Treatment Delivery Systems Research Articles

Clinical commissioning of intensity-modulated proton therapy systems: Report of AAPM Task Group 185.

Proton therapy is an expanding radiotherapy modality in the United States and worldwide. With the number of proton therapy centers treating patients increasing, so does the need for consistent, high-quality clinical commissioning practices. Clinical commissioning encompasses the entire proton therapy system's multiple components, including the treatment delivery system, the patient positioning system, and the image-guided radiotherapy components. Also included in the commissioning process are the x-ray computed tomography scanner calibration for proton stopping power, the radiotherapy treatment planning system, and corresponding portions of the treatment management system. This commissioning report focuses exclusively on intensity-modulated scanning systems, presenting details of how to perform the commissioning of the proton therapy and ancillary systems, including the required proton beam measurements, treatment planning system dose modeling, and the equipment needed.

The effects of MgS nanoparticles-Cisplatin-bio-conjugate on SH-SY5Y neuroblastoma cell line.

Magnesium sulfide nanoparticles (MgS NPs) is a nanomaterial that has an important place in diagnosis, treatment, diagnosis, and drug delivery systems. Neuroblastoma, a type of brain cancer, is an extremely difficult cancer to treat with today's treatment options. This study was carried out to determine the cytotoxic, oxidant, and antioxidant effects on the neuroblastoma cancer line (SH-SY5Y cell line) along with the green synthesis and characterization of MgS NPs structures. MgS NPs were synthesized by green synthesis using Na2S and Punica granatum, a cleaner method for toxic effects, and characterized using Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, X-Ray diffraction methods. In cell culture, SH-SY5Y cells were grown in a suitable nutrient medium under favorable conditions. Five different doses of MgS NPs (10, 25, 50, 75, and 100µg/mL) were applied to the cell line for 24h. The analysis of the MgS NPs applications was performed with MTT cytotoxicity test and total oxidant and total antioxidant tests. According to the data obtained, 75μg/mL MgS NPs application decreased cancer cell viability up to 48.54%. MgS NPs exhibited a dose-dependent effect on the SH-SY5Y cell line. Also, it was determined that MgS NPs increased oxidant activity in neuroblastoma cells, which was compatible with the cytotoxicity test. As a result, MgS NPs exhibited an effective activity on the neuroblastoma cell line. It was clearly seen that NPs obtained by green synthesis prevented the related cancer line from proliferating.

Technical Note: Extended field-of-view (FOV) MRI distortion determination through multi-positional phantom imaging.

Comprehensive characterization of geometric distortions for MRI simulators and MRI‐guided treatment delivery systems is typically performed with large phantoms that are costly and unwieldy to handle. Here we propose an easily implementable methodology for MR distortion determination of the entire imaging space of the scanner through the use of a compact commercially available distortion phantom. The MagphanRT phantom was scanned at several locations within a MR scanner. From each scan, an approximate location of the phantom was determined from a subset of the fiducial spheres. The fiducial displacements were determined, and a displacement field was fitted to the displacement data using the entire multi‐scan data set. An orthogonal polynomial expansion fitting function was used that had been augmented to include independent rigid‐body transformations for each scan. The rigid‐body portions of the displacement field were thereafter discarded, and the resultant fit then represented the distortion field. Multi‐positional scans of the phantom were used successfully to determine the distortion field with extended coverage. A single scan of the phantom covered 20 cm in its smallest dimension. By stitching together overlapping scans we extended the distortion measurements to 30 cm. No information about the absolute location or orientation of each scan was required. The method, termed the Multi‐Scan Expansion (MSE) method, can be easily applied for larger field‐of‐views (FOVs) by using a combination of larger phantom displacements and more scans. The implementation of the MSE method allows for distortion determination beyond the physical limitations of the phantom. The method is scalable to the user’s needs and does not require any specialized equipment. This approach could open up for easier determination of the distortion magnitude at distances further from the scanner’s isocenter. This is especially important in the newly proposed methodologies of MR‐only simulation in RT and in adaptive replanning in MR linac systems.

Synergistic effects of Cinnamomum cassia L. essential oil in combination with polymyxin B against carbapenemase-producing Klebsiella pneumoniae and Serratia marcescens.

Multidrug resistance prompts the search for new sources of antibiotics with new targets at bacteria cell. To investigate the antibacterial activity of Cinnamomum cassia L. essential oil (CCeo) alone and in combination with antibiotics against carbapenemase-producing Klebsiella pneumoniae and Serratia marcescens. The antimicrobial susceptibility of the strains was determined by Vitek® 2 and confirmed by MALDI-TOF/TOF. The antibacterial activity of CCeo and its synergism with antibiotics was determined using agar disk diffusion, broth microdilution, time-kill, and checkboard methods. The integrity of the bacterial cell membrane in S. marcescens was monitored by protein leakage assay. CCeo exhibited inhibitory effects with MIC = 281.25 μg.mL-1. The association between CCeo and polymyxin B showed a decrease in terms of viable cell counts on survival curves over time after a 4 hour-treatment with a FIC index value of 0.006. Protein leakage was observed with increasing concentrations for CCeo and CCeo + polymyxin B treatments. CCeo showed antibacterial activity against the studied strains. When associated with polymyxin B, a synergistic effect was able to inhibit bacterial growth rapidly and consistently, making it a potential candidate for the development of an alternative treatment and drug delivery system for carbapenemase-producing strains.

Multi-institutional dosimetric delivery assessment of intracranial stereotactic radiosurgery on different treatment platforms

Background and purposeAssessment of dosimetric accuracy of radiosurgery on different treatment platforms. Material and methodsThirty-three single fraction treatment plans were assessed at thirty centres using an anthropomorphic head phantom with target and brainstem structures. The target being a single irregular shaped target, ~8 cc, 10 mm from the brainstem. The phantom was “immobilised”, scanned, planned and treated following the local protocols. EBT-XD films and alanine pellets were used to measure absolute dose, inside both the target and the brainstem, and compared with TPS predicted dose distributions. ResultsPTV alanine measurements from gantry-based linacs showed a median percentage difference to the TPS of 0.65%. Cyberknife (CK) had the highest median difference of 2.3% in comparison to the other platforms. GammaKnife (GK) showed the smallest median of 0.3%. Similar trends were observed in the OAR with alanine measurements showing median percentage differences of1.1%, 2.0% and 0.4%, for gantry-based linacs, CK and GK respectively. All platforms showed comparable gamma passing rates between axial and sagittal films. ConclusionsThis comparison has highlighted the dosimetric variation between measured and TPS calculated dose for each delivery platform. The results suggest that clinically acceptable agreement with the predicted dose distributions is achievable by all treatment delivery systems.

Avoiding indirect effects of COVID-19 on maternal and child health

Avoiding indirect effects of COVID-19 on maternal and child health

A Multidisciplinary Approach to Implement Image-Guided Craniospinal Irradiation

ButLes considérations pratiques dictent un changement dans la technique craniospinale (CSI). Nous faisons rapport de notre expérience dans l’élaboration et l'affinage des paramètres de planification et de traitement CSI, en utilisant la technique de radiothérapie à modulation d'intensité guidée par l'image (IG-IMRT). Méthodologie et matérielDeux valeurs institutionnelles ont guidé le développement: la prise de décision multidisciplinaire et la coordination des considérations tout au long de la simulation, de la planification et de la prestation des soins. La paramètres d'immobilisation du patient et de simulation ont été choisis en fonction des limitations des systèmes de prestation des traitements. Des cartes de mesure de fluence ont été acquises afin de vérifier la dose dans les zones de chevauchement. Une analyse de robustesse a été faite afin d’évaluer les répercussions des erreurs potentielles de positionnement mesurées par la vérification IGRT. Les considérations liées au traitement comprennent l'ordre d'imagerie des isocentres et l'ordre de traitement, ainsi que les valeurs respectives de fréquence IGRT, de modalité et de seuils de superposition d'images. RésultatsLes mesures globales sur film se situaient à moins de 3% des doses planifiées, confirmées par des mesures sur fantôme composite montrant que tous les points se situaient à au moins 97% de la dose planifiée. L'analyse de sensibilité du positionnement suggère qu'une tolérance de positionnement de 3 mm était suffisante pour assurer la confiance envers le plan administré. Comme les organes à risque les plus importants se situaient dans l'isocentre supérieur, l'ordre de traitement quotidien des isocentre a été confirmé ainsi: supérieur, milieu, inférieur. Le guidage quotidien par tomodensitométrie à faisceau conique a été retenu pour tous les isocentres (seuil de rotation de 3°). Sauf dans la direction supéro-inférieure des isocentres du milieu et inférieur, ajustée à 3 mm conformément aux résultats de l'analyse de sensibilité, un seuil translationnel de 1 mm a été utilisé. ConclusionsUne technique CSI pour la radiothérapie à modulation d'intensité guidée par l'image a été développée et mise en œuvre dans notre institution en utilisant une approche multidisciplinaire. Ce processus met en lumière l'approche collaborative et itérative utilisée pour intégrer avec succès une nouvelle technique de traitement dans une ère de guidage par l'image.

Halcyon clinical performance evaluation: A log file-based study in comparison with a C-arm Linac

PurposeThe aim of this study is to compare the dosimetric and mechanical accuracy of Volumetric Modulation Arc Therapy (VMAT) delivery on the Halcyon, a recent ring-shaped Treatment Delivery System (TDS) featuring fast rotating gantry, with a conventional C-arm Linac. MethodsThe comparison was performed via log file analysis, where mechanical parameters of related components was extracted. 480 and 3951 VMAT log files of clinically delivered fractions from a Halcyon and a TrueBeam Linac were analyzed respectively. The relations between mechanical parameters and errors were extensively explored to further investigate the differences between the two Linacs. The mechanical parameter fluctuations were taken into account for dose recalculations, and the Dose Volume Parameters (DVP) on the PTV were evaluated to quantify such dosimetric variations. ResultsThe Multi-Leaf Collimator (MLC) leaf mean Root Mean Square (RMS) errors were 0.028 mm and 0.031 mm for Halcyon and TrueBeam respectively. Maximum systematic error on the MLC leaves introduced by the gravity effect were 0.04 mm and 0.01 mm for the Halcyon and TrueBeam respectively. Thanks to the O-ring design, the Halcyon achieved 0.035° in mean RMS error in gantry angle compared with the 0.065° of the TrueBeam. Overall mechanical errors introduced similar levels of dose-volume parameter variations (about 0.1%) on both Linacs. Conclusion: The Halcyon TDS can achieve similar mechanical leaf positioning accuracy compared with the TrueBeam TDS with a doubled delivery speed. In terms of dosimetric accuracy, The DVP standard deviations on the studied TB are generally larger than that on the Halcyon.

Abstract P4-12-29: Utility of surface guide radiation therapy (SGRT) in radiation therapy for breast cancer

Abstract Purpose: Radiation therapy has been shown to be a highly effective treatment for breast cancer. Historically, patient setup for daily treatment has required a set of permanent tattoos. However, due to a variety of reasons, it may be hard to align patients to these marks and the marks can also cause distress in many patients. National Comprehensive Cancer Network’s (NCCN) radiation therapy guidelines recommend weekly radiation ports films; however, many centers perform daily image guidance using x-rays for breast treatments prior to radiation delivery, increasing both radiation dose and treatment time. Surface Guided Radiation Therapy (SGRT) is a technique which is being adopted by radiation therapy centers to aid in patient’s setup and treatment delivery accuracy. SGRT is safe and non-invasive, using visible light to compare the patient’s skin surface in the treatment room to the planned treatment position with sub-millimeter accuracy. SGRT can also automatically signal for the treatment delivery system to pause radiation if the patient moves out of the desired position. The aim of this study was to evaluate the AlignRT (Vision RT, Ltd, London, United Kingdom) SGRT system for patient setup accuracy in comparison to a 3-point tattoo setup and daily KV pair imaging. Methods: A total of 20 breast cancer patients (600 radiation fractions) were setup using a 3-point tattoo technique and then positioned using AlignRT. Inter-fraction positions were analyzed between all three techniques, namely tattoo, AlignRT and kV imaging. In addition, the AlignRT system was used to evaluate that patient’s position during breath hold. This deep inspiration breath hold (DIBH) technique is designed to provide cardiac sparing during left breast radiotherapy. Results: Using 3-point tattoo setup, an average magnitude of 5.7±3 mm error from isocenter was measured, compared to 2.4±1 mm using surface guidance. Statistically significant 3d shift vectors were found between patient setup using 3-point tattoo and SGRT techniques, however between SGRT and daily KV imaging 3d shift vectors were not statistically significant. AlignRT based DIBH showed the distance between the heart and chest-wall at the mid tangential beam level, based on weekly port films, to be within 2±1 mm of the planned level. Conclusion: SGRT has been shown to improve the accuracy of patient setup compared to 3-point tattoos and is comparable to daily KV imaging for isocentric setup. SGRT can be used in clinics to reduce the frequency of KV imaging and therefore additional radiation exposure. SGRT can also remove setup tattoo requirements which are placed during simulation which provide a permanent reminder to patients of their cancer and treatment. SGRT has also been demonstrated to ensure adequate and reproducible breath hold for DIBH left sided breast treatments. Citation Format: Snehal Desai. Utility of surface guide radiation therapy (SGRT) in radiation therapy for breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-29.

A standardized commissioning framework of Monte Carlo dose calculation algorithms for proton pencil beam scanning treatment planning systems.

Treatment planning systems (TPSs) from different vendors can involve different implementations of Monte Carlo dose calculation (MCDC) algorithms for pencil beam scanning (PBS) proton therapy. There are currently no guidelines for validating non-water materials in TPSs. Furthermore, PBS-specific parameters can vary by 1-2 orders of magnitude among different treatment delivery systems (TDSs). This paper proposes a standardized framework on the use of commissioning data and steps to validate TDS-specific parameters and TPS-specific heterogeneity modeling to potentially reduce these uncertainties. A standardized commissioning framework was developed to commission the MCDC algorithms of RayStation 8A and Eclipse AcurosPT v13.7.20 using water and non-water materials. Measurements included Bragg peak depth-dose and lateral spot profiles and scanning field outputs for Varian ProBeam. The phase-space parameters were obtained from in-air measurements and the number of protons per MU from output measurements of 10×10cm2 square fields at a 2cm depth. Spot profiles and various PBS field measurements at additional depths were used to validate TPS. Human tissues in TPS, Gammex phantom materials, and artificial materials were used for the TPS benchmark and validation. The maximum differences of phase parameters, spot sigma, and divergence between MCDC algorithms are below 4.5µm and 0.26mrad in air, respectively. Comparing TPS to measurements at depths, both MC algorithms predict the spot sigma within 0.5mm uncertainty intervals, the resolution of the measurement device. Beam Configuration in AcurosPT is found to underestimate number of protons per MU by ~2.5% and requires user adjustment to match measured data, while RayStation is within 1% of measurements using Auto model. A solid water phantom was used to validate the range accuracy of non-water materials within 1% in AcurosPT. The proposed standardized commissioning framework can detect potential issues during PBS TPS MCDC commissioning processes, and potentially can shorten commissioning time and improve dosimetric accuracies. Secondary MCDC can be used to identify the root sources of disagreement between primary MCDC and measurement.

Matrix stiffness modulates ILK-mediated YAP activation to control the drug resistance of breast cancer cells

One of the hallmarks of cancer progression is strong drug resistance during clinical treatments. The tumor microenvironment is closely associated with multidrug resistance, the optimization of tumor microenvironments may have a strong therapeutic effect. In this study, we configured polyacrylamide hydrogels of varying stiffness [low (10 kPa), intermediate (38 kPa) and high (57 kPa)] to simulate tissue physical matrix stiffness across different stages of breast cancer. After treatment with doxorubicin, cell survival rates on intermediate stiffness substrate are significantly higher. We find that high expression of ILK and YAP reduces the survival rates of breast cancer patients. Drug resistance is closely associated with the inactivation of the hippo pathway protein Merlin/MST/LATS and the activation of YAP. These results not only highlight the understanding of drug resistance mechanisms but also serve as a new basis for developing breast cancer treatment delivery systems.

EXTH-18. PEPTIDE NANO-STRUCTURES ENHANCE PEDIATRIC BRAIN TUMOR CHEMOTHERAPEUTIC EFFICACY

Abstract Pediatric gliomas, particularly high-grade gliomas, which include diffuse intrinsic pontine gliomas (DIPGs), are among the most formidable and devastating cancers in children. These tumors remain incurable, despite many treatment approaches. We recently identified a small population of glioma cells with stem-like features in pediatric gliomas (glioma stem cells: GSCs), that may be responsible, for therapeutic resistance. Bone morphogenetic protein 4 (BMP4), essential for CNS development, increases GSC therapeutic sensitivity and is a promising adjuvant for glioma treatment. Mechanisms through which BMP4 increases therapeutic sensitivity need to be elucidated, as this can lead to identification of additional treatment targets and delivery systems for BMP4 administration in a clinical setting. Additionally, extension of BMP4 short half-life would enhance its’ clinical application. Here we show that BMP4 increases chemosensitivity by decreasing H3K4me3 at the promoter of multidrug resistant gene 1 (MDR1), resulting in decreased MDR1 expression. BMP4 appears to bring about this effect by decreasing hSETD1A, an H3K4me3 methyltransferase. Our work also demonstrates the first use of a novel sulfated glycopeptide (glyco-PA) nanostructure as a vector for BMP4 delivery. Glyco-PA markedly extended and enhanced BMP4 function, and increased chemotherapeutic anti-tumor activity against pediatric malignant glioma cells in culture. Overall, this work illuminates BMP4 effects on pediatric glioma therapeutic sensitivity through epigenetic mechanisms, and demonstrates the potential of bioactive glyco-PA nanostructures as a delivery mechanism for treating pediatric malignant gliomas and other tumors.

Optimizing the electrospun parameters which affect the preparation of nanofibers

By electrospinning technique, nanofiber can be produced due to applied high potential voltage on polymer solution, leading to the formation of a jet from polymer solution that is collected on a collector in a nanofiber shape. In the last decade of the twentieth century with appearance of nanotechnology, work and publications on optimization of electrospinning and its applications increased exponentially. Morphology of produced nanofiber depends on three groups of parameters: 1- process conditions (applied voltage, flow rate and needle-to-collector distance) 2- solution conditions (concentration, molecular weight and degree of hydrolysis) 3- ambient conditions (temperature and humidity). Brief history from observation of change of the spherical shape of liquid droplet by the effect of the electrical force to conical shape, passing by Formhals patents to use portable electrospinning techniques will be mentioned. Because of various advantages of nanofiber such as high pore density and enormous surface area per volume ratio, there are vital applications based on nanofiber, for example water treatment, air filtration, sensors/biosensors, energy storage, tissue engineering, wound dressing and drug delivery system.

Field-in-field breast planning for a jawless, double-stack MLC LINAC using flattening-filter-free beams.

BackgroundThis study intends to develop an efficient field‐in‐field (FiF) planning technique with the Eclipse treatment planning system (TPS) to determine the feasibility of using the Halcyon treatment delivery system for 3D treatment of breast cancer.MethodsTen treatment plans were prepared on the Halcyon treatment planning system and compared to the same patients’ clinically delivered TrueBeam plans which used flattened 6 MV and 10 MV beams. Patients selected for this study were treated via simple, tangential breast irradiation and did not receive radiotherapy of the supraclavicular or internal mammary lymph nodes. Planning target volumes (PTV) volumes ranged from 519 cc to 1211 cc with a mean target volume of 877 cc. Several planning techniques involving collimator, gantry rotation, and number of FiF segments were investigated as well as the use of the dynamically flattened beam (DFB) — a predefined MLC pattern that is designed to provide a flattened beam profile at 10 cm depth on a standard water phantom. For comparison, the clinically delivered TrueBeam plans remained unaltered except for normalization of the target coverage to more readily compare the two treatment delivery techniques.ResultsUsing the physician defined PTV, normalized such that 98% of the volume was covered by 95% of the prescribed dose, the Halcyon plans were deemed clinically acceptable and comparable to the TrueBeam plans by the radiation oncologist. Resulting average global maximum doses in the test patients were identical between the TrueBeam and Halcyon plans (108% of Rx) and a mean PTV dose of 102.5% vs 101.6%, respectively.ConclusionsFrom this study a practical and efficient planning method for delivering 3D conformal breast radiotherapy using the Halcyon linear accelerator has been developed. When normalized to the clinically desired coverage, hot spots were maintained to acceptable levels and overall plan quality was comparable to plans delivered on conventional C‐arm LINACs.

Diverse diagnostic profiles associated with prescription opioid use disorder in a nationwide sample: One crisis, multiple needs.

The opioid crisis has had devastating effects on individuals and communities, and it has rapidly increased in severity. However, we still lack nationally representative information on the diversity of comorbidity patterns among prescription opioid use disorder (P-OUD), other substance use disorders (SUDs), and psychopathology using the newest edition of the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013). This impedes planning for multiple aspects of intervention, including society-wide allocation of treatment resources, program design at individual treatment centers, and personalized care to individual patients. To address this critical gap in information, we evaluated clinical profiles of American adults via latent class analysis in a large, recently collected epidemiological dataset that uses structured diagnostic assessment for DSM-5 psychopathology (National Epidemiologic Survey on Alcohol and Related Conditions-III; N = 36,309). Variables considered for profiles included lifetime diagnosis for multiple SUDs, various externalizing and internalizing conditions, and demographic variables. We then associated clinical profiles with demographic variables and functional impairment. Comorbid psychopathology and other SUDs were common in latent classes with elevated and very high rates of P-OUD. To illustrate, alcohol use disorder rates were greater than 45%, and posttraumatic stress disorder rates were greater than 28% in classes with higher P-OUD rates. Higher P-OUD rates were associated with White/non-Hispanic and American Indian/Alaska Native populations. Relationships between P-OUD rates and functional impairment were inconsistent. Many current treatment delivery systems are not designed to accommodate the heterogeneous profiles associated with high P-OUD rates. We provide specific suggestions for improvements to the mental health service system, individual clinical care programs, and future research approaches. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Error detection using an electromagnetic tracking system in multi-catheter breast interstitial brachytherapy

The hybrid treatment delivery system (HTDS) has been proposed as a possible option for a quality assurance in the multi-catheter interstitial brachytherapy for breast cancer patients. The system, which consists out of a prototype afterloader with an integrated electromagnetic tracking (EMT) sensor and an EMT system, allows the automatic measurement of implanted catheters.To test the feasibility of the system for error detection, possible treatment planning errors and treatment delivery errors were simulated. Planning errors such as an incorrect offset value, an incorrect indexer length, tip/connector end swaps, and partial swaps, and; treatment delivery errors such as catheter shifts and catheter connection swaps were manually simulated using phantoms. An in-house Matlab routine was used to assess geometrical deviations between the dwell positions defined based on CT and EMT measurement. Additionally, the influence of implant motion on the detection ability of the system was assessed. An algorithm for the detection and specification of errors based on the error simulation results was developed. At the University Hospital Erlangen, a patient study is ongoing, where errors in patient data were analyzed using the proposed algorithm.All simulated planning errors were detected. Catheter connection swaps can be detected 100% of the time. A shift detection rate of >97% was observed for shifts larger than 1.1 mm, both in the static and the motion measurements. Catheter reconstruction uncertainties and catheter shifts <2 mm were found to be the most common treatment planning and delivery errors in patient data. HTDS proved to be a reliable method for error detection.

Estimation of inter-fractional variations in interstitial multi-catheter breast brachytherapy using a hybrid treatment delivery system

PurposeIrradiation of the tumor bed using interstitial multi-catheter brachytherapy is one of the treatment options for breast cancer patients. In order to ensure the planned dose delivery an advanced quality intervention method using an electromagnetic tracking (EMT) system is presented. The system is used to assess inter-fractional variations within the framework of a patient study. Methods and materialsUntil now 41 patients were included in the study for the evaluation and overall 355 EMT measurements were performed. The catheter traces are measured automatically and sequentially using an afterloader prototype (Flexitron, Elekta, Veenendaal, The Netherlands) equipped with an EMT sensor. The implant geometry is tracked directly after implantation, after CT imaging and after each irradiation fraction. The acquired data is rigidly registered to the catheter traces defined in the treatment plan and the dwell positions (DP) are reconstructed. DPs defined in treatment planning serve as reference. Breathing motion was corrected and recorded using three reference 6DoF sensors placed on the patients’ skin. The Euclidean distance between the planned and reconstructed DPs provides information about possible inter-fractional deviations. Further, the influence of various factors on the occurrence of large deviations was investigated, like the patients’ age, the length of the catheter, the breast volume, etc. ResultsOver all patient measurements a median Euclidean distance of 2.19 mm was determined between the reconstructed DPs and the reference DPs. The median deviation combining all datasets was minimal (1.67 mm) at the measurement directly after CT imaging. The deviations between the different fractions have a median distance of 2.31 mm which could be improved to 2.05 mm by adapting the treatment plan according to the follow-up CT. No correlation between the distance to the skin, ribs, mammilla or the breast volume and the occurrences of large deviations was found. The largest deviations were determined in the upper inner quadrant of the breast. ConclusionThe afterloader prototype could be well integrated into the clinical routine and is beneficial for ensuring the quality of the brachytherapy. Overall, a small median DP deviation, lower than the used step size of 2.5 mm, was detected.

A Team Approach to Commissioning Online MRI-Guided Adaptive Radiotherapy

Magnetic resonance imaging guided adaptive radiation therapy (MRgART) has led to a major paradigm shift resulting in personalized daily patient treatment. Implementing a online MRgART program requires commissioning the adaptive process. This process is performed primarily by medical physicists. In this work, we propose an efficient team approach to the commissioning process. This approach involves dividing different aspects of the verification process among all individuals involved in the adaptive workflow including: qualified medical physicists (QMP), clinical medical dosimetrists (CMD), radiation therapists (RT), and radiation oncologists (RO). Phantom- and volunteer-based commissioning approaches were performed. The phantom based approach is not discussed here. We have implemented a team approach to verifying the ART workflow using volunteers. The commissioning process was divided into the verification of: 1) the treatment planning system (TPS), and 2) the treatment delivery system (TDS). MRI simulations were performed by the RT and images were imported into the TPS by a CMD. Target structures were drawn by a RO. Organ at risk (OAR) structures and structures specific to the ART workflow were drawn by a CMD; including density override and optimization structures. Boolean operations were added to minimize contouring time on the machine. Clinically acceptable plans were then generated by the CMD and reviewed by the QMP; this included verifying contours, Boolean operations, correct electron density override assignment, and appropriate settings. The RO then reviewed the plan quality and approved for delivery. Patient specific QA was then performed by the QMP. The second part was verifying the TDS by simulating a patient treatment. For each volunteer; set-up, image acquisition and registration were performed by the RT and reviewed by the RO. A CMD edited OAR structures followed by RO review. The QMP applied density overrides and Boolean operations who then re-calculated dose on the daily images. The RO reviewed the plan and made a decision on whether to re-optimize. The QMP performed the optimization and a secondary check using a Monte Carlo based algorithm. Volunteers were imaged to commission the adaptive workflow over a week. Daily MR images were acquired and image segmentation was performed. The volunteer approach for commissioning took 2.5 times longer than the phantom based approach. However, the time for commissioning was halved using volunteers with a team based approach. Team members gained more confidence and were better prepared to start the MRgART program. Efficiency was increased when a team approach to commission MRgART program was adapted. This approach served as a proactive training for individuals involved in the adaptive workflow. Patients treated during the initial implementation phase of the adaptive program benefit from this approach due to the confidence and deep understanding of their radiation therapy team.

Radiation Oncology-External-Beam Radiation Therapy.

The application of structural shielding design techniques and goals as outlined in the National Council on Radiation Protection and Measurements Report 151, Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-Ray Radiotherapy Facilities (2005), continues to be the basis for treatment vault design in 2018 with some updated information. Treatment techniques have changed significantly with the dominant usage of intensity-modulated radiation therapy techniques today based on concurrent imaging. Some of the developments in linear accelerator technology over the past 15 y include flattening filter-free modes, which enable higher instantaneous dose rates; three-dimensional conformal radiation therapy resulting in potentially higher workloads since healthy tissue is spared; improved intensity-modulated radiation therapy treatment delivery systems with lower monitor units per centigray delivered than traditional step and shoot intensity-modulated radiation therapy; stereotactic body radiation therapy with higher treatment fractions and increased workloads; and increased use of stereotactic radiosurgery with conventional linear accelerators as well as robotic arm-mounted linear accelerators with higher treatment fractions. These new treatment units also incorporate multiple-energy x-ray beams (2 to 5 MV typical), which require a significant change in the specification of a workload to be used in each vault. As the equipment in radiation oncology departments has evolved to state-of-the-art modalities, the requirements for adequate radiation shielding for these modalities has become more rigorous. Architectural designs no longer depend on standard maze design rectangular rooms. Innovative layouts and utilization of multiple layers of shielding materials allow much greater flexibility in room designs. Maze-less rooms with direct-shielded doors are part of these challenging designs and are very common today. Use of multiple-density concrete blocks allows quicker construction of vaults and requires less space for the equivalent shielding provided. Combinations of high-density or normal-density concrete, steel, and lead are used in designs to make optimum use of available space and cost. Additional shielding needed at the edges of these single- or bi-parting sliding doors as well as baffle designs for heating, ventilation, and air conditioning systems and communication cable penetrations require detailed calculations. Examples of these designs will be given in this presentation. Consideration of the radiation levels around the planned vault must also include adjacent multistory buildings.

Role and future of MRI in radiation oncology.

Technical innovations and developments in areas such as disease localization, dose calculation algorithms, motion management and dose delivery technologies have revolutionized radiation therapy resulting in improved patient care with superior outcomes. A consequence of the ability to design and accurately deliver complex radiation fields is the need for improved target visualization through imaging. While CT imaging has been the standard of care for more than three decades, the superior soft tissue contrast afforded by MR has resulted in the adoption of this technology in radiation therapy. With the development of real time MR imaging techniques, the problem of real time motion management is enticing. Currently, the integration of an MR imaging and megavoltage radiation therapy treatment delivery system (MR-linac or MRL) is a reality that has the potential to provide improved target localization and real time motion management during treatment. Higher magnetic field strengths provide improved image quality potentially providing the backbone for future work related to image texture analysis-a field known as Radiomics-thereby providing meaningful information on the selection of future patients for radiation dose escalation, motion-managed treatment techniques and ultimately better patient care. On-going advances in MRL technologies promise improved real time soft tissue visualization, treatment margin reductions, beam optimization, inhomogeneity corrected dose calculation, fast multileaf collimators and volumetric arc radiation therapy. This review article provides rationale, advantages and disadvantages as well as ideas for future research in MRI related to radiation therapy mainly in adoption of MRL.