@article{pmid18066947,

title = {Towards scarless surgery: an endoscopic ultrasound navigation system for transgastric access procedures},

author = {Raúl San José Estépar and Nicholas Stylopoulos and Randy Ellis and Eigil Samset and Carl-Fredrik Westin and Christopher Thompson and Kirby Vosburgh},

doi = {10.3109/10929080701746892},

issn = {1092-9088},

year  = {2007},

date = {2007-11-01},

journal = {Comput Aided Surg},

volume = {12},

number = {6},

pages = {311--324},

abstract = {OBJECTIVE: Scarless surgery is an innovative and promising technique that may herald a new era in surgical procedures. We have created a navigation system, named IRGUS, for endoscopic and transgastric access interventions and have validated it in in vivo pilot studies. Our hypothesis is that endoscopic ultrasound procedures will be performed more easily and efficiently if the operator is provided with approximately registered 3D and 2D processed CT images in real time that correspond to the probe position and ultrasound image.nnMATERIALS AND METHODS: The system provides augmented visual feedback and additional contextual information to assist the operator. It establishes correspondence between the real-time endoscopic ultrasound image and a preoperative CT volume registered using electromagnetic tracking of the endoscopic ultrasound probe position. Based on this positional information, the CT volume is reformatted in approximately the same coordinate frame as the ultrasound image and displayed to the operator.nnRESULTS: The system reduces the mental burden of probe navigation and enhances the operator's ability to interpret the ultrasound image. Using an initial rigid body registration, we measured the mis-registration error between the ultrasound image and the reformatted CT plane to be less than 5 mm, which is sufficient to enable the performance of novice users of endoscopic systems to approach that of expert users.nnCONCLUSIONS: Our analysis shows that real-time display of data using rigid registration is sufficiently accurate to assist surgeons in performing endoscopic abdominal procedures. By using preoperative data to provide context and support for image interpretation and real-time imaging for targeting, it appears probable that both preoperative and intraoperative data may be used to improve operator performance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17573503,

title = {Gender differences in the severity of CT emphysema in COPD},

author = {Mark T Dransfield and George R Washko and Marilyn G Foreman and Raul San Jose Estepar and John Reilly and William C Bailey},

doi = {10.1378/chest.07-0863},

issn = {0012-3692},

year  = {2007},

date = {2007-08-01},

journal = {Chest},

volume = {132},

number = {2},

pages = {464--470},

abstract = {BACKGROUND: The hallmark of COPD is airflow obstruction, but this can develop on the basis of airway disease, emphysema, or both. There are gender differences in the natural history of COPD, and these may in part be explained by differences in the pathophysiology of airflow obstruction. We aimed to determine if there are gender differences in the severity of CT emphysema among COPD patients.nnMETHODS: Current and former smokers enrolled in the National Lung Screening Trial (NLST) at the University of Alabama at Birmingham were recruited at the time of an annual screening CT examination. We recorded demographics and smoking history, and subjects performed spirometry. Subjects were classified into modified (prebronchodilator) Global Initiative for Chronic Obstructive Lung Disease stages, and their CT scans were analyzed to determine regional and total emphysema (defined as the percentage of low attenuation areas [LAA%]; < - 950 Hounsfield units). Differences between genders were examined, and univariate and multivariate predictors of LAA% were determined.nnRESULTS: A total of 396 subjects participated. Men had more regional and total CT emphysema at all stages of COPD than women (stage 0, 3.9% vs 2.4%, p = 0.001; stage I, 7.0% vs 3.7%, p = 0.015; stage II, 7.8% vs 5.5%, p = 0.063; stages III/IV, 15.8% vs 8.7%, p = 0.024). In multivariate regression analysis, only gender (p < 0.001) and FEV(1)/FVC ratio (p < 0.001) predicted total LAA%.nnCONCLUSIONS: At all stages of COPD severity, men have more CT emphysema than women. This difference in radiologic expression may in part explain gender differences in the presentation and natural history of COPD. The NLST (NCT00047385) is registered at www.clinicaltrials.gov. Registered at www.clinicaltrials.gov; no.NCT00047835.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17466206,

title = {EUS with CT improves efficiency and structure identification over conventional EUS},

author = {Kirby G Vosburgh and Nicholas Stylopoulos and Raul San Jose Estepar and Randy E Ellis and Eigil Samset and Christopher C Thompson},

doi = {10.1016/j.gie.2006.09.021},

issn = {0016-5107},

year  = {2007},

date = {2007-05-01},

journal = {Gastrointest Endosc},

volume = {65},

number = {6},

pages = {866--870},

abstract = {BACKGROUND: EUS is complicated because of the subtleties of US interpretation, small fields of observation, and uncertainty of probe position and orientation.nnOBJECTIVE: Improved EUS performance is sought by providing contextual information to support US probe positioning and identification of features in US images. Our aims were to demonstrate the feasibility of the image registered gastroscopic US (IRGUS) system in a porcine model and to compare the effectiveness and the efficiency of IRGUS with traditional EUS.nnDESIGN: Animal feasibility study.nnINTERVENTIONS: The IRGUS system uses preprocedure CT and miniature US probe trackers to create real-time synthetic displays of the position of the probe tip and a matched slice of CT data for comparison with the US image. Participants used EUS and IRGUS systems in a porcine model to evaluate the speed and accuracy of structure identification.nnMAIN OUTCOME MEASUREMENTS: The performance and utility of IRGUS were determined by the number of correctly identified structures in a timed trial, kinematic variables, and a structured survey.nnRESULTS: IRGUS was twice as effective as EUS in localizing and identifying individual structures. In timed trials, IRGUS users identified over 25% more structures than EUS users. Improvement in examination efficiency and accuracy of feature identification was statistically significant, and 90% of the users preferred IRGUS to EUS for these tasks.nnCONCLUSIONS: IRGUS appears feasible and may be superior to conventional EUS in efficiency and accuracy of probe positioning and in image interpretation. IRGUS has the potential to shorten the EUS learning curve and to broaden the adoption of EUS techniques by gastroenterologists.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17296643,

title = {Interobserver variability in the determination of upper lobe-predominant emphysema},

author = {Craig P Hersh and George R Washko and Francine L Jacobson and Ritu Gill and Raul San Jose Estepar and John J Reilly and Edwin K Silverman},

doi = {10.1378/chest.06-1040},

issn = {0012-3692},

year  = {2007},

date = {2007-02-01},

journal = {Chest},

volume = {131},

number = {2},

pages = {424--431},

abstract = {BACKGROUND: Appropriateness for lung volume reduction surgery is often determined based on the results of high-resolution CT (HRCT) scanning of the chest. At many centers, radiologists and pulmonary physicians both review the images, but the agreement between readers from these specialties is not known.nnMETHODS: Two thoracic radiologists and three pulmonologists retrospectively reviewed the HRCT scans of 30 patients with emphysema involved in two clinical studies at our institution. Each reader assigned an emphysema severity score and assessed upper lobe predominance, using a methodology similar to that of the National Emphysema Treatment Trial. In addition, the percentage of emphysema at -910 Hounsfield units was objectively determined by density mask analysis.nnRESULTS: For the emphysema severity scores, (Spearman) correlation between readers ranged from 0.59 (p = 0.0005) to 0.87 (p < 0.0001), with generally stronger correlations among readers from the same medical specialty. Emphysema severity scores were significantly correlated with prebronchodilator and postbronchodilator spirometry findings, as well as with density mask analysis. In the assessment of upper lobe predominance, kappa statistics for agreement ranged from 0.20 (p = 0.4) to 0.60 (p = 0.0008). Examining all possible radiologist-pulmonologist pairs, the two readers agreed in their assessments of emphysema distribution in 75% of the comparisons. Readers agreed on upper lobe-predominant disease in 9 of the 10 patients in which regional density mask analysis clearly showed upper lobe predominance.nnCONCLUSIONS: In a group of patients with varying emphysema severity, interobserver agreement in the determination of upper lobe-predominant disease was poor. Agreement between readers tended to be better in cases with clear upper lobe predominance as determined by densitometry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid18051037,

title = {Geodesic-loxodromes for diffusion tensor interpolation and difference measurement},

author = {Gordon Kindlmann and Raúl San José Estépar and Marc Niethammer and Steven Haker and Carl-Fredrik Westin},

doi = {10.1007/978-3-540-75757-3_1},

year  = {2007},

date = {2007-01-01},

journal = {Med Image Comput Comput Assist Interv},

volume = {10},

number = {Pt 1},

pages = {1--9},

abstract = {In algorithms for processing diffusion tensor images, two common ingredients are interpolating tensors, and measuring the distance between them. We propose a new class of interpolation paths for tensors, termed geodesic-loxodromes, which explicitly preserve clinically important tensor attributes, such as mean diffusivity or fractional anisotropy, while using basic differential geometry to interpolate tensor orientation. This contrasts with previous Riemannian and Log-Euclidean methods that preserve the determinant. Path integrals of tangents of geodesic-loxodromes generate novel measures of over-all difference between two tensors, and of difference in shape and in orientation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17377333,

title = {Natural Orifice Transluminal Endoscopic Surgery (NOTES): an opportunity for augmented reality guidance},

author = {Kirby G Vosburgh and Raúl San José Estépar},

issn = {0926-9630},

year  = {2007},

date = {2007-01-01},

journal = {Stud Health Technol Inform},

volume = {125},

pages = {485--490},

abstract = {Laparoscopic techniques have gained wide acceptance because they offer a safe and less invasive alternative to open surgery. To further reduce the invasiveness of peritoneal access, the next logical step is to eliminate the incision through the abdominal wall using natural orifices as entry points. This Natural Orifice Transluminal Endoscopic Surgery (NOTES) approach has the potential to replace or augment current techniques. Several research groups have cut through the stomach or colon wall (per-oral transgastric or per-anal transcolonic) to perform organ resections in animal models, and some procedures in humans have been reported anecdotally. Widespread use of these techniques will depend on providing the physician with adequate visual feedback, clear indicators of instrument location and orientation, and support in the recognition of anatomic structures. Compared with laparoscopy, successful endoscopy must accommodate several additional complexities: (1) The flexibility of the endoscope tip complicates the understanding of its distal orientation. Successful navigation inside the stomach and in the abdominal cavity generally requires two years of sub-specialty training. (2) Several surgical targets lie in a retrograde position with respect to an incision in the stomach wall. Efficient and safe access to the pancreas, gall bladder, or the kidneys requires detailed knowledge of the tip placement relative to adjacent anatomic structures. (3) Since there is limited direct access to the abdomen, iatrogenic injuries, such as the accidental cutting of an artery, will be more dangerous and difficult to manage. We present here approaches to resolving these limitations though augmented reality techniques using pre-procedure CT or MRI imaging, real time tracking and reference image registration, and display to the operating physician. As an example, the utility of image registration techniques for orientation for the gastric access puncture is discussed in detail. It is anticipated that such augmentation will make intra-cavitary interventional techniques easier to master and use in practice, and thus more likely to be widely adopted.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid16677953,

title = {Complementary aspects of diffusion imaging and fMRI; I: structure and function},

author = {Robert V Mulkern and Peter E Davis and Steven J Haker and Raul San Jose Estepar and Lawrence P Panych and Stephan E Maier and Michael J Rivkin},

doi = {10.1016/j.mri.2006.01.007},

issn = {0730-725X},

year  = {2006},

date = {2006-05-01},

journal = {Magn Reson Imaging},

volume = {24},

number = {4},

pages = {463--474},

abstract = {Studying the intersection of brain structure and function is an important aspect of modern neuroscience. The development of magnetic resonance imaging (MRI) over the last 25 years has provided new and powerful tools for the study of brain structure and function. Two tools in particular, diffusion imaging and functional MRI (fMRI), are playing increasingly important roles in elucidating the complementary aspects of brain structure and function. In this work, we review basic technical features of diffusion imaging and fMRI for studying the integrity of white matter structural components and for determining the location and extent of cortical activation in gray matter, respectively. We then review a growing body of literature in which the complementary aspects of diffusion imaging and fMRI, applied as separate examinations but analyzed in tandem, have been exploited to enhance our knowledge of brain structure and function.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid16306256,

title = {Volume-related and volume-independent effects of posture on esophageal and transpulmonary pressures in healthy subjects},

author = {George R Washko and Carl R O'Donnell and Stephen H Loring},

doi = {10.1152/japplphysiol.00697.2005},

issn = {8750-7587},

year  = {2006},

date = {2006-03-01},

journal = {J Appl Physiol (1985)},

volume = {100},

number = {3},

pages = {753--758},

abstract = {Ventilator management decisions in acute lung injury could be better informed with knowledge of the patient's transpulmonary pressure, which can be estimated using measurements of esophageal pressure. Esophageal manometry is seldom used for this, however, in part because of a presumed postural artifact in the supine position. Here, we characterize the magnitude and variability of postural effects on esophageal pressure in healthy subjects to better assess its significance in patients with acute lung injury. We measured the posture-related changes in relaxation volume and total lung capacity in 10 healthy subjects in four postures: upright, supine, prone, and left lateral decubitus. Then, in the same subjects, we measured static pressure-volume characteristics of the lung over a wide range of lung volumes in each posture by using an esophageal balloon catheter. Transpulmonary pressure during relaxation (PLrel) averaged 3.7 (SD 2.0) cmH2O upright and -3.3 (SD 3.2) cmH2O supine. Approximately 58% of the decrease in PLrel between the upright and supine postures was due to a corresponding decrease in relaxation volume. The remaining 2.9-cmH2O difference is consistent with reported values of a presumed postural artifact. Relaxation volumes and pressures in prone and lateral postures were intermediate. To correct estimated transpulmonary pressure for the effect of lying supine, we suggest adding 3 cmH2O (95% confidence interval: -1 to +7 cmH2O). We conclude that postural differences in estimated transpulmonary pressure at a given lung volume are small compared with the substantial range of PLrel in patients with acute lung injury.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17354764,

title = {Accurate airway wall estimation using phase congruency},

author = {Raúl San José Estépar and George G Washko and Edwin K Silverman and John J Reilly and Ron Kikinis and Carl-Fredrik Westin},

doi = {10.1007/11866763_16},

year  = {2006},

date = {2006-01-01},

journal = {Med Image Comput Comput Assist Interv},

volume = {9},

number = {Pt 2},

pages = {125--134},

abstract = {Quantitative analysis of computed tomographic (CT) images of the lungs is becoming increasingly useful in the medical and surgical management of subjects with Chronic Obstructive Pulmonary Disease (COPD). Current methods for the assessment of airway wall work well in idealized models of the airway. We propose a new method for airway wall detection based on phase congruency. This method does not rely on either a specific model of the airway or the point spread function of the scanner. Our results show that our method gives a better localization of the airway wall than "full width at a half max" and is less sensitive to different reconstruction kernels and radiation doses.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17959492,

title = {On diffusion tensor estimation},

author = {Marc Niethammer and Raul San Jose Estepar and Sylvain Bouix and Martha Shenton and Carl-Fredrik Westin},

doi = {10.1109/IEMBS.2006.260927},

issn = {1557-170X},

year  = {2006},

date = {2006-01-01},

journal = {Conf Proc IEEE Eng Med Biol Soc},

volume = {Suppl},

pages = {6707--6710},

abstract = {In this paper we propose a formal formulation for the estimation of Diffusion Tensors in the space of symmetric positive semidefinite (PSD) tensors. Traditionally, diffusion tensor model estimation has been carried out imposing tensor symmetry without constraints for negative eigenvalues. When diffusion weighted data does not follow the diffusion model,due to noise or signal drop, negative eigenvalues may arise. An estimation method that accounts for the positive definiteness is desirable to respect the underlying principle of diffusion. This paper proposes such an estimation method and provides a theoretical interpretation of the result. A closed-form solution is derived that is the optimal data-fit in the matrix 2-norm sense,removing the need for optimization-based tensor estimation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17946125,

title = {On diffusion tensor estimation},

author = {Marc Niethammer and Raul San Jose Estepar and Sylvain Bouix and Martha Shenton and Carl-Fredrik Westin},

doi = {10.1109/IEMBS.2006.259826},

issn = {1557-170X},

year  = {2006},

date = {2006-01-01},

journal = {Conf Proc IEEE Eng Med Biol Soc},

volume = {2006},

pages = {2622--2625},

abstract = {In this paper we propose a formal formulation for the estimation of Diffusion Tensors in the space of symmetric positive semidefinite (PSD) tensors. Traditionally, diffusion tensor model estimation has been carried out imposing tensor symmetry without constraints for negative eigenvalues. When diffusion weighted data does not follow the diffusion model, due to noise or signal drop, negative eigenvalues may arise. An estimation method that accounts for the positive definiteness is desirable to respect the underlying principle of diffusion. This paper proposes such an estimation method and provides a theoretical interpretation of the result. A closed-form solution is derived that is the optimal data-fit in the matrix 2-norm sense, removing the need for optimization-based tensor estimation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17946653,

title = {Image quality assessment based on local variance},

author = {Santiago Aja-Fernández and Raúl San José Estépar and Carlos Alberola-López and Carl-Fredrik Westin},

doi = {10.1109/IEMBS.2006.259516},

issn = {1557-170X},

year  = {2006},

date = {2006-01-01},

journal = {Conf Proc IEEE Eng Med Biol Soc},

volume = {2006},

pages = {4815--4818},

abstract = {A new and complementary method to assess image quality is presented. It is based on the comparison of the local variance distribution of two images. This new quality index is better suited to assess the non-stationarity of images, therefore it explicitly focuses on the image structure. We show that this new index outperforms other methods for the assessment of image quality in medical images.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17946126,

title = {A kernel-based approach for user-guided fiber bundling using diffusion tensor data},

author = {Raúl San José Estépar and Marek Kubicki and Martha Shenton and Carl-Fredrik Westin},

doi = {10.1109/IEMBS.2006.259829},

issn = {1557-170X},

year  = {2006},

date = {2006-01-01},

journal = {Conf Proc IEEE Eng Med Biol Soc},

volume = {2006},

pages = {2626--2629},

abstract = {This paper describes a novel user-guided method for grouping fibers from diffusion tensor MRI tractography into bundles. The method finds fibers, that passing through user-defined ROIs, still fit to the underlying data model given by the diffusion tensor. This is achieved by filtering the data and the ROIs with a kernel derived from a geodesic metric between tensors. A standard approach using binary decisions defining tracts passing through ROIs is critically dependent on ROIs that includes all trace lines of interest. The method described in this paper uses a softer decision mechanism through a kernel which enables grouping of bundles driven less exact, or even single point, ROIs. The method analyzes the responses obtained from the convolution with a kernel function along the fiber with the ROI data. Results in real data shows the feasibility of the approach to fiber bundling.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17354921,

title = {Towards scarless surgery: an endoscopic-ultrasound navigation system for transgastric access procedures},

author = {Raúl San José Estépar and Nicholas Stylopoulos and Randy E Ellis and Eigil Samset and Carl-Fredrik Westin and Christopher Thompson and Kirby Vosburgh},

doi = {10.1007/11866565_55},

year  = {2006},

date = {2006-01-01},

journal = {Med Image Comput Comput Assist Interv},

volume = {9},

number = {Pt 1},

pages = {445--453},

abstract = {Scarless surgery is a new and very promising technique that can mark a new era in surgical procedures. We have created and validated a navigation system for endoscopic and transgastric access interventions in in vivo pilot studies. The system provides augmented visual feedback and additional contextual information by establishing a correspondence between the real time endoscopic ultrasound image and a preoperative CT volume using rigid registration. The system enhances the operator's ability to interpret the ultrasound image reducing the mental burden used in probe placement. Our analysis shows that rigid registration is accurate enough to help physicians in endoscopic abdominal surgery where, by using preoperative data for context and real-time imaging for targeting, distortions that limit the use of only preoperative data can be overcome.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid14974598,

title = {Comparison of single-shot echo-planar and line scan protocols for diffusion tensor imaging},

author = {Marek Kubicki and Stephan E Maier and Carl-Frederik Westin and Hatsuho Mamata and Hal Ersner-Hershfield and Raul Estepar and Ron Kikinis and Ferenc A Jolesz and Robert W McCarley and Martha E Shenton},

doi = {10.1016/s1076-6332(03)00563-4},

issn = {1076-6332},

year  = {2004},

date = {2004-02-01},

journal = {Acad Radiol},

volume = {11},

number = {2},

pages = {224--232},

abstract = {RATIONALE AND OBJECTIVES: Both single-shot diffusion-weighted echo-planar imaging (EPI) and line scan diffusion imaging (LSDI) can be used to obtain magnetic resonance diffusion tensor data and to calculate directionally invariant diffusion anisotropy indices, ie, indirect measures of the organization and coherence of white matter fibers in the brain. To date, there has been no comparison of EPI and LSDI. Because EPI is the most commonly used technique for acquiring diffusion tensor data, it is important to understand the limitations and advantages of LSDI relative to EPI.nnMATERIALS AND METHODS: Five healthy volunteers underwent EPI and LSDI diffusion on a 1.5 Tesla magnet (General Electric Medical Systems, Milwaukee, WI). Four-mm thick coronal sections, covering the entire brain, were obtained. In addition, one subject was tested with both sequences over four sessions. For each image voxel, eigenvectors and eigenvalues of the diffusion tensor were calculated, and fractional anisotropy (FA) was derived. Several regions of interest were delineated, and for each, mean FA and estimated mean standard deviation were calculated and compared.nnRESULTS: Results showed no significant differences between EPI and LSDI for mean FA for the five subjects. When intersession reproducibility for one subject was evaluated, there was a significant difference between EPI and LSDI in FA for the corpus callosum and the right uncinate fasciculus. Moreover, errors associated with each FA measure were larger for EPI than for LSDI.nnCONCLUSION: Results indicate that both EPI- and LSDI-derived FA measures are sufficiently robust. However, when higher accuracy is needed, LSDI provides smaller error and smaller inter-subject and inter-session variability than EPI.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid14732598,

title = {Shape of caudate nucleus and its cognitive correlates in neuroleptic-naive schizotypal personality disorder},

author = {James J Levitt and Carl Fredrik Westin and Paul G Nestor and Raul S J Estepar and Chandlee C Dickey and Martina M Voglmaier and Larry J Seidman and Ron Kikinis and Ferenc A Jolesz and Robert W McCarley and Martha E Shenton},

doi = {10.1016/j.biopsych.2003.08.005},

issn = {0006-3223},

year  = {2004},

date = {2004-01-01},

journal = {Biol Psychiatry},

volume = {55},

number = {2},

pages = {177--184},

abstract = {BACKGROUND: We measured the shape of the head of the caudate nucleus with a new approach based on magnetic resonance imaging (MRI) in schizotypal personality disorder (SPD) subjects in whom we previously reported decreased caudate nucleus volume. We believe MRI shape analysis complements traditional MRI volume measurements.nnMETHODS: Magnetic resonance imaging scans were used to measure the shape of the caudate nucleus in 15 right-handed male subjects with SPD, who had no prior neuroleptic exposure, and in 14 matched normal comparison subjects. With MRI processing tools, we measured the head of the caudate nucleus using a shape index, which measured how much a given shape deviates from a sphere.nnRESULTS: In relation to comparison subjects, neuroleptic never-medicated SPD subjects had significantly higher (more "edgy") head of the caudate shape index scores, lateralized to the right side. Additionally, for SPD subjects, higher right and left head of the caudate SI scores correlated significantly with poorer neuropsychological performance on tasks of visuospatial memory and auditory/verbal working memory, respectively.nnCONCLUSIONS: These data confirm the value of measuring shape, as well as volume, of brain regions of interest and support the association of intrinsic pathology in the caudate nucleus, unrelated to neuroleptic medication, with cognitive abnormalities in the schizophrenia spectrum.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid12659913,

title = {A theoretical framework to three-dimensional ultrasound reconstruction from irregularly sampled data},

author = {Raúl San José-Estépar and Marcos Martín-Fernández and P Pablo Caballero-Martínez and Carlos Alberola-López and Juan Ruiz-Alzola},

doi = {10.1016/s0301-5629(02)00762-7},

issn = {0301-5629},

year  = {2003},

date = {2003-02-01},

journal = {Ultrasound Med Biol},

volume = {29},

number = {2},

pages = {255--269},

abstract = {Several techniques have been described in the literature in recent years for the reconstruction of a regular volume out of a series of ultrasound (US) slices with arbitrary orientations, typically scanned by means of US freehand systems. However, a systematic approach to such a problem is still missing. This paper focuses on proposing a theoretical framework for the 3-D US volume reconstruction problem. We introduce a statistical method for the construction and trimming of the sampling grid where the reconstruction will be carried out. The results using in vivo US data demonstrate that the computed reconstruction grid that encloses the region-of-interest (ROI) is smaller than those obtained from other reconstruction methods in those cases where the scanning trajectory deviates from a pure straight line. In addition, an adaptive Gaussian interpolation technique is studied and compared with well-known interpolation methods that have been applied to the reconstruction problem in the past. We find that the proposed method numerically outperforms former proposals in several control studies; subjective visual results also support this conclusion and highlight some potential deficiencies of methods previously proposed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}