Fluorescence molecular tomography of DiR-labeled mesenchymal stem cell implants for osteochondral defect repair in rabbit knees.

OBJECTIVES: To assess labelling efficiency of rabbit mesenchymal stem cells (MSCs) using the near-infrared dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR) and detection of labelled MSCs for osteochondral defect repair in a rabbit model using fluorescence molecular tomography-X-ray computed tomography (FMT-XCT). METHODS: MSCs were isolated from New Zealand White rabbits and labelled with DiR (1.25-20 µg/mL). Viability and induction of apoptosis were assessed by XTT- and Caspase-3/-7-testing. Chondrogenic potential was evaluated by measurement of glycosaminoglycans. Labelled cells and unlabeled controls (n = 3) underwent FMT-XCT imaging before and after chondrogenic differentiation. Osteochondral defects were created surgically in rabbit knees (n = 6). Unlabeled and labelled MSCs were implanted in fibrin-clots and imaged by FMT-XCT. Statistical analyses were performed using multiple regression models. RESULTS: DiR-labelling of MSCs resulted in a dose-dependent fluorescence signal on planar images in trans-illumination mode. No significant reduction in viability or induction of apoptosis was detected at concentrations below 10 µg DiR/mL (p > .05); the chondrogenic potential of MSCs was not affected (p > .05). FMT-XCT of labelled MSCs in osteochondral defects showed a significant signal of the transplant (p < .05) with additional high-resolution anatomical information about its osteochondral integration. CONCLUSIONS: FMT-XCT allows for detection of stem cell implantation within osteochondral regeneration processes. KEY POINTS: • DiR-labelling of MSCs shows no toxic side effects or impairment of chondrogenesis. • Fluorescence molecular tomography allows for detection of MSCs for osteochondral defect repair. • FMT-XCT helps to improve evaluation of cell implantation and osteochondral regeneration processes.

Magnetic resonance imaging of ferumoxide-labeled mesenchymal stem cells in cartilage defects: in vitro and in vivo investigations.

The purpose of this study was to (1) compare three different techniques for ferumoxide labeling of mesenchymal stem cells (MSCs), (2) evaluate if ferumoxide labeling allows in vivo tracking of matrix-associated stem cell implants (MASIs) in an animal model, and (3) compare the magnetic resonance imaging (MRI) characteristics of ferumoxide-labeled viable and apoptotic MSCs. MSCs labeled with ferumoxide by simple incubation, protamine transfection, or Lipofectin transfection were evaluated with MRI and histopathology. Ferumoxide-labeled and unlabeled viable and apoptotic MSCs in osteochondral defects of rat knee joints were evaluated over 12 weeks with MRI. Signal to noise ratios (SNRs) of viable and apoptotic labeled MASIs were tested for significant differences using t-tests. A simple incubation labeling protocol demonstrated the best compromise between significant magnetic resonance signal effects and preserved cell viability and potential for immediate clinical translation. Labeled viable and apoptotic MASIs did not show significant differences in SNR. Labeled viable but not apoptotic MSCs demonstrated an increasing area of T2 signal loss over time, which correlated to stem cell proliferation at the transplantation site. Histopathology confirmed successful engraftment of viable MSCs. The engraftment of iron oxide-labeled MASIs by simple incubation can be monitored over several weeks with MRI. Viable and apoptotic MASIs can be distinguished via imaging signs of cell proliferation at the transplantation site.

Depicting adoptive immunotherapy for prostate cancer in an animal model with magnetic resonance imaging.

Genetically modified natural killer (NK) cells that recognize tumor-associated surface antigens have recently shown promise as a novel approach for cancer immunotherapy. To determine NK cell therapy response early, a real-time, noninvasive method to quantify NK cell homing to the tumor is desirable. The purpose of this study was to evaluate if MR imaging could provide a noninvasive, in vivo diagnosis of NK cell accumulation in epithelial cell adhesion molecule (EpCAM)-positive prostate cancers in a rat xenograft model. Genetically engineered NK-92-scFv(MOC31)-ζ cells, which express a chimeric antigen receptor specific to the tumor-associated EpCAM antigen, and nontargeted NK-92 cells were labeled with superparamagnetic particles of iron-oxides (SPIO) ferumoxides. Twelve athymic rats with implanted EpCAM positive DU145 prostate cancers received intravenous injections of 1.5×10(7) SPIO labeled NK-92 and NK-92-scFv(MOC31)-ζ cells. EpCAM-positive prostate cancers demonstrated a progressive and a significant decline in contrast-to-noise-ratio data at 1 and 24 h after injection of SPIO-labeled NK-92-scFv(MOC31)-ζ cells. Conversely, tumor contrast-to-noise-ratio data did not change significantly after injection of SPIO-labeled parental NK-92 cells. Histopathology confirmed an accumulation of the genetically engineered NK-92-scFv(MOC31)-ζ cells in prostate cancers. Thus, the presence or absence of a tumor accumulation of therapeutic NK cells can be monitored with cellular MR imaging. EpCAM-directed, SPIO labeled NK-92-scFv(MOC31)-ζ cells accumulate in EpCAM-positive prostate cancers.

Labeling human embryonic stem-cell-derived cardiomyocytes for tracking with MR imaging.

BACKGROUND: Human embryonic stem cells (hESC) can generate cardiomyocytes (CM), which offer promising treatments for cardiomyopathies in children. However, challenges for clinical translation result from loss of transplanted cell from target sites and high cell death. An imaging technique that noninvasively and repetitively monitors transplanted hESC-CM could guide improvements in transplantation techniques and advance therapies. OBJECTIVE: To develop a clinically applicable labeling technique for hESC-CM with FDA-approved superparamagnetic iron oxide nanoparticles (SPIO) by examining labeling before and after CM differentiation. MATERIALS AND METHODS: Triplicates of hESC were labeled by simple incubation with 50 µg/ml of ferumoxides before or after differentiation into CM, then imaged on a 7T MR scanner using a T2-weighted multi-echo spin-echo sequence. Viability, iron uptake and T2-relaxation times were compared between groups using t-tests. RESULTS: hESC-CM labeled before differentiation demonstrated significant MR effects, iron uptake and preserved function. hESC-CM labeled after differentiation showed no significant iron uptake or change in MR signal (P < 0.05). Morphology, differentiation and viability were consistent between experimental groups. CONCLUSION: hESC-CM should be labeled prior to CM differentiation to achieve a significant MR signal. This technique permits monitoring delivery and engraftment of hESC-CM for potential advancements of stem cell-based therapies in the reconstitution of damaged myocardium.

MRI DTI and PDFF as Biomarkers for Lower Motor Neuron Degeneration in ALS.

OBJECTIVE: To evaluate the utility of nerve magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and muscle MRI multi-echo Dixon for assessing lower motor neuron (LMN) degeneration in amyotrophic lateral sclerosis (ALS). METHODS: In this prospective observational cohort study, 14 patients with ALS and 13 healthy controls underwent a multiparametric MRI protocol, including DTI of the sciatic nerve and assessment of muscle proton density fat fraction of the biceps femoris and the quadriceps femoris muscles by a multi-echo Dixon sequence. RESULTS: In ALS patients, mean fractional anisotropy values of the sciatic nerve were significantly lower than those of healthy controls. The quadriceps femoris, but not the biceps femoris muscle, showed significantly higher intramuscular fat fractions in ALS. INTERPRETATION: Our study provides evidence that multiparametric MRI protocols might help estimate structural nerve damage and neurogenic muscle changes in ALS.

In vivo magnetic resonance imaging and optical imaging comparison of viable and nonviable mesenchymal stem cells with a bifunctional label.

The purpose of this study was to compare viable and nonviable bilabeled mesenchymal stem cells (MSCs) in arthritic joints with magnetic resonance imaging (MRI) and optical imaging (OI). MSCs were labeled with ferucarbotran and DiD. MRI and OI of bilabeled cells were compared with controls. Six rats with arthritis received intra-articular injections of bilabeled viable MSCs into the right knee and nonviable MSCs into the left knee. Animals underwent MRI and OI preinjection and at 4, 24, 48, and 72 hours postinjection. The results were analyzed with a mixed random effects model and Fisher probability. Bilabeled MSCs showed increased MRI and OI signals compared to unlabeled controls (p < .0001). After intra-articular injection, bilabeled MSCs caused significant T2 and T2* effect on MRI and fluorescence on OI up to 72 hours postinjection (p < .05). There was no significant difference between viable and nonviable MSC signal in the knee joints; however, some of the viable cells migrated to an adjacent inflamed ankle joint (p < .05). Immunohistochemistry confirmed viable MSCs in right knee and ankle joints and nonviable MSCs in the left knee. Viable and nonviable cells could not be differentiated with MRI or OI signal intensity but were differentiated based on their ability to migrate in vivo.

Breast cancers: MR imaging of folate-receptor expression with the folate-specific nanoparticle P1133.

PURPOSE: To assess the capability of the folate receptor (FR)-targeted ultrasmall superparamagnetic iron oxide (USPIO) P1133 to provide FR-specific enhancement of breast cancers on magnetic resonance (MR) images. MATERIALS AND METHODS: This study was approved by the institutional Animal Care and Use Committee. The FR-targeted contrast agent P1133 was incubated with various FR-positive human breast cancer cell lines, with and without free folic acid (FFA) as a competitor. Labeling efficiencies were evaluated with MR imaging and inductively coupled plasma mass spectrometry. Subsequently, six athymic rats with implanted FR-positive MDA-MB-231 breast cancers underwent MR imaging at 3 T before and up to 1 hour and 24 hours after injection of P1133. Six athymic rats with implanted FR-positive MDA-MB-231 cancers injected with the non-FR-targeted USPIO P904 and nine athymic rats with implanted FR-negative A549 lung cancers injected with P1133 (n = 6) or P904 (n = 3) served as controls. Data of the in vitro studies were compared for significant differences with the Wilcoxon test for two independent samples. Tumor signal-to-noise-ratios (SNRs) were compared between different experimental groups by using the Kruskal-Wallis test and were correlated with histopathologic findings. Differences with P < .05 were considered significant. RESULTS: FR-positive breast cancer cells showed a significant P1133 uptake which was inhibited by FFA. MDA-MB-231 cells showed the highest level of P1133 uptake and the strongest T2 effect on MR images. In vivo, all tumors showed an initial perfusion effect. At 24 hours after injection, only MDA-MB-231 tumors injected with P1133 showed significantly decreased SNR data compared with baseline data (P < .05). MR findings were confirmed by using histopathologic findings. CONCLUSION: The FR-targeted USPIO P1133 demonstrates a specific retention in FR-positive breast cancers. Because FR expression correlates with tumor aggressiveness and prognosis, persistent P1133 tumor enhancement may be used as a noninvasive indicator for tumors with poor outcome.

Bifunctional Labeling of Rabbit Mesenchymal Stem Cells for MR Imaging and Fluorescence Microscopy.

PURPOSE: Longitudinal imaging studies are important in the translational process of stem cell-based therapies. Small animal imaging models are widely available and practical but insufficiently depict important morphologic detail. In contrary, large animal models are logistically challenging and costly but offer greater imaging quality. In order to combine the advantages of both, we developed an intermediate-sized rabbit animal model for cartilage imaging studies. PROCEDURES: Rabbit mesenchymal stem cells (rMSC) were isolated as primary cultures from the bone marrow of New Zealand white rabbits. rMSC were subsequentially transduced lentivirally with eGFP and magnetically labeled with the iron oxide ferucarbotran. eGFP expression was evaluated by flow cytometry and iron uptake was analyzed by isotope dilution mass spectrometry and Prussian blue staining. Fluorescence microscopy of eGFP-transduced rMSC was performed. Viability and induction of apoptosis were assessed by XTT and caspase-3/-7 measurements. The chondrogenic potential of labeled cells was quantified by glycosaminoglycan contents in TGF-ß3 induced pellet cultures. Labeled and unlabeled cells underwent magnetic resonance imaging (MRI) at 1.5 T before and after differentiation using T1-, T2-, and T2*-weighted pulse sequences. Relaxation rates were calculated. rMSCs were implanted in fibrin clots in osteochondral defects of cadaveric rabbit knees and imaged by 7 T MRI. T2* maps were calculated. Statistical analyses were performed using multiple regression models. RESULTS: Efficiency of lentiviral transduction was greater than 90 %. Fluorescence signal was dose dependent. Cellular iron uptake was significant for all concentrations (p < 0.05) and dose dependent (3.3-56.5 pg Fe/cell). Labeled rMSC showed a strong, dose-dependent contrast on all MR pulse sequences and a significant decrease in T2 and T2* relaxation rates. Compared with non-transduced or unlabeled controls, there were no adverse effects on cell viability, rate of apoptosis, or chondrogenic differentiation. MRI of labeled rMSCs in osteochondral defects showed a significant signal of the transplant with additional high-resolution anatomical information. CONCLUSIONS: This intermediate-sized rabbit model and its bifunctional labeling technique allow for improved depiction of anatomic detail for noninvasive in vivo rMSC tracking with MRI and for immunohistological correlation by fluorescence microscopy.

Relaxation effects of ferucarbotran-labeled mesenchymal stem cells at 1.5T and 3T: discrimination of viable from lysed cells.

Human mesenchymal stem cells (hMSCs) were labeled with Ferucarbotran by simple incubation and cultured for up to 14 d. Iron content was determined by spectrometry and the intracellular localization of the contrast agent uptake was studied by electron and confocal microscopy. At various time points after labeling, ranging from 1 to 14 d, samples with viable or lysed labeled hMSCs, as well as nonlabeled controls, underwent MRI. Spin-echo (SE) and gradient-echo (GE) sequences with multiple TRs and TEs were used at 1.5T and 3T on a clinical scanner. Spectrometry showed an initial iron oxide uptake of 7.08 pg per cell. Microscopy studies revealed lysosomal compartmentalization. Contrast agent effects of hMSCs were persistent for up to 14 d after labeling. A marked difference in the T(2) effect of compartmentalized iron oxides compared to free iron oxides was found on T(2)-weighted sequences, but not on T(2)*-weighted sequences. The observed differences may be explained by the loss of compartmentalization of iron oxide particles, the uniformity of distribution, and the subsequent increase in dephasing of protons on SE images. These results show that viable cells with compartmentalized iron oxides may-in principle-be distinguished from lysed cells or released iron oxides.

An optical imaging method to monitor stem cell migration in a model of immune-mediated arthritis.

The objective of this work is to establish an optical imaging technique that would enable monitoring of the integration of mesenchymal stem cells (MSC) in arthritic joints. Our approach is based on first developing a labeling technique of MSC with the fluorescent dye DiD followed by tracking the cell migration kinetics from the spatial distribution of the DiD fluorescence in optical images (OI). The experimental approach involves first the in vitro OI of MSC labeled with DiD accompanied by fluorescence microscopy measurements to establish localization of the signal within the cells. Thereafter, DiD-labeled MSC were injected into polyarthritic, athymic rats and the signal localization within the experimental animals was monitored over several days. The experimental results indicate that DiD integrated into the cell membrane. DiD-labeled MSC localization in the arthritic ankle joints was observed with OI indicating that this method can be applied to monitor MSC in arthritic joints.

Decreased aortic growth and middle aortic syndrome in patients with neuroblastoma after radiation therapy.

BACKGROUND: Long-term CT follow-up studies are required in pediatric patients who have received intraoperative radiation therapy (IORT) and external beam radiation therapy (EBRT) to assess vascular toxicities and to determine the exact complication rate. OBJECTIVE: To analyze with CT the effects of radiation therapy (RT) on the growth of the aorta in neuroblastoma patients. MATERIALS AND METHODS: Abdominal CT scans of 31 patients with intraabdominal neuroblastoma (stage II-IV), treated with RT (20 IORT+/-EBRT, 11 EBRT alone), were analyzed retrospectively. The diameter of the abdominal aorta was measured before and after RT. These data were compared to normal and predicted normal aortic diameters of children, according to the model of Fitzgerald, Donaldson and Poznanski (aortic diameter in centimeters = 0.844 + 0.0599 x age in years), and to the diameters of a control group of children who had not undergone RT. Statistical analyses for the primary aims were performed using the chi-squared test, t-test, Mann-Whitney test, nonparametric Wilcoxon matched-pairs test and analysis of variance for repeated measures. Clinical files and imaging studies were evaluated for signs of late vascular complications of neuroblastoma patients who had received RT. RESULTS: The mean diameter before and after RT and the growth of the aorta were significantly lower than expected in patients with neuroblastoma (P<0.05 for each) and when compared to the growth in a control group with normal and nonirradiated aortas. Among the patients who had received RT, there was no difference due to the type of RT. Seven patients from the IORT+/-EBRT group developed vascular complications, which included hypertension (five), middle aortic syndrome (two), death due to mesenteric ischemia (one) and critical aortic stenosis, which required aortic bypass surgery (two). CONCLUSION: Patients with neuroblastoma who had received RT showed impaired growth of the abdominal aorta. Significant long-term vascular complications occurred in seven patients who received IORT+/-EBRT. Thus, CT evaluation of patients with neuroblastoma who receive RT should include not only reports of changes in tumor extension, but also documentation of perfusion, and the size and growth of the aorta and its branches over time.

MRI detects peripheral nerve and adjacent muscle pathology in non-systemic vasculitic neuropathy (NSVN).

BACKGROUND: Diagnosis and disease monitoring of non-systemic vasculitic neuropathy (NSVN) are based on electrophysiological and clinical measures. However, these methods are insensitive to detect subtle differences of axonal injury. We here assessed the utility of a multiparametric MRI protocol to quantify axonal injury and neurogenic muscle damage in NSVN. METHODS: Ten NSVN patients and ten age-matched controls were investigated in this single-center prospective study. All participants were assessed by diffusion tensor imaging (DTI) of the tibial nerve and multiecho Dixon MRI of soleus and gastrocnemius muscles. These data were correlated with clinical and electrophysiological data. RESULTS: DTI scans of the tibial nerves of patients with NSVN showed significantly lower mean fractional anisotropy (FA) values (0.32 ± 0.02) compared to healthy controls (0.42 ± 0.01). FA values of NSVN patients correlated negatively with clinical measures of pain. Multiecho Dixon MRI scans revealed significantly higher intramuscular fat fractions in the soleus muscle (19.86 ± 6.18% vs. 5.86 ± 0.74%, p = 0.0015) and gastrocnemius muscle (26.09 ± 6.21% vs. 3.59 ± 0.82%, p = 0.0002) in NSVN patients compared to healthy controls. CONCLUSION: Our data provide a proof of concept that MRI can render information about nerve integrity and muscle pathology in NSVN. Further studies are warranted to evaluate DTI and multiecho Dixon MRI as surrogate markers in NSVN.

Detection of postoperative granulation tissue with an ICG-enhanced integrated OI-/X-ray System.

BACKGROUND: The development of postoperative granulation tissue is one of the main postoperative risks after lumbar spine surgery. This granulation tissue may lead to persistent or new clinical symptoms or complicate a follow up surgery. A sensitive non-invasive imaging technique, that could diagnose this granulation tissue at the bedside, would help to develop appropriate treatments. Thus, the purpose of this study was to establish a fast and economic imaging tool for the diagnosis of granulation tissue after lumbar spine surgery, using a new integrated Optical Imaging (OI)/X-ray imaging system and the FDA-approved fluorescent contrast agent Indocyanine Green (ICG). METHODS: 12 male Sprague Dawley rats underwent intervertebral disk surgery. Imaging of the operated lumbar spine was done with the integrated OI/X-ray system at 7 and 14 days after surgery. 6 rats served as non-operated controls. OI/X-ray scans of all rats were acquired before and after intravenous injection of the FDA-approved fluorescent dye Indocyanine Green (ICG) at a dose of 1 mg/kg or 10 mg/kg. The fluorescence signal of the paravertebral soft tissues was compared between different groups of rats using Wilcoxon-tests. Lumbar spines and paravertebral soft tissues were further processed with histopathology. RESULTS: In both dose groups, ICG provided a significant enhancement of soft tissue in the area of surgery, which corresponded with granulation tissue on histopathology. The peak and time interval of fluorescence enhancement was significantly higher using 10 mg/kg dose of ICG compared to the 1 mg/kg ICG dose. The levels of significance were p < 0.05. Fusion of OI data with X-rays allowed an accurate anatomical localization of the enhancing granulation tissue. CONCLUSION: ICG-enhanced OI is a suitable technique to diagnose granulation tissue after lumbar spine surgery. This new imaging technique may be clinically applicable for postoperative treatment monitoring. It could be also used to evaluate the effect of anti-inflammatory drugs and may even allow evaluations at the bedside with new hand-held OI scanners.

Tracking of [18F]FDG-labeled natural killer cells to HER2/neu-positive tumors.

INTRODUCTION: The objective of this study was to label the human natural killer (NK) cell line NK-92 with [(18)F]fluoro-deoxy-glucose (FDG) for subsequent in vivo tracking to HER2/neu-positive tumors. METHODS: NK-92 cells were genetically modified to NK-92-scFv(FRP5)-zeta cells, which express a chimeric antigen receptor that is specific to the tumor-associated ErbB2 (HER2/neu) antigen. NK-92 and NK-92-scFv(FRP5)-zeta cells were labeled with [(18)F]FDG by simple incubation at different settings. Labeling efficiency was evaluated by a gamma counter. Subsequently, [(18)F]FDG-labeled parental NK-92 or NK-92-scFv(FRP5)-zeta cells were intravenously injected into mice with implanted HER2/neu-positive NIH/3T3 tumors. Radioactivity in tumors was quantified by digital autoradiography and correlated with histopathology. RESULTS: The NK-92 and NK-92-scFv(FRP5)-zeta cells could be efficiently labeled with [(18)F]FDG by simple incubation. Optimal labeling efficiencies (80%) were achieved using an incubation period of 60 min and additional insulin (10 IU/ml). After injection of 5x10(6) [(18)F]FDG-labeled NK-92-scFv(FRP5)-zeta cells into tumor-bearing mice, digital autoradiography showed an increased uptake of radioactivity in HER2/neu-positive tumors at 60 min postinjection. Conversely, injection of 5x10(6) NK-92 cells not directed against HER2/neu receptors did not result in increased uptake of radioactivity in the tumors. Histopathology confirmed an accumulation of the NK-92-scFv(FRP5)-zeta cells, but not the parental NK cells, in tumor tissues. CONCLUSION: The human NK cell line NK-92 can be directed against HER2/neu antigens by genetic modification. The genetically modified NK cells can be efficiently labeled with [(18)F]FDG, and the accumulation of these labeled NK cells in HER2/neu-positive tumors can be monitored with autoradiography.

MRI biomarkers of proximal nerve injury in CIDP.

Objective: To evaluate the utility of nerve diffusion tensor imaging (DTI), nerve cross-sectional area, and muscle magnetic resonance imaging (MRI) multiecho Dixon for assessing proximal nerve injury in chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: In this prospective observational cohort study, 11 patients with CIDP and 11 healthy controls underwent a multiparametric MRI protocol with DTI of the sciatic nerve and assessment of muscle proton-density fat fraction of the biceps femoris and the quadriceps femoris muscles by multiecho Dixon MRI. Patients were longitudinally evaluated by MRI, clinical examination, and nerve conduction studies at baseline and after 6 months. Results: In sciatic nerves of CIDP patients, mean cross-sectional area was significantly higher and fractional anisotropy value was significantly lower, compared to controls. In contrast, muscle proton-density fat fraction was significantly higher in thigh muscles of patients with CIDP, compared to controls. MRI parameters showed high reproducibility at baseline and 6 months. Interpretation: Advanced MRI parameters demonstrate subclinical proximal nerve damage and intramuscular fat accumulation in CIDP. Data suggest DTI and multiecho Dixon MRI might be useful in estimating axonal damage and neurogenic muscle changes in CIDP.

Fast high-spatial-resolution MRI of the ankle with parallel imaging using GRAPPA at 3 T.

OBJECTIVE: The purpose of our study was to compare an autocalibrating parallel imaging technique at 3 T with standard acquisitions at 3 and 1.5 T for small-field-of-view imaging of the ankle. MATERIALS AND METHODS: MRI of the ankle was performed in three fresh human cadaver specimens and three healthy volunteers. Axial and sagittal T1-weighted, axial fat-saturated T2-weighted, and coronal intermediate-weighted fast spin-echo sequences, as well as a fat-saturated spoiled gradient-echo sequence, were acquired at 1.5 and 3 T. At 3 T, reduced data sets were reconstructed using a generalized autocalibrating partially parallel acquisition (GRAPPA) technique, with a scan time reduction of approximately 44%. All images were assessed by two radiologists independently concerning image quality. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in every data set. In the cadaver specimens, macroscopic findings after dissection served as a reference for the pathologic evaluation. RESULTS: SNR and CNR in the GRAPPA images were comparable to the standard acquisition at 3 T. The image quality was rated significantly higher at 3 T with both normal and parallel acquisition compared with 1.5 T. There was no significant difference in ligament and cartilage visualization or in image quality between standard and GRAPPA reconstruction at 3 T. Ankle abnormalities were better seen at 3 T than at 1.5 T for both normal and parallel acquisitions. CONCLUSION: Using higher field strength combined with parallel technique, MR images of the ankle were obtained with excellent diagnostic quality and a scan time reduction of about 44%. In addition, parallel imaging can provide more flexibility in protocol design.

Volumetric quantitative CT of the spine and hip derived from contrast-enhanced MDCT: conversion factors.

OBJECTIVE: The purposes of this study were to perform volumetric quantitative CT (QCT) of the spine and hip using nondedicated contrast-enhanced standard MDCT data sets and to derive a conversion factor for bone mineral density (BMD) assessment based on dedicated volumetric QCT data sets. SUBJECTS AND METHODS: Forty postmenopausal women with a mean +/- SD age of 71 +/- 9 years underwent routine contrast-enhanced abdominal and pelvic MDCT. Before this imaging examination, standard volumetric QCT of the spine (L1-L3, n = 40) and hip (n = 21) was performed. Relations between QCT and contrast-enhanced MDCT findings were assessed with linear regression analysis. RESULTS: Mean lumbar BMD was 84.1 +/- 35.8 mg/mL, and mean femoral BMD was 0.62 +/- 0.12 g/cm2, as determined with QCT. Contrast-enhancement values with MDCT were on average 30.3% higher than those of QCT in the spine and 2.3% higher in the proximal femur (p < 0.05). Based on linear regression, a correlation coefficient of r = 0.98 was calculated for lumbar BMD with the equation BMD(QCT) = 0.96xBMD(MDCT) - 20.9 mg/mL. A coefficient of r = 0.99 was calculated for the proximal femur with the equation BMD(QCT) = 0.99xBMD(MDCT) - 12 mg/cm2 (p < 0.01). In 17 of 40 patients, 33 vertebral fractures were found. The dedicated QCT and enhanced MDCT data sets did not show a significant difference (p > 0.05) between patients with fractures and those without fractures. CONCLUSION: With the conversion factors, reliable volumetric BMD measurements can be calculated for the hip and the spine from routine abdominal and pelvic MDCT data sets.

Detection of intramyocardially injected DiR-labeled mesenchymal stem cells by optical and optoacoustic tomography.

The distribution of intramyocardially injected rabbit MSCs, labeled with the near-infrared dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbo-cyanine-iodide (DiR) using hybrid Fluorescence Molecular Tomography-X-ray Computed Tomography (FMT-XCT) and Multispectral Optoacoustic Tomography (MSOT) imaging technologies, was investigated. Viability and induction of apoptosis of DiR labeled MSCs were assessed by XTT- and Caspase-3/-7-testing in vitro. 2 × 106, 2 × 105 and 2 × 104 MSCs labeled with 5 and 10 µg DiR/ml were injected into fresh frozen rabbit hearts. FMT-XCT, MSOT and fluorescence cryosection imaging were performed. Concentrations up to 10 µg DiR/ml did not cause apoptosis in vitro (p > 0.05). FMT and MSOT imaging of labeled MSCs led to a strong signal. The imaging modalities highlighted a difference in cell distribution and concentration correlated to the number of injected cells. Ex-vivo cryosectioning confirmed the molecular fluorescence signal. FMT and MSOT are sensitive imaging techniques offering high-anatomic resolution in terms of detection and distribution of intramyocardially injected stem cells in a rabbit model.

Long-term symptom control after endoscopic laser-assisted diverticulotomy of Zenker's diverticulum.

OBJECTIVE: To assess the long-term outcome after endoscopic laser-assisted diverticulotomy. METHODS: The medical files of patients who underwent endoscopic Zenker's diverticulum (ZD) surgery were reviewed retrospectively. Patients were interviewed using a questionnaire which assessed symptoms, other relevant disorders and satisfaction after the surgery. RESULTS: Mean follow-up period from 62 surgeries was 100 months (range 11-216 months). Follow-up data were obtained from 34 patients (response rate: 55%) in total. The surgery resulted in a significant reduction of symptoms (regurgitation, dysphagia and globus sensation). In four cases (12%) a postoperative impairment of swallowing solid food was reported, whereas, persisted difficulty of swallowing liquids was observed in two patients (6%). There was no reported case of impairment associated with everyday habits. The majority of patients were satisfied with the overall outcome of the surgery (n=31, 91%). CONCLUSION: The endoscopic laser-assisted diverticulotomy is an effective method of treating Zenker's diverticulum. The presented long-term results confirm that this technique offers a very high degree of symptom relief and patient's satisfaction.

Matrix-assisted autologous chondrocyte transplantation for remodeling and repair of chondral defects in a rabbit model.

Articular cartilage defects are considered a major health problem because articular cartilage has a limited capacity for self-regeneration (1). Untreated cartilage lesions lead to ongoing pain, negatively affect the quality of life and predispose for osteoarthritis. During the last decades, several surgical techniques have been developed to treat such lesions. However, until now it was not possible to achieve a full repair in terms of covering the defect with hyaline articular cartilage or of providing satisfactory long-term recovery (2-4). Therefore, articular cartilage injuries remain a prime target for regenerative techniques such as Tissue Engineering. In contrast to other surgical techniques, which often lead to the formation of fibrous or fibrocartilaginous tissue, Tissue Engineering aims at fully restoring the complex structure and properties of the original articular cartilage by using the chondrogenic potential of transplanted cells. Recent developments opened up promising possibilities for regenerative cartilage therapies. The first cell based approach for the treatment of full-thickness cartilage or osteochondral lesions was performed in 1994 by Lars Peterson and Mats Brittberg who pioneered clinical autologous chondrocyte implantation (ACI) (5). Today, the technique is clinically well-established for the treatment of large hyaline cartilage defects of the knee, maintaining good clinical results even 10 to 20 years after implantation (6). In recent years, the implantation of autologous chondrocytes underwent a rapid progression. The use of an artificial three-dimensional collagen-matrix on which cells are subsequently replanted became more and more popular (7-9). MACT comprises of two surgical procedures: First, in order to collect chondrocytes, a cartilage biopsy needs to be performed from a non weight-bearing cartilage area of the knee joint. Then, chondrocytes are being extracted, purified and expanded to a sufficient cell number in vitro. Chondrocytes are then seeded onto a three-dimensional matrix and can subsequently be re-implanted. When preparing a tissue-engineered implant, proliferation rate and differentiation capacity are crucial for a successful tissue regeneration (10). The use of a three-dimensional matrix as a cell carrier is thought to support these cellular characteristics (11). The following protocol will summarize and demonstrate a technique for the isolation of chondrocytes from cartilage biopsies, their proliferation in vitro and their seeding onto a 3D-matrix (Chondro-Gide, Geistlich Biomaterials, Wollhusen, Switzerland). Finally, the implantation of the cell-matrix-constructs into artificially created chondral defects of a rabbit's knee joint will be described. This technique can be used as an experimental setting for further experiments of cartilage repair.