Tangential Technique Research Articles

EP-1975: Comparison of Field in Field and Tangential Wedged Beams techniques in radiotherapy of breast cancer

EP-1975: Comparison of Field in Field and Tangential Wedged Beams techniques in radiotherapy of breast cancer

Evaluation of dose distributions in PTV and organs at risk in left-sided breast cancer, treated by tangential wedged technique in Tohid radiotherapy center in Sanandaj

Evaluation of dose distributions in PTV and organs at risk in left-sided breast cancer, treated by tangential wedged technique in Tohid radiotherapy center in Sanandaj

Deep Inspiration Breath Hold Techniques in the Radiotherapeutic Management of Left-Sided Breast Cancer-Active Breathing Coordinator vs. Voluntary Breath Hold

Purpose: Deep Inspiration Breath Hold (DIBH) is a well-established method in reducing their radiation of the heart and lung when treating Left sided Breast cancer with EBRT. There is, however, limited literature comparing different methods of DIBH. The purpose of our study is to compare the efficacy of Active Breathing Co-ordinator (ABC) against Voluntary Breath Hold (VBH). Methods and Materials: 20 patients were selected whom had left sided Breast cancer and underwent EBRT. 10 patients underwent Active Breathing Coordinator (ABC) using specialized Elekta equipment and 10 performed Voluntary Breath Hold (VBH) following the JOVE protocol. All 20 patients had two CT simulation scans: one in FB and the other in DIBH. Treatment plans were generated using a tangential radiation therapy technique. A dosimetric comparison was made between the two plans as per EviQ guidelines. Measurements were collected for Lung V20 (%), Ipsilateral Lung Maximum Depth (cm), Heart V25 (%), Heart (Gy), and Contralateral Breast V3 (%). 9 patients had LAD mean values measured. Results: When using the Mann-Whitney U test to compare ABC to VBH: the VBH technique yielded a median Heart (Gy) of 1.75 (IQR=1.15) and median Contralateral Breast V3 of 0.31% (IQR=0.89%). The ABC technique yielded a median Heart (Gy) of 1.44 (IQR=.60) and for the Contralateral Breast V3 a median of 0.00% (IQR=0.00%). The ABC technique was statistically superior with U=15.000 p =.008 (Heart (Gy)) and U=24.500 p=.035 (Contralateral Breast V3) respectively. None of the other parameters had statistically significant median differences. When using the Wilcoxon signed-rank test to compare DIBH to FB: The VBH technique yielded a median Ipsilateral Lung max (cm) of 2.3, Ipsilateral Lung V20 of 13.92%, Lung V20 of 6.45%, Heart V25 of 2.41%, Heart (Gy) of 2.7, and LAD mean (Gy) of 23.4. The DIBH technique was statistically superior in these parameters and yielded a median Ipsilateral Lung max (cm) of 2.6 (Z=-3.072 p=.002), Ipsilateral Lung V20 of 12.33% (Z=-2.576 p=.01), Lung V20 of 5.84% (Z=-2.296 p=.01), Heart V25 of 0.26% (Z=- 3.921 p<.001), Heart (Gy) of 1.43 (Z=-3.921 p<.001), and LAD mean (Gy) of 7.7 (Z=-2.201 p=.028). Conclusion: ABC is a superior breath hold technique when compared to VBH and will yield lesser long-term cardiac complications. However, it is a more expensive modality and can be poorly tolerated by patients. Surrounding structures incur significantly less radiation when using DIBH than FB which is consistent with previous studies in the literature. Further studies are required to confirm this data.

WALL THICKNESS MEASUREMENT OF CARBON STEEL PIPES BY USING DIGITAL RADIOGRAPHY

One of the major field NDT areas is pipe inspection, which involves testing for corrosion and erosion as well as examining the quality of welds in pipes. In order to perform of the wall thickness measurements that include pitting, we can use one of the two following techniques: Tangential Technique and Double Wall Technique. In this study, carbon steel pipes which have 2, 3, and 4 inch diameter were irradiated from 1m by Gamma-Ray, besides, their histogram were analyzed via Tangential Technique for different periods. Furthermore, the results were compared by gathered results which measured by Ultrasonic Test.

Conformity Index and Homogeneity Index of the Postoperative Whole Breast Radiotherapy.

BACKGROUND:The treatment of breast cancer involves a multidisciplinary approach in which radiotherapy plays a key role.AIM:The conformity index and the homogeneity index are two analysis tools of a treatment plan using conformal radiotherapy. The purpose of this article is an analysis of these two parameters in the assessment of the treatment plans in 58 patients undergoing postoperative radiotherapy of the whole breast.MATERIALS AND METHODS:All 58 patients participating in the study had a conservatively treated early-stage breast cancer. The treatment was performed using a standard regimen of fractionation in 25 fractions up to a total dose of 50 Gy. Dose-volume histograms were generated for both plans with and without segmental fields.RESULTS:Pair samples t-test was used. The technique with segmental fields allowed us more homogeneity distribution when compared to standard two tangential field techniques. The HI values were 1.08 ± 0.01 and 1.09 ± 0.01 for segment and technique with two tangential fields (p < 0.001). The DHI values were 0.92 ± 0.02 and 0.901 ± 0.01 for segment and technique with two tangential fields (p < 0.001). The CI values were 1.38 ± 0.02 and 1.43 ± 0.3 for segment and technique with two tangential fields (p = 0.0018).CONCLUSION:The results showed that the conformity and the homogeneity index are important tools in the analysis of the treatment plans during radiation therapy in patients with early-stage breast cancer. Adding segment fields in the administration of radiotherapy in patients with conservatively treated breast cancer can lead to improved dosage homogeneity and conformity.

A New Approach for Incorporating Hoek–Brown Failure Criterion in Kinematic Approach — Case of a Rock Slope

This paper develops a novel approach to incorporate the generalized Hoek–Brown criterion in the kinematic approach. Two analytical expressions for the equivalent friction angle and the equivalent cohesion in the context of the Hoek–Brown criterion are derived as a function of the minimum principal stress. As an illustrative example, the stability of a rock slope is investigated. The spatial discretization technique is employed to generate a slope failure mechanism considering the spatial variation of the equivalent friction angle corresponding to the minimum principal stress. In order to simplify this problem, the minimum principal stress is taken as an additional parameter in the optimization process of the kinematical approach. For the numerical modeling, three kinds of stress distributions are considered in the optimization process. The proposed approach is validated by comparison with available numerical results with good agreement. It is also shown that with the uniform distribution of minimum principal stress, the proposed approach gives the same solutions as those by the classical tangential line technique, and with more complicated distributions, the proposed approach yields a better solution than the classical tangential line technique, especially for large values of geological strength index (GSI).

Nonlinear shear behavior of rock joints using a linearized implementation of the Barton–Bandis model

Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing, inducing dilation and resulting in nonlinear joint shear strength and shear stress vs. shear displacement behaviors. The Barton–Bandis (BB) joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints. The BB model accounts for asperity roughness and strength through the joint roughness coefficient (JRC) and joint wall compressive strength (JCS) parameters. Nevertheless, many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr–Coulomb (M−C) model, which is only appropriate for smooth and non-dilatant joints. This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior. To bridge the BB and the M−C models, this paper aims to provide a linearized implementation of the BB model using a tangential technique to obtain the equivalent M−C parameters that can satisfy the nonlinear shear behavior of rock joints. These equivalent parameters, namely the equivalent peak cohesion, friction angle, and dilation angle, are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing. The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre- and post-peak regions of shear displacement, respectively. Likewise, the pre- and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established. Verifications of the linearized implementation of the BB model show that the shear stress-shear displacement curves, the dilation behavior, and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.

Industrial Purification Strategies for Monoclonal Antibodies

The global monoclonal antibody market in 2016 was around USD 85.4 billion and is expected to reach USD 140 billion by end of 2024 i.e., approximately 1.5 fold increase in market rate within 10 years. The therapeutics purification process monoclonal antibody through chromatography technique is expected to grow by 5% from 2011 to 2017, with a prediction of reaching to USD 9 billion by end of 2017. The global market interest is shifting from monoclonal antibody to fragmented antibody; nearly 60 fragmented antibodies have gone into clinical trials as of 2010. In this review, recovery of monoclonal antibody by centrifugation, depth filtration followed by purification by chromatography techniques i.e., capture step by affinity chromatography, intermediate step by anionic chromatography in flow through mode and polishing step by cationic chromatography is reviewed. The production of antigen binding fragment is carried out by enzymatic method followed by affinity chromatography, multimode chromatography and cationic chromatography. Monoclonal antibodies have been developed by these methods are used for targeting range of diseases. Many of such monoclonal antibodies have been approved and many such is still in development pipeline. This review gives an overview on the structure of antibody, production of monoclonal antibody and the downstream purification of monoclonal antibody. The downstream purification covers the basic techniques followed for most of the mAb purification done commercially. The downstream purification steps discussed here include centrifugation, tangential flow filtration, depth filtration and chromatographic techniques.

Effect of Different Composite Restorations on the Cuspal Deflection of Premolars Restored with Different Insertion Techniques- An In vitro Study

This study was conducted to assess the effect of different composite materials on the cuspal deflection of premolars restored with bulk placement of resin composite in comparison to horizontal incremental placement and modified tangential incremental placement. The aim of this study was to evaluate the cuspal deflection caused by different composite materials when different insertion techniques were used. Two different composite materials were used that is Tetric N Ceram (Ivoclar Vivadent marketing, India) and SonicFillTM (Kerr Sybron Dental). Forty standardized Mesio-Occluso-Distal (MOD) preparations were prepared on maxillary first premolars. Each group was divided according to composite insertion technique (n=10), as follows: Group I - bulk insertion using Tetric N Ceram, Group II - Horizontal incremental insertion technique using Tetric N Ceram, Group III- Modified tangential incremental technique using Tetric N Ceram, and Group IV- bulk insertion using SonicFillTM. Preparations were acid-etched, and bonded with adhesive resin to provide micro mechanical attachment before restoration using a uniform etching and bonding protocol in all the groups. All groups received the same total photo-polymerization time. Cuspal deflection was measured during the restorative procedure using customized digital micrometer assembly. One-way ANOVA test was applied for the analysis of significant difference between the groups, p-value less than 0.05 was considered statistically significant. The average cuspal deflections for the different groups were as follows: Group I 0.045±0.018, Group II 0.029±0.009, Group III 0.018±0.005 and Group IV 0.017±0.004. The intergroup comparison revealed statistically significant difference. A measurable amount of cuspal deflection was present in all the four studied groups. In general, bulkfill restoration technique with conventional composite showed significantly highest cusp deflection. There were no significant differences in cuspal deflection among sonicFillTM and modified tangential incremental insertion techniques.

Effects of nonlinear strength parameters on stability of 3D soil slopes

Actual slope stability problems have three-dimensional (3D) characteristics and the soils of slopes have curved failure envelopes. This incorporates a power-law nonlinear failure criterion into the kinematic approach of limit analysis to conduct the evaluation of the stability of 3D slopes. A tangential technique is adopted to simplify the nonlinear failure criterion in the form of equivalent Mohr-Coulomb strength parameters. A class of 3D admissible rotational failure mechanisms is selected for soil slopes including three types of failure mechanisms: face failure, base failure, and toe failure. The upper-bound solutions and corresponding critical slip surfaces can be obtained by an efficient optimization method. The results indicate that the nonlinear parameters have significant influences on the assessment of slope stability, especially on the type of failure mechanism. The effects of nonlinear parameters appear to be pronounced for gentle slopes constrained to a narrow width. Compared with the solutions derived from plane-strain analysis, the 3D solutions are more sensitive to the values of nonlinear parameters.

Dosimetric evaluation of volumetric modulated arc therapy for bilateral breast carcinoma

Introduction Patients with bilateral breast carcinoma are usually treated with two sets of tangential beams with different iso-centers. Single iso-center Volumetric Arc Therapy (VMAT) treatment plan can give several logistical advantages, avoiding also the overlapping of tangential fields. Purpose Perform a dosimetric study to evaluate the enforcement of Volumetric Modulated Arc Therapy (VMAT) on bilateral breast carcinoma radiotherapy. Materials and methods Treatment plans for 5 patients, previously treated with 50.4 Gy/28 fractions, using 3D Conformal Radiotherapy planned with a standard tangential field technique, were replanned with VMAT technique. The PTV used in the optimization was expanded 2 cm to the external direction, in order to correct respiratory movement. VMAT plans were optimized with 2-arcs, 3-arcs and 4-arcs, all plans using one iso-center, avoiding angles between 140° and 220°. Results VMAT presents evident logistical advantages for bilateral breast treatment; one iso-center reduces patient setup time, and treatment time. 4-arcs plan and 3-arcs plan had similar dosimetric results, being 2-arcs plan the worst solution. Comparing to the standard tangential field technique, VMAT had better PTV dose coverage (Conformity Index improved in a 13%), avoiding hotspots, which can appear on 3DCRT standard tangential field technique. VMAT also reduces high doses to OARs. On the other hand, VMAT increase lower doses to the whole body, increasing slightly the mean heart dose. Conclusion VMAT technique showed logistical advantages for the treatment of bilateral breast carcinoma, but also dosimetric improvements. 3DCRT had greater high doses to OARs, but save lower doses to the whole body.

Evaluation and optimization of cardiac and left anterior descending artery DVHs in radiotherapy of left breast cancer patients

Introduction The potential heart damage in left-sided breast cancer radiotherapy is well known; nevertheless the biological mechanisms are only partially understood. Radiotherapy guidelines impose dose-volume constrains for the whole heart but newer data propose that excessive dose to the Left Anterior Descending artery (LAD) endothelium may cause cardiac toxicity. Purpose To evaluate the dose-volume data for the whole heart and LAD and performed dose distribution optimization based on a LAD dose constrain. Materials and methods 11 left-sided breast cancer patients were retrospectively selected for this study. All patients underwent 3D-CRT with 2-field tangential irradiation technique. The dose prescription was 50–60 Gy in 2 Gy/fraction. LAD was delineated for all patients and DVHs were calculated and compared. Every plan was acceptable regarding the V25 Results The measured D mean was 2.9 Gy to the heart and 24.8 Gy to the LAD. Volumes below 1.5% of the heart received dose ⩾50 Gy in 6 patients (55%). LAD D mean in 6 cases (55%) was > 20 Gy. Plan optimization based on LAD dose reduction was possible for 5 cases where D max reduced 13.6-38.3% and D mean reduced 35.1–52%. Conclusion In left-sided breast cancer 3D-CRT, even when the DVH constrain is met for the whole heart; the LAD receives significant higher doses. In the case that LAD dose is responsible for cardiac toxicity, new dose constrain should be added for plan optimization.

SU-G-TeP1-11: Predictors of Cardiac and Lung Dose Sparing in DIBH for Left Breast Treatment

Purpose: This retrospective study of left sided whole breast radiation therapy (RT) patients investigates possible predictive parameters correlating to cardiac and left lung dose sparing by deep inspiration breath-hold (DIBH) technique compared to free-breathing (FB). Methods: Thirty-one patients having both DIBH and FB CT scans were included in the study. All patients were planned with a standard step-and-shoot tangential technique using MV photons, with prescription of 50Gy or 50.4Gy. The displacement of the breath hold sternal mark during DIBH, the cardiac contact distances of the axial (CCDax) and parasagittal (CCDps) planes, and lateral-heart-to-chest (LHC) distance on FB CT scans were measured. Lung volumes, mean dose and dose-volume histograms (V5, V10 and V20) were analyzed and compared for heart and left lung for both FB and DIBH techniques. Correlation analysis was performed to identify the predictors for heart and left lung dose sparing. Two-tailed Student's t-test and linear regression were used for data analysis with significance level of P≤0.05. Results: All dosimetric metrics for the heart and left lung were significantly reduced (P<0.01) with DIBH. Breath hold sternal mark displacement ranged from 0.4–1.8 cm and correlated with mean (P=0.05) and V5 (P=0.02) of heart dose reduction by DIBH. FB lung volume showed correlation with mean lung dose reduction by DIBH (P<0.01). The FB-CCDps and FB-LHC distance had strong positive and negative correlation with FB mean heart dose (P<0.01) and mean heart dose reduction by DIBH (P<0.01), respectively. FB-CCDax showed no correlation with dosimetric changes. Conclusion: DIBH technique has been shown to reduce dose to the heart and left lung. In this patient cohort, FB-CCDps, FB-LHC distance, and FB lung volume served as significant predictors for heart and left lung. These parameters can be further investigated to be used as a tool to better select patients who will benefit from DIBH.

Three Dimensional Limit Analysis of Slope Stability with Nonlinear Criterion: Comparison the Effect of Volumetric Strain

In view of the complexity of three-dimensional analysis, traditional slope stability analysis was mainly conducted in 2-dimensional scope, namely in the case of plane strain condition. Based on the 3-dimensional failure mechanism proposed by Michalowski, three-dimensional upper bound analysis of the soil slope was presented in this paper. The two different conditions of both with and without volumetric strain taken into consideration are analyzed. The nonlinear failure criterion was introduced into analysis by virtue of the generalized tangential technique method, and the earthquake action was analyzed on the basis of pseudo-static method. The formulas of external work rate and interior energy dissipation were deduced, and the stability factors of slope with respect to diverse parameters were calculated through optimization. The results show that, with the increase of B/H, the difference between the stability factors of the two conditions decrease. Moreover, the change law of the stability factors of the different conditions is similar.

A Quantitative Analysis of Dose Distributions of Two Tangential Whole Breast Irradiation Techniques

A Quantitative Analysis of Dose Distributions of Two Tangential Whole Breast Irradiation Techniques

Novel liquid bubble dissection technique for DMEK lenticule preparation.

Descemet endothelial keratoplasty (DMEK) has replaced penetrating keratoplasty in many cases of endothelial cell disorders. While DMEK has been greatly improved by the introduction of no-touch injection cartridges, the tear-free preparation of the delicate Descemet's membrane (DM) remains a critical step. We present a novel liquid bubble dissection technique for DM preparation that could offer several advantages. After identification of the iris base, a sharp dissection until Schwalbe's line was performed. Then, a narrow tunnel was created with a blunt spatula using a tangential dissection technique. After the tunnel was created, the liquid bubble dissection was performed. The complete detachment process took only a few seconds after a successful preparation of the tunnel in the correct plane between the DM and corneal stroma. Between February and September 2015, we consecutively performed 86 DMEK lenticule preparations using the liquid bubble technique. The preparation time until complete detachment was about 3min (mean 194 ± 20s). Ninety-two percent of preparations were completely uncomplicated; the total success rate was 99%. One graft could not be used for transplantation because of a central tear. The graft failure rate was 1.16%, similar to other authors. The presented novel liquid bubble technique is easy, can be learned and performed rapidly, is highly reproducible in a standardized fashion with minor tissue manipulation (no touch) and, with a low rate of graft preparation failure, necessitates no special equipment and allows for a simultaneous and selective staining of the stromal side of DM, thus avoiding direct contact.

Comparison of build-up region doses in oblique tangential 6 MV photon beams calculated by AAA and CCC algorithms in breast Rando phantom

The purpose of this study is to compare the build-up region doses on breast Rando phantom surface with the bolus covered, the doses in breast Rando phantom and also the doses in a lung that is the heterogeneous region by two algorithms. The AAA in Eclipse TPS and the collapsed cone convolution algorithm in Pinnacle treatment planning system were used to plan in tangential field technique with 6 MV photon beam at 200 cGy total doses in Breast Rando phantom with bolus covered (5 mm and 10 mm). TLDs were calibrated with Cobalt-60 and used to measure the doses in irradiation process. The results in treatment planning show that the doses in build-up region and the doses in breast phantom were closely matched in both algorithms which are less than 2% differences. However, overestimate of doses in a lung (L2) were found in AAA with 13.78% and 6.06% differences at 5 mm and 10 mm bolus thickness, respectively when compared with CCC algorithm. The TLD measurements show the underestimate in buildup region and in breast phantom but the doses in a lung (L2) were overestimated when compared with the doses in the two plannings at both thicknesses of the bolus.

Seismic and static 3D stability of two-stage rock slope based on Hoek–Brown failure criterion

Two-stage slope is beneficial to improve slope stability in comparison with single-stage slope. Based on nonlinear Hoek–Brown criterion, a three-dimensional failure mechanism is employed to estimate the stability of two-stage rock slope, with the effect of seismic inertia force being taken into account. A generalized tangential technique is used to formulate the stability factor problem as a classical optimization problem corresponding to the dissipated energy. The upper-bound solutions are obtained by minimizing the objective function with respect to the location of sliding body center and the location of tangency point. The seismic inertia force is considered and incorporated into the objective function. In comparison with previously published solutions using the linear Mohr–Coulomb criterion, the validity of the present solutions is shown. The analytical expressions for two-stage slope are derived to estimate the seismic stability of slopes. Numerical results for different types of rocks are presented for practical use in engineering, and the effects of different parameters on slope stability are discussed.

Limit analysis of 3D rock slope stability with non-linear failure criterion

The non-linear Hoek-Brown failure criterion has been widely accepted and applied to evaluate the stability of rock slopes under plane-strain conditions. This paper presents a kinematic approach of limit analysis to assessing the static and seismic stability of three-dimensional (3D) rock slopes using the generalized Hoek.Brown failure criterion. A tangential technique is employed to obtain the equivalent Mohr-Coulomb strength parameters of rock material from the generalized Hoek-Brown criterion. The least upper bounds to the stability number are obtained in an optimization procedure and presented in the form of graphs and tables for a wide range of parameters. The calculated results demonstrate the influences of 3D geometrical constraint, non-linear strength parameters and seismic acceleration on the stability number and equivalent strength parameters. The presented upper-bound solutions can be used for preliminary assessment on the 3D rock slope stability in design and assessing other solutions from the developing methods in the stability analysis of 3D rock slopes.

Upper Bound Solution of Safety Factor for Shallow Tunnels Face Using a Nonlinear Failure Criterion and Shear Strength Reduction Technique

A method to evaluate the stability of tunnel face is proposed in the framework of upper bound theorem. The safety factor which is widely applied in slope stability analysis is introduced to estimate the stability of tunnel face using the upper bound theorem of limit analysis in conjunction with a strength reduction technique. Considering almost all geomaterials following a nonlinear failure criterion, a generalized tangential technique is used to calculate the external work and internal energy dissipation in the kinematically admissible velocity field. The upper bound solution of safety factor is obtained by optimization calculation. To evaluate the validity of the method proposed in this paper, the safety factor is compared with those calculated by limit equilibrium method. The comparison shows the solutions derived from these two methods match each other well, which shows the method proposed in this paper can be considered as effective.