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.

Background: Single Photon Emission Computed Tomography (SPECT) imaging is widely implemented in nuclear medicine for detecting coronary artery diseases. To increase the accuracy of the diagnosis, it is necessary to improve the quality of the SPECT images that can be degraded by noise. The aim of this study was to evaluate the effectiveness of using different filters such as Butterworth, Gaussian, Wiener with kernel sizes 3×3 and 5×5, and Median Modified Wiener Filters (MMWF with kernel sizes 3×3 and 5×5 to improve the quality of myocardial perfusion SPECT images with 99mTc-MIBI. Methods: A Siemens Symbia T2 dual head SPECT/CT scanner equipped with a low-energy and high-resolution collimator (LEHR) was used for collecting data for this cross-sectional-applied study. The noise ratio (SNR), peak to noise ratio (PSNR) and contrast to noise ratio (CNR) were the indices used to asses the quality of the myocardial perfusion SPECT images of 30 patients after the filters mentioned above have been applied to the images. Findings: Wiener filter with kernel size of 5×5 4. 90 ±,0. 69 and 2. 65 ±,0. 57 were found be the highest SNR and CNR indices respectively. However, it had the lowest PSNR in the range of 29. 93 ±,3. 13 (dB). In addition, the highest PSNR values were associated with the Gaussian filter as 50. 09 ±,10. 63 (dB). Conclusion: The results of this study show that the wiener filter of kernel size of 5×5 outperformed the others to improve the quality of myocardial perfusion SPECT images used in this study.

Introduction: In Single Photon Emission Computed Tomography (SPECT), the projection data used for image reconstruction are distorted by several factors, including attenuation and scattering of gamma rays, collimator structure, data acquisition method, organ motion, and washout of radiopharmaceuticals. All these make reconstruction of a quantitative SPECT image very difficult. Simulation of a SPECT system is a convenient method to assess the impact of these factors on the image quality.Materials and Methods: The SIMIND Monte Carlo program was employed to simulate a Siemens E.CAM SPECT system. Verification of the simulation was performed by comparing the performance parameters of the system. The verified system was used for SPECT simulations of homogenous and inhomogeneous voxelized phantoms in conjugation with hardware modifications. The resulting data were compared with those obtained from the simulated system without any modifications. Image quality was assessed by comparing the Structural SIMularity index (SSIM), contrast, and resolution of images.Results: The energy spectra acquired from both simulated and real SPECT systems demonstrated similar energy peak regions. The resulting full-widths-at-half-maximums were 13.92 keV for the simulation and 13.58 keV for experimental data, corresponding to energy resolutions of 9.95% and 9.61 %, and with calculated sensitivities of 85.39 and 85.11 cps/MBq, respectively. Better performance parameters were obtained with a hardware-modified system constructed using a 0.944 cm thickness NaI (TI) crystal covered by a layer of 0.24 cm aluminum, a slat of 4.5 cm Pyrex as a backscattering medium, and a parallel hole collimator of Pb-Sb alloy with 2.405 cm thickness.Conclusion: The modeling of a Siemens E.CAM SPECT system was performed with the SIMIND Monte Carlo code. Results obtained with the code are in good agreement with experimental results. The findings demonstrate that the proposed hardware modifications in the system appear to be suitable for further improvement of the performance parameters of the system, indicating that future investigations can be conducted on using the system for supplementary studies on image improvement in the field of nuclear medicine.

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.

Objective(s): Only few studies have assessed the use of gallium citrate-67 Single-Photon Emission Computed Tomography/Computed Tomography (67Ga-SPECT/CT) for localizing the foci of classic fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Hence, the current study aimed to assess the diagnostic contribution of 67Ga-SPECT/CT in a tertiary referral setting where nuclear imaging tests are performed after an unsuccessful comprehensive primary diagnostic workup. Methods: We retrospectively assessed the medical records of 27 adult patients with FUO/IUO who had an unsuccessful diagnostic workup and who underwent 67Ga-SPECT/CT for the localization of FUO/IUO foci in our university hospital between 2013 and 2019. The primary outcome was diagnostic yield. The secondary outcomes were overall clinical efficacy and spontaneous rEmission of FUO/IUO symptoms in patients with a negative 67Ga-SPECT/CT finding. Results: Almost all patients completed the recommended diagnostic workup, except for urine culture and abdominal ultrasonography. Moreover, prior to 67Ga-SPECT/CT, all patients underwent thoraco-abdominopelvic CT scan, which was a non-diagnostic procedure. After a median follow-up of 843 days, the cause was identified in 16 (59%) patients. 67Ga-SPECT/CT successfully localized the FUO/IUO foci in eight patients (diagnostic yield = 30%; 95% confidence interval [CI]: 14%– 50%). However, the causes remained unknown during follow-up in 11 (41%) patients. Among them, five experienced spontaneous regression of symptoms. 67Ga-SPECT/CT was negative in four of the five patients with spontaneous regression in symptoms without a definite cause. Considering this an important event, the overall clinical efficacy of 67Ga-SPECT/CT increased to 44% (95% CI: 25%– 65%). Conclusion: 67Ga-SPECT/CT had an acceptable diagnostic yield for the localization of FUO/IUO foci, which are challenging to diagnose, in a contemporary tertiary referral care setting. In patients who experienced spontaneous regression in symptoms with an unexplained cause, the absence of abnormal uptake might indicate prospective spontaneous rEmission. Thus, 67Ga-SPECT/CT could be an active first-line nuclear imaging modality in settings where fluorine-18-fluorodeoxy glucose positron Emission Tomography and Computed Tomography is not available for the assessment of FUO/IUO causes.