The impact of a high-definition multileaf collimator for spine SBRT.

PURPOSE: Advanced radiotherapy delivery systems designed for high-dose, high-precision treatments often come equipped with high-definition multi-leaf collimators (HD-MLC) aimed at more finely shaping radiation dose to the target. In this work, we study the effect of a high definition MLC on spine stereotactic body radiation therapy (SBRT) treatment plan quality and plan deliverability. METHODS AND MATERIALS: Seventeen spine SBRT cases were planned with VMAT using a standard definition MLC (M120), HD-MLC, and HD-MLC with an added objective to reduce monitor units (MU). M120 plans were converted into plans deliverable on an HD-MLC using in-house software. Plan quality and plan deliverability as measured by portal dosimetry were compared among the three types of plans. RESULTS: Only minor differences were noted in plan quality between the M120 and HD-MLC plans. Plans generated with the HD-MLC tended to have better spinal cord sparing (3% reduction in maximum cord dose). HD-MLC plans on average had 12% more MU and 55% greater modulation complexity as defined by an in-house metric. HD-MLC plans also had significantly degraded deliverability. Of the VMAT arcs measured, 94% had lower gamma passing metrics when using the HD-MLC. CONCLUSION: Modest improvements in plan quality were noted when switching from M120 to HD-MLC at the expense of significantly less accurate deliverability in some cases.

Use and performance of the evolut FX transcatheter aortic valve system.

BACKGROUND: The next generation supra-annular, self-expanding Evolut FX transcatheter aortic valve (TAV) system was designed to improve catheter deliverability, provide stable and symmetric valve deployment, and assess commissural alignment during the procedure. The impact of these modifications has not been clinically evaluated. METHODS: Procedural information was collected by survey in 2 Stages: Stage I comprised 23 centers with extensive experience with Evolut TAV systems, and Stage II comprised an additional 46 centers with a broad range of balloon- and self-expanding system experience. Operators were to compare the experience with the Evolut FX to the predicate Evolut PRO+ system. RESULTS: There were 285 cases during Stage I from June 24 to August 12, 2022, and 254 cases during Stage II from August 15 to September 11, 2022. Overall, the cusp overlap technique was used in 88.6 %, and commissural alignment was achieved in 96.1 % of these cases. Compared to implanter's previous experience with the Evolut PRO+ system, less resistance was noted with the Evolut FX system: in 83.0 % of cases during vascular insertion, in 84.7 % of cases while tracking through the vasculature, in 84.4 % of cases while traversing over the arch, and 76.1 % of cases in advancing across the valve. Better symmetry of valve depth was observed in 423 of 525 cases (80.6 %). CONCLUSION: Evolut FX system design modifications translated into improvements in catheter deliverability, deployment symmetry and stability, and commissural alignment as assessed by experienced self-expanding and balloon expandable operators.

Generating 3D images of VMAT plans for predictive models and activation maps associated with plan deliverability.

BACKGROUND: Intensity modulation with dynamic multi-leaf collimator (MLC) and monitor unit (MU) changes across control points (CPs) characterizes volumetric modulated arc therapy (VMAT). The increased uncertainty in plan deliverability required patient-specific quality assurance (PSQA), which remained inefficient upon Quality Assurance (QA) failure. To prevent waste before QA, plan complexity metrics (PCMs) and machine learning models with the metrics were generated, which were lack of providing CP-specific information upon QA failures. PURPOSE: By generating 3D images from digital imaging and comminications in medicine in radiation therapy (DICOM RT) plan, we proposed a predictive model that can estimate the deliverability of VMAT plans and visualize CP-specific regions associated with plan deliverability. METHODS: The patient cohort consisted of 259 and 190 cases for left- and right-breast VMAT treatments, which were split into 235 and 166 cases for training and 24 cases from each treatment for testing the networks. Three-channel 3D images generated from DICOM RT plans were fed into a DenseNet-based deep learning network. To reflect VMAT plan complexity as an image, the first two channels described MLC and MU variations between two consecutive CPs, while the last channel assigned the beam field size. The network output was defined as binary classified PSQA results, indicating deliverability. The predictive performance was assessed by accuracy, sensitivity, specificity, F1-score, and area under the curve (AUC). The gradient-weighted class activation map (Grad-CAM) highlighted the regions of CPs in VMAT plans associated with deliverability, compared against PCMs by Spearman correlation. RESULTS: The DenseNet-based predictive model yielded AUCs of 92.2% and 93.8%, F1-scores of 97.0% and 93.8% and accuracies of 95.8% and 91.7% for the left- and right-breast VMAT cases. Additionally, the specificity of 87.5% for both cases indicated that the predictive model accurately detected QA failing cases. The activation maps significantly differentiated QA failing-labeled from passing-labeled classes for the non-deliverable cases. The PCM with the highest correlation to the Grad-CAM varied from patient cases, implying that plan deliverability would be considered patient-specific. CONCLUSION: This work demonstrated that the deep learning-based network based on visualization of dynamic VMAT plan information successfully predicted plan deliverability, which also provided control-point specific planning parameter information associated with plan deliverability in a patient-specific manner.

Implementation, Dosimetric Assessment, and Treatment Validation of Knowledge-Based Planning (KBP) Models in VMAT Head and Neck Radiation Oncology.

The aim of this study was to evaluate knowledge-based treatment planning (KBP) models in terms of their dosimetry and deliverability and to investigate their clinical benefits. Three H&N KBP models were built utilizing RapidPlan™, based on the dose prescription, which is given according to the planning target volume (PTV). The training set for each model consisted of 43 clinically acceptable volumetric modulated arc therapy (VMAT) plans. Model quality was assessed and compared to the delivered treatment plans using the homogeneity index (HI), conformity index (CI), structure dose difference (PTV, organ at risk-OAR), monitor units, MU factor, and complexity index. Model deliverability was assessed through a patient-specific quality assurance (PSQA) gamma index-based analysis. The dosimetric assessment showed better OAR sparing for the RapidPlan™ plans and for the low- and high-risk PTV, and the HI, and CI were comparable between the clinical and RapidPlan™ plans, while for the intermediate-risk PTV, CI was better for clinical plans. The 2D gamma passing rates for RapidPlan™ plans were similar or better than the clinical ones using the 3%/3 mm gamma-index criterion. Monitor units, the MU factors, and complexity indices were found to be comparable between RapidPlan™ and the clinical plans. Knowledge-based treatment plans can be safely adapted into clinical routines, providing improved plan quality in a time efficient way while minimizing user variability.

Real World Experience of a Biodegradable Polymer Sirolimus-Eluting Stent (Yukon Choice PC Elite) in Patients with Acute ST-Segment Elevation Myocardial Infarction Undergoing Primary Angioplasty: A Multicentric Observational Study (The Elite India Study).

BACKGROUND: The durable polymer drug-eluting stents (DPDES) reduce the risk of repeated target vessel revascularisation (TLR) compared with BMS, but are associated with increased risk of late adverse events. In broadly inclusive populations, the biodegradable-polymer drug-eluting stents (BPDES) have favourable results compared with DPDES in the long term. However, its use in primary angioplasty has not been adequately studied, and data of real-world clinical experience is lacking. AIM: Aim of this study was to assess the safety and efficacy of Yukon Choice PC Elite sirolimus-eluting stent (a novel BPDES) in STEMI patients undergoing primary angioplasty. METHODS: We have presented here one-year clinical follow-up data of the Yukon Choice PC Elite sirolimus-eluting stent in patients undergoing primary angioplasty. A total of 636 patients were enrolled in this single arm, prospective observational study from five centres. RESULTS: This multicentric observational study showed excellent safety and efficacy profile of the novel device at one year follow up. The device-oriented composite endpoint (DOCE) of cardiac death, target-vessel reinfarction, and target-lesion revascularisation (TLR) was 2.7%, and the patient-oriented composite endpoint (POCE) of all-cause death, any myocardial infarction, and any revascularisation was 4.2% at one year. Definite or probable stent thrombosis rate was 0.6%, and no events were recorded beyond 6 months of follow up. CONCLUSIONS: In patients with STEMI undergoing primary angioplasty, the use of Yukon Choice PC Elite (biodegradable polymer sirolimus-eluting stent) has excellent results at one year. It, therefore, represents an attractive alternative to second generation DES in this high-risk population.

Organ-specific modulation complexity score for the evaluation of dose delivery.

The purpose of this study was to correlate the modulation complexity score (MCS) with organ location and to predict potential dose errors for organs before beam delivery for intensity-modulated radiation therapy (IMRT) dosimetry. Sixteen head and neck cancer patients treated with IMRT were selected. Distribution of the relative dose error on each beam was performed using forward projection to the planned dose to compute the predicted dose after doing per-beam quality assurance. Original organ-specific modulation complexity score (oMCS) was created based on a modified MLC, which depended on organ location. First, MCS was calculated based on the change in leaf position between adjacent MLC leaves. Second, the segment edge map (SEM) calculated from the intensity map for each beam was applied to the calculation volume. The oMCS with segment edge (oMCSedge) was derived from the product of oMCS and SEM. The correlation between the dose errors (planned and predicted) and oMCSedge values was evaluated for the target and organs at risk. We have also expanded the original MCS concept to oMCSedge including the organ location. We observed a moderate correlation between the dose errors and oMCSedge for all organs and volumes of interest except the gross tumor volume, brain stem, and spinal cord. In other organs, a moderate improvement in sensitivity was observed on the SEM, which was correlated with dose errors. Although the implementation of oMCSedge would be impractical for normal clinical settings, it is expected that oMCSedge would help a treatment planner to judge whether or not the treatment plan would be acceptably delivered.

Still room for improvement: Preclinical and bench testing of a thin-strut cobalt-chromium bare-metal stent with passive coating.

There is a renewed interest in bare-metal stent (BMS) design as degradable polymer coatings are increasingly used as drug-delivery vehicles in drug-eluting stents (DESs), leaving it to the BMS platform to determine the long-term outcome of DES treatment. In this study comprising preclinical and bench tests, we compare two modern thin-strut BMSs of different design. Angiography, morphometry, and histopathology data were acquired in a porcine coronary artery model in a 28-day single-stent study (13 hybrid farm pigs) and in a 90-day overlapping-stent study (8 Yucatan mini-pigs). Standardized bench tests including ion release test were performed to compare mechanical performance of the two stent systems. We found that the optimized stent group induced significantly less neointimal formation and less inflammation than Multi-Link Vision in both (single stent and overlapping stent) porcine studies. The higher efficacy was also associated with a markedly reduced release of cobalt, nickel, chromium, and tungsten ions in physiological solution and better performance in mechanical delivery tests. In conclusion, a further increase in efficacy and better safety profile than the well-known Multi-Link Vision BMS can be achieved by careful optimization of the BMS backbone. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1612-1621, 2017.

Deliverability of the Resolute Integrity stent and a post hoc comparison of radial and femoral access: the DELIVER study.

BACKGROUND/PURPOSE: DELIVER (DELiverability of the Resolute Integrity Stent in All-Comer Vessels and Cross-OvER stenting) was a prospective, multicenter, all-comers registry to assess the deliverability of the Resolute Integrity™ zotarolimus-eluting stent (R-ZES). METHODS/MATERIALS: Patients (n=7740 patients, 10449 lesions) undergoing percutaneous coronary intervention and deemed suitable for R-ZES implantation were enrolled and treated according to standard practice of the participating centers in 30 countries. Outcomes included delivery success and in-hospital target lesion failure (TLF), major adverse cardiac event (MACE), and Academic Research Consortium definite/probable stent thrombosis. We performed a post hoc analysis comparing deliverability, in-hospital clinical outcomes and resource utilization with radial vs. femoral access. RESULTS: A high proportion of the population had complex disease (71%): mean lesion length was 26.7±17.5 mm, 35% of lesions were moderately/severely calcified and 17% were bifurcated. Femoral and radial accesses were used in 53% and 46% of patients, respectively. Patients treated using femoral access had more complex coronary artery disease. Primary delivery success was 98.9% and did not differ by approach. Radial access was associated with lower stent and balloon utilization, but higher guide catheter utilization, lower procedure duration, and contrast administered compared with femoral access. In-hospital TLF and MACE occurred in 1.6% of patients; definite or probable stent thrombosis occurred in 0.2%. Clinical outcomes did not differ by vascular access. CONCLUSIONS: R-ZES was found to be highly deliverable in a complex, all-comers, international population, regardless of whether radial or femoral access was used. In-hospital outcomes were excellent with very low risk of complications.

When is respiratory management necessary for partial breast intensity modulated radiotherapy: a respiratory amplitude escalation treatment planning study.

PURPOSE: The impact of typical respiratory motion amplitudes (∼2 mm) on partial breast irradiation (PBI) is minimal; however, some patients have larger respiratory amplitudes that may negatively affect dose homogeneity. Here we determine at what amplitude respiratory management may be required to maintain plan quality. METHODS AND MATERIALS: Ten patients were planned with PBI IMRT. Respiratory motion (2-20 mm amplitude) probability density functions were convolved with static plan fluence to estimate the delivered dose. Evaluation metrics included target coverage, ipsilateral breast hotspot, homogeneity, and uniformity indices. RESULTS: Degradation of dose homogeneity was the limiting factor in reduction of plan quality due to respiratory motion, not loss of coverage. Hotspot increases were observed even at typical motion amplitudes. At 2 and 5 mm, 2/10 plans had a hotspot greater than 107% and at 10 mm this increased to 5/10 plans. Target coverage was only compromised at larger amplitudes: 5/10 plans did not meet coverage criteria at 15 mm amplitude and no plans met minimum coverage at 20 mm. CONCLUSIONS: We recommend that if respiratory amplitude is greater than 10 mm, respiratory management or alternative radiotherapy should be considered due to an increase in the hotspot in the ipsilateral breast and a decrease in dose homogeneity.