Evaluation of Platinum-catalyzed Silicones for Fabrication of Biocompatible Patient-specific Elastic Bolus

Abstract Purpose We investigated the properties of platinum-catalyzed silicones with suitable characteristics for a biocompatible patient-specific elastic bolus. Materials & Methods We applied a platinum-catalyzed silicone (Ecoflex™ 0030) and a platinum cure liquid silicone (Dragon Skin™ 10 MEDIUM) to fabricate a biocompatible bolus using a mold and casting method with a 3D printer. We conducted physical evaluations including the shore hardness, cure time, transparency, and mixed viscosity. The dosimetric characteristics were basically investigated with surface dose and beam quality. For dosimetric evaluations using humanoid phantom, the dose differences between calculated dose and measured dose were compared with those of Dragon skin. To evaluate which boluses fit best, the volume of unwanted air gaps between the bolus and phantom was obtained from CT images. Biological evaluations were conducted on the skin sensitization, skin irritation, and cytotoxicity to ensure safe patient application. Results Ecoflex were biologically evaluated as safety materials. In addition, Ecoflex shows excellent physical properties with respect to a low shore hardness (00–30), short curing time (4 h), and low mixed viscosity (3,000). For the dosimetric properties using humanoid phantom, the average dose difference between the calculated dose and measured dose for Ecoflex is about 0.5% better than that of Dragon skin. In addition, a relatively smaller volume of unwanted air gaps for Ecoflex also showed than for Dragon skin, which these results tended to be the same as the dosimetric results. Conclusion The physical properties of Ecoflex including excellent adhesive strength, lower shore hardness reduces unwanted air gaps and ensures an accurate dose distribution. Therefore, it is a suitable material for fabricating biocompatible patient-specific elastic bolus. It would be an alternative to other materials of bolus and thus improve the efficiency for clinical use.

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Curtailing patient-specific IMRT QA procedures from 2D dose error distribution

Journal of Radiation Research ◽

10.1093/jrr/rrv084 ◽

2016 ◽

Vol 57 (3) ◽

pp. 258-264 ◽

Cited By ~ 2

Author(s):

Keita Kurosu ◽

Iori Sumida ◽

Hirokazu Mizuno ◽

Yuki Otani ◽

Michio Oda ◽

...

Keyword(s):

Error Distribution ◽

Planning System ◽

Treatment Planning System ◽

Patient Specific ◽

Dose Error ◽

Imrt Qa ◽

Pelvic Region ◽

Measured Dose ◽

Calculated Dose ◽

Medical Physicists

Abstract A patient-specific quality assurance (QA) test is conducted to verify the accuracy of dose delivery. It generally consists of three verification processes: the absolute point dose difference, the planar dose differences at each gantry angle, and the planar dose differences by 3D composite irradiation. However, this imposes a substantial workload on medical physicists. The objective of this study was to determine whether our novel method that predicts the 3D delivered dose allows certain patient-specific IMRT QAs to be curtailed. The object was IMRT QA for the pelvic region with regard to point dose and composite planar dose differences. We compared measured doses, doses calculated in the treatment planning system, and doses predicted by in-house software. The 3D predicted dose was reconstructed from the per-field measurement by incorporating the relative dose error distribution into the original dose grid of each beam. All point dose differences between the measured and the calculated dose were within ±3%, whereas 93.3% of them between the predicted and the calculated dose were within ±3%. As for planar dose differences, the gamma passing rates between the calculated and the predicted dose were higher than those between the calculated and the measured dose. Comparison and statistical analysis revealed a correlation between the predicted and the measured dose with regard to both point dose and planar dose differences. We concluded that the prediction-based approach is an accurate substitute for the conventional measurement-based approach in IMRT QA for the pelvic region. Our novel approach will help medical physicists save time on IMRT QA.

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Feasibility of hybrid TomoHelical- and TomoDirect-based volumetric gradient matching technique for total body irradiation

Radiation Oncology ◽

10.1186/s13014-019-1435-5 ◽

2019 ◽

Vol 14 (1) ◽

Cited By ~ 3

Author(s):

Chae-Seon Hong ◽

Min-Joo Kim ◽

Jihun Kim ◽

Kyung Hwan Chang ◽

Kwangwoo Park ◽

...

Keyword(s):

Total Body Irradiation ◽

Dose Distribution ◽

Longitudinal Direction ◽

Target Volume ◽

Average Dose ◽

Setup Error ◽

Matching Technique ◽

Calculated Dose ◽

Total Body ◽

Dose Measurements

Abstract Background Tomotherapy-based total body irradiation (TBI) is performed using the head-first position (HFP) and feet-first position (FFP) due to treatment length exceeding the 135 cm limit. To reduce the dosimetric variation at the match lines, we propose and verify a volumetric gradient matching technique (VGMT) by combining TomoHelical (TH) and TomoDirect (TD) modes. Methods Two planning CT image sets were acquired with HFP and FFP using 15 × 55 × 18 cm3 of solid water phantom. Planning target volume (PTV) was divided into upper, lower, and gradient volumes. The junction comprised 2-cm thick five and seven gradient volumes (5-GVs and 7-GVs) to create a dose distribution with a gentle slope. TH-IMRT and TD-IMRT plans were generated with 5-GVs and 7-GVs. The setup error in the calculated dose was assessed by shifting dose distribution of the FFP plan by 5, 10, 15, and 20 mm in the longitudinal direction and comparing it with the original. Doses for 95% (D95) and 5% of the PTV (D5) were calculated for all simulated setup error plans. Absolute dose measurements were performed using an ionization chamber in the junction. Results The TH&TD plan produced a linear gradient in junction volume, comparable to that of the TH&TH plan. D5 of the PTV was 110% of the prescribed dose when the FFP plan was shifted 0.7 cm and 1.2 cm in the superior direction for 5-GVs and 7-GVs. D95 of the PTV decreased to < 90% of the prescribed dose when the FF plan was shifted 1.1 cm and 1.3 cm in the inferior direction for 5-GVs and 7-GVs. The absolute measured dose showed a good correlation with the calculated dose in the gradient junction volume. The average percent difference (±SD) in all measured points was − 0.7 ± 1.6%, and the average dose variations between depths was − 0.18 ± 1.07%. Conclusion VGMT can create a linear dose gradient across the junction area in both TH&TH and TH&TD and can minimize the dose sensitivity to longitudinal setup errors in tomotherapy-based TBI.

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Evaluating small field dosimetry with the Acuros XB (AXB) and analytical anisotropic algorithm (AAA) dose calculation algorithms in the eclipse treatment planning system

Journal of Radiotherapy in Practice ◽

10.1017/s1460396919000104 ◽

2019 ◽

Vol 18 (4) ◽

pp. 353-364

Author(s):

Sepideh Behinaein ◽

Ernest Osei ◽

Johnson Darko ◽

Paule Charland ◽

Dylan Bassi

Keyword(s):

Treatment Planning ◽

Planning System ◽

Treatment Planning System ◽

Patient Specific ◽

Average Dose ◽

Water Phantom ◽

Acuros Xb ◽

Small Fields ◽

Dose Measurements ◽

The Brain

AbstractBackground:An increasing number of external beam treatment modalities including intensity modulated radiation therapy, volumetric modulated arc therapy (VMAT) and stereotactic radiosurgery uses very small fields for treatment planning and delivery. However, there are major challenges in small photon field dosimetry, due to the partial occlusion of the direct photon beam source’s view from the measurement point, lack of lateral charged particle equilibrium, steep dose-rate gradient and volume averaging effect of the detector response and variation of the energy fluence in the lateral direction of the beam. Therefore, experimental measurements of dosimetric parameters such as percent depth doses (PDDs), beam profiles and relative output factors (ROFs) for small fields continue to be a challenge.Materials and Methods:In this study, we used a homogeneous water phantom and the heterogeneous anthropomorphic stereotactic end-to-end verification (STEEV) head phantom for all dose measurements and calculations. PDDs, lateral dose proﬁles and ROFs were calculated in the Eclipse Treatment Planning System version 13·6 using the Acuros XB (AXB) and the analytical anisotropic algorithms (AAAs) in a homogenous water phantom. Monte Carlo (MC) simulations and measurements using the Exradin W1 Scintillator were also accomplished for four photon energies: 6 MV, 6FFF, 10 MV and 10FFF. Two VMAT treatment plans were generated for two different targets: one located in the brain and the other in the neck (close to the trachea) in the head phantom (CIRS, Norfolk, VA, USA). A Varian Truebeam linear accelerator (Varian, Palo Alto, CA, USA) was used for all treatment deliveries. Calculated results with AXB and AAA were compared with MC simulations and measurements.Results:The average difference of PDDs between W1 Exradin Scintillator measurements and MC simulations, AAA and AXB algorithm calculations were 1·2, 2·4 and 3·2%, respectively, for all field sizes and energies. AXB and AAA showed differences in ROF of about 0·3 and 2·9%, respectively, compared with W1 Exradin Scintillator measured values. For the target located in the brain in the head phantom, the average dose difference between W1 Exradin Scintillator and the MC simulations, AAA and AXB were 0·2, 3·2 and 2·7%, respectively, for all field sizes. Similarly, for the target located in the neck, the respective dose differences were 3·8, 5·7 and 3·5%.Conclusion:In this study, we compared dosimetric parameters such as PDD, beam profile and ROFs in water phantom and isocenter point dose measurements in an anthropomorphic head phantom representing a patient. We observed that measurements using the W1 Exradin scintillator agreed well with MC simulations and can be used efficiently for dosimetric parameters such as PDDs and dose profiles and patient-specific quality assurance measurements for small fields. In both homogenous and heterogeneous media, the AXB algorithm dose prediction agrees well with MC and measurements and was found to be superior to the AAA algorithm.

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CT dosimetry at the Australian Synchrotron for 25–100 keV photons and 35–160 mm-diameter biological specimens

Journal of Synchrotron Radiation ◽

10.1107/s1600577518018015 ◽

2019 ◽

Vol 26 (2) ◽

pp. 517-527

Author(s):

Stewart Midgley ◽

Nanette Schleich ◽

Alex Merchant ◽

Andrew Stevenson

Keyword(s):

Effective Dose ◽

Beam Quality ◽

Absorbed Dose ◽

Body Region ◽

Average Dose ◽

Dose Length Product ◽

Organ Doses ◽

Ct Dose ◽

Radiation Output ◽

Ct Dosimetry

The dose length product (DLP) method for medical computed tomography (CT) dosimetry is applied on the Australian Synchrotron Imaging and Medical Beamline (IMBL). Beam quality is assessed from copper transmission measurements using image receptors, finding near 100% (20 keV), 3.3% (25 keV) and 0.5% (30–40 keV) relative contributions from third-harmonic radiation. The flat-panel-array medical image receptor is found to have a non-linear dose response curve. The amount of radiation delivered during an axial CT scan is measured as the dose in air alone, and inside cylindrical PMMA phantoms with diameters 35–160 mm for mono-energetic radiation 25–100 keV. The radiation output rate for the IMBL is comparable with that used for medical CT. Results are presented as the ratios of CT dose indices (CTDI) inside phantoms to in air with no phantom. Ratios are compared for the IMBL against medical CT where bow-tie filters shape the beam profile to reduce the absorbed dose to surface organs. CTDI ratios scale measurements in air to estimate the volumetric CTDI representing the average dose per unit length, and the dose length product representing the absorbed dose to the scanned volume. Medical CT dose calculators use the DLP, beam quality, axial collimation and helical pitch to estimate organ doses and the effective dose. The effective dose per unit DLP for medical CT is presented as a function of body region, beam energy and sample sizes from neonate to adult.

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CLINICAL AND LABORATORY TESTING OF A NEW MODIFICATION OF TWO-LAYER "SILEP" DENTURES USED IN PROSTHETIC DENTISTRY

Southern Brazilian Journal of Chemistry - Southern Brazilian Journal of Chemistry, Volume 28, No. 28, 2020 ◽

10.48141/sbjchem.v28.n28.2020.08_timoshin_pgs_53_62.pdf ◽

2020 ◽

Vol 28 (28) ◽

pp. 53-62

Author(s):

Anton TIMOSHIN ◽

Nikolay MITIN ◽

Alexander OLEYNIKOV ◽

Maria TIMOSHINA ◽

Evgeniya MITINA

Keyword(s):

Tensile Strength ◽

Laboratory Testing ◽

Polymer Materials ◽

Shore Hardness ◽

Physical Strength ◽

Suitable Material ◽

Removable Prosthesis ◽

First Time ◽

Compound Materials ◽

The Ideal

Dentistry is a part of medicine, where various polymer materials were used for the first time. Many factors forced researchers to find more stable, versatile, and hygienic materials for the manufacture of dental products. It is important to note that the search for the ideal polymer dental material is still ongoing. This is because modern polymers, in some cases, do not meet the specified requirements for chemical, physical, strength, and elastic properties. Based on the data on the method of creating and using silicone material for the base of the removable prosthesis "Gossil", an improved silicone material for two-layer dentures "Silep" was developed, as well as a special primer for better connection of the lining with the rigid acrylic base of the prosthesis. To evaluate the most suitable compound, materials were tested for several parameters, such as tensile strength, elongation, and shore hardness. In addition to selecting a suitable material for modification, the selection and testing of an adhesive that allows the chemical bonding of the acrylate surface to the siloxane surface were carried out.

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Non-leaching bactericidal cotton fabrics with well-preserved physical properties, no skin irritation and no toxicity

Cellulose ◽

10.1007/s10570-018-1943-8 ◽

2018 ◽

Vol 25 (9) ◽

pp. 5415-5426 ◽

Cited By ~ 16

Author(s):

Jingwei Gu ◽

Lingjun Yuan ◽

Ze Zhang ◽

Xinhui Yang ◽

Junxuan Luo ◽

...

Keyword(s):

Physical Properties ◽

Skin Irritation ◽

Cotton Fabrics

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Estimation of [177Lu]PSMA-617 tumor uptake based on voxel-wise 3D Monte Carlo tumor dosimetry in patients with metastasized castration resistant prostate cancer

Nuklearmedizin ◽

10.1055/a-1204-9932 ◽

2020 ◽

Vol 59 (05) ◽

pp. 365-374

Author(s):

Theresa Ida Götz ◽

Elmar Wolfgang Lang ◽

Olaf Prante ◽

Michael Cordes ◽

Torsten Kuwert ◽

...

Keyword(s):

Prostate Cancer ◽

Monte Carlo ◽

Three Dimensional ◽

Absorbed Dose ◽

Whole Body ◽

Patient Specific ◽

Average Dose ◽

Castration Resistant Prostate Cancer ◽

Castration Resistant ◽

Before And After

Abstract Objective Patients with advanced prostate cancer are suitable candidates for [177Lu]PSMA-617 therapy. Integrated SPECT/CT systems have the potential to improve the accuracy of patient-specific tumor dosimetry. We present a novel patient-specific Monte Carlo based voxel-wise dosimetry approach to determine organ and total tumor doses (TTD). Methods 13 patients with histologically confirmed metastasized castration-resistant prostate cancer were treated with a total of 18 cycles of [177Lu]PSMA-617 therapy. In each patient, dosimetry was performed after the first cycle of [177Lu]PSMA-617 therapy. Regions of interest were defined manually on the SPECT/CT images for the kidneys, spleen and all 295 PSMA-positive tumor lesions in the field of view. The absorbed dose to normal organs and to all tumor lesions were calculated by a three dimensional dosimetry method based on Monte Carlo Simulations. Results The average dose values yielded the following results: 2.59 ± 0.63 Gy (1.67–3.92 Gy) for the kidneys, 0.79 ± 0.46 Gy (0.31–1.90 Gy) for the spleen and 11.00 ± 11.97 Gy (1.28–49.10 Gy) for all tracer-positive tumor lesions. A trend towards higher TTD was observed in patients with Gleason Scores > 8 compared to Gleason Scores ≤ 8 and in lymph node metastases compared to bone metastases. A significant correlation was determined between the serum-PSA level before RLT and the TTD (r = –0.57, p < 0.05), as well as between the TTD with the percentage change of serum-PSA levels before and after therapy was observed (r = –0.57, p < 0.05). Patients with higher total tumor volumes of PSMA-positive lesions demonstrated significantly lower kidney average dose values (r = –0.58, p < 0.05). Conclusion The presented novel Monte Carlo based voxel-wise dosimetry calculates a patient specific whole-body dose distribution, thus taking into account individual anatomies and tissue compositions showing promising results for the estimation of radiation doses of normal organs and PSMA-positive tumor lesions.

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Topology and FEA modeling and optimization of a patient-specific zygoma implant

10.25518/esaform21.756 ◽

2021 ◽

Author(s):

Abhijit Cholkar ◽

David Kinahan ◽

Dermot Brabazon

Keyword(s):

Additive Manufacturing ◽

Optimum Design ◽

Optimization Technique ◽

Operating Time ◽

Topological Optimization ◽

Implant Design ◽

Patient Specific ◽

Stainless Steel 316L ◽

Element Analysis ◽

Suitable Material

Additive manufacturing has proven to be a very beneficial production technology in the medical and healthcare industries. While existing for over four decades, recent work has seen great improvements in the quality of products; particularly in medical devices such as implants. Improved customization reduced operating time and increased cost-effectiveness associated with Metal AM for these products offers a new value proposition. This paper investigates and evaluates modelling methods for the zygoma bone (human jawbone) and explores the most suitable material and optimum design for this critical biomedical implant. This paper proposes an innovative and efficient pre-process methodology that includes modelling, design validation, topological optimization, and numerical analysis. The method includes the generation of the model using reverse engineering of CT scan data and a topology optimization technique which makes the implant lightweight without causing excessive stress concentration. Static structural Finite Element Analysis was conducted to test three different biocompatible materials (Ti6Al4V, stainless steel 316L and CoCr alloys) which are commonly available for metal additive manufacturing. The stresses and conditions in the analysis were that of the human mastication process and all the implant design were tested with the three material types. The Taguchi method was used to determine the optimum design which was found to result in the highest mass reduction of 25% with Ti6Al4V as the implant material.

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Production stages, microbiological risk and benefits on health of herbal teas

Herba Polonica ◽

10.2478/hepo-2020-0020 ◽

2020 ◽

Vol 66 (4) ◽

pp. 68-78

Author(s):

Gül Akduman ◽

Irem Omurtag Korkmaz

Keyword(s):

Physical Properties ◽

Chemical Constituents ◽

Climatic Conditions ◽

Therapeutic Effects ◽

Herbal Tea ◽

Suitable Material ◽

Production Stages ◽

Botanical Characteristics ◽

Microbial Risks ◽

Herbal Infusions

Summary Plants have been used to prepare herbal infusions for centuries. Production of herbal tea consists of several steps, beginning with harvesting, cleaning form residues, drying, storage of herb in a suitable material, grinding, and blending. Te plants grow in different regions and climatic conditions, varying by their physical properties. They are consumed for different purposes and due to their chemical constituents. Many of them have therapeutic effects. Besides their various benefits and even antimicrobial effects, they also carry some microorganisms. Thus, the botanical characteristics and effects on the health of frequently consumed herbal teas and recommendations on their consumption with considered microbial risks are reviewed in this article.

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Adaptive current-flow models of ECT: Explaining individual static impedance, dynamic impedance, and brain current delivery

10.1101/2020.11.08.373712 ◽

2020 ◽

Author(s):

Gozde Unal ◽

Jaiti K Swami ◽

Carliza Canela ◽

Samantha Cohen ◽

Niranjan Khadka ◽

...

Keyword(s):

Physical Properties ◽

Current Flow ◽

Seizure Threshold ◽

Patient Specific ◽

Transcranial Electrical Stimulation ◽

Fixed Tissue ◽

Tissue Conductivity ◽

Dynamic Impedance ◽

Subject Specific ◽

The Brain

Background: Improvements in electroconvulsive therapy (ECT) outcomes have followed refinement in device electrical output and electrode montage. The physical properties of the ECT stimulus, together with those of the patient's head, determine the impedances measured by the device and govern current delivery to the brain and ECT outcomes. Objective: However, the precise relations among physical properties of the stimulus, patient head anatomy, and patient-specific impedance to the passage of current are long-standing questions in ECT research and practice. Methods: We developed anatomical MRI-derived models of transcranial electrical stimulation (tES) that included changes in tissue conductivity due to local electrical current flow. These adaptive models simulate ECT both during therapeutic stimulation using high (~1 A) current and when dynamic impedance is measured, as well as prior to stimulation when low (~1 mA) current is used to measure static impedance. We modeled two scalp layers: a superficial scalp layer with adaptive conductivity that increases with electric field up to a subject specific maximum, and a deep scalp layer with a subject-specific fixed conductivity. Results: We demonstrate that variation in these scalp parameters explain clinical data on subject-specific static impedance and dynamic impedance, their imperfect correlation across subjects, their relationships to seizure threshold, and the role of head anatomy. Adaptive tES models demonstrate that current flow changes local tissue conductivity which in turn shapes current delivery to the brain in a manner not accounted for in fixed tissue conductivity models. Conclusions: Our predictions that variation in individual skin properties, rather than other aspects of anatomy, largely govern the relationship between static impedance, dynamic impedance, and current delivery to the brain, are themselves subject to assumptions about tissue properties. Broadly, our novel pipeline for tES models is important in ongoing efforts to optimize devices, personalize interventions, and explain clinical findings.

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