Treatment plan quality for stereotactic treatment of multiple cranial metastases: Comparison of C-arm and O-ring treatment platforms.

C-arm linacs have been used widely to treat multiple cranial metastases using stereotactic radiosurgery (SRS). A new generation of O-ring linacs offer several workflow advantages when compared to C-arm platforms. However, O-ring linacs are not able to employ couch rotations for noncoplanar beams used in SRS treatments. This study was conducted in order to simulate further possible developments of O-ring treatment units by assessing their geometrical efficiency. In this work we compare the plan quality for C-arm versus an O-ring platform including metrics that are relevant to SRS for multiple metastases. The comparison is conducted by incorporating tilted arcs on the O-ring platform therefore introducing noncoplanarity. Total 40 patients previously treated for SRS with 20 Gy single fraction were replanned for C-arm with a standard noncoplanar 5-arc arrangement and O-ring with both coplanar and noncoplanar beams. For the O-ring plans, we considered a default 3-arc coplanar arrangement, as well as 3- and 5-arc arrangements with arcs tipped up to 10 degrees from the axial plane. Target coverage, organ-at-risk (OAR) doses, monitor unit (MU) efficiency, conformity and gradient indices were assessed for all plans. For most metrics the O-ring geometries, even the coplanar arrangement, produced statistically comparable results to the C-arm. Small but significant differences were found for the 3 arc O-ring for PTV: D90%, D2% and MU/Gy and for the 5 arc O-ring at D2% when both were compared to the C-arm. Cumulative dose volume histograms (DVHs) for normal brain showed a cross-over between the C-arm and coplanar O-ring geometry at a low dose (2.3 ± 1.8 Gy), with O-ring associated with higher volumes above this cross-over dose. However, no statistical difference was seen in the brainstem, optic pathway and volumes of normal brain receiving 12 Gy or 20 Gy. This study has found that O-ring geometry linacs can produce SRS plans of comparable quality to those from a C-arm for multiple cranial metastases.

An Experiment on the Dwell Time Effect of Rubber Seal O-Rings: Friction Force in Intermittent Reciprocating Motion.

The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring's rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.

Setup time analysis for stereotactic body radiotherapy in O-ring linear accelerator without rotational correction.

This study analyse setup time (ST) and frequency of on-board imaging for stereotactic abdomen (liver, stomach), lung, and spine radiotherapy in the absence of automatic rotational correction. Total 53 stereotactic body radiotherapy (SBRT) patients, 28 of abdomen, 19 lung, and 6 spine treated for 230 sessions in O-ring gantry accelerator were evaluated for ST analysis. The mean setup time for all patients, abdomen, lung, and spine cases were 7.7 ± 7.4 min, 9.2 ± 9.2 min, 6.3 ± 4.1 min, and 5.5 ± 3.3 min, respectively. Median number CBCT was 2. 96% of cases had a CBCT between 1 and 3, and 9 (4%) had ≥ 4 CBCTs. Overall, 38.1%, 35.5%, 22.1%, 2.2%, and 2.2% of setup time fall into window of 0-5 min, 5-10 min, 10-20 min, 20-30 min, and > 30 min. Most difficult challenge is to negotiate with unknown rotational errors. It will be easy to dealt with them without automatic rotational correction if values are known.

Comparison of skin dose in IMRT and VMAT with TrueBeam and Halcyon linear accelerator for whole breast irradiation.

With the increasing use of flattening filter free (FFF) beams, it is important to evaluate the impact on the skin dose and target coverage of breast cancer treatments. This study aimed to compare skin doses of treatments using FFF and flattening filter (FF) beams for breast cancer. The study established treatment plans for left breast of an anthropomorphic phantom using Halcyon's 6-MV FFF beam and TrueBeam's 6-MV FF beam. Volumetric modulated arc therapy (VMAT) with varying numbers of arcs and intensity modulated radiation therapy (IMRT) were employed, and skin doses were measured at five points using Gafchromic EBT3 film. Each measurement was repeated three times, and averaged to reduce uncertainty. All plans were compared in terms of plan quality to ensure homogeneous target coverage. The study found that when using VMAT with two, four, and six arcs, in-field doses were 19%, 15%, and 6% higher, respectively, when using Halcyon compared to TrueBeam. Additionally, when using two arcs for VMAT, in-field doses were 10% and 15% higher compared to four and six arcs when using Halcyon. Finally, in-field dose from Halcyon using IMRT was about 1% higher than when using TrueBeam. Our research confirmed that when treating breast cancer with FFF beams, skin dose is higher than with traditional FF beams. Moreover, number of arcs used in VMAT treatment with FFF beams affects skin dose to the patient. To maintain a skin dose similar to that of FF beams when using Halcyon, it may be worth considering increasing the number of arcs.

Feasibility of fast, four-dimensional computed tomography-based O-ring LINAC plans for lung stereotactic body radiotherapy in patients with poor performance status.

Purpose: We aimed to retrospectively analyzed the feasibility of fast four-dimensional computed tomography (4DCT)-based O-ring LINAC treatment for patients with an average respiratory amplitude was< 0.5 cm and who cannot endure long treatment times due to poor performance status in lung 4D-stereotactic body radiotherapy (SBRT). Methods: This study included data of 38 patients who received lung 4D-SBRT and had average respiratory amplitude< 0.5 cm in the full phase. C-arm LINAC plans were based on 4DCT data obtained at phase values ranging from 20-70% using a C-arm LINAC. O-ring LINAC plans were retrospectively established based on 4DCT data obtained at phase values of 0-90% using an O-ring LINAC. The conformity index (CI), homogeneity index (HI), and gradient measurement of the planning target volumes (PTV) were analyzed to compare dosimetric data between C-arm LINAC and O-ring LINAC plans. Organs at risk were analyzed in accordance with the Radiation Therapy Oncology Group 0915 protocol. Treatment delivery time and total monitor units were analyzed to compare the efficiency of treatment delivery. Statistical comparisons were performed using the Wilcoxon signed-rank test (P< 0.05). Results: For the PTV, there was no significant difference in the CI or HI between C-arm LINAC and O-ring LINAC plans. For organs-at-risk, all plans met the criteria for dose constraint. There was a significant difference between C-arm LINAC and O-ring LINAC plans except in the spinal cord. Treatment delivery time was 92% longer for C-arm LINAC plans than for O-ring LINAC plans. The total MU value for C-arm LINAC plans was 9.6% higher than that for O-ring LINAC plans. Conclusion: We verified the feasibility of fast 4DCT-based O-ring LINAC treatment for patients with average respiratory amplitude< 0.5 cm and who cannot endure long treatment times due to poor performance status in lung 4D-SBRT.

Comparison of the Ventral Approach to the Canine Hip Joint Using Gelpi Retractors and an Elastic O-Ring Wound Retractor.

This study included 10 fresh adult cadavers of large breed dogs (6 males and 4 females). Their weight ranged from 25 to 45 kg (mean ± SD: 33.9 ± 6.2 kg). The breeds represented were crossbreed dogs (n = 5), German shepherds (n = 2), Bernese mountain dogs (n = 1), American Staffordshire terriers (n = 1), and Gordon setters (n = 1). Access to the target area and identification of the femoral head and neck was achieved with two Gelpi retractors inserted orthogonally and with the O-WR in all procedures. In each dog, the approach to the hip joint was made on the left and right sides. There was no significant difference in the area of the surgical wound bed between the two sides using either the Gelpi retractors (-0.52 ± 1.87 cm2; CI 95%: -1.86, 0.81 cm2; p = 0.398) or the O-WR (-0.27 ± 2.34 cm2; CI 95%: -1.94, 1.41 cm2; p = 0.729). The area of the surgical wound bed was 6.28 ± 1.72 cm2 (2.72-9.70 cm2) for the Gelpi retractors and 6.34 ± 1.81 cm2 (4.13-10.77 cm2) for the O-WR, and the difference between the Gelpi retractors and the O-WR was not significant (-0.06 ± 1.72 cm2; CI 95%: -0.86, 0.74 cm2; p = 0.879).

Novel antibiotic irrigation device versus standard O-ring wound retractor in the prevention of surgical site infection following colorectal resection.

PURPOSE: We sought to compare the effectiveness of a novel antibiotic irrigation device to the standard O-ring wound retractor in preventing surgical site infections (SSIs) following colorectal resections. METHODS: This single-arm clinical trial included patients undergoing colorectal resections utilizing the novel device. A retrospective cohort of patients undergoing the same procedures with the O-ring retractor was selected as the control group. The primary outcome assessed was SSI. Secondary outcomes assessed were overall complications, hospital length of stay (LOS), and 30-day readmission. A univariable and multivariable logistic regression model was built to evaluate the association between SSI as the outcome variable and the use of the novel device as the main independent variable. The model was adjusted for any confounding variables. RESULTS: Eighty-six novel device cases and 170 O-ring retractor cases were enrolled. There were no significant differences between the two groups in terms of demographics and preoperative comorbidities. Cases with the novel device had fewer Pfannenstiel incisions (1.2% vs. 14.6%, p < 0.001). There were no other significant differences in intraoperative variables. SSI rates were significantly lower in the novel device group (1.2% vs. 9.1%, p = 0.014). There were no other significant differences in postoperative complications. Multivariable logistic regression with backward elimination showed that the use of the novel device was significantly more effective against SSI by 92.5% compared to the use of the O-ring retractor. CONCLUSION: The novel device may contribute to lower SSI rates compared to the O-ring retractor following colorectal resection.

Quality assessment of automatically planned O-Ring linac SBRT plans for pelvic lymph node metastases, finding the optimal minimum target size by comparison with robotic SBRT.

PURPOSE: The purpose of this study is to assess the quality of automatic planned O-Ring Halcyon linac SBRT plans for pelvic lymph node metastases and to establish an absolute PTV volume threshold as a plan quality prediction criterion. Compliance of the plans to institutional SBRT plan evaluation criteria and differences in plan quality and treatment delivery times between Halcyon Linac and CyberKnife robotic SBRT were evaluated. METHODS: Twenty-one CyberKnife treatment plans were replanned for Halcyon. Prescription doses range was 26-40 Gy in mean three fractions. The mean/median planning target volume was 4.0/3.6 cm3 . Institutional criteria for the plan evaluation were: New Conformity Index (NCI), Conformity Index (CI), Modified Gradient Index (MGI), selectivity index reciprocal (PIV/TVPIV ), and the target coverage by prescription isodose (%PIV). Statistical analysis based on the receiver operating characteristic (ROC) curve was used to determine a plan quality predictor threshold of the PTV volume. Comparative analysis of normal tissue complication probabilities (NTCP) was used to assess the risk of toxicity in healthy tissues. RESULTS: Seventy-one percent (n = 15)/95% (n = 20) of Halcyon and 81% (n = 17)/100% (n = 21) of CK plans fulfilled all ideal/tolerance criteria. For PTVs above a found optimal threshold of 2.6 cm3 (71%, n = 15), no statistically significant difference was observed between the CI, NCI, PIV/TVPIV , and MGI indexes of both groups, while the coverage (%PIV) was statistically but not clinically significantly different between cohorts. Significantly shorter delivery times are expected with Halcyon. No significant differences in NTCP were observed. CONCLUSION: All but one automatically optimized Halcyon treatment plans demonstrated ideal or acceptable performance. PTV threshold of 2.6 cm3 can be used as decision criteria in clinical settings. The results of our study demonstrated the promising performance of the Halcyon for pelvic SBRT, although plan-specific QA is required to verify machine performance during plan delivery.

Effective and Secure Closure after Duodenal Endoscopic Submucosal Dissection: Combination of Endoscopic Ligation with O-Ring Closure and Over-the-Scope Clip.

Duodenal endoscopic submucosal dissection (ESD) is associated with high incidences of intraoperative complications and delayed adverse events (AEs). Delayed AEs can be reduced by closing the post-ESD defects. We developed a new method of closure after duodenal ESD, combining endoscopic ligation with O-ring closure (E-LOC) with an over-the-scope clip (OTSC) (Band OTSC; B-OTSC). Here, we conducted a single-center, retrospective, observational study to investigate the efficacy and safety of the B-OTSC method for preventing delayed AEs in patients undergoing duodenal ESD. The study included nine patients with superficial nonpapillary duodenal epithelial tumors who underwent ESD and were closed with B-OTSC from February 2021 to February 2023. There were no delayed AEs (0%), the mean (± standard deviation) closure time was 53 ± 21.6 min, the complete closure rate was 100%, and the mean hospital stay was 7.8 ± 1.8 days. The sustained closure rates at postoperative days 3 and 7 were 88.9% and 88.9%, respectively. The historical analysis indicated a significant difference in cost between B-OTSC and conventional OTSC (p < 0.01). In conclusion, B-OTSC was a safe, secure, and cost-effective method of closure after duodenal ESD, even in patients with post-ESD defects of more than half the circumference.

A Leakage Prediction Model for Sealing Performance Assessment of EPDM O-Rings under Irradiation Conditions.

In this work, a model for predicting the leakage rate was developed to investigate the effect of irradiation on the sealing performance of ethylene propylene diene monomer (EPDM) O-rings. The model is based on a mesoscopic interfacial gap flow simulation and accurately predicts the sealing performance of irradiated and non-irradiated materials by utilizing the gap height as an indicator in a mechanical simulation of the O-ring under operating conditions. A comparison with vacuum test results indicates that the model is a good predictor of leak initiation. The positive pressure leakage of the O-rings was investigated numerically. The results show the following. The sealing performance of the non-irradiated O-ring is much better than that of the irradiated one. The sealing performance is the worst at 0. 713 MGy and the best at 1.43 MGy, and the seal is maintained at an absorbed dose of 3.55 MGy. A theoretical analysis of the non-monotonic variation using the proposed model shows that the leakage behavior of the O-rings depends not only on the material properties but also on the roughness and prestressing properties. Finally, a method was proposed to classify the sealing performance, using the maximum allowable leakage rate as an indicator.

Alexis O-ring wound retractor versus traditional metal retractors for the prevention of postcaesarean surgical site infections.

BACKGROUND: Postcaesarean surgical site infections (SSI) remain a burden globally. The Alexis® O C-Section Retractor, a plastic sheath retractor known to have decreased incidence of SSIs in gastrointestinal surgery, is yet to have its efficacy established during caesarean section (CS). This study aimed to compare the differences in the rate of postcaesarean surgical wound site infections between the Alexis® retractor and traditional metal retractors during CS at a large tertiary hospital in Pretoria. METHODS: Pregnant women scheduled for elective CS were prospectively randomised to either the Alexis® retractor group or the traditional metal retractor group at a tertiary hospital in Pretoria between August 2015 and July 2016. The defined primary outcome was development of SSI, and secondary outcomes comprised patients' peri-operative parameters. All participants' wound sites were observed in the hospital for 3 days before discharge and again at 30 days postpartum. Data were analysed using SPSS version 25 with p  0.05 considered significant. RESULTS: A total of 207 participants were involved, Alexis® (n = 102) and metal retractors (n = 105). None of the participants developed postsurgical site wound infection after 30 days, and there were no differences in time to delivery, total operative time, estimated blood loss or postoperative pain between the two arms of study. CONCLUSION: The study found no difference in participants' outcomes using the Alexis® retractor in comparison with the traditional metal wound retractors. We suggest that the use of Alexis® retractor be at the surgeon's discretion and its routine use not advised for now.Contribution: This research being the first of its kind in South Africa in which patients' clinical outcomes were compared post caesarean section from Alexis's plastic sheath group and metal retractors group in an attempt to proffer solution to the high burden of SSI. Although no difference was seen at this point, the research was pragmatic, as it was carried out in a setting with high burden of SSI. The study is going to serve as a baseline against which studies carried out in future can be compared.

Retention force of Molloplast-B with ball attachment in implant-supported overdentures: An in vitro study.

Aim: The purpose of this study is to evaluate the retention effectiveness of Molloplast B as a female attachment compared to O rings' in implant supported overdentures. Settings and Design: This systematic review and meta-analysis was evaluated using the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Materials and Methods: Sixteen female part models were divided into two groups: eight female parts made with O ring (Group A) and eight female parts made with Molloplast B (Group B). All of the models were soaked in artificial saliva for 24 h, then, their retention force was measured in Newton using a Universal mechanical testing machine, initially, after 500, after 1000, and after 1500 of loading and dislodging cycles. Statistical Analysis Used: : The statistical analysis was conducted by using one way ANOVA test and Bonferroni test. SPSS Software (SPSS, Version 27, IBM Co., Chicago, IL, USA). Results: After 1500 loading and dislodging cycles, Group B has the highest mean retention force (4.09), followed by Group A, which has a mean retention force of 3.73. Conclusion: Molloplast B with a 2.7 mm diameter ball attachment lost the least amount of retention force after 1500 loading and dislodging cycles.

Research on the Material Compatibility of Elastomer Sealing O-Rings.

Significant attention has been paid to combustion engines for the utilization of new liquid fuels and their testing at the present. Research activities in ensuring the optimum function of the engine by watching sealing and distribution rubber elements, which are part of fuel systems, should be an integral part of fuels research. When evaluating fuels utilization in combustion engines, the issue has to be judged in a complex. However, when using biofuels in combustion engines, it is not always simple owing to the different degradation properties of these products. Elastomer material is not entirely resistant to various types of fuels. More or less, it is possible to expect changes in its mechanical properties. For the evaluation of the functionality of elastomer sealing elements based on ACM, HNBR and FVMQ type O-rings with pure and blended fuels, the evaluation of changes in mass, hardness Shore A, permanent deformation CS, tensile strength TS and deformation Eb after immersion with the tested fuel is mainly used. Permanent changes were found by the tests. The degradation of elastomer O-rings was more pronounced for the tested fuels containing ethanol, iso-butanol, n-butanol, methanol and dodecanol. HVO 100 fuel containing hydrotreated vegetable oil did not show significant degradation of elastomer O-ring seals. Of the O-rings tested, the FVMQ type O-rings showed the best performance in terms of material compatibility for all fuels tested.

Examination of conversion method of dose distribution of lung cancer IMRT using fluence reversible calculation function in O-ring type linac and C-type linac.

Generally, converting irradiation plans between C-arm linacs (C-linac) when the linac fails is possible without recalculating the dose distribution using a treatment planning system (TPS), because they have similar mechanical structure. However, the O-ring-type linac (O-linac) differs from the C-linac in forming the dose distribution. Therefore, if O-linac breaks down, it is necessary to formulate a treatment plan from scratch. In this study, we investigated a method for converting irradiation from an O-linac to a C-linac. Thirty patients with lung cancer who underwent volumetric-modulated arc therapy with an O-linac were included in this study. The O-linac dose distribution was converted into energy fluence by the function of the TPS. The alternative linac multi-leaf collimator (MLC) was then optimized to achieve energy fluence. The homogeneity index, conformity index, and planning treatment volume (D95%, D2%) of the converted plan were compared with the original plan. For organ at risk (OAR), the dose-volume histograms (DVHs) of the lung, esophagus, heart, and spinal cord were evaluated. Additionally, the shapes of the isodose curves were compared using the Dice similarity coefficient (DSC). There was no significant difference between the target and OARs (p > 0.05). The mean DSCs of 30% to 100% isodose curves of the prescribed dose and the isodose ≥ 105% and ≤ 20%were > 0.8 and < 0.8, respectively. Due to the structural differences of MLC, the dose-volume and generation positions were different in the dose range of ≥ 105% and ≤ 20%; hence, DSCs decreased. However, no statistically significant difference in the DVH was identified for either treatment plan. Based on this result, we propose a simple replanning method for performing MLC fitting after converting the dose to the energy fluence.

[Gantry QA Using Three-dimensional Diode Array Detector on O-ring Linear Accelerator].

PURPOSE: It is necessary to perform gantry quality assurance (QA) in high precision radiotherapy. However, the O-ring type linear accelerator (Halcyon) does not have a light field and laser as a reference of isocenter point. The aim of this study is to investigate the usefulness of a three-dimensional diode array detector for gantry angle QA, and an O-ring type linear accelerator. METHOD: The gantry angle and rotational center were verified using the ArcCHECK 3D diode array on the general linear accelerator (TrueBeam) as a reference and Halcyon. The gantry angles were measured at 0, 90, 180, and 270°. The accuracy of the gantry rotational center was evaluated using rotational irradiation in the clockwise and counterclockwise directions between 181° and 179°. RESULTS: The QA system with ArcCHECK was able to apply on the TrueBeam and Halcyon. As a result of the accuracy of the gantry angle, the maximum error of value calculated from ArcCHECK was 0.1° compared with the nominal gantry angle of Halcyon. As a result of the accuracy of the gantry rotation isocenter of Halcyon, the distance between the isocenter and the gantry rotation center was 0.45 mm and 0.41 mm in the clockwise and counterclockwise directions, respectively. CONCLUSION: The QA system with ArcCHECK was useful for the gantry angle and the rotation center accuracy on the Halcyon.

Early Experience with the New Ovation Alto Stent Graft in Endovascular Abdominal Aortic Aneurysm Repair.

INTRODUCTION: Since 2010, the Ovation Abdominal Stent Graft System has offered a new sealing concept, achieved by a sealing ring filled with polymer 13 mm from the renal arteries. In the latest version, called Ovation Alto, the sealing ring is relocated 6 mm closer to the top of the fabric. This study describes the early clinical outcomes, after CE Mark approval in August 2020, of endovascular aneurysm repair with the Alto endograft. REPORT: Eleven patients underwent endovascular aneurysm repair with implantation of Ovation Alto endografts. All patients were male, and the median age was 75 (IQR 5.5) years. Hostile proximal aortic neck (<10 mm) was identified in six cases (54.5%). All procedures were performed using bilateral percutaneous approaches with no groin complications. The median procedure time was 58 (IQR 7.2) minutes, the median contrast volume used was 65 (IQR 4.2) mL, and the median blood loss 40 (IQR 12.4) mL. Technical success was achieved in all cases. The median stent graft landing distance between the top of the fabric and the lowest renal artery was 1.4 (IQR 0.8) mm. No intra-operative high flow endoleaks were registered. At one and six month follow up, there was 100% clinical success (no type I/III endoleak, sac enlargement, stent graft migration, polymer leakage, abdominal aortic aneurysm related mortality, or secondary intervention). DISCUSSION: Initial experience confirms the early technical and clinical success of the new Ovation Alto stent graft. Technical modifications to the endograft could allow for accommodation of a more comprehensive range of anatomies on label. Further studies are needed to evaluate long term durability outcomes.

Evaluation of Changes in the Mechanical Properties of O-Ring in One Piece and Two Piece Ball Retained Implant Supported Overdentures: A Three-Year Retrospective Study.

The O-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of O-rings after 3 years in function in 1 and 2-piece implant-supported overdentures. The O-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 × 13 mm) and 2-piece (Neo Biotech, 3.3 × 13 mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage, and elasticity using Pin on Disc method, USB Digital Camera in 30× zoom and Universal Tensile Machine, respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the 2-piece system with an abrasive type of damage while 46% wear in the 1-piece system with a compressive type of damage. The O-rings in 1-piece system showed increase in elongation and maximum displacement to 2% and 7%, respectively, whereas the 2-piece system showed decrease in elongation and maximum displacement by 13% and 6%, respectively. In 1-piece system, the loss of retention was more with slow wear rate, and in 2-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.

Modification of O-ring intrauterine devices (IUDs) in mares: Contraception without estrus suppression.

A significant welfare concern for those within the horse industry is that of the overpopulation in free-roaming horses in the western US. The goal of the present study was to identify a humane and inexpensive means of providing contraception and reducing pregnancy rates in a way that could be applied to free-roaming horses on the western U.S. open range lands. A series of studies was conducted utilizing the previously-described silastic O-ring intrauterine devices (IUDs). Throughout these studies pregnancy was successfully prevented in mares with an O-ring IUD, but collective retention rates failed to exceed 50% regardless of size or durometer (material hardness/malleability). When the O-ring IUDs were compared to the recently-described Y-design IUDs (Holyoak et al., 2021) the Y-design IUDs had a markedly greater rate of retention; therefore, the Y-design IUDs would be most appropriate for potential use in free-roaming horses. Assessment of mare records revealed that the vast majority of mares continued to have ovulations and mating continued to occur while the IUDs were in place. A few mares had multiple small ovarian follicles when the IUD was in utero. Findings indicate that utilizing an IUD with the expectation of estrus suppression in mares would fail to be fruitful.

Automated treatment planning of prostate stereotactic body radiotherapy with focal boosting on a fast-rotating O-ring linac: Plan quality comparison with C-arm linacs.

PURPOSE: The integration of auto-segmentation and automated treatment planning methods on a fast-rotating O-ring linac may improve the time efficiency of online adaptive radiotherapy workflows. This study investigates whether automated treatment planning of prostate SBRT with focal boosting on the O-ring linac could generate plans that are of similar quality as those obtained through manual planning on clinical C-arm linacs. METHODS: For 20 men with prostate cancer, reference treatment plans were generated on a TrueBeam STx C-arm linac with HD120 MLC and a TrueBeam C-arm linac with Millennium 120 MLC using 6 MV flattened dual arc VMAT. Manual planning on the Halcyon fast-rotating O-ring linac was performed using 6 MV FFF dual arc VMAT (HA2-DL10) and triple arc VMAT (HA3-DL10) to investigate the performance of the dual-layer MLC system. Automated planning was performed for triple arc VMAT on the Halcyon linac (ET3-DL10) using the automated planning algorithms of Ethos Treatment Planning. The prescribed dose was 35 Gy to the prostate and 30 Gy to the seminal vesicles in five fractions. The iso-toxic focal boost to the intraprostatic tumor nodule(s) was aimed to receive up to 50 Gy. Plan deliverability was verified using portal image dosimetry measurements. RESULTS: Compared to the C-arm linacs, ET3-DL10 shows increased seminal vesicles PTV coverage (D99% ) and reduced high-dose spillage to the bladder (V37Gy ) and urethra (D0.035cc ) but this came at the cost of increased high-dose spillage to the rectum (V38Gy ) and a higher intermediate dose spillage (D2cm). No statistically significant differences were found when benchmarking HA2-DL10 and HA3-DL10 with the C-arm linacs. All plans passed the patient-specific QA tolerance limit. CONCLUSIONS: Automated planning of prostate SBRT with focal boosting on the fast-rotating O-ring linac is feasible and achieves similar plan quality as those obtained on clinical C-arm linacs using manual planning.

A systematic review and meta-analysis of the attachments used in implant-supported overdentures.

AIM: To evaluate the survival rate, tissue response, and patient satisfaction of different attachments used in implant overdenture. SETTINGS AND DESIGN: Systematic Review and Meta-analysis. MATERIALS AND METHODS: Electronic search of peer-review articles published between 2001 and 2019 assessing the attachments used for implant-supported overdentures was done according to PRISMA Guidelies. The review evaluated sixteen articles related to survival of the attachments, the reaction of the soft and hard tissues along with repair and maintenance of the attachments, and overall performance of the overdenture attachments. STATISTICAL ANALYSIS USED: There is statistically significant heterogeneity (Q =374.7403, df = 15, and P < 0.0001). The statistics of fixed-effect model reported an MD of - 0.0880 (95% CI = -0.1536; 0.0225). RESULT: The review evaluated the 16 articles that met with the inclusion and search criteria. The studies were the combination of bar and ball attachments and their subtypes, magnetic and bar attachments, and locator in combination with other attachments. The meta-analysis of combined 16 studies reported acceptable heterogeneity among 16 studies (I 2 = 96%) and reported to be statistically significant (P < 0.01). CONCLUSION: The survival rate of attachments was in the range of 95.8%-97.5% for bar, 96.2%-100% for ball, 90%-92% for magnet and locator attachments were in the range of 97% after a mean follow-up period of 3 years. The bar attachments reported moderate tissue reaction in the form of mucosal changes, gingival inflammation, and bone resorption. The locator attachments require higher maintenance and repair. The magnetic attachments produce higher bone resorption and readily displace under functional force. Patient satisfaction and compliance was higher for ball, locator, and bar attachments as well as low for magnetic attachment. Thus, the ball and locator attachments excellently perform in terms of survival rate, tissue response, and patient satisfaction.