Keywords:
Dosimetric comparison, Radiation safety, Equipment, Comparative studies, Digital radiography, Paediatric
Authors:
L. Bowden, A. Moran, C. Saidlear, A. Mooney, Y. Sheikh, E. L. Twomey, S. Ryan; Dublin/IE
DOI:
10.26044/ecr2019/C-2816
Results
Table 2 presents the results of the dose audit.
The average (and range of) exposure factors for both systems are indicated.
The average dose used in the DR system was found to be 32% less than the dose when using the CR system.
Figure 2 shows a comparison of a CR image with a DR for patients of similar age.
While there is a slight perceived reduction in the sharpness and contrast of the of the DR image,
the position of the femoral head and the configuration of the acetabula can be equally assessed in each image.
Diagnostic information is thus preserved.
When the image diagnostic quality review was undertaken by the Radiologists they agreed that the lowest point of iliac bone was clearly defined on all of the sample images regardless of modality. The point of junction of the lateral border of the iliac bone and the outer end of the roof of the acetabulum bone was clearly identifiable on all CR images and on all but one hip (95% Y,
5%N) on DR radiographs.
Both radiologists agreed that accurate assessment of the position of the femoral head was possible in all images.
Discussion
In infant hip radiographs for diagnosis and management of DDH,
we have achieved a significant reduction in radiation dose when using DR compared to radiographs obtained by CR.
In relation to image quality of the baby radiographs for DDH,
two main features are assessed:
- the position of the femoral head – whether in the joint or displaced or dislocated,
- the configuration of the acetabulum - normal or dysplastic (shallow).
The acetabular angle is used to measure the configuration of the acetabulum. This is an angle between a horizontal line connecting both triradiate cartilages (Hilgenreiner Line) and a second line along the acetabular roof (Figure 3). To acurately measure the acetabular angle one needs to be able to identify the lowest point of the iliac bone in the acetabulum and the outer edge of the actabular roof. These therefore were the criteria used to assess the diagnostic quality of the these radiographs. We have shown that accurate identification of these points is possible in both DR and CR images. Diagnostic accuracy for DDH asessment is therefore preserved.
Other studies comparing CR and DR technologies have also shown reduction in patient dose with DR.
Bacher et.al.[1] measured the entrance surface dose using thermoluminescent dosimeters on patients and found reductions up to 59% for Chest X-rays done using DR systems compare to those done with a CR system.
Gruber et.
al.[2] undertook CR and DR PA Chest images on the same patients.
The DR X-rays were performed using 50% of the dose required for the CR image.
A blind side-by-side comparison was undertaken by Radiologist who concluded that the DR image was equivalent or even superior to the CR image taken with the higher dose.
De Boo et.
al.[3] looked at portable DR systems compared with CR for chest X-rays taken in an adult ICU environment.
They also found a dose reduction of up to 50% without compromising image quality. No prior study has compared CR and DR for infant hip radiographs for diagnosis and management of DDH.