tài liệu phần mềm siêu âm

• Zafar Sajjad Shahbaz Alam, “Magnetic Resonance Spectroscopy: Basic principles and application in focal brain. lesions”[r]

TECHNIQUE AND APPLICATION OF THE

BRAIN

LÊ THANH PHONG R

August 24, 2019

LÊ THANH PHONG Rt

LÊ VĂN PHƯỚC Prof CAO THIÊN TƯỢNG PhD

•Principles and methods

CONTENTS

•Technique

•Metabolites of MRS

•Application

•Conclusion

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)

•However, MRS in present clinical use are mainly Hydrogen

spectroscopy because of its widespread use

MRS nomal human brain.

In 1.5T MR system

TE = 135 ms

NAA peak highest.

METHODS

There are two basic methods:

a.STimulated EchoAcquisitionMode – STEAM

b. PointRESolvedSpectroscopy – PRESS

•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

•The signal is strong with better SNR

* 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 usually takes 3‐5 minutes for data acquisition

•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 2 or 3 dimensional

•Single spectra related to single voxels:

•Metabolite images:

•Spectral maps:p p

•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 metabolites have short TE and long TE:

* N‐acetyl aspartate (NAA)

* Creatine (Cr)

* Choline (Cho)

* Lactate (Lac)

* Metabolites only have short TE:

* Lipid (Lip)

TE = 30ms TE = 135ms TE =270ms

ATTENTIONS!

•Instruct the patient to keep still

•The location of voxel must avoid blood, products of blood,

gas, cerebrospinal fluid, fat, areas of necrosis, metal, calcium

and bone

•

High quality spectrum Low quality spectrum

CORRECTIVE MEASURE

•Used larger bandwidth to improved SNR → longerg p g

acquisition times

•Select another voxel location

•Increase voxel size to increase SNR

NAA: N‐acetyl aspartate 2.02ppm

Glx: Glutamate và Glutamine 2-2.45ppm 3.6-3.8ppm

CLINICAL USES OF 1H‐MRS

•Brain tumors, Stroke, Close head trauma

•Neonatal hypoxia

•Metabolic disorders and white matter diseases

•Epilepsy and Multiple Sclerosis

•Alzheimer’s dementia

•

*NAA and Cr decrease

*Latate: doublet

Astrocytoma grade III

*Cho: normal

*NAA: decrease

*Elevated Lactate

*Cho: normal

*NAA decrease

Abscess

Metastasis

*Cho: increase

* NAA & Cr decrease

TE 30 TE 135 TE 270

TE = 30ms TE = 135ms TE =270ms

*Infection disease.

*Lipid peak at short TE

•Select the single voxel or multi voxel?

•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 các tiến bộ kỹ thuật MRI trong lĩnh vực thần kinh sọ PGS.TS Lê văn Phước Trưởng khoa CĐHA BV Chợ

Rẫy.

• Nguyễn Thị Ánh Hồng, “Cộng hưởng từ phổ trong chẩn đoán u não”, tạp chí y học Thành phố Hồ Chí Minh 2003.

• Nguyễn Thị Ánh Hồng, “Bước đầu khảo sát MRS trong u não", 2001.

ổ

• Luận văn nghiên cứu “cộng hưởng từ phổ trong khảo sát u não” của 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.