| Divya
Dinish | CT
Image Reconstruction and Microbeam Radiation Therapy Dose Distribution Calculations
at Brookhaven National Laboratory.
Divya
Dinesh, Stony Brook University; Renat Yakupov, Tigran Bacarian, and F. Avraham
Dilmanian, Medical Department, Brookhaven National Laboratory, Upton, New York
The first part of this project was within the ongoing research program at Brookhaven
National Laboratory (BNL) known as Microbeam Radiation Therapy (MRT). MRT is an
innovative experimental technique that uses arrays of parallel, thin (<100
µm wide) planes of synchrotron-generated x-ray beams to treat tumors. It
has been shown at the National Synchrotron Light Source (NSLS), where the method
was initiated in the 1990s, and at the European Synchrotron Radiation Facility
(ESRF), Grenoble, France, that these microbeam arrays spare the normal tissue
at doses ten times larger than those tolerated by conventional, unsegmented beams.
It has also been shown that microbeams can kill malignant tumors by irradiation
from a single direction, and a single exposure session. In choosing the MRT irradiation
parameters, one should assure that the dose leakage between the individual microbeams
(called the "valley" dose, caused by photon scattering, as well as the
finite range of electrons on tissue) is adequately low to allow survival of the
supportive cells between the beams. For this, Monte Carlo simulations are necessary
to calculate the dose distribution in the tissue in a spatial resolution of a
few µms. My first assignment was to develop a user interface for the EGS4
code (a general purpose package for the Monte Carlo simulations of coupled transport
of electrons and photons in arbitrary geometries). For that, I had to learn the
programming languages FORTRAN and MORTRAN. The User Code written in MORTRAN currently
runs on the BNL's SUN2 mainframe using UNIX operating system. The code includes
the beam-target geometries, beam energy spectrum and beam polarization, as well
as the EGS4 variables. I then installed the subroutines LSCAT (handling low-energy
photon scattering), and PRESTA (handling short-step electron stopping). My results
showed that the valley dose from a 4 cm x 4 cm array of microbeams made of 90
µm beam width, 400 µm beam spacing, 90% linear polarization perpendicular
to the planes of the microbeams, and 120 keV median beam energy, in the center
of a soft-tissue cylindrical phantom of 16 cm diameter and 16 cm length (where
the beam impinged perpendicularly in the center of one of the two cylinder's face)
was 9.8% of the peak dose. My second assignment was related to x-ray imaging.
It required mastering a software package written in C by Tigran Bacarian at BNL
for computed tomography (CT) image simulation and reconstruction, and applying
it to new studies. I was required to evaluate image contrast to noise ratio (CNR)
in phantoms containing different contrast agents imaged with x-ray beams of different
energy spectra. I ran the code for an Acrylic, "cylindrical" phantoms
(with round or elliptical cross section), with axial channels filled with different
concentrations of iodine and gadolinium as contrast agents. It uses different
simulated beam spectra, produced analytically with normal noise added to them,
to generate simulated CT projection. The projections were then combined into a
sinogram, which was reconstructed using a Filtered Back Projection algorithm.
The package included a routine for beam-hardening correction, and used different
reconstruction filters to adjust image noise versus the spatial resolution. Using
the image processing tools of IDL (Interactive Data Language) I was able to calculate
the CNR. The CNR values for 2 mg Gd/ml and 2 mg I/ml contrast agent concentrations,
a 100 kVp energy spectrum filtered with 1.2 mm Al, and a 0.03Gy surface dose,
were 5.5 and 3.0, respectively. In addition to the above work, I also participated
in experiments at the NSLS to study the microbeam effects on the normal and cancerous
rats brain tissues. During the course of this fellowship, I got the opportunity
to attend the BNL-IBM blue gene science workshop held on July 31st and August
1st, 2003 at BNL. This research opportunity was supported by theWISE-Battelle
summer Fellowship.
|
| Alicia
Handy | Closing
the Water Budget of a Small Watershed: The Department of Energy Pilot Study.
Alicia
Handy, Stony Brook University; Mark Miller (Advisor), Mary Jane Bartholomew
(Co-Advisor), Earth Systems Sciences Division, Brookhaven National Laboratory.
Understanding the impacts
of precipitation and evaporation on surface water runoff and ground water is essential
in determining the water supply of an area. For this study, these measurements
were taken at the White Water River Watershed, which is a part of the Walnut River
Water Basin. The basin is located in the southern section of Kansas and is a small
part of the Atmospheric Radiation Measurement (ARM) Program's Southern Great Plains
Site. This study focuses on data taken from March 2000. Daily evaporation rates
were calculated based on the latent heat flux obtained from the ARM data archive.
From there, the evaporation rates were compared to the average daily precipitation
rates for that area (426 square miles). The total atmospheric contribution of
water was determined based on the difference between the precipitation and evaporation
values. This value was then compared to stream flow data for March 2000. There
was a correlation between the amount of precipitation received at the site and
the volume of water flowing through the site. Flow increased approximately one
day after significant rainfall had occurred. Because of the importance of ground
water in Kansas, an estimate of the recharge rate was determined based on the
difference between total atmospheric input and stream flow. The recharge rate
also showed a correlation between water input and output. The purpose of this
study is to enable us to get a better understanding of the water budget in order
to be able to forecast and predict potential water supply issues on local, regional,
and global scales. This work was supported by the WISE-Battelle Fellowship.
|
| Michael
Michaelides | The
Role of Dopamine D2 Receptors (DRD2) in Obesity: A microPET Model
Michael
Michaelides, Stony Brook University; and Peter Thanos, Medical Department,
Brookhaven National Laboratory. The
mechanism(s) underlying obesity is not well understood. The dopamine neurotransmitter
is among the possible factors that are involved. Here we used Zucker rats, which
have a leptin deficiency that make them more prone to becoming obese. There are
two types of Zucker rats: lean (Le) and obese (Ob). The present study consisted
of 4 groups: 1) Obese (Ob)- previously unrestricted diet (PUD), 2) Ob - previously
restricted (20g/day) diet (PRD), 3) Lean (Le) - PUD, 4) Le- PRD. The rats were
scanned in a mPET R4 scanner at 8, 18 and 52 weeks. At 18 weeks, the environmental
conditions were altered, and the rats that were previously on a restricted diet
were then on an unrestricted one and vice versa. What the study was primarily
focused on were the effects of aging and environmental conditions (food intake)
on the levels of DRD2 receptors in both Obese and Lease rats. The tracer used
for the mPET imaging was [c-11] raclopride. The scans were then analyzed using
the PMOD (Pixelwise Modeling) software. This was done by ROI designation as well
as MRI/PET coregistration combined with ROI designation. Data analysis (t-tests,
ANOVA's) were carried out and showed a significant difference (P<0.001) in
DRD2 receptors between Ob PUD and Le PUD groups at 8, 18, and 52 weeks. There
was also a significant difference (P<0.001) in Le PUD and Le-PRD rats at 18
and 52 weeks. As well, there was a significant difference (P<0.001) between
Ob PRD and Le PUD, and between Ob PUD and Le PRD, both at 18 weeks. There was
no significant difference between these four latter groups at 52 weeks. This work
was supported with funding from Battelle. |
| Kimberly
Odynocki | Effect
of Ether Substitutions on Properties of Ionic Liquids.
Kimberly
Odynocki, Stony Brook University; Alison Funston and James Wishart, Chemistry
Department, Brookhaven National Laboratory.
The purpose of this
project was to synthesize new ionic liquids with different anions or ether groups,
and to characterize the effects of the modifications on the properties of the
liquids. Ionic liquids are salts that have low melting points (below 100ºC)
and no vapor pressure, which prevents them from evaporating. The reason ionic
liquids are being so widely studied is because they would be safer, more environmentally
friendly solvents for reactions than the volatile organic solvents used today.
However, some ionic liquids are too viscous to be used effectively in industry,
which is why ether substitutions were studied. It had been observed anecdotally
that ether substitutions can lower the viscosity and melting point of an ionic
liquid without significantly changing other properties, and this project was designed
to quantify this effect. Five ionic liquids were synthesized, namely:
(1) Tributyl(methoxyethyl)ammonium
bromide (Bu3(MeOEt)N+Br-)
(2) Tributyl(methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide
(Bu3(MeOEt)N+NTf2-)
(3) Tetrabutylammonium bis(trifluoromethylsulfonyl)imide
(Bu4N+NTf2-)
(4) Trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide
(Hx3TdP+NTf2-)
(5) Methyltributylammonium dicyanoamide. (MeBu3N+N(CN)2-)
To
synthesize an ionic liquid, the reactants (tertiary amines and alkyl halides)
were refluxed in ethyl acetate under a blanket of nitrogen gas at elevated temperature
for a given length of time. Metathesis reactions were generally done by mixing
aqueous solutions of the cation halide and the alkali metal salt of the desired
anion to produce a separate ionic liquid phase which was then purified. For the
Bu3(MeOEt)N+Br- synthesis, it was found that refluxing the reaction at high temperature
(76 ºC) for four days resulted in a product that was darker, but easier to
clean and higher in yield than the same reaction run at 47 ºC for two weeks.
After synthesizing new ionic liquids, it became clear that addition of an ether
group results in ionic liquids with lower melting points and lower viscosities.
This can be seen by comparing Bu3(MeOEt)N+NTf2- with Bu4N+NTf2-. Having an ether
group on the cation instead of a butyl group decreases the melting point about
45 ºC (see chart). Replacing the bromide anion with the NTf2- anion also
showed a significant decrease in melting point and viscosity. An example of this
would be Bu3(MeOEt)N+Br-, whose melting point drops about 15 ºC by exchanging
the Br- anion for an NTf2-. One exciting finding is that while Bu3(MeOEt)N+NTf2-
is solid at room temperature, it has a very low viscosity once it is melted. This
could be beneficial to industry because it can be easily transported as a solid,
used as a solvent when melted with a small amount of heat, and then recrystalized
again for storage. This project was funded by the Battelle Summer Research Fellowship
Program.
|
