AMI Centre facilities - Miscellaneous

MRI at AMI, an introduction guide to users

Preliminary information to user groups can be found from this document.

Acoustic noise in MRI

Akukon Oy measured the acoustic noise of AMI Centre's MRI scanner (Magnetom Skyra 3.0 T) on 20th of June, 2012 (report available in PDF-document, in Finnish). A microphone was placed on a head phantom next to the phantom's ear and the noise levels of various MRI sequences were recorded as a function of time. The RF-pulses were switched off because the RF signal was found to interfere with the acoustic noise measurements. The main source of the acoustic noise is due to the gradient coils whereas the RF pulses are expected to increase the sound pressure only slightly (see e.g. Counter S.A. et al. JMRI, 7, 606-611, (1997)). However, AMI Centre will study the effect of the RF-pulses on the acoustic noise levels in more detail in near future.

We want to emphasize that these results are preliminary and they should be used merely as guidelines. Further analysis of the noise measurements will be carried out in August 2012 and the rough values shown here may change. The first eight sequences were run using the 20 channel head/neck coil and the rest using the 32 channel head coil. We have also included some user sequences which are regularly used. Further details of the measured sequences and the parameters used can be obtained from AMI Centre's personnel.

Sequence Comments LAeq (dB) LAFmax (dB) LZpeak (dB)
Most typical sequences used with the 20 channel head/neck coil.
 3-plane localizer    96  112  139
 MPRAGE sag (MGH-variant)    94  99  110
 EPI 64 p2 GRAPPA    103  112  139
User sequences    
EPI 64 p2 Hanna Renvall 102 105 115
EPI 96 Teemu Rinne 97 98 110
EPI 64 p2 Mia Liljeström 104 105 116
 ep2d_20ch Lauri Nummenmaa  103  104  115
  Foam padding on both sides of the head coil (otherwise same as previous).  98  99  108
         
Most typical sequences used with the 32-channel head coil
 3-plane localizer    95  111  140
 MPRAGE Lo-re Sag (p3)    109  118 139
 MPRAGE sag (MGH-var)  gradients=fast  96  113  139
   gradients=normal  97  112  140
   gradients=whisper  93  97  107
 FLASH (MGH-variant)    93  95  106
 DTI 64dir (mddw, p2)    97  112  139
 T2 TSE Axial    93  96  109
 T2 TDF (FLAIR)    89  96  108
 SPACE (T2 3D) Could not switch off all the RF-pulses.  100  111  120
Effect of the matrix size.
 EPI 64  matrix = 64 x 64  107  108  118
 EPI 96  matrix = 96 x 96  107  108  115
 EPI 128  matrix = 128 x 128  110  111  117
Effect of the parallel imaging and the accelaration factor.    
EPI 64, p2 GRAPPA Parallel imaging 107 108 118
EPI 64, p3 GRAPPA   105 106 118
EPI 64, p4 GRAPPA   103 103 116
EPI 64 p2 mSENSE   107 108 119
Effect of using the whole 32 channel head coil vs. only the posterior part.
EPI 64 p2, 2.0 mm slice Posterior + anterior 106 106 116
  Posterior only 116 116 126
Effect of the gradient mode.    
EPI 64 p2 GRAPPA Gradients = fast 107 108 119
  Gradients = normal 105 106 115
Effect of the TE.    
EPI 64 p2 GRAPPA TE = 13 ms 107 108 117
  TE = 20 ms 107 108 118
  TE = 30 ms 106 106 116
Effect of the TR (with maximum number of slices)    
EPI 64 p2 GRAPPA TR = 100 ms 105 106 116
  TR = 1000 ms 105 106 116
  TR = 3000 ms 105 106 116
 Effect of the number of slices
EPI 64 p2 GRAPPA Number of slices = 5 99 104 119
  Number of slices = 20 105 106 119
  Number of slices = 35 107 109 119
Effect of the slice thickness
EPI 64 p2 GRAPPA Slice thickness = 2.0 mm 106 106 116
  Slice thickness = 3.0 mm 106 113 139
  Slice thickness = 4.0 mm 106 106 116
Effect of the field of view
EPI 64 p2 GRAPPA FoV = 129 mm 98 99 111
  FoV = 129 mm 102 103 116
  FoV = 129 mm 100 101 113
Effect of the echo spacing
 EPI 64 p2 GRAPPA Echo spacing = 0.50 ms 108 113 140
  Echo spacing = 0.55 ms 103 104 115
  Echo spacing = 0.60 ms 103 104 113
User sequences
EPI 64 p2 Elvira Brattico 107 108 119
ep2d_32ch_41volumes Simo Vanni (PMRIQUAD) 116 117 127
EPI 64 spin-echo Lauri Nurminen 104 105 113
         
Acoustic noise in the console room
EPI 64 p2 Noise in the scanner 106 106 116
  Noise in front of the computer 45 46 72
  Noise in front of the RF tube (empty tube) 49 51 70

Separate preparation room

AMI Centre has a separate preparation room for users (the glass door on the left when standing in the lobby of Magnethouse). During the following times, the separate preparation room is always by definition reserved for the user/group that has made a reservation of the magnet:

a) half an hour before their scheduled magnet reservation starts (15 minutes if the previous reservation is only one 30-min slot)

and

b) half an hour after their scheduled magnet reservation ends (15 minutes it the next group has reserved only one 30-min slot).

All the other times must be discussed and agreed with the reserving group if you want/need to deviate from this prioritization (check contact information from the reservation calendar).

Please note that this policy means that the reserving group cannot use the separate preparation room immediately after their magnet reservation starts or just before their magnet reservation ends, because the previous/next group then has the priority to the separate preparation room so that they can do preparations for measurement or finish their interviews etc. If there are no previous/following magnet reservations, then you can use it, of course.

Slice order

In which order does the Siemens scanner acquire slices? Read the below document to find out.

ANI

Aalto NeuroImaging Infrastructure

ANI research infrastructure houses four functional neuroimaging modalities, navigated transcranial magnetic stimulation (nTMS) at Aalto TMS, functional magnetic resonance imaging (fMRI) at Advanced Magnetic Imaging (AMI) Centre, magnetoencephalography (MEG) at MEG Core and Aalto Behavioral Laboratory (ABL).

Aalto Behavioral Laboratory

Aalto Behavioral Laboratory

Aalto Behavioral Laboratory (ABL) has various different monitoring and stimulus systems for behavioral studies in controlled environment. The laboratory consists of two measurement rooms: a shielded room which is especially intended for EEG and remote eye tracking measurements; and a room for behavioral measurements which doesn’t require shielded conditions.

Services
Aalto TMS

Aalto Transcranial Magnetic Stimulation

Aalto TMS offers researchers unique possibilities for multi-modal neuroimaging techniques. The laboratory contains top-of-the-line electroencelography (EEG) and transcranial magnetic stimulation (TMS) systems.

Services
Magnetoencephalography (MEG)

MEG Core

MEG Core offers excellent environment for MEG measurements. MEG Core has a modern 306-channel MEG device (Elekta Neuromag™, Elekta Oy, Helsinki, Finland) in a high-end 3-layered magneticaly shielded roo (Imedco AG, Hägendorf, Switzerland). MEG Core has extremely low magnetic ambient noise level. MEG Core has a wide variety of MEG-compatible stimulators and monitoring devices.

Services
This service is provided by:

Aalto NeuroImaging Infrastructure

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