Plus-Hex CLINICAL
Radiation safety is paramount when carrying out pelvic radiography due to the high exposure levels . All personnel involved must wear appropriate personal protective equipment . This should include a lead gown , thyroid guard and dosimeter badges , and lead gloves for the plate holder – although the plate should be held only if absolutely necessary , and ideally a plate-holding stand or gantry should be used .
The generator that creates the X-ray beam needs to be powerful enough to enable the high exposure settings required , but easy to manoeuvre , for the safety of both patient and operator . The generator is large and heavy and , as mentioned earlier , should be supported by a stand or gantry , rather than being held by hand .
The large , dense tissues require high exposures , and the primary beam is often directed horizontally or upwards , resulting in significant scatter . Depending on the area being imaged , a minimum of three or four people may be required in the radiography suite : one to hold the plate ( if needed ), one to hold the horse , one to take the radiograph and one to potentially abduct the limb for ventrodorsal projections . Other team members may have a clinical interest in these X-rays , as they are not regularly taken , but their involvement and the images required must be weighed against the risk of radiation exposure .
A grid should be used to reduce the amount of scatter , although it will increase the amount of radiation used . The grid focuses the X-ray beam to produce a clearer image by reducing the amount of scatter produced [ 3 ] . If the image quality is poor or undiagnostic , stop and evaluate the technique ; even experienced radiographers occasionally need to adopt a different approach .
Radiograph settings
As radiation safety is paramount , radiograph settings should be kept as low as possible while still providing an image of diagnostic quality . Table 1 shows examples of the settings used by the author as a baseline for a 500 kg horse .
Table 1 . Examples of radiograph settings .
Area kV mAs Tuber coxae 76 80 Coxofemoral 119 125 Ilial shaft 150 200 Ischium 110 140
Specific projections and positioning
Coxofemoral joint / acetabulum | Ventromedial 10 ° – dorsolateral oblique
A minimum of three people are required to acquire images of the coxofemoral joint and acetabulum ( Figure 1 ): a horse handler , someone to abduct the limb and someone to take the image . A fourth person may be needed to hold the plate , but it is preferable to use a stand . Most plates will have an anti-scatter grid with lead behind to obtain the best possible image . The patient should be standing squarely where possible , and in most cases will be lightly sedated . The affected limb is lifted by an assistant , flexed and abducted as much as the patient will tolerate . The generator is positioned under the horse from the opposite side to the affected limb , with the beam centred in the inguinal region immediately lateral to the midline ( Figure 2 ).
Figure 1 . Radiographic image of a left hip joint .
Plate with grid
Generator
Figure 2 . Positioning of the plate and generator .
Volume 39 ( 2 ) • April 2024
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