RESUMO
BACKGROUND: 82Rb PET is commonly performed using the same injected activity in all patients, resulting in lower image quality in larger patients. This study compared 82Rb dosing with exponential vs proportional functions of body weight on the standardization of myocardial perfusion image (MPI) quality. METHODS: Two sequential cohorts of N = 60 patients were matched by patient weight. Rest and dipyridamole stress 82Rb PET was performed using 0.1 MBq·kg-2 exponential and 9 MBq·kg-1 proportional dosing. MPI scans were compared qualitatively with visual image quality scoring (IQS) and quantitatively using the myocardium-to-blood contrast-to-noise ratio (CNR) and blood background signal-to-noise ratio (SNR) as a function of body weight. RESULTS: Average (min-max) patient body weight was 81 ± 18 kg (46-137 kg). Proportional dosing resulted in decreasing CNR, SNR, and visual IQS with increasing body weight (P < 0.05). Exponential dosing eliminated the weight-dependent decreases in these image quality metrics that were observed in the proportional dosing group. CONCLUSION: 82Rb PET dosing as an exponential (squared) function of body weight produced consistent stress perfusion image quality over a wide range of patient weights. Dramatically lower doses can be used in lighter patients, with the equivalent population dose shifted toward the heavier patients to standardize diagnostic image quality.
Assuntos
Doença da Artéria Coronariana , Imagem de Perfusão do Miocárdio , Humanos , Tomografia por Emissão de Pósitrons/métodos , Tomografia Computadorizada por Raios X , Dipiridamol , Radioisótopos de Rubídio , Peso Corporal , Imagem de Perfusão do Miocárdio/métodos , Doença da Artéria Coronariana/diagnóstico por imagemRESUMO
BACKGROUND: In addition to acquired photon counts, image noise depends on the image reconstruction algorithm. This work develops patient-specific activity or acquisition time protocols to standardize the average noise in a reconstructed image for different patients, cameras, and reconstruction algorithms. METHODS: Image noise was calculated for images from 43 patients acquired on both a conventional and a multiple-pinhole cardiac SPECT camera. Functions were found to relate image noise to radiotracer activity, scan time, and body mass and were validated by normalizing the image noise in a test set of 58 patients. RESULTS: There was a 3.6-fold difference in photon sensitivity between the two cameras but a 16-fold difference in activity-scan time was necessary to match the noise levels. Image noise doubled from 45 to 128 kg for the conventional camera (12.8 minutes) and tripled for the multiple-pinhole camera (5 minutes) for 350 MBq (9.5 mCi) 99mTc-tetrofosmin. It was 16.3% and 6.1% respectively for an average sized patient. CONCLUSIONS: A linear scaling of activity with respect to the patient weight normalizes image noise but the scaling factors depend on the choice of camera and image reconstruction parameters. Therefore, equivalent numbers of acquired photon counts are not sufficient to guarantee equivalent image noise.
Assuntos
Câmaras gama , Coração/diagnóstico por imagem , Processamento de Imagem Assistida por Computador , Imagem de Perfusão do Miocárdio , Tomografia Computadorizada de Emissão de Fóton Único , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Artefatos , Peso Corporal , Protocolos Clínicos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Compostos Radiofarmacêuticos , Valores de Referência , Estudos Retrospectivos , Sensibilidade e Especificidade , Fatores de TempoAssuntos
Protocolos Clínicos/normas , Angiografia por Tomografia Computadorizada/estatística & dados numéricos , Planejamento de Assistência ao Paciente/estatística & dados numéricos , Padrões de Prática Médica/estatística & dados numéricos , Embolia Pulmonar/diagnóstico , Adolescente , Adulto , Fatores Etários , Criança , Angiografia por Tomografia Computadorizada/efeitos adversos , Angiografia por Tomografia Computadorizada/normas , Estudos Transversais , Relação Dose-Resposta à Radiação , Feminino , Hospitais/estatística & dados numéricos , Humanos , Noruega , Planejamento de Assistência ao Paciente/normas , Padrões de Prática Médica/normas , Gravidez , Artéria Pulmonar/diagnóstico por imagem , Embolia Pulmonar/etiologia , Inquéritos e Questionários/estatística & dados numéricosRESUMO
Acute neurologic emergencies in pregnancy often require neuroimaging to guide diagnosis and treatment. Implementation of a patient-centered care model in radiology can alleviate a patient's stress, reinforce appropriate imaging workup, improve patient satisfaction, and lead to improved outcomes. The authors present the evaluation, differential diagnosis, and recommended imaging protocols for the three most common acute neurologic symptoms in pregnancy and the postpartum period: headache, seizure, and focal neurologic deficits. With the patient's symptoms as a reference point, the referring physician in consultation with the radiologist can effectively implement the optimal imaging procedures.