In situ and minimally invasive breast cancer: morphologic and kinetic features on contrast-enhanced MR imaging

Purpose: This retrospective study was undertaken to investigate the morphologic and dynamic features of in situ and minimally invasive breast cancer on contrast-enhanced (c.-e.) MR imaging and to examine possible associations to pathology features. Material and methods: A total of 71 patients underwent MR imaging. T1-weighted FLASH-3D images were obtained before and after intravenous administration of Gd-DTPA. Histopathologic analysis of 78 lesions revealed ductal carcinoma in situ (DCIS)n=50 and DCIS with microinvasionn=28. MR features were correlated with histopathologic findings. Results: Enhancement in DCIS was focal (73%), diffuse (10%) or ductal (17%). No enhancement occurred in two cases (4%). In 65% enhancement speed was classified as delayed. There was a tendency toward a more ill-defined (83 vs. 43%) enhancement pattern in high grade DCIS and a more ductal (29 vs. 12%) and faster (50 vs. 29%) enhancement in comedo type DCIS. However, significant differences in the enhancement behaviour could neither be demonstrated between high grade and non high grade DCIS nor between comedo and non comedo type DCIS. No significant differences were noted between pure and microinvasive DCIS. Conclusion: In this retrospective analysis the majority (96%) of DCIS lesions show contrast enhancement. However, in only about 50% of DCIS the criteria of a so-called ‘typical’ enhancement behaviour was fulfilled, that means strong, early, focal ill-circumscribed or ductal. Enhancement that follows a duct is often associated with malignancy, however this feature was only present in 17% of the cases. c.-e. MR imaging allowed the detection of 25 additional foci of DCIS. Therefore malignant in situ lesions can be present with atypical enhancement, and should be taken into consideration in high-risk patients in particular.     

In situ and minimally invasive breast cancer: morphologic and kinetic features on contrast-enhanced MR imaging

PURPOSE: This retrospective study was undertaken to investigate the morphologic and dynamic features of in situ and minimally invasive breast cancer on contrast-enhanced (c.-e.) MR imaging and to examine possible associations to pathology features. MATERIAL AND METHODS: A total of 71 patients underwent MR imaging. T1-weighted FLASH-3D images were obtained before and after intravenous administration of Gd-DTPA. Histopathologic analysis of 78 lesions revealed ductal carcinoma in situ (DCIS) n = 50 and DCIS with microinvasion n = 28. MR features were correlated with histopathologic findings. RESULTS: Enhancement in DCIS was focal (73%), diffuse (10%) or ductal (17%). No enhancement occurred in two cases (4%). In 65% enhancement speed was classified as delayed. There was a tendency toward a more ill-defined (83 vs. 43%) enhancement pattern in high grade DCIS and a more ductal (29 vs. 12%) and faster (50 vs. 29%) enhancement in comedo type DCIS. However, significant differences in the enhancement behaviour could neither be demonstrated between high grade and non high grade DCIS nor between comedo and non comedo type DCIS. No significant differences were noted between pure and microinvasive DCIS. CONCLUSION: In this retrospective analysis the majority (96%) of DCIS lesions show contrast enhancement. However, in only about 50% of DCIS the criteria of a so-called 'typical' enhancement behaviour was fulfilled, that means strong, early, focal ill-circumscribed or ductal. Enhancement that follows a duct is often associated with malignancy, however this feature was only present in 17% of the cases. c.-e. MR imaging allowed the detection of 25 additional foci of DCIS. Therefore malignant in situ lesions can be present with atypical enhancement, and should be taken into consideration in high-risk patients in particular.     

Dynamic contrast-enhanced MR imaging of the entire breast with spectral-selective inversion fast three dimensional sequence

Dynamic contrast-enhanced images with high spatial and temporal resolutions were acquired with a fast 3D spoiled gradient echo (SPGR) sequence using spectral selective inversion recovery (IR) pulse. Five healthy volunteers and 12 patients with 14 pathologically proven breast lesions were studied. Fat suppressed volume image data covering the entire breast were obtained with a sufficient spatial resolution (0.9×1.5×3.0 mm³) and an imaging time of 57 s. By using the criteria including peripheral enhancement and presence of spiculation, sensitivity, specificity, and accuracy in detecting malignant lesions were 88.9, 80.0 and 85.%, respectively. Although the C/N and S/N ratios were approximately 30% less than those of the conventional fat suppressed 3D technique, fast 3D SPGR imaging with spectral IR method demonstrated sufficient image quality for both time intensity analysis and morphological evaluation of the breast lesions with a data acquisition time less than half of the conventional method. This technique can substantially improve spatial and temporal resolutions of dynamic MR images of the breast and will be useful in evaluating malignant and benign breast lesions.     

MR imaging of the prostate in clinical practice

Magnetic resonance imaging (MRI) is the imaging tool of choice in the evaluation of prostate cancer. The main applications of MR imaging in the management of prostate cancer are: (1) to guide targeted biopsy when prostate cancer is clinically suspected and previous ultrasound-guided biopsy results are negative; (2) to localize and stage prostate cancer and provide a roadmap for treatment planning; and (3) to detect residual or locally recurrent cancer after treatment. Other MR techniques such as proton MR spectroscopic imaging (MRSI), diffusion-weighted imaging (DWI), and contrast-enhanced MRI (CE-MRI) complement conventional MR imaging by providing metabolic and functional information that can improve the accuracy of prostate cancer detection and characterization. In everyday clinical practice, and to account for patient comfort, MR imaging studies are limited to 1 h. To obtain consistently high-quality images, a well-designed protocol is necessary. Routine MR imaging can be supplemented by other MR techniques such as MRSI, DWI or CE-MRI depending on the expertise available and the clinical questions that need to be answered. This review summarizes the role of MR imaging in the management of prostate cancer and describes practical approaches to implementing anatomic, metabolic and functional MR imaging techniques in the clinic.     

Preliminary characterization of an experimental breast cancer cells brain metastasis mouse model by MRI/MRS

PURPOSE: Chemotherapy increases survival in breast cancer patients. Consequently, cerebral metastases have recently become a significant clinical problem, with an incidence of 30-40% among breast carcinoma patients. As this phenomenon cannot be studied longitudinally in humans, models which mimic brain metastasis are needed to investigate its pathogenesis. Such models may later be used in experimental therapeutic approaches. MATERIAL AND METHODS/RESULTS: We report a model in which 69% of the animals (9/13 BALB/c nude mice) developed MR-detectable abnormal masses in the brain parenchyma within a 20 to 62-day time window post intra-carotid injection of 435-Br1 human cells. The masses detected in vivo were either single (7 animals) or multiple (2 animals). Longitudinal MR (MRI/MRS) studies and post-mortem histological data were correlated, revealing a total incidence of experimental brain metastases of 85% in the cases studied (11/13 animals). ADC maps perfectly differentiated edema and/or CSF areas from metastasis. Preliminary MRS data also revealed additional features: decrease in N-acetyl aspartate (NAA) was the first MRS-based marker of metastasis growth in the brain (micrometastasis); choline-containing compounds (Cho) rose and creatine (Cr) levels decreased as these lesions evolved, with mobile lipids and lactate also becoming visible. Furthermore, MRS pattern recognition-based analysis suggested that this approach may help to discriminate different growth stages. CONCLUSIONS: This study paves the way for further in vivo studies oriented towards detection of different tumor progression states and for improving treatment efficiency.     

Long-term follow-up of patients with acute myocarditis by magnetic resonance imaging

Magnetic resonance imaging (MRI) reveals cardiac signal intensity changes in patients with acute myocarditis; however, the natural history of these changes and their relationship to individual outcomes are unknown. The relationship of MRI findings to long-term outcome was studied by serial MRI studies in 16 patients with acute myocarditis who were followed for 30±4 (SE) months. Myocardial contrast enhancement was monitored using contrast-enhanced T1-weighted fast spin-echo images. Left ventricular ejection fraction was measured with gradient-echo sequences. Clinical symptoms were scored. The results were compared to a control group of 26 age-matched, healthy volunteers. Myocardial contrast enhancement, which was markedly increased in the early course of the disease, decreased at 4 weeks and remained within the normal range in most patients after 30 months. Contrast enhancement 4 weeks after onset of symptoms was predictive for the functional and clinical long-term outcome. Contrast-enhanced MRI may be a useful, noninvasive tool for long-term follow-up of patients with acute myocarditis. Furthermore, relatively early MRI findings may predict longer-term outcomes. Electronic Publication     

Magnetic resonance imaging in patients with granulomatosis with polyangiitis (Wegener’s) and subglottic stenosis

Objective

To evaluate the ability of MRI to detect subglottic stenosis and to differentiate between active and inactive subglottic inflammation in patients with granulomatosis with polyangiitis (GPA).

Materials and methods

MRI studies of the larynx of 18 GPA patients with suspected SGS were included. The MRI protocol included T1- and T2-weighted and STIR-sequences, dynamic contrast enhancement (DCE) and diffusion weighted imaging (DWI). Two independent observers reviewed the MR images. SGS were identified and quantified, inflammatory activity was assessed using edema imaging, DCE and DWI. Final MRI diagnoses were compared to the clinical, laryngoscopic and histopathologic results.

Results

MRI confirmed SGS in all GPA patients with significant narrowing of the airway lumen and thickening of subglottic wall. Assessing the subglottic inflammatory activity, MRI showed a sensitivity of 87.5 % and a specificity of 60.0 %. Interrater agreement was κ = 0.769. Of the different MR technical approaches tested, edema imaging was most sensitive and specific. DWI led to significant differences in the apparent diffusion coefficient between active and inactive subglottic inflammation. No significant differences were found with DCE imaging.

Conclusion

MR imaging has shown the ability to detect and grade SGS in patients with GPA. It non-invasively assesses the status of inflammatory activity utilizing edema sensitive sequences and DWI.     

Multiple channel phased arrays for echo planar imaging

A new interface combining phased arrays and echo-planar imaging (EPI) technologies was developed for two channel breast MR EPI applications. A detailed design for a dual-channel, EPI-compatible, phased array breast coil is described. EPI digital data multiplexing, signal controlling and sampling schemes are also presented. Results from breast phantoms and patients demonstrate a 55% improvement in signal-to-noise ratio when compared to a conventional two-loop, single channel coil configuration. This method can be easily expanded to a four or more channel, EPI-compatible, phased array system to improve field-of-view coverage and signal-to-noise ratio.     

Molecular imaging and therapy directed at the neovasculature in pathologies

We have discussed the impact of molecular imaging on clinical and preclinical medicine. We have presented the potential problems of delivering the effective therapeutic dose and the properties that can help contribute to the drug efficacy. The rationale for the design of new antiangiogenic agents that can be used for imaging and therapy was presented. Finally, results from imaging and targeted nanoparticle based therapies were presented. In vivo imaging of angiogenic tumors using anti-alpha(v)beta3 -targeted polymerized vesicles composed of the murine antibody LM609 attached to NPs labeled with the MR contrast agent gadolinium in the V2 carcinoma model in rabbits. MRI studies using this targeted contrast agent revealed large areas of alpha(v)beta3 integrin expression in tumor-associated vasculature that conventional MRIs failed to show. Other investigators have used microemulsions conjugated to an antibody targeted against alpha(v)beta as imaging agents. These materials also show contrast enhancement of tumor vasculature undergoing angiogenesis. Other markers, such as the PECAM-1 (CD-31), VCAM-1 (CD54) and VEGF receptor (flk-1), have been shown to be upregulated on tumor endothelium and associated with angiogenesis but have not been used in imaging studies. Furthermore, by modification of the NPs, we were able to use this imaging agent as an antiangiogenic gene delivery system. The results from these studies are very promising and are being further pursued.     

Is there a correlation in breast carcinomas between tumor size and number of tumor vessels detected by gadolinium-enhanced magnetic resonance mammography?

Tumor vessels are known as a sign of malignancy in breast tumors. Is there a correlation between tumor size and the number of vessels in cases of breast tumor examined by dynamic gadolinium (Gd)-enhanced MR imaging? Eighteen patients (mean age, 46±7 years) underwent dynamic Gd-enhanced MR imaging of the breast by three-dimensional gradient echo sequence using thin-layer technique (2.5 mm) at 1.5T. The dynamic study included one precontrast and four postcontrast sequences (every 90 seconds) in coronal slices. Postprocessing by subtraction method and reconstruction in both transverse and sagittal planes were performed. All carcinomas showed rapid Gd enhancement. Tumor size (0.5 to 31.5 cm³; mean, 6.3±3.7 cm³) and number of vessels (1 to 10; mean, 3±2.1) were detected in summation of all three directions. A significant correlation was found between number of vessels and tumor size (r=0.787,p≤0.01). Breast tumor size significantly correlated with the number of vessels detected by Gd-enhanced MR mammography. The introduced method is a further important step in differentiating a carcinoma from a benign lesion.     

Clinical evaluation of ultra-high-field MRI for three-dimensional visualisation of tumour size in uveal melanoma patients,with direct relevance to treatment planning

Objectives

To assess the tumour dimensions in uveal melanoma patients using 7-T ocular MRI and compare these values with conventional ultrasound imaging to provide improved information for treatment options.

Materials and methods

Ten uveal melanoma patients were examined on a 7-T MRI system using a custom-built eye coil and dedicated 3D scan sequences to minimise eye-motion-induced image artefacts. The maximum tumour prominence was estimated from the three-dimensional images and compared with the standard clinical evaluation from 2D ultrasound images.

Results

The MRI protocols resulted in high-resolution motion-free images of the eye in which the tumour and surrounding tissues could clearly be discriminated. For eight of the ten patients the MR images showed a slightly different value of tumour prominence (average 1.0 mm difference) compared to the ultrasound measurements, which can be attributed to the oblique cuts through the tumour made by the ultrasound. For two of these patients the more accurate results from the MR images changed the treatment plan, with the smaller tumour dimensions making them eligible for eye-preserving therapy.

Conclusion

High-field ocular MRI can yield a more accurate measurement of the tumour dimensions than conventional ultrasound, which can result in significant changes in the prescribed treatment.

     

7 T renal MRI: challenges and promises

The progression to 7 Tesla (7 T) magnetic resonance imaging (MRI) yields promises of substantial increase in signal-to-noise (SNR) ratio. This increase can be traded off to increase image spatial resolution or to decrease acquisition time. However, renal 7 T MRI remains challenging due to inhomogeneity of the radiofrequency field and due to specific absorption rate (SAR) constraints. A number of studies has been published in the field of renal 7 T imaging. While the focus initially was on anatomic imaging and renal MR angiography, later studies have explored renal functional imaging. Although anatomic imaging remains somewhat limited by inhomogeneous excitation and SAR constraints, functional imaging results are promising. The increased SNR at 7 T has been particularly advantageous for blood oxygen level-dependent and arterial spin labelling MRI, as well as sodium MR imaging, thanks to changes in field-strength-dependent magnetic properties. Here, we provide an overview of the currently available literature on renal 7 T MRI. In addition, we provide a brief overview of challenges and opportunities in renal 7 T MR imaging.     

Mri of renal angiomyolipomas

The MR appearance of 13 renal angiomyolipomas in 11 patients were reviewed. The fatty tissue in angiomyolipomas which demonstrated hyperintensity on Tl-weighted imaging was considered to be a key point for diagnosis with MRI. Renal angiomyolipomas were classified into three types according to the proportion of fatty tissue in tumours. Fatty tissue comprises more than 80% of the volume of an angiomyolipoma in type I, 20–80% in type II and less than 20% in type III tumours. It was easy to diagnose types I and II renal angiomyolipomas with MRI, but it was quite difficult to differentiate type III renal angiomyolipomas from other solitary occupying lesions such as renal cell carcinoma. Other MR characteristics of renal angiomyolipomas are summarized and are thought to have diagnostic uses.     

Magnetic resonance imaging and67ga scan versus computed tomography in the staging and in the monitoring of mediastinal malignant lymphoma: a prospective pilot study

Purpose: To assess the potential value of magnetic resonance imaging (MRI) combined with⁶⁷Ga single-photon emission computed tomography (SPECT) versus computed tomography (CT) in the staging and in the monitoring of mediastinal malignant lymphoma. Materials and methods: Twenty-three patients, referred to our institute for the evaluation of lymphoma, underwent CT,⁶⁷Ga scan, and MRI between April 1993 and February 1996 at sequential intervals. The tests studied (MRI,^67Ga, and CT) were performed according to the following schedule: 1) before start of therapy; 2) after four courses of chemotherapy; and 3) 2, 6, 12, and 18 months after the end of treatment. Results: All patients studied at the time of diagnosis had abnormal gallium accumulation in the mediastinum as well as pathologic CT and pathologic signal intensity at MRI. Six months after the end of treatment full consistency was found between the results of MRI and SPECT, whereas during treatment and 2 months after the end of therapy MRI and⁶⁷Ga scan were not in agreement in nine patients. In the 23 patients in follow-up, in CT there were nine false-positive and three false-negative findings; in SPECT three false negatives; in MRI one false positive and one false negative. Conclusion: MRI can give morphologic information similar to CT, even superior due to multiplanarity and with major precision in the distinction between fibrosis and active disease. MRI is thus an alternative to CT. The association with SPECT allows a great diagnostic accuracy in the positive and negative predictive value.     

PET/MRI in cancer patients: first experiences and vision from Copenhagen

Combined PET/MRI systems are now commercially available and are expected to change the medical imaging field by providing combined anato-metabolic image information. We believe this will be of particular relevance in imaging of cancer patients. At the Department of Clinical Physiology, Nuclear Medicine & PET at Rigshospitalet in Copenhagen we installed an integrated PET/MRI in December 2011. Here, we describe our first clinical PET/MR cases and discuss some of the areas within oncology where we envision promising future application of integrated PET/MR imaging in clinical routine. Cases described include brain tumors, pediatric oncology as well as lung, abdominal and pelvic cancer. In general the cases show that PET/MRI performs well in all these types of cancer when compared to PET/CT. However, future large-scale clinical studies are needed to establish when to use PET/MRI. We envision that PET/MRI in oncology will prove to become a valuable addition to PET/CT in diagnosing, tailoring and monitoring cancer therapy in selected patient populations.     

Enhancement characteristics of hepatic focal nodular hyperplasia and its scar by dynamic magnetic resonance imaging

Rationale and objectives: To determine the relationship between the lesion and the scar enhancement characteristics in a series of hepatic Focal Nodular Hyperplasia (FNH) lesions studied with dynamic MR imaging.Methods: Nine patients with FNH were studied. The slice showing the largest scar was selected for the dynamic single slice T1-weighted Gradient-echo sequence before and after contrast administration (15 images, one every 20 s). Analysis was performed with ROI measurements in the lesion and the scar. Signal-intensity and enhancement curves were obtained from both structures.Results: Dynamic MRI showed the typical homogeneous early enhancement of the lesion with delayed enhancement of the scar. The scar enhanced early and vigorously in all cases. Two patterns of enhancement curves were defined. In the parallel pattern, both curves started early, quickly reaching a plateau maintained over time (77.8%). In the divergent pattern the curve of the scar was above the curve of the FNH (22.2%). after the maximum slope was reached, with progressive separation of the curves.Conclusion: There is a hypervascular scar enhancement within FNH lesions with either a parallel or divergent course after the maximum early enhancement.     

Prediction of pathological tumor volume in clinically localized prostate cancer: value of endorectal coil magnetic resonance imaging

The purpose of this study was to determine whether endorectal coil magnetic resonance imaging (MRI) enables accurate assessment of pathologic tumor volume in patients with clinically localized prostate carcinoma. Twenty-four patients with biopsy-proved prostate carcinoma underwent MRI at 0.5 T before radical prostatectomy. Tumor volumes were determined independently on axial fast-spin-echo (SE) T₂-weighted MR images and whole-mount pathology slides of the surgical specimens. At pathology, tumor volumes ranged from 0.17 to 9.42 cm³ (mean±SD, 3.11±2.99 cm³). A strong correlation (r=.944) was found between measurements of tumor volume based on MR images and pathological specimens. The error was less than 0.5 cm³ in 14 cases, in the range of 0.5–1 cm³ in 7 cases, and more than 1 cm³ in 3 cases. By using an MR tumor volume of 2 cm³ as cutoff value, extracapsular tumor spread could be predicted with a sensitivity of 81.2%, a specificity of 100%, and an accuracy of 87.5%. Tumor volume determinations based on MR images seem to be accurate enough to be helpful in clinical decision-making.     

Multiple channel phased arrays for echo planar imaging

A new interface combining phased arrays and echo-planar imaging (EPI) technologies was developed for two channel breast MR EPI applications. A detailed design for a dual-channel. EPI-compatible, phased array breast coil is described. EPI digital data multiplexing, signal controlling and sampling schemes are also presented. Results from breast phantoms and patients demonstrate a 55% improvement in signal-to-noise ratio when compared to a conventional two-loop, single channel coil conliguration. This method can be easily expanded to a four or more channel. EPI-compatible, phased array system to improve field-of-view coverage and signal-to-noise ratio.     

Measurement of weak electric currents in copper wire phantoms using MRI: influence of susceptibility enhancement

The use of magnetic resonance imaging (MRI)-based methods for the direct detection of neuronal currents is a topic of intense investigation. Much experimental work has been carried out with the express aim of establishing detection thresholds and sensitivity to flowing currents. However, in most of these experiments, magnetic susceptibility enhancement was ignored. In this work, we present results that show the influence of a susceptibility artefact on the detection threshold and sensitivity. For this purpose, a novel phantom, consisting of a water-filled cylinder with two wires of different materials connected in series, was constructed. Magnitude MR images were acquired from a single slice using a gradient-echo echo planar imaging (EPI) sequence. The data show that the time course of the detected MR signal magnitude correlates very well with the waveform of the input current. The effect of the susceptibility artefacts arising from the two different wires was examined by comparing the magnitudes of the MR signals at different voxel locations. Our results indicate the following: (1) MR signal enhancement arising from the magnetic susceptibility effect influences the detection sensitivity of weak current; (2) the detection threshold and sensitivity are phantom-wire dependent; (3) sub-μ A electric current detection in a phantom is possible on a 1.5-T MR scanner in the presence of susceptibility enhancement.     

Non-breath-hold lung magnetic resonance imaging with real-time navigation

Magnetic resonance imaging (MRI) with navigating techniques based on consecutive breath-holds demand a level of respiratory control that is often beyond the capability of patients with lung disease. The objectives of this investigation were to develop and evaluate a navigating technique for lung MRI that does not rely on patient cooperation. Navigating techniques were implemented at 0.5 T using conventional imaging techniques of short echo-time and imaging during normal breathing in the diastolic phase of the cardiac cycle. A column of spins, orthogonal to the diaphragm, was excited both immediately before and after the imaging segment. These signals were processed in real time to provide the position of the lung-diaphragm interface. An imaging segment was considered correctly acquired only when the interface position was within the acceptance window both before and after the acquisition of the segment. A distribution of lung-diaphragm interface positions obtained during normal respiration was employed to define the acceptance window. In the case of multislice techniques, the position of the lung-diaphragm interface immediately before the imaging segment was also employed to decide which phase-encoding step to acquire next, therefore reducting the apparent frequency of the respiratory motion. A distribution of interface position, updated in real time, served as a reference for the allocation of phase-encoding steps according to diaphragm position. The lung images obtained represent a significant advance in image quality, improving further the ability of MR to detect and monitor pulmonary disease. Motion artifacts were reduced, and images reliably demonstrated smaller vessels, which are not normally visible without navigation.