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Showing papers in "Iranian Journal of Medical Physics in 2007"


Journal ArticleDOI
TL;DR: It is stated that MS has a diffused nature and the white matter abnormalities occurring outside T2-visible lesions affect the whole brain tissue.
Abstract: Introduction: Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS), affecting mostly young people at a mean age of 30 years. Magnetic resonance imaging (MRI) is one of the most specific and sensitive methods in diagnosing and detecting the evolution of multiple sclerosis disease. But it does not have the ability to differentiate between distinct histopathological heterogeneities that occur in MS lesions and brain tissue.Quantitative magnetization transfer imaging (qMTI) is a relatively new MRI technique which can be used to examine the pathological processes of the brain parenchyma which occur in MS patients.This quantitative MRI technique can provide more complete information about the extent and nature of the brain tissue destruction in multiple sclerosis, which cannot be detected by conventional MRI. Material and Methods: In this study, twelve patients with relapsing-remitting MS and twelve healthy control subjects underwent conventional MR imaging including: T2-FSE, T1-SE and FLAIR sequences as well as quantitative magnetization transfer imaging. All the focal lesions were identified on T2-weighted images and were classified according to their signal hypointensity on T1-weighted scans. The white matter and MS lesions were segmented using a semi-automated system. MT ratio (MTR) histogram analysis was performed for the brain white matter and the average MTR value was calculated for the classified MS lesions. Results: A significant reduction was found in MTR value of the normal appearing white matter (NAWM) in patients with relapsing-remitting MS, suggesting that MS is a more diffuse disease, affecting the whole brain tissue. A wide range changes in MTR values can be observed in MS lesions. MTR reduction is correlated with the degree of lesion hypointensity on T1-weighted scans. The lower MTR values of lesions that appear progressively more hypointense on T1-weigted images reflect varying degrees of demyelination and breakdown in the macromolecular structure of MS lesions. There was also a significant difference in MTR histogram parameters between the patients and control groups, accompanied by a total shift of NAWM-MTR histogram to the left. Discussion and Conclusion: Based on theobtained result itcan be stated that MS has a diffused nature and the white matter abnormalities occurring outside T2-visible lesions affect the whole brain tissue. Quantitative magnetization transfer imaging can be used as a reliable method to assess both the overall disease burden and the intrinsic nature of the individual lesions in MS patients

1 citations


Journal ArticleDOI
TL;DR: It is predicted that the increased strength or duration of the pulse will enhance the cell electropermeability provided the cell does not die and the cell membrane is not interrupted.
Abstract: Introduction: Electroporation is a practical technique used to transport the molecules across the cell membrane. The utilization of fluorescent molecules is the method widely used to evaluate the electropermeability of cell membrane as a result of pulse application. It is also possible to use mathematical methods to predict the changes caused in cell electropermeability as a result of the changes made in the pulse parameters. So the technique can be managed in such a way that the maximum permeability and minimum cell death can be achieved when desirable. Material and Methods: In this study, MCF-7 cell line of human breast adenocarcinoma tumor was used. Propidium Iodide (PI) and Fluorometry technique was used to monitor the cell electropermeability and the cell survival. The cells were incubated in PI and electrical pulses were applied affecting the cell permeability. As a result the cell membrane is disrupted releasing the fluorescent molecules affiliated with PI. The fluorescence signal emitted by the dead cells was determined by fluorometry and the obtained result was used to generate a curve in terms of the signal and the percent cell survival. The curve was used to resolve the fluorescence signal emitted by the permeated live cells. The incubation of the cells in PI and its uptake by the cells affects their electric pulses. The permeability and cell survival for six different doses of electrical pulses was assessed immediately and also 72 hours after the application of the pulses. Results: The maximum fluorescence emission and excitation wavelengths of PI solution attained at 540 and 600 nanometers, respectively. The highest permeability signal and the least cell survival percentage were recorded for electrical pulses of 1500 volts at 25-microsecond duration and 800 volts at 500-microsecond duration, respectively. The cell death rate, immediately after getting the pulses was assessed lower than the one after 72 hours. Discussion and Conclusion: It is predicted that the increased strength or duration of the pulse will enhance the cell electropermeability provided the cell does not die and the cell membrane is not interrupted. A mathematical equation was obtained in terms of the level of electropermeability signals, cell survival percentage and pulse parameters. Based on the equation the permeability is correlated to the pulse duration by the second power and pulse strength by the first power. It seems that there are some processes that not only induce immediate cell death but also inhibit the injured cells to recover or proliferate. These processes are activated as a result of the damage caused by the application of increased strength and duration of the electrical pulses.

1 citations


Book ChapterDOI
TL;DR: Hoffman Brain Phantom is modified in such a way that only software capability is evaluated in routine single photon emission tomography (SPECT) studies.
Abstract: Introduction: The purpose of this study was to define an optimal parameter for the tomographic reconstruction procedure in routine single photon emission tomography (SPECT) studies. In this study Hoffman Brain Phantom is modified in such a way that only software capability is evaluated. The phantom is composed of several independent slice that can be imaged individually (planar) or in 3-D composition (SPECT).

1 citations


Book ChapterDOI
TL;DR: The accuracy of MR images considered by phantom study and the reproducibility of images evaluated by repeated phantom measurements are considered and decreasing of geometric distortion use of suitable coil and protocol are expected.
Abstract: Image distortion is one of the major deficits of magnetic resonance (MR) imaging for use in 3DMRI, velocity MRI, fMRI and radiotherapy treatment planning (RTTP). It is widely known the most obviously effect of inhomogenity of magnetic fields and the nonlinearity of gradient is the Geometric Distortion of MR tomograms. In this study, the accuracy of MR images considered by phantom study and the reproducibility of images evaluated by repeated phantom measurements. A cube-shaped Perspex phantom, 20×20×5 cm, was designed for measurement of geometric distortion. There is a grid pattern inside the phantom, with grid space of 10 mm, the thickness grids of 2 mm and the depth of 40 mm contains 4mM/l magnevist solution. MR scans were performed with two 1.5 Tesla super-conductive MR systems (Picker VISTA TM HPQ & GE Signa Echo Speed), using head coil. For Geometric Distortion reproducibility the T1W, PDW and T2W SE protocols with TR/TE=500ms/20ms, 1000ms/20ms, 1000ms/100ms respectively and ST/FOV/MATRIX/NEX=5mm/24cm/256×256/1 were used. The Geometric Distortion was measured manually and by an edge detection program in MATLAB. The geometric distortion generally tended to be large in peripheral area of the images than in central area in all images. Average of displacements in Picker MRI were 3 pixel in y and 1 pixel in x direction and in GE MRI were 1 pixel in x and y directions for 24 cm FOV (1 pixel=0.9mm). Since the positional variation were within 1 to 3 pixels for head coil, it will be possible to use this MR system in 3DMRI, velocity MRI, FMRI and RTTP. For decreasing of geometric distortion use of suitable coil and protocol are expected.