ABSTRACT
Different Types of collimators have been introduced in the practical usage of the gamma camera. The choice of the collimator depends firstly on the energy of the isotope, the required resolution sensitivity of the applied scan, and finally the size of the organ to be imaged. In the present study the fan-beam collimator was studied versus the parallel-hole collimator to clarify the importance of their properties in imaging of particular organs with the gamma camera. The study was done on a [Axis] dual head SPECT gamma camera provided with both parallel-hole and fan-beam collimators. The important part of this study was the clinical part at which the selected patients were coming for evaluation of the treatment response for brain tumors and detection of residual lesions or recurrence following surgical or radiotherapy treatment. Thirty patients with brain tumors of various histopathologic types including medalloblastoma, astrocytoma, glioblastoma multiformis and oligodenderoma were subjected to brain SPECT imaging. Three tests were done on each patient's reconstructed image: The ratio between the lesion average counts [total count I number of pixels] to the background average counts, the contrast of the lesion in each clinical case and the area of the lesion is also compared between the two collimators for the same patient's lesion. In conclusion fan beam is an accurate and good tool for imaging and assessment of the treatment response as well as planning in the radiotherapy unit