Using three-dimensional difference maps to assess changes in scoliotic deformities

Abstract

The three-dimensional nature of scoliosis, coupled with changes due to natural history or treatment, is often difficult to quantify and visualise. A difference map was developed to compare the sequential surface topography of subjects over their treatment period. Three-dimensional surface maps representing patients' trunk surfaces were captured with a laser scanner. Patient surface maps from two clinic visits were matched using a manual best-fit technique that accounted for growth and positioning. The surfaces were subtracted, generating a colour-coded three-dimensional difference map displaying the surface changes. The difference maps were compared with known clinical measures, indicating good agreement (78% specific) with the clinical parameters in detecting change. Full agreement or agreement with the clinical parameters occurred in the surgical, brace and no treatment groups: 76%, 80% and 85%, respectively. A difference index (average of the absolute value of differences on a point-by-point basis) was calculated from the difference map, enabling quantification of change. The difference index, with zero being a perfect match, averaged 5 +/- 1 for repeated measures 7 +/- 2 for subjects deemed to have no change, 9 +/- 2 for subjects with slight change, and 14 +/- 2 for subjects with significant change. The difference map showed the extent and location of changes and is a useful tool for assessing surface topography changes.

Non-Rigid Surface Matching Technique as a Tool in Scoliosis Deformation Modelling

“…The numerical result of the transformation parameters is presented in Table 4. Meanwhile, the result obtained in this research was compared with the manual matching method defined in [10]. The final results were matched indicating this matching algorithm is feasible and favourable for scoliosis deformation monitoring.…”

Métodos não invasivos de avaliação postural da escoliose: Uma revisão sistemática

“…Classificação da evidência 1 2 3 4 5 6 8 9 10 11 14 Furlanetto et al (2012) × Berg et al (2002) ? Korovessis et al (1996)    ?…”

“…No que se refere ao sistema de escaneamento a laser, foi possível observar uma boa concordância com os parâmetros clínicos em detetar a mudança, indicando que os mapas de diferença podem detetar e descrever as alterações nas curvas escolióticas, entretanto, em alguns casos o instrumento apresentou desacordo com o exame clínico, o que impossibilita a sua utilização isolada para fins de diagnóstico (Berg et al, 2002). Além disso, questões relevantes sobre a validade do sistema ainda precisam ser investigadas.…”

Quantifying torso deformity in scoliosis

“…A technique which involves subtracting aligned surface maps of the back shape to obtain 'difference maps' that can be used to assess changes in back shape features over time was proposed by Berg et al 8 . The technique yields a continuous measure of the changes in back shape that are difficult to capture from physical measures of deformity.…”