Recent advances in non-invasive magnetic resonance imaging assessment of hepatocellular carcinoma

Magnetic resonance(MR) imaging of the liver is an important tool for the detection and characterization of focal liver lesions and for assessment of diffuse liver disease,having several intrinsic characteristics,represented by high soft tissue contrast,avoidance of ionizing radiation or iodinated contrast media,and more recently,by application of several functional imaging techniques(i.e.,diffusion-weighted sequences,hepatobiliary contrast agents,perfusion imaging,magnetic resonance(MR)-elastography,and radiomics analysis). MR functional imaging techniques are extensively used both in routine practice and in the field of clinical and pre-clinical research because,through a qualitative rather than quantitative approach,they can offer valuable information about tumor tissue and tissue architecture,cellular biomarkers related to the hepatocellular functions,or tissue vascularization profiles related to tumor and tissue biology. This kind of approach offers in vivo physiological parameters,capable of evaluating physiological and pathological modifications of tissues,by the analysis of quantitative data that could be used in tumor detection,characterization,treatmentselection,and follow-up,in addition to those obtained from standard morphological imaging. In this review we provide an overview of recent advanced techniques in MR for the diagnosis and staging of hepatocellular carcinoma,and their role in the assessment of response treatment evaluation.

Rectal cancer staging: Multidetector-row computed tomography diagnostic accuracy in assessment of mesorectal fascia invasion

AIM: To assess the diagnostic accuracy of multidetectorrow computed tomography(MDCT) as compared with conventional magnetic resonance imaging(MRI), in identifying mesorectal fascia(MRF) invasion in rectal cancer patients.METHODS: Ninety-one patients with biopsy proven rectal adenocarcinoma referred for thoracic and abdominal CT staging were enrolled in this study. The contrast-enhanced MDCT scans were performed on a 256 row scanner(ICT, Philips) with the following acquisition parameters: tube voltage 120 KV, tube current 150-300 m As. Imaging data were reviewed as axial and as multiplanar reconstructions(MPRs) images along the rectal tumor axis. MRI study, performed on 1.5 T with dedicated phased array multicoil, included multiplanar T2 and axial T1 sequences and diffusion weighted images(DWI). Axial and MPR CT images independently were compared to MRI and MRF involvement was determined. Diagnostic accuracy of both modalities was compared and statistically analyzed.RESULTS: According to MRI, the MRF was involved in 51 patients and not involved in 40 patients. DWI allowed to recognize the tumor as a focal mass with high signal intensity on high b-value images, compared with the signal of the normal adjacent rectal wall or with the lower tissue signal intensity background. The number of patients correctly staged by the native axial CT images was 71 out of 91(41 with involved MRF; 30 with not involved MRF), while by using the MPR 80 patients were correctly staged(45 with involved MRF; 35 with not involved MRF). Local tumor staging suggested by MDCT agreed with those of MRI, obtaining for CT axial images sensitivity and specificity of 80.4% and 75%, positive predictive value(PPV) 80.4%, negative predictive value(NPV) 75% and accuracy 78%; while performing MPR the sensitivity and specificity increased to 88% and 87.5%, PPV was 90%, NPV 85.36% and accuracy 88%. MPR images showed higher diagnostic accuracy, in terms of MRF involvement, than native axial images, as compared to the reference magnetic resonance images. The difference in accuracy was statistically significant(P = 0.02). CONCLUSION: New generation CT scanner, using high resolution MPR images, represents a reliable diagnostic tool in assessment of loco-regional and whole body staging of advanced rectal cancer, especially in patients with MRI contraindications.

Role of dynamic perfusion magnetic resonance imaging in patients with local advanced rectal cancer

BACKGROUND The management of rectal cancer patients is mainly based on the use of the magnetic resonance imaging(MRI)technique as a diagnostic tool for both staging and restaging.After treatment,to date,the evaluation of complete response is based on the histopathology assessment by using different tumor regression grade(TRG)features(e.g.,Dworak or Mandard classifications).While from the radiological point of view,the main attention for the prediction of a complete response after chemotherapy treatment focuses on MRI and the potential role of diffusion-weighted images and perfusion imaging represented by dynamiccontrast enhanced MRI.The main aim is to find a reliable tool to predict tumor response in comparison to histopathologic findings.AIM To investigate the value of dynamic contrast-enhanced perfusion-MRI parameters in the evaluation of the healthy rectal wall and tumor response to chemo-radiation therapy in patients with local advanced rectal cancer with histopathologic correlation.METHODS Twenty-eight patients with biopsy-proven rectal adenocarcinoma who underwent a dynamic contrast-enhanced MR study performed on a 1.5 T MRI system(Achieva,Philips),before(MR1)and after chemoradiation therapy(MR2),were enrolled in this study.The protocol included T1 gadolinium enhanced THRIVE sequences acquired on axial planes.A dedicated workstation was used to generate color permeability maps.Region of interest was manually drawn on tumor tissue and normal rectal wall,hence the following parameters were calculated and statistically analyzed:Relative arterial enhancement(RAE),relative venous enhancement(RVE),relative late enhancement(RLE),maximum enhancement(ME),time to peak and area under the curve(AUC).Perfusion parameters were related to pathologic TRG(Mandard’s criteria;TRG1=complete regression,TRG5=no regression).RESULTS Ten tumors(36%)showed complete or subtotal regression(TRG1-2)at histology and classified as responders;18 tumors(64%)were classified as non-responders(TRG3-5).Perfusion MRI parameters were significantly higher in the tumor tissue than in the healthy tissue in MR1(P<0.05).At baseline(MR1),no significant difference in perfusion parameters was found between responders and nonresponders.After chemo-radiation therapy,at MR2,responders showed significantly(P<0.05)lower perfusion values[RAE(%)54±20;RVE(%)73±24;RLE(%):82±29;ME(%):904±429]compared to non-responders[RAE(%):129±45;RVE(%):154±39;RLE(%):164±35;ME(%):1714±427].Moreover,in responders group perfusion values decreased significantly at MR2[RAE(%):54±20;RVE(%):73±24;RLE(%):82±29;ME(%):904±429]compared to the corresponding perfusion values at MR1[RAE(%):115±21;RVE(%):119±21;RLE(%):111±74;ME(%):1060±325];(P<0.05).Concerning the time-intensity curves,the AUC at MR2 showed significant difference(P=0.03)between responders and non-responders[AUC(mm2×10-3)121±50 vs 258±86],with lower AUC values of the tumor tissue in responders compared to nonresponders.In non-responders,there were no significant differences between perfusion values at MR1 and MR2.CONCLUSION Dynamic contrast perfusion-MRI analysis represents a complementary diagnostic tool for identifying vascularity characteristics of tumor tissue in local advanced rectal cancer,useful in the assessment of treatment response.