B.S. in Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Dec. 1990, GPA 3.6/4.0 (Note: Additional Major in Physics completed concurrently with this degree)

Work Experience:

Associate Scientist, Dept. of Medical Physics, University of Wisconsin, Madison, WI, Jan. 2003-Present

Assistant Scientist, Dept. of Medical Physics, University of Wisconsin, Madison, WI, Sept. 1999-Dec. 2002.

Design improved atmospheric well-type ionization chamber for low energy photon brachytherapy sources

Investigated dosimetry for catheter based x-ray source using Monte Carlo transport methods

Model and investigate the response of pressurized and atmospheric for photon and beta sources

Model and generate TG-43 dosimetry parameters for a Cs brachytherapy tube source using Monte Carlo transport methods

Model, implement variance reduction, and investigate shield for 24 MV clinical linac using Monte Carlo methods

Investigated using Monte Carlo methods

Investigated low energy and its impact on Monte Carlo based dosimetry

Model, investigate, and assist in design of (WAFAC) for brachytherapy seed calibration using Monte Carlo methods

Model and investigate ferroelectric detector for mammography using Monte Carlo methods

Model and investigate a beta shield for air kerma strength measurements of a mixed photon/beta brachytherapy source

Develop and write research grant applications (including NIH and DOE)

Represent the Medical School for Grid Laboratory of Wisconsin (396 node cluster of clusters)

Design, assemble, and perform site specific maintenance on (66 nodes)

Designed, built, and maintained a 24

node parallel computer

Assist and guide graduate students with Monte Carlo transport and high performance computing research activities

Teach aspects of Monte Carlo methods for Department of Medical Physics/NEEP classes (NEEP 602MC, MP 569)

Substitute teach Health Physics Labs (MP 569)

of intravascular brachytherapy sources using Monte Carlo transport methods and radiochromic film

of radiochromic film using Monte Carlo transport methods

fast neutron

beamlines for radiotherapy treatment planning software

Assisted with system administration of

UNIX, PC, network hardware, and department web server

Post Doctoral Research Associate, Dept. of Medical Physics, University of Wisconsin, Madison, WI, Aug. 1996-Aug. 1999.

Designed, built, and maintained a 24

node parallel computer

of intravascular brachytherapy sources using Monte Carlo methods

of intravascular brachytherapy sources using radiochromic film

fast neutron

beams for radiotherapy treatment planning software

Assisted with Monte Carlo lectures for Department of Medical Physics/NEEP classes

Assisted with neutron time-of-flight measurements at tandem accelerator facility

Assisted with system administration of UNIX, PC, network hardware, and department web server

Research Assistant, Dept. of Nuclear Engineering, University of Wisconsin, Madison, WI, Jan. 1991 - Aug. 1996

Developed mesh methods for neutron transport

Developed for managing neutron transport calculations for reactor vessels

Performed a sensitivity for reactor vessel neutron flux calculations

Investigated and performed dose calculations for

in-vessel flux dosimetry capsules

Investigated power plant life extension and reactor vessel embrittlement issues

Engineering Assistant, JI Case Research and Development, Wausau, WI, Summer 1989

Assisted in set-up and execution of coolant systems test for large earth-movers

Maintained test equipment including flow meters, thermocouples, and pressure transducers

Upgraded data acquisition and analysis codes for coolant tests

Assisted in diesel engine battery testing

Refereed Journal Publications:

T.D. Bohm, S.L. Griffin, P.M. DeLuca Jr., and L.A. DeWerd, The effect of ambient pressure on well chamber response:Monte Carlo calculated results for the HDR 1000 Plus, accepted Medical Physics, Jan, 2005.

S.L. Griffin, L.A. DeWerd, J.A. Micka, and T.D. Bohm The effect of ambient pressure on well chamber response:Experimental results with empirical correction factors, accepted Medical Physics, Jan, 2005.

W.S. Culberson, L.A. DeWerd, B.R. Thomadsen, J.A. Micka, and T.D. Bohm, Calibration of the photon component of 198-Au stents, Brachytherapy, Vol. 4, pg 51-58, 2005.

T.D. Bohm, P.M. DeLuca Jr., L.A. DeWerd, Brachytherapy dosimetry of 125I and 103Pd sources using an updated cross section library for the MCNP Monte Carlo transport code, Medical Physics, Vol. 30 number 4, April, 2003.

T.D. Bohm, F.A. Mourtada, R.K. Das, Dose Rate Table for a Guidant P-32 Intravascular Brachytherapy Source from Monte Carlo Calculations, Medical Physics, Vol. 28 number 8, August, 2001.

T.D. Bohm, D. W. Pearson, R.K. Das, Measurements and Monte Carlo Calculations to Determine the Absolute Detector Response of Radiochromic Film for Brachytherapy Dosimetry, Medical Physics, Vol. 28 number 2, February, 2001.

T.D. Bohm, P.M. DeLuca Jr., R.L. Maughan,

D.T.L. Jones, Arlene Lennox, Monte Carlo Calculations to Characterize the

Source for Neutron Therapy Facilities, Medical Physics, Vol. 26 number 5, May, 1999.

Conference Proceedings Publications:

M. A. Avila-Rodriguez, P.M. DeLuca Jr.,T.D. Bohm, Simulation of Medical Electron Linac Bremsstrahlung Beam Transport in Typical Shielding Materials, 10th International Conference on Radiation Shielding (ICRS-10)/13th American Nuclear Society Radiation Protection and Shielding

Division (RPSD 2004) Conference, Madeira, Portugal, May 9-14, 2004. (presented by Avila-Rodriguez)

T.D. Bohm, P.M. DeLuca Jr., L.A. DeWerd, Dosimetry of permanent prostate implants using Monte Carlo calculations, American Nuclear Society Radiation Protection and Shielding

Division (RPSD) Conference, Sante Fe, New Mexico, April 14-17, 2002. (presented by Bohm)

L.J. Cox, T.D. Bohm, M.B. Chadwick, P.M. DeLuca

Jr., J.V. Siebers, PEREGRINE Monte Carlo Dose Calculations for Radiotherapy using Clinically Realistic Neutron and Proton Beams, Proceedings International Conference on Nuclear Data for Science and Technology, Trieste, Italy, May 19-24, 1997. (presented by Cox)

Invited Conference Talks:

Monte Carlo Transport for Fast Neutron Therapy, International Workshop on Clinical High-energy Neutron Dosimetry, Batavia, IL, April 15-17, 2004.

Conference Sessions Chaired:

Advances in Diagnostic and Therapeutic Radiation Medicine, American Nuclear Society Radiation Protection and Shielding

Division (RPSD) Conference, Sante Fe, New Mexico, April 14-17, 2002.

Grants Awarded:

Industrial and Economic Development Research (I&EDR) Program

2004 ``Development of an Improved Radiation Calibration Chamber for

Radiation Therapy'' Tim Bohm-Principal Investigator, $28,772.

Academic Staff Professional Development Grant (travel grant) ``Monte Carlo

Radiation Transport Conference and Training'', April 2005, $736

Journal Articles Refereed:

Medical Physics-5 articlesInternational Journal of Radiation Oncology Biology Physics-1 article

Computer Skills:

Substantial experience with MCNP/MCNPX, EGSnrc, LAHET, and DORT/TORT Radiation Transport Codes (including patching MCNP and its cross section libraries as needed)

Extensive experience in parallel computer cluster design and administration

Substantial programming experience in FORTRAN

Significant experience running PVM and MPI based codes as well as programming with MPI

Significant experience with Perl and Bash scripting languages

Significant experience in UNIX/Linux system

administration

Familiar with C++ computer language

Proficient in UNIX, Windows, and Macintosh environments

Familiar with HTML language and design of World Wide Web pages

Proficient in document preparation software on UNIX, Windows, and MacsActivities:

Member American Nuclear Society

Webmaster for UW Women's Club Hockey Team

Introductory Physics Tutor (Greater University Tutoring Service-GUTS)

Student Awards & Honors:

UW-Madison Undergraduate Engineering Merit Award

Institute of Nuclear Power Operator's Undergraduate Scholarship

Institute of Nuclear Power Operator's Graduate Fellowship

Research SummariesLow energy photon dosimetry and cross section data

Permanent implantation of low energy (20-40 keV) photon emitting radioactive

seeds to treat prostate cancer is rapidly becoming the treatment of

choice for patients due to reduced complications compared to other

treatment modalities. The many existing as well as newly proposed complex

radioactive seed designs are difficult to fully characterize and calibrate

experimentally. Monte Carlo based transport calculations can provide

substantial insight into the problem of characterizing these sources.

Work is being done to improve the data libraries used by the Monte Carlo

transport codes. This new data will then be used to fully characterize

the many source designs as well as calibration equipment necessary for patient

treatment planning. This new data will also be useful for modeling

mammography and diagnostic x-ray systems.

Well Chambers

Treatment planning for permanent implant brachytherapy requires accurate

knowledge of the radioactive seeds' air kerma strength. Calibrated Well

chambers are used to determine the air kerma strength of seeds on-site at

clinics. Accurate calibration of these Well chambers can be difficult

due to varying chamber designs and operation conditions.

Work is being done to model several chambers and to discover how each design

affects the response of the chamber. Work is also being done to discover

the cause of unexpected chamber responses that may be encountered with some

chamber designs. An improved chamber design is being developed to overcome

the unexpected chamber response.

Wide Angle Free Air Chamber

Treatment planning for permanent implant brachytherapy requires accurate

knowledge of the radioactive seeds' air kerma strength. The primary standard

air kerma strength measurement of a given seed is determined using a Wide

Angle Free Air Chamber (WAFAC) at the National Institute of Standards and

Technology (NIST).

Work is being done to model the NIST WAFAC to understand some of the phenomena

seen in calibrating various seed designs. Monte Carlo modeling is also being

done to design a WAFAC for use here at the UWRCL.

Intravascular Brachytherapy and Radiochromic Film

Several brachytherapy sources

are being proposed for use in intravascular irradiation

to prevent restenosis following coronary angioplasty . The most

commonly proposed sources are P-32 and Sr-90 beta sources and an

Ir-192 photon source. Determination

of the dosimetry for this type of treatment is very difficult due to

the small sizes and very close distances involved (1-2 mm) in the

treatment region. Monte Carlo calculations can be used to estimate

the dose to regions surrounding these brachytherapy sources.

Radiochromic film can be used to measure the dose and verify the Monte Carlo

calculations. Monte Carlo calculations of radiochromic film response are being combined

with film measurements to reduce the overall uncertainty of the dose

delivered by these sources. As part of this investigation, Monte

Carlo calculations and radiochromic film measurements are being

performed using ortho-voltage through mega-voltage photon machines as well as P-32

brachytherapy sources.

Fast Neutron Beam Characterization

Monte Carlo radiation

treatment planning codes can provide a more accurate model of

particle transport and dose distributions resulting in better patient

treatment than existing methods. In order to achieve an accurate

result with the Monte Carlo planning codes, the radiation source must

be characterized accurately.

Fast neutron therapy sources are often produced by bombarding a Be target using

protons or deuterons with an energy near 50 MeV and then shaping the resulting

neutron beam with various filters and collimators. The particle

transport codes LAHET and MCNP along with extended evaluated nuclear

data were used to model the incident beam and

target, as well as the neutron beam and collimators for three neutron

therapy facilities. The results of these calculational models were

compared to measurements and previous calculations of the neutron

phase space. These calculational models of the neutron phase space

at a position before any patient dependent beam modifiers are being

used to develop a source for the PEREGRINE all-particle Monte Carlo

treatment planning code.

Thesis Research

Determining the neutron exposure

to the reactor vessel in a pressurized water reactor is important in

determining the embrittlement of the vessel materials. The degree of

vessel embrittlement influences the operating conditions of the reactor

and any possibilities of life extension for the nuclear power plant.

The standard method used to calculate neutron exposure to the vessel

uses a type of diamond difference method to solve the discrete

ordinates form of the neutron transport equation. This method is

computationally simple but requires small mesh sizes to achieve good

accuracy. Linear-linear and constant-linear nodal discrete ordinates

methods have been developed that can use larger mesh sizes and still

achieve accurate results. A quadratic-linear nodal discrete ordinates

method for x-y geometry was developed to make comparisons to existing

methods. These three nodal methods were implemented and compared to a

production code's diamond difference type scheme while solving three

test problems in x-y geometry.

Nuclear Engineering

In pressurized water reactors,

neutron irradiation embrittlement of the reactor vessel has been

identified as the most critical issue in terms of aging of the

power plant's components. Neutron fluence and iron displacements per

atom (DPA) can be used to estimate the embrittlement of the vessel. A two

dimensional (R-Theta) model of the reactor was developed using the

DORT discrete ordinates code. A supplementary code package was also

developed that

allows a user to input the pin by pin power and burn-up files for a

given fuel cycle and then creates the DORT input file. Following the

transport calculation, the code package retrieves neutron flux and DPA

profiles for

both the vessel and surveillance capsules. The code package was

developed for an electric utility to allow them to make routine vessel

fluence calculations. In developing the

calculational model, a sensitivity study was carried out to identify

parameters that are important in calculating the vessel flux. Some of

these parameters included the power of the inner fuel bundles, the

fission spectrum, the cross section library, and

the effect of Hafnium fuel assemblies. The results of the

calculational model were compared to previous calculations and

surveillance capsule measurements.

Email: Tim Bohm/

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