AMI Centre facilities - Miscellaneous

Information about the acoustic noise in MRI, slice order, separate preparation room and an introduction guide for user.

MRI at AMI, an introduction guide to users

Preliminary information to user groups can be found from the document below.

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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 below, 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. 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

AMI Centre - Akukon noise measurements

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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.

AMI Centre - Slice order

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Information about the MRI scanner, stimulus equipment and monitoring devices.

Aalto NeuroImaging (ANI) Infrastructure

Published: 17.3.2020
Updated: 13.5.2020