On dosimetric characteristics of detectors for relative dosimetry in small fields: a multicenter experimental study.

. In this multicentric collaborative study, we aimed to verify whether the selected radiation detectors satisfy the requirements of TRS-483 Code of Practice for relative small field dosimetry in megavoltage photon beams used in radiotherapy, by investigating four dosimetric characteristics. Furthermore, we intended to analyze and complement the recommendations given in TRS-483.

Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for Pancreatic and Other Intra-Abdominal Cancers.

A 1.5T MRI combined with a linear accelerator (Unity, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer's pre-set MRI sequences (i.

A detailed process map for clinical workflow of a new biology-guided radiotherapy (BgRT) machine.

Purpose: Biology-guided radiotherapy (BgRT) is a new external beam radiation therapy modality combining PET-CT with a linear accelerator that has the potential to track and treat one or more tumors in real-time. The use of PET and radiopharmaceutical tracers introduces new processes that are different from the existing treatment processes. In this study, we have developed a process map for the clinical implementation of a prototype BgRT machine.

Application of TG-100 risk analysis methods to the acceptance testing and commissioning process of a Halcyon linear accelerator.

Purpose: A new type of linear accelerator (linac) was recently introduced into the market by a major manufacturer. Our institution is one of the early users of this preassembled and preconfigured dual-layer multileaf collimator (MLC), ring-gantry linac - Halcyon™ (1st version). We performed a set of full acceptance testing and commissioning (ATC) measurements for three Halcyon machines and compared the measured data with the standard beam model provided by the manufacturer.

A dosimetric evaluation of the IAEA-AAPM TRS483 code of practice for dosimetry of small static fields used in conventional linac beams and comparison with IAEA TRS-398, AAPM TG51, and TG51 Addendum protocols.

Purpose: The International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) have jointly published a new code of practice (CoP), TRS483, for the dosimetry of small static photon fields used in external beam radiotherapy. It gave recommendations on how to perform reference dosimetry in nonstandard machine-specific reference (msr) fields and measure field output factors in small fields. The purpose of this work was to perform a dosimetric evaluation of the recommendations given in this CoP.

Comparison of the recommendations of the AAPM TG-51 and TG-51 addendum reference dosimetry protocols.

This work quantified differences between recommendations of the TG-51 and TG-51 addendum reference dosimetry protocols. Reference dosimetry was performed for flattened photon beams with nominal energies of 6, 10, 15, and 23 MV, as well as flattening-filter free (FFF) beam energies of 6 and 10 MV, following the recommendations of both the TG-51 and TG-51 addendum protocols using both a Farmer ionization chamber and a scanning ionization chamber with calibration coefficients traceable to absorbed dose-to-water (D ) standards. Differences in D determined by the two protocols were 0.

Electromechanical and structural alterations in the aging rabbit heart and aorta.

Aging increases the risk for arrhythmias and sudden cardiac death (SCD). We aimed at elucidating aging-related electrical, functional, and structural changes in the heart and vasculature that account for this heightened arrhythmogenic risk. Young (5-9 mo) and old (3.

ATLAS CONSTRUCTION FROM HIGH ANGULAR RESOLUTION DIFFUSION IMAGING DATA REPRESENTED BY GAUSSIAN MIXTURE FIELDS.

Groupwise image registration is an essential part of atlas construction which is a very import and challenging task in medical image analysis. In this paper, we present a novel atlas construction technique using a groupwise registration of high angular resolution diffusion (MR) imaging datasets each of which is represented by a Gaussian Mixture field. To solve the registration problem, an L(2) distance is used to measure the similarity between two Gaussian Mixtures, which leads to an energy function whose gradient can be computed in closed form.

Regularized positive-definite fourth order tensor field estimation from DW-MRI.

In Diffusion Weighted Magnetic Resonance Image (DW-MRI) processing, a 2nd order tensor has been commonly used to approximate the diffusivity function at each lattice point of the DW-MRI data. From this tensor approximation, one can compute useful scalar quantities (e.g.