Skin Surface Dose Research Articles

Effect of different CTV shrinkage and skin flash margins on skin dose for left chest wall IMRT: A dosimetric study

In postmastectomy radiation therapy (PMRT), the adequate skin surface dose remains a problem. In this study, the effect of different CTV shrinkage and Skin flash margins on skin dose was investigated, and the accuracy of skin surface dose calculated by TPS for PMRT using thermoluminescent dosimeters (TLDs) was evaluated. Eighty-eight measurement points were determined on the Alderson Rando phantom. To determine the effects of shrinkage margin on skin dose, separate CTVs were generated for 2 mm, 3 mm and 5 mm shrinkage. The prescribed dose was 50 Gy to CTV with a daily fraction dose of 2 Gy. A total of 12 plans were created using four different skin flash thicknesses for each CTV shrinkage margin. After applying 0 mm, 10 mm, 15 mm and 20 mm skin flash thicknesses for each area of the 7F-IMRT treatment plan, the plans were recalculated, and the SF-0, SF-10, SF-15 and SF-20 plans were created, respectively. The increase in skin flash thickness in IMRT plans resulted in a significant increase in skin dose. There was a significant difference between TPS and TLD doses in all chest wall areas for SF-0, SF-10, and SF-15 (p < 0.05). However, there was no significant difference in all areas of the chest wall for SF-20 (p > 0.05). The shrinkage margin thickness of the CTV was found to be inversely proportional to the skin dose for all treatment plans. In tumors near the surface, bolus or skin flash techniques can get the skin adequately dosed. However, the skin flash technique has shown superiority in the application. In PMRT, it is recommended to keep the shrinkage margin as small as possible and use the skin flash thickness of 20 mm for the skin to receive a sufficient dose.

Analysis of Skin Dose and Position Stability for a New Personalized Device for Breast Radiotherapy

Whole breast irradiation is the standard treatment for patients with early-stage breast cancer. We previously developed a personalized breast support device (PERSBRA) that reduced heart and lung radiation exposure. However, the skin dose was concerned for the device due to its thickness. In this study, we designed the new honeycomb structures to reduce the dose to the skin and maintain stable breast position with this device. Three different structures of PERSBRA were designed. They were solid structure, honeycomb structures with 3.5 mm wall thickness and honeycomb structures with 4.5 mm wall thickness respectively. Those patients who scheduled to receive whole breast irradiation were enrolled for anthropometric breast position analysis. Stability of breast position in supine with PERSBRA were analyzed by scanning with a 3D infrared scanner. The distances between the nipples, between the nipple and the xiphoid process, and between the nipple and the inframammary fold were used to be the index. 32 patients were enrolled for anthropometric breast position analysis. The skin dose was simulated using the thermoluminescent dosimeter (TLD) positioned on the phantom with PERSBRA in the treatment scenario. The displacements between two nipples, the nipple and the infra mammary point, and the nipple and the xiphoid process were 1.4%, 1.2%, and 0.4% for 3.5 mm honeycomb structure. Meanwhile, these displacements were 0.8%, 0.7% and 0.2% for solid 10% structure. Compared to these results, there were no significant difference for the two designations. The surface dose simulating the treatment scenario were 78.27%, 89.39% and 91.9% of prescribed dose for the 3.5mm, 4.5 mm honeycomb structure and the solid 10% filled structure, respectively. The 3.5 mm honeycomb structure reduce the surface dose significantly compared to another two designations. The honeycomb structures do not jeopardize mechanical properties of PERSBRA or the breast positional stability support. Moreover, honeycomb structure with 3.5 mm thickness effectively reduces skin surface dose on a breast phantom. These data encourage further clinical studies to investigate the effects of such design on radiation dermatitis during whole breast irradiation.

Effect of topical agents on skin surface dose in volumetric modulated arc therapy for head and neck cancer.

In volumetric modulated arc therapy (VMAT), the effect of an increase in skin surface dose due to topical agents might be negligible. We investigated the bolus effects of three types of topical agents in VMAT for head and neck cancer (HNC). Topical agents of different thicknesses (0.1, 0.5 and 2mm) were prepared. When each topical agent was set, the surface doses were measured for the anterior static field and VMAT, with and without a thermoplastic mask. No significant differences were observed among the three topical agents. For topical agent thicknesses of 0.1, 0.5 and 2mm, the increases in surface dose for the anterior static field without the thermoplastic mask were 7-9, 30-31 and 81-84%, respectively. With the thermoplastic mask, the corresponding increases were 5, 12-15 and 41-43%, respectively. The increases in surface dose for VMAT without the thermoplastic mask were 5-8, 16-19 and 36-39%, respectively, and those with the thermoplastic mask were 4, 7-10 and 15-19%, respectively. The rate of increase in surface dose with the thermoplastic mask was smaller than that without the thermoplastic mask. The increase in surface dose with topical agents of clinical standard thickness (0.02mm) was estimated to be 2% with the thermoplastic mask. The increase in surface dose with topical agents in dosimetric simulation, compared with control situation, is not significant in clinical conditions for HNC patients.

Assessment of out-of-field radiation doses for high dose per pulse intraoperative electron beam radiotherapy using TLD-100

PurposeThis research aims to assess the out-of-field surface doses for different combinations of electron energy, applicator size, and distance from the applicator wall of high dose-per-pulse IntraOperative electron Radiation Therapy (IOeRT) using thermoluminescent dosimeters (TLDs). Materials and methodsThe out-of-field doses for various combinations of IOeRT electron beam energy/applicator size were measured using ionometric dosimetry. The calibrated LiF:Mg,Ti dosimeters (TLD-100) were used to make the measurements. TLD results were benchmarked using an Advanced Markus chamber and a polymethyl methacrylate slab phantom. TLDs were read out using a HARSHAW (type 4000) manual TLD reader. ResultsThe TLDs received out-of-field absorbed doses ranging from 0.033 to 0.545 mGy/MU depending on the applicator size, electron energy, and distance from the applicator's outer wall. The mean discrepancies between TLDs and Advanced Markus ion chamber measured data were about 1.82% in the PMMA slab phantom at a depth of maximum dose for each electron energy. ConclusionThe skin surface dose can be significant during IOeRT. The maximum out-of-field doses have occurred at high electron beam energy and closer distances around the applicator wall. TLD can measure the skin's dose level according to its good agreement with the reference Advanced Markus dosimeter. The TLD-100 can be used as a reliable dosimeter for intraoperative radiation dosimetry.

Comparison of the Y-90 brachytherapy and Ir-192 brachytherapy of skin tumors: a simulation study

Abstract Skin brachytherapy is a successful practice for treating skin cancer patients. Although a gamma source like an Iridium-192 (Ir-192) is commonly used in the skin brachytherapy, the use of a beta source like Yttrium-90 (Y-90) has also been investigated for this purpose. In the current study, we simulated the dose distribution of a proposed Y-90 applicator and an Ir-192 Leipzig applicator in a skin phantom, and compared the performance of each of the methods in treating three tumors in three hypothetical scenarios. Results of this simulation study showed that because of the sharp dose falloff of beta radiation in tissue, the Y-90 applicator may lead to better protection of the bone and/or cartilage under thin tumors. However, it may lead to excessive skin surface dose if thick skin tumors are treated. To choose between the Ir-192 and Y- 90 applicators, one may need to consider the thickness of the tumor and the thickness of the adipose layer between the tumor and the bone.

Skin Surface Dose for Whole Breast Radiotherapy Using Personalized Breast Holder: Comparison with Various Radiotherapy Techniques and Clinical Experiences.

Simple SummaryBreast immobilization with personalized breast holder (PERSBRA) is a promising approach to reduce the toxicity in the lungs and heart during whole breast radiotherapy. In this study, we designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on a Rando phantom. Hybrid, intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) techniques were used to deliver a prescribed dose. The dose measurement with EBT3 film and TLD were taken on Rando phantom with no PERSBRA, large mesh, fine mesh, and solid PERSBRA for tumor doses and surface doses. This innovative PERSBRA provides another radiotherapy option for patients with left breast cancer.Purpose: Breast immobilization with personalized breast holder (PERSBRA) is a promising approach for normal organ protection during whole breast radiotherapy. The aim of this study is to evaluate the skin surface dose for breast radiotherapy with PERSBRA using different radiotherapy techniques. Materials and methods: We designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on an anthropomorphic(Rando) phantom. Treatment planning was generated using hybrid, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques to deliver a prescribed dose of 5000 cGy in 25 fractions accordingly. Dose measurement with EBT3 film and TLD were taken on Rando phantom without PERSBRA, large mesh, fine mesh and solid PERSBRA for (a) tumor doses, (b) surface doses for medial field and lateral field irradiation undergoing hybrid, IMRT, VMAT techniques. Results: The tumor dose deviation was less than five percent between the measured doses of the EBT3 film and the TLD among the different techniques. The application of a PERSBRA was associated with a higher dose of the skin surface. A large mesh size of PERSBRA was associated with a lower surface dose. The findings were consistent among hybrid, IMRT, or VMAT techniques. Conclusions: Breast immobilization with PERSBRA can reduce heart toxicity but leads to a build-up of skin surface doses, which can be improved with a larger mesh design for common radiotherapy techniques.

Skin Dose Modeling and Measurement in a High Field In-Line MRI-Linac System

The Australian MRI-Linac prototype radiotherapy system has been shown to generate significant entry skin or surface dose increases. This arises from electron contamination focusing toward the isocenter caused by the 1 T MRI field being in-line with the x-ray beam. The aim of this study is to present accurate Monte Carlo modeling of these skin dose changes and to compare them with previous experimental measurements. Accurate skin dose modeling will improve confidence in the pathway forward to treatment planning for clinical trials. A COMSOL Multiphysics model of the Australian MRI-Linac system was used to generate a 3D magnetic field map to be used in corresponding Geant4 Monte Carlo simulations. The Geant4 simulations included the x-ray source (6 MV Linac), multileaf collimators (MLCs), and a 30 cm × 30 cm × 30 cm water phantom located with its front surface at the beam isocenter. Simulations were performed with a source to surface distance (SSD) of 1,819 mm for nominal field sizes 2 cm × 2 cm, 6 cm × 6 cm, and 10 cm × 10 cm. Central axis percentage depth dose (PDD) and surface (or skin) doses at 70 μm depth were calculated by using high-resolution scoring voxels of 10 μm thickness. The results were compared with corresponding experimental data collected using MOSkin™ on the Australian MRI-Linac prototype system. The accurate modeling provides great detail into how the electron contamination is heavily confined and focused toward the beam central axis due to the presence of in-line magnetic field. This concentration significantly increases the skin dose up to 320% for the field size of 10 cm × 10 cm. For 2 cm × 2 cm and 6 cm × 6 cm, the surface skin dose is 128% and 217%, respectively, as compared to the skin dose in the absence of the magnetic field. The simulation results are in generally good agreement, ±10%, with previously collected experimental data for the same nominal field sizes. For the first time, detailed Geant4 Monte Carlo simulations of the electron contamination in the Australian MRI-Linac system have been performed and confirmed to be sufficiently accurate. These simulations will provide a solid framework for estimating the skin dose changes in more clinically relevant treatment plan scenarios that are envisaged in the near future.

Estimation of the Surface Dose in Breast Irradiation by the Beam Incident Angle and the 1 cm Depth Dose.

To develop a method of estimating surface dose in whole breast irradiation, we used an anthropomorphic phantom with accessories for the simulation of different breast sizes. The surface points, which are measured by TLDs, are set along with two main directions, superior-inferior and medial-lateral. The incident angle between the photon beam and the surface and the doses at 1 cm beneath the surface at every point are assessed by a computerized treatment planning system (cTPS). With the prescription dose of 200 cGy, the average surface doses under tangential irradiation are 97.73 (±14.96) cGy, 99.90 (±10.73) cGy, and 105.26 (±9.21) cGy for large, medium, and small breast volumes, respectively. The surface dose increased in the model of small breast volume without significance (p = 0.39). The linear analysis between surface dose and the incident angle is y = 0.5258x + 69.648, R2 = 0.7131 (x: incident angle and y: surface dose). We develop the percentage of skin surface dose with reference to a depth of 1 cm (PSDR1cm) to normalize the inhomogeneous dose. The relationship between incident angle and PSDR1cm is y = 0.1894x + 36.021, R2 = 0.6536 (x: incident angle and y: PSDR1cm) by linear analysis. In conclusion, the surface dose in whole breast irradiation could be estimated from this linear relationship between PSDR1cm and incident angle in daily clinical practice by cTPS. Further in vivo data should be studied to verify this formula.

Skin Dose Distributions from Total Skin Electron Irradiation Therapy (TSET)

Skin Dose Distributions from Total Skin Electron Irradiation Therapy (TSET)

Reference Person Dose-Area Product and Organ Dose-Area Product Estimates During Pelvis Radiography in Some Selected Centres in Lagos Conurbation, Nigeria

Background: In diagnostic radiology, focus on patient’s dose measurement has been on the estimation of entrance skin surface dose and its equivalent risk assessor (effective and organ doses). So, this study identified DAP’s as capable of performing same function as ESD in patient dose monitoring. Thus, reported estimates on dose area product (DAP) and the equivalent risk to organ’s exposed in adult patients during pelvis examination in Lagos State, Nigeria. Patients and Methods: Gender percentage ratio of 39.4 and 60.4 for male and female respectively, from six selected centres, exposed for both pelvis AP and LAT of the procedures were monitored using mathematical approach and dose Cal version 2.31 software, designed to monitor organ’s dose and DAP. Results: The average DAP and it equivalent organ dose area product (ODAP) values recorded from a population of 278 adult patients studied were found to be within expected limits for a reference adult person. Though, DAP for pelvis AP was found almost twice that recorded for the pelvis LAT. High and low organ DAP recorded for both gender from urinary bladder and lungs respectively for pelvis AP whilst these were pelvis bone and lungs for male and ovaries and lungs for female from pelvis LAT respectively. High values were equally recorded for the reproductive organs (Testicles and Ovaries) during pelvis AP. Conclusion: This study therefore suggest that better understanding of organ anatomical position in relation to specific examination will better promote as low as reasonable practicable.

Monte Carlo study on dose distributions from total skin electron irradiation therapy (TSET)

Total skin electron therapy (TSET) has been used to treat mycosis fungoides since the 1950s. Practitioners of TSET rely on relatively crude, phantom-based point measurements for commissioning and treatment plan dosimetry. Using Monte Carlo simulation techniques, this study presents whole-body dosimetry for a patient receiving rotational, dual-field TSET. The Monte Carlo codes, BEAMnrc/DOSXYZnrc, were used to simulate 6 MeV electron beams to calculate skin dose from TSET. Simulations were validated with experimental measurements. The rotational dual-field technique uses extended source-to-surface distance with an acrylic beam degrader between the patient and incident beams. Simulations incorporated patient positioning: standing on a platform that rotates during radiation delivery. Resultant patient doses were analyzed as a function of skin depth-dose coverage and evaluated using dose-volume-histograms. Good agreement was obtained between simulations and measurements. For a cylinder with a 30 cm diameter, the depths that dose fell to 50% of the surface dose was 0.66 cm, 1.15 cm and 1.42 cm for thicknesses of 9 mm, 3 mm and without an acrylic scatter plate, respectively. The results are insensitive to cylinder diameter. Relatively uniform skin surface dose was obtained for skin in the torso area although large dose variations (>25%) were found in other areas resulting from partial beam shielding of the extremities. To achieve 95% mean dose to the first 5 mm of skin depth, the mean dose to skin depth of 5–10 mm and depth of 10–15 mm from the skin surface was 74% (57%) and 50% (25%) of the prescribed dose when using a 3 mm (9 mm) thickness scatter plate, respectively. As a result of this investigation on patient skin dose distributions we changed our patient treatments to use a 3 mm instead of a 9 mm thickness Acrylic scatter plate for clinically preferred skin depth dose coverage.

Verification using in vivo optically stimulated luminescent dosimetry of the predicted skin surface dose in patients receiving postmastectomy radiotherapy

The purpose of this study was to evaluate whether dose to the skin surface underneath bolus, was accurately predicted by a 3D treatment planning system (TPS) in patients receiving 50 Gy/25# postmastectomy radiotherapy (PMRT) using optically stimulated luminescent dosimetry (OSLD) for verification. In vivo dosimetry using OSLDs was performed in 20 consecutive patients receiving PMRT. An array of 9 OSLDs were applied to the chest wall or neobreast in a grid arrangement. Dosimetry data were recorded on 3 separate treatment fractions, averaged, and extrapolated to 25 fractions. On the 3D TPS, the predicted dose was calculated using the departmental planning algorithm at points corresponding to the OSLDs. The mean within patient difference between the planned and measured dose at each of the 9 points was calculated and Bland-Altman limits of agreement used to quantify the extent of agreement. Paired t-tests were used to test for evidence of systematic bias at each point. The coefficient of variation of the 3 OSLD readings per patient at each of the 9 points was low for 8 points (≤4.4%) demonstrating comparable dose received per fraction at these points. The mean ratio between the in vivo measured extrapolated OSLD (IVME OSLD) dose and the planned TPS dose ranged between 0.97 and 0.99 across all points (standard deviation range 0.05 to 0.08). The mean within patient difference between the IVME OSLD and planned TPS was <1 Gy at 7 of the 9 points and the t-test for evidence of systematic bias was significant (p = 0.03) at only 1 of the 9 points. Our commercially available 3D TPS closely predicted PMRT skin surface dose underneath bolus as verified by OSLDs. At all sites, the average ratio of delivered to predicted dose was >0.97 but <1. This practical and feasible OSLD assessment of only 3 of 25 fractions facilitates quality assurance of a TPS in predicting skin surface dose under bolus.

Assessment of the Air-Electron Streaming Effect for MRI Guided Lung SBRT: A Treatment Planning Study

Electron streams outside the body are inevitably generated in the presence of magnetic field during MRI guided radiotherapy. This study aims to investigate the air-electron streaming effects for lung Stereotactic Body Radiotherapy (SBRT) treated on the 1.5T MRI Linac. Three lung SBRT cases with prescription dose ranging from 30Gy to 60Gy in four to five fractions were investigated in this study. The original curative treatment plan was designed by using step-and-shoot intensity modulated radiotherapy (IMRT) technique and then calculated with Monaco (v5.40.01) Monte Carlo dose engine under the 1.5 T magnetic field. To investigate the effect of air-electron streaming, another comparable treatment plan without 1.5T magnetic field was generated using the same planning parameters. In order to display the in-air dose distribution outside the body in Monaco system, an auxiliary structure was created by extending the external with margin of 8cm in anterior. The two plans with or without magnetic field were then compared in terms of in air dose distribution outside the body and dose to the chin. Electron stream effects outside the body were obviously observed for all 3 lung SBRT cases when in the presence of magnetic field, while which were not observed in the absence of magnetic field. From sagittal view, the electron stream can travel a long distance in air along the magnetic field direction, even can reach to the patient’s chin. But only two of the three cases have CT scan including the chin region. For that two cases, the chin surface skin doses were 1.47Gy (2.45% of 60Gy) and 2.24Gy (7.47% of 30Gy) respectively. While for the plans without magnetic field, the corresponding chin surface skin dose were 0.18Gy (0.3% of 60Gy) and 0.32Gy (1.07% of 30Gy) respectively. For the last case, the streaming electrons were expected to reach at the chin area, but due to which was not scanned in CT image, it’s hard to evaluate quantitatively. Electron streaming effects outside the body were also observed in MRI guided lung SBRT plans and which could lead to a higher chin dose compared to conventional scenario without magnetic field. It is therefore recommended for the MRI guided lung SBRT patients that the chin region should be scanned and included in planning CT image. Other suggestions for example shielding with bolus or keeping the patient’s head tilted to the opposite side should also be considered.

EVALUATION OF OCCUPATIONAL RADIATION EXPOSURE IN A RADIO-DIAGNOSTIC FACILITY IN KATSINA- NIGERIA

Poor implementation of quality assurance programs in the radiation industry has been a major setback in our locality. Several studies revealed that occupational workers are exposed to many potential hazards of ionizing radiation during radio-diagnostic procedures, yet radiation workers are often not monitored. This study aims to evaluate the occupational exposure of the radiation workers in Federal Medical Centre Katsina, and to compare the exposure with recommended occupational radiation dose limits. The quarterly readings of 20 thermo-luminescent dosimeters (TLDs') used by the radiation workers from January to December, 2019 were collected from the facility's radiation monitoring archive, and subsequently assessed and analyzed. The results indicate that the average annual equivalent dose per occupational worker range from 0.74 to 1.20 mSv and 1.28 to 2.21 mSv for skin surface and deep skin dose, measured at 10 mm and 0.07 mm tissue depth respectively. The occupational dose was within the recommended national and international limits of 5 mSv per annum or an average of 20 mSv in 5 years. Therefore, there was no significant radiation exposure to all the occupational workers in the study area. Though, the occupational radiation dose is within recommended limit, this does not eliminate stochastic effect of radiation. The study recommended that the occupational workers should adhere and strictly comply with the principles of radiation protection which includes distance, short exposure time, shielding and proper monitoring of dose limits. Furthermore, continuous training of the radiation workers is advised.

Post-mastectomy Radiotherapy Bolus Across the North and East London Radiotherapy Network

Purpose: Post-mastectomy radiotherapy decreases locoregional recurrence and reduces breast cancer mortality in a select group [1–4]. Recurrence is most common at the chest wall, and bolus is used to increase skin surface dose [1,2]. Studies have shown huge variability in bolus use post-mastectomy, with no proven optimum regimen [1,2,5]. When using skin bolus, thickness and frequency of use increases skin toxicity [1,2,6]. Severe toxicity including pain, or moist desquamation, can lead to treatment cessation, resulting in inferior local control [1,2].

Dosimetric impact of tracheostomy devices in head and neck cancer patients.

IntroductionThe tracheostomy site and adjacent skin is at risk for recurrence in head/neck squamous cell cancer patients. The tracheostomy tube is an in situ device located directly over the tracheostomy site and may have clinical implications on the radiation dose delivered to the peristomal region. This study aimed to investigate this effect by comparing the prescribed treatment planning dose with the actual dose in vivo to the peristomal clinical target region. A retrospective, dosimetric study was performed with approval of the institutional research ethics board.MethodsFifteen patients who had received high‐dose radiotherapy to the tracheostomy region with in vivo dose measurements were included. The radiation dose at the skin surface underneath the tracheostomy device was measured using an optically stimulated luminescent dosimeter (OSLD) and was compared with the prescribed dose from the radiation planning system. The effect of the tracheostomy flange and/or soft tissue equivalent bolus on the peristomal dose was calculated.Results and discussionPatients with tracheostomy equipment in situ were found to have a 3.7% difference between their prescribed and actual dose. With a tissue equivalent bolus there was a 2.0% difference between predicted and actual. The mean prescribed single fraction dose (mean = 191.8 cGy, SD = 40.18) and OSLD measured dose (mean = 194.02 cGy, SD = 44.3) were found to have no significant difference. However, with the flange excluded from the planning simulation (density = air) target skin dose deviated from predicted by an average of 55.3% (range = 12.4–72.9, SD = 22.5) and volume coverage was not achieved.ConclusionIn summary, the tracheostomy flange acts like bolus with a twofold increase in the skin surface dose. Changes in the peristomal apparatus from simulation to treatment needs to be considered to ensure that the simulated dose and coverage is achieved.

Estimation of Surface Skin Dose Using TPS and TLD of Breast Radiotherapy Using Co-60 Teletherapy Unit

Estimation of surface skin dose is very important for patients who undergo breast radiotherapy to show that the skin dose is under the safe level and to avoid tumor recurrence. The aim of this study is utilizing the thermolumiscent dosimeters (TLDs) as quality control in conventional radiotherapy procedures. Twenty patients undergo breast remove were stimulated by treatment planning system (TPS) and six lithium florid TLD-LiF chips have applied at the irradiated breast area. All measurements were performed using a Co-60 teletherapy (open field). All TLD chips were measured using the Harshaw 6600 reader system. Results have been shown that the correlation coefficient and the Bland–Altman agreement plot of 20 patients at six points illustrated that no significant difference (p>0.05) between TPS calculations and TLD measurements except at beams centers, there is high significance difference (p<0.001), where the high dose was applied. Thus, the conclusion is that not all locations in the area of treatment absorbed the same dose either using TLD measurements or using TPS values

Breast Radiation Therapy Using a Breast Cup: Moving the Target, Not the Patient

PurposeTo compare whole-breast radiation therapy dose distributions with and without the use of breast cups to reposition the breast itself. Methods and MaterialsA fitted plastic breast cup repositions the breast on the anterior chest wall, reducing the lateral fall and ptosis of the breast. Eighteen patients requiring breast cups were identified on an initial simulation computed tomography scan (without breast cup); subsequently, a second scan with the breast cup fitted was performed. An optimal treatment plan was then created on both scans with the differences in radiation dose to underlying organs compared. In vivo measurements were performed to assess any possible bolusing effect on skin dose owing to the breast cup. ResultsBreast cups significantly reduce dose to both lung and heart for all left-sided cases. All lung dose metrics decreased for all right-sided cases. Right-sided heart dose metrics did not significantly decrease with the use of breast cups; however, heart mean dose for these cases was all under 100 cGy. A 16% increase in skin surface dose was observed in an anthropomorphic phantom when using a breast cup. ConclusionsUse of the breast cup in breast radiation therapy decreases dose to underlying organs at risk and is cost-effective. It can be easily integrated with deep inspiration breath hold, intensity modulated radiation therapy, and volumetric-modulated arc therapy techniques. With use of the device, a supine patient position can be maintained, meaning nodal regions can be treated mono-isocentrically.

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.

Verification Using Osld In Vivo Dosimetry of the Predicted Skin Surface Dose in Patients Receiving Post-Mastectomy Radiotherapy

In patients receiving post-mastectomy radiotherapy (PMRT), the skin overlying the chest wall is considered at-risk of tumour recurrence, often necessitating the use of bolus material. The accuracy with which three-dimensional treatment planning systems predict radiation dose delivered to the skin surface is poorly characterised. The purpose of this study was to evaluate whether dose to the skin surface, underneath bolus, was accurately predicted by a commercially available 3D-treatment planning system in the PMRT clinical setting. Optically stimulated luminescent dosimeters (OSLDs) are a widely used method of in vivo dosimetry, with their use at the skin surface having been examined previously. However, their use in the evaluation of skin surface dose in the setting of PMRT has not previously been documented. In vivo dosimetry using OSLDs was performed prospectively in 20 patients receiving PMRT following ethics approval. An array of 9 OSLDs were applied in a 3x3 grid arrangement, over a 10x10cm field on the ipsilateral chest wall or neobreast (non-autologous reconstruction post-mastectomy), referenced to the midline tattoo. Dosimetry data were recorded on three separate days during the first half of the PMRT course (50 Gy/25#) for each patient. The 9 in vivo dosimetry points corresponded to the same anatomical location on the 3D treatment planning DICOM image, 0.45mm below the skin surface, from which the predicted dose was calculated using the departmental planning algorithm. Estimated bias was calculated using the mean difference between the planned and measured dose, and a p-value of a t-test for systematic bias given for each point. Bland-Altman limits of agreement are stated, which are the values between which 95% of within subject differences in measurement are expected to fall. The coefficient of variation (CV) of the 3 OSLD readings at each of the 9 points was low for 8 points (≤ 4.4%) demonstrating comparable dose-received per fraction at each point; only the inferior-medial point CV was higher at 7.6%. The mean difference for each of the 9 points ranged between 0.47-1.30 Gy (0.94%-2.6% of prescribed dose), representing less dose received compared to the planned dose. For 7 of 9 points, the mean estimated bias was < 1 Gy of predicted radiation dose. Bland-Altman limits of agreement were widest at the superior medial position ( -5.98Gy to 7.70Gy). T-test for systematic bias was significant (p=0.03) in only one of the 9 points (inferior-lateral point). Our data indicate that the skin surface dose underneath bolus is predicted with a reasonable level of accuracy utilising a commercially available 3D treatment-planning system. Bland-Altman limits of agreement were wide, indicating a limitation of the study being the limited number of fractions (3 of 25) from which our data could be extrapolated.