Scope and Technic of Soft-Tissue Roentgenography

Abstract

The systematic investigation of soft tissue by radiographic methods has been attempted spasmodically since the days of pioneers. Technical difficulties, however, have been such that, with a few exceptions, the method has not become a general routine. That soft tissue roentgenography has advanced the diagnostic scope of the roentgenologist there can be no doubt. Moreover, the attention to technical details necessary for this work will result in films of improved quality even when employing the usual technics. Let us consider briefly the practical value of soft-tissue roentgenography. We demand the same detail in the soft tissues as is necessary in the study of bones; the usual conception of mere outlines of various muscle groups, for instance, will not suffice. It is possible to visualize the normal arteries and veins, particularly at the flexures; the earliest calcification in their walls becomes visible. It is possible to delineate varicose veins. This is particularly significant as regards the deep-seated ones to determine whether or not injection therapy should be used. Non-osseous tumors form an interesting group of cases. Often valuable information can be obtained as to extent, location, or presence of invasive properties. Muscle structure is well shown. This affords a fine opportunity to study soft anatomy, especially in relation to the bone. Calcification in muscles and rupture, if in a favorable location, can be diagnosed. While of necessity the dense bone detail is unsatisfactory, very early periosteal changes, malignant or inflammatory, become demonstrable; also early callus formation. Gall-bladder shadows following the administration of dye, particularly by the oral method, become denser and there is considerable improvement in the delineation of abdominal masses over the usual technic. The basic essential principle is to use a low peak voltage and high milliampere-second ratio. The three important limiting factors are: (1) capacity of x-ray tube; (2) thickness of the part, and (3) speed necessary to stop motion. In general, a 250 to 300 milliampere-second ratio, keeping the kilovoltage as low as possible consistent with adequate penetration, is best. This means for the majority of work 100 ma. for three seconds, the K.V.P. to be varied according to the thickness of part. A decrease in the time factor must of necessity mean an increase of the load on the tube. The use of a high milliampere-second ratio improves soft-tissue detail even if the Potter-Bucky diaphragm is used. A word as to machines: Any outfit having an honest rating of 100 ma., with autotrans-former control of not more than 2.5 K.V.P. steps should suffice. The finer the regulation of the machine the better will be the results. A fluctuating supply line will interfere with consistent results. Intensifying screens are used if soft-tissue detail alone is desired. If bone and soft tissues together are to be studied, film holders are employed.