In Single Photon Emission Computed Tomography (SPECT), collimator selection, optimization, and also geometric calibration have a major impact on the acquired image quality and also on an accurate detectability and diagnosis. The collimator optimization phenomena consider some parameters such as field of view, resolution, sensitivity, resolution at depth, septal thickness and penetration for a specific application task. While the parallel hole collimator is usually used in SPECT and planar imaging but due to the limited solid angle covered by the collimator, the system sensitivity and resolution were highly reduced. Meanwhile, other types of collimators such as pin-hole, multi-pin-hole, slant and slit-slat collimators were introduced with a trade-off between sensitivity and resolution. This article reviews improvements on collimators also by considering the geometry and geometric calibration methods for improving the image quality in Single Photon Emission Computed tomography.

Anosmia following head trauma is relatively common and in many cases is persistent and irreversible. The ability to objectively measure such a decline in smelling, for both clinical and medicolegal goals, is very important. The aim of this study was to find results of brain Single Photon Emission Computed Tomography (SPECT) in anosmic subjects after closed head trauma. This case-control cross sectional study was conducted in a tertiary referral University Hospital. The brain perfusion state of nineteen anosmic patients and thirteen normal controls was evaluated by means of the SPECT with 99mtc- ECD infusionbefore and after olfactory stimulation. The orbitofiontal lobe of the brain was assumed as the region of interest and changes in perfusion of this area before and after the stimulations were compared in two groups. The mean of brain perfusion in controls before and after the stimulation was 8.26% 0±19% and 9.89%± 0.54%, respectively (P<0.0001). Among patients group, these quantities were 7.97%±1.05% and 8.49%± 1.5%, respectively (P<0.004). The difference between all the measures in cases and controls were statistically significant (P<0.0001). There were no differences in age and sex between two groups. The brain SPECT is an objective technique suitable for evaluating anosmia following the head trauma and it may be used with other diagnostic modalities.

Documented evidences available from both developed and developing countries reveal that the number of clinical imaging procedures and instruments have continued to increase over the past decades, confirming the increasing demand for these clinical imaging modalities. Accordingly, concerns about over-utilization and inappropriate use in imaging have been raised, and consequently medical authorities and clinicians who were slow to respond to spiraling costs of cardiac imaging years ago, now recognize the need to promote appropriate and cost-conscious use of imaging, mainly through the development of appropriateness criteria and guidelines, which are focused on eliminating unnecessary testing to decrease health care costs.

Introduction: Myocardial perfusion SPECT by 99mTc-Sestamibi and 99mTc-Tetrofosmin radiopharmaceuticals usually presents a false significant increase in the radiotracer uptake in the inferior myocardium due to the uptake in organs such as liver, bowel, stomach and biliary system. The present study evaluated a suitable Slit angle for differentiating extra-cardiac activities by Slit Slat collimation.Methods: The Siemens E.CAM gamma camera equipped with a Low Energy High Resolution (LEHR) collimator was simulated with the Simulating Medical Imaging Nuclear Detectors (SIMIND) Monte Carlo program. Following the verification of the simulation, a Slit Slat collimator was simulated for SPECT imaging of a NURBS-based Cardiac Torso (NCAT) phantom with different Slit angels ranged from 0 to 30 degrees. The reconstructed images were qualitatively assessed with blinded observer method by three nuclear medicine specialists.Results: The improved differentiation of the bowel activity from the cardiac was obtained by a Slit-Slat collimator with the Slit angle of 7 degree. While for gastric activity differentiation an angle of 15 degree for the Slit was useful.Conclusion: The results showed that Slit Slat collimation with 7 and 15 Slit angle provide a suitable differentiation of the bowel and gastric activities from the cardia, respectively.

Background: We sought to evaluate the association between hypertension (HTN) and left ventricular (LV) mechanical synchrony parameters derived via the phase analysis of gated Single-Photon Emission Computed tomography (GSPECT) myocardial perfusion imaging (MPI). Methods: Ninety-nine patients with no known coronary heart disease (CHD) who underwent GSPECT MPI and had normal resting and post-stress scan with a recent normal echocardiographic examination and a positive history of HTN were recruited. The gated images were analyzed by Cedar– Sinai’ s quantitative GSPECT. The global and regional LV mechanical synchrony indices— including phase histogram bandwidth (PHB), phase standard deviation (PSD), and entropy— were derived and compared with the results of the control group, which had previously been defined with the same protocol for a group of 100 patients with a low likelihood for CHD. Results: Comparisons between the study and control groups revealed that neither global nor regional wall-based indices for PHB, PSD, and entropy were significantly different between the 2 groups (P> 0. 05), whether or not HTN was accompanied by comorbid diabetes. Congruent with the control group, a significant difference was detected between the global LV phase parameters of the 2 genders (P<0. 05). Conclusions: HTN does not intrinsically have a significant impact on the mechanical synchrony indices of GSPECT MPI.

Background: Phase analysis assesses left ventricular (LV) dyssynchrony from gated SinglePhoton Emission Computed tomography myocardial perfusion imaging (GSPECT-MPI). This study aimed to determine the impact of diabetes mellitus (DM) on phase parameters. Methods: The study population consisted of 121 diabetic patients with no history of coronary artery disease, hypertension, or dyslipidemia and no evidence of perfusion abnormalities or systolic dysfunction in GSPECT-MPI. The resting-state images of MPI were further analyzed using the Cedar–, Sinai quantitative GSPECT, and LV phase parameters, including phase histogram bandwidth (PHB), phase standard deviation (PSD), and entropy, were derived. The results were compared with the corresponding figures previously defined in a control group, consisting of 100 subjects with low likelihoods of coronary artery disease, in our center. Results: Significant differences existed in the derived values for PHB, PSD, and entropy between the DM and control groups concerning global whole LV synchrony (P>. 05). Likewise, PHB and PSD demonstrated no significant differences between the 2 groups regarding the regional wall-based analysis (P>. 05). In contrast, the entropy indices of the LV septum (P=. 019) and anterior wall (P=. 022) were significantly higher in the DM group. Conclusions: It appears that except for the regional wall-based entropy of the septum and the anterior wall, DM does not inherently impose any significant alterations on the mechanical synchrony indices of GSPECT-MPI. Consequently, the provided normal databases for GSPECT-MPI-derived synchrony parameters could be utilized in DM patients.