Werner A. Kaiser

Magnetic resonance imaging of the breast: Recommendations from the EUSOMA working group

The use of breast magnetic resonance imaging (MRI) is rapidly increasing. EUSOMA organised a workshop in Milan on 20-21st October 2008 to evaluate the evidence currently available on clinical value and indications for breast MRI. Twenty-three experts from the disciplines involved in breast disease management - including epidemiologists, geneticists, oncologists, radiologists, radiation oncologists, and surgeons - discussed the evidence for the use of this technology in plenary and focused sessions. This paper presents the consensus reached by this working group. General recommendations, technical requirements, methodology, and interpretation were firstly considered. For the following ten indications, an overview of the evidence, a list of recommendations, and a number of research issues were defined: staging before treatment planning; screening of high-risk women; evaluation of response to neoadjuvant chemotherapy; patients with breast augmentation or reconstruction; occult primary breast cancer; breast cancer recurrence; nipple discharge; characterisation of equivocal findings at conventional imaging; inflammatory breast cancer; and male breast. The working group strongly suggests that all breast cancer specialists cooperate for an optimal clinical use of this emerging technology and for future research, focusing on patient outcome as primary end-point.

Physical limits of hyperthermia using magnetite fine particles

Structural and magnetic properties of fine particles of magnetite are investigated with respect to the application for hyperthermia. Magnetic hysteresis losses are measured in dependence on the field amplitude for selected commercial powders and are discussed in terms of grain size and structure of the particles. For ferromagnetic powders as well as for ferrofluids, results of heating experiments within organic gels in a magnetic high frequency field are reported. The heating effect depends strongly on the magnetic properties of the magnetite particles which may vary appreciably for different samples in dependence on the particle size and microstructure. In particular, the transition from ferromagnetic to superparamagnetic behavior causes changes of the loss mechanism, and accordingly, of the heating effect. The maximum attainable heating effect is discussed in terms of common theoretical models. Rise of temperature at the surface of a small heated sample as well as in its immediate neighborhood in the surrounding medium is measured in dependence on time and is compared with solutions of the corresponding heat conductivity problem. Conclusions with respect to clinical applications are given.

Application of magnetite ferrofluids for hyperthermia

A comparative study is presented for the specific loss power generated by an external magnetic field in superparamagnetic as well as ferromagnetic magnetite particles suspended in molten and solidified gel. The field amplitude dependence of magnetic losses obeys power laws of third order for ferromagnetic samples and second order for superparamagnetic samples, respectively. Calorimetrically determined data are compared with results of hysteresis measurements. Consequences for the application for hyperthermia are discussed.

Development, standardization, and testing of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging studies

The purpose of this study was to develop, standardize, and test reproducibility of a lexicon for reporting contrast‐enhanced breast magnetic resonance imaging (MRI) examinations. To standardize breast MRI lesion description and reporting, seven radiologists with extensive breast MRI experience developed consensus on technical detail, clinical history, and terminology reporting to describe kinetic and architectural features of lesions detected on contrast‐enhanced breast MR images. This lexicon adapted American College of Radiology Breast Imaging and Data Reporting System terminology for breast MRI reporting, including recommendations for reporting clinical history, technical parameters for breast MRI, descriptions for general breast composition, morphologic and kinetic characteristics of mass lesions or regions of abnormal enhancement, and overall impression and management recommendations. To test morphology reproducibility, seven radiologists assessed morphology characteristics of 85 contrast‐enhanced breast MRI studies. Data from each independent reader were used to compute weighted and unweighted kappa (κ) statistics for interobserver agreement among readers. The MR lexicon differentiates two lesion types, mass and non‐mass‐like enhancement based on morphology and geographical distribution, with descriptors of shape, margin, and internal enhancement. Lexicon testing showed substantial agreement for breast density (κ = 0.63) and moderate agreement for lesion type (κ = 0.57), mass margins (κ = 0.55), and mass shape (κ = 0.42). Agreement was fair for internal enhancement characteristics. Unweighted kappa statistics showed highest agreement for the terms dense in the breast composition category, mass in lesion type, spiculated and smooth in mass margins, irregular in mass shape, and both dark septations and rim enhancement for internal enhancement characteristics within a mass. The newly developed breast MR lexicon demonstrated moderate interobserver agreement. While breast density and lesion type appear reproducible, other terms require further refinement and testing to lead to a uniform standard language and reporting system for breast MRI. J. Magn. Reson. Imaging 2001;13:889–895.

High-resolution MR venography at 3.0 Tesla.

Purpose The aim of this study was to investigate the visualization of small venous vessels in the normal human brain at a field strength of 3 Tesla. Methods T2*-weighted, three-dimensional gradient-echo images were acquired by exploiting the magnetic susceptibility difference between oxygenated and deoxygenated hemoglobin in the vasculature and microvasculature. The spatial resolution was 0.5 × 0.5 × 1 mm3, and sequence parameters were varied to obtain good vessel delineation. Improved visibility of venous vessels was obtained by creating phase mask images from the magnetic resonance phase images and multiplying these by the magnitude images. Venograms were created by performing a minimum intensity projection over targeted volumes. Results Highly detailed visualization of venous structures deep in the brain and in the superficial cortical areas were obtained without administration of an exogenous contrast agent; compared with similar studies performed at 1.5 T, the echo time could be reduced from typically 40–50 ms to 17–28 ms. Conclusion Imaging at high-field strength offers the possibility of improved resolution and the delineation of smaller vessels compared with lower field strengths.

Temperature distribution as function of time around a small spherical heat source of local magnetic hyperthermia

A spherical region containing magnetic particles embedded in extended muscle tissue is taken as model of small breast carcinomas. Using analytically derived equations the spatial temperature distribution is calculated as function of the time for exposing to an alternating magnetic field. In vitro measurements with muscle tissue yielded such an agreement with the calculations that treatment of small tumors in slightly vascularized tissues on the base of mathematical predictions seems now to be more promising than in the past.

Decreased frontal activation in schizophrenics during stimulation with the continuous performance test--a functional magnetic resonance imaging study.

Summary ‐ The Continuous Performance Test (CPT) has become an essential constituent of the neuropsychological investigation of schizophrenia. Also, a vast number of brain imaging studies, mostly PET investigations, have employed the CPT as a cognitive challenge and established a relative hypofrontality in schizophrenics compared to controls. The aim of the present investigation was to clarify whether this predescribed hypofrontality could also be verified using functional magnetic resonance imaging (fMRI). 20 healthy volunteers and 14 schizophrenics on stable neuroleptic medication were included. Imaging was performed using the CPT-double-T-version and a clinical 1.5 T MRI-scanner with a single slice technique and a T2*-weighted gradient-echo-sequence. The schizophrenics exhibited a decreased activation in the right mesial prefrontal cortex, the right cingulate and the left thalamus compared to controls. These results obtained by fMRI are discussed in relation to published findings using PET.

Brain activation during cognitive stimulation with the Wisconsin Card Sorting Test--a functional MRI study on healthy volunteers and schizophrenics.

It has been demonstrated by single photon emission computed tomography (SPECT) and positron emission tomography (PET) that frontal brain regions are stimulated during performance of the Wisconsin Card Sorting Test (WCST). The WCST is also regarded as one of the standard tests for the assessment of frontal activity in brain imaging studies of schizophrenia. In this study cerebral activation was assessed by means of functional magnetic resonance imaging (fMRI). In healthy volunteers WCST stimulation resulted in a right lateralized frontal activation. In 13 chronic schizophrenics on stable neuroleptic medication, a lack of activation in the right prefrontal cortex and--as a trend--an increased left temporal activity during execution of the WCST was noted compared to controls. Since a one-slice technique was used, no information about the activation pattern in adjacent brain regions was obtained. However, as fMRI possesses a superior spatial resolution compared to SPECT and PET, the anatomical localization of the activation effect in the measured slice can be defined more precisely. Beside these methodological considerations, the results are discussed in relation to prior findings of a reduced ability of schizophrenics to coordinate cerebral function.

Cardiac Involvement in Churg-strauss Syndrome: Impact of Endomyocarditis

Cardiac disease is a major contributor to disease-related death in Churg-Strauss syndrome (CSS). We conducted the current study to determine the prevalence and clinical impact of cardiac involvement in CSS patients. We performed a multicenter, cross-sectional analysis of patients diagnosed with CSS. Cardiac workup included electrocardiography, echocardiography, cardiac magnetic resonance imaging (MRI), and endomyocardial biopsy. We analyzed 49 patients with CSS: 22 patients had clinical evidence of cardiac involvement. A negative antineutrophil cytoplasmic antibodies (ANCA) test and much higher eosinophil counts (9947 vs. 3657/&mgr;L, respectively, p < 0.001) distinguished patients with cardiac involvement from those without. Impaired left ventricular function (50%), mild to severe valvular insufficiencies (73%), and pericardial effusions (41%) were common findings in these patients. Endomyocarditis was found in 13 patients (59%) as detected by cardiac MRI, cardiac thrombus formation, and endomyocardial biopsy, and was associated with impaired cardiac function. After a mean follow-up of 47 months, most patients had regained or maintained good cardiac function. However, patients with endomyocarditis had a more severe outcome. Two patients died (61 and 99 mo after diagnosis, respectively), both due to severe cardiomyopathy and heart failure. Cardiac involvement is common in patients with CSS and is associated with the absence of ANCA and high eosinophil counts. Endomyocarditis may represent the most severe manifestation eventually causing fatal outcome. A structured clinical assessment incorporating cardiac imaging with echocardiography and MRI can identify impaired cardiac function and endomyocardial abnormalities. Abbreviations: ANCA = antineutrophil cytoplasmic antibodies, CSS = Churg-Strauss syndrome, ECG = electrocardiography, FFS = Five Factor Score, IgE = immunoglobulin, LVEF = left ventricular ejection fraction, MRI = magnetic resonance imaging.

Heating potential of iron oxides for therapeutic purposes in interventional radiology.

RATIONALE AND OBJECTIVES In addition to their diagnostic applications, iron oxides could be used therapeutically to eliminate tumors with heat if their heating powers are adequate. The authors therefore examined the specific absorption rate (SAR) of different iron oxide (magnetite) samples suspended in water and in liquid or solidified gel. MATERIALS AND METHODS The authors compared two ferromagnetic fine powders (total particle size, >350 nm and 100 nm), five superparamagnetic ferrofluidic samples (total particle size, 10-280 nm), and a commercially available contrast medium (ferumoxides injectable solution, Endorem). The SARs of the magnetic material-suspended in distilled water or in liquid or solid agar-were estimated from time-dependent calorimetric measurements during exposure to an alternating current magnetic field (amplitude, 6.5 kA/m; frequency, 400 kHz). RESULTS SARs varied considerably between the different iron oxide samples. The highest value was found for a ferrofluidic sample (>93 W/g), while Endorem had little heating power (<0.1 W/g). The SAR was clearly dependent on the aggregation state of the matrix only for the large-particle-size ferromagnetic sample, yielding the highest values for particle suspensions in water (74 W/g) and lowest for solid agar (8 W/g). The heating power of the smaller-particle-size ferromagnetic sample did not exceed 8 W/g. CONCLUSION Heating powers differed according to the interaction of multiple physical parameters. Iron oxides should be selected carefully for therapeutic applications in magnetic heating.