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PURPOSE: To implement in software the procedures described in AAPM Task Group 150's draft recommendations for image receptor performance testing, and to evaluate the effectiveness and practicality of these procedures. METHODS: Images of flat fields were acquired using digital x-ray image receptors at 6 cooperating institutions. Four flat field images obtained with each detector spanned a range of input detector air kerma. Software based on AAPM TG150's draft report processed the test images and generated results. Image receptor response and several measures of non-uniformity were evaluated. Images were divided into 10 mm square regions, after eliminating 10 mm borders. For each region, signal (mean), noise (standard deviation) and SNR were calculated. Characteristic signal, noise and SNR were calculated based on average values from all regions. Local non-uniformity for signal (SLN), noise (NLN) and SNR (SNRLN) were expressed as the maximum ratio of the absolute difference between each region's value and its 4 nearest neighbors, to the respective characteristic value. Global non-uniformity (SGN, NGN, SNRGN) were expressed similarly but differences between maximum and minimum values obtained from the regions were used (without comparison to local neighbors). RESULTS: TG150 tests discriminated between good and poorly performing detectors. Improper detector calibration was detectable, with noise non-uniformity proving to be a more sensitive measure than signal or SNR non-uniformity. Detector rotation relative to calibration conditions produced a greater change in signal non-uniformity than the other measures. Image receptor structured noise was characterized by an increase in noise non-uniformity with incident air kerma. CONCLUSIONS: AAPM TG150's proposed approach to image receptor testing was implemented and evaluated. The approach appears to be an effective and practical one for routine quality assurance testing of digital radiographic image receptors.
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There are many recommendations for appropriate quality control for computed tomography scanners. The breadth of the recommendations is large and this has led to confusion as to what quality control is indeed necessary. The American College of Radiology is producing a QC Manual for CT under the auspices of the CT Accreditation Program. The draft manual is currently under final stages of review. LEARNING OBJECTIVES: 1. Review current recommendations for CT quality control 2. Describe the draft QC program of the ACR CT QC Manual 3. Discuss the status of the ACR CT QC Manual.
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The potential dose distribution advantages associated with proton therapy, and particularly with pencil beam scanning (PBS) techniques, have lead to considerable interest in this modality in recent years. However, the large capital expenditure necessary for such a project requires careful financial consideration and business planning. The complexity of the beam delivery systems impacts the capital expenditure and the PBS only systems presently being advocated can reduce these costs. Also several manufacturers are considering "one-room" facilities as less expensive alternatives to multi-room facilities. This presentation includes a brief introduction to beam delivery options (passive scattering, uniform and modulated scanning) and some of the new technologies proposed for providing less expensive proton therapy systems. Based on current experience, data on proton therapy center start-up costs, running costs and the financial challenges associated with making this highly conformal therapy more widely available will be discussed. Issues associated with proton therapy implementation that are key to project success include strong project management, vendor cooperation and collaboration, staff recruitment and training. Time management during facility start up is a major concern, particularly in multi-room systems, where time must be shared between continuing vendor system validation, verification and acceptance testing, and user commissioning and patient treatments. The challenges associated with facility operation during this period and beyond are discussed, focusing on how standardization of process, downtime and smart scheduling can influence operational efficiency. LEARNING OBJECTIVES: 1. To understand the available choices for proton therapy facilities, the different beam delivery systems and the financial implications associated with these choices. 2. To understand the key elements necessary for successfully implementing a proton therapy program. 3. To understand the challenges associated with on-going facility management to achieve an efficient fully operational system.
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Intensity modulated radiation therapy (IMRT) is a technology intensive treatment modality involving the delivery of highly conformal dose distributions to patients. IMRT is becoming a standard of care for many disease sites and approximately 30%-60% of cancer patients in the United States receive IMRT treatments. Given the complexity of the IMRT treatment planning and delivery processes, a number of AAPM reports and guidance documents addressed the technical aspects of IMRT, including the need for comprehensive acceptance testing, commissioning, and QA programs for IMRT planning and delivery equipment. The implementation of these verification programs is essential to ensure the accuracy of IMRT delivery. Despite the critical role of patient-specific IMRT verification QA to ensure the safe delivery of IMRT treatments to patients as planned, there is little systematic guidance on the type of methodologies, tools, and acceptable tolerance levels that are needed in clinical practice. Furthermore, there are limited discussion on the pros and cons of the different delivery methods for QA measurements, and no recommendations on how to assess the clinical relevance of failed IMRT plans. LEARNING OBJECTIVES: 1. To discuss commonly employed IMRT measurement methods and discuss the pros and cons of each method. 2. To review methodologies for absolute dose verification (single small-volume, 1D, 2D methods), and review dose-difference, DTA, and Gamma analysis techniques including the variability of vendors implementation 3. To review IMRT QA passing rates for given tolerances and action levels, and discuss the clinical relevance of failed IMRT QA.