| 1. |
- Giantsoudi, D., et al.
(författare)
-
A gEUD-based inverse planning technique for HDR prostate brachytherapy : Feasibility study
- 2013
-
Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405 .- 2473-4209. ; 40:4, s. 041704-
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this work was to study the feasibility of a new inverse planning technique based on the generalized equivalent uniform dose for image-guided high dose rate (HDR) prostate cancer brachytherapy in comparison to conventional dose-volume based optimization. Methods: The quality of 12 clinical HDR brachytherapy implants for prostate utilizing HIPO (Hybrid Inverse Planning Optimization) is compared with alternative plans, which were produced through inverse planning using the generalized equivalent uniform dose (gEUD). All the common dose-volume indices for the prostate and the organs at risk were considered together with radiobiological measures. The clinical effectiveness of the different dose distributions was investigated by comparing dose volume histogram and gEUD evaluators. Results: Our results demonstrate the feasibility of gEUD-based inverse planning in HDR brachytherapy implants for prostate. A statistically significant decrease in D-10 or/and final gEUD values for the organs at risk (urethra, bladder, and rectum) was found while improving dose homogeneity or dose conformity of the target volume. Conclusions: Following the promising results of gEUD-based optimization in intensity modulated radiation therapy treatment optimization, as reported in the literature, the implementation of a similar model in HDR brachytherapy treatment plan optimization is suggested by this study. The potential of improved sparing of organs at risk was shown for various gEUD-based optimization parameter protocols, which indicates the ability of this method to adapt to the user's preferences.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Mavroidis, Panayiotis, et al.
(författare)
-
Expected Clinical Impact of the Differences Between Planned and Delivered IMRT Dose Distributions
- 2007
-
Ingår i: Proceedings in 49th AAPM Annual Meeting, Minneapolis, Minnesota, USA, July 22-26, 2007. - : Wiley.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: Due to the highly conformal distributions that can be obtained with intensity modulated radiation therapy (IMRT), any discrepancy between the intended and delivered distributions would likely affect the clinical outcome. Consequently, there is a need for a measure that would quantify those differences in terms of a change in the expected clinical outcome.Material and Methods: To evaluate such a measure, the case of a cervix cancer was used where the bladder and rectum, are proximal and partially overlapping with the internal target volume. A solid phantom simulating the pelvic anatomy was fabricated and a treatment plan was developed to deliver the prescribed dose to the phantom. The phantom was then irradiated with films positioned in several transverse planes. The racetrack microtron at 50MV was used in the treatment planning and delivery processes. The dose distribution delivered was analyzed based on the film measurements and compared against the treatment plan. The differences in the measurements were evaluated using both physical and biological criteria.Results: For the computerized treatment plan, the maximum value of P+ was 84.1%, for a mean dose to the ITV of = 93.3Gy, associated relative standard deviation D/ = 16.8% and biologically effective uniform dose, ITV of 89.2 Gy. The delivered dose distribution from all the beams produced a P+ value of 77.0% for ITV = 93.2Gy, D/ = 19.0% and ITV of 83.5 Gy.Discussion and Conclusions: Whereas the physical comparison of dose distributions can assess the geometric accuracy of delivery, it does not reflect the clinical impact of any measured dose discrepancies. With highly conformal IMRT, the accuracy of the patient setup and treatment delivery, are critical for the success of the treatment. A method is proposed to evaluate the precision of the delivered plan based on changes in complication and control rates as they relate to uncertainties in dose delivery.
|
|
| 10. |
- Papanikolaou, N, et al.
(författare)
-
Investigation of the Use of Transmission Type Detectors for Daily IMRT Patient Dose Reconstruction
- 2007
-
Ingår i: Proceedings in 49th AAPM Annual Meeting, Minneapolis, Minnesota, USA, July 22-26, 2007. - : Wiley.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: To study the feasibility of using transmission type detectors for daily IMRT patient dose reconstruction and verification. Methods and Materials: Because of the complexity of IMRT there is a need for quality assurance for every patient. However, the daily delivered intensities may vary slightly from the planned ones. In this work we investigated the use of transmission type detectors and films for the verification of daily dose delivered to the patient. Films were placed at various distances from the source in air to measure the beam intensity. The fluence maps were also reconstructed from calculations of the TPS at the same planes. Monte Carlo simulations of the same geometries were performed and the intensity maps were also extracted at the same planes. Intead of film, a tray mounted transmission detector can also be used. Results: The film measurements were compared to TPS predicted intensity maps. Corrections based on the Monte Carlo study were applied to remove the electron contamination from the measured intensity maps since it was not accounted by the TPS. MC results indicate that the corrections due to the contaminant electrons can be 15 to 20% for 6MV beams. The corrected measured intensity map was used to calculate and reconstruct the daily dose to the patient using Monte Carlo. The results show good agreement between measurements using films and Monte Carlo calculations. Conclusions: Transmission detectors such as films can be used in order to compare the delivered intensity maps against the TPS predicted ones. The dose to the patient can be reconstructed using Monte Carlo based on the delivered intensity map and the dose can be potentially verified for each fraction, especially if a cone beam CT is performed daily.
|
|
