Together or Separate: What is best practice when imaging bilateral hands for rheumatoid arthritis examinations?

introductionA current gap identified in medical imaging (MI) literature is a standardised approach to bilateral hand examinations. This examination performed concurrently or unilaterally results in different effects on radiation dose and image quality, both of which are important to the diagnostic and follow-up imaging of rheumatoid arthritis (RA) patients.

methodsAn experimental study was undertaken using anthropomorphic hand phantoms at the Queensland University of Technology (QUT) MI Simulation laboratory. Images of the hand were acquired individually and then concurrently with both hands together. Radiation dose was calculated by observing dose area product (DAP) reading on a digital radiography system, with the additional use of an exposure metre as a secondary data collection method. Image quality was quantified through measuring distortion caused by beam divergence, by exploring the separation of two metal rings fixed to the hand phantom.

resultsThe overall radiation dose was higher for the unilateral technique by 10.15% at the digital radiography system console and 11.96% recorded by the exposure metre. In the second part of the experiment, the unilateral technique produced 0 mm of distortion when the phantom was positioned in the central part of the beam. The concurrent technique demonstrated an average of 3.65 mm of distortion, when both hands were positioned with the central part of the beam between them.

conclusionThe unilateral technique should be performed for bilateral hand examinations. The increase in distortion from the concurrent technique is clinically significant, as the diagnostic grading of RA is measured in millimetre increments. The additional overall examination dose is minimal when compared to the improvement in image quality.