Commercial Bolus Research Articles

Feasibility of using tungsten functional paper as a thin bolus for electron beam radiotherapy.

Containing 80% tungsten by weight, tungsten functional paper (TFP) is a radiation-shielding material that is lightweight, flexible, disposable, and easy to cut. Through experimental measurements and Monte Carlo simulations, we investigated the feasibility of using TFP as abolus in electron beam radiotherapy. Commercial boluses of thickness 5 and 10mm and from one to nine layers of TFPs (0.3-2.7mm) were positioned on the surface of water-equivalent phantoms. The percentage depth dose curves and transverse dose profiles were measured using a 9-MeV electron beam from a clinical linear accelerator. Normalized to the value at the depth of maximum dose without bolus, the relative doses at the phantom surface for no bolus, 5-mm bolus, 10-mm bolus, 1 TFP, 3 TFPs, 6 TFPs, and 9 TFPs were 78%, 88%, 92%, 84%, 92%, 102%, and 112%, respectively; the therapeutic depths corresponding to a 90% dose level were 29.1mm, 22.7mm, 17.7mm, 26.6mm, 23.2mm, 19.3mm, and 15.8mm, respectively. The TFP contributed to increased skin dose and provided dose uniformity within the target volume. However, it also resulted in increased lateral constriction and penumbra width. The results of Monte Carlo simulation produced similar trends as the experimental measurements. Our findings suggest that using TFP as a novel thin and flexible skin bolus for electron beam radiotherapy is feasible.

Characterization of natural rubber as a bolus material for electron beam radiotherapy

Bolus is an accessory that is directly placed on the surface region to shift the radiation dose up to the skin during high energy photon and electron beam irradiations. The aim of this study was to mold the bolus using natural rubber material and assess both the physical and dosimetric characteristics. A natural rubber with additional plasticizer material was fabricated as a bolus sheet. The physical properties of natural rubber bolus sheets have been investigated using computed tomography (CT) images. Gafchromic EBT3 films were used to acquire the dose at depth of 0, 2, 3, and 3.5 cm for the 9-MeV therapeutic electron beam. A comparison of our natural rubber bolus sheets to the commercial bolus sheets was studied. The in-house natural rubber bolus sheets with the thickness of 0.32 and 0.52 cm were successfully made. Relative electron density of the two sheets was consistent with each other. However, similar to the commercial boluses, the natural rubber boluses were not provided with the same CT number over the whole sheet. Different bolus material gave different dose at the surface. Both material and thickness of the bolus showed a stronger impact on the dose beyond the depth of maximum dose. Because of the density, simple fabrication, and vast availability, natural rubber material has an effective potential to be used as a bolus sheet in radiotherapy.

Dosimetric Comparison of Superflab and Specially Prepared Bolus Materials Used in Radiotherapy Practice.

This study compares standard commercial bolus material (Superflab) to custom prepared silicone dental impression material (CDIM) and play dough material (PDM) with respect to dosimetric properties and applicability by using ion chamber measurement and calculated dose values. The CDIM bolus was prepared by mixing dental impression silicone material with enough water to maintain a density of about 1.0 g/cm3. The prepared bolus material is applied on an RW3 solid phantom by covering 10x10 cm2 area with 0.5-1 cm thickness. Ion chamber measurements were performed separately with and without bolus material application. The setup was scanned in CT and the same procedure was repeated in the TPS using the scan data, in which the Pencil Beam Convolution dose calculation algorithm was used. To compare the effect of bolus material on tissue, the Superflab bolus and CDIM bolus were applied with 1 cm of thickness on postmastectomy scar and dose calculations on TPS were performed. After comparison of the dosimetric values for Superflab, CDIM and PDM, we obtained statistically meaningful results between superflab and CDIM. For PDM, the results obtained with TPS and ion chamber measurements indicated that, it is not suitable to use in radiotherapy application due to its material properties. For the simulated skin dose values obtained at five random points on the scar tissue, the comparison of Superflab and CDIM TPS calculation results were not statistically significant. The CDIM is easy to prepare and apply on irregular mastectomy scar tissue and it prevents formation of air gaps in the application surface. Especially for curved anatomical regions such as scar tissue, inclusion of the bolus material in treatment planning protocol will reduce dose uncertainty in application. It is safe to use CDIM as an alternative to Superflab in radiotherapy application, whereas PDM is not useful in clinical practice due to its material properties.

Bacterial Nanocellulose Membrane As Bolus in Radiotherapy: “Proof of Concept”

Bolus characterize materials with an electromagnetic radiation attenuation coefficient similar to biological tissue and which are positioned on the skin of patients during radiotherapy treatment. Such devices are responsible for the superficialization of the maximum dose of high energy photons and electrons, restricting its penetration and improving the coverage of the treatment isodose. The development of new materials, mainly from sustainable biotechnological routes, will contribute to increasing efficiency and expanding the use of these technologies. The objective of this research was to develop the “proof of concept” regarding the use of the bacterial nanocellulose membrane (BNCm) as a bolus for radiotherapy procedures. For this purpose, 1.4 cm thick BNCm were produced from static cultivation of the K. rhaeticus, purified and subjected to the physical‐chemical characterization process by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT‐IR). The samples were then subjected to the determination of the radiological density (RD), by computed tomography, and the radiation attenuation potential (%), after being irradiated with 6MV photons in a linear accelerator using ionization and phantom chamber at doses of 100 and 50 UM. The results were compared with data from the analyzes in a commercial bolus (CB) with same thickness. The physical‐chemical analysis demonstrated the constitution of a pure, highly hydrated, homogeneous and nanostructured network of cellulose fibers. The mean RD of BNCm was 1.1 and 5 Hounsfield units respectively, demonstrating high water (0HU) equivalence from BNCm. The values corresponding to the radiation attenuation at the dose of 100 MU were 5.1 ± 0.1% and 4.6 ± 0.2%, for CB and BNCm respectively. The values for the dose of 50 MU were 3.8 ± 0.1% and 3.0 ± 0.2%. In both doses, the attenuation of BNCm was similar to the CB. It stands out the superiority of the BNCm moldability and the possibility to change its composition to improve the radiation attenuation. The results support the concept of use the BNCm as an effective biotechnological device, align to the sustainability idea, as a bolus for radiotherapy treatment.Support or Funding InformationI.P.F.B. Indústria de Produtos Farm. e Biotecnológicos Ltda.

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.

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.

A dosimetric study on the use of 3D-printed customized boluses in photon therapy: A hydrogel and silica gel study.

PurposeThe aim of the study was to compare the dose differences between two kinds of materials (silica gel and hydrogel) used to prepare boluses based on three‐dimensional (3D) printing technologies and commercial bolus in head phantoms simulating nose, ear, and parotid gland radiotherapy.Methods and materialsWe used 3D printing technology to make silica gel and hydrogel boluses. To evaluate the clinical feasibility, intensity modulated radiation therapy (IMRT) plans were created for head phantoms that were bolus‐free or had a commercial bolus, a silica gel bolus, or a hydrogel bolus. Dosimetry differences were compared in simulating nose, ear, and parotid gland radiotherapy separately.ResultsThe air gaps were smaller in the silica gel and hydrogel bolus than the commercial one. In nose plans, it was shown that the V 95% (relative volume that is covered by at least 95% of the prescription dose) of the silica gel (99.86%) and hydrogel (99.95%) bolus were better than the commercial one (98.39%) and bolus‐free (87.52%). Similarly, the homogeneity index (HI) and conformity index (CI) of the silica gel (0.06; 0.79) and hydrogel (0.058; 0.80) bolus were better than the commercial one (0.094; 0.72) and bolus‐free (0.59; 0.53). The parameters of results (HI, CI, V 95%) were also better in 3D printing boluses than in the commercial bolus or without bolus in ear and parotid plans.ConclusionsSilica gel and hydrogel boluses were not only good for fit and a high level of comfort and repeatability, but also had better parameters in IMRT plans. They could replace the commercial bolus for clinical use.

P177] 3D Rapid manufacturing bolus vs commercial bolus – Skin dose comparison

Purpose Most of the breast treatments uses a megavoltage photon beams. This kind of energy exhibits a skin-sparing effect that is a concern in some stages of both breast conservative and post-mastectomy irradiation. To overwhelm this effect a bolus material is placed on the skin. However, when using commercial non-customized bolus, small air gaps can occur in certain regions of the treatment area where the bolus cannot establish the perfect match with the irregular skin of the patient, altering locally the expected skin dose. The objective of this study is to verify the improvement in the breast radiotherapy treatment using a customized bolus produced by 3D rapid manufacturing (3D-RM) techniques, and compare it with the commercial ones. Measurement of the surface dose and comparisons with the doses calculated by the Treatment Planning System (TPS) were also performed. Methods The customized 3D rapid manufactured bolus was prepared for an anthropomorphic female phantom breast area. 3D-CRT treatment plans for right breast were performed on CT scans of the phantom both with the customized and commercial bolus. The skin dose was measured in 5 points on the phantom breast surface using a MOSFET-based system. Results A better fitting to the surface of the phantom was observed for the customized bolus, reducing the air gaps and improving the daily positioning on the irregular breast surfaces. The average differences between calculated and measured doses in the customized and commercial bolus ranged from 2 to 10%. However, the highest dose difference (approximately 10%) was observed for the commercial bolus. Conclusions The 3D rapid manufactured bolus can reduce the uncertainty in the daily positioning and help to overcome the dose discrepancy due to unwanted air gaps affecting breast cancer radiation therapy. With the commercial bolus a higher dose difference relatively to TPS was observed. The skin dose increase is observed in the same proportion for both boluses.

Characterization of Water-Clear Polymeric Gels for Use as Radiotherapy Bolus

Our purpose was to investigate polymeric gels for use as a highly transparent radiotherapy bolus and determine the relevant physical and dosimetric properties. We first quantified tensile properties (maximum stress, strain, and Young modulus) for various polymeric gels, along with a commercial bolus product in order to illustrate the wide variety of potential materials. For a select polymeric gel with tensile properties similar to currently used radiotherapy bolus, we also evaluated mass and electron density, effective atomic number, optical transparency, and percent depth dose in clinical megavoltage photon and electron beams. For this polymeric gel, mass density was 872 ± 12 and 896 ± 13 g/cm3 when measured via weight/volume and computed tomography Hounsfield units, respectively. Electron density was 2.95 ± 0.04 ×1023 electrons/cm3. Adding fused silica (9% by weight) increases density to that of water. The ratio of the effective atomic number to that of water without and with added silica was 0.780 and 0.835 at 1 MeV, 0.767 and 0.826 at 6 MeV, and 0.746 and 0.809 at 20 MeV. Percent depth dose for 6 MV photons was within 2% of water within the first 2.5 cm and after scaling by the density coincided within 1% out to >7 cm. For 6 and 20 MeV electrons, after scaling for density D80% was within 1.3 and 1.5 mm of water, respectively. The high transparency and mechanical flexibility of polymeric gels indicate potential for use as a radiotherapy bolus; differences in density from water may be managed via either using “water equivalent thickness” or by incorporating fused silica into the material.

Three-dimensional customized bolus for intensity-modulated radiotherapy in a patient with Kimura's disease involving the auricle

In radiotherapy, a commercial bolus often does not provide a suitable fit over irregular surfaces. To address this issue, we fabricated a customized bolus using 3D printing technology. The aim of our study was to evaluate the application of this 3D-printed bolus in a clinical setting. The patient was a 45-year-old man with recurrent Kimura's disease involving the auricle, receiving radiotherapy in our oncology department. A customized bolus, 5mm in thickness, was fabricated based on reconstruction of computed tomography (CT) images. The bolus was printed on a Dimension 1200 series SST 3D printer. Repeat CT-based simulation indicated an acceptable fit of the 3D-printed bolus to the target region, with a maximum air gap of less than 5mm at the tragus. Most of the surface area of the target region was covered by the 95% isodose line. The plan with the 3D-printed bolus improved target coverage compared to that without a bolus. And the plan with the 3D-printed bolus yielded comparable results to those with the paraffin wax bolus. In conclusion, a customized bolus using a 3D printer was successfully applied to an irregular surface.

Comparative Study on the Surface Dose of Some Bolus Materials

In order to investigate the possibility of using different materials as bolus in radiotherapy, five samples denoted by S2 - S6 were prepared and analyzed by comparison with one available commercial bolus denoted by S1. Sample S1 was a thermoplastic material from Qfix; S2 was a moldable silicon rubber (RTV-530 from Prochima); S3 and S4 were obtained by adding micrometric particles of Al and Cu respectively (at the same mass concentration of 5.5%); S5 was another moldable silicon rubber (GSP400 from Prochima) and S6 was a mixture of GSP400 and micrometric particles of Cu (at the mass concentration of 5.5%). The measurements of normalized transmitted dose as a function of sample thickness were performed for all samples (S1 - S6) at two values of electron beam energy (6 and 9 MeV) produced by a linear accelerator VARIAN 2100SC. The results showed that the maximum of the normalized transmitted dose of manufactured samples (S2 - S6) is registered at smaller sample thicknesses than for the analyzed commercial bolus (sample S1). The smallest sample thickness corresponding to normalized maximum point dose is obtained for sample S2 (RTV-530). Measurements performed for electron beam energy of 6 and 9 MeV have proven the possibility of using the manufactured samples as bolus in radiotherapy.

Practice Patterns in the Delivery of Radiation Therapy After Mastectomy Among the University of California Athena Breast Health Network

BackgroundPractice patterns vary with the planning and delivery of PMRT. In our investigation we examined practice patterns in the use of chest wall bolus and a boost among the Athena Breast Health Network (Athena). Materials and MethodsAthena is a collaboration among the 5 University of California Medical Centers that aims to integrate clinical care and research. From February 2011 to June 2011, all physicians specializing in the multidisciplinary treatment of breast cancer were invited to take a Web-based practice patterns survey. Sixty-two of the 239 questions focused on radiation therapy practice environment, decision-making processes, and treatment management, including the use of a bolus or boost in PMRT. ResultsNinety-two percent of the radiation oncologists specializing in breast cancer completed the survey. All of the responders use a material to increase the surface dose to the chest wall during PMRT. Materials used included brass mesh, commercial bolus, and custom-designed wax bolus. Fifty percent used tissue equivalent superflab bolus. Fifty-five percent of the respondents routinely use a boost to the chest wall in PMRT. Eighteen percent give a boost depending on the margin status, and 3 of 11 (27%) do not use a boost. ConclusionOur investigation documents practice pattern variation for the use of a PMRT boost and the use of chest wall bolus among the University of California breast cancer radiation oncologists. Further understanding of the practice pattern variation will help guide clinicians in our cancer centers to a more uniform approach in the delivery of PMRT.

Ultrasound transmission gel as a bolus device for skin irradiation of irregular surfaces: technical note

This paper describes an uncommon radiation treatment of the external ear, with ultrasound (US) transmission gel used as bolus device to compensate for the irregularity of the target surface. Postoperative radiotherapy for cutaneous carcinoma was performed with a single high-energy electron beam directed over the ear auricle. Due to the irregular surface of the target, a "missing tissue" compensator was employed. Daily, after patient positioning, the concha was filled and flattened with US gel, and a dose of 54 Gy in 27 fractions was delivered. Water equivalence of the gel was verified by comparing the gel's computed tomography (CT) number [Hounsfield units (HU)] and density with the corresponding values for water and another commercial bolus device. Whereas ultrasound gel and water had comparable values (HU: 0; density 1 g/cm(3) for both), the corresponding values for the commercial device were slightly higher (HU: 80; density 1.02 g/cm(3)). Ultrasound gel proved to be an easy, fast and cheap compensating tool. Its water equivalence allows it to be used as an alternative to water, though easier to position and with lower risk of displacement. Thus, it is recommendable as a practical tool for most irregular sites. Further investigations are warranted to validate this solution in more complex irradiation techniques.

Evaluation of the retention of electronic identification boluses in the forestomachs of cattle1,2

A total of 1,203 beef calves were used to evaluate 2 series of electronic identification boluses. Calves were intensively fattened and slaughtered at approximately 1 yr of age. Series 1 (n = 576 calves) consisted of 10 types of boluses with the same external dimensions (o.d. x length: 21 x 68 mm) but varying in weight (11 to 75 g) and specific gravity (0.63 to 3.36). Six boluses were made of ceramic (5 prototypes and 1 commercial bolus) and 4 were tubes made of plastic filled with concrete. Series 2 (n = 627 calves) consisted of 3 prototypes and 5 commercial boluses of different ceramic materials varying in external dimensions (o.d.: 15 to 21 mm; length: 39 to 78 mm), weight (20 to 73 g), and specific gravity (3.00 to 3.87). Boluses were administered to milk-fed calves (2 to 5 wk of age) by using adapted balling guns. To determine the anatomical limit for a bolus passing through the gastrointestinal tract, the size of the reticuloomasal orifice was measured in 90 male and 62 female fattened calves at slaughter. Three calves in series 1 (0.3%) could not swallow the 21-mm (o.d.) bolus at the first attempt and received the bolus 1 wk later. No problems for early administration were found with thinner boluses (o.d. < 20 mm) in series 2, and no signs of disease or growth alteration were detected in any bolused calves. Retention rate until slaughter varied according to bolus features and ranged from 0 to 100% (series 1), and from 69.7 to 100% (series 2). Inadequately dimensioned boluses were regurgitated or passed through the gastrointestinal tract and were excreted with the feces. The diameter of the reticuloomasal orifice differed between male and female yearling calves (32.5 and 29.9 mm, respectively; P < 0.01) and was greater than the o.d. of the retained boluses. Retention rate was predicted from bolus weight and volume by a logistic regression (R2 = 0.99, P < 0.001), in which the minimum bolus weight estimated to reach a 99.5% retention rate was 61 g when volume and specific gravity were 22.4 mL and 2.72, respectively. To achieve an effective retention rate of electronic identification boluses in the forestomachs of fattening calves, bolus volume and specific gravity, in addition to weight, should be optimized. No boluses of specific gravity lower than 3.0 and thicker than 20 mm o.d. are recommended for identification of cattle from early rearing (< 20 d of age) to slaughtering.

PLAY‐DOH® AND WATER‐SOAKED GAUZE SPONGES AS ALTERNATIVE BOLUS MATERIAL FOR COBALT‐60 TELETHERAPY

A study was performed to determine if carefully made boluses of either Play-Doh, or water-soaked cotton gauze sponges differed from the commercial bolus material, Superflab, in producing maximum radiation dose when irradiated with cobalt-60 photons. The radiation doses were measured with thermoluminescent dosimeters calibrated to be accurate for cobalt-60 photon energies at doses less than 10.0 cGy. The resulting radiation doses were similar when using Play-Doh, water-soaked sponges, or Superlab. Doses resulting from Play-Doh boluses more consistently approximated those of Superflab. The results of this study suggest that either Play-Doh or water-soaked cotton gauze sponges can suffice as material for carefully made bolus for cobalt-60 teletherapy.

COPPER AND SELENIUM SUPPLEMENTATION TO CALVES BY MEANS OF A SOLUBLE GLASS BOLUS

Two hundred and thirty-nine calves were used to assess the effectiveness of a commercial soluble glass bolus as an intraruminal supplement of copper and selenium. Administration of two boluses per animal raised serum selenium concentration from marginal to adequate but did not prevent the decrease of serum copper concentration from adequate to deficient in some calves over the summer. Key words: Copper, selenium, mineral supplementation, soluble glass, calves