Computed Metric Library

Metric Library

The following metrics are available in ProKnow as computed metrics. You can also define custom metrics to track other factors that are important to you.

• Dose (Gy) covering specified volume (%) of ROI
• Dose (Gy) covering specified volume (cc) of ROI
• Dose (Gy) covering whole ROI minus specified volume (cc)
• Volume (%) of ROI covered by specified dose (Gy)
• Volume (cc) of ROI covered by specified dose (Gy)
• Volume (%) of ROI covered by a specified dose range (Gy)
• Volume (cc) of ROI covered by a specified dose range (Gy)
• Total ROI volume (cc)
• Min ROI dose (Gy)
• Mean ROI dose (Gy)
• Max ROI dose (Gy)
• Integral ROI dose (Gy · cc)
• Global max dose (Gy)
  Max dose value over the whole dose grid
• Conformation Number
  (Specified ROI volume-at-dose)²/(vol ROI · total irradiated volume-at-dose)
• Conformality Index
  (Volume receiving specified dose)/(volume of specified ROI)
• Dose Spillage
  Total volume (cc) covered by specified dose (Gy) / Volume (cc) of the specified structure covered by specified dose (Gy)
• Gradient Index
  Total volume (cc) covered by lower specified dose (Gy) / Total volume (cc) covered by higher specified dose (Gy)
• Modified Gradient Index
  Total volume (cc) covered by lower specified dose (Gy) / Volume (cc) of the specified structure covered by higher specified dose (Gy)
• Homogeneity Index
  (Specified ROI D01% – D99%)/(prescription dose)
• Inhomogeneity Index
  (Max ROI dose – min ROI dose)/(mean ROI dose)
• Volume of Regret
  Volume (cc) receiving specified dose but outside specified ROI
• Irradiated Volume
  Total volume (cc) receiving specified dose over whole grid
• Cumulative meterset
  (MU or min) over all treatment beams
• Dose (%) relative to specified prescription covering specified volume (%) of the specified structure
• Dose (%) relative to specified prescription covering specified volume (cc) of the specified structure
• Dose (%) relative to specified prescription covering the total volume (cc) minus specified volume (cc) of the specified structure
• Volume (cc) of the specified structure covered by specified percent (%) dose relative to specified prescription
• Volume (%) of the specified structure covered by specified percent (%) dose relative to specified prescription
• Volume (%) of ROI covered by a specified dose range (%) dose relative to specified prescription
• Volume (cc) of ROI covered by a specified dose range (%) dose relative to specified prescription
• Minimum dose (%) relative to specified prescription to the specified structure
• Maximum dose (%) relative to specified prescription to the specified structure
• Mean dose (%) relative to specified prescription to the specified structure
• Global max dose (%) relative to specified prescription
  Max dose value over the whole dose grid relative to the specified prescription
• Volume of Regret (Relative
  Volume (cc) receiving specified percent of specified prescription dose but outside of the specified ROI
• Irradiated Volume (Relative)
  Total volume (cc) receiving specified percent of specified prescription dose over whole grid
• Conformation Number (Relative)
  (Specified ROI volume-at-prescription-dose)²/(vol ROI · total irradiated volume-at-prescription-dose)
• Conformality Index (Relative)
  (Volume receiving specified prescription dose)/(volume of specified ROI)
• Dose Spillage (Relative)
  Total volume (cc) covered by specified percent (%) dose relative to specified prescription / Volume (cc) of the specified structure covered by specified percent (%) dose relative to specified prescription
• Gradient Index (Relative)
  Total volume (cc) covered by lower specified percent (%) dose relative to specified prescription / Total volume (cc) covered by higher specified percent (%) dose relative to specified prescription
• Modified Gradient Index (Relative)
  Total volume (cc) covered by lower specified percent (%) dose relative to specified prescription / Volume (cc) of the specified structure covered by higher specified percent (%) dose relative to specified prescription
• Homogeneity Index (Relative)
  (Specified ROI D01% – D99%)/(prescription dose)

Frequently Asked Questions

Q: Why does my treatment planning system report different metric values from ProKnow?

Some treatment planning systems calculate DVHs differently from ProKnow. Read more about these differences in How ProKnow Calculates DVH Values.

Q: What is the "Conformation Number" metric?

There are many conformity indices in our field, some more useful than others.

We often use the “Conformation Number” (CN) metric which was originally described by Van’t Riet et al. The CN does a great job in capturing both the coverage of the target by the reference dose and the shaping of the reference dose outside the target.

The CN is summarized by the equation:

CN = (TVRI * TVRI)/(TV * VRI)

TVRI = Target volume covered by the reference dose (cc), TV = Total target volume (cc), VRI = Volume of the reference dose (cc)

References

Feuvret et al. “Conformity Index: A Review,” Int. J. Radiation Oncology Biol. Phys 2006; 64(2).