The violation of Fitts' Law: an examination of displacement biases and corrective submovements.

Fitts' Law holds that, to maintain accuracy, movement times of aiming movements must change as a result of varying degrees of movement difficulty. Recent evidence has emerged that aiming to a target located last in an array of placeholders results in a shorter movement time than would be expected by the Fitts' equation-a violation of Fitts' Law. It has been suggested that the violation emerges because the performer adopts an optimized movement strategy in which they partially pre-plan an action to the closest placeholder (undershoot the last placeholder) and rely on a secondary acceleration to propel the limb toward the last location when it is selected as the target (Glazebrook et al. in Hum Mov Sci 39:163-176, 2015). In the current study, we examine this proposal and further elucidate the processes underlying the violation by examining limb displacement and corrective submovements that occur when performers aim to different target locations. For our Main Study, participants executed discrete aiming movements in a five-placeholder array. We also reanalyzed data from a previously reported study in which participants aimed in placeholder and no-placeholder conditions (Blinch et al. in Exp Brain Res 223:505-515, 2012). The results showed the violation of Fitts' Law unfolded following peak velocity (online control). Further, the analysis showed that movements to the last target tended to overshoot and had a higher proportion of secondary submovements featuring a reversal than other categories of submovement (secondary accelerations, discontinuities). These findings indicate that the violation of Fitts' Law may, in fact, result from a strategic bias toward planning farther initial displacements of the limb which accommodates a shorter time in online control.

MRI-assisted cervix cancer brachytherapy pre-planning, based on application in paracervical anaesthesia: final report.

BACKGROUND: Optimal applicator insertion is a precondition for the success of cervix cancer brachytherapy (BT). We aimed to assess feasibility and efficacy of MRI-assisted pre-planning, based on applicator insertion in para-cervical anaesthesia (PCA). PATIENTS AND METHODS: Five days prior to BT, the pre-planning procedure was performed in 18 cervix cancer patients: tandem-ring applicator was inserted under PCA, pelvic MRI obtained and applicator removed. Procedure tolerability was assessed. High risk clinical target volume (HR CTV) and organs at risk were delineated on the pre-planning MRI, virtual needles placed at optimal positions, and dose planning performed. At BT, insertion was carried out in subarachnoidal anaesthesia according to pre-planned geometry. Pre-planned and actual treatment parameters were compared. RESULTS: Pre-planning procedure was well tolerated. Median difference between the pre-planned and actual needle insertion depth and position were 2 (0-10) mm and 4 (0-30) degrees, respectively. The differences between the pre-planned and actual geometric and dosimetric parameters were statistically non-significant. All actual needles were positioned inside the HR CTV and outside the organs at risk (OAR). CONCLUSIONS: Our pre-planning approach is well tolerated and effective. Pre-planned geometry and dose distribution can be reproduced at BT.

Three-dimensional printed models as an effective tool for the management of complex congenital heart disease.

Introduction: Three-dimensional printed models are widely used in the medical field for surgical and interventional planning. In the context of complex cardiovascular defects such as pediatric congenital heart diseases (CHDs), the adoption of 3D printed models could be an effective tool to improve decision-making. In this paper, an investigation was conducted into the characteristics of 3D printed models and their added value in understanding and managing complex pediatric congenital heart disease, also considering the associated cost. Methods: Volumetric MRI and CT images of subjects with complex CHDs were retrospectively segmented, and the associated 3D models were reconstructed. Different 3D printing technologies and materials were evaluated to obtain the 3D printed models of cardiac structures. An evaluation of time and costs associated with the 3D printing procedure was also provided. A two-level 3D printed model assessment was carried out to investigate the most suitable 3D printing technology for the management of complex CHDs and the effectiveness of 3D printed models in the pre-surgical planning and surgical strategies' simulations. Results: Among the different techniques, selective laser sintering resulted to be the most suitable due to its reduced time and cost and for the positive clinical feedback (procedure simulation, surface finish, and reproduction of details). Conclusion: The adoption of 3D printed models contributes as an effective tool in the management of complex CHDs, enabling planning and simulations of surgical procedures in a safer way.

A novel design for prosthetic ear guiding device: A technical note.

This article describes a newly designed Prosthetic Auricular Guide (PAG) that allows for accurate planning and positioning of both the auricular implants and the prosthetic auricle. The design aims to provide a cost-effective guiding device for more esthetic ear prostheses which is the patient's main concern. Along with determining the best clinically accepted position of the ear, the device can be used while taking CBCT which allows for the integration of the clinically approved position with the remaining bone for accurate planning of implant positions. Furthermore, the device can be fixed during surgery for accurate transmission of the planned position. The device is also adjustable making it suitable for all patterns of auricular defects, different ages, and even for patients with asymmetric faces.

PRE-PLANNING ANKLE ARTHRODESIS USING 3D RECONSTRUCTED TOMOGRAPHIES.

OBJECTIVE: To implement one analysis method of the ankle bone contour that could make a more precise ankle arthrodesis. METHODS: Twenty tomographies were submitted to 3D reconstruction. Seven points of anatomic interest for ankle arthrodesis with the three screws technique were marked with a triplannar marker. The median of the position of markers was estimated, and the union of the seven median points allow the construction of one median ankle for that population. Using this median ankle, sizes and angles for the screws position were determined. RESULTS: Two median ankles were reconstructed, left and right. The position of the screw passage were determined considering the anatomical parameters. In the right ankle the lateral to medial screw should enter 4.56 cm and 0.79 above and posterior to lateral malleolus, with one inclination of 17.34° in relation to tibial longitudinal axis; and 0° in relation to tibial axial plane. The position for the other two screws is also described. CONCLUSION: Our article is the first to presents one precise guide for ankle arthrodesis based on a populational assessment. Level of evidence II, Diagnostic Studies.

OBJETIVO: Implementar método de análise do contorno e alinhamento ósseos no tornozelo de uma população normal, possibilitando uma artrodese tibiotársica mais precisa. MÉTODOS: Tomografias de vinte tornozelos foram submetidas à reconstrução 3D. Nesses exames, 7 pontos anatômicos de interesse para a técnica de fixação com 3 parafusos foram identificados e marcados com indicadores da posição triplanar. As médias das localizações de cada ponto foram calculadas. A união dessas médias permitiu a reconstrução de um tornozelo padrão daquela população. Nesses tornozelos médios estudou-se os comprimentos e ângulos para a passagem dos parafusos. RESULTADOS: Dois tornozelos, direito e esquerdo, foram reconstruídos. A posição para a passagem dos parafusos em relação a parâmetros anatômicos foi determinada. Para o tornozelo direito, a passagem do parafuso de lateral para medial deve ocorrer com o ponto de entrada 4,56 cm acima e 0,79 cm posterior à ponta do maléolo lateral, com inclinação de 17,34° em relação ao eixo longitudinal e 0° em relação ao eixo axial da tíbia. As posições dos outros dois parafusos também estão descritas. CONCLUSÃO: Esse é o primeiro trabalho que apresenta um guia preciso para realização da artrodese do tornozelo, baseado em um estudo populacional. Nível de evidência II, Estudos Diagnósticos.

Total virtual workflow in CAD-CAM bony reconstruction with a single step free fibular graft and immediate dental implants.

The Surgical reconstruction of defects of the face is challenging. Local and regional flaps have an important part to play, but large defects of bone and soft tissue are a greater problem. Microvascular tissue transfer has become the standard for such patients, and preoperative planning of bony reconstructions is now common. To use these preplanning tools best the implants should be placed in the prosthetically ideal place, and the bone positioned to surround the implants - that is, truly backward planning of the position of the bone. The buccolingual angulation and the actual position of the implants during operation can be difficult to verify. Using commonly available software and 3-dimensional printing solutions, therefore, we have constructed an algorithm to optimise the position of these implants during the operation, and to get their position as close to the planned outcome as possible. This algorithm is adaptable to any implant system and is potentially possible in any implant or preplanning software unit.

Pre-planning ankle arthrodesis using 3d reconstructed tomographies / Desenvolvimento da artrodese do tornozelo baseada na tomografia com reconstrução 3d

ABSTRACT Objective: To implement one analysis method of the ankle bone contour that could make a more precise ankle arthrodesis. Methods: Twenty tomographies were submitted to 3D reconstruction. Seven points of anatomic interest for ankle arthrodesis with the three screws technique were marked with a triplannar marker. The median of the position of markers was estimated, and the union of the seven median points allow the construction of one median ankle for that population. Using this median ankle, sizes and angles for the screws position were determined. Results: Two median ankles were reconstructed, left and right. The position of the screw passage were determined considering the anatomical parameters. In the right ankle the lateral to medial screw should enter 4.56 cm and 0.79 above and posterior to lateral malleolus, with one inclination of 17.34° in relation to tibial longitudinal axis; and 0° in relation to tibial axial plane. The position for the other two screws is also described. Conclusion: Our article is the first to presents one precise guide for ankle arthrodesis based on a populational assessment. Level of evidence II, Diagnostic Studies.

RESUMO Objetivo: Implementar método de análise do contorno e alinhamento ósseos no tornozelo de uma população normal, possibilitando uma artrodese tibiotársica mais precisa. Métodos: Tomografias de vinte tornozelos foram submetidas à reconstrução 3D. Nesses exames, 7 pontos anatômicos de interesse para a técnica de fixação com 3 parafusos foram identificados e marcados com indicadores da posição triplanar. As médias das localizações de cada ponto foram calculadas. A união dessas médias permitiu a reconstrução de um tornozelo padrão daquela população. Nesses tornozelos médios estudou-se os comprimentos e ângulos para a passagem dos parafusos. Resultados: Dois tornozelos, direito e esquerdo, foram reconstruídos. A posição para a passagem dos parafusos em relação a parâmetros anatômicos foi determinada. Para o tornozelo direito, a passagem do parafuso de lateral para medial deve ocorrer com o ponto de entrada 4,56 cm acima e 0,79 cm posterior à ponta do maléolo lateral, com inclinação de 17,34° em relação ao eixo longitudinal e 0° em relação ao eixo axial da tíbia. As posições dos outros dois parafusos também estão descritas. Conclusão: Esse é o primeiro trabalho que apresenta um guia preciso para realização da artrodese do tornozelo, baseado em um estudo populacional. Nível de evidência II, Estudos Diagnósticos.

Validation of accuracy in image co-registration with computed tomography and magnetic resonance imaging in Gamma Knife radiosurgery.

The latest version of Leksell GammaPlan (LGP) is equipped with Digital Imaging and Communication in Medicine (DICOM) image-processing functions including image co-registration. Diagnostic magnetic resonance imaging (MRI) taken prior to Gamma Knife treatment is available for virtual treatment pre-planning. On the treatment day, actual dose planning is completed on stereotactic MRI or computed tomography (CT) (with a frame) after co-registration with the diagnostic MRI and in association with the virtual dose distributions. This study assesses the accuracy of image co-registration in a phantom study and evaluates its usefulness in clinical cases. Images of three kinds of phantoms and 11 patients are evaluated. In the phantom study, co-registration errors of the 3D coordinates were measured in overall stereotactic space and compared between stereotactic CT and diagnostic CT, stereotactic MRI and diagnostic MRI, stereotactic CT and diagnostic MRI, and stereotactic MRI and diagnostic MRI co-registered with stereotactic CT. In the clinical study, target contours were compared between stereotactic MRI and diagnostic MRI co-registered with stereotactic CT. The mean errors of coordinates between images were < 1 mm in all measurement areas in both the phantom and clinical patient studies. The co-registration function implemented in LGP has sufficient geometrical accuracy to assure appropriate dose planning in clinical use.

MRI assisted cervix cancer brachytherapy pre-planning, based on insertion of the applicator in para-cervical anaesthesia: preliminary results of a prospective study.

PURPOSE: To report on preliminary results of a prospective study on MRI-assisted cervix cancer brachytherapy pre-planning. MATERIAL AND METHODS: In six locally advanced cervix cancer patients, five days before the first brachytherapy fraction, tandem & ring applicator was inserted under para-cervical anaesthesia, MRI performed and applicator removed. Procedure-time and patient-tolerability were recorded. High risk CTV and organs at risk were delineated, virtual needles placed and dose planning performed. At brachytherapy, insertion was carried out under subarachnoidal anaesthesia, according to pre-planned geometry. Pre-planned and actual needle positions and DVH parameters were compared. RESULTS: The procedure was well tolerated and short. All inserted needles were inside high risk CTV and outside organs at risk. Differences in pre-planned and actual DVH parameters and implant geometry were small. CONCLUSIONS: The procedure was well tolerated and feasible. Pre-planned geometry could be reproduced thoroughly at brachytherapy application.

Comparison of 2D- and 3D-guided implantation in accelerated partial breast irradiation (APBI).

PURPOSE: In this study two different pre-planning methods (2D vs. 3D) were compared in respect to the implant quality as judged by volumetric and dose parameters of the treatment plans. The aim of this work was to evaluate the influence of the imaging modalities used for pre-planning purpose to the treatment plan quality. MATERIAL AND METHODS: Twenty-four patients treated with HDR multicatheter implants were randomly selected for experiment. All patients underwent breast conserving surgery. Flexible catheters were implanted into the breast through the template. Inter-catheter distance, number of planes and catheters were adjusted, in respect to the size and location of the target. Pre-planning was used to evaluate the implant geometry in respect to the target. Needles number and position were modified if necessary. There were two experimental subgroups consisted of 12 patients each. Different pre-planning procedure was employed in each group. In the first group 2D X-ray imaging system was used. In the second one the 3D pre-planning method based on CT was performed. Treatment plans were evaluated with parameters calculated based on dose-volume histograms (DVHs). Volumetric and dose parameters were used for comparison of the dose distribution between the two experimental subgroups. RESULTS: The mean value of target coverage VPTV100 is higher for 3D pre-planning than for 2D (91.7% vs. 86.1%). The dose that covers 90% of the PTV (D90) is also higher for 3D pre-planning than for 2D (4.2 Gy vs. 3.6 Gy). Similar relation can be observed for the values of dose homogeneity index where DHI obtained for 3D pre-planning is 0.60 and 0.53 for 2D. All differences were statistically significant with p < 0.05. CONCLUSIONS: Analysis presented in this paper showed that 3D pre-planning method improves the geometrical quality of the implant.