Balanced steady-state free precession MRCP is a robust alternative to respiration-navigated 3D turbo-spin-echo MRCP.

BACKGROUND: Despite synchronization to respiration, respiration-navigated (RN) 3D turbo-spin-echo MRCP is limited by susceptibility to motion artifacts. The aim of this study was to assess the quality of pancreaticobiliary duct visualization of a non-RN MRCP alternative based on balanced steady-state free precession imaging (BSSFP) with overlapping slices compared with RN-MRCP. METHODS: This is a retrospective study on 50 patients without pancreaticobiliary duct disease receiving MRCP at 1.5 T. We performed an intraindividual comparison of coronal RN-MRCP with combined coronal and transverse BSSFP-MRCP. Image quality was scored by 3 readers for 6 pancreaticobiliary duct segments (3 pancreatic, 3 biliary) using a 6-point scale. A segment score of 3 or lower as assessed by at least 2 of 3 readers was defined as insufficient segment visualization. Nonparametric tests and interrater reliability testing were used for statistical analysis. RESULTS: Overall duct visualization averaged over all readers was scored with 4.5 ± 1.1 for RN-MRCP (pancreatic, 4.1 ± 0.5; biliary, 5.0 ± 0.4) and 4.9 ± 0.9 for combined coronal and transverse BSSFP-MRCP (pancreatic, 4.6 ± 0.6; biliary, 5.1 ± 0.6), respectively (p < 0.001). The number of segments visualized insufficiently was 81/300 for RN-MRCP and 43/300 for BSSFP-MRCP (p < 0.001). Segments visualized insufficiently only in RN-MRCP had a mean score of 4.4 ± 0.8 in BSSFP-MRCP. Overall interrater agreement on superiority of BSSFP-MRCP segment scores over corresponding RN-MRCP was 0.70. Mean acquisition time was 98% longer for RN-MRCP (198.0 ± 98.7 s) than for combined coronal and transverse BSSFP-MRCP (100.2 ± 0.4 s). CONCLUSIONS: Non-RN BSSFP-MRCP with overlapping slices is a fast alternative to RN-MRCP, frequently providing sufficient duct visualization when RN-MRCP fails.

Measurement of real-time tissue elastography in a phantom model and comparison with transient elastography in pediatric patients with liver diseases.

PURPOSE: We aimed to determine the comparability of real-time tissue elastography (RTE) and transient elastography (TE) in pediatric patients with liver diseases. MATERIALS AND METHODS: RTE was performed on the Elasticity QA Phantom Model 049 (Computerized Imaging Reference Systems Company Inc., Norfolk, Virginia, USA), which has five areas with different levels of stiffness. RTE measurements of relative stiffness (MEAN [mean value of tissue elasticity], AREA [% of blue color-coded stiffer tissue]) in the phantom were compared with the phantom stiffness specified in kPa (measurement unit of TE). RTE and TE were performed on 147 pediatric patients with various liver diseases. A total of 109 measurements were valid. The participants had following diseases: metabolic liver disease (n=25), cystic fibrosis (n=20), hepatopathy of unknown origin (n=11), autoimmune hepatitis (n=12), Wilson's disease (n=11), and various liver parenchyma alterations (n=30). Correlations between RTE and TE measurements in the patients were calculated. In addition, RTE was performed on a control group (n=30), and the RTE values between the patient and control groups were compared. RESULTS: The RTE parameters showed good correlation in the phantom model with phantom stiffness (MEAN/kPa, r=-0.97; AREA/kPa, r=0.98). However, the correlation of RTE and TE was weak in the patient group (MEAN/kPa, r=-0.23; AREA/kPa, r=0.24). A significant difference was observed between the patient and control groups (MEAN, P = 5.32 e-7; AREA, P = 1.62 e-6). CONCLUSION: In the phantom model, RTE was correlated with kPa, confirming the presumed comparability of the methods. However, there was no direct correlation between RTE and TE in patients with defined liver diseases under real clinical conditions.

Normal values of liver elasticity measured by real-time tissue elastography (RTE) in healthy infants and children.

PURPOSE: To define normal values of liver elasticity measured by real-time tissue elastography (RTE) in healthy infants and children. METHODS: RTE was performed on 91 children and adolescents by two experienced observers (female, n = 43; male, n = 48) and in two age groups (0-10 years, n = 45; 11-20 years, n = 46). Hepatopathies were excluded clinically by extensive laboratory testing and by ultrasound. RTE provides a histogram from a region of interest (ROI) in the liver representing the degree of stiffness of the liver. The distribution of the colors in the histogram corresponds to organ elasticity. By calculating the mean of stiffness values, a numerical value is expressed in arbitrary units (a.u.) representing the mean elasticity of the liver (MEAN). Additionally, the percentage values of relatively stiffer areas (color coded in blue) in the ROI can be calculated (%AREA). A Mann-Whitney U test was performed for these two parameters according to gender. The reproducibility of these values was determined with an intraclass correlation coefficient (ICC) test on another group of 18 healthy volunteers. RESULTS: The median elasticity was 106 a.u. Gender did not have an influence on the parameters (MEAN: p = 0.052; %AREA: p = 0.051). Age-specific analyses did not yield any significant difference between the two age groups for either of the two analyzed parameters (MEAN: p = 0.059; %AREA: p = 0.058). The ICC test demonstrated a moderate agreement for MEAN (ICC = 0.582) and %AREA (ICC = 0.659). CONCLUSION: Real-time elastography is a new sonography-based method and may be used as a supportive analysis to assess liver parenchyma elasticity in children, especially when fibrosis is suspected. We measured RTE normal values in children as reference data.

Real-time tissue elastography (RTE) for noninvasive evaluation of fibrosis in liver diseases in children in comparison to liver biopsy.

PURPOSE: To determine the value of real-time tissue elastography (RTE) in pediatric liver diseases in comparison to liver biopsy. METHODS: RTE was performed on 34 patients (♀, n = 17; ♂, n = 17; range 0-21 years) with various acute and chronic liver diseases: autoimmune hepatitis (n = 5), liver transplantation (n = 5), Wilson's disease (n = 4), hepatopathy of unknown origin (n = 4), unclear cholestatic hepatitis (n = 2), thalassemia major (n = 2), glycogenosis (n = 2), hereditary fructose intolerance (n = 1), alpha-1-antitrypsin deficiency (n = 1), diabetes mellitus type 1 (n = 1), chronic intestinal pseudo-obstruction (n = 1), primary sclerosing cholangitis (n = 1), hepatitis B (n = 1), cirrhosis of unknown origin (n = 1), drug-induced hepatopathy (n = 1), unexplained transaminase elevation (n = 1), and nonalcoholic steatohepatitis (n = 1). Included children were biopsied. RTE was performed on a control group (n = 30; ♀, n = 15; ♂, n = 15). The mean value of strain (MEAN) in arbitrary units and the ratio of blue color-coded harder tissue (AREA) were calculated based on an elasticity histogram of the selected region of interest in liver parenchyma. They were compared with the histologically defined grade of liver fibrosis. RESULTS: In comparison to the scoring systems, a moderate correlation was observed for MEAN and AREA by excluding the F0 patients [MEAN r = -0.575 to -0.645, AREA r = 0.545-0.607 (p < 0.05)]. Differentiation of the control group and low-grade fibrosis (F1) from high-grade fibrosis (F2-4) was significantly possible (p values <0.001 at 5 % significance level). CONCLUSION: RTE parameters enable a possible differentiation of high fibrosis; however, their correlation with fibrosis stage was moderate. RTE seems to be a promising method in liver fibrosis grading in children.

Feasibility study and control values of transient elastography in healthy children.

Transient elastography (TE) is a new technique for the non-invasive assessment of liver fibrosis. The degree of fibrosis is equivalent to the liver stiffness measured in kilopascal (kPa). It is frequently used in adult patients with a mean normal stiffness of 4.4-5.5 kPa. Since 2008, liver stiffness can be measured even in small children and infants following the availability of a new probe with a smaller diameter (S-probe 5 mm) than the regular probe (M-probe 7 mm). We report control values for healthy children between 0 and 18 years and investigated the feasibility of this technique in a pediatric population. For control values, TE was performed in infants and children after exclusion of liver disease by medical history, clinical examination, blood investigation, and abdominal ultrasound. For feasibility analyses the results of all TE performed in our clinic were analyzed irrespective of the underlying disease. Liver stiffness was measured with the S-probe (thorax diameter <45 cm (S1) or 45-75 cm (S2)) and the M-probe (thorax diameter >75 cm) according to the manufacturer's recommendations. A total of 240 healthy children were analyzed to establish control values. The median liver stiffness was 4.7 kPa resulting in an upper limit of normal of 6.47 kPa. Median values of stiffness were significantly age dependent with 4.40, 4.73, and 5.1 kPa in children 0-5, 6-11, and 12-18 years (p = 0.001) while the interquartile range decreased with age (0.8, 0.7, and 0.6 kPa). The resulting upper limit of normal (median plus 1.64 times standard deviation) was 5.96, 6.65, and 6.82 kPa. Girls between 11 and 18 years showed a significantly lower median stiffness than boys of the same age (4.7 vs. 5.6 kPa; p < 0.005). Feasibility was tested in 975 consecutive liver stiffness measurements (LSM) in children 0-18 years of age. Patients with invalid LSM were significantly younger than those with valid LSM (5.8 vs. 9.7 years, p < 0.0001), showed a significantly higher stiffness (10.2 vs. 6.17, p < 0.0001), and examinations took significantly longer (202 vs. 160 s, p < 0.0001). TE is technically possible in children of all age groups. The upper limit of normal increases significantly with age. Due to movement artifacts the measurement is reliable from the age of 6 without sedation. In younger children the number of invalid measurements increases significantly. Further studies are needed to asses the value of TE in the diagnosis and follow-up of liver disease in pediatric hepatology.