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Biomedical subjects

M Recht

Publications and source records attributed to M Recht.

16 recordsLinked to original sources
PubMed2001

Magnetic resonance imaging of articular cartilage.

Magnetic resonance imaging is the optimal modality for assessing articular cartilage because of superior soft tissue contrast, direct visualization of articular cartilage, and multiplanar capability. Despite these advantages, there has been disagreement as to the efficacy of magnetic resonance imaging of articular cartilage. The reason for this controversy is multifactorial but in part is attributable to the lack of the use of optimized pulse sequences for articular cartilage. The current authors will review the current state of the art of magnetic resonance imaging of articular cartilage and cartilage repair procedures, discuss future new directions in imaging strategies and methods being developed to measure cartilage thickness and volume measurements, and propose a magnetic resonance imaging protocol to evaluate cartilage that is achievable on most magnetic resonance scanners, vendor independent, practical (time and cost efficient), and accepted and used by a majority of musculoskeletal radiologists.

Arthrography↗
PubMed2000

Percutaneous CT guided resection of osteoid osteoma of the tibial plafond.

Osteoid osteomas of the foot and ankle are relatively rare and notoriously difficult to diagnose. Juxta-articular osteoid osteomas are more difficult to treat and often have a significant delay in diagnosis. We report a case of a juxta-articular osteoid osteoma of the tibial plafond. Once the diagnosis was made, excisional biopsy was performed percutaneously under computed tomography (CT) guidance as an outpatient in the radiology suite. The patient had complete resolution of symptoms and remains pain free at two years follow-up. CT guided resection can be a lower morbidity and more cost effective technique to treat this lesion than traditional methods.

Biopsy, Needle↗
PubMed1998

Interferon-gamma expression by Th1 effector T cells mediated by the p38 MAP kinase signaling pathway.

Signal transduction via MAP kinase pathways plays a key role in a variety of cellular responses, including growth factor-induced proliferation, differentiation and cell death. In mammalian cells, p38 MAP kinase can be activated by multiple stimuli, such as pro-inflammatory cytokines and environmental stress. Although p38 MAP kinase is implicated in the control of inflammatory responses, the molecular mechanisms remain unclear. Upon activation, CD4+ T cells differentiate into Th2 cells, which potentiate the humoral immune response or pro-inflammatory Th1 cells. Here, we show that pyridinyl imidazole compounds (specific inhibitors of p38 MAP kinase) block the production of interferon-gamma (IFNgamma) by Th1 cells without affecting IL-4 production by Th2 cells. These drugs also inhibit transcription driven by the IFNgamma promoter. In transgenic mice, inhibition of the p38 MAP kinase pathway by the expression of dominant-negative p38 MAP kinase results in selective impairment of Th1 responses. In contrast, activation of the p38 MAP kinase pathway by the expression of constitutivelyactivated MAP kinase kinase 6 in transgenic mice caused increased production of IFNgamma during the differentiation and activation of Th1 cells. Together, these data demonstrate that the p38 MAP kinase is relevant for Th1 cells, not Th2 cells, and that inhibition of p38 MAP kinase represents a possible site of therapeutic intervention in diseases where a predominant Th1 immune response leads to a pathological outcome. Moreover, our study provides an additional mechanism by which the p38 MAP kinase pathway controls inflammatory responses.

Animals↗
PubMed1998

Differences in platelet alpha-granule release between normals and immune thrombocytopenic patients and between young and old platelets.

The risk of serious bleeding in patients with immune thrombocytopenic purpura (ITP) appears to be less than in comparably thrombocytopenic patients with megakaryocytic hypoplasia. It has been proposed that this difference is due to enhanced hemostatic activity of young platelets, which are increased in the circulation during ITP. We examined alpha-granule release in reticulated platelets (RP), which are thought to be the youngest circulating platelets, and in older non-reticulated platelets (non-RP) in normal human controls and ITP patients. Normal controls had a mean RP of 7%, compared with 42% in ITP patients. The mean concentration of thrombin receptor agonist peptide (TRAP) causing 50% of control RP to express CD62P (EC50) was 0.82+/-0.08 microM (SEM), significantly higher than the TRAP CD62P EC50 for RP in ITP, 0.57+/-0.06 microM (p = 0.04). Similarly, the TRAP EC50 for non-RP in controls, 0.84+/-0.09 microM, was significantly higher than in ITP, 0.56+/-0.07 microM (p = 0.03), suggesting that all platelets in ITP have an enhanced alpha-granule threshold response to TRAP compared with controls, while RP and older platelets within each patient group have similar threshold sensitivities to TRAP. By contrast, high-dose TRAP caused RP to express twice as much mean and total CD62P as non-RP in both ITP patients and controls (p <0.05 for both comparisons). We conclude that compared with controls, all platelets in ITP are primed to undergo alpha-granule release to TRAP, while in both ITP and controls, the newly circulating, reticulated platelets have the potential to contribute greater amounts of CD62P surface ligand compared with older platelets (non-RP) after stimulation. Both the increased RP% and enhanced platelet response to agonist in ITP may contribute to maintenance of hemostasis despite thrombocytopenia.

Adult↗
PubMed1997

Implementation of an electronic teaching file using web technology.

The implementation of an electronic teaching file using web technology is discussed in this article. A web client server model is used for a standard web browser capable of displaying joint photographic Experts Group (JPEG) compression images. Like other web-based teaching files, this teaching file in a similar way uses a database containing information. This database section of the teaching file allows flexible database querying and viewing of pages generated by hypertext markup language (HTML). Because the browser client is so flexible, images types such as video and 3D representations with virtual reality markup language (VRML) can be displayed.

Computer Communication Networks↗
PubMed1997

MR imaging of tophaceous gout.

OBJECTIVE: MR imaging is not routinely used for evaluation of tophaceous gout. However, gout may present clinically in an atypical, unusual, or confusing manner. A gouty tophus occasionally mimics an infectious or neoplastic process, and MR imaging may be obtained under these circumstances. The purpose of this study was to determine the MR imaging characteristics of intraosseous and soft-tissue tophi. MATERIALS AND METHODS: We identified 13 MR imaging examinations performed during a 27-month period on nine patients with gouty arthritis. All were men 42-70 years old. T1-, proton density-, and T2-weighted spin-echo MR images were obtained for all the examinations. Nine examinations included contrast-enhanced MR images. The findings were then evaluated, as were the corresponding radiographs. RESULTS: Five patients presented with articular involvement, three patients with an isolated soft-tissue mass, and one patient with persistent soft-tissue swelling. The duration of symptoms ranged from 3 months to more than 20 years. Nearly all the tophi were of intermediate signal intensity on T1-weighted images. On T2-weighted images, three sites revealed an overall increase in the signal intensity of the tophi, whereas 10 studies showed a heterogeneous decrease in signal intensity. All but one tophus showed homogeneous enhancement. Erosion of adjacent bone, synovial pannus, joint effusion, soft-tissue edema, and bone marrow edema were common associated findings. CONCLUSION: The MR appearance of tophi in patients with tophaceous gout is constant on T1- but quite variable on T2-weighted images. This variability in signal intensity could be related to calcium within a tophus. Tophaceous gout should be considered in the differential diagnosis when a mass reveals heterogeneously low to intermediate signal intensity, particularly if the adjacent bone shows typical erosive changes or if other joints are involved. When faced with this situation, radiologists may find it helpful to obtain a further clinical history and recommend evaluating the patient's serum urate level.

Adult↗
PubMed1997

Severe multicentric reticulohistiocytosis: disease stabilization achieved with methotrexate and hydroxychloroquine.

Multicentric reticulohistiocytosis is a rare systemic disease that typically manifests as erosive polyarthritis. The particularly aggressive nature of multicentric reticulohistiocytosis has led many to recommend treatment with high dose corticosteroids, alkylating agents, or both. We describe a 56-year-old woman with erosive polyarthritis successfully treated exclusively for 30 months with hydroxychloroquine and methotrexate. This regimen may have the potential to provide longterm disease control with reduced risk of serious drug related toxicity.

Arthritis↗
PubMed1994

Method for the quantitative assessment of contrast agent uptake in dynamic contrast-enhanced MRI.

In previous papers relative signal intensity increase was used as a quantitative assessment parameter for contrast uptake in contrast-enhanced MRI. However, relative signal intensity increase does not only reflect contrast uptake but depends also on tissue parameters (native T1 relaxation time) and sequence parameters (repetition time and flip angle); thus, the contrast uptake cannot be assessed accurately using relative signal intensity increase. Based on an analysis of the contrast behavior of spoiled gradient echo sequences, a method is described in this paper that overcomes the limitations of relative signal intensity increase measurement. A parameter, called "enhancement factor" (EF) is introduced that approximates differential T1 relaxation rate. The enhancement factor scales linearly with contrast uptake and is independent of tissue and sequence parameters. The additional measurement time involved in determining the enhancement factor is less than 1 min and computation is straightforward. The practicality of the new method was confirmed by phantom measurements using T1-weighted and proton density-weighted spoiled gradient echo sequences (FLASH-2D). Enhancing tissues were simulated by water phantoms doped with increasing concentrations of Gd-DTPA.

Algorithms↗
PubMed1993

Blood flow in the portal vein: velocity quantitation with phase-contrast MR angiography.

Quantitative phase-contrast magnetic resonance (MR) angiography of the portal vein was prospectively evaluated in 79 fasting patients and 23 healthy volunteers. Images were obtained during a 12-second breath-hold acquisition in the coronal (n = 102) and axial (n = 11) planes. Pathologic correlation was available in 55 of 79 patients and included findings of cholangiocarcinoma, cirrhosis, hepatocellular carcinoma, hepatitis, and metastatic disease. Forty-one patients had correlative Doppler ultrasound (US) findings. MR and US findings correlated as to flow direction in all cases. In nine patients, Doppler US velocity measurements were available and closely correlated with MR findings. A comparison of axial and coronal portal venous phase-contrast measurements in 11 patients revealed no substantial difference with regard to the plane used. Quantitative phase-contrast MR angiography is a simple and rapid technique for the assessment of portal venous patency, flow direction, and flow velocity and, combined with high-resolution conventional MR imaging, may obviate the current use of both computed tomographic and US examinations.

Blood Flow Velocity↗
PubMed1992

Breath-hold T2-weighted sequences of the liver: a comparison of four techniques at 1.0 and 1.5 T.

T2-weighted images are considered the most sensitive for lesion detection at high field; however, long imaging time is problematic. Accordingly, the authors compared four breath-hold T2 or T2* weighted sequences comprising T2*-weighted FLASH, T2*-weighted PSIF, T2-weighted rapid spin echo (RASE), and T2-weighted Turbo-FLASH (Turbo) in 20 different healthy volunteers, 10 at 1.0 T and 10 at 1.5 T with reference to regular T2-weighted spin echo. Images were evaluated quantitatively by liver signal to noise (S/N) and spleen-liver signal difference to noise (SD/N) ratios and qualitatively for presence of artifacts and image quality. Data were evaluated for 1.0 T and 1.5 T separately and combined. In the combined evaluation, T2*-FLASH had good S/N (23.1 + 5.1) but low SD/N (2.9 + 1.7) and suffered from susceptibility artifacts. T2* PSIF had good S/N (28.1 + 10.0) and moderate SD/N (6.0 + 2.4), but occasionally had heterogeneous signal intensity. Flow signal void was an attractive feature. T2 RASE had very low S/N (4.4 + 1.9) and low SD/N (2.3 + 1.1) and suffered from flow artifacts. T2-Turbo had good S/N (24.6 + 8.6) and SD/N (8.9 + 2.5). Flow signal void was present, but small matrix size decreased image quality. The results of our study suggest that T2*-PSIF and T2-Turbo have good S/N and SD/N and fair image quality which may be clinically useful for breath-hold T2-weighted sequences of the liver.

Adult↗
PubMed1991

A human 15-kDa IFN-induced protein induces the secretion of IFN-gamma.

A 15,000 molecular weight protein (15-kDa), induced and secreted by human PBMC after treatment with IFN-alpha or -beta, was assessed for its ability to modulate cellular function. Although it had no effect on growth or 2'5'-A synthetase activity in Daudi, U-937, or HL-60 cells, when incubated with fresh human PBMC, LPS-induced monocyte cytotoxicity against WEHI-164 target cells was augmented. This stimulation was inhibited by both an antibody against TNF-alpha and a rabbit polyclonal antiserum to the 15-kDa protein. Furthermore, when the 15-kDa protein was added to PBMC an increase in GTP cyclohydrolase I activity, as assessed by neopterin secretion, resulted. Neopterin secretion by PBMC in response to the 15-kDa was increased in a dose-responsive manner up to more than sixfold over baseline, with a 15-kDa concentration of less than 10 ng/ml effective. The 15-kDa protein also stimulated indoleamine 2,3-dioxygenase (IDO) activity in fresh, human PBMC. Induction of neopterin secretion and IDO activity was inhibited by a polyclonal antiserum to 15-kDa. LPS-induced cytotoxic activity was not augmented by 15-kDa pretreatment of purified monocytes, indicating the need for the presence of a second cell population and the indirect action of the 15-kDa on the induction of monocyte activities. When PBMC or purified CD3+ cells, but not purified CD14+ cells, were incubated with the 15-kDa protein, secretion of a factor was induced that resulted in the induction of IDO activity in PMA-differentiated THP-1 cells. An antibody to IFN-gamma, but not IFN-alpha, inhibited the induction of IDO activity by this secreted factor. In addition, antiserum to the 15-kDa blocked the secretion of IFN-gamma from the CD3+ cells. Thus, a 15-kDa product of IFN-alpha- and IFN-beta-treated monocytes and lymphocytes can stimulate secretion of IFN-gamma from CD3+ cells.

Cell Division↗
PubMed1991

T1-weighted sequences for MR imaging of the liver: comparison of three techniques for single-breath, whole-volume acquisition at 1.0 and 1.5 T.

The authors compared three T1-weighted magnetic resonance imaging techniques that acquire images encompassing the entire liver in one breath hold. Twenty healthy volunteers were imaged--10 at 1.0 T and 10 at 1.5 T--and the results compared with those of regular short repetition time/echo time spin-echo imaging. Rapid acquisition spin echo was resistant to artifacts and had good image quality but had the lowest liver signal-to-noise (S/N) and spleen-liver signal-difference-to-noise (SD/N) values. Fast low-angle shot (FLASH) had the highest S/N and SD/N, very good image quality, and only mild artifacts. TurboFLASH had good S/N and SD/N, but reduced matrix size decreased image quality. All three sequences had better SD/N than regular spin echo, and FLASH and TurboFLASH had higher S/N. On the basis of this study, the FLASH sequence appears the most attractive for T1-weighted breath-hold imaging.

Adult↗
PubMedDate not supplied

MR appearance of idiopathic synovial osteochondromatosis.

OBJECTIVE: A retrospective review of the MR examinations in 21 patients with idiopathic synovial osteochondromatosis (ISO) was performed to determine its MRI characteristics. MATERIALS AND METHODS: Twenty-one patients diagnosed with ISO had undergone MRI prior to surgery. The MR images were retrospectively evaluated for configuration and extent of lesion as well as for signal characteristics. RESULTS: Three distinct MR patterns were seen in ISO: A--lobulated homogeneous intraarticular signal isointense to slightly hyperintense to muscle on T1-weighted images and hyperintense on T2-weighted images (n = 3); B--pattern A plus foci of signal void on all pulse sequences (n = 17); and C--features of pattern A and B plus foci of peripheral low signal surrounding central fat-like signal (n = 2). The foci of signal void in pattern B and C corresponded to areas of calcification and the foci of peripheral low signal surrounding central fat-like signal in pattern C corresponded to areas of ossification. CONCLUSION: The MR appearance of ISO appears sufficiently unique to allow its differentiation from other causes of intraarticular pathology.

Adolescent↗