The traditional evaluation of the patient includes the history and physical examination and a well-planned set of diagnostic tests, often including imaging. Dramatic advances in imaging not only supplement the physical examination, but also now may begin to substitute for part of it. Medical imaging provides an approach for dividing patients into patients who have an acute compared with a chronic medical problem and patients who have an anatomic compared with a "biochemical" illness. These determinations are crucial for prompt and effective medical and surgical therapy. A key issue for clinicians is determining the appropriate role for imaging in a patient. Ultrasonography is highly accurate for the diagnosis of cholelithiasis, but it is less clear how to decide when a patient with right upper quadrant pain needs ultrasonography, computed tomography (CT), an upper gastrointestinal radiographic series , endoscopy , or no imaging study whatsoever. Optimum choices among the armamentarium of tests guide efficient and cost-effective care.
[...] STAGING OF ONCOLOGIC DISEASES Diagnostic imaging is a principal method for presurgical staging of neoplastic disease and is essential for evaluating the response to therapy and long-term surveillance. Extent of the primary tumor, invasion or encasement of adjacent structures, presence of regional or distant lymphadenopathy, and distant metastases can be evaluated by cross-sectional imaging with great accuracy. PET is highly sensitive but nonspecific for neoplastic disease. The search for an unknown primary tumor in the presence of metastatic disease is challenging ( Chapter 210 With the advent of MRI and high-resolution multislice CT, more than 50% of initially unknown primary tumors now can be found. [...]
[...] ULTRASOUND Medical ultrasound imaging grew out of the SONAR (SOnic Navigation And Ranging) technology developed during World War II for submarine warfare. Images are created based on the time delay and intensity of echos returned from tissue after a short pulse of ultrasonic energy, emitted and received by a transducer held in contact with the body. Ultrasound is nonionizing radiation and considered safe for the unborn fetus and other sensitive tissues. With appropriate instrumentation, it is possible to create "tomographic" or slice images, with real-time motion, of body parts if the path of the sound does not hit gas or bone, both of which severely attenuate the sound. [...]
[...] At least three other imaging choices exist: no imaging study, a plain radiographic series of the abdomen (technically and economically similar to the chest radiograph but generally not as useful), and MRI of the abdomen or pelvis (usually reserved for more complex situations or after failure to diagnose with other methods). Other than identifying free intraperitoneal air (perforated viscus), gas patterns of bowel obstruction, and radiodense ureteral calculi, the traditional abdominal series, although the least expensive test, is considered generally inferior to CT and has been largely replaced by CT. [...]
[...] Arenito Applications and limitations of diagnostic imaging The traditional evaluation of the patient includes the history and physical examination and a well-planned set of diagnostic tests, often including imaging. Dramatic advances in imaging not only supplement the physical examination, but also now may begin to substitute for part of it. Medical imaging provides an approach for dividing patients into patients who have an acute compared with a chronic medical problem and patients who have an anatomic compared with a "biochemical" illness. [...]
[...] It is crucial to base the choice of imaging examination on the presenting problem of the patient to gain the most information on which to narrow the differential diagnostic possibilities. For many, but not all, abnormalities (pulmonary embolism being the most prominent exception), a conventional radiograph can help distinguish among pulmonary, cardiac, and thoracic causes. The most common pulmonary causes of shortness of breath are consolidative pneumonia, atelectasis (collapse), pleural effusion with or without atelectasis, pneumothorax, and pulmonary embolism. For otherwise healthy patients with documented pulmonary embolism, the chest radiograph is often normal. [...]
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