Optimal b-values for diffusion kurtosis imaging of the liver and pancreas in MR examinations.

PURPOSE: The objective was to optimise the number of b-values for diffusion kurtosis imaging (DKI) of the liver and pancreas in MR examinations to ensure reliable results with the shortest possible acquisition time. METHODS: Twenty healthy volunteers underwent DKI at 3.0 T Siemens Magnetom Skyra using 7 b-values (b = 0, 200, 500, 750, 1000, 1500, 2000 s/mm2). The regions of interest (ROIs) were placed in the liver (right lobe, left lobe) and pancreas (head, tail). DKI parameters (Dapp, Kapp) for ROIs were calculated for 7 b-values utilising the nonlinear least-squares (NLLS) Marquardt-Levenberg algorithm. All calculations were repeated for ten subsets of data, with the number of b-values reduced to 4. DKI parameters calculated for subsets were compared with parameters calculated for all 7 b-values. RESULTS: The correlation coefficient between DKI parameters calculated for 7 b-values and subsets ranged from 0.65 to 1.00. The coefficient of variation (CoV) of DKI parameters calculated for a group of volunteers varied from 8% to 42% and was not affected by the reduction of the b-values number. Only one subset of data (b = 0, 500, 1500 and 2000 s/mm2) simultaneously met two criteria: no statistical difference (p < 0.05) from results obtained for 7 b-values and very good correlation with them. CONCLUSIONS: DKI acquisition with 4 b-values (b = 0, 500, 1500 and 2000 s/mm2), compared to DKI acquisition utilising 7 b-values, allowed for the reduction of acquisition time by 36%, without affecting the calculated DKI parameters.

Cystic lymphangiomatous lesions of the adrenal gland: A clinicopathological study of 37 cases including previously unreported cysts with papillary endothelial proliferation.

Published data regarding lymphangiomatous cysts of the adrenal glands (also known as adrenal cystic lymphangiomas) are limited to case reports and a few small case series. We analyzed the clinicopathologic features and histomorphologic spectrum of 37 cases of adrenal cystic lymphangiomatous lesions. There were 26 females and 11 males ranging from 12 to 67 years old (median, 34 years). Twenty two lesions (59.5%) were diagnosed incidentally on imaging studies for unrelated causes, while 15 cases (40.5%) were symptomatic: 8 patients presented with abdominal or flank pain and 7 patients presented with arterial hypertension. Clinically, 4 lesions (10.8%) were reported to have concurrent hormonal hypersecretion. Follow-up data were available for 23 patients (62.2%), ranging from 6 to 156 months (median, 52 mo). One of the 22 patients showed local recurrence at 12 months after partial adrenalectomy. The median size of the adrenal lymphangiomatous cysts was 4.5 cm (range, 1.5 to 10 cm). Based on the histopathologic findings these lesions were grouped into three, morphologically distinct types: typical multicystic lymphatic malformation (n = 16), typical unilocular lymphangiomatous cyst (n = 14) and lymphangiomatous cyst with papillary endothelial proliferation (n = 7). The median patient age of the first group was significantly higher than that of the other groups and calcifications in these cysts were more common than in the other two groups. The unilocular lymphangiomatous cysts were more frequently associated with a history of previous intra-abdominal surgical procedures and/or inflammatory processes than the other two groups. Cysts with papillary endothelial proliferation were significantly larger than other cysts and shared some microscopic features with a vascular neoplasm known as papillary intralymphatic angioendothelioma (PILA). In conclusion, adrenal lymphangiomatous cysts are usually asymptomatic, incidentally diagnosed lesions with a female predominance. They may imitate other adrenal tumors, both radiologically and clinically. Despite being non-functioning lesions, they should be considered as a possible cause of pseudopheochromocytoma. Although most adrenal lymphangiomatous cysts seem to be non-neoplastic, vascular abnormalities (malformations or lymphangiectasias), those with papillary endothelial proliferations may represent true neoplastic lesions.

State-of-the-art MR Imaging of Fat-containing Focal Lesions of the Liver.

BACKGROUND: Fat can be identified in numerous liver lesions, and usually is not a specific finding. Distinguishing between different kinds of fatty deposits is an important part of differential diagnosis. Magnetic Resonance Imaging (MRI) is superior to other imaging techniques because it allows distinguishing intracellular from macroscopic fat. DISCUSSION: Intracellular lipid may be found in focal hepatic steatosis, hepatic adenoma, hepatocellular carcinoma and, less commonly, in focal nodular hyperplasia as well as regenerative and dysplastic nodules. Macroscopic fat is seen in angiomyolipoma, lipoma, metastases from fatcontaining neoplasms, primary or metastatic liposarcoma, hydatid cyst, pseudolipoma of the Glisson capsule, pericaval fat collection, lipopeliosis, hepatic teratoma, focal hepatic extramedullary haematopoiesis and adrenal rest tumour. CONCLUSION: Liver nodules should be characterised with regard to underlying liver condition, MRI characteristics and contrast enhancement pattern, including hepatobiliary phase. In many cases, identification of fatty content may help narrowing the differential diagnosis.

State-of-the-art MR Imaging of Uncommon Hepatocellular Tumours: Fibrolamellar Hepatocellular Carcinoma and Combined Hepatocellularcholangiocarcinoma.

BACKGROUND: Fibrolamellar Carcinoma (FLC) and Combined Hepatocellular- Cholangiocarcinoma (CHC) are rare primary liver tumours, which are related to different clinical settings. In both tumours, correlation with clinical data and laboratory tests are extremely important. DISCUSSION: Typically, FLC is diagnosed in young patients without any chronic disease and with normal biochemical tests, whereas CHC arises in cirrhotic patients with elevated tumour markers: AFP and/or CA 19-9. The review describes epidemiology, aetiology, pathogenesis, radiological features and treatment of these tumours. Imaging features typical for FLC are: The presence of central scar, calcifications, the large size, heterogeneous and early contrast-enhancement. CONCLUSION: The diagnosis of CHC may be suggested in case of elevation of both AFP and CA 19- 9 or inconsistency between elevated tumour markers and imaging findings (i.e., elevated CA 19-9 and radiological features of HCC, or elevated AFP with imaging findings characteristic of ICC).

Magnetic Resonance Imaging of Uncommon Hepatic Mesenchymal Tumours: Haemangioendothelioma and Angiosarcoma.

BACKGROUND: Primary Hepatic Epithelioid Haemangioendothelioma (HEHE) and Primary Hepatic Angiosarcoma (PHA) are rare mesenchymal tumours with different malignant potential. Whereas HEHE demonstrates low to intermediate malignant potential, PHA is an aggressive malignancy with poor prognosis. The knowledge of typical imaging features of these lesions may facilitate correct diagnosis; however, the ultimate diagnosis of HEHE and PHA is based on histopathologic examination. DISCUSSION: The most typical findings helpful in diagnosing HEHE are: Presence of multiple, confluent nodules located at the liver periphery (in young to middle-aged woman), retraction of the liver capsule, marked hyperintensity on T2-weighted images, "target-sign" appearance, progressive centripetal contrast enhancement, and relatively high Apparent Diffusion Coefficient (ADC) values. More than ≥50% of nodules are hyper- or isointense on Hepatobiliary Phase (HBP) images. CONCLUSION: The imaging features suggestive of PHA are: Occurrence of metastases (lungs, spleen) at the time of diagnosis, presence of a large dominant mass with smaller satellites, heterogeneity and areas of haemorrhage in a dominant mass, progressive contrast enhancement, slightly elevated ADC values as compared to other malignant liver tumours.

Reproducibility of intravoxel incoherent motion of liver on a 3.0T scanner: free-breathing and respiratory-triggered sequences acquired with different numbers of excitations.

PURPOSE: To optimise the intravoxel incoherent motion (IVIM) imaging of the liver on a 3.0T scanner by assessing parameter reproducibility on free-breathing (FB) and respiratory-triggered (RT) sequences acquired with different numbers of signal averages (NSA). MATERIAL AND METHODS: In this prospective study 20 subjects (M/F: 10/10; age: 25-62 years, mean: 39 years) underwent IVIM magnetic resonance imaging (MRI) on a 3.0T scanner using an 18-channel phase-arrayed coil and four different echo-planar sequences, each with 10 b values: 0, 10, 30, 50, 75, 100, 150, 200, 500, and 900 s/mm2. Images were acquired with FB and RT with NSA = 1-4 (FBNSA1-4, RTNSA1-4) and with NSA = 3-6 (FBNSA3-6, RTNSA3-6). Subsequently, for the assessment of reproducibility of IVIM-derived parameters (f, D, D*), each subject was scanned again with an identical protocol during the same session. IVIM parameters were calculated. The distribution of IVIM-parameters for each DWI sequence were given as the median value with first and third quartile. Inter-scan reproducibility for each IVIM parameter was evaluated using coefficient of variance and Bland-Altman difference. Differences between FB sequence and RT sequence were tested using non-parametric Wilcoxon signed-rank test. RESULTS: Mean coefficient of variance (%) for f, D, and D* ranged from 60 to 64, from 58 to 84, and from 82 to 99 for FBNSA1-4 sequence; from 50 to 69, from 41 to 97, and from 80 to 82 for RTNSA1-4 sequence; from 22 to 27, 15, and from 70 to 80 for FBNSA3-6 sequence; and from 21 to 32, from 12 to, and from 50 to 80 for RTNSA3-6 sequence, respectively. CONCLUSIONS: Increasing the number of signal averages for IVIM acquisitions allows us to improve the reproducibility of IVIM-derived parameters. The sequence acquired during free-breathing with NSA = 3-6 was optimal in terms of reproducibility and acquisition time.

The Role of Computed Tomography in the Diagnostics of Diaphragmatic Injury After Blunt Thoraco-Abdominal Trauma.

BACKGROUND: Diaphragmatic injuries occur in 0.8-8% of patients with blunt trauma. The clinical diagnosis of diaphragmatic rupture is difficult and may be overshadowed by associated injuries. Diaphragmatic rupture does not resolve spontaneously and may cause life-threatening complications. The aim of this study was to present radiological findings in patients with diaphragmatic injury. MATERIAL/METHODS: The analysis of computed tomography examinations performed between 2007 and 2012 revealed 200 patients after blunt thoraco-abdominal trauma. Diaphragmatic rupture was diagnosed in 13 patients. Twelve of these patients had suffered traumatic injuries and underwent a surgical procedure that confirmed the rupture of the diaphragm. Most of diaphragmatic ruptures were left-sided (10) while only 2 of them were right-sided. In addition to those 12 patients there, another patient was admitted to the emergency department with left-sided abdominal and chest pain. That patient had undergone a blunt thoracoabdominal trauma 5 years earlier and complained of recurring pain. During surgery there was only partial relaxation of the diaphragm, without rupture. The most important signs of the diaphragmatic rupture in computed tomography include: segmental discontinuity of the diaphragm with herniation through the rupture, dependent viscera sign, collar sign and other signs (sinus cut-off sign, hump sign, band sign). RESULTS: In our study blunt diaphragmatic rupture occurred in 6% of cases as confirmed intraoperatively. In all patients, coronal and sagittal reformatted images showed herniation through the diaphragmatic rupture. In left-sided ruptures, herniation was accompanied by segmental discontinuity of the diaphragm and collar sign. In right-sided ruptures, predominance of hump sign and band sign was observed. Other signs were less common. CONCLUSIONS: The knowledge of the CT findings suggesting diaphragmatic rupture improves the detection of injuries in thoraco-abdominal trauma patients.

Biliary complications after liver transplantation: The role of MR imaging using different hydrographic sequences in patients with biliary-enteric and duct-to-duct biliary anastomosis.

BACKGROUND: To aim of this study was to assess the diagnostic performance of the state-of-the-art magnetic resonance cholangiography (MRC) comprising several 2D and 3D hydrographic sequences in patients after liver transplantation with biliary-enteric and duct-to-duct biliary anastomosis. MATERIAL AND METHODS: Retrospective analysis included MRC examinations of 42 patients (21 men, 21 women) performed from 18 days to 86 months (average, 18.9 months) after liver transplantation. Studies were carried out on 1.5 T units, using 4 hydrographic (turbo spin echo, TSE) sequences. The analysis included accuracy of MRC in detecting biliary complications, as well as frequency of specific complications in patients with biliary-enteric anastomosis (n=15) and duct-to-duct biliary anastomosis (n=27). In 34 patients the results were correlated with endoscopic retrograde cholangiopancreatography ERCP (n=9), ERCP and CT (n=5), ERCP and percutaneous cholangiography (n=2), ERCP and T-tube cholangiography (n=1), ERCP, PTC, and histopathology (n=1), PTC (n=1), PTC and CT (n=1), PTC and histopathology (n=1), T-tube cholangiography (n=4), T-tube cholangiography and CT (n=1), fistulography (n=1), CT (n=4), and histopathology (n=3). In the remaining 8 patients other imaging studies (US, CT, follow-up MRC), laboratory liver function tests, and clinical status were the standard of reference. Results MRC yielded 94.6% sensitivity in detecting biliary complications in patients after liver transplantation. In patients with biliary-enteric anastomosis, disseminated biliary strictures were more frequent than in patients with duct-to-duct biliary anastomosis (20% vs. 7%). Less frequently, the biliary-enteric anastomosis was accompanied by anastomotic strictures (40% vs. 56%) and the presence of stones/sludge (20% vs. 37%), but the differences did not show statistical significance. CONCLUSIONS: MRC allowed accurate diagnosis of biliary complications in patients after liver transplantation and therefore can be used as a safe alternative to invasive diagnostic procedures such as ERCP and PTC, especially in patients with biliary-enteric anastomosis, in which invasive diagnostic procedures are technically challenging. The main limitation of MR hydrography is its low accuracy in distinguishing bilomas from other fluid collections.

Epithelioid hemangioendothelioma of the liver: the role of hepatobiliary phase imaging for the preoperative diagnosis and qualification of patients for liver transplantation -- preliminary experience.

BACKGROUND: The aim of this study was to determine if the appearance of hepatic epithelioid hemangioendothelioma (HEHE) on state-of-the-art MRI including hepatocyte phase after administration of hepatobiliary contrast agent can facilitate preoperative diagnosis and identification of potential candidates for liver transplantation. MATERIAL AND METHODS: The study group comprised 6 patients with pathologically confirmed HEHE. Analysis included signal characteristics of 55 tumor nodules (maximum of 10 lesions per patient) on T2-weighted images, dynamic contrast-enhanced, 5-minute delayed, and hepatobiliary phase images. RESULTS: The most common feature of HEHE, observed in 84% of lesions, was progressive contrast-enhancement, followed by subcapsular location (66%), confluent appearance (60%) and hyper- or isointensity on hepatobiliary phase images (53%). In 5 of 6 patients, capsular retraction was observed. CONCLUSIONS: The appearance of HEHE on hepatobiliary phase images was variable, but examined tumors often demonstrated hyper- or isointensity, most probably due to prolonged retention of contrast material. These features, along with typical morphology (subcapsular, confluent nodules, with progressive enhancement and capsular retraction), may contribute to correct diagnosis and recognition of potential candidates for liver transplantation.

Angiomyolipoma of the liver: analysis of typical features and pitfalls based on own experience and literature.

We present imaging findings (ultrasound, computed tomography, and magnetic resonance imaging) of eight patients with hepatic angiomyolipoma (HAML). The lesions were solitary in seven patients, and one patient had multiple tumors (n=11). Angiomyolipoma, even though a rare liver tumor, should be included in the differential diagnosis in cases of highly vascularized lesion containing a significant amount of fat. Suggestion of the diagnosis of HAML might be helpful for the pathologist in the selection of the typical histochemical staining of the tumor, allowing accurate diagnosis, which, in turn, determines the implementation of appropriate therapeutic intervention.

Characterization of focal liver lesions using quantitative techniques: comparison of apparent diffusion coefficient values and T2 relaxation times.

OBJECTIVES: To compare the efficacy of two quantitative methods for discrimination between benign and malignant focal liver lesions (FLLs): apparent diffusion coefficient (ADC) values and T2 relaxation times. METHODS: Seventy-three patients with 215 confirmed FLLs (115 benign, 100 malignant) underwent 1.5-T MRI with respiratory-triggered single-shot SE DWI (b = 50, 400, 800) and dual-echo T2TSE (TR = 3,000 ms; TE1 = 84 ms; TE2 = 228 ms). ADC values and T2 relaxation times of FLLs were calculated. Sensitivity, specificity and accuracy of both techniques in diagnosing malignancy were assessed. RESULTS: The mean ADC value of malignant tumours (1.07 × 10(-3) mm(2)/s) was significantly lower (P < 0.05) than that of benign lesions (1.86 × 10(-3) mm(2)/s ); however, with the use of the optimal cut-off value of 1.25 × 10(-3) mm(2)/s, 20 false positive (FP) and 20 false negative (FN) diagnoses of malignancy were noted, generating 79 % sensitivity, 82.6 % specificity and 80.9 % accuracy. The mean T2 relaxation time of malignant tumours (64.4 ms) was significantly lower (P < 0.05) than that of benign lesions (476.1 ms). At the threshold of 107 ms 22 FP and 1 FN diagnoses were noted; the sensitivity was 99 %, specificity 80.9 % and accuracy 89.3 %. CONCLUSIONS: Quantitative analysis of T2 relaxation times yielded significantly higher sensitivity and accuracy in diagnosing malignant liver tumour than ADC values. KEY POINTS: • Diffusion-weighted magnetic resonance imaging is increasingly used for liver lesions. • But ADC values demonstrated only moderate accuracy for differentiation of liver lesions. • T2 relaxation times yielded higher accuracy in diagnosing malignant liver tumours. • Both ADC and T2 values overlapped between focal nodular hyperplasia and malignant lesions. • Nevertheless T2 liver mapping could be valuable for evaluating focal liver lesions.