Validation and predictive modeling of a portable bladder scanner for precision bladder management in pelvic...

Validate the accuracy of a portable bladder scanner (Caresono PadScan HD5) against planning CT and demonstrate its clinical application to optimize bladder preparation in pelvic radiotherapy.

Two retrospective cohorts were analyzed: 114 patients assessed with HD5 and 111 historical controls. Agreement between HD5-measured volume (VHD5) and planning CT (VCT) was evaluated with correlation, regression, Bland-Altman, and paired tests. Initial CBCT repetition rates were compared between cohorts. Subgroup analyses (bladder volume [BV]<300 vs ≥300 mL; age<65 vs ≥ 65 years); sex and multivariable linear regression with interaction terms explored predictors of measurement error.

V HD5 correlated with VCT (r = 0.723, P < .001) but underestimated volumes (mean bias -34.39 mL). Underestimation was markedly greater at VCT ≥300 mL (-71.46 vs -18.64 mL, P < .001). Multivariable regression confirmed BV as the primary driver, with an age-dependent interaction showing steeper underestimation in younger (<65 years) patients (P < .001). Following HD5 implementation, initial CBCT repetition rates decreased from 48.7% to 22.8% (P < .001).

HD5 enables reliable, though negatively biased, BV estimates. Embedding an age-stratified, moderate-fill workflow reduces repeat initial CBCT and standardizes bladder preparation.

We quantify volume-dependent underestimation and an age interaction, and translate them into a predictive, age-stratified protocol that operationalizes HD5 measurements for routine pelvic RT bladder management.