Stefano Colagrande

Liver stiffness measurement predicts severe portal hypertension in patients with HCV‐related cirrhosis

Measurement of hepatic venous pressure gradient (HVPG) is a standard method for the assessment of portal pressure and correlates with the occurrence of its complications. Liver stiffness measurement (LSM) has been proposed as a noninvasive technique for the prediction of the complications of cirrhosis. In this study, we evaluated the ability of LSM to predict severe portal hypertension compared with that of HVPG in 61 consecutive patients with HCV‐related chronic liver disease. A strong relationship between LSM and HVPG measurements was found in the overall population (r = 0.81, P < 0.0001). However, although the correlation was excellent for HVPG values less than 10 or 12 mm Hg (r = 0.81, P = 0.0003 and r = 0.91, P < 0.0001, respectively), linear regression analysis was not optimal for HVPG values ≥10 mm Hg (r2 = 0.35, P < 0.0001) or ≥12 mm Hg (r2 = 0.17, P = 0.02). The AUROC for the prediction of HVPG ≥10 and ≥12 mm Hg were 0.99 and 0.92, respectively and at LSM cutoff values of 13.6 kPa and 17.6 kPa, sensitivity was 97% and 94%, respectively. In patients with cirrhosis, LSM positively correlated with the presence of esophageal varices (P = 0.002), although no correlation between LSM and esophageal varices size was detected. The area under the ROC for the prediction of EV was 0.76 and at a LSM cutoff value of 17.6 kPa sensitivity was 90%. Conclusion: LSM represents a non‐invasive tool for the identification of chronic liver disease patients with clinically significant or severe portal hypertension and could be employed for screening patients to be subjected to standard investigations including upper GI endoscopy and hemodynamic studies. (HEPATOLOGY 2007;45:1290–1297.)

Hepatocellular Adenoma and Focal Nodular Hyperplasia: Value of Gadoxetic Acid–enhanced MR Imaging in Differential Diagnosis

PURPOSE To retrospectively evaluate the utility of gadoxetic acid-enhanced magnetic resonance (MR) imaging in the differential diagnosis of hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH). MATERIALS AND METHODS This study had institutional review board approval; the requirement for informed consent was waived. Eighty-two patients (58 patients with FNH and 24 patients with HCAs) with 111 lesions were included in the study. There were 74 female patients and eight male patients (mean age, 41.9 years±13.2 [standard deviation]; age range, 11-78 years). Two readers reviewed all images in terms of signal intensity (SI) features on unenhanced, dynamic, and hepatobiliary phase images. For quantitative analysis, contrast enhancement ratio (CER), lesion-to-liver contrast (LLC), and SI ratio on dynamic and hepatobiliary phase images were calculated. RESULTS The CER of FNH in the arterial phase (mean, 94.3%±33.2) was significantly higher than that of HCAs (mean, 59.3%±28.1) (P<.0001). During the hepatobiliary phase, the LLC of FNH showed minimally positive values (mean, 0.05±0.01) and that of HCAs demonstrated strong negative values (mean, -0.67±0.24) (P<.0001). The area under the receiver operating characteristic curve of the hepatobiliary phase SI ratio for differentiation of the two tumors was 0.97, and a sensitivity of 92% and specificity of 91% were found with a cutoff value of 0.87. Among six FNH lesions that showed atypical hypointensity during the hepatobiliary phase, four had a large central scar, one contained a substantial fat component, and one had abundant radiating fibrous septa. Three HCAs were isointense during the hepatobiliary phase owing to severe hepatic steatosis. CONCLUSION Gadoxetic acid-enhanced MR imaging facilitates the differentiation of FNH from HCA.

In vivo ultrasound assessment of respiratory function of abdominal muscles in normal subjects

Ultrasonography has recently been proposed for assessing changes in thickness and motion of the diaphragm during contraction in humans. Data on ultrasound assessment of abdominal muscles in humans are scarce. We therefore investigated the changes in thickness and the relevant mechanical effects of abdominal muscles using this technique during respiratory manoeuvres in normal subjects. We evaluated the thickness of the abdominal muscle layers in six normal male subjects (aged 26-36 yrs) using a 7.5 MHz B-mode ultrasound transducer. Gastric (Pg) and mouth pressures, muscle thickness of external oblique (EO), internal oblique (IO), transversus abdominis (TA) and rectus abdominis (RA) were assessed at functional residual capacity (FRC), residual volume (RV), total lung capacity (TLC), during progressive (PEEs) and maximal expiratory efforts (MEEs) against a closed airway and during homolateral (HTR) and contralateral (CTR) trunk rotation. Abdominal muscle thickness was found to be reproducible (coefficient of variation and two-way analysis of variance). Compared to FRC, the thickness of IO, TA and RA significantly increased at RV and during MEEs, whereas EO remained unchanged; at TLC, the thickness of IO and TA significantly decreased. During PEEs, a significant relationship between increase in Pg and TA thickness was observed in all subjects, the thickness of the other abdominal muscles being inconsistently related to Pg. Finally, a significant increase in the thickness of IO and EO was found during HTR and CTR, respectively. We conclude that during maximal expiratory manoeuvres, transversus abdominis, internal oblique and rectus abdominis thickened similarly. Transversus abdominis seems to be the major contributor in generating abdominal expiratory pressure during progressive expiratory efforts. External oblique seems to be preferentially involved during trunk rotation. These results suggest the possible value of studying the abdominal muscles by ultrasonography in various respiratory disorders.

Magnetic resonance diffusion–weighted imaging: extraneurological applications

Diffsion–weighted (Dw) imaging has for a number of years been a diagnostic tool in the field of neuroradiology, yet only since the end of the 1990s, with the introduction of echoplanar imaging (EPI) and the use of sequences capable of performing diffusion studies during a single breath hold, has it found diagnostic applications at the level of the abdomen. The inherent sensitivity to motion and the magnetic susceptibility of Dw sequences nonetheless still create problems in the study of the abdomen due to artefacts caused by the heartbeat and intestinal peristalsis, as well as the presence of various parenchymal–gas interfaces. With regard to focal liver lesions, a review of the literature reveals that Dw imaging is able to differentiate lesions with high water content (cysts and angiomas) from solid lesions. With regard to the latter, although there are differences between benign forms [focal nodular hyperplasia (FNH), adenoma] and malignant forms [metastasis, hepatocellular carcinoma (HCC)] in their apparent diffusion coefficient (ADC) in the average values for histological type, there is a significant overlap in values when lesions are assessed individually, with the consequent problem of their correct identification. One promising aspect is the possibility of quantifying the degree of fibrosis in patients with chronic liver disease and cirrhosis given that the deposit of collagen fibres “restricts” the motion of water molecules and therefore reduces ADC values. However, even in this field, studies can only be considered preliminary and far from real clinical applications. The retroperitoneum is less affected by motion artefacts and similarly deserves the attention of Dw imaging. Here it is possible to differentiate mucin–producing tumours of the pancreas from pseudocystic forms on the basis of ADC values even though the limited spatial resolution of Dw imaging does not enable the identification of small lesions. Dw imaging may be applied to the study of the kidney to differentiate hydronephrosis from pyonephrosis and with regard to tumours, solid from pseudocystic forms. In addition, given that renal parenchyma has significantly variable ADC values on the basis of the anatomic section and physiological conditions, the possibility of assessing functional alterations is currently being studied. Indeed, a good correlation has been found between ADC values and glomerular filtration rate. With regard to musculoskeletal applications, the absence of motion artefacts in the regions studied has enabled the development of sequences less sensitive to magnetic susceptibility and with greater spatial resolution than EPI. Attempts have therefore been made to use Dw imaging in the characterization of soft–tissue tumours although the findings so far have been disputed. Greater agreement has been found regarding sensitivity of the technique in assessing response of these tumours to chemotherapy: tumour necrosis is thought to increase ADC whereas the persistence of vital neoplastic tissue tends to lower it. One of the most promising applications of Dw imaging is without doubt the assessment of vertebral collapse where a high ADC has been shown to be associated with an osteoporotic cause and a low ADC with a neoplastic cause. Nonetheless, even here, a moderate overlap between ADC values of the two types has been encountered. Dw imaging has also been used in the assessment of bone marrow cellularity: areas of tightly packed cells show a higher ADC value than hypocellular areas. In particular, no significant difference in ADC is noted between normal hypercellular bone marrow and hypercellular bone marrow secondary to lymphomatous infiltration whereas this difference is significant between hypocellular, normocellular and haematopoietic hypercellular bone marrow. With regard to the study of joints, the limited structure dimensions, particularly cartilage, creates technical difficulties related to spatial resolution and an adequate signal–to–noise ratio, problems that can only be solved by further technological developments. Lastly, a significant difference in ADC values between degenerative and inflammatory effusion has been found, a fact that may be explained as the result of the activity of hyaluronidase present in inflammatory forms, which causes a reduction in the concentration of hyaluronic acid with a consequent decrease in viscosity.

Additional value of gadoxetic acid-DTPA-enhanced hepatobiliary phase MR imaging in the diagnosis of early-stage hepatocellular carcinoma: comparison with dynamic triple-phase multidetector CT imaging.

To assess the value of hepatobiliary phase gadoxetic acid (EOB)‐enhanced magnetic resonance imaging (MRI) for the diagnosis of early stage hepatocellular carcinoma (HCC) (<3 cm) compared to triple‐phase dynamic multidetector computed tomography (MDCT).

Can MR fluoroscopic triggering technique and slow rate injection provide appropriate arterial phase images with reducing artifacts on gadoxetic acid-DTPA (Gd-EOB-DTPA)-enhanced hepatic MR imaging?

To evaluate whether using MR fluoroscopic triggering technique and slow rate injection improves the quality of arterial phase images in gadoxetic acid‐DTPA‐enhanced (Gd‐EOB‐DTPA) MR imaging because of proper acquisition timing and reduction of artifacts.

Transient Hepatic Intensity Differences: Part 2, Those Not Associated with Focal Lesions

OBJECTIVE The purpose of our study was to evaluate and to show the range of appearance of transient hepatic signal intensity differences when not associated with focal lesions, and to correlate morphology, cause, and pathogenesis. CONCLUSION Hepatic arterial phenomena, visualized on MRI and CT, must be considered important signs of underlying liver disorders, which these phenomena contribute to evaluate. Accordingly, the hepatic arterial phase must always be performed on MRI as well as on CT, even if no focal lesion is expected.

MR-diffusion weighted imaging of healthy liver parenchyma: repeatability and reproducibility of apparent diffusion coefficient measurement.

To compare repeatability and reproducibility of four different methods of apparent diffusion coefficient (ADC) evaluation of liver parenchyma. In fact, repeatability and reproducibility assessment is mandatory in quantitative evaluations, however, these have not been accurately investigated in liver MR‐diffusion‐weighted studies.

Persistent contrast enhancement by sterically stabilized paramagnetic liposomes in murine melanoma

In the present research, we investigated the use of paramagnetic liposomes as contrast agents (CAs) for the detection of solid tumors. The liposomes were sterically stabilized by a polyethylene glycol (PEG) coating, and their size was constrained to ∼100 nm. Dimyristoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐diethylene‐triaminepentaacetate (DMPE‐DTPA) was used as the gadolinium‐carrying fatty acid chain. The relaxation properties were characterized through nuclear magnetic relaxation dispersion (NMRD) measurements, and analyzed with the use of theories and computer programs that are adequate for slowly rotating systems. Their relaxivity at 1.5 T was found to be acceptable for in vivo use. We then tested the liposomes against B16‐F10 murine melanomas using standard T1‐weighted schemes at 1.5 T, and concentrations corresponding to 0.03 mmol/kg of gadolinium (i.e., three to six times lower than the concentration of the small gadolinium complexes in clinical use). The blood half‐life was found to be 120 ± 20 min. The experiments show a good contrast enhancement in the tumor (33% ± 22%) 2 hr after administration, a further increase (43 ± 27%) 20 hr after administration, and a decrease (25% ± 14%) 54 hr after administration. High persistence of the CA was also observed in the liver and intestine, as expected in a hepatobiliar excretion pathway. Magn Reson Med 52:669–672, 2004.

The Influence of Diffusion-and Relaxation-Related Factors on Signal Intensity : An Introductive Guide to Magnetic Resonance Diffusion-Weighted Imaging Studies

In magnetic resonance diffusion-weighted imaging, signal intensity is influenced simultaneously by temperature, diffusivity, b value, pseudodiffusion, macroscopic motion, and T2-weighted intensity value. The purpose of this pictorial essay is to discuss and exemplify the influence that such factors and the related modifications have on signal intensity. Apparent diffusion coefficient, shine-through and pseudodiffusion will also be examined to show how T2-weighted signal intensity value and nondiffusional intravoxel incoherent motion can affect the diffusion-weighted imaging.