A Feasibility Study on the Role of Ultrasound Imaging of Bladder Volume as a Method to Improve Concordance of Bladder Filling Status on Treatment with Simulation

[Benefits and limitations of using a portable ultrasound scanner (bladderscan) in pelvic radiotherapy. Narrative review of the literature]

PURPOSE

The reproducibility of bladder filling influences the target volume position for pelvis radiotherapy. The objective of this study was to summarize the current knowledge on the use of portable echograph systems named Bladderscan (BS) in this context.

MATERIAL AND METHODS

Review of the PubMed and Google Scholar publication databases was performed between September 2020 and April 2021. Results of this research were filtered in accordance to a set of eligibility criterias and are presented in this article.

RESULTS

Keyword search yielded a total of 2407 publications, which filtered down to 10 relevant articles in accordance to the eligibility criterias. These publications described the viability of the BS measures as well as their clinical and organizational repercussions.

CONCLUSION

According to multiple studies, BS allows to measure the bladder volume before each radiotherapy session. The use of BS decreases the amount of Cone Beam Computer Tomography potentially rejected due to non-conformed bladder filling, and improve the throughput of patients.

Improvement in bladder volume reproducibility using A-mode portable ultrasound bladder scanner in moderate-hypofractionated volumetric modulated arc therapy for prostate cancer patients

Purpose

This study introduced an A‐mode portable ultrasound bladder scanner, the Lilium® α‐200 (here after Lilium; Lilium Otsuka, Kanagawa, Japan), for the treatment of prostate cancer patients with hypofractionated volumetric modulated arc therapy to improve the reproducibility of bladder volume (BV).

Materials and methods

Thirty patients were advised to maintain full BV prior to computed tomography (CT) simulation and daily treatment. Among these, the BV of 15 patients was measured using Lilium until a BV of 80% in the simulation was achieved (with the Lilium group). Daily cone‐beam CT (CBCT) was performed for treatment. The correlation between BV measured by CBCT and Lilium was assessed. The differences in the BV and dosimetric parameters of the bladder in the CBCT versus planning CT were compared between the groups with and without Lilium.

Results

There was a significantly strong relationship (r = 0.796, p < 0.05) between the BVs measured using CBCT and Lilium. The relative BV ratios to simulation CT < 0.5 and > 2 were observed in 10.3% and 12.7%, respectively, of treatment sessions without Lilium group, while these ratios were 1% and 2.8%, respectively, in the Lilium group. The mean absolute difference in the range of V_30Gy to V_40Gy without Lilium sessions was significantly larger (p < 0.05) than that in the Lilium group.

Conclusion

The use of the A‐mode portable ultrasound bladder scanner significantly improved the reproducibility of the BV, resulting in few variations in the dosimetric parameters for the bladder.

Bladder volume reproducibility after water consumption in patients with prostate cancer undergoing radiotherapy: A systematic review and meta-analysis

BACKGROUND

To minimize toxicity due to radiotherapy in patients with prostate cancer, high bladder volume reproducibility is essential. Water consumption is often used to increase bladder volume reproducibility, but the optimal amount of water required to be consumed remains unclear. We aimed to analyzed the relationship between water consumption and bladder volume reproducibility in patients undergoing radiotherapy for prostate cancer.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials and cohort studies that assessed bladder volume change after water consumption in patients with prostate cancer undergoing radiotherapy. MEDLINE, Embase, and Cochrane Central Register of Controlled Trials were searched for relevant studies published from database inception up until July 4, 2020. The Newcastle-Ottawa Scale was used to evaluate the risk of bias in the included studies. The outcome was the mean difference (MD) of bladder volume after water consumption, evaluated through meta-analysis using a random-effects model.

RESULTS

Ten cohort studies and one randomized controlled trial with a total of 417 patients were included. For 300-400 ml water consumption, the bladder volume MD between during treatment and at computer tomography-simulation (95% confidence interval [CI]) was -11.97 (-51.68 to 27.74), was -45.99 (-82.85 to -9.13) for 500-540 ml water consumption and -45.92 (-78.86 to -12.98) for water consumption until full-bladder sensation was reached.

CONCLUSION

Consuming 300-400 ml of water potentially leads to the best bladder volume reproducibility; moreover, the higher the water consumption volume, the lower the bladder volume reproducibility.

Daily Ultrasound Imaging for Patients Undergoing Postprostatectomy Radiation Therapy Predicts and Ensures Dosimetric Endpoints

Purpose

Patients who receive radiation therapy (RT) for prostate cancer are routinely positioned through radiographic means. We set out to establish a data-driven process that defines bladder volume required to meet V40/65 constraints using daily bladder ultrasound (US) and comparative cone beam CT (CBCT) before placing a patient on the treatment table.

Methods and Materials

This was a single institution retrospective study of 20 patients (390 CBCT scans) who received postprostatectomy RT. Each patient received a daily US before treatment. CBCT alignment was performed 3 times a week. The bladder and rectum were contoured on each CBCT and a session dose was recorded. A mixed-effect model was used to estimate trajectory slopes of radiation exposure with organs-at-risk volume increase. Slope differences by V40/65 for prostate fossa (PF) and pelvic lymph nodes (PF/pLN) were tested using a 3-way-interaction term with Bonferroni correction.

Results

For the 20 patients, 10 received treatment to PF and 10 received RT to the PF/pLN. Predefined bladder constraints were V65 < 50%, V40 < 70%, and rectal constraints were V65 < 35%, V40 < 55%. The CBCT bladder volume (76-578 cm³) was greater than the pretreatment bladder US (87-466 cm³) due to volume filling between measurements (r = 0.8 ± 0.05). Mixed model detected a statistically significant 3-way interaction (P < .01) for bladder volume and V40/65. Both PF and PF/pLN patients showed improvement in V40/65 with an increase in bladder volume. For PF patients, bladder constraints were met when the US volume was >108 cm³ and for PF/pLN patients when the US bladder volume was >200 cm³. Rectal filling showed no association with CBCT volume.

Conclusions

Daily US of the bladder before postprostatectomy RT allows for dosimetric predictions before daily treatment. This should translate into fewer CBCT for the patient and improved machine throughput. This technique is easy to institute and ensures organs-at-risk volumetric constraints are met based on daily US measurements.