Comparing the diagnostic accuracy of MR dacryocystography (MRD) and dacryoscintigraphy (DSG) in NLDO-related acquired epiphora.

PROPOSE: This study aimed to compare the diagnostic accuracy of MR dacryocystography (MRD) and dacryoscintigraphy (DSG) in the diagnosis of acquired epiphora related to NLDO. A total of 15 patients with acquired epiphora and suspected NLDO were included in this study. METHODS: All patients underwent MRD and DSG examinations. MRD was performed using a 3-Tesla magnetic resonance imaging (MRI) scanner, while DSG involved injection of a radiotracer into the lacrimal drainage system followed by DSG. The results of both imaging methods were compared with the reference standard that was a combination of clinical examination findings and surgical exploration. RESULTS: The results of this study showed that no abnormal findings were observed in MR-DCG in patients before the Valsalva maneuver. However, after the Valsalva maneuver, stenosis/obstruction at the canal surface was observed in all 15 patients diagnosed by DSG, giving a sensitivity of 100% for canal stenosis. Moreover, the results revealed that among these 15 patients, 9 showed stenosis or simultaneous obstruction at the level of the canal and lacrimal sac, but MR-DCG showed these lesions in only 9 patients, giving a sensitivity of 60%. The specificity of MRD and DSG were 85% and 76.7%, respectively. There was a statistically significant difference in the sensitivity of MRD and DSG (p < 0.05). CONCLUSION: This study demonstrated that MRD has a higher diagnostic accuracy in the diagnosis of acquired epiphora associated with NLDO compared to DSG. MRD showed significantly higher sensitivity and specificity than DSG. Therefore, MRD can be considered as the preferred imaging modality in the diagnosis of acquired epiphora due to NLDO. By accurately identifying the underlying cause of NLDO, MRD can help determine the most appropriate treatment approach for patients and lead to better outcomes.

Single-Center Experience of Pulmonary Endarterectomy for Chronic Thromboembolic Pulmonary Hypertension: The Results from the Tabriz University Medical Sciences (TUMS) CTEPH Program.

INTRODUCTION: Pulmonary endarterectomy (PEA) remains the preferred and potentially curative option for patients with chronic thromboembolic pulmonary hypertension (CTEPH). This study aimed to report the results of PEA for CTEPH in a tertiary center in Tabriz, Iran. METHODS: We analyzed the results of 42 CTEPH patients undergoing PEA, who were enrolled in the Tabriz University of Medical Sciences (TUMS-CTEPH) from January 2016 to October 2020. The main outcome measures included the New York Heart Association (NYHA) functional classification, the 6-Minute Walk Distance, hemodynamic measures in right heart catheterization, morbidity, and mortality. RESULTS: There was a significant improvement in the NYHA function class (2.6 ± 0.5 vs 1.1 ± 0.34), mean pulmonary arterial pressure (47.1 ± 13 vs 27.9 ± 8 mm Hg), cardiac output (4.3 ± 1.06 vs 5.9 ± 1.2 L/min), and pulmonary vascular resistance (709.4 ± 297.5 vs 214 ± 77 dyn s/cm5). Fifteen patients (35%) developed complications. The most common complication (10 [23%]) was reperfusion injury. Also, postsurgical mortality was 4% during hospital admission and 1-year follow-up. CONCLUSION: This is the first single-center report of PEA from Iran. Post-PEA and 1-year survival were acceptable as a referral center. PEA can be performed safe with low mortality. Greater awareness of PEA and patients' access to experienced CTEPH centers are important issues.

Outcome of Surgery for Chronic Thromboembolic Pulmonary Disease without Pulmonary Hypertension.

BACKGROUND: Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious condition that results from incomplete resolution of thromboemboli in pulmonary arteries. Symptomatic patients with chronic thromboembolic disease may have normal hemodynamic at rest. The aim of this study is to evaluate the outcome of pulmonary endarterectomy (PEA) in symptomatic patients with chronic thromboembolic pulmonary disease (CTEPD) in the absence of pulmonary hypertension as currently defined (mean pulmonary artery pressure [mPAP] < 20 mm Hg). PATIENTS AND METHODS: Here, we report four symptomatic patients with chronic thromboembolic and normal hemodynamic at rest (mPAP ≤20 mm Hg or 20 < mPAP < 25 mm Hg and pulmonary vascular resistance [PVR] < 240 dyn·s/cm5) who underwent PEA between September 2015 and September 2019. The main outcome measures were functional New York Heart Association class, 6-minute walk distance (6MWD), hemodynamic measures in right heart catheterization (RHC), morbidity, and mortality. RESULTS: There were significant improvement in function class (2.6 ± 0.54 vs. 1 ± 0.2, p = 0.00), mPAP (preoperative: 23.3 ± 0.5 mm Hg vs. postoperative: 18.6 ± 1.5 mm Hg, p = 0.02), 6MWD (preoperative: 378.2 ± 68.7 m vs. postoperative: 432.9 ± 44.5 m, p = 0.01), and PVR (215.33 ± 91 vs. 101 ± 32 dyn·s/cm5, p = 0.1) 6 months after surgery based on data from RHC which was done during exercise. Also, RHC showed a significant decrease in mPAP (preoperative: 37 ± 7.7 mm Hg vs. postoperative 28 ± 3.2 mm Hg, p = 0.06). CONCLUSION: PEA could improve function class and hemodynamic in patients with CTEPD. Considering hemodynamic improvement in this group of patients after PEA, definition of CTEPH may need to be revised.

Impact of Wolfmet Tungsten Alloys as Parallel-Hole Collimator Material on Single-Photon Emission Computed Tomography Image Quality and Functional Parameters: A Simulating Medical Imaging Nuclear Detectors Monte Carlo Study.

Objectives Collimators have a significant role in image quality and detectability in single-photon emission computed tomography (SPECT) imaging. Using an appropriate alloy that effectively absorbs scattered photons, without induced secondary x-rays, and with proper rigidity and weight may provide an effective approach to the image improvement that conventionally collimators made of lead (Pb). Materials and Methods A Siemens E.CAM SPECT imaging system equipped with low-energy high-resolution (LEHR) collimator was simulated by the Simulating Medical Imaging Nuclear Detectors Monte Carlo program. Experimental and simulated data were compared based on a 2-mm 99m Tc point source in an acrylic cylindrical Deluxe phantom (Data Spectrum, Inc). Seven types of tungsten (W) alloys (Wolfmet), with W content from 90 to 97% by weight, were then used as collimator materials of the simulated system. Camera parameters, such as energy- and spatial resolution, image contrast, and collimator-related parameters, such as fraction of septal penetration, scatter-to-primary ratios, and percentage of induced secondary x-rays, due to interactions in the collimator, were evaluated. Results Acceptable conformity was found for the simulated and experiment systems in terms of energy spectra, 10.113 and 10.140%, full width at half-maximum (FWHM) of the point spread function (PSF) curves, 8.78 and 9.06 mm, sensitivity, 78.46 and 78.34 cps/MBq, and contrast in images of 19.1 mm cold spheres in the Deluxe phantom, 79.17 and 78.97%, respectively. Results on the parameters of the simulated system with LEHR collimator made from the alloys showed that the alloy consisting of 90% W, 6% nickel, and 4% copper provided an FWHM of 8.76 mm, resulting in a 0.2% improvement in spatial resolution. Furthermore, all the Wolfmet collimators showed a 48% reduction in the amount of X-rays production compared to the Pb. Conclusion A Wolfmet LEHR collimator, made by a combination of W (90%), Ni (6%), and Cu (6%) provides a better image quality and detectability compared to the Pb.

Effects of parenteral administration of tylosin and ivermectin on abomasal emptying rate in healthy suckling lambs by use of nuclear scintigraphy.

Abomasal hypomotility is one of the important causes of neonatal mortality in small ruminants. Various pharmaceutical agents have been studied to address this problem in large ruminants. The aim of this study was to determine the effect of parenteral administration of tylosin and ivermectin on abomasal emptying rate in neonatal suckling lambs. Abomasal emptying rate was assessed using nuclear scintigraphic method in 10 healthy female Iranian fat tailed Ghezel lambs. Each lamb was tested three times, once as a control (1 ml of saline 0.9%, IM) and twice after the injection of tylosin (17.6 mg/kg, IM) and ivermectin (200 µg/kg, SC) in a crossover study. Based on radiopharmaceutical counts, remnant activity in abomasums at 90 min were 48.3 ± 3.5, 45.6 ± 7.5 and 41.6 ± 2.9% in control, tylosin and ivermectin groups, respectively. Administration of tylosin (p = 0.049) and ivermectin (p = 0.045) to lambs, significantly caused faster abomasal emptying rate compared to control. Evaluating the ROIs revealed that the half emptying time (T1/2) in control, tylosin and ivermectin groups were 67.1 ± 8.6, 62.6 ± 14.2 and 54.3 ± 9.9 min, respectively. These difference between all groups, statistically were significant (p = 0.026). However, the clinical efficacy of abomasal emptying rate facilitating by tylosin or ivermectin administration in lambs remains to be determined.

Value of early rest myocardial perfusion imaging with SPECT in patients with chest pain and non-diagnostic ECG in emergency department.

Evaluation of atypical presentation of angina chest pain in emergency department is difficult. Hospitalization of this patient may impose additional costs and waste the time, early discharge may lead to miss the patients. The aim of this study was to determine volubility of Single Photon Emission Computed Tomography (SPECT) in management of patients admitted to emergency department with atypical manifestations of angina pain, un-diagnostic Electrocardiogram (ECG) and negative enzyme. Half of 100 patients admitted to emergency department with atypical chest pain and un-diagnostic ECG who were candidate for admission, underwent ECG gated resting SPECT. According to the results of SPECT, low risk patient discharged after negative stress SPECT. All discharged patients were followed up for major cardiac events (cardiac death, nonfatal myocardial infarction and repeat admission for congestive heart failure) for 12 months. According to rest SPECT Myocardial Perfusion Imaging (MPI), about 70% of patients in case group was low risk and 30% of them had moderate or high risk. Case group represented lower hospitalization rate and lower need for Coronary Artery Angiography (CAG) in comparison with control group. Mean cost in case group was significantly lower than control group (175.15$ vs. 391.33$, P < 0.001). In one year follow- up no cases of mortality or major cardiovascular events as cardiac infraction were found in discharged patients in case group. our study showed that rest SPECT fulfillment in admitted patients in emergency department was validated method for assessing patients' risk which avoids unnecessary hospitalizations and additional costs.

A Monte Carlo study on the performance evaluation of a parallel hole collimator for a HiReSPECT: A dedicated small-animal SPECT.

Collimator geometry has an important contribution on the image quality in SPECT imaging. The purpose of this study was to investigate the effect of parallel hole collimator hole-size on the functional parameters (including the spatial resolution and sensitivity) and the image quality of a HiReSPECT imaging system using SIMIND Monte Carlo program. To find a proper trade-off between the sensitivity and spatial resolution, the collimator with hole diameter ranges of 0.3-1.5 mm (in steps of 0.3 mm) were used with a fixed septal and hole thickness values (0.2 mm and 34 mm, respectively). Lead, Gold, and Tungsten as the LEHR collimator material were also investigated. The results on a 99mTc point source scanning with the experimental and also simulated systems were matched to validate the simulated imaging system. The results on the simulation showed that decreasing the collimator hole size, especially in the Gold collimator, improved the spatial resolution to 18% and 3.2% compared to the Lead and the Tungsten, respectively. Meanwhile, the Lead collimator provided a good sensitivity in about of 7% and 8% better than that of Tungsten and Gold, respectively. Overall, the spatial resolution and sensitivity showed small differences among the three types of collimator materials assayed within the defined energy. By increasing the hole size, the Gold collimator produced lower scatter and penetration fractions than Tungsten and Lead collimator. The minimum detectable size of hot rods in micro-Jaszczak phantom on the iterative maximum-likelihood expectation maximization (MLEM) reconstructed images, were determined in the sectors of 1.6, 1.8, 2.0, 2.4 and 2.6 mm for scanning with the collimators in hole sizes of 0.3, 0.6, 0.9, 1.2 and 1.5 mm at a 5 cm distance from the phantom. The Gold collimator with hole size of 0.3 mm provided a better image quality with the HiReSPECT imaging.

A study on drug delivery tracing with radiolabeled mesoporous hydroxyapatite nanoparticles conjugated with 2DG/DOX for breast tumor cells.

BACKGROUND: Mesoporous nanoparticles have a great potential in targeted therapy approaches due to their ideal properties for encapsulation of various drugs, proteins and also biologically active molecules. MATERIAL AND METHODS: We used mesoporous hydroxyapatite (HA) nanoparticles as a drug carrier and developed radiolabeled mesoporous HA containing of 2-deoxy-D-glucose (2DG) and Doxorubicin (DOX) with technetium-99m (99mTc) for imaging in in vitro and in vivo studies. RESULTS: 2DG and DOX in presence of mesoporous HA nanoparticles more reduced the fraction of viable cells in the MDA-MB-231, MCF-7 human and MC4-L2 Balb/c mice breast cancer cells. The radiochemical purity of the nano-2DG-DOX complex with 99mTc was calculated to 96.8%. The results of cellular uptake showed a 44.77% increase in uptake of the [99mTc]-nano-2DG-DOX compared to the complex without nanoparticles (p < 0.001). CONCLUSION: Radioisotopic imaging demonstrated a high biochemical stability for [99mTc]-nano-2DG-DOX complex. The results demonstrated that [99mTc]-nano-2DG-DOX, may be used as an attractive candidate in cancer imaging and treatment managing.

Cadmium Telluride Semiconductor Detector for Improved Spatial and Energy Resolution Radioisotopic Imaging.

The detector in single-photon emission computed tomography has played a key role in the quality of the images. Over the past few decades, developments in semiconductor detector technology provided an appropriate substitution for scintillation detectors in terms of high sensitivity, better energy resolution, and also high spatial resolution. One of the considered detectors is cadmium telluride (CdTe). The purpose of this paper is to review the CdTe semiconductor detector used in preclinical studies, small organ and small animal imaging, also research in nuclear medicine and other medical imaging modalities by a complete inspect on the material characteristics, irradiation principles, applications, and epitaxial growth method.

A Monte Carlo study for optimizing the detector of SPECT imaging using a XCAT human phantom.

BACKGROUND: Acquiring a high quality image has assigned an important concern for obtaining accurate diagnosis in nuclear medicine. Detector is a critical component of Single Photon Emission Computed Tomography (SPECT) imaging system for giving accurate information from exact pattern of radionuclide distribution in the target organ. The images are strongly affected by the attenuation, scattering, and response of the detector. The conventional detector is mainly made from sodium iodide activated by thallium [NaI(Tl)] in nuclear medicine imaging. THE AIM OF THE STUDY: This study has planned to introduce a suitable for an optimized SPECT imaging. SIMIND Monte Carlo program was utilized for simulating a SPECT imaging system with a NaI(Tl) detector, and a low-energy high-resolution (LEHR) collimator. MATERIAL AND METHODS: The Planar and SPECT scans of a 99mTc point source and also an extended Cardiac-Torso (XCAT) computerized phantom with the experiment and simulated systems were prepared. After verification and validation of the simulated system, the similar scans of the phantoms were compared from the point of view of image quality for 7 scintillator crystals including: NaI(Tl), BGO, YAG:Ce, YAP:Ce, LuAG:Ce, LaBr3 and CZT. The parameters of energy and spatial resolution, and sensitivity of the systems were compared. Images were analyzed quantitatively by SSIM algorithm with Zhou Wang and Rouse/Hemami methods, and also qualitatively by two nuclear medicine specialists. RESULTS: Energy resolutions of the mentioned crystals obtained were: 9.864, 9.8545, 10.229, 10.221, 10.230, 10.131and10.223 percentage for 99mTc photopeak 140 Kev, respectively. Finally, SSIM indexes for the related phantom images were calculated to 0.794, 0.738, 0.735, 0.607, 0.760 and 0.811 compared to the NaI(Tl) acquired images, respectively. Medical diagnosis of the SPECT images of the phantom showed that the system with BGO crystal potentially provides a better detectability for hot and cold lesions in the liver of XCAT phantom. CONCLUSIONS: The results showed that BGO crystal has a high sensitivity and resolution, and also provides a better lesion detectability from the point of view of image quality on XCAT phantom.

Value of 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) gated SPECT for the detection of silent myocardial ischemia in hemodialysis patients: clinical variables associated with abnormal test results.

BACKGROUND: Although coronary artery disease is a major cause of mortality and morbidity in patients undergoing hemodialysis, there is no accurate diagnostic strategy for these patients. AIM: To assess the value of 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) gated single-photon emission computed tomography for the detection of silent myocardial ischemia in patients undergoing hemodialysis and to evaluate the clinical variables associated with abnormal test results. METHODS: Thirty-one asymptomatic patients undergoing hemodialysis (20 men, 11 women), with a mean age of 45 years (range, 25-75 years), were included in the study. Serum electrolytes, creatinine, homocysteine and adhesion molecules were measured prior to dialysis. Ambulatory blood pressure, carotid intima-media thickness measurements, echocardiography and stress 99mTc-MIBI imaging were performed in all patients, whereas coronary angiography was performed only in patients with abnormal myocardial perfusion scintigraphy and/or echocardiography. RESULTS: Gated myocardial perfusion scintigraphy results were abnormal in nine patients (29%) and coronary angiography was abnormal in six patients. After a median follow-up of 20 months (range, 14-28 months), nine patients experienced a cardiac event. Seven of the nine patients (78%) with abnormal myocardial perfusion scintigraphy suffered a cardiac event, compared with only two of 22 patients (9%) with normal myocardial perfusion scintigraphy (P<0.0001). Patients with abnormal perfusion scintigraphy had higher serum C-reactive protein, homocysteine and adhesion molecule levels and the duration of hemodialysis was significantly longer. CONCLUSION: In asymptomatic hemodialysis patients, gated myocardial perfusion scintigraphy is a safe and non-invasive screening technique for the detection of coronary artery disease and for predicting future cardiac events. The presence of ischemia correlates significantly with markers of inflammation. The discordant results (abnormal myocardial perfusion scintigraphy/normal coronary angiography) can be attributed to angiographically unrecognized occult atherosclerotic changes and abnormal vasodilatation capacity of the coronary circulation.

A Study on Determination of an Optimized Detector for Single Photon Emission Computed Tomography.

The detector is a critical component of the single photon emission computed tomography (SPECT) imaging system for giving accurate information from the exact pattern of radionuclide distribution in the target organ. The SIMIND Monte Carlo program was utilized for the simulation of a Siemen's dual head variable angle SPECT imaging system with a low energy high resolution (LEHR) collimator. The Planar and SPECT scans for a (99m)Tc point source and a Jaszczak Phantom with the both experiment and simulated systems were prepared and after verification and validation of the simulated system, the similar scans of the phantoms were compared (from the point of view of the images' quality), namely, the simulated system with the detectors including bismuth germanate (BGO), yttrium aluminum garnet (YAG:Ce), Cerium-doped yttrium aluminum garnet (YAG:Ce), yttrium aluminum perovslite (YAP:Ce), lutetium aluminum garnet (LuAG:Ce), cerium activated lanthanum bromide (LaBr3), cadmium zinc telluride (CZT), and sodium iodide activated with thallium [NaI(Tl)]. The parameters of full width at half maximum (FWHM), energy and special resolution, sensitivity, and also the comparison of images' quality by the structural similarity (SSIM) algorithm with the Zhou Wang and Rouse/Hemami methods were analyzed. FWHMs for the crystals were calculated at 13.895, 14.321, 14.310, 14.322, 14.184, and 14.312 keV and the related energy resolutions obtained 9.854, 10.229, 10.221, 10.230, 10.131, and 10.223 %, respectively. Finally, SSIM indexes for comparison of the phantom images were calculated at 0.22172, 0.16326, 0.18135, 0.17301, 0.18412, and 0.20433 as compared to NaI(Tl). The results showed that BGO and LuAG: Ce crystals have high sensitivity and resolution, and better image quality as compared to other scintillation crystals.

Collimator and energy window optimization for 9°Y bremsstrahlung SPECT imaging: A SIMIND Monte Carlo study.

Treatment efficacy of radioembolization using Yttrium-90 ((90)Y) microspheres is assessed by the (90)Y bremsstrahlung single photon emission computed tomography (SPECT) imaging following radioembolization. The radioisotopic image has the potential of providing reliable activity map of (90)Y microspheres distribution. One of the main reasons of the poor image quality in (90)Y bremsstrahlung SPECT imaging is the continuous and broad energy spectrum of the related bremsstrahlung photons. Furthermore, collimator geometry plays an impressive role in the spatial resolution, sensitivity and image contrast. Due to the relatively poor quality of the (90)Y bremsstrahlung SPECT images, we intend to optimize the medium-energy (ME) parallel-hole collimator and energy window. The Siemens e.cam gamma camera equipped with a ME collimator and a voxelized phantom was simulated by the SImulating Medical Imaging Nuclear Detectors (SIMIND) program. We used the SIMIND Monte Carlo program to generate the (90)Y bremsstrahlung SPECT projection of the digital Jaszczak phantom. The phantom consist of the six hot spheres ranging from 9.5 to 31.8mm in diameter, which are used to evaluate the image contrast. In order to assess the effect of the energy window on the image contrast, three energy windows ranging from 60 to 160 KeV, 160 to 400 KeV, and 60 to 400 KeV were set on a (90)Y bremsstrahlung spectrum. As well, the effect of the hole diameter of a ME collimator on the image contrast and bremsstrahlung spectrum were investigated. For the fixed collimator and septa thickness values (3.28 cm and 1.14 mm, respectively), a hole diameter range (2.35-3.3mm) was chosen based on the appropriate balance between the spatial resolution and sensitivity. The optimal energy window for (90)Y bremsstrahlung SPECT imaging was extended energy window from 60 to 400 KeV. Besides, The optimal value of the hole diameter of ME collimator was obtained 3.3mm. Geometry of the ME parallel-hole collimator and energy window are indeed important indicators of the image quality in (90)Y bremsstrahlung imaging. The obtained optimal ME collimator and optimal energy window have the potential to improve the image contrast of (90)Y bremsstrahlung images. Subsequently, high quality (90)Y bremsstrahlung images can provide reliable estimate of the (90)Y microsphere activity distribution after radioembolization.

Intrathoracic splenosis: a rare false-positive cause of somatostatin imaging in characterization of solitary pulmonary nodule.

Scanning using a somatostatin receptor analog such as Tc-EDDA/HYNIC-TOC has sensitivity and specificity similar to those of FDG-PET, which has high accuracy in the characterization of a solitary pulmonary nodule (SPN). We describe a 63-year-old man with well-defined SPN in the left lung on chest x-ray and CT scan. Whole-body scanning and chest SPECT were performed with Tc-EDDA/HYNIC-TOC for the characterization of SPN. Abnormal focal increased radiotracer uptake in the left hemithorax was detected. In addition, no spleen activity was observed in the anatomical location. Cytopathologic evaluation of SPN revealed splenosis.

Development of Scintillators in Nuclear Medicine.

High-quality image is necessary for accurate diagnosis in nuclear medicine. There are many factors in creating a good image and detector is the most important one. In recent years, several detectors are studied to get a better picture. The aim of this paper is comparison of some type of these detectors such as thallium activated sodium iodide bismuth germinate cesium activated yttrium aluminum garnet (YAG: Ce) YAP: Ce "lutetium aluminum garnet activated by cerium" CRY018 "CRY019" lanthanum bromide and cadmium zinc telluride. We studied different properties of these crystals including density, energy resolution and decay times that are more important factors affecting the image quality.

The Effect of Parallel-hole Collimator Material on Image and Functional Parameters in SPECT Imaging: A SIMIND Monte Carlo Study.

The collimator in single-photon emission computed tomography (SPECT) is a critical component of the imaging system and plays an impressive role in the imaging quality. In this study, the effect of the collimator material on the radioisotopic image and its functional parameters was studied. The simulating medical imaging nuclear detectors (SIMIND) Monte Carlo program was used to simulate a Siemens E.CAM SPECT (Siemens Medical Solutions, Erlangen, Germany) system equipped with a low-energy high-resolution (LEHR) collimator. The simulation and experimental data from the SPECT imaging modality using (99m)Tc were obtained on a point source and Jaszczak phantom. Seventeen high atomic number materials were considered as LEHR collimator materials. In order to determine the effect of the collimator material on the image and functional parameters, the energy resolution, spatial resolution, contrast, and collimator characteristics parameters such as septal penetration and scatter-to-primary ratio were investigated. Energy spectra profiles, full width at half maximums (FWHMs) (mm) of the point spread function (PSF) curves, system sensitivity, and contrast of cold spheres of the Jaszczak phantom for the simulated and experiment systems have acceptability superimposed. The results of FWHM and energy resolution for the 17 collimators showed that the collimator made of 98% lead and 2% antimony could provide the best FWHM and energy resolution, 7.68 mm and 9.87%, respectively. The LEHR collimator with 98% lead and 2% antimony offers the best resolution and contrast when compared to other high atomic number metals and alloys.

Advances in SPECT for Optimizing the Liver Tumors Radioembolization Using Yttrium-90 Microspheres.

Radioembolization (RE) with Yttrium-90 ((90)Y) microspheres is an effective treatment for unresectable liver tumors. The activity of the microspheres to be administered should be calculated based on the type of microspheres. Technetium-99m macroaggregated albumin ((99m)Tc-MAA) single photon emission computed tomography/computed tomography (SPECT/CT) is a reliable assessment before RE to ensure the safe delivery of microspheres into the target. (90)Y bremsstrahlung SPECT imaging as a posttherapeutic assessment approach enables the reliable determination of absorbed dose, which is indispensable for the verification of treatment efficacy. This article intends to provide a review of the methods of optimizing (90)Y bremsstrahlung SPECT imaging to improve the treatment efficacy of liver tumor RE using (90)Y microspheres.

Advances in pinhole and multi-pinhole collimators for single photon emission computed tomography imaging.

The collimator in single photon emission computed tomography (SPECT), is an important part of the imaging chain. One of the most important collimators that used in research, preclinical study, small animal, and organ imaging is the pinhole collimator. Pinhole collimator can improve the tradeoff between sensitivity and resolution in comparison with conventional parallel-hole collimator and facilities diagnosis. However, a major problem with pinhole collimator is a small field of view (FOV). Multi-pinhole collimator has been investigated in order to increase the sensitivity and FOV with a preserved spatial resolution. The geometry of pinhole and multi-pinhole collimators is a critical factor in the image quality and plays a key role in SPECT imaging. The issue of the material and geometry for pinhole and multi-pinhole collimators have been a controversial and much disputed subject within the field of SPECT imaging. On the other hand, recent developments in collimator optimization have heightened the need for appropriate reconstruction algorithms for pinhole SPECT imaging. Therefore, iterative reconstruction algorithms were introduced to minimize the undesirable effect on image quality. Current researches have focused on geometry and configuration of pinhole and multi-pinhole collimation rather than reconstruction algorithm. The lofthole and multi-lofthole collimator are samples of novel designs. The purpose of this paper is to provide a review on recent researches in the pinhole and multi-pinhole collimators for SPECT imaging.