Slit-beam digital radiography system

Last revised by Andrew Murphy on 11 Apr 2024

EOS® imaging system (also known as a slot-scanning device or slit-beam digital radiography system) is an x-ray technology that allows simultaneous acquisition of AP and lateral images of the entire body in a natural, erect position, and is also capable of performing three-dimensional reconstructions from these images. It is primarily used in the evaluation of scoliosis, and resultant changes in the sagittal and coronal balance 1.  

Clinical applications

The main use of the system is the assessment of scoliosis, and the resultant changes in posture (sagittal and coronal balance, pelvic tilt) 2. It can also be used to evaluate degenerative changes of the spine, osteoporosis, to perform measurements of the lower limb bones and angles, and to determine implant positioning for hip or knee arthroplasty or leg length discrepancies.

Slit-beam digital radiography systems are considered favorable in some settings due to:

  • ~5 times 3 lower patient dose compared to conventional radiography 4

  • higher detail in larger patients due to a decrease in scatter 5

  • three-dimensional imaging 

Physical principles

The scan is performed in a normal standing position. Unlike conventional x-ray systems, it utilizes a thin slit-beam x-ray source (eliminating the need for a grid) that moves superior-inferiorly concurrently in both planes (anterior-posterior and lateral) resulting in two acquisitions in one mechanical motion. The scan takes longer than normal radiography (10-25 s) 1.

With a bundled dedicated software, three-dimensional reconstructions of the axial skeleton can be reconstructed, and numerous quantitative parameters for the spine and limbs can be obtained. The main advantages of the system over conventional radiography are the significant reduction of radiation dose, and the possibility of three-dimensional reconstructions 1

  • slow image acquisition increases the risk of movement artifacts, this is quite problematic in younger populations

  • edge enhancement artifacts around metallic implants (algorithms have been designed to overcome this and must be implemented at the radiographer level) 

  • severe limb deformities can influence the semi-automatic 3D reconstructions and can result in biased calculations. 

  • concerns have been raised about the cost-effectiveness of the system 6

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