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Three-dimensional treatment planning
Proceedings of the 35th Annual ASTRO Meeting
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303 THE DESIGN AND CLINICAL APPLICATION OF DIGITAL PORTAL IMAGING SYSTEMS Shlomo Shalev, Ph.D. Dept. of Medical Physics, Manitoba Cancer Treatment and Research Foundation, Winnipeg, Canada m: To review the current status of digital portal imaging and to describe the major design, functional and operational aspects of clinical systems. Participants will obtain a clear understanding of the advantages of using electronic portal imaging systems, and the potential benefits for impmved patient management. The recent introduction of electronic portal imaging devices (EPID’s) opens up new possibilities for verifying the accuracy of radiation treatments, reducing set-up and treatment errors, and ensuring the precise delivery of dose to the prescribed target volume. Various designs are available, based on ionization chambers, solid state detectors, and video imaging systems, and their relative merits are compared with computed radiography and with conventional portal films. The factors influencing portal image quality are discussed in terms of dose utilization, contrast and spatial resolution, temporal response, and digital image processing. Image acquisition and display techniques include localization @e-treatment) and verification (post-treatment) static images, intra-treatment movies, and intertreatment time-lapse displays. A number of approaches are being investigated for the verification of treatment accuracy. Field size and shape, and block positioning, can be checked automatically by very rapid (cl sec.) analysis of the portal image at the beginning of treatment, with interruption of treatment if errors are detected in excess of pre-defined action levels. Field location relative to the patient’s anatomy requires alignment of the portal image with a prescription image, (usually the first portal image or a digitized simulation film), and both rigid-body and mom robust alignment techniques are described. The application of on-line portal imaging in routine radiotherapy is reviewed, with examples showing the type and frequency of errors that are detected. The cost/benefit of interventional portal imaging is discussed, as well as projections regarding the further development of this technology.
304 CLINICAL BRACHYTHERAPY FOR HEAD AND NECK (HAN) CANCER Alain P. Gerbaulet, M.D.*, Christine M. Haie-Meder, M.D., Jean-Louis Habrand, M.D. *Head of Brachytherapy Department Institut Gustave-Roussy, 94805 Villejuif, France . . se/OThe purpose of this course is to determine the role of brachytherapy in the conservative treatment of HAN ca, insisting on the rules of implant, of dose calculation and showing the results (survival, local control, complications rate) according to the different tumor sites in which bmchytherapy is used. Following the initial radium implantations in 1905, interstitial brachytherapy became progressively the mainstay in the treatment of accessible sites like the mobile tongue. Nonetheless, in the mid-fifties, megavoltage equipments gained the favor of most radiation oncologists and various technical modalities were tested as “cone down” boosts (external, inua-oral cones). The renovation of brachytherapy dates back to the introduction of miniaturized artificial elements, mainly the Iridium 192, afterloaded in non-active preparations by henshke and Hilaris in the United States and, soon thereafter, by Pierquin and Chassagne in Europe. Modern treatment plannings using brachytherapy call now for strict rules of implantation and computerized dose-calculations. HAN carcinoma still represents, in developed countries, an overriding concern and poses oncological and functional problems largely unsolved. Interstitial implants play in our experience a major role among the conservative procedures. Brachytherapy techniques have been diversified, so that they can be adapted to various anatomical situations: plastic tubes, guide gutters, hypodermic needles, guide needles, silk wires . . . But, the keys of success include a precise definition of the tumor extension and a careful evaluation of the nodal status and possibly associated second primary. In most situations, brachytherapy should be part of multi-nodal strategies, along with neck nodal dissection and/or external irradiation. The indications and treatment protocols will be detailed by anatomical sites (eyelid, nose, lip, oral cavity, oropharynx, nasophsrynx, metastatic cervical nodes, HAN pediatric malignancies) with TNM staging and practical guidelines based on clinical situation. Research programs exploring the use of modern imaging or high dose rates will also be reviewed. Co clua: Brachytherapy can offer very interesting possibilities of conservative and effective treatment in HAN cancers: survival (6070; ), local control (70-!%I%),complications (15-2096).
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303 THE DESIGN AND CLINICAL APPLICATION OF DIGITAL PORTAL IMAGING SYSTEMS Shlomo Shalev, Ph.D. Dept. of Medical Physics, Manitoba Cancer Treatment and Research Foundation, Winnipeg, Canada m: To review the current status of digital portal imaging and to describe the major design, functional and operational aspects of clinical systems. Participants will obtain a clear understanding of the advantages of using electronic portal imaging systems, and the potential benefits for impmved patient management. The recent introduction of electronic portal imaging devices (EPID’s) opens up new possibilities for verifying the accuracy of radiation treatments, reducing set-up and treatment errors, and ensuring the precise delivery of dose to the prescribed target volume. Various designs are available, based on ionization chambers, solid state detectors, and video imaging systems, and their relative merits are compared with computed radiography and with conventional portal films. The factors influencing portal image quality are discussed in terms of dose utilization, contrast and spatial resolution, temporal response, and digital image processing. Image acquisition and display techniques include localization @e-treatment) and verification (post-treatment) static images, intra-treatment movies, and intertreatment time-lapse displays. A number of approaches are being investigated for the verification of treatment accuracy. Field size and shape, and block positioning, can be checked automatically by very rapid (cl sec.) analysis of the portal image at the beginning of treatment, with interruption of treatment if errors are detected in excess of pre-defined action levels. Field location relative to the patient’s anatomy requires alignment of the portal image with a prescription image, (usually the first portal image or a digitized simulation film), and both rigid-body and mom robust alignment techniques are described. The application of on-line portal imaging in routine radiotherapy is reviewed, with examples showing the type and frequency of errors that are detected. The cost/benefit of interventional portal imaging is discussed, as well as projections regarding the further development of this technology.
304 CLINICAL BRACHYTHERAPY FOR HEAD AND NECK (HAN) CANCER Alain P. Gerbaulet, M.D.*, Christine M. Haie-Meder, M.D., Jean-Louis Habrand, M.D. *Head of Brachytherapy Department Institut Gustave-Roussy, 94805 Villejuif, France . . se/OThe purpose of this course is to determine the role of brachytherapy in the conservative treatment of HAN ca, insisting on the rules of implant, of dose calculation and showing the results (survival, local control, complications rate) according to the different tumor sites in which bmchytherapy is used. Following the initial radium implantations in 1905, interstitial brachytherapy became progressively the mainstay in the treatment of accessible sites like the mobile tongue. Nonetheless, in the mid-fifties, megavoltage equipments gained the favor of most radiation oncologists and various technical modalities were tested as “cone down” boosts (external, inua-oral cones). The renovation of brachytherapy dates back to the introduction of miniaturized artificial elements, mainly the Iridium 192, afterloaded in non-active preparations by henshke and Hilaris in the United States and, soon thereafter, by Pierquin and Chassagne in Europe. Modern treatment plannings using brachytherapy call now for strict rules of implantation and computerized dose-calculations. HAN carcinoma still represents, in developed countries, an overriding concern and poses oncological and functional problems largely unsolved. Interstitial implants play in our experience a major role among the conservative procedures. Brachytherapy techniques have been diversified, so that they can be adapted to various anatomical situations: plastic tubes, guide gutters, hypodermic needles, guide needles, silk wires . . . But, the keys of success include a precise definition of the tumor extension and a careful evaluation of the nodal status and possibly associated second primary. In most situations, brachytherapy should be part of multi-nodal strategies, along with neck nodal dissection and/or external irradiation. The indications and treatment protocols will be detailed by anatomical sites (eyelid, nose, lip, oral cavity, oropharynx, nasophsrynx, metastatic cervical nodes, HAN pediatric malignancies) with TNM staging and practical guidelines based on clinical situation. Research programs exploring the use of modern imaging or high dose rates will also be reviewed. Co clua: Brachytherapy can offer very interesting possibilities of conservative and effective treatment in HAN cancers: survival (6070; ), local control (70-!%I%),complications (15-2096).