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T1 TimeForum -
related threads
 
The T1 relaxation time (also called spin lattice or longitudinal relaxation time), is a biological parameter that is used in MRIs to distinguish between tissue types. This tissue-specific time constant for protons, is a measure of the time taken to realign with the external magnetic field. The T1 constant will indicate how quickly the spinning nuclei will emit their absorbed RF into the surrounding tissue.
As the high-energy nuclei relax and realign, they emit energy which is recorded to provide information about their environment. The realignment with the magnetic field is termed longitudinal relaxation and the time in milliseconds required for a certain percentage of the tissue nuclei to realign is termed 'Time 1' or T1. Starting from zero magnetization in the z direction, the z magnetization will grow after excitation from zero to a value of about 63% of its final value in a time of T1. This is the basic of T1 weighted images.
The T1 time is a contrast determining tissue parameter. Due to the slow molecular motion of fat nuclei, longitudinal relaxation occurs rather rapidly and longitudinal magnetization is regained quickly. The net magnetic vector realigns with B0 leading to a short T1 time for fat.
Water is not as efficient as fat in T1 recovery due to the high mobility of the water molecules. Water nuclei do not give up their energy to the lattice (surrounding tissue) as quickly as fat, and therefore take longer to regain longitudinal magnetization, resulting in a long T1 time.

See also T1 Weighted Image, T1 Relaxation, T2 Weighted Image, and Magnetic Resonance Imaging MRI.
 
Images, Movies, Sliders:
 Anatomic MRI of the Knee 2  Open this link in a new window
    
SlidersSliders Overview

 Breast MRI Images T2 And T1  Open this link in a new window
 Brain MRI Images T1  Open this link in a new window
      

 
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    • Repetition Time
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    • Short T1-Relaxation Gastrointestinal Agents
 
Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
A practical guideline for T1 reconstruction from various flip angles in MRI
Saturday, 1 October 2016   by journals.sagepub.com    
Magnetic resonance imaging - From Wikipedia, the free encyclopedia.
   by en.wikipedia.org    
  News & More:
New technique could allow for safer, more accurate heart scans
Thursday, 10 December 2015   by www.gizmag.com    
Rockland Technimed: Tissue Viability Imaging
Saturday, 15 December 2007   by www.onemedplace.com    
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Radiology  (9) Open this link in a new windowUltrasound  (52) Open this link in a new window
Medical Imaging
 
The definition of imaging is the visual representation of an object. Medical imaging began after the discovery of x-rays by Konrad Roentgen 1896. The first fifty years of radiological imaging, pictures have been created by focusing x-rays on the examined body part and direct depiction onto a single piece of film inside a special cassette. The next development involved the use of fluorescent screens and special glasses to see x-ray images in real time.
A major development was the application of contrast agents for a better image contrast and organ visualization. In the 1950s, first nuclear medicine studies showed the up-take of very low-level radioactive chemicals in organs, using special gamma cameras. This medical imaging technology allows information of biologic processes in vivo. Today, PET and SPECT play an important role in both clinical research and diagnosis of biochemical and physiologic processes. In 1955, the first x-ray image intensifier allowed the pick up and display of x-ray movies.
In the 1960s, the principals of sonar were applied to diagnostic imaging. Ultrasonic waves generated by a quartz crystal are reflected at the interfaces between different tissues, received by the ultrasound machine, and turned into pictures with the use of computers and reconstruction software. Ultrasound imaging is an important diagnostic tool, and there are great opportunities for its further development. Looking into the future, the grand challenges include targeted contrast agents, real-time 3D ultrasound imaging, and molecular imaging.
Digital imaging techniques were implemented in the 1970s into conventional fluoroscopic image intensifier and by Godfrey Hounsfield with the first computed tomography. Digital images are electronic snapshots sampled and mapped as a grid of dots or pixels. The introduction of x-ray CT revolutionised medical imaging with cross sectional images of the human body and high contrast between different types of soft tissue. These developments were made possible by analog to digital converters and computers. The multislice spiral CT technology has expands the clinical applications dramatically.
The first MRI devices were tested on clinical patients in 1980. The spread of CT machines is the spur to the rapid development of MRI imaging and the introduction of tomographic imaging techniques into diagnostic nuclear medicine. With technological improvements including higher field strength, more open MRI magnets, faster gradient systems, and novel data-acquisition techniques, MRI is a real-time interactive imaging modality that provides both detailed structural and functional information of the body.
Today, imaging in medicine has advanced to a stage that was inconceivable 100 years ago, with growing medical imaging modalities:
Single photon emission computed tomography (SPECT)
Positron emission tomography (PET)

All this type of scans are an integral part of modern healthcare. Because of the rapid development of digital imaging modalities, the increasing need for an efficient management leads to the widening of radiology information systems (RIS) and archival of images in digital form in picture archiving and communication systems (PACS). In telemedicine, healthcare professionals are linked over a computer network. Using cutting-edge computing and communications technologies, in videoconferences, where audio and visual images are transmitted in real time, medical images of MRI scans, x-ray examinations, CT scans and other pictures are shareable.
See also Hybrid Imaging.

See also the related poll results: 'In 2010 your scanner will probably work with a field strength of', 'MRI will have replaced 50% of x-ray exams by'
Radiology-tip.comradDiagnostic Imaging
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Medical-Ultrasound-Imaging.comMedical Imaging
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• View the NEWS results for 'Medical Imaging' (81).Open this link in a new window.
 
Further Reading:
  Basics:
Image Characteristics and Quality
   by www.sprawls.org    
Multimodal Nanoparticles for Quantitative Imaging(.pdf)
Tuesday, 13 December 2011   by alexandria.tue.nl    
Medical imaging shows cost control problem
Tuesday, 6 November 2012   by www.mysanantonio.com    
  News & More:
iMPI: An Exploration of Post-Launch Advancements
Friday, 29 September 2023   by www.diagnosticimaging.com    
Advances in medical imaging enable visualization of white matter tracts in fetuses
Wednesday, 12 May 2021   by www.eurekalert.or    
Positron Emission Tomographic Imaging in Stroke
Monday, 28 December 2015   by www.ncbi.nlm.nih.gov    
Multiparametric MRI for Detecting Prostate Cancer
Wednesday, 17 December 2014   by www.onclive.com    
Combination of MRI and PET imaging techniques can prevent second breast biopsy
Sunday, 29 June 2014   by www.news-medical.net    
3D-DOCTOR Tutorial
   by www.ablesw.com    
MRI Resources 
Contrast Enhanced MRI - MRI Reimbursement - MR Myelography - MRA - Spectroscopy pool - Research Labs
 
Imaginary Numbers
 
An imaginary number is a part of a complex number. Complex numbers are an extension of the real numbers. A complex number has a real and an imaginary part. The imaginary unit (i) is equal to the square root of -1. The complex conjugate is a pair of complex numbers with identical real parts and imaginary parts which differ only in sign (e.g.: 3 + 7i and 3 - 7i).
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Further Reading:
  Basics:
Imaginary Numbers
   by en.wikipedia.org    
Imaginary Number
   by mathworld.wolfram.com    
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Quadrature Detection
 
Quadrature detection is used in magnetic resonance imaging as well as in Doppler ultrasound and is also called quadrature demodulation or phase quadrature technique.
With this phase sensitive demodulation technique the complex demodulated signal is separated into two components. One is called the real channel; the second part is called the imaginary channel and is located 90° away from the real channel. The signals from both channels are combined to produce a single set of quadrature detected real and imaginary spectra. In MRI, the parts of the demodulated MR signal are further processed by Fourier transformation analysis. All information on the MR signal components e.g. amplitude, phase, and frequency is given by this quadrature detection combined with Fourier analysis.
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Radiology  (9) Open this link in a new windowUltrasound  (52) Open this link in a new window
Cartesian Coordinate System
 
The coordinate system most frequently used to quantitatively describe a n-dimensional space.
In 2 dimensions, i.e. a plane, it describes any point as a function of 2 perpendicular unit vectors (1,0) and (0,1) and in 3 dimensions as a function of 3 perpendicular unit vectors (1,0,0), (0,1,0) and (0,0,1). Functions in 2 dimensions are often conveniently described using the so-called theory of functions. When using this type of mathematical description, the imaginary number
i = √(-1) is introduced to label the y-axis.
a + ib is then actually a 2 dimensional vector with a x-axis component of 'a' and a y-axis component of 'b'.
The 'a' is called the real part and the 'b' the imaginary part of the function, an expression that is frequently encountered in MRI, where the real image is a pixel-wise representation of 'a' and the imaginary image a pixel-wise representation of 'b', with 'a' and 'b' the components of the xy-magnetization along the x- and y-axis, respectively.
(Renatus Cartesius/Rene Descartes, 1596-1650, French philosopher and mathematician)
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