Bolus Material Research Articles

Fabrication and Characterization of Bolus Material Using Propylene Glycol for Radiation Therapy

Introduction: This study aimed to evaluate the efficacy of a synthesized bolus in the reduction of damage to body tissues and the protection of the organ at risk (OAR) in radiotherapy application. Several properties of the synthesized bolus, including density, transmission factor, and effective mass attenuation coefficient, were investigated. Material and Methods: The materials used comprising of propylene glycol (PG), silicone rubber (SR), and aluminum (Al). The dimension of the synthesized bolus was measured using an acrylic case with a size of 11×11 cm² and thickness sizes of 0.5, 1, and 1.5 cm. Furthermore, the boluses were irradiated by linear accelerator with the photon beam energies of 6 and 10 MV, using linier accelerator (LINAC) Varian 2300ix. Results: In this research,the density of synthesized bolus was evaluated by mass per volume equation. The results showed that the density of bolus was similar to the density of tissue/water, fat, and air. . Furthermore the bolus with the composition of PG 24%, SR 8%, and Al 1.5% of all energies, transmission factors of 0.978 and 0.984, thickness of 1.5 cm, and effective mass attenuation coefficients of 0.0144 and 0.0107 cm²/g had the closest properties to the body tissues in terms of dosimetry characterization. Conclusion: The results revealed that the synthesized bolus could increase the percentage surface dose, reduce skin-sparing effect, and protect OAR. The findings indicated that the synthesized bolus had a potential application in clinical therapy.

Design and manufacture of a high precision personalized electron bolus device for radiation therapy

AbstractThis paper investigates a novel design and manufacturing methodology for an unmet need in radiation therapy—dose optimization of electron beam bolus. A thin‐walled bolus design was proposed which when filled with water, optimized the dose distribution for the electron beam radiation therapy. The fabrication of this design was accomplished by the fused deposition modelling (FDM) additive manufacturing (3D Printing) technique. Acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) materials were employed for fabricating the electron boluses. Our data show that both the materials displayed expected radiation modulation. The designed boluses were subjected to higher radiation doses (50 Gy) and revealed permissible deformations based on the dimensional deviation analysis. Mechanical deformation tests were performed to evaluate the bolus design and materials under different loading conditions. The results showed that the ABS material had superior mechanical strength and deformation behaviour as compared to PC. Finite element analysis of the bolus designs revealed regions of stress concentration and potential failure modes which were validated by experimental results. The design of experiments analysis showed that bolus thickness and material type had a profound influence on the mechanical deformation of the bolus. The proposed radiation device technology is cost‐effective, eco‐friendly and amenable to changes in the tumour size and shape, compared to current methods. This paper provides a framework for the design and manufacture of radiation modulation devices that can be implemented for proton, electron and photon cancer therapies.

Polyvinyl alcohol (PVA) based bolus material for high energy photons and electrons

The study focused on the use of fabricated bolus materials based on the polyvinyl alcohol (PVA) to increase the surface dose on high energy photons and electrons. The PVA based bolus materials were fabricated at 2.5, 5, 7.5 and 10% PVA in water at target density of 1.0 g/cm3. The PVA based boluses were scanned by using the computed tomography (CT) scanner along with the solid water phantoms. The percentage depth (PDD) dose of the solid water phantoms and the PVA based bolus materials were measured by using the treatment planning software (TPS) at 6 and 10 MV photons and 6 and 9 MeV electrons. The PDD curved obtained were compared to that of the standard bolus material and the surface dose were measured. The results showed that the PDD curves of solid water phantoms with PVA based bolus materials were consistent with that in standard bolus material within 1.4% percentage of difference for both 6 and 10 MV photons and within 2.9 and 1.4% percentage of differences in 6 and 9 MeV electrons respectively. The increment of surface dose in PVA based bolus materials were in excellent agreement to the standard bolus material and the percentage of PVA did not significantly affect the surface dose. The overall results showed the potential use of the PVA to be used as bolus material for clinical photons and electrons.

Comparison of Dosimetry Characteristics from Some Bolus Materials for 6 and 10 MV Photons Beam Radiation Therapy

In radiation therapy, bolus material is often used for increased surface dose, compensate for surface irregularities and internal heterogeneities. Bolus has properties equivalent to water and soft tissue. In this study, the mixture of Silicone Rubber (SR) and Bismuth was used for bolus fabrication and then compared to commercial boluses such as Paraffin, Play-Doh, and Paraffin Wax. The study aims to evaluate the comparison of relative electron density (RED), effective mass attenuation coefficient, transmission factor, percentage of surface dose (PSD), and Percentage Depth Dose (PDD) for all boluses. The bolus was made with the size 11 × 11 × 0.5 cm3. Physical density of the synthesized bolus was assessed by computerized tomography (CT) Scanning. The results of the RED analysis for the mixture of Silicone Rubber (SR) and Bismuth, Paraffin, Play-Doh, and Paraffin Wax were 0.954; 0.743; 0.933; and 0.878, respectively. The values of RED for all boluses has a similar to water and soft tissue. These results prove that the bolus is equivalent to soft tissue density such as fat, breast, lungs, and liver. Furthermore, for other dosimetry tests such as transmission factors and attenuation coefficients using Linear Accelerator (LINAC) with photon energy sources 6 and 10 MV. In general, Percentage of surface dose at 6 MV is higher than 10 MV. The highest percentage of the surface dose was achieved by paraffin wax at 6 MV energy by 85%. For effective mass attenuation coefficient result, the highest is the mixture of silicone rubber and bismuth at -0.0030 cm2/g for 6 MV and Play-Doh at -0.0114 cm2/g for 10 MV.

Evaluation of Dosimetric Characterization of Homemade Bolus for Radiation Therapy

The bolus is also known a tissue compensation that has material similar to body tissue and placed directly onto the skin surface for radiation therapy. This study aims to characterize and evaluate the synthesized homemade bolus using Natural Rubber, Paraffin Candle, Play-Doh, and Paraffin Wax Pure for radiation therapy using a photon beam. Several dosimetry properties of the synthesized of the bolus, including relative electron density (RED), transmission factor, attenuation coefficient, and percentage of surface dose (PSD), were investigated. All the synthesized bolus made with the same dimension of 11×11 cm2 with the thickness is 1 cm. CT-Scan was used to measure relative electron density (RED) where as LINAC 2300iX with energies 6 and 10 MV were used to evaluate percentage of surface dose. The RED value of all bolus material is in accordance with the provisions of bolus as a tissue compensation of the human body, which is almost the same as the value of HU in breast organs, skin, fat and adult bones. Large transmission factors and attenuation coefficients of each bolus correspond to bolus from paraffin candles as the default bolus of the hospital. The maximum bolus dose value increases when compared to measurements without bolus.

A Comparative Study of Dosimetric Characterization of Bolus Based on Natural Rubber (Hevea Brasiliensis) and Clinical Bolus for Therapy with Megavolt Electron Radiation

The aim of this study is to evaluate the dosimetry properties of the synthesized bolus material from natural rubber compared to clinical boluses (Play-Doh and Paraffin Wax), involving the values of relative electron density (RED), transmission factor value (TF), mass attenuation coefficient (MAC), percentage surface dose (PSD), and curve of percentage depth dose. In this study, all boluses have dimensions of 11×11×0.5 cm3. Bolus density was measured and analyzed using a CT SCAN and treatment planning system. On the other side, the dosimetry test was performed using Linear Accelerator (LINAC) and detector plan parallel chamber (PPC-40) with an electron beam energy source (6, 9, 12 MeV). Relative electron density for natural rubber bolus, Play-Doh, and paraffin wax were obtained around 0.80, 0.91, and 0.79, respectively. These results indicate that the natural rubber bolus has close to the value of soft tissues such as the lung. Based on the calculation, the transmission factor and the mass attenuation coefficient of natural rubber have the best absorber properties achieved at 12 MeV energy with the results of 99.83% and 0.0045 cm2/g; this also occurred in the clinical boluses. The surface dose experienced an increase in each addition of energy as much as 8.73, 5.35, and 4.79% for energy sources 6, 9, and 12 MeV, respectively. Therefore it can be concluded that the bolus synthesized by natural rubber can be used as an alternative bolus alongside the clinical bolus in this study (paraffin wax and Play-Doh) in the treatment of superficial cancer using megavolt electron energy.

Evaluation of a pixelated large format CMOS sensor for x-ray microbeam radiotherapy.

PurposeCurrent techniques and procedures for dosimetry in microbeams typically rely on radiochromic film or small volume ionization chambers for validation and quality assurance in 2D and 1D, respectively. Whilst well characterized for clinical and preclinical radiotherapy, these methods are noninstantaneous and do not provide real time profile information. The objective of this work is to determine the suitability of the newly developed vM1212 detector, a pixelated CMOS (complementary metal‐oxide‐semiconductor) imaging sensor, for in situ and in vivo verification of x‐ray microbeams.MethodsExperiments were carried out on the vM1212 detector using a 220 kVp small animal radiation research platform (SARRP) at the Helmholtz Centre Munich. A 3 x 3 cm2 square piece of EBT3 film was placed on top of a marked nonfibrous card overlaying the sensitive silicon of the sensor. One centimeter of water equivalent bolus material was placed on top of the film for build‐up. The response of the detector was compared to an Epson Expression 10000XL flatbed scanner using FilmQA Pro with triple channel dosimetry. This was also compared to a separate exposure using 450 µm of silicon as a surrogate for the detector and a Zeiss Axio Imager 2 microscope using an optical microscopy method of dosimetry. Microbeam collimator slits with range of nominal widths of 25, 50, 75, and 100 µm were used to compare beam profiles and determine sensitivity of the detector and both film measurements to different microbeams.ResultsThe detector was able to measure peak and valley profiles in real‐time, a significant reduction from the 24 hr self‐development required by the EBT3 film. Observed full width at half maximum (FWHM) values were larger than the nominal slit widths, ranging from 130 to 190 µm due to divergence. Agreement between the methods was found for peak‐to‐valley dose ratio (PVDR), peak to peak separation and FWHM, but a difference in relative intensity of the microbeams was observed between the detectors.ConclusionsThe investigation demonstrated that pixelated CMOS sensors could be applied to microbeam radiotherapy for real‐time dosimetry in the future, however the relatively large pixel pitch of the vM1212 detector limit the immediate application of the results.

Fabrication of Alternative Bolus for Cobalt-60 Teletherapy Using Two Locally Available Materials

Bolus is a tissue equivalent material which is use in radiation therapy in order to eliminate skin sparing effect of higher energy photon beams that always reduce the surface dose. There are several commercially bolus material such as Superflab, Aquaplast and gels for use but literature have shown that they are expensive and are not readily available in developing countries. This work presents the fabrication of an alternative bolus for Cobalt-60 Teletherapy using two locally available materials (Beeswax and Petroleum jelly). Beeswax was liquefied at a temperature of 60°C followed by the addition of Petroleum jelly at ratio 3:1 by weight for proper molding and flexibility. In order to determine the depth of maximum dose, Thermoluminescent Dosimeter (TLD) chips were inserted in between ten bolus materials of thickness 0.5 cm that were arranged in layers and placed on a solid water phantom. This was then irradiated with Cobalt-60 radiation source using field size ranging from 5 cm x 5 cm to 10 cm x 10 cm field size. For all the field size, maximum absorbed dose was found to be at 0.5 cm depth. This depth of maximum dose was compared to two tissue equivalent materials in use in radiation therapy: water and Superflab for Cobalt-60 Teletherapy and found to be in agreement. The percentage dose deviation when compared with water for 1 cm, 2 cm, 3 cm, 4 cm and 5 cm were less than 2%. The flexibility of the bolus material and the analysis of the absorbed dose measured have shown that the fabricated bolus material of thickness 0.5 cm can be used as an alternative bolus material for Cobalt-60 Teletherapy.

Influence of Air Gap under Bolus in the Dosimetry of a Clinical 6 MV Photon Beam.

Aim:In some situations of radiotherapy treatments requiring application of tissue-equivalent bolus material (e.g., gel bolus), due to material's rigid/semi-rigid nature, undesirable air gaps may occur beneath it because of irregularity of body surface. The purpose of this study was to evaluate the dosimetric parameters such as surface dose (Ds), depth of dose maximum (dmax), and depth dose along central axis derived from the percentage depth dose (PDD) curve of a 6 MV clinical photon beam in the presence of air gaps between the gel bolus and the treatment surface.Materials and Methods:A bolus holder was designed to hold the gel bolus sheet to create an air gap between the bolus and the radiation field analyzer's (RFA-300) water surface. PDD curves were taken for field sizes of 5 cm × 5 cm, 10 cm × 10 cm, 15 cm × 15 cm, 20 cm × 20 cm, and 25 cm × 25 cm, with different thicknesses of gel bolus (0.5, 1.0, and 1.5 cm) and air gap (from 0.0 to 3.0 cm), using a compact ionization chamber (CC13) with RFA-300 keeping 100 cm source-to-surface (water) distance. The dosimetric parameters, for example, “Ds,“ “dmax,“ and difference of PDD (maximum air gap vs. nil air gap), were analyzed from the obtained PDD curves.Results:Compared to ideal conditions of full contact of bolus with water surface, it has been found that there is a reduction in “Ds“ ranging from 14.8% to 3.2%, 14.9% to 1.1%, and 12.6% to 0.7% with the increase of field size for 0.5, 1.0, and 1.5 cm thickness of gel boluses, respectively, for maximum air gap. The “dmax“ shows a trend of moving away from the treatment surface, and the maximum shift was observed for smaller field size with thicker bolus and greater air gap. The effect of air gap on PDD is minimal (≤1%) beyond 0.4 cm depth for all bolus thicknesses and field sizes except for 5 cm × 5 cm with 1.5 cm bolus thickness.Conclusions:The measured data can be used to predict the probable effect on therapeutic outcome due to the presence of inevitable air gaps between the bolus and the treatment surface.

Study on the radiation attenuation properties of locally available bees-wax as a tissue equivalent bolus material in radiotherapy

In radiation therapy field, bolus material is frequently utilized when treating different areas of a patient, like at the ears or nose, and to provide build-up of dose to the skin surface. The bolus material must be cost effective, suitably flexible to conform to the surface of the patient, and most importantly should be tissue equivalent. The main objective of this work was to estimate the photon attenuation properties of locally available bees-wax and to assess the feasibility of using this bees-wax as a bolus material practice for treatment of cancer patient. The mass attenuation coefficient (μ/ρ) values have been calculated by using MCNP5 simulation code over the wide range of photon energy (0.015–10 MeV). Some related parameters such as the effective atomic number and the mean free path were also calculated to understand the photon attenuation ability of the investigated bolus material. The attenuation properties were also computed for water, tissue and commercial bolus materials for comparison. Evaluation of the results showed that the radiation attenuation properties of locally available bees-wax have a good similarity to water/tissue. Referring to the results of this study, it is proposed that locally available bees-wax is a suitable substance to be used as bolus material practice for treat of cancer patient.

Dosimetric Characteristics of Transparent Bolus for External Beam Radiotherapy

Introduction: In radiotherapy, the bolus is often used while treating the tumor under the uneven surfaces of the patients for correcting the anatomical irregularities and increasing skin dose. Wet cotton and wet gauze are still used in developing countries, since the use of wet cotton and wet gauze has certain disadvantages, there is a need for transparent bolus which should be similar to a universally accepted bolus in terms of properties with a lower cost (50% less expensive). Material and Methods: The present study was conducted to investigate the characteristics of transparent bolus (Senflab) material, such as transmission factor, percentage depth dose (PDD), stability over time and high dose, homogeneity and transparency using 6 and 15 MV photons beam and 12, 15, and 18 MeV electrons beam. Moreover, the new bolus material was compared with those of the commercially available Superflab and RW3 slab. Results: The percentage difference in the transmission factor of Senflab was less than ±1.9%, compared with Superflab and RW3. For PDD, the percentage difference was ±2.88% and ±1.26% for photons and electron beams, respectively. The performance of bolus remained constant both physically and dosimetrically after higher dose exposure. The percentage standard deviation was 0.0002% for a period of one month, and 0.0003% for the homogeneity. The transparency of the bolus material was good enough to display the set radiation treatment field. Conclusion: This study shows the suitability of the new bolus for routine use in radiotherapy.

The Properties of Bolus Material using Silicone Rubber

Bolus is a material equivalent to tissue and used in radiotherapy process to increase a dose surface using electron beam. The bolus synthesis from a material equivalent to tissue is not easy, one of the alternative materials used is silicone rubber (SR). In this research bolus was synthesized with dimension of length x width x thickness is (17 x 17 x 1) cm3. Bolus has been characterized by CT-Scan to find relative electron density (RED) and linear accelerator (LINAC) to investigate percentage of surface dose (PSD) with two energy (8 MeV and 10 MeV). The RED value for bolus is 1.176, these results show the RED value for bolus between soft tissue and solid tissue. The PSD value at 8 MeV and 10 MeV are 102.32% and 101.32%, respectively. These results indicate that the silicone rubber material can be used as an alternative bolus material because it corresponds to the bolus function in radiotherapy.

Simple and Rapid Creation of Customized 3D Printed Bolus Utilizing iPhone X True Depth Camera

Three-dimensional (3D) printing has effectively produced patient-specific bolus materials during radiation treatment for superficial tumors along irregular skin surfaces. Traditional bolus materials in comparison, are often difficult to manipulate for proper fit, and can be difficult to reproduce. Current 3D printed boluses are made from either pre-existing computed tomography (CT) scans or complex surface scanning methods. Here, we introduce an inexpensive, convenient approach to generating 3D printed bolus from surface scanning technology available in common smartphones. 3D printed bolus was designed using surface scans from iphone X true depth cameras and a low cost 3D printer. The percentage density infill was adjusted to achieve tissue equivalence. To evaluate the clinical feasibility, fit against skin surface and radiation dose distribution was compared to traditional bolus. We fabricated customized 3D printed bolus for different areas of the face utilizing an iphone X camera and an inexpensive commercially available 3D printer. When printed at 100% density this bolus material approximated soft tissue/water and provided an equivalent dose distribution to that found with standard bolus materials on direct comparison. The bolus material was inexpensive and produces an ideal fit with the scanned anatomy. We present a simplified method of highly customized bolus production that requires minimal experience with computer modeling programs and can be accomplished with an iphone true depth camera.

Dosimetric Comparison of Existing Bolus Materials to a 3D Printed Custom Bolus

Current bolus types, including synthetic gel and thermoplastic materials, have been shown to be dosimetrically near-water equivalent and are approved for use in the clinic. However, these materials are difficult to conform to irregular surfaces, resulting in air gaps between the bolus and patient surface, contributing to dose differences during treatment delivery. 3D printed bolus materials can solve the problem of air gaps under the bolus and ensure easier setup reproducibility. A 3D printer was used to print a 5mm thick custom scalp bolus made from a rigid plastic chosen because it meets USP class VI requirements and is suitable for medical devices. The bolus shape was designed in the treatment planning system (TPS) to fit the scalp of an anthropomorphic phantom. Custom boluses were created using 5mm and 4.8mm thick synthetic gel (SG) and thermoplastic (TP) sheets respectively. Each material was designed according to standard clinical practice to fit the area specified by the TPS planned bolus. CT scans of the phantom with the three bolus materials were taken to evaluate the fit of each and used to create a simple en face photon treatment plan. For the dose calculation, the Hounsfield Units (HUs) for each bolus were set to match the known HUs of the material. Doses under the different boluses were measured using Gafchromic film and OSLDs and were compared to the corresponding point doses dose from the TPS. The fit, size and shape of the three boluses were compared to the TPS bolus using Hausdorff distances and Dice similarity coefficients (DSCs) of the 3D rendered volumes. The TPS calculated dose under each of the bolus materials was less than 1% different from the dose measured by the film and less than 5% different from the dose measured by the OSLD (see Table 1). Of the three bolus materials, the 3D printed bolus best matched the shape of the planned bolus with a Hausdorff distance of 0.7cm and the TP bolus fit the worst with a Hausdorff distance of 2.0cm. The SG bolus had a Hausdorff distance of 1.8cm. Further, the DSCs between the physical boluses and the TPS planned bolus were 0.78 for SG, 0.77 for the 3D printed rigid, and 0.63 for the TP bolus. Each of the bolus materials is dosimetrically viable for use as scalp bolus as long as the TPS accurately characterizes the HU of the material. If bolus is added to the plan retrospectively, there can be issues with matching bolus thickness and shape using conventional bolus methods. The 3D printed bolus is the best option to match the TPS designed bolus with its high DSCs and low Hausdorff distance, especially for irregular surfaces.Abstract 3636; Table 1Measured and TPS Expected Doses from under the BolusSynthetic GelThermoplastic3D RigidOSLD Dose (cGy)185.0203.0201.5Film Dose (cGy)181.0201.4199.0TPS Calculated Dose (cGy)179.6200.8198.1Difference From Expected - OSLD3.01%1.08%1.69%Difference From Expected - Film0.74%0.30%0.46% Open table in a new tab

Tumor-Treating Field Arrays Do Not Reduce Target Volume Coverage for Glioblastoma Radiation Therapy

PurposeTo inform development of procedures for using tumor-treating field arrays (TTFields) during glioblastoma radiation therapy by determining whether the placement and repositioning of arrays affects target volume coverage and cranial skin dose. Methods and MaterialsRadiation plans from 10 consecutive patients treated for glioblastoma were copied to a cranial phantom and reoptimized for phantom anatomy. Dose distributions were then recalculated on 3 additional computed tomographic scans of the phantom with the TTFields electrode arrays placed over distinct locations on the phantom scalp to compare planning target volume (PTV) coverage and skin dose with and without TTFields in place in varying positions. Percent depth dose curves were also measured for radiation beams passing through the electrodes and compared with commonly used bolus material. ResultsThe presence of TTFields arrays decreased PTV V97% and D97% by as much as 1.7% and 2.7%, respectively, for a single array position, but this decrease was mitigated by array repositioning. On averaging the 3 array positions, there was no statistically significant difference in any dosimetric parameter of PTV coverage (V95-97%, D95-97%) across all cases compared with no array. Mean increases in skin D1cc and D20cc of 3.1% were calculated for the cohort. Surface dose for TTFields electrodes was less than that with a 5-mm superflab bolus. ConclusionsOur work demonstrates that placement of TTFields arrays does not significantly affect target volume coverage. We show that repositioning of TTFields arrays, as is required in clinical use, further minimizes any dosimetric changes and eliminates the need for replanning when arrays are moved. A slight, expected bolus effect is observed, but the calculated increases in skin dose are not clinically significant. These data support the development of clinical trials to assess the safety and efficacy of combining concurrent chemoradiotherapy with TTFields therapy for glioblastoma.

A modern mold room: Meshing 3D surface scanning, digital design, and 3D printing with bolus fabrication.

PurposeThis case series represents an initial experience with implementing 3‐dimensional (3D) surface scanning, digital design, and 3D printing for bolus fabrication for patients with complex surface anatomy where traditional approaches are challenging.Methods and MaterialsFor 10 patients requiring bolus in regions with complex contours, bolus was designed digitally from 3D surface scanning data or computed tomography (CT) images using either a treatment planning system or mesh editing software. Boluses were printed using a fused deposition modeling printer with polylactic acid. Quality assurance tests were performed for each printed bolus to verify density and shape.ResultsFor 9 of 10 patients, digitally designed boluses were used for treatment with no issues. In 1 case, the bolus was not used because dosimetric requirements were met without the bolus. QA tests revealed that the bulk density was within 3% of the reference value for 9 of 12 prints, and with more judicious selection of print settings this could be increased. For these 9 prints, density uniformity was as good as or better than our traditional sheet bolus material. The average shape error of the pieces was less than 0.5 mm, and no issues with fit or comfort were encountered during use.ConclusionsThis study demonstrates that new technologies such as 3D surface scanning, digital design and 3D printing can be safely and effectively used to modernize bolus fabrication.

Sole-ground contact and sitting leg position influence suprahyoid and sternocleidomastoid muscle activity during swallowing of liquids.

Clinically, the stable sole‐ground contact in the diet is considered as important for achieving safe swallows in the dysphagic patients. However, the effects of varied sole‐ground contacts on swallow‐related muscles activities remain unclear. The aim of this study was to investigate the effects of sole‐ground contacts on the muscle activities during swallow for various materials; 26 healthy adult subjects participated in this study. Three different sole‐ground contact conditions were investigated; sole‐ground contact with knees bent to 90° (KB 90°), sole‐ground contact with knees bent to 135° (KB 135°), and sole‐ground off the floor (Off). Participants swallowed four bolus materials (saliva, 5‐ml water, 10‐ml water, and 5‐ml yogurt) in each sole‐ground contact condition. The muscular activities of the suprahyoid (SH) muscle and the sternocleidomastoid muscle during swallowing were detected and recorded using surface electromyography. The sole‐ground contact pressure was evaluated using the data acquisition system. Duration of SH during 10‐ml water swallow for Off was significantly longer than that for KB 90°. Duration of SH during 5‐ml yogurt swallow for Off was significantly longer than that for KB 90°. Integration of SH during 10‐ml water swallow for Off was significantly greater than that for KB 135°. Integration of SH during 5‐ml yogurt swallow for Off was significantly greater than that for KB 90°. No significant differences were found in peak of SH. Sole‐ground contact conditions had significant effect on swallow‐related muscles activities. The stable sitting positions might be more advantageous for performing effective swallows compared with less stable sitting positions.

Assessment of imaging Cherenkov and scintillation signals in head and neck radiotherapy

The goal of this study was to test the utility of time-gated optical imaging of head and neck (HN) radiotherapy treatments to measure surface dosimetry in real-time and inform possible interfraction replanning decisions. The benefit of both Cherenkov and scintillator imaging in HN treatments is direct daily feedback on dose, with no change to the clinical workflow. Emission from treatment materials was characterized by measuring radioluminescence spectra during irradiation and comparing emission intensities relative to Cherenkov emission produced in phantoms and scintillation from small plastic targets. HN treatment plans were delivered to a phantom with bolus and mask present to measure impact on signal quality. Interfraction superficial tumor reduction was simulated on a HN phantom, and cumulative Cherenkov images were analyzed in the region of interest (ROI). HN human patient treatment was imaged through the mask and compared with the dose distribution calculated by the treatment planning system. The relative intensity of radioluminescence from the mask was found to be within 30% of the Cherenkov emission intensity from tissue-colored clay. A strong linear relationship between normalized cumulative Cherenkov intensity and tumor size was established (). The presence of a mask above a scintillator ROI was found to decrease mean pixel intensity by >40% and increase distribution spread. Cherenkov imaging through mask material is shown to have potential for surface field verification and tracking of superficial anatomy changes between treatment fractions. Imaging of scintillating targets provides a direct imaging of surface dose on the patient and through transparent bolus material. The first imaging of a patient receiving HN radiotherapy was achieved with a signal map which qualitatively matches the surface dose plan.

Dosimetry analysis of homemade bolus using propylene glycol for photon MegaVoltage and electron radiation therapy

Bolus is widely used to protect and reduce irradiation in organ at risk in the process of radiotherapy. Generally, the bolus was made from polymer material due to had property is similar or equivalent to tissue. This study aimed to determine the density, transmission factor, effective mass attenuation coefficient on bolus with radiation of photons and electrons. The bolus material (B) was used Propylene Glycol (PG), Silicon Rubber (SR) and Aluminium Powder (Al), and had four types of bolus namely B - PG 24%, B - PG 24%; SR 8%, B - PG 24%; SR 8%; Al 0,5%, and B - PG 24%; SR 8%; Al 1,5% with dimensions of 11 × 11 cm and thickness of 1 and 1.5 cm. The bolus density is evaluated through the mass of each volume. The measured data revealed that all of the boluses have density values which are similar to tissue or water and air in the range from 0,864 - 1,202 g/cm3. For dosimetry testing, the bolus is irradiated using Linear Accelerator with 6 and 10 MV for photon source and 6 and 12 MeV for an electron source. The results showed that B - PG 24%; SR 8%; Al 1.5% for dosimetry testing both 6 and 10 MV photons obtained properties that resemble soft tissue. Meanwhile, for both dosimetry testing of 12 MeV electrons, the B - PG 24%; SR 8% with addition silicone rubber and aluminum have nature closest to soft tissue. All of the boluses that have been fabricated have properties similar to soft tissue for photon therapy whereas the addition of more aluminum making a bolus has features as a shield on the process of radiotherapy.

Implementation of total body photon irradiation as part of an institutional bone marrow transplant program for the treatment of canine lymphoma and leukemias.

A total body irradiation (TBI) protocol was developed to support a bone marrow transplant (BMT) program for the treatment of canine hematologic malignancies. The purpose of this prospective study is to describe implementation of the protocol and resultant dosimetry. Nongraphic manual treatment planning using 6 MV photons, isocentric delivery, 40×40cm field size, wall-mounted lasers to verify positioning, a lucite beam spoiler (without use of bolus material), a dose rate of 8.75 cGy/min at patient isocenter, and a source-to-axis distance of 338cm were used for TBI. A monitor unit calculation formula was derived using ion chamber measurements and a solid water phantom. Five thermoluminescent dosimeters (TLDs) were used at various anatomic locations in each of four cadaver dogs, to verify fidelity of the monitor unit formula prior to clinical implementation. In vivo dosimetric data were then collected with five TLDs at various anatomic locations in six patients treated with TBI. A total dose of 10Gy divided into two 5Gy fractions was delivered approximately 16h apart, immediately followed by autologous stem cell transplant. The mean difference between prescribed and delivered doses ranged from 99% to 109% for various sites in cadavers, and from 83% to 121% in clinical patients. The mean total body dose in cadavers and clinical patients when whole body dose was estimated by averaging doses measured by variably placed TLDs ranged from 98% to 108% and 93% to 102% of the prescribed dose, respectively, which was considered acceptable. This protocol could be used for institutional implementation of TBI.