cost effective manner while maintaining proper patient care. Gamma camera collimators are acquired at additional cost and the pinhole collimator is often more expensive than the more commonly used Low-energy-high-resolution (LEHR) collimator. The aim of this study was to compare the image quality of a pinhole and parallel-hole col- limator using a thyroid phantom. Materials and Methods. The thyroid phantom is a perspex block of 10 Â 10 cm with thickness of 3 cm. It contained a cavity of an aver- age human thyroid with one hot spot and three cold spots of differ- ent sizes and locations. A defect was placed on the phantom at different locations and 53 MBq Tc-99m was injected into the phan- tom and imaged using the following imaging protocols; (i) clinical protocol as specified by the manufacturer, (ii) equivalent count den- sities for the pinhole and parallel hole, (iii) equivalent zoom factor for both collimators, (iv) variable detector to phantom distance for the parallel hole collimator. The images were assessed for defect detectability, contrast and sensitivity using human observers. Results. All the observers could find the defect for all imaging pro- tocols when the pinhole collimator was used, while in the case of the parallel hole collimator this was only possible when the detector to phantom distance was decreased. The pinhole collimator had supe- rior contrast to that of the parallel hole collimator. As expected the sensitivity of the pinhole collimator was less than that of the parallel hole collimator. Conclusion. From this study it is evident that the image quality of the pinhole collimator is superior to the parallel-hole collimator and therefore acquiring a pinhole collimator for thyroid imaging on the gamma camera is justified. http://dx.doi.org/10.1016/j.ejmp.2016.07.039 O32. Technetium-99m and Gold-198 activity quantification using SPECT/CT Monte Carlo Simulations M. Morphis, J. Van Staden, H. du Raan Department of Medical Physics, University of the Free State, Bloem- fontein, South Africa Introduction. Accurate activity quantification is important for radi- ation dose calculations in Nuclear Medicine. Quantification accuracy varies due to inherent limitations of imaging methods, object shape, size and background levels. The aim of this study was to evaluate the accuracy of activity quantification for Tc-99m and Au-198 with a SPECT/CT system using Monte Carlo (MC) simulations. Materials and methods. Segmented CT images of each phantom setup were used as input for the MC simulations. Three phantom studies and a patient study were simulated with Tc-99m and Au- 198 respectively. A radioactive concentration of 0.27 MBq/ml * was placed in all cylinders or spheres mentioned below. (i) Cylinder phantom study: Six different sized cylinders filled with radioactivity * were simulated in the water filled large cylinder phantom (LCP), with two levels of background activity. (ii) Sphere phantom study: Six different sized spheres filled with radioactivity * were positioned in the LCP and simulated as men- tioned above. (iii) RSD thorax phantom study: Two spheres filled with radioac- tivity * were positioned in the RSD phantom with three different levels of organ and background activity. This was repeated for three different sphere sizes. (iv) Patient study: A patient study with two spherical lesions was simulated. Corrections for attenuation, scatter and collimator response were applied during image reconstruction. Using CT regions of interest, counts from reconstructed SPECT images were converted to activity using a partial volume correction (PVC) and a calibration factor. Results. For cylindrical sources, good accuracies were observed (610% for Tc-99m and 640% for Au-198). Similar results were obtained for the spherical sources in the LCP, RSD phantom and patient study (610% for Tc-99m and 620% for Au-198). Conclusion. The accuracy of activity quantification varies with object size and from the results it is evident that a PVC remains nec- essary for the smallest sphere sizes. http://dx.doi.org/10.1016/j.ejmp.2016.07.040 O33. The value of different reconstruction algorithms for quan- tification of FDG PET brain imaging T.C.G. Moalosi a , P. Dupont b , M. Mix c , J. Warwick a , M. du Toit a , A. Doruyter a a Stellenbosch University, Stellenbosch, South Africa b KU Leuven, Belgium c University of Freiburg, Germany Introduction. Reconstruction influences the quantitative results in PET imaging. The aim of this study was the evaluation of different image reconstruction parameters and their impact on quantification for 18 F-FDG PET of the brain. The reconstruction parameters studied were the number of iterations, smoothing levels (relaxation param- eter lambda), and the use of time of flight (TOF) information. In addi- tion, we investigated the effect of signal-to-noise ratio on each of these reconstructed brain images, as well as the effect of scan dura- tion on image quality. Materials and Methods. A Philips Ò Gemini-TF Big bore PET/CT was used for acquiring data of a 3D Hoffman Brain phantom. Data was acquired for 25 minutes in list mode format after injection of 40 MBq FDG, and reconstructed with a voxel size of 2 Â 2 Â 2 mm 3 using two different iterative reconstruction algorithms: LOR- RAMLA and BLOB-OS. The number of iterations and subsets was var- ied successive from 3/33 (vendor default) to 30/33, acquisition scan duration from 1 to 25 minutes, lambda was selected as smooth (0.7) and normal (1.0), and TOF was switched on and off for BLOB-OS. The impact on image quality was analyzed in 15 cortical and subcortical brain regions (volumes of interest, VOIs) and for grey and white matter. Results. Contrast increased for all regions of the brain and for grey matter/white matter (GM/WM) ratio if the number of iterations increased. Image convergence was reached after fifteen iterations for all different algorithms. When varying the smoothing filter it was found that lambda 1.0 resulted in a faster convergence than 0.7. The coefficient of variation (COV) for all VOIs showed BLOB-OS with TOF to be superior to the other algorithms. The COV results for different scan durations showed only a minimal improvement after 5 minutes in high-activity regions (GM), and after 10 minutes in low-activity regions (WM). Conclusion. Based on phantom data 18 F-FDG brain imaging for 10 minutes and reconstructed with the BLOB-OS algorithm including TOF information with 15 iterations is optimal on the Philips Gemini TF Big bore PET/CT. Further analyses is planned using patient data to verify if these findings remain valid in a clinical setting. http://dx.doi.org/10.1016/j.ejmp.2016.07.041 O34. Update on phase III randomized clinical trial investigating the effects of the addition of electro-hyperthermia to chemora- diotherapy for cervical cancer patients in South Africa C. Minnaar a , A. Baeyens a,b,c , J. Kotzen a Abstratcs / Physica Medica 32 (2016) 141–160 151