Evaluation of a synthetic single-crystal diamond detector for relative dosimetry on the Leksell Gamma Knife Perfexion radiosurgery system

Purpose: To evaluate the new commercial PTW-60019 synthetic single-crystal microDiamond detector (PTW, Freiburg, Germany) for relative dosimetry measurements on a clinical Leksell Gamma Knife Perfexion radiosurgery system. Methods: Detector output ratios (DORs) for 4 and 8 mm beams were measured using a micro- Diamond (PTW-60019), a stereotactic unshielded diode [IBA stereotactic field detector (SFD)], a shielded diode (IBA photon field detector), and GafChromic EBT3 films. Both parallel and transversal acquisition directions were considered for PTW-60019 measurements. Measured DORs were compared to the new output factor reference values for Gamma Knife Perfexion (0.814 and 0.900 for 4 and 8 mm, respectively). Profiles in the three directions were also measured for the 4 mm beam to evaluate full width at half maximum (FWHM) and penumbra and to compare them with the corresponding Leksell GammaPlan profiles. Results: FWHM and penumbra for PTW-60019 differed from the calculated values by less than 0.2 and 0.3 mm, for the parallel and transversal acquisitions, respectively. GafChromic films showed FWHM and penumbra within 0.1 mm. The output ratio obtained with the PTW-60019 for the 4 mm field was 1.6% greater in transverse direction compared to the nominal value. Comparable differences up to 0.8% and 1.0% for, respectively, GafChromic films and SFD were found. Conclusions: The microDiamond PTW-60019 is a suitable detector for commissioning and routine use of Gamma Knife with good agreement of both DORs and profiles in the three directions

A comparative analysis of business and hospitality majors: summer cooperative and field work experiences

Includes bibliographical references

Organ and Effective Doses from A Multidetector Computed Tomography in Chest Examination

The growth of Multidetector Computed Tomography (MDCT) associated with the large number of images per examination offers many clinical benefits. It is easy to use for radiologist and physician, and these reasons are the cause of increasing exposure for populations rapidly. Organ and effective doses from CT examination are the important quantities to assess radiation risk. The objective of this study is to calculate the organ and effective doses from patient data. The beam data was collected for 30 cases of patient over 20 years old underwent 64 slices GE VCT MDCT scanner in the chest examinations. The computed tomography dose index (CTDI) values were measured in air and in body phantom with SOLIDOSE ionization chamber then the CTDI values and the exposed parameters were entered in ImPACT CT Patient Dosimetry Calculator version 1.0 for calculation of organ and effective doses. The exposure parameters of chest protocol were 120 kVp, 330 mA, 0.6 sec rotation time, and 1.375 pitch. The average scan length was 34.9 cm for the range of 23.1 to 56.5 cm. The high organ doses in the irradiated field occurred in lung, breast, esophagus, heart, stomach, liver, adrenal gland, kidney, pancreas, spleen and small intestine, the maximum dose ranged from 15 to 23.0 mGy. The average effective dose was 8.6 mSv with the range of 5.7 to 13.0 mSv.  The maximum number of scan series of examination was three which made the maximum effective dose of 39.0 mSv. The scan length was one of the variable factors that made the higher organ and effective doses in CT examination. The more series of examination was another factor to increase the organ and effective doses. The estimated radiation risk for cancer and hereditary effect for chest CT examination was about 5 cases for 10,000 populations. This study has shown that the CT doses used in clinical practice are not higher than commonly report but the careful used of radiation must be considered. Estimated organ and effective doses in chest MDCT scanning are a guide line for radiologists and physicians in order to judge the frequency of scan and suitable scan length. Keywords: organ dose, effective dose, Computed Tomography Dose Index, Multidetector Computed Tomograph

Brief histories of medical physics in Asia-Oceania

The history of medical physics in Asia-Oceania goes back to the late nineteenth century when X-ray imaging was introduced, although medical physicists were not appointed until much later. Medical physics developed very quickly in some countries, but in others the socio-economic situation as such prevented it being established for many years. In others, the political situation and war has impeded its development. In many countries their medical physics history has not been well recorded and there is a danger that it will be lost to future generations. In this paper, brief histories of the development of medical physics in most countries in Asia-Oceania are presented by a large number of authors to serve as a record. The histories are necessarily brief; otherwise the paper would quickly turn into a book of hundreds of pages. The emphasis in each history as recorded here varies as the focus and culture of the countries as well as the length of their histories varies considerably