Cone Research Articles

Dosimetric effects of incorrect jaw settings in cranial radiosurgery

A small circular field used in stereotactic radiosurgery is obtained using a cone accessory attached to a LINAC. Such beam modification requires that the LINAC jaws be set to a specific size, an adjustment which, in many cases, must be explicitly made by the LINAC operator. Given that treatment planning systems are commissioned with correct jaw settings, it is difficult to quantify the leakage dose to the patient when the jaw setting is larger than recommended. However, there are documented cases indicating that the resulting overexposure can lead to long-term disability and death. This study quantifies the dose differences between correct and incorrect jaw settings by simulating a realistic treatment plan using a Varian LINAC with a BrainLab circular cone accessory. Using Monte Carlo methods, the details of the LINAC head and cone accessory were simulated, with calculated doses benchmarked against measurements. Calculations were based on a realistic treatment plan for right side trigeminal neuralgia delivering 90 Gy using a 6 MV (4 mm cone) beam with 7 arcs. The calculated doses to target and normal tissue with jaws set correctly (5 × 5 cm2) and incorrectly (settings ranging from 10 × 10 cm2 to 20 × 20 cm2) were then compared. Incorrect jaw settings resulted in an increase in the target dose of less than 6%. This implies that pre-treatment QA based only on point dose measurements at the isocenter will not detect jaw setting errors. However, extremely high doses (>25 Gy) occurred 5 cm away from the isocenter. For example, dose to 50% of the volume, D50, in the eyes increased from 15 cGy with the correct jaw setting to 5318 cGy with an incorrect jaw setting of 20 × 20 cm2. D50 in the brain increased from 27 cGy with the correct jaw setting to 4335 cGy for a setting of 20 × 20 cm2. The leakage radiation is shown to originate beyond the outer edge of the beam limiting cone (outer radius = 5 cm). Leakage dose can reach 15%, 40%, and 60% of target dose when incorrect jaw settings of 10 × 10 cm2, 15 × 15 cm2 and 20 × 20 cm2 are used in the beam delivery.

Stone Cone® in ureteroscopic ballistic lithotripsy of proximal ureteral stones

Stone Cone® (Microvasive-Boston Scientific Corp, USA) is a device which prevents retrograde calculus migration during endoscopic ureterolithotripsy. We have studied the safety and efficacy of this device in endoscopic ureterolithotripsy with ballistic energy in proximal ureteral stones. MATERIALS AND METHODS. From 01/02/2006 to 01/02/2008 we carried out 36 ureterorenoscopies (URS) for proximal ureteral stones (average age: 46, range: 15-73). A ballistic energy was used for stones fragmentation. In 18 patients (Group A) we carried out URS with the aid of Stone Cone®, which was not used in the other 18 patients (Group B). Semirigid 8 Ch or 10 Ch Storz ureteroscope and ballistic lithotriptor Swiss Lithoclast Master EMS® were used. In cases of migration, edema, and ureteral damage, a ureteral stent was used. RESULTS. In Group B patients (URS performed without Stone Cone®) the migration of the whole stone, or of clinically significant fragments, occurred 8 times (45%). All of these patients underwent external shockwave lithotripsy (ESWL) at a center equipped with a lithotriptor. A ureteral stent was placed in 14 cases (78%). In Group A, the migration of a stone requiring ESWL treatment occurred only once (5%). The ureteral stent was placed 8 times (45%). We had no significant complications during the procedure. CONCLUSIONS. The Stone Cone® is a safe and easy-to-use device. The cost of this device can be balanced by the reduction of postoperative ESWL treatments for lithiasic fragments pushing up into the kidneys (p<0.01), and of ureteral stent applications at the end of the procedure (p<0.05).

Simulations of the unsteady fluid-structure coupling characteristics of a conical orifice valve

Simulations of the unsteady fluid-structure coupling characteristics of a conical orifice valve

A new type of fuzzy systems using pyramid membership functions (PMFs) and approximation properties

This paper focuses on improving the precision and simplifying the structure of fuzzy systems. A new type of fuzzy systems that using a proposed pyramid membership function (PMF) is constructed. The original compound of fuzzy rule antecedents is replaced by PMF. Specifically, the commonly used one-dimensional triangular membership functions are generalized to three kinds of two-dimensional PMFs. Cone fuzzy systems (CFSs) with the proposed rectangular pyramid, circular cone and triangular mesh pyramid membership functions are, respectively, given. Approximation properties of CFS, including universal approximation property and approximation accuracy, are proved theoretically. It is shown that, rectangular pyramid fuzzy system and triangular mesh pyramid fuzzy system are capable of achieving first-order and second-order accuracy, respectively. Two experimental examples are presented to demonstrate the effectiveness of CFS. Both theoretical and numerical results illustrate that CFS is capable of obtaining good accuracy.

Observations on Malenchus geraerti n. sp. (Rhabditida: Tylenchidae), a morphological and molecular phylogenetic study.

Malenchus geraerti n. sp., recovered from natural regions of northern Iran, is described and illustrated based on morphological, morphometric and molecular data. The new species is characterized by having females with a short body, an anteriorly wide S-shaped amphidial opening narrowing posteriorly, cuticle with prominent annuli, lateral field a plain band with smooth margins, muscular metacorpus with well-developed valve and corresponding plates, spermatheca filled with small spheroid sperm cells, vulva sunken in body with large epiptygma and no flap, and conical tail tapering gradually to a more or less pointed tip. Males of the new species are characterized by having a short body, tylenchoid spicules, adcloacal bursa with smooth margin and tail similar to that of the female. Morphologically, the new species is similar to five known species of the genus: M. fusiformis, M. machadoi, M. pachycephalus, M. solovjovae and M. undulatus. It most closely resembles M. pachycephalus, but as a cryptic species it can be differentiated using morphological and molecular characteristics. Comparisons with the four other aforementioned species are also discussed. Molecular phylogenetic studies using partial sequences of small and large subunit ribosomal DNA fragments reveal that the new species forms a clade with the species M. neosulcus in the small subunit (SSU) rDNA, and two species of Lelenchus in the large subunit (LSU) rDNA tree.

Monte Carlo calculation of photo-neutron dose produced by circular cones at 18MV photon beams.

The aim of this study is to calculate neutron contamination at the presence of circular cones irradiating by 18MV photons using Monte Carlo code. Small photon fields are one of the most useful methods in radiotherapy. One of the techniques for shaping small photon beams is applying circular cones made of lead. Using this method in high energy photon due to neutron contamination is a crucial issue. Initially, Varian linac producing 18MV photons was simulated and after validating the code, various circular cones were also simulated. Then, the number of neutrons, neutron equivalent dose and absorbed dose per Gy of photon dose were calculated along the central axis. Number of neutrons per Gy of photon dose had their maximum value at depth of 2cm and these values for 5, 10, 15, 20 and 30mm circular cones were 9.02, 7.76, 7.61, 6.02 and 5.08 (ncm-2Gy-1), respectively. Neutron equivalent doses per Gy of photon dose had their maximum at the surface of the phantom and these values for mentioned collimators were 1.48, 1.33, 1.31, 1.12 and 1.08 (mSvGy-1), respectively. Neutron absorbed doses had their maximum at the surface of the phantom and these values for mentioned collimators sizes were 103.74, 99.71, 95.77, 81.46 and 78.20 (μGy/Gy), respectively. As the field size gets smaller, number of neutrons, equivalent and absorbed dose per Gy of photon increase. Also, neutron equivalent dose and absorbed dose are maximum at the surface of phantom and then these values will be decreased.

Jaw pain secondary to atypical maxillary torus near the incisive canal: A cone beam computed tomography study

Pain in the anterior maxilla can be odontogenic or nonodontogenic. If it is not related to the teeth, then the differential diagnosis is based on a clinical exam, radiographic exam, and often, on advanced imaging. This case report is based on a 58-year-old male with a chief complaint of chronic pain with acute exacerbations in the region of the rugae of the maxillary central incisors. Clinical examination and planar radiography led to the suspicion of a cyst in the region of the incisive foramen. The patient was referred for advanced imaging. Cone beam computed tomography imaging confirmed the presence of an unusual tori in the region of the incisive foramen that led to periodic inflammation in the region. A differential diagnosis of the pain included pain secondary to a localized inflammation of the incisive canal and nasopalatine duct, and an inflammation of the soft tissue interdental col in the region of the central incisors as well as the benign and malignant minor salivary gland tumors. Because the rugae is attached to the palate, any expansion of the soft tissues in this region causes pain that must be diagnosed accurately to treat the cause.

Field and laboratory assessment of ground subsidence induced by underground cavity under the sewer pipe

In densely populated urban areas with a large amount of infrastructure, ground subsidence events can result in massive casualties and economic losses. In South Korea, the incidence of ground subsidence in urban areas has increased in recent years and the number of underground cavities suspected of causing such events has significantly increased. Therefore, it is essential to develop techniques to prevent the occurrence of underground and ground subsidence. In this study, a field test, laboratory test, and numerical analysis were conducted to determine the optimal compaction degree of the upper support layer of any underground cavity below the level of sewer pipes in order to prevent such cavities from collapsing and leading to ground subsidence accidents. During the field test, an underground cavity was simulated using ice, and the generation of the cavity was confirmed using ground penetrating radar. The ground investigation was performed using a cone penetration test, and the compaction of the ground where ground subsidence occurred was evaluated with a laboratory test. The behaviour of the ground under various conditions was predicted using a numerical analysis based on the data obtained from the field test and previous studies. Based on these results, the optimal compaction degree of the ground required to prevent the underground cavity from causing ground subsidence was predicted and presented.

Reliability of breast density estimation based on cone beam breast CT

Reliability of breast density estimation based on cone beam breast CT

Radiation safety protocol in dentistry: A neglected practice

Aim: The ready availability of radiodiagnostic aids has led to its overuse in dental practice. In addition, failure to reinforce the radiation safety procedures has unknowingly resulted in the negligence of the as low as reasonably achievable (ALARA) principles among many dentists. Apart from patients, the dentists and dental assistants are being exposed to radiation in the clinics during regular practice. The current survey was designed to assess the awareness, concern, and practice of radiation protection in general dental practice. Materials and Methods: The survey consisted of 86 dentists in Bangalore city. A cross-sectional self-administered questionnaire consisting of a total of 31 items was used. The obtained data were compiled and analyzed using the Statistical Package for the Social Sciences version 20.0 software (IBM Corporation, New York, United States). Results: All the dentists responded in the study (100%); the participants had limited knowledge regarding the radiation equipment. Majority of the participants were using rounded collimator (96.5%) and short cone (61.6%). E-speed film was used by most of the dentists (90.7%). Bisecting angle technique was preferred by most of the practitioners (69.8%) for making periapical radiographs. Only 20.9% of the dentists made their patients wear lead apron during X-ray exposure. None of them were using thyroid collar. Most of the dentists practiced at a safe distance of 6 ft from the X-ray tube, whereas 10.5% of the dentists assisted holding the radiographic receptor beside the patient. Radiation monitoring was performed by only 20% of the practitioners. Conclusion: The knowledge and practice of radiation protection were not satisfactory. Repeated reinforcement in the form of continued dental education program is necessary, and, most importantly, change in the attitude of the dentist to follow ALARA should be advocated.

Analysis of Protection Capability of a Conical Shaped Protector

Analysis of Protection Capability of a Conical Shaped Protector

МОДЕЛИРОВАНИЕ ПРОНИКАНИЯ НЕОСЕСИММЕТРИЧНЫХ ТЕЛ В ГРУНТ ПО ИНЕРЦИИ ПРИ УЧЕТЕ ТРЕНИЯ

The problem of a normal impact and penetration of rigid spatial bodies of a finite mass into a half-space occupied by an elastoplastic soil medium. The penetrated medium is modeled by linearly compressible elastoplastic Grigoryan medium, with the yield strength linearly depending on pressure. The problem is analyzed in a 3D formulation, using software package LS-DYNA. The elastoplastic penetrated medium is analyzed on a fixed Eulerian grid with empty meshes, where the material flows to in the process of deformation. Spatial strikers are modeled by a rigid non-deformable body in a Lagrangian coordinate system. The effect of surface friction during the penetration of strikers of various forms (a round cone, a four-ray star and a pyramidal body) into elastoplastic Grigoryan soil medium is studied. The cross-section of the star-shaped body is generated by two rhombs with the ration of diagonals of 1:2; the base of the pyramid is a rhomb with the ratio of diagonals of 1:3. The analyzed bodies have equal areas of the bases and equal inclinations of the side surface (the angle between the direction of the motion velocity vector of the body and a normal to the side surface). A circular cone with the same base area is considered for comparison.The considered strikers moved with constant velocities and mechanically, in the velocity range of 150 to 600 m/s, corresponding to subsonic and supersonic velocities. The surface friction coefficient is close to the value of the friction coefficient in sandy soils of natural composition. The results are compared with the earlier obtained computational results for a zero friction coefficient. It is found that resistance to penetration and penetration depth can be described using binomial Resale's penetration law with a quadratic velocity. The disagreement between the forces of resistance to penetration of a pyramidal, conical and star-shaped bodies of the same height are within the interval of 10-20%.

Influence of Tool Rotational speed and Pin Profile on Mechanical and Microstructural Characterization of Friction Stir Welded 5083 Aluminium Alloy

A study was made of weldability of 4mm-thick Aluminium alloy 5083 plates using friction stir welding. The plan of experiments was prepared based on abilities of universal milling machine. The tool rotational speeds of 900r/min, 1120r/min, 1400r/min and 1800r/min, the welding speed of at 40mm/min were taken. The tool pin geometries are taper threaded profile tool and conical taper profile tool. Samples for microstructure analyses, Vickers micro-hardness measurements, and tensile-testing samples were prepared. It was observed that the better mechanical properties were achieved at moderate tool rotational speed, and equi-axed grains obtained at conical taper tool profile as compared with taper threaded tool. Analysis is made with the Samples for microstructure analyses, Vickers micro-hardness measurements and tensile-testing samples were prepared.

Performance Analysis of Joint-Sparse Recovery from Multiple Measurement Vectors via Convex Optimization: Which Prior Information is Better?

In sparse signal recovery of compressive sensing, the phase transition determines the edge, which separates successful recovery and failed recovery. The phase transition can be seen as an indicator and an intuitive way to judge, which recovery performance is better. Traditionally, the multiple measurement vectors (MMVs) problem is usually solved via $\ell _{2,1}$ -norm minimization, which is our first investigation via conic geometry in this paper. Then, we are interested in the same problem but with two common constraints (or prior information): prior information relevant to the ground truth and the inherent low rank within the original signal. To figure out which constraint is most helpful, the MMVs problems are solved via $\ell _{2,1}$ - $\ell _{2,1}$ minimization and $\ell _{2,1}$ -low rank minimization, respectively. By theoretically presenting the necessary and sufficient condition of successful recovery from MMVs, we can have a precise prediction of phase transition to judge, which constraint or prior information is better. All our findings are verified via simulations and show that, under certain conditions, $\ell _{2,1}$ - $\ell _{2,1}$ minimization outperforms $\ell _{2,1}$ -low rank minimization. Surprisingly, $\ell _{2,1}$ -low rank minimization performs even worse than $\ell _{2,1}$ -norm minimization. To the best of our knowledge, we are the first to study the MMVs problem under different prior information in the context of compressive sensing.

Effects of cone combinations on the signal enhancement by nitrogen in LA-ICP-MS

The geometry of the skimmer cone is an important factor for signal enhancement and the reduction of oxides by the addition of nitrogen in LA-ICP-MS.

A singular value decomposition linear programming (SVDLP) optimization technique for circular cone based robotic radiotherapy

With robot-controlled linac positioning, robotic radiotherapy systems such as CyberKnife significantly increase freedom of radiation beam placement, but also impose more challenges on treatment plan optimization. The resampling mechanism in the vendor-supplied treatment planning system (MultiPlan) cannot fully explore the increased beam direction search space. Besides, a sparse treatment plan (using fewer beams) is desired to improve treatment efficiency. This study proposes a singular value decomposition linear programming (SVDLP) optimization technique for circular collimator based robotic radiotherapy. The SVDLP approach initializes the input beams by simulating the process of covering the entire target volume with equivalent beam tapers. The requirements on dosimetry distribution are modeled as hard and soft constraints, and the sparsity of the treatment plan is achieved by compressive sensing. The proposed linear programming (LP) model optimizes beam weights by minimizing the deviation of soft constraints subject to hard constraints, with a constraint on the l1 norm of the beam weight. A singular value decomposition (SVD) based acceleration technique was developed for the LP model. Based on the degeneracy of the influence matrix, the model is first compressed into lower dimension for optimization, and then back-projected to reconstruct the beam weight. After beam weight optimization, the number of beams is reduced by removing the beams with low weight, and optimizing the weights of the remaining beams using the same model. This beam reduction technique is further validated by a mixed integer programming (MIP) model. The SVDLP approach was tested on a lung case. The results demonstrate that the SVD acceleration technique speeds up the optimization by a factor of 4.8. Furthermore, the beam reduction achieves a similar plan quality to the globally optimal plan obtained by the MIP model, but is one to two orders of magnitude faster. Furthermore, the SVDLP approach is tested and compared with MultiPlan on three clinical cases of varying complexities. In general, the plans generated by the SVDLP achieve steeper dose gradient, better conformity and less damage to normal tissues. In conclusion, the SVDLP approach effectively improves the quality of treatment plan due to the use of the complete beam search space. This challenging optimization problem with the complete beam search space is effectively handled by the proposed SVD acceleration.

HEAT TRANSFER IN VISCOPLASTIC BOUNDARY-LAYER FLOW FROM A VERTICAL PERMEABLE CONE WITH MOMENTUM AND THERMAL WALL SLIP: NUMERICAL STUDY

A mathematical model is presented for the laminar free convection boundary layer flow of Casson viscoplastic non-Newtonian fluid external to a vertical penetrable circular cone in the presence of thermal and hydrodynamic slip conditions. The cone surface is maintained at non-uniform surface temperature. The boundary layer conservation equations, which are parabolic in nature, are transformed into non-dimensional form via appropriate similarity variables, and the emerging boundary value problem is solved computationally with the second order accurate implicit Keller-box finite-difference scheme. The influence of velocity (momentum) slip, thermal slip and Casson non-Newtonian parameter on velocity, temperature, skin friction and Nusselt number are illustrated graphically. Validation of solutions with earlier published work is included. The computations show that the flow near the cone surface is strongly decelerated with increasing momentum slip whereas the temperature and thermal boundary layer thickness are increased. Increasing Casson parameter generally decelerates the flow and also decreases temperatures. Both velocity and thermal boundary layer thickness are reduced with greater Prandtl number. The study is relevant to petro-chemical engineering (polymer) processing systems.

Verification of relative output factor measurement using Gafchromic films for small-field radiosurgery photon beams.

Accurate dosimetry of small-field photon beams has always been difficult to achieve, due to the steep dose gradient and absence of lateral electronic equilibrium. The purpose of this study was to verify the measurement of relative output factor (ROF), which is one of the dosimetric parameter required for stereotactic radiosurgery (SRS) treatment planning. The ROFs for Radionics circular cone collimators with diameter in the range of 10.0 to 45.0 mm were measured using Gafchromic EBT2 and EBT3 films. The measurements were then compared with the ROFs obtained using a PinPoint ionisation chamber and Monte Carlo (MC) simulation. From the results, the ROFs measured by the ionisation chamber, EBT2, and EBT3 films were good agreement with the MC simulation, with deviations of less than 1.5, 2.6, and 5.0 % respectively. Based on the film dosimetry, the EBT2 film showed in a more reliable measurement for field size ranging from 15.0 to 45.0 mm, compared with EBT3. As a conclusion, based on the special characteristic of the small-field photon beams, ROF measurement using PinPoint ionisation chamber are being favoured, due to its accuracy. However, the EBT2 film can be used as an alternative, when high spatial resolution is required.

Influence of Conical Taper Tool Profile on Mechanical and Micro Structural Characterization of Friction Stir Welded 5083 Aluminum Alloy

Influence of Conical Taper Tool Profile on Mechanical and Micro Structural Characterization of Friction Stir Welded 5083 Aluminum Alloy

Evaluation of latent variances in Monte Carlo dose calculations with Varian TrueBeam photon phase-spaces used as a particle source

The purpose of this study was to evaluate the latent variance (LV) of Varian TrueBeam photon phase-space files (PSF) for open 10 × 10 cm2 and small stereotactic fields and estimate the number of phase spaces required to be summed up in order to maintain sub-percent LV in Monte Carlo (MC) dose calculations. BEAMnrc/DOSXYZnrc software was used to transport particles from Varian phase-space files (PSFA) through the secondary collimators. Transported particles were scored into another phase-space located under the jaws (PSFB), or transported further through the cone collimators and scored straight below, forming PSFC. Phase-space files (PSFB) were scored for 6 MV-FFF, 6 MV, 10 MV-FFF, 10 MV and 15 MV beams with 10 × 10 cm2 field size, and PSFC were scored for 6 MV beam under circular cones of 0.13, 0.25, 0.35, and 1 cm diameter. Both PSFB and PSFC were transported into a water phantom with particle recycling number ranging from 10 to 1000. For 10 × 10 cm2 fields 0.5 × 0.5 × 0.5 cm3 voxels were used to score the dose, whereas the dose was scored in 0.1 × 0.1 × 0.5 cm3 voxels for beams collimated with small cones. In addition, for small 0.25 cm diameter cone-collimated 6 MV beam, phantom voxel size varied as 0.02 × 0.02 × 0.5 cm3, 0.05 × 0.05 × 0.5 cm3 and 0.1 × 0.1 × 0.5 cm3. Dose variances were scored in all cases and LV evaluated as per Sempau et al. For the 10 × 10 cm2 fields calculated LVs were greatest at the phantom surface and decreased with depth until they reached a plateau at 5 cm depth. LVs were found to be 0.54%, 0.96%, 0.35%, 0.69% and 0.57% for the 6 MV-FFF, 6 MV, 10 MV-FFF, 10 MV and 15 MV energies, respectively at the depth of 10 cm. For the 6 MV phase-space collimated with cones of 0.13, 0.25, 0.35, 1.0 cm diameter, the LVs calculated at 1.5 cm depth were 75.6%, 25.4%, 17.6% and 8.0% respectively. Calculated LV for the 0.25 cm cone-collimated 6 MV beam were 61.2%, 40.7%, 22.5% in 0.02 × 0.02 × 0.5 cm3, 0.05 × 0.05 × 0.5 cm3 and 0.1 × 0.1 × 0.5 cm3 voxels respectively. In order to achieve sub-percent LV in open 10 × 10 cm2 field MC simulations a single PSF can be used, whereas for small SRS fields (0.13–1.0 cm) more PSFs (66–8 PSFs) would have to be summed.