Minimal-invasive magnetic heating of tumors does not alter intra-tumoral nanoparticle accumulation, allowing for repeated therapy sessions: an in vivo study in mice.

Localized magnetic heating treatments (hyperthermia, thermal ablation) using superparamagnetic iron oxide nanoparticles (MNPs) continue to be an active area of cancer research. For generating the appropriate heat to sufficiently target cell destruction, adequate MNP concentrations need to be accumulated into tumors. Furthermore, the knowledge of MNP bio-distribution after application and additionally after heating is significant, firstly because of the possibility of repeated heating treatments if MNPs remain at the target region and secondly to study potential adverse effects dealing with MNP dilution from the target region over time. In this context, little is known about the behavior of MNPs after intra-tumoral application and magnetic heating. Therefore, the present in vivo study on the bio-distribution of intra-tumorally injected MNPs in mice focused on MNP long term monitoring of pre and post therapy over seven days using multi-channel magnetorelaxometry (MRX). Subsequently, single-channel MRX was adopted to study the bio-distribution of MNPs in internal organs and tumors of sacrificed animals. We found no distinct change of total MNP amounts in vivo during long term monitoring. Most of the MNP amounts remained in the tumors; only a few MNPs were detected in liver and spleen and less than 1% of totally injected MNPs were excreted. Apparently, the application of magnetic heating and the induction of apoptosis did not affect MNP accumulation. Our results indicate that MNP mainly remained within the injection side after magnetic heating over a seven-days-observation and therefore not affecting healthy tissue. As a consequence, localized magnetic heating therapy of tumors might be applied periodically for a better therapeutic outcome.

Evaluation of the early phase of Bell's palsy using 3 T MRI.

This prospective study on Bell's palsy investigated the value of 3 T MRI as a diagnostic tool to evaluate pathophysiological changes (i.e. edema) of facial nerve segments and the possibility to differentiate patients with high risk for incomplete recovery from patients who recover completely within 3 days after symptoms onset. For this institutional review board approved investigation, thirty patients (14 male, 16 female, mean age 44 years) with Bell's palsy underwent pre and postcontrast 3 T MRI of the cerebellopontine angle. T1-weighted imaging was performed (TR 20.0 ms, TE 2.46 ms, isotropic voxel size: 0.6 mm). Region-of-interest measurements were performed on the healthy and paralyzed side. To obtain normalized values, signal intensity increase percentage (SIIP) values were divided by contralateral results of the healthy side. Signal intensity measurements of examined nerve segments were compared using Wilcoxon and Mann-Whitney U tests and correlated to clinical findings categorized by the House-Brackmann score. The lesion side showed significantly higher signal intensities in the premeatal segment before and after contrast agent administration (P < 0.001). SIIP was highest in the premeatal segment compared to the geniculate ganglion (P < 0.001). Correlation analyses revealed no association between signal intensity measurements, clinical findings or early recovery rates after 3 months (P > 0.05). According to our results, early palsy-associated pathophysiological changes in the facial nerve premeatal segment might also be related to accumulation of proteins and not exclusively to edema. However, contrast agent enhancement quantification was not suitable as a diagnostic tool to distinguish different prognostic groups.

Sensitivity and specificity of unilateral edema on T2w-TSE sequences in MR-Mammography considering 974 histologically verified lesions.

The objective of this investigation was to determine the diagnostic value of unilateral edema in differentiating benign from malignant breast disease on T2w-TSE images in MR-Mammography (MRM). All patients from a 10-year period undergoing surgery in the same institution after having received MRM in our department were included in this prospective analysis of previous acquired examinations. To eliminate bias caused by prior procedures, all patients having had biopsy, operation, radiation therapy, or chemotherapy before MRM were excluded. T2w-TSE images were acquired after a dynamic contrast-enhanced series of T1-weighted images in a standardized examination protocol (1.5 T). Edema was defined as a high-signal intensity on T2w-TSE images and it was categorized as absent, perifocal, or diffuse. Examinations were rated by two experienced observers blinded to all procedures and results following MRM. In cases of disconcordance, the opinion of a third radiologist decided. Statistical testing included Pearson's Chi-squared test and Fisher's exact testing. A total of 1,010 patients with a mean age of 55 years (SD: 11.6 years, range: 16-87 years) with 1,129 histologically verified lesions were included in this investigation. After removing all patients with prior procedures from the patient collective, 974 lesions were left for statistical analysis. Perifocal edema was highly significantly (p < 0.001) associated with malignant disease, leading to a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 33.5%, 93.9%, 89.6, and 57.1%, respectively. Unilateral edema in general showed the following diagnostic parameters: sensitivity 53.0%, specificity 80.5%, PPV 80.9%, and NPV 52.3%. Edema seems to be associated with malignancy in the majority of cases. Especially, specificity and PPV were found to be high. These findings may be helpful in diagnostic decisions on otherwise equivocal cases.

Improvement of visualization of the intermediofacial nerve in the temporal bone using 3T magnetic resonance imaging: part 1: the facial nerve.

PURPOSE: This study examines the identifiability of the intratemporal motor facial nerve using 3-T and 1.5-T magnetic resonance imaging (MRI). METHODS: Twenty subjects underwent T1- and T2-weighted MRI of the temporal bone. Acquisition was performed using a head coil at 3 and 1.5 T as well as a surface coil at 3 T. Layer thicknesses were 0.6 mm for 3-T and 0.8 mm for 1.5-T MRI. Eight topodiagnostically relevant facial nerve and branch structures were statistically evaluated. RESULTS: The main trunk could be identified in all examinations. Sequences acquired with a head coil at 3 T yielded statistically significant superiority (P < 0.001) over 3-T surface coil and 1.5-T head coil measurements. The precise identifiability of the smallest structures (eg, stapedial nerve) succeeded best by means of T1-weighted 3-T MRI. CONCLUSIONS: Due to the precise identifiability of the smallest branches, 3-T MRI improves diagnostics particularly with regard to preoperative planning.

Lesion type and reader experience affect the diagnostic accuracy of breast MRI: a multiple reader ROC study.

PURPOSE: To evaluate the influence of lesion type (mass versus non-mass) and reader experience on the diagnostic performance of breast MRI (BMRI) in a non-screening setting. MATERIALS AND METHODS: Consecutive patients (mean age, 55 ± 12 years) with breast lesions that were verified by biopsy or surgery, and who had had BMRI as part of their diagnostic workup, were eligible for this retrospective single-center study. Cancers diagnosed by biopsy before BMRI were excluded to eliminate biological and interpretation bias due to biopsy or chemotherapy effects (n=103). Six blinded readers (experience level, high (HE, n=2); intermediate (IE, n=2); and low (LE, n=2)) evaluated all examinations and assigned independent MRI BI-RADS ratings. Lesion type (mass, non-mass, focal) was noted. Receiver operating characteristics (ROC) and logistic regression analysis was performed to compare diagnostic accuracies. RESULTS: There were 259 histologically verified lesions (123 malignant, 136 benign) investigated. There were 169 mass (103 malignant, 66 benign) and 48 non-mass lesions (19 malignant, 29 benign). Another 42 lesions that met the inclusion criteria were biopsied due to conventional findings (i.e., microcalcifications, architectural distortions), but did not enhance on MRI (41 benign, one DCIS). ROC analysis revealed a total area under the curve (AUC) between 0.834 (LE) and 0.935 (HI). Logistic regression identified a significant effect of non-mass lesions (P<0.0001) and reader experience (P=0.005) on diagnostic performance. CONCLUSIONS: Non-mass lesion type and low reader experience negatively affect the diagnostic performance of breast MRI in a non-screening setting.

Phonological processing in dyslexic children: a study combining functional imaging and event related potentials.

Difficulties in phonological processing are currently considered one of the major causes for dyslexia. Nine dyslexic children and eight control children were investigated using functional magnetic resonance imaging (fMRI) during non-oral reading of German words. All subjects silently read words and pronounceable non-words in an event related potentials (ERP) investigation, as well. The fMRI showed a significant difference in the activation in the left inferior frontal gyrus between the dyslexic and control groups, resulting from a hyperactivation in the dyslexics. The ERP scalp distribution showed a significant distinction between the two groups concerning the topographic difference for left frontal electrodes in a time window 250-600 ms after stimulus onset for non-word reading. Both the fMRI and the ERP results support differences in phonological processing between dyslexic and normal-reading children.

Assessment of rat antigen-induced arthritis and its suppression during glucocorticoid therapy by use of hemicyanine dye probes with different molecular weight in near-infrared fluorescence optical imaging.

PURPOSE: Arthritic joints are ideal disease entities to be assessed via optical imaging. Here, we investigated the selective accumulation behavior of two differently sized hemicyanine optical probes in arthritic joints and its modification during glucocorticoid therapy in the course of inflammation. MATERIALS AND METHODS: The well-standardized preclinical antigen-induced arthritis (AIA) model in rats was used. The animals were divided into 3 groups: arthritic, arthritic and dexamethasone-treated, and immunized only. After intravenous coinjection of DY-752 (size, 800 Da) and DY-682-(rat) IgG (size, 150 kDa) probes, spectrally unmixed near-infrared fluorescence images were acquired and analyzed semiquantitatively. Probe organ distribution, joint swelling, blood cell counts, joint vessel density, and histological scoring of arthritis were determined. RESULTS: The local joint accumulation kinetics of the DY-752 probe differed from the DY-682-IgG one. In the course of AIA, probe signaling in arthritic joints was similar between each other. Joint swelling and histological scoring were in accordance with signaling. Dexamethasone treatment of rats with AIA significantly reduced both the near-infrared fluorescence signals and severity of arthritis but did not change the joint vascular density or the uptake of the probes by phagocytes. A differential biodistribution of both probes was encountered, but such an accumulation was prevented by dexamethasone treatment. CONCLUSIONS: Near-infrared fluorescence signaling in the course of AIA closely reflects the pathophysiological events of the arthritic joint and the effects of therapy independently of the molecular size of the probe. The results show the suitability of our hemicyanine probes for imaging of arthritis.

Can we accurately quantify nanoparticle associated proteins when constructing high-affinity MRI molecular imaging probes?

Targeted magnetic resonance contrast agents (e.g. iron oxide nanoparticles) have the potential to become highly selective imaging tools. In this context, quantification of the coupled amount of protein is essential for the design of antibody- or antibody fragment-conjugated nanoparticles. Nevertheless, the presence of magnetic iron oxide nanoparticles is still an unsolved problem for this task. The aim of the present work was to clarify whether proteins can be reliably quantified directly in the presence of magnetic iron oxide nanoparticles without the use of fluorescence or radioactivity. Protein quantification via Bradford was not influenced by the presence of magnetic iron oxide nanoparticles (0-17.2 mmol Fe l(-1) ). Instead, bicinchoninic acid based assay was, indeed, distinctly affected by the presence of nanoparticle-iron in suspension (0.1-17.2 mmol Fe l(-1) ), although the influence was linear. This observation allowed for adequate mathematical corrections with known iron content of a given nanoparticle. The applicability of our approach was demonstrated by the determination of bovine serum albumin (BSA) content coupled to dextrane-coated magnetic nanoparticles, which was found with the QuantiPro Bicinchoninic acid assay to be of 1.5 ± 0.2 µg BSA per 1 mg nanoparticle. Both Bradford and bicinchoninic acid assay protein assays allow for direct quantification of proteins in the presence of iron oxide containing magnetic nanoparticles, without the need for the introduction of radioactivity or fluorescence modules. Thus in future it should be possible to make more precise estimations about the coupled protein amount in high-affinity targeted MRI probes for the identification of specific molecules in living organisms, an aspect which is lacking in corresponding works published so far. Additionally, the present protein coupling procedures can be drastically improved by our proposed protein quantification method.

Reproducibility and repeatability of volumetric measurements for olfactory bulb volumetry: which method is appropriate? An update using 3 Tesla MRI.

RATIONALE AND OBJECTIVES: The aim of this study was to compare different sequences for olfactory bulb volumetry using 3-T magnetic resonance imaging, evaluating reproducibility, repeatability, and systematic biases. MATERIALS AND METHODS: Twenty-two volunteers underwent 3-T magnetic resonance imaging of the frontal skull base in this prospective study. Imaging included constructive interference in steady state (CISS), T2-weighted (T2w) three-dimensional (3D) sampling perfection with application-optimized contrasts using different flip-angle evolutions, and T2w two-dimensional (2D) turbo spin-echo sequences. Two observers independently performed two olfactory bulb volumetric studies per bulb and sequence. Intraobserver and interobserver reliability was assessed using intraclass correlation coefficients. For the evaluation of reproducibility, concordance correlation coefficients were determined, and for repeatability and systematic biases, Bland-Altman plots were analyzed. RESULTS: Intraclass correlation coefficient analysis of the specialized observer yielded almost perfect results for intraobserver reliability (0.94, 0.85, and 0.93 for the CISS, T2w 3D, and T2w 2D sequences, respectively). For the less experienced observer, the results were 0.86 0.78, and 0.74 for the CISS, T2w 3D, and T2w 2D sequences, respectively. Interobserver reliability showed almost perfect agreement for all sequences (0.92, 0.86, and 0.86, respectively). The CISS sequence yielded the highest concordance correlation coefficient (0.84), precision (0.85), and accuracy (0.99). Bland-Altman plot analyses revealed the lowest repeatability coefficients for the T2w 2D sequence. Volumetric measurements of T2w 2D imaging showed systematically lower volumetric results compared to the CISS sequence (-22.7%) and the T2w 3D sequence (-8.3%). CONCLUSIONS: Comparison of three imaging sequences for olfactory bulb volumetry yielded the best values for the CISS sequence in terms of intraobserver and interobserver reliability, reproducibility, accuracy, and precision. Given that even less experienced observers achieve almost perfect results, the CISS sequence is recommended for olfactory bulb volumetry.

Visual grading characteristics (VGC) analysis of diagnostic image quality for high resolution 3 Tesla MRI volumetry of the olfactory bulb.

RATIONALE AND OBJECTIVES: The aim of this study was to evaluate the suitability of 3-T magnetic resonance imaging (MRI) for olfactory bulb volumetry, comparing image quality obtained using different sequences on the basis of physical characteristics in combination with observer performance. MATERIALS AND METHODS: Twenty-two healthy volunteers (11 men, 11 women; mean age, 25 years) underwent 3-T MRI of the frontal skull base in this prospective study. Imaging was performed using a constructive interference in steady state (CISS) three-dimensional Fourier transformation sequence, a three-dimensional T2-weighted (3D-T2w) sequence, and a two-dimensional T2-weighted (2D-T2w) sequence. The relative performance of sequences was assessed using visual grading characteristic analysis. Interobserver agreement was assessed using κ statistics. For evaluation of physical image quality characteristics, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared using Wilcoxon's test. SNR and CNR measurements were correlated with visual grading results. RESULTS: Visual grading characteristic analysis showed significantly better image quality ratings for the CISS sequence compared to the 3D-T2w and 2D-T2w sequence, and the 2D-T2w sequence performed significantly better compared to the 3D-T2w sequence (P < .001). Interobserver agreement was substantial (κ = 0.66-0.73). Wilcoxon's test revealed significantly higher SNR and CNR values for the 2D-T2w sequence compared to the 3D-T2w and CISS sequences, and SNR and CNR values for the 3D-T2w sequence were significantly higher compared to those for the CISS sequence (P < .001 for each). Significant correlation between SNR and CNR and visual grading was found for the 3D-T2w sequence (SNR: ρ = 0.510, P = .015; CNR: ρ = 0.546, P = .009). CONCLUSIONS: High-resolution 3-T MRI resulted in excellent values for SNR and CNR, suggesting the appropriateness of the sequences for olfactory bulb MRI volumetry. Visual grading characteristic analysis revealed the CISS sequence to be the most suitable for olfactory bulb volumetry.

In vitro comparison of water displacement method and 3 Tesla MRI for MR-volumetry of the olfactory bulb: which sequence is appropriate?

RATIONALE AND OBJECTIVES: Magnetic resonance imaging olfactory bulb (OB) volumetry (OBV) is already used as a complementary prognostic tool to assess olfactory disorders. However, a reference standard in imaging for OBV has not been established. The aim of this in vitro study was to compare volumetric results of different magnetic resonance sequences for OBV at 3 T to genuine OB volumes measured by water displacement. MATERIALS AND METHODS: The volumes of 15 human cadaveric OBs were measured using the water displacement method in this institutional review board-approved prospective study. The magnetic resonance imaging protocol at 3 T included constructive interference in steady state (CISS), T2-weighted (T2w) three-dimensional (3D) sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE), T2w two-dimensional (2D) turbo spin-echo (TSE), and T1-weighted (T1w) 3D fast low-angle shot (FLASH) sequences. Two blinded observers independently performed two OB volumetric assessments per bulbus and sequence. Intraobserver and interobserver reliabilities were assessed by intraclass correlation coefficients. Bland-Altman plots were analyzed to evaluate systematic biases and concordance correlation coefficients to assess reproducibility. RESULTS: For both observers, intraclass correlation coefficient analysis yielded almost perfect results for intraobserver reliability (CISS, 0.94-0.98; T2w 3D SPACE, 0.93-0.98; T2w 2D TSE, 0.98-0.98; T1w 3D FLASH, 0.95-0.99). Interobserver reliability showed almost perfect agreement for all sequences (CISS, 0.98; T2w 3D SPACE, 0.89; T2w 2D TSE, 0.93; T1w 3D FLASH, 0.97). The CISS sequence yielded the highest mean concordance correlation coefficient (0.95) and the highest combination of precision (0.97) and accuracy (0.98) values. In comparison with the water displacement method, Bland-Altman analyses revealed the lowest systematic bias (-0.5%) for the CISS sequence, followed by T1w 3D FLASH (-1.3%), T2w 3D SPACE (-7.5%), and T2w 2D TSE (-10.9%) sequences. CONCLUSIONS: Compared to the water displacement method, the CISS sequence is suited best to validly and reliably measure OB volumes because of its highest values for accuracy and precision and lowest systematic bias.

Detection of multiple intracranial hemorrhages in a child with acute lymphocytic leukemia (ALL) by susceptibility weighted imaging (SWI).

Susceptibility weighted imaging (SWI) combines magnitude and phase information from a high-resolution, fully velocity compensated, three-dimensional (3D) gradient echo sequence. We report on the use of this MRI technique in a young patient with acute lymphocytic leukemia (ALL) and demonstrate a higher detection rate of hemorrhagic lesion in comparison with other T2*-weighted sequences.

Assessment of DNA damage in target tumor cells after thermoablation in mice.

PURPOSE: To determine the effects of temperature on cell death for cells in culture and to compare these effects with the results of in vivo experiments in which heating is induced in mice with implanted human adenocarcinoma by using magnetic methods. MATERIALS AND METHODS: Experimentation was approved by the regional animal care committee. Human adenocarcinoma cells (MX-1) and human fibroblasts (HTB-125) were exposed to defined temperatures of 45 degrees -90 degrees C for 4 minutes. Single- and double-strand DNA breaks (expressed as a percentage of the total DNA in tail) were identified by using the alkaline comet assay, and cell survival was determined by using the cloning assay and trypan blue exclusion. For in vivo experiments, MX-1 tumors were implanted into 14 mice. Magnetic heating at temperatures of 59 degrees -96 degrees C was subsequently performed by injecting magnetic material into the tumor (7 mg +/- 3 [+/- standard deviation] magnetite per tumor) and applying an alternating magnetic field (8.8 kA/m; 400 kHz) for 4 minutes. The efficiency of the temperature-dependent induction of DNA damage in isolated tumor cells was quantified and compared with that in cultured cells. RESULTS: Results of experiments with cell cultures revealed a strong correlation between DNA damage, cell survival, and temperature, as determined with the cloning assay and trypan blue exclusion. The threshold thermoablasive temperature for tumor cell elimination was found to be 55 degrees-60 degrees C. Moreover, a strong impairment in cell survival was found when damaged DNA accounted for more than 50% of the total DNA. The heating sensitivities of malignant and nonmalignant cells did not differ. After the magnetic heating of tumors in vivo to temperatures of up to 96 degrees C (rectal temperatures between 27 degrees C +/- 2 and 29 degrees C +/- 2), isolated tumor cells showed a mean of 71.9% +/- 24.5 of total DNA in the tail per cell compared with nontreated tumors, which showed 8.0% +/- 3.1. CONCLUSION: There appears to be a threshold temperature for the induction of irreversible DNA damage. This is reflected by the results of in vivo experiments in tumor-bearing mice after high temperatures were applied to tumors by using magnetic heating.