Peer-based credentialing for brachytherapy: Application in permanent seed implant

PurposeThe purpose of the study was to establish a quantitative method for implant quality evaluation in permanent seed implant brachytherapy for credentialing. Delivery-based credentialing will promote consistency in brachytherapy seed delivery and improve patient outcomes.MethodsA workflow for delivery-based credentialing was outlined and applied to permanent breast seed implant brachytherapy. Delivery simulations were performed on implantable anthropomorphic breast phantoms. Two institutions experienced in permanent seed implant brachytherapy demonstrated the peer credentialing process. Each delivery was evaluated for seed placement accuracy as the measure of implant quality, both for implant accuracy and across five simulations to assess implant variation. Initial credentialing criteria are set based on two factors; the mean seed placement accuracy (implant accuracy) and the mean standard deviation (seed variation) with the threshold for each set with the addition of two standard deviations.ResultsAcross two institutions, seed placement accuracy (±standard deviation) was calculated for all five delivery simulations to yield 6.1 (±2.6) mm. To set credentialing criteria, the implant accuracy (6.1 mm) plus two standard deviations (2.0 mm) and the seed variation (2.6 mm) plus two standard deviations (0.8) mm yield a threshold of 8.1 ± 3.4 mm. It is expected that 95% of experienced institutions would perform the phantom simulation within this threshold.ConclusionBrachytherapy programs should validate delivery accuracy by formal credentialing, which is standard in external beam programs. This quantitative implant evaluation should be combined with current credentialing standards for permanent seed brachytherapy to form a comprehensive validation of institutional brachytherapy program quality.     

Dosimetric consequences of seed placement accuracy in permanent breast seed implant brachytherapy

PurposeThis study quantifies the dosimetric impact of implant accuracy and derives a quantitative relationship relating implant accuracy to target dosimetry.Methods and MaterialsA framework was developed to simulate multiple implants for error combinations. Spherical clinical target volumes (CTVs) were modeled with volumes 1.4 cm³, 9.2 cm³, and 20.6 cm³, representing the range seen clinically. Each CTV was expanded 10 mm isotropically to create a planning target volume (PTV).. Random and systematic seed placement errors were simulated by shifting needles from their planned positions. Implant errors were simulated over the range of clinically practical errors in permanent breast seed implant. The relative effect on target coverage was evaluated. Regression analysis was performed to derive relationships between CTV dosimetry and the magnitude of implant accuracy. The validity of the clinically used 10 mm PTV margin for each of the CTVs was assessed.ResultsIntroducing practical implant errors resulted in CTV V_90% median (10th and 90th percentile) of 97.7% (85.9% and 100%), 96.2% (86.8% and 99.7%), and 100% (77.8% and 100%) for the typical, large, and small CTV, respectively. All CTVs show similar trends in target coverage. Polynomials were derived relating seed placement accuracy to median (R² = 0.82) and 10th percentile (R² = 0.78) CTV V_90%._.ConclusionsThis work quantitatively describes the relationship between implant accuracy and CTV coverage. Based on simulations, the 10 mm PTV margin is adequate to maintain target coverage. These equations can be used with institutional seed placement accuracy to estimate coverage.     

Characterization and registration of 3D ultrasound for use in permanent breast seed implant brachytherapy treatment planning

PurposePermanent breast seed implant (PBSI) brachytherapy is a novel technique for early-stage breast cancer. Computed tomography (CT) images are used for treatment planning and freehand 2D ultrasound for implant guidance. The multimodality imaging approach leads to discrepancies in target identification. To address this, a prototype 3D ultrasound (3DUS) system was recently developed for PBSI. In this study, we characterize the 3DUS system performance, establish QA baselines, and develop and test a method to register 3DUS images to CT images for PBSI planning.Methods and Materials3DUS system performance was characterized by testing distance and volume measurement accuracy, and needle template alignment accuracy. 3DUS-CT registration was achieved through point-based registration using a 3D-printed model designed and constructed to provide visible landmarks on both images and tested on an in-house made gel breast phantom.ResultsThe 3DUS system mean distance measurement accuracy was within 1% in axial, lateral, and elevational directions. A volumetric error of 3% was observed. The mean needle template alignment error was 1.0° ± 0.3 ° and 1.3 ± 0.5 mm. The mean 3DUS-CT registration error was within 3 mm when imaging at the breast centre or across all breast quadrants.ConclusionsThis study provided baseline data to characterize the performance of a prototype 3DUS system for PBSI planning and developed and tested a method to obtain accurate 3DUS-CT image registration for PBSI planning. Future work will focus on system validation and characterization in a clinical context as well as the assessment of impact on treatment plans.     

Demonstration of simulated annealing optimization for permanent breast seed implant treatment planning

PurposePermanent breast seed implant (PBSI) is a developing brachytherapy technique for the treatment of early-stage breast cancer. In current practice, PBSI uses manual planning strategies to generate clinical treatment plans. In this work, a simulated annealing-based algorithm is developed to demonstrate the first application of inverse optimization for PBSI.Methods and MaterialsTarget, skin, and chest wall muscle contours, exported from a treatment planning system in digital imaging and communications in medicine format, are used as inputs. To optimize, the user defines the dose–volume histogram objectives for the target and specifies a relative weighting for target and skin constraints. A 10-patient cohort of previously treated patients was planned by using the inverse optimization algorithm. Plan quality was compared to the clinically treated manually generated plans using the V_90%, V_100%, V_150%, and V_200% for the planning target volume (PTV), V_90% and D_0.2 cc for skin dose, and PTV conformity indices.ResultsFor each of the 10 patients, patient-wise paired differences between inverse and manual plans were analyzed and presented in box plots. Comparing inverse and manual planning techniques, a statistical difference was not observed (p > 0.05) in PTV coverage criteria (V_90%, V_100%) and dose to skin_2mm. A statistical difference was observed in the inverse plans as a reduction of the V_150% (mean of 6.2%) and increase in conformity index of the 20%, 50%, 90%, and 100% isodose lines.ConclusionsThis work presents the first application of inverse optimization used to generate PBSI treatment plans. A 10-patient cohort previously treated with PBSI was retrospectively planned for comparison with the clinically treated manually generated plans.     

Treatment planning considerations for permanent breast seed implant

PurposeTo determine an optimal planning strategy for permanent breast seed implant that minimizes dose heterogeneity without degrading coverage and conformity.Methods and MaterialsA simple model was developed to investigate planning strategies incorporating a range of ¹⁰³Pd seed activities, needle and seed spacings, and implants in which seed positions are either restricted to or permitted outside of spherical planning target volumes (PTVs). To address more realistic target geometries, model parameters were used to retrospectively replan a 10-patient cohort in MIM Symphony.ResultsWe confirm that the current clinical modified uniform implantation pattern provides the most favorable dose distributions, given the resolution of the template grid and spacer length. We show that needle and seed counts for replans with seed placement permitted 0.3 cm outside of the PTV are most comparable to clinical preplans, but offer a 13 ± 11% average reduction in the V_PTV150%. Replans produced with seed placement 0.5 cm outside of the PTV provide the largest improvement in dose homogeneity, at the cost of a slight increase in irradiated volume and an increase in the number of needles and seeds.ConclusionsImplanting seeds beyond the PTV within a 0.3–0.5 cm margin, and optimizing seed activity on a per patient basis, allows for improvement in dose homogeneity. However, these plans require higher needle and seed counts and result in a small increase in irradiated volume. Before planning recommendations can be made, the implications of these changes must be investigated in the context of clinical outcome for permanent breast seed implant.     

Appropriate timing for postimplant imaging in permanent breast seed implant: Results from a serial CT study

PurposePostimplant analysis in permanent breast seed implant (PBSI) is performed at inconsistent times subsequent to seed implantation across cancer centers, creating challenges in the interpretation of dosimetric data and ultimately the correlation with clinical outcomes. The purpose of this study is to determine the most appropriate time postimplant to perform this analysis.Methods and MaterialsNine patients treated at our institution with PBSI were included in this analysis. Each underwent 4 postimplant CT scans: 0, 15, 30, and 60 days postimplant. A model of the accumulated dose was created by deformably registering the Day 15, 30, and 60 postimplant CT scans and dose matrices to the Day 0 scan, scaling for seed decay. The results from this model were compared to each individual postplan by integral comparison of dose–volume histogram curves for a dose evaluation volume.ResultsThe Day 30 postplan showed the best agreement with the accumulated dose model and the smallest interpatient variability across the patient cohort. The mean (±SD) for the dose evaluation volume V₉₀, V₁₀₀, V₁₅₀, and V₂₀₀ for the accumulated dose model was 90 ± 7%, 86 ± 8%, 66 ± 14%, and 41 ± 16%, respectively.ConclusionsBased on the results of this patient cohort, we recommend that postimplant dosimetric analysis for PBSI be performed approximately 30 days following the implant.     

Assessment of a theoretical formalism for dose estimation in CT: an anthropomorphic phantom study

Dose assessment in computed tomography (CT) is challenging due to the vast variety of CT scanners and imaging protocols in use. In the present study, the accurateness of a theoretical formalism implemented in the PC program CT-EXPO for dose calculation was evaluated by means of phantom measurements. Phantom measurements were performed with four 1-slice, four 4-slice and two 16-slice spiral CT scanners. Firstly, scanner-specific _nCTDI_w values were measured and compared with the corresponding standard values used for dose calculation. Secondly, effective doses were determined for three CT scans (head, chest and pelvis) performed at each of the ten installations from readings of thermoluminescent dosimeters distributed inside an anthropomorphic Alderson phantom and compared with the corresponding dose values computed with CT-EXPO. Differences between standard and individually measured _nCTDI_w values were less than 16%. Statistical analysis yielded a highly significant correlation (P<0.001) between calculated and measured effective doses. The systematic and random uncertainty of the dose values calculated using standard _nCTDI_w values was about –9 and ±11%, respectively. The phantom measurements and model calculations were carried out for a variety of CT scanners and representative scan protocols validate the reliability of the dosimetric formalism considered—at least for patients with a standard body size and a tube voltage of 120 kV selected for the majority of CT scans performed in our study.     

A reliable skin toxicity predictor in permanent breast seed implant brachytherapy

PurposeTo establish skin dose–outcome relationships using a reliable metric in permanent breast seed implant (PBSI).MethodsSixty-seven consecutive patients who underwent PBSI at our institution were included. Skin doses were calculated using two skin dose indices: maximum point dose to the skin surface, D_max, and D_0.2cc for a 2-mm internal skin rind (a surrogate to the dose to 1 cm² area of skin) from CT-based postoperative treatment plans. Toxicity data were extracted from patients’ charts and photographs. The associations between skin dose and skin toxicity were investigated using the analysis of variance, and the predictive performance of skin dose measures was evaluated using receiver operating characteristic curves.ResultsFor acute reactions, 49.3% of patients had Grade 1, 4.5% Grade 2, and 1.5% Grade 3 toxicity. For telangiectasia at 3 years, very minor and minimally apparent telangiectasia was observed in 25% of patients. Moderate but asymptomatic telangiectasia was observed in 9.1% of cases. Both metrics were significantly associated with the occurrence of acute toxicity and telangiectasia at 3 years (p < 0.01). The predictive values for D_max and D_0.2cc were 0.779 and 0.763, respectively, (p < 0.0001) for acute skin toxicity and 0.786 and 0.810 for telangiectasia (p < 0.0002). Extreme dose outliers (up to 878 Gy) and a high variability were observed for D_max but not for D_0.2cc, illustrating the superior reliability of D_0.2cc.ConclusionD_0.2cc, as an alternate skin dose measure to D_max, is a robust metric for measuring skin dose that is simple to calculate, yet is clinically relevant and not prone to inaccuracies inherent to point dose measurement.     

Determination of age specific 131I S-factor values for thyroid using anthropomorphic phantom in geant4 simulations

Using anthropomorphic phantom in Geant4, determination of β- and γ-absorbed fractions and energy absorbed per event due to ¹³¹I activity in thyroid of individuals of various age groups and geometrical models, have been carried out. In the case of ¹³¹I β-particles, the values of the absorbed fraction increased from 0.88 to 0.97 with fetus age. The maximum difference in absorbed energy per decay for soft tissue and water is 7.2% for γ-rays and 0.4% for β-particles. The new mathematical MIRD embedded in Geant4 (MEG) and two-lobe ellipsoidal models developed in this work have 4.3% and 2.9% lower value of S-factor as compared with the ORNL data.     

CT引导下125I籽源植入近距离放射治疗多发性椎体转移癌

目的探讨~(125)I籽源植入近距离放射治疗多发性椎体转移患者的价值。方法15例癌症多发椎体转移患者(共43个椎体)进行了CT引导下~(125)I籽源植入近距离放射治疗。肺癌术后椎体转移7例,乳腺癌术后椎体转移4例,肝癌术后椎体转移2例,前列腺癌术后椎体转移1例,左肾癌术后椎体转移1例。共43个椎体转移,每例椎体转移数为2～5个。在CT引导下按共轴针法投放籽源,视病变情况采取椎弓根入路、侧方入路、前入路等3种方式将~(125)I籽源植入椎体病变区,籽源呈倒V形、X形或平行分布,籽源距椎体后缘3～10mm。~(125)I籽源总活度由公式(长 宽 高)(cm)/3×5mCi计算或"放射性粒子源植入治疗计划系统"计算获得,单椎体植入剂量8～22mCi。椎旁软组织病变内同时植入~(125)I籽源。结果术后随访3～30个月,平均12.3个月,15例患者术后均未出现脊髓、神经损伤等并发症,未出现放射相关不良反应。11个没有疼痛的部位未出现新的疼痛,18/32部位症状体征消失,14/32部位部分消失。最短术后第3天觉得症状已有缓解。影像表现,10例患者29个椎体影像回访,治疗3个月以后7例17个椎体CT可见病灶稳定,边缘形成硬化环。4个椎体病变进展,见硬化环不完整,破坏区有扩大。3例8个椎体MRI显示骨水肿明显减轻,病变区T_2WI信号减低。结论~(125)I籽源植入近距离放射治疗多发性椎体转移癌具有疗效高,创伤小,并发症发生率低等优点,是一种较好的微创治疗方法,不仅适合于未经治疗的患者,也适合于放射治疗后复发的患者,具有较高的耐受性和安全性。     

Dosimetric investigation of 103Pd permanent breast seed implant brachytherapy based on Monte Carlo calculations

PurposePermanent breast seed implant using ¹⁰³Pd is emerging as an effective adjuvant radiation technique for early stage breast cancer. However, clinical dose evaluations follow the water-based TG-43 approach with its considerable approximations. Toward clinical adoption of advanced TG-186 model-based dose evaluations, this study presents a comprehensive investigation for permanent breast seed implant considering both target and normal tissue doses.Methods and MaterialsDose calculations are performed with the free open-source Monte Carlo (MC) code, egs_brachy, using two types of virtual patient models: TG43sim (simulated TG-43 conditions) and MCref (heterogeneous tissue modeling from patient CT, seeds at implant angle) for 35 patients. The sensitivity of dose metrics to seed orientation and tissue segmentation are assessed.ResultsIn the target volume, D₉₀ is 14.1 ± 5.8% lower with MCref than with TG43sim, on average. Conversely, normal tissue doses are generally higher with MCref than with TG43sim, for example, by 22 ± 13% for skin D_1cm2, 82 ± 7% for ribs D_max, and 71 ± 23% for heart D_1cm3. Discrepancies between MCref and TG43sim doses vary over the patient cohort, as well as with the tissue and metric considered. Skin doses are particularly sensitive to seed orientation, with average difference of 4% (maximum 28%) in D_1cm2 for seeds modeled vertically (egs_brachy default) compared with those aligned with implant angle.ConclusionsTG-43 dose evaluations generally underestimate doses to critical normal organs/tissues while overestimating target doses. There is considerable variation in MCref and TG43sim on a patient-by-patient basis, motivating clinical adoption of patient-specific MC dose calculations. The MCref framework presented herein provides a consistent modeling approach for clinical implementation of advanced TG-186 dose calculations.     

An anthropomorphic pelvis phantom for optimization of the diagnosis of lymph node metastases in the pelvis

Objective  An anthropomorphic pelvis phantom was made by the modification of a National Electrical Manufacturers Association (NEMA) phantom, currently the most popular one, and its clinical usefulness was evaluated. Methods  The NEMA plus bone phantom was made by placing the pelvic bone model in the NEMA phantom. The NEMA plus bladder phantom was made by placing an imitation of the urinary bladder in the NEMA phantom. The pelvis phantom was also made by placing both the pelvic bone model and the bladder in the NEMA phantom. Four kinds of phantoms were imaged by both 2D and 3D dynamic modes, and for each phantom, prompt coincidence count rates, random ones, true plus scatter ones, and single photon rates were measured and these coincidence count rates were compared with those from the actual clinical data. After image reconstruction, the contrast ratio and image noise were also investigated. Results  For the random coincidence count rate, the data obtained from each phantom showed good correspondence to the clinical data. The prompt coincidence count rates and true plus scatter ones of the clinical data were different from those obtained from NEMA phantom, NEMA plus bone one and NEMA plus bladder one, whereas there was a good correspondence between the data of the pelvis phantom and the clinical data. For the contrast ratio and image noise, there were discrepancies between the data of NEMA phantom and pelvis phantoms. Conclusions  We made an anthropomorphic pelvis phantom by the simple modification of a NEMA phantom. This phantom showed performance similar to that of the actual human pelvis, suggesting clinical usefulness in the evaluation of new acquisition protocols and reconstruction algorithms.     

胸部能谱成像模式与常规CT扫描的辐射剂量及图像质量的仿真体模研究

目的 通过仿真胸部体模研究胸部能谱CT不同方案成像模式与常规胸部CT扫描的辐射剂量、图像质量、对比噪声比及主观评分对比,获得最佳能谱扫描参数。方法 对仿真胸部体模分别进行常规胸部CT扫描以及3种不同扫描方式的能谱CT成像。3种能谱模式为宝石能谱CT （GSI）Assist模式（方案A）、管电流平均值时的GSI模式（方案B）及管电流最大值时的GSI模式（方案C）。所有扫描方式分别在噪声指数（NI）=9和11时,螺距0.984∶1,依次扫描。记录辐射剂量,同时测量感兴趣区（ROIs）5个不同层面水平的脂肪和肌肉组织的图像噪声值（SD）以评价图像质量。所有扫描序列由两位资深放射医师对肺窗肺纹理及分支5分制主观评分。结果 NI=9和11时,常规CT平扫与方案A、B、C的有效剂量（E）值分别为（8.0、8.5、6.2、10.4）和（5.3、5.1、4.3、6.2）mSv。NI=9时,常规胸部CT平扫与方案A、C的SD值差异有统计学意义（F=4.496,P<0.05）;NI=11时,方案A、B、C与常规胸部CT平扫SD值差异有统计学意义（F=8.425,P<0.05）;常规胸部CT扫描中,NI分别为9和11时SD值差异有统计学意义（t=－2.570,P<0.05）;在相同能谱扫描模式中,NI不同,SD值差异均无统计学意义（P>0.05）。NI相同扫描模式不同及扫描模式相同NI不同时,CNR及主观评分差异均无统计学意义（P>0.05）。结论 合理的能谱扫描模式与常规扫描的辐射剂量没有明显差异,但能谱扫描模式可以获得较高的图像质量。此外,选择合适的噪声指数在图像质量相仿的同时可以明显降低辐射剂量。综合辐射剂量及图像质量,能谱CT智能模式可以达到辐射剂量及图像质量的双向平衡。     

Comparison of accuracy and time-efficiency of CT colonography between conventional and panoramic 3D interpretation methods: An anthropomorphic phantom study

Purpose

To retrospectively compare the conventional three-dimensional (3D) interpretation method with the panoramic 3D method with regard to accuracy and time-efficiency in the detection of colonic polyps, using pig colonic phantoms as the standard of reference.

Materials and methods

One-hundred and sixty-two polyps were created in 18 pig colonic phantoms. CT colonography was performed with a 64-row detector CT scanner. Two-week interval reviews for the CTC image dataset with both the conventional and the panoramic 3D interpretation method were independently performed by three radiologists. The sensitivities of both methods were compared with the McNemar test. The mean interpretation time for each interpretation method was also assessed and compared with the Wilcoxon signed-rank test.

Results

Compared with the conventional 3D method (0.96 for reader 1, 0.89 for reader 2, and 0.97 for reader 3), the panoramic method revealed comparable sensitivities (0.91 for reader 1, 0.86 for reader 2, and 0.93 for reader 3) (p > 0.05). Interpretation time was significantly shorter with the panoramic method (115.1 ± 32.7 s for reader 1, 229.7 ± 72.2 s for reader 2, and 282.6 ± 113.7 s for reader 3) than with the conventional method (218.9 ± 59.9 s for reader 1, 379.4 ± 117.0 s for reader 2, and 458.7 ± 149.4 s for reader 3) for all readers (p < 0.05).

Conclusion

Compared with the conventional 3D interpretation method, the panoramic 3D interpretation method shows improved time-efficiency and comparable sensitivity in the detection of colonic polyps.     

Dosimetric and radiobiological investigation of permanent implant prostate brachytherapy based on Monte Carlo calculations

PurposePermanent implant prostate brachytherapy plays an important role in prostate cancer treatment, but dose evaluations typically follow the water-based TG-43 formalism, ignoring patient anatomy and interseed attenuation. The purpose of this study is to investigate advanced TG-186 model-based dose calculations via retrospective dosimetric and radiobiological analysis for a new patient cohort.Methods and MaterialsA cohort of 155 patients treated with permanent implant prostate brachytherapy from The Ottawa Hospital Cancer Centre is considered. Monte Carlo (MC) dose calculations are performed using tissue-based virtual patient models. Dose–volume histogram (DVH) metrics (target, organs at risk) are extracted from 3D dose distributions and compared with those from calculations under TG-43 assumptions (TG43). Equivalent uniform biologically effective dose and tumor control probability are calculated.ResultsFor the target, D₉₀ (V₁₀₀) is 136.7 ± 20.6 Gy (85.8% ± 7.8%) for TG43 and 132.8 ± 20.1 Gy (84.1% ± 8.2%) for MC; D₉₀ is 3.0% ± 1.1% lower for MC than TG43. For organs at risk, MC D_1cc = 104.4 ± 27.4 Gy (TG43: 106.3 ± 28.3 Gy) for rectum and 80.8 ± 29.7 Gy (TG43: 78.4 ± 28.4 Gy) for bladder; D_1cc = 185.9 ± 30.2 Gy (TG43: 191.1 ± 32.0 Gy) for urethra. Equivalent uniform biologically effective dose and tumor control probability are generally lower when evaluated using MC doses. The largest dosimetric and radiobiological discrepancies between TG43 and MC are for patients with intraprostatic calcifications, for whom there are low doses (cold spots) in the vicinity of calcifications within the target, identified with MC but not TG43.ConclusionsDVH metrics and radiobiological indices evaluated with TG43 are systematically inaccurate by upward of several percent compared with MC patient-specific models. Mean cohort DVH metrics and their MC:TG43 variances are sensitive to patient cohort and clinical practice, underlining the importance of further retrospective MC studies toward widespread clinical adoption of advanced model-based dose calculations.     

Time course of prostatic edema post permanent seed implant determined by magnetic resonance imaging

PurposeTo quantify the time course of postimplant prostatic edema magnitude and spatial isotropy using serial magnetic resonance imaging (MRI).Methods and MaterialsForty patients with histologic diagnosis of prostate cancer received an iodine-125 seed implant (Day 0) and consented to 1.5-T MRI on Days ?1, 0, 14, and 28. Seeds of strength 0.39 mCi were placed in a modified peripheral loading pattern to deliver 145 Gy to the target volume. MR images consisted of 3–4 mm thick axial slices with no gap. The image sets were anonymized and randomized to minimize contouring bias, then contoured by a single radiation oncologist. Contours were reoriented about their center of mass to align the prostate long axis with the superior–inferior (S?I) direction; prostate volumes and dimensions in the left–right (L?R), anterior–posterior (A?P), and S?I directions through the center of mass were calculated.ResultsThe average relative edema volume was 1.18 ± 0.14 (1 standard deviation) on Day 0 and 1.01 ± 0.15 on Day 30. Between Days 0 and 30, the edema resolved linearly with time on average. Average relative edema dimensions on Day 0 in the L?R, A?P, and S?I directions were 1.01 ± 0.07, 1.11 ± 0.09, and 1.08 ± 0.13, respectively.ConclusionsAs measured using MRI, the average edema magnitude for our study population was ～20% on Day 0 and resolved linearly with time to ～0% on Day 30. The edema exhibited spatial anisotropy, the prostate expanding on Day 0 by ～10% in each of the A?P and S?I directions and by ～0% in the L?R direction.     

Monte Carlo study of the relationship between skin dose and optically stimulated luminescence dosimeter dose in Pd-103 permanent breast seed implant brachytherapy

PurposeTo establish a method for estimating skin dose for patients with permanent breast seed implant based on in vivo optically stimulated luminescence dosimeters (OSLDs) measurements.Methods and MaterialsMonte Carlo simulations were performed in a simple breast phantom using the EGSnrc user code egs_brachy. Realistic models of the IsoAid Advantage Pd-103 brachytherapy source and Landauer nanoDot OSLD were created to model in vivo skin dose measurements where an OSLD would be placed on the skin of a patient with permanent breast seed implant following implantation. Doses to a 0.2 cm³ volume of skin beneath the OSLD and to the sensitive volume within the OSLD were calculated, and the ratio of these values was found for various seed positions inside the breast phantom. The maximum value of this ratio may be used as a conversion factor that would allow skin dose to be estimated from in vivo OSLD measurements.ResultsConversion factors of 0.5 and 1.44 are recommended for OSLDs calibrated to dose to Al₂O₃ and water, respectively, at the point of measurement in the OSLD. These factors were not significantly affected by the addition of extra seeds in the dose calculations.ConclusionsA method for estimating skin dose from OSLD measurements was proposed. Individual institutions should calibrate OSLDs to Pd-103 seeds to apply the results of this work clinically.     

Establishing a simulation-based education program for radiation oncology learners in permanent seed implant brachytherapy: Building validation evidence

PurposeThe purpose of this study was to establish a simulation-based education program for radiation oncology learners in permanent seed implant brachytherapy. The first step in formalizing any education program is a validation process that builds evidence-based verification that the learning environment is appropriate.Methods and MaterialsThe primary education task allowed practitioners to use an anthropomorphic breast phantom to simulate a permanent seed implant brachytherapy delivery. Validation evidence is built by generating data to assess learner and expert cohorts according to their proficiency. Each practitioner's performance during the simulation was evaluated by seed placement accuracy, procedural time-to-complete, and two qualitative evaluation tools—a global rating scale and procedural checklist.ResultsThe average seed placement accuracy (±SD) was 8.1 ± 3.5 mm compared to 6.1 ± 2.6 mm for the learner and expert cohort, respectively. The median (range) procedural time-to-complete was 64 (60–77) minutes and 43 (41–50) minutes for the learner and expert cohort, respectively. Seed placement accuracy (student t-test, p < 0.05) and procedural time-to-complete (Mann–Whitney U-test, p < 0.05) were statistically different between the cohorts. In both the global rating scale and procedural checklist, the expert cohort demonstrated improved proficiency compared to the learner cohort.ConclusionsThis validation evidence supports the utilization of this simulation environment toward appropriately capturing the delivery experience of practitioners. The results demonstrate that, in all areas of evaluation, expert cohort proficiency was superior to learner cohort proficiency. This methodology will be used to establish a simulation-based education program for radiation oncology learners in permanent seed implant brachytherapy.     

Radiological response of ceramic and polymeric devices for breast brachytherapy

In the present study, the radiological visibility of ceramic and polymeric devices implanted in breast phantom was investigated for future applications in brachytherapy. The main goal was to determine the radiological viability of ceramic and polymeric devices in vitro by performing simple radiological diagnostic methods such as conventional X-ray analysis and mammography due to its easy access to the population. The radiological response of ceramic and polymeric devices implanted in breast phantom was determined using conventional X-ray, mammography and CT analysis.