A guided ray satisfies the relation given by where θr is the angle the ray makes with the fiber axis, r is the radial position, i.e. , radial distance, of the ray from the fiber axis, nr is the refractive index at the radial distance r from the fiber axis, and na is the refractive index at the core radius, a, i.e. , at the core-claddinginterface. Guided rays correspond to bound modes, i.e. , guided modes, in terms of modes rather than rays. Synonymsbound ray, trapped ray.
X-ray guided aspiration of joint fluid followed by injection of anesthetic and steroid into the joint.
The purpose is obtain sample of joint fluid for analysis (if fluid is present), determine if the joint is the cause of pain (as determined by response to injection), and to obtain temporary pain relief lasting hours to months.
X-ray or ultrasound guided placement of a needle into an abnormality found on physical exam or radiology examination.
Mammography is an excellent way to detect breast abnormalities, but in many cases it is not possible to tell from the imaging studies alone whether a growth is benign or cancerous.
X-ray images also are used to place a guide wire into the suspicious area in order to help locate the lesion during open surgical biopsy, which is performed in an operating room.
Lesions accompanied by diffuse calcium deposits scattered throughout the breast are difficult to target by stereotactic biopsy.
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