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In the present research, the navigation of a flexible needle into the human liver in the context of the robotic-assisted intraoperative treatment of the liver tumors, is reported. Cosserat (micropolar) elasticity is applied to describe the interaction between the needle and the human liver. The theory incorporates the local rotation of points and t...
Citations
... Several surgery processes, the surgical needle requires inserting into soft tissue, and the boundary of the soft tissue would be distorted under the needle insertion load. 18 The target also shifts with the soft tissue deformation; therefore, the surgical needle could not reach the aim appropriately. All of the works mentioned above are numerical methods with the help of useful equations but not a biomechanical investigation. ...
Surgical needle insertion is generally used in the current advanced surgery process, particularly in the area of biopsy, MIS or minimally invasive surgery, brachytherapy, etc. During the needle insertion performance into the soft tissue, one of the most important issues is the tissue deformation that affects the needle engagement inside the tissue material. We have presented an energy-based insertion model, and the conical shape of deformed tissue is assumed. The tests are performed on PVA gel samples, and the model is analyzed to determine the tissue deformation volume during needle insertion into soft tissue. The procedures for evaluating the puncture force which creates the deformation of the contact point. With the help of the needle insertion experimental investigation, a geometric model of tissue deformation phenomenon and insertion force was investigated. The active needle-soft tissue contacts are studied, and with the help of the energy-based insertion model, the different factors like strain energy, potential, and dissipated energies are investigated. The tests are completed on the tissue mimic PVA gel samples, and the results show the volume and area of tissue deformation; at the time of initial needle insertion, the maximum tissue deformation arises and during the needle movement in the post-perforation stage, the deformation gradually decreases as the more peripheral work is altered into the vicious and degenerate energies. The maximum insertion force was noticed in 14°b evel angle needle tip and at 3 mm/s needle insertion speed, the volume of tissue deformation was maximum. The maximum deformation of the issue arises at the initial perforate position, and the distortion reduces along with the raises of the needle movement during the post-insertion period as the needle insertion work is converted into vicious and dissolute energies.
... In the calculation, shear modulus (G) ranged from 0.1 to 12.0 kPa in 0.1 increments. Poisson's ratio was set to 0.45, 0.49, and 0.499995 based on previous studies (Chen et al 1996, Barnes et al 2007, Chiroiu et al 2021. Therefore, using the linear elasticity model, the displacement was calculated with 360 parameters for each patient's liver model. ...
Objective:
This study aimed to produce a three-dimensional liver elasticity map using the finite element method (FEM) and respiration-induced motion captured by T1-weighted magnetic resonance images (FEM-E-map) and to evaluate whether FEM-E-maps can be an imaging biomarker comparable to magnetic resonance elastography (MRE) for assessing the distribution and severity of liver fibrosis.
Approach:
We enrolled 14 patients who underwent MRI and MRE. T1-weighted MR images were acquired during shallow inspiration and expiration breath-holding, and the displacement vector field (DVF) between two images was calculated using deformable image registration. FEM-E-maps were constructed using FEM and DVF. First, three Poisson's ratio settings (0.45, 0.49, and 0.499995) were validated and optimized to minimize the difference in liver elasticity between the FEM-E-map and MRE. Then, the whole and regional liver elasticity values estimated using FEM-E-maps were compared with those obtained from MRE using Pearson's correlation coefficients. Spearman rank correlations and chi-square histograms were used to compare the voxel-level elasticity distribution.
Main results:
The optimal Poisson's ratio was 0.49. Whole liver elasticity estimated using FEM-E-maps was strongly correlated with that measured using MRE (r = 0.96). For regional liver elasticity, the correlation was 0.84 for the right lobe and 0.82 for the left lobe. Spearman analysis revealed a moderate correlation for the voxel-level elasticity distribution between FEM-E-maps and MRE (0.61 ± 0.10). The small chi-square distances between the two histograms (0.11 ± 0.07) indicated good agreement.
Significance:
FEM-E-maps represent a potential imaging biomarker for visualizing the distribution of liver fibrosis using only T1-weighted images obtained with a common MR scanner, without any additional examination or special elastography equipment. However, additional studies including comparisons with biopsy findings are required to verify the reliability of this method for clinical application.
Accurate needle targeting is critical for many clinical procedures, such as transcutaneous biopsy or radiofrequency ablation of tumors. However, targeting errors may arise, limiting the widespread adoption of these procedures. Advances in flexible needle (FN) steering are emerging to mitigate these errors. This review summarizes the state-of-the-art developments of FNs and addresses possible targeting errors that can be overcome with steering actuation techniques. FN steering techniques can be classified as passive and active. Passive steering directly results from the needle-tissue interaction forces, whereas active steering requires additional forces to be applied at the needle tip, which enhances needle steerability. Therefore, the corresponding targeting errors of most passive FNs and active FNs are between 1 and 2 mm, and less than 1 mm, respectively. However, the diameters of active FNs range from 1.42 to 12 mm, which is larger than the passive steering needle varying from 0.5 to 1.4 mm. Therefore, the development of active FNs is an area of active research. These active FNs can be steered using tethered internal direct actuation or untethered external actuation. Examples of tethered internal direct actuation include tendon-driven, longitudinal segment transmission and concentric tube transmission. Tendon-driven FNs have various structures, and longitudinal segment transmission needles could be adapted to reduce tissue damage. Additionally, concentric tube needles have immediate advantages and clinical applications in natural orifice surgery. Magnetic actuation enables active FN steering with untethered external actuation and facilitates miniaturization. The challenges faced in the fabrication, sensing, and actuation methods of FN are analyzed. Finally, bio-inspired FNs may offer solutions to address the challenges faced in FN active steering mechanisms.
