Object ID: 00000018WIA30DC1970GYZ
Topic ID: id_40022204 Version: 1.4
Date: Mar 15, 2022 5:51:53 PM

T2 Map scan protocol

When using Multi-echo FGRE/FSPGR for tissues with short T2* relaxation times, the echo spacing and first echo should be as small as possible (around 1 ms for first echo time) to ensure confidence in the fit of the R2* value. The best way to achieve this is by using a high band width, low matrix, and not using User CV-16, positive gradient polarity.

Consider these tradeoffs as you change scan parameters for images that are post processed with the T2 Map protocol.

Table 1. T2 Map protocol example
Scan parameters	1.5T value	Considerations
TR	1000 ms	To shorten scan time, it is possible to reduce TR much more than what would be normally needed for T2 imaging. This is because the T1 relaxation time of cartilage is quite short (in the range of 200 to 400 ms), and thus there is almost no T1 saturation in cartilage when reducing TR. Reduce TR below the suggested values, decreases the overall SNR and also introduces some T1 saturation effect that could generate additional slice cross talk effects that affect T2 relaxation.
TE	Determines the number of images acquired at each location	TE is the primary scan parameter that controls T2 image contrast. It is not a selectable parameter with the T2 Map application.
Bandwidth	32
Field of View	16	The value does not change for field strength.
Slice thickness	3
Slice spacing	0	If slice spacing is less than 20% of the slice thickness and if the TR prescribed can accommodate the prescribed slices in a single acquisition, the system will automatically change the prescription to two acquisitions in order to reduce the cross talk effects.
Frequency	256
Phase	256	Consider a 192 phase matrix to reduce the total scan time below 7-8 minutes.
Scan plane	Axial	Patellofemoral Joint
Scan plane	Sagittal or Coronal	Femoral Condyle and Tibial Plateau
Imaging options	ASSET or ARC	A Phase factor > 1.0 on the Acceleration tab can be used in order to reduce scan time. Any larger acceleration factor might rapidly degrade SNR and therefore the T2 Map image quality. If available, use AIR Recon DL to increase SNR of this sequence, especially when phase acceleration factor >= 2.0.