Imaging dose from cone beam computed tomography in radiation therapy

AbstractImaging dose in radiation therapy has traditionally been ignored due to its low magnitude and frequency in comparison to therapeutic dose used to treat patients. The advent of modern, volumetric, imaging modalities, often as an integral part of linear accelerators, has facilitated the implementation of image-guided radiation therapy (IGRT), which is often accomplished by daily imaging of patients. Daily imaging results in additional dose delivered to patient that warrants new attention be given to imaging dose. This review summarizes the imaging dose delivered to patients as the result of cone beam computed tomography (CBCT) imaging performed in radiation therapy using current methods and equipment. This review also summarizes methods to calculate the imaging dose, including the use of Monte Carlo (MC) and treatment planning systems (TPS). Peripheral dose from CBCT imaging, dose reduction methods, the use of effective dose in describing imaging dose, and the measurement of CT dose index (CTDI) in CBCT systems are also reviewed

Tartumaa kuvand ettevõtluskeskkonnana ekspertide ja ettevõtjate hinnangul

The purpose of this thesis was to find out the image of Tartu county as a business environment among entrepreneurs and entrepreneurship experts. For this purpose, nine interviews were conducted. The interviewees were divided into two groups: three interviewees were specialists responsible for developing a proper environment for entrepreneurship; and six interviewees were entrepreneurs. Most of the latter were lately unemployed people who had decided to found their own business. The main questions in the thesis were: 1. What is Tartu county’s image among small and big entrepreneurs and does that image entice people to start their own business? 2. How do the entrepreneurship specialists perceive the image of Tartu county as a business environment? The main hypotheses of the thesis were: 1. When starting a new business, the closeness of one’s home and existence of proper production facilities is more important than the image; 2. The image of Tartu county as a business environment benefits from the closeness of universities and the qualified workforce produced by them; 3. Tartu county is different from other counties because of the availability of proper production facilities and the attitude of county’s leaders; 4. A negative impact on Tartu county’s image as a business environment is the weak infrastructure that connects the county to rest of Estonia and the world; 5. Entrepreneurship specialists are rather positive about the Tartu county; 6. Social responsibility is secondary for entrepreneurs. It appeared from the thesis that the image of Tartu county as a business environment depends on different experiences gained in time and therefore it consists of many different aspects. The image of Tartu county consists of factors that define the region. These are: • Thanks to many universities in the county there’s always a supply of educated workforce that allows companies to hire the best of the best; • Due to many governmental institutions in Tarty county, it’s more difficult for entrepreneurs to employ the best graduates; • The lack of business-orientated local leaders means there is no discussion with the entrepreneurs and no efforts to entice more entrepreneurs into the county; • There is no common system to support entrepreneurs in the county. That affects smaller businesses the most since they need mostly financial aid to start a business; • The image of Tartu county suffers from the lack of means to arrive in the county—unfinished road between Tallinn and Tartu, the lack of airlines. Although in theory image influences people’s decisions to certain extent, it didn’t appear, based on the interviews conducted in the purposes of this thesis, that image had influenced entrepreneurs to invest in Tartu county. Image is important for international investors who, without knowing the country and the county, must make their decisions based on hearsay or image.http://tartu.ester.ee/record=b2561464~S1*es

A Monte Carlo Method to Estimate Radiation Dose from Cone Beam Computed Tomography

Objectives: This study compares effective dose determination of four large field of view CBCT units (NewTom-3G, Galileos Comfort Plus, CS-9300, iCat-FLX,) using a Monte Carlo software analysis method (PCXMC) and dosimetry using anthropomorphic phantoms. Methods: Previous research provided phantom effective dose comparisons. Field-of-view and phantom positioning were duplicated in the software. Software and phantom dosimetry values were compared. Descriptive statistics, chi-square, and logistic regression, were used to analyze the data. The null-hypothesis that there is no statistically significant difference between the dosimetry values of the anthropomorphic phantom and the calculated values of the PCXMC software was tested. Results: PCXMC simulated scans produced dose values within 20% of the phantom dosimetry 48-58% of the time. Conclusions: While the software calculations are simpler to perform than phantom dosimetry, imprecise calculated results make this program less effective for CBCT dosimetry in dentistry.Master of Scienc

Low-severity Musculoskeletal Complaints Evaluated in the Emergency Department

Patients with musculoskeletal disorders represent a considerable percentage of emergency department volume. Although patients with acute or high-severity conditions are encouraged to seek care in the emergency department, patients with nonacute, low-severity conditions may be better served elsewhere. This study prospectively assessed patients presenting to the emergency department with nonacute, low-severity musculoskeletal conditions to test the hypothesis that these patients have access to care outside the emergency department. One thousand ten adult patients with a musculoskeletal complaint were identified, and a detailed questionnaire was completed by 862 (85.3%) during their emergency department stay. Three hundred fifty (40.6%) patients presented with nonacute, low-severity conditions. Patients with nonacute, low-severity problems were less likely to have a primary care physician (62.5% versus 72.3%) or to have medical insurance (82.5% versus 87.7%), but a majority had both (59.3%). Only 14.3% had neither. Forty-four percent of all patients with primary care physicians believed their primary care physician was incapable of managing musculoskeletal problems. Appropriate use of the emergency department by patients with musculoskeletal disorders may require not only increased access to insurance and primary care, but also improved public understanding of the scope of care offered by primary care physicians and the conflicting demands placed on emergency department providers

Measurement of the diffractive cross-section in deep inelastic scattering

Diffractive scattering of $\gamma^* p \to X + N$, where $N$ is either a proton or a nucleonic system with $M_N~<~4$~GeV has been measured in deep inelastic scattering (DIS) at HERA. The cross section was determined by a novel method as a function of the $\gamma^* p$ c.m. energy $W$ between 60 and 245~GeV and of the mass $M_X$ of the system $X$ up to 15~GeV at average $Q^2$ values of 14 and 31~GeV$^2$. The diffractive cross section $d\sigma^{diff} /dM_X$ is, within errors, found to rise linearly with $W$. Parameterizing the $W$ dependence by the form d\sigma^{diff}/dM_X \propto (W^2)^{(2\overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} -2)} the DIS data yield for the pomeron trajectory \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} = 1.23 \pm 0.02(stat) \pm 0.04 (syst) averaged over $t$ in the measured kinematic range assuming the longitudinal photon contribution to be zero. This value for the pomeron trajectory is substantially larger than \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} extracted from soft interactions. The value of \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} measured in this analysis suggests that a substantial part of the diffractive DIS cross section originates from processes which can be described by perturbative QCD. From the measured diffractive cross sections the diffractive structure function of the proton F^{D(3)}_2(\beta,Q^2, \mbox{x_{_{I\hspace{-0.2em}P}}}) has been determined, where $\beta$ is the momentum fraction of the struck quark in the pomeron. The form F^{D(3)}_2 = constant \cdot (1/ \mbox{x_{_{I\hspace{-0.2em}P}}})^a gives a good fit to the data in all $\beta$ and $Q^2$ intervals with $a = 1.46 \pm 0.04 (stat) \pmComment: 45 pages, including 16 figure