuse thickening of the stomach wall in the linitis plastica on a transverse image through the epigastric region B. Intussusception is commonly seen in children as ileocolic or jejunojejunal intussusception and sometimes associated with a lead point in the form of a tumor or hypertrophied Peyer patches.
In adults, intussusception is commonly associated with a lead point in the form of a tumor.
The sonographic appearance of concentric rings in the transverse section is pathognomonic for intussuception. It predisposes to bowel obstruction and infarction. On sonography, an abnormal relationship between the superior mesenteric vein and superior mesenteric artery is suggestive of this diagnosis. On a transverse sonogram, reversal of the normal relationship between the mesenteric vessels is seen; the superior mesenteric vein is on the ventral left aspect of the superior mesenteric artery Figure 16 , A and B.
Infection is a common cause of colitis. Other causes for colitis include ischemic factors, parasites, and radiation.