Conventional Dynamic Contrast-enhanced Magnetic Resonance Imaging Research Articles

Value of dynamic contrast enhanced magnetic resonance imaging in the differentiation between post-treatment changes and recurrent salivary gland tumors

Purpose: The purpose of this study was to investigate the diagnostic value of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in the differentiation between post-treatment changes and recurrent salivary gland tumors. Patients and methods: A prospectively designed study was conducted on 37 patients having salivary gland malignant tumors treated by surgery or chemo/radiotherapy or both. All patients underwent conventional MRI and DCE-MRI. The obtained DCE-MRI data were interpreted semi quantitatively (using time intensity curves, TIC and time to peak TTP) and quantitatively (using wash in and washout rates). The obtained TICs were classified into four types (A, B, C, and D). Results: There was a significant statistical difference as regards TICs, wash in and washout rates of recurrent salivary gland tumors and that of post treatment changes, whereas there was no significant difference as regards TTP. Receiver Operating Characteristic (ROC) analysis revealed cutoff points of >10.25, and >6.25 for the wash in and washout rates used to differentiate recurrent tumors from post-treatment changes, respectively. Conclusion: We concluded that DCE MRI has a valuable diagnostic value in the differentiation of recurrent malignant salivary gland tumors from post-treatment changes, especially, for cases that remain unsolved by conventional MR imaging techniques.

Initial Experience of Applying TWIST-Dixon With Flexible View Sharing in Breast DCE-MRI

IntroductionWe developed a new fast imaging technique with flexible time-resolved angiography with stochastic trajectories (TWIST) view sharing to achieve variable temporal resolution and with flexible echo time Dixon to achieve robust fat suppression and to evaluate its application in breast dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI). Materials and MethodsThe TWIST-Dixon technique was improved with more flexible view sharing and echo times (TWIST-Dixon-Flex). In a dynamic series, each measurement can be separately prescribed as “full,” “partial,” or “center-only.” The spatial and temporal resolution can then be adjusted throughout the measurements to match the dynamic characteristics of contrast enhancement at different phases. The potential advantages of TWIST-Dixon-Flex were evaluated with 18 clinical breast DCE MRI cases. A mixed-effects analysis of variance (ANOVA) was performed to compare the image quality with that of the conventional images. ResultsThe ANOVA showed that the quality of postcontrast TWIST-Dixon-Flex images was significantly higher than that of the conventional images. The TWIST-Dixon-Flex technique also provided the capability to detect differences in rapid contrast uptake from different regions of the breast tumor, which is not possible with conventional breast DCE-MRI. ConclusionThe new TWIST-Dixon-Flex technique provides potentially valuable information about early tumor enhancement, and maintains excellent image quality at peak and postcontrast enhancement. This technique could help overcome the compromise on spatial over temporal resolution in clinical breast imaging.

Molecular magnetic resonance imaging of angiogenesis in vivo using polyvalent cyclic RGD-iron oxide microparticle conjugates.

Angiogenesis is an essential component of tumour growth and, consequently, an important target both therapeutically and diagnostically. The cell adhesion molecule αvβ3 integrin is a specific marker of angiogenic vessels and the most prevalent vascular integrin that binds the amino acid sequence arginine-glycine-aspartic acid (RGD). Previous studies using RGD-targeted nanoparticles (20-50 nm diameter) of iron oxide (NPIO) for magnetic resonance imaging (MRI) of tumour angiogenesis, have identified a number of limitations, including non-specific extravasation, long blood half-life (reducing specific contrast) and low targeting valency. The aim of this study, therefore, was to determine whether conjugation of a cyclic RGD variant [c(RGDyK)], with enhanced affinity for αvβ3, to microparticles of iron oxide (MPIO) would provide a more sensitive contrast agent for imaging of angiogenic tumour vessels. Cyclic RGD [c(RGDyK)] and RAD [c(RADyK)] based peptides were coupled to 2.8 μm MPIO, and binding efficacy tested both in vitro and in vivo. Significantly greater specific binding of c(RGDyK)-MPIO to S-nitroso-n-acetylpenicillamine (SNAP)-stimulated human umbilical vein endothelial cells in vitro than PBS-treated cells was demonstrated under both static (14-fold increase; P < 0.001) and flow (44-fold increase; P < 0.001) conditions. Subsequently, mice bearing subcutaneous colorectal (MC38) or melanoma (B16F10) derived tumours underwent in vivo MRI pre- and post-intravenous administration of c(RGDyK)-MPIO or c(RADyK)-MPIO. A significantly greater volume of MPIO-induced hypointensities were found in c(RGDyK)-MPIO injected compared to c(RADyK)-MPIO injected mice, in both tumour models (P < 0.05). Similarly, administration of c(RGDyK)-MPIO induced a greater reduction in mean tumour T2* relaxation times than the control agent in both tumour models (melanoma P < 0.001; colorectal P < 0.0001). Correspondingly, MPIO density per tumour volume assessed immunohistochemically was significantly greater for c(RGDyK)-MPIO than c(RADyK)-MPIO injected animals, in both melanoma (P < 0.05) and colorectal (P < 0.0005) tumours. In both cases, binding of c(RGDyK)-MPIO co-localised with αvβ3 expression. Comparison of RGD-targeted and dynamic contrast enhanced (DCE) MRI assessment of tumour perfusion indicated sensitivity to different vascular features. This study demonstrates specific binding of c(RGDyK)-MPIO to αvβ3 expressing neo-vessels, with marked and quantifiable contrast and rapid clearance of unbound particles from the blood circulation compared to NPIO. Combination of this molecular MRI approach with conventional DCE MRI will enable integrated molecular, anatomical and perfusion tumour imaging.

MRI and conservative treatment of locally advanced breast cancer

Aims The objectives of this study were to compare the efficacy of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in assessing the response of primary breast carcinoma to neoadjuvant chemotherapy compared to conventional imaging modalities, and to see how surgical outcome was influenced as a result of these findings. Methods Thirty-four patients with locally advanced primary breast cancer underwent conventional imaging and DCE-MRI following six cycles of neoadjuvant chemotherapy prior to surgery. Changes in surgical management based on the post-chemotherapy DCE-MRI findings were recorded. Results Prior to neoadjuvant chemotherapy, 22 of the 34 patients were assessed as requiring mastectomy and the remaining 12 were considered inoperable. Following chemotherapy two patients were still considered inoperable. In 11 of the 34 patients, the final decision to proceed to either mastectomy or non-surgical management was based primarily on pre-treatment disease status or patient choice. DCE-MRI findings, therefore, contributed to the operative decision in 21 of 34 patients. Two of these 21 patients were spared surgery as DCE-MRI demonstrated complete response to chemotherapy and one declined surgery. The remaining 18 were able to undergo wide local excision, with only two patients subsequently requiring mastectomy for involved margins. Conclusions DCE-MRI is able to accurately predict those patients suitable for breast conserving surgery following neoadjuvant chemotherapy and should be the imaging modality of choice in assessing the response of patients with primary breast carcinoma to neoadjuvant chemotherapy.