A practical method of estimating medium-heterogeneity corrected dose without a Monte Carlo calculation in ocular brachytherapy using 125I COMS plaques.

PURPOSE: To provide a practical method of estimating medium-heterogeneity corrected dose without a Monte Carlo (MC) calculation in ocular brachytherapy using 125I Collaborative Ocular Melanoma Study (COMS) plaques. METHODS AND MATERIALS: Using egs_brachy, MC simulations (1) under task group-43 assumptions with fully loaded seed configurations in water (HOMO) and (2) with effects of plaque backing, insert and inter-seed interactions (HETERO) were performed for seven 125I COMS plaques (10 mm-22 mm in diameter), and homogeneous dose (DHOMO) and heterogeneous dose (DHETERO) for central-axis and off-axis points were determined. For DHOMO, 85 Gy was normalized to a depth of 5 mm. Central-axis heterogeneity correction factors (HCFs) from a depth of 0 mm (inner sclera) to 22 mm (opposite retina) were derived from a ratio of DHETERO to DHOMO. Off-axis HCFs for optic disc/macula and lens as a function of distance from optic disc/macula (DT/MT) for various basal dimensions of tumor (BD/BM) were derived from DHETERO/DHOMO. RESULTS: Central-axis HCF varied with a dose reduction of 10.3-19.8% by heterogeneity. Off-axis HCF for optic disc/macula varied significantly depending on DT/MT and BD/BM with a dose reduction of 11.3-38.3%. Off-axis HCF for lens had a dependence on MT and BM with its variation of 11.0-19.0%. A clinical example of using HCFs to estimate DHETERO was presented. CONCLUSIONS: The practical method of using depth-dependent central-axis HCF and DT/MT- and BD/BM-dependent off-axis HCF provided in this study will facilitate a heterogeneous dose estimate for 125I COMS plaques without MC calculations.

A novel multi-modality imaging phantom for validating interstitial needle guidance for high dose rate gynecological brachytherapy.

PURPOSE: To design, manufacture, and validate a female pelvic phantom for multi-modality imaging (CT, MRI, US) to benchmark a commercial needle tracking system with application in HDR gynecological (GYN) interstitial procedures. MATERIALS AND METHODS: A GYN needle-tracking phantom was designed using CAD software to model an average uterus from a previous patient study, a vaginal canal from speculum dimensions, and a rectum to accommodate a transrectal ultrasound (TRUS) probe. A target volume (CTVHR ) was designed as an extension from the cervix-uterus complex. Negative space molds were created from modeled anatomy and 3D printed. Silicone was used to cast the anatomy molds. A 3D printed box was constructed to house the manufactured anatomy for structural integrity and to accommodate the insertion of a speculum, tandem, needles, and TRUS probe. The phantom was CT-imaged to identify potential imperfections that might impact US visualization. Free-hand TRUS was used to guide interstitial needles into the phantom. The commercial tracking system was used to generate a 3D US volume. After insertion, the phantom was imaged with CT and MR and the uterus and CTVHR dimensions were verified against the CAD model. RESULTS/CONCLUSIONS: The manufactured phantom allows for accurate visualization with multiple imaging modalities and is conducive to applicator and needle insertion. The phantom dimensions from the CAD model were verified with those from each imaging modality. The phantom is low cost and can be reproducibly manufactured with the 3D printing and molding processes. Our initial experiments demonstrate the ability to integrate the phantom with a commercial tracking system for future needle tracking validation studies.

Association of Knowledge About Dementia with Two Dimensional Attitudes Among a Community Population in South Korea.

BACKGROUND: Providing correct information about dementia and people living with dementia and improving the attitude toward the disease have important implications in overcoming prejudice and negative perceptions and strengthening the social support system. However, studies are limited about which aspects of dementia knowledge affect attitudes toward it and the influence of such knowledge on particular aspects of such attitudes. OBJECTIVE: This study examined which part of dementia knowledge affects attitudes toward dementia and, furthermore, the influence of such knowledge on two aspects of attitudes in the general population. METHODS: A population-based cross-sectional survey of 1,200 participants aged 20 years or older was adopted. A landline and wireless telephone survey was conducted from October 12 to October 22, 2021. The survey data included self-report questions about dementia knowledge, dementia attitudes, demographics, and family information. Multiple linear regression analysis was performed. RESULTS: Dementia knowledge was positively associated with global dementia attitudes. In terms of the relationship between the two dimensions of dementia attitudes and knowledge, the latter displayed a significant positive association with accepting attitudes (ß= 0.121, p < 0.001) but not with affective attitudes (ß= 0.064, p = 0.084). Among dementia knowledge, dementia symptom/diagnosis and policy categories were positively associated with accepting attitudes (ß= 0.198, p = 0.006; ß= 0.357, p < 0.001). CONCLUSION: Our study suggests that people with more dementia knowledge have more accepting attitudes toward dementia. It may be effective to continue education on dementia to improve the public accepting attitudes. However, to improve negative emotional attitudes toward dementia, various approaches beyond education may be needed.

Correction: Mineralized biomimetic collagen/alginate/silica composite scaffolds fabricated by a low-temperature bio-plotting process for hard tissue regeneration: fabrication, characterisation and in vitro cellular activities.

Correction for 'Mineralized biomimetic collagen/alginate/silica composite scaffolds fabricated by a low-temperature bio-plotting process for hard tissue regeneration: fabrication, characterisation and in vitro cellular activities' by HyeongJin Lee et al., J. Mater. Chem. B, 2014, 2, 5785-5798, https://doi.org/10.1039/c4tb00931b.

Field output correction factors of stereotactic cones for a diode detector: Dependence on cone size, measurement setup, reference field size and photon energy.

This study investigated if field output correction factors (FOCFs) of Varian stereotactic cones for Edge detectorTM had dependence on cone size, measurement setup, reference field size and/or photon energy. Field output factors (FOFs) of stereotactic cones were measured at three depths (1.5 cm, 5 cm and 10 cm) in two different setups (source-to-surface distance (SSD) and source-to-axis distance (SAD)) with two photon energies (6 MV and 6 MV flattening filter free) using the Edge detector and Exradin® W2 scintillator. Two reference fields (10 × 10 cm2 and 4 × 4 cm2) were chosen. FOCFs for the Edge detector were determined by calculating FOFW2/FOFEdge and compared among cones and between depths, setups, reference fields and energies. It is concluded that FOCFs for the Edge detector have dependence on cone size, SSD/SAD setup and energy for small cones, but do not have dependence on depth and reference field size.

Ear, Nose, and Throat Foreign Bodies in Children: A Retrospective Study.

BACKGROUND: This study analyzed the presentation, characteristics, and management of foreign bodies in different age groups of pediatric patients with ear, nose, and throat foreign bodies. METHODS: A retrospective study was performed using data from October 2012 to September 2020. A total of 1285 patients with ear, nose, and throat foreign bodies who were less than 12 years of age and who presented to the emergency room were included in this study. Their biographical data, clinical presentations, foreign body types and locations, and management outcomes were obtained from medical records and analyzed as three age groups (infancy: <2 years old; early childhood: 2-5 years old; and late childhood: 6-12 years old). RESULTS: The early childhood group had the highest number of patients (n = 672; 52.2%). Throat was the most common location (59.2%), and bone was the most common type of foreign body. Among the children who visited our hospital, foreign bodies were actually found in only 657 patients (51.1%) and removed by an otolaryngologist in 625 (95.1%) cases. CONCLUSION: Our study could provide guidance for the diagnosis and management of pediatric patients who present to emergency departments with foreign bodies.

Dual-source strength seed loading for eye plaque brachytherapy using eye physics eye plaques: A feasibility study.

Purpose: This study quantifies the dosimetric impact of incorporating two iodine-125 (125I) seed source strengths in Eye Physics eye plaques for treatment of uveal melanoma. Material and methods: Plaque Simulator was used to retrospectively plan 15 clinical cases of three types: (1) Shallow tumors (< 5.5 mm) with large base dimensions (range, 16-19 mm); (2) Tumors near the optic nerve planned with notched plaques; and (3) Very shallow (< 3.0 mm) tumors with moderate base dimensions (range, 13.5-15.5 mm) planned with larger plaques than requested by the ocular oncologist. Circular plaques were planned with outer ring sources twice the source strength of inner sources, and notched plaques with the six seeds closest to the notch at twice the source strength. Results: In cases of type (1), the dual-source strength plan decreased prescription depth, and doses to critical structures were lower: inner sclera -25% ±2%, optic disc -7% ±3%, and fovea -6% ±3%. In four out of five cases of type (2), the dual-source strength plan decreased prescription depth, and dose to inner sclera was lower (-22% ±5%), while dose to optic disc (17% ±7%) and fovea (20% ±12%) increased. In cases of type (3), a smaller dual-source strength plaque was used, and scleral dose was lower (-45% ±3%), whereas dose to optic disc (1% ±14%) and fovea (5% ±5%) increased. Conclusions: Dual-source strength loading as described in this study can be used to cover tumor margins and decrease dose to sclera, and therefore the adjacent retina, but can either decrease or increase radiation dose to optic disc and fovea depending on location and size of the tumor. This technique may allow the use of a smaller plaque, if requested by the ocular oncologist. Clinical determination to use this technique should be performed on an individual basis, and additional QA steps are required. Integrating the use of volumetric imaging may be warranted.

Electronic brachytherapy for treatment of non-melanoma skin cancers: clinical results and toxicities.

PURPOSE: Although surgical approaches are standard for most non-melanomatous skin cancers, some patients are not candidates due to medical co-morbidities or functional or cosmetic or lesion location. High-dose-rate electronic brachytherapy (HDR-EBT) may be an alternative treatment modality. MATERIAL AND METHODS: A retrospective chart review was conducted from April 2011 to April 2013. All lesions were pathologically confirmed as malignant basal cell or squamous cell carcinoma. A HDR-EBT system delivered a median biological equivalent dose of 50 Gy total to a depth of 0.1-0.5 cm using various sizes of applicators. Treatment feasibility, acute and late toxicity, cosmetic outcomes, and local recurrence were assessed. RESULTS: Thirty-three patients with a mean age of 76 years with 50 cutaneous lesions were treated. Locations included 17 extremity lesions and 33 head and neck lesions. After treatments, acute grade 3 moist desquamation developed in 9 of the lesions (18%). Acute grade 4 ulceration developed in 3 lesions in the lower extremity (6%) and 1 upper lip lesion (2%). These toxicities were improved after a median of 20 days. Amongst the 4 lesions with grade 4 toxicities, a greater proportion were in lower extremity lesions compared to head and neck lesions (75% vs. 25%). There was no difference in the rate of grade 3 and 4 toxicities between patients aged ≤ 75 years and aged > 75 years (p = 0.082). With a mean long-term follow-up of 45.6 months, there was 1 local recurrence treated with surgery and no reported late toxicities. CONCLUSIONS: Our experience with HDR-EBT for non-melanomatous skin cancers is encouraging in terms of efficacy and convenience for patients. Our long-term follow-up shows a good response in all treated sites. Caution should be used for extremity sites, and more fractionated regimens should be considered to avoid severe acute toxicities.

A patient-specific QA comparison between 2D and 3D diode arrays for single-lesion SRS and SBRT treatments.

The purpose of this study is to compare patient-specific quality assurance (PSQA) results between two dimensional (2D) diode (SRS MapCHECK®) and 3D diode (ArcCHECK®) arrays. Twenty-eight intracranial stereotactic radiosurgery (SRS) and 26 lung stereotactic body radiation therapy (SBRT) clinical plans with a single lesion were selected and categorized into 4 groups: 20 SRS dynamic conformal arc therapy (DCAT) plans (Group A), 8 SRS volumetric modulated arc therapy (VMAT) plans (Group B), 6 SBRT DCAT plans (Group C) and 20 SBRT VMAT plans (Group D). An individual field of each plan was delivered on SRS MapCHECK and ArcCHECK and QA analysis was performed using 4 gamma criteria of dose difference/distance-to-agreement of 3%/3 mm, 3%/2 mm, 2%/2 mm and 2%/1 mm. Statistical analysis was performed to compare PSQA results between the 2 QA devices. For all 4 groups and all 4 gamma criteria, average gamma passing rates were higher with SRS MapCHECK.

Optic Disc Dose Comparison Between 125I and 103Pd Collaborative Ocular Melanoma Study (COMS) Plaques Based on Current Clinical Practice.

Purpose The purpose of this study is to compare optic disc dose (ODD) between 125I and 103Pd Collaborative Ocular Melanoma Study (COMS) plaques in ocular brachytherapy. Methods A previously validated in-house brachytherapy dose calculation program was used for ODD calculations. ODD was calculated as a function of tumor margin-to-optic disc distance (DT) up to 5 mm for various tumor basal dimensions (BDs), for a prescription depth of 5 mm, and for standard and notched COMS plaques loaded with 125I (model: IAI-125A) and 103Pd (model: IAPd-103A) seeds. ODD calculations were repeated for prescription depths from 2 mm to 10 mm in 1 mm intervals. A prescribed dose of 85 Gy (irradiation time: 120 hours) was normalized to each prescription depth. Dose conversion factors (DCFs) for each prescription depth were calculated by taking a ratio of [total reference air kerma (TRAK) per seed]prescription depth to [TRAK per seed]5 mm. ODD reduction by notched COMS plaques was calculated for each prescription depth by subtracting ODD for notched COMS plaques from ODD for standard COMS plaques. Results Trends of ODD as a function of DT for various BDs are similar between the two seed types in both standard and notched COMS plaques. However, due to the energy difference, there exists a transition distance (dt) for each BD in each plaque at which ODD for 125I COMS plaques equals that for 103Pd COMS plaques. For small BDs, at DT dt, the opposite is observed. For the largest 1-3 BD(s), contrarily, dt occurs within the tumor, and thus, ODD for 125I COMS plaquesis always higher. Trends of ODD reduction by notched COMS plaques as a function of DT for various BDs are the same for the two seed types except that maximum ODD reduction by 103Pd COMS notched plaques is larger. DCF increases with increasing prescription depth for both seed types. Conclusions There exist ODD differences between 125I and 103Pd COMS plaques and the differences depend on DT, BD, plaque size, and prescription depth.

Recommendations for intraoperative mesh brachytherapy: Report of AAPM Task Group No. 222.

Mesh brachytherapy is a special type of a permanent brachytherapy implant: it uses low-energy radioactive seeds in an absorbable mesh that is sutured onto the tumor bed immediately after a surgical resection. This treatment offers low additional risk to the patient as the implant procedure is carried out as part of the tumor resection surgery. Mesh brachytherapy utilizes identification of the tumor bed through direct visual evaluation during surgery or medical imaging following surgery through radiographic imaging of radio-opaque markers within the sources located on the tumor bed. Thus, mesh brachytherapy is customizable for individual patients. Mesh brachytherapy is an intraoperative procedure involving mesh implantation and potentially real-time treatment planning while the patient is under general anesthesia. The procedure is multidisciplinary and requires the complex coordination of multiple medical specialties. The preimplant dosimetry calculation can be performed days beforehand or expediently in the operating room with the use of lookup tables. In this report, the guidelines of American Association of Physicists in Medicine (AAPM) are presented on the physics aspects of mesh brachytherapy. It describes the selection of radioactive sources, design and preparation of the mesh, preimplant treatment planning using a Task Group (TG) 43-based lookup table, and postimplant dosimetric evaluation using the TG-43 formalism or advanced algorithms. It introduces quality metrics for the mesh implant and presents an example of a risk analysis based on the AAPM TG-100 report. Recommendations include that the preimplant treatment plan be based upon the TG-43 dose calculation formalism with the point source approximation, and the postimplant dosimetric evaluation be performed by using either the TG-43 approach, or preferably the newer model-based algorithms (viz., TG-186 report) if available to account for effects of material heterogeneities. To comply with the written directive and regulations governing the medical use of radionuclides, this report recommends that the prescription and written directive be based upon the implanted source strength, not target-volume dose coverage. The dose delivered by mesh implants can vary and depends upon multiple factors, such as postsurgery recovery and distortions in the implant shape over time. For the sake of consistency necessary for outcome analysis, prescriptions based on the lookup table (with selection of the intended dose, depth, and treatment area) are recommended, but the use of more advanced techniques that can account for real situations, such as material heterogeneities, implant geometric perturbations, and changes in source orientations, is encouraged in the dosimetric evaluation. The clinical workflow, logistics, and precautions are also presented.

Surface brachytherapy: Joint report of the AAPM and the GEC-ESTRO Task Group No. 253.

The surface brachytherapy Task Group report number 253 discusses the common treatment modalities and applicators typically used to treat lesions on the body surface. Details of commissioning and calibration of the applicators and systems are discussed and examples are given for a risk-based analysis approach to the quality assurance measures that are necessary to consider when establishing a surface brachytherapy program.

Optic disc dose reduction in ocular brachytherapy using 125 I notched COMS plaques: A simulation study based on current clinical practice.

PURPOSE: Although notched Collaborative Ocular Melanoma Study (COMS) plaques have been widely used, optic disc dose reduction by notched COMS plaques has not been discussed in the literature. Therefore, this study investigated optic disc dose reduction in ocular brachytherapy using 125 I notched COMS plaques in comparison with optic disc dose for 125 I standard COMS plaques. METHODS: For this simulation study, an in-house brachytherapy dose calculation program was developed using MATLAB software by incorporating the American Association of Physicists in Medicine Task Group-43 Update (AAPM TG-43U1) dosimetry formalism with a line source approximation in a homogeneous water medium and COMS seed coordinates in the AAPM TG 129. Using this program, optic disc doses for standard COMS plaques (from 12 to 22 mm in diameter in 2 mm increments) and notched COMS plaques with one seed removed (Case #1, from 12 to 22 mm) and with two seeds removed (Case #2, from 14 to 22 mm) were calculated as a function of tumor margin-to-optic disc distance (DT) for various tumor basal dimensions (BDs) for prescription depths from 1 to 10 mm in 1 mm intervals. A dose of 85 Gy for an irradiation time of 168 h was prescribed to each prescription depth. Then absolute and relative optic disc dose reduction by notched COMS plaques (Cases #1 and #2) was calculated for all prescription depths. RESULTS: Optic disc dose reduction by notched COMS plaques (Cases #1 and #2) had five unique trends related to maximum optic disc dose reduction and corresponding optimal DT for each BD in each plaque. It increased with increasing prescription depth. CONCLUSIONS: The results presented in this study would enable the clinician to choose an adequate plaque type among standard and notched 125 I COMS plaques and a prescription depth to minimize optic disc dose.

Circular collimator arc versus dynamic conformal arc treatment planning for linac-based stereotactic radiosurgery of an intracranial small single lesion: a perspective of lesion asymmetry.

BACKGROUND: Although circular collimator arcs (CCA) and dynamic conformal arcs (DCA) are commonly used linear accelerator-based treatment planning techniques for intracranial stereotactic radiosurgery (SRS) of a small single lesion, these two techniques have not been rigorously compared in terms of tumor shape. Therefore, this study compared clinical CCA plans with re-planned DCA plans using conformity index (CI) and V12Gy (volume of normal brain tissue receiving 12 Gy or higher) from a perspective of asymmetry (Asym) of planning target volume (PTV). METHODS: Ninety-five clinical CCA plans delivered for a small single lesion with PTV size < 1.4 cm3 were selected and re-planned using DCA. PTV Asym (%) was defined and calculated from three dimensions of PTV. A pair of the 95 plans was first considered as one group without grouping and then categorized into two groups with respective to either PTV size or PTV Asym, and four groups with respect to PTV size and PTV Asym. For grouping, median values of PTV size and PTV Asym were used. A non-parametric paired test was performed for CI and V12Gy to compare CCA and DCA plans in each group. RESULTS: Median values of PTV size and PTV Asym were 0.415 cm3 (range: 0.076 cm3-1.369 cm3) and 6.12% (range: 0.52-25.74%), respectively. DCA plans had a lower average CI value than CCA plans for all groups. CCA plans had a smaller average V12Gy value than DCA plans for lesions with PTV Asym ≤6.12%, while CCA and DCA plans had similar average V12Gy values for lesions with PTV Asym > 6.12%. CONCLUSIONS: The DCA technique is recommended when a lesion has PTV Asym > 6.12% regardless of PTV size. For lesions with PTV Asym ≤6.12%, a technique choice would depend on the preference of CI or V12Gy.

A practical approach to estimating optic disc dose and macula dose without treatment planning in ocular brachytherapy using 125I COMS plaques.

BACKGROUND: It has been reported that proximity of the tumor to the optic disc and macula, and radiation dose to the critical structures are substantial risk factors for vision loss following plaque brachytherapy. However, there is little dosimetry data published on this. In this study, therefore, the relationship between distance from tumor margin and radiation dose to the optic disc and macula in ocular brachytherapy using 125I Collaborative Ocular Melanoma Study (COMS) plaques was comprehensively investigated. From the information, this study aimed to allow for estimation of optic disc dose and macula dose without treatment planning. METHODS: An in-house brachytherapy dose calculation program utilizing the American Association of Physicists in Medicine Task Group-43 U1 formalism with a line source approximation in a homogenous water phantom was developed and validated against three commercial treatment planning systems (TPS). Then optic disc dose and macula dose were calculated as a function of distance from tumor margin for various tumor basal dimensions for seven COMS plaques (from 10 mm to 22 mm in 2 mm increments) loaded with commercially available 125I seeds models (IAI-125A, 2301 and I25.S16). A prescribed dose of 85 Gy for an irradiation time of 168 h was normalized to a central-axis depth of 5 mm. Dose conversion factors for each seed model were obtained by taking ratios of total reference air kerma per seed at various prescription depths (from 1 mm to 10 mm in 1 mm intervals) to that at 5 mm. RESULTS: The in-house program demonstrated relatively similar accuracy to commercial TPS. Optic disc dose and macula dose decreased as distance from tumor margin and tumor basal dimension increased. Dose conversion factors increased with increasing prescription depth. There existed dose variations (<8%) among three 125I seed models. Optic disc dose and macula dose for each COMS plaque and for each seed model are presented in a figure format. Dose conversion factors for each seed model are presented in a tabular format. CONCLUSIONS: The data provided in this study would enable clinicians in any clinic using 125I COMS plaques to estimate optic disc dose and macula dose without dose calculations.

Failure modes and effects analysis for ocular brachytherapy.

PURPOSE: The aim of the study was to identify potential failure modes (FMs) having a high risk and to improve our current quality management (QM) program in Collaborative Ocular Melanoma Study (COMS) ocular brachytherapy by undertaking a failure modes and effects analysis (FMEA) and a fault tree analysis (FTA). METHODS AND MATERIALS: Process mapping and FMEA were performed for COMS ocular brachytherapy. For all FMs identified in FMEA, risk priority numbers (RPNs) were determined by assigning and multiplying occurrence, severity, and lack of detectability values, each ranging from 1 to 10. FTA was performed for the major process that had the highest ranked FM. RESULTS: Twelve major processes, 121 sub-process steps, 188 potential FMs, and 209 possible causes were identified. For 188 FMs, RPN scores ranged from 1.0 to 236.1. The plaque assembly process had the highest ranked FM. The majority of FMs were attributable to human failure (85.6%), and medical physicist-related failures were the most numerous (58.9% of all causes). After FMEA, additional QM methods were included for the top 10 FMs and 6 FMs with severity values > 9.0. As a result, for these 16 FMs and the 5 major processes involved, quality control steps were increased from 8 (50%) to 15 (93.8%), and major processes having quality assurance steps were increased from 2 to 4. CONCLUSIONS: To reduce high risk in current clinical practice, we proposed QM methods. They mainly include a check or verification of procedures/steps and the use of checklists for both ophthalmology and radiation oncology staff, and intraoperative ultrasound-guided plaque positioning for ophthalmology staff.

Evaluation of impact of an external breast shield (FlexiShield) in electronic brachytherapy for breast IORT: A phantom study.

PURPOSE: To investigate Axxent (iCAD, Inc., San Jose, CA) electronic brachytherapy balloon deformation and its dosimetric impact because of an external flexible shield (FlexiShield [FS]; iCAD, Inc.). METHODS AND MATERIALS: Prostheses breast tissue phantom overlaid three spherical balloon applicators to simulate three clinical scenarios depending on minimum skin-to-balloon surface spacing (SS): balloon with SS of 2 cm, 1 cm, and balloon with 1 cm SS and touching the chest wall. Two sets of megavoltage CT (MVCT) scans were obtained with or without FS for 15 different sizes of balloons. For 45 pairs of MVCT scans, balloon deformation was measured in superior-inferior (dSI) dimension on coronal and sagittal planes and anterior-posterior (dAP) and lateral (dLAT) dimensions on the equatorial plane of balloon. SS was also compared. A treatment plan was made on each MVCT scan. Doses at four balloon surface points and skin were compared. Conformity index value was also compared to evaluate three-dimensional dose distribution. Clinically, 20 Gy was prescribed to the surface of balloon. RESULTS: Balloon deformation was observed with compression in SI and AP dimensions and expansion in lateral dimension. Average SI compression was 0.5 mm. Average dLat - dAP was 2.4 mm, which resulted in elevated point doses at AP dimension by 10.8% of prescribed dose and reduced point doses at lateral dimension by 4.6%. FS decreased SS by 1.8 mm, increasing skin dose by 1.2 Gy, on average. Conformity index value was decreased from 0.922 to 0.908, on average. CONCLUSIONS: This phantom study demonstrates that use of skin shielding during breast intraoperative radiation therapy can cause balloon deformation and SS reduction, resulting in dosimetric changes that are disregarded in current practice.

Versatile design of hydrogel-based scaffolds with manipulated pore structure for hard-tissue regeneration.

In recent years, a variety of biomimetic hydrogel scaffolds have been used in tissue engineering because hydrogels can provide reasonable soft-tissue-like environmental conditions for various cell responses. However, although hydrogels can provide an outstanding biofunctional platform, their poor mechanical stability and low processability have been obstacles for their usage as biomedical scaffolds. To overcome this limitation, we propose a simple and versatile method using 3D printing supplemented with a low-temperature working plate and coating process to reinforce the mechanical properties and various cellular activities by accommodating the poly(ε-caprolactone) (PCL). To determine the efficiency of the method, we used two typical hydrogels (alginate and collagen), which were deposited in a multi-layer configuration, and PCL as a coating agent. The scaffolds were evaluated in terms of various physical and cellular activities (metabolic activity and osteogenic activity). Throughout the experiments, significant increases in the tensile modulus (>6-fold), cell proliferation (>1.2-fold), and calcium deposition (>1.3-fold) were observed for the hydrogel/PCL scaffolds compared to those for pure hydrogel. Based on the experimental results, we can confirm that the proposed hydrogel scaffold can be a highly promising biomedical scaffold for application in tissue regeneration.

Commissioning of a 3D image-based treatment planning system for high-dose-rate brachytherapy of cervical cancer.

The objective of this work is to present commissioning procedures to clinically implement a three-dimensional (3D), image-based, treatment-planning system (TPS) for high-dose-rate (HDR) brachytherapy (BT) for gynecological (GYN) cancer. The physical dimensions of the GYN applicators and their values in the virtual applicator library were varied by 0.4 mm of their nominal values. Reconstruction uncertainties of the titanium tandem and ovoids (T&O) were less than 0.4 mm on CT phantom studies and on average between 0.8-1.0 mm on MRI when compared with X-rays. In-house software, HDRCalculator, was developed to check HDR plan parameters such as independently verifying active tandem or cylinder probe length and ovoid or cylinder size, source calibration and treatment date, and differences between average Point A dose and prescription dose. Dose-volume histograms were validated using another independent TPS. Comprehensive procedures to commission volume optimization algorithms and process in 3D image-based planning were presented. For the difference between line and volume optimizations, the average absolute differences as a percentage were 1.4% for total reference air KERMA (TRAK) and 1.1% for Point A dose. Volume optimization consistency tests between versions resulted in average absolute differences in 0.2% for TRAK and 0.9 s (0.2%) for total treatment time. The data revealed that the optimizer should run for at least 1 min in order to avoid more than 0.6% dwell time changes. For clinical GYN T&O cases, three different volume optimization techniques (graphical optimization, pure inverse planning, and hybrid inverse optimization) were investigated by comparing them against a conventional Point A technique. End-to-end testing was performed using a T&O phantom to ensure no errors or inconsistencies occurred from imaging through to planning and delivery. The proposed commissioning procedures provide a clinically safe implementation technique for 3D image-based TPS for HDR BT for GYN cancer.

Phage as versatile nanoink for printing 3-D cell-laden scaffolds.

Bioprinting is an emerging technology for producing tissue-mimetic 3-D structures using cell-containing hydrogels (bioink). Various synthetic and natural hydrogels with key characteristics, including biocompatibility, biodegradability, printability and crosslinkability, have been employed as ink materials in bioprinting. Choosing the right cell-containing "bioink" material is the most essential step for fabricating 3-D constructs with a controlled mechanical and biochemical microenvironment that can lead to successful tissue regeneration and repair. Here, we demonstrate that the genetically engineered M13 phage holds great potential for use as a versatile nanoink for printing 3-D cell-laden matrices. In particular, M13 phages displaying integrin-binding (GRGDS) and calcium-binding (DDYD) domains on their surface were blended with alginate to successfully form Ca(2+)-crosslinked hydrogels. Furthermore, 3-D cell-laden scaffolds with high cell viability were generated after optimizing the printing process. The MC3T3-E1 cells within these scaffolds showed enhanced proliferation and differentiation rates that increased proportionally with the concentration of phages in the 3-D matrices compared with the rates of cells in pure alginate scaffolds. STATEMENT OF SIGNIFICANCE: Bioprinting is an emerging technology for producing tissue-mimetic 3-D structures using cell-containing hydrogels called bioink. Choosing the right bioink is essential for fabricating 3-D structures with controlled mechanical and biochemical properties which lead to successful tissue regeneration. Therefore, there is a growing demand for a new bioink material that can be designed from molecular level. Here, we demonstrate that genetically engineered M13 phage holds great potential for use as versatile bioink. The phage-based bioink benefits from its replicability, self-assembling property, and tunable molecular design and enables bioprinted scaffolds to exhibit improved cell viability, proliferation and differentiation. This study opens the door for the development of genetically tunable nanofibrous bioink materials which closely mimic natural structural proteins in the extracellular matrix.