1 UI - 95192820 AU - Bayouth JE AU - Macey DJ AU - Boyer AL AU - Champlin RE IN - Department of Radiation Physics, Texas Univ. M.D. Anderson Can. Ctr., Houston, TX 77030; United States of America. CP - United States of America TI - Radiation dose distribution within the bone marrow of patients receiving holmium-166-labeled-phosphonate for marrow ablation. SO - Medical Physics Vol 22(6) (pp 743-753), 1995. MH - *Multiple Myeloma/rt [Radiotherapy] MH - Radiation Dose MH - Radiation Absorption MH - Bone Marrow Biopsy MH - Scintillation Camera MH - Dose Calculation MH - Dosimetry MH - clinical protocol MH - Human MH - Clinical Article MH - Priority Journal MH - Article MH - *Holmium MH - Radioisotope MH - Phosphonic Acid Derivative MH - Unclassified Drug MH - 1,4,7,10 tetraazacyclododecane 1,4,7,10 tetramethylene phosphonic MH - acid AB - The primary objective of this work was to estimate the absorbed dose distribution to the bone marrow of six multiple myeloma patients who received holmium-166 (166Ho) DOTMP (1,4,7,10-tetraazacyclododecane-1,4,7,10- tetramethylene-phosphonic acid) for the purpose of bone marrow ablation. A methodology based on gamma camera images was developed to estimate the regional absorbed dose distributions delivered to the bone marrow, and this was compared with values calculated from the MIRD technique and bone marrow biopsies. The activity concentration in various skeletal regions was calculated from the activity in the region of interest (ROI) drawn on whole body gamma camera images, and the mass of bone in each ROI was derived from a dual x-ray absorptiometry image. The radiation absorbed dose to the bone marrow was calculated from this activity concentration using an adaptation of Bragg-Gray cavity theory. The radiation absorbed dose delivered to the bone marrow in the six patients calculated from the MIRD 'S' factors ranged from 15.0 to 46.3 Gy. The gamma camera measured activity concentration in skeletal regions predominantly composed of trabecular bone was approximately five to six times higher than that in cortical regions. The skeletal activity concentration in each patient ranged from highs in such regions as the ribs to lows in such regions as the shin and foot by a factor of nearly 20, producing a heterogeneous distribution of absorbed dose within the marrow. Dose volume histograms calculated for these patients indicated that 15%-20% of the marrow received an absorbed dose significantly larger than the average value, while 5%-10% of the marrow received a substantially lower dose. Weighted mean dose estimates from the regional technique were typically 30% greater than the average dose estimates calculated with the MIRD 'S' factors. Finally, absorbed dose estimates for the marrow calculated from the regional technique correlated more closely with the clinical response of blood cells and abnormal proteins measured in bone marrow aspirates and peripheral blood samples than estimates from the MIRD 'S' factors. RN - 7440-60-0 IS - 0094-2405 LG - English PT - Journal EM - 9506 2 UI - 95156130 AU - Liu HB AU - Brugger RM AU - Laster BH AU - Greenberg DD AU - Gordon CR AU - Warkentien LS IN - Medical Department, Brookhaven National Laboratory, Upton, NY 11973; United States of America. CP - United States of America TI - Physical and biological doses produced from neutron capture in a 235U foil. SO - Medical Physics Vol 22(5) (pp 591-596), 1995. MH - *Neutron Capture Therapy MH - Phantom MH - Fission Neutron MH - Cell Survival MH - Dosimetry MH - Brachytherapy MH - Beta Radiation MH - Gamma Irradiation MH - System Analysis MH - Mathematical Analysis MH - Cancer Radiotherapy MH - Controlled Study MH - Priority Journal MH - Article MH - *Uranium MH - Carbon 14 MH - Cesium 137 MH - Nitrogen AB - As a follow-on study to the feasibility of neutron capture therapy (NCT) with 235U brachytherapy seeds, physical doses were calculated and measured for the radiation from a 235U foil in a lucite phantom which was irradiated at the epithermal neutron irradiation port of the Brookhaven Medical Research Reactor. In addition, cell survival experiments were performed to obtain the relative biological effectiveness (RBE) for the neutron part of the radiation. The calculated absorbed doses agree with the measured ones. From cell survival experiments, it is deduced that the fission neutrons from the 235U foil have a RBE of 3.0 while the fast neutrons in the beam have a RBE of 3.8. Also observed is that, with the cells 7 mm from the foil, a significant amount of absorbed dose comes from the beta rays of 235U fission events. This absorbed dose from beta rays is a significant addition to the therapeutic dose. Due to the limited ranges of beta rays in tissue, this absorbed dose is restricted to the vicinity of the foil. This is the first demonstration of beta rays as part of NCT. RN - 7440-61-1. 14762-75-5. 10045-97-3. 7727-37-9 IS - 0094-2405 LG - English PT - Journal EM - 9506 3 UI - 95156129 AU - Wallace SA AU - Mathur JN AU - Allen BJ IN - Physics Department, University of Wollongong, Northfields Ave., Wollongong, NSW 2522; Australia. CP - United States of America TI - The influence of heavy water on boron requirements for neutron capture therapy. SO - Medical Physics Vol 22(5) (pp 585-590), 1995. MH - *Neutron Capture Therapy MH - System Analysis MH - Mathematical Model MH - Skull MH - Brain MH - Water MH - Dosimetry MH - Cancer Radiotherapy MH - Priority Journal MH - Article MH - *Boron 10 AB - Neutron penetration in tissue is a major limitation of thermal NCT, as such much work has centered upon the epithermal neutron beam in an effort to improve this situation. Further gains in neutron flux penetration, and thus therapeutic ratios, are possible if natural water is replaced with heavy water prior to therapy. Applying MCNP to a heterogeneous ellipsoidal skull/brain model, advantage depth and therapeutic depth parameters are studied as a function of heavy water replacement for a range of tumor to blood boron ratios. Both thermal (0.025 eV) and epithermal (2-7 keV) ideal neutron beams are analyzed. Using 10B ratios in the range of documented human uptake, the thermal advantage depth improved by approximately 0.7 cm for 20% D2O replacement, however, the therapeutic depth increased by less than half this value. For the epithermal beam, both the advantage depth and the therapeutic depth increased by over 1 cm. Effects of heavy water replacement on 10B requirements to therapeutically treat the midline of the brain are also evaluated. RN - 7732-18-5. 14798-12-0 IS - 0094-2405 LG - English PT - Journal EM - 9506 4 UI - 95156125 AU - Rustgi SN IN - Department of Radiology, Metrohealth Medical Center, Case Western Reserve University, Cleveland, OH 44109; United States of America. CP - United States of America TI - Evaluation of the dosimetric characteristics of a diamond detector for photon beam measurements. SO - Medical Physics Vol 22(5) (pp 567-570), 1995. MH - *Brachytherapy MH - *Stereotaxic Surgery MH - Photon MH - Ionization Chamber MH - Radiosensitivity MH - Radiosurgery MH - Dosimetry MH - X Ray MH - Priority Journal MH - Article MH - *Cobalt 60 MH - diamond AB - The dosimetric properties of a new diamond detector for the measurement of relative dose in photon beams have been investigated and compared to those of a silicon p-type photon diode and a 0.14 cm3 ionization chamber. The mass energy absorption ratio of carbon to water is nearly constant over a wide energy range making the diamond detector nearly tissue equivalent. The directional dependence of the radiation response of the diamond detector for cobalt 60, 6 MV and 18 MV photon beams was more uniform than that of the diode. As the incident photon beam moves from 0 [degree] (parallel to the detector stem) to a direction transverse to the detector stem (90 [degree] ), the diamond detector sensitivity remains nearly uniform whereas the diode sensitivity diminishes by approximately 15%-22%. The spatial resolution of the diamond detector, as measured by penumbra width, is slightly less than that of the diode detector but clearly superior to that of the 0.14 cm3 ionization chamber. The tissue maximum ratio measurements for small size photon fields (diameter <=4 cm) with the diamond, diode, and a Markus parallel plate chamber are in excellent agreement. The diamond detector with high radiation sensitivity and spatial resolution is an excellent choice as a detector in photon fields with high dose gradients such as brachytherapy and radiosurgery. RN - 10198-40-0. 7782-40-3 IS - 0094-2405 LG - English PT - Journal EM - 9506 5 UI - 95156123 AU - Meigooni AS AU - Mishra V AU - Panth H AU - Williamson J IN - Mallinckrodt Institute of Radiology, Washington Univ. School of Medicine, St. Louis, MO 63110; United States of America. CP - United States of America TI - Instrumentation and dosimeter-size artifacts in quantitative thermoluminescence dosimetry of low-dose fields. SO - Medical Physics Vol 22(5) (pp 555-562), 1995. MH - *Linear Accelerator MH - *Brachytherapy MH - Thermoluminescence MH - X Irradiation MH - Gamma Irradiation MH - Radiation Dose MH - Dosimetry MH - Mathematical Analysis MH - Artifact MH - Priority Journal MH - Article MH - *Cesium 137 MH - *Nitrogen AB - Thermoluminescence dosimetry is extensively used for quantitative dose measurements in various irradiation fields such as dosimetry of brachytherapy sources. In this application, small doses on the order of 0.5 cGy must be accurately measured, which requires careful control of instrumentation, energy-dependence, and nonlinearity of detector response. Several investigators have observed the presence of some undesirable signals when the thermoluminescent dosimeters (TLDs) were read without any nitrogen gas flow in the TLD reader. Others have indicated that the 'prereadout' annealing technique is the same as the 'preirradiation' technique for doses above 10 cGy, but they have not extended their study to lower doses. The goal of this study is to investigate dependence of sensitivity and linearity of the TLD response to the flow of nitrogen gas in the TLD reader at low dose level, annealing technique, and TLD size. The effect of nitrogen flow sensitivity and linearity of two different sizes of lithium fluoride TLD-100 chips has been studied. Our data indicate a large standard deviation of TLD sensitivity, up to a factor of 2, when TLDs were read without nitrogen gas flow in the TLD reader. In addition, a large deviation from linearity was observed for doses below 5 cGy. When the reading-chamber was purged with nitrogen gas, dispersion of the responses of the TLDs that were exposed to the same dose fell to within 5%. At precision levels of 2% and 5%, the low dose limits are 1 cGy and 0.5 cGy, respectively, for large chips and 15 cGy and 1 cGy for small chips, if TLDs are read with nitrogen gas flow in the TLD reader. The full results of our investigation are presented. RN - 10045-97-3. 7727-37-9 IS - 0094-2405 LG - English PT - Journal EM - 9506 6 UI - 95156122 AU - Tiourina TB AU - Dries WJF AU - Van der Linden PM IN - Department of Radiotherapy, Catharina Hospital, P.O. Box 1350 5602 ZA, Eindhoven; Netherlands. CP - United States of America TI - Measurements and calculations of the absorbed dose distribution around a 60Co source. SO - Medical Physics Vol 22(5) (pp 549-554), 1995. MH - *Cobalt Therapy MH - *Brachytherapy MH - System Analysis MH - Radiation Dose MH - Air MH - Water MH - Dosimetry MH - Mathematical Analysis MH - Priority Journal MH - Article MH - *Cobalt 60 AB - The data from Meisberger et al. [Radiology 90, 953-957 (1968)] are often used as a basis for dose calculations in brachytherapy. In order to describe the absorbed dose in water around a brachytherapy point source, Meisberger provided a polynomial fit for different isotopes taking into account the effect of attenuation and scattering. The validity of the Meisberger coefficients is restricted to distances up to 10 cm from the source, which is regarded to be satisfactory for most brachytherapy applications. However, for more distant organs it may lead to errors in calculated absorbed dose. For this reason dose measurements have been performed in air and in water around a high activity 60Co source used in high dose rate brachytherapy. Measurements were carded out to distances of 20 cm, using ionization chambers. These data show that at a distance of about 15 cm the amount of scattered radiation virtually equals the amount of primary radiation. This emphasizes the contribution of scattered radiation to the dose in healthy tissue far from the target volume, even with relatively high energy photon radiation of 60Co. It is also shown that the Meisberger data as well as the approach of Van Kleffens and Star [Int. J. Radiat. Oncol. Phys. 5, 557-563 (1979)] lead to significant errors in absorbed dose between distances of 10 and 20 cm from the source. In addition to these measurements, the Monte Carlo code has been used to calculate separately primary dose and scattered dose from a cobalt point source. The calculated results agree with the experimental data within 1% for a most distant dose scoring region. RN - 7732-18-5. 10198-40-0 IS - 0094-2405 LG - English PT - Journal EM - 9506 7 UI - 95156118 AU - Rogers DWO AU - Faddegon BA AU - Ding GX AU - Ma C-M AU - We J AU - Mackie TR IN - Ionizing Radiation Standards, Inst for Natl. Measurement Standards, National Research Council Canada, Ottawa, Ont. K1A 0R6; Canada. CP - United States of America TI - BEAM: A Monte Carlo code to simulate radiotherapy treatment units. SO - Medical Physics Vol 22(5) (pp 503-524), 1995. MH - *Linear Accelerator MH - *Cobalt Therapy MH - System Analysis MH - Photon MH - Electron MH - Energy Transfer MH - Dosimetry MH - Mathematical Analysis MH - Priority Journal MH - Article MH - *Cobalt 60 AB - This paper describes BEAM, a general purpose Monte Carlo code to simulate the radiation beams from radiotherapy units including high-energy electron and photon beams, 60Co beams and ortho-voltage units. The code handles a variety of elementary geometric entities which the user puts together as needed (jaws, applicators, stacked cones, mirrors, etc.), thus allowing simulation of a wide variety of accelerators. The code is not restricted to cylindrical symmetry. It incorporates a variety of powerful variance reduction techniques such as range rejection, bremsstrahlung splitting and forcing photon interactions. The code allows direct calculation of charge in the monitor ion chamber. It has the capability of keeping track of each particle's history and using this information to score separate dose components (e.g., to determine the dose from electrons scattering off the applicator). The paper presents a variety of calculated results to demonstrate the code's capabilities. The calculated dose distributions in a water phantom irradiated by electron beams from the NRC 35 MeV research accelerator, a Varian Clinac 2100C, a Philips SL75-20, an AECL Therac 20 and a Scanditronix MM50 are all shown to be in good agreement with measurements at the 2 to 3% level. Eighteen electron spectra from four different commercial accelerators are presented and various aspects of the electron beams from a Clinac 2100C are discussed. Timing requirements and selection of parameters for the Monte Carlo calculations are discussed. RN - 12587-47-2. 10198-40-0 IS - 0094-2405 LG - English PT - Journal EM - 9506 8 UI - 95134664 AU - Cadman P IN - Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alta. T2N 4N2; Canada. CP - United States of America TI - A dosimetric investigation of scatter conditions for dual asymmetric collimators in open fields. SO - Medical Physics Vol 22(4) (pp 457-463), 1995. MH - *Dosimetry MH - *Collimator MH - Radiation Scattering MH - Phantom MH - Receptive Field MH - Radiation Depth Dose MH - Dose Calculation MH - Nonhuman MH - Priority Journal MH - Article MH - *Scatter Factor AB - An investigation of the scattering effects of dual asymmetric collimators on open fields is presented. It has been determined that the output measured in air and in a phantom is radially symmetric and that the scatter as a function of field size is independent of field center offset, for a wide variety of square and rectangular field shapes. The analysis has led to a new and simplified method to represent primary off-center ratios (POCRs), which requires a minimum set of symmetric field data, including beam profiles, collimator and phantom scatter factors, and tissue maximum ratios. The field edge correction (FEC) method proposed has been shown to accurately model the POCRs to a distance of 17.5 cm from the collimator rotation axis in a plane perpendicular to the isocenter and at depths up to 30 cm without the need for extrapolation of the POCRs or special measurements setups, which may be required for POCR modeling techniques that measure narrow beam attenuation coefficients. RN - 67256-21-7 IS - 0094-2405 LG - English PT - Journal EM - 9506 9 UI - 95065386 AU - Frye DMD AU - Paliwal BR AU - Thomadsen BR AU - Jursinic P IN - University of Wisconsin Hospital, Madison, WI; United States of America. CP - United States of America TI - Intercomparison of normalized head-scatter factor measurement techniques. SO - Medical Physics Vol 22(2) (pp 249-254), 1995. MH - *Dosimetry MH - Intermethod Comparison MH - Measurement MH - Technique MH - Radiation Dose MH - Dose Calculation MH - Mathematical Analysis MH - Nonhuman MH - Priority Journal MH - Article MH - *Scatter Factor AB - Normalized head-scatter factors were measured with cylindrical beam coaxial miniphantoms and high purity graphite buildup caps for 4-, 6-, 10-, and 24-MV photon beams at field sizes from 4 x 4 to 40 x 40 cm2. The normalized head-scatter factors determined by the two methods matched well for 4- and 6-MV photon beams. The miniphantom technique produced normalized head-scatter factors 1.5% and 4.8% lower than the buildup caps for the 10- and 24-MV beams for large field sizes, respectively. At small field sizes, the miniphantom technique produced larger normalized head-scatter factors than the buildup caps. Measurements made with an electromagnet indicate that a significant portion of the ionization measured in the buildup cap at 24 MV arises from contamination electrons. Measurements made with the miniphantom and magnet found no contamination electron contribution. The miniphantom technique may exclude such contamination electrons, potentially leading to inaccuracies in tissue-maximum ratios and phantom scatter factors, as well as inaccuracies in monitor unit calculations. RN - 67256-21-7 IS - 0094-2405 LG - English PT - Journal EM - 9503 10 UI - 95033424 AU - Meijer JG AU - Van Wieringen N AU - Koedooder C AU - Nieuwenhuys GJ AU - Van Dijk JDP IN - Kamerlingh Onnes Laboratory, Leiden State University, Leiden; Netherlands. CP - United States of America TI - The development of PdNi thermoseeds for interstitial hyperthermia. SO - Medical Physics Vol 22(1) (pp 101-104), 1995. MH - *Hyperthermic Therapy MH - Implant MH - Cancer Therapy MH - Magnetism MH - Priority Journal MH - Article MH - *Ferromagnetic Material MH - *Palladium MH - *Nickel AB - Magnetic induction heating of thermoseed implants can be used to produce highly localized hyperthermia in deep-seated tumors. Automatic temperature control throughout the tumor can be achieved by the self-regulating character of ferromagnetic seeds, which corrects for local variations in heat loss due to blood perfusion. An increased sharpness of the ferromagnetic transition at the Curie temperature, T(c), improves the performance of self-regulating control. This was realized for palladium-nickel alloys by a 'cold working' procedure preceded and followed by annealing. Palladium nickel seeds with a predetermined T(c) were produced, showing a sharp decrease at T(c) of the magnetic susceptibility and the heat production. RN - 7440-02-0 IS - 0094-2405 LG - English PT - Journal EM - 9503