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جهاز Imr الطبي

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  1. [11]
    م.الدمشقي
    م.الدمشقي غير متواجد حالياً
    عضو شرف
    الصورة الرمزية م.الدمشقي


    تاريخ التسجيل: Apr 2005
    المشاركات: 326

    وسام الشكر

     وسام كبار الشخصيات

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    اخي العزيز مثال عكاب
    الاسم الصحيح للجهاز هو MRI والاسم هوMagnetic Resonance Imaging
    والجهاز الذي ذكره الاخ مفاعل نوويNuclear Magnetic Resonance Imaging
    هو نفسه MRI
    وهذه ما هي الى تسمية اخرى له والاختصار هو NMR
    هذا ما وجدته بعد البحث
    اذا كان كلامي خطا فارجو من من عنده المعلومه الصحيحه ان يصوبني
    تحياتي

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    قال رسول اللة صلى اللة علية وسلم(ان الله يحب اذا عمل احدكم عملا ان يتقنة)
    من فلسطين الجريحة
    احب كل من يحب عمر وابو بكر رضي الله عنهم واكره من يكرههم

  2. [12]
    مثال عكاب
    مثال عكاب غير متواجد حالياً
    عضو فعال


    تاريخ التسجيل: Jun 2006
    المشاركات: 110
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    الى الاخ م الدمشقي بارك الله فيك على المجهود وانى جدا ممنون منك يا اخي العزيز

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  3. [13]
    مفاعل_نووي
    مفاعل_نووي غير متواجد حالياً
    زائر


    تاريخ التسجيل: Aug 2005
    المشاركات: 442
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    اقتباس المشاركة الأصلية كتبت بواسطة م.الدمشقي
    هل لك ان توضح لنا الفرق يا مفاعل نووي
    لتعم الفائده اخي الكريم
    Dear brother,
    I do not understand your question ..sorry
    I gave a definition for the IRM (IRMN
    it's the same:
    IRM=IRMN
    else if you mean some thing, i would like to answer you..
    salam aleikum

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  4. [14]
    مفاعل_نووي
    مفاعل_نووي غير متواجد حالياً
    زائر


    تاريخ التسجيل: Aug 2005
    المشاركات: 442
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    اقتباس المشاركة الأصلية كتبت بواسطة مثال عكاب
    شكرا جزيلا للاخ مفاعل نووي وهل ليك معلومات اخرى او صور حول الموضوع
    الاخ عكاب ،
    اطلب منك ان تكون اكثر دقة في تحديد طلبك؛ لان مجال الــ IRMN واسع جدا..
    -هل انت مبتدئ تريد معرفة هذه التقنية فقط؟
    - في اي مجال تريد دراستها، ولاي غرض ..
    -هل تريد معرفة ادوات التقنية فقط (هندسة اكترونية و غيرها)...
    - هل تريد معرفة الـ IRMN او RMN
    على العموم :
    الـ RMN هي طريقة استخلاص الاشارة الدالة psectrum على الاجسام و الجزيئات..تستعمل خصيصا في الكيمياء و الطب و البيولوجيا
    الـ IRMN هي طريقة اعم واشمل، اذ اظافة لـاستخلاص الاشارة الدالة psectrum على الاجسام و الجزيئات، تقوم ببناء صور حقيقية دقيقة للجسم المراد دراسته وتبلغ دقة التصوير الى ما تحت 1 مايكرون .. :)

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  5. [15]
    مفاعل_نووي
    مفاعل_نووي غير متواجد حالياً
    زائر


    تاريخ التسجيل: Aug 2005
    المشاركات: 442
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    Discovery
    Nuclear magnetic resonance was first described independently by Felix Bloch and Edward Mills Purcell, in 1946, both of whom shared the Nobel Prize in physics in 1952 for their discovery.

    Purcell had worked on the development and application of RADAR during World War II at Massachusetts Institute of Technology's Radiation Laboratory. His work during that project on the production and detection of radiofrequency energy, and on the absorption of such energy by matter, preceded his discovery of NMR and probably contributed to his understanding of it and related phenomena.
    They noticed that magnetic nuclei, like 1H and 31P, could absorb RF energy when placed in a magnetic field of a specific strength. When this absorption occurs the nucleus is described as on resonance. Interestingly, for analytical scientists, different atoms within a molecule resonate at different frequencies at a given field strength. The observation of the resonance frequencies of a molecule allows a user to discover structural information about the molecule.
    The development of nuclear magnetic resonance as a technique of analytical chemistry and biochemistry parallels the development of electromagnetic technology and its introduction into civilian use.

    [SIZE="3"]Magnetic resonance imaging (MRI), formerly referred to as magnetic resonance tomography (MRT) or nuclear magnetic resonance (NMR), is a method used to visualize the inside of living organisms as well as to detect the composition of geological structures. It is primarily used to demonstrate pathological or other physiological alterations of living tissues and is a commonly used form of medical imaging. MRI has also found many novel applications outside of the medical and biological fields such as rock permeability to hydrocarbons and certain non-destructive testing methods such as produce and timber quality characterization. [1] The devices used in medicine are expensive, costing approximately $1 million USD per tesla for each unit (common field strength ranges from 0.3 to 3 teslas), with several hundred thousand dollars per year of upkeep costs.
    Magnetic resonance imaging was developed from knowledge gained in the study of nuclear magnetic resonance. The original name for the medical technology is nuclear magnetic resonance imaging (NMRI), but the word nuclear is almost universally dropped. This is done to avoid the negative connotations of the word nuclear, and to prevent patients from associating the examination with radiation exposure, which is not one of the safety concerns for MRI. Scientists still use NMR when discussing non-medical devices operating on the same principles.

    Medical MRI most frequently relies on the relaxation properties of excited hydrogen nuclei in water. When the object to be imaged is placed in a powerful, uniform magnetic field the spins of the atomic nuclei with non-zero spin numbers (essentially, an unpaired proton or neutron) within the tissue all align in one of two opposite directions: parallel to the magnetic field or antiparallel. Common magnetic field strengths range from 0.3 to 3 teslas, although research instruments range as high as 20 teslas, and commercial suppliers are investing in 7 tesla platforms.

    Technique
    An excess of only one in a million nuclei align themselves with the magnetic field since the thermal energy far exceeds the difference between the parallel and antiparallel states. Yet the vast quantity of nuclei in a small volume sum to produce a detectable change in field. Most basic explanations of NMR and MRI will say that the nuclei align parallel or anti-parallel with the static magnetic field though, because of quantum mechanical reasons beyond the scope of this article, the individual nuclei are actually set off at an angle from the direction of the static magnetic field. The bulk collection of nuclei can be partitioned into a set whose sum spin are aligned parallel and a set whose sum spin are anti-parallel.

    The magnetic dipole moment of the nuclei then precesses around the axial field. While the proportion is nearly equal, slightly more are oriented at the low energy angle. The frequency with which the dipole moments precess is called the Larmor frequency. The tissue is then briefly exposed to pulses of electromagnetic energy (RF pulse) in a plane perpendicular to the magnetic field, causing some of the magnetically aligned hydrogen nuclei to assume a temporary non-aligned high-energy state. The frequency of the pulses is governed by the Larmor equation.

    In order to selectively image different voxels (picture elements) of the material in question, orthogonal magnetic gradients are applied. Although it is relatively common to apply gradients in the principal axes of a patient (so that the patient is imaged in x, y, and z from head to toe), MRI allows completely flexible orientations for images. All spatial encoding is obtained by applying magnetic field gradients which encode position within the phase of the signal. In 1 dimension, a linear phase with respect to position can be obtained by collecting data in the presence of a magnetic field gradient. In 3 dimensions, a plane can defined by "slice selection", in which an RF pulse of defined bandwidth is applied in the presence of a magnetic field gradient in order to reduce spatial encoding to 2 dimensions. Spatial encoding can then be applied in 2D after slice selection, or in 3D without slice selection. In either case, a 2D or 3D matrix of spatially-encoded phases is acquired, and these data represent the spatial frequencies of the image object. Images can be created from the acquired data using the Discrete Fourier Transform (DFT).

    In order to understand MRI contrast, it is important to have some understanding of the time constants involved in relaxation processes that establish equilibrium following RF excitation. As the high-energy nuclei relax and realign, they emit energy at rates which are recorded to provide information about their environment. The realignment of nuclear spins with the magnetic field is termed longitudinal relaxation and the time (typically about 1 sec) required for a certain percentage of the tissue nuclei to realign is termed "Time 1" or T1. T2-weighted imaging relies upon local dephasing of spins following the application of the transverse energy pulse; the transverse relaxation time (typically < 100 ms for tissue) is termed "Time 2" or T2. A subtle but important variant of the T2 technique is called T2* imaging. T2 imaging employs a spin echo technique, in which spins are refocused to compensate for local magnetic field inhomogeneities. T2* imaging is performed without refocusing. This sacrifices some image integrity in order to provide additional sensitivity to relaxation processes that cause incoherence of transverse magnetization. Applications of T2* imaging include functional MRI (fMRI) or evaluation of baseline perfusion (CBF and CBV) using injected agents as described above; in these cases, there is an inherent trade-off between image quality and detection sensitivity. Because T2*-weighted sequences are sensitive to magnetic inhomogeneity (as can be caused by deposition of Fe-containing blood-degradation products), such sequences are utilized to detect subtle areas of recent or chronic intracranial hemorrhage ("Heme sequence").

    Image contrast is created by using a selection of image acquisition parameters that weights signal by T1, T2 or T2*, or no relaxation time ("proton-density images"). In the brain, T1-weighting causes fiber tracts (nerve connections) to appear white, congregations of neurons to appear gray, and cerebrospinal fluid to appear dark. The contrast of "white matter," "gray matter'" and "cerebrospinal fluid" is reversed using T2 or T2* imaging, whereas proton-weighted imaging provides little contrast in normal subjects. Additionally, functional information (CBF, CBV, blood oxygenation) can be encoded within T1, T2, or T2*; see functional MRI (fMRI) and the section below.

    Diffusion Weighted Imaging (DWI) uses very fast scans with an additional series of gradients (diffusion gradients) rapidly turned on and off. Protons from water diffusing randomly within the brain, via Brownian motion, lose phase coherence and, thus, signal during application of diffusion gradients. Within acutely infarcted brain, water diffusivity is impaired, and signal loss on DWI sequences is less than in normal brain. DWI is the most sensitive method of detecting cerebral infarction (stroke) and can identify an infarct within 30 minutes of ictus.

    Typical medical resolution is about 1 mm3, while research models can exceed 1 &#181;m3.


    ]

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  6. [16]
    مفاعل_نووي
    مفاعل_نووي غير متواجد حالياً
    زائر


    تاريخ التسجيل: Aug 2005
    المشاركات: 442
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    Application
    In clinical practice, MRI is used to distinguish pathologic tissue (such as a brain tumor) from normal tissue. One advantage of an MRI scan is that it is harmless to the patient. It uses strong magnetic fields and non-ionizing radiation in the radio frequency range. Compare this to CT scans and traditional X-rays which involve doses of ionizing radiation and may increase the chance of malignancy, especially in a fetus.

    While CT provides good spatial resolution (the ability to distinguish two structures an arbitrarily small distance from each other as separate), MRI provides comparable resolution with far better contrast resolution (the ability to distinguish the differences between two arbitrarily similar but not identical tissues). The basis of this ability is the complex library of pulse sequences that the modern medical MRI scanner includes, each of which is optimized to provide image contrast based on the chemical sensitivity of MRI.

    For example, with particular values of the echo time (TE) and the repetition time (TR), which are basic parameters of image acquisition, a sequence will take on the property of T2-weighting. On a T2-weighted scan, fat-, water- and fluid-containing tissues are bright (most modern T2 sequences are actually fast T2 sequences). Damaged tissue tends to develop edema, which makes a T2-weighted sequence sensitive for pathology, and generally able to distinguish pathologic tissue from normal tissue. With the addition of an additional radio frequency pulse and additional manipulation of the magnetic gradients, a T2-weighted sequence can be converted to a FLAIR (Fluid Light Attenuation Inversion Recovery) sequence, in which free water is now dark, but edematous tissues remain bright. This sequence in particular is currently the most sensitive way to evaluate the brain for demyelinating diseases, such as multiple sclerosis.

    The typical MRI examination consists of 5-20 sequences, each of which are chosen to provide a particular type of information about the subject tissues. This information is then synthesized by the interpreting physician.

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  7. [17]
    مفاعل_نووي
    مفاعل_نووي غير متواجد حالياً
    زائر


    تاريخ التسجيل: Aug 2005
    المشاركات: 442
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    اقتباس المشاركة الأصلية كتبت بواسطة م.الدمشقي
    اخي العزيز مثال عكاب
    الاسم الصحيح للجهاز هو MRI والاسم هوMagnetic Resonance Imaging
    والجهاز الذي ذكره الاخ مفاعل نوويNuclear Magnetic Resonance Imaging
    هو نفسه MRI
    وهذه ما هي الى تسمية اخرى له والاختصار هو NMR
    هذا ما وجدته بعد البحث
    اذا كان كلامي خطا فارجو من من عنده المعلومه الصحيحه ان يصوبني
    تحياتي
    انبهكم يا اخوان ان الجهاز يدعى بالانجليزي
    MRI SCANNER

    و بالاحرى عند التقنيين (وخاصة بالفرنسية) فيسمى:
    MR SPECTROMETRE
    اي ان التسمية المختصرة MRI تطلق على اطريقة او التقنية. و اما الجهاز فهو عبارة عن:

    محرض و ملتقط (قارئ) للاشارة الواردة من جزيئات الجسم المدروس.
    واما IMAGING فهي عملية بناء الصور ، وتتم بواسطة الحاسب COMPUTER عن طريق تحويل الاشارة الملتقطة الى صور (ثلاتية الابعاد)..

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  8. [18]
    مثال عكاب
    مثال عكاب غير متواجد حالياً
    عضو فعال


    تاريخ التسجيل: Jun 2006
    المشاركات: 110
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    الى الاخ العزيز مفاعل_نووي انا اشكرك جدا جدا على هذه المعلومات القيمه جزاك الله خيرا

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  9. [19]
    م.الدمشقي
    م.الدمشقي غير متواجد حالياً
    عضو شرف
    الصورة الرمزية م.الدمشقي


    تاريخ التسجيل: Apr 2005
    المشاركات: 326

    وسام الشكر

     وسام كبار الشخصيات

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    جزاك الله خيرا يا مفاعل نووي
    ولكن انت لم تقل لي
    هل Mri وnmr
    تسميتان لجهاز واحد

    0 Not allowed!


    قال رسول اللة صلى اللة علية وسلم(ان الله يحب اذا عمل احدكم عملا ان يتقنة)
    من فلسطين الجريحة
    احب كل من يحب عمر وابو بكر رضي الله عنهم واكره من يكرههم

  10. [20]
    مفاعل_نووي
    مفاعل_نووي غير متواجد حالياً
    زائر


    تاريخ التسجيل: Aug 2005
    المشاركات: 442
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    Exclamation

    اقتباس المشاركة الأصلية كتبت بواسطة م.الدمشقي
    جزاك الله خيرا يا مفاعل نووي
    ولكن انت لم تقل لي
    هل Mri وnmr
    تسميتان لجهاز واحد
    ركز على ما كتبته لك سابقا و ستجد الجواب..
    Mri وnmr كلمتان معناهما:
    Mri = Magnetic Resonance Imaging =يقصد بها تقنية التصوير بالرنين المغنطيسي" ر.م."
    nmr= Nuclear Magnetic Resonance = الرنين المغنطيسي النووي= ويقصد بها تقنية تحريض واستخلاص الاشارة من الاجسام و الاشياء .
    على العموم نحن هنا لم نتكلم عن جهاز بعينه.
    انما الاجهزة كلها التي تستعمل تقنية الــ NMR يصح تسميتها SPECTOMETER ، و بالانجليزي SCANNER و كلاهما يؤدي نفس المعنى لكن الاول اعم و اشمل..
    لان التقنية الاساسية تسمى غالبا SPETROMETRIE اي قياس الطيف (قياس الاشارة). وتستعمل سواء في مجال الكيمياء او البيولوجيا او الطب لتحديد مركبات الاجسام و الجزيئات. وهي نفسها التي نستعملها في مقدمة تقنية الـ nmri بشيئ من التعقيد و المعالجة و الدقة في استخلاص دلائل عديدة من جزيئات الجسم ( FONTOM = الشبح )..

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