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

Low-dose whole-spine imaging using slot-scan digital radiography: a phantom study

BACKGROUND

Slot-scan digital radiography (SSDR) is equipped with detachable scatter grids and a variable copper filter. In this study, this function was used to obtain parameters for low-dose imaging for whole-spine imaging.

METHODS

With the scatter grid removed and the beam-hardening (BH) filters (0.0, 0.1, 0.2, or 0.3 mm) inserted, the tube voltage (80, 90, 100, 110, or 120 kV) and the exposure time were adjusted to 20 different parameters that produce equivalent image quality. Slot-scan radiographs of an acrylic phantom were acquired with the set parameters, and the optimal parameters (four types) for each filter were determined using the figure of merit. For the four types of parameters obtained in the previous section, SSDR was performed on whole-spine phantoms by varying the tube current, and the parameter with the lowest radiation dose was determined by visual evaluation.

RESULTS

The parameters for each filter according to the FOM results were 90 kV, 400 mA, and 2.8 ms for 0.0 mm thickness; 100 kV, 400 mA, and 2.0 ms for 0.1 mm thickness; 100 kV, 400 mA, and 2.8 ms for 0.2 mm thickness; and 110 kV, 400 mA, and 2.2 ms for 0.3 mm thickness. Visual evaluation of the varying tube currents was performed using these four parameters when the BH filter thicknesses were 0.0, 0.1, 0.2, and 0.3 mm. The entrance surface dose was 59.44 µGy at 90 kV, 125 mA, and 2.8 ms; 57.39 µGy at 100 kV, 250 mA, and 2.0 ms; 46.89 µGy at 100 kV, 250 mA, and 2.8 ms; and 39.48 µGy at 110 kV, 250 mA, and 2.2 ms, indicating that the 0.3-mm BH filter was associated with the minimum dose.

CONCLUSION

Whole-spine SSDR could reduce the dose by 79% while maintaining the image quality.

A Clinically Optimal Protocol for the Imaging of Enteric Tubes: On the Basis of Radiologist Interpreted Diagnostic Utility and Radiation Dose Reduction

RATIONALE AND OBJECTIVES

The purpose of this study was to develop and evaluate a patient thickness-based protocol specifically for the confirmation of enteric tube placements in bedside abdominal radiographs. Protocol techniques were set to maintain image quality while minimizing patient dose.

MATERIALS AND METHODS

A total of 226 pre-intervention radiographs were obtained to serve as a baseline cohort for comparison. After the implementation of a thickness-based protocol, a total of 229 radiographs were obtained as part of an intervention cohort. Radiographs were randomized and graded for diagnostic quality by seven expert radiologists based on a standardized conspicuity scale (grades: 0 non-diagnostic to 3+). Basic patient demographics, body mass index, ventilatory status, and enteric tube type were recorded and subgroup analyses were performed. Effective dose was estimated for both cohorts.

RESULTS

The dedicated thickness-based protocol resulted in a significant reduction in effective dose of 80% (p-value < 0.01). There was no significant difference in diagnostic quality between the two cohorts with 209 (92.5%) diagnostic radiographs in the baseline and 221 (96.5%) diagnostic radiographs in the thickness-based protocol (p-value 0.06).

CONCLUSION

A protocol optimized for the confirmation of enteric tube placements was developed. This protocol results in lower patient effective dose, without sacrificing diagnostic accuracy. The technique chart is provided for reference. The protocol development process outlined in this work could be readily generalized to other imaging clinical tasks.

Accuracy of biplanar linear radiography versus conventional radiographs when used for lower limb and implant measurements

INTRODUCTION

The current standard of care for measuring lower extremity length and angular discrepancies is using a full-length standing anteroposterior radiograph. However, there has been increasing interest to use biplanar linear EOS imaging as an alternative. This study aims to compare lower extremity length and implant measurements between biplanar linear and conventional radiographs.

MATERIALS AND METHODS

In this 5-year retrospective study, all patients who had a standing full-length anteroposterior and biplanar linear radiographs (EOS®) that include the lower extremities done within one year of each other were included. Patients who underwent surgery in between the imaging, underwent surgeries that could result in graduated length or angulated corrections and inadequate exposure of the lower extremity were excluded. Four radiographic segments were measured to assess lower limb alignment and length measurements. Height and width measurements of implants were performed for patients who had implants in both imaging.

RESULTS

When comparing imaging and actual implant dimensions, biplanar linear radiographs were accurate in measuring actual implant height (median difference = - 0.14 cm, p = 0.66), and width (median difference = - 0.13 cm, p = 0.71). However, conventional radiographs were inaccurate in measuring actual implant height (median difference = 0.19 cm, p = 0.01) and width (median difference = 0.61 cm, p < 0.01). When comparing conventional and biplanar linear radiographs, there was statistically significant difference in all measurements. This includes anatomical femoral length (median difference = 3.53 cm, p < 0.01), mechanical femoral length (median difference = 3.89 cm, p < 0.01), anatomical tibial length (median difference = 2.34 cm, p < 0.01) and mechanical tibial length (median difference = 2.20 cm, p < 0.01).

CONCLUSION

First, there is a significant difference in the lower extremity length when comparing conventional and biplanar linear radiographs. Second, biplanar linear radiographs are found to be accurate while conventional radiographs are not as accurate in implant measurements of length and width in the lower extremity.

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.

Application of an advanced noise reduction algorithm for imaging of hands in rheumatic diseases: evaluation of image quality compared to standard-dose images

OBJECTIVES

X-ray is the fundamental imaging technique in both diagnosis and follow-up of rheumatic diseases. As patients often require sequential X-rays over many years, dose reduction is of great importance. New advanced noise reduction algorithms allow for a dose reduction of up to 50%. The aim of this study was to evaluate whether quality of low-dose images is non-inferior to standard-dose images and, therefore, application of this technique is possible in the context of imaging of rheumatic diseases.

METHODS

A total of 298 patients with known or suspected rheumatic disease were enrolled prospectively into this study, separated into three consecutive groups: 80%, 64% and 50% tube charge reduction. All patients received imaging of one hand (laterality randomly assigned) with low-dose technique and imaging of the contralateral hand with standard-dose protocol. Images were evaluated by two independent readers who scored (on a scale of 1-5) the visualization of bony cortex, trabeculae and joint spaces of fingers and wrist separately. Additionally, soft tissue and overall contrast were evaluated on the same scale.

RESULTS

Overall image quality (expressed by mean sum score out of 40) of the 50% low-dose images was 31.52 (SD 1.94) vs. 31.66 (SD 1.82) for standard images (p = 0.068). Bony contours as well as trabeculae were equally well visualized in both image sets. Median scores for soft tissue visualization was slightly lower for low dose compared to standard images [4 (IQR 3.5-4) vs. 4 (IQR 3.88-4); p = 0.001].

CONCLUSIONS

Overall image quality of low-dose images was not inferior to standard-dose images. Therefore, the application of low-dose technology based on advanced noise estimation algorithms in the context of imaging of rheumatic diseases is possible.

Comparison of weight-bearing full-length radiographs and computed-tomography-scan-based three-dimensional models in the assessment of knee joint coronal alignment

BACKGROUND

The aim of the study was to determine any discrepancies among preoperative full-leg standing radiographs (LLR) and supine non-weight-bearing computed tomography (CT)-scan-based three-dimensional (3D) models in the assessment of the lower limb alignment prior to total knee arthroplasty (TKA) and answer the question of whether the LLR study can be obviated in preoperative planning when TKA is performed with patient-specific instrumentation (PSI).

METHODS

LLR and CT-scan-based 3D models of 227 knees (183 patients) were measured. LLR data was then compared to 3D alignment data used to design the PSI for TKA surgery.

RESULTS

Alignment on LLR ranged from 153 to 194° versus 161.5 to 190.5° with CT-scan-based 3D models. The mean (standard deviation, SD) difference among techniques was 1.9° (1.15°) with a statistically significant difference (P = 2e-16, namely P < .0001). Supine CT-scan-based 3D models underestimated the deformity in 167 cases (73.6%), exactly matched the value of LLR in 24 cases (10.6%) and overestimated the deformity in 36 cases (15.8%).

CONCLUSION

CT-scan-based models underestimate the degree of deformity at the knee joint. Despite the accurate information provided by the CT-scan and the 3D models (which is the basis for the planning of bone cuts), weight-bearing LLR should not be overlooked in the planning of TKA surgery to assess the extent of the coronal mediolateral instability.