more on SIME

content/model_compartmental_fitting.html

 ---
 title: Model fitting
 author: Vesa Oikonen
-updated_at: 2019-12-03
+updated_at: 2021-06-07
 created_at: 2014-01-23
 tags:
   - Modeling
@@ -124,7 +124,8 @@ one or more common parameters, all of the parameters can in theory be estimated
 (<a href="https://www.ncbi.nlm.nih.gov/pubmed/8046480">Raylman et al., 1994</a>;
 <a href="https://doi.org/10.1109/42.640758">Huesman &amp; Coxson, 1997</a>).
 However, the number of parameters to fit in SIME methods can be very large, and many usual 
-optimization methods do not work reliably.</p>
+optimization methods do not work reliably. With modern computers, after extensive method refinement 
+and testing, however, reliable results can be obtained.</p>
 
 <p>The <a href="./input_function.html">input function</a> can be assumed to be the same for all
 regions, which is utilized in <a href="./input_mbif.html">model-based input function</a>
@@ -135,6 +136,12 @@ of the input function, <a href="./model_cardiac_pvc.html">PVC</a>, and kinetic m
 myocardial muscle, to the regional TACs of the myocardial muscle and cavity
 (<a href="https://doi.org/10.2967/jnumed.107.047613">Fang &amp; Muzic, 2008</a>).</p>
 
+<p>In compartmental models for brain receptor radioligands, a common assumption has been that
+<em>K<sub>1</sub>/k<sub>2</sub></em> is the same in all grey matter regions. This can be directly
+used in SIME
+(<a href="https://doi.org/10.1016/j.neuroimage.2014.12.038">Ogden et al., 2015</a>; 
+<a href="https://doi.org/10.1016/j.neuroimage.2018.11.020">Plavén-Sigray et al., 2019</a>).</p>
+
 
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