title: Custom Search Parameter for Extensions Resource on FHIR
body: <p>Does FHIR support search based on Extension values?</p>
  <p>I have added this extension under the ImagingStudy Resource</p>
  <pre><code>{
    &quot;extension&quot;: [
      {
        &quot;url&quot;: &quot;http://hl7.org/fhir/SearchParameter/institution-name&quot;,
        &quot;valueString&quot;: &quot;Apollo&quot;
      }
    ]
  }
  </code></pre>
  <p>Is it possible to have a custom search parameter added for this extension such that it can be searched accordingly? If possible, how can I register it?</p>