Physica Medica: European Journal of Medical Physics

Aims & Scope & Editorial Board

2010-01-01

The European Federation of Organisations for Medical Physics. Policy Statement No. 12: The present status of Medical Physics Education and Training in Europe. New perspectives and EFOMP recommendations

Teresa Eudaldo, Kjeld Olsen — 2009-04-10

Abstract: A recently published EFOMP's survey on the status of Education and Training in Europe, has showed the important role played by the NMOs in the organisation of the Medical Physics education and training in most countries and their efforts to fulfil EFOMP recommendations. However, despite of this, there is still a wide variety of approaches within Europe, not only in the education and training programmes but also in professional practice.There is right now some European issues that can affect not only education and training but also the future of Medical Physics as a profession: 1. the harmonisation of the architecture of the European Higher Education System, arising from the “Bologna Declaration”, for 2010, 2. the recently issued European directive: “Directive 2005/36/EC of the European Parliament and of the Council of 7 September 2005 on the recognition of professional qualifications”.EFOMP is now challenged to make recommendations for education and training in Medical Physics, within the context of the current developments in the European Higher Education Area arising from “The Bologna Declaration”, and with a view to facilitate the free movement of professionals within Europe, according to the new Directive.

Analytical theory for the fluence, planar fluence, energy fluence, planar energy fluence and absorbed dose of primary particles and their fragments in broad therapeutic light ion beams

J. Kempe, A. Brahme — 2009-04-06

Abstract: The purpose of the present work is to develop analytical expressions for the depth variation of the fluence, planar fluence, the energy fluence, planar energy fluence, the mean energy and absorbed dose of primary ions and their associated fragments in tissue-like media with ranges of clinical interest. The analytical expressions of the primary ions and associated fragments take into account nuclear interactions, energy losses, range straggling and multiple scattering. The analytical models of the radiation field quantities were compared with the results of the modified Monte Carlo (MC) code SHIELD-HIT+. The results show that the shape of the depth absorbed dose distribution of the primary particles is characterized by an increasingly steep exponential fluence decrease with depth as the charge and atomic weight increase. This is accompanied by a compensating increased energy loss towards the Bragg peak as the charge of the ion increases. These largely compensating mechanisms are the main reason that the depth absorbed dose curve of all light ions is surprisingly similar. In addition, a rather uniform dose in the plateau region is obtained since the increasing fragment production almost precisely compensates the loss of primaries. The dominating light fragments such as protons and alpha particles are characterized by longer ranges than the primaries and their depth dose curves to some extent coincide well with the depth fluence curves due to a rather slow variation of mean stopping powers. In contrast, the heavier fragments are characterized by the build up of a slowing down spectrum similar to that of the primaries but with initially slightly shorter or longer ranges depending on their mass to atomic number ratio. The presented analytical theory for the light ion penetration in matter agree quite well with the MC and experimental data and may be very useful for fast analytical calculations of quantities like mean energy, fluence, energy fluence, absorbed dose, and LET.

Evaluation of PENFAST – A fast Monte Carlo code for dose calculations in photon and electron radiotherapy treatment planning

B. Habib, B. Poumarede, F. Tola, J. Barthe — 2009-04-02

Abstract: The aim of the present study is to demonstrate the potential of accelerated dose calculations, using the fast Monte Carlo (MC) code referred to as PENFAST, rather than the conventional MC code PENELOPE, without losing accuracy in the computed dose. For this purpose, experimental measurements of dose distributions in homogeneous and inhomogeneous phantoms were compared with simulated results using both PENELOPE and PENFAST. The simulations and experiments were performed using a Saturne 43 linac operated at 12 MV (photons), and at 18 MeV (electrons). Pre-calculated phase space files (PSFs) were used as input data to both the PENELOPE and PENFAST dose simulations. Since depth–dose and dose profile comparisons between simulations and measurements in water were found to be in good agreement (within ±1% to 1 mm), the PSF calculation is considered to have been validated. In addition, measured dose distributions were compared to simulated results in a set of clinically relevant, inhomogeneous phantoms, consisting of lung and bone heterogeneities in a water tank. In general, the PENFAST results agree to within a 1% to 1 mm difference with those produced by PENELOPE, and to within a 2% to 2 mm difference with measured values. Our study thus provides a pre-clinical validation of the PENFAST code. It also demonstrates that PENFAST provides accurate results for both photon and electron beams, equivalent to those obtained with PENELOPE. CPU time comparisons between both MC codes show that PENFAST is generally about 9–21 times faster than PENELOPE.

Impact of patient setup error in the treatment of head and neck cancer with intensity modulated radiation therapy

2009-07-06

Abstract: Purpose: To study the impact of setup errors on the dose to the target volume and critical structures in the treatment of cancer of nasopharynx with intensity modulated radiation therapy (IMRT).Methods and materials: Twelve patients of carcinoma of nasopharynx treated by IMRT with simultaneous integrated boost technique were enrolled. The gross tumor volume, clinical target volume and low-risk nodal region were planned for 70, 59.4 and 54Gy, respectively, in 33 fractions. Based on the constraints, treatment plans were generated. Keeping it as the base plan, the patient setup error was simulated for 3, 5 and 10mm by shifting the isocenter in all three directions viz. anterior, posterior, superior, inferior, right and left lateral. The plans were evaluated for mean dose, maximum dose, volume of PTV receiving >110% and <93% of the prescribed dose. For both the parotids, the mean dose and the dose received by >50% of the parotid were evaluated. The maximum dose and dose received by 2cc of spinal cord were also analyzed.Results: The dose to the target volume decreases gradually with increase in setup error. The superior and inferior shifts play major role in tumor under-dosage. A setup error of 3mm along the posterior and lateral directions significantly affects the dose to the spinal cord. Similarly, setup error along lateral and anterior directions affects the dose to both parotids.Conclusions: The isocenter position should be verified regularly to ensure that the goal of IMRT is achieved.

The feasibility of computational modelling technique to detect the bladder cancer

Ahmad Keshtkar, Asghar Mesbahi, S.H. Rasta, Asghar Keshtkar — 2009-07-15

Abstract: A numerical technique, finite element analysis (FEA) was used to model the electrical properties, the bio impedance of the bladder tissue in order to predict the bladder cancer. This model results showed that the normal bladder tissue have significantly higher impedance than the malignant tissue that was in opposite with the impedance measurements or the experimental results. Therefore, this difference can be explained using the effects of inflammation, oedema on the urothelium and the property of the bladder as a distensible organ. Furthermore, the different current distributions inside the bladder tissue (in histological layers) in normal and malignant cases and finally different applied pressures over the bladder tissue can cause different impedances for the bladder tissue. Finally, it is believed that further studies have to be carried out to characterise the human bladder tissue using the electrical impedance measurement and modelling techniques.

Evaluation criteria for film based intensity modulated radiation therapy quality assurance

Muhammad Naeem Anjum, William Parker, Russell Ruo, Muhammad Afzal — 2009-07-21

Abstract: The aim of this study was to use different gamma histogram criteria for the comparison of planned dose with irradiated dose distribution and find that what percent of pixels passing a certain criteria imitate a good quality plan. The dose was calculated for 156 patients by inverse planning optimization using the Corvus treatment planning system. Gafchromic films in combination with 2571 0.6cm3 Farmer type ionization chamber and Farmer 2570/1 electrometer from NE Technology were used to measure the delivered dose in solid water phantom. All the measurements were performed on Varian CL21EX linear accelerator (Varian Medical Systems, Palo Alto, CA) fitted with a Millennium 120 leaf collimator. In this study the mean value of the percent of passing pixels within the region of interest under the criterion of 3% DD and 3mm DTA is 90.2±7.1% for head and neck cases and 92.2±5.8% for non-head and neck cases. If we choose the criteria of 3% DD and 3mm DTA then 96.3% head and neck plans have the percent of passing pixels≥75% and 95.1% non-head and neck plans have the percent of passing pixels≥80%. It is evident from the results of this study that the criterion of 5% DD and 3mm DTA with the percent of passing pixels≥90 for non-head and neck cases while the percent of passing pixels≥85 for head and neck cases endorse that a plan is good. The results of this study may be useful for other institutions which use verification software and EBT films for patient specific IMRT QA.

Spatial distribution of beta extremity doses in nuclear medicine: A feasibility study with thin α-Al2O3:C TLDs

Pietro Mancosu, Marie Claire Cantone, Ivan Veronese, Augusto Giussani — 2009-04-09

Abstract: Exposures to the extremities have increased due to new therapeutic protocols involving beta sources. In this study, thermoluminescent dosimeters based on α-Al2O3:C were used to map the dose distribution to the extremities of physicians and paramedical personnel handling beta emitters. The results showed a strong inhomogeneous dose distribution between different phalanxes, fingers and hands of all the investigated subjects, without an indication of systematic trends in the dose patterns. Consequently, conventional dosimetric practices, based on the use of wrist or ring dosimeters, may be not suitable for providing reliable assessments of the inhomogeneous doses received at the fingertip.

Influence of different Fletcher–Suit applicator geometries on sagittal dose distribution

Jeno Palvolgyi — 2009-04-22

Abstract: Introduction: One of the brachytherapy treatment modality of cervix carcinomas is insertion with Fletcher–Suit (FS) applicator. Depending on the patient anatomy and pathology and on the construction of the FS applicator different geometrical arrangements in ovoid separation, in ovoids' sagittal level with respect to the tandem were experienced. The multiple insertions show minor differences in applicator geometries. The aim of the study is to evaluate the influence of main geometrical parameters: the ovoid separation, symmetry and the ovoids' sagittal shift on dose distribution in different FS applicator arrangements. We tested the effect of dwell time settings in improvement of dose distribution of less adequate insertions. We also investigated the effect of inter-fractional variation of applicator geometry.Materials and methods: We considered 73 treatment fractions of 22 patients. All insertions were performed by the same gynaecologist with the same type of FS applicator, while the treatment plans were generated by the same physicist using the same treatment planning method. We compared the sagittal dose distribution of different FS applicator geometries with dose levels at two applicator points, defined 2cm apart from the tandem towards the bladder and rectum. We computed the Pearson correlation coefficients between the dose levels at the applicator points and the ovoid separation, symmetry and the ovoids' sagittal shift. We also investigated the effect of dwell time settings in ovoids in order to decrease the dose to organs at risk. The inter-fractional variation of the FS applicator geometries and the influence on the dose levels at the two applicator points were also tested.Results and conclusions: Strong correlation was found between the ovoid separation and dose values to applicator points defined in sagittal direction of FS applicator arrangements. Also strong correlation was between the ovoids' sagittal position with respect to the tandem and the applicator point defined towards the rectum, while the ovoid symmetry had no influence on the sagittal dose distribution. The standard deviations of inter-fractional variation of the ovoid separation and the ovoids' sagittal position were within ±5.2mm and ±10.2mm respectively. The inter-fractional variations in FS applicator geometry resulted in variation in dose levels at the applicator points ±0.8Gy typically, while the largest value was ±1.6Gy.

Thanks to Reviewers

2010-01-01

The Editor-in-Chief and Associate Editors of the European Journal of Medical Physics wish to express their appreciation to the following persons who acted as reviewers over the last 12 months.