We have calculated the dose enhancements close to metal implants in Gamma Knife radiosurgery using different beam sizes, i.e., 4, 8 and 18 mm collimator helmets sin addition to the previous calculations using the 14 mm collimator helmetd. For the 8 and 18 mm helmets, the obtained results were similar to those obtained using the 14 mm helmet, which can be explained by the similar beam profiles w...

A thermal diode is a two-terminal nonlinear device that rectifies energy carriers (for example, photons, phonons and electrons) in the thermal domain, the heat transfer analogue to the familiar electrical diode. Effective thermal rectifiers could have an impact on diverse applications ranging from heat engines to refrigeration, thermal regulation of buildings and thermal logic. However, experim...

The single-hole collimator limits the field of view of a scintillation probe to a single organ. The sensitivity for counting is approximately equal over the entire field of view. The most common use of this collimator is for iodine uptake measurements of the thyroid. An example of this "flat-field collimator" is shown (Fig. I). The sensitivity profile at the working distance illustrates the rel...

The spatial resolution of a collimated CdZnTe Frisch collar detector was experimentally investigated for two different tungsten collimator designs using a Au gamma-ray source at 412 keV. A two-dimensional model for the detector–collimator–source geometry was developed and applied with some simplifying assumptions. The CdZnTe detector was fabricated from a single crystal using a copper shim as t...

According to the control requirements of the leaves’ position precision in the multi-leaf collimator, the structure and working principle of the multi-leaf collimator in the conformal radiation therapy apparatus are described. The motor that drives the leaf of the MLC is taken as the control object. The module of the motor has been established. Then the PSO algorithm is used for the parameter o...

For scintigraphic instruments such as scanners and scintillation cameras, collimatore with greatly dif ferent characteristics have become available during recent years. In general little information is given concerning the performance of focused collimatore to the physician or physicist who has to select the proper collimator for a particular application.! Only the number of holes, the focal le...

Gamma-ray spectrometry is widely applied in several science fields, and particular non-destructive gamma scanning emission tomography of irradiated nuclear fuel. Often, a collimator used the experimental setup, to selectively interrogate region interest For optimization instrument design, as well for planning measurement campaigns, predictive models transmitted gamma-ray intensity through are n...

Abstract Purpose The quantitative accuracy of Nuclear Medicine images, acquired for both planar and SPECT studies, is influenced by the isotope-collimator combination as well image corrections incorporated in iterative reconstruction process. These factors can be investigated optimised using Monte Carlo simulations. This study aimed to evaluate quantification 123 I with low-energy high resoluti...

attached to an external detector system, the thyroid uptake of iodine was measured at 6 and 24 hr. The external detector consisted of a 1Â1⁄4x 1 in. NaI(Tl) scintillation crystal and a flat-field lead collimator. A Lucite extension of the collimator was shaped to fit the neck and assure good geometry with a neck-to crystal distance of 20 cm. A standard neck phantom was used with standard capsul...

INTRODUCTION One of the important input factors in the commissioning of the radiotherapy treatment planning systems is the phantom scatter factor (Sp) which requires the same collimator opening for all radiation fields. In this study, we have proposed an analytical method to overcome this issue. METHODS The measurements were performed using Siemens Primus Plus with photon energy 6 MV for fiel...