Imaging Group Academic Terms: ROI and VOI

🛠 Tools and Programming
1

In medical imaging and computer vision, the acronym ROI stands for:

Region of Interest

In Chinese, it is translated as: Region of Interest.

1. Layman’s Explanation

Imagine you are looking at a full-body MRI scan, but today you only want to study the patient’s psoas major muscle. Among the entire large image, only that small region corresponding to the psoas major is meaningful to you. You use your mouse—or an algorithm—to outline this region; that outlined portion is called the ROI.

2. Specific Meaning in Your Project

Based on your prior code and context, ROI means the following for you:

  • Input side: The mask.nii.gz file you see in your code is, mathematically, the representation of the ROI. It instructs the AI: “Analyze only this region—ignore everything else (e.g., internal organs, skin).”
  • Computation side: Radiomics features are not extracted from the entire image, but exclusively from the pixels covered by the ROI. For example, when extracting texture features of the psoas major, the system computes them only within the region labeled “1.”

3. Related Term: VOI

If you are working with 3D images (e.g., a stack of consecutive slices), you may also encounter VOI:

  • VOI (Volume of Interest): Volume of Interest
  • Since NIfTI files are typically 3D, you are effectively defining a “volume of interest” in 3D space. However, in everyday usage, people commonly refer to it simply as ROI.