In recent years there has been a significant economic growth in South East Asia, along with it a concurrent development of medical physics. The status of four countries--Malaysia, Thailand, the Philippines and Indonesia are presented. Medical physicists in these countries have been experiencing the usual problems of lack of recognition, low salaries, and insufficient facilities for education and training opportunities. However the situation has improved recently through the initiative of local enthusiastic medical physicists who have started MS graduate programs in medical physics and begun organizing professional activities to raise the profile of medical physics. The tremendous support and catalytic roles of the American Association of Physicists in Medicine (AAPM) and international organizations such as International Organization for Medical Physics (IOMP), International Atomic Energy Agency (IAEA), World Health Organization (WHO), and International Center for Theoretical Physics (ICTP) have been instrumental in achieving progress. Contributions by these organizations include co-sponsorship of workshops and conferences, travel grants, medical physics libraries programs, and providing experts and educators. The demand for medical physicists is expected to rise in tandem with the increased emphasis on innovative technology for health care, stringent governmental regulation, and acceptance by the medical community of the important role of medical physicists.
Generally there is a significant delay before optimized performance of mammography is fully realized in the developing countries. To evaluate the status of mammographic performance, a survey of mammographic image quality and exposure was performed in nine hospitals from four selected South East Asian countries. The entrance exposure on the surface of the American College of Radiology (ACR) mammographic phantom (ACR-RMI model 156) was made using both thermoluminescent dosimeters (TLDs) and an ionization chamber. The TLDs were mailed from the University of Wisconsin Radiation Calibration Laboratory (UWRCL) to the cooperating hospitals. The surveyed hospitals processed the images and returned them to the UWRCL for subsequent evaluation of the image quality of the mammographic phantom. Machine-specific data, technique factors and sensitometric data were also obtained. At 28 kVp, the mean entrance exposure is 0.91 R (0.46 to 2.6 R), mean glandular dose is 1.61 mGy (0.90 to 4.15 mGy), mean optical density is 1.37 (0.66 to 2.30), mean total phantom image score is 9.1(4-12). Only three of the nine hospitals tested achieved an acceptable score above the minimum 10. Results for 25 and 30 kVp showed similar trend. The variation between the ion chamber measurements and TLD measurements ranged from 4 to 24%. There is a wide variation in the image quality and entrance exposure among hospitals in South East Asia. There is a need for a quality assurance program. The factors that cause low score in the phantom images must be corrected. Calibration and the use of appropriate ionization chambers for mammography is important.
Development of computer-based medical inference systems is always confronted with some difficulties. In this paper, difficulties of designing an inference system for the diagnosis of arthritic diseases are described, including variations of disease manifestations under various situations and conditions. Furthermore, the need for a huge knowledge base would result in low efficiency of the inference system. We proposed a hierarchical model of the fuzzy inference system as a possible solution. With such a model, the diagnostic process is divided into two levels. The first level of the diagnosis reduces the scope of diagnosis to be processed by the second level. This will reduce the amount of input and mapping for the whole diagnostic process. Fuzzy relational theory is the core of this system and it is used in both levels to improve the accuracy.
This is a study using LiF:Mg;Ti thermoluminescent dosimeter (TLD) rods in phantoms to investigate the effect of lack of backscatter on exit dose. Comparing the measured dose with anticipated dose calculated using tissue maximum ratio (TMR) or percentage depth dose (PDD) gives rise to a correction factor. This correction factor may be applied to in-vivo dosimetry results to derive true dose to a point within the patient. Measurements in a specially designed humanoid breast phantom as well as patients undergoing radiotherapy treatment were also been done. TLDs with reproducibility of within +/- 3% (1 SD) are irradiated in a series of measurements for 6 and 10 MV photon beams from a medical linear accelerator. The measured exit doses for the different phantom thickness for 6 MV beams are found to be lowered by 10.9 to 14.0% compared to the dose derived from theoretical estimation (normalized dose at dmax). The same measurements for 10 MV beams are lowered by 9.0 to 13.5%. The variations of measured exit dose for different field sizes are found to be within 2.5%. The exit doses with added backscatter material from 2 mm up to 15 cm, shows gradual increase and the saturated values agreed within 1.5% with the expected results for both beams. The measured exit doses in humanoid breast phantom as well as in the clinical trial on patients undergoing radiotherapy also agreed with the predicted results based on phantom measurements. The authors' viewpoint is that this technique provides sufficient information to design exit surface bolus to restore build down effect in cases where part of the exit surface is being considered as a target volume. It indicates that the technique could be translated for in vivo dose measurements, which may be a conspicuous step of quality assurance in clinical practice.
Wavelet-based image coding algorithms (lossy and lossless) use a fixed perfect reconstruction filter-bank built into the algorithm for coding and decoding of images. However, no systematic study has been performed to evaluate the coding performance of wavelet filters on medical images. We evaluated the best types of filters suitable for medical images in providing low bit rate and low computational complexity. In this study a variety of wavelet filters are used to compress and decompress computed tomography (CT) brain and abdomen images. We applied two-dimensional wavelet decomposition, quantization and reconstruction using several families of filter banks to a set of CT images. Discreet Wavelet Transform (DWT), which provides efficient framework of multi-resolution frequency was used. Compression was accomplished by applying threshold values to the wavelet coefficients. The statistical indices such as mean square error (MSE), maximum absolute error (MAE) and peak signal-to-noise ratio (PSNR) were used to quantify the effect of wavelet compression of selected images. The code was written using the wavelet and image processing toolbox of the MATLAB (version 6.1). This results show that no specific wavelet filter performs uniformly better than others except for the case of Daubechies and bi-orthogonal filters which are the best among all. MAE values achieved by these filters were 5 x 10(-14) to 12 x 10(-14) for both CT brain and abdomen images at different decomposition levels. This indicated that using these filters a very small error (approximately 7 x 10(-14)) can be achieved between original and the filtered image. The PSNR values obtained were higher for the brain than the abdomen images. For both the lossy and lossless compression, the 'most appropriate' wavelet filter should be chosen adaptively depending on the statistical properties of the image being coded to achieve higher compression ratio.
A thermoluminescent dosimetry (TLD) postal dose inter-comparison was carried out amongst radiotherapy centres in Malaysia. The aim of this TLD inter-comparison was to compare the uniformity involved in the measurement of absorbed dose among the participating centres. A set of 5 TLD chips placed within acrylic trays were mailed to all participating centres for irradiation to an absorbed dose to water of 2 Gy. Measurements were made for 6 MV and 60Co photon beams. Results show an agreement of +/- 5% for all but three radiotherapy centres. The ratios of the TLD readings to that of the reference centre are comparable with other national/regional dose inter-comparisons. The importance of a proper ongoing quality assurance program is essential in maintaining the consistency and uniformity of doses delivered.
Increased inter-equipment connectivity coupled with advances in Web technology allows ever escalating amounts of physiological data to be produced, far too much to be displayed adequately on a single computer screen. The consequence is that large quantities of insignificant data will be transmitted and reviewed. This carries an increased risk of overlooking vitally important transients. This paper describes a technique to provide an integrated solution based on a single algorithm for the efficient analysis, compression and remote display of long-term physiological signals with infrequent short duration, yet vital events, to effect a reduction in data transmission and display cluttering and to facilitate reliable data interpretation. The algorithm analyses data at the server end and flags significant events. It produces a compressed version of the signal at a lower resolution that can be satisfactorily viewed in a single screen width. This reduced set of data is initially transmitted together with a set of 'flags' indicating where significant events occur. Subsequent transmissions need only involve transmission of flagged data segments of interest at the required resolution. Efficient processing and code protection with decomposition alone is novel. The fixed transmission length method ensures clutter-less display, irrespective of the data length. The flagging of annotated events in arterial oxygen saturation, electroencephalogram and electrocardiogram illustrates the generic property of the algorithm. Data reduction of 87% to 99% and improved displays are demonstrated.
Illuminance level in the softcopy image viewing room is a very important factor to optimize productivity in radiological diagnosis. In today's radiological environment, the illuminance measurements are normally done during the quality control procedure and performed annually. Although the room is equipped with dimmer switches, radiologists are not able to decide the level of illuminance according to the standards. The aim of this study is to develop a simple real-time illuminance detector system to assist the radiologists in deciding an adequate illuminance level during radiological image viewing. The system indicates illuminance in a very simple visual form by using light emitting diodes. By employing the device in the viewing room, illuminance level can be monitored and adjusted effectively.
The oxidation of ferrous to ferric ions due to ionizing radiation has been used for chemical dosimetry since 1927. The introduction of metal indicator dye xylenol orange (XO) sensitises the measurement of ferric ion yield. A ferrous sulphate- agarose- xylenol orange (FAX) gel was prepared and the gel then exposed to dose ranging from 0.2 to 10 Gy using various high energy photon and electron beams from a linear accelerator. Some general characteristics of FAX such as energy dependence, optical density (OD)-dose relationship, reproducibility and auto-oxidation of ferrous ions were analysed. The radiation yield G of the gel was calculated for gels prepared in oxygen and in air and the values were 46.3 +/- 2.1 and 40.9 +/- 1.4 Fe3+ per 100 eV for photons respectively. However for stock gel which was kept for 5 days pre-irradiation the G value decreased to 36.6 +/- 1.1. The gel shows linearity in OD-dose relationship, energy independence and reproducibility over the dose range investigated. Auto-oxidation of ferrous ions resulted in optical density changes of less than 1.5% per day.
Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tumours with rich macroscopic and microscopic blood supply. The main risks related to this procedure are haemorrhage and implantation of tumour cells in the needle tract after the biopsy needle is withdrawn. From numerous conducted studies, it was found that heating the needle tract using alternating current in radiofrequency (RF) range has a potential to minimize these effects. However, this solution requires the use of specially designed needles, which would make the procedure relatively expensive and complicated. Thus, we propose a simple solution by using readily available coaxial core biopsy needles connected to a radiofrequency ablation (RFA) generator. In order to do so, we have designed and developed an adapter to interface between these two devices. For evaluation purpose, we used a bovine liver as a sample tissue. The experimental procedure was done to study the effect of different parameter settings on the size of coagulation necrosis caused by the RF current heating on the subject. The delivery of the RF energy was varied by changing the values for delivered power, power delivery duration, and insertion depth. The results showed that the size of the coagulation necrosis is affected by all of the parameters tested. In general, the size of the region is enlarged with higher delivery of RF power, longer duration of power delivery, and shallower needle insertion and become relatively constant after a certain value. We also found that the solution proposed provides a low cost and practical way to minimizes unwanted post-biopsy effects.
The advancement of digital imaging has prompted more medical institutions to go filmless. The computed radiography (CR) system is becoming an important tool not only in diagnostic imaging, but also in radiation oncology. A new CR system that was specially designed for the use in radiation oncology, Fuji IP cassette type PII has been introduced to the market in the middle of year 2006. This project aimed to study some basic physical characteristics of this new type of cassette and explore its application for performing quality assurance (QA) tests and portal imaging in radiotherapy. All the images were read by FCR 5000 Plus reader. The image was found to reach its saturation value of 1023 (due to the image was stored in 10 bits data) by depending on the sensitivity value being adjusted. The uniformity test gave the result of 0.12%. The cassette was used to perform the QA tests which were previously performed using film. All the results met the specification as stated in AAPM Task Group 40. The comparison for the portal images of PortalVision contrast-detail phantom showed that the spatial resolution of the images obtained by CR system (Fujifilm Co., Ltd., Tokyo, Japan) were better than the EPID (Varian Medical Systems, Inc., Palo Alto, USA) and film system (Eastman Kodak Co., New York, USA). The IP cassette type PII was found to be suitable as an alternative QA test tool and portal imaging in radiotherapy.
From the time when Roentgen and other physicists made the discoveries which led to the development of radiology, radiotherapy and nuclear medicine, medical physicists have played a pivotal role in the development of new technologies that have revolutionized the way medicine is practiced today. Medical physicists have been transforming scientific advances in the research laboratories to improving the quality of life for patients; indeed innovations such as computed tomography, positron emission tomography and linear accelerators which collectively have improved the medical outcomes for millions of people. In order for radiation-delivery techniques to improve in targeting accuracy, optimal dose distribution and clinical outcome, convergence of imaging and therapy is the key. It is timely for these two specialties to work closer again. This can be achieved by means of cross-disciplinary research, common conferences and workshops, and collaboration in education and training for all. The current emphasis is on enhancing the specific skill development and competency of a medical physicist at the expense of their future roles and opportunities. This emphasis is largely driven by financial and political pressures for optimizing limited resources in health care. This has raised serious concern on the ability of the next generation of medical physicists to respond to new technologies. In addition in the background loom changes of tsunami proportion. The clearly defined boundaries between the different disciplines in medicine are increasingly blurred and those between diagnosis, therapy and management are also following suit. The use of radioactive particles to treat tumours using catheters, high-intensity focused ultrasound, electromagnetic wave ablation and photodynamic therapy are just some areas challenging the old paradigm. The uncertainty and turf battles will only explode further and medical physicists will not be spared. How would medical physicists fit into this changing scenario? We are in the midst of molecular revolution. Are we prepared to explore the newer technologies such as nanotechnology, drug discovery, pre-clinical imaging, optical imaging and biomedical informatics? How are our curricula adapting to the changing needs? We should remember the late Professor John Cameron who advocated imagination and creativity - these important attributes will make us still relevant in 2020 and beyond. To me the future is clear: "To achieve more, we should imagine together."
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.
Second cancer induction in the contralateral breast (CB) is an issue of some concern in breast radiotherapy especially for women under the age of 45 years at the time of treatment. The CB dose from 2-field and 3-field techniques in post-mastectomy chest wall irradiations in an anthropomorphic phantom as well as in patients were measured using thermoluminescent dosimeters (TLDs) at the local radiotherapy center. Breast and chest wall radiotherapy treatments were planned conformally (3D-CRT) and delivered using 6-MV photons. The measured CB dose at the surface fell sharply with distance from the field edge. However, the average ratio of the measured to the calculated CB dose using the pencil beam algorithm at the surface was approximately 53%. The mean and median measured internal dose at the posterior border of CB in a phantom was 5.47+/-0.22 cGy and 5.44 cGy, respectively. The internal CB dose was relatively independent of depth. In the present study the internal CB dose is 2.1-4.1% of the prescribed dose which is comparable to the values reported by other authors.
Homogenous strain analysis (HSA) was developed to evaluate regional cardiac function using tagged cine magnetic resonance images of heart. Current cardiac applications of HSA are however limited in accurately detecting tag intersections within the myocardial wall, producing consistent triangulation of tag cells throughout the image series and achieving optimal spatial resolution due to the large size of the triangles. To address these issues, this article introduces a harmonic phase (HARP) interference method. In principle, as in the standard HARP analysis, the method uses harmonic phases associated with the two of the four fundamental peaks in the spectrum of a tagged image. However, the phase associated with each peak is wrapped when estimated digitally. This article shows that special combination of wrapped phases results in an image with unique intensity pattern that can be exploited to automatically detect tag intersections and to produce reliable triangulation with regularly organized partitioning of the mesh for HSA. In addition, the method offers new opportunities and freedom for evaluating myocardial function when the power and angle of the complex filtered spectra are mathematically modified prior to computing the phase. For example, the triangular elements can be shifted spatially by changing the angle and/or their sizes can be reduced by changing the power. Interference patterns obtained under a variety of power and angle conditions were presented and specific features observed in the results were explained. Together, the advanced processing capabilities increase the power of HSA by making the analysis less prone to errors from human interactions. It also allows strain measurements at higher spatial resolution and multi-scale, thereby improving the display methods for better interpretation of the analysis results.
The performance of a digital mammography system (Siemens Mammomat Novation) using different target/filter combinations and tube voltage has been assessed. The objective of this study is to optimize beam quality selection based on contrast-to-noise ratio (CNR) and mean glandular dose (MGD). Three composition of breast were studied with composition of glandular/adipose of 30/70, 50/50, and 70/30. CNR was measured using 2, 4 and 6 cm-thick simulated breast phantoms with an aluminium sheet of 0.1 mm thickness placed on top of the phantom. Three target/filter combinations, namely molybdenum/molybdenum (Mo/Mo), molybdenum/rhodium (Mo/Rh) and tungsten/rhodium (W/Rh) with various tube voltage and mAs were tested. MGD was measured for each exposure. For 50/50 breast composition, Mo/Rh combination with tube voltage 26 kVp is optimal for 2 cm-thick breast. W/Rh combination with tube voltage 27 and 28 kVp are optimal for 4 and 6 cm-thick breast, respectively. For both 30/70 and 70/30 breast composition, W/Rh combination is optimal with tube voltage 25, 26 and 27 kVp, respectively. From our study it was shown that there are potential of dose reduction up to 11% for a set CNR of 3.0 by using beam quality other than that are determined by AEC selection. Under the constraint of lowest MGD, for a particular breast composition, calcification detection is optimized by using a softer X-ray beam for thin breast and harder X-ray beam for thick breast. These experimental results also indicate that for breast with high fibroglandular tissues (70/30), the use of higher beam quality does not always increase calcification detection due to additional structured noise caused by the fibroglandular tissues itself.
The classification of the cancer tumors based on gene expression profiles has been extensively studied in numbers of studies. A wide variety of cancer datasets have been implemented by the various methods of gene selection and classification to identify the behavior of the genes in tumors and find the relationships between them and outcome of diseases. Interpretability of the model, which is developed by fuzzy rules and linguistic variables in this study, has been rarely considered. In addition, creating a fuzzy classifier with high performance in classification that uses a subset of significant genes which have been selected by different types of gene selection methods is another goal of this study. A new algorithm has been developed to identify the fuzzy rules and significant genes based on fuzzy association rule mining. At first, different subset of genes which have been selected by different methods, were used to generate primary fuzzy classifiers separately and then proposed algorithm was implemented to mix the genes which have been associated in the primary classifiers and generate a new classifier. The results show that fuzzy classifier can classify the tumors with high performance while presenting the relationships between the genes by linguistic variables.
Driver drowsiness has been one of the major causes of road accidents that lead to severe trauma, such as physical injury, death, and economic loss, which highlights the need to develop a system that can alert drivers of their drowsy state prior to accidents. Researchers have therefore attempted to develop systems that can determine driver drowsiness using the following four measures: (1) subjective ratings from drivers, (2) vehicle-based measures, (3) behavioral measures and (4) physiological measures. In this study, we analyzed the various factors that contribute towards drowsiness. A total of 15 male subjects were asked to drive for 2 h at three different times of the day (00:00-02:00, 03:00-05:00 and 15:00-17:00 h) when the circadian rhythm is low. The less intrusive physiological signal measurements, ECG and EMG, are analyzed during this driving task. Statistically significant differences in the features of ECG and sEMG signals were observed between the alert and drowsy states of the drivers during different times of day. In the future, these physiological measures can be fused with vision-based measures for the development of an efficient drowsiness detection system.
Surface electromyography (SEMG) signals can provide important information for prosthetic hand control application. In this study, time domain (TD) features were used in extracting information from the SEMG signal in determining hand motions and stages of contraction (start, middle and end). Data were collected from ten healthy subjects. Two muscles, which are flexor carpi ulnaris (FCU) and extensor carpi radialis (ECR) were assessed during three hand motions of wrist flexion (WF), wrist extension (WE) and co-contraction (CC). The SEMG signals were first segmented into 132.5 ms windows, full wave rectified and filtered with a 6 Hz low pass Butterworth filter. Five TD features of mean absolute value, variance, root mean square, integrated absolute value and waveform length were used for feature extraction and subsequently patterns were determined. It is concluded that the TD features that were used are able to differentiate hand motions. However, for the stages of contraction determination, although there were patterns observed, it is determined that the stages could not be properly be differentiated due to the variability of signal strengths between subjects.
Cricket bowling generates forces with torques on the upper limb muscles and makes the biceps brachii (BB) muscle vulnerable to overuse injury. The aim of this study was to investigate whether there are differences in the amplitude of the EMG signal of the BB muscle during fast and spin delivery, during the seven phases of both types of bowling and the kinesiological interpretation of the bowling arm for muscle contraction mechanisms during bowling. A group of 16 male amateur bowlers participated in this study, among them 8 fast bowlers (FB) and 8 spin bowlers (SB). The root mean square (EMGRMS), the average sEMG (EMGAVG), the maximum peak amplitude (EMGpeak), and the variability of the signal were calculated using the coefficient of variance (EMGCV) from the BB muscle of each bowler (FB and SB) during each bowling phase. The results demonstrate that, (i) the BB muscle is more active during FB than during SB, (ii) the point of ball release and follow-through generated higher signals than the other five movements during both bowling categories, (iii) the BB muscle variability is higher during SB compared with FB, (iv) four statistically significant differences (p<0.05) found between the bowling phases in fast bowling and three in spin bowling, and (v) several arm mechanics occurred for muscle contraction. There are possible clinical significances from the outcomes; like, recurring dynamic contractions on BB muscle can facilitate to clarify the maximum occurrence of shoulder pain as well as biceps tendonitis those are medically observed in professional cricket bowlers, and treatment methods with specific injury prevention programmes should focus on the different bowling phases with the maximum muscle effect. Finally, these considerations will be of particular importance in assessing different physical therapy on bowler's muscle which can improve the ball delivery performance and stability of cricket bowlers.