Collimator systems used in Intensity Modulated Radiation Therapy can form different geometric aperture shapes depending on their physical capabilities. We compare the efficiency of using regular, rotating and dual multileaf collimator (MLC) systems under different combinations of consecutiveness, interdigitation and rectangular constraints. We also create a virtual freeform collimator, which ca...

To more easily estimate accurate values of collimator scatter facor, S(c), we suggest a two-component saturation model that accounts for scatter from the primary collimator and flattening filter and from the collimator jaws. This model, which assumes an exponential distribution of scatter intensity, was tested by in-air measurements using a mini-phantom for 4 MV and 10 MV X-rays of a Clinac 210...

As for the optical measurement, the longer the focal length of collimator is, the less the measurement error is. However, the longer the focal length is, the more difficult the optical design is. It's higher application value to design long focal length collimator with wide-view. The paper designs a collimator with 2000mm focal length, 4 degree field of view and its wavelength range is from 480...

UNLABELLED Ex vivo measurements in animals are used frequently in the field of nuclear medicine for the characterization of newly developed radioligands and for drug development. In vivo SPECT would replace these ex vivo measurements in a relatively large number of cases if one were able to adequately image small organs. The pinhole collimator has been used extensively to obtain greater detail ...

PURPOSE The use of the low-energy high-resolution (LEHR) collimator for lymphoscintigraphy causes the appearance of star-shaped artifacts at injection sites. The aim of this study was to confirm whether the lower resolution of the low- to medium-energy general-purpose (LMEGP) collimator is compensated by decrease in the degree of septal penetration and the reduction in star-shaped artifacts. ...

A high sensitivity Cardiac SPECT system using curved crystals with pinhole collimation was proposed previously (Dey, IEEE TNS 2012, Bhusal et al, Med. Phys. 2019). Here, we hypothesize that a curvature hemi-ellipsoid detector results in measurable differences light distribution from events at different depths the crystal. This tested by analyzing scintillation Monte-Carlo (Geant4) and evaluatio...

Abstract Higher energy and intensity X-ray radiotherapy treatments are coming into wider use, having the benefit of requiring fewer treatment fractions hospital visits per patient. However, small percentage errors in multileaf collimator positioning dose become bigger problems with higher doses fraction. Hence, real-time verification becomes essential. Where devices downstream from patient suff...

The Leksell Gamma Knife is a standard radiosurgical tool for treating brain lesions by directing beams of gamma radiation to a specific region. The diameter of the gamma beams is confined by collimator systems and available collimator sizes are 4, 8, 14 and 18 mm. The reduction in dose rate for each collimator helmet is called the output factor (OPF). Experimental determination of OPFs is diffi...

The EGS4 Monte Carlo simulation technique was used to obtain the energy spectra of photons arriving at a detector from the pulse height distributions measured by the same detector. First, the measured pulse height distribution for incident photons from several radiation sources such as 60Co, 137Cs, 152Eu and 207Bi with a collimator are compared with those calculated using the EGS4 code to inves...