CT guided biopsy

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Percutaneous biopsy has become a widely used method of obtaining specimens for cytologic, bacteriologic, or pathologic examinations. Its usefulness in the lung,1, 2 genitourinary tract,2 liver, and bone2 has been repeatedly documented. Fluoroscopic and ultrasonic guidance have been beneficial in increasing the accuracy in yield of such percutaneous procedures, but there are certain shortcomings with both. The purpose of this paper is to (1) explain the imaging properties of computed tomography (CT) scanning which make it a useful tool for guiding percutaneous procedures; (2) describe techniques and instruments which can be utilized by this means; (3) discuss the indications for utilizing CT guided procedures compared to other conventional guidance means; and (4) review in each organ system the abnormalities we believe are suited to CT percutaneous procedure.

Advantages of CT guidance

The first distinct advantage of the CT method is the remarkable quality of the image provided by the scanner for detecting the pathology and guiding the instruments. The image is a complete anatomic cross section of all structures within the transverse slice including the solid parenchymal organs, major blood vessels, gas-filled intestine, and adjacent bony structures. Such a cross section “lays out” the anatomy without the superimposition of densities which can occur when using fluoroscopy or plain film. Because the CT scanner employs an x-ray beam which can penetrate both gas and bone, these two extremes of density can be displayed without such interference as occurs with ultrasound. Besides imaging extremes of density, the scanner can discriminate 2% density changes . . .



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