Med Phys
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Conventional radiography has been for decades the standard method of evaluation for cervical spine trauma patients. However, currently available helical multidetector CT scanners allow multiplanar reconstruction of images, leading to increased diagnostic accuracy. The purpose of this study was to determine the relative benefit/risk ratio between cervical spine CT and cervical spine radiography and between cervical spine CT and cervical spine radiography, followed by CT as an adjunct for positive findings. ⋯ According to the decision model calculations, the use of CT is more favorable over the use of radiography alone or radiography with CT by a factor of 13, for low risk 20 yr old patients, to a factor of 23, for high risk patients younger than 80 yr old. The radiography/CT imaging strategy slightly outperforms plain radiography for high and moderate risk patients. Regardless of the patient age, sex, and fracture risk, the higher diagnostic accuracy obtained by the CT examination counterbalances the increase in dose compared to plain radiography or radiography followed by CT only for positive radiographs and renders CT utilization justified and the radiographic screening redundant.
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Daily setup for head and neck (HN) radiotherapy (RT) can vary randomly due to neck rotation and anatomy change. These differences cannot be totally corrected by the current practice of image guided RT with translational repositioning. The authors present a novel rapid correction scheme that can be used on-line to correct both interfractional setup variation and anatomy change for HN RT. ⋯ The target coverage and OAR sparing for the SAM/SWO plans were found to be equivalent to the original plan. The SAM/SWO process took 5-8 min for the head and neck cases studied. The proposed aperture morphing with weight optimization is an effective on-line approach for correcting interfractional patient setup and anatomic changes for head and neck cancer radiotherapy.
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Accurate segmentation of lungs with severe interstitial lung disease (ILD) in thoracic computed tomography (CT) is an important and difficult task in the development of computer-aided diagnosis (CAD) systems. Therefore, we developed in this study a texture analysis-based method for accurate segmentation of lungs with severe ILD in multidetector CT scans. ⋯ Our lung segmentation method provided accurate segmentation results for abnormal CT scans with severe ILD and would be useful for developing CAD systems for quantification, detection, and diagnosis of ILD.
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The aim of this study was to develop a 4D-modeling algorithm, designated "3D+," to simulate organ movement and deformation for 4D dose calculation without the need for 4D-CT or deformable image registration and to assess the validity of this algorithm. ⋯ 4D modeling of the thorax utilizing the 3D+ algorithm shows acceptable accuracy and is more suited for routine clinical use in terms of processing time than conventional 4D-CT and deformable image registration. The 3D+ algorithm may be useful for simulating dose distribution for advanced beam delivery techniques, such as real-time tumor tracking irradiation and adaptive radiation therapy.
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Matching the penumbra of a 6 MeV electron beam to the penumbra of a 6 MV photon beam is a dose optimization challenge, especially when the electron beam is applied from an extended source-to-surface distance (SSD), as in the case of some head and neck treatments. Traditionally low melting point alloy blocks have been used to define the photon beam shielding over the spinal cord region. However, these are inherently time consuming to construct and employ in the clinical situation. Multileaf collimators (MLCs) provide a fast and reproducible shielding option but generate geometrically nonconformal approximations to the desired beam edge definition. The effects of substituting Cerrobend for the MLC shielding mode in the context of beam matching with extended-SSD electron beams are the subject of this investigation. ⋯ The weighted DDVH comparison techniques allowed the composite dosimetry resulting from the interplay of the abovementioned variables to be ranked. The MLC dosimetry ranked as good or better than that resulting from beam matching with Cerrobend for all except large field overlaps (-2.5 mm gap). The results for the linear-weighted DDVH comparison suggest that optimal MLC abutment dosimetry results from an optical surface gap of around 1 +/- 0.5 mm. Furthermore, this appears reasonably lenient to abutment gap variation, such as that arising from uncertainty in beam markup or other setup errors.