TY - JOUR
AU - Shepard, Robert D.
AB - Practical Application of the 0.3-mm. Focal Spot A Special Cassette Holder Ollie J. Sparks , R.T. and Robert D. Shepard , M.D. Lexington, Ky. Excerpt Following the acquisition of a tube with a 0.3-mm. focal spot, a study was instituted to determine the progression of healing in femoral neck fractures with “macro” views. During the initial phase of the research, difficulty was experienced in obtaining an entirely satisfactory lateral view since the cassette for this projection was held at the desired angle and distance by sandbags alone. It was quickly realized that this crude method would never suffice, since it was practically impossible to be certain that the film was held perpendicular to the central beam. The unsharpness associated with the use of double-emulsion film is well known. It is also common knowledge that this inherent unsharpness is further aggravated by angulation of the x-ray focus with respect to the plane of the film. Also, the increased object-film distance in direct enlargement procedures obviates the necessity of having the plane of the film angled with respect to the central ray, since the film can be rotated so as to intercept the ray in the perpendicular plane. To overcome this problem and to assure precise centering of film and focal spot, a special detachable cassette holder was designed by one of the authors (O.J.S.). This device, shown in use in Figure 1, is constructed of light aluminum tubing and consists of three parts: (1) a vise-type clamp (A, Fig. 2) permanently attached to the tube housing between the housing and cone track; (2) a short horizontal frame with a second vise-type clamp at its outer end (B, Fig. 2); (3) a vertical frame (C, Fig. 2), held by this clamp, with the cassette holder at the lower end. These three parts, when assembled, are in relatively the same position as shown in Figure 2. The design is such that the film is always centered to the central ray regardless of tube angulation. There is a maximal adjustable length of 16 inches, permitting a variation of target-film distance from 44 to 60 inches. When in use, the tube is angled to the desired degree and the cassette holder is then stabilized by resting its weight on an aluminum rod (Fig. 1). This rod slides in a pivot-pin arrangement that can be manually tightened at the desired height. Figure 1 illustrates the cassette holder in relation to tube angulation and the patient. The table used in this particular technic is an old, war-surplus, portable unit with a Micarta top. The legs have been immobilized by an angle-iron, rectangular brace to provide improved structural strength, and rubber casters allow mobility of the unit. Attached to the legs are threaded bolts with a crank to lower them to the floor for the purpose of anchoring the table. A more practical application of this device was found in the examination of seriously injured patients; that is, persons who had sustained serious vertebral injuries that would not allow movement other than in a horizontal plane.
TI - Practical Application of the 0.3-mm. Focal Spot
JF - Radiology
DO - 10.1148/69.4.578
DA - 1957-10-01
UR - https://www.deepdyve.com/lp/radiological-society-of-north-america-inc/practical-application-of-the-0-3-mm-focal-spot-zXjePzT5BW
SP - 578
VL - 69
IS - 4
DP - DeepDyve
ER -