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Träfflista för sökning "L773:0284 186X OR L773:1651 226X srt2:(1995-1999)"

Sökning: L773:0284 186X OR L773:1651 226X > (1995-1999)

  • Resultat 61-70 av 138
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61.
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62.
  • Lennernäs, Bo, 1963, et al. (författare)
  • Calculated effects of displacement errors in external beam radiotherapy of prostatic adenocarcinoma.
  • 1999
  • Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 38, s. 203-
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to evaluate the impact on the biological effective dose (BED) of irradiation delivered to a tumour with large displacement errors (LDE) and to estimate the effect on local control, simulated treatment of prostatic adenocarcinoma was performed. The calculation of BED in combination with the critical-voxel model and the LQ model was used to evaluate the effect of different combinations of LDEs. The model is called the Dose Volume Inhomogeneity Corrected BED (DVIC-BED) model. The dose-response curve was assumed to follow Poisson statistics. Different combinations of radiobiological parameters were used to test the model. A simulated clinical treatment with a dose of 66-80 Gy in 2 Gy fractions was carried out to evaluate displacement errors and non-optimal dose distributions. Five random LDEs excluding 33% of the target volume corresponded to an overall dose reduction of 3-5 Gy compared with a 10 Gy reduction if 100% of the target is missed five times. A 5 Gy decrease in dose corresponds to a reduction in clinical or chemical control up to 10-25% in the interval 65-85 Gy. LDEs in different directions are less deleterious than errors occurring in the same direction. Different alpha/beta-ratios (3-15) had little effect on the DIC-BED, but the effect of different alpha values (0.05, 0.2 and 0.5) was large. However, the results depend on radiobiological parameters for prostatic adenocarcinoma, which not are well known, and further studies in the field should be encouraged.
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63.
  • Lennernäs, Bo, 1963, et al. (författare)
  • Patient positioning using artificial intelligence neural networks, trained magnetic field sensors and magnetic implants.
  • 1999
  • Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 38:8, s. 1109-12
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this study was to evaluate the precision of a sensor and to ascertain the maximum distance between the sensor and the magnet, in a magnetic positioning system for external beam radiotherapy using a trained artificial intelligence neural network for position determination. Magnetic positioning for radiotherapy, previously described by Lennernäs and Nilsson, is a functional technique, but it is time consuming. The sensors are large and the distance between the sensor and the magnetic implant is limited to short distances. This paper presents a new technique for positioning, using an artificial intelligence neural network, which was trained to position the magnetic implant with at least 0.5 mm resolution in X and Y dimensions. The possibility of using the system for determination in the Z dimension, that is the distance between the magnet and the sensor, was also investigated. After training, this system positioned the magnet with a mean error of maximum 0.15 mm in all dimensions and up to 13 mm from the sensor. Of 400 test positions, 8 determinations had an error larger than 0.5 mm, maximum 0.55 mm. A position was determined in approximately 0.01 s.
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64.
  • Levitt, SH, et al. (författare)
  • Adjuvant therapy of breast cancer--an overview
  • 1998
  • Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 37:5, s. 403-409
  • Tidskriftsartikel (refereegranskat)
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65.
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66.
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67.
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68.
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69.
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70.
  • Lindblom, A, et al. (författare)
  • Hereditary cancer
  • 1999
  • Ingår i: Acta oncologica (Stockholm, Sweden). - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 38:4, s. 439-447
  • Tidskriftsartikel (refereegranskat)
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  • Resultat 61-70 av 138

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