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Minor touch ups
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mathieuboudreau committed Oct 9, 2024
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Expand Up @@ -29,15 +29,15 @@ Simplified pulse sequence diagram of an MTR imaging sequence. An off-resonance a

Each MRI vendor optimizes their MT-weighted protocol parameters (eg MT shape, duration, frequency, and amplitude), and few of these details are typically shared with the end-user. [](#mtrTable2) shares protocol parameters used by different MRI manufacturers as reported by two publications.

:::{table} Literature MTR protocol parameters
:::{table} Literature MTR protocol parameters (sources: [@Brown2013-eg;@Karakuzu2022-af])
:label: mtrTable2
:enumerator: 6.2

<table>
<tr>
<th colspan="1" align="center"></th>
<th colspan="2" align="center">[@Brown2013-eg]</th>
<th colspan="2" align="center">[@Karakuzu2022-af]</th>
<th colspan="2" align="center">Brown 2013</th>
<th colspan="2" align="center">Karakuzu 2022</th>
</tr>
<tr>
<th colspan="1" align="center"></th>
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Expand Up @@ -28,7 +28,7 @@ This introduction provides a glimpse into the theoretical basis of MTsat, its pr

```{figure} img/sequence.png
:label: mtsatFig1
:enumerator: 6.14
:enumerator: 6.14
Simplified pulse sequence diagram of an MTR imaging sequence. An off-resonance and high powered MT-preparation pulse is followed by a spoiler gradient to destroy any transverse magnetization prior the application of the imaging sequence, in this case a spoiled gradient recalled echo (SPGR).
```

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Expand Up @@ -115,18 +115,18 @@ R_{1}=\frac{1}{2}\cdot \frac{\frac{S_{T_{1}}\alpha_{T_{1}}}{\text{TR}_{T_{1}}}-\

Remember, like MTR, MTsat is calculated from the equations above following the acquisition of the protocol images; no numerical fitting to a model is required. So effectively, the processing time to produce MTsat maps is the same as MTR, which is nearly instantaneous. Also, unlike MTR, which represents the steady-state signal difference due to the MT effect, MTsat represents the fraction of the longitudinal magnetization saturation caused by a single MT pulse within a TR, after a steady-state is achieved. Conventionally, it is represented as a percentage %, so MTsat is typically reported as {math}`\delta \cdot 100`. Note that MTR and MTsat are not expected to have the same values in magnitude despite both being represented as %, as they represent different changes. A major benefit of MTsat is that it’s expected to have less _T_{sub}`1`-dependency than MTR, as _T_{sub}`1` (1/R{sub}`1`) is separately calculated and accounted for in the calculation of MTsat using the equations above. Although the MTsat metric is more robust against _T_{sub}`1` changes, it is inherently sensitive to the MT preparation pulse properties (due to what MTsat physically represents, which is the saturation due to the MT pulse), and thus MTsat is not truly considered a fully quantitative metric as its value will change depending on the chosen protocol parameters and is not solely specific to the tissue properties or the field properties. [](#mtsatProtocolTable)lists some MTsat protocol parameters that have been reported in the literature.

:::{table} Some reported MTsat protocol parameters in the scientific literature.
:::{table} Some reported MTsat protocol parameters in the scientific literature (sources: [@Helms2008-wf;@Weiskopf2013-lp;@Campbell2018-hi;@Karakuzu2022-af;@York2022-fl])
:label: mtsatProtocolTable
:enumerator: 6.4

<table>
<tr>
<th colspan="2" align="center"></th>
<th colspan="1" align="center">[@Helms2008-wf]</th>
<th colspan="1" align="center">[@Weiskopf2013-lp]</th>
<th colspan="1" align="center">[@Campbell2018-hi]</th>
<th colspan="2" align="center">[@Karakuzu2022-af]</th>
<th colspan="1" align="center">[@York2022-fl]</th>
<th colspan="1" align="center">Helms 2008</th>
<th colspan="1" align="center">Weiskopf 2013</th>
<th colspan="1" align="center">Campbell 2018</th>
<th colspan="2" align="center">Karakuzu 2022</th>
<th colspan="1" align="center">York 2022</th>

</tr>
<tr>
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Expand Up @@ -21,7 +21,7 @@ This content of this section is still a work-in-progress and has not been proofr

## Derivation

From the MTR protocol in [Brown2013-eg] of the MTR section, {math}`\alpha_{1}`=15 deg and TR = 0.03 s, so assuming a _T_{sub}`1` at 1.5T (field strength that Brown used) of 0.55 s in healthy WM, so _R_{sub}`1` = 1.8, we can calculate the signal from [#mtsatEq6] of an experiment with no MT pulse ({math}`\alpha_{2}` = 0).
From the MTR protocol in [@Brown2013-eg] of the MTR section, {math}`\alpha_{1}`=15 deg and TR = 0.03 s, so assuming a _T_{sub}`1` at 1.5T (field strength that Brown used) of 0.55 s in healthy WM, so _R_{sub}`1` = 1.8, we can calculate the signal from [#mtsatEq6] of an experiment with no MT pulse ({math}`\alpha_{2}` = 0).



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