Bladder Filling Research Articles

PO0261: Dosimetric Analysis of Intrafraction Bladder Filling Effect on Dose Reporting for Intracavitary Brachytherapy (IGBT)

PO0261: Dosimetric Analysis of Intrafraction Bladder Filling Effect on Dose Reporting for Intracavitary Brachytherapy (IGBT)

Bladder Responses to Thoracolumbar Epidural Stimulation in Female Urethane-Anesthetized Rats with Graded Contusion Spinal Cord Injuries.

Spinal cord epidural stimulation (scES) is a therapeutic option that promotes functional improvements in sensory, motor, and autonomic functions following spinal cord injury (SCI). Previous scES mapping studies targeting the lower urinary tract (LUT) in rats demonstrated functional response variability based upon lumbosacral level, parameters used, extent of injury (spinally intact vs. chronic anatomically complete spinal transections), and sex. In the current study, female rats with clinically relevant graded incomplete T9 contusion injuries were mapped with scES at 60 days post-injury at three spinal levels (T13, L3, L6) with a novel miniature 15-electrode array designed to deliver optimal specificity. The results obtained during bladder fill and void cycles conducted under urethane anesthesia indicate frequency dependent sub-motor threshold effects on LUT function with a single row of electrodes positioned across the full medio-lateral extent of the dorsal cord. The findings of improved storage and emptying, represented by significantly longer inter-contractile intervals with T13 scES and L3 scES and by a significantly increased estimated void efficiency with L6 scES, respectively, are consistent with previous studies using intact and chronic complete transected male and female rats. The data support the efficacy of selective spinal network stimulation to drive functionally relevant networks for storage versus emptying phases of the urinary cycle. The current findings further demonstrate the translational promise of scES for SCI individuals with LUT dysfunctions, regardless of injury severity.

Impact of Sonographer Experience, Insonation Angle, and Bladder Filling on Uterine Artery Doppler Measurements in the First Trimester of Pregnancy.

To investigate the influence of different measurement conditions and ultrasound training level on uterine artery pulsatility index (UtA-PI) measurements as required for combined first trimester preeclampsia (PE) screening. This was a prospective study of consecutive patients with singleton pregnancies presenting for an ultrasound examination between 11 and 14 weeks' gestation. UtA-PI measurements were conducted by residents in training and repeated by experienced sonographers thereafter. UtA-PI measurements were conducted under different examination conditions. First, the trainee sonographers performed transabdominal sagittal and transverse UtA-PI measurements without bladder filling. These measurements were then repeated by the expert sonographers. Additionally, the expert sonographers also performed transvaginal UtA-PI measurements and transabdominal measurements with bladder filling. Statistical analysis was conducted with the statistical software R and included descriptive statistics as well as 2-sided paired t tests. A total of 100 women were included in the study. Mean age was 31.7 ± 4.92 years and mean gestational week was 12.5 ± 0.53 weeks. A total of 56% were nulliparous and 44% were parous. UtA-PI was significantly lower if performed by a sonographer in training versus an experienced sonographer (P = .031). No significant difference was observed in comparing transverse and sagittal techniques (P = .241). There was also no significant difference in transabominal versus transvaginal measurements (P = .806) and with an empty versus full bladder (P = .444). Experience of sonographer has a significant impact on UtA-PI. Supervised onsite training is necessary to improve reliability and consistency of UtA-PI measurements and make PE screening reliable for implementation in a universal screening setting.

An Introduction to Ventra: A Programmable Abdominal Phantom for Training, Educational, Research, and Development Purposes.

Intra-abdominal pressure (IAP) is a critical parameter in the care of critically ill patients, as elevated IAP can lead to reduced cardiac output and organ perfusion, potentially resulting in multiple organ dysfunction and failure. The current gold standard for measuring IAP is an indirect technique via the bladder. According to the Abdominal Compartment Society's Guidelines, new measurement methods/devices for IAP must be validated against the gold standard. This study introduces Ventra, an abdominal phantom designed to simulate different IAP levels, abdominal compliance, respiration-related IAP variations, and bladder dynamics. Ventra aims to facilitate the development and validation of new IAP measurement devices while reducing reliance on animal and cadaveric studies. Additionally, it offers potential applications in training and education for biomedical engineering students. This study provides a thorough explanation on the phantom's design and fabrication, which provides a low-cost solution for advancing IAP measurement research and education. The design concept, technical aspects, and a series of validation experiments determining whether Ventra is a suitable tool for future research are presented in this study. Ventra's performance was evaluated through a series of validation tests using a pressure gauge and two intra-gastric (Spiegelberg and CiMON) and two intra-bladder (Accuryn and TraumaGuard) pressure measurement devices. The mean and standard deviation of IAP recordings by each device were investigated. Bland-Altman analysis was used to evaluate bias, precision, limits of agreement, and percentage error for each system. Concordance analysis was performed to assess the ability of Ventra in tracking IAP changes. The phantom demonstrated excellent agreement with reference pressure measurements, showing an average bias of 0.11 ± 0.49 mmHg. A concordance coefficient of 100% was observed for the phantom as well. Ventra accurately simulated different abdominal compliances, with higher IAP values resulting in lower compliance. Abdominal volume changes showed a bias of 0.08 ± 0.07 L/min, and bladder fill volume measurements showed an average difference of 0.90 ± 4.33 mL for volumes ranging from 50 to 500 mL. The validation results were in agreement with the research guidelines of the world abdominal society. Ventra is a reliable tool that will facilitate the development and validation of new IAP measurement devices. It is an effective educational tool for biomedical engineering students as well.

Adaptive radiotherapy for muscle invasive bladder cancer: a retrospective audit of two bladder filling protocols

BackgroundRadical radiotherapy for muscle-invasive bladder cancer (MIBC) is challenging due to large variations in bladder shape, size and volume during treatment, with drinking protocols often employed to mitigate geometric uncertainties. Utilising adaptive radiotherapy together with CBCT imaging to select a treatment plan that best fits the bladder target and reduce normal tissue irradiation is an attractive option to compensate for anatomical changes. The aim of this retrospective study was to compare a bladder empty (BE) protocol to a bladder filling (BF) protocol with regards to variations in target volumes, plan of the day (PoD) selection and plan dosimetry throughout treatment.MethodsForty patients were included in the study; twenty were treated with a BE protocol and twenty with a BF protocol to a total prescribed dose of 55 Gy in 20 fractions. Small, medium and large bladder plans were generated using three different CTV to PTV margins. Bladder (CTV) volumes were delineated on planning CTs and online pre-treatment CBCTs. Differences in CTV volumes throughout treatment, plan selection, PTV volumes and resulting dose metrics were compared for both protocols.ResultsMean bladder volume differed significantly on both the planning CTs and online pre-treatment CBCTs between the protocols (p < 0.05). Significant differences in bladder volumes were observed between the planning CT and pre-treatment CBCTs for BF (p < 0.05) but not for BE (p = 0.11). Both protocols saw a significant decrease in bladder volume between first and final treatment fractions (p < 0.05). Medium plans were preferentially selected for BE whilst when using the BF protocol the small plan was chosen most frequently. With no significant change to PTV coverage between the protocols, the volume of body receiving 25.0–45.8 Gy was found to be significantly smaller for BE patients (p < 0.05).ConclusionsThis work provides evidence in favour of a BE protocol compared to a BF protocol for radical radiotherapy for MIBC. The smaller treatment volumes observed in the BE protocol led to reduced OAR and total body doses and were also observed to be more consistent throughout the treatment course. These results highlight improvements in dosimetry for patients who undergo a BE protocol for MIBC.

Naturalistic Bladder Filling Reveals Subtypes in Overactive Bladder Syndrome That Differentially Engages Urinary Urgency-Related Brain Circuits: Results From the Symptoms of Lower Urinary Tract Dysfunction Research Network (LURN).

Overactive bladder (OAB) may be attributed to dysfunction in supraspinal brain circuits. Overactive bladder participants enrolled in the LURN (Symptoms of Lower Urinary Tract Dysfunction Research Network) study reported sensations of urinary urgency during a bladder-filling paradigm while undergoing brain functional MRI to map supraspinal dysfunction. OAB participants and controls (CONs) completed 2 resting-state functional MRI scans following consumption of 350 mL water. Scans were conducted at fuller and emptier bladder states, interleaved with voiding. Urgency ratings (0-10) were assessed. Patterns of urgency during bladder filling were investigated using latent class trajectory models. Clusters of participants encompassing each pattern (ie, subtype) were derived from aggregated groups of OAB and CON independent of diagnosis. Two distinct patterns of urgency trajectories were revealed: first subtype with OAB and CON who were unresponsive to bladder filling (OAB-1 and CON-1) and second highly responsive subtype predominantly containing OAB (OAB-2). OAB-2 participants scored significantly higher on urinary symptoms but not pain or psychosocial measures. Neuroimaging analyses showed change in urgency due to both bladder filling and voided volume related to multiple loci of brain network connectivity in OAB-2, and in some cases, different than OAB-1 and/or CON-1. Sensorimotor to dorsomedial/dorsolateral prefrontal connectivity mediated the relationship between stimulus (voided volume) and percept (urgency) in OAB-2. Our results reveal different OAB subtypes with latent class trajectory models of urgency ratings during natural bladder filling. Functional MRI revealed differences in pathophysiology between subtypes, namely sensorimotor-prefrontal connectivity is a key locus in OAB patients with higher urinary symptoms.

Effectiveness of Bladder Filling Control during Online MR-Guided Adaptive Radiotherapy for Rectum Cancer

MR-guided adaptive radiotherapy (MRgART) treatment sessions at MR-Linac are time-consuming and changes in bladder filling during the session can impact the treatment dosimetry. In this work, we present the procedure implemented in the clinical workflow to stabilize bladder filling during the MR based adaptive radiotherapy sessions and evaluate its effectiveness and the resulting dosimetric impact on the adaptive plan. Twenty-five rectum cancer patients treated at 1.5T MR-Linac with a short course radiotherapy (25 Gy in 5 fractions of 5 Gy each) were included in this retrospective study. Patients were treated with the adapt-to-shape workflow consisting of a plan adaptation based on the MRI acquired in each session and optimized on the corresponding MR-based synthetic CT. Considering the significant interval time between the acquisition of the first daily MRI used for plan adaptation, and the beam delivery, a bladder catheter was used to stabilize the bladder filling; the procedure consists of emptying the bladder and refilling it with a well-known amount of physiological solution before each MRI acquisition. Two MRIs were acquired at each session: the first was used for plan adaptation and the second was acquired while approving the adapted plan, to be rigidly registered with the first to ensure the appropriateness of the isodoses on the ongoing delivery treatment. A total of 125 sessions and 250 MRI images and bladder contours were analyzed; for each fraction, the time interval between the first and second MRI and the corresponding bladder volumes were recorded; the consistency of bladder volumes and shapes along each online session was assessed with the dice similarity index (DSC) and Hausdorff distance (HD); the impact on plan dosimetry was evaluated by comparing target and bladder DVH cut off points of the plan on the two different MRI datasets. The time interval between the first and second MRI, averaged over the 125 sessions is 39.0 min, range (18.6-75.8) min. The changes in bladder volumes, DSC index, HD, and the differences between the bladder and target DVH cut-off points are shown in the table below. The DSC and HD are comparable to inter-observer variability in manual contour segmentation, with an average DSC of 0.91 and average HD of 2.13 mm; the average differences in bladder and target dosimetry remain under 0.63% and 0.10%, respectively. The use of a procedure in the clinical workflow of MRgART to stabilize the bladder filling throughout the online session may be helpful to guarantee the accuracy of the ongoing delivered treatment.

Assessment of Bladder Filling Type on Radiation Dose to Organs at Risk in MR-Guided Intracavity Brachytherapy for Cervical Cancer

In this study, we evaluated whether the classification of bladder shape affects the absorbed dose (Gy) of OARs and its geometrical position to normal organs in MR-guided intracavitary brachytherapy (ICBT). In this study, 269 patients who underwent MR-guided ICBT for cervical cancer from 2016 to 2022 were included. The applicator-inserted bladder filling type (BFT) classification was divided into three types (tilted, curved, and other shapes: group E). The anatomical positional relationship between the uterus and its surroundings was measured on pre-MR images and ICBT simulation MR images. Spearman's rank correlation analysis was used for bladder volume and OAR dose according to BFT. Anatomical differences were analyzed by ANOVA by measuring the distance from the center to both bladder walls. In the correlation analysis considering the shape of the bladder, the tilted, curved, and group E had Spearman's ρ of 0.211; -0.323, 0.412; -0.307 and -0.035; -0.209 for maximum absorbed dose (D2cc) of bladder and small bowel, respectively. It was statistically significant in the tilted type and curved type. The average left and right bladder lengths differences of the tilted type were the highest at 8.47 cm and 7.11 cm, respectively. It was a statistically significant between bladder shape and the difference in left and right bladder lengths differences (p< 0.01). In this study, it was confirmed that bladder distension increased the maximum bladder dose (D2cc) and decreased the maximum bowel dose (D2cc) to the tilted type and curved type. In addition, if the left and right bladder lengths are measured in pre-MR, the degree of bladder distension can be evaluated in advance by checking the shape of the bladder in the case of the tilting type before ICBT. Based on these findings, a prospective study is needed to evaluate the effect of ICBT on cervical cancer treatment outcomes through bladder type classification.

In Vitro Validation of a Novel Continuous Intra-Abdominal Pressure Measurement System (TraumaGuard).

Introduction: Intra-abdominal pressure (IAP) has been recognized as an important vital sign in critically ill patients. Due to the high prevalence and incidence of intra-abdominal hypertension in surgical (trauma, burns, cardiac) and medical (sepsis, liver cirrhosis, acute kidney injury) patients, continuous IAP (CIAP) monitoring has been proposed. This research was aimed at validating a new CIAP monitoring device, the TraumaGuard from Sentinel Medical Technologies, against the gold standard (height of a water column) in an in vitro setting and performing a comparative analysis among different CIAP measurement technologies (including two intra-gastric and two intra-bladder measurement devices). A technical and clinical guideline addressing the strengths and weaknesses of each device is provided as well. Methods: Five different CIAP measurement devices (two intra-gastric and three intra-vesical), including the former CiMON, Spiegelberg, Serenno, TraumaGuard, and Accuryn, were validated against the gold standard water column pressure in a bench-top abdominal phantom. The impacts of body temperature and bladder fill volume (for the intra-vesical methods) were evaluated for each system. Subsequently, 48 h of continuous monitoring (n = 2880) on top of intermittent IAP (n = 300) readings were captured for each device. Using Pearson's and Lin's correlations, concordance, and Bland and Altman analyses, the accuracy, precision, percentage error, correlation and concordance coefficients, bias, and limits of agreement were calculated for all the different devices. We also performed error grid analysis on the CIAP measurements to provide an overview of the involved risk level due to wrong IAP measurements and calculated the area under the curve and time above a certain IAP threshold. Lastly, the robustness of each system in tracking the dynamic variations of the raw IAP signal due to respirations and heartbeats was evaluated as well. Results: The TraumaGuard was the only technology able to measure the IAP with an empty artificial bladder. No important temperature dependency was observed for the investigated devices except for the Spiegelberg, which displayed higher IAP values when the temperature was increased, but this could be adjusted through recalibration. All the studied devices showed excellent ability for IAP monitoring, although the intra-vesical IAP measurements seem more reliable. In general, the TraumaGuard, Accuryn, and Serenno showed better accuracy compared to intra-gastric measurement devices. On average, biases of +0.71, +0.93, +0.29, +0.25, and -0.06 mm Hg were observed for the CiMON, Spiegelberg, Serenno, TraumaGuard, and Accuryn, respectively. All of the equipment showed percentage errors smaller than 25%. Regarding the correlation and concordance coefficients, the Serenno and TraumaGuard showed the best results (R2 = 0.98, p = 0.001, concordance coefficient of 99.5%). Error grid analysis based on the Abdominal Compartment Society guidelines showed a very low associated risk level of inappropriate treatment strategies due to erroneous IAP measurements. Regarding the dynamic tracings of the raw IAP signal, all the systems can track respiratory variations and derived parameters; however, the CiMON was slightly superior compared to the other technologies. Conclusions: According to the research guidelines of the Abdominal Compartment Society (WSACS), this in vitro study shows that the TraumaGuard can be used interchangeably with the gold standard for measuring continuous IAP, even in an empty artificial bladder. Confirmation studies with the TraumaGuard in animals and humans are warranted to further validate these findings.

PO24: Impact of Bladder Fill Change: What Happens When You're Not Looking?

PO24: Impact of Bladder Fill Change: What Happens When You're Not Looking?

Anatomical changes in the male pelvis between the supine and upright positions-A feasibility study for prostate treatments in the upright position.

Treating and imaging patients in the upright orientation is gaining acceptance in radiation oncology and radiology and has distinct advantages over the recumbent position. An IRB approved study to investigate the positions and orientations of the male pelvic organs between the supine and upright positions was conducted. The study comprised of scanning 15 male volunteers (aged 55-75 years) on a 0.6 T Fonar MRI scanner in the supine and upright positions with a full bladder and in the upright position with an empty bladder. The Pelvic study revealed that in the upright position the 1. Position and shape of the prostate are not impacted significantly by bladder fill. 2. Distance between the sacrum and the anterior bladder wall is significantly smaller. 3. Anterior-Posterior length and the bladder width is significantly larger. 4. Seminal vesicles are pushed down by the bladder. 5. Top of the penile bulb is further away from the apex of the prostate. These observed differences could positively impact upright prostate treatments by 1. Reducing the risk of small bowel approximating the treatment volume. 2. Prostate treatments can be done with a reduced focus on bladder fill. 3. Radiation beams for treating intermediate risk prostrate can be made smaller or a larger portion of the seminal vesicles can be treated with the same beam size than typically used for supine treatments. 4. Reducing the average dose to the penile bulb.

Which Bladder Filling Method for Pelvic Ultrasound is best? A Comparison Study of Three Standard Non-Foley-Catheter-Based Bladder Filling Methods (Oral, Intravenous, Oral/IV) in Preparation for Pelvic (Transabdominal) Ultrasound

Which Bladder Filling Method for Pelvic Ultrasound is best? A Comparison Study of Three Standard Non-Foley-Catheter-Based Bladder Filling Methods (Oral, Intravenous, Oral/IV) in Preparation for Pelvic (Transabdominal) Ultrasound

The Maximal Urethral Pressure at Rest and during Normal Bladder Filling Is Only Determined by the Activity of the Urethral Smooth Musculature in the Female

The aim of this opinion paper is to determine the entities that define the maximal urethral pressure (MUP) during rest and during bladder filling that is needed to guarantee continence in females. For the development of this opinion, the literature was searched for via the Pubmed database and historic sources. Animal studies indicate that the maximal urethral pressure is determined by the smooth muscle activity in the mid-urethra. Additionally, during increased smooth muscle tone development, the largest sympathetic responses are found in the middle part of the urethra. This could be confirmed in human studies that are unable to find striated EMG activity in this area. Moreover, the external urethral striated sphincter is situated at the distal urethra, which is not the area with the highest pressure. The external urethral sphincter only provides additional urethral pressure in situations of exertion and physical activity. From a physics point of view, the phasic pressure of the external striated sphincter at the distal urethra cannot be added to the tonic pressure generated by the smooth muscle in the mid-urethra. The assertion that mid-urethral pressure is the result of different pressure forces around the urethra, including that of the external striated sphincter, is not supported by basic research evidence combined with physical calculation and should therefore be considered a misconception in the field of functional urology.

Minimization of Treatment Time Using Partial-Arc Volumetric Modulated Arc Therapy with Bladder Filling Protocol for Prostate Cancer

Hojeong Lee, Dong Woon Kim, Ji Hyeon Joo, Yongkan Ki, Wontaek Kim , Dahl Park, Jiho Nam, Dong Hyeon Kim, Hosang Jeon. Progress in Medical Physics 2022;33:101-7. https://doi.org/10.14316/pmp.2022.33.4.101

Retrograde Bladder Filling after Outpatient Gynecologic Surgery: A Systematic Review and Meta-Analysis

<h3>Study Objective</h3> To systematically review and meta-analyze randomized controlled trials (RCTs) comparing postoperative bladder retrofilling to passive filling after outpatient gynecologic surgery to evaluate effects on postoperative outcomes. <h3>Design</h3> Systematic review and meta-analysis. <h3>Setting</h3> N/A. <h3>Patients or Participants</h3> Two reviewers screened 1465 articles after searching MEDLINE, PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, and ClinicalTrials.gov from 1947 to August 2020. We included RCTs comparing postoperative bladder retrofilling to passive filling in patients who underwent outpatient gynecologic surgery by any approach. The primary outcome was time to first void. Secondary outcomes included time to discharge, postoperative urinary retention, urinary tract infection, and patient satisfaction. <h3>Interventions</h3> N/A. <h3>Measurements and Main Results</h3> We included eight studies with 1173 patients. Bladder retrofilling in the operating room resulted in a significant decrease in time to first void (mean difference (MD) –33.5 minutes; 95% confidence interval (CI): –49.1 to –17.9, 4 studies, 403 patients) and time to discharge (MD –32.0 minutes; 95% CI: –51.5 to –12.6, 8 studies, 1164 patients). Bladder retrofilling did not shorten time to discharge when performed in the post-anesthetic care unit (MD –14.8 min; 95% CI: –62.6 to 32.9, 3 studies, 258 patients) or after laparoscopic hysterectomy (MD –26.0 min; 95% CI: –56.5 to 4.5, 5 studies, 657 patients). There were no differences in patient satisfaction, postoperative urinary retention, or risk of urinary tract infection between groups. <h3>Conclusion</h3> Retrofilling the bladder in the operating room after outpatient gynecologic surgery reduces the time to first void and discharge with no increase in adverse events.

Bladder Volumes Matter: Clinical Significance of Bladder Filling in Salvage Radiotherapy for Prostate Cancer

<h3>Purpose/Objective(s)</h3> Salvage radiotherapy (SRT) is the only curative option for recurrent prostate cancer after radical prostatectomy. Urinary bladder is the major organ at risk in this setting. Different bladder filling protocols are used to reduce radiation dose to the bladder and thus limit genitourinary (GU) side effects. However, constant bladder volume is hard to maintain throughout the treatment course. A pronounced inter-fractional variation in bladder volume is a well-recognized problem in SRT. The purpose of this study was to investigate if there is a relationship between actual bladder volumes measured on daily cone-beam computer tomography (CBCT) images and GU adverse effects. <h3>Materials/Methods</h3> Consecutive patients treated with SRT at Karolinska university hospital, Sweden, in 2019-2020 (n=126) were included. Patients received either 35 × 2 Gy (n=103) or 35 × 2.2 Gy and/or pelvic lymph node irradiation (n=23) with IMRT (n=82) or four-field box-technique (n=44). All patients were treated with image-guided radiotherapy (IGRT) including daily cone-beam CT (CBCT). Bladder volumes were graded (visual analogue scale) on CBCT images (n=4410) at each treatment fraction. Internal validation of bladder volume measurements was performed in 22 patients by manually delineating bladders on daily CBCTs (n=770). Clinician-reported outcome (ClinRO) and patient-reported outcome measures (PROM) were available in 103 (83%) and 80 (66%) cases, respectively, ClinRO and PROM combined in 68 (54%) patients. Baseline bladder volumes, within-patient volume variation as well as average of 35 CBCT bladder volumes for the entire treatment course were compared between groups of patients with and without GU adverse events during 12 months of follow-up. <h3>Results</h3> Manually delineated and visually graded bladder volumes were strongly correlated (r=0.869, p<0.001). ClinRO and PROM were significantly associated (Chi-square =33.1, p<0.001). A repeated-measures ANOVA determined that mean bladder volumes did not differ across 35 CBCT measurements (p=0.16). Average actual bladder volumes were significantly smaller than baseline volumes (Wilcoxon S-R test Z=-2.68, p<0.007). Bladder volumes were significantly smaller in patients with GU adverse events compared to asymptomatic patients, measured with both ClinRO (p=0.006) and PROM (p=0.003). <h3>Conclusion</h3> In conclusion, our detailed analysis indicates that patients with GU adverse effects had significantly smaller bladder volumes during SRT. Clinical use of bladder filling protocol to increase bladder size during SRT is thus justified.

HIDRATE PRO – Interim Analysis of a Prospective Feasibility Trial Using a Digital Behavioral Intervention to Improve Bladder Filling Compliance in Prostate Cancer Patients Undergoing Radiotherapy

<h3>Purpose/Objective(s)</h3> Prostate cancer (PCa) patients undergoing radiation therapy (RT) need comfortably full bladders during RT to reduce toxicities. Sensory awareness of a comfortably full bladder can be improved with biofeedback training. Additionally, poor compliance is common with standard of care written/verbal instructions, leading to wasted patient-valued (PVT) and linear accelerator valued-time (LVT). Herein, we assessed the feasibility and acceptability of a digital behavioral intervention (DBI) to improve bladder filling compliance and methods for quantifying behavioral biomarkers and wasted PVT/LVT. <h3>Materials/Methods</h3> Sixteen non-metastatic PCa patients planned for definitive RT will be enrolled in a prospective, single arm feasibility trial using a DBI. The DBI consists of an investigational device-exempt smart water bottle and phone app. Both pieces alert the patient to empty his bladder and drink a personalized volume goal (VG), based on simulation bladder volume, 1.25 hrs prior to scheduled RT. Patients were trained to adjust their VG and notification times to achieve comfortably full bladders. Primary endpoint was > 80% patient engagement on > 50% of RTs. Secondary endpoints were qualitative (QLC) and quantitative compliance (QNC) > 80%, acceptability via Service User Technology Acceptability Questionnaire (SUTAQ), and impact of DBI on PVT and LVT. For QLC, patients were asked if they prepared their bladders before daily RT. QNC was met if bladder volumes on daily CBCT were > 75% of the simulation's volume. The SUTAQ was given pre- and post-DBI. PVT and LVT were measured by time spent in clinic and on the treatment table (TT), respectively. Biometric data was probed for insights on optimal drinking behaviors. <h3>Results</h3> Thirteen patients have been enrolled and ten have data available for analysis. Thus far, 100% of patients engaged on > 50% of RTs (mean 85.6% of the time). QLC (94.4%) and QNC (90.4%) goals were met. SUTAQ's pre- and post-DBI scores were 3.95 vs. 4.27 for ease of adoption, 4.07 vs 4.28 for benefit, and 3.6 vs 3.9 for minimal privacy issues or harm. Empty bladders resulted in lost PVT (81.1 vs 40.3 min, p=0.004) and LVT (24.20 vs 11.41 min, p<0.001). $410 was lost per empty bladder, based on 2021 CMS reimbursement for 40 fraction IMRT. Patients with empty bladders were more likely to finish their VG quicker than those with prepared bladders (17.07 vs 27.85 min, p=0.027). <h3>Conclusion</h3> Our preliminary analysis shows high feasibility and acceptability with this DBI to improve bladder filling compliance. We showed that empty bladders can be quantified by wasted patient and linear accelerator valued time, which allows an estimation of the impact on patient experience and economics of inefficient machine throughput. DBI should be incorporated into larger clinical trials to assess clinical efficacy. Additional digital biomarkers should be obtained to generate a comprehensive behavioral phenotype.

Study on the Effect of Different Bladder Filling Volume on Target Area and Organs at Risk during Three-Dimensional Brachytherapy for Postoperative Early Cervical Cancer

<h3>Purpose/Objective(s)</h3> To investigate the optimal bladder filling volume in the 3D brachytherapy of postoperative cervical cancer. <h3>Materials/Methods</h3> Patients of early cervical cancer with a positive incisal margin or insufficient safety boundary were included. 50ml, 60ml, 70ml, 80ml, 90ml, and 100ml of normal saline were randomly filled into their bladders. There was a total of 6 groups. The CT simulation positioning was performed. According to ICRU89 report, high-risk clinical target volume, bladder, rectum, and other organs at risk were delineated. The radiotherapy treatment planning system was used to make the treatment plan. The volume of HR-CTV, D90, and D2cc and D1cc of organs at risk under different volumes were recorded respectively. <h3>Results</h3> A total of 111 patients were enrolled and there were 398 person-times of 3D brachytherapy treatment program were performed. Among them, there were 66 person-times in the 50ml group, 69 person-times in the 60ml group, 66 person-times in the 70ml group, 69 person-times in the 80ml group, 72 person-times in the 90ml group, and 56 person-times in the 100ml group. Compared with the 60ml group, the volume and dosage of HR-CTV in the groups of 50ml, 70ml, 80ml, 90ml, and 100ml had no significant difference (P>0.05), D2cc and D1cc of the bladder and rectum significantly decreased, the difference was statistically significant (P<0.05). Pairwise comparison between other 5 groups, the volume and dosage of HR-CTV, D2cc and D1cc of bladder and rectum had no significant difference (P>0.05). <h3>Conclusion</h3> In the 3D brachytherapy of postoperative early cervical cancer, compared with other volumes, the bladder perfusion of 60ml can ensure the volume and dose of HR-CTV and reduce better the dose of the bladder and rectum.

Reducing PTV Margins with Daily Adaptive Radiotherapy to the Prostatic Fossa

<h3>Purpose/Objective(s)</h3> In modern trials, traditional planning target volume (PTV) margins for postoperative prostate radiotherapy have been large (7-10 mm) to account both for daily changes in patient positioning / motion and target deformation (from changes in adjacent bladder fill and/or rectal distension). With daily adaptive radiotherapy, these inter-fractional changes could be minimized, potentially reducing the margins required for treatment and improving adjacent normal tissue dosimetry. <h3>Materials/Methods</h3> A single-center retrospective study was conducted from 03/2021 to 11/2021. Patients receiving conventionally fractionated radiotherapy to their prostatic fossa +/- elective nodes with pre- and post-treatment CBCT imaging (CBCTpre and CBCTpost, respectively) were included. Clinical target volumes (CTV) were contoured by a single observer on all CBCTs (only the prostatic fossa CTV was analyzed in this study). CBCTpre and CBCTpost images were registered using the same shifts used on the day of treatment. Motion was calculated from the center of mass of CBCTpre to that of CBCTpost, which was used to determine predicted margins with Van Herk's formula. Adequate coverage with the proposed margins was verified by performing a symmetric expansion on all CBCTpre scans (PTVpre) and evaluating the overlap with CBCTpost. <h3>Results</h3> Twenty patients were included with 263 image sets available and with 248 image sets included after exclusion. The average time between scans was 10.7 ± 3.0 minutes. The estimated margins predicted to achieve ≥95% coverage for 90% of the population were 1.6 mm, 2.0 mm, and 2.2 mm (x, y, and z axes, respectively). After symmetrically expanding all CBCTpre's CTVs by 1mm, 2mm, 3mm, and 4mm, the percent of image sets achieving ≥95% coverage were 73.6%, 92.2%, 97.1%, and 98.8%. <h3>Conclusion</h3> Using daily adaptive radiotherapy could significantly decrease the required PTV margin expansions for postoperative prostate radiotherapy, as a symmetric expansion of 3 mm achieved excellent coverage in this cohort which compared favorably to historical data. Given these results were obtained from CBCTpre and CBCTpost scans in the non-adaptive setting, these results will need to be validated in a prospective cohort.

Real-World Dose Delivery Accuracy of Prostate SBRT with Tomotherapy Based Target Tracking

<h3>Purpose/Objective(s)</h3> The frameless robotic radiosurgery system target tracking system was recently adapted to Tomotherapy. While a previous dosimetric study has demonstrated comparable prostate SBRT plans between the two systems, we report here our real-world dose delivery accuracy of synchronization technology motion compensation for prostate SBRT and the initial clinical outcomes. <h3>Materials/Methods</h3> Patients undergo insertion of 3 fiducials and hydrogel before planning CT and MRI. Prostate and proximal seminal vesicles were included in the CTV. A PTV margin of 3 to 5 mm was utilized. Prescription was 40 Gy in 5 fractions. Patient motion files were analyzed and the maximum shift and gradient in each direction calculated to allow for motions to be categorized. Eight patients were enrolled in the TPS which uses daily imaging to deform VOI's and accumulate delivered doses based on organ volume and position changes. <h3>Results</h3> 14 patients with Gleason 6/7 prostate cancer were included with median prostate volume of 32.3 cm³ (17.7 - 99.6 cm³). Patient motion files showed 20 deliveries had motions <2 mm, 26 with slow position changes ≥ 2 mm. 10 deliveries had rapid position changes <5 mm and 14 had rapid changes ≥5 mm. For most OARs delivered D_max was within 2% of the planned dose. Larger differences were found for OARs located superiorly or inferiorly to the target, due to the rapid dose fall off in this direction. Large reductions in the D_max and D50 to the bladder and sigmoid are seen in patients who were asked to increase their bladder fill to reduce bowel dose. Mean dose to the CTV and PTV was found to agree to within 1.5% and 2.0% respectively. From 12 patients with median follow up time of 1 month (1 – 9 months), 3 reported grade 1 GU toxicities. 2 patients reported grade 1 GI toxicities and grade 1 fatigue. <h3>Conclusion</h3> The range of motions measured highlight the need for compensation techniques for precise dose deposition with Tomotherapy. Daily OAR variations resulted in dose delivery accuracy within 2% of planned dose.