Solid pancreatic lesions: characterization by using timing bolus dynamic contrast-enhanced MR imaging assessment--a preliminary study

Dynamic contrast-enhanced magnetic resonance imaging for pancreatic ductal adenocarcinoma at 3.0-T magnetic resonance: correlation with histopathology

PURPOSE

The aim of this study was to discuss the correlation of quantitative dynamic contrast-enhanced magnetic resonance imaging (QDCE-MRI) at 3.0-T magnetic resonance and histopathology for pancreatic ductal adenocarcinoma (PDA).

METHODS

Twenty-three patients with histopathologically proven PDA were included in this study after 75 cases of suspected pancreatic tumors had been performed by QDCE-MRI. The quantitative kinetic parameters analyzed by 2-compartment and 3-compartment models were calculated automatically, which included the volume transfer constant of the contrast agent, the rate constant (Kep), the volume as a percentage of the extravascular extracellular leakage space, the time of arrival of contrast agent, the time of peaking of contrast agent, the maximum slope of signal intensity ascent, and the contrast enhancement ratio. According to magnetic resonance images, tissue section were selected and stained for evaluating tumor differentiation, tumor fibrosis, tumor microvessel density, the expression of tumor vascular endothelial growth factor (VEGF) and Ki67. Subsequently, the relationship between the parameters of QDCE-MRI and histopathology of PDA was analyzed.

RESULTS

The tumor Kep and extravascular extracellular leakage space showed a statistically significant correlation with tumor fibrosis; the tumor volume transfer constant of the contrast agent 2-compartment showed a statistically significant correlation with the expressions of tumor VEGF; and the tumor Kep, maximum slope of signal intensity ascent, and contrast enhancement ratio showed a statistically significant correlation with the expression of tumor Ki67.

CONCLUSIONS

The parameters of QDCE-MRI of PDA can be used to evaluate the degrees of tumor fibrosis and the expressions of VEGF and Ki67.

New imaging strategies using a motion-resistant liver sequence in uncooperative patients

MR imaging has unique benefits for evaluating the liver because of its high-resolution capability and ability to permit detailed assessment of anatomic lesions. In uncooperative patients, motion artifacts can impair the image quality and lead to the loss of diagnostic information. In this setting, the recent advances in motion-resistant liver MR techniques, including faster imaging protocols (e.g., dual-echo magnetization-prepared rapid-acquisition gradient echo (MP-RAGE), view-sharing technique), the data under-sampling (e.g., gradient recalled echo (GRE) with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), single-shot echo-train spin-echo (SS-ETSE)), and motion-artifact minimization method (e.g., radial GRE with/without k-space-weighted image contrast (KWIC)), can provide consistent, artifact-free images with adequate image quality and can lead to promising diagnostic performance. Understanding of the different motion-resistant options allows radiologists to adopt the most appropriate technique for their clinical practice and thereby significantly improve patient care.

Application of 3.0 tesla magnetic resonance imaging for diagnosis in the orthotopic nude mouse model of pancreatic cancer

The aim of this study was to successfully establish an orthotopic murine model using two different human pancreatic adenocarcinoma cell lines and to propose a 3.0 tesla MRI protocol for noninvasive characterization of this model. SW1990 and MIAPaca-2 tumor cells were injected into the pancreas of BALB/C nu/nu mice. Tumor growth rate and morphological information were assessed by 3.0 tesla MRI (T1WI, T2WI and DCE-MRI) and immunohistology. Proliferation of SW1990 was significantly faster than that of MIAPaca-2 (P=0.000), but MIAPaca-2 mice had a significantly shorter survival than SW1990 mice (41 days and 44 days respectively, P=0.027). MRI could reliably monitor tumor growth in both cell lines: the tumors exhibiting a spherical growth pattern showed a high-intensity signal, and the SW1990 group developed significantly larger tumors compared with the MIAPaCa-2 group. There were no statistical differences between the two groups in which tumor size was assessed using electronic calipers and an MRI scan (P=0.680). Both tumors showed a slow gradual enhancement pattern. Immunohistochemistry demonstrated tumor tissues showing high expression of Ki-67. This model closely mimics human pancreatic cancer and permits monitoring of tumor growth and morphological information by noninvasive 3.0 tesla MRI studies reducing the number of mice required.

Dynamic contrast-enhanced MRI of gastric cancer: Correlation of the perfusion parameters with pathological prognostic factors

PURPOSE

To investigate the feasibility of dynamic, contrast-enhanced, magnetic resonance imaging (DCE-MRI) for perfusion quantification of gastric cancers, and to correlate the DCE-MRI parameters with the pathological prognostic factors.

MATERIALS AND METHODS

This prospective study was approved by our Institutional Review Board. Twenty-seven patients with gastric cancers underwent DCE-MRI using a free-breathing, radial, gradient-echo (GRE) sequence with k-space weighted image contrast (KWIC) reconstruction on a 3T scanner. The DCE-MRI parameters (volume transfer coefficient [K(trans) ], reverse reflux rate constant [Kep ], extracellular extravascular volume fraction [Ve ], and initial area under the gadolinium concentration curve during the first 60 seconds [iAUC]) of gastric cancer and normal wall were measured and compared with each other using the Wilcoxon signed rank test. The relationship between the DCE-MRI parameters of gastric cancer and the pathological prognostic factors were evaluated using the Mann-Whitney test or the Spearman rank correlation test.

RESULTS

DCE-MRIs were of diagnostic quality in 22 patients (81.5%). Ve and iAUC were significantly higher in gastric cancer than in normal gastric wall (P < 0.05). Ve showed significant positive correlation with T-staging of gastric cancers (P < 0.05). K(trans) was significantly correlated with the grades of epidermal growth-factor receptor expression (P < 0.05).

CONCLUSION

DCE-MRI using a radial GRE with KWIC reconstruction is feasible for quantification of the perfusion dynamics of gastric cancers, and the DCE-MRI parameters of gastric cancers may provide prognostic information.

Imaging diagnosis of pancreatic cancer: A state-of-the-art review

Pancreatic cancer (PC) remains one of the deadliest cancers worldwide, and has a poor, five-year survival rate of 5%. Although complete surgical resection is the only curative therapy for pancreatic cancer, less than 20% of newly-diagnosed patients undergo surgical resection with a curative intent. Due to the lack of early symptoms and the tendency of pancreatic adenocarcinoma to invade adjacent structures or to metastasize at an early stage, many patients with pancreatic cancer already have advanced disease at the time of their diagnosis and, therefore, there is a high mortality rate. To improve the patient survival rate, early detection of PC is critical. The diagnosis of PC relies on computed tomography (CT) and/or magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP), or biopsy or fine-needle aspiration using endoscopic ultrasound (EUS). Although multi-detector row computed tomography currently has a major role in the evaluation of PC, MRI with MRCP facilitates better detection of tumors at an early stage by allowing a comprehensive analysis of the morphological changes of the pancreas parenchyma and pancreatic duct. The diagnosis could be improved using positron emission tomography techniques in special conditions in which CT and EUS are not completely diagnostic. It is essential for clinicians to understand the advantages and disadvantages of the various pancreatic imaging modalities in order to be able to make optimal treatment and management decisions. Our study investigates the current role and innovative techniques of pancreatic imaging focused on the detection of pancreatic cancer.

Radial volumetric imaging breath-hold examination (VIBE) with k-space weighted image contrast (KWIC) for dynamic gadoxetic acid (Gd-EOB-DTPA)-enhanced MRI of the liver: advantages over Cartesian VIBE in the arterial phase

OBJECTIVES

To compare radial volumetric imaging breath-hold examination with k-space weighted image contrast reconstruction (r-VIBE-KWIC) to Cartesian VIBE (c-VIBE) in arterial phase dynamic gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (DCE-MRI) of the liver.

METHODS

We reviewed 53 consecutive DCE-MRI studies performed on a 3-T unit using c-VIBE and 53 consecutive cases performed using r-VIBE-KWIC with full-frame image subset (r-VIBEfull) and sub-frame image subsets (r-VIBEsub; temporal resolution, 2.5-3 s). All arterial phase images were scored by two readers on: (1) contrast-enhancement ratio (CER) in the abdominal aorta; (2) scan timing; (3) artefacts; (4) visualisation of the common, right, and left hepatic arteries.

RESULTS

Mean abdominal aortic CERs for c-VIBE, r-VIBEfull, and r-VIBEsub were 3.2, 4.3 and 6.5, respectively. There were significant differences between each group (P < 0.0001). The mean score for c-VIBE was significantly lower than that for r-VIBEfull and r-VIBEsub in all factors except for visualisation of the common hepatic artery (P < 0.05). The mean score of all factors except for scan timing for r-VIBEsub was not significantly different from that for r-VIBEfull.

CONCLUSIONS

Radial VIBE-KWIC provides higher image quality than c-VIBE, and r-VIBEsub features high temporal resolution without image degradation in arterial phase DCE-MRI.

KEY POINTS

Radial VIBE-KWIC minimised artefact and produced high-quality and high-temporal-resolution images. Maximum abdominal aortic enhancement was observed on sub-frame images of r-VIBE-KWIC. Using r-VIBE-KWIC, optimal arterial phase images were obtained in over 90 %. Using r-VIBE-KWIC, visualisation of the hepatic arteries was improved. A two-reader study revealed r-VIBE-KWIC's advantages over Cartesian VIBE.

DCE and DSC MR perfusion imaging in the differentiation of recurrent tumour from treatment-related changes in patients with glioma

AIM

To retrospectively compare the utility of perfusion magnetic resonance imaging (MRI) in distinguishing treatment-related changes from recurrent disease in glioma patients.

MATERIALS AND METHODS

Thirty-one patients with histologically diagnosed gliomas and increased enhancement after or during concurrent (chemo-) radiation therapy were enrolled. They underwent dynamic contrast-enhanced (DCE) permeability MRI followed by dynamic susceptibility contrast (DSC) perfusion MRI. The vascular transfer constant (rK(trans)) and initial areas under the concentration curve (riAUC) were obtained from DCE MRI, and cerebral blood volume (rCBV) was obtained from DSC MRI. Patients were classified as having treatment-related changes or recurrent tumours based on clinicoradiological results or pathological results from surgery.

RESULTS

Nineteen patients were diagnosed as having recurrences and 12 patients as having treatment-related changes. The rK(trans), riAUC, and rCBV values in the recurrent group were significantly higher than the values in the group with treatment-related changes (p < 0.05). For all 31 patients, there was no significant difference between DSC MRI and DCE MRI for the differentiating power between recurrence and treatment-related changes (p = 0.7227). However, when including only the 24 patients with concordant values of rK(trans) and riAUC, DCE MRI showed a significant AUC value of 0.786 in the receiver operating characteristic (ROC) curve analysis (p = 0.003), whereas DSC MRI did not (AUC = 0.643, p = 0.229).

CONCLUSION

MRI perfusion images appear to show promise in distinguishing treatment-related changes from recurrent tumours. When both rK(trans) and riAUC show concordant values, DCE MRI seems to be more powerful than DSC MRI in the differentiation of recurrence from treatment-related changes.