Design, construction, and dosimetry of 3D printed heterogeneous phantoms for synchrotron brain cancer radiation therapy quality assurance.

Objective.This study aims to design, manufacture, and test 3D printed quality assurance (QA) dosimetry phantoms for synchrotron brain cancer radiation therapy at the Australian synchrotron.Approach.Fabricated 3D printed phantoms from simple slab phantoms, a preclinical rat phantom, and an anthropomorphic head phantom were fabricated and characterized. Attenuation measurements of various polymers, ceramics and metals were acquired using synchrotron monochromatic micro-computed tomography (CT) imaging. Polylactic acid plus, VeroClear, Durable resin, and tricalcium phosphate were used in constructing the phantoms. Furthermore, 3D printed bone equivalent materials were compared relative to ICRU bone and hemihydrate plaster. Homogeneous and heterogeneous rat phantoms were designed and fabricated using tissue-equivalent materials. Geometric accuracy, CT imaging, and consistency were considered. Moreover, synchrotron broad-beam x-rays were delivered using a 3 Tesla superconducting multipole wiggler field for four sets of synchrotron radiation beam qualities. Dose measurements were acquired using a PinPoint ionization chamber and compared relative to a water phantom and a RMI457 Solid Water phantom. Experimental depth doses were compared relative to calculated doses using a Geant4 Monte Carlo simulation.Main results.Polylactic acid (PLA+) shows to have a good match with the attenuation coefficient of ICRU water, while both tricalcium phosphate and hydroxyapatite have good attenuation similarity with ICRU bone cortical. PLA+ material can be used as substitute to RMI457 slabs for reference dosimetry with a maximum difference of 1.84%. Percent depth dose measurement also shows that PLA+ has the best match with water and RMI457 within ±2.2% and ±1.6%, respectively. Overall, PLA+ phantoms match with RMI457 phantoms within ±3%.Significance and conclusion.The fabricated phantoms are excellent tissue equivalent equipment for synchrotron radiation dosimetry QA measurement. Both the rat and the anthropomorphic head phantoms are useful in synchrotron brain cancer radiotherapy dosimetry, experiments, and future clinical translation of synchrotron radiotherapy and imaging.

Characterization of selected additive manufacturing materials for synchrotron monochromatic imaging and broad-beam radiotherapy at the Australian synchrotron-imaging and medical beamline.

Objective.This study aims to characterize radiological properties of selected additive manufacturing (AM) materials utilizing both material extrusion and vat photopolymerization technologies. Monochromatic synchrotron x-ray images and synchrotron treatment beam dosimetry were acquired at the hutch 3B and 2B of the Australian Synchrotron-Imaging and Medical Beamline.Approach.Eight energies from 30 keV up to 65 keV were used to acquire the attenuation coefficients of the AM materials. Comparison of theoretical, and experimental attenuation data of AM materials and standard solid water for MV linac was performed. Broad-beam dosimetry experiment through attenuated dose measurement and a Geant4 Monte Carlo simulation were done for the studied materials to investigate its attenuation properties specific for a 4 tesla wiggler field with varying synchrotron radiation beam qualities.Main results.Polylactic acid (PLA) plus matches attenuation coefficients of both soft tissue and brain tissue, while acrylonitrile butadiene styrene, Acrylonitrile styrene acrylate, and Draft resin have close equivalence to adipose tissue. Lastly, PLA, co-polyester plus, thermoplastic polyurethane, and White resins are promising substitute materials for breast tissue. For broad-beam experiment and simulation, many of the studied materials were able to simulate RMI457 Solid Water and bolus within ±10% for the three synchrotron beam qualities. These results are useful in fabricating phantoms for synchrotron and other related medical radiation applications such as orthovoltage treatments.Significance and conclusion.These 3D printing materials were studied as potential substitutes for selected tissues such as breast tissue, adipose tissue, soft-tissue, and brain tissue useful in fabricating 3D printed phantoms for synchrotron imaging, therapy, and orthovoltage applications. Fabricating customizable heterogeneous anthropomorphic phantoms (e.g. breast, head, thorax) and pre-clinical animal phantoms (e.g. rodents, canine) for synchrotron imaging and radiotherapy using AM can be done based on the results of this study.

Superficial parasternal intercostal plane blocks in cardiac surgery: a systematic review and meta-analysis.

PURPOSE: Traditional multimodal analgesic strategies have several contraindications in cardiac surgery patients, forcing clinicians to use alternative options. Superficial parasternal intercostal plane blocks, anesthetizing the anterior cutaneous branches of the thoracic intercostal nerves, are being explored as a straightforward method to treat pain after sternotomy. We sought to evaluate the literature on the effects of superficial parasternal blocks on pain control after cardiac surgery. METHODS: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs). We searched MEDLINE, Embase, CENTRAL, and Web of Science databases for RCTs evaluating superficial parasternal intercostal plane blocks in adult patients undergoing cardiac surgery via midline sternotomy published from inception to 11 March 2022. The prespecified primary outcome was opioid consumption at 12 hr. The risk of bias was assessed with the Cochrane Collaboration Risk of Bias Tool, and the quality of evidence was evaluated using the grading of recommendations, assessments, development, and evaluations. Outcomes were analyzed with a random-effects model. All subgroups were prespecified. RESULTS: We reviewed 1,275 citations. Eleven RCTs, comprising 756 patients, fulfilled the inclusion criteria. Only one study reported the prespecified primary outcome, precluding the possibility of meta-analysis. This study reported a reduction in opioid consumption (-11.2 mg iv morphine equivalents; 95% confidence interval [CI], -8.2 to -14.1) There was a reduction in opioid consumption at 24 hr (-7.2 mg iv morphine equivalents; 95% CI, -5.6 to -8.7; five trials; 436 participants; moderate certainty evidence). All five studies measuring complications reported that none were detected, which included a sample of 196 blocks. CONCLUSION: The literature suggests a potential benefit of using superficial parasternal blocks to improve acute postoperative pain control after cardiac surgery via midline sternotomy. Future studies specifying dosing regimens and adjuncts are required. STUDY REGISTRATION: PROSPERO (CRD42022306914); first submitted 22 March 2022.

RéSUMé: OBJECTIF: Il existe plusieurs contre-indications aux stratégies analgésiques multimodales traditionnelles chez la patientèle de chirurgie cardiaque, ce qui oblige les clinicien·nes à se tourner vers d'autres options. Les blocs des plans intercostaux parasternaux superficiels, anesthésiant les branches cutanées antérieures des nerfs intercostaux thoraciques, sont l'une des méthodes simples actuellement explorées pour traiter la douleur après une sternotomie. Nous avons cherché à évaluer la littérature sur les effets des blocs parasternaux superficiels sur le contrôle de la douleur après une chirurgie cardiaque. MéTHODE: Nous avons réalisé une revue systématique et une méta-analyse des études randomisées contrôlées (ERC). Nous avons fait des recherches dans les bases de données MEDLINE, Embase, CENTRAL et Web of Science pour en tirer les ERC évaluant les blocs des plans intercostaux parasternaux superficiels chez les patient·es adultes bénéficiant d'une chirurgie cardiaque par sternotomie médiane publiées depuis leur création jusqu'au 11 mars 2022. Le critère d'évaluation principal préspécifié était la consommation d'opioïdes à 12 heures. Le risque de biais a été évalué à l'aide de l'outil Cochrane Collaboration Risk of Bias, et la qualité des données probantes à l'aide de l'outil GRADE. Les résultats ont été analysés à l'aide d'un modèle à effets aléatoires. Tous les sous-groupes étaient préspécifiés. RéSULTATS: Nous avons examiné 1275 citations. Onze ERC, comprenant 756 patient·es, remplissaient les critères d'inclusion. Une seule étude a rapporté le critère d'évaluation principal préspécifié, ce qui a exclu la possibilité d'une méta-analyse. Cette étude a rapporté une réduction de la consommation d'opioïdes (−11,2 mg équivalents de morphine iv; intervalle de confiance [IC] à 95 %, −8,2 à −14,1). Il y a eu une réduction de la consommation d'opioïdes à 24 heures (−7,2 mg équivalents de morphine iv; IC 95 %, −5,6 à −8,7; cinq études; 436 participant·es; données probantes de certitude modérée). Les cinq études mesurant les complications ont rapporté qu'aucune complication n'avait été détectée, en incluant un échantillon de 196 blocs. CONCLUSION: La littérature suggère un avantage potentiel de l'utilisation de blocs parasternaux superficiels pour améliorer le contrôle de la douleur postopératoire aiguë après une chirurgie cardiaque par sternotomie médiane. Des études futures précisant les schémas posologiques et les adjuvants sont nécessaires. ENREGISTREMENT DE L'éTUDE: PROSPERO (CRD42022306914); soumis pour la première fois le 22 mars 2022.