A novel device to concurrently assess leukocyte extravasation and interstitial migration within a defined 3D environment.

Leukocyte extravasation and interstitial migration are key events during inflammation. Traditional in vitro techniques address only specific steps of cell recruitment to tissues and fail to recapitulate the whole process in an appropriate three-dimensional (3D) microenvironment. Herein, we describe a device that enables us to qualitatively and quantitatively assess in 4D the interdependent steps underlying leukocyte trafficking in a close-to-physiology in vitro context. Real-time tracking of cells, from initial adhesion to the endothelium and subsequent diapedesis to interstitial migration towards the source of the chemoattractant within the 3D collagen matrix, is enabled by the use of optically transparent porous membranes laid over the matrix. Unique features of the device, such as the use of non-planar surfaces and the contribution of physiological flow to the establishment of a persistent chemoattractant gradient, were assessed by numerical simulations and validated by proof-of-concept, simultaneous testing of differentially treated primary mouse neutrophils. This microfluidic platform offers new and versatile tools to thoroughly investigate the stepwise process of circulating cell recruitment to target tissues in vitro and to test novel therapeutics targeting various steps of the process.

A micro-optical system for endoscopy based on mechanical compensation paradigm using miniature piezo-actuation.

The goal of the study was to investigate the feasibility of a novel miniaturized optical system for endoscopy. Fostering the mechanical compensation paradigm, the modeled optical system, composed by 14 lenses, separated in 4 different sets, had a total length of 15.55mm, an effective focal length ranging from 1.5 to 4.5mm with a zoom factor of about 2.8×, and an angular field of view up to 56°. Predicted maximum lens travel was less than 3.5mm. The consistency of the image plane height across the magnification range testified the zoom capability. The maximum predicted achromatic astigmatism, transverse spherical aberration, longitudinal spherical aberration and relative distortion were less than or equal to 25µm, 15µm, 35µm and 12%, respectively. Tests on tolerances showed that the manufacturing and opto-mechanics mounting are critical as little deviations from design dramatically decrease the optical performances. However, recent micro-fabrication technology can guarantee tolerances close to nominal design. A closed-loop actuation unit, devoted to move the zoom and the focus lens sets, was implemented adopting miniaturized squiggle piezo-motors and magnetic position encoders based on Hall effect. Performance results, using a prototypical test board, showed a positioning accuracy of less than 5µm along a lens travel path of 4.0mm, which was in agreement with the lens set motion features predicted by the analysis. In conclusion, this study demonstrated the feasibility of the optical design and the viability of the actuation approach while tolerances must be carefully taken into account.

A tool for computer-controlled lipoaspirate deposition in autologous fat grafting.

BACKGROUND: In autologous fat grafting applied for tissue regeneration and morphologic/volumetric restoration, clinical evidence suggests that the uniformity of tissue distribution in the receiver site may influence regenerative outcomes and rates of complications. METHODS: This technical report describes the prototype of a computer-assisted deposition tool designed to maximize deposition uniformity. This is obtained by modulating the lipoaspirate flow through the cannula of the syringe as a function of the tool withdrawal speed by means of a DC motor that controls the movement of the syringe plunger. Although simpler technologies for speed detection may be applied, the authors' prototype features a wireless connection with an infrared (IR) motion-tracking system for real-time detection of position, orientation, and speed of the surgical tool. The integrated motion-tracking instrumentation grants combined computer-controlled lipoaspirate deposition and real-time surgical navigation to maximize fat tissue uniformity along a planned, patient-specific insertion pattern. CONCLUSIONS: The presented tool ensures the uniformity of tissue deposition through integration of the plunger motion with control of the tool movement, allowing for reduced onset of postintervention complications. EBM level 5 LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

A multi-tissue mass-spring model for computer assisted breast surgery.

The aim of this work was to develop and validate a 3D female breast deformation model for computer assisted breast surgery. Magnetic resonance (MR) image data of a patient undergoing breast biopsy, were acquired using two different protocols with the patient in prone position: (i) uncompressed breast and (ii) compressed breast, with lateral single breast compression, realized with a movable slab. The acquired images were then segmented using a semi-automatic procedure and from the extracted volumes of interest tetrahedral meshes representing skin, fat and mammary glands were generated. Tissue deformation was ruled by a mass-spring model: first, an iterative approximation algorithm was implemented to estimate the spring's rest length and stiffness, accounting for gravity force; then the resulting parameters were used to deform the uncompressed breast model in order to reach the real compressed one (ground truth). Results showed that gravity force applied to the mesh was properly compensated by the internal elastic forces, leading to a distance between the deformed mesh and the reference data of 0.036±0.092 mm (median±inter quartile range). The point to mesh residual distance between the deformed mesh and the ground truth was 1.224±2.202 mm (median±inter quartile range). Further investigation on a larger patient dataset is required for a more robust confirmation of model accuracy in predicting breast deformations.

Comparative assessment of 3D surface scanning systems in breast plastic and reconstructive surgery.

In this work, we compared accuracy, repeatability, and usability in breast surface imaging of 2 commercial surface scanning systems and a hand-held laser surface scanner prototype coupled with a patient's motion acquisition and compensation methodology. The accuracy of the scanners was assessed on an anthropomorphic phantom, and to evaluate the usability of the scanners on humans, thorax surface images of 3 volunteers were acquired. Both the intrascanner repeatability and the interscanner comparative accuracy were assessed. The results showed surface-to-surface distance errors inferior to 1 mm and to 2 mm, respectively, for the 2 commercial scanners and for the prototypical one. Moreover, comparable performances of the 3 scanners were found when used for acquiring the breast surface. On the whole, this study demonstrated that handheld laser surface scanners coupled with subject motion compensation methods lend themselves as competitive technologies for human body surface modeling.

Computer assisted planning of autologous fat grafting in breast.

Autologous fat grafting is an emerging and promising surgical technique in regenerative medicine, and its application is quickly spreading in plastic and reconstructive surgery of the breast. However, despite the advantages of the technique, surgical complications may occur, such as implanted tissue necrosis and resorption and onset of microcalcifications. In view of the hypothesis that the uniformity of the lipoaspirate transplantation is related to graft survival and a lower probability of complications, we developed an interactive lipomodeling planning software application based on a genetic algorithm that allows automatic optimization of the uniformity of fat tissue distribution. The input dataset consists of a 3D model of the patient's thorax, created from MRI scans, on which relevant structures are segmented. The developed software was tested starting from either an automatically generated plan or an initial guess of the optimal surgical plan, and in both cases the application yielded a consistent improvement in the planned fat tissue distribution by optimizing the position of the insertion points and the direction of the insertion pathways. On the basis of the simulations performed, the use of genetic algorithms for optimization of the geometry of autologous fat transfer in the breast proved to be effective. These results will foster further activities focused on the comparison of predicted optimized geometries and those obtained in real surgical cases as a means of obtaining a deeper knowledge of the potential influence of a uniform fat tissue distribution on the quality of the surgical outcome. The presented application is also put forward as representing a noteworthy step towards the clinical application of computer assisted planning tools in breast surgery.

Simulation of functional tricuspid regurgitation using an isolated porcine heart model.

BACKGROUND AND AIM OF THE STUDY: The results of tricuspid annuloplasty to treat functional tricuspid regurgitation (FTR) are sometimes suboptimal, and alternative techniques are needed. In the absence of reliable FTR models, and in an effort to minimize the need for animal experiments, a reproducible bench-model was developed of FTR, that allowed the simulation of the anatomic features of the condition. METHODS: A fresh porcine heart was mounted on a rigid support that was placed into a basin filled with saline; a closed circuit was then created with a centrifugal pump, equipped with connection tubes. The inflow tube of the pump conveyed saline from the basin to the pump; the outflow cannula was inserted through the pulmonary artery, across the pulmonary valve, into the right ventricle. The pump was activated to pressurize the right ventricle, thus inducing tricuspid valve regurgitation (TVR). The regurgitant flow through the valve was quantified using a flow-meter. Radiopaque markers were sutured to the head of each papillary muscle and to the tricuspid annulus, in order to trace the geometric changes of the tricuspid valve at increasing pump rates, using fluoroscopy. The efficacy of the bench-model was validated with 10 hearts. RESULTS: The TVR was increased proportionally with the right ventricular pressure (RVP) (TVR = 0.089xRVP - 1.515; R2 = 0.89). The increase in TVR was associated with increases in the annular-to-papillary muscles distance (APML) (TVR = 0.059xAPML - 2.94; R2 = 0.96), of the inter-papillary muscles distance (PMD) (TVR = 0.058xPMD - 8.58; R2 = 0.94), and of the triscuspid annular dilatation (TAD) (TVR = 0.05xTAD - 1.85; R2 = 0.89). Of these parameters, APML was the strongest predictor of TVR. CONCLUSION: The porcine heart bench model represents a reproducible system to simulate the physiopathology of FTR, and has the potential to serve as a complementary method for the evaluation of new 'in vitro' technologies and therapies for FTR.

New technologies for the assessment of breast surgical outcomes.

BACKGROUND: Although interest in objective and quantitative breast surgical outcome assessment is rapidly increasing, published reports have yet to make a real impact on everyday clinical practice. OBJECTIVE: The authors offer a preliminary report on an innovative methodology customized for breast shape evaluation that, in our opinion, could overcome most of the technical and conceptual limitations of previous studies. METHODS: Three-dimensional/four-dimensional breast scanning was performed using a breast-dedicated prototype laser scanner made up of a handheld device, including a charge-coupled device (CCD) camera coupled to a spot laser source. Two additional motion analyzer cameras were used for handheld device tracking and the acquisition of patient motion. RESULTS: Seven female volunteers, including both subjects who had undergone cosmetic or reconstructive breast surgery and those with no such history, underwent a dynamic breast shape survey. Curvature mapping on three-dimensional mesh warranted precise measurements of local geometric properties of the breast surface. Elaboration and representation of breast dynamic behavior during common motor tasks (eg, walking, running, sitting, and lying) was also possible. CONCLUSIONS: The scanning methodology reported here reliably describes the breast surface not only in a static position, but also at specific postures or during motion of the body. It also opens the door for quantitative static and dynamic assessment of surgical outcomes, the intraoperative assessment of breast shape, and other applications. Limitations include the relatively long amount of time required for each scan and the need for technical and clinical validation, particularly with respect to four-dimensional assessment.

Motion compensation in hand-held laser scanning for surface modeling in plastic and reconstructive surgery.

The purpose of this work is to develop a new integrated methodology for breast morphology assessment in plastic and reconstructive surgery. Such a methodology comprises hand-held laser scanning with active compensation of breathing motion and involuntary movements, in order to obtain a thorough and artifacts-free representation of patient breast shape. This was obtained by tracking surface motion with a configuration of passive markers fitted on the patient's thoraco-abdominal region. The proposed method, based on a mapping procedure, has been compared with respiratory gating, that is commonly used in radiotherapy and biomedical imaging applications. The results show that the implemented procedure is adequately able to compensate for motion, resulting in quantitative surface description to be used for clinical evaluation.