Bolus Thickness Research Articles

Assessment of dose uniformity and optimal CT number for virtual bolus in breast VMAT planning

Background: ICRU Report No. 83 proposes using the Flash Region in the strategic design of breast cancer treatment. However, concerns persist regarding the delivery of the designated radiation dose to breast cancer patients undergoing Volumetric Modulated Arc Therapy (VMAT) with virtual bolus in the irradiation plan. Objective: This study aimed to assess dose uniformity in breast VMAT treatment with a virtual bolus, validate the planning dose by comparing it with nanoDotTM measurements on a Rando phantom, and determine the optimal CT number for the virtual bolus in breast VMAT planning. Materials and Materials and methods: To assess dose uniformity in the breast VMAT plan, nine nanoDot™ dosimeters were placed on the breast of Rando phantom, followed by CT simulation and VMAT treatment planning. The clinical target volume (CTV) and organs at risk were contoured, and the planning target volume (PTV) boundaries were expanded by 5 mm and 10 mm for virtual bolus thicknesses of 10 mm and 15 mm, respectively. The CT number of the virtual bolus varied from 0 to -700 HU. The planning doses at 9 points were determined, and the coefficient of variation (%CV) was calculated. Additionally, measurements at these 9 points were performed using nanoDot™ dosimeters. The calculated and measured doses were then compared. Finally, VMAT treatment plans with a virtual bolus were implemented in 10 breast cancer patients, using the virtual bolus with varying CT numbers as in the phantom study to evaluate the optimal CT number of the bolus. Results: The doses among the 9 points for each plan were uniform, with a %CV of less than 4. For calculated dose validation, the percentage differences between the measured and calculated dose for all treatment plans, with variations in the CT number and the bolus thickness, were within ±5%. To determine the optimal CT number for the virtual bolus, the breast cancer treatment plan that met the dose criteria for tumors and organs at risk was the plan with a CT number of 0 HU for both virtual bolus thicknesses of 10 and 15 mm. Conclusion: Virtual bolus provides uniform dose distribution for breast VMAT planning, which measurements from nanoDotTM can validate. The appropriate CT number for the virtual bolus is 0 HU for both bolus thicknesses. In future studies, measurements should be conducted on actual patients.

Clinical use of Gafchromic EBT4 film for in vivo dosimetry for total body irradiation.

In vivo dosimetry is a common requirement to validate dose accuracy/uniformity in total body irradiation (TBI). Several detectors can be used for in vivo dosimetry, including thermoluminescent dosimeters (TLDs), diodes, ion chambers, optically stimulated luminescent dosimeters (OSLDs), and film. TLDs are well established for use in vivo but required expertise and clinical system availability may make them impractical for multifractionated TBI. OSLDs offer quick readout, but recalls have restricted their use. The purpose of this work was to validate the newly available Gafchromic EBT4 film for TBI in vivo dosimetry. Film calibration curves were created under standard conditions (6MV/15MV, 1.5/3.0cm depth, 100cm source-to-surface distance (SSD), 10 × 10 cm2 field), and films were scanned at several time points (0.5-24h) to determine the shortest development time that yielded accurate dose measurements. 4 × 4 cm2 films were placed under 1.5cm thick bolus on the anterior and posterior sides of a solid water phantom to measure entrance and exit dose under TBI conditions (∼600cm SSD, 39.5 × 39.5 cm2 field, 6 MV/15 MV). These measurements were compared to ion chamber and diode readings for validation. Film measurements were also compared to OSLD measurements for three TBI patients. The shortest development time that resulted in accurate dosimetry and allowed for adequate physician review time was 4h (±4% dose accuracy). Film entrance and exit dose measurements were within±3.8% of ion chamber and diode readings for 6MV and 15MV beams. Patient film measurements were within ∼±5% for the majority of anatomical measurement locations; however, film and OSLD readings for some anatomic locations deviated by>10%. These results indicate that EBT4 film can be utilized for accurate in vivo dosimetry for TBI patients and shows good agreement with diode and ion chamber measurements. Further investigation into film and OSLD differences was not possible due to OSLD recalls.

Investigation of the effect of bolus on skin dose in breast cancer treatment with tomotherapy and LINAC radiotherapy devices

In postmastectomy radiation therapy (PMRT), it is important that the chest wall skin is included in the target volume and receives an adequate dose. This study aims to investigate the effect of bolus on skin dose in breast cancer treatment with Tomotherapy and LINAC radiotherapy devices and to examine the accuracy of the surface dose calculated by treatment planning system (TPS) with thermoluminescence dosimetry (TLD). Female Alderson Rando Phantom's chest wall is virtually divided into 9 regions. Computed tomography (CT) images of the phantom were obtained with a section thickness of 3 mm. Two plans, with and without bolus, were created for each of the helical tomotherapy (HT), intensity-modulated radiotherapy (IMRT) and field-in-field (FiF) techniques. A bolus thickness of 0.5 cm was used for all bolus plans. Doses calculated from TPSs were obtained for 88 predetermined points on the chest wall. After irradiation, doses measured with TLDs were obtained. The effect of bolus use on the chest wall surface was examined. The increase in surface dose due to bolus use was 50.35%, 55.35% and 68.56% for HT, IMRT and FiF techniques in TPS, respectively. This increase in TLD measurements was 58.18%, 30.90% and 46.31% for HT, IMRT and FiF techniques, respectively. The best agreement between TPS and TLD doses for bolus and non-bolus plans was found in the HT technique. The difference between TPS and TLD doses decreased within the three treatment techniques due to bolus use. Since the chest wall skin cannot receive the required dose in IMRT and FiF techniques, bolus use is recommended until acute skin reactions occur. There is no need to use a bolus for the HT technique.

Correlation of thickness changes and daily dose detection of delivery analysis (DA) software in helical tomotherapy

Abstract Purpose: To assess the correlation between the dose distribution provided by the delivery analysis (DA) software and the measured dose distribution using an ArcCHECK (AC) phantom in the presence of thickness variation. Materials and Methods: Two sets of targets were established within the phantom. Target A was placed on the detector areas, whereas Target B was positioned at the centre of the phantom. Bolus was applied to the surface of the phantom at different thicknesses ranging from 0 to 2 cm to verify the dose distribution in both TomoHelical (HT) and TomoDirect (TD) techniques. The gamma passing rate (GPRs) were evaluated against predefined thresholds of 3%/3 mm and 3%/2 mm. Correlation study evaluated the level of agreement between DA and AC values. Results: Both AC and DA exhibited a decline in GPRs as the bolus thickness decreased. Significant correlations were observed between AC and DA for both HT and TD techniques, with a p value of less than 0.001. Conclusion: The results indicate that DA software has the capability to detect anatomical changes during tomotherapy treatments. This is substantiated by the statistical association found between DA and the standard AC phantom system for dose distributions in both HT and TD methods.

Investigation of Effect of Air Gap between Surface and Bolus on Dose Distribution for 6 MV Photon Beam

In radiotherapy, tissue equivalent boluses are frequently used in the treatment of superficially located tumors. The air gap between the patient's skin and the bolus may cause dosimetric uncertainties. This study aims to dosimetrically investigate the effect of the air gap between the surface and the bolus on dose distribution. Computed tomography (CT) images of the phantom were obtained and transferred to the treatment planning system (TPS). In the TPS, a bolus was placed on the phantom surface and then air gaps were created between the bolus and the surface. The effect of the air gaps between the surface and the 5 mm thick bolus on the dose distribution was analyzed with the point doses obtained from the TPS. For the 6 MV X-ray, it was observed that the air gap negatively affected the surface doses calculated by TPS. Accordingly, an inverse correlation was found between air gap and surface dose. It is recommended that bolus use, especially in curved anatomical regions, should be applied before CT scanning as much as possible. When using bolus material in radiotherapy, it is recommended to be careful not to leave an air gap between the surface and the bolus.

Internal lead shielding for clinical electron treatments.

Electron beams are often used to treat superficial lesions of the lip, cheek, nose, and ear. Lead is frequently used to block distal structures. It is customary to place an internal bolus of low atomic number in between the tissue and the lead to reduce electron backscatter from the lead. Space for the lead and the internal bolus is quite limited. A previous method for estimating the thickness of the lead plus internal bolus is not self-consistent and leads to a larger than necessary thickness. A new method is described here to provide a quick, accurate, and self-consistent estimate of the minimum necessary thickness of the internal bolus and the lead for incident electron beam energies of 4, 6, 8, 9, and 10 MeV as a function of the thickness of the overlying tissue. This method limits the dose enhancement at the tissue/bolus interface due to the underlying lead to 10%. Measurements made with gafchromic film validate this methodology.

Quantitative study on dose distribution of Freiburg flap for keloid high-dose-rate brachytherapy based on MatriXX.

To quantify the dose distribution effect of insufficient scattering conditions in keloid HDR brachytherapy with Freiburg fFlap (FF) applicator. A phantom composed of FF applicator, MatriXX and solid water slices was designed and scanned for treatment planning. Bolus with different thicknesses were covered to offer different scatter conditions. Planar dose distributions were measured by MatriXX. The maximum value (Max), average value (Avg) and γ passing rate (3mm/3%) were evaluated by the software MyQA Platform. The maximum and average doses measured by MatriXX were lower than the calculated values. The difference increased as field size decreased. The Max value, found at 0.86cm level in the two tube case, was -20.0%, and the avg value was -11.9%. All the γ values were less than 95%. This difference gradually decreased with increasing bolus thickness and the γ values were significantly improved. MatriXX could be used for dose verification of HDR brachytherapy with an FF applicator. When the FF applicator was applied for keloid, insufficient scattering conditions would cause an insufficient target dose. This difference could be reduced by covering the bolus with different thicknesses on the applicator. The smaller the field, the thicker the bolus required.

Evaluation of the Ethos synthetic computed tomography for bolus-covered surfaces

PurposeEthos allows online adaption of radiotherapy treatment plans. Dose is calculated on synthetic computed tomographies (sCT), CT-like images generated by deforming planning CTs (pCT) onto daily cone beam CTs (CBCT) acquired during treatment sessions. Errors in sCT density distribution may lead to dose calculation errors. sCT correctness was investigated for bolus-covered surfaces. MethodspCTs were recorded of a slab phantom covered with bolus of different thicknesses and with air gaps introduced by spacer rings of variable diameters and heights. Treatment plans were irradiated following the adaptive workflow with different bolus configurations present in the pCT and CBCT. sCT densities were compared to those of the pCT for the same air gap size. Additionally, the neck region of an anthropomorphic phantom was imaged using a plane standard bolus versus an individual bolus adapted to the phantom’s outer contour. ResultsVarying bolus thickness by 5 mm between pCT and CBCT was reproduced in the sCT within 2 mm accuracy. Different air gaps in pCT and CBCT resulted in highly variable bolus thickness in the sCT with a typical error of 5 mm or more. In extreme cases, air gaps were filled with bolus material density in the sCT or the phantom was unrealistically deformed near changed bolus geometries. Changes in bolus thickness and deformation also occurred in the anthropomorphic phantom. ConclusionsCTs must be critically examined and included in plan-specific quality assurance. The use of tight-fitting air gap-free bolus should be preferred to increase the similarity between sCT and CBCT.

Post-mastectomy radiotherapy: Impact of bolus thickness and irradiation technique on skin dose

PurposeTo determine 10 MV IMRT and VMAT based protocols with a daily bolus targeting a skin dose of 45 Gy in order to replace the 6 MV tangential fields with a 5 mm thick bolus on alternate days method for post-mastectomy radiotherapy. MethodWe measured the mean surface dose along the chest wall PTV as a function of different bolus thicknesses for sliding window IMRT and VMAT plans. We analyzed surface dose profiles and dose homogeneities and compared them to our standard 6 MV strategy. All measurements were performed on a thorax phantom with Gafchromic films while dosimetric plans were computed using the Acuros XB algorithm (Varian). ResultsWe obtained the best compromise between measured surface dose (mean dose and homogeneity) and skin toxicity threshold obtained from the literature using a daily 3 mm thick bolus. Mean surface doses were 91.4 ± 2.8% [85.7% – 95.4%] and 92.2 ± 2.3% [85.6% – 95.2%] of the prescribed dose with IMRT and VMAT techniques, respectively. Our standard 6 MV alternate days 5 mm thick bolus leads to 89.0 ± 3.7% [83.6% – 95.5%]. Mean dose differences between measured and TPS results were < 3.2% for depths as low as 2 mm depth. Conclusion10 MV IMRT-based protocols with a daily 3 mm thick bolus produce a surface dose comparable to the standard 6 MV 5 mm thick bolus on alternate days method but with an improved surface dose homogeneity. This allows for a better control of skin toxicity and target volume coverage.

SurVolT: Surface to Volume conversion Tool. A proof of concept

Purpose:To develop SurVolT, a conversion tool able to apply volumetric changes to DICOM Computed Tomography (CT) data using daily surface (obj) data acquired with AlignRT® (VisionRT Ltd.), primarily designed and validated for breast treatments. Materials and Methods:SurVolT proceeds in 4 steps: 1. AlignRT .obj files extraction, 2. Contour deformation where the surface data points are matched to the initial external contour on a Region Of Interest, ROImatch, on which the anatomy is supposed to be unchanged. Then, external contour substitution is performed on the ROIttt covering the treated breast area. This is validated on a female torso phantom with a tissue-equivalent bolus mimicking an edema. The Planning Treatment Volume (PTV) contour from the initial CT is also deformed according to the new external contour in the ROIttt. 3. Volumetric data estimation according to the new external contour, validated on an anthropomorphic pelvis phantom. 4. Import of new DICOM data into the Treatment Planning System (TPS). Finally, the workflow is applied on a first patient presenting an anatomical change during the treatment. Results:The validation of step 2 and 3 shows a bolus thickness estimation of 5.8±1.2mm (expected 5 mm) and the non-rigid deformation of initial CT images follows the new external contour at the ROIttt bolus site while revealing negligible deformation elsewhere. Conclusion:This first proof of concept introducing a Surface Guided Radiotherapy (SGRT) tool allowing daily surface data to volume conversion is a fundamental step toward SGRT-based adaptive radiotherapy.

Influence of Adhesive Use on Swallowing in Removable Complete Denture Wearers

Background: The objective of conventional complete dentures is to reestablish the functions of the stomatognathic system in edentulous individuals. Adhesives are used for denture retention to help the masticatory function. The objective of this investigation was to evaluate the effect of denture adhesive on the swallowing of complete denture wears. Methods: Nine upper and lower complete denture wearers and 14 individuals with teeth were assessed with videofluoroscopy at 30 frames by second and analyzed frame by frame. The denture wears subjects were assessed without dentures, with dentures without adhesive, and with dentures and adhesive. Duplicate assessments were made with swallows of 10-mL thin-liquid bolus, 10-mL extremely-thick bolus, 5-g cookies, and 2-g toasts. Results: Laryngeal vestibule closure, pharyngeal transit, upper esophageal sphincter opening, and oropharyngeal transit took longer in denture wearers than in controls. Laryngeal vestibule closure time and upper esophageal sphincter opening when swallowing thin liquid were shorter with dentures and adhesive than without adhesive. With extremely thick bolus, the pharyngeal transit time and upper esophageal sphincter opening were shorter with adhesive use. Residues in the oral cavity occurred more frequently in the denture wearers than in the controls, for all boluses. Removable complete denture wearers have longer pharyngeal transit of thin liquid and extremely thick boluses, which decreases with adhesive use. Conclusion: Adhesive use cause a favorable effect on pharyngeal swallowing of thin and thick boluses in complete denture wearers.

Robustness of VMAT to setup errors in postmastectomy radiotherapy of left-sided breast cancer: Impact of bolus thickness.

Volumetric modulated arc therapy (VMAT) with varied bolus thicknesses has been employed in postmastectomy radiotherapy (PMRT) of breast cancer to improve superficial target coverage. However, impact of bolus thickness on plan robustness remains unclear. The study enrolled ten patients with left-sided breast cancer who received radiotherapy using VMAT with 5 mm and 10 mm bolus (VMAT-5B and VMAT-10B). Inter-fractional setup errors were simulated by introducing a 3 mm shift to isocenter of the original plans in the anterior-posterior, left-right, and inferior-superior directions. The plans (perturbed plans) were recalculated without changing other parameters. Dose volume histograms (DVH) were collected for plan evaluation. Absolute dose differences in DVH endpoints for the clinical target volume (CTV), heart, and left lung between the perturbed plans and the original ones were used for robustness analysis. VMAT-10B showed better target coverage, while VMAT-5B was superior in organs-at-risk (OARs) sparing. As expected, small setup errors of 3 mm could induce dose fluctuations in CTV and OARs. The differences in CTV were small in VMAT-5B, with a maximum difference of -1.05 Gy for the posterior shifts. For VMAT-10B, isocenter shifts in the posterior and right directions significantly decreased CTV coverage. The differences were -1.69 Gy, -1.48 Gy and -1.99 Gy, -1.69 Gy for ΔD95% and ΔD98%, respectively. Regarding the OARs, only isocenter shifts in the posterior, right, and inferior directions increased dose to the left lung and the heart. Differences in VMAT-10B were milder than those in VMAT-5B. Specifically, mean heart dose were increased by 0.42 Gy (range 0.10 ~ 0.95 Gy) and 0.20 Gy (range -0.11 ~ 0.72 Gy), and mean dose for the left lung were increased by 1.02 Gy (range 0.79 ~ 1.18 Gy) and 0.68 Gy (range 0.47 ~ 0.84 Gy) in VMAT-5B and VMAT-10B, respectively. High-dose volumes in the organs were increased by approximate 0 ~ 2 and 1 ~ 3 percentage points, respectively. Nevertheless, most of the dosimetric parameters in the perturbed plans were still clinically acceptable. VMAT-5B appears to be more robust to 3 mm setup errors than VMAT-10B. VMAT-5B also resulted in better OARs sparing with acceptable target coverage and dose homogeneity. Therefore 5 mm bolus is recommended for PMRT of left-sided breast cancer using VMAT.

Dosimetric impact of applying a model-based dose calculation algorithm for skin cancer brachytherapy (interventional radiotherapy).

Brachytherapy (BT, interventional radiotherapy) is a well-established radiotherapy technique capable of delivering high doses to tumors while sparing organs at risk (OARs). Currently, the clinically accepted dose calculation algorithm used is TG-43. In the TG-186 report, new model-based dose calculation algorithms (MBDCA), such as Elekta's advanced collapsed cone engine (ACE), have been introduced, although their clinical application is yet to be fully realized. This study aimed to investigate two aspects of TG-186: firstly, a comparison of dose distributions calculated with TG-43 and TG-186 for skin tumors; and secondly, an exploration of the impact of using a water bolus on the coverage of clinical target volume (CTV) and OARs. Ten treatment plans for high-dose-rate IRT were developed. All plans were initially calculated using the TG-43 algorithm, and were subsequently re-calculated with TG-186. In addition, one of the treatment plans was assessed with both TG-43 and TG-186, using 10 different water bolus thicknesses ranging from 0 to 5 cm. To assess dose variations, the following dose-volume histogram (DVH) parameters were compared: D2cc and D0.01cc for OARs, and V150, V100, V95 and V90 for CTV coverage. The average dosimetric results for CTV and OARs, as calculated by both algorithms, revealed statistically significant lower values for TG-186 when compared with TG-43. The presence of a bolus was observed to enhance CTV coverage for the TG-186 algorithm, with a bolus thickness of 2 cm being the point at which ACE calculations matched those of TG-43. This study identified significant differences in dosimetric parameters for skin tumors when comparing the TG-43 and TG-186 algorithms. Moreover, it was demonstrated that the inclusion of a water bolus increased CTV coverage in TG-186 calculations.

Dose verification of virtual bolus application for helical tomotherapy.

The objective of the study is to verify the dose delivered on helical tomotherapy based on treatment plan with varying virtual bolus (VB) thickness. The target was localized on the ArcCHECK image by 3 mm margin from the phantom surface. The dimension of target, which includes the ArcCHECK's detectors, with the 4.0 cm width and length 12.0 cm along the phantom The 5 treatment plans were generated, 1 plan without VB application (NoVB) and the 4 plans with varying of VB thickness on the phantom surface by 0.5 cm (VB0.5), 1.0 cm (VB1.0), 1.5 cm (VB1.5), and 2.0 cm (VB2.0), in treatment planning but absent during irradiation. For measurement analysis, the ionization chamber and the ArcCHECK detectors were used for point dose and dose distribution by investigating the percentage of dose difference and the gamma passing rate. The VB thickness 0.5, 1.0 and 1.5 cm showed acceptable value with less than 2% for dose difference by 0.37% (VB0.5), -0.11% (VB1.0) and -0.37% (VB1.5) at the center of ArcCHECK. The accuracy of dose distribution showed an acceptable gamma passing rate of 99.8% (VB0.5), 100% (VB1.0), and 90.2% (VB1.5) for gamma criteria by 3%/3mm for absolute dose analysis. However, the gamma passing rate of VB2.0 down to 71.2% of absolute mode for gamma criteria by 3%/3mm. The treatment plans with VB thickness less than 15 mm deliver doses that are comparable to treatment plans without virtual bolus based on gamma analysis. However, the deviation showed a trend increasing when VB thickness increased. The VB2.0 was not acceptable for point dose and dose distribution verification by more than 2% dose difference and less than 90% of gamma passing rate.

Impact of In-House Bolus Thickness on The Percentage of Surface Dose for 10 and 12 MeV Electron Beams

The surface dose on electron irradiation which is received by the skin does not reach 100%, so a bolus is needed as a compensator material in order to reach or approach 100%. This study aims to create, test, and describe the effect of different thicknesses of boluses that are made of 3D printed TPU, silicone sealant and resin on equivalence with tissue and the percentage of surface dose produced. A bolus with a size of 15x15 cm2 and with variations in thickness of 0.3 cm, 0.5 cm, and 1 cm was imaged by a CT-Scan to analyze the CT-Number value and relative electron density using imageJ software. After that, the bolus was irradiated by a Linac with an energy of 10 MeV and 12 MeV to measure the surface dose using an advances marcus detector. The result of this study showed that 3D printed TPU, silicone sealant and resin are similar to some soft tissues. Silicone sealant has the highest flexibility of the two boluses. In addition, silicone sealant also produces the highest increase in the percentage of surface dose in phantom.

Pharyngeal Bolus Transit During Swallowing Before and Short-Term After Thyroidectomy

Background: Thyroid nodules are common in the population and may be associated with dysphagia. The surgical treatment of these nodules is a risk for lesion of cranial nerves branches with the possibility of swallowing and voice impairment. Dysphagia may be a complaint after the surgery even without nerves lesions. The objective of this investigation was to evaluate the pharyngeal bolus transit before and short-term after surgical treatment of thyroid nodules. Methods: Thirty-eight consecutive patients with thyroid nodules had videofluoroscopic evaluation of swallowing timing before the surgery. Dysphagia was a complaint in 20 (53%). In 21 (55%) the nodules were benign. Twenty-seven (71%) were submitted to total thyroidectomy. In 26 the swallow was also evaluated one to five days (median two days) after the surgery. The control group comprised 21 healthy volunteers. In videofluoroscopy patients and volunteers swallowed, in duplicate and random sequence, 5 mL and 10 mL of boluses of two consistencies, moderately thick and extremely thick. Results: Before the surgery patients had a delay in upper esophageal sphincter opening after the bolus arrived at the sphincter. After the surgery the patients had a shorter swallowing reaction time with 5 mL moderately thick bolus and shorter pharyngeal clearance with 10 mL extremely thick bolus. Conclusion: Before thyroid surgery patients with thyroid nodules had a delay in the upper esophageal sphincter opening related to bolus reach the sphincter. Few days after thyroidectomy there is an improvement of pharyngeal clearance of an extremely thick bolus.

Evaluating Anatomic Conformity of 3D Printer-Assisted Thermoplastic Bolus: A Novel Approach to Patient-Specific Bolus Generation

<h3>Purpose/Objective(s)</h3> To assess the anatomic conformity of custom thermoplastic boluses generated based on patient-specific 3D-printed molds. <h3>Materials/Methods</h3> A retrospective review of consecutive cases of 3D printer-assisted custom thermoplastic bolus was performed. For each case, target volume-specific contours (molds) were generated using computed tomography-based (CT) simulation scans in a treatment planning system. Molds were exported into a standard tessellation language (STL) file for rapid manufacturing on a 3D Printer using polylactic acid (PLA) filament. STL files were converted into G-code script and printed on slicer settings of 220°C nozzle temperature, 0.3 mm layer height, and 20% infill. The thickness of the thermoplastic bolus utilized was based on the treating radiation oncologist's prescription and ranged between 5.0 and 10.0 mm. Once heated, thermoplastic boluses were shaped using the 3D printed target volume-specific PLA molds. The quality of 3D printer-assisted thermoplastic boluses was confirmed on CT scanners before clinical use. Anatomic conformity of the boluses was quantified as mean/standard deviation (SD) of bolus-to-body air gap measured at five points equidistant from the center of the target volume. These isocentric points were assessed on first-fraction cone-beam CT scans. <h3>Results</h3> From September 2018 to January 2022, 13 3D printer-assisted thermoplastic boluses were generated for treatment to the scalp (4), nose (6), anus (2), and vulva (1) with a median dose of 50.0 Gy (range 24-70) and median of 20.0 fx prescribed (range 5-35). All treatments were 6MV/MeV with a median bolus thickness of 5.0 mm (range 5.0-10.0). The mean air gap visualized was 2.0 mm (range 0.0-6.8) ± 0.16 SD. Based on Malone Bolus Fit Classification System (excellent: no gap; good: <5 mm; tolerable: 5-10mm; poor: >10 mm), 12 cases were considered "good fit" with one case categorized as "excellent fit" with no notable air gaps. <h3>Conclusion</h3> This novel approach in generating 3D printer-assisted thermoplastic boluses allows for rapid offline manufacturing of patient-specific boluses without sacrificing quality in anatomic conformity.

Conformity between modified Swallowing Outcome After Laryngectomy questionnaire and Flexible Endoscopic Evaluation of Swallowing in laryngeal carcinoma patients after total laryngectomy

Background:One of the impacts in anatomic laryngeal and phariyngeal changes after total laryngectomy (TL) is oropharyngeal dysphagia (OPD). The detection of neopharyngeal residue as a sign of OPD can be performed by videofluoroscopy (VFS) and flexible endoscopic evaluation of swallowing (FEES). The availability of these tools in rural areas is still limited, thus the treatment of OPD is not maximal. There is a need for a more practical tool, including the modified swallowing outcomes after laryngectomy (SOAL) questionnaire.Methods:This was an analytic observational diagnostic study with a cross-sectional approach. Samples were obtained in Otorhinolaryngology Oncology Clinic and Outpatient Clinic of Dr. Soetomo General Academic Hospital, Surabaya, Indonesia, who filled SOAL modified questionnaire followed by FEES. Samples were obtained within 3 months from 10 May to 10 August 2021. The number of samples obtained through simple random sampling was 16 post-TL patients from a total population of 17 patients who met the inclusion and exclusion criteria. The conformity test between modified SOAL questionnaire and FEES was analyzed using McNemar comparison test and Kappa association test.Results:McNemar test showed no significant difference between both assessment tools (p > 0.05), and the Kappa test showed an association between both tools (p < 0.05). The results of this study stated that there was conformity between modified SOAL questionnaire and FEES in patients after TL in all types of food bolus had Kappa score of >0.81, showing a reliable association between these tools. Kappa test also showed that out of all three types of boluses, the soft bolus had the highest conformity with a Kappa score of 0.875, followed by thick bolus with 0.839, and watery bolus with 0.818.Conclusion:There was a conformity between the results of the modified SOAL questionnaire and FEES in head and neck surgery patients after TL.

Analisis Penggunaan Bolus Berbahan Plastisin pada Pasien Fibrosarcoma dengan Treatment Planning System (TPS)

Bolus is a material that has properties similar to body tissues and is used to maximize the absorbed dose on the skin surface. The purpose of this research was to determine the most optimal treatment to kill fibrosarcoma on the patient’s skin surface by comparing the isodose curve and the value of the radiation absorption dose on the physical bolus (from CT-Scan) and model bolus (TPS). This study used data in the form of bolus images (with a bolus thickness of 0 cm, 0.5 cm and 1.0 cm) and phantom image. Then the data was processed with Treatment Planning System (TPS) and given energy variations in the form of electrons (10 MeV, 12 MeV, dan 15 MeV) and photons (6 MV and 10 MV). The result of this research was an isodosis curve that describes the distribution of the dose and the value of the absorbed dose of radiation received by the skin surface. The conclusion of this research is a bolus thickness of 0,5 cm and an electron energy of 15 MeV, has more even isodose curve (covering the entire tumor) and the maximum absorption dose value were 5720 cGy for physical bolus and 5710 cGy for TPS bolus.

Peripheral and surface dose assessment using diode and Gafchromic EBT3 films dosimeters for different radiotherapy techniques

PurposeTreatment planning systems (TPSs) still face challenges in determining the peripheral and surface doses specially when using thermoplastic mask and bolus. This study aims to assess the peripheral and surface dose using diode and Gafchromic EBT3 films dosimeters. In addition to investigate the impact of thermoplastic mask with different thickness of bolus on these doses. MethodsThe measurements were performed for an Alderson Rando phantom. The maxilla and prostate were delineated as the target, because the maxilla is close to the surface, to determine the impact of thermoplastic mask and bolus on the skin dose. ResultsThe measured surface dose for IMRT was higher compared to TPS with an average difference of 21.5%, 20.2%, 18.7%, and 13.4% in the absence of thermoplastic mask and bolus, with mask, with bolus 5 mm and with bolus 10 mm respectively. For 3D-CRT, the measured surface dose was also higher compared to TPS with an average difference of 20.7%, 19.6%, 16.1%, and 13.3% in the absence of thermoplastic mask and bolus, with mask, with bolus 5 mm and with bolus 10 mm respectively. For the prostate, the PD that is close to the target was in good agreement between peripheral dose measured with diode and acquired from ‏TPS. Whereas TPS underestimated the PD for both 3D-CRT and IMRT‏ at locations that are away from the target. Moreover, when comparing 3D-CRT to IMRT for PD, 3D-CRT resulted in higher for distances close to the target, whereas the IMRT indeed delivered higher than 3D-CRT to locations that are away from the target. ConclusionsThis study showed that diode dosimeter is recommended to estimate both peripheral and surface doses whereas EBT3 films dosimeter is recommended to estimate surface dose and ‏ ‏not for PD.