BACKGROUND This work explores how the choice of prescription isodose line (IDL) affects the dose gradient, target coverage, and treatment time for Gamma Knife radiosurgery when a smaller shot is encompassed within a larger shot at the same stereotactic coordinates (shot within shot technique). METHODS Beam profiles for the 4, 8, and 16 mm collimator settings were extracted from the treatment ...

Computer tomography has become a most important area in biomedical imaging system to reconstruct 3D image. Several exact CT reconstruction algorithms, such as the generalized filtered-back projection and back projection-filtration methods and fan beam reconstruction algorithm have been developed to solve the long object problem. Although the well-known 3D Shepp–Logan phantom is often used to va...

PURPOSE A novel end-to-end system using a CCD camera and a scintillator based phantom that is capable of measuring the beam-by-beam delivery accuracy of Robotic Radiosurgery has been developed and reported in our previous work. This work investigates its application to end-to-end type daily QA for Robotic Radiosurgery (Cyberknife) with Variable Aperture Collimator (Iris). METHODS The phantom ...

This paper explains in detail the solution to the forward and inverse problem faced in this research. In the forward problem section, the projection geometry and the sensor modelling are discussed. The dimensions, distributions and arrangements of the optical fibre sensors are determined based on the real hardware constructed and these are explained in the projection geometry section. The gener...

A bowtie is a filter used to shape an x-ray beam and equalize its flux reaching different detector channels. For development of spectral CT with energy discriminating photon-counting (EDPC) detectors, here we propose and evaluate a dynamic bowtie for performance optimization based on a patient model or a scout scan. With a mechanical rotation of a dynamic bowtie and an adaptive adjustment of an...

BACKGROUND Pencil beam dual energy x ray absorptiometry (DXA) has been shown to provide valid estimates of body fat (%BF), but DXA fan beam technology has not been adequately tested to determine its validity. OBJECTIVE To compare %BF estimated from fan beam DXA with %BF determined using two and three compartment (2C, 3C) models. METHODS Men (n = 25) and women (n = 31), aged 18-41 years, par...

A model for beam customization with collimators and a range-compensating filter based on the phase-space theory for beam transport is presented for dose distribution calculation in the treatment planning of radiotherapy with protons and heavier ions. Independent handling of pencil beams in conventional pencil-beam algorithms causes unphysical collimator-height dependence in the middle of large ...

This article compares two algorithms for determining beam weights and wedge filters for conformal treatment planning. One algorithm, which is based on dose-gradient analysis, provides analytic formulas for determining beam weights, wedge angles, and collimator angles (i.e., wedge orientations) so that the dose distribution is homogeneous in the target volume. The second algorithm is based on th...

Piezoelectric fans are thin elastic beams whose vibratory motion is actuated by means of a piezoelectric material bonded to the beam. These fans have found use as a means to enhance convective heat transfer while requiring only small amounts of power. The objective of the present work is to quantify the influence of each operational parameter and its relative impact on thermal performance. Of p...

Statistical methods for tomographic image reconstruction have shown considerable potential for improving image quality in X-ray CT. Penalized-likelihood (PL) image reconstruction methods require maximizing an objective function that is based on the log-likelihood of the sinogram measurements and on a roughness penalty function to control noise. In transmission tomography, PL methods (and MAP me...