ConRad MRI Safety Testing Texas Childrens

1.Background
2.Testing Setup
3.Protocol
4.Results
5.Conclusions
6.Limitations

1.Background

The patients under HIFU procedure loss their temperature very quick due to convection and conduction and radiation. We have purchased a special thermal blanket to keep patients warm. The thermal blanket, bought from Veterinary Warming Solutions LLC, is labeled as ConRad (MRI-Safe) Technical Information. There are two component layers inside: 1) a heat insulative layer made of Rayon 2) a heat trapping layer made of polyurethane. Therefore, there are no ferromagnetic and conductive material to cause hazards in the MR environment. However, since the company haven’t test it on a scanner for human, we are going to perform a test focusing on artifacts and possible heating related safety on our clinic 3T Siemens Skyra scanner.

2.Testing Setup

Phantom: A 5 liters phantom was wrapped inside the ConRad thermal blanket and put in the center of a 20-channel head coil. The temperature probe was firmly attached to the surface of the phantom using tapes. The temperature changes is displayed on the monitor. The setup is shown in the following figure:

Volunteer: Second part was the tests on a volunteer with 178 cm height and 82 kilogram weight. The blanket was set on top of the volunteer’s chest since its size is not large enough to wrap around the participant body. This would be a significant difference between our test and what is expected in the reality of HIFU procedure on pediatric patients. The temperature probe was put under armpit for recording the temperature change. 

3.Protocol

Phantom: Two sequences was used in the testing: 1. DWI epi sequence for testing of artifacts. 2. T2 space for testing heat deposition.

 Institution Name Texas Childrens Main Texas Childrens Main Texas Childrens Main
Manufacturer's Model Name  Skyra Skyra Skyra
Software Versions(s) syngo MR E11 syngo MR E11 syngo MR E11
Series Description localizer_quiet DWI ep2d_diff_orth_p2 AX T2 SPACE
Series Number 1 2 5
Number of Averages 2 4 12
Repetition Time 10 5900 1400
Echo Time 3.69 102 155
Flip Angle 20 90 135
Slice Thickness 7 4 0.600000024
Rows 512 192 384
Columns 512 192 384
Number of Phase Encoding Steps 233 143 304
Echo Train Length 1 71 69
Percent Sampling 91 100 100
Percent Phase Field of View 100 100 100
Pixel Spacing 0.48828*0.48828 1.1458*1.1458 0.57292*0.57292
MR Acquisition Type 2D 2D 3D
Imaging Frequency 123.262462 123.262514 123.262507
Pixel Bandwidth 355 1040 290
SAR 0.016362395 0.135543143 0.507811481
duration (minutes) 2 1.2 44.4

 

Volunteer: The testing sequences includes high SAR T2 TSE, EPI DWI, EPI fMRI and fieldmap, aiming to find out any discomfort and image artifacts caused by the blanket. Totally it takes around 10 minutes.

Institution Name Texas Childrens Main Texas Childrens Main Texas Childrens Main Texas Childrens Main Texas Childrens Main
Manufacturer's Model Name MAGNETOM Vida MAGNETOM Vida MAGNETOM Vida MAGNETOM Vida MAGNETOM Vida
Software Versions(s) syngo MR XA20 syngo MR XA20 syngo MR XA20 syngo MR XA20 syngo MR XA20
Series Description ead_scout_64ch-head-coil_MPR AX DWI_TRACEW AX T2 gre_field_mapping measurement functiona
Series Number 3 5 7 8 10
Number of Averages 1 2 2 1 1
Repetition Time 3.15 7000 6430 400 3000
Echo Time 1.37 114 95 4.92 30
Flip Angle 8 90 150 60 90
Slice Thickness 1.6 4 4 3 3
Rows 162 296 512 94 94
Columns 162 292 512 94 94
Number of Phase Encoding S 160 148 358 94 94
Echo Train Lengthssss 1 73 13 0 47
Percent Sampling 100 100 70 100 100
Percent Phase Field of View 100 101.37 100 100 100
Pixel Spacing 1.6*1.6 0.85616*0.85616 0.48828*0.48828 2.6596*2.6596 2.6596*2.6596
MR Acquisition Type 3D 2D 2D 2D 2D
Imaging Frequency 123.243655 123.243679 123.243655 123.243674 123.243681
Pixel Bandwidth 539 1631 195 598 1773
gain 391.561 391.561 391.561 391.561 391.561
SAR 0.028502319 0.173783505 0.541391252 0.157953401 0.138823148
duration (min:sec) 1:30 2:30 5:15 1:42 0:45

 

4.Results

Phantom: There was no extra artifact found on images of the DWI EPI sequence (see figure left)

The temperature gradually increased along with time during the 45 minutes continue scan. 


The temperature increased at a rate of 0.04 (oC) per minute. The maximum increase of temperature was 1.7 (oC) within 45 minutes continue scan. This was normal energy deposition by a high SAR sequence. The blanket didn’t raise any concern of MR safety.

Volunteer: The temperature increased within one degree Celsius from 34.9 oC to 35.5 oC. No notable extra artifacts were found on fieldmap, DWI and fMRI images:

According to the Volunteer, there was no discomfort during the MR session.

6.Limitations

Our volunteer test was performed on adult which is very different from an infant in our HIFU study in terms of SAR and artifacts. 

5.Conclusions

Since no ferromagnetic and no metal components was contented in the blanket according to the description from the manufacture in combination of our tests, it is safe to conclude that the ConRad thermal blanket should be safe in our HIFU 3T MR system.

Patient Warming

General Use – ConRad Thermal Blankets are available individually or as a Complete Set (Small, Medium, Large)

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