Quality-controlled dose reduction of full-leg radiography in patients with knee malalignment

Clinical utility of postprocessed low-dose radiographs in skeletal imaging

OBJECTIVES

Radiography remains the mainstay of diagnostic and follow-up imaging. In view of the risks and the increasing use of ionizing radiation, dose reduction is a key issue for research and development. The introduction of digital radiography and the associated access to image postprocessing have opened up new opportunities to minimize the radiation dosage. These advances are contingent upon quality controls to ensure adequate image detail and maintenance of diagnostic confidence. The purpose of this study was to investigate the clinical applicability of postprocessed low-dose images in skeletal radiography.

METHODS

In our study setting, the median radiation dose for full dose X-rays was 9.61 dGy*cm2 for pelvis, 1.20 dGy*cm2 for shoulder and 18.64 dGy*cm2 for lumbar spine exams. Based on these values, we obtained 200 radiographs for each anatomic region in four consecutive steps, gradually reducing the dose to 84%, 71%, 60% and 50% of the baseline using an automatic exposure control (AEC). 549 patients were enrolled for a total of 600 images. All X-rays were postprocessed with a spatial noise reduction algorithm. Two radiologists assessed the diagnostic value of the radiographs by rating the visualization of anatomical landmarks and image elements on a five-point Likert scale. A mean-sum score was calculated by averaging the two reader's total scores. Given the non-parametric distribution, we used the Mann-Whitney U test to evaluate the scores.

RESULTS

Median dosage at full dose accounted for 38.4%, 48 and 53.2% of the German reference dose area product for shoulder, pelvis and lumbar spine, respectively. The applied radiation was incrementally reduced to 21.5%, 18.4% and 18.7% of the respective reference value for shoulder, pelvis and lumbar spine. Throughout the study, we observed an estimable tendency of superior quality at higher dosage in overall image quality. Statistically significant differences in image quality were restricted to the 50% dose groups in shoulder and lumbar spine images. Regardless of the applied dosage, 598 out of 600 images were of sufficient diagnostic value.

CONCLUSION

In digital radiography image postprocessing allows for extensive reduction of radiation dosage. Despite a trend of superior image detail at higher dose levels, overall quality and, more importantly, diagnostic utility of low-dose images was not significantly affected. Therefore, our results not only confirm the clinical utility of postprocessed low-dose radiographs, but also suggest a widespread deployment of this advanced technology to ensure further dose limitations in clinical practice.

ADVANCES IN KNOWLEDGE

The diagnostic image quality of postprocessed skeletal radiographs is not significantly impaired even after extensive dose reduction by up to 20% of the reference value.

Radiation dose reduction in plain radiography of the full-length lower extremity and full spine

OBJECTIVE

To compare the diagnostic performance of standard- and low-dose radiographs of the full-length lower extremity and spine.

METHODS

This study included 223 patients who visited our hospital and received full-length lower extremity standing radiographs and full-spine radiographs. We determined the dose area product (DAP) of each image, and effective doses (ED, mSv) were calculated based on the DAP. Subjective evaluation of the full-length radiographs was based on image quality, which was assessed by bony cortex and trabecula evaluation, and on diagnostic performance, which was assessed by leg length measurement. Subjective evaluation of the full-spine radiographs was based on image quality, which was assessed by viewing the vertebral endplate, pedicle and lateral border of vertebral body, and on diagnostic performance from measurement of Cobb's angle.

RESULTS

For the full-length view and the full-spine view both the mean DAP and ED values of the standard-dose group were significantly higher than those of the low-dose group (p < 0.05). Mean scores for subjective values did not significantly differ based on the radiation dosage (p-values, 0.15-0.99). The subjective value scores for the full-length view were 2.94-2.98 in the standard-dose group and 2.91-3.00 in the low-dose group. Of note, both groups had very high scores. Additionally, the diagnostic performance scores between the two groups were also very high (range from 2.92 to 3.00).

CONCLUSION

Reducing mAs by 50% of the standard dose does not affect the radiograph image quality or its clinical validity. Advances in knowledge: Radiation dose reduction (50% of the standard dose of mAs) in plain radiography of the full-length lower extremity and full spine do not affect the clinical validity and the image quality.

Quality-controlled dose-reduction of pelvic X-ray examinations in infants with hip dysplasia

BACKGROUND

Digital plain radiography (DR) examinations of the pelvis are frequently performed in infants with hip dysplasia.

OBJECTIVE

The purpose was to reduce the radiation dose and to determine objective quality control criteria to ensure accurate assessment. This seems feasible because of higher quantum efficiency of DR and easy assessable anatomical structures for most orthopaedic measurements.

MATERIALS AND METHODS

Institutional review board approval was obtained. In this prospective randomized study, 264 patients underwent X-ray examination of the pelvis with standard and reduced dose. The evaluation of the plain-radiographs was conducted using the following criteria: acetabular and center edge angle, closing of the epiphyseal plates and maturation of the femoral head. Two radiologists evaluated these criteria using a score ranging from 1 (definitely assessable) to 4 (not assessable). If a single criterion had been evaluated with a score of 3 or more points or more than 2 criteria with 2 points, the radiograph was scored as "not assessable". The statistical analysis was conducted as non-inferiority-trial.

RESULTS

Five (1.9%) examined X-rays were scored as not assessable. There was no statistical inferiority between the examinations with standard (4.57 μSv) or reduced dose (3.06 μSv). Also, the individual evaluation of the defined criteria was dose-independent.

CONCLUSION

The adequate evaluation of hip dysplasia in children and young adults on pelvic radiographs is possible with reduced radiation dose, by simple using an exposure class of 800 instead of 400.