• Zafar Sajjad Shahbaz Alam, “Magnetic Resonance Spectroscopy: Basic principles and application in focal brain. lesions”[r]
(1)MR‐SPECTROCOPY:
TECHNIQUE AND APPLICATION OFTHE
BRAIN
LÊ THANH PHONG R
August 24, 2019
LÊTHANHPHONG.Rt LÊVĂNPHƯỚC.Prof CAOTHIÊNTƯỢNG.PhD
•Principles and methods
CONTENTS
•Technique
•Metabolites of MRS
•Application
C l i
(2)PRINCIPLES
•Magnectic Resonance Spectroscopy – MRS: is a new
technique to assess various metabolites in the brain technique to assess various metabolites in the brain
•MR Imaging and Spectroscopy share the same physical
principle MRI looks at the geometrical distribution of water molecules
•MRS looks at the chemical composition of the tissue of interest and displays it in a spectrum
PRINCIPLES
•MRS was approved by the US Food and Drug Administration (FDA) in 1995
(FDA) in 1995
•MRS can be performed with spins or nuclei of Hydro (H), Phospho (P) and Carbon (C)
(3)MRS nomal human brain In 1.5T MR system TE = 135 ms NAA peak highest
METHODS
There are two basic methods:
(4)STEAM
•The volume of interest is excited by three 90 degree pulses
•Allows short echo times
•Since the echo is stimulated signal is weak
•Voxel selected
PRESS
•One 90 degree and 180 degree pulses are applied along three orthogonal planes
three orthogonal planes
•Allows longer and shorter echo times
(5)TECHNIQUES
* There are two techniques:
•Single voxel ( SV )
•Multi voxel ( MV )
SINGLE VOXEL MULTI VOXEL
SINGLE VOXEL
•Voxels must be place beside the sources of magnetic
sensitive images and lipids
•SVS can be used volume 2x2x2 cm (8cm3) for diffuse
diseases
•Volume can decrease for local diseases
•SVS ll t k i t f d t i iti
(6)MULTI VOXEL
•Known as Chemical Shift Imaging (CSI)
•A large area is covered and divided into multiple voxels
•Acquisition of multiple voxels Many voxels within the same dataset
•Can be slice selected of or dimensionalCan be slice selected of or dimensional
•Single spectra related to single voxels:
•Metabolite images:
(7)ECHO TIMES
•Data acquisition depends on TR and TE, because brain
metabolites have different T1 and T2 metabolites have different T1 and T2
•TR and TE are important parameters
•Improved SNR is obtained at a longer TR ( #1500ms )
•Commonly used TEs are 20‐30ms, 135‐145ms and 270ms.Commonly used TEs are 20 30ms, 135 145ms and 270ms
* Commonly metabolites have short TE and long TE: * N‐acetyl aspartate (NAA)
* Creatine (Cr) * Choline (Cho) * Lactate (Lac)
(8)TE = 30ms TE = 135ms TE =270ms
ATTENTIONS!
•Instruct the patient to keep still
•The location of voxel must avoid blood, products of blood,The location of voxel must avoid blood, products of blood, gas, cerebrospinal fluid, fat, areas of necrosis, metal, calcium and bone
(9)High quality spectrum Low quality spectrum
CORRECTIVE MEASURE
•Used larger bandwidth to improved SNR → longerg p g acquisition times
•Select another voxel location
(10)MAJOR METABOLITES OF 1H‐MRS
Metabolites Peakpositioninppm Secondpeak
NAA: N‐acetyl aspartate 2.02ppm
Cr: Creatine 3.0ppm 3.94pmm
Cho: choline 3.22ppm
mI: Myo‐Inositol 3.56ppm 4.1ppm
Lac: Lactate 1.3ppm
Lac: Lactate 1.3ppm
Glx: Glutamate Glutamine 2-2.45ppm 3.6-3.8ppm
Lipids 0.9, 1.3, 1.5ppm
CLINICAL USES OF 1H‐MRS
•Brain tumors, Stroke, Close head trauma
•Neonatal hypoxia.Neonatal hypoxia
•Metabolic disorders and white matter diseases
•Epilepsy and Multiple Sclerosis
•Alzheimer’s dementia
(11)*Cho increase
*NAA and Cr decrease *Latate: doublet
Astrocytoma grade III
(12)*Cho: normal *NAA decrease
Abscess
Metastasis
(13)TE 30 TE 135 TE 270
TE = 30ms TE = 135ms TE =270ms
(14)CONCLUSION
•Select the single voxel or multi voxel?
S l i f TE i
•Selection of TE are important parameters
•Select the voxel location correctly to get a high quality spectrum
•MRS can not replace MRI, but it provides more information to diagnosis.g
•Can used in 1.5T or 3T MR systems
REFERENCES
• Ứng dụng tiến bộkỹthuật MRI lĩnh vực thần kinh sọ PGS.TS Lê văn Phước Trưởng khoa CĐHA BV Chợ
Rẫy
• Nguyễn ThịÁnh Hồng, “Cộng hưởng từphổtrong chẩnđốn u não”, tạp chí y học Thành phốHồChí Minh 2003
• Nguyễn ThịÁnh Hồng, “Bướcđầu khảo sát MRS u não", 2001
ổ
• Luận văn nghiên cứu “cộng hưởng từphổtrong khảo sát u não” BS CK2 Cao Thiên Tượng, Khoa CĐHA BV Chợ
Rẫy
• Magnectic resonance spectroscopy of the brain, review of metabolites and clinical applications, D.P Soaresa and
M.Lawb, clinical radiology volume 64, Issue 1, January 2009
• Brandao Lara A.Domigues Romeu C “ MR spectroscopy of the brain” 2004
• Zafar Sajjad Shahbaz Alam, “Magnetic Resonance Spectroscopy: Basic principles and application in focal brain
lesions” Pak J Neurol Sci 2007 lesions Pak J Neurol Sci 2007
(15) hinhanhykhoa.com