Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session J21: Medical Physics: Approaches to Cancer Treatment |
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Sponsoring Units: DBP Chair: Paul Gueye, Hampton University Room: Colorado Convention Center 106 |
Tuesday, March 6, 2007 11:15AM - 11:51AM |
J21.00001: The use of Monte Carlo methods in heavy charged particle radiation therapy. Invited Speaker: This presentation will demonstrate the importance of Monte Carlo (MC) simulations in proton therapy. MC applications will be shown which aim at 1. Modeling of the beam delivery system. MC can be used for quality assurance verification in order to understand the sensitivity of beam characteristics and how these influence the dose delivered. 2. Patient treatment dose verification. The capability of reading CT information has to be implemented into the MC code. Simulating the ionization chamber reading in the treatment head allows the dose to be specified for treatment plan verification. 3. 4D dose calculation. The patient geometry may be time dependent due to respiratory or cardiac motion. To consider this, patient specific 4D CT data can be used in combination with MC simulations. 4. Simulating positron emission. Positron emitters are produced via nuclear interactions along the beam path penetration and can be detected after treatment. Comparison between measured and MC simulated PET images can provide feedback on the intended dose in the patient. 5. Studies on radiation induced cancer risk. MC calculations based on computational anthropomorphic phantoms allow the estimation of organ dose and particle energy distributions everywhere in the patient. [Preview Abstract] |
Tuesday, March 6, 2007 11:51AM - 12:03PM |
J21.00002: Simulating the migration of multiple cancer cells in the bloodstream Keng-Hwee Chiam We model the migration of cancer cells that have broken away from a tumor and are circulating in the bloodstream. Using the immersed boundary method and culling from literature the material properties of cancer cells, we solve for the deformation of the cells represented as ``immersed boundaries'' being advected by the shear flow of the bloodstream. We solve for the magnitude of the deformation as a function of the flow magnitude as well as the adhesive properties between the cancer cells and the endothelial cells of the bloodstream. We also simulate the migration characteristics as a function of the migrating cell density. From these, we calculate rough approximations of the metastatic rate and efficiency. [Preview Abstract] |
Tuesday, March 6, 2007 12:03PM - 12:15PM |
J21.00003: Multicatheter Device for Brachytherapy Treatment Carlos Velasco, Paul Gueye, Cynthia Keppel Low dose rate brachytherapy treatment for prostate cancer encompasses the delivery of capsules containing radioactive material into the prostate's cancerous tissue via injection through needles. High dose rate brachytherapy treatment for prostate cancer follows the same concept with the difference that the radioactive source has a higher activity and it is placed temporarily into the patient. For this reason, the source is driven by an afterloading device that moves the source into the catheters and back into a shielded container. From both HDR and LDR brachytherapy, two issues remain unaddressed: homogeneity and localization. Sources not being homogeneous result in a delivered dose that does not correspond to the treatment plan. In the case of HDR, the afterloader not always places the source where it should within the catheter. This results in undertreatment of the cancerous tissue as well as damage to healthy tissue. To address both issues we have placed scintillating fiber into brachytherapy needles. If placed geometrically around the radioactive seeds we are able to check for homogeneity in the sources. At the same time, by analyzing the detected signals we are trying to determine the exact physical position of the seeds within the catheter. Using a radioactive source, we have taken measurements to calibrate the device and measurements under water to simulate living tissue environment. Results are discussed. [Preview Abstract] |
Tuesday, March 6, 2007 12:15PM - 12:27PM |
J21.00004: Calibration Of An Active Mammosite Using A Low Activity Sr-90 Radioactive Source Jacquelyn Winston The latest involvement of the Brachytherapy research group of the medical physics program at Hampton University is in the development of a scintillating fiber based detector for the breast cancer specific Mammosite (balloon device) from Cytyc Inc. Recent data were acquired at a local hospital to evaluate the possibility of measuring the dose distribution during breast Brachytherapy cancer treatments with this device. Since sub-millimeter accuracy in position is required, precision of the device relies on the accurate calibration of the scintillating fiber element. As part of a collaboration work, data were acquired for that purpose at Hampton University and subsequently analyzed at Morgan State University. An 8 mm diameter strontium-90 radioactive field source with a low activity of 25 $\mu $Ci was used along with a dedicated LabView data acquisition system. We will discuss the data collected and address some of the features of this novel system. [Preview Abstract] |
Tuesday, March 6, 2007 12:27PM - 12:39PM |
J21.00005: Brachytherapy with an improved MammoSite Radiation Therapy System Nanda Karthik, Cynthia Keppel, Vahagn Nazaryan Accelerated partial breast irradiation treatment utilizing the MammoSite Radiation Therapy System (MRTS) is becoming increasingly popular. Clinical studies show excellent results for disease control and localization, as well as for cosmesis. Several Phase I, II, and III clinical trials have found significant association between skin spacing and cosmetic results after treatment with MRTS. As a result, patients with skin spacing less then 7 mm are not recommended to undergo this treatment. We have developed a practical innovation to the MammoSite brachytherapy methodology that is directed to overcome the skin spacing problem. The idea is to partially shield the radiation dose to the skin where the skin spacing is less then 7 mm, thereby protecting the skin from radiation damage. Our innovation to the MRTS will allow better cosmetic outcome in breast conserving therapy (BCT), and will furthermore allow more women to take advantage of BCT. Reduction in skin radiation exposure is particularly important for patients also undergoing adjuvant chemotherapy. We will present the method and preliminary laboratory and Monte Carlo simulation results. [Preview Abstract] |
Tuesday, March 6, 2007 12:39PM - 1:15PM |
J21.00006: Recent advances in radiation cancer therapy Invited Speaker: This paper presents the recent advances in radiation therapy techniques for the treatment of cancer. Significant improvement has been made in imaging techniques such as CT, MRI, MRS, PET, ultrasound, etc. that have brought marked advances in tumor target and critical structure delineation for treatment planning and patient setup and target localization for accurate dose delivery in radiation therapy of cancer. Recent developments of novel treatment modalities including intensity-modulated x-ray therapy (IMXT), energy- and intensity modulated electron therapy (MERT) and intensity modulated proton therapy (IMPT) together with the use of advanced image guidance have enabled precise dose delivery for dose escalation and hypofractionation studies that may result in better local control and quality of life. Particle acceleration using laser-induced plasmas has great potential for new cost-effective radiation sources that may have a great impact on the management of cancer using radiation therapy. [Preview Abstract] |
Tuesday, March 6, 2007 1:15PM - 1:27PM |
J21.00007: An Active MammoSite{\copyright} for Breast Cancer Treatment Alice Quan Breast brachytherapy using the MammoSite{\copyright} balloon catheter is one of the latest developments in breast cancer treatment and is the most performed method of brachytherapy. A high activity $^{192}$Ir radioactive source is pushed inside the shaft of the device until it reaches the center of the balloon. The latest involvement of the Brachytherapy research group of the medical physics program at Hampton University is in the development of a scintillating fiber based detector for the breast cancer specific MammoSite{\copyright} balloon catheter from Cytyc, Inc. During the summer 2006, data were acquired at a local hospital (Bon Secours DePaul Medical Center) to evaluate the possibility of measuring the source location and dose distribution during breast brachytherapy cancer treatments with this device. Two 0.5 mm$^{2}$ and 1.0 mm$^{2}$ scintillating fibers were used for these experiments. We used two modified MammoSite{\copyright} devices, each housing an extra tubing within which the fibers were inserted. The results from these runs confirm the possibility of an active MammoSite{\copyright} to monitor the location of the source as well its dose distribution during patient treatment. We will describe the experimental setup and discuss the data. [Preview Abstract] |
Tuesday, March 6, 2007 1:27PM - 1:39PM |
J21.00008: Optical Interferometric Response of Living Tissue to Cytoskeletal Anticancer Drugs David Nolte, Kwan Jeong, John Turek Living tissue illuminated by short-coherence light can be optically sectioned in three dimensions using coherent detection such as interferometry. We have developed full-field coherence-gated imaging of tissue using digital holography. Two-dimensional image sections from a fixed depth are recorded as interference fringes with a CCD camera located at the optical Fourier plane. Fast Fourier transform of the digital hologram yields the depth-selected image. When the tissue is living, highly dynamic speckle is observed as fluctuating pixel intensities. The temporal autocorrelation functions are directly related to the degree of motility at depth. We have applied the cytoskeletal drugs nocodazole and colchicine to osteogenic sarcoma multicellular spheroids and observed the response holographically. Colchicine is an anticancer drug that inhibits microtubule polymerization and hence prevents spindle formation during mitosis. Nocodazole, on the other hand, depolymerizes microtubules. Both drugs preferentially inhibit rapidly-dividing cancer cells. We observe dose-response using motility as an effective contrast agent. This work opens the possibility for studies of three-dimensional motility as a multiplexed assay for drug discovery. [Preview Abstract] |
Tuesday, March 6, 2007 1:39PM - 1:51PM |
J21.00009: Characterization and modeling of relative efficiency of optically stimulated luminescence Al$_{2}$O$_{3}$:C detectors exposed to heavy charged particles Gabriel Sawakuchi, Eduardo Yukihara Medical dosimetry of heavy charged particles (HCPs) and personnel space dosimetry are becoming important areas with the development of new facilities for cancer therapy of heavy ions and the increase of human activities in space. In particular, the measurement of dose in the space radiation field is one of the most challenging problems in personnel dosimetry due to the presence of a mixture of different particles with a wide range of energies. HCP creates a pattern of energy deposition around its path which is a characteristic of the type of particle and its energy. Due to different spatial distribution of dose around the HCP path, the response of the dosimeter can be significantly different for different types of particles and energies. This work characterizes the optically stimulated luminescence (OSL) response of Al$_{2}$O$_{3}$:C personnel dosimeter to different HCPs and energies. Also, a model based on track structure theory to predict the OSL response of the dosimeter is presented. [Preview Abstract] |
Tuesday, March 6, 2007 1:51PM - 2:03PM |
J21.00010: Computed Tomography Measurements Using Optically Stimulated Luminescence of KBr:Eu In Real-Time. David Klein, David Peakheart, Razvan Gaza, X. John Rong, Stephen McKeever Increasing complexity in modern scanning geometries invalidates the concept of computed tomography dose index (CTDI) for CT dosimetry. A real-time dosimetry system using optically stimulated luminescence (OSL) of KBr:Eu is evaluated in comparison with a pencil ionization chamber for CT dosimetry in this study. CT scans were measured over a relevant range of energies and tube currents using a GE LightSpeed Ultra scanner. Complete OSL signals were obtained before, during, and after the CT scans at a rate of 10Hz. Performance was determined in part by normalizing both the initial OSL intensity and the background-subtracted integral OSL to exposure reported by an ionization chamber. OSL response normalized to exposure shows good correlation with coefficients of variation of $\sim ${\%}5 or less. Results show that this OSL dosimetry system possesses great potential for faster, higher-resolution CT characterization and may prove a valuable alternative to CTDI. [Preview Abstract] |
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