Pencil Beam and Collapsed Cone Algorithm Calculations for a Lung-Type Volume Using Ct and the Omp Treatment Planning System

7831 Words May 23rd, 2012 32 Pages
Pencil Beam and Collapsed Cone Algorithm Calculations for a
Lung-type Volume Using CT and the OMP Treatment Planning System
Methods
Measurements have been carried out in both phantom and a specifically designed phantom which simulated human lung volume. Samples were taken from the Lung Planning CT images for 15 patients using the Oncentra Masterplan OMP Treatment Planning System. The X-axis was, following convention, taken to be horizontal, and the Y-axis to be vertical; accordingly, abscissa and ordinate distances to the skin, heart and the lungs were measured (see figure 8). Figures 4 and 5 show typical CT images for a patient’s lungs, while Tables 1 and 2 give the beam information and dose information for typical patients. The X-ray
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They were made of an epoxy resin-based tissue-equivalent material to represent water (WT1, density=1.02 gcm-3), lung (LN10 density=0.27 gcm-3) and bone (IB7, density=1.13 gcm-3). Some of the square blocks of WT1 were drilled to accommodate a 0.6 cm3 graphite ionisation chamber. The phantoms were composed by putting the epoxy blocks within an adjustable wooden frame in desired configurations. The frame was held together using a series of small wooden pins with diameters of 5 mm. | Skin to Lung (cm) | Lung to heart (cm) | Heart (cm) | Heart to Lung (cm) | Lung to Skin (cm) | X,Y axis | Average for patient(Lateral) | 2.8 | 4.2 | 4.2 | 3.3 | 3.1 | 17.4 | Average for patient (Ant-post) | 2.3 | 1.9 | 4.4 | 1.3 | 2.6 | 11.1 | Average for Phantom(X) | 4 | 8 | 4 | 8 | 4 | 28 | Average for Phantom(Y) | 4 | 4 | 6 | 2 | 4 | 20 | MAX in X axis for patients (Lateral) | 19 | MIN in X axis for patients (Lateral) | 15 | MAX in Y axis for patients (Ant-post) | 13.7 | MIN in Y axis for patients (Ant-post) | 9.6 | RANGE in X axis for patients (Lateral) | 4 | RANGE in Y axis for patients (Ant-post) | 4.1 |
Table 3: The area for Lateral and Ant-post in 15 Patients (average and range for 15 patients) and average for Multiblock phantom
Figures 9 and 10 below depict various stages in the construction of the thorax phantom within its frame. Expanded polystyrene spacer elements with triangular cross sections stabilised

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