Imaging with [99mTc]HMPAO – a novel perspective: investigation of [99mTc]HMPAO leg muscle uptake in metabolic diseases

Background Sensitive imaging modalities in the diagnosis of microcircular complications of the lower extremities induced by metabolic diseases are becoming a focus of interest. Purpose To investigate the [99mTc]HMPAO uptake of the legs in type 2 diabetes mellitus (T2DM) and obesity, and to search for associations with clinical parameters and nerve conducting studies. Material and Methods A total of 57 patients with controlled T2DM and 46 obese participants without DM were enrolled in the study. [99mTc]HMPAO SPECT/CT examinations were performed to evaluate the radiopharmaceutical accumulation of the legs. For the quantitative assessment of tracer uptake, standardized uptake value (SUVpeak) was measured in fixed spheric volumes of interest placed on both sural muscles on the attenuation-corrected images. Measurement of current perception threshold applying Neurometer (NM-01/CPT) was used to evaluate peripheral nerve dysfunction. Laboratory parameters assessing the glucose homeostasis of the study participants were also measured. Results In the diabetic group, significantly lower leg SUV values were detected compared to the non-DM obese group (median: 0.517 vs. 0.607; P < 0.001). Body mass index (BMI) ( P < 0.0001), age ( P = 0.0283), HbA1c ( P = 0.0068), and glucose level ( P = 0.0044) proved to be significant predictors of muscle tracer uptake. Neurometer studies showed positive correlation with HbA1c levels in the T2DM group ( P = 0.0002). Conclusion We assume that [99mTc]HMPAO uptake of leg muscles is associated with microcirculation, so quantitative [99mTc]HMPAO SPECT/CT might be a sensitive method for evaluating lower limb microvascular alterations. BMI, age, HbA1c, and glucose level may be significant predictors of peripheral vascular abnormalities triggered by metabolic disturbances.

The Diagnostic Value of 99mTc-HMPAO-Labelled White Blood Cell Scintigraphy and 18F-FDG PET/CT in Cardiac Device-Related Infective Endocarditis—A Systematic Review

(1) Background: Treatment of cardiac arrhythmias and conduction disorders with the implantation of a cardiac implantable electronic device (CIED) may lead to complications. Cardiac device-related infective endocarditis (CDRIE) stands out as being one of the most challenging in terms of its diagnosis and management. Developing molecular imaging modalities may provide additional insights into CDRIE diagnosis. (2) Methods: We performed a systematic literature review to critically appraise the evidence for the diagnostic performance of the following hybrid techniques: single photon emission tomography with technetium99m-hexamethylpropyleneamine oxime–labeled autologous leukocytes (99mTc-HMPAO-SPECT/CT) and positron emission tomography with fluorodeoxyglucose (18F-FDG PET/CT). An analysis was performed in accordance with PRISMA and GRADE criteria and included articles from PubMed, Embase and Cochrane databases. (3) Results: Initially, there were 2131 records identified which had been published between 1971–2021. Finally, 18 studies were included presenting original data on the diagnostic value of 99mTc-HMPAO-SPECT/CT or 18F-FDG PET/CT in CDRIE. Analysis showed that these molecular imaging modalities provide high diagnostic accuracy and their inclusion in diagnostic criteria improves CDRIE work-up. (4) Conclusions: 99mTc-HMPAO-SPECT/CT and 18F-FDG PET/CT provide high diagnostic value in the identification of patients at risk of CDRIE and should be considered for inclusion in the CDRIE diagnostic process.

Assessment of informative value of effective cerebral blood flow calculation technique according to 99mTc-HMPAO polyphase scintigraphy data

Background. According to single-photon emission computed tomography (SPECT) data, the most common technique to calculate volume cerebral blood flow (VCBF) is N.A. Lassen method. Following it, VCBF in different segments of the brain is assessed in comparison with blood flow in the cerebellum, where it is considered to be constant. However, this approach does not take into account that in some pathologies, in particular, injuries, occlusions of blood vessels, VCBF of the cerebellum also does change. Therefore, an original technique of calculating regional VCBF based on polyphase scintigraphy has been developed, which will make it possible to make a more accurate assessment of the effective perfusion of the brain. Purpose – to evaluate the clinical informative value of the developed technique for calculating effective cerebral blood flow according to 99mTc-HMPAO (hexamethylpropyleneaminoxime) polyphase brain scintigraphy data. Materials and methods. The study is focused on analyzing two groups of patients: Group A represented by patients with signs of chronic cerebral ischemia and Group B enrolling patients in the interim and long term of explosive minor brain injury (n=22). Group A patients were divided into two subgroups, depending on the presence of structural and hemodynamic changes in the vertebral arteries (VA) according to ultrasound (US) of the major vessels of the brain. I-A subgroup (n=13) was made up by those patients who had structural lesions of the vertebrobasilar basin; II-A (n=27) patients had no relevant signs. All patients underwent a comprehensive clinical examination including neuropsychological testing, ultrasound of major vessels, magnetic resonance imaging, single-photon emission computed tomography (SPECT). Effective volume cerebral blood flow (VCBF), according to the SPECT data, was calculated based on the original technique (VCBFSB). VCBFSB values were compared with the SPECT data using N.A. Lassen (VCBFLassen) method and the ultrasound data. Results and discussion. Analysing the data of the groups of patients with hemodynamic impairment in the vertebro-basilar basin shows that, according to the scintigraphy of VCBF, I-A group patients differ from II-A group on average 1.82± 0.06 times the amount for CBFSB and 0.95± 0.04 for CBFLassen. The total mean blood flow in the carotid and vertebral arteries of I-A group patients was 748.19±198.42 mL/min, II-A group patients – 1112.23±63.71 mL/min. Comparing the mean values of the hemodynamic parameters of the brain of Group B patients with the data of Group II-A patients, VCBFSB was 1.33±0.25-fold decreased, while CBFLassen showed 1.03±0.14-fold decrease of perfusion (in total average blood flow of vertebral and carotid arteries according to US of Group B – 1760±580 ml/min). Conclusions. Preliminary clinical studies, using the developed technique for calculating volume cerebral blood flow according to 99mTc-HMPAO scintigraphy data with the corresponding software, showed a rather high sensitivity in assessing VCBF in case of pathological changes in the brain, especially, in occlusion of the major vessels of the brain and contusions resulting from battle trauma, whereas N.A. Lassen method was insufficiently informative. The regression analysis of US data, SPECT data and neuropsychological testing shows clear linear correlation relationships, but they do also differ in sign depending on the diagnosis and the degree of pathological changes.

Effects of cranioplasty in cerebral blood perfusion using quantification with 99mTc-HMPAO SPECT-CT

PURPOSE: SSFS is an underdiagnosed complication of craniectomized patients, which mainly presents with headache, motor weakness, and cognitive impairments. In these patients, cranioplasty improves these symptoms. Furthermore, patients without a classical SSFS have been shown to improve their neurological functions after reconstructive surgery. Amongst the many different pathophysiological theories proposed, the changes of CBP caused by the cranial defect might have a role in the neurological deficiencies. We have studied CBP in twelve cortical areas of both hemispheres, using 99mTc-HMPAO SPECT-CT before and after cranioplasty.METHODS: Twenty-eight craniectomized patients subject to reconstructive surgery were studied with 99mTc- HMPAO in three different times, before cranioplasty, a week after, and three months later. The images were processed with quantification software comparing CBP of 24 cortical areas with a reference area , and with a database of normal individuals. A mixed effects model was used to determine the signification of CBP changes in the cortex regions of both the damaged and undamaged brain hemispheres.RESULTS: CBP increased significantly in both hemispheres after cranioplasty both in ratio (β=0.019 p-value=0,030 first post-surgical SPECT-CT and β=0.021 p-value=0,015 in the second study, vs. pre-surgical) and Z-score (β=0.220 p-value=0,026 and β=0.279 p-value=0,005 respectively). Nine of twelve areas of the damaged side had a significant lower CBP ratio and Z-score than the undamaged. Posterior cingulate showed an increased CBP ratio (p-value=0,034) and Z-score(p-value0,028) in the first post-surgical SPECT-CT.CONCLUSION: CBP changes significantly in specific cortical areas after cranioplasty, which might explain the clinical improvements observed. Posterior cingulate changes might explain some improvements in attention impairments described. 99mTc-HMPAO SPECT-CT might be a valid tool to assess CBP changes in these patients and could have a role in the management of craniectomized individuals.CLINICAL TRIAL REGISTRATIONNot applicable

Atlas of 99mTc-HMPAO SPECT brain perfusion in pediatric brain disorders

Background: Blood flow to the brain is in parallel with brain metabolism in almost all brain disorders except in brain tumors and therefore regional cerebral blood flow can be used as a marker of metabolic brain activity and hence it is closely linked to neuronal activity, the activity distribution is presumed to reflect neuronal activity levels in different areas of the brain. Purpose: The aim of this work is to demonstrate to pediatrician in general and pediatric neurologist in particular the variations in cerebral perfusion during normal development which should be taken into consideration at the time of interpreting SPECT brain perfusion scan in different pediatric brain disorders. Method: Brain SPECT was performed 10 minutes after an intravenous injection of 11.1 MBq/kg (0.3 mCi/kg), and the minimum dose is 185 MBq (5 mCi) of 99mTc-HMPAO (4). Results: This was a retrospective analysis of SPECT brain perfusion scan of pediatric patients performed between October 2015 and December 2019 at our institution. We selected normal and abnormal studies in pediatric population with age range (5 months - 14 years). Conclusion: Although anatomic cross sectional imaging give details of neurological structural changes, SPECT perfusion mirrors indirectly both metabolic and neuronal activity changes. Therefore, accurate interpretation of SPECT perfusion will consolidate its role as part of the diagnostic protocol and used when the findings of other imaging modalities do not explain the symptoms or fail partially or completely in determining the etiology of brain disorders in pediatric patients.