Achieving daily consistent bladder volume is acknowledged as challenging for patients undergoing radiotherapy to the cervix or endometrium. We investigated if use of an ultrasound bladder volume scanner (BioCon-700) improves bladder reproducibility when used during an active volume correction protocol.

During our method-comparison study, prospectively recruited patients (n=20) followed a fluid-loading protocol to achieve acceptable bladder volume. Bladder ultrasound was performed daily to verify planned volume, with patients actively correcting volumes outside a planned range up to a maximum of three times. Using the Bland–Altman method, we compared mean ultrasound readings (USMean) with mean cone-beam computed tomography (CBCT) volumes (CBCTMean). We also conducted staff focus groups exploring issues encountered during implementation of bladder scanning.

Comparing USMean with CBCTMean produced a mean of the differences −10±49·92 mL (1 SD), demonstrating that bladder volume scanning is equivalent to our standard measure for the stated confidence levels. The cohort mean bladder volume decrease from week 1 to 5 was only 8·4%. Mean USMean was 323 mL, mean CBCTMean was 313 mL. Staff experience with the scanner overall was positive.

The BioCon-700 is suitable for the purpose of daily pre-treatment volume verification, facilitating daily assessment and modification of bladder volume, resulting in reproducible treatment volumes.