Variation of the spatial position computed by Roentgen Stereophotogrammetric Analysis (RSA) under non-standard conditions

Raffaella Soavi, Mario Motta, Andrea Visani

Research output: Contribution to journalArticlepeer-review


Roentgen Stereophotogrammetric Analysis (RSA) has been applied to different kinds of research in order to obtain important information in the biomechanics field. Operative requirements change according to the type of investigation and sometimes practical conditions do not always permit one to respect standard specifications. The aim of this paper is to verify the reliability of the system under non-standard conditions, studying the effects of the focus-to-film distance on the determination of 3D co-ordinates of markers. The application of statistical analysis, consisting of two and three way ANalysis Of VAriance (ANOVA), showed that focus-to-film distance is not a significant source of variation, i.e., the system can correctly compute the marker position inside the calibrated space under all conditions of magnification. Since we obtained a fluctuation due to focal distance change of 10-5 mm (LSD for 95% confidence level), we can assert that this source causes a variation strictly within the limits required by clinical investigations. Thus, this study contributes to improving the flexibility of RSA in clinical applications, making the technical requirements of the radiographic set-up less constraining. Copyright (C) 1999 IPEM.

Original languageEnglish
Pages (from-to)575-581
Number of pages7
JournalMedical Engineering and Physics
Issue number8
Publication statusPublished - Oct 1999


  • 3D co-ordinate variation
  • Focus-to-film distance
  • Radiographic set-up
  • Roentgen Stereophotogrammetric Analysis

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Psychology(all)


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