Add T1 chapter

content/intro/intro.md → Introduction to qMRI/01-intro.md

@@ -1,5 +1,5 @@
 ---
-title: Foreword
+title: Basics of MRI and qMRI
 date: 2024-07-25
 authors:
   - name: Agah Karakuzu

T1 Mapping/Inversion Recovery T1 Mapping/01-introduction.md

@@ -0,0 +1,25 @@
+---
+title: Abstract
+subtitle: Inversion Recovery
+date: 2024-07-25
+authors:
+  - name: Mathieu Boudreau
+    affiliations:
+      - NeuroPoly Lab, Polytechnique Montreal, Quebec, Canada
+numbering:
+  heading_2: false
+  figure:
+    template: Fig. %s
+---
+
+## Inversion Recovery T<sub>1</sub> Mapping
+
+Widely considered the gold standard for T<sub>1</sub> mapping, the inversion recovery technique estimates T<sub>1</sub> values by fitting the signal recovery curve acquired at different delays after an inversion pulse (180°). In a typical inversion recovery experiment ([](#irFig1)), the magnetization at thermal equilibrium is inverted using a 180° RF pulse. After the longitudinal magnetization recovers through spin-lattice relaxation for predetermined delay (`inversion time`, TI), a 90° excitation pulse is applied, followed by a readout imaging sequence (typically a spin-echo or gradient-echo readout) to create a snapshot of the longitudinal magnetization state at that TI.
+
+Inversion recovery was first developed for NMR in the 1940s [@Hahn1949;@Drain1949], and the first T<sub>1</sub> map was acquired using a saturation-recovery technique (90° as a preparation pulse instead of 180°) by [@Pykett1978]. Some distinct advantages of inversion recovery are its large dynamic range of signal change and an insensitivity to pulse sequence parameter imperfections [@Stikov2015]. Despite its proven robustness at measuring T<sub>1</sub>, inversion recovery is scarcely used in practice, because conventional implementations require repetition times (TRs) on the order of 2 to 5 T<sub>1</sub> [@Steen1994], making it challenging to acquire whole-organ T<sub>1</sub> maps in a clinically feasible time. Nonetheless, it is continuously used as a reference measurement during the development of new techniques, or when comparing different T<sub>1</sub> mapping techniques, and several variations of the inversion recovery technique have been developed, making it practical for some applications [@Messroghli2004;@Piechnik2010].
+
+```{figure} img/ir_pulsesequences.svg
+:label: irFig1
+
+Figure 1. Pulse sequence of an inversion recovery experiment.
+```