摘要:

Although mammography has been demonstrated to reduce mortality from breast cancer, it is widely recognized in the imaging community that patients with dense breasts generally suffer from inadequate mammograms. As a potential solution to this problem, we are studying the use of a dedicated breast CT scanner which is capable of producing tomographic images of the breast. To assess the potential of breast CT, we have performed experiments in regards to the size distribution of the breasts, the dose levels required for breast CT, and the contrast to noise ratio that breast CT may be able to deliver. Using dose levels comparable to mammography, our results indicate that breast CT is capable of excellent image quality and therefore breast CT has clear potential in breast cancer screening. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615091

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Electrical stimulation of the nervous tissue has been proposed as a method to treat some neurological disorders, such as epilepsy. Epileptic seizures result from excessive, synchronous, abnormal firing patterns of neurons that are located predominantly in the cerebral cortex. Many people with epilepsy continue presenting seizures even though they are under regimens of antiepileptic medications. An alternative therapy for treatment resistant epilepsy is cerebral electrical stimulation. The present study is focused to review the effects of different types of electrical stimulation and specifically changes in amino acids. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615092

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We present results obtained with a single photon counting system consisting of 384 silicon microstrips of 100 micron pitch equipped with 6 RX64 ASICs. The ASIC includes a charge preamplifier, a shaper, a discriminator and a 20‐bit counter for each of its 64 channels. The energy resolution of the system has been measured in the range from 8 keV to 32 keV using fluorescence X‐ray lines from several targets, using either an Am‐241 source or an X‐ray tube. Then, the efficiency of the system has been determined using the specially developed quasi‐monochromatic X‐ray beams in the energy range 18–36 KeV. Good efficiency has been obtained in the edge‐on configuration, which is more suitable for the intended applications. The spatial resolution of the system has been verified using a special microfocus X‐ray tube equipped with capillaries. Finally, images of angiographic and mammographic test objects have been obtained with dual energy X‐ray beams and have then been processed with the dual energy subtraction technique. In particular, the contrast for the angiographic test object has been evaluated for different concentrations of an iodate solution injected into 1 mm and 2 mm diameter vessels. Further developments, including a double threshold version of the ASIC, are also discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615093

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

An analysis of the therapeutic effectiveness of the pulsed GaAs semiconductor laser light (904 nm) is presented. The study was performed with the information obtained from a designed questionnaire, on the application of the low level laser therapy (LLLT) in different medical specialties from 15 hospitals. The results of the treatment for some studied diseases have been compared with other author’s reports. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615094

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We report autofluorescence measurements of different ex‐vivo human tissues excited with 365.0 nm ultraviolet radiation. A narrow spectral band approach was used for studying human tissue autofluorescence taking the central wavelength at 465 nm. Significant differences in autofluorescence measurement between tumors and the corresponding control site were found indicating that this non‐spectroscopic approach could be useful for discriminating malignant tissues from normal one. We have also carried out a pilot study of the temporal dynamics of human skin and mammary tissues. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615095

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Computer assisted surgery (CAS) systems can provide different levels of assistance to a surgeon during training and execution of a surgical procedure. This is done through the integration of : measurements taken on medical images; computer graphics techniques; and positioning or tracking mechanisms which accurately locate the surgical instruments inside the operating site. According to the type of assistance that is provided to the surgeon, CAS systems can be classified as: Image guided surgery systems; Assistant robots for surgery; and Training simulators for surgery. In this work are presented the main characteristics of CAS systems. It is also described the development of a computer simulator for training on Transurethral Resection of the Prostate (TURP) based on a computer model of the prostate gland which is able to simulate, in real time, deformations and resections of tissue. The model is constructed as a 3D mesh with physical properties such as elasticity. We describe the main characteristics of the prostate model and its performance. The prostate model will also be used in the development of a CAS system designed to assist the surgeon during a real TURP procedure. The system will provide 3D views of the shape of the prostate of the patient, and the position of the surgical instrument during the operation. The development of new computer graphics models which are able to simulate, in real time, the mechanical behavior of an organ during a surgical procedure, can improve significantly the training and execution of other minimally invasive surgical procedures such as laparoscopic gall bladder surgery. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615096

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The objective is to present a description and the main clinical applications of this dedicated Linac for benign and malignant tumors in the central nervous system. The Novalis (BrainLab, Germany) is a 6 MV dedicated linac for a single high dose Radiosurgery (RS) and for fractionated doses in Stereotactic Radiotherapy with a high level of precision at the isocenter. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615097

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The National Institute of Neurology and Neurosurgery in Mexico City has acquired a Novalis® shaped beam radiosurgery unit. The institute is pioneer in the use of new technologies for neuroscience. The Novalis® unit allows the use of conformal beam radiosurgery/therapy and the more advanced modality of conformal therapy: Intensity Modulated Radiation Therapy (IMRT). In the present work we present the first cases of treatments that use the IMRT technique and show its ability to protect organs at risk, such as brainstem and optical vias. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615098

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Reviewing the methods and physical principles used in body composition measurements (BCM), it is evident that more accurate, reliable, and easily handled methods are required. The use of bio‐impedance analysis (BIA) has been very useful in BCM. This technique, in the single frequency mode, has some commercial versions to perform BCM. However these apparatus have significant variability in the BCM values. The multi‐frequency option of the bio‐impedance technique has still a lot of challenges to overcome. We studied the variability of the body impedance spectrum (from 1 Hz to 1 MHz) in a group of subjects compared to the values obtained from commercial apparatus. We compared different anatomical body regions, some of them with less subcutaneous body fat (frontal, anterior tibial, knee, and frontal regions); others with more subcutaneous body fat (pectoral, abdominal, and internal calf regions). In order to model the bio‐impedance spectrum, we analyzed layered samples with different thickness and material composition. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615099

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The GPCALMA (Grid Platform for Computer Assisted Library for MAmmography) collaboration involves several departments of physics, INFN (National Institute of Nuclear Physics) sections, and italian hospitals. The aim of this collaboration is developing a tool that can help radiologists in early detection of breast cancer. GPCALMA has built a large distributed database of digitised mammographic images (about 5500 images corresponding to 1650 patients) and developed a CAD (Computer Aided Detection) software which is integrated in a station that can also be used to acquire new images, as archive and to perform statistical analysis. The images (18×24 cm2, digitised by a CCD linear scanner with a 85 &mgr;m pitch and 4096 gray levels) are completely described: pathological ones have a consistent characterization with radiologist’s diagnosis and histological data, non pathological ones correspond to patients with a follow up at least three years. The distributed database is realized throught the connection of all the hospitals and research centers in GRID tecnology. In each hospital local patients digital images are stored in the local database. Using GRID connection, GPCALMA will allow each node to work on distributed database data as well as local database data. Using its database the GPCALMA tools perform several analysis. A texture analysis, i.e. an automated classification on adipose, dense or glandular texture, can be provided by the system. GPCALMA software also allows classification of pathological features, in particular massive lesions (both opacities and spiculated lesions) analysis and microcalcification clusters analysis. The detection of pathological features is made using neural network software that provides a selection of areas showing a given “suspicion level” of lesion occurrence. The performance of the GPCALMA system will be presented in terms of the ROC (Receiver Operating Characteristic) curves. The results of GPCALMA system as “second reader” will also be presented. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1615100

出版商:AIP    

年代:1903

数据来源: AIP