Sci‐AM1 Sat ‐ 05: Fractal and motion modeling of PET/CT tumours

Abstract

Objective: To generate realistic computer‐simulated PET/CT tumour images with characteristics typical of the tumour (shape, pixel intensity and movement over time) and of the imaging system (acquisition parameters and resolution). Methods: An initial tumour volume was segmented from the CT scan of a lung cancer patient via region growing. To improve the axial resolution and mimic the contour curvature and pixel variations in the transaxial plane, fractal analysis and interpolation was used. Breathing motion with a period and extents typical of lung cancer patients was then applied to the fractal tumour. To produce PET and CT images, the moving tumour was sampled according to acquisition characteristics typical of the two modalities. For CT, a slice thickness of 3.0mm, acquisition time of 0.7s and resolution of 2mm was assumed. For PET, it was assumed that tumour motion was captured within one bed position over an acquisition time of 180s, and the imager resolution was 6mm. Results: Following fractal interpolation, the tumour exhibited similar curvature and gray‐level gradation in all three imaging planes. Application of motion and blurring produced CT images different in appearance from the stationary fractal tumour volume and the total volume traced by the moving object. Motion and blurring produced PET images similar to the volume traced by the moving object, graded by the time spent in each location within the volume and blurred due to the degraded resolution of the scanner. Conclusions: Realistic computer‐simulated PET/CT tumour images can be generated using fractal analysis and motion modeling.