Validation of an external ultrasound device for bladder volume measurements in prostate conformal radiotherapy

A prospective comparative study on bladder volume measurement with portable ultrasound scanner and CT simulator in pelvic tumor radiotherapy

OBJECTIVE

The consistency of bladder volume is very important in pelvic tumor radiotherapy, and portable bladder scanner is a promising device to measure bladder volume. The purpose of this study was to investigate whether the bladder volume of patients with pelvic tumor treated with radiotherapy can be accurately measured using the Meike Palm Bladder Scanner PBSV3.2 manufactured in China and the accuracy of its measurement under different influencing factors.

METHODS

A total of 165 patients with pelvic tumor undergoing radiotherapy were prospectively collected. The bladder volume was measured with PBSV3.2 before simulated localization. CT simulated localization was performed when the bladder volume was 200-400ml. The bladder volume was measured with PBSV3.2 immediately after localization and recorded. The bladder volume was then delineated on CT simulation images and recorded. To compare the consistency of CT simulation bladder volume and bladder volume measured by PBSV3.2. To investigate the accuracy of PBSV3.2 in different sex, age, treatment purpose, and bladder volume.

RESULTS

There was a significant positive correlation with bladder volume on CT and PBSV3.2 (r = 0.874; p < 0.001). The mean difference between CT measured values and PBSV3.2 was (-0.14 ± 50.17) ml. The results of the different variables showed that the overall mean of PBSV3.2 and CT measurements were statistically different in the age ≥ 65 years, bladder volumes > 400ml and ≤ 400ml groups (p = 0.028, 0.002, 0.001). There was no statistical significance between the remaining variables. The volume difference between PBSV3.2 measurement and CT was 12.87ml in male patients, which was larger than that in female patients 3.27ml. Pearson correlation analysis showed that the correlation coefficient was 0.473 for bladder volume greater than 400ml and 0.868 for bladder volume less than 400ml; the correlation coefficient of the other variables ranged from 0.802 to 0.893.

CONCLUSION

This is the first large-sample study to evaluate the accuracy of PBSV3.2 in a pelvic tumor radiotherapy population using the convenient bladder scanner PBSV3.2 made in China. PBSV3.2 provides an acceptable indicator for monitoring bladder volume in patients with pelvic radiotherapy. It is recommended to monitor bladder volume with PBSV3.2 when the planned bladder volume is 200-400ml. For male and patients ≥ 65 years old, at least two repeat measurements are required when using a bladder scanner and the volume should be corrected by using a modified feature to improve bladder volume consistency.

Does a patient-specific bladder-filling protocol affect bladder volume and dose in postprostatectomy radiotherapy?

PURPOSE

Our aim is to develop a patient-specific bladder-filling protocol (PSP) using an ultrasound-based bladder scanner (BS) and compare the volumetric and dosimetric parameters with those of the standard filling protocol (SP) in postprostatectomy patients.

METHODS

Twenty postprostatectomy patients who received salvage radiotherapy (72 Gy/36 fx) were included. For PSP, the patient was asked to drink 500 mL of water after emptying his bladder. Bladder volume was measured using BS every 10 min. Each patient's unique time to reach a 150-200 cc volume was used for simulation and treatment. For the SP, the patient was asked about the feeling of having a full bladder. Organs at risk (OAR) were contoured on cone-beam computed tomography (CBCT) scans that were transferred to the treatment planning system (TPS). Treatment plans were applied to CBCTs. Changes in bladder volume and doses for planning computed tomography (PCT) and CBCT were determined.

RESULTS

In the SP, there was no significant difference in mean bladder volume for PCT and CBCT (p = 0.139); however, there was a trend for significance in the mean bladder dose (p = 0.074). In PSP, there was no significant difference in the mean bladder volume or dose for PCT and CBCT (p = 0.139 and p = 0.799, respectively). There was a significant difference in terms of mean CBCT bladder volume between the two protocols (p = 0.007), whereas no significant difference was detected in terms of bladder dose (p = 0.130).

CONCLUSION

With PSP, optimal bladder filling was obtained and maintained throughout the whole treatment course, and it was reproducible in every fraction.

[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.

Assessment of an ultrasound bladder scanner in prostate radiotherapy: A validation study and analysis of bladder filling variability

INTRODUCTION

During prostate radiotherapy treatment, it is important to ensure the position of the bladder and prostate is consistent between treatments. The aim of this study was to provide a quantitative basis for incorporating ultrasound bladder volume estimates into local practice for prostate radiotherapy.

METHODS

Agreement between bladder volume estimates obtained using computed tomography (CT) and ultrasound was assessed. Analysis of bladder volumes between planning and treatment scans was used to quantify expected variations in bladder volume over the course of radiotherapy. Dose-volume statistics were estimated and compared to planned dose constraints to propose a target bladder volume and tolerance.

RESULTS

Bladder volume measurements were obtained from 19 radiotherapy patients using ultrasound and CT. Ultrasound underestimated bladder volume compared to CT with a mean bias of -28 ± 30 ml. Pre-treatment (planning) bladder volumes varied from 71 to 383 ml with a mean of 200 ml. Treatment bladder volumes reduced by more than half in 9% of patients during the course of their treatment, potentially leading to a 30% increase in mean bladder dose. Patients with pre-treatment bladder volumes < 200 ml were most likely to exhibit differences in bladder volume, resulting in 'out of tolerance' increases in dose.

CONCLUSIONS

A pragmatic individualised drinking protocol, aimed at achieving a minimum ultrasound bladder volume of 200 ml at planning CT, may be beneficial to reproducibility in radiotherapy treatment. Ultrasound measurements prior to treatment should ideally confirm that bladder volume is at least half the volume measured at planning.

BladderScan Feedback Method in Predicting Bladder Filling for Prostate Radiotherapy: A Prospective Study

Purpose:

Approximately 5%–10% of men who receive prostate cancer radiotherapy will suffer from radiation cystitis. Bladder filling before the administration of radiotherapy results in lower radiation exposure to the bladder. BladderScan, an ultrasound-based bladder volume scanner, has the potential to evaluate bladder volume during radiotherapy; thus, a prospective pilot study was initiated.

Methods:

Eleven men receiving tomotherapy for localized prostate cancer were enrolled. The validity of BladderScan was evaluated by comparing the measurements from BladderScan with the calculated volume from megavoltage computed tomography (MVCT). With a crossover design to compare different methods in bladder filling, the radiotherapy was divided into 2 sequences. Conventional method: the patient was asked to drink water after voiding urine. The amount of water and the duration of waiting were the same as in the setting of the simulation. BladderScan feedback method: the bladder filling procedure depended on the BladderScan measurements.

Results:

There were 314 sets of data from 11 patients. The correlation coefficient between V^BS and V^CT was 0.87, where V^BS is the mean volume of 3 measurements by BladderScan and V^CT is the bladder volume derived from MVCT. The BladderScan feedback method resulted in a significant larger bladder volume than the conventional method, with a mean difference of 36.9 mL. When the failure was defined as V^CT <80% of planned volume, the BladderScan feedback method brought about a relative reduction in the failure rate with an odds ratio of 0.44 and an absolute reduction of 9.1%.

Conclusion:

The accuracy of BladderScan was validated by MVCT in our study. The BladderScan feedback method can help patients fill the bladder adequately, with a larger bladder volume and a lower failure rate.

Maintaining consistent bladder filling during external beam radiotherapy for prostate cancer

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Radiation for prostate cancer is preferably provided with a full urinary bladder.

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There are discrepancies how well current methods achieve consistent bladder filling.

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A urinary catheter with a check-valve controlled by a float is under development.

Radiation therapy for patients with prostate cancer is preferably provided with a full urinary bladder. Full bladder can potentially move the small intestine out of the radiation treatment regions, and results in decreased small bowel radiation dose and gastrointestinal toxicity. Maintaining consistent bladder filling during computerized tomography simulation scan used for treatment planning and at daily radiation treatments is challenging. Here we present an in-development urinary catheter with a floating balloon that drains the bladder only when urine reaches to a prespecified level, and review current methods used in clinic to ensure consistent bladder filling. These includes bladder filling protocols, ultrasound scanning and biofeedback techniques.

A comparison of bladder volumes based on treatment planning CT and BladderScan® BVI 6100 ultrasound device in a prostate radiation therapy population

OBJECTIVE:

The aim of this study is to investigate if a handheld ultrasound device (BladderScan® BVI 6100) can accurately measure bladder volumes in prostate radiotherapy (RT) patients.

METHODS:

A comparison was made of contoured bladder volumes based on treatment planning CT (TPCT) and BladderScan® BVI 6100 ultrasound device in a large prostate RT population. Three bladder volume (BV) measurements were taken using the bladder volume instrument (BVI) device on prostate RT patients immediately prior to TPCT (n = 190). The CT delineation bladder volumes were also recorded. The mean of the three BVI readings (BVImean) and the maximum (BVImax) of the readings were considered for a comparative analysis.

RESULTS:

There was a strong positive correlation between the BVI and CT delineated bladder volumes (BVImean r = 0.825; BVImax r = 0.830). The mean difference [± standard deviation (SD)] was an underestimation of BV for both BVImean and BVImax (44.8 ± 88.2 ml and 32.9 ± 87.5 ml, respectively).

CONCLUSION:

This is the largest study to date (n = 190), assessing the accuracy of the BladderScan® BVI 6100 in the prostate RT population. The BVI 6100 provides an acceptable indication of BV for use in prostate RT patients for the purposes of monitoring BV.

ADVANCES IN KNOWLEDGE:

The BladderScan® BVI 6100 provides a convenient and non-irradiating method of indicating BV for use in prostate RT patients.

Implementation of ultrasound bladder volume scanning for patients receiving intensity-modulated radiotherapy to the cervix or endometrium: clinical experiences from a United Kingdom radiotherapy department

Background and purpose

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.

Materials and methods

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.

Results

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.

Conclusions

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.

Use of a prospective cohort study in the development of a bladder scanning protocol to assist in bladder filling consistency for prostate cancer patients receiving radiation therapy

INTRODUCTION

Evidence of variations in bladder filling effecting prostate stability and therefore treatment and side-effects is well established with intensity modulated radiation therapy (IMRT). This study aimed to increase bladder volume reproducibility for prostate radiation therapy by implementing a bladder scanning (BS) protocol that could assist patients' bladder filling at computed tomography (CT) simulation and treatment.

METHODS

Based on a retrospective review of 524 prostate cancer patients, a bladder volume of 250-350 mL was adopted as 'ideal' for achieving planning dose constraints. A prospective cohort study was conducted to assess the clinical utility of measuring patients' bladder volumes at CT simulation using an ultrasound bladder scanner (Verathon 9400 BladderScan(®)). A revised bladder preparation protocol was utilised by a bladder scan group (BS) and a non-BS group followed the standard departmental bladder preparation protocol. Time and volume data for the BS group (n = 17) were compared with the non-BS group (n = 17).

RESULTS

The BS cohort had a CT bladder volume range of 221-588 mL; mean 379 mL, SD 125 mL. The non-BS group had a larger range: 184-757 mL; mean 373 mL, SD 160 mL (P = 0.9171). There was a positive correlation between CT volume and BS volume in the BS group (r = 0.797; P = 0.0002) although BS volumes were smaller: range 160-420 mL; mean 251 mL; SD 91 mL; P < 0.0001). The maximum bladder volume receiving 50 Gy (V50) from the BS group was 46.4%, mean 24.5%. The maximum bladder V50 from the non-BS group was 50.9%, mean 27.3% (P = 0.5178). Treatment data from weekly cone beam CT scans were also compared over 6 weeks. They were assessed as being a pass if bladder and bowel requirements were acceptable. The BS group proceeded to treatment on the basis of a pass 92.7% of the time, whereas the pass rate for non-BS group was 75%; difference 17.7% (P < 0.0001).

CONCLUSION

The BS is a useful tool for achieving consistent, appropriately sized bladder volumes in prostate cancer patients.

Prostate bed radiation therapy: the utility of ultrasound volumetric imaging of the bladder

AIMS

To evaluate the effect of incorporating daily ultrasound scanning to reduce variation in bladder filling before prostate bed radiotherapy. The primary aim was to confirm that coverage of the planning target volume (PTV) with the 95% isodose was within tolerance when the ultrasound-determined bladder volume was within individualised patient limits.

MATERIALS AND METHODS

Cone beam computed tomography (CBCT) images were acquired on 10 occasions during the course of treatment to assess systematic changes in rectal or bladder volume as part of a standard offline image-guided radiotherapy (IGRT) protocol. In addition, through a two-part study an ultrasound scan of the bladder was added to the IGRT protocol. In the Part 1 study, the ultrasound-determined bladder volume at the time of treatment simulation in 26 patients was compared with the simulation computed tomography cranio-caudal bladder length. The relationship between the two was used to establish bladder volume tolerance limits for the interventional component of the Part 2 study. In the Part 2 study, 24 patients underwent ultrasound scanning before treatment. When bladder volumes were outside the specified limits, they were asked to drink more water or void as appropriate until the volume was within tolerance.

RESULTS

Based on the results of the Part 1 study, a 100 ml tolerance was applied in the Part 2 study. Seventy-six per cent of patients found to have bladder volumes outside tolerance were able to satisfactorily adjust their bladder volumes on demand. Comparing the bladder volumes with the CBCT data revealed that the bladder scanner correctly predicted that the target volume would be accurately targeted (using surrogate end points) in 83% of treatment fractions.

CONCLUSION

A simple hand-held ultrasound bladder scanner provides a practical, inexpensive, online solution to confirming that the bladder volume is within acceptable, patient-specific limits before treatment delivery, with the potential to improve overall treatment accuracy.

A randomized trial comparing bladder volume consistency during fractionated prostate radiation therapy

PURPOSE

Organ motion is a contributory factor to the variation in location of the prostate and organs at risk during a course of fractionated prostate radiation therapy (RT). A prospective randomized controlled trial was designed with the primary endpoint to provide evidence-based bladder-filling instructions to achieve a consistent bladder volume (BV) and thus reduce the bladder-related organ motion. The secondary endpoints were to assess the incidence of acute and late genitourinary (GU) and gastrointestinal (GI) toxicity for patients and patients' satisfaction with the bladder-filling instructions.

METHODS AND MATERIALS

One hundred ten patients were randomly assigned to 1 of 2 bladder-filling protocols; 540 mL (3 cups) of water or 1080 mL (6 cups) of water, in a single institution trial. A portable ultrasound device, BladderScan BVI 6400 (Verathon Inc, Bothell, WA), measured BVs at treatment planning computed tomography (TPCT) scan and 3 times per week during RT. Maximum bladder dose and BV receiving ≥ 50, 60, and 70 Gy were recorded. Acute and late GU and GI toxicity were evaluated, as were patients' comfort, perception of urinary symptoms, and quality of life (QoL).

RESULTS

There was significantly less BV variation in the 540 mL arm when compared with 1080 mL (median: 76 mL vs 105 mL, P = .003). Larger BVs on initial TPCT correlated with larger BV variations during RT (P < .0005). There were no statistically significant associations between arm and GU/GI toxicity, dose median comfort scores, or median QoL scores.

CONCLUSIONS

The 540 mL bladder-filling arm resulted in reproducible BVs throughout a course of RT, without any deterioration in QoL or increase in toxicities for prostate patients.