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Radiation Protection in Nuclear Medicine PRACTICAL SESSION 8 GAMMACAMERA IMAGING BACKGROUND The quality of a gamma camera image is dependent on several operational factors such as the count density, which affects the noise level and the contrast resolution, the distance between the detector and the patient, which affects the geometric resolution, and the window setting, which affects the registered amount of scattered radiation. A proper operation of the gammacamera by a well-trained staff is essential for a high quality practice. AIM The aim of this practical section is to demonstrate how an optimised use of the equipment will increase the image quality and hence the diagnostic quality (sensitivity and specificity). MATERIAL Sources Tc-99m Other equipment Total performance phantom for planar imaging (emission or transmission) PROCEDURE Fill the phantom with about 50 MBq Tc99m. Use an all purpose collimator on the gammacamera. Acquire images in 256 x 256 matrix. Count density Acquire images with 50000, 100000, 200000, 500000 and 1000000 counts. Analyse the images in terms of contrast resolution. Distance Acquire images (1000000 counts) with the phantom at 0, 10 and 20 cm from the collimator. Analyse the images in terms of geometric resolution. Window setting Acquire images (1000000 counts) with a centered energy window, with the energy window centered 10% towards lower energy and centered 10% towards higher energy. Record the imaging times. Analyse the images in terms of contrast resolution and geometric resolution. 1 Radiation Protection in Nuclear Medicine PRACTICAL SESSION 8 CONCLUSIONS 2