Clinical Feasibility of Deep Learning-Based Attenuation Correction Models for Tl-201 Myocardial Perfusion SPECT.

PURPOSE: We aimed to develop deep learning (DL)-based attenuation correction models for Tl-201 myocardial perfusion SPECT (MPS) images and evaluate their clinical feasibility. PATIENTS AND METHODS: We conducted a retrospective study of patients with suspected or known coronary artery disease. We proposed a DL-based image-to-image translation technique to transform non-attenuation-corrected images into CT-based attenuation-corrected (CT AC ) images. The model was trained using a modified U-Net with structural similarity index (SSIM) loss and mean squared error (MSE) loss and compared with other models. Segment-wise analysis using a polar map and visual assessment for the generated attenuation-corrected (GEN AC ) images were also performed to evaluate clinical feasibility. RESULTS: This study comprised 657 men and 328 women (age, 65 ± 11 years). Among the various models, the modified U-Net achieved the highest performance with an average mean absolute error of 0.003, an SSIM of 0.990, and a peak signal-to-noise ratio of 33.658. The performance of the model was not different between the stress and rest datasets. In the segment-wise analysis, the myocardial perfusion of the inferior wall was significantly higher in GEN AC images than in the non-attenuation-corrected images in both the rest and stress test sets ( P < 0.05). In the visual assessment of patients with diaphragmatic attenuation, scores of 4 (similar to CT AC images) or 5 (indistinguishable from CT AC images) were assigned to most GEN AC images (65/68). CONCLUSIONS: Our clinically feasible DL-based attenuation correction models can replace the CT-based method in Tl-201 MPS, and it would be useful in case SPECT/CT is unavailable for MPS.

Impact of medical radionuclide discharges on people and the environment.

We present a novel methodology to dynamically calculate dose rates to people and wildlife from hospital-released radionuclides reaching the environment through water treatment plants (WTPs), using the biokinetic model D-DAT for aquatic wildlife, applied to 18F, 123I, 131I, 153Sm, 99mTc and 201Tl. We have also developed a method to calculate doses to WTP workers and to farmers from agricultural practices. This proof-of-concept study simulates a generic source term of radionuclide levels in the Belgian Molse Nete River during the year 2018, chosen because the river flow was very low during that year, which constitutes a very conservative, bounding case. The dose rates to wildlife calculated for this hypothetical scenario under conservative assumptions, are well below the ERICA predicted no effects dose rate to wildlife of 10 µGy h-1. Human exposures are also very low, in most cases not exceeding 10 µSv y-1. This work identifies important data gaps and areas of uncertainty in the assessment of radiopharmaceutical effluents. The study, which is part of the EC project SINFONIA, paves the way for a dynamic screening assessment methodology able to perform consistently assessments of the impact of radiopharmaceuticals on people and wildlife. This is particularly relevant since discharges of radiopharmaceuticals in rivers are on the increase and it is necessary to explicitly demonstrate that people and the environment are adequately protected.

Integrating subvolume dose and myocardial perfusion imaging parameters to assess the impact of radiation therapy on heart function in breast cancer patients: A comparative analysis between left- and right-sided breast cancer.

BACKGROUND: This study aimed to utilize an innovative method of integrating the 20 subvolume dose of left ventricle and the Tl-201 single photon emission computed tomography (SPECT) with myocardial perfusion imaging (MPI) parameters in patients with left- and right-sided breast cancer after radiation therapy. METHODS: Female patients with breast cancer underwent SPECT MPI before commencing radiotherapy and 12 months later were enrolled from January 2014 to December 2018. The images of CT simulation and SPECT MPI were integrated into the treatment planning system. The differences of doses and parameters of MPI in all cardiac subvolumes between left- and right-sided breast cancer patients were analyzed. RESULTS: Patients with left-sided breast cancer (n = 61) received a higher radiation dose to the heart, left ventricular, and its territories and subvolumes, compared to patients with right-sided breast cancer (n = 19). The 20-segment analysis also showed statistically significant disparities in the average radiation doses received by the two groups. In different coronary artery territories, the end-diastolic perfusion and end-systolic perfusion showed a decrease in both sides, with no significant differences. However, the wall motion and wall thickening showed a significant decline in subregions within the left- and right-sided coronary artery territories. CONCLUSION: This study demonstrates an innovative integrated method combining the left ventricular 20 regional doses with SPECT MPI which shows that left-sided breast cancer patients receive a higher subvolume dose than right-sided breast cancer patients. Further research is needed to confirm the potential impact on heart function after radiotherapy on both sides.

Optimized SPECT Imaging of 224Ra α-Particle Therapy by 212Pb Photon Emissions.

In preparation for an α-particle therapy trial using 1-7 MBq of 224Ra, the feasibility of tomographic SPECT/CT imaging was of interest. The nuclide decays in 6 steps to stable 208Pb, with 212Pb as the principle photon-emitting nuclide. 212Bi and 208Tl emit high-energy photons up to 2,615 keV. A phantom study was conducted to determine the optimal acquisition and reconstruction protocol. Methods: The spheres of a body phantom were filled with a 224Ra-RaCl2 solution, and the background compartment was filled with water. Images were acquired on a SPECT/CT system. In addition, 30-min scans were acquired for 80- and 240-keV emissions, using triple-energy windows, with both medium-energy and high-energy collimators. Images were acquired at 90-95 and 29-30 kBq/mL, plus an explorative 3-min acquisition at 20 kBq/mL (using only the optimal protocol). Reconstructions were performed with attenuation correction only, attenuation plus scatter correction, 3 levels of postfiltering, and 24 levels of iterative updates. Acquisitions and reconstructions were compared using the maximum value and signal-to-scatter peak ratio for each sphere. Monte Carlo simulations were performed to examine the contributions of key emissions. Results: Secondary photons of the 2,615-keV 208Tl emission produced in the collimators make up most of the acquired energy spectrum, as revealed by Monte Carlo simulations, with only a small fraction (3%-6%) of photons in each window providing useful information for imaging. Still, decent image quality is possible at 30 kBq/mL, and nuclide concentrations are imageable down to approximately 2-5 kBq/mL. The overall best results were obtained with the 240-keV window, medium-energy collimator, attenuation and scatter correction, 30 iterations and 2 subsets, and a 12-mm gaussian postprocessing filter. However, all combinations of the applied collimators and energy windows were capable of producing adequate results, even though some failed to reconstruct the 2 smallest spheres. Conclusion: SPECT/CT imaging of 224Ra in equilibrium with daughters is possible, with sufficient image quality to provide clinical utility for the current trial of intraperitoneally administrated activity. A systematic scheme for optimization was designed to select acquisition and reconstruction settings.

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

BACKGROUNDS: The 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. METHODS: Myocardial 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. RESULTS: The 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. CONCLUSION: The 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.

125I-labeled 2-[4-(2-iodophenyl)piperidino]cyclopentanol (125I-OI5V) imaging visualized augmented sigma-1 receptor expression according to the severity of myocardial ischemia.

BACKGROUND: We aimed to explore how the severity of myocardial ischemia affects myocardial sigma-1 receptor (Sig-1R) expression using 125I-labeled 2-[4-(2-iodophenyl)piperidino]cyclopentanol (125I-OI5V) imaging. METHODS AND RESULTS: The left coronary artery was occluded for 30, 20, and 10 minute, to vary the severity of myocardial ischemia, followed by reperfusion. Dual-tracer autoradiography of the left ventricular short-axis slices was performed 3 and 7 days after reperfusion. 125I-OI5V was injected 30 minute before sacrifice and the area at risk (AAR) was evaluated by 99mTc-MIBI. Intense 125I-OI5V uptake was observed in the AAR and was significantly increased with increasing ischemia duration. To evaluate salvaged and nonsalvaged areas (preserved and decreased perfusion areas), triple-tracer autoradiography was performed 3 days after reperfusion. After dual-tracer autoradiography, 201Tl was injected 20 minute post 125I-OI5V injection. On triple-tracer autoradiography, the AAR/normally perfused area 125I-OI5V uptake ratio was positively correlated with the nonsalvaged area/whole left ventricular (LV) area ratio (P < .05). The AAR/normally perfused area 125I-OI5V uptake ratio was negatively correlated with the 201Tl uptake ratio of the AAR to normally perfused areas (P < .05). The comparison of the immunostaining distribution of 125I-OI5V and the macrophage marker CD68 revealed that 125I-OI5V was present mainly in, and immediately adjacent to the macrophage infiltration area. CONCLUSIONS: Significant 125I-OI5V uptake in the AAR depends on the duration of ischemia and reduced 201Tl uptake; furthermore, 125I-OI5V was found in and around the macrophage infiltrate area. These results indicate that iodine-labeled OI5V is a promising tool for visualizing Sig-1R expression according to the ischemic burden.

Relative contributions to patient effective dose in SPECT-CT hybrid imaging.

Medical imaging using ionising radiation, while commonplace, has an associated risk of cancer induction. In trying to manage this risk it is beneficial to be able to quantify it through the use of effective dose. Estimates of effective dose resulting from radiopharmaceutical administration are well established in published data but the equivalent data for the computed tomography (CT) component of nuclear medicine hybrid imaging is less well-known. This study aims to estimate the absolute and relative contributions to effective dose from radiopharmaceutical and CT components of common single photon emission computed tomography (SPECT)-CT procedures. Using patient dose-audit data from three SPECT-CT systems we estimated the effective dose resulting from radiopharmaceutical administration by scaling the published effective dose data according to administered activity. The corresponding effective dose resulting from the CT component was estimated using the ImPACT CT dosimetry tool. Absolute effective dose from radiopharmaceutical administrations ranged from 0.2 (Tc-99m colloid head and neck sentinel lymph node imaging) to 14.2 mSv (dual-isotope Tc-99m sestamibi/I-123 sodium iodide parathyroid imaging). Effective dose from the CT components ranged from 0.3 (Tl-201 chloride brain scans - scan range covering the brain) to 4.4 mSv (Tc-99m HYNIC Ty3-Octreotide scans which use a scan range from the top of the brain to bottom of pelvis). Relative contributions (radiopharmaceutical/CT) ranged from 11/89 (Tc-99m colloid head and neck sentinel lymph node imaging) to 98/2% (Tl-201 chloride brain scans). There is a wide range of effective dose from radiopharmaceutical and CT components of hybrid imaging and both aspects can benefit from optimisation efforts, with the largest benefit coming from the CT components.

PET plastics as a Trojan horse for radionuclides.

Mismanaged plastic waste interacts with secondary environmental pollutants, potentially aggravating their impact on ecosystems and human health. Here we characterized the natural and artificial radionuclides in polyethylene terephthalate (PET) bottles collected from the industrial littoral discharge of a phosphate fertilizer plant. The activity concentrations in littered bottles ranged from 0.47 (208Tl) to 12.70 Bq·kg-1 (226Ra), with a mean value of 5.30 Bq·kg-1. All the human health risk assessment indices (annual intake, annual effective dose, and excess lifetime cancer risk) estimated for radionuclides associated with ingestion and inhalation of microplastics were below international safety limits. Our results demonstrated that PET can be loaded with natural and artificial radionuclides, and potentially act as a carrier to transfer radionuclides to humans, posing a new potential health risk. Increased use, mismanagement and fragmentation of plastic waste, and continued interaction of plastic waste with radioelements may lead to enhanced radiation exposure in the future.

Dosimetry of [212Pb]VMT01, a MC1R-Targeted Alpha Therapeutic Compound, and Effect of Free 208Tl on Tissue Absorbed Doses.

[212Pb]VMT01 is a melanocortin 1 receptor (MC1R) targeted theranostic ligand in clinical development for alpha particle therapy for melanoma. 212Pb has an elementally matched gamma-emitting isotope 203Pb; thus, [203Pb]VMT01 can be used as an imaging surrogate for [212Pb]VMT01. [212Pb]VMT01 human serum stability studies have demonstrated retention of the 212Bi daughter within the chelator following beta emission of parent 212Pb. However, the subsequent alpha emission from the decay of 212Bi into 208Tl results in the generation of free 208Tl. Due to the 10.64-hour half-life of 212Pb, accumulation of free 208Tl in the injectate will occur. The goal of this work is to estimate the human dosimetry for [212Pb]VMT01 and the impact of free 208Tl in the injectate on human tissue absorbed doses. Human [212Pb]VMT01 tissue absorbed doses were estimated from murine [203Pb]VMT01 biodistribution data, and human biodistribution values for 201Tl chloride (a cardiac imaging agent) from published data were used to estimate the dosimetry of free 208Tl. Results indicate that the dose-limiting tissues for [212Pb]VMT01 are the red marrow and the kidneys, with estimated absorbed doses of 1.06 and 8.27 mGyRBE = 5/MBq. The estimated percent increase in absorbed doses from free 208Tl in the injectate is 0.03% and 0.09% to the red marrow and the kidneys, respectively. Absorbed doses from free 208Tl result in a percent increase of no more than 1.2% over [212Pb]VMT01 in any organ or tissue. This latter finding indicates that free 208Tl in the [212Pb]VMT01 injectate will not substantially impact estimated tissue absorbed doses in humans.

Toward Bifunctional Chelators for Thallium-201 for Use in Nuclear Medicine.

Auger electron therapy exploits the cytotoxicity of low-energy electrons emitted during radioactive decay that travel very short distances (typically <1 µm). 201Tl, with a half-life of 73 h, emits ∼37 Auger and other secondary electrons per decay and can be tracked in vivo as its gamma emissions enable SPECT imaging. Despite the useful nuclear properties of 201Tl, satisfactory bifunctional chelators to incorporate it into bioconjugates for molecular targeting have not been developed. H4pypa, H5decapa, H4neunpa-NH2, and H4noneunpa are multidentate N- and O-donor chelators that have previously been shown to have high affinity for 111In, 177Lu, and 89Zr. Herein, we report the synthesis and serum stability of [nat/201Tl]Tl3+ complexes with H4pypa, H5decapa, H4neunpa-NH2, and H4noneunpa. All ligands quickly and efficiently formed complexes with [201Tl]Tl3+ that gave simple single-peak radiochromatograms and showed greatly improved serum stability compared to DOTA and DTPA. [natTl]Tl-pypa was further characterized using nuclear magnetic resonance spectroscopy (NMR), mass spectroscopy (MS), and X-ray crystallography, showing evidence of the proton-dependent presence of a nine-coordinate complex and an eight-coordinate complex with a pendant carboxylic acid group. A prostate-specific membrane antigen (PSMA)-targeting bioconjugate of H4pypa was synthesized and radiolabeled. The uptake of [201Tl]Tl-pypa-PSMA in DU145 PSMA-positive and PSMA-negative prostate cancer cells was evaluated in vitro and showed evidence of bioreductive release of 201Tl and cellular uptake characteristic of unchelated [201Tl]TlCl. SPECT/CT imaging was used to probe the in vivo biodistribution and stability of [201Tl]Tl-pypa-PSMA. In healthy animals, [201Tl]Tl-pypa-PSMA did not show the myocardial uptake that is characteristic of unchelated 201Tl. In mice bearing DU145 PSMA-positive and PSMA-negative prostate cancer xenografts, the uptake of [201Tl]Tl-pypa-PSMA in DU145 PSMA-positive tumors was higher than that in DU145 PSMA-negative tumors but insufficient for useful tumor targeting. We conclude that H4pypa and related ligands represent an advance compared to conventional radiometal chelators such as DOTA and DTPA for Tl3+ chelation but do not resist dissociation for long periods in the biological environment due to vulnerability to reduction of Tl3+ and subsequent release of Tl+. However, this is the first report describing the incorporation of [201Tl]Tl3+ into a chelator-peptide bioconjugate and represents a significant advance in the field of 201Tl-based radiopharmaceuticals. The design of the next generation of chelators must include features to mitigate this susceptibility to bioreduction, which does not arise for other trivalent heavy radiometals.

Usefulness of dual isotope 123I-IMP and 201Tl SPECT for the diagnosis of primary central nervous system lymphoma and glioblastoma.

BACKGROUND: Preoperative differential diagnosis between primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM) is important because these tumors require different surgical strategies. This study investigated the usefulness of dual isotope, iodine-123-labeled N-isopropyl-p-iodo-amphetamine (123I-IMP) and thallium-201 chloride single-photon emission computed tomography (201Tl SPECT) for the differential diagnosis. METHODS: Twenty-five PCNSL patients and 27 GBM patients who underwent dual isotope imaging, 123I-IMP and 201Tl SPECT, are included. Tumor-to-normal (T/N) ratio was calculated from the ratio of maximum tracer counts in the lesion to the mean counts in the contralateral cerebral cortex. The mean and minimum apparent diffusion coefficient values (ADCmean and ADCmin, respectively) on magnetic resonance imaging were also analyzed. RESULTS: Delayed phase 123I-IMP SPECT was the most useful imaging examination for the differentiation between PCNSL and GBM compared with early phase 123I-IMP SPECT, early and delayed phase 201Tl SPECT, ADCmean, and ADCmin. However, the median T/N ratios of PCNSL and GBM were 1.32 and 0.83, respectively, in the delayed phase 123I-IMP SPECT. On the other hand, the median T/N ratios of PCNSL and GBM were 3.10 and 2.34, respectively, in the delayed phase 201Tl SPECT, with excellent tumor detection. CONCLUSION: Delayed phase 123I-IMP SPECT could differentiate between PCNSL and GBM with high accuracy, but T/N ratio was low and tumor detection was poor. 201Tl SPECT was useful for estimation of the malignancy and localization of the tumors with high T/N ratio. Dual isotope 123I-IMP and 201Tl SPECT was useful for the preoperative diagnosis of PCNSL and GBM.

Clinical Utility of a Slow 201Tl Washout Rate in the Detection of Multi-Vessel Coronary Artery Disease Using a Simultaneous Acquisition Rest 99 mTc/Stress 201Tl Protocol and a Semiconducting Gamma Camera.

BACKGROUND: The diagnostic accuracy of stress myocardial perfusion single-photon emission computed tomography (SPECT) to detect coronary artery disease (CAD) is reduced by the balanced reduction of myocardial perfusion in patients with multi-vessel or left main trunk CAD (multi-vessel group). This study investigated the diagnostic performance of a simultaneous acquisition rest 99 mTc/stress 201Tl dual-isotope protocol for myocardial perfusion SPECT (MPS) in a multi-vessel group by examining the assessment of a slow 201Tl washout rate (WR) finding in comparison to the accuracy of perfusion assessments.Methods and Results: This study enrolled 91 patients who had undergone angiography within 3 months after MPS. The diagnostic performances of perfusion assessments and a slow 201Tl WR parameter were compared using the area under the curve (AUC) in a multi-vessel group of patients with mild ischemia (2≤summed difference score [SDS]≤7). The AUC of a slow WR parameter was significantly larger compared with that for perfusion assessments, in patients with mild ischemia, (AUC, 0.736 vs. 0.504-0.558, P value: <0.01-0.05). CONCLUSIONS: Among patients with mild ischemia, a slow 201Tl WR parameter improved the detection of CAD in a multi-vessel group.

Incidental Finding of Moderna COVID-19 Vaccination-Related Axillary Lymphadenopathy on 201Tl Myocardial Perfusion Imaging.

ABSTRACT: We presented here a 71-year-old man with a history of thyroid cancer post total thyroidectomy and 131I ablation and right renal cell carcinoma post right partial nephrectomy. He reported persistent chest tightness and pain after the first dose of the Moderna COVID-19 (mRNA-1273) vaccine. Thus, coronary heart disease was suspected, and the patient was referred for MPI (myocardial perfusion imaging). Focal 201Tl uptake in the left axillary region was found incidentally on MPI, and SPECT/CT revealed enlarged benign-looking lymph nodes. The diagnostic is in favor of reactive hyperplasia after the intramuscular injection of vaccine into left deltoid muscle.

Insights into Nuclear Cardiology in the United States from the first 3 years of the ImageGuide Registry.

BACKGROUND: Data registries facilitate knowledge acquisition and quality improvement. ImageGuide is a registry developed by the American Society of Nuclear Cardiology collecting data since 2015, providing insight into current nuclear cardiology practice. METHODS AND RESULTS: HIPAA de-identified data on > 100 practice- and patient-related variables from 19 US practices were obtained from ImageGuide. Continuous variables are reported as the mean ± standard deviation; discrete variables are reported as N (%). Practices were from 12 states; 9520 studies were submitted. The average patient was a 66-year-old man. Chest pain was the most common indication; 96% of studies were appropriate. Rest/stress 1-day studies were most common; stress/rest 1- and 2-day studies comprised < 5%. Tc-99 m was the most common radiopharmaceutical. Tl-201 was used in 14% of rest studies. Most studies were not corrected for attenuation. 89% were of good or better quality. 62% of studies were normal. CONCLUSIONS: Practice diversity is limited, but patient demographics are reflective of reported current practice. Most studies are appropriate and may obviate the need for invasive testing. Radiation dosimetry could be decreased with wider adoption of stress/rest studies and avoidance of Tl-201. ImageGuide will be an important tool to guide non-invasive cardiac imaging in the future.

Assessment of left ventricular volumes and ejection fraction using ultra-low-dose thallium-201 SPECT on a CZT camera: a comparison with magnetic resonance imaging.

BACKGROUND: Cadmium-Zinc-Telluride (CZT) technology allows use of low activities of radiopharmaceuticals. The aim was to verify the values of left ventricular volume parameters, obtained via ultra-low-dose thallium Single Photon Emission Computed Tomography (SPECT) using a CZT camera. METHODS AND RESULTS: Forty-five patients referred for an assessment of myocardial perfusion or viability imaging were examined using CZT-SPECT and 1.5 T magnetic resonance (MRI) scanner. The ultra-low-dose protocol with 0.5 Mbq 201-Tl per kg of body weight was used. The values of end-systolic (ESV) and end-diastolic volumes (EDV), left ventricular ejection fraction (EF) and myocardial mass (MM) were assessed using both techniques. A very good correlation was found between the EF, ESV, and EDV values assessed with CZT-SPECT and cardiac magnetic resonance MRI; the Pearson coefficients were 0.86, 0.95, and 0.91, respectively. A moderate correlation was found for myocardial mass, r = 0.57. Compared to MRI, SPECT systematically overestimated ESV and MM, while it underestimates the EF, with P ≤ .001 in all cases. There was no difference in EDV estimation. CONCLUSIONS: Left ventricular volumes and ejection fraction assessed via ultra-low-dose CZT-SPECT showed very good correlation with the values obtained by MRI. A moderate correlation was found for myocardial mass.

Kinetics of Thallium-201 in Acute Phase of Myocardial Infarction: A Case Report.

BACKGROUND Thallium-201 has been widely used in clinical practice for the management of coronary heart disease, but little is known regarding its kinetics in the acute phase of myocardial infarction. CASE REPORT We report a 78-year-old man who developed acute inferior myocardial infarction during exercise thallium-201 scintigraphy. The patient underwent exercise testing with thallium-201 myocardial scintigraphy because of a single episode of chest pain. The workload was started with 25 watts and increased by 25 watts every 2 min on a bicycle ergometer with continuous monitoring of 12-lead electrocardiography. Thallium-201 was injected intravenously at 85% of the age-predicted maximal heart rate, and ST-segment elevations refractory to medication subsequently developed in the inferior leads, followed by chest pain. Scintigraphic image acquisition was deferred and he was transferred to the catheter laboratory in this hospital. Emergency coronary angiography showed occlusion in the right coronary artery, and stent implantation was successfully performed. The peak level of creatine kinase in the clinical course was 201 U/l. Scintigraphic images obtained 4 h after the onset of ST-segment elevation showed severely reduced activity in the left ventricular inferior wall, with partial redistribution 24 h later. Follow-up imaging performed 4 months later revealed increased accumulation of thallium-201 in the inferior wall. CONCLUSIONS Our case highlights the kinetics of thallium-201 during acute myocardial infarction.

Long-term prognostic value of computed tomography-based attenuation correction on thallium-201 myocardial perfusion imaging: A cohort study.

BACKGROUND: Myocardial perfusion imaging (MPI) is a well-established diagnostic tool to evaluate coronary artery disease (CAD) and also an effective prognostic tool for patients with CAD. However, few studies investigated the prognostic value of attenuation correction (AC) in MPI, and the results were controversial. OBJECTIVES: To investigate the prognostic value of computed tomography (CT)-based AC thallium-201 (Tl-201) MPI. METHODS: A total of 108 consecutive patients who underwent Tl-201 MPI and received coronary angiography within 90 days were included. Medical records were reviewed and missing information was completed after telephone contact. The prognostic value was evaluated by Kaplan-Meier analysis, univariable and multivariable Cox proportional hazards model. RESULTS: After a mean follow-up of 7.72 ± 3.72 years, 27 patients had died, 41 had been readmitted for cardiovascular (CV)-related events and 44 had reached the composite of death plus CV-related re-admission. Kaplan-Meier curves for all-cause mortality for SSS with a cutoff value of 13 for AC and 16 for non-AC (NAC) images showed a significant difference between the two curves for both AC and NAC images (p = 0.011 for AC and p = 0.021 for NAC). In the multivariable model, SSS and SRS showed similar independent predictive values in predicting all-cause mortality and composite of all-cause mortality plus CV-related re-admission, in both AC and NAC images. Subgroup analysis implicated that AC MPI possibly provided better risk stratification in obese patients. CONCLUSION: CT-based AC and NAC MPI showed similar value and were the only significant predictors for the composite of mortality and CV events.