Recommendations for using analytical anisotropic algorithm and AcurosXB for epidermal dose calculations in breast radiotherapy from an in vivo Gafchromic film study.

BACKGROUND AND PURPOSE: This study recommends clinical epidermal dose calculation methods based on in-vivo film measurements and registered skin dose distributions with the Eclipse (Varian Medical Systems) treatment planning system's Analytical Anisotropic Algorithm (AAA) and Acuros XB (AXB) dose calculation algorithms. MATERIALS AND METHODS: Eighteen AAA V13.6 breast plans were recalculated using AXB (dose to medium) V13.5 with the same beam parameters and monitor units as in the original plans. These are compared against in-vivo Gafchromic film measurements from the lateral and inferior breast regions. Three skin structures in the treatment planning system are evaluated: a surface layer of voxels of the body contour, a 0.2 cm internal skin rind, and a 0.5 cm internal skin rind. RESULTS: Systematic shifts are demonstrated between the film measurements of skin dose and the Eclipse dose calculations. On average, the dose to the surface layer of pixels is underestimated by AAA by 8% and overestimated by AXB by 3%. A 5 mm skin rind extended into the body can increase epidermal dose calculations on average by 8% for AAA and 4% for AXB. CONCLUSION: This is the first study to register in-vivo skin dose distributions in the breast to the treatment planning system for comparison. Based on the results from this study it is recommended that epidermal dose is calculated with a 0.5 cm skin rind for the AAA algorithm and with rind thickness up to 0.2 cm for the AXB algorithm.

Electron streaming dose measurements and calculations on a 1.5 T MR-Linac.

PURPOSE: To evaluate the accuracy of different dosimeters and the treatment planning system (TPS) for assessing the skin dose due to the electron streaming effect (ESE) on a 1.5 T magnetic resonance (MR)-linac. METHOD: Skin dose due to the ESE on an MR-linac (Unity, Elekta) was investigated using a solid water phantom rotated 45° in the x-y plane (IEC61217) and centered at the isocenter. The phantom was irradiated with 1 × 1, 3 × 3, 5 × 5, 10 × 10, and 22 × 22 cm2 fields, gantry at 90°. Out-of-field doses (OFDs) deposited by electron streams generated at the entry and exit surface of the angled phantom were measured on the surface of solid water slabs placed ±20.0 cm from the isocenter along the x-direction. A high-resolution MOSkin™ detector served as a benchmark due to its shallower depth of measurement that matches the International Commission on Radiological Protection (ICRP) recommended depth for skin dose assessment (0.07 mm). MOSkin™ doses were compared to EBT3 film, OSLDs, a diamond detector, and the TPS where the experimental setup was modeled using two separate calculation parameters settings: a 0.1 cm dose grid with 0.2% statistical uncertainty (0.1 cm, 0.2%) and a 0.2 cm dose grid with 3.0% statistical uncertainty (0.2 cm, 3.0%). RESULTS: OSLD, film, the 0.1 cm, 0.2%, and 0.2 cm, 3.0% TPS ESE doses, underestimated skin doses measured by the MOSkin™ by as much as -75.3%, -7.0%, -24.7%, and -41.9%, respectively. Film results were most similar to MOSkin™ skin dose measurements. CONCLUSIONS: These results show that electron streams can deposit significant doses outside the primary field and that dosimeter choice and TPS calculation settings greatly influence the reported readings. Due to the steep dose gradient of the ESE, EBT3 film remains the choice for accurate skin dose assessment in this challenging environment.

Occupational skin dose from radionuclide contamination: one country's approach at standardising skin dose estimates using Varskin.

The manipulation of unsealed radiopharmaceuticals by healthcare workers can cause accidental personal contamination leading to occupational radiation skin dose. The UK Ionising Radiations Regulations 2017 require that potential skin doses arising from reasonably foreseeable accident scenarios are included in risk assessments. Workers must be designated as classified if these dose estimates exceed 150 mSv equivalent dose averaged over 1 cm2. Updates from the UK Health and Safety Executive recently prompted many in the UK to review the classification of workers in Nuclear Medicine. Skin dose from contamination cannot be measured, it must be estimated. Varskin+ is a code that is widely recommended for estimating skin dose. The subjective choices made by users when defining modelled scenarios in Varskin+ lead to significant variation in the calculated skin doses. At the time of writing there is no definitive calculation method and all calculations rely on theoretical models. NHS Health Boards in Scotland have adopted a standardised framework for performing skin dose estimates for risk assessments. The parametric sensitivity of Varskin+ inputs were examined and the available evidence was reviewed. Generic, reasonably forseeable, worst-case accident scenarios were decided upon for: direct skin contamination, glove contamination and needlestick injury. Standardised inputs and assumptions for each scenario were compiled in a protocol that has been adopted by the Scottish Health Boards. The protocol allows for differences in practice between departments, but standardises most inputs. While significant uncertainty remains in the estimated skin doses, this approach reduces variation and enables the comparison of estimated skin doses between departments. The framework facilitates continuous improvement as more evidence is gathered to refine the standardised assumptions. Task by task skin dose estimates were made for workers in Nuclear Medicine in Scotland and many workers were designated classified as a result.

Radiation exposure in augmented fluoroscopic bronchoscopy procedures: a comprehensive analysis for patients and physicians.

Cancer is a major health challenge and causes millions of deaths worldwide each year, and the incidence of lung cancer has increased. Augmented fluoroscopic bronchoscopy (AFB) procedures, which combine bronchoscopy and fluoroscopy, are crucial for diagnosing and treating lung cancer. However, fluoroscopy exposes patients and physicians to radiation, and therefore, the procedure requires careful monitoring. The National Council on Radiation Protection and Measurement and the International Commission on Radiological Protection have emphasised the importance of monitoring patient doses and ensuring occupational radiation safety. The present study evaluated radiation doses during AFB procedures, focusing on patient skin doses, the effective dose, and the personal dose equivalent to the eye lens for physicians. Skin doses were measured using thermoluminescent dosimeters. Peak skin doses were observed on the sides of the patients' arms, particularly on the side closest to the x-ray tube. Differences in the procedures and experience of physicians between the two hospitals involved in this study were investigated. AFB procedures were conducted more efficiently at Hospital A than at Hospital B, resulting in lower effective doses. Cone-beam computed tomography (CT) contributes significantly to patient effective doses because it has higher radiographic parameters. Despite their higher radiographic parameters, AFB procedures resulted in smaller skin doses than did image-guided interventional and CT fluoroscopy procedures. The effective doses differed between the two hospitals of this study due to workflow differences, with cone-beam CT playing a dominant role. No significant differences in left and right eyeHp(3) values were observed between the hospitals. For both hospitals, theHp(3) values were below the recommended limits, indicating that radiation monitoring may not be required for AFB procedures. This study provides insights into radiation exposure during AFB procedures, concerning radiation dosimetry, and safety for patients and physicians.

Establishing a priori and a posteriori predictive models to assess patients' peak skin dose in interventional cardiology. Part 2: results of the VERIDIC project.

BACKGROUND: Optimizing patient exposure in interventional cardiology is key to avoid skin injuries. PURPOSE: To establish predictive models of peak skin dose (PSD) during percutaneous coronary intervention (PCI), chronic total occlusion percutaneous coronary intervention (CTO), and transcatheter aortic valve implantation (TAVI) procedures. MATERIAL AND METHODS: A total of 534 PCI, 219 CTO, and 209 TAVI were collected from 12 hospitals in eight European countries. Independent associations between PSD and clinical and technical dose determinants were examined for those procedures using multivariate statistical analysis. A priori and a posteriori predictive models were built using stepwise multiple linear regressions. A fourfold cross-validation was performed, and models' performance was evaluated using the root mean square error (RMSE), mean absolute percentage error (MAPE), coefficient of determination (R²), and linear correlation coefficient (r). RESULTS: Multivariate analysis proved technical parameters to overweight clinical complexity indices with PSD mainly affected by fluoroscopy time, tube voltage, tube current, distance to detector, and tube angulation for PCI. For CTO, these were body mass index, tube voltage, and fluoroscopy contribution. For TAVI, these parameters were sex, fluoroscopy time, tube voltage, and cine acquisitions. When benchmarking the predictive models, the correlation coefficients were r = 0.45 for the a priori model and r = 0.89 for the a posteriori model for PCI. These were 0.44 and 0.67, respectively, for the CTO a priori and a posteriori models, and 0.58 and 0.74, respectively, for the TAVI a priori and a posteriori models. CONCLUSION: A priori predictive models can help operators estimate the PSD before performing the intervention while a posteriori models are more accurate estimates and can be useful in the absence of skin dose mapping solutions.

Patient exposure dose in interventional cardiology per clinical and technical complexity levels. Part 1: results of the VERIDIC project.

BACKGROUND: Patients can be exposed to high skin doses during complex interventional cardiology (IC) procedures. PURPOSE: To identify which clinical and technical parameters affect patient exposure and peak skin dose (PSD) and to establish dose reference levels (DRL) per clinical complexity level in IC procedures. MATERIAL AND METHODS: Validation and Estimation of Radiation skin Dose in Interventional Cardiology (VERIDIC) project analyzed prospectively collected patient data from eight European countries and 12 hospitals where percutaneous coronary intervention (PCI), chronic total occlusion PCI (CTO), and transcatheter aortic valve implantation (TAVI) procedures were performed. A total of 62 clinical complexity parameters and 31 technical parameters were collected, univariate regressions were performed to identify those parameters affecting patient exposure and define DRL accordingly. RESULTS: Patient exposure as well as clinical and technical parameters were collected for a total of 534 PCI, 219 CTO, and 209 TAVI. For PCI procedures, body mass index (BMI), number of stents ≥2, and total stent length >28 mm were the most prominent clinical parameters, which increased the PSD value. For CTO, these were total stent length >57 mm, BMI, and previous anterograde or retrograde technique that failed in the same session. For TAVI, these were male sex, BMI, and number of diseased vessels. DRL values for Kerma-area product (PKA), air kerma at patient entrance reference point (Ka,r), fluoroscopy time (FT), and PSD were stratified, respectively, for 14 clinical parameters in PCI, 10 in CTO, and four in TAVI. CONCLUSION: Prior knowledge of the key factors influencing the PSD will help optimize patient radiation protection in IC.

Evaluation of the contamination droplet model used for the assessment of skin dose during the manipulation of radiopharmaceuticals.

The manipulation of radiopharmaceuticals in nuclear medicine can result in the droplet contamination of operators resulting in the accumulation of a significant skin dose. Current methods to estimate this skin dose often utilise a 50µl cylindrical droplet model, which can lead to unrealistically high estimated skin doses for some radiopharmaceuticals. By conducting experiments to measure the volume of real droplets arising from simulating the manipulation of radiopharmaceuticals, this work found that 50µl is an overestimation of a realistic contamination droplet. For almost all radiopharmaceuticals considered in this work, incorporating a smaller droplet volume into skin dose simulations resulted in higher estimates of skin dose rate per unit of activity, which, when combined with appropriate activity concentrations and droplet volumes, resulted in lower skin doses for contamination droplet incidents. The results presented in this work challenge the 50µl contamination droplet volume and highlight the importance of having an accurate model when estimating the skin dose for contamination scenarios.

Gold-nanoparticle-enriched breast tissue in breast cancer treatment using the INTRABEAM® system: a Monte Carlo study.

Using a 50-kV INTRABEAM® system after breast-conserving surgery, breast skin injury and long treatment time remain the challenging problems when large-size spherical applicators are used. This study has aimed to address these problems using gold (Au) nanoparticles (NPs). For this, surface and isotropic doses were measured using a Gafchromic EBT3 film and a water phantom. The particle propagation code EGSnrc/Epp was used to score the corresponding doses using a geometry similar to that used in the measurements. The simulation was validated using a gamma index of 2%/2 mm acceptance criterion in the gamma analysis. After validation Au-NP-enriched breast tissue was simulated to quantify any breast skin dose reduction and shortening of treatment time. It turned out that the gamma value deduced for validation of the simulation was in an acceptable range (i.e., less than one). For 20 mg-Au/g-breast tissue, the calculated Dose Enhancement Ratio (DER) of the breast skin was 0.412 and 0.414 using applicators with diameters of 1.5 cm and 5 cm, respectively. The corresponding treatment times were shortened by 72.22% and 72.30% at 20 mg-Au/g-breast tissue concentration, respectively. It is concluded that Au-NP-enriched breast tissue shows significant advantages, such as reducing the radiation dose received by the breast skin as well as shortening the treatment time. Additionally, the DERs were not significantly dependent on the size of the applicators.

Characterizing magnetically focused contamination electrons by off-axis irradiation on an inline MRI-Linac.

PURPOSE: The aim of this study is to investigate off-axis irradiation on the Australian MRI-Linac using experiments and Monte Carlo simulations. Simulations are used to verify experimental measurements and to determine the minimum offset distance required to separate electron contamination from the photon field. METHODS: Dosimetric measurements were performed using a microDiamond detector, Gafchromic® EBT3 film, and MOSkinTM . Three field sizes were investigated including 1.9 × 1.9, 5.8 × 5.8, and 9.7 × 9.6 cm2 . Each field was offset a maximum distance, approximately 10 cm, from the central magnetic axis (isocenter). Percentage depth doses (PDDs) were collected at a source-to-surface distance (SSD) of 1.8 m for fields collimated centrally and off-axis. PDD measurements were also acquired at isocenter for each off-axis field to measure electron contamination. Monte Carlo simulations were used to verify experimental measurements, determine the minimum field offset distance, and demonstrate the use of a spoiler to absorb electron contamination. RESULTS: Off-axis irradiation separates the majority of electron contamination from an x-ray beam and was found to significantly reduce in-field surface dose. For the 1.9 × 1.9, 5.8 × 5.8, and 9.7 × 9.6 cm2 field, surface dose was reduced from 120.9% to 24.9%, 229.7% to 39.2%, and 355.3% to 47.3%, respectively. Monte Carlo simulations generally were within experimental error to MOSkinTM and microDiamond, and used to determine the minimum offset distance, 2.1 cm, from the field edge to isocenter. A water spoiler 2 cm thick was shown to reduce electron contamination dose to near zero. CONCLUSIONS: Experimental and simulation data were acquired for a range of field sizes to investigate off-axis irradiation on an inline MRI-Linac. The skin sparing effect was observed with off-axis irradiation, a feature that cannot be achieved to the same extent with other methods, such as bolusing, for beams at isocenter.

Application of reference air kerma alert levels for pediatric fluoroscopic examinations.

The purpose of this study was to provide an empirical model to develop reference air kerma (RAK) alert levels as a function of patient thickness or age for pediatric fluoroscopy for any institution to use in a Quality Assurance program. RAK and patient thickness were collected for 10&663 general fluoroscopic examinations and 1500 fluoroscopically guided interventions (FGIs). RAK and patient age were collected for 6137 fluoroscopic examinations with mobile-C-arms (MC). Coefficients of linear regression fits of logarithmic RAK as a function of patient thickness or age were generated for each fluoroscopy group. Regression fits of RAK for 50%, 90%, and 98% upper prediction levels were used as inputs to derive an empirical formula to estimate alert levels as a function of patient thickness. A methodology is presented to scale results from this study for any patient thickness or age for any institution, for example, the patient thickness dependent RAK alert level at the top 1% of expected RAK can be set using the 98% upper prediction interval boundary given by: RAK 98 % = e m . x avg + s 98 . c ̂ ${\rm{RAK}}_{98\% } = {e}^{m.{x}_{{\rm{avg}}} + {s}_{98}.\hat{c}}\ $ , where xavg is the institute's average patient thickness or age, and c ̂ $\hat{c}$ is the intercept based on the average RAK of the patient population calculated as c ̂ = ln ( RAK avg ) - m . x avg . RA K avg $\hat{c} = \ln ( {{\rm{RAK}}_{{\rm{avg}}}} )\ - m.{x}_{{\rm{avg}}}{\rm{.RA}}{{\rm{K}}}_{{\rm{avg}}}$ is the institution's average RAK (mGy). m and s98 are constants presented for each type of fluoroscope and RAK group and represent slope of the fit and scale factor, respectively. An empirical equation, which estimates alert levels expressed as air Kerma without backscatter at the interventional reference point as a function of patient thickness or age is provided for each fluoroscopic examination type. The empirical equations allow any facility with limited data to scale the results of this study's single facility data to model their practice's unique RAK alert levels and patient population demographics to establish pediatric alert levels for fluoroscopic procedures.

Dosimetric effects of supine immobilization devices on the skin in intensity-modulated radiation therapy for breast cancer: a retrospective study.

BACKGROUND: The dose perturbation effect of immobilization devices is often overlooked in intensity-modulated radiation therapy (IMRT) for breast cancer (BC). This retrospective study assessed the dosimetric effects of supine immobilization devices on the skin using a commercial treatment planning system. METHODS: Forty women with BC were divided into four groups according to the type of primary surgery: groups A and B included patients with left and right BC, respectively, who received 50 Gy radiotherapy in 25 fractions after radical mastectomy, while groups C and D included patients with left and right BC, respectively, who received breast-conservation surgery (BCS) and 40.05 Gy in 15 fractions as well as a tumor bed simultaneous integrated boost to 45 Gy. A 0.2-cm thick skin contour and two sets of body contours were outlined for each patient. Dose calculations were conducted for the two sets of contours using the same plan. The dose differences were assessed by comparing the dose-volume histogram parameter results and by plan subtraction. RESULTS: The supine immobilization devices for BC resulted in significantly increased skin doses, which may ultimately lead to skin toxicity. The mean dose increased by approximately 0.5 and 0.45 Gy in groups A and B after radical mastectomy and by 2.7 and 3.25 Gy in groups C and D after BCS; in groups A-D, the percentages of total normal skin volume receiving equal to or greater than 5 Gy (V5) increased by 0.54, 1.15, 2.67, and 1.94%, respectively, while the V10 increased by 1.27, 1.83, 1.36, and 2.88%; the V20 by 0.85, 1.87, 2.76, and 4.86%; the V30 by 1.3, 1.24, 10.58, and 11.91%; and the V40 by 1.29, 0.65, 10, and 10.51%. The dose encompassing the planning target volume and other organs at risk, showed little distinction between IMRT plans without and with consideration of immobilization devices. CONCLUSIONS: The supine immobilization devices significantly increased the dose to the skin, especially for patients with BCS. Thus, immobilization devices should be included in the external contour to account for dose attenuation and skin dose increment. TRIAL REGISTRATION: This study does not report on interventions in human health care.

Assessment of skin doses in small field radiotherapy for 6 MV photons and beam spectral analysis at skin surface: an EGSnrc based Monte Carlo study.

This study aims at the estimation of skin doses during small field radiotherapy with 6 MV photons and analysis of beam spectra at skin surface. The EGSnrc Monte Carlo code was used for spectral analysis and dose scoring in a water phantom. Percent skin dose (PSD) was calculated at a depth of 70 µm (relative to 10 cm depth), and the effects of field size, collimation, source-to-surface distance, and tissue inhomogeneity (bone/air) below the skin were evaluated. Low-energy photons and contaminant electrons from the machine head or back-scattered from underlying tissue were found to be the major contributors to skin dose. As the field size was reduced, the beam hardened, while the photon and electron fluences at the skin decreased compared to those at the reference depth of 10 cm. This resulted in a PSD reduction for fields smaller than the reference field size. Multi leaf collimators increased the PSD (up to 4%) while variation in source-to-skin dose showed a negligible effect. A substantial increase in PSD has been observed (up to 6%) when high Z material like bone was placed below the skin. In contrast, air as underlying material decreased the skin dose. The skin dose varied considerably with various clinical and geometric parameters. It is concluded that, although the skin doses were low for small fields compared to those for the reference field, skin doses may become substantial when escalated target doses are delivered with multi leaf collimators. Moreover, the presence of high Z materials such as bones or metallic implants below the skin can result in significant enhancement of the skin dose.

Validation of a method for estimating peak skin dose from CT-guided procedures.

A method for estimating peak skin dose (PSD) from CTDIvol has been published but not validated. The objective of this study was to validate this method during CT-guided ablation procedures. Radiochromic film was calibrated and used to measure PSD. Sixty-eight patients were enrolled in this study, and measured PSD were collected for 46 procedures. CTDIvol stratified by axial and helical scanning was used to calculate an estimate of PSD using the method [1.2 × CTDIvol (helical) + 0.6 × CTDIvol (axial)], and both calculated PSD and total CTDIvol were compared to measured PSD using paired t-tests on the log-transformed data and Bland-Altman analysis. Calculated PSD were significantly different from measured PSD (P < 0.0001, bias, 18.3%, 95% limits of agreement, -63.0% to 26.4%). Measured PSD were not significantly different from total CTDIvol (P = 0.27, bias, 3.97%, 95% limits of agreement, -51.6% to 43.7%). Considering that CTDIvol is reported on the console of all CT scanners, is not stratified by axial and helical scanning modes, and is immediately available to the operator during CT-guided interventional procedures, it may be reasonable to use the scanner-reported CTDIvol as an indicator of PSD during CT-guided procedures. However, further validation is required for other models of CT scanner.

Vendor-independent skin dose mapping application for interventional radiology and cardiology.

PURPOSE: The purpose of this paper is to present and validate an originally developed application SkinCare used for skin dose mapping in interventional procedures, which are associated with relatively high radiation doses to the patient's skin and possible skin reactions. METHODS: SkinCare is an application tool for generating skin dose maps following interventional radiology and cardiology procedures using the realistic 3D patient models. Skin dose is calculated using data from Digital Imaging and Communications in Medicine (DICOM) Radiation Dose Structured Reports (RDSRs). SkinCare validation was performed by using the data from the Siemens Artis Zee Biplane fluoroscopy system and conducting "Acceptance and quality control protocols for skin dose calculating software solutions in interventional cardiology" developed and tested in the frame of the VERIDIC project. XR-RV3 Gafchromic films were used as dosimeters to compare peak skin doses (PSDs) and dose maps obtained through measurements and calculations. DICOM RDSRs from four fluoroscopy systems of different vendors (Canon, GE, Philips, and Siemens) were used for the development of the SkinCare and for the comparison of skin dose maps generated using SkinCare to skin dose maps generated by different commercial software tools (Dose Tracking System (DTS) from Canon, RadimetricsTM from Bayer and RDM from MEDSQUARE). The same RDSRs generated during a cardiology clinical procedure (percutaneous coronary intervention-PCI) were used for comparison. RESULTS: Validation performed using VERIDIC's protocols for skin dose calculation software showed that PSD calculated by SkinCare is within 17% and 16% accuracy compared to measurements using XR-RV3 Gafchromic films for fundamental irradiation setups and simplified clinical procedures, respectively. Good visual agreement between dose maps generated by SkinCare and DTS, RadimetricsTM and RDM was obtained. CONCLUSIONS: SkinCare is proved to be very convenient solution that can be used for monitoring delivered dose following interventional procedures.

Review of extremity dosimetry in nuclear medicine.

The exposure of the fingers is one of the major radiation protection concerns in nuclear medicine (NM). The purpose of this paper is to provide an overview of the exposure, dosimetry and protection of the extremities in NM. A wide range of reported finger doses were found in the literature. Historically, the highest finger doses are found at the fingertip in the preparation and dispensing of18F for diagnostic procedures and90Y for therapeutic procedures. Doses can be significantly reduced by following recommendations on source shielding, increasing distance and training. Additionally, important trends contributing to a lower dose to the fingers are the use of automated procedures (especially for positron emission tomography (PET)) and the use of prefilled syringes. On the other hand, the workload of PET procedures has substantially increased during the last ten years. In many cases, the accuracy of dose assessment is limited by the location of the dosimeter at the base of the finger and the maximum dose at the fingertip is underestimated (typical dose ratios between 1.4 and 7). It should also be noted that not all dosimeters are sensitive to low-energy beta particles and there is a risk for underestimation of the finger dose when the detector or its filter is too thick. While substantial information has been published on the most common procedures (using99mTc,18F and90Y), less information is available for more recent applications, such as the use of68Ga for PET imaging. Also, there is a need for continuous awareness with respect to contamination of the fingers, as this factor can contribute substantially to the finger dose.

Calculation and benchmark of fluence-to-local skin equivalent dose coefficients for neutrons with FLUKA, MCNP, and GEANT4 Monte-Carlo codes.

Dose equivalent limits for single organs are recommended by the ICRP (International Commission for the Radiological Protection publication 103). These limits do not lend themselves to be measured. They are assessed by convoluting conversion factors with particle fluences. The Fluence-to-Dose conversion factors are tabulated in the ICRP literature. They allow assessing the organ dose of interest using numerical simulations. In particular, the literature lacks the knowledge of local skin equivalent dose (LSD) coefficients for neutrons. In this article, we compute such values for neutron energies ranging from 1 meV to 15 MeV. We use FLUKA, MCNP and GEANT4 Radiation transport Monte-Carlo simulation codes to perform the calculations. A comparison between these three codes is performed. These calculated values are important for radiation protection studies and radiotherapy applications.

In search of a one plan solution for VMAT post-mastectomy chest wall irradiation.

PURPOSE: This study was designed to evaluate skin dose in both VMAT and tangent treatment deliveries for the purpose of identifying suitable bolus use protocols that should produce similar superficial doses. METHODS: Phantom measurements were used to investigate skin dose in chest wall radiotherapy with and without bolus for 3D and rotational treatment techniques. Optically stimulated luminescence dosimeters (OSLDs) with and without housing and EBT3 film were used. Superflab (3, 5, and 10 mm) and brass mesh were considered. Measured doses were compared with predictions by the Eclipse treatment planning system. Patient measurements were also performed and the bolusing effect of hospital gowns and blankets were highlighted. The effect of flash for VMAT plans was considered experimentally by using 2 mm couch shifts. RESULTS: For tangents, average skin doses without bolus were 0.64 (EBT3), 0.62 (bare OSLD), 0.77 (jacketed OSLD), and 0.68 (Eclipse) as a fraction of prescription. For VMAT, doses without bolus were 0.53 (EBT3), 0.53 (bare OSLD), 0.64 (jacketed OSLD), and 0.60 (Eclipse). For tangents, the average doses with different boluses as measured by EBT3 were 0.99 (brass mesh), 1.02 (3 mm), 1.03 (5 mm), and 1.07 (10 mm). For VMAT with bolus, average doses as measured by EBT3 were 0.83 (brass), 0.96 (3 mm), 1.03 (5 mm), and 1.04 (10 mm). Eclipse doses agreed with measurements to within 5% of measurements for all Superflab thicknesses and within 15% of measurements for no bolus. The presence of a hospital gown and blanket had a bolusing effect that increased the surface dose by approximately 10%. CONCLUSIONS: Results of this work allow for consideration of different bolus thicknesses, materials, and usage schedules based on desired skin dose and choice of either tangents or an arc beam techniques.

In vivo monitoring of total skin electron dose using optically stimulated luminescence dosimeters.

AIM: This study retrospectively analysed the results of using optically stimulated radiation dosimeters (OSLDs) for in vivo dose measurements during total skin electron therapy (TSET, also known as TSEI, TSEB, TSEBT, TSI or TBE) treatments of patients with mycosis fungoides. BACKGROUND: TSET treatments are generally delivered to standing patients, using treatment plans that are devised using manual dose calculations that require verification via in vivo dosimetry. Despite the increasing use of OSLDs for radiation dosimetry, there is minimal published guidance on the use of OSLDs for TSET verification. MATERIALS AND METHODS: This study retrospectively reviewed in vivo dose measurements made during treatments of nine consecutive TSET patients, treated between 2013 and 2018. Landauer nanoDot OSLDs were used to measure the skin dose at reference locations on each patient, as well as at locations of clinical interest such as the head, hands, feet, axilla and groin. RESULTS: 1301 OSLD measurements were aggregated and analysed, producing results that were in broad agreement with previous TLD studies, while providing additional information about the variation of dose across concave surfaces and potentially guiding future refinement of treatment setup. In many cases these in vivo measurements were used to identify deviations from the planned dose in reference locations and to identify anatomical regions where additional shielding or boost treatments were required. CONCLUSIONS: OSLDs can be used to obtain measurements of TSET dose that can inform monitor unit adjustments and identify regions of under and over dosage, while potentially informing continuous quality improvement in TSET treatment delivery.

Nickel deposition and penetration into the stratum corneum after short metallic nickel contact: An experimental study.

BACKGROUND: Knowledge about the skin deposition and penetration of nickel into the stratum corneum (SC) after short contact with metallic items is limited. OBJECTIVE: To quantify nickel skin deposition and penetration into the SC after short contact with metallic nickel. METHODS: Sixteen nickel-allergic participants and 10 controls were exposed to 3 pure nickel discs and 1 aluminium disc on each volar forearm for 3 × 10 minutes. Before exposure, 1 forearm was irritated with 0.5% sodium lauryl sulfate under 24-hour occlusion. Immediately, as well as 24 and 72 hours after metallic disc exposure, outer SC layers were removed with adhesive tapes and the nickel content was measured. RESULTS: Nickel deposition and SC penetration capable of eliciting allergic nickel dermatitis were found immediately and after 24 hours. Significantly higher nickel amounts were found on normal skin and in the SC of nickel-allergic participants than in controls both immediately and after 24 hours, and on irritated skin immediately after exposure. CONCLUSIONS: Nickel deposition and SC penetration is considerable after nickel skin exposure of 3 × 10 minutes. Combined with the allergic responses resulting from the same exposures reported previously, this study highlights that short skin exposure to nickel-releasing items may cause allergic nickel dermatitis.

Optimization of skin dose using in-vivo MOSFET dose measurements in bolus/non-bolus fraction ratio: A VMAT and a 3DCRT study.

In-phantom and in-vivo three dimensional conformal radiation therapy (3DCRT) and volumetric modulated arc therapy (VMAT) skin doses, measured with and without bolus in a female anthropomorphic phantom RANDO and in patients, were compared against treatment planning system calculated values. A thorough characterization of the metal oxide semiconductor field effect transistor measurement system was performed prior to the measurements in phantoms and patients. Patients with clinical indication for postoperative external radiotherapy were selected. Skin dose showed higher values with 3DCRT technique compared with VMAT. The increase in skin dose due to the use of bolus was quantified. It was observed that, in the case of VMAT, the bolus effect on the skin dose was considerable when compared with 3DCRT. From the point of view of treatment time, bolus cost, and positioning reproducibility, the use of bolus in these situations can be optimized.