Page 31 - A Practical Guide to Equine Radiography

12 A PRACTICAL GUIDE TO EQUINE RADIOGRAPHY

• It is influenced by the following. ○ Using plate and X-ray machine stands
VetBooks.ir − Focus–film distance (FFD): the bigger, rather than hand-holding equipment.

This has the added advantage of reduc-
the sharper; try to avoid going below the
standard 100 cm FFD. The focus point of a ing radiation exposure to yourself and
others.
high-output machine is usually marked by ○ Use of a head stand may help steady the
a red dot; in portable machines you may whole horse.
assume it is somewhere in the centre. ○ Adequate sedation; a combination of
− Distance between the object and the X-ray butorphanol and detomidine or romifi-
plate: the smaller, the sharper. Make sure dine usually works well.
you keep your plate as close to the horse ○ Keeping exposure times as short as
as is safely possible. This also minimizes possible. This may be challenging for
magnification (Fig. 3.1). the higher exposure radiographs since
− Movement blur: this can be caused by small machines are limited in their mA
movement of the horse, the plate or the output, hence times must lengthen for
X-ray generator. The risk of movement higher exposures. As a rule of thumb, try
blur can be minimized by the following: to keep the exposure time under 0.2 s.

Figure 3.1 This figure illustrates the effect of object–plate distance on image sharpness and magnification.
In the image on the top, the plate was close to the fetlock joint on this lateromedial radiograph, compared to
the bottom image where there was a distance between the two. The image on the top has sharper edges and
is smaller compared to the bottom image.

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