CTA/MRA of Pediatric Hepatic Masses Radiology-Pathology Correlation

Transcription

1 Acta Radiológica Portuguesa, Vol.XVIII, nº70, pág , Abr.-Jun., 2006 CTA/MRA of Pediatric Hepatic Masses Radiology-Pathology Correlation Marilyn J. Siegel Mallinckrodt Institute of Radiology, Washington University School of Medicine, ST. Louis Distinguished Scientist, Armed Forces Institute of Pathology Learning Objectives Review CT and MR technical factors Discuss imaging features in common tumors US, CT and MRI Identify features most helpful in distinguishing among malignant and benign tumors Routine Liver CTA Non-contrast Dual phase contrast imaging Arterial phase»wt < 10 kg: 12 to 15 sec»wt > 10 kg: 20 to 25 sec 55 to 60 sec for venous phase Dual images help in lesion characterization Technical Factors 1.2 to 1.5 mm collimation Fast table feed Low mas and kvp Shortest scan time (0.5 sec) Normal Liver: Biphasic Imaging 2 year old boy Arterial 15 sec Venous/Hepatic 55 sec Contrast Injection Rate Power Injection Antecubital catheter Flow rate: variable»22g ml/sec»20 g ml/sec»24g or central line 1.0 ml/sec Manual Injection Peripherally positioned catheter Nonionic 2mL/kg Post processing Techniques Surgical planning (not diagnosis) Volume rendering or MIP slabs Volume Rendering- Normal HA Maximum Intensity Projection ARP 41

2 Routine Liver MRI Hemangioendothelioma Variable scout (Ax, Cor, Sag) Coronal, axial T1W Axial T2W fat sat Axial in-phase/out-of-phase Axial dynamic GE image precontrast image HA: sec PV: sec Delayed images as needed 2mmol/kg Benign vascular tumor of infancy Vascular spaces lined by plump endothelium Symptomatic: high-output failure, hepatomegaly, thrombocytopenia Involution (12-18 months) Courtesy Frank Mitros, M.D. Important Diagnostic Clues Hemangioendothelioma Clinical features Age Symptoms (heart failure) Underlying liver disease or syndrome»hemihypertrophy»glycogen storage disease History of extrahepatic malignancy Hemangioendothelioma: CT Important Diagnostic Clues Imaging features Enhancement profile Central scar Fat/hemorrhage Invasiveness (Size, margins less helpful) Precontrast: HA phase: PV phase: Lesion density = vessel density Nodular peripheral enhancement Lesion density = vessel density Progressive centripetal enhancement Benign Hepatic Lesions Neonate: Hemangioendothelioma Arteriovenous malformation Cystic mesenchymal hamartoma Older child & adolescent Hemangioma Focal nodular hyperplasia Adenoma (rare) Hemangioendothelioma Early peripheral enhancement & delayed fill-in HA PV 42 ARP

3 Atypical Enhancement Large Lesions Arteriovenous Malformations Other symptomatic hepatic mass of infancy Congenital anomaly characterized by direct arteriovenous connections and shunting No associated soft tissue mass Types of shunts Portal vein to hepatic vein Portal vein to IVC Hepatic artery to portal vein Thrombosis and fibrosis typical of large tumors Atypical Enhancement Portal Vein to Hepatic Vein Fistula Small lesions show early complete enhancement MRI: Vascular Hepatic Neoplasms Portal Vein to Inferior Vena Cava T1-WT: hypointense Fat-sat T2-WT: hyperintense Post-Gadolinium: early nodular puddling delayed filling-in Hemangioendothelioma Portal Vein to Inferior Vena Cava ARP 43

4 Hepatic Artery to Portal Vein Fistula Vascular Hepatic Lesions: Adolescents Cavernous hemangioma Dilated vascular channels Flat endothelial cell lining Incidental findings Focal nodular hyperplasia Cystic Mesenchymal Hamartoma Cavernous Hemangioma Congenital lesion Disorganized liver cells, bile ducts and mesenchyme Asymptomatic mass Boys < 4 years of age Large mass with multiple cysts Frank Mitros, MD Mesenchymal Hamartoma Hemangioma: Typical CT Criteria Precontrast: Lesion density = vessel density HA phase: PV phase: Nodular peripheral enhancement Lesion density = vessel density Progressive centripetal enhancement Mesenchymal Hamartoma: MR Cavernous Hemangioma: MRI 44 ARP

5 CT: Hemangioma Focal Nodular Hyperplasia Globular enhancement: sensitivity: 67% specificity: 100% Depends on size of lesion more typical of tumors > 2cm < 5cm Iso- or hypoechoic, central flow Hemangioma: Atypical Findings Central areas of non-enhancement typical of very large tumors (> 5 cm) reflects central necrosis or fibrosis Bright dot sign typical of small tumors (< 2 cm) CT: Focal Nodular Hyperplasia Hypervascular HA images Homogeneous enhancement (except scar) Scar may enhance on delayed images Atypical Hepatic Hemangiomas Focal Nodular Hyperplasia Show rapid enhancement and washout Nonenhancing-globular peripheral enhancement allows diagnosis Dot sign HA PV Focal Nodular Hyperplasia Focal Nodular Hyperplasia Adolescents Usually subcapsular Central fibrous scar Composed of normal liver with bile ductules Fat, hemorrhage rare Most asymptomatic Stellate scar Characteristic features : T2-W bright scar Gd shows intense enhancement and rapid washout ARP 45

6 Focal Nodular Hyperplasia Delayed enhancement of scar Heterogeneous enhancement Rapid wash-out No scar Smooth borders Variable lipid content Hepatic Adenoma HA PV Post-Gd (Bolus) Post-Gd (Delay) Hemangioma vs. FNH Hepatic Adenoma May contain fat Hepatocellular Adenoma Women of reproductive age tendency to bleed Associated with use of oral contraceptives and glycogen storage disease Path: normal hepatocytes, lack bile ducts & vessels May contain fat Hepatocellular Adenoma May contain fat T1W GRE In-phase Opposed-phase Hepatic Adenoma Malignant Tumors Hepatocellular carcinoma Embryonal sarcoma Hypo-, iso- or hyperechoic, central or peripheral flow 46 ARP

7 Malignant Tumors Age < 3 years (mean, 1-2 yrs) Abdominal mass, pain Associated conditions Beckwith-Wiedemann syndrome hemihypertrophy familial adenomatous polyposis Heterogeneous enhancement (except small lesions) Large tumors - often up to 20 cm in diameter Liver otherwise normal No cirrhosis Primitive epithelial cells and mesenchymal (osteoid) elements May contain calcifications MRI: Malignant Hepatic Tumors T1-WT images: hypointense Fat-sat T2 images: hyperintense Gd dynamic imaging: early heterogeneous enhancement rapid wash-out vessel displacement vessel encasement CT: Malignant Hepatic Tumors Precontrast: hypo or isodense to liver HA phase: PV phase: heterogenous enhancement early enhancement & washout hypovascular (rapid washout) ARP 47

8 Embryonal Sarcoma May invade vessels Hepatocellular Carcinoma Age > 5 years Mean age 9 yrs Chronic liver disease tyrosinemia glycogen storage disease Abdominal mass, pain Embryonal Sarcoma Hepatocellular Carcinoma Older children 6 to 10 years of age Large tumors (7-20 cm) Myxoid stroma, bile ducts and hepatocytes Hemorrhage and cyst formation common Cystic/necrotic on imaging studies Embryonal Sarcoma Hepatocellular Carcinoma Can mimic benign hamartoma Arterial HV/Parenchymal Appearance similar to hepatoblastoma Heterogenous enhancement 48 ARP

9 Hepatocellular Carcinoma MR: Fibrolamellar-HCC Arterial Phase Portal venous Hepatocellular Carcinoma May invade hepatic vessels Central Scar Hepatic Vein IVC Invasion Portal Vein Invasion Fibrolamellar Carcinoma Subtype of HCC Malignant eosinophilic hepatocytes arranged in cords Mean patient age yrs Well-defined mass»central scar»calcifications Secondary Liver Neoplasms Neonate Neuroblastoma presents as hepatomegaly Infants & children Wilms tumor Neuroblastoma Rhabdomyosarcoma Lymphoma Fibrolamellar HCC (HCC Variant) Hepatic Metastases Multiple discrete lesions Typically hypovascular small (< 2-3 cm) Rarely, diffuse replacement Usually neuroblastoma Seen best in portal venous phase Heterogenous enhancement Calcified central scar (40%) Courtesy D. Papadatos, M.D. ARP 49

10 Metastases Hepatic Cysts Rare Look at kidneys Polycystic disease Von-Hippel Lindau Turner syndrome Leave alone lesion Multiple Solitary Hepatic Metastases Characterizing Hepatic Masses In Summary: Helpful Features Lymphoma Sarcoma Enhancement pattern Central scar Hemorrhage/fat Vascular invasion Clinical context Importance of arterial phase Hepatic Metastases HA Enhancement Patterns Arterial Portal Venous Heterogeneous or hypodense Primary malignancy Metastases Hyperdense: globular Hemangioendothelioma Hemangioma Hyperdense: homogeneous Focal nodular hyperplasia Nonenhancing: cysts Diffuse Replacement Neuroblastoma Metastases 50 ARP