Using the computer code Monte Carlo N-Particle (MCNP), doses were calculated for organs of interest such as the large intestine, urinary bladder, testes, and kidneys while patients were undergoing prostate brachytherapy. This research is important because the doses delivered to the prostate are extremely high and the organs near the prostate are potentially at risk for receiving high doses of radiation, leading to increased probabilities of adverse health effects such as cancer. In this research, two MCNP version 4C codes were used to calculate the imparted energies to the organs of interest delivered by 125I and 103Pd. As expected, the organs nearest to the prostate received the highest energy depositions and the organs farthest from the prostate received the lowest energy depositions. Once the energy depositions were calculated, the doses to the organs were calculated using the known volumes and densities of the organs. Finally, the doses to the organs over an infinite time period were calculated.

Using the computer code Monte Carlo N-Particle (MCNP), doses were calculated for organs of interest such as the large intestine, urinary bladder, testes, and kidneys while patients were undergoing prostate brachytherapy. This research is important because the doses delivered to the prostate are extremely high and the organs near the prostate are potentially at risk for receiving high doses of radiation, leading to increased probabilities of adverse health effects such as cancer. In this research, two MCNP version 4C codes were used to calculate the imparted energies to the organs of interest delivered by 125I and 103Pd. As expected, the organs nearest to the prostate received the highest energy depositions and the organs farthest from the prostate received the lowest energy depositions. Once the energy depositions were calculated, the doses to the organs were calculated using the known volumes and densities of the organs. Finally, the doses to the organs over an infinite time period were calculated.

<p>Since 1986 patients with ocular malignant melanoma have been treated with Ru-106 plaques at S:t Erik Eye Hospital. In 1998 I-125 radioactive seed plaques was presented as an alternative to Ru-106 when treating tumors with an apical height greater than 7 mm. Until June 2005 the doseplanning of these plaques was based on a depth-dose curve made in the dose planning system Cadplan supplied by Varian Medical Systems. In the recent years the capabilities of computerized 3D dose planning system has increased greatly. The number of types of seeds on the market has also increased.</p><p>In order to implement the modern 3D dose planning system Brachy Vision 7.3.10 in planning the I-125 plaques, a review of the dose planning process have been done.</p><p>The ultra sound equipment used by the ophthalmologist to determine the apical height of the tumor has been investigated in terms of accuracy. A phantom has been developed for this task.</p><p>As new seeds entered the market a comparision have been made comparing the Amersham 6711 seed with the Bebig I25.S06 seed. A method for measuring the activity of the single seeds has also been developed.</p><p>The dose planning system Brachy Vision 7.3.10 have been compared to the old dose planning method, and an implementation of the plaques into Brachy Vision have been made.</p><p>The ultra sound equipment was accurate in the regions of interest. It was also discovered that the Bebig I25.S06 seed gave slightly higher dose compared to the Amersham 6711 with the same activity. The difference between the seeds is however small. The results indicate that the old dose planning method gave a slight underdosage.</p>

Since 1986 patients with ocular malignant melanoma have been treated with Ru-106 plaques at S:t Erik Eye Hospital. In 1998 I-125 radioactive seed plaques was presented as an alternative to Ru-106 when treating tumors with an apical height greater than 7 mm. Until June 2005 the doseplanning of these plaques was based on a depth-dose curve made in the dose planning system Cadplan supplied by Varian Medical Systems. In the recent years the capabilities of computerized 3D dose planning system has increased greatly. The number of types of seeds on the market has also increased. In order to implement the modern 3D dose planning system Brachy Vision 7.3.10 in planning the I-125 plaques, a review of the dose planning process have been done. The ultra sound equipment used by the ophthalmologist to determine the apical height of the tumor has been investigated in terms of accuracy. A phantom has been developed for this task. As new seeds entered the market a comparision have been made comparing the Amersham 6711 seed with the Bebig I25.S06 seed. A method for measuring the activity of the single seeds has also been developed. The dose planning system Brachy Vision 7.3.10 have been compared to the old dose planning method, and an implementation of the plaques into Brachy Vision have been made. The ultra sound equipment was accurate in the regions of interest. It was also discovered that the Bebig I25.S06 seed gave slightly higher dose compared to the Amersham 6711 with the same activity. The difference between the seeds is however small. The results indicate that the old dose planning method gave a slight underdosage.

The TG-43 dosimetry parameters of the AdvantageTM 125I model IAI-125A brachytherapy seed were studied. An investigation using modern MCNP radiation transport code with updated cross-section libraries was performed. Twelve different simulation conditions were studied for a single seed by varying the coating thickness, mass density, photon energy spectrum and cross-section library. The dose rate was found to be 6.3% lower at 1 cm in comparison to published results. New TG-43 dosimetry parameters are proposed. The dose distribution for a brachytherapy eye plaque, model EP917, was investigated, including the effects of collimation from high-Z slots. Dose distributions for 26 slot designs were determined using Monte Carlo methods and compared between the published literature, a clinical treatment planning system, and physical measurements. The dosimetric effect of the composition and mass density of the gold backing was shown to be less than 3%. Slot depth, width, and length changed the central axis (CAX) dose distributions by < 1% per 0.1 mm in design variation. Seed shifts in the slot towards the eye and shifts of the 125I-laden silver rod within the seed had the greatest impact on the CAX dose distribution, changing it by 14%, 9%, 4.3%, and 2.7% at 1, 2, 5, and 10 mm, respectively, from the inner scleral surface. The measured, full plaque slot geometry delivered 2.4% ± 1.1% higher dose along the plaque’s CAX than the geometry provided by the manufacturer and 2.2%±2.3% higher than Plaque SimulatorTM (PS) treatment planning software (version 5.7.6). The D10 for the simulated tumor, inner sclera, and outer sclera for the measured slot plaque to manufacturer provided slot design was 9%, 10%, and 19% higher, respectively. In comparison to the measured plaque design, a theoretical plaque having narrow and deep slots delivered 30%, 37%, and 62% lower D10 doses to the tumor, inner sclera, and outer sclera, respectively. CAX doses at –1, 0, 1, and 2 mm were also lower by a factor of 2.6, 1.72, 1.50, and 1.39, respectively. The study identified substantial sensitivity of the EP917 plaque dose distributions to slot design.

Imaging Iodine-125 requires an increased focus on developing an understanding of how fundamental processes used by imaging systems work to provide quantitative output for the imaging system. Isotopes like I-125 pose specific imaging problems that are a result of low energy emissions as well as how closely spaced those emissions are in the spectrum. This work seeks to characterize the performance of a small animal SPECT-CT imaging system with respect to imaging I-125 for use in a preclinical translational research environment and to understand how the performance of this system relates to critical applications such as attenuation and scatter correction. The specific aims of this work examined several key areas of system function and performance with respect to I-125 imaging. The first aim examined the geometric SPECT calibration routine used for the Inveon imaging system with a particular focus on determining the accuracy of the calibration as well as the robustness of the algorithm under routine and adverse imaging conditions. The second aim was to characterize detector uniformity issues that may arise by comparing the uniformity performance of the system with both I-125 and Co-57 as well as examining the possibility of altering the acquisition method for normalization scans to increase the uniformity performance. The third aim sought to optimize the energy window used for acquisition of I-125 data and to determine the effects the selection of the window had on valid and scatter events. The fourth aim used the optimized windows, determined by the third aim, to assess the performance of a reconstruction algorithm, currently under development, that corrects for attenuation and scatter effects. The fifth and final aim of this work sought to assess the feasibility acquiring SPECT-CT data simultaneously and to assess the quality of data that could be achieved if simultaneous acquisition of the two imaging modalities was, in fact, possible. This work met these aims by performing an extensive series of studies examining the response of the system to I-125 imaging. These included multiple series of phantom imaging using both manufacturer as well as custom-designed sources for use with measurements involving I-125 and Co-57. Statistics from over 60 datasets with analysis in greater than 480 regions of interest were used for the analysis of attenuation and scatter correction data alone. The final study involving simultaneous SPECT-CT acquisition required modification of the imaging hardware to enable this type of data collection as well as development of a reconstruction algorithm to correctly handle the CT data acquired in a step-and-shoot helical mode. A number of key findings resulted from this work including the validation of the calibration routine of this imaging system, even under non-ideal imaging conditions for both the SPECT and CT modalities. Uniformity performance with I-125 was found to be a challenge with this imaging system but reductions in performance compared to other isotopes were not significant enough to introduce severe artifacts into the image data. Optimization of I-125 parameters resulted in improvements of the processed data indicating that the recommended settings provided by the manufacturer could be altered to provide results that better balance between minimizing scatter effects and maximizing detection of valid events. Assessment of the proposed scatter and attenuation correction algorithm for this system showed marked improvement as compared to data processed without these corrections. The final study of simultaneous SPECT-CT imaging proved this acquisition method to be feasible on a commercial system with minimal The primary conclusions drawn from this study indicate that the system is adequate for imaging with I-125 when care is taken to properly maintain the system as well as keeping sources current and properly centered in the scanner field of view during calibration. The study strongly illustrates the necessity of compensating any data collected using I-125 for attenuation and scatter effects; with some regions showing greater than 25% attenuation and approximately 30% improvement in quantitative values for scatter affected regions with the corrections applied. The study also concludes that simultaneous SPECT-CT is feasible with minor adjustments to a commercial platform.

No description available.

Radioactive seed implant brachytherapy is a common radiotherapy treatment method for prostate cancer. In current clinical practice, a seed consists of a single isotope, such as 125I or 103Pd. A seed containing a mixture of two isotopes has been proposed for prostate cancer treatment. This study investigates a method for defining a prescription dose for new seed compositions based on matching the biological equivalent dose (BED) of a reference plan. Ten prostate cancer cases previously treated using single isotope seeds (5 using 125I seeds and 5 using 103Pd seeds) were selected for this study. Verification of the method was done by calculating prescription doses for 103Pd and 125I seeds. A prescription dose for a 50/50 hybrid seed was calculated. Number and location of seeds remained invariant within each case. The BED distributions for hybrid and single isotope seed plans were generated and matched to the BED distribution generated off of the optimized plans. For the 125I isotopes, the dose necessary to cover 90% of the prostate with a BED of 110 Gy is 145 Gy. For the same BED coverage, the dose for 103Pd and 50/50 hybrid seed is 120 Gy and 137 Gy respectively. A method is introduced for obtaining prescription doses for new brachytherapy sources. The method was verified by obtaining doses for 125I and 103Pd isotopes which match clinical prescription doses. The method developed is robust enough to calculate prescription doses in any region of interest, for any seed type, and for any isotope as long as the BED coverage remains invariant with respect to the treatment plan. Numerical calculations were performed to derive analytical conversions of total dose to BED for 50/50, 75/25 and 25/75 hybrid seeds. These analytical conversions are faster than the original numerical methods employed allowing for real-time BED optimization for hybrid seeds. Varying seed distribution was seen not to influence the analytical conversions. It was observed that when total dose remained invariant while individual isotope contributions varied, the value of BED varied. The BED variance was seen to be the smaller at larger BED values (~2% at 100 Gy). Using the conversions derived in this paper, BED based optimization for hybrid seeds are now performable. However, these conversions should only be used in high dose regions due to high uncertainty in the low regime.