Evaluation of Ultrasound Probe for Use in Adaptive Bladder Radiotherapy

All experiments and data analysis will be performed in the Magnetic Resonance Imaging (MRI) and Radiotherapy departments respectively, at the Queen Elizabeth Hospital.

Five volunteers will be recruited to this study. They will each be required to follow a documented drinking protocol prior to each of three scan sessions. The drinking protocol is specific to this study and will not be intended for use with patients. To address the primary endpoint of the study (i.e. the precision of the ultrasound probe for measurement of bladder volume), measurement of a wide range of bladder volumes is required. In order to address this aim while making efficient use of the limited available MRI scanner time, the drinking protocol has been designed such that the volunteer will begin each scan session with an empty bladder and finish it with a full bladder. To this end, each volunteer will be required to void their bladder upon arrival and then consume 500ml of water immediately prior to the start of the scan session.

Each volunteer will then be positioned on the scanner couch according to the same protocol used for patients and alternate MRI and ultrasound scans will then be acquired. Given the time required for each scan it is anticipated that five MRI scans and fifteen ultrasound scans (three scans at a time to reduce the noise on the results, i.e. ultimately giving five ultrasound bladder volume measurements) will be acquired in each session. Each volunteer will be asked to attend for three sessions over the course of a number of weeks so that the repeatability of bladder filling patterns can be determined.

Data processing and analysis

The volume measurements from the ultrasound probe will be recorded and each of the MRI images will be exported to the Radiotherapy department where the bladder volume will be determined. The precise timings of all scan acquisitions will be recorded during the imaging session. Bladder volumes measured by the ultrasound probe, which can be read instantly, will be recorded during the session. To evaluate the primary endpoint, the precision and accuracy of the ultrasound probe will be quantified by comparing the measured values to those expected from the MRI volumes. Each volume measurement from the MRI scans will be checked by a second observer to minimise any associated researcher error.