Approach to Best Practices for Adult DRS: Processing and Quantification

ParameterBest practice
 WK ROIIs essential for relative function measurement; generally adequate if kidney function is normal
 Cortical ROIIncludes only parenchyma, not CS and calyces; optimal for assessing functional parameters such as 20-min/max (renal retention) and Tpeak
 CS ROIExcludes parenchyma and has been shown to better represent CS drainage when calculating T-½
 Background ROIIs C-shaped or reniform, 2 pixels wide, and 1 pixel away from cortex
 Relative (split) functionMust 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
 Relative (split function)Normal is 45%–55%; abnormal if <40%
 TpeakNormal is <5 min
 T-½ emptyingNormal is <10–15 min; abnormal does not equate to obstruction
 20-min/maxNormal is <0.35 as measured 20 min after Tpeak
 Tissue transit timeActivity should be seen in CS by 5 min; >8 min is delayed
 Postvoid kidney to maximumPostvoid image is acquired 30 min after start, and activity is compared with Tpeak
 Output efficiencyHelps overcome confounding effect of poor renal function on CS drainage assessment; requires special processing software
 Normalized residual activityNormal 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.