Vascular and angiogenic processes provide an important target for novel cancer therapeutics. Dynamic contrast-enhanced magnetic resonance imaging is being used increasingly to noninvasively monitor ...the action of these therapeutics in early-stage clinical trials. This publication reports the outcome of a workshop that considered the methodology and design of magnetic resonance studies, recommending how this new tool might best be used.
To describe the protocol of a multi-vendor, multi-site quantitative MRI study for knee post-traumatic osteoarthritis (PTOA), and to present preliminary results of cartilage degeneration using MR T1ρ ...and T2 imaging 10 years after anterior cruciate ligament reconstruction (ACLR).
This study involves three sites and two MR platforms. The patients are from a nested cohort (termed as Onsite cohort) within the Multicenter Orthopaedic Outcomes Network (MOON) cohort 10 years after ACLR. Phantoms and controls were scanned for evaluating reproducibility. Cartilage was automatically segmented, and T1ρ and T2 were compared between operated, contralateral, and control knees.
Sixty-eight ACL-reconstructed patients and 20 healthy controls were included. In phantoms, the intra-site coefficients of variation (CVs) of repeated scans ranged 1.8–2.1% for T1ρ and 1.3–1.7% for T2. The inter-site CVs ranged 1.6–2.1% for T1ρ and 1.1–1.4% for T2. In human subjects, the intra-site scan/rescan CVs ranged 2.2–3.5% for T1ρ and 2.6–4.9% for T2 for the six major compartments. In patients, operated knees showed significantly higher T1ρ and T2 values mainly in medial femoral condyle, medial tibia and trochlear cartilage compared with contralateral knees, and showed significantly higer T1ρ and T2 values in all six compartments compared to healthy control knees. The patient contralateral knees showed higher T1ρ and T2 values mainly in the lateral femoral condyle, lateral tibia, trochlear, and patellar cartilage compared to healthy control knees.
A platform and workflow with rigorous quality control has been established for a multi-vendor multi-site quantitative MRI study in evaluating PTOA 10 years after ACLR. Our preliminary report suggests significant cartilage matrix changes in both operated and contralateral knees compared with healthy control knees.
Dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) is the acquisition of serial MRI images before, during, and after the administration of an MR contrast agent. Unlike conventional ...enhanced MRI, which simply provides a snapshot of enhancement at one point in time, DCE‐MRI permits a fuller depiction of the wash‐in and wash‐out contrast kinetics within tumors, and thus provides insight into the nature of the bulk tissue properties. Such data is readily amenable to two‐compartment pharmacokinetic modeling from which parameters based on the rates of exchange between the compartments can be generated. These parameters can be used to generate color‐encoded images that aid in the visual assessment of tumors. DCE‐MRI is used currently to characterize masses, stage tumors, and noninvasively monitor therapy. While DCE‐MRI is in clinical use, there are also a number of limitations, including overlap between malignant and benign inflammatory tissue, failure to resolve microscopic disease, and the inconsistent predictive value of enhancement pattern with regard to clinical outcome. Current research focuses on improving understanding of the meaning of DCE‐MRI at a molecular level, evaluating macromolecular and targeted contrast agents, and combining DCE‐MRI with other physiologic imaging techniques such as positron emission tomography. Efforts to standardize DCE‐MRI acquisition, analysis, and reporting methods will allow wider dissemination of this useful functional imaging technique. J. Magn. Reson. Imaging 2003;17:509–520. Published 2003 Wiley‐Liss, Inc.
Although there exist some reference and stereotactic anatomical human brain atlases, there is no equivalent cerebrovascular atlas. A 3D reference atlas of the human cerebrovasculature that is ...interactive, stereotactic, very detailed, completely parcellated, fully labeled, extendable, dissectible, deformable, and user friendly, is needed in education, training, research, and clinical applications.
We constructed a sophisticated and very detailed cerebrovascular atlas with 1325 vascular segments, the smallest of 80μm in diameter. The atlas was created from multiple 3 and 7T scans by employing tools and methods developed in our lab. In contrast to a sort of “sampled” vascular geometry cited in the literature, we provide information about the “continuous” geometry of the vascular model measurable in 3D at every location and along any vascular segment for both hemispheres.
This cerebrovascular atlas was validated taking into account domain knowledge from various fields including angiography, neurosurgery, neuroradiology, (clinical) neuroanatomy, and terminology. Validation was considered as a confirmation of the created vascular model to a typical (conventional) cerebrovascular system with nearly average dimensions. It was done in terms of vessel subdivision, origin, course, surrounding anatomy, patterns, length, diameter, and branches. This validation demonstrates that the constructed cerebrovascular model generally represents a normal, typical cerebrovasculature with its dimensions close to average.
This 7T atlas along with the vascular model is a rich source of knowledge about the human cerebrovasculature. The atlas is applicable in education, research, and clinical applications; it has already been applied in deep brain stimulation.
T2 hypointensity in the basal ganglia of patients with MS has been associated with clinical progression and cognitive decline. Our objectives were the following: 1) to compare signal in T2WI, R2 (ie, ...1/T2), and R2* (ie, 1/T2*) relaxation rates and quantitative susceptibility mapping; and 2) to investigate the associations among MR imaging, clinical scores, and cognitive measures of inhibitory control linked to basal ganglia functioning.
Twenty-nine patients with MS underwent a battery of neuropsychological tests including the Flanker and Stroop tasks. 7T MR imaging included 3D gradient-echo and single-echo multishot spin-echo EPI. Quantitative susceptibility mapping images were calculated by using a Wiener filter deconvolution algorithm. T2WI signal was normalized to CSF. R2 and R2* were calculated by log-linear regression. Average MR imaging metrics for the globus pallidus, putamen, and caudate were computed from manually traced ROIs including the largest central part of each structure.
Marked spatial variation was consistently visualized on quantitative susceptibility mapping and T2/T2*WI within each basal ganglia structure. MR imaging metrics correlated with each other for each basal ganglia structure individually. Notably, caudate and putamen quantitative susceptibility mapping metrics were similar, but the putamen R2 was larger than the caudate R2. This finding suggests that tissue features contribute differently to R2 and quantitative susceptibility mapping. Caudate and anterior putamen quantitative susceptibility mapping correlated with the Flanker but not Stroop measures; R2 did not correlate with inhibitory control measures. Putamen quantitative susceptibility mapping and caudate and putamen R2 correlated with the Expanded Disability Status Scale.
Our study showed that quantitative susceptibility mapping and R2 may be complementary indicators for basal ganglia tissue changes in MS. Our findings are consistent with the hypothesis that decreased performance of basal ganglia-reliant tasks involving inhibitory control is associated with increased quantitative susceptibility mapping.
Summary Objective To evaluate healing of surgically created large osteochondral defects in a weight-bearing femoral condyle in response to delayed percutaneous direct injection of adenoviral (Ad) ...vectors containing coding regions for either human bone morphogenetic proteins 2 (BMP-2) or -6. Methods Four 13 mm diameter and 7 mm depth circular osteochondral defects were drilled, 1/femoral condyle ( n = 20 defects in five ponies). At 2 weeks, Ad-BMP-2, Ad-BMP-6, Ad-green fluorescent protein (GFP), or saline was percutaneously injected into the central drill hole of the defect. Quantitative magnetic resonance imaging (qMRI) and computed tomography (CT) were serially performed at 12, 24, and 52 weeks. At 12 (one pony) or 52 weeks, histomorphometry and microtomographic analyses were performed to assess subchondral bone and cartilage repair tissue quality. Results Direct delivery of Ad-BMP-6 demonstrated delayed gadolinium-enhanced MRI of cartilage ( dGEMRIC ) and histologic evidence of greater Glycosaminoglycan (GAG) content in repair tissue at 12 weeks, while Ad-BMP-2 had greater non-mineral cartilage at the surface at 52 weeks ( p < 0.04). Ad-BMP-2 demonstrated greater CT subchondral bone mineral density (BMD) by 12 weeks and both Ad-BMP-2 and -6 had greater subchondral BMD at 52 weeks ( p < 0.05). Despite earlier (Ad-BMP-6) and more persistent (Ad-BMP-2) chondral tissue and greater subchondral bone density (Ad-BMP-2 and -6), the tissue within the large weight-bearing defects at 52 weeks was suboptimal in all groups due to poor quality repair cartilage, central fibrocartilage retention, and central bone cavitation. Delivery of either BMP by this method had greater frequency of subchondral bone cystic formation ( p < 0.05). Conclusions Delivery of Ad-BMP-2 or Ad-BMP-6 via direct injection supported cartilage and subchondral bone regeneration but was insufficient to provide long-term quality osteochondral repair.
Although there exist some reference and stereotactic anatomical human brain atlases, there is no equivalent cerebrovascular atlas. A 3D reference atlas of the human cerebrovasculature that is ...interactive, stereotactic, very detailed, completely parcellated, fully labeled, extendable, dissectible, deformable, and user friendly, is needed in education, training, research, and clinical applications. We constructed a sophisticated and very detailed cerebrovascular atlas with 1325 vascular segments, the smallest of 80 microm in diameter. The atlas was created from multiple 3 and 7 T scans by employing tools and methods developed in our lab. In contrast to a sort of "sampled" vascular geometry cited in the literature, we provide information about the "continuous" geometry of the vascular model measurable in 3D at every location and along any vascular segment for both hemispheres. This cerebrovascular atlas was validated taking into account domain knowledge from various fields including angiography, neurosurgery, neuroradiology, (clinical) neuroanatomy, and terminology. Validation was considered as a confirmation of the created vascular model to a typical (conventional) cerebrovascular system with nearly average dimensions. It was done in terms of vessel subdivision, origin, course, surrounding anatomy, patterns, length, diameter, and branches. This validation demonstrates that the constructed cerebrovascular model generally represents a normal, typical cerebrovasculature with its dimensions close to average. This 7 T atlas along with the vascular model is a rich source of knowledge about the human cerebrovasculature. The atlas is applicable in education, research, and clinical applications; it has already been applied in deep brain stimulation.
The aim of this study was to evaluate changes in both size and contrast enhancement of breast tumors during neoadjuvant chemotherapy, using dynamic MRI with high temporal resolution. Patients with ...advanced breast cancer (n=21) underwent a 1.5-T MRI scan prior to and following neoadjuvant chemotherapy with four cycles. Dynamic contrast enhancement was measured using a fast turbo-FLASH sequence and quantified using a two-compartment model with the parameters k(ep) and amplitude. Image analysis was done on images overlayed with a color map of parameters. The correlation between tumor diameter measured by histopathology and MRI was 0.7 (p<0.003). A reduction of tumor size after chemotherapy of more than 25% was associated with a decrease of both analyzed contrast enhancement parameters (k(ep): p<0.002; amplitude: p<0.006), where k(ep) began to drop already after the first cycle of chemotherapy (p<0.008). A clear reduction of tumor size was only noted after the third cycle (p<0.008). In patients without tumor regression there was also a trend towards an early reduction of contrast enhancement. We assume that MRI with high temporal resolution and color mapping is a novel tool to assess therapeutic effects of neoadjuvant chemotherapy in breast tumors, which deserves further prospective evaluation.
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