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ABSTRACT: Recommendations of the American Association of Physicists in Medicine (AAPM) for the practice of brachytherapy physics are presented. These guidelines were prepared by a task group of the AAPM Radiation Therapy Committee and have been reviewed and approved by the AAPM Science Council. No preview · Article · Nov 1997 · Medical Physics

Source Available from: aapm.net
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ABSTRACT: Recommendations of the American Association of Physicists in Medicine (AAPM) for the practice of
brachytherapy
physics are presented. These guidelines were prepared by a task group of the AAPM
Radiation
Therapy Committee and have been reviewed and approved by the AAPM
Science Council. Preview · Article · Oct 1997 · Medical Physics

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ABSTRACT: Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies No preview · Article · Aug 1993 · Medical Physics

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ABSTRACT: Dose calculations in multiseed brachytherapy implants are done by adding the contribution of each individual seed and by assuming that radiation from each seed is unaffected by the presence of the other seeds. To test the validity of this assumption, dose measurements with various configurations of multiseed implants of 125I model 6702 and 125I model 6711 sources were performed. For a linear configuration of three 125I model 6702 seeds at 1cm separation, with their transverse axes coincident, doses at distances of 3.05 and 5.09 cm from the center along the transverse axis were found to be about 8% lower than the sum of doses from the three individual seeds. However, for three seeds at 1cm intervals with their longitudinal axes coincident, doses at 3.05 and 5.09 cm distances from the center along the longitudinal axis were found to be about equal to the dose sums from individual seeds. These initial experiments indicated that the magnitude of the interseed effect depends upon the orientation of the seed relative to each other in an implant. To evaluate the importance of this interseed effect for multiseed configurations of 125I model 6702 and 125I model 6711 seeds, dose rates at various distances from a twoplane implant (each plane containing a 3 x 3 array of sources in a 1cm spacing square grid) were measured in a Solid Water phantom with LiF TLDs. These measurements were carried out in two different planes at different orientations relative to the implant. The average values of the interseed effect at distances ranging from 1 to 7 cm outside the implant were observed to be about the same for 125I model 6702 and model 6711 sources. The mean value of the interseed effect was 6% and the maximum was 12%. On the whole, the interseed effect reduces the dose at the periphery of the iodine implant by 6%. No preview · Article · Mar 1992 · Medical Physics

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ABSTRACT: A technique, compatible with accelerators having independent collimators, is presented, which greatly simplifies alignment of pencil eyelens shields. The patient is placed so that the eye to be shielded is on the central axis of the beam and the accelerator's collimators are adjusted independently to define the field. A divergent lead shield 14 cm long is suspended from a wire that hangs along the central axis from a blocking tray in its usual location. The suspension length is variable and adjusted on the first day so that the shield is about 1 cm above the patient's eye. On subsequent treatment days, the wire is simply put in place on the tray with no further adjustment required. This technique reduces setup time and makes the shield positioning highly reproducible. No preview · Article · Feb 1992 · Medical Dosimetry

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ABSTRACT: Dose rates along the transverse axes of 125I model 6702, 125I model 6711 and 192Ir 0.2mm steel sources for interstitial brachytherapy have been measured in a solidwater phantom for distances up to 10 cm using LiF thermoluminescent dosimeters (TLDs). Specific dose rate constants, the dose rates in water per unit source strength 1 cm along the perpendicular bisector of the source, are determined to be 0.90 +/ 0.03, 0.85 +/ 0.03, and 1.09 +/ 0.03 cGy h1 U1 for 125I model 6702, 125I model 6711 and 192Ir 0.2mm steel sources, respectively (1 U = unit of air kerma strength = 1 microGy m2 h1 = 1 cGy cm2 h1). In older and obsolete units of source strength (i.e., mCi apparent), these are 1.14 +/ 0.03, 1.08 +/ 0.03, and 4.59 +/ 0.15 cGy h1 mCi1 (apparent). Currently accepted values of specific dose rate constant for 125I sources are up to 20% higher than our measured values which are in good agreement with the results of our Monte Carlo simulations. But for 192Ir there is good agreement between our measured value of the specific dose rate constant and currently accepted values. The radial dose function for 125I model 6702 is found to be consistently larger than that for 125I model 6711, with an increasing difference as the distance from the source increases. Our measured values for the radial dose function for 125I sources are in good agreement with the results of our Monte Carlo simulation as well as the measured values of Schell et al. [Int. J. Radiat. Oncol. Biol. Phys. 13, 795799 (1987)] for model 6702 and Ling et al.(ABSTRACT TRUNCATED AT 250 WORDS) No preview · Article · Jan 1990 · Medical Physics

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ABSTRACT: Dose rates along the transverse axes of Â¹Â²âµI model 6702, Â¹Â²âµI model 6711 and Â¹â¹Â²Ir 0.2mm steel sources for interstitial brachytherapy have been measured in a solidwater phantom for distances up to 10 cm using LiF thermoluminescent dosimeters (TLDs). Specific dose rate constants, the dose rates in water per unit source strength 1 cm along the perpendicular bisector of the source, are determined to be 0.90{plus minus}0.03, 0.85{plus minus}0.03, and 1.09{plus minus}0.03 cGy hâ»Â¹ Uâ»Â¹ for Â¹Â²âµI model 6702, Â¹Â²âµI model 6711 and Â¹â¹Â²Ir 0.2mm steel sources, respectively (1 U=unit of air kerma strength =1 Î¼Gy mÂ² hâ»Â¹=1 cGy cmÂ² hâ»Â¹). In older and obsolete units of source strength (i.e., mCi apparent), these are 1.14{plus minus}0.03, 1.08{plus minus}0.03, and 4.59{plus minus}0.15 cGy hâ»Â¹ mCiâ»Â¹ (apparent). Currently accepted values of specific dose rate constant for Â¹Â²âµI sources are up to 20% higher than our measured values which are in good agreement with the results of our Monte Carlo simulations. But for Â¹â¹Â²Ir there is good agreement between our measured value of the specific dose rate constant and currently accepted values. The radial dose function for Â¹Â²âµI model 6702 is found to be consistently larger than that for Â¹Â²âµI model 6711, with an increasing difference as the distance from the source increases. Our measured values for the radial dose function for Â¹Â²âµI sources are in good agreement with the results of our Monte Carlo simulation as well as the measured values of Schell {ital et} {ital al}. (Int. J. Radiat. Oncol. Biol. Phys. {bold 13}, 795799 (1987)) for model 6702 and Ling {ital et} {ital al}. (Int. J. Radiat. Oncol. Biol. Phys. {bold 9}, 17471752 (1983)) for model 6711. No preview · Article · Jan 1990 · Medical Physics

Jerome A. Meli
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ABSTRACT: Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies No preview · Article · Sep 1989 · Medical Physics

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ABSTRACT: Malignant brain tumors, in general, and anaplastic astrocytoma and glioblastoma multiforme in particular, have been highly refractory to conventional treatments including surgery, chemotherapy and externalbeam irradiation. Although better local control can be achieved with highdose, external beam irradiation, necrosis of normal brain tissue reduces the quality of life and survival. In order to localize the radiation dose given to brain tumors, the temporary implantation of 125I and 192Ir seeds is undergoing clinical trials at several medical centers. Computers play a key role in this treatment modality: in addition to being essential for image reconstruction of CT scans, a computer is used to reconstruct a tumor volume from outlined regions on individual cuts; a programable calculator is used in conjunction with a stereotaxic head holder to obtain the coordinates of the radioactive seeds; a radiationtherapy, treatmentplanning computer is used to optimize the radioactiveseed positions and strengths, and to generate the corresponding dose distribution. No preview · Article · May 1989 · Computerized Medical Imaging and Graphics

No preview · Article · Jan 1989 · Medical Physics

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ABSTRACT: Absolute dose measurements around low activity seeds used in brachytherapy are difficult to perform with ionisation chambers. The physical size of the chamber does not allow good resolution close to the seeds and the ionisation current generated is very low. Small thermoluminescent dosimeters (TLDs) overcome these problems but the energy dependence of their response should be considered. In this work, dose in polystyrene was measured at several distances from the high activity 192Ir source (370 GBq) of a remote afterloading device using an ionisation chamber and LiF TLD chips. These data show that over a range of 110 cm from the source the sensitivity of LiF varies by up to 8.5%. This is attributed to the higher response of LiF to the lower photon energies, and to the shift of the photon spectrum to lower energies with increasing depth. The sensitivity of LiF to 192Ir was also calculated by weighting the energydependent response of LiF by the Monte Carlo calculated photon spectra. The calculations give a similar change in sensitivity with distance from the source. No preview · Article · Nov 1988 · Physics in Medicine and Biology

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ABSTRACT: Dosimetry of brachytherapy sources is critically dependent on precise measurement of the sourcedetector distance. A solid phantom can be precisely machined and hence distances can be accurately determined. In this work LiF thermoluminescent chips are used for absolute dose rate measurements in solid water, polymethylmethacrylate (PMMA), and polystyrene. These media are examined for their suitability in the dosimetry of 125I by comparing depth doses in each phantom. Measurements and Monte Carlo calculations show that solid water is equivalent to water for the dosimetry of 125I seeds, however, polystyrene and PMMA are not equivalent to water. Also, photon energy spectra for several depths in each phantom material have been calculated and are used to determine average photon energy and mass energy absorption coefficients as a function of depth. No preview · Article · Sep 1988 · Medical Physics

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ABSTRACT: Dosimetric characteristics of polystyrene, solid water, and polymethylmethacrylate were examined and compared to water to determine the suitability of these solid materials for the dosimetry of 192Ir. Ionization charge measured in each of the four media as a function of depth and depthdose curves calculated by Monte Carlo simulation show that the three solids are equivalent to each other and to water under full scattering conditions. Photon energy spectra generated from the Monte Carlo simulation show little variation for the different media. Mass energy absorption coefficients and exposuretodose conversion factors were calculated as a function of depth for these spectra. Measured tissue attenuation factors are in excellent agreement with Meisberger's "selected" values. The radial dose function, which describes the change in dose with distance in phantom exclusive of the inverse square law, was calculated from the tissue attenuation factor and found to be in significant disagreement with Dale's Monte Carlo values. The reason for this discrepancy is discussed. No preview · Article · Apr 1988 · International Journal of Radiation OncologyBiologyPhysics