Economic and healthcare resource utilization assessments of PET imaging in Coronary Artery Disease diagnosis: a systematic review and discussion of opportunities for future economic evaluations.

AIMS: This systematic literature review (SLR) consolidated economic and healthcare resource utilization (HCRU) evidence for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to inform future economic evaluations. MATERIALS AND METHODS: An electronic search was conducted in MEDLINE, Embase, and Cochrane databases from 2012-2022. Economic and HCRU studies in adults who underwent PET- or SPECT-MPI for coronary artery disease (CAD) diagnosis were eligible. A qualitative methodological assessment of existing economic evaluations, HCRU, and downstream cardiac outcomes was completed. Exploratory meta-analyses of clinical outcomes were performed. RESULTS: The search yielded 13,439 results, with 71 records included. Economic evaluations and comparative clinical trials were limited in number and outcome types (HCRU, downstream cardiac outcomes, and diagnostic performance) assessed. No studies included all outcome types and only one economic evaluation linked diagnostic performance to HCRU. The meta-analyses of comparative studies demonstrated significantly higher rates of early- and late-invasive coronary angiography and revascularization for PET- compared to SPECT-MPI; however, the rate of repeat testing was lower with PET-MPI. The rate of acute myocardial infarction was lower, albeit non-significant with PET- vs. SPECT-MPI. LIMITATIONS AND CONCLUSIONS: This SLR identified economic and HCRU evaluations following PET- and SPECT-MPI for CAD diagnosis and determined that existing studies do not capture all pertinent outcome parameters or link diagnostic performance to downstream HCRU and cardiac outcomes, thus, resulting in simplified assessments of CAD burden. A limitation of this work relates to heterogeneity in study designs, patient populations, and follow-up times of existing studies. Resultingly, it was challenging to pool data in meta-analyses. Overall, this work provides a foundation for the development of comprehensive economic models for PET- and SPECT-MPI in CAD diagnosis, which should link diagnostic outcomes to HCRU and downstream cardiac events to capture the full CAD scope.

Quantificação da área de infarto usando-se SPECT de perfusão miocárdica de alta resolução em ratos / Myocardial infarction area quantification using high-resolution SPECT images in rats

FUNDAMENTO: Técnicas de imageamento in vivo permitem avaliar sequencialmente a morfologia e a função dos órgãos em diversos modelos experimentais. Desenvolvemos um dispositivo de adaptação de uma gama-câmara clínica para obter imagens tomográficas por emissão de fótons singulares (SPECT) de alta resolução, baseado em colimador pinhole. OBJETIVO: Determinar a acurácia desse sistema na quantificação da área de infarto miocárdico em ratos. MÉTODOS: Treze ratos Wistar machos (250 g) foram submetidos a infarto do miocárdio por oclusão da artéria coronária esquerda. Após 4 semanas, foram adquiridas imagens tomográficas com o sistema desenvolvido, 1,5 hora após a injeção endovenosa de 555MBq de 99mTc-Sestamibi. Na reconstrução tomográfica, utilizamos software especialmente desenvolvido baseado no algoritmo de Máxima Verossimilhança. Comparamos as médias e analisamos a correlação entre a extensão dos defeitos perfusionais detectados pela cintilografia e a extensão da fibrose miocárdica avaliada pela histologia. RESULTADOS: As imagens apresentaram ótima relação órgão-alvo/fundo, com apropriada visualização das paredes e da cavidade do ventrículo esquerdo. Todos os animais exibindo áreas de infarto foram corretamente identificados pelas imagens de perfusão. Não houve diferença entre a área do infarto medida pelo SPECT (21,1 ± 21,2%) e pela histologia (21,7 ± 22,0%; p = 0,45), obtendo forte correlação entre os valores da área de infarto mensurada pelos dois métodos (r = 0,99; p < 0,0001). CONCLUSÃO: O sistema desenvolvido apresentou resolução espacial adequada e elevada acurácia para detecção e quantificação das áreas de infarto miocárdico, sendo uma opção de baixo custo e grande versatilidade na obtenção de imagens em SPECT de alta resolução de órgãos de pequenos roedores.

BACKGROUND: Imaging techniques enable in vivo sequential assessment of the morphology and function of animal organs in experimental models. We developed a device for high-resolution single photon emission computed tomography (SPECT) imaging based on an adapted pinhole collimator. OBJECTIVE: To determine the accuracy of this system for quantification of myocardial infarct area in rats. METHODS: Thirteen male Wistar rats (250 g) underwent experimental myocardial infarction by occlusion of the left coronary artery. After 4 weeks, SPECT images were acquired 1.5 hours after intravenous injection of 555 MBq o f 99mTc-Sestamibi. The tomographic reconstruction was performed by using specially developed software based on the Maximum Likelihood algorithm. The analysis of the data included the correlation between the area of perfusion defects detected by scintigraphy and extent of myocardial fibrosis assessed by histology. RESULTS: The images showed a high target organ/background ratio with adequate visualization of the left ventricular walls and cavity. All animals presenting infarction areas were correctly identified by the perfusion images. There was no difference of the infarct area as measured by SPECT (21.1 ± 21.2%) and by histology (21.7 ± 22.0%; p=0.45). There was a strong correlation between individual values of the area of infarction measured by these two methods. CONCLUSION: The developed system presented adequate spatial resolution and high accuracy for the detection and quantification of myocardial infarction areas, consisting in a low cost and versatile option for high-resolution SPECT imaging of small rodents.

Dopamine transporter imaging in clinically unclear cases of parkinsonism and the importance of Scans Without Evidence of Dopaminergic Deficit (SWEDDs) / Neuroimagem do transportador de dopamina em casos de parkinsonismo clinicamente indefinidos e a importância dos SWEDDs (exames sem evidência de déficit dopaminérgico)

The clinical diagnosis of Parkinson's disease (PD) is susceptible to misdiagnosis, especially in the earlier stages of the disease. Recently, in vivo imaging techniques assessing the presynaptic dopamine transporter (DAT) have emerged as a useful tool in PD diagnosis, improving its accuracy. OBJECTIVE: It was to illustrate the clinical usefulness of a brain single-photon emission computed tomography (SPECT) DAT ligand, and highlight relevant aspects of scans without evidence of dopaminergic deficit (SWEDDs) in this context. CASES: We described four representative patients with clinically unclear parkinsonian syndromes who underwent [99mTc]-TRODAT-1 SPECT and reviewed the clinical implications. CONCLUSION: DAT-SPECT is an important, cost-effective, technique for the differential diagnosis of parkinsonian syndromes. Additionally, SWEDD cases present clinical and paraclinical peculiarities that may retrospectively identify them as essential/dystonic tremor. The lack of histopathological data limits further conclusions.

O diagnóstico clínico da doença de Parkinson (DP) pode estar sujeito a erros especialmente nas fases iniciais da doença. Recentemente, técnicas de imagem in vivo que avaliam o transportador de dopamina pré-sináptico (DAT) surgiram como uma ferramenta empregada no diagnóstico da DP, melhorando sua acurácia. OBJETIVO: Foi demonstrar a utilização clínica de um traçador de tomografia computadorizada por emissão de fóton único (SPECT) e destacar importantes aspectos dos casos de SWEDDs (exames sem evidência de déficit dopaminérgico) neste contexto. CASOS: Descrevemos quatro pacientes representativos de síndromes parkinsonianas clinicamente incertas submetidos a [99mTc]-TRODAT-1 SPECT e revisamos suas implicações. CONCLUSÃO: O DAT-SPECT é uma técnica importante e eficiente para o diagnóstico diferencial das síndromes parkinsonianas. Além disso, os casos de SWEDDs apresentam peculiaridades clínicas e paraclínicas que podem retrospectivamente identificá-los como tremor essencial ou tremor distônico. As conclusões têm alcance limitado pela falta de dados histopatológicos.