Soft Tissue Visualization Using a Highly Efficient Megavoltage Cone ...

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The corrected (Offset, Gain, Dead pixel) and pre-processed (resolution/dose adaptive filtering) projection images were normalized using the pixel data in the open area of the image. /////// Volumetric reconstruction is accomplished with using an extension of Feldkamp filtered back projection in cone beam geometry 5 . The reconstruction time for generating 256 3 CT data was ?? 2.6 Phantoms for Image Quality Analysis The followings are the list of phantoms that were used and all were positioned at isocenter. The source to imager distance (SID) was 140cm for all phantom images. • A QC-3V phantom 3 was used to determine the spatial resolution and contrast to noise ratio (CNR) of 2D projection images. • A ball phantom with a diameter of 16cm consisting of water-equivalent plastic was used for contrast/spatial resolution experiments. The 1cm thick slice in the middle of the ball contains several tissue equivalent inserts that are 3 cm in diameter (Figure-2). There are also some inserts with smaller diameters (1, 0.5, and 0.25 cm). There are air filled holes with diameters of 1, 1.5, 2, and 3mm within the middle slice of phantom for spatial resolution analysis. • A Quality Assurance System for Advanced Radiotherapy (QUASAR) body phantom 4 that contains Electron Density (ED) rods of lung inhale, polyethylene, water equivalent, trabecular bone, and dense bone with EDs of 0.190, 0.945, 1.002, 1.117, and 1.512; respectively. The ED of acrylic is 1.137. • An anthropomorphic head phantom with implanted gold seeds (1mm in diameter and 3mm long)
3.1 2D QC-3V phantom Projections Figure 2: Contrast resolution phantom 3. Results Figures 3a and 3b illustrate the QC-3V phantom images acquired with receptors 1 and 2. The QC images were analyzed by the PIPS-pro 3 software to compute the CNR, f50, f40, f30, and are shown in Table-1. Receptor Dose (cGy) CNR f50 (lp/mm) f40 (lp/mm) f30 (lp/mm) 1 0.025 43 0.39 0.50 0.64 2 0.035 69 0.41 0.53 0.66 Table-1: Computed spatial resolution and CNR
Page 1 and 2: Soft Tissue Visualization Using a H
Page 3: Two image receptors that were used
Page 7 and 8: (a) 18cGy QUASAR (b) 18cGy contrast
Page 9 and 10: Figure 8: Axial view of the pelvic
Page 11 and 12: Figure 13 shows neck/chest MVCT axi

Soft Tissue Visualization Using a Highly Efficient Megavoltage Cone ...

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