A low-dose biplanar X-ray imager has RSA level precision in total knee arthroplasty.

BACKGROUND AND PURPOSE: The low radiation biplanar X-ray imager (EOS imaging, Paris, France) scans patients in a weight-bearing position, provides calibrated images, and limits radiation, an asset for serial radiostereometric analysis (RSA) studies. RSA in vivo precision values have not been published for this type of imaging system, thus the goal of this study was to assess the precision of RSA in vivo utilizing a low radiation biplanar imager. PATIENTS AND METHODS: At a mean of 5 years post-surgery (range 1.4-7.5 years), 15 total knee arthroplasty (TKA) participants (mean age 67 years at the time of imaging, 12 female, 3 male) with RSA markers implanted during index surgery were scanned twice at the same visit in the EOS imager. Precision of marker-based analysis was calculated by comparing the position of the implant relative to the underlying bone between the 2 examinations. RESULTS: The 95% limit of precision was 0.11, 0.04, and 0.15 mm along the x, y, and z axes, respectively and 0.15°, 0.20°, and 0.14° around the same axes. CONCLUSION: This precision study has shown an in vivo RSA precision of ≤ 0.15 mm and ≤ 0.20°, well within published uniplanar values for conventional arthroplasty RSA, with the added benefit of weight-bearing imaging, a lower radiation dose, and without the need for a reference object during the scan.

High-pitched tin-filtered CT pulmonary angiography in radiation dose reduction for pulmonary embolism investigations in young females.

INTRODUCTION: Computed tomography pulmonary angiography (CTPA) is the gold standard test to investigate pulmonary embolism (PE). This technique carries significant radiation risk in young females because of radiosensitive breast and thyroid tissues. A high-pitched CT technique offers significant radiation dose reduction (RDR) and minimises breathing artefact. The addition of CT tube tin-filtration may offer further RDR. The aim of this retrospective study was to assess RDR and image quality (IQ) of high-pitch tin-filtered (HPTF)-CTPA against conventional-CTPA. METHODS: Retrospective review of consecutive adult females age < 50 years undergoing high pitch tin filtration (HPTF) and standard pitch no tin filtration (SPNF) during a 3-year period beginning in November 2017. CTs in both groups were compared for radiation dose, pulmonary arteries contrast density (Hounsfield units (HU)) and movement artefact. Findings of both groups were compared with the Student's T-test and Mann-Whitney U test, where p < 0.05 being considered significant. Diagnostic quality was also recorded. RESULTS: Ten female patients (mean age 33, 6/10 pregnant) in HPTF group and 10 female patients (mean age 36, 1/10 pregnant) in SPNF group were included. The HPTF group achieved 93% RDR (dose length product: 25.15 mGy.cm vs 337.10 mGy.cm, p < 0.01). There was significant contrast density difference between the two groups in the main, left or right pulmonary arteries (322.72 HU, 311.85 HU and 319.41 HU in HPTF group vs 418.60 HU, 405.10 HU and 415.96 HU in SPNF group respectively, p = 0.03, p = 0.03 and p = 0.04). 8/10 HPTF group and 10/10 in the control group were > 250 HU in all three vessels; the remaining 2 HPTF CTPA were > 210HU. All CT scans in both groups were of diagnostic quality and none exhibited movement artefact. CONCLUSION: This study was the first to demonstrate significant RDR with the HPTF technique whilst maintaining IQ in patients undergoing chest CTPA. This technique is particularly beneficial in young females and pregnant females with suspected PE.

The reliability of radiostereometric analysis in determining physeal motion in slipped capital femoral epiphysis in standard uniplanar and low-dose EOS biplanar radiography: a phantom model study.

Physeal closure after slipped capital femoral epiphysis fixation can be difficult to assess on two-dimensional conventional radiographs. Radiostereometric analysis offers improved motion detection over conventional radiography, whereas the EOS biplanar imager provides a means for low radiation weight-bearing images. This phantom study assessed the reliability of measuring motion using radiostereometric analysis in the EOS using a slipped capital femoral epiphysis model. The accuracy and precision were better than 0.09±0.05 mm and 0.20°±0.36° when centered in the imaging space, were within the limits of clinical significance, and were not different from a standard uniplanar radiostereometric system.