# Accuracy Verification of an Anatomical Model Manufactured Using Low-Cost Additive Production
## 4 Discussion  
The article was focused on the comparison of software applications for DICOM data processing, model creation, and its printing on a low-cost 3D printer and subsequent digitization using 3D scanners to determine the impact of printing and verify the use of these technologies. A CT scan with a resolution of 0.287 \(\times\) 0.287 \(\times\) 0.625 mm was used for the production of our anatomical model, while the articles [11; 13; 14; 34] show that the most commonly used image slice thickness is in the range of 0.4-1 mm and for long bones 2 mm. A comparison of the software packages shows that, with respect to the VGStudio MAX model, the maximum deviation at 95% surface coverage was 0.935 mm for Mimics and 0.825 mm for inVesalius. When comparing medically oriented software (Mimics, inVesalius), the maximum deviation was 0.356 mm. The review of the literature shows that in the case of evaluating the accuracy of the production of anatomical models, the authors dealt with the evaluation and mutual comparison of selected length dimensions between the CT scan and the printed model. [PERSON] et al. [38] report accuracy for models larger than 10 mm at 1.5% of the observed dimension, [PERSON] et al. [1] wrote that interclass correlation coefficient was in the range of R = 0.799-0.977, [PERSON] et al. [19] stated that the correlation coefficient between actual and nominal image was R = 0.99 and [PERSON] et al. [15] that the percentage difference depending on the monitored body was 0.78-2.53%. The presented paper deals with deviations in 3D space, so it is possible to determine the differences between the reference model printed by the anatomical model at each point of the model and, if necessary, adjust the parameters of 3D printing in order to increase accuracy. Globally, the deviation of our anatomical model ranges from 0.272-0.361 mm (per side) depending on the scanner used (Table 2), which represents a difference of 1.088-1.440% at 50 mm. This is the maximum deviation, as the deviation at the measured points may be smaller. In the case of comparing the outputs from the scanners to the reference model, it can be stated that there were no significant differences between them, as 95% coverage was in the range of 0.100 mm (Table 2). This also applies to the mutual comparison of scanners, where the difference is at the level of 0.06 mm (Table 3). The cost of producing models using stereolithography by [PERSON] et al. [39] ranges from $20-400 for spinal surgical guides and $300-3000 for spinal surgery planning with a delivery time of 16 h-7 d for spinal surgical guides and up to 2 d for spinal surgery planning. In our case, the price of the material was less than $1, the time required to  
Figure 10: Histogram of the distribution of deviations. \begin{table}
\begin{tabular}{c c c} \hline
**3 Shape D700** & **Steinbichler Comet** & **Creaform EXAscan** \\ \hline DEV50 (\%) & 34.300 & 24.500 \\ PER95 (mm) & 0.305 & 0.363 \\ \hline \end{tabular}
\end{table} 
Table 3: Comparison with the reference scan of the model. separate the model from the CT data was 25 min, and to print, 3 h. From a time and financial point of view, the use of inVesalius in combination with Meshmixer was optimal for generating output from CT data and GOM Inspect for data control, as it is freeware. The result shows that a low-cost FFF printer with low acquisition costs and operation is also suitable for the creation of anatomical models. Hardware costs ranged from $700 per PC, $1000 per 3D printer as freeware programs. In the experiment, three software with different focus and functions were compared. VGStudio MAX is primarily intended for data processing from industrial computed tomographs and measurements. Mimics and inVesalius are primarily designed to work with data from medical CT devices and therefore have an optimized and predefined environment. Mimics is a medical software with ISO 13485:2016 certification, and InVesalius is a freeware enabling surface generation to a STL file.