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An enzyme-fueled transient volume phase transition (TVPT) of hydrogels under out-of-equilibrium conditions is reported. The approach takes inspiration from the metabolic cycle, comprising nutrient intake and anabolism/catabolism followed by waste excretion. The incorporation of methacrylic acid and acrylated trypsin in a polymeric hydrogel allowed the TVPT of the gel to be fueled by lysozyme. With the intake of lysozyme as fuel, the construction/destruction of electrostatic cross-linkages induced transient shrinkage/swelling of the gel accompanied by the depletion of lysozyme activity. The system's transient response could be flexibly programmed by adjusting not only the fuel concentration but the chemical composition of materials. The lysozyme-fueled TVPT of the gel could be exploited to transient changes in the mechanical properties of the gel. Our work opens a route toward a new class of stimuli-responsive hydrogels for biomedical applications. [ABSTRACT FROM AUTHOR]

A metabolic cycle‐inspired hydrogel which exhibits the biomacromolecule‐fueled transient volume phase transition is reported. This hydrogel has the affinity and digestive capacity for a fuel α‐poly‐L‐lysine by incorporating acrylic acid and trypsin. The hydrogel captured fuel and transiently shrank owing to the construction of electrostatic cross‐linkages. This process was inherently connected with the digestion of these cross‐linkages and the release of oligo‐lysine as waste, which induced the reswelling of the hydrogel at equilibrium. The transient volume change of the hydrogel realized the fuel‐stimulated transient release of a payload. This study provides a strategy for engineering materials with biomacromolecule‐fueled dynamic functions under the out‐of‐equilibrium condition. [ABSTRACT FROM AUTHOR]

This paper describes a ultrasound (3-D US) system that aims to achieve augmented reality (AR) visualization during laparoscopic surgery, especially for the liver. To acquire 3-D US data of the liver, the tip of a laparoscopic ultrasound probe is tracked inside the abdominal cavity using a magnetic tracker. The accuracy of magnetic trackers, however, is greatly affected by magnetic field distortion that results from the close proximity of metal objects and electronic equipment, which is usually unavoidable in the operating room. In this paper, we describe a calibration method for intraoperative magnetic distortion that can be applied to laparoscopic 3-D US data acquisition; we evaluate the accuracy and feasibility of the method by in vitro and in vivo experiments. Although calibration data can be acquired freehand using a magneto-optic hybrid tracker, there are two problems associated with this method--error caused by the time delay between measurements of the optical and magnetic trackers, and instability of the calibration accuracy that results from the uniformity and density of calibration data. A temporal calibration procedure is developed to estimate the time delay, which is then integrated into the calibration, and a distortion model is formulated by zeroth-degree to fourth-degree polynomial fitting to the calibration data. In the in vivo experiment using a pig, the positional error caused by magnetic distortion was reduced from 44.1 to 2.9 mm. The standard deviation of corrected target positions was less than 1.0 mm. Freehand acquisition of calibration data was performed smoothly using a magneto-optic hybrid sampling tool through a trocar under guidance by realtime 3-D monitoring of the tool trajectory; data acquisition time was less than 2 min. The present study suggests that our proposed method could correct for magnetic field distortion inside the patient's abdomen during a laparoscopic procedure within a clinically permissible period of time, as well as enabling an accurate 3-D US reconstruction to be obtained that can be superimposed onto live endoscopic images. Index Terms--Accuracy validation, computer-assisted surgery, intrabody tracking, laparoscopic ultrasound, magnetic field distortion, temporal calibration.

Abiotic oligomeric ligands with a strong affinity for a target peptide sequence were isolated by affinity purification from a pool of 30-mer acrylic random ter-oligomers that were synthesized via a controlled radical polymerization process. Our results indicate that the oligomeric ligands with suitable sequence and/or stereochemical configurations for the target can be isolated from as-polymerized random co-polymers based on the affinity to the target. This process will be a powerful tool for the development of stable and inexpensive ligands that can be used to detect, neutralize and purify proteins with a target epitope sequence. [ABSTRACT FROM AUTHOR]

pKa tuning of Brønsted acids in synthetic nano-materials is of great importance for the design of ion exchange and bio-/molecular-separation media and polymer catalysis. It has been reported that hydrogel nanoparticles with carboxylic acids that show large and reversible pKa shifts in response to thermal stimuli can be prepared by copolymerization of N-isopropylacrylamide (NIPAm), acrylic acids (AAc) and N,N′-methylene bisacrylamide (BIS) via the proton imprinting polymerization process. However, the reported range of pKa shifts is limited to the range of 5.3 to 7.5. In this study, we report a procedure to prepare proton imprinted NPs that show pKa shifts in the tuned pKa range and demonstrate applications of the NPs. pKa values ranging from 4.3 to 8.7 were achieved by designing the structure of monomers containing carboxylic acids and applying the proton imprinting procedure. It was demonstrated that proton-imprinted NPs with different pKa values could be used for the reversible and selective protonation of target molecules which have specific pKa values. Our results establish the generality of the proton imprinting procedure and provide a guide for designing stable and inexpensive materials for sophisticated purification processes. [ABSTRACT FROM AUTHOR]

To facilitate robotic nerve-sparing radical prostatectomy, we developed a novel three-dimensional (3D) surgical navigation model that is displayed on the TilePro function of the da Vinci® surgeon console. Based on 3D transrectal ultrasonography (TRUS)-guided prostate biopsies, we reconstructed a 3D model of the TRUS-visible, histologically confirmed 'index' cancer lesion in 10 consecutive patients. Five key anatomic structures (prostate, image-visible biopsy-proven 'index' cancer lesion, neurovascular bundles, urethra, and recorded biopsy trajectories) were image-fused and displayed onto the TilePro function of the robotic console. The 3D model facilitated careful surgical dissection in the vicinity of the biopsy-proven index lesion. Geographic location of the index lesion on the final histology report correlated with the software-created 3D model. Negative surgical margins were achieved in 90%, except for one case with extensive extra-prostate extension. At postoperative 3 months, prostate-specific antigen levels were undetectable (<0.03 ng/mL) in all cases. The initial experience of the navigation model is presented. [ABSTRACT FROM AUTHOR]

We report the effect of physicalproperties, such as flexibilityand polymer density, of nanogel particles (NPs) on the association/dissociationrates constant (konand koff) and equilibrium constants (Kd) of multipoint protein recognition process. NPs having differentflexibilities and densities at 25 °C were synthesized by tuningcross-linking degrees and the volume phase transition (VPT) temperature.Rate constants were quantified by analyzing time course of proteinbinding process on NPs monitored by a quartz crystal microbalance(QCM). Both konand koffof swollen phase NPs increased with decreasing cross-linkingdegree, whereas cross-linking degree did not affect konand koffof the collapsedphase NPs, indicating that polymer density of NPs governs konand koff. Theresults also suggest that the mechanical flexibility of NPs, definedas the Young’s modulus, does not always have crucial rolesin the multipoint molecular recognition process. On the other hand, Kdwas independent of the cross-linking degreeand depended only on the phase of NPs, indicating that molecular-scaleflexibility, such as side-chain and segmental-mode mobility, as wellas the conformation change, of polymer chains assist the formationof stable binding sites in NPs. Our results reveal the rationale fordesigning NPs having desired affinity and binding kinetics to targetmolecules. [ABSTRACT FROM AUTHOR]

This paper describes augmented reality visualization for the guidance of breast-conservative cancer surgery using ultrasonic images acquired in the operating room just before surgical resection. By combining an optical three-dimensional (3-D) position sensor, the position and orientation of each ultrasonic cross section are precisely measured to reconstruct geometrically accurate 3-D tumor models from the acquired ultrasonic images. Similarly, the 3-D position and orientation of a video camera are obtained to integrate video and ultrasonic images in a geometrically accurate manner. Superimposing the 3-D tumor models onto live video images of the patient's breast enables the surgeon to perceive the exact 3-D position of the tumor, including irregular cancer invasions which cannot be perceived by touch, as if it were visible through the breast skin. Using the resultant visualization, the surgeon can determine the region for surgical resection in a more objective and accurate manner, thereby minimizing the risk of a relapse and maximizing breast conservation. The system was shown to be effective in experiments using phantom and clinical data. Index Terms - Augmented reality, breast cancer, breast-conservative therapy, computer-assisted surgery, optical 3-D sensor, ultrasound imaging.

Although a number of procedures to create synthetic polymer nanoparticles (NPs) with an intrinsic affinity to target biomacromolecules have been published, little has been reported on strategies to control the binding kinetics of target recognition. Here, we report an enzyme-mimic strategy to control binding/dissociation rate constants of NPs, which bind proteins through multipoint interactions, by taking advantage of the temperature-responsive coil-globule phase transition of poly-N-isopropylacrylamide (PNIPAm)-based NPs. PNIPAm NPs with a "flexible" random-coil conformation had a faster binding rate than NPs with a "rigid" globule conformation; however, the dissociation rate constant remained unchanged, resulting in stronger affinity. The dissociation rate of the "flexible" NPs was decelerated by the "induced-fit"-type conformation change of polymers around the coil-globule phase transition temperature, resulting in the formation of the most stable NP-protein complexes. These results provide a guide for designing plastic antibodies with tailor-made binding kinetics and equilibrium constants. [ABSTRACT FROM AUTHOR]

Abstract: Zero-ischemia robotic and laparoscopic partial nephrectomy, a novel concept, eliminates ischemia to the tumor-free normal kidney. Anatomic microdissection of tertiary/higher-order tumor-specific arteries is performed to selectively devascularize only the tumor, maintaining normal perfusion of the remaining kidney. A thorough understanding of renovascular tumor anatomy is essential. Based on 0.5-mm-slice thickness computed tomography scans, we developed a novel three-dimensional (3D) reconstruction technique that fuses three key anatomic aspects: surface-rendered tumor, semitransparent kidney, and extra- and intrarenal arterial anatomy. Four central completely intrarenal hilar masses underwent 3D reconstruction for surgical navigation during zero-ischemia partial nephrectomy. Negative surgical margins were obtained in all four cases, with no intraoperative complications or transfusions. For these challenging laparoscopically invisible masses, 3D image navigation precisely identified tumor-specific arterial branches, thus facilitating zero-ischemia partial nephrectomy without hilar cross clamping. [Copyright &y& Elsevier]

To create a textured virtual model of a real object, the 3D geometric model that is generally measured by a laser scanner must be aligned with the 2D image that is obtained from image sensors excluding some sensors for which geometric and photometric information are obtained at the same time. One conventional registration method that has been proposed compares the contour lines of the silhouette image of the 3D geometric model and of the 2D image and estimates the relative positions of both according to iterative calculations. However, a method that uses point correspondences of contour points in the 2D image and contour points of the silhouette image must find the nearest neighboring points for each iterative calculation, and the computational cost is high. Therefore, in this paper, the authors propose a new registration algorithm of grayscale images and 3D geometric models by using 2D distance maps that are constructed by using the Fast Marching Method from the boundary of an object on the grayscale image. They also show the effectiveness of the proposed method by performing simulation experiments and experiments using actual images. © 2007 Wiley Periodicals, Inc. Syst Comp Jpn, 38(14): 52–62, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20634 [ABSTRACT FROM AUTHOR]

In surgical navigation systems, system error analysis is performed because of the need for correct superposition of three-dimensional data obtained with three-dimensional position sensors and different coordinate systems for the images. Lea and colleagues proposed a registration graph for providing a systematic description with a graph of the geometrical position of the system and performing error analysis. However, the registration graph requires the explicit input of errors for each 3D data item. The authors expanded this system to automatically calculate individually occurring errors from system design information through a simulation, and to perform direct error analysis from the system design information. As a result, a user without specialized knowledge of error analysis can automatically perform error analysis by virtually designing a 3D data integration system on a computer. In this paper, the authors constructed a system simulator for modeling point-to-point registration and 3D position sensors, performing automatic error calculation with the simulation based thereon, and designing a system easily using a GUI. Furthermore, as a demonstration of the simulator, the simulator was applied to error analysis for a system including point-to-point registration and 3D position sensors, and its effectiveness and reliability were confirmed. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(8): 45–59, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20377 [ABSTRACT FROM AUTHOR]

This paper presents a new registration algorithm of two-dimensional (2-D) color images and 3-D geometric models for the navigation system of a surgical robot. A 2-D–3-D registration procedure is used to precisely superimpose a tumor model on an endoscopic image and is, therefore, indispensable for the surgical navigation system. Thus, the performance of the 2-D–3-D registration procedure influences directly the usability of the surgical robot operating system. One of the typical techniques that has been developed is the use of external markers. However, the accuracy of this method is reduced by the breathing or heartbeat of the patient, as well as other unknown factors. For precise registration of 3-D models and 2-D images without external markers or special measurement devices, a new registration method is proposed that utilizes the 2-D images and their distance maps as created by the Fast Marching Method. Here, we present results of fundamental experiments performed using simulated models and actual images of the endoscopic operation. [ABSTRACT FROM AUTHOR]

This paper proposes a camera projection model for an oblique-viewing endoscope, intended for application to an extended virtual reality system. The oblique-viewing endoscope differs from the forward-viewing endoscope by the fact that the view field can be shifted by rotating the scope cylinder. The projection model proposed in this study describes the systematic relation between the rotation angle of the scope cylinder and the external parameters of the camera model. A calibration method is also proposed for estimating the parameters of the projection model, and its accuracy is investigated. The oblique-viewing projection model is derived as an extension of the general pinhole camera model by adding two axes of rotation as parameters and using the angle of rotation of the scope cylinder as the input. In the experiment, an abdominal endoscope is used as the real equipment. A rotary encoder with an angular resolution of 0.25° is used to input the rotation angle of the scope cylinder. The accuracy is examined by the above condition for a scope cylinder rotation angle of 0 to 132°. The average projection error in the proposed model is 2.4 pixels. When the parameters needed in the model are not estimated, the error is increased to 5 to 8 pixels compared to the case in which they are estimated. It is thus shown that the parameters of the proposed model are indispensable in the description of the actual oblique-viewing endoscope. Even if the number of data points for each angle is 2, an accuracy such that the average error is less than 2.8 pixels is obtained. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 88(2): 19–31, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20145 [ABSTRACT FROM AUTHOR]

Oblique-viewing endoscopes (oblique scopes) are widely used in medical practice. They are essential for certain procedures such as laparoscopy, arthroscopy and sinus endoscopy. In an oblique scope the viewing directions are changeable by rotating the scope cylinder. Although a camera calibration method is necessary to apply augmented reality technologies to oblique endoscopic procedures, no method for oblique scope calibration has yet been developed. In the present paper, we formulate a camera model and a calibration procedure for oblique scopes. In the calibration procedure, Tsai's calibration is performed at zero rotation of the scope cylinder, then the variation of the external camera parameters corresponding to the rotation of the scope cylinder is modeled and estimated as a function of the rotation angle. Accurate estimation of the rotational axis is included in the procedure. The accuracy of this estimation was demonstrated to have a significant effect on overall calibration accuracy in the experimental evaluation, especially with large rotation angles. The projection error in the image plane was approximately two pixels. The proposed method was shown to be clinically applicable. [ABSTRACT FROM AUTHOR]

At the preoperative planning stage of CT-based computer-assisted total hip replacement, a surgeon determines the parameters such as size, position, and orientations of the implants based on interactive visualization of 3D models of the implants and hip joint bone. However, the parameters depend on surgeon''s visual assessment of spatial relationship between the hip joint bone and implants. Our objective is to investigate objective criteria for determination of the optimal parameters and formulate an automated determination procedure based on the criteria. We objectified expertise in the preoperative planning of an experienced surgeon into quantitative evaluations and geometrical constraints, then formulated the automated procedure as an optimization problem. The automated planning system was applied to three cases of patient data sets and compared with an experienced surgeon. In the preliminary results, the planning parameters determined by the system were generally acceptable as a pilot experiment. [Copyright &y& Elsevier]

SUMMARY:To investigate the outcome of aneurysmal subarachnoid haemorrhage (SAH) in patients on maintenance haemodialysis (HD), eight patients on maintenance HD and 245 patients not on HD who suffered from SAH, all of whom were surgically treated at our institution between 1993 and 1997, were reviewed. The clinical features and 3-month outcome of SAH were analysed in the eight HD patients (three males, five females) and compared with those in the 245 non-HD patients (77 males, 168 females). Although there were no significant differences in the patient’s age, gender and pre-operative grading of SAH with the Hunt and Hess grading scale, the mortality rate in HD patients was significantly higher than that in non-HD patients (50% [4/8] vs 13% [32/245]; P < 0.01). It was concluded that the outcome of aneurysmal SAH in HD patients was extremely poor. The explanation for the worse prognosis in HD patients seems not to lie in systemic heparization but in a vulnerability to SAH, because SAH in all HD patients occurred after anticoagulant activity from the previous dialysis had already disappeared. [ABSTRACT FROM AUTHOR]

The article discusses two clinical case studies which involve the use of a prototypical three-dimensional (3D) navigation software for invasive urological oncologic surgical procedures. It describes how 3D imaging allowed effective surgical planning for zero ischemia partial nephrectomy in an elderly patient with intrarenal hilar tumor. The creation of a 3D surgical navigation model in order to determine the exact location of the index lesion in an elderly patient is also reported.