Comparative Analysis of Eximius Med and MNPS Software for Stereotactic Neurosurgical Planning: A Precision and Accuracy Study

Abstract

Objective

To compare the geometric registration in the Eximius Med (Artis Tecnologia) and MNPS (Mevis Informática Médica LTDA.) stereotactic software.

Materials and Methods

The study design included acquisition of skull images by computed tomography, marking of point coordinates (X, Y, and Z) in the MNPS and Eximius Med software performed by two independent evaluators, and statistical evaluations of precision and accuracy. Data were expressed as means, variances, and standard deviation. For comparisons between variables, the Euclidean distance, Student's t-test, Levene's test, the calculation of Cohen's D, and the intraclass correlation coefficient (ICC) were used. Values of p < 0.05 were considered statistically significant.

Results

The mean Euclidean distance was 0.07 ± 0.056 (95%CI: −0.037–0.18) mm. It is possible to state that there is a submillimetric difference in the coordinates with low effect size between the measurements made in Eximius and MNPS. The intraobserver evaluation showed that there is a positive correlation (ICC = 1) in the markings of each evaluator, while in the interobserver evaluation, there was no significant difference in any of the coordinates (p > 0.5) between the two software, when comparing evaluators 1 and 2.

Conclusion

Eximius Med, therefore, is a consistent, comparable, precise, and highly accurate alternative for use in cranial stereotaxy.

 

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Resumo

Objetivo

Comparar o registro geométrico nos softwares estereotáxicos Eximius Med (Artis Tecnologia) e MNPS (Mevis Informática Médica LTDA.).

Materiais e Métodos

O desenho do estudo incluiu aquisição de imagens do crânio por tomografia computadorizada, marcação das coordenadas de pontos (X, Y e Z) nos softwares MNPS e Eximius Med, realizadas por dois avaliadores independentes, e avaliações estatísticas de precisão e exatidão. Os dados foram expressos como médias, variâncias e desvio padrão. Para comparações entre variáveis, foram utilizados a distância euclidiana, o teste t de Student, o teste de Levene, o cálculo de D de Cohen e o coeficiente de correlação intraclasse (CCI). Valores de p < 0,05 foram considerados estatisticamente significativos.

Resultados

A média da distância euclidiana foi 0,07 ± 0,056 (IC95%: −0,037–0,18) mm. É possível afirmar que há uma diferença submilimétrica nas coordenadas com baixo tamanho de efeito entre as medições feitas no Eximius Med e no MNPS. A avaliação intraobservador mostrou uma correlação positiva (CCI = 1) nas marcações de cada avaliador, enquanto na avaliação interobservador não houve diferença significativa em nenhuma das coordenadas (p > 0,5) entre os softwares, ao comparar os avaliadores 1 e 2.

Conclusão

O Eximius Med, portanto, é uma alternativa consistente, comparável, precisa e de alta acurácia para uso em estereotaxia craniana.

 

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Keywords

neurosurgery - software - imaging - three-dimensional

Palavras-chave

neurocirurgia - software - imagem - tridimensional

Introduction

The advent of stereotactic techniques in human neurosurgery, pioneered by Spiegel and Wycis in 1947, revolutionized the field by enabling precise, mathematically calculated targeting of intracranial structures. This innovation allowed for the insertion of rigid needles with millimeter accuracy, obviating the need for direct lesion visualization.[1]

In Brazil, contemporary stereotactic software platforms have evolved to incorporate sophisticated capabilities, including multimodal volumetric image coregistration, encompassing computed tomography (CT) and various magnetic resonance imaging (MRI) sequences, and integration of diverse functional stereotactic atlases. The MNPS (Mevis Informática Médica LTDA.) is a stereotactic planning software with a three-decade history, exemplifies the long-standing tools available in clinical practice.

Recent advancements in stereotactic programming have yielded more sophisticated resources, such as robust image manipulation frameworks and touch screen-compatible interfaces. Eximius Med (Artis Tecnologia LTDA.) is an emergent software for image manipulation and surgical planning, featuring a stereotactic module under development. This module is designed to support all stereotactic frame systems currently in use in Brazil.

The primary objective of this study is to rigorously assess the accuracy and precision of the stereotactic coordinates generated by Eximius Med following geometric registration, thereby evaluating its potential as a next generation planning tool.

 

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Materials and Methods

Study Design

This investigation employed a comparative analysis of stereotactic coordinates derived from CT images of the skull. Two independent evaluators marked coordinates (X, Y, Z) using both the MNPS and Eximius Med software. Subsequent statistical analyses assessed precision and accuracy.

 

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Image Acquisition

The skull CT images were obtained using a Brilliance CT 64 System (Koninklijke Philips N.V.) with the following parameters: collimation 20 × 0.625, pitch 0.348, 512 × 512 matrix, field of view 200 mm, 140 kVp, 278 to 600 mA, and slice thickness 1 mm.

 

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Precision and Accuracy Assessment

Two independent evaluators marked 60 points distributed throughout skull CT imaging. The MNPS coordinates served as the gold standard. The primary error metric, target registration error (TRE), was defined as the Euclidean distance between points marked on MNPS (x₁, y₁, z₁) and corresponding points on Eximius Med (x₂, y₂, z₂), calculated as:

D² = (x₁ - x₂)² + (y₁ - y₂)² + (z₁ - z₂)²

Stereotactic Cartesian coordinates of 60 target points were exported from MNPS ([Fig. 1]). The corresponding examinations were then imported into Eximius Med, where identical points were marked and their coordinates exported ([Fig. 2]). All tests were conducted in a computer-simulated environment.

Fig. 1 Stereotaxis module interface in the MNPS software.

Fig. 2 Stereotaxis module interface in the Eximius Med software.

 

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Statistical Analysis

Data were expressed as means and standard deviations for normally distributed continuous variables. Comparisons between quantitative variables utilized Student's t test, with p < 0.05 considered statistically significant.

Accuracy was assessed by calculating the mean distance between MNPS and Eximius Med points, while precision was evaluated using standard deviation. Effect size was quantified using Cohen's D. Intraobserver agreement was determined via intraclass correlation coefficient (ICC), and interobserver agreement was assessed using the t test. All statistical analyses were performed using the jamovi (free and open source) software, version 2.3.28.[2]

 

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Results

The mean Euclidean distance between corresponding points marked in Eximius Med and MNPS software was of 0.07 ± 0.056 (95%CI: −0.037–0.18) mm. The inclusion of zero in the CI suggests potential equivalence between the two software platforms. Analysis of individual coordinates ([Fig. 3]) revealed statistically significant systematic differences.

Fig. 3 Systematic error analysis in each coordinate (X, Y, Z), with statistical significance at p < 0.05.

Despite statistical significance, these differences were submillimetric, with low effect sizes (Cohen's D) and minimal clinical relevance ([Table 1]). The scatter-plot analysis ([Fig. 4]) yielded a linear regression line with a tangent of the slope of 1 (f(x) = 1), providing additional evidence for equivalence between MNPS and Eximius Med. The ICC assessment of measurement between the software platforms demonstrated a perfect positive correlation (ICC = 1), further supporting their equivalence.

Table 1 Paired differences and interclass correlation coefficient (ICC) in the Eximius Med and MNPS software

Paired differences
Pair	N	Mean ± standard error of the mean	95% CI of the lower difference	95% CI of the upper difference	Correlation (ICC)
X Eximius Med and X MNPS	120	0.10 ± 0.02	0.06	0.14	1.0*
Y Eximius Med and Y MNPS	120	−0.46 ± 0.02	−0.51	−0.41	1.0*
Z Eximius Med and Z MNPS	120	−0.09 ± 0.03	−0.16	−0.03	1.0*

Note: *p < 0.05.

Fig. 4 Scatter plot comparing coordinates between the Eximius Med and MNPS software.

Interobserver evaluation revealed no significant differences for any of the assessed coordinates in either Eximius Med or MNPS ([Table 2]). This finding indicates that both evaluators marked points with comparable accuracy across both software tools, independent of the platform used.

Table 2 Interobserver assessment in the Eximius Med and MNPS software

Interobserver Assessment
	Evaluator	N	Mean ± standard error of the mean	p-value
X Eximius Med	1	60	−3.14 ± 3.64	0.98
	2	60	−2.99 ± 3.65
Y Eximius Med	1	60	−9.53 ± 3.62	0.99
	2	60	−9.67 ± 3.61
Z Eximius Med	1	60	58.56 ± 3.55	1.00
	2	60	58.38 ± 3.55
X MNPS	1	60	−3.10 ± 3.65	0.98
	2	60	−3.22 ± 3.66
Y MNPS	1	60	−9.14 ± 3.62	0.98
	2	60	−9.15 ± 3.61
Z MNPS	1	60	58.67 ± 3.51	1.00
	2	60	58.46 ± 3.55

 

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Discussion

This study evaluated the equivalence between Eximius Med and MNPS software in defining stereotactic coordinates. Our findings demonstrate a high level of consistency and accuracy between both platforms, with a mean Euclidean distance of 0.07 ± 0.056 (95%CI: −0.037–0.18) mm between corresponding points. This submillimetric difference is clinically insignificant in the context of stereotactic neurosurgery, where frame graduations and practical limitations typically constrain precision to the millimeter scale.

Stereotaxy is a widely used method of image-guided surgery particularly useful for minimally invasive approaches and device implantation, with reported morbidity rates of 0 to 6.5%, mortality rates of 0 to 9%, and accuracy rates of 88 to 100%.[3] A critical understanding of the mathematics involved in coordinate transformations is essential, as it has direct implications during surgery.[4] [5] [6] [7] [8] [9] [10] [11] [12]

The observed systematic differences in individual coordinates (X: 0.11 ± 0.02 mm; p = 0.04; Y: −0.56 ± 0.04 mm; p < 0.001; and Z: −0.26 ± 0.04 mm; p < 0.001), while statistically significant, are well within the acceptable range for stereotactic procedures. The perfect positive correlation (ICC = 1) between measurements from both software platforms further supports their equivalence. This high level of agreement is crucial for the interchangeability of these tools in clinical practice, potentially allowing for seamless transitions between platforms without compromising the accuracy of surgical planning.

Moreover, the lack of significant interobserver differences in coordinate marking across both software platforms ([Table 2]) underscores the reliability and user-friendliness of these tools. This consistency between evaluators is essential in clinical settings where multiple team members may be involved in surgical planning. Eximius Med, primarily developed as a medical imaging processing tool, has successfully integrated stereotactic functionality comparable to the established MNPS software. This expansion of capabilities is particularly relevant given the increasing complexity of neurosurgical planning and the growing demand for precise, image-guided interventions.

Eximius Med, primarily a medical imaging processing tool enabling visualization, three-dimensional reconstruction, and surgical planning based on CT and MRI scans, has expanded its functionality to include a stereotactic module. This module incorporates various tools commonly used in image-guided neurosurgery, from measurement tools to image coregistration.

There is a demonstrated lower distortion and greater precision in CT- compared to MRI-based procedures.[5] The submillimetric differences observed in our study were deemed clinically irrelevant, given that stereotactic frames are graduated in discrete millimeter values. This finding aligns with observations by Paraskevopoulos et al.,[6] where statistically significant measurement differences did not necessarily impact surgical outcomes.[5] [6] [7]

Previous clinical studies have shown that neuronavigation software, as Eximius Med, is highly effective for surgical planning, with an average error of 4.05 ± 3.62 mm between virtual image and actual location. This high accuracy has been associated with minimized craniotomy sizes, albeit with a slight increase in average surgical procedure time.[8] [9]

Stereotactic techniques have also improved the accuracy and efficiency of deep brain stimulation (DBS) in treating Parkinson's disease, essential tremor, and primary dystonia.[10] In a study utilizing the MicroTargeting Microtable (FHC, Inc.) platform, the mean Euclidean positioning error of DBS electrodes was 0.97 ± 0.37 mm, with a mean radial error of 0.80 ± 0.41 mm (n = 9), demonstrating submillimetric precision comparable to our findings.[11]

Stereotaxy has also proven valuable in accurate lesion diagnosis through biopsies. Studies comparing stereotactic biopsy (SB) with open surgical resection have reported concordance rates between 43 and 100%.[13] [14] [15] [16] [17] In a series of 47 patients, SB diagnoses showed 80% concordance with postresection or postmortem diagnoses,[14] highlighting its potential as a safe and accurate diagnostic method.

Our findings support the equivalence of these software platforms in stereotactic planning applications. This equivalence is crucial, as accurate stereotactic planning is fundamental to enhancing patient safety, optimizing surgical precision, and improving clinical outcomes across a range of neurosurgical procedures, including DBS, tumor biopsies, and minimally invasive interventions.

Limitations of this study include the absence of evaluations in real surgical settings, which may impact the generalizability of the results. While our study provides robust evidence for the reliability of Eximius Med in stereotactic planning, future research should focus on larger-scale clinical implementations and real-world surgical outcomes, to further validate these findings. As stereotactic techniques continue to evolve, ongoing evaluation and refinement of planning tools will be essential to ensure the highest standards of care in neurosurgical practice.

 

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Conclusion

In this comparative analysis of the Eximius Med and MNPS software for stereotactic coordinate determination, we found high consistency between the systems, with only clinically insignificant systematic errors. The submillimetric differences observed were well within the acceptable range for these procedures, given the inherent limitations of frame graduation and the practical constraints of neurosurgical interventions.

 

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Conflict of Interests

The authors have no conflict of interests to declare.

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Publication History

Received: 22 November 2024

Accepted: 20 March 2025

Article published online:
01 July 2025