Lymph node ratio,an independent prognostic factor for patients with stage II-III rectal carcinoma

BackgroundIdentification of the proper surgical method and the most reliable prognostic parameters of rectal carcinomas is a challenging issue. The aim of this paper was to determine the possible prognostic role of the number of harvested lymph nodes versus lymph node ratio (LNR) in patients with rectal carcinomas, and the proper value of LNR that can be used as prognostic parameter.Materials and methodsA retrospective study was performed in 186 consecutive patients with rectal carcinomas that underwent surgical resection. The LNR was calculated for cases from stage II-III, and was correlated with classic prognostic parameters and overall survival (OS).ResultsA statistically significant difference was found between LNR of 0.15 and OS (p = 0.03), respectively LNR > 0.15 and TNM stage (p < 0.0001), but also tumor infiltration level (p < 0.05). The number of harvested lymph nodes was not correlated with the tumor stage (r = 0.148, p = 0.06) and this parameter did not influence the OS, when the number of 12 or 14 lymph nodes was used as the ideal value (p = 0.6 and p = 0.66, respectively).ConclusionIn patients with rectal carcinomas that underwent preoperative chemoradiotherapy, a LNR of 0.15 is a parameter with independent prognostic value, comparing with the number of harvested lymph nodes. The specific LNR should be calculated in larger cohorts.     

3D simulation of needle-tissue interaction with application to prostate brachytherapy.

This paper presents a needle-tissue interaction model that is a 3D extension of prior work based on needle and tissue models discretized using the Finite Element Method. The use of flexible needles necessitates remeshing the tissue during insertion, since simple mesh-node snapping to the tip can be detrimental to the simulation. In this paper, node repositioning and node addition are the two methods of mesh modification examined for coarse meshes. Our focus is on numerical approaches for fast implementation of these techniques. Although the two approaches compared, namely the Woodbury formula (matrix inversion lemma) and the boundary condition switches, have the same computational complexity, the Woodbury formula is shown to perform faster due to its cache-efficient order of operations. Furthermore, node addition is applied in constant time for both approaches, whereas node repositioning requires longer and variable computational times. A method for rendering the needle forces during simulated insertions into a 3D prostate model has been implemented. Combined with a detailed anatomical segmentation, this will be useful in teaching the practice of prostate brachytherapy. Issues related to discretization of such coupled (e.g., needle-tissue) models are also discussed.     

Achieving competency in bronchoscopy: Challenges and opportunities

Bronchoscopy education is undergoing significant changes in step with other medical and surgical specialties that seek to incorporate simulation‐based training and objective measurement of procedural skills into training programmes. Low‐ and high‐fidelity simulators are now available and allow learners to gain fundamental bronchoscopy skills in a zero‐risk environment. Testing trainees on simulators is currently possible by using validated assessment tools for both essential bronchoscopy and endobronchial ultrasound skills, and more tools are under development for other bronchoscopic techniques. Educational concepts including the ‘flipped classroom’ model and problem‐based learning exercises are increasingly used in bronchoscopy training programmes. These learner‐centric teaching modalities require well‐trained educators, which is possible thorough the expansion of existing faculty development programmes.     

Identifying the mechanical properties of tissue by ultrasound strain imaging

A new elastography method is presented that images the mechanical properties of soft tissue. The tissue is externally vibrated over a range of frequencies simultaneously and the resulting displacement is recorded at multiple locations and time instants with a sequence of ultrasound images. Two methods are proposed for estimating the mechanical properties from the recorded data. In the first method, equations of motion are written for a tissue model of masses, springs and dampers. The equations are solved to identify the model parameters and construct an image. The second method performs a transfer function analysis of the tissue motion. The tissue properties are identified from the shape the of transfer function. Simulations show good performance of the new method compared with static elastography. Initial experimental results from homogeneous and layered tissue phantoms also demonstrate the ability quantitatively to image tissue stiffness. Preliminary results are obtained for viscosity and density estimation. Further work is needed to extend the formulation to 3-D and improve robustness of the viscosity and density estimates.     

The effects of physical constraints in laparoscopic surgery

In order to provide guidelines for the development and evaluation of advanced laparoscopic instrumentation (including teleoperated devices), we assessed the impact of constrained motion on surgeons' ability to perform standardized pick-and-place and suturing tasks when using an emulation of a perfectly transparent teleoperator under direct, binocular vision. The surgeons' performance when using the emulator represents an upper bound on performance using any conceivable teleoperator with one-to-one force and motion scaling. Our analysis examines the mean differences in task completion time between three open tool configurations and two laparoscopic tool configurations with various degrees of freedom (DOFs). Fifteen laparoscopic surgeons participated in the study. We show that avoiding reversed hand and tool motions and adding DOFs significantly improves suturing performance. In the pick-and-place task, avoiding the reversed motions also improves performance, but adding DOFs to an open tool configuration does not. For both tasks, subjects who use open tools constrained to four DOF complete their tasks in approximately 38% less time than when using standard four-DOF laparoscopic tools. The marginal benefit to overall surgical time of adding two additional degrees of freedom is likely to be small (approximately 2%), although surgeons may then feel confident in attempting more difficult procedures.     

Denoising of pre-beamformed photoacoustic data using generative adversarial networks

We have trained generative adversarial networks (GANs) to mimic both the effect of temporal averaging and of singular value decomposition (SVD) denoising. This effectively removes noise and acquisition artifacts and improves signal-to-noise ratio (SNR) in both the radio-frequency (RF) data and in the corresponding photoacoustic reconstructions. The method allows a single frame acquisition instead of averaging multiple frames, reducing scan time and total laser dose significantly. We have tested this method on experimental data, and quantified the improvement over using either SVD denoising or frame averaging individually for both the RF data and the reconstructed images. We achieve a mean squared error (MSE) of 0.05%, structural similarity index measure (SSIM) of 0.78, and a feature similarity index measure (FSIM) of 0.85 compared to our ground-truth RF results. In the subsequent reconstructions using the denoised data we achieve a MSE of 0.05%, SSIM of 0.80, and a FSIM of 0.80 compared to our ground-truth reconstructions.