Colorectal liver metastases: ADC as an imaging biomarker of tumor behavior and therapeutic response.

PURPOSE: To correlate the ADC values of colorectal liver metastases, evaluated before (preADC) and after (postADC) neoadjuvant chemotherapy (ChT), as well as their difference (ΔADC), with the histological tumor regression grade (TRG) and to determine whether the preADC value can be predictive of the lesion ChT response. METHOD: Twenty-four patients with colorectal liver metastases, who had undergone 3 T-MRI before and after ChT and were subsequently treated by parenchymal-spearing surgery, were retrospectively included. Diffusion-weighted MRI (DW-MRI) was performed using a spin-echo echo-planar sequence with multiple b values, obtaining an ADC map. Fitted ADC values were calculated for each lesion before and after ChT. The maximum diameter of each lesion in both examinations was recorded. Diameter variations and RECIST1.1 criteria were assessed. All MRI findings were histopathologically correlated to TRG of resected liver metastases. Statistical analysis was performed on a per-lesion basis. RESULTS: A total of 58 colorectal liver metastases were analysed; after ChT, 8 out of 58 lesions disappeared. TRG1, TRG2, TRG3, TRG4 and TRG5 were observed in 6, 12, 12, 13 and 7 lesions, respectively. The preADC values showed a different distribution according to the TRG scores (p = 0.0027), even though the distribution was not linear. The postADC and ΔADC values were significant different based on the TRG system (both p < 0.0001). A significant correlation between the lesion TRG and the evaluation according to RECIST1.1 criteria was observed by a per-lesion analysis (p = 0.0009). CONCLUSIONS: PostADC and ΔADC could be proposed as reliable biomarkers to assess tumor treatment response after preoperative ChT in patients with colorectal liver metastases.

Gadoxetate Disodium-Enhanced MR Cholangiography for Evaluation of Biliary-Enteric Anastomoses: Added Value Beyond Conventional T2-Weighted Images.

OBJECTIVE. The objective of our study was to evaluate image quality and reader confidence in MR cholangiography of bile ducts using conventional T2-weighted MR cholangiography alone in comparison with T2-weighted MR cholangiography and gadoxetate disodium-enhanced MR cholangiography in a series of patients with biliary-enteric anastomosis (BEA). SUBJECTS AND METHODS. Fifty patients with BEA and clinically and sonographically suspected complications underwent 1.5-T MRI. After acquisition of T1- and T2-weighted images, conventional MR cholangiography was performed using 3D fast relaxation fast spin-echo (FRFSE) and single-shot fast spin-echo (SSFSE) T2-weighted sequences (image set 1). In each patient, a 3D fat-suppressed Liver Acquisition with Volume Acceleration (LAVA) sequence was performed before and 15, 20, 25, 30, and 40 minutes after IV administration of 0.1 mL/kg of gadoxetate disodium (Primovist) (image set 2). Two radiologists in consensus evaluated image quality in the anatomic segments of the biliary tract and recorded diagnostic confidence scores for image set 1 alone and image sets 1 and 2 together. MRI findings were compared with postsurgical specimen if surgery was performed, conventional cholangiography, or 12 months of imaging follow-up. RESULTS. A significant improvement in image quality for visualization of all biliary segments was found using gadoxetate disodium-enhanced MR cholangiography in comparison with T2-weighted MR cholangiography alone. Readers judged diagnostic confidence of image set 1 alone and image sets 1 and 2 together as very confident in three and 37 cases, confident in 30 and 11, not confident in 14 and one, and not confident at all in three and 1, respectively. Concordance between image set 1 alone and image sets 1 and 2 together and the reference standard results was present in 23 of 50 cases (46%) and 47 of 50 cases (94%), respectively (p < 0.0001). CONCLUSION. Gadoxetate disodium-enhanced MR cholangiography can improve image quality for visualization of the biliary tract and further enhanced the diagnostic performance of conventional T2-weighted MR cholangiography in the evaluation of patients with BEA.

3 T MR perfusion of solid pancreatic lesions using dynamic contrast-enhanced DISCO sequence: Usefulness of qualitative and quantitative analyses in a pilot study.

PURPOSE: To assess the usefulness of qualitative and quantitative analyses of pancreatic focal diseases by using the dynamic contrast-enhanced Differential Subsampling with Cartesian Ordering (DISCO) sequence at 3 T MR device. MATERIALS AND METHODS: Ten patients without pancreatic diseases and twenty-five patients with pathologically confirmed pancreatic focal disease (ductal adenocarcinoma, n = 14; endocrine tumour, n = 8; focal chronic pancreatitis, n = 3), underwent MRI by 3 T-device. Multiphasic contrast-enhanced MR perfusion, consisting of a 3D axial navigator, based free-breathing T1-weighted DISCO sequence, was repeated for 5 min. A dose of 0.1 mL/kg of Gadobutrolo with a 20 mL saline flush was injected at a flow rate of 5 mL/s. Perfusion MRI were processed using a dedicated software package (GeniQ; GE Healthcare), obtaining both a time-signal-intensity curve (TSIC) and perfusion maps for each healthy pancreatic parenchyma and focal disease. The TSIC were grouped into four types according to their shapes and the MR perfusion parameters (Ktrans, Kep, Ve, IAUGC) were calculated. The one-way analysis of variance and the Student's t-test were used to correlate the quantitative and qualitative parameters with the tissue histology. RESULTS: All 10 patients with healthy pancreas presented a TSIC-type 1; TSIC-type 2 was observed in all 14 ductal adenocarcinomas and in one neuroendocrine tumour; TSIC-type 3 was recognized in the remaining 7 neuroendocrine neoplasms; TSIC-type 4 was identified in all 3 focal chronic pancreatitis. All perfusion parameters were significantly different (p < 0.0001) for each type of lesion. Furthermore, Ve was also very useful to discriminate between normal and pathological tissues (p = 0.0005). CONCLUSION: Qualitative and quantitative analyses of contrast-enhanced 3 T MR perfusion, using the dynamic contrast-enhanced DISCO sequence, could be considered an interesting tool to improve the diagnosis of focal pancreatic diseases, of solid lesions in particular. Further investigations with prospective larger sample studies are required to confirm these preliminary results.

Biliary complications after liver transplantation: Assessment with MR cholangiopancreatography and MR imaging at 3T device.

PURPOSE: Our study was aimed to assess the diagnostic value of MR cholangiopancreatography (MRCP) and MR imaging at 3 T device when evaluating biliary adverse events after liver transplantation. MATERIALS AND METHODS: A series of 384 MR examinations in 232 liver transplant subjects with suspected biliary complications (impaired liver function tests and/or biliary abnormalities on ultrasound) were performed at 3 T device (GE-DISCOVERY MR750; GE Healthcare). After the acquisition of axial 3D dual-echo T1-weighted images and T2-weighted sequences (propeller and SS-FSE), MRCP was performed through coronal thin-slab 3D-FRFSE and coronal oblique thick-slab SSFSE T2w sequences. DW-MRI of the liver was performed using an axial spin-echo echo-planar sequence with multiple b values (150, 500, 1000, 1500 s/mm2) in all diffusion directions. Contrast-enhanced MRCP was performed in 25/232 patients. All MR images were blindly evaluated by two experienced abdominal radiologists in consensus to determine the presence of biliary complications, whose final diagnosis was based on direct cholangiography, surgery and integrating clinical follow-up with ultrasound and/or MRI findings. RESULTS: In 113 patients no biliary abnormality was observed. The remaining 119 subjects were affected by one or more of the following complications: non-anastomotic strictures including typical ischemic-type biliary lesions (n = 67), anastomotic strictures (n = 34), ampullary dysfunction (n = 4), anastomotic leakage (n = 4), stones, sludge and casts (n = 65), vanishing bile duct (n = 1). The sensitivity, specificity, PPV, NPV and diagnostic accuracy of the reviewers for the detection of all types of biliary complications were 99%, 96%, 95%, 99% and 97%, respectively. CONCLUSION: MR cholangiopancreatography and MR imaging at 3 T device are extremely reliable for detecting biliary complications after liver transplantation.

3T diffusion-weighted MRI in the response assessment of colorectal liver metastases after chemotherapy: Correlation between ADC value and histological tumour regression grading.

PURPOSE: The purpose of the study was to correlate the apparent diffusion coefficient (ADC) values of diffusion-weighted MR imaging (DW-MRI) by 3T device with the histological tumour regression grading (TRG) analysis of colorectal liver metastases after preoperative chemotherapy. MATERIALS AND METHODS: Our study included thirty-five patients with colorectal liver metastases who had undergone MRI by 3T device (GE DISCOVERY MR750; GE Healthcare) after preoperative chemotherapy. DW-MRI was performed using a single-shot spin-echo echo-planar sequence with multiple b-values (0, 150, 500, 1000, 1500s/mm2), thus obtaining an ADC map. For each liver lesion (more than 1cm in diameter) the fitted ADC values were calculated by two radiologists in conference and three ROIs were drawn: around the entire tumour (ADCe), at the tumour periphery (ADCp) and at the tumour center (ADCc). All ADC values were correlated with histopathological findings after surgery. Hepatic metastases were pathologically classified into five groups on the basis of TRG. Statistical analysis was performed on a per-lesion basis utilizing the one-way analysis of variance (ANOVA). This retrospective study was approved by our institutional review board; written informed consent was obtained from all patients. RESULTS: A total of 106 colorectal liver metastases were included for image analysis. TRG1, TRG2, TRG3, TRG4 and TRG5 were observed in 4, 14, 36, 35 and 17 lesions, respectively. ADCe and ADCp values were significantly higher in lesions classified as TRG1 (2.40±0.12×10-9m2/s and 2.28±0.26×10-9m2/s, respectively) and as TRG2 (1.40±0.31×10-9m2/s and 1.44±0.35×10-9m2/s), compared to TRG3 (1.16±0.13×10-9m2/s and 1.01±0.18×10-9m2/s), TRG4 (1.10±0.26×10-9m2/s and 0.97±0.24×10-9m2/s), and TRG5 (0.93±0.17×10-9m2/s and 0.82±0.28×10-9m2/s). ADCe, ADCp and ADCc values were significantly different in TRG classes (p<0.0001). Statistical correlations were found between the ADCe, ADCp, ADCc values and the TRG classes (Spearman correlation coefficient were -0.568, -0.542 and -0.554, respectively). CONCLUSION: Our study showed a significant correlation between ADC values of 3T DW-MRI and histological TRG of colorectal liver metastases after preoperative chemotherapy.

Secretin-stimulated MR cholangiopancreatography: spectrum of findings in pancreatic diseases.

MR cholangiopancreatography (MRCP) is an imaging technique that has evolved over the past 2 decades and that continues to have a fundamental role in the non-invasive detection of morphologic features of the pancreatic ducts. In several studies, MRCP has shown a good correlation with endoscopic retrograde cholangiopancreatography in the evaluation of diseases and anatomic variants of the pancreatic ductal system. However, in physiologic conditions the pancreatic ducts are not always easily recognisable. More recently, secretin-enhanced MRCP protocols have been developed for a more complete assessment of pancreatic ducts and glandular function, including monitoring of pancreatic flow dynamics and duodenal filling after pancreatic hormonal stimulation with secretin. The injection of this hormone causes temporary dilation of the pancreatic ducts, principally by increasing pancreatic exocrine secretions, and thus improving MRCP detection of the ducts and characterisation of pancreatic disorders and allowing the assessment of the exocrine pancreatic reserve. The purpose of this pictorial review is to summarise the technical aspects of secretin-stimulated MRCP, to report the secretin-stimulated MRCP findings of pancreatic duct abnormalities and to review the diagnostic capabilities of secretin-stimulated MRCP in various pancreatic ductal system conditions. MAIN MESSAGES: • MRCP has a fundamental role in the non-invasive detection of pancreatic ducts. • In physiologic conditions pancreatic ducts are not always well detected on MRCP. • Secretin injection causes temporary dilation of pancreatic ducts and thus improves MRCP detection. • Secretin-stimulated MRCP may allow the assessment of the exocrine pancreatic reserve. • Secretin increases the diagnostic capabilities of MRCP for evaluating pancreatic disorders.