Design and evaluation of learning strategies for a group of radiographers in radiostereometric analysis (RSA)

Projective geometric model for automatic determination of X-ray-emitting source of a standard radiographic system

BACKGROUND AND OBJECTIVE

Currently, many orthopedic operations are planned by analyzing X-rays. The exact position of the focus is needed to calculate the real size of an object that is represented in conical projection, although in practice, this position is difficult to determine using current X-ray commercial systems. In this paper, a new geometric model is proposed in order to determine accurately, practically, and economically the location of the emitting source of commercial imaging systems using a single standard X-ray image.

METHOD

The method requires a specific reference locator object to be positioned in the visual field of radiographic image. Because this object cannot implement ideal geometric points, but instead works with small spheres, it was necessary to experimentally validate the proposed methodology. The implemented software that was developed to validate the model was used in four series of tests. In these tests, we studied the influence on the final result of: 1. the selection of a specific set of markers in radiography, 2. the focus position variation in relation to radiograph and 3. the possible rotated angle of locator object about Z axis.

RESULTS

The results for 164 tests that were performed with this software showed that the expected error for 99.5% of values ranges with maximum error of [-0.35%, +0.39%], which shows that the model is independent of the design of locator object and its position and orientation in the radiographic field. The software used to validate the proposed model has been found useful to verify its reliability, effectiveness, ease of implementation, and accuracy.

CONCLUSIONS

This model is effective to calculate the precise position of the X-ray focus of any standard radiographic system accurately.

The effect of personalized versus standard patient protocols for radiostereometric analysis (RSA)

INTRODUCTION

Increasing pressure in the clinic requires a more standardized approach to radiostereometric analysis (RSA) imaging. The aim of this study was to investigate whether implementation of personalized RSA patient protocols could increase image quality and decrease examination time and the number of exposure repetitions.

METHODS

Forty patients undergoing primary total hip arthroplasty were equally randomized to either a case or a control group. Radiographers in the case group were assisted by personalized patient protocols containing information about each patient's post-operative RSA imaging. Radiographers in the control group used a standard RSA protocol.

RESULTS

At three months, radiographers in the case group significantly reduced (p < 0.001) the number of exposures by 1.6, examination time with 19.2 min, and distance between centrum of prosthesis and centrum of calibration field with 34.1 mm when compared to post-operative (baseline) results. At twelve months, the case group significantly reduced (p < 0.001) number of exposures by two, examination time with 22.5 min, and centrum of prosthesis to centrum of calibration field distance with 43.1 mm when compared to baseline results. No significant improvements were found in the control group at any time point.

CONCLUSION

There is strong evidence that personalized RSA patient protocols have a positive effect on image quality and radiation dose savings. Implementation of personal patient protocols as a RSA standard will contribute to the reduction of examination time, thus ensuring a cost benefit for department and patient safety.