Abstract 1

The effect of acquisition slice thickness on volume measurement accuracy using three-dimensional reconstructed MRI: evaluation in a novel acrylic meniscal cartilage phantom

Kurmis AP¹, Slavotinek JP & Reynolds KJ.

¹ Department of Orthopaedics, Division of Surgery, Repatriation General Hospital, Daws Road, Daw Park, South Australia, Australia.

The fundamental influence of base-image acquisition slice thickness (AST) remains a poorly defined contributor to the determination of three-dimensional (3-D) volume measurement accuracy. Using a novel, paired meniscal cartilage phantom, fashioned from a high-density acrylic polymer, this study aimed to quantitate this relationship in the setting of non-invasive evaluation of the adult human knee.

The study-designed meniscal phantoms were submersed in an aqueous medium and subjected to sectional MR analysis, at various ASTs representative of the routine clinical scanning range. Post-imaging, a 3-D reconstructed image of each menisci, at each AST, was created using commercially-available reconstructive software. A volumetric measurement was obtained for each image and directly compared to the known physical parameters of the phantoms, allowing determination of a relative percentage measurement error (PME).

PMEs achieved ranged from 19.42% (4.0 mm) to 1.05% (1.0 mm) and appeared to follow a near-linear relationship with AST. In reflecting on the available literature, it can be suggested that the PMEs achieved using the finer slices may have exceeded clinical relevance (i.e. error range unlikely to negative influence clinical decision making), and hence be considered a highly reliable measure for surgical management. In summary, the findings of this investigation demonstrate the achievement of highly precise volume measurement accuracy, attainable using conventional MR slice thickness parameters, thus making these results applicable to the majority of routine imaging sites. With the capacity to delve into sub-millimetre ASTs, there is the theoretic potential to further improve volume measurement accuracy, if a clinicallyjustifiable need can be identified.

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