Catálogo de publicaciones - libros

Significant advances in the development of transgenic and knockout animal models of human disease have made whole-animal imaging an important new application for micro CT. In many studies of genetically altered animals, investigators require a non-destructive, 3D technique to characterize the phenotype of the animal. However, a fundamental limitation which should be considered, especially in experiments involving imaging the same animal over time, is the inherent use of ionizing radiations which may approach the lethal dose for small rodents. Digital Tomosynthesis (DTS) is a fast, low-dose 3D imaging approach which yields image with excellent in-plane resolution, though low plane-to-plane resolution. A stack of DTS slices can be reconstructed from a singlelimited arc scan, with typical scan angles ranging from 10°-60° and acquisition time of less than 10 seconds. This study evaluates the reconstructed tomograms for small animal imaging system using µCT and µDTS, for three different DTS scan angles (20°, 40°, and 60°). Resulting DTS slice show soft tissue contrast approaching that of full cone-beam CT.

Honeycombing in High-Resolution CT (HRCT) indicates the presence of a number of diseases involving fibrosis of the lung. Honeycombing is difficult to detect due to its textural and structural appearance, which changes with the progression of the diseases. Structure-based and texture-based methods, developed for detecting the honeycombing pattern, are presented and compared. Machine learning is used to generate rules for honeycomb detection using examples of its appearance in HRCT images, provided by radiologists. The effectiveness of each method was evaluated using cross validation on 16692 examples of regions with and without honeycombing from 42 images of 8 patients.

BOLD T2*-weighted MR images reflects cortical blood flow and oxygenation alterations. fMRI study relies on the detection of localized changes in BOLD signal intensity. Since fMRI measures the very small modulations in BOLD signal intensity that occur during changes in brain activity, it is also very sensitive to small signal intensity variations caused by physiologic noise during the scan. Due to the complexity of movement of various organs associated with heart beat, it is important to reduce cardiac related noise rather than other physiological noise which could be required with relatively simple method. Therefore, a number of methods have been developed for the estimation and reduction of cardiac noise in fMRI study. But, each method has limitation. In this study, we proposed a new estimation method for brain activities influenced by blood pulsation effect using regression analysis with blood pulsation signal and the correspond slice of fMRI. We could find out that the right anterior cingulate cortex and right olfactory cortex and left olfactory cortex were largely influenced by blood pulsation effect for new method.

This paper proposes the use of sequential feature selection for classification of prostatic tissues. The technique aims to classify microscopic samples taken by needle biopsy for the purpose of prostate Cancer diagnosis. Four major classes (representing different grades of abnormality from normal to cancer respectively: Stroma, BPH, PIN, PCa) have to be discriminated. To achieve that, the same feature vector, based on texture measurements, was derived for each class. Haralick features have been used to describe textures. Sequential forward selection (SFS) and sequential backward selection (SBS) has been used to reduce the dimensionality of the generated feature vector into a manageable size. Tests have been carried out using k nearest neighbor (kNN) method and have shown that the use of feature selection algorithms SFS and SBS can significantly improve the classification performance.

In the research of electroporation, we often need to know the percent of electroporated cells under different experimental conditions. Manual counting of the cells in digital images is time-consuming and subjective, especially on phase contrast images. In this paper, we present an automatic cell counting method based on optimization of ITCN (Image-based Tool for Counting Nuclei) algorithm’s parameters to fit training data that is based on counts from user or expert. In comparing the results of automatic cell counting and user manual counting 94,21 % average agreement was achieved what is good.

Data analysis of the optical scattering spectra obtained in the clinical trials of the optical biopsy system is presented. The major types of spectra were revealed characterizing malignant and benign tumors.

In order to achieve homogenous dose distribution in target volume several approaches are possible. We are discussing the possibility of field intensity modulation with wax filter compensators and comparing the technique with other techniques. The case report of the head and neck region radiotherapy with the use of 2D wax filter compensator is presented. The 3D wax filter compensators technique is further discussed as a substitute to the step and shoot IMRT or to the sliding window IMRT technique. The advantages and disadvantages of the wax filter compensators are put side by side. The case of meduloblastoma treatment is outlined as the case where whit applying 3D wax filter compensators the benefit would be the greatest.

The paper describes a lung model, which illustrates the pressure - volume - flow relationships in the lungs. The model includes three airway segments in series; the resistance of one of them is a function of transmural pressure and a constant related to airway compressibility. The model can be used to obtain IVPF curves and flow-volume curves, and various assumptions concerning the distribution of airway resistance, the magnitude of lung elastic recoil; and other factors can be tested with it.

The aim of the study was to assure a proper treatment by using pairs of opposed abutting half-beams. Different beam arrangements were studied with the treatment planning system. The delivered dose in the region of beam abutment was measured with the film dosimetry and compared to the planned dose. A noticeable dose difference was found in the area of few millimetres around the abutment of the half-beams. The dose difference, resulting from inaccurate positioning of Y jaws, was up to 22%. The displacement of the jaws was evaluated and the correction of the position of the jaw was made.

Accuracy in the dose delivery in the Stereotactic Radiosurgery is one of the most important components in this sophisticated radiotherapy treatment of benign and malignant intracranial diseases. In the present study, we carried out the measurements with small volume cylindrical ionization chamber PTW 31006 (PinPoint), together with specially designed and elaborated bullet-shaped white polystyrene phantom in order to verify the dose calculation by the commercially available 3D treatment planning system BrainScan from BrainLab company. Comparison of the doses was done in four simulated simple treatments, applying non-coplanar circular arc technique with tertiary conical collimators on linear accelerator Varian Clinac 2100 C/D with high energy photon beams of 6 MV. We found systematic differences in all four cases. The differences were found to range from 2.4% to 3.9% - the measured doses were always higher than the calculated ones. Although the results of our study could confirm the accuracy of the treatment planning dose calculations, as the differences lie within the recommended 5% value of the International Commission on Radiation Units and Measurements (ICRU), it is advisable to investigate further the origin of these, most probably systematic errors.