INTERVIEW - PTW

INTERVIEW
Interview with the Winner of the PTW Dosimetry Award 2011,
Mr. Hui Khee Looe, M.Sc., Medical Radiation Physics,
Carl-von-Ossietzky University / Pius-Hospital Oldenburg, Germany
“Detector research takes us one step forward
towards improving accuracy in radiation therapy”
First of all, congratulations on the
PTW Dosimetry Award, Mr Looe!
In your award-winning paper, you present
the results of a comprehensive study which
you conducted to determine the effective
point of measurement of various detectors.
Can you briefly describe how you came to
undertake this particular study and what
you and your co-authors discovered?
What is the next step in this study?
We started this study as a contribution to a
German DIN standard, in which the concept
of the effective point of measurement is treated.
The general result of this study is the invariance,
for a given detector, of the shift of the effective
point of measurement in the presence of an
arbitrary dose gradient. This finding is
complemented with a theoretical explanation
derived from the fact that the displacement
effect is proportional to the gradient of the
fluence of the directly ionizing particles in the
spatial region of the surrounding medium
occupied by the detector.
Our results have also revealed the shortcomings
of the "water equivalent depth" formula for flat
ionization chambers given in the DIN standard.
Besides atomic interactions of the primary beam
in all layers of the entrance window, other
perturbation effects are playing a role in shifting
the effective point of measurement. For the
cylindrical chambers, the ratio of the shift of the
effective point of measurement to the radius
was observed to increase with the radius itself.
All measurements in this study were performed
in water equivalent material. There now remains
the interesting question whether the shift of the
effective point of measurement would remain
unchanged if the detector is embedded in a
medium with a density different to that of water.
Our next step is therefore to conduct measurements
in other mediums and extend the energy
range of the test radiations to lower energies,
such as those commonly used in brachytherapy.
Hui Khee Looe, M.Sc. (Picture: H. K. Looe)
Which applications and aspects of
clinical dosimetry are of special interest
to you? What research projects are you
currently involved with?
One of my research interests is the
understanding of the implications of radiation
transport effects and detector dimensions
on the accuracy in clinical radiation dosimetry.
Our group works on the characterization of
the response functions for single detectors.
Appropriate methods for correction are derived
based on these response functions to allow
for accurate characterization of beam profiles,
especially in small-field dosimetry.
State-of-the-art techniques in radiation therapy
often involve the use of highly modulated dose
distribution with steep gradients. The obtained
knowledge for single detectors is transferred
to two-dimensional detector arrays commonly
used for dosimetric plan verification.
We propose solutions based on physical and
mathematical models that can be used to
increase the resolution of these detector arrays
and to facilitate the accurate characterization
of complex dose distributions.
PTW-Freiburg • Lörracher Strasse 7 • 79115 Freiburg • Germany
Phone: +49 761 49055-0 • FAX: +49 761 49055-70 • info@ptw.de • www.ptw.de 1

INTERVIEW
What do you like about your daily work
as a medical physicist?
I like the wide range of responsibilities of a
medical physicist. Successful radiation therapy
is the result of multidisciplinary input, with the
medical physicists playing a significant role.
To be part of a competent team in the Clinic of
Radiation Therapy at Pius Hospital Oldenburg
is a very fulfilling experience for me.
I also appreciate the balance between the
clinical routine and my research work which
I think complement each other well. Clinical
experience exposes me to the important
aspects of dosimetry in need of improvement
which translate into research activities.
The outcome of my research will contribute to
improve the accuracy and reliability of clinical
practices. I am grateful to our medical director
Dipl. Phys. Dr. med. Kay C. Willborn for his
support towards my research and my mentors
Prof. Dr. Björn Poppe, Dr. Antje Rühmann and
Prof. em. Dr. Dietrich Harder for their guidance
and encouragement.
What prompted you to specialize in
medical physics quite early on in
your career?
While I was studying in Oldenburg, I had the
chance to work in the Clinic of Radiation
Therapy at Pius Hospital. My responsibilities
were to perform morning quality assurance of
the linear accelerators and to provide assistance
to the medical physicists in their daily clinical
work. I was lucky to be surrounded by very
competent medical physicists, from whom
I have learned a lot. At that time, I became
attracted by medical physics and decided to
specialize in this field during my studies.
After I had obtained my master’s degree,
I was given the opportunity to pursue my
doctorate degree at the Carl-von-Ossietzky
University and at the same time to perform
my clinical training at Pius Hospital. This was
how my career as a medical physicist began.
In 2000, you left Malaysia to study
physics at Oldenburg University.
Why did you come to Germany and
Oldenburg in particular?
To be honest, Germany was not my first choice
for my undergraduate studies. Coming to
Germany, however, especially to Oldenburg,
is a decision I will never regret. When I was
still at college in Malaysia, I came across
a newspaper article about the opportunities
of further education offered in Germany.
I gave it a try and sent my application to
numerous universities in Germany offering
physics degree programs, and the first reply
I received was from the university in Oldenburg.
Three months later, I landed in Frankfurt.
What did you miss most when you
came to Germany?
The only German words I knew when I arrived in
Germany were “Guten Tag” and “Danke” which
I learned from a travel book. It was a tough time
at the beginning and I missed my family very
much. I am thankful to my parents and my wife
for their unrelenting support and love, without
which I would not have achieved this far.
Mr. Looe, thank you for the interview and
much success with your future projects.
Personal
Hui Khee Looe,
originally from Malaysia,
came to Germany in
2000 to study physics
at Carl-von-Ossietzky
University in Oldenburg.
After receiving his B.E.
in Engineering Physics,
he continued to study for his master’s degree
which he completed in 2006.
As a research assistant, Hui Khee Looe
is a member of the medical radiation physics
research team headed by Professor
Björn Poppe at Oldenburg University and
works as a medical physicist at Pius Hospital
in Oldenburg. He is currently pursuing his
PhD studies on deconvolutions and resolution
corrections in clinical radiation dosimetry
aimed to improve the accuracy of radiation
therapy.
Contact:
Hui Khee Looe, M.Sc.,
Medical Radiation Physics,
Carl-von-Ossietzky University /
Pius Hospital Oldenburg, Germany,
hui.k.looe@uni-oldenburg.de
Media Contact at PTW
Ute Wüstefeld
Marketing Manager
PTW-Freiburg
+49 (0) 761 49055-591
ute.wuestefeld@ptw.de
PTW-Freiburg • Lörracher Strasse 7 • 79115 Freiburg • Germany
Phone: +49 761 49055-0 • FAX: +49 761 49055-70 • info@ptw.de • www.ptw.de 2