Cross-calibration journal of same make and model (Hologic Horizon Wi) installed on Mobile container in different scanner environment

Abstract

Purpose: ISCD Official positions (2019) has provided appropriate guidance to multiple DXA scanner institutions wishing to offer patients flexibility and convenience, and clearly define good clinical practice requirements to attain it. NHG Diagnostics has launched the project for our DXA machine installed on mobile containers to ensure that our results are comparable with the cross-calibration assessment methodology as described by ISCD Official position (2019). Methods: Atop from the methodology described by ISCD's Official Position, the possible variations within the scanner's environment installed within the mobile container and the choice of tool used for the assessment will be explored (Stage 1: Pretest) & the assessment journal (Stage 2: Cross-calibration journal). Hologic Horizon Wi DXA Machine (S/N 301900M) is identified to be the index scanner, and Hologic Horizon Wi DXA Machine (S/N 304277M) is identified to be the additional scanner during the test. Stage 1: As NHGD has the existing DXA Machine installed within a mobile container with UPS running while tapping on various power source, we have reviewed our QC plots for 6 months (from March 2021 to Sept 2021). When determining the choice of tool, we have performed 10x phantom scans without repositioning at various deployment locations. The %CV and Percentage difference in mean BMD are calculated. Stage 2: The chosen choice of tool will be scanned once daily throughout 20 different days on two machines, operated by a radiographer who has completed the precision assessment. Due to vast distance between the two machines, we have planned and sourced out for courier in transporting the phantom in a shockproof case from one location to another. Once the scan of the day was completed, the scan will be analyzed and the values will be recorded. At the end of the project, the mean BMD will be calculated and the percentage difference between two machines is required to be within 0.5%. If the mean BMD difference is greater than 0.5%, the machine is required to be recalibrated and Stage 2 will be repeated. Results: Stage 1: Spine Phantom (SN #10122) was chosen to be the choice of tool for the cross-calibration assessment due to its lightweight and lower %CV (%CV: 0.09-0.18%) compared to Spine phantom (SN #13684) (%CV: 0.29-0.47%). The 6-month QC Plot Review indicated that the %CV for individual deployment location and average deployment location are less significant and mostly similar. Hologic Horizon Wi DXA Machine (S/N 304277M) has the highest %CV at 0.35% and averaged 0.32% across different locations. Hologic Horizon Wi DXA Machine (S/N 301900M) has the highest %CV at 0.33% and averaged 0.24% across different locations. Stage 2: At the end of the 20 days’ period, the data points were recorded and tabulated. The mean BMD is observed to be 0.890 g/cm2 and 0.888 g/cm2 respectively on Hologic Horizon Wi (S/N 304277M) and Hologic Horizon Wi (S/N 301900M), with a percentage difference of 0.29%. Conclusion: The above additional scanner (Hologic Horizon Wi (S/N 304277M)) which is of good working order within NHGD is observed to be cross calibrated to the index scanner (Hologic Horizon Wi DXA Machine (S/N 301900M)). The data obtained from both machines can be compared with each other when having multi scan site deployment with convenience.