Single Photon Emission Computed Tomography Data Research Articles

Validation of computational fluid dynamics models for airway deposition with SPECT data of the same population

This study compared computational fluid dynamic (CFD) model predictions on aerosol deposition in six asthmatic patients to the in-vivo results of the same group. Patient-specific ventilation and internal air distribution were prescribed using inspiratory and expiratory CT scans of each patient, accounting for individual lobar air flow distribution. Moreover, the significant influence of realistic mouth and throat geometries on regional deposition is demonstrated. The in-vivo data were obtained from single photon emission computed tomography (SPECT) in 6 subjects with mild asthma selected from a database of historical clinical trials. The governing flow and particle tracking equations were solved numerically using a commercial CFD tool, and the modeled deposition results were compared to the SPECT data. Good agreement was found between the CFD model, applying k-ω SST turbulence model, and SPECT in terms of aerosol deposition. The average difference for the lobar deposition obtained from CFD model and SPECT/CT data was 2.1%. The high level of agreement is due to applying patient specific airway geometries and inspiratory/expiratory CT images, anatomical upper airways, and realistic airway trees. The results of this study show that CFD is a powerful tool to simulate patient-specific deposition if correct boundary conditions are applied and can generate similar information obtained with functional imaging tools, such as SPECT.

Detectability of cold tumors by xSPECT bone technology compared with hot tumors: a supine phantom study.

Detecting cold as well as hot tumors is vital for interpreting bone tumors on single-photon emission computed tomography (SPECT) images. This study aimed to visually and quantitatively demonstrate the detectability of cold tumors using xSPECT technology compared with that of hot tumors in the phantom study. Five tumors of different sizes and normal bone contained a mixture of 99mTc and K2HPO4 in a spine phantom. We acquired SPECT data using an xSPECT protocol and transverse images were reconstructed using xSPECT Bone (xB) and xSPECT Quant (xQ). Mean standardized uptake values (SUVmean) in volumes of interest (VOI) were calculated. Recovery coefficients (RCs) for each tumor site were calculated with reference to radioactive concentrations. The SUVmeans of the whole vertebral body for hot tumor bone image in cortical bone phantom reconstructed by with xB and xQ were 5.77 and 4.86 respectively. The SUVmean of xB was similar to the true value. The SUVmeans for xB and xQ reconstructed images of cold tumors were both approximately 0.16. The RC of the cold tumor on xQ images increased as the tumor diameter decreased, whereas that of xB remained almost constant regardless of the tumor diameter. In conclusion, the quantitative accuracy of detecting hot and cold tumors was higher in the xB image than in the xQ image. Moreover, the visual detectability of cold tumors was also excellent in xB images.

Association between Gray and White Matter Lesions and Its Involvement in Clinical Symptoms of Alzheimer's-Type Dementia.

Not only gray matter lesions (GMLs) but also white matter lesions (WMLs) can play important roles in the pathology of Alzheimer's disease (AD). The progression of cognitive impairment (CI) and behavioral and psychological symptoms of dementia (BPSD) might be caused by a concerted effect of both GML and WML. This study aimed to investigate the association between GML and WML and how they are involved in the symptoms of CI and BPSD in dementia patients by means of imaging technology. Patients in our memory clinic, who were diagnosed with AD-type dementia or amnestic mild cognitive impairment (aMCI) and had undergone both single-photon emission computed tomography (SPECT) and brain MRI, were consecutively enrolled (n = 156; 61 males and 95 females; 79.8 ± 7.4 years old). Symptoms of CI and BPSD were obtained from patients' medical records. For the analysis of GMLs and WMLs, SPECT data and MRI T1-weighted images were used, respectively. This study followed the Declaration of Helsinki, and all procedures were approved by the institutional ethics committee. According to a multivariate analysis, disorientation and disturbed attention demonstrated a relationship between the precuneus and WMLs in both hemispheres. Hyperactivity in BPSD showed multiple correlations between GMLs on both sides of the frontal cortex and WMLs. Patients with aMCI presented more multiple correlations between GMLs and WMLs compared with those with AD-type dementia regarding dementia symptoms including BPSD. The interaction between GMLs and WMLs may vary depending on the symptoms of CI and BPSD. Hyperactivity in BPSD may be affected by the functional relationship between GMLs and WMLs in the left and right hemispheres. The correlation between GMLs and WMLs may be changing in AD-type dementia and aMCI.

Proposal for a Display Method for Myocardial Single Photon Emission Computed Tomography Based on Left Ventricular Volume.

Bull's eye view for the display of myocardial single-photon emission computed tomography (SPECT) 3-D perfusion maps does not reflect left ventricular (LV) volume, an important parameter. We created and evaluated a myocardial SPECT display method that reflects the LV volume.Using Digital Imaging and Communications in Medicine data, short-axis slices from the apex to the base were reconstructed and interpolated into 0.5-mm thickness. We obtained the radial lengths at 1° intervals throughout 360°, and calculated the length of the LV long axis and half circumference (1/2 circ). Myocardial perfusion was displayed as 2 ellipsoidal developments that exhibited the left anterior descending coronary artery (LAD) and non-LAD regions. We created a system that can display these processes on a personal computer. Myocardial SPECT data from 526 individuals without heart disease were analyzed. The long axis and 1/2 circ were compared with the body size, LV end-diastolic diameter (LVDd) obtained by echocardiography, and the end-diastolic volume (EDV) obtained by electrocardiogram-gated SPECT analysis. The 1/2 circle correlated with the LVDd and EDV. The images obtained allowed a diagnosis comparable to that made using the conventional coordinate display system.The new myocardial display reflects ischemia and LV volume within a single image, which cannot be achieved with conventional SPECT image display. Additional studies of this display system are required to allow its application to patients with heart disease.

Enhancing the diagnostic performance of CZT SPECT myocardial perfusion imaging with myocardial blood flow information

Abstract Background The use of cadmium-zinc-telluride (CZT) single photon emission computed tomography (SPECT) for measuring myocardial blood flow (MBF) has been established as a valuable tool for improving diagnostic accuracy. However, the clinical significance of incorporating MBF into the interpretation of stress SPECT myocardial perfusion imaging (MPI) remains largely unknown. Purpose The objective of this study is to determine the effect of MBF information on the interpretation of CZT SPECT MPI. Methods A cohort of 411 patients underwent a rest/stress gated perfusion and MBF imaging procedure using full-dose 99mTc-tetrofosmin. MBF and flow reserve were calculated using the Corridor4DM v2018 software (INVIA, Ann Arbor, MI). The SPECT data were analyzed twice, once without and once with MBF results. The criteria for abnormal myocardial flow reserve were set at 2.0, while stress flow was set at 1.8 ml/min/g. The interpretations were categorized into normal, equivocal, or abnormal and interpretive certainty was classified into five groups: definitely normal/abnormal, probably normal/abnormal, or equivocal. The overall results were evaluated, along with differences between men and women. Statistical significance was determined using contingency table analysis and chi-squared testing. Results The study cohort had a mean age of 62.5 ± 9.8 years, with 71% of the participants being male. The addition of MBF altered the MPI interpretation in 10.7% of patients (44/411), with a change from abnormal or equivocal to normal in 45.5% (20/44) of cases. The frequency of equivocal MPI interpretations dropped significantly from 4.6% without MBF to 1.5% with MBF (P=0.008). Interpretive certainty improved with a significant decrease in equivocal scans (P=0.006). 89.1% of MPI with MBF were reported as definitely normal or abnormal, compared to 83.0% without MBF (P=0.012) (Figure 1). Further analysis by gender showed similar results for men, while no significant changes were observed in women's MPI interpretation and certainty (Figure 2). Conclusion The inclusion of MBF had a significant impact on the interpretation of CZT SPECT MPI scans, with changes observed in 10.7% of cases. Interpretative certainty improved with fewer equivocal scans and a higher proportion of definitely normal or definitely abnormal interpretations. These findings were evident in men, but not in women (possible due to smaller sample size).Figure 1Figure 2

Lung-to-heart ratio analysis using virtual planar images obtained from myocardial perfusion SPECT data: A phantom and clinical studies

BackgroundsThe lung-to-heart ratio (L/H ratio) in myocardial perfusion scintigraphy (MPS) is a useful marker that complements the sensitivity of ischemia detection. However, it requires planar imaging acquired following a separate protocol in addition to single-photon emission computed tomography (SPECT). We developed a novel method for constructing virtual planar image (VPI) from SPECT data. MethodsMyocardial phantoms using Tl-201 were built with different amounts of radioactivity in the lungs. SPECT data and conventional planar images of these phantoms were collected with an Anger-type gamma camera. VPIs were constructed by adding all coronal images reconstructed from SPECT data. The clinical utility of VPIs obtained from 52 patients who underwent MPS with Tc-99m sestamibi was evaluated. ResultsThe radioactivity linearity of VPIs was satisfactory, with a correlation coefficient of r ≥ .99 between the measured amounts of radioactivity and image counts. The L/H ratios obtained from VPI analysis were strongly correlated with those of conventional planar images with a correlation coefficient of r ≥ .99 in the phantom study and r = .929 in clinical application. ConclusionThe accuracy of VPI-based L/H ratio analysis was comparable to that of conventional planar image-based analysis. VPIs could be used as an alternative method of obtaining planar images in clinical settings.

Striatal dopamine transporter binding differs between dementia with Lewy bodies and Parkinson’s disease with dementia

123I-ioflupane single-photon emission computed tomography (SPECT) is a highly sensitive and established neuroimaging technique for parkinsonian syndromes (PS). However, differentiating PS by visual inspection or analysis of regions of interest is challenging. To date, image analysis has not been able to differentiate dementia with Lewy bodies (DLB) from Parkinson's disease with dementia (PDD). This study aimed to differentiate PS based on the characteristics of striatal dopamine transporter (DAT) binding using voxel-based analysis. We acquired 123I-ioflupane SPECT data from patients with DLB (n = 30), Parkinson's disease (PD; n = 122), PDD (n = 19), multiple system atrophy with predominant parkinsonism (MSA-P; n = 18), and progressive supranuclear palsy (PSP; n = 45). DAT binding was reduced in the posterior striatum of patients with PD and PDD, whereas it was similar in MSA-P, PSP, and DLB. Hippocampal atrophy, visually evaluated by cerebral magnetic resonance imaging, did not affect striatal DAT binding in DLB. DAT binding in the anterior striatum was inversely correlated with the severity of parkinsonism in PD and PDD but not in DLB. Thus, the appearance of striatal DAT binding might indicate different pathological processes in DLB and PDD.

Triple modality image reconstruction of PET data using SPECT, PET, CT information increases lesion uptake in images of patients treated with radioembolization with ^{90}Y micro-spheres

PurposeNuclear medicine imaging modalities like computed tomography (CT), single photon emission CT (SPECT) and positron emission tomography (PET) are employed in the field of theranostics to estimate and plan the dose delivered to tumors and the surrounding tissues and to monitor the effect of the therapy. However, therapeutic radionuclides often provide poor images, which translate to inaccurate treatment planning and inadequate monitoring images. Multimodality information can be exploited in the reconstruction to enhance image quality. Triple modality PET/SPECT/CT scanners are particularly useful in this context due to the easier registration process between images. In this study, we propose to include PET, SPECT and CT information in the reconstruction of PET data. The method is applied to Yttrium-90 (^{90}Y) data.MethodsData from a NEMA phantom filled with ^{90}Y were used for validation. PET, SPECT and CT data from 10 patients treated with Selective Internal Radiation Therapy (SIRT) were used. Different combinations of prior images using the Hybrid kernelized expectation maximization were investigated in terms of VOI activity and noise suppression.ResultsOur results show that triple modality PET reconstruction provides significantly higher uptake when compared to the method used as standard in the hospital and OSEM. In particular, using CT-guided SPECT images, as guiding information in the PET reconstruction significantly increases uptake quantification on tumoral lesions.ConclusionThis work proposes the first triple modality reconstruction method and demonstrates up to 69% lesion uptake increase over standard methods with SIRT ^{90}Y patient data. Promising results are expected for other radionuclide combination used in theranostic applications using PET and SPECT.

Integration of advanced 3D SPECT modelling for pinhole collimators into the open-source STIR framework

Single-photon emission computed tomography (SPECT) systems with pinhole collimators are becoming increasingly important in clinical and preclinical nuclear medicine investigations as they can provide a superior resolution-sensitivity trade-off compared to conventional parallel-hole and fanbeam collimators. Previously, open-source software did not exist for reconstructing tomographic images from pinhole-SPECT datasets. A 3D SPECT system matrix modelling library specific for pinhole collimators has recently been integrated into STIR—an open-source software package for tomographic image reconstruction. The pinhole-SPECT library enables corrections for attenuation and the spatially variant collimator–detector response by incorporating their effects into the system matrix. Attenuation correction can be calculated with a simple single line-of-response or a full model. The spatially variant collimator–detector response can be modelled with point spread function and depth of interaction corrections for increased system matrix accuracy. In addition, improvements to computational speed and memory requirements can be made with image masking. This work demonstrates the flexibility and accuracy of STIR’s support for pinhole-SPECT datasets using measured and simulated single-pinhole SPECT data from which reconstructed images were analysed quantitatively and qualitatively. The extension of the open-source STIR project with advanced pinhole-SPECT modelling will enable the research community to study the impact of pinhole collimators in several SPECT imaging scenarios and with different scanners.

Association between the results of neuropsychological testing and indicators of regional cerebral blood flow according to SPECT data of cardiac surgical patient

Highlights. The article provides new data on the association between changes in regional cerebral blood flow during SPECT and cognitive impairment in patients who underwent coronary artery bypass grafting and combined carotid endarterectomy and coronary artery bypass grafting with cardiopulmonary bypass. The possibilities of using SPECT as a diagnostic tool in localization of areas with a similar association, in assessing the dynamics in brain perfusion and cognitive functions in the pre- and postoperative period are shown.Aim. To determine the presence of an association between the indicators of regional cerebral blood flow according to single-photon emission computed tomography (SPECT) data and the data of neuropsychological testing in cardiac surgery patients.Methods. We studied the parameters of regional cerebral blood flow (rCBF) and the data of neuropsychological testing in 34 cardiac surgical patients who underwent coronary artery bypass grafting (CABG, n = 13) and combined carotid endarterectomy and CABG (n = 21). The state of the brain was assessed by SPECT using a radiopharmaceutical 99mTc-HMPAO (Ceretek). Assessment of cognitive functions before surgery, 2–3 days before, and in the early postoperative period, on days 5–7, was carried out using a hardware-software complex Status-PF.Results. A statistically significant relationship was found between the indices of rCBF according to neuropsychological testing data in the pre- and postoperative period. We noted a moderate correlation with the Beck Depression Scale indicators in the 1st (p = 0.010943) and 2nd (p = 0.000604) groups before surgery. There was a high correlation with visual-motor response time (VMR) before (p = 0.003878) and after the procedure (p = 0.001251), a moderate correlation with the number of errors (VMR) before the procedure (p = 0.042911) and a high correlation after the procedure (p = 0.003521) in the 1st group; in the 2nd group, there was a moderate correlation before (p = 0.004625) and after the procedure (p = 0 .005689). A moderate correlation with the indicators of attention after the procedure (p = 0.049611) was noted in the 1st group, in the 2nd group, we noted a moderate correlation before (p = 0.021969) and after the procedure (p = 0.008905). In the 2nd group there was a moderate correlation with the number of processed symbols (the Bourdon test) during the 1st minute before the procedure (p = 0.016491), a high correlation after the procedure (p = 0.007920), and a high correlation with the number of processed symbols during the 4th minute before the procedure (p = 0.001473). There was a moderate correlation with a total with number of processed symbols in the 2nd group before (p = 0.029073) and after the procedure (p = 0.024164), and a high correlation with the number of errors made after the procedure in the 1st (p = 0.006367) and 2nd (p = 0.013780) groups. A high correlation with indicators of attention after surgery (p = 0.000153) was noted as wellConclusion. The indicators of regional cerebral blood flow obtained by SPECT in patients undergoing isolated CABG and combined CAE and CABG were associated with the data of neuropsychological testing and reflect changes in the cognitive status of patients.

An Iterative Based Motion Correction for SPECT with Simulated Data

Purpose: Single Photon Emission Computed Tomography (SPECT) is one of the important imaging modality in nuclear medicine used for diagnostic imaging of different organs of human body. Patient movement during the acquisition time is a well-known cause of artifacts in reconstructed SPECT data. These motion artifacts may significantly affect the diagnostic accuracy. Therefore, the motion correction of patients in tomography images is very much essential for more accurate diagnosis and hence achieves the quality of the images. Objective: The aim of this project is to develop and evaluate a data driven approach to motion correction without necessity for motion tracking system. Methods: It has been proposed a method to iteratively estimate and compensate this motion during the reconstruction. The rigid motion was estimated view-by-view in every iteration and then used to update the system matrix. The initial reconstructed image is motion contaminated; it can be used to generate a first rough motion estimate. This motion is taken into account in a reconstruction process to generate a motion-corrected image at the first iteration. Then the motion-corrected image and the motion estimate are alternately updated to increase the likelihood, the iterations are stopped when the updated motion seems to have converged. The image update is done by applying multiple iterations of the OSEM algorithm. A final iterative reconstruction was performed with the last motion estimate. Results: The method was evaluated on simulations phantom study. From the simulations phantom data, we produced the several simulated motion induced data. Motion correction algorithms were applied with the simulated motion induced data. The quality of the reconstructed images was improved substantially after the compensation. Mean structural similarity was increased. In the simulation studies, most of the motion blurring in the reconstructed images disappeared after the compensation. Conclusions: The proposed method effectively eliminated motion-induced artifacts in SPECT scans. Since only measured raw data are needed for the motion estimation and compensation, the proposed method can be applied retrospectively to SPECT scans affected by motion. Bangladesh J. Nuclear Med. 26(1): 19-24, 2023

Novel noninvasive identification of patient-specific epileptic networks in focal epilepsies: Linking single-photon emission computed tomography perfusion during seizures with resting-state magnetoencephalography dynamics.

Single-photon emission computed tomography (SPECT) during seizures and magnetoencephalography (MEG) during the interictal state are noninvasive modalities employed in the localization of the epileptogenic zone in patients with drug-resistant focal epilepsy (DRFE). The present study aims to investigate whether there exists a preferentially high MEG functional connectivity (FC) among those regions of the brain that exhibit hyperperfusion or hypoperfusion during seizures. We studied MEG and SPECT data in 30 consecutive DRFE patients who had resective epilepsy surgery. We parcellated each ictal perfusion map into 200 regions of interest (ROIs) and generated ROI time series using source modeling of MEG data. FC between ROIs was quantified using coherence and phase-locking value. We defined a generalized linear model to relate the connectivity of each ROI, ictal perfusion z score, and distance between ROIs. We compared the coefficients relating perfusion z score to FC of each ROI and estimated the connectivity within and between resected and unresected ROIs. We found that perfusion z scores were strongly correlated with the FC of hyper-, and separately, hypoperfused ROIs across patients. High interictal connectivity was observed between hyperperfused brain regions inside and outside the resected area. High connectivity was also observed between regions of ictal hypoperfusion. Importantly, the ictally hypoperfused regions had a low interictal connectivity to regions that became hyperperfused during seizures. We conclude that brain regions exhibiting hyperperfusion during seizures highlight a preferentially connected interictal network, whereas regions of ictal hypoperfusion highlight a separate, discrete and interconnected, interictal network.

Association of right precuneus compression with apathy in idiopathic normal pressure hydrocephalus: a pilot study

Apathy is frequently observed in idiopathic normal pressure hydrocephalus (iNPH) and worsens cognitive impairment and gait disturbance. In this study, we evaluated the regions associated with apathy in iNPH using statistical imaging analysis on the whole brain, both in terms of cerebral blood flow and gray matter volume. Twenty-seven patients with iNPH were assigned to two groups based on their scores on the neuropsychiatric inventory items related to apathy; 18 patients were assigned to the group with apathy (iNPH + APA) and 9 to the group without apathy (iNPH − APA). The magnetic resonance images and cerebral blood flow single-photon emission computed tomography data of the two groups were compared using statistical parametric mapping 12. The regional gray matter volume of the right precuneus was significantly larger in the iNPH + APA group than in the iNPH − APA group, but the regional cerebral blood flow in any region of the brain was not significantly different between the two groups. These results suggested that the larger gray matter volume, which is thought to reflect gray matter compression, in the precuneus might be involved in apathy in iNPH.

The preoperative focal cerebral blood flow status may be associated with slow flow in the bypass graft after combined surgery for moyamoya disease.

The aim of this study was to investigate the association between early postoperative slow flow in bypass grafts and preoperative focal cerebral blood flow (CBF) in patients who underwent combined surgery for moyamoya disease (MMD). The subjects were 18 patients (22 surgeries) who underwent single photon emission computed tomography (SPECT) before surgery. The CBF value of the middle cerebral artery territory was extracted from the SPECT data, and the value relative to the ipsilateral cerebellar CBF (relative CBF, or RCBF) was calculated. The association between RCBF and early postoperative slow flow in the bypass graft was investigated. In addition, the correlation between the revascularization effect and preoperative RCBF was analyzed. In four of 22 surgeries (18.2%), slow flow in the bypass graft was identified in the early postoperative period. Preoperative RCBF in the slow flow and patent groups was 0.86 ± 0.15 and 0.87 ± 0.15, respectively, with no significant difference (P = 0.72). The signal intensity of four slow-flowed bypasses was improved in all cases on magnetic resonance angiography images captured during the chronic phase (mean of 3.3 months postoperatively). The revascularization scores were 2 ± 0.82 and 2.1 ± 0.68 in the slow flow and patent groups, respectively, and did not differ significantly (P = 0.78). A significant correlation was not observed between preoperative RCBF and the revascularization effect. No significant association was observed between preoperative RCBF and early postoperative slow flow in bypass grafts in patients with MMD undergoing combined surgery. Given the high rate of improved depiction of slow-flowed bypass in the chronic postoperative phase, the conceptual significance of an opportune surgical intervention is to maintain CBF by supporting the patient's own intracranial-extracranial conversion function.

287 (PB067) - Investigation of a novel radionuclide carrier for targeted radionuclide therapy

Background: In internal radiation therapy of cancer, optimal targeting ligand and type of therapeutic radionuclide must be considered carefully for effective treatment. In addition, optimal ligand and nuclide type may vary depending on diverse parameters characterizing the tumor. Thus, for use in various cancers, there is a need for the development of a carrier that can firmly bind to a variety of nuclides. Here we introduce a biocompatible iron oxide nano radionuclide carrier. By reacting nanoparticles and nuclides using our conjugate synthesizer, it is possible to bind near-permanently nuclides to our nanocarriers. Material and methods: To test the carrier’s biocompatibility, particles were labeled with a fluorescence dye and injected intravenously into female CD-1 mice. Mice were anesthetized and carrier biodistribution was recorded. In addition, to test the carrier’s radionuclide binding capabilities, carriers were radiolabeled with radioactive iodine and injected intravenously in CD-1 mice that were anesthetized and scanned using single-photon emission computed tomography (SPECT). Ligand-mediated cellular uptake of the carriers was demonstrated per iron content in human origin cancer cells qualitatively through Prussian blue staining and quantitatively by ICP-MS. Results: As a result of biodistribution studies, carriers circulated through the body during initial time points were rapidly excreted through the kidney and could be detected in the bladder at 3 hours post-injection. Rapid excretion of carriers allows for lowered whole-body radiation toxicity. SPECT data showed stable distribution of radioactive iodine throughout the whole body. Given that the normal distribution of free radioiodine is for it to accumulate in the thyroid, such a result is evidence of firm binding of nuclides to the carrier. Ligand-receptor-mediated cellular uptake of nanocarriers increased dose-dependently up to 24 hours post-treatment. Conclusions: Here we have introduced a biocompatible radionuclide carrier. Its biodistribution and near-permanent nuclide binding properties make it an admirable platform for targeted radionuclide therapy. Further in vivo studies have been carried out to test the carrier’s application for treating triple-negative breast cancers (TNBC) and platinum-resistant ovarian cancers using131I and folic acid targeted ligands. No conflict of interest.

Persistent brain damage in reversible cerebral vasoconstriction syndrome on 99mTc-ethyl cysteinate dimer single-photon emission computed tomography: A long-term observational study

BackgroundBlood-brain barrier (BBB) breakdown is considered a key step in the pathophysiology of reversible cerebral vasoconstriction syndrome (RCVS); however, its temporal course remains unclear. Based on the characteristics and dynamics of 99mTc-ethyl cysteinate dimer (99mTc-ECD) as a tracer, 99mTc-ECD single-photon emission computed tomography (SPECT) can detect not only hypoperfusion but also BBB breakdown and/or brain tissue damage. Therefore, this study aimed to investigate this course using 99mTc-ECD SPECT. MethodsBetween 2011 and 2019, we enrolled seven patients (one male and six female patients) with RCVS without ischemic or hemorrhagic stroke or posterior reversible encephalopathy syndrome. 99mTc-ECD SPECT was performed repeatedly in each patient. SPECT data were statistically analyzed using an easy Z-score imaging system. ResultsThunderclap headache was the initial symptom in all the patients and was most commonly triggered by bathing (three patients). All the patients exhibited vasoconstriction and reduced cerebral uptake of 99mTc-ECD during the acute stage. Follow-up assessment from 3 to 16 months showed that reduced cerebral uptake persisted in all the patients, even after the vasoconstriction had resolved. ConclusionReduced cerebral uptake of 99mTc-ECD persisted in the late stage of RCVS, even after vasoconstriction and headache subsided. BBB breakdown and/or brain tissue damage may underlie this phenomenon. 99mTc-ECD SPECT is an effective neuroimaging method to detect brain functional abnormalities, reflecting BBB breakdown or tissue damages, throughout the treatment course of RCVS.

Influence of CT metal artifact reduction on SPECT/CT quantification of bone scintigraphy – Retrospective study for selected types of metal implants

Implanted metal prostheses can cause severe artifacts in reconstructed computed tomography (CT) images. To reduce the diagnostic impact of these artifacts and improve attenuation correction in single photon emission computed tomography (SPECT), an algorithm of iterative metal artifact reduction (iMAR) for SPECT/CT systems was developed. The aims of this study were (a) to assess the difference in visual image quality by comparing CT and SPECT images reconstructed with and without iMAR and (b) to determine the influence of iMAR on quantitative 99mTc-uptake in SPECT/CT. This retrospective study includes 21 patients with implanted metal prostheses who underwent SPECT/CT bone scintigraphy. CT data were reconstructed with iMAR and without (noMAR) and were used for attenuation correction of SPECT data for xSPECT Quant and xSPECT Bone reconstruction. The effect of iMAR on image quality was evaluated by visual analysis and the effect on quantitative SPECT/CT was assessed by measuring HU values and absolute uptake values (kBq/mL) in volumes of interest (VOIs). There was a significant reduction of visible metal artifacts with iMAR (p<0.01) in the CT images, but visual differences in the SPECT images were minor. The values of quantitative tracer uptake in VOIs near metal implants were lower for iMAR vs. noMAR xSPECT Quant (p<0.01). Only VOIs near metal showed significant differences in HU values, which were 14.6% lower for iMAR CT (p<0.01). The use of iMAR reduces metal artifacts in CT and improves the perceived image quality. Although in some cases a significant difference in the quantitative evaluation of SPECT/CT was observed, the influence of iMAR can be considered small in relation to other factors in the clinical setting.

ОСОБЕННОСТИ РАДИОНУКЛИДНОЙ ДИАГНОСТИКИ СИГНАЛЬНЫХ ЛИМФАТИЧЕСКИХ УЗЛОВ У БОЛЬНЫХ РАКОМ МОЛОЧНОЙ ЖЕЛЕЗЫ С ПОМОЩЬЮ НОВОГО ОТЕЧЕСТВЕННОГО РАДИОФАРМПРЕПАРАТА НА ОСНОВЕ ОКСИДА АЛЮМИНИЯ, МЕЧЕННОГО 99mТс

Purpose: To study the possibility of using [99mТс]-Al2O3 for the diagnosis of sentinel lymph nodes (SLN) in patients with breast cancer, to analyze the results obtained in comparison with a phytate colloid labeled with 99mTc. Material and methods: The study included 86 patients with breast cancer. [99mTc]-phytate colloid (31 patients) and [99mТс]-Al2O3 (55 patients) were used as radiopharmaceutical. Results: The optimal time interval between the injection of [99mТс]-Al2O3 and the acquisition of a scintigraphic image was determined to be 18-20 hours, when the maximum possible number of lymph nodes (LNs) with the most optimal level of radioactivity for their detection is visualized. In the group of patients who were injected with [99mTc]-phytate colloid, SLN were visualized in 27 out of 31 patients, a total of 37 LNs were detected in this group. The median number of detected LNs in one patient was 1 [0–3], the intensity of accumulation of [99mTc]-phytate colloid according to single-photon emission computed tomography (SPECT) was 1.75% [0.5–4.3%], intraoperatively using gamma -probe – 2.95% [1.1–5.6%]. When [99mТс]-Al2O3 was used as radiopharmaceutical, SLNs were detected in 51 patients out of 55. In total, 111 LNs were detected in this group, the median number of detected LNs in one patient was 2 [0-6], the intensity of accumulation of [99mТс]-Al2O3 according to SPECT data – 6.1% [0.5–18.4%], intraoperatively – 7.2% [1.3–22.1%]. In the absence of radiopharmaceuticals accumulation in regional LNs (n=7 in total), 3 patients had total metastatic lesions of the SLN, in two of them other regional LNs were also affected by metastases. Conclusion: A comparative analysis of the indices of two radiopharmaceuticals shows that studies with [99mТс]-Al2O3 are characterized by statistically significantly higher accumulation rates in the SLN compared with [99mTc]-phytate colloid. The number of detected LNs when using [99mТс]-Al2O3 was also higher than in the group with [99mTc]-phytate colloid. As a result, when [99mТс]-Al2O3 is used, the method is characterized by higher sensitivity in detecting SLN (94.5%).

Influence of minimum counts in brain perfusion SPECT: phantom and clinical studies.

The counts per pixel of brain perfusion single photon emission computed tomography (SPECT) images depend on the administration dose, acquisition time or patient condition, and they sometimes become poor acquisition counts in daily clinical study. The aim of this study was to evaluate the effect of different acquisition counts on qualitative images and statistical imaging analysis and to determine the minimum acquisition counts necessary for accurate examinations. Methods: We performed a brain phantom experiment simulating normal accumulation of 99mTc -ethyl-cysteinate dimer (99mTc-ECD) as a brain uptake of 5.5 %. The SPECT data were acquired in a continuous repetitive rotation. Ten types of SPECT images with different acquisition counts were created by varying the addition of the number of rotations. We used the normalized mean squared error (NMSE) and visual analysis. For the clinical study, we used 25 patients acquired in a continuous repetitive rotation, and created six brain images with different acquisition counts by varying the number of rotations added from 1 to 6. The contrast-to-noise ratio (CNR) was calculated from the mean counts with ROIs in gray and white matter. In addition, the severity, extent and ratio of disease-specific regions were evaluated as indices of statistical imaging analysis. Results: For the phantom study, the curve of NMSE showed a tendency of convergence from approximately 23.6 counts/pixel. Furthermore, the visual score showed that images with 23.6 counts/pixel or more were barely diagnosable. For the clinical study, the CNR was significantly decreased at 11.5 counts/pixel or less. Severity and extent tended to increase with decreasing acquisition counts, and a significant increase was shown at 5.9 counts/pixel. On the other hand, there was no significant difference in ratio values among defferent acquisition counts. Conclusion: Based on comprehensive assessment of phantom and clinical studies, we suggested that 23.6 counts/pixel or more were necessary to keep image quality of qualitative images and to accurately calculate indices of statistical imaging analysis.

CLINICAL CHARACTERISTICS OF WOMEN REFERRED TO CARDIAC SPECT: WHEN AND WHO? DATA FROM LATVIAN CARDIAC SPECT REGISTRY

Population based cross-sectional study of cardiovascular risk (CVR) factors in Latvia from year 2009 till 2019 revealed that women in age 25 -74 are in a very high CVR group: 61% of women have dyslipidemia, more than 33% have arterial hypertension (AH) and 28% are overweight. The data indicates the necessity for focused diagnostics and early detection of cardiovascular disease. The aim of study was to define the clinical profile and risk factors for women with suspected coronary artery disease (CAD) reffered to cardiac single photon emission computed tomography (SPECT) in Latvia and to find out the correlation between nuclear test result and patient clinical presentation.Cardiac SPECT was performed in a single centre from 2018 till 2021. The women patients were analyzed by risk factors and previous diagnosis of CAD. Exercise test was performed in all cases. Patients were divided into 2 groups: normal myocardial perfusion or true myocardial perfusion defect, defined as area of ischemia more than 10% of the left ventricle myocardium mass.726 SPECT data were analyzed. The mean age of women patients was 62.6 ± 10.6 years. More than half of the patients (n = 486,66.9%) were overweight (BMI> 25.0 kg/m2) and 33.3%(n = 242) were obese (BMI> 30.0 kg/m2). 87 (11.9%) women were current or ex-smokers. Dyslipidemia was present in in 614 (84.6%), AH in 535 (73.7%) and type 2 Diabetes mellitus (T2DM) in 60 (8.3%) patients. 104 (14.3%) patients were asymptomatic, but with intermediate to high pre-test probability for CAD. Known CAD was present in 298 (41.0%) patients. Exercise test was found positive in 306 (42.1%) patients and the test result was not always associated with ischaemia in SPECT (p = 0.063). True myocardial perfusion defect was detected in 125 patients (17.2%). Correlation was found between significant perfusion defect in SPECT and risk factors - AH (p = 0.013) and dyslipidemia (p = 0.029).The registry proves the high value of imaging with cardiac SPECT for diagnostics of CAD. Women patients with intermediate or high pre-test probability - even asymptomatic or with non informative exercise test should be reffered for cardiac SPECT.