Assessment of an Unshielded Electron Field Diode Dosimeter for Beam Scanning in Small-to Medium-Sized 6 MV Photon Fields

Abstract Introduction Radiotherapy planning systems require many percentage depth dose (PDD) and profile measurements and there are various dosimeters that can be used to obtain these scans. As dose perturbation is particularly troublesome in smaller photon fields, using a low-perturbation, unshielded electron field diode (EFD) in these fields is of interest. The aim of this work was to investigate the suitability of an unshielded diode for beam scanning in 3×3 cm 2 , 5×5 cm 2 , and 10×10 cm 2 , 6 MV fields. Materials and Methods An EFD was used for all the scans. For comparison, in profile measurements, a tungsten-shielded photon field diode (PFD) was also used. PDDs were measured using the PFD and an RK ionization chamber. Results Very good agreement (0.4%) was found between the PDDs measured with EFD and PFD for the two larger fields. However, the difference between them exceeded 1.0% slightly for the smallest field, which may be attributed to the effect of the larger PFD perturbation. The RK chamber PDDs around 10 cm depth were 1-2% lower than those measured with the diodes. There was good agreement (<1 mm) between EFD-and PFD-measured penumbra widths. Conclusion The EFD generally agrees well with the PFD and may even perform better in smaller fields

INVESTIGATION OF THE RELATIONSHIP BETWEEN ENTREPRENEURIAL OPPORTUNITY RECOGNITION AND ENTREPRENEURIAL CAPITALS

ABSTRAC

Dosimetric verification of the Elekta motorized wedge

Elekta linear accelerator is equipped with a motorized wedge which produces the wedge angles of less than 60° continuously by the combination of a wedged field and an open field with appropriate proportions. The effective wedge angles for various field sizes and depths were calculated using an analytical formula and a 2-D array detector data. The validity of the effective wedge angles has been done by determining wedge angles in accordance with ICRU-24. The effect of the field size on the wedge angle and wedge factor was investigated for motorized wedge. The maximum difference between planned and measured angles was found to be about 10̊. The planned dose for different wedge angles and field sizes compared with measured doses and their differences were found to be less than 3%. The calculating wedge factor throughout linear interpolation method for all field sizes from a few selected measurements had been proved for physical wedge beforehand. This method was applied to obtain the wedge factors with field size and compared with measured data for motorized wedge. The errors were in agreement with ICRU proposed error and less than treatment planning system error. The linear relation between wedge angle and output factor and depth were investigated and the linear interpolation method was proved to calculate wedge angle for any output factor and depth. 

Calculation of Secondary Neutron Dose Equivalent in Proton Therapy of Thyroid Gland Using FLUKA Code

Proton radiotherapy (PRT) is becoming an established treatment modality for cancer. The localized tumors, the same as undifferentiated thyroid tumors are insufficiently handled by conventional radiotherapy, while protons would propose the prospect of increasing the tumor dose without exceeding the tolerance of the surrounding healthy tissues. In spite of relatively high advantages in giving localized radiation dose to the tumor region, in proton therapy, secondary neutron production can have significant contribution on integral dose and lessen advantages of this modality contrast to conventional radiotherapy techniques. Furthermore, neutrons have high quality factor, therefore, even a small physical dose can cause considerable biological effects. Measuring of this neutron dose is a very critical step in prediction of secondary cancer incidence. It has been found that FLUKA Monte Carlo code simulations have been used to evaluate dose due to secondaries in proton therapy. In this study, first, by validating simulated proton beam range in water phantom with CSDA range from NIST for the studied proton energy range (34-54 MeV), a proton therapy in thyroid gland cancer was simulated using FLUKA code. Secondary neutron dose equivalent of some organs and tissues after the target volume caused by 34 and 54 MeV proton interactions were calculated in order to evaluate secondary cancer incidence. A multilayer cylindrical neck phantom considering all the layers of neck tissues and a proton beam impinging normally on the phantom were also simulated. Trachea (accompanied by Larynx) had the greatest dose equivalent (1.24×10-1 and 1.45 pSv per primary 34 and 54 MeV protons, respectively) among the simulated tissues after the target volume in the neck region

Calculation of Secondary Neutron Dose Equivalent in Proton Therapy of Thyroid Gland Using FLUKA Code

Proton radiotherapy (PRT) is becoming an established treatment modality for cancer. The localized tumors, the same as undifferentiated thyroid tumors are insufficiently handled by conventional radiotherapy, while protons would propose the prospect of increasing the tumor dose without exceeding the tolerance of the surrounding healthy tissues. In spite of relatively high advantages in giving localized radiation dose to the tumor region, in proton therapy, secondary neutron production can have significant contribution on integral dose and lessen advantages of this modality contrast to conventional radiotherapy techniques. Furthermore, neutrons have high quality factor, therefore, even a small physical dose can cause considerable biological effects. Measuring of this neutron dose is a very critical step in prediction of secondary cancer incidence. It has been found that FLUKA Monte Carlo code simulations have been used to evaluate dose due to secondaries in proton therapy. In this study, first, by validating simulated proton beam range in water phantom with CSDA range from NIST for the studied proton energy range (34-54 MeV), a proton therapy in thyroid gland cancer was simulated using FLUKA code. Secondary neutron dose equivalent of some organs and tissues after the target volume caused by 34 and 54 MeV proton interactions were calculated in order to evaluate secondary cancer incidence. A multilayer cylindrical neck phantom considering all the layers of neck tissues and a proton beam impinging normally on the phantom were also simulated. Trachea (accompanied by Larynx) had the greatest dose equivalent (1.24×10-1 and 1.45 pSv per primary 34 and 54 MeV protons, respectively) among the simulated tissues after the target volume in the neck region

The Combination of Soft System and Quality Function Deployment Methodologies in the Design and Development of the Comprehensive Model for World Class Manufacturing Processes

The present paper attempts to design and develop a comprehensive model based on which the manufacturing processes can be promoted toward a world class manufacturing level. In this paper, it is believed that the Soft System Methodologies (SSM) can be utilized in a synthesized fashion to attain the world – class manufacturing status and the Quality Function Deployment (QFD) to analyze and assess customer needs and requirements and to design production processes used for the achievement of high–quality products. It is believed that such a combination can lead to the successful design of a model of key success criteria for the purpose of achieving the above mentioned goal. To achieve the above mentioned goal, the SSM and QFD Methodologies are combined to establish the major components influencing manufacturing processes in the form of a model consisting of 12 components (strategy, system, organization, work process, value, personnel, culture, quality, price, speed, flexibility, and customer services). .Key words: World class manufacturing; Soft system methodology; Quality function deployment; Modeling; critical success factors; Production process desig

A Comprehensive Model for Status Assessments’ Gap Evaluation in the World Class Manufacturing -- Based on Modifications’ Development of ESCAP Approach

In this paper we generalize and develop a comprehensive model upon which we can determine the position of and gap in the world class manufacturing processes. This paper is based on the belief that for evaluation of world class manufacturing processes, we can use determination of gap in world class manufacturing processes, generalized from ESCAP (United Nations Economic and Social Commission for Asia and the Pacific). In order to achieve the above objective, and to determine the total position and gap in question, ESCAP model was used to generate a formula called Situation Contribution Coefficient (SCC) for Manufacturing Position at the global level.Key words: Manufacturing processes; Determining the position of world class processes; ESCAP mode

The influence of using different reconstruction algorithms on sensitivity of quantitative 18F-FDG-PET volumetric measures to background activity variation

Introduction: This study aims to investigate the influence of background activity variation on image quantification in differently reconstructed PET/CT images. Methods: Measurements were performed on a Discovery-690 PET/CT scanner using a custom-built NEMA-like phantom. A background activity level of 5.3 and 2.6 kBq/ml 18F-FDG were applied. Images were reconstructed employing four different reconstruction algorithms: HD (OSEM with no PSF or TOF), PSF only, TOF only, and TOFPSF, with Gaussian filters of 3 and 6.4 mm in FWHM. SUVmax and SUVpeak were obtained and used as cut-off thresholding; Metabolic Tumor Volume (MTV) and Total Lesion Glycolysis (TLG) were measured. The volume recovery coefficients (VRCs), the relative percent error (�MTV), and Dice similarity coefficient were assessed with respect to true values. Results: SUVmax and SUVpeak decreased and MTV increased as function of increasing the background dose. The most differences occur in smaller volumes with 3-mm filter; Non-TOF and Non-PSF reconstruction methods were more sensitive to increasing the background activity in the smaller and larger volumes, respectively. The TLG values were affected in the small lesions (decrease up to 12). In a range of target volumes, differences between the mean �MTV in the high and low background dose varied from -11.8 to 7.2 using SUVmax and from 2.1 to 7.6 using SUVpeak inter reconstruction methods. Conclusion: The effect of the background activity variation on SUV-based quantification in small lesion was more noticeable than large lesion. The HD and TOFPSF algorithms had the lowest and the highest sensitivity to background activity, respectively. © 2018 Iranian Journal of Nuclear Medicine. All Rights Reserved

Medical image registration using unsupervised deep neural network: A scoping literature review

In medicine, image registration is vital in image-guided interventions and other clinical applications. However, it is a difficult subject to be addressed which by the advent of machine learning, there have been considerable progress in algorithmic performance has recently been achieved for medical image registration in this area. The implementation of deep neural networks provides an opportunity for some medical applications such as conducting image registration in less time with high accuracy, playing a key role in countering tumors during the operation. The current study presents a comprehensive scoping review on the state-of-the-art literature of medical image registration studies based on unsupervised deep neural networks is conducted, encompassing all the related studies published in this field to this date. Here, we have tried to summarize the latest developments and applications of unsupervised deep learning-based registration methods in the medical field. Fundamental and main concepts, techniques, statistical analysis from different viewpoints, novelties, and future directions are elaborately discussed and conveyed in the current comprehensive scoping review. Besides, this review hopes to help those active readers, who are riveted by this field, achieve deep insight into this exciting field