Local and Non-local Regularization Techniques in Emission (PET/SPECT) Tomographic Image Reconstruction Methods. - Munir Ahmad; Tasawar Shahzad; Khalid Masood; Khalid Rashid; Muhammad Tanveer; Rabail Iqbal; Nasir Hussain; Abubakar Shahid; Fazal-e-Aleem (J. Digit. Imaging, 2016)