~ Part.1 ~

Examination of the effect of RF shielding, using an

electromagnetic wave shield materials

offered commercially in MRI 「第1法 MRIにおける市販電磁波遮蔽材を用いたRF遮蔽効果の検討」

Friday , Sep 9 , 2016

The44th JSMRM in Saitama

Sumitomo Hospital

• Hideki Matsui MEDICAL-AID Co.,LTD

• Masanari Taniguchi 谷口正成

Toshihiko Nishida ,Hidekazu Niikawa ,Daichi Shimokawa , Tatsuya Kuwagaki ,

Kouta Uematsu ,Akira Tamada

General Foundation Corporation Sumitomo Hospital 財団法人 住友病院

The author has no conflict of

interest to with respect to this

presentation

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© 2016 by Japanese Society

for Magnetic Resonance in Medicine

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Background

Not only considering various risks, but also

managing strict safety control, we carry out

the MRI examination.

We think that the heat generated by the

metal in the human body is the most

problematic in the various risks.

In recent years, various kinds of

electromagnetic shielding products including

carbon fiber are offered in the market.

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Purpose

We have focused on the shielding effect

of electromagnetic waves of carbon

fiber and silver fiber.

We examined the effect of RF shielding

of carbon fiber electromagnetic

shielding material and silver fiber

electromagnetic shielding material.

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Materials MRI

・GE Co. SignaHDxt 1.5T

・SIEMENS Co. Magnetom Skyra 3.0T

COIL

・GE Co. HD Body Array Coil

・SIEMENS Co. Body18 , Spine 32

PHANTOM

・GE Co. SNR Phantom Square

ELECTROMAGNETIC WAVE SHIEDING MATERIAL

(size:1m*1m/sheets)

・Toray Industries,Inc. Torayca Cross(CO6343)

・MEDICAL-AID,Inc. EMC sheet(ES100)

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Method 1. We shielded by winding carbon fiber or silver fiber

around a half of the phantom.

2. The center of the magnetic field was matched up with

the central part of shielding in the phantom.

3. The number of electromagnetic wave shielding

materials were changed from one to four.

4. By using a T1 weight fast SE method , it was taken

sagittal images and coronal images in the center of

the phantom were taken.

5. Those images were taken by 1.5T MRI and 3.0T MRI

under the same conditions.

6. SNR and Sensitivity distribution were measured by

using image analysis software..

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Imaging parameter of each T1W imaging technique

Sequence parameter T1 Weighted Image

MRI Unit Siemens Skyra3.0T GE signaHDx1.5T

Pulse Sequense 2D-Quiet TSE 2D-FSE XL

Sacning orientation Sagittal Coronal Sagittal Coronal

Field of view(FOV)(mm) 400 400

Matrix 256*256 256*256

Slice thickness(mm) 10 10

Repetition time(TR)(ms) 600 600

Echo time(TE)(ms) 20 24 20 24

PAT mode GRAPPA ASSET2.0

Band width 300(Hz/Px) 201(Hz/Px ) 80(MHz) 128(MHz)

TSE factor 3 3

Flip angle(deg) 150 90

Phase enc.dir F>>H R>>L F>>H R>>L

FOV phase(%) 100 100

Averages 1 1 2 2

Coil elements Body123,Spine123 HD/Body Full

Filter Prescannormalize medium PURE

Distotion corr

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Figure.1

• Putting a mark on the surface in order to indicate the center

of the square phantom.

• The oral care product “BREATH CARE" was used as a mark.

Figure.2

• The Square phantom and a phase array coil.

• Putting a mark on the center of the coil, the square phantom

was placed in the center of the phase array coil.

Figure.2

Length : 33.3cm

Height : 16.5cm

Width

: 22.6cm

Figure.1

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• Each fiber was wound around the square phantom.

• Wrapped the surface of the box with carbon fiber

and silver fiber.

• Insert the phantom into this box.

Figure.4 : Carbon fiber Shield

Figure.5 : Silver fiber Shield

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• Shielding a half of the square phantom by using

carbon fiber or silver fiber.

• The number of electromagnetic wave shielding

materials were changed from one to four.

• The center of the magnetic field was matched up

with the central part of shielding in the phantom.

Figure.4

Silver fiber Shield material in 3.0TMRI Figure.5

Silver fiber Shield material in 3.0TMRI

1. Room temperature 20℃

2. The frequency of each imaging was three

times.

3. Measurement interval for preparation of

each set of shielding materials was at least

10 minutes

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Conditions of measurement

1. Sensitivity distribution(RF wave attenuation curve )

2. SNR SNR（ROI2）＝Mean（ave.）/SD(ave.)

Measured by image analysis software(Image J)

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Study of contents

Setting conditions of ROI

½ line

¼ line

ROI2

ROI1 ROI1

ROI2

Coronal image Sagittal image

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By using a T1 weight fast SE method, Sagittal image and Coronal image

were taken.

1.5T Sag

Control

Carbon

Silver

1.5T Cor 3.0T Sag 3.0T Cor

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Results

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①

0

500

1000

1500

2000

2500

0

9.3

75

18

.75

28

.12

5

37

.5

46

.87

5

56

.25

65

.62

5

75

84

.37

5

93

.75

10

3.1

25

11

2.5

12

1.8

75

13

1.2

5

14

0.6

25

15

0

15

9.3

75

16

8.7

5

17

8.1

25

18

7.5

19

6.8

75

20

6.2

5

21

5.6

25

22

5

23

4.3

75

24

3.7

5

25

3.1

25

26

2.5

27

1.8

75

28

1.2

5

29

0.6

25

30

0

30

9.3

75

31

8.7

5

32

8.1

25

MEA

N

Length(mm)

1.5T Control

1.5T Carbon 1

1.5T Carbon 2

1.5T Carbon 3

1.5T Carbon 4

1.5T Silver 1

1.5T Silver 2

1.5T Silver 3

1.5T Silver 4

3.0T Control

3.0T Carbon 1

3.0T Carbon 2

3.0T Carbon 3

3.0T Carbon 4

3.0Ｔ Silver 1

3.0Ｔ Silver 2

3.0Ｔ Silver 3

3.0Ｔ Silver 4

n.s.

Sensitivity distribution in the Sagittal image of 3.0T

MRI and 1.5T MRI (RF wave attenuation curve )

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Sensitivity distribution in the Coronal image of 3.0T

MRI and 1.5T MRI (RF wave attenuation curve )

①

n.s.

0

500

1000

1500

2000

2500

0

9.3

75

18.7

5

28.1

25

37.5

46.8

75

56.2

5

65.6

25

75

84.3

75

93.7

5

103.1

25

112.5

121.8

75

131.2

5

140.6

25

150

159.3

75

168.7

5

178.1

25

187.5

196.8

75

206.2

5

215.6

25

225

234.3

75

243.7

5

253.1

25

262.5

271.8

75

281.2

5

290.6

25

300

309.3

75

318.7

5

328.1

25

MEA

N

Length(cm)

1.5Ｔ Control

1.5T Carbon 1

1.5T Carbon 2

1.5T Carbon 3

1.5T Carbon 4

1.5T Silver 1

1.5T Silver 2

1.5T Silver 3

1.5T Silver 4

3.0T Control

3.0T Carbon 1

3.0T Carbon 2

3.0T Carbon 3

3.0T Carbon 4

3.0Ｔ Silver 1

3.0Ｔ Silver 2

3.0Ｔ Silver 3

3.0Ｔ Silver 4

n.s.

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6.17 6.17

3.31 3.31

2.08 1.32 1.35 1.56 1.70 1.58 1.38 1.22

1.69 1.52 1.44 1.34 1.65 1.60 1.30 1.31

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

Carbon Silver Carbon Silver

3.0T Sag 3.0T Cor

SN

R

Electromagnetic wave shield material

3.0T SNR(ROI2)=Mean(ave.)/SD(ave.)

0 sheets

1 sheet

2 sheets

3 sheets

4 sheets

（n.s.）

（n.s.）

（n.s.）

66.3 ％ 72.4

％ 72.6 ％

73.3 ％ 78.6

％

74.4 ％

75.4 ％

74.1 ％

59.2 ％

58.3 ％

56.5 ％

60.1 ％

52.9 ％ 63.1

％

59.5 ％

60.4 ％

Making a comparison between SNR of the Carbon

fiber and Silver fiber in 3.0T MRI

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Making a comparison between SNR of the Carbon

fiber and Silver fiber in 1.5T MRI

29.32 29.32 30.09 30.09

1.34 1.78 1.09 1.39 1.21 1.39 0.97 1.15 1.40 1.41 0.99 1.14 1.37 1.51 1.06 1.13 0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

Carbon Silver Carbon Silver

1.5T Sag 1.5T Cor

SN

R

Electromagnetic wave shield material

1.5T SNR(ROI2)=Mean(ave.)/SD(ave.)

0 sheets

1 sheet

2 sheets

3 sheets

4 sheets

（n.s.） （n.s.）

（n.s.）

95.4 ％

95.9 ％

95.2 ％

95.3 ％

93.9 ％

95.2 ％

95.2 ％

94.8 ％

96.4 ％

96.8 ％ 96.7

％ 96.5 ％

95.4 ％

96.2 ％

96.2 ％

96.2 ％

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Measurement result of sensitivity distribution

(RF attenuation curve)

Create a plot profile curve, RF wave attenuation rate is assumed.

The difference of the resonant frequency.

RF wave attenuation rate ⇒ 3.0T< 1.5T

Attenuation distance that MEAN value attenuates to 500.

⇒ 1.5T=6.05cm(ave.), 3.0T=9.2cm(ave.)

RF signal of the surface portion of the phantom was easily shielded.

RF signal of the central portion of the phantom was absorbed into the

phantom and was lost.

By the action of Prescan-nomaraize image filter , the signal attenuated

by the shielding materials was strongly corrected.

※ Statistically significant difference were not observed.

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Results of SNR

Both sagittal section and coronal section in 1.5T showed steady

signals and uniform measurement results.

Both sagittal section and coronal section in 3.0T showed uneven

signals and non-uniform measurement results.

⇒Signal of the central part and the edges of the phantom

is low. Donut-like signal distribution.

Shielding effects of the electromagnetic wave shielding materials

were dependent on the resonant frequency.

⇒ RF wave attenuation curve rate

3.0T (128MHz) ＜ 1.5T (64MHz)

※ Statistically significant difference were not observed.

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Results

Magnetic field

strength Cross section Image Material

Good

Number

of sheets

Attenuation

rate(%)

3.0T

Sagittal Carbon fiber 4 73.3

Siver fiber １ 78.1

Coronal Carbon fiber 4 60.1

Siver fiber 2 68.1

3.0T MRI *** *** 3 69.9

Magnetic field

strength Cross section Image

Good

material

Good

Number

of sheets

Attenuation

rate(%)

1.5T

Sagittal Carbon fiber 2 95.9

Siver fiber 2 95.2

Coronal Carbon fiber 2 96.8

Siver fiber 2 96.2

1.5T MRI *** *** 2 96.0

SNR

Carbon：80.43% Silver : 81.34%

Overall results in the SNR comparison was 80.89%(ave) .

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Conclusion

We must use sealed carbon fiber in plastic bags

because of prevention of scatter of carbon fiber.

Carbon fiber has a negative impact on the human

body through direct contact,such as itch and rash.

Therefore, Care should be taken when handling

carbon fiber.

カーボン繊維は、飛散する恐れがあるため、ビニール袋に封入してから使用する必要があった。また、人体に直接触れるとかぶれや痒みを伴うため、カーボン繊維の取り扱いには注意が必要である。

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Conclusion In contrast , silver fiber has a strong affinity for the

human body , and offers great flexibility.

Because there is no risk of scattering, it is safe and

easy for us to handle silver fiber.

Therefore, silver fiber is suitable for use in an

electromagnetic wave shield material in MRI, for the

reason of diamagnet and high heat dissipation with

the help of honeycomb structure.

それに比べ、銀繊維は、人体との親和性が高く、柔軟性に富み、飛散する恐れがなく、安全で取り扱いも簡便であった。ハニカム構造のため放熱性が高く、反磁性体であるためＭＲＩにおける電磁波遮蔽材として適材である。

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“Thank you for your attention.”