Clin. RadioL (1970) 21, 320-322

A S I M P L E M E T H O D T O D E M O N S T R A T E T H E R I B S A N D

LEON MORRIS and J. BAILEY

From the Radiodiagnostic Department, The London Hospital, E.1

S T E R N U M

A simple, reliable method to demonstrate the ribs and sternum is described and illustrated. The method relies on mechanical fixation of the thoracic cage by a Bucky band with consequent blurring of the lung markings by diaphragmatic breathing. The film is exposed during quiet respiration.

CLEAR radiographic demonstration of the ribs is often difficult, and small lesions may easily be overlooked. This is mainly because pulmonary shadows tend to obscure bone detail. The same applies to a lesser extent to the sternum. This paper describes a simple method whereby these structures may be demonstrated with greater clarity.

METHOD The patient lies prone on a Bucky radiographic

table. A broad Bucky band is drawn firmly across the patient's chest to include the lower ribs. For demonstrating the ribs, the patient is placed so that the area in question is projected clear of the dorsal

spine. Only minor degrees of rotation are usually necessary. Alternatively, the patient may lie fiat and the tube can be off-centred to produce the same effect. For examination of the sternum, the patient is rotated just sufficiently to throw the sternal shadow clear of the dorsal spine. The left anterior oblique position is preferable because the sternum is not only projected clear of the dorsal spine, but the heart shadow is partly eliminated. Exposure factors depend on the generator used, film and screen speed, and the build of the patient. The main essentials are a relatively low kilovoltage and an exposure time of 1.5 to 2 secs. Average factors for this series have been: 70 KvP, 50 Ma, for 1.5 to 2 secs. at a focal-film distance of 48 in. (120 cm.). With

Fro. 1 FIG. 2

FIG 1.--Oblique view of ribs and sternum using chest fixation, and long exposure. Normal appearances. FIo. 2.--Oblique view of sternum using chest fixation and long exposure. Fenestration in the lower sternum is clearly seen. (arrows)

320

A S I M P L E M E T H O D TO D E M O N S T R A T E THE RIBS A N D STERNUM 321

FIG. 3A FIG. 3B

FIG. 3A.--Postero-anterior view of left ribs using conventioaal technique. Normal appearances. FIG. 3B.--Same case as Fig. 3A Patient slightly oblique,

using chest fixation and long exposure.

FIG. 4A FIG. 4B"

FIG. 4A.--Film of left ribs using conventional technique. There is an irregular expanding lesion in the sixth left rib. FIG. 4B.--Same case as Fig. 4A using chest fixation and long exposure. The lesion in the sixth left

rib is more dear ly shown.

322 CLINICAL RADIOLOGY

thin patients, and especially where low milliamper- age settings are not possible, it may be necessary to mask the back screen of the cassette with opaque paper to avoid overblackening. Normal breathing is allowed to continue during the exposure of the film.

DISCUSSION

By placing the patient in the prone position, the body weight and the added restriction provided by the tight Bucky bank almost completely elimate rib movement, and only diaphragmatic respiration can take place. This combination of factors renders a clear demonstration of the ribs and at the same time blurs out the lung shadows. Similar results were obtained by Finkelshtein (1967) using a slightly different method. He laid the patient on 2 moulded blocks, one under the chest and the other under the pelvis, thus transferring the body weight to two relatively small areas, and so restricting movement. No Bucky band was used. However, this method is rather uncomfortable, particularly in elderly or ill patients, and our method would appear to have no disadvantages when compared with that of Finkel- shtein.

I t may be noted that, a recent rib fracture may inhibit movement so that a clear picture may result without the need for mechanical restriction of the rib cage, or of respiration during exposure (Fig. 5).

FI~. 6 Zonogram of the right ribs. Only the anterior

ends of the ribs are clearly seen.

Narrow angle tomography (zonography) using a linear movement, which gives a greater depth of cut than conventional tomography (Ettinger and Fain- singer 1966), was compared with our method. It produced satisfactory visualisation of the unblurred portion of the ribs (Fig. 6), but was limited to only part of the ribs. Similarly, in demonstrating the sternum, our method produced delineation of structures as clear as, or clearer, than did zonography, but had the advantages of wider coverage and simpler technique.

In demonstrating the sternum, the use of the "quiet breathing film" (Clark 1964) will produce satisfactorily clear pictures, but movement of the bony thorax is not actively restricted, and some movement of the sternum inevitably occurs, allow- ing blurring of the image. The method described here eliminates this disadvantage.

Aeknowledgement.--We wish to thank Mr. R. F. Ruddick and the staff of the Photographic Department, The London Hospital, who prepared the illustrations.

FIG. 5

Oblique film of left ribs showing a fracture of the fifth rib. No mechanical chest fixation, but the

fracture inhibits rib movement.

REFERENCES CLARK, K. C. (1964). Positioning in Radiography. Ilford,

p. 234. ETTINGER, A. & FAINSINGER, M. H. (1966). Zonography in

daily radiological practice. Radiology, 87, 82-86. FINKELSHTEIN, S. I. (1967). Radiological examination of the

ribs. Vest. Rentg. Radiol., 42, 46-52.