Biophysics Honours Projects 2003

School of Physics, UWA


Magnetotactic Bacteria

Supervisors: Ralph James and Tim St Pierre

Several species of bacteria are found to contain small quantities of ferrimagnetic material that render the bacterium permanently magnetic. As such ,these motile bacteria act as swimming compass needles. They tend to swim along the geomagnetic field lines in approximately straight paths. We have recently found several species living in local rivers, ponds, and lakes. Each species seems to move in a characteristic fashion when viewed under a microscope. This project aims to gain a greater understanding of the physics of the magnetoreception of these organisms through the use of video monitoring of bacterial motion under varying magnetic field conditions, transmission electron microscopy of the magnetic particles within the cells, and computer simulation of bacterial motion.


Magnetic Properties of Pathological Iron Deposits in Mammalian Tissue

Supervisor: Tim St Pierre

Iron overload diseases are very common around the globe. These diseases cause iron to be deposited within tissues in the form of nanoparticles of rust. These particles have the ability to catalyse cell-damaging reactions and hence there is great interest in their chemical and physical properties. This project will employ magnetic measurement techniques to obtain information about the structure of the iron oxide nanoparticles within rat spleen tissue. Highly sensitive superconducting quantum interference device magnetometry methods will be used to measure the magnetic energy barrier distributions within spleen tissue in order to obtain information about the particle sizes and surface properties of the iron oxide nanoparticles.


Bioacoustics and Musical Perception

Supervisor: Ralph James

 

Recent decades have seen great advances in our understanding of human audition. When presented with two pure tones of close but distinct frequencies, we perceive the sound as either a single pitch with amplitude variation (beats) or as two tones forming a musical interval. This project will investigate the link between this audition process and what is called the 'critical band' in cochlear response. The ultimate goal of the project is to begin to explain some of the subjective aspects of music such as choice of scale, mode, the relationship of major and minor chords and the correspondance of rythm and harmony.


Department of Medical Physics, Royal Perth Hospital


A Novel Diagnostic Tool for Malaria

Supervisor: Sean Geoghegan

Malaria is a serious global health problem affecting a large portion of the world's population and to which many international travellers are exposed. The World Health Organisation (WHO) estimates that malaria causes over two million deaths (mainly due to falciparum malaria) and more than 300 million clinical cases annually. WHO declared Australia malaria free in 1981, however our proximity to Asia, climatic factors, and international travel mean that many Australians, particularly in northern Australia, are still at risk.

A rapid and accurate diagnosis of malaria is potentially life saving. The standard technique used for diagnosis is a blood smear. This procedure needs to be performed by a highly trained microscopist who can recognise the various species and stages of the malaria parasite. Recently we have found a potentially valuable property of the malaria parasite that may lead to the development of a novel technique that distinguishes between parasitised and unparasitised blood as well as differentiating between the different species of the parasite. Most excitingly, we believe that this technique may also distinguish between the various isolates of each species that would make it possible to identify drug resistant infections. This would lead to more suitable clinical treatments being given.

This project would require the student to spend a significant amount of time working at Fremantle Hospital to grow malaria cultures. A motivated and independent person is required for this project.


Simulating Radiation Transport for Stents

Supervisors: Sean Geoghegan and Richard Fox

Since the discovery of radium, radioactive substances have been used in the treatment of various diseases. The techniques used to treat health threatening conditions using radiation have been developed over the years into the practice of radiotherapy. The most common disease treated using radiotherapy is cancer, however new applications of ionising radiation are currently being investigated around the world.

At Royal Perth Hospital, clinical trials are underway to investigate the effect of the irradiation of arteries to prevent or reduce narrowing of the arteries (restenosis) following balloon angioplasty. Restenosis is a serious problem for the patient and we have found that appropriate doses of ionising radiation will prevent it. One method that we are investigating to deliver therapeutic doses of ionising radiation is the use of stents plated with a gamma emitting radionuclide. The dose received by the patient at the artery wall and within healthy tissue needs to be accurately known so that a relationship between the dose delivered and the clinical effects can be determined.

In this project the Monte Carlo method will be used to determine the dose delivered to tissue by irradiation by a stent coated by a gamma emitting radionuclide. This project involves the use of the EGSnrc Monte Carlo code system, the analysis of the produced Monte Carlo data and participation in the development of recommendations for the safe clinical use of irradiated stents.


 

Medical Technology & Physics, Sir Charles Gairdner Hospital


Radioisotope Production in a Medical Cyclotron

Supervisor: A/Prof Roger Price

 

Background

In early 2003 an 18MeV (medium energy), proton/deuteron, multi-target Medical Cyclotron and a supporting Current Good Manufacturing Practice (cGMP)-level radiopharmaceutical production laboratory will be commissioned at Sir Charles Gairdner Hospital (SCGH), in the Department of Medical Technology & Physics. The Cyclotron and Lab form the RAdiopharmaceutical ProductIon and Development (RAPID) division of the WA Clinical PET Centre, and will be a world-class facility. Though primarily for production of "conventional" liquid- and gaseous-target Positron Emission Tomography (PET) isotopes [1, 2] (eg 18-F) , and their applications to the labeling of bio-active molecules (eg 18-FDG [3]), RAPID will offer exciting research opportunities, including in the development of solid targetry suitable for production of more esoteric isotopes. Solid targetry is emerging as a "sunrise" topic, given the general shift away from production of certain isotopes such as 123-I and 64-Cu by large production cyclotrons (>30 MeV proton primary energy) towards using medium-energy machines (<18 MeV), often located in major teaching hospitals. Successful developments in this area could have important commercial implications.

 

The Project-

This project is a feasibility study of the production of 123-I by solid target bombardment of a tellurium target. 123I is a SPECT isotope with a T1/2 of 13 hours, that decays with a g emission of 159 keV. The use of 123-I in nuclear medicine and medical research derives from its excellent SPECT properties, its ability to bind chemically to a wide range of proteins (including a ligand for certain receptors in breast cancer), and its thyrotrophic properties. There is a strong indication that 123-I is superior to the ubiquitous 131-I for brachytherapy treatment of thyroid cancer, since (for example) "thyroid stunning" is less reported with 123-I. Current production of 123-I at the 30MeV National Medical Cyclotron (Australia's only source) utilises the reaction 124-Xe (p, 2n) 123-Cs ¦ 123-Xe ¦ 123-I. 123-Cs and 123-Xe are both positron emitters. 124-Xe is a separated isotope of natural abundance 0.096% and is extremely expensive and special precautions are required to avoid loss of target material. Biomedical applications of 123-I in Australia are limited by its cost. With the recent commercial availability of enriched 123-Te (natural abundance 0.9%, boosted to 67-95% [4]), the reaction 123-Te (p,n) 123-I is possible at proton energies <18MeV [4]. Recently, a prototype version of a 123-Te target system has become available, and this will likely form the basis of this project (Ion Beam Applications, Louvaine, Belgium, pers. comm.) The significant problem of 124-I contamination of the product (from the reaction 124-Te (p,n) 124-I , arising from "contaminant" 124-Te [ natural abundance 4.6%] in the enriched target) will be one of the research questions addressed.

 

Bombardment of a solid target by an 18 MeV proton beam of sufficient current (~ >10 mA) to produce usable activities of a radioisotope, presents several physics, engineering and chemical challenges; eg: (i) choosing a nuclear reaction (usually [p,n]) with adequate p-capture cross-section; (ii) designing a target geometry permitting efficient exposure to the beam; (iii) preventing destruction of the target layer (and ensuring retention of the reaction product) during synthesis; (iv) removing substantial heat from the target and its substrate; (v) transporting the highly radioactive target to a hot cell; (vi) chemically separating and purifying the product; (vii) designing a GMP production and QA protocol allowing administration to humans. All of these topics will be addressed (at least in part) in this project. More details are available in the Project Source File [5].

References

1. Jones T 1996. The role of positron emission tomography within the spectrum of medical imaging. Eur J of Nucl Med 23: 207-211.

2. Von Schulthess GK 1999. Clinical MR in the year 2010. MAGMA 8: 133-145.

3. Tochon-Danguy HJ et al 1999. Positron emission tomography: radioisotope and radiopharmaceutical production. Austr Phys & Eng Sci in Med 22: 136-144.

4. Kaliteevsky AK, Godisov ON, Mjazin LP, Shepelev PK. High purity Iodine-123 produced via P, N Reaction. In: "Cyclotrons and their Applications 98", Caen, France pp 70-73.

5. Price RI 2002. Research Proposal: 2003. Radioisotope Production using Solid Targetry and a Medium Energy Medical Cyclotron: A Feasibility Study of 123-I Production. (Project Source File; Med. Tech. & Phys, SCGH).

 

Contact: A/Prof. Roger Price, Medical Technology & Physics, SCGH; 9346 4288; price@cyllene.uwa.edu.au


 

Further projects are likely to become available over the next couple of months.

Contact A/Prof Tim St Pierre for the latest information.

 

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