| 1. |
- Alonso, Fabiola, 1980-, et al.
(author)
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Comparison of Three Deep Brain Stimulation Lead Designs under Voltage and Current Modes
- 2015
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In: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2. - Cham : Springer. - 9783319193861 - 9783319193878 ; , s. 1196-1199
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Conference paper (peer-reviewed)abstract
- Since the introduction of deep brain stimulation (DBS) the technique has been dominated by Medtronic sys-tems. In recent years, new DBS systems have become available for patients, and some are in clinical trials. The present study aims to evaluate three DBS leads operated in either voltage or current mode. 3D finite element method (FEM) models were built in combination with a neuron model for this purpose. The axon diameter was set to D = 5 μm and simulations performed in both voltage (0.5-5 V) and current (0.5-5 mA) mode. The evaluation was achieved based on the distance from the lead for neural activation and the electric field (EF) extension at 0.1 V/mm. The results showed that the neural activation distance agrees well between the leads with an activation distance dif-ference less than 0.5 mm. The shape of the field at the 0.1 V/mm isopotential surface in 3D is mostly spherical in shape around the activated section of the steering lead.
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| 2. |
- Dasu, Alexandru, et al.
(author)
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Impact of increasing irradiation time on the treatment of prostate cancers
- 2015
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In: 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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Conference paper (peer-reviewed)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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| 3. |
- Gharehbaghi, Arash, et al.
(author)
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A hybrid model for diagnosing sever aortic stenosis in asymptomatic patients using phonocardiogram
- 2015
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In: IFMBE Proceedings. - Cham : Springer. - 9783319193878 - 9783319193861 ; , s. 1006-1009
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Conference paper (peer-reviewed)abstract
- This study presents a screening algorithm for severe aortic stenosis (AS), based on a processing method for phonocardiographic (PCG) signal. The processing method employs a hybrid model, constituted of a hidden Markov model and support vector machine. The method benefits from a preprocessing phase for an enhanced learning. The performance of the method is statistically evaluated using PCG signals recorded from 50 individuals who were referred to the echocardiography lab at Linköping University hospital. All the individuals were diagnosed as having a degree of AS, from mild to severe, according to the echocardiographic measurements. The patient group consists of 26 individuals with severe AS, and the rest of the 24 patients comprise the control group. Performance of the method is statistically evaluated using repeated random sub sampling. Results showed a 95% confidence interval of (80.5%-82.8%) /(77.8%- 80.8%) for the accuracy/sensitivity, exhibiting an acceptable performance to be used as decision support system in the primary healthcare center.
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| 4. |
- Lauri, K., et al.
(author)
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Can Removal of Middle Molecular Uremic Retention Solutes be Estimated by UV-absorbance Measurements in Spent Dialysate?
- 2015
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In: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2. - Cham : Springer. - 9783319193878 - 9783319193861 ; , s. 1297-1300
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Conference paper (peer-reviewed)abstract
- The objectives of this study were: (1) to compare removal of the middle molecular (MM) and small uremic retention solutes; (2) to investigate if MM removal can be assessed by UV-absorbance at the wavelength of 297 nm during various dialysis treatment modalities. Seven uremic patients, four females and three males, mean age 58.1 +/- 8.7 years, were included into the study during 28 chronic hemodialysis sessions. A parameter, reduction ratio (RR) in percentage, was calculated for a small uremic retention solute urea, for a MM retention solute beta2-microglobulin (B2M), and for UV-absorbance at the wavelength of 297 during different dialysis modalities: conventional hemodialysis (HD), high flux hemodialysis (HF-HD), and postdilutional online hemodiafiltration (HDF) with different parameter settings. Achieved results were compared regarding mean values and SD, and by systematic and standard errors (BIAS +/- SE). It was found that RR is similar for small and MM uremic retention solutes in case of dialysis modality with the highest convective transport, HDF (78.9 +/- 8.1% for urea and 78.1 +/- 6.8% for B2M, N=7). Moreover, RR of small uremic retention solutes can be estimated with sufficient accuracy by UV-absorbance at 297 nm in the spent dialysate for all modalities (BIAS +/- SE: 1.7 +/- 4.0%, N=28), and for MM uremic retention solutes only for HDF (BIAS +/- SE: 1.1 +/- 7.1%, N=7). The results should be confirmed by appropriate kinetic modeling in the next studies.
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| 5. |
- Movahed, Allen, et al.
(author)
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International multi-institutional bench mark study on dosimetric and volumetric modulation using helical tomotherapy treatment planning for malignant pleural mesothelioma tumors
- 2015
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In: World Congress on Medical Physics and Biomedical Engineering, 2015. - Cham : Springer International Publishing. - 9783319193861 - 9783319193878 ; 51, s. 381-383
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Conference paper (peer-reviewed)abstract
- Determining the most desirable and achievable target dose and organ at risk (OAR) sparing using helical TomoTherapy planning system for mesothelioma treatment plans. A range of planning parameters was used. The reviewers’ ranking assessment (Ranking in Groups: 1 = Good, 2 = Above Average, 3 = Average, 4 = Poor).The overall rankings revealed that a plan with a balanced tradeoff among all planning objectives was preferred by most participants and reviewers. Other studies found low doses to the contralateral lung to be limiting. This was not the case in our study, with TomoTherapy we found the dose to contra lateral lung to be as low as V5Gy=0.87%. A pitch value of 0.287 or 0.43 would provide better result. A delivered modulation factor of above 1.7 and a treatment time around 500 sec will be beneficial consideration in planning.
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| 6. |
- Toma-Dasu, Iuliana, et al.
(author)
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The value of individual measurements for tumor control probability predictions in head and neck patients
- 2015
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In: World Congress on Medical Physics and Biomedical Engineering, June 7-12, 2015, Toronto, Canada. - Cham : Springer. - 9783319193861 - 9783319193878 ; 51, s. 1675-1678
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Conference paper (peer-reviewed)abstract
- In the age of personalized cancer medicine, individual measurements of in vitro radiosensitivity and proliferation parameters have great potential for predicting treatment outcome. However, cellular radiosensitivity is quite heterogeneous and therefore concerns exist towards its impact on treatment predictions. It was therefore the purpose of this study to investigate this aspect. Individually-determined radiosensitivities and potential doubling times, as well as tumor volumes from 46 head-and-neck carcinomas treated with radiotherapy, were used to predict tumor control probabilities (TCP) under various biologically-relevant assumptions for heterogeneity in radiosensitivity. TCP predictions were then compared to clinical local control using a ROC curve analysis. The analysis showed that TCP calculated under the assumption of heterogeneous radiosensitivity have the same power of distinguishing between patients with or without local control as from single values for the radiobiological parameters (a sensitivity of 66% and a specificity of 80% for an area under the curve of 0.69). The only difference was in the discrimination criterion (TCP>93% for single parameters and TCP>65% for heterogeneous parameters), illustrating the difference in appearance of the TCP curve under the assumption of heterogeneity. Nevertheless, the results showed that individually determined radiobiological parameters could be quite effective towards predicting treatment outcome for individual patients.
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| 7. |
- Gharehbaghi, Arash, et al.
(author)
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An intelligent method for discrimination between aortic and pulmonary stenosis using phonocardiogram
- 2015
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In: IFMBE Proceedings. - Cham : Springer. - 9783319193878 ; , s. 1010-1013
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Conference paper (peer-reviewed)abstract
- This study presents an artificial intelligent-based method for processing phonocardiographic (PCG) signal of the patients with ejection murmur to assess the underlying pathology initiating the murmur. The method is based on our unique method for finding disease-related frequency bands in conjunction with a sophisticated statistical classifier. Children with aortic stenosis (AS), and pulmonary stenosis (PS) were the two patient groups subjected to the study, taking the healthy ones (no murmur) as the control group. PCG signals were acquired from 45 referrals to the children University hospital, comprised of 15 individuals of each group; all were diagnosed by the expert pediatric cardiologists according to the echocardiographic measurements together with the complementary tests. The accuracy of the method is evaluated to be 90% and 93.3% using the 5-fold and leave-one-out validation method, respectively. The accuracy is slightly degraded to 86.7% and 93.3% when a Gaussian noise with signal to noise ratio of 20 dB is added to the PCG signals, exhibiting an acceptable immunity against the noise. The method offered promising results to be used as a decision support system in the primary healthcare centers or clinics.
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