Jeudi 5 octobre 2006 4 05 /10 /Oct /2006 09:55
Par SPINNEUR - Publié dans : ANATOMIE . ANATOMY
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Mercredi 4 octobre 2006 3 04 /10 /Oct /2006 12:15

 

.

 
Out of Phase  
 

Water and fat signals being in or out of phase result from the FFE method and the slight difference in resonance frequencies of the protons.

 It can cause black "outlining" of tissues and decrease in signal from voxel containing both water and fat.

 At 1.5 T, the water and fat signal are in phase when TE is an even multiple, and out of phase when TE is an odd multiple of 2.3 ms.


1.5T: OUT of PHASE = 2.3, 6.9, 11.5, 16.1, 20.7 ms
1.0T: OUT of PHASE = 3.5, 10.4, 17.3, 24.2 ms
0.5T: OUT of PHASE = 6.9, 20.7 ms
See also
Opposed Phase Image.

 
 
Images:
 MRI Liver Out Of Phase  Open this link in a new window  
 
     
 
 
 
Further Reading:
  Basics:
 
Out of Phase  
 

Water and fat signals being in or out of phase result from the FFE method and the slight difference in resonance frequencies of the protons. It can cause black "outlining" of tissues and decrease in signal from voxel containing both water and fat. At 1.5 T, the water and fat signal are in phase when TE is an even multiple, and out of phase when TE is an odd multiple of 2.3 ms.
1.5T: OUT of PHASE = 2.3, 6.9, 11.5, 16.1, 20.7 ms
1.0T: OUT of PHASE = 3.5, 10.4, 17.3, 24.2 ms
0.5T: OUT of PHASE = 6.9, 20.7 ms
See also Opposed Phase Image.

 
 
Images:
 MRI Liver Out Of Phase  Open this link in a new window  
 
     
 
 
 
Further Reading:
  Basics:
ROUTINE BODY MRI PROTOCOLSOpen this link in a new window
   by www.rad.uab    
kidneys, adrenals and bladderOpen this link in a new window
   by mripractice.tripod.com    
  News & More:
Adrenal MyelolipomaOpen this link in a new window
Tuesday, 19 June 2001   by www.emedicine.com    
 
 
Abdominal Imaging MRI Resource Directory:
                                                - Abdominal Imaging -
 

General MRI of the abdomen can consist of T1 or T2 weighted spin echo, fast spin echo (FSE, TSE) or gradient echo sequences with fat suppression and contrast enhanced MRI techniques. The examined organs include liver, pancreas, spleen, kidneys, adrenals as well as parts of the stomach and intestine. Respiratory compensation and breath hold imaging is mandatory for a good image quality.
T1 weighted sequences are more sensitive for lesion detection than T2 weighted sequences at 0.5 T, while higher field strengths (greater than 1.0 T), T2 weighted and spoiled gradient echo sequences are used for focal lesion detection. Gradient echo in phase T1 breath hold can be performed as a dynamic series with the ability to visualize the blood distribution. Phases of contrast enhancement include the capillary or arterial dominant phase for demonstrating hypervascular lesions, in liver imaging the portal venous phase demonstrates the maximum difference between the liver and hypovascular lesions, while the equilibrium phase demonstrates interstitial disbursement for edematous and malignant tissues.
Out of phase gradient echo imaging for the abdomen is a lipid-type tissue sensitive sequence and is useful for the visualization of focal hepatic lesions, fatty liver, haemochromatosis, adrenal lesions and renal masses. The standards for abdominal MRI vary according to clinical sites based on sequence availability and MRI equipment. Specific abdominal imaging coils and liver-specific contrast agents targeted to the reticuloendothelial system (RES) of the liver and spleen, improve the detection and localization of lesions in the liver.
See also Hepatobiliary Contrast Agents, Reticuloendothelial Contrast Agents, and Oral Contrast Agents.

 
 
Images:
 MR Colonography Gadolinium per Rectum  Open this link in a new window  
 
       

Courtesy of  Robert R. Edelman
 Anatomic Imaging of the Liver  Open this link in a new window  
 
       
 

 
 
 
Out of Phase  
 

Water and fat signals being in or out of phase result from the FFE method and the slight difference in resonance frequencies of the protons. It can cause black "outlining" of tissues and decrease in signal from voxel containing both water and fat. At 1.5 T, the water and fat signal are in phase when TE is an even multiple, and out of phase when TE is an odd multiple of 2.3 ms.
1.5T: OUT of PHASE = 2.3, 6.9, 11.5, 16.1, 20.7 ms
1.0T: OUT of PHASE = 3.5, 10.4, 17.3, 24.2 ms
0.5T: OUT of PHASE = 6.9, 20.7 ms
See also Opposed Phase Image.

 
 
Images:
 MRI Liver Out Of Phase  Open this link in a new window  
 
     
 
 
 
Further Reading:
  Basics:
ROUTINE BODY MRI PROTOCOLSOpen this link in a new window
   by www.rad.uab    
kidneys, adrenals and bladderOpen this link in a new window
   by mripractice.tripod.com    
  News & More:
Adrenal MyelolipomaOpen this link in a new window
Tuesday, 19 June 2001   by www.emedicine.com    
 
 
Abdominal Imaging MRI Resource Directory:
                                                - Abdominal Imaging -
 

General MRI of the abdomen can consist of T1 or T2 weighted spin echo, fast spin echo (FSE, TSE) or gradient echo sequences with fat suppression and contrast enhanced MRI techniques. The examined organs include liver, pancreas, spleen, kidneys, adrenals as well as parts of the stomach and intestine. Respiratory compensation and breath hold imaging is mandatory for a good image quality.
T1 weighted sequences are more sensitive for lesion detection than T2 weighted sequences at 0.5 T, while higher field strengths (greater than 1.0 T), T2 weighted and spoiled gradient echo sequences are used for focal lesion detection. Gradient echo in phase T1 breath hold can be performed as a dynamic series with the ability to visualize the blood distribution. Phases of contrast enhancement include the capillary or arterial dominant phase for demonstrating hypervascular lesions, in liver imaging the portal venous phase demonstrates the maximum difference between the liver and hypovascular lesions, while the equilibrium phase demonstrates interstitial disbursement for edematous and malignant tissues.
Out of phase gradient echo imaging for the abdomen is a lipid-type tissue sensitive sequence and is useful for the visualization of focal hepatic lesions, fatty liver, haemochromatosis, adrenal lesions and renal masses. The standards for abdominal MRI vary according to clinical sites based on sequence availability and MRI equipment. Specific abdominal imaging coils and liver-specific contrast agents targeted to the reticuloendothelial system (RES) of the liver and spleen, improve the detection and localization of lesions in the liver.
See also Hepatobiliary Contrast Agents, Reticuloendothelial Contrast Agents, and Oral Contrast Agents.

 
 
Images:
<img height="17" alt="" src="http

 

ADRENAL MYELOLIPOMA  OUT OF PHASE MRI

http://www.emedicine.com/radio/topic18.htm

 

 

 

 

Par SPINNEUR - Publié dans : PULSE SEQUENCES ASPECT SIGNAL
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Mercredi 4 octobre 2006 3 04 /10 /Oct /2006 11:29

 

In Phase

Forum -
            related threads
        http://mr-tip.com/serv1.php?type=db1&dbs=In%20Phase      

Water and fat signals being in or out of phase result from the gradient echo method and the slight difference in resonance frequencies of the protons.

 At 1.5 T, the water and fat signal are in phase when TE is an even multiple, and out of phase when TE is an odd multiple of 2.3 ms.

With FFE Imaging, it is often advisable to use a TE value equal or close to an in phase value.
1.5T: IN PHASE = 4.6, 9.2, 13.8, 18.4, 23.0 ms
1.0T: IN PHASE = 6.9, 13.8, 20.7, 27.6 ms
0.5T: IN PHASE = 13.8, 27.6 ms
See also
Out of Phase.

                             
Further Reading:
  Basics:
ROUTINE BODY MRI PROTOCOLSOpen this link in a new window
   by www.rad.uab    
  News & More:
Adrenal MetastasesOpen this link in a new window
Friday, 15 March 2002   by www.emedicine.com    
               •• There are 20 news about 'In Phase'.            
 
In Phase Image  
 

The term in phase refers to an image in which the signals from two spectral components (such as fat and water) add constructively in a voxel.

T1 weighted in phase images are acquired by a gradient echo-based technique with a short TR, TE and a high flip angle greater than 60 degrees.

 To some degree, in phase sequences are more sensitive to detection of focal hepatic lesions than out of phase for evaluating reduced lesion-to-liver contrast, but the choice for a T1 gradient echo sequence is still based on field strength, advanced imaging techniques (breath hold imaging), and physician preference.

 
 
Images:
 MRI Liver In Phase  Open this link in a new window  
 
     
 
 
   
           
 
  Searchterm 'In Phase' was also found in the following services of MR-TIP.com:  
 
News  (20)   Forum  (1)    
 
           
 
Spin Phase Effect InfoSheet: - Artifacts -
                        Case Studies,
                        Reduction Index,
                        etc.
 

The spins flow with the blood through a slice and experience a RF pulse.

If they flow out of the slice by the time the signal is recorded (because the repetition time (TR) is asynchronous with the pulsatile flow), the flowing blood produces intravascular signal void by 'time of flight' effects, turbulent dephasing and first echo dephasing.

The liquid flow occasionally produces an intravascular high signal intensity due to flow related enhancement, even echo rephasing and diastolic pseudogating.


See also
Flow Artifact and Flow Effects.

   
   
           
 
Field Echo with Echo Time set for Water and Fat Signals in Phase InfoSheet: - Sequences -
                        Intro,
                        Overview,
                        Types of,
                        etc.
 

(FESUM) See Gradient Recalled Echo Sequence and In Phase Image.

   
   
           
 
  Searchterm 'In Phase' was also found in the following services of MR-TIP.com:  
 
News  (20)   Forum  (1)    
 
           
 
Abdominal Imaging MRI Resource Directory:
                        - Abdominal Imaging -
 

General MRI of the abdomen can consist of T1 or T2 weighted spin echo, fast spin echo (FSE, TSE) or gradient echo sequences with fat suppression and contrast enhanced MRI techniques. The examined organs include liver, pancreas, spleen, kidneys, adrenals as well as parts of the stomach and intestine. Respiratory compensation and breath hold imaging is mandatory for a good image quality.
T1 weighted sequences are more sensitive for lesion detection than T2 weighted sequences at 0.5 T, while higher field strengths (greater than 1.0 T), T2 weighted and spoiled gradient echo sequences are used for focal lesion detection. Gradient echo in phase T1 breath hold can be performed as a dynamic series with the ability to visualize the blood distribution. Phases of contrast enhancement include the capillary or arterial dominant phase for demonstrating hypervascular lesions, in liver imaging the portal venous phase demonstrates the maximum difference between the liver and hypovascular lesions, while the equilibrium phase demonstrates interstitial disbursement for edematous and malignant tissues.
Out of phase gradient echo imaging for the abdomen is a lipid-type tissue sensitive sequence and is useful for the visualization of focal hepatic lesions, fatty liver, haemochromatosis, adrenal lesions and renal masses. The standards for abdominal MRI vary according to clinical sites based on sequence availability and MRI equipment. Specific abdominal imaging coils and liver-specific contrast agents targeted to the reticuloendothelial system (RES) of the liver and spleen, improve the detection and localization of lesions in the liver.
See also Hepatobiliary Contrast Agents, Reticuloendothelial Contrast Agents, and Oral Contrast Agents.

 
 
Images:
 MR Colonography Gadolinium per Rectum  Open this link in a new window  
 
       

Courtesy of  Robert R. Edelman
 Anatomic Imaging of the Liver  Open this link in a new window  
 
       
 

 
 
Further Reading:
  Basics:
Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CTOpen this link in a new window
2000
MAGNETIC RESONANCE IMAGING OF FOCAL LIVER LESIONS(.pdf)Open this link in a new window
2002
LIVER-SPECIFIC CONTRAST AGENTS FOR MRI(.pdf)Open this link in a new window
  News & More:
MRI reveals liver cancer in time to save lives Open this link in a new window
2000
Forum -
            related threads
                                 
 
 
ROUTINE BODY MRI PROTOCOLSOpen this link in a new window
   by www.rad.uab    
  News & More:
Adrenal MetastasesOpen this link in a new window
Friday, 15 March 2002   by www.emedicine.com    
               •• There are 20 news about 'In Phase'.            
 
 
   
 
 
Images:
 MRI Liver In Phase  Open this link in a new window  
 
       
 
 
   
           
 
  Searchterm 'In Phase' was also found in the following services of MR-TIP.com:  
 
News  (20)   Forum  (1)    
 
           
 

 

 http://irmresonance.over-blog.com

.

Par SPINNEUR - Publié dans : PULSE SEQUENCES ASPECT SIGNAL
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:34

 

 

ARTICLE LINKS:
Fulltext  |  PDF (1.34 M)
Magnetic Resonance Imaging of Diffuse Liver Diseases.

Hepatic Magnetic Resonance Imaging, Issue Editor

 

ARTICLE LINKS:
Fulltext  |  PDF (1.34 M)
Magnetic Resonance Imaging of Diffuse Liver Diseases.

Hepatic Magnetic Resonance Imaging, Issue Editor

Topics in Magnetic Resonance Imaging. 13(3):151-163, June 2002.
Martin, Diego R. M.D., Ph.D.

, Inc.

 


Copyright © 2006, Lippincott Williams & Wilkins. All rights reserved.
Published by Lippincott Williams & Wilkins.
Copyright/Disclaimer NoticePrivacy Policy
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Topics in Magnetic Resonance Imaging. 13(3):151-163, June 2002.
Martin, Diego R. M.D., Ph.D.

Abstract:
Summary:

The intrinsic soft tissue contrast and exquisite sensitivity to contrast agents are unique attributes of magnetic resonance imaging that are beneficial when evaluating diffuse liver disease.

 Much like a pathologist uses different tissue or cell marker stains,

 the magnetic resonance imager can use a variety of imaging strategies to elucidate pathologic liver processes in vivo, including

processes leading to abnormal lipid metabolization,

iron deposition,

perfusion abnormalities related to inflammation,

 fibrosis,

vascular occlusion

, or infarction

and hemorrhage.

This article reviews the most important diffuse liver diseases and the corresponding magnetic resonance imaging features.

(C) 2002 Lippincott Williams & Wilkins, Inc.

 

 
Par SPINNEUR - Publié dans : FOIE-LIVER
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:31

 

 

 

Fat and water separation in balanced steady-state free precession using the Dixon method
Teng-Yi Huang 1 2, Hsiao-Wen Chung 1 2 *, Fu-Nien Wang 1, Cheng-Wen Ko 1 3, Cheng-Yu Chen 2
1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C
2Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, R.O.C
3Department of Computer Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, R.O.C
email: Hsiao-Wen Chung (chung@cc.ee.ntu.edu.tw)

*Correspondence to Hsiao-Wen Chung, Department of Electrical Engineering, National Taiwan University, Rm. 238, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10764, R.O.C

Funded by:
 National Science Council; Grant Number: NSC-91-2213-E-002-078
 National Center for Research Resource; Grant Number: P41RR14075
 Mental Illness and Neuroscience Discovery (MIND) Institute
 Ministry of Education
 National Science Council

Keywords
fat-water separation • Dixon method • in-phase and out-of-phase images • steady-state free precession • frequency offset
Abstract

In this work the feasibility of separating fat and water signals using the balanced steady-state free precession (SSFP) technique is demonstrated.

The technique is based on the observation (Scheffler and Hennig, Magnetic Resonance in Medicine 2003;49:395-397)

 that at the nominal values of TE = TR/2 in SSFP imaging, phase coherence can be achieved at essentially only two orientations (0° and 180°)

relative to the RF pulses in the rotating frame, under the assumption of TR << T2, and independently of the SSFP angle.

This property allows in-phase and out-of-phase SSFP images to be obtained by proper choices of the center frequency offset, and thus allows

the Dixon subtraction method to be utilized for effective fat-water separation.

 The TR and frequency offset for optimal fat-water separation are derived from theories. Experimental results from healthy subjects, using a 3.0 Tesla system, show that nearly complete fat suppression can be accomplished. Magn Reson Med 51:243-247, 2004. © 2004 Wiley-Liss, Inc.


Received: 28 April 2003; Revised: 26 June 2003; Accepted: 26 September 2003

Digital Object Identifier (DOI)

10.1002/mrm.10686  About DOI   

 

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  • Find other articles like this in Wiley InterScience
  • Find articles in Wiley InterScience written by any of the authors

Wiley InterScience is a member of CrossRef.

Cross Ref Memeber

 

http://mr-tip.com/serv1.php?type=db1&dbs=In%20Phase

 

 

 

 
Par SPINNEUR - Publié dans : PULSE SEQUENCES ASPECT SIGNAL
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:31

 

 

 

Fat and water separation in balanced steady-state free precession 

using the Dixon method
Teng-Yi Huang 1 2, Hsiao-Wen Chung 1 2 *, Fu-Nien Wang 1, Cheng-Wen Ko 1 3, Cheng-Yu Chen 2
1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C
2Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, R.O.C
3Department of Computer Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, R.O.C
email: Hsiao-Wen Chung (chung@cc.ee.ntu.edu.tw)

*Correspondence to Hsiao-Wen Chung, Department of Electrical Engineering, National Taiwan University, Rm. 238, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10764, R.O.C


 

Funded by:
 National Science Council; Grant Number: NSC-91-2213-E-002-078
 National Center for Research Resource; Grant Number: P41RR14075
 Mental Illness and Neuroscience Discovery (MIND) Institute
 Ministry of Education
 National Science Council

Keywords
fat-water separation • Dixon method • in-phase and out-of-phase images • steady-state free precession • frequency offset
Abstract

In this work the feasibility of separating fat and water signals using the balanced steady-state free precession (SSFP) technique is demonstrated.

The technique is based on the observation

(Scheffler and Hennig, Magnetic Resonance in Medicine 2003;49:395-397)

 that at the nominal values of TE = TR/2

in SSFP imaging,

 phase coherence

can be achieved at

essentially only two orientations (0° and 180°)

relative to the RF pulses in the rotating frame, under the assumption of TR << T2, and independently of the SSFP angle.

This property allows in-phase and out-of-phase SSFP images to be obtained by proper choices of the center frequency offset, and thus allows

the Dixon subtraction method to be utilized for effective fat-water separation.

 The TR and frequency offset for optimal fat-water separation are derived from theories.

.Experimental results from healthy subjects, using a 3.0 Tesla system, show that nearly complete fat suppression can be accomplished. Magn Reson Med 51:243-247, 2004. © 2004 Wiley-Liss, Inc.


Received: 28 April 2003; Revised: 26 June 2003; Accepted: 26 September 2003

Digital Object Identifier (DOI)

10.1002/mrm.10686  About DOI 

 

Related Articles

  • Find other articles like this in Wiley InterScience
  • Find articles in Wiley InterScience written by any of the authors

Wiley InterScience is a member of CrossRef.

Cross Ref Memeber

 
Par SPINNEUR - Publié dans : PULSE SEQUENCES ASPECT SIGNAL
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:24

 

Le lipome périsudoral (The perisudoral lipoma)


Auteur(s) / Author(s)

AIT-OURHROUIL M. (1) ; GROSSHANS E. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Laboratoire d'Histopathologie cutanée de la Clinique dermatologique universitaire de Strasbourg, FRANCE

Résumé / Abstract

Introduction. A la suite de la publication en 1993 de Hitchcock, Hurt et Santa Cruz, nous avons identifié 11 cas de la variante de lipome superficiel, décrite et dénommée par ces auteurs adénolipome cutané.

Malades et méthodes. Notre étude a porté sur 1 742 lésions enregistrées au Laboratoire d'Histopathologie cutanée de janvier 1989 à août 1996 et correspondant à

397 lipomes,

 1 325 molluscums pendulums dont 120 à axe graisseux

et 20 hamartomes conjonctifs divers dont 7 hamartomes lipomateux superficiels.

 Nous avons recherché parmi ces 1 742 lésions l'adénolipome cutané.

 Nous avons identifié 11 cas, soit une fréquence globale de 0,63 p. 100 pour l'ensemble des lésions examinées et de 2 p. 100 des 524 lésions cutanées lipomateuses (lipomes, hamartomes lipomateux et fibrolipomes).

 L'âge moyen des malades était de 50 ans et le rapport F/H de 1,75. Le siège de la tumeur était 7 fois aux membres inférieurs, (dont 4 fois à la cuisse), 3 fois au tronc et 1 fois dans la région scapulaire.

 Discussion. L'adénolipome cutané est une lésion lipomateuse distincte des lipomes habituels ;

 

 il se développe dans le derme ou dans l'hypoderme.

 Il est remarquable par son caractère solitaire, sa localisation préférentielle aux racines des membres, aux cuisses en particulier et son histogénèse.

Il s'agit d'une tumeur graisseuse lobulée et encapsulée, se développant apparemment à partir de la graisse périsudorale, se développant apparemment à partir de la graisse périsudorale normale.

Les glandes sudorales sont incluses dans le lipome sans y proliférer et la dénomination de lipome périsudoral paraît de ce fait préférable à celle d'adénolipome cutané.

Son diagnostic différentiel est à faire avec le fibrolipome

 (molluscum pendulum à axe graisseux) et l'hamartome lipomateux superficiel.

Revue / Journal Title

Annales de dermatologie et de vénéréologie  (Ann. dermatol. vénéréol.)  ISSN 0151-9638  CODEN ADVED7

Source / Source

1997, vol. 124, no12, pp. 845-848 (3 ref.)

Langue / Language

Français

Editeur / Publisher

Masson, Paris, FRANCE (1977) (Revue)

Mots-clés anglais / English Keywords

Lipoma ; Skin ; Case study ; Human ; Adipose tissue disorders ; Benign neoplasm ; Skin disease ;

Mots-clés français / French Keywords

Lipome ; Peau ; Etude cas ; Homme ; Tissu adipeux pathologie ; Tumeur bénigne ; Peau pathologie ;

002b08a ;

Mots-clés espagnols / Spanish Keywords

Lipoma ; Piel ; Estudio caso ; Hombre ; Tejido adiposo patología ; Tumor benigno ; Piel patología ;

 

  .

Par SPINNEUR - Publié dans : irm resonance magnétique
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:22
Par SPINNEUR - Publié dans : irm resonance magnétique
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:16

 

 

 

Keywords:

 NMR spectroscopy, Fat, Lipid, Body

SRM, Spectroscopie par Résonance magnétique , Suppression de graisse .

 

http://www.clinicalimaging.org/article/PIIS0899707102004916/abstract


a Department of Radiology, Wake Forest University, Bowman-Gray Medical Center, Winston-Salem, NC 27157, USA
 * Tel.: +1-336-716-6255; fax: +1-336-716-2029 

doi: 10.1016/S0899-7071(02)00491-6

© 2003 Elsevier Science Inc. All rights reserved.

Abstract
The presence or absence of fat in lesions can have important diagnostic implications.

Current MR techniques for the evaluation of fat within lesions in the body rely on indirect imaging methods.

The goal of this study was to develop a rapid clinically practical proton spectroscopy procedure for the direct observation of a localized fat–water signal within the body.

The technique developed reliably determined fat–water ratios in phantoms and from lesions in vivo in 6 s with single voxel sizes as small as 0.125 cc.

 

Keywords: NMR spectroscopy, Fat, Lipid, Body


a Department of Radiology, Wake Forest University, Bowman-Gray Medical Center, Winston-Salem, NC 27157, USA
 * Tel.: +1-336-716-6255; fax: +1-336-716-2029 

doi: 10.1016/S0899-7071(02)00491-6

© 2003 Elsevier Science Inc. All rights reserved.

 

 

 http://irmresonance.over-blog.com/

.

Par SPINNEUR - Publié dans : S.R.M .
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Mardi 3 octobre 2006 2 03 /10 /Oct /2006 20:01

In-phase/Out-of-phase MRI, IP/OP Sequences .

DIXON Method,

Fat-Water separation .


 

 

 

LIVER

 

ADRENAL

 1  : http://www.annals.org/cgi/content/full/130/9/759

Imaging Procedures Adrenocortical
space


Diagnosis of adrenal neoplasms depends on the identification of an adrenal mass on computed tomography (CT) or magnetic resonance imaging (MRI). Both normal and abnormal adrenal glands are readily visible on CT because of the surrounding adipose tissue in the retroperitoneum (125).

Computed tomography provides information about size, homogeneity, presence of calcifications, areas of necrosis, and extent of local invasion, making it helpful in decisions about the potential malignancy and resectability of the neoplasm.

Adrenal masses as small as 10 mm can be reliably detected by CT (126, 127), although the relative lack of retroperitoneal fat in children might decrease the sensitivity of the test in this population (128).

Adrenal CT is 70% to 80% sensitive in detecting aldosterone-producing adenomas. In one large series (111), mean tumor size was 1.8 cm, but 20% of these tumors were smaller than 1 cm. Adrenal incidentalomas are also common in older adults; thus, adrenal CT is considered adjunctive and is usually not used to direct adrenalectomy without other confirmatory data.

Whether MRI will prove superior to CT in diagnosing and differentiating among adrenal masses remains to be seen. Magnetic resonance imaging can show the invasion of an adrenocortical carcinoma into blood vessels, particularly the inferior vena cava and the adrenal and renal veins, in which tumor thrombi may occasionally be identified (125). It can also distinguish fairly accurately among primary malignant adrenocortical tumors, nonfunctioning adenomas, and pheochromocytomas by comparing the ratio of the signal intensity of each type of adrenal mass to that of the liver (128). Primary malignant adrenocortical lesions have intermediate-to-high signal intensity on T2-weighted images, nonfunctional adenomas have low signal intensity, and pheochromocytomas have extremely high signal intensity. In-phase out-of-phase MRI is emerging as a reliable method for distinguishing between adrenal incidentalomas and metastases (68, 129, 130) and proved useful in identifying an aldosterone-producing adenoma in a patient with hyperaldosteronism and bilateral nodules (125) (Figure 5).

Other imaging methods, such as iodocholesterol scanning, venography, and arteriography, are rarely indicated (115, 128, 131), but recent data show that selenocholesterol scanning may prove useful in assessing malignancy (95).



View larger version (71K):
[in this window]
[in a new window]
 

Figure 5. Computed tomography (CT) and magnetic resonance imaging (MRI)

of aldosterone-secreting adenomas. Top.

Adrenal CT of a 61-year-old woman with primary hyperaldosteronism and bilateral adrenal nodules (arrows) did not identify an increased lipid content in either adenoma.

Middle.

 In-phase MRI also failed to differentiate between the two sides.

Bottom. A loss of signal content of the functional aldosteronoma was shown by out-of-phase MRI.

Venous sampling and surgery confirmed a right aldosteronoma. (Courtesy of J.L. Doppman).

 

 

 

 

 

 

 

 

 

 

Adrenal venous sampling remains the gold standard for the differential diagnosis of primary aldosteronism, especially because it has recently become clear that many tests used in the subtype evaluation of this condition provide variable and often inconclusive results (132). Comparison of aldosterone-to-cortisol ratios in the adrenal veins and the inferior vena cava allows detection of unilateral or bilateral sources of aldosterone hypersecretion. Although the cut-off for lateralization is controversial, ratios of 5:1 and 10:1 have been advocated (132, 133).



Rapid proton fat–water spectroscopy for the characterization of non-CNS lesions in vivo

 
            http://www.clinicalimaging.org/article/PIIS0899707102004916/abstract
           

 

Gerard Riedy  Corresponding Author Information Send E-mail to Author*
Received 5 April 2002; accepted 10 May 2002.

 

            Abstract
The presence or absence of fat in lesions can have important diagnostic implications.

Current MR techniques for the evaluation of fat within lesions in the body rely on indirect imaging methods.

The goal of this study was to develop a rapid clinically practical proton spectroscopy procedure for the direct observation of a localized fat–water signal within the body.

 The technique developed reliably determined fat–water ratios in phantoms and from lesions in vivo in 6 s with single voxel sizes as small as 0.125 cc.                          

Keywords: NMR spectroscopy, Fat, Lipid, Body, SRM


a Department of Radiology, Wake Forest University, Bowman-Gray Medical Center, Winston-Salem, NC 27157, USA
 

  Communication

Fat and water separation

 in balanced steady-state free precession

using the

Dixon method

Teng-Yi Huang 1 2, Hsiao-Wen Chung 1 2 *, Fu-Nien Wang 1, Cheng-Wen Ko 1 3, Cheng-Yu Chen 2
1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C
2Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, R.O.C
3Department of Computer Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, R.O.C
email: Hsiao-Wen Chung (chung@cc.ee.ntu.edu.tw)

*Correspondence to Hsiao-Wen Chung, Department of Electrical Engineering, National Taiwan University, Rm. 238, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10764, R.O.C

Funded by:
 National Science Council; Grant Number: NSC-91-2213-E-002-078
 National Center for Research Resource; Grant Number: P41RR14075
 Mental Illness and Neuroscience Discovery (MIND) Institute
 Ministry of Education
 National Science Council

Keywords
fat-water separation • Dixon method • in-phase and out-of-phase images • steady-state free precession • frequency offset

Abstract

In this work the feasibility of separating fat and water signals using the balanced steady-state free precession (SSFP) technique is demonstrated.

 The technique is based on the observation (Scheffler and Hennig, Magnetic Resonance in Medicine 2003;49:395-397)

that at the nominal values of

TE = TR/2 in SSFP imaging,

phase coherence can be achieved at essentially only two orientations (0° and 180°)

relative to the RF pulses in the rotating frame,

under the assumption of TR << T2, and independently of the SSFP angle.

 

This property allows

in-phase and

 out-of-phase SSFP images

 to be obtained by proper choices of the center frequency offset,

 and thus allows the Dixon subtraction method

 to be utilized for effective fat-water separation.

 The TR and frequency offset for optimal fat-water separation are derived from theories.

 Experimental results from healthy subjects, using a 3.0 Tesla system, show that nearly complete fat suppression can be accomplished. Magn Reson Med 51:243-247, 2004. © 2004 Wiley-Liss, Inc.


Received: 28 April 2003; Revised: 26 June 2003; Accepted: 26 September 2003

Digital Object Identifier (DOI)

10.1002/mrm.10686  About DOI

     

 

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