Magnetic Resonance Elastography

Abstract

Objective To evaluate the utility of magnetic resonance elastography (MRE) in screening patients for hepatic fibrosis, cirrhosis, and hepatocellular carcinoma after Fontan operation. Patients and Methods Hepatic MRE was performed in conjunction with cardiac magnetic resonance imaging in patients with prior Fontan operation between 2010-2014. Liver stiffness was calculated using previously reported techniques. Comparisons to available clinical, laboratory, imaging, and histopathologic data were made. Results Overall, 50 Fontan patients aged 25 (21-33) years were evaluated. The median interval between Fontan creation and MRE was 22 (16-26) years. Mean liver stiffness values were increased; 5.5±1.4 kilopascals relative to normal subjects. Liver stiffness directly correlated with liver biopsy total fibrosis score, time since operation; mean Fontan pressure; γ-glutamyl transferase (GGT); MELD score; creatinine; and pulmonary vascular resistance index (PVR). Liver stiffness was inversely correlated with cardiac index (CI). All 3 subjects with hepatic nodules exhibiting decreased contrast uptake on delayed post-contrast imaging and elevated nodule stiffness had biopsy-proven hepatocellular carcinoma. Conclusion The association between hepatic stiffness and fibrosis scores, MELD scores, and GGT, suggests that MRE may be useful to detect (and possibly quantify) hepatic cirrhosis in Fontan patients. Correlation between stiffness and post-Fontan time interval, mean Fontan pressure, PVR and reduced CI suggests a role for long term hepatic congestion in creating these hepatic abnormalities. MRE was useful in detecting abnormal nodules ultimately diagnosed as hepatocellular carcinoma. The relationship between stiffness with advanced fibrosis and hepatocellular carcinoma provides a strong argument for additional study and broader application of MRE in these patients.

Mechanotransduction in cancer

“…The rigid nature of tumors is the basis for using palpation as a diagnostic method in soft tissues like breast and abdomen, and more recently, as the basis for high-resolution detection of small lesions by MRI elastography [1 • ,2 • ,3 • ] or ultrasound [4 • ]. These clinical observations, together with in vitro experiments which demonstrate that stiffness-sensing by cancer and stromal cells influence cell survival and proliferation, opened the door for many investigations that employ novel biocompatible materials with tunable viscoelastic properties.…”

Avaliação da frequência de nódulos hepáticos em pacientes submetidos ao procedimento de Fontan: o papel da ultrassonografia, tomografia computadorizada e ressonância magnética

“…Em concordância com estudos prévios, a maioria dos pacientes apresentou elevação dos níveis séricos de GGT (33,57,62,77,79,80) . Kaulitz et al também demonstraram aumento persistente de GGT durante avaliação seriada de pacientes após PF, bem como encontraram uma correlação entre os níveis de GGT iniciais e os parâmetros hemodinâmicos, como pressão média da artéria pulmonar (80) .…”

“…Shimizu et al observaram em sua população que os pacientes com cirrose apresentavam níveis significativamente maiores de GGT. Poterucha et al demonstraram que os níveis de GGT se correlacionaram com o grau de fibrose (62) . Porém, Munsterman et al não demonstraram diferença significativa entre pacientes com fibrose leve e acentuada (56) .…”

“…Já dentre os métodos seccionais com resultados discordantes, a frequência de NH variou entre 0,2% e 26% (24,29,30,55,56,62,66,68,82,83) . A menor frequência de 0,2% foi obtida no estudo de Kuwabara et al (55) Kiesewetter et al (24) e Serai et al (82) também obtiveram frequências menores de NH, 18,2% e 25%, porém o número de pacientes incluídos foi pequeno, o que pode justificar essa diferença de frequência.…”

“…A menor frequência de 0,2% foi obtida no estudo de Kuwabara et al (55) Kiesewetter et al (24) e Serai et al (82) também obtiveram frequências menores de NH, 18,2% e 25%, porém o número de pacientes incluídos foi pequeno, o que pode justificar essa diferença de frequência. Poterucha et al (62) incluíram 50 pacientes na análise retrospectiva e 26% dos pacientes apresentavam NH na RM. Já Munsterman et al (56) (27,30,42,61,62,84) .…”