| 1. |
- Albinsson, John, et al.
(författare)
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Tracking Performance of Several Combinations of Common Evaluation Metrics and Sub-pixel Methods
- 2015
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Ingår i: 16th Nordic-Baltic Conference on Biomedical Engineering. - Cham : Springer International Publishing. - 1680-0737. ; 48, s. 13-16, s. 13-16
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Konferensbidrag (refereegranskat)abstract
- Motion estimation in a series of consecutive images is used in a variety of areas, e.g. video compression and investigation of tissue characteristics and organ function in medical images. Several methods exist both for estimating motions on a pixel level, e.g. block-matching in which two blocks in consecutive images are compared by an evaluation metric, and on a sub-pixel level. In this paper, we have evaluated the tracking performance of all combinations between three evaluation metrics and eight sub-pixel estimation methods. The tracking performance of a sub-pixel method varies depending on the evaluation metric used. This indicates that a reported tracking performance for a sub-pixel estimation method can be significantly different when combined with another evaluation metric. Also there is a large variation in the time needed for the motion estimations depending primarily on the sub-pixel method used but also on the evaluation metric.
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| 2. |
- Arvidsson, Jonathan, 1986, et al.
(författare)
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Automated estimation of in-plane nodule shape in chest tomosynthesis images
- 2015
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Ingår i: International Federation for Medical and Biological Engineering Proceedings. - Cham : Springer International Publishing. - 1680-0737. - 9783319129679 ; 48, s. 20-23
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to develop an automated segmentation method for lung nodules in chest tomo-synthesis images. A number of simulated nodules of different sizes and shapes were created and inserted in two different locations into clinical chest tomosynthesis projections. The tomosynthesis volumes were then reconstructed using standard cone beam filtered back projection, with 1 mm slice interval. For the in-plane segmentation, the central plane of each nodule was selected. The segmentation method was formulated as an optimization problem where the nodule boundary corresponds to the minimum of the cost function, which is found by dynamic programming. The cost function was composed of terms related to pixel intensities, edge strength, edge direction and a smoothness constraint. The segmentation results were evaluated using an overlap measure (Dice index) of nodule regions and a distance measure (Hausdorff distance) between true and segmented nodule. On clinical images, the nodule segmentation method achieved a mean Dice index of 0.96 ± 0.01, and a mean Hausdorff distance of 0.5 ± 0.2 mm for isolated nodules and for nodules close to other lung structures a mean Dice index of 0.95 ± 0.02 and a mean Hausdorff distance of 0.5 ± 0.2 mm. The method achieved an acceptable accuracy and may be useful for area estimation of lung nodules.
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| 3. |
- Ask, Per, et al.
(författare)
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Certification of Clinical Engineers in Sweden
- 2009
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Ingår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 12. - Berlin, Heidelberg : Springer Science Business Media. - 1680-0737. ; 25:12, s. 430-431
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish Society for Biomedical Engineering and Physics have certified clinical engineers since 1994. The certification is done on tow levels: Master of science and Bachelor of science. We have in total had 614 applications and certified 341 engineers We have certified a total of 341 persons of which 75 are at the master level and 266 at the bachelor level. We are pleased to note that through the years so many engineers have applied and have get a certification. The interest for applying was very large in the beginning but decreased after some years.
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| 4. |
- Blad, Börje
(författare)
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An electrical impedance model for deep brain stimulation of Parkinson's disease
- 2007
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Ingår i: 13th International Conference on Electrical Bioimpedance and the 8th Conference on Electrical Impedance Tomography. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737. - 9783540738404 ; 17, s. 60-61
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Konferensbidrag (refereegranskat)abstract
- Deep brain stimulation is an accepted technique for the treatment of Parkinson's disease. Deep brain stimulation affects the electrical functions of neurons and several explanations are available to describe this treatment modality. Such as depolarization blockade, synaptic inhibition, synaptic depression and stimulation induced modulation of pathological network activity. An electrical impedance model of the treatment area around the electrodes in the brain is determined to further increase the understanding of deep brain stimulation. This model shows the contact impedance between the electrodes and the tissue, the extra cellular resistance, the intra cellular resistance of the neurons and the effect of deep brain stimulation on the treated area in the brain, which in this case is stimulation of the sub thalamic nucleus. The generated electrical field near the electrodes is high enough to perform an electropermeabilization of the cell membranes. This is modelled as a cell membrane capacitance in series with a resistance. The resistance is the consequence of electropermeabilization of the cell membranes. Many observed parameters that occur during deep brain stimulation is reduced tremor activity, influence on speech, the same effect as a lesion, increased axon activity downstream, followed by durations of nerve silence.
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| 5. |
- Blad, Börje, et al.
(författare)
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Beam Adjustments for Unflattened X-ray Beam Modes for an Elekta Synergy Linear Accelerator
- 2012
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Ingår i: IFMBE Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737. - 9783642235085 ; 37, s. 683-685
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Konferensbidrag (refereegranskat)abstract
- A flattening filter free x-ray beam mode was added to an Elekta linear accelerator by placing a flat copper plate in the filter carousel and recalibrating the electron steering servo, gun servo and dosimetry system. Machine configurations were saved onto a separate hard disk in order to remain separate from the clinical configuration. Profile measurements with a Schuster BMS diode array show that the beam is stable and start up performance is similar to the normal filtered beam.
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| 6. |
- Chen, Y., et al.
(författare)
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Brain injury prediction for vulnerable road users in vehicle accidents using mathematical models
- 2010
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Ingår i: International Federation for Medical and Biological Engineering Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737. - 9783540790389 ; 31, s. 497-500
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Konferensbidrag (refereegranskat)abstract
- The objective was to analyze the brain tissue responses and predict head-brain injuries. Accident reconstructions were carried out by using MBS and FE models based on real-life accident investigation. Thirty cases of VRUs accidents were selected from IVAC and GIDAS databases for simulation study. The brain injury parameters were calculated in terms of coup/countercoup pressure, von Mises and maximum shear stresses at the cerebrum, the callosum, the cerebellum and the brain stem. The correlation of calculated parameters was determined with injury codes observed in accident data. The results indicated that peak coup/countercoup pressures often occur at the cerebrum, while von Mises and maximum shear stresses are both concentrated at the upper end of the brain stem. Physical parameters employed in this study are capable of predicting brain injuries. © 2010 International Federation for Medical and Biological Engineering.
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| 7. |
- Dasu, Alexandru, et al.
(författare)
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Dose painting by numbers - do the practical limitations of the technique decrease or increase the probability of controlling tumours?
- 2013
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Ingår i: IFMBE Proceedings. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 1680-0737 .- 1433-9277. ; 39, s. 1731-1734, s. 1731-1734
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Tidskriftsartikel (refereegranskat)abstract
- One of the important questions regarding the feasibility of dose-painting-by-numbers approaches for treatment planning concerns the influence of the averaging of the imaging techniques used and the resolution of the planned and achieved dose distributions. This study investigates the impact of these aspects on the probability of controlling dynamic tumours. The effectiveness of dose painting approaches to target tumour hypoxia has been investigated in terms of the predicted tumour control probabilities (TCP) for tumours with dynamic oxygenations. Several levels of resolution for the resistance of the tumour or the planned dose distributions have been investigated. A very fine heterogeneous dose distribution ideally calculated at voxel level for a high target TCP would fail to control a tumour with dynamic oxygenation during the course of fractionated radiotherapy as mismatches between hotspots in the dose distribution and resistant hypoxic foci would lead to a significant loss in TCP. Only adaptive treatment would lead to reasonably high TCP. A coarse resolution for imaging or for dose distributions might compensate microscale mismatches in dynamic tumours, but the resulting tumour control could still be below the target levels. These results indicate that there is a complex relationship between the resolution of the dose-painting-by-numbers approaches and the dynamics of tumour oxygenation. Furthermore, the clinical success of hypoxia targeting strategies in the absence of adaptive approaches might be explained by changes in tumour radiation resistance through reoxygenation.
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| 8. |
- Dasu, Alexandru, et al.
(författare)
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Impact of increasing irradiation time on the treatment of prostate cancers
- 2015
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Ingår i: World Congress on Medical Physics and Biomedical Engineering, June 7-12, 2015, Toronto, Canada. - Cham : Springer. - 9783319193861 - 9783319193878 ; 51, s. 490-493
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Konferensbidrag (refereegranskat)abstract
- This study aimed to investigate the expected impact of intrafraction repair during increasing irradiation times for the treatment of prostate cancers. Lengthy sessions are indeed expected for some advanced irradiation techniques capable to deliver the large fractional doses required by the increased fractionation sensitivity of the prostates. For this purpose, clinically-derived parameters characterizing repair rates and dose response curves for prostate tumors have been used to calculate the expected loss of effectiveness when increasing the irradiation time. The results have shown that treatment sessions lasting more than about 20 to 40 minutes could reduce the probability of biochemical control of prostate tumors by more than 20 to 30 percentage points. These results are in agreement with some observed clinical results and therefore they suggest that treatment durations in prostate radiation therapy should be carefully recorded in order to explicitly account for intrafraction repair, especially when irradiation techniques make use of multiple beams and imaging sessions. Failure to do so might overestimate the expected effectiveness of the treatment and could lead to disappointing clinical results precisely from the demanding treatment modalities expected to increase the therapeutic gain in prostate radiotherapy.
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| 9. |
- Dasu, Alexandru, et al.
(författare)
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The risk for secondary cancers in patients treated for prostate carcinoma – An analysis with the competition dose response model
- 2009
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Ingår i: IFMBE Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737 .- 1433-9277. ; 25/III, s. 237-240
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Tidskriftsartikel (refereegranskat)abstract
- The risk for radiation-induced cancers has become increasingly important as patient survival following radiotherapy has increased due to the advent of new methods for early detection and advanced treatment. Attempts have been made to quantify the risk of cancer that may be associated with various treatment approaches, but the accuracy of predictions is rather low due to the influence of many confounding factors. It is the aim of this paper to investigate the impact of dose heterogeneity and inter-patient anatomical heterogeneity that may be encountered in a population of patients undergoing radiotherapy and are thought to influence risk predictions. Dose volume histograms from patients treated with radiation for the carcinoma of the prostate have been used to calculate the risk for secondary malignancies using a competition dose-response model previously developed. Biologically-relevant parameters derived from clinical and experimental data have been used for the model. The results suggested that dose heterogeneity plays an important role in predicting the risk for secondary cancer and that it should be taken into account through the use of dose volume histograms. Consequently, dose-response relationships derived for uniform relationships should be used with care to predict the risk for secondary malignancies in heterogeneously irradiated tissues. Inter-patient differences could lead to considerable uncertainties in the shape of the relationship between predicted risk and average tissue dose, as seen in epidemiological studies. They also lead to rather weak correlations between the risk for secondary malignancies and target volumes. The results stress the importance of taking into account the details of the clinical delivery of dose in radiotherapy for treatment plan evaluation or for retrospective analyses of the induction of secondary cancers. Nevertheless, the levels of risks are generally low and they could be regarded as the price of success for the advances in the radiotherapy of the prostate.
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| 10. |
- Dukov, Nikolay, et al.
(författare)
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Experimental Evaluation of Physical Breast Phantoms for 2D and 3D Breast X-Ray Imaging Techniques
- 2021
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Ingår i: 8th European Medical and Biological Engineering Conference - Proceedings of the EMBEC 2020. - Cham : Springer International Publishing. - 1433-9277 .- 1680-0737. - 9783030646097 ; 80, s. 544-552
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Konferensbidrag (refereegranskat)abstract
- Anthropomorphic phantoms are models of real or virtual parts of the body, organ or tissue, represented by tissue-equivalent materials that aim to provide a realistic and accurate representation of their anatomy and properties. The aim of this study is to evaluate experimentally the suitability of 3D printed materials in the production of both, physical breast phantoms and abnormalities, to be used in optimization tasks in breast imaging. For this purpose, we designed three computational breast models, composed of skin, duct tree, adipose compartments and lesions. Subsequently, they were printed by using two 3D printing technologies and different printing materials, which were previously studied in details. The physical phantoms were scanned at a mammography machine, which allows 2D and 3D mammography (tomosynthesis) modes. The images were evaluated from an experienced radiologist. The results showed that tomosynthesis images are characterized with better realism compared to 2D mammography images. Next step is improvement in the printing quality of tumour formations as well as quantitative evaluation of the obtained results.
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