W. Howell Round

The Role, Responsibilities and Status of the Clinical Medical Physicist in AFOMP

This document is the first of a series of policy statements being issued by the Asia-Oceania Federation of Organizations for Medical Physics (AFOMP). The document was developed by the AFOMP Professional Development Committee (PDC) and was endorsed for official release by AFOMP Council in 2006. The main purpose of the document was to give guidance to AFOMP member organizations on the role and responsibilities of clinical medical physicists. A definition of clinical medical physicist has also been provided. This document discusses the following topics: professional aspects of education and training; responsibilities of the clinical medical physicist; status and organization of the clinical medical physics service and the need for clinical medical physics service.

Superposition on a multicomputer system.

Superposition (convolution using a noninvariant kernel) has been shown to be a highly promising technique for use in calculating dose distributions in radiotherapy treatment planning. However, one major difficulty that currently prevents use in routine planning is the computational effort required to perform the calculation in three dimensions. To help solve this problem the superposition technique has been implemented on a parallel processor multicomputer in order to examine the performance characteristics of such a system. Up to eight elements have been connected in a pipeline (linear array), and tree networks of three and seven processors have also been constructed (using INMOS T800 transputers). The significant results obtained with these networks are: (1) Both topologies provide near-linear speedup with increasing processor number (8 processors provide 7.81 times the computing power of a single processor when using an optimal communication packet size); (2) increasing communication packet size from 1 voxel to an optimum of approximately 40 voxels significantly reduces communication overhead per processor. Overhead per processor for a 7-element linear array is 6.9% when using 1-voxel packets, but only 1.8% when using 40-voxel packets; (3) the topology of the network has some effect on communication overhead: Arranging 7 processors in a 1-2-4 binary tree reduces overhead to 80.1% of that encountered using a 7-element linear array (with packet size of 1 voxel).

Continuing professional development systems for medical physicists: A global survey and analysis

Continuing professional development (CPD) and continuing professional education (CPE) are seen as being necessary for medical physicists to ensure that they are up-to-date with current clinical practice. CPD is more than just continuing professional education, but can include research publication, working group contribution, thesis examination and many other activities. A systematic way of assessing and recording such activities that a medical physicist undertakes is used in a number of countries. This can be used for certification and licensing renewal purposes. Such systems are used in 27 countries, but they should be implemented in all countries where clinical medical physicists are employed. A survey of the CPD systems that are currently operated around the world is presented. In general they are quite similar although there are a few countries that have CPD systems that differ significantly from the others in many respects. Generally they ensure that medical physicists are kept up-to-date, although there are some that clearly will fail to achieve that. An analysis of what is required to construct a useful medical physics CPD system is made. Finally, the need for medical physicist professional organizations to cooperate and share in the production and distribution of CPD and CPE materials is emphasized.

Supercapacitor energy storage in solar application: A design approach to minimize a fundamental loss issue by partitioning the load and the storage device

When an ideal voltage source is used to replenish an electro-chemical battery with an open circuit voltage of V and a charge of Q coulombs, it stores an energy of QV in the battery, if the charging loop is ideal with no losses. However, if the electro-chemical battery is to be replaced by a capacitor, the energy stored will be ½QV and the loop resistance will dissipate ½QV of energy creating an overall charging efficiency of only 50%. In a solar type application if a supercapacitor (SC) bank replaces a battery, due to its long life and its ability to deliver high power bursts into a load, the designer has to be concerned about this fundamental charging efficiency limitation. However, by splitting the load and the SC bank into two identical halves, and using a series charging scheme where in any given charging process the load and the SC bank comes into series mode, this fundamental loss can be circumvented. The other half of SC bank can deliver energy to the other part of the load.

Energy-Limited Transient-Mode Fast Supercapacitor Charger Topology

Electric double-layer capacitors, commonly known as supercapacitors (SC), provide excellent energy storage solutions to short-term high-power requirements. Compared to a typical dc-dc converter with a resistive load, SC charging circuits do not have to supply a continuous dissipative load. A capacitor chargers operation is defined by the maximum charge to be stored in the capacitor bank. To achieve a practical energy-limited fast SC charger, a new circuit topology is proposed where the SC bank is divided into two parts. One is charged by an overrated voltage source with capacitor terminal voltage monitoring, and the other is charged from the energy stored in a coupled inductor. This letter provides an overview of the concept together with experimental and simulation results for two 100-F, 15-V SC banks with 3-W·h rated energy storage.

Design approaches for fast supercapacitor chargers for applications like SCATMA, SRUPS

The proliferation of electric vehicles (EV) creates a need for fast battery chargers. In order for systems of supercapacitors (SC) to reach adequate energy density levels to replace battery packs, fast SC chargers will also be required. However, when a fully discharged supercapacitor pack is charged from an ideal voltage source, the five-time-constant charging bottleneck comes into play. This issue can be addressed by using the high-voltage charging topology proposed here. The new approach partitions the SC bank into two parts. One part is charged by a high voltage charging source, and the other is replenished by the energy stored in a coupled inductor within the charging path used for the first half of the bank. Early experimental results for a 30 V, 15 F SC bank are presented.

Hybridisation techniques for a supercapacitor-assisted temperature modification apparatus for inline water heating

A hybrid energy source allows a designer to meet extraordinary application requirements without having to make any performance sacrifices [1]. Most available hybridisation techniques in the literature are applied to automobile applications, describing solutions to pulsed load profile characteristics [2]. This study involves an instant water heater having a load profile of 18kW to 25 kW for 30s to 60s repeating once every 15 min, which cannot be modelled as a pulsed power application. In a commercial product development process, where the total product cost has to be kept low, the present cost of supercapacitors (SC) requires the application of battery-SC hybridisation, with an aim to lower the cost of SCs, without compromising the battery life [3]. This paper presents hybrid power source design options for a representative instant water heater system along with simulation and experimental results.

Effect of the time characteristics of the Compton camera on its performance

EPSM-ABEC 2011 Conference 14–18 August, 2011, Darwin Convention Centre, Northern Territory, Australia Australasian College of Physical Scientists and Engineers in Medicine 2011

A Monte Carlo study of two Compton camera’s first plane detectors

EPSM-ABEC 2011 Conference 14–18 August, 2011, Darwin Convention Centre, Northern Territory, Australia Australasian College of Physical Scientists and Engineers in Medicine 2011

Computer vision and image processing at the University of Waikato

This paper presents an up to date summary of computer vision and image processing research within the School of Engineering at the University of Waikato. Four important areas of research, namely full-field AMCW range imaging, hyperspectral image formation, digital line scan photography and retinal imaging are summarised. The contributions of the School are summarised, current research questions are addressed and questions for future research are raised.