INTRODUCTION Chemical shift-encoded techniques for quantitatively measuring the presence of fat have a number of important applications in MRI, including bone marrow, muscle, brain, liver and heart studies. However, inaccurate modeling of the acquired signal can result in significant bias in the estimates of fat amplitude or fat fraction. Specifically, modeling the T2* decay (or the decay rate ...

BACKGROUND Patient-specific dose verification for treatment planning in helical tomotherapy is routinely performed using a homogeneous virtual water cylindrical phantom of 30 cm diameter and 18 cm length (Cheese phantom). Because of this small length, treatment with total marrow irradiation (TMI) requires multiple deliveries of the dose verification procedures to cover a wide range of the targe...

Purpose: Fiber carbon is the most common material used in treating couch as it causes less beam attenuation than other materials. Beam attenuation replaces build-up region, reduces skin-sparing effect and causes target volume under dosage. In this study, we aimed to evaluate beam attenuation and variation of build-up region in 550 TxT radiotherapy couch.Materials and Methods: In this study, we ...

Relative absorbed dose energy response correction, R, for various radiochromic films in water phantom is calculated by the use of the Monte Carlo-based EGSnrc code system for high energy brachytherapy sources 60Co, 137Cs, 192Ir and 169Yb. The corrections are calculated along the transverse axis of the sources (1-15 cm). The radiochromic films investigated are EBT, EBT2 (lot 020609 and lot 03110...

State-of-the-art radiotherapy treatment planning systems provide reliable estimates of the therapeutic radiation but are known to underestimate or neglect the stray radiation exposures. Most commonly, stray radiation exposures are reconstructed using empirical formulas or lookup tables. The purpose of this study was to develop the basic physics of a model capable of calculating the total absorb...

Figure 3. Angular d-PFG experiments performed on a bi-compartmental phantom consisting of microcapillaries with inner diameter of 19 μm in the SDC and 20 μl of water in the FDC. The diffusion periods were sufficiently long to probe the boundaries. Symbols represent experimental data, while the solid lines represent the theoretical fitting to the experimental data. Accounting for free and restri...

Absorbed dose to water in a cobalt-60 gamma-ray beam has been determined using a thick-walled graphite ionization chamber. The chamber was calibrated in a graphite phantom against a graphite calorimeter, and the graphite calibration factor was converted to a water calibration factor using published energy absorption coefficient ratios and a measured replacement factor. Comparisons between the g...

The absolute permeability of porous media is an important parameter for various technological applications ranging from ground water hydrology to hydrocarbon recovery microfluidics. We investigate the max-flow min-cut theorem which states that maximum flow through any network exactly sum edge weights define minimum cut. hypothesize can be related a network. find correspondence between measured ...

At BNM-LNHB, the references in terms of absorbed dose to water are based on graphite calorimeter measurements. In the cobalt-60 beam, measurements were performed directly with the graphite calorimeter in a graphite phantom. Absorbed dose to water in a water phantom was then determined using a transfer method by means of relative measurements made with ionisation chambers and Fricke dosimeters. ...

The American Association of Physicists in Medicine (AAPM) presents a new protocol, developed by the Radiation Therapy Committee Task Group 61, for reference dosimetry of low- and medium-energy x rays for radiotherapy and radiobiology (40 kV < or = tube potential < or = 300 kV). It is based on ionization chambers calibrated in air in terms of air kerma. If the point of interest is at or close to...