"section level2">
    <h2 id="value">Value<a class="anchor" aria-label="anchor" href="#value"></a></h2>
    <p>A data frame with voxel-level ROI information.</p><ul><li><p><code>group</code> – Combined identifier built from <code>region</code> and <code>number</code>.</p></li>
<li><p><code>z</code>, <code>x</code>, <code>y</code> – Voxel coordinates.</p></li>
<li><p><code>pet</code> – Binary value indicating ROI membership (<code>1</code> = ROI, <code>0</code> = non-ROI).</p></li>
</ul><p>If <code>sav