Approach to Best Practices for Adult DRS: Processing and Quantification
| Parameter | Best practice |
|---|---|
| Processing | |
| WK ROI | Is essential for relative function measurement; generally adequate if kidney function is normal |
| Cortical ROI | Includes only parenchyma, not CS and calyces; optimal for assessing functional parameters such as 20-min/max (renal retention) and Tpeak |
| CS ROI | Excludes parenchyma and has been shown to better represent CS drainage when calculating T-½ |
| Background ROI | Is C-shaped or reniform, 2 pixels wide, and 1 pixel away from cortex |
| Relative (split) function | Must be derived from WK ROIs; may be measured using 2- to 3-min intervals, but intervals of 1–2 or 1–2.5 min are recommended if F=0 protocol is used |
| Quantification | |
| Relative (split function) | Normal is 45%–55%; abnormal if <40% |
| Tpeak | Normal is <5 min |
| T-½ emptying | Normal is <10–15 min; abnormal does not equate to obstruction |
| 20-min/max | Normal is <0.35 as measured 20 min after Tpeak |
| Tissue transit time | Activity should be seen in CS by 5 min; >8 min is delayed |
| Postvoid kidney to maximum | Postvoid image is acquired 30 min after start, and activity is compared with Tpeak |
| Output efficiency | Helps overcome confounding effect of poor renal function on CS drainage assessment; requires special processing software |
| Normalized residual activity | Normal is <1.0 for 20- to 21-min interval and <0.10 when using 1-min interval acquired after voiding at 60 min from examination start |
Many quantitative values are dependent on protocol and cannot be universally applied.