Accurate Localization Method Research Articles

Radioactive Seed Localization of Breast Lesions: An Adequate Localization Method without Seed Migration

Preoperative localization is important to optimize the surgical treatment of breast lesions, especially in nonpalpable lesions. Radioactive seed localization (RSL) using iodine-125 is a relatively new approach. To provide accurate guidance to surgery, it is important that the seeds do not migrate after placement. The aim of this study was to assess short-term and long-term seed migration after RSL of breast lesions. In 45 patients, 48 RSL procedures were performed under ultrasound or stereotactic guidance. In the first 12 patients, the lesion was localized with two markers: an iodine-125 seed and a reference marker. In 33 patients, 36 RSL procedures were performed using a single iodine-125 seed. All patients received control mammograms after seed placement and prior to surgery. In the patients with two markers, migration was defined as the difference in the largest distance between the markers observed in the mammograms. For single-marked lesions, migration was assessed by comparing distances between anatomical landmarks in the mammograms. RSL was successful in all patients. Seeds were in-situ for 59.5 days on average (3-136 days). The detection rate during surgery was 100%. Overall, an average seed migration of 0.9 mm (standard deviation 1.0 mm) was observed. Neither differences in lesion type, nor days in situ, type of surgery or radiologic localization method were found to have impact on seed migration. RSL is an accurate preoperative localization method for breast lesions with negligible seed migration, independent of time in-situ.

Pinpointing Phosphorylation Sites: Quantitative Filtering and a Novel Site-specific x-Ion Fragment

Phosphoproteomics deals with the identification and quantification of thousands of phosphopeptides. Localizing the phosphorylation site is however much more difficult than establishing the identity of a phosphorylated peptide. Further, recent findings have raised doubts of the validity of the site assignments in large-scale phosphoproteomics data sets. To improve methods for site localization, we made use of a synthetic phosphopeptide library and SILAC-labeled peptides from whole cell lysates and analyzed these with high-resolution tandem mass spectrometry on an LTQ Orbitrap Velos. We validated gas-phase phosphate rearrangement reactions during collision-induced dissociation (CID) and used these spectra to devise a quantitative filter that by comparing signal intensities of putative phosphorylated fragment ions with their nonphosphorylated counterparts allowed us to accurately pinpoint which fragment ions contain a phosphorylated residue and which ones do not. We also evaluated higher-energy collisional dissociation (HCD) and found this to be an accurate method for correct phosphorylation site localization with no gas-phase rearrangements observed above noise level. Analyzing a large set of HCD spectra of SILAC-labeled phosphopeptides, we identified a novel fragmentation mechanism that generates a phosphorylation site-specific neutral loss derived x-ion, which directly pinpoints the phosphorylated residue. Together, these findings significantly improve phosphorylation site localization confidence.

Targeting of the pedunculopontine nucleus by an MRI-guided approach: a cadaver study

Laboratory evidence suggests that the pedunculopontine nucleus (PPN) plays a central role in the initiation and maintenance of gait. Translational research has led to reports on deep brain stimulation (DBS) of the rostral brainstem in parkinsonian patients. However, initial clinical results appear to be rather variable. Possible factors include patient selection and the wide variability in anatomical location of implanted electrodes. Clinical studies on PPN DBS efficacy would, therefore, benefit from an accurate and reproducible method of stereotactic localization of the nucleus. The present study evaluates the anatomical accuracy of a specific protocol for MRI-guided stereotactic targeting of the PPN in a human cadaver. Imaging at 1.5 and 9.4T confirmed electrode location in the intended region as defined anatomically by the surrounding fiber tracts. The spatial relations of each electrode track to the nucleus were explored by subsequent histological examination. This confirmed that the neuropil surrounding each electrode track contained scattered large neurons morphologically consistent with those of the subnucleus dissipatus and compactus of the PPN. The results support the accuracy of the described specific MR imaging protocol.

MIND: A Nonparametric Decision Fusion Method for Accurate Indoor Localization using Sensors with Monotonically Increasing Error Functions

A nonparametric fusion method for extracting accurate distance measurements from low-quality sensors is proposed. The method applies to sensors with error functions that are monotonically increasing with respect to (w.r.t.) the actual value to be measured (arguments are presented on why a monotonically increasing error function is something to be expected with range-estimating sensors). The proposed method has been developed in order to enhance the performance of localization systems that utilize commercially available sensors for range estimation to achieve localization through triangulation of range estimates. The proposed method is based on evaluating multiple sensor measurements and using the minimum measured distance as a more efficient estimate of the real distance compared with calculating and selecting the distance average. Thus, the proposed method is code-named MIND (from MINimum Distance). It is shown analytically that MIND outperforms, in terms of location estimation accuracy, the sensor with the minimum mean error when used in a multi-sensor configuration. An experimental testbed consisting of four Cricket sensors in a symmetric bundle configuration was used to evaluate the MIND fusion method experimentally. For each Cricket sensor, performance characteristics were established through extensive laboratory analysis and were found to yield highly inaccurate range estimates. However, when these low-quality Cricket sensors were fused in a four-sensor symmetric configuration, it was shown experimentally that the MIND fusion method exhibits near-optimal performance and largely overcomes most of the flaws of the underlying low-quality Cricket sensors, delivering a localization solution of extended accuracy, availability, and robustness.

Accurate Localization of Metal Electrodes Using Magnetic Resonance Imaging

Purpose : Localization using MRI is difficult due to susceptibility induced artifacts caused by metal electrodes. Here we took an advantage of the B0 pattern induced by the metal electrodes by using an oblique-view imaging method. Materials and Methods : Metal electrode models with various diameters and susceptibilities were simulated to understand the aspect of field distortion. We set localization criteria for a turbo spin-echo (TSE) sequence usingconventional (90� view) and 45�oblique-view imaging method through simulation of images with various resolutions and validated the criteria usingphantom images acquired by a 3.0T clinical MRI system. For a gradient-refocused echo (GRE) sequence, which is relatively more sensitive to field inhomogeneity, we used phase images to find the center of electrode. Results : There was least field inhomogeneity along the 45�line that penetrated the center of the electrode. Therefore, our criteria for the TSE sequence with 45� obliqueview was coincided regardless of susceptibility. And with 45�oblique-view angle images, pixel shifts were bidirectional so we can detect the location of electrodes even in low resolution. For the GRE sequence, the 45�oblique-view anglemethod madethe lines where field polarity changes become coincident to the Cartesian grid so the localization of the center coordinates was more facilitated. Conclusion : We suggested the method for accurate localization of electrode using 45� oblique-view angle imaging. It is expected to be a novelmethodto monitoring an electrophysiological brain study and brain neurosurgery.

A method for accurate localisation of EBSD pattern centres

The moving screen technique for pattern centre localisation is revisited. A cross-correlation based iterative procedure is developed to find both the zoom factor and the zoom centre (which is also the pattern centre) between two EBSD diffraction patterns acquired at two camera positions. The procedure involves two steps: first, a rough estimate of the pattern centre position and zoom factor (the ratio of the two detector distances) is obtained by cross-correlating the entire images. Then, based on this first estimate, cross-correlation of smaller regions of interest (ROIs) gives the displacement field which is interpreted as a zoom factor misfit coupled with a zoom centre position misfit. These misfits are iteratively decreased until the displacement field is reduced to the noise level. The procedure is first applied to simulated patterns and it is shown that the iterative procedure converges very rapidly to the exact solution with an accuracy better than 1/100th of pixel. The potential of this technique for experimental patterns is discussed and recommendations for new EBSD detectors are proposed.

Percutaneous Placement of Radiopaque Markers at the Pedicle of Interest for Preoperative Localization of Thoracic Spine Level

Retrospective review. To describe an accurate method of intraoperative localization of thoracic spine levels with percutaneously placed radiopaque markers at the pedicle of the level of interest. Intraoperative localization of thoracic spine levels can be difficult in cases without obvious vertebral body deformation (compression fracture, tumor), such as thoracic discectomy, as well as in surgery of the midthoracic spine and in the morbidly obese. Intraoperative fluoroscopy or plain radiographs are useful but can often be difficult to interpret in these cases. Fourteen patients requiring anterior thoracic spine surgery for thoracic disc herniations underwent preoperative localization and placement of radiopaque marker. Using standard percutaneous techniques, the radiopaque markers were placed using biplanar fluoroscopy at the pedicle at the level of interest. Eight patients subsequently underwent thoracoscopic discectomy and fusion, and 6 patients underwent mini-open thoracotomy for discectomy and fusion. Placement of radiopaque markers was successfully completed without complications in all 14 patients. Intraoperatively, the markers were easy to identify and assisted in identification of the correct surgical level in all cases. Preoperative placement of radiopaque markers at the level of interest before surgery of the thoracic spine is a safe and effective technique for avoiding wrong-level surgery in cases in which standard localization techniques may be difficult.

Intraoperative portable abdominal radiograph for tumor localization: a simple and accurate method for laparoscopic gastrectomy

During laparoscopic gastrectomy, it is impossible to identify early gastric cancer (EGC) lesions; therefore, a precise localization technique is required. In this study, we evaluated a novel method of intraoperative portable abdominal radiograph for localization of EGC lesions after preoperative endoscopic clipping. A retrospective study of 80 patients who had undergone laparoscopic gastrectomies with our intraoperative abdominal radiographic method of tumor localization was performed. During preoperative endoscopy, endoscopic metal clips were applied just proximal to the tumor. A plain abdominal radiograph taken immediately after oral administration of effervescent agents was employed to select candidates for intraoperative localization. Intraoperative vessel clips were laparoscopically applied along the greater and lesser curvatures, and a portable abdominal radiograph was taken to identify the location of endoscopic clips relative to laparoscopic vessel clips. In all patients, endoscopic clips were applied proximal to the lesion without complications. Both intraluminally and extraluminally placed clips were successfully detected by intraoperative portable abdominal radiograph in all patients. Mean±standard deviation (SD) proximal margin length was 34.2±20.2mm. All patients had tumor-free resection margin. Preoperative endoscopic clipping and intraoperative portable abdominal radiograph is an accurate and simple tumor localization method in laparoscopic gastrectomy.

Broadband Source Localization From an Eigenanalysis Perspective

Broadband source localization has several applications ranging from automatic video camera steering to target signal tracking and enhancement through beamforming. Consequently, there has been a considerable amount of effort to develop reliable methods for accurate localization over the last few decades. Essentially, the localization process consists in finding the candidate source location that maximizes the synchrony between the properly time-shifted microphone outputs. In addition to using well known cross-correlation-based criteria such as the steered response power (SRP), minimum variance (MV), and multichannel cross-correlation (MCCC), this synchrony can also be measured using the averaged magnitude difference function (AMDF) and the averaged magnitude sum function (AMSF) whose calculations involve low computational cost. In earlier related works, the latter techniques have been used for time delay estimation (TDE) of a target source observed by only one pair of microphones. Their generalization to the multiple microphone case and application to source localization have not been studied yet. In this paper, we consider both categories, i.e., cross-correlation and AMDF (with AMSF)-based approaches, using an arbitrary number of microphones, and analyze their performance. Specifically, we first provide a unifying study of the most popular cross-correlation-based techniques, such as the SRP, MV, and MCCC. In this paper, we use the eigenanalysis of the parameterized spatial correlation matrix (PSCM) to classify these methods and gain some insight into their performance. We demonstrate, for instance, that the MV and SRP consist in searching the major eigenvalue of the PSCM, while the MCCC, essentially, combines its minor eigenvalues when scanning for the source location. Inspired by this analysis, we show, in the second part of this work, the efficiency of the AMDF and AMSF in localizing an acoustic source using multiple microphones. Indeed, we propose two new parameterized matrices named as the parameterized averaged magnitude difference matrix (PAMDM) and the parameterized averaged magnitude sum matrix (PAMSM). The eigenanalysis of these matrices also reveals new criteria for acoustic source localization. Simulation results are provided to illustrate the effectiveness of all the investigated and proposed methods.

Electro-structural correlations, elastic and optical properties among the nanolaminated ternary carbides Zr 2AC

We have performed ab initio calculations for the nanolaminates Zr 2AC (A = Ti, In, Tl, Si, Ge, Sn, Pb, P, As, S) ceramics to study their electronic structure, elastic and optical properties. In this work, we used the accurate augmented plane wave plus local orbital method with density functional theory to find the equilibrium structural parameters, dielectric functions and to compute the full elastic tensors. The obtained elastic constants were used to quantify the stiffness of the Zr 2AC phases and to appraise their mechanical stability. The relationship between elastic, electronic and valence electron concentration is discussed. Our results show that the bulk modulus and shear modulus increase across the periodic table for Zr 2AC. Furthermore, trends in elastic stiffness are well explained in terms of electronic structure analysis, as occupation of valence electrons in states near the Fermi level of Zr 2AC. We show that increments of bulk moduli originate from additional valence electrons filling states involving Zr d–A p. We show also that Zr d–A p hybridizations are located just below the Fermi level and are weaker bonds than the Zr d–C p hybridizations, which are deeper in energy. As a function of the p-state filling of the A element the Zr d–A p bands are driven to deeper energy. The optical spectra were analyzed by means of the electronic structure, which provides theoretical understanding of the conduction mechanism of these ceramics.

1A2-B18 電波を用いた往復伝播時間測定による位置同定法の実験的研究

A method for accurate localization of a space rover on a surface of a small planetary body has been developed for guiding it to a destination point. The method uses round-trip propagation delay of radio waves, range, between a mother spacecraft and the rover. Numerical simulations proved that the developed method is able to estimate the position of the rover with reasonable accuracy assuming that the measurement noise is Gaussian. Laboratory experiments have been conducted via range measurement tool to validate the convergence of the proposed method of estimation, whose results are reported in this paper. These results proved that the estimation converges even the measurement data includes real noise existed in the range measurement tool, which supports the feasibility of the proposed method of estimation.

Semi-automatic stereotactic coordinate identification algorithm for routine localization of Deep Brain Stimulation electrodes

Deep Brain Stimulation (DBS) is a routine therapy for movement disorders, and has several emerging indications. We present a novel protocol to define the stereotactic coordinates of metallic DBS implants that may be routinely employed for validating therapeutic anatomical targets. Patients were referred for troubleshooting or new DBS implantation. A volumetric MRI of the brain obtained prior to or during this protocol was formatted to the Anterior Commissure–Posterior Commissure (AC–PC) coordinate system. Patients underwent a CT scan of the brain in an extended Hounsfield unit (EHU) mode. A semi-automatic detection algorithm based on a Normalized Mutual Information (NMI) co-registration method was implemented to measure the AC–PC coordinates of each DBS contact. This algorithm was validated using manual DBS contact identification. Fifty MRI-CT image pairs were available in 39 patients with a total of 336 DBS electrodes. The median and mean Euclidean distance errors for automatic identification of electrode locations were 0.20 mm and 0.22 mm, respectively. This method is an accurate method of localization of active DBS contacts within the sub-cortical region. As the investigational indications of DBS expand, this method may be used for verification of final implant coordinates, critical for understanding clinical benefit and comparing efficacy between subjects.

Intra-operative MRI-assisted spinal localization

Level localization in the thoracic spine can be problematic. We describe a new method that can be used in difficult cases, e.g., ones where lesions are mid-thoracic, small, or only visible on MRI. Intra-operatively, a midline incision was made and the thoracic spinous processes were exposed. A length of contrast-filled tubing was wound around the processes and the incision was temporarily closed and the patient was transferred to the radiology department for MRI under general anesthetic. Upon return to theatre, the cross sections of contrast-filled tubing and the lesion itself were visible on the MRI scan, allowing localization of the level. This method was accurate and minimized the extent of bone removal required for access. This technique, while not appropriate in every case, is repeatable, and does not require specialized equipment or training. It is an extremely accurate method of localization for difficult cases.

NEEDLESCOPIC RESECTION OF SMALL PULMONARY NODULE AFTER PREOPERATIVE DUAL LOCALIZATION WITH HOOK WIRE AND LIPIODOL

PURPOSE: The needlescopic surgery using instruments with a diameter of 2-mm is devised to leave minimal scarring and reduce the need for postoperative analgesia. For needlescopic lung biopsy for small pulmonary nodule, accurate and convenient method for preoperative localization is necessary. The aim of this study is to evaluate the usefulness of combined mammographic hook wire anchoring and lipiodol injection for localization of small pulmonary nodules before needlescopic lung biopsy.

A probabilistic MR atlas of the human cerebellum

The functional organization of the cerebellum is reflected in large part by the unique afferent and efferent connectivity of the individual cerebellar lobules. This functional diversity on a relatively small spatial scale makes accurate localization methods for human functional imaging and anatomical patient-based research indispensable. Here we present a probabilistic atlas of the cerebellar lobules in the anatomical space defined by the MNI152 template. We separately masked the lobules on T1-weighted MRI scans (1 mm isotropic resolution) of 20 healthy young participants (10 male, 10 female, average age 23.7 yrs). These cerebella were then aligned to the standard or non-linear version of the whole-brain MNI152 template using a number of commonly used normalization algorithms, or to a previously published cerebellum-only template (Diedrichsen, J., 2006. A spatially unbiased atlas template of the human cerebellum. NeuroImage 33, 127–138.). The resulting average overlap was higher for the cerebellum-only template than for any of the whole-brain normalization methods. The probabilistic maps allow for the valid assignment of functional activations to specific cerebellar lobules, while providing a quantitative measure of the uncertainty of such assignments. Furthermore, maximum probability maps derived from these atlases can be used to define regions of interest (ROIs) in functional neuroimaging and neuroanatomical research. The atlas, made freely available online, is compatible with a number of widely used analysis packages.

A hybrid approach to fast and accurate localization for legged robots

SUMMARYThis paper describes a hybrid approach to a fast and accurate localization method for legged robots based on Fuzzy-Markov (FM) and Extended Kalman Filters (EKF). Both FM and EKF techniques have been used in robot localization and exhibit different characteristics in terms of processing time, convergence, and accuracy. We propose a Fuzzy-Markov–Kalman (FM–EKF) localization method as a combined solution for a poor predictable platform such as Sony Aibo walking robots. The experimental results show the performance of EKF, FM, and FM-EKF in a localization task with simple movements, combined behaviors, and kidnapped situations. An overhead tracking system was adopted to provide a ground truth to verify the performance of the proposed method.

The Umbilical Locator: Bringing Simplicity to Surgery

Introduction: The purpose of this article is to introduce the Umbilical Locator and demonstrate how it simplifies umbilical transposition in abdominal surgeries in both the cosmetic and reconstructive fields. Materials and Methods: The Umbilical Locator is a new device that was designed and patented by one of the authors (F.F.) to help surgeons who are performing umbilical translocation during abdominal surgeries. The Umbilical Locator is safe, disposable, sterilizable, made of a nonlatex plastic, and can be used with any surgical method preferred by the surgeon. It was designed specifically for use in abdominoplasties. It was developed, manufactured, and marketed for sale by Innovative Med Inc, Irvine, California. Results: To date, the Umbilical Locator has been used exclusively by one of the authors (F.F.), with excellent results. He has used this innovative device in 20 recent abdominoplasties, with no resultant umbilical slough or ischemia. Furthermore, there have been no complications noted with positioning, anchoring, or removal of the device. Discussion: In abdominoplasty, an aesthetic and natural appearance of the umbilicus is a key factor to the end result. The Umbilical Locator can be used with any surgical method to create the umbilicus. The purpose of the product is only to help locate the position of the umbilicus on the skin. The surgeon is allowed to use the incision or surgical method of his or her choice on top of the umbilicus after the skin has been redraped prior to excision to precisely locate the umbilicus. Conclusions: These preliminary data provide promising evidence for the continued and future use of the Umbilical Locator as a more reliable and accurate method of umbilical localization in abdominoplasty than prior techniques, such as the use of a spinal needle to pinpoint the location of the umbilicus. The Umbilical Locator has the potential to decrease the incidence of deformities, wound tension, and resulting ischemia, and to reduce umbilical hypertrophic scarring. What has been to date a technically imprecise, unsophisticated phase of an abdominoplasty has now been simplified and refined using the Umbilical Locator.

A Geometric Method for Nipple Localization

An important part of preoperative assessment in breast reduction surgery is to locate the site of the nipple-areola complex for the newly structured breast. Inappropriate location is difficult to correct secondarily. Traditional methods of nipple localization taught and practiced suggest the nipple to be located anterior to the inframammary fold. Trying to project this point on the anterior surface of the breast requires either large calipers or feeling the posteriorly placed finger on the anterior surface of a large breast. This certainly introduces some subjectivity to the calculation. To introduce an easy and accurate method of nipple localization to reduce the learning curve for trainee surgeons. Aesthetic placement of the nipples is at the lower angles of an equilateral or a short isosceles triangle on the chest with its apex at the sternal angle. This triangle can be thought of as two right-angled triangles with their Y-axis on the median plane. The base and vertical limb are measured, and the hypotenuse is calculated. The location of the lower angle is marked on the anterior surface of the breast and represents the new position of the nipple. Forty patients had nipple localization performed in the above-described manner, with satisfactory placement of the nipple-areola complex. The above technique introduces some objective measurements to the localization of the nipple in breast reduction surgery. It is easy to practice, and infuses confidence in trainees marking their initial breast reductions.

A method for accurate localization of the first heart sound and possible applications

We have previously developed a method for localization of the first heart sound (S1) using wavelet denoising and ECG-gated peak-picking. In this study, an additional enhancement step based on cross-correlation and ECG-gated ensemble averaging (EA) is presented. The main objective of the improved method was to localize S1 with very high temporal accuracy in (pseudo-) real time. The performance of S1 detection and localization, with and without EA enhancement, was evaluated on simulated as well as experimental data. The simulation study showed that EA enhancement reduced the localization error considerably and that S1 could be accurately localized at much lower signal-to-noise ratios. The experimental data were taken from ten healthy subjects at rest and during invoked hyper- and hypotension. For this material, the number of correct S1 detections increased from 91% to 98% when using EA enhancement. Improved performance was also demonstrated when EA enhancement was used for continuous tracking of blood pressure changes and for respiration monitoring via the electromechanical activation time. These are two typical applications where accurate localization of S1 is essential for the results.

3D MR spectroscopic and diffusion-weighted imaging of prostate cancer with phased-array surface coil at 3 T for tumor definition in the intensity-modulated radiation therapy

Purpose: Serum prostate-specific antigen screening, digital rectal examination, and transrectal ultrasound-guided biopsies are the major methods for clinical diagnosis and staging of prostate cancer, but their low sensitivity and specificity as well as multifocal nature of disease in most patients demand a more appropriate method for accurate localization and staging. In this prospective cross-sectional study, a combination of MR spectroscopic, diffusion-, and T2-weighted imaging were implemented to optimize the intensity-modulated radiation therapy by definition of dominant intraprostatic tumors.