Accurate automatic segmentation of the prostate in ultrasound images is still a challenging research problem. In this work, we propose the use of gray level images, constructed with a sample of gray level profiles perpendicular to the contour of the prostate. A two dimensional principal component analysis (2D PCA) was performed on a set of training contour images. The reconstruction error from the 2D PCA was used as an objective function for automatic adjustment of a point distribution model of the prostate. Our method was validated on 9 ultrasound images of the prostate and compared to the optimization of an objective function based on the mean Mahalanobis distance of a sampled gray level profile to the corresponding statistical profile model. Our new method based on a 2D PCA shows improved prostate segmentation results.
An indirect method of tissue consistency measurement is proposed, based on intensity and texture features of conventional ultrasound (US) cervix images. Calibration and validation were carried out in five phantoms simulating different cervical firmness, as well as in short and long cervices. Several image features attributed to the histogram, the co–occurrence matrix and the run–length encoding matrix were extracted and analyzed to evaluate their ability to distinguish between degrees of phantoms’ firmness. The most indicative of firmness indices were selected by correlating their values with the phantoms’ elasticities determined through Young’s moduli. Also, a random forest classifier was implemented, allowing to identify the features that contribute the most to class separation between phantoms. Using both tests, six features were selected: mean, standard deviation, entropy, skewness and two RLE-matrix features. A 6–fold cross validation was used to evaluate the model, obtaining a 98.9±0.79% accuracy. Finally, a preliminary case study was conducted upon closed and opened cervical US images, classifying them between both groups using a random forest model, obtaining an 84.34% accuracy. The indicated tests show that intensity and texture features extracted from conventional US images provide indirect and less–invasive information than other methods regarding tissue consistency, and therefore may be used to measure changes in cervical firmness.
Abdominal electrocardiography (AECG) is an indirect method for obtaining a continuous reading of fetal heart rate and is widely used during pregnancy as a method for assessing fetal well-being. Information obtained by AECG is used for early identification of fetal risk and may help in the anticipation of future complications; however, improper interpretation of the AECG recordings, related with inter- and intra-individual variability, may lead to inadequate treatments that can cause the death of the fetus. A set of 33 indices (4 maternal, 5 temporals, 23 time-frequency and 1 non-linear), extracted from AECG recordings and maternal information, were tested with a Random Forest (RF) classification method for the identification of normal fetuses and fetuses with intrauterine growth restriction. Because RFs may perform poorly when confronted with a high number of features compared to the number of training data available, a Genetic Algorithm (GA) was used to select the minimum set of features that improves the outcome of the RF. The accuracy of the RF method using the 33 indices was of 60%. After a run of the GA, the best individual in the last generation had an accuracy value of 85% and reduced the number of used indices from 33 to 11.
Computer Assisted Orthopedic Surgery (CAOS) requires a correct registration between the patient in the operating room and the virtual models representing the patient in the computer. In order to increase the precision and accuracy of the registration a set of new techniques that eliminated the need to use fiducial markers have been developed. The majority of these newly developed registration systems are based on costly intraoperative imaging systems like Computed Tomography (CT scan) or Magnetic resonance imaging (MRI). An alternative to these methods is the use of an Ultrasound (US) imaging system for the implementation of a more cost efficient intraoperative registration solution. In order to develop the registration solution with the US imaging system, the bone surface is segmented in both preoperative and intraoperative images, and the registration is done using the acquire surface. In this paper, we present the a preliminary results of a new approach to segment bone surface from ultrasound volumes acquired by means 3D freehand ultrasound. The method is based on the enhancement of the voxels that belongs to surface and its posterior segmentation. The enhancement process is based on the information provided by eigenanalisis of the multiscale 3D Hessian matrix. The preliminary results shows that from the enhance volume the final bone surfaces can be extracted using a singular value thresholding.
Image-guided interventions allow the physician to have a better planning and visualization of a procedure. 3D freehand ultrasound is a non-invasive and low-cost imaging tool that can be used to assist medical procedures. This tool can be used in the diagnosis and treatment of breast cancer. There are common medical practices that involve large needles to obtain an accurate diagnosis and treatment of breast cancer. In this study we propose the use of 3D freehand ultrasound for planning and guiding such procedures as core needle biopsy and radiofrequency ablation. The proposed system will help the physician to identify the lesion area, using image-processing techniques in the 3D freehand ultrasound images, and guide the needle to this area using the information of position and orientation of the surgical tools. We think that this system can upgrade the accuracy and efficiency of these procedures.
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