Dose distributions can often be significantly improved by modulating the two-dimensional intensity profile of the individual x-ray beams. One technique for delivering intensity modulated beams is dynamic multileaf collimation (DMLC). However, DMLC is complex and requires extensive quality assurance. In this paper a new method is presented for a pretreatment dosimetric verification of these inte...

BACKGROUND In radiotherapy treatments, it is crucial to monitor the performance of linac components including gantry, collimation system, and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method is suggested in conjunction with an algorithm to investigate the stability of these systems at various gantry angles with the aim of evalu...

In-vivo dosimetry techniques are currently being applied only by a few Centers because they require time-consuming implementation measurements, and workload for detector positioning and data analysis. The transit in-vivo dosimetry performed by the electronic portal imaging device (EPID) avoids the problem of solid-state detector positioning on the patient. Moreover, the dosimetric characterizat...

PURPOSE To perform a quantitative study to verify that the mechanical field center coincides with the radiation field center when both are off from the isocenter during the single-isocenter technique in linear accelerator-based SRS/SBRT procedure to treat multiple lesions. METHODS We developed an innovative method to measure this accuracy, called the off-isocenter Winston-Lutz test, and here ...

AIMS This study investigates the impact of cine acquisition mode on the dosimetric characteristics of a Varian aS500 amorphous silicon electronic portal imaging device (a-Si EPID). MATERIALS AND METHODS The performance of an a-Si EPID operated in cine mode was assessed and compared to its performance when operated in an integrated mode and dose measurements using an ionization chamber. This s...

PURPOSE To investigate the feasibility of fully automated detection of fiducial markers implanted into the prostate using portal images acquired with an electronic portal imaging device. METHODS AND MATERIALS We have made a direct comparison of 4 different methods (2 template matching-based methods, a method incorporating attenuation and constellation analyses and a cross correlation method) ...

PURPOSE To evaluate three different percutaneous portosystemic shunts created with magnetic resonance (MR) imaging and fluoroscopy guidance in a swine model. MATERIALS AND METHODS In stage 1 of the experiment, an active MR intravascular needle system was created for needle tracking and extracaval punctures. Twenty inferior vena cava (IVC)/superior mesenteric vein (SMV)/portal vein (PV) punctu...

PURPOSE We summarize our experience with a series of morbidly obese men treated using daily online portal imaging and implanted gold markers to guide external beam radiation therapy (EBRT). METHODS AND MATERIALS Three consecutive morbidly obese men were treated with EBRT for localized prostate cancer. Daily electronic portal imaging was used to verify patient position. The magnitude and direc...