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PubMed2006

Incidence of visualization of the normal appendix on different MRI sequences.

The purpose of this paper is to assess the incidence of visualization of the normal appendix on magnetic resonance imaging (MRI) examinations of the pelvis in a large adult population and to compare the yield of commonly used sequences. Pelvic MRI scans of 111 randomly selected patients were retrospectively reviewed by two fellowship-trained body imagers. Thirty-six cases, where the entire cecum and terminal ileum were not included in the field of view, were excluded. A normal appendix was definitively visualized in 55 of 71 patients on T1 spin echo (SE) sequences (78%). The appendix was seen on 25 of 42 (60%) half-Fourier single-shot turbo spin echo T2. Visualization rates were 42% on pre-gadolinium T1 FS GRE, 54% on post-gadolinium T1 fat-suppressed gradient echo, and 17% of short tau inversion recovery sequences. MRI is an effective modality for visualization of the normal appendix. This may have important implications in patients with abdominal or pelvic pain, as visualization of a normal appendix should exclude the possibility of acute appendicitis from the differential diagnosis.

Appendix↗

PubMed1998

Magnetic resonance imaging of fistula-in-ano: STIR or SPIR?

Patients with clinically suspected anorectal sepsis were studied using MRI in order to determine if T2 weighted sequences with fat suppression conveyed any additional benefit over conventional short tau inversion recovery (STIR) sequences. 23 consecutive patients (16 male) undergoing MRI for suspected perianal sepsis were studied prospectively using a 1.0 T whole body system and body coil. Axial and coronal T1 weighted turbo spin echo sequences were obtained, followed by STIR and T2 weighted spectral fat saturation inversion recovery (SPIR) sequences. Images were assessed for the presence of sepsis or fistula, and information provided by the sequences compared. Active disease was diagnosed in 17 patients, 14 of whom had fistula-in-ano; one intersphincteric, 10 transsphincteric and three extrasphincteric. Internal openings were identified in all of these 14 patients; anal in 10, rectal in two, and both in two. Diagnosis and fistula classification was possible in all of these 14 subjects on the basis of STIR sequences alone. The anal sphincters and pelvic floor musculature were better resolved by STIR than SPIR, leading to easier and more confident determination of fistula anatomy in eight of the 14 (57%). In no case did STIR sequences fail to resolve inflammation seen subsequently on SPIR, despite reduced track intensity. T1 weighted sequences were generally non-contributory. Both STIR and SPIR sequences are adequate to classify fistula-in-ano, but classification was easier with STIR due to superior resolution of pelvic floor structures.

Abscess↗

PubMed2000

Evaluation of bone contusions with fat-saturated fast spin-echo proton-density magnetic resonance imaging.

OBJECTIVE: To evaluate the efficacy of fast spin-echo proton-density magnetic resonance imaging (MRI) with fat saturation sequences in the evaluation of bone contusions at the knee. METHODS: Analysis of 46 consecutive knee MRI examinations performed on patients referred from a sports medicine clinic after knee trauma. All examinations included coronal fast spin-echo proton-density fat saturation, fast spin-echo proton-density and fast spin-echo T2-weighted sequences. All 3 coronal sequences were blindly reviewed independently of each other by 3 experienced musculoskeletal radiologists to identify and grade bone contusions. RESULTS: Thirty-five bone contusions were identified in 24 patients. All bone contusions were identified on fast spin-echo proton-density fat saturation sequences, which was significantly greater than the percentage identified on either fast spin-echo T2-weighted sequences (21/35, 60%, p < 0.001) or fast spin-echo proton-density sequences (10/35, 29%, p < 0.001). Fourteen (40%) of the contusions were identified only on the fast spin-echo proton-density fat saturation sequences. The average grade of contusion for all 35 examinations was also significantly higher on the fast spin-echo proton-density fat saturation sequences than on the fast spin-echo proton-density and fast spin-echo T2-weighted sequences (p < 0.05). CONCLUSION: Fast spin-echo proton-density fat saturation sequences are more sensitive in the detection of bone contusions than fast spin-echo proton-density and fast spin-echo T2-weighted sequences. Assessment of other structures in the knee with fast spin-echo proton-density fat saturation MRI provides good spatial resolution and adequate T2-weighted information. It may have advantages over the more heavily T2-weighted fast spin-echo T2 fat saturation and inversion recovery sequences.

Adult↗

PubMed1991

Interesting sequence differences between the pilin gene inversion regions of Moraxella lacunata ATCC 17956 and Moraxella bovis Epp63.

The bacterium Moraxella lacunata is a causative agent of human conjunctivitis and keratitis. We have previously reported construction of plasmid pMxL1, which includes a 5.9-kb fragment on which the pilin gene inversion region of M. lacunata resides. The inversion region of pMxL1 was shown to invert when pMxL1 was in an Escherichia coli host cell. In this report, we present Western immunoblot analysis using Moraxella bovis Epp63 anti-I and anti-Q pilin sera which demonstrate that pMxL1 makes pilin only when in orientation 1. The sequence of the pMxL1 plasmid containing the invertible region contains a perfect tandem repeat of 19 bp in the orientation 1 nonexpressed pilin gene at the middle of the recombination junction site. This 19-bp insert causes a frameshift and disrupts the pilin gene. The predicted amino acid sequence of this nonfunctional pilin gene (with the 19-bp repeat subtracted) bears closest resemblance to M. bovis Epp63 Q pilin sequence, although the other (functional) M. lacunata pilin encoded by pMxL1 shows slightly higher homology to Q pilin. Comparison of the pMxL1 sequence with that of the M. bovis Epp63 sequence shows two other particularly interesting differences. One is a 15-bp sequence addition found in pMxL1 at the 60-bp region previously reported as a possible M. bovis recombinational enhancer. The second is an AT deletion in pMxL1 compared with Epp63 within an open reading frame (tfpB) which results in the pMxL1 tfpB open reading frame being one-third shorter than in Epp63. The DNA sequences in these three altered regions from the M. lacunata strain from which pMxL1 was derived were amplified by polymerase chain reaction and sequenced. The parent strain was found to contain the differences seen in pMxL1. Comparison of the M.bovis and M. lacunata pilin gene amino acid sequences is also presented.

Amino Acid Sequence↗

PubMed1990

[A comparative study between Gd-BOPTA, a biliary excretion contrast medium, and Gd-DTPA in the magnetic resonance imaging of the rat liver].

A new lipophilic compound, Gd-BOPTA, presenting a high rate (38.6%) of biliary excretion was tested as an hepato-specific MR contrast agent. Its adequacy was compared to that of Gd-DTPA in laboratory animals. T1-weighted spin-echo sequences (TR 220 ms, TE 20 ms) both before and after the administration of the 2 contrast agents (doses: 0.25, 0.5, and 1.0 mmol/kg) showed better liver enhancement with Gd-BOPTA than with Gd-DTPA. Gd-BOPTA superiority was more evident at lower doses, while at 1.0 mmol/kg a comparable enhancement was achieved. Inversion recovery sequence at the T-null of liver parenchyma before contrast (TR 800 ms, TE 30 ms, TI 100 ms) was performed after the injection of 0.1 and 0.5 mmol/kg of Gd-DTPA and Gd-BOPTA. This sequence allowed the good and long-lasting liver enhancement achieved with Gd-BOPTA to be even better demonstrated, while Gd-DTPA provided only a slight and early enhancement with 0.1 mmol/kg and returned to baseline values 60' after the injection of the highest dose (0.5 mmol/kg). Gd-BOPTA proved to be a good contrast agent to obtain prolonged liver enhancement, thus providing the radiologist with the long time needed to acquire conventional T1-weighted pulse sequences.

Acetates↗

PubMed1996

A novel DNA inversion causing severe hemophilia A.

Almost half of all cases of severe hemophilia A are caused by recurrent DNA inversions, which disrupt the factor VIII (FVIII) gene. These inversions generally occur between a region of intron 22 (int22h) and one of two homologous copies of this region, located 300 to 400 kb telomeric to the FVIII gene. They are routinely detected by a Bcl I Southern blot assay in which the sizes of two of the three normal hybridization bands are characteristically altered. However, atypical hybridization patterns have been observed, and this report describes the first detailed analysis of a hemophilia A patient with such a pattern. The abnormal result was found to be caused by a novel FVIII inversion involving an extra copy of int22h from a site only 70 to 200 kb telomeric of the FVIII gene. Polymerase chain reaction (PCR) allowed one of the inversion junctions to be analyzed, showing that the int22h sequence at this inversion junction was truncated. This patient and his novel inversion provide further evidence that int22h is associated with instability in Xq28.

Base Sequence↗

PubMedDate not supplied

Differentiation of anal sphincters with high-resolution magnetic resonance imaging using contrast-enhanced fast low-angle shot 3-dimensional sequences.

OBJECTIVE: The imaging of the anal apparatus is becoming more and more important in the management of patients who suffer from anorectal disease. The exact differentiation of the sphincter muscles is a major requirement for the detection of disorders of the anal canal. The purpose of this study was to evaluate a new magnetic resonance (MR) imaging protocol using contrast-enhanced, high-resolution, fast low-angle shot, 3-dimensional (3D) sequences and image subtraction regarding the visualization and differentiation of the internal and external sphincter muscles. METHODS: High-resolution pelvic MR imaging (1.5 T) was performed in 85 patients (42 male, 43 female; age range: 12-81 years) with a phased-array body coil. For an anatomic overview of the pelvic region, a short tau inversion recovery sequence in the coronal plane was carried out, followed by a 3D, high-resolution, fat-saturated, T1-weighted, gradient echo sequence before and after intravenous administration of a contrast agent (gadobenic acid, 0.15 mmol/kg). To optimize the visualization of the sphincter muscles, subtraction of the unenhanced from the contrast-enhanced sequences was routinely performed. The signal intensities of the internal and external sphincter muscles were measured in the axial plane on the subtracted images. RESULTS: The distribution of the mean signal intensities of the internal and external sphincter muscles as well as the difference between both revealed a normal deviation. The confidence interval on a 95% significance level ranged between 1.6941 and 1.9393, with a mean of 1.81. In the whole study group, the signal intensity of the internal sphincter muscle was significantly higher than that of the external sphincter, thus facilitating the identification and differentiation of the 2 components of the anal sphincter complex. CONCLUSION: The presented MR imaging protocol is robust, provides a high image quality, and is well accepted by patients because of its noninvasiveness.

Adolescent↗

PubMed1991

Flow-independent magnetic resonance projection angiography.

The performance of current, flow-based sequences for imaging vasculature using MR is severely restricted in regions with inherently slow flow. We address this problem with a flow-independent imaging method. Specifically, we generate projection images of blood in the limbs while suppressing signal from all other tissues (primarily skeletal muscle, bone marrow, and subcutaneous fat) using a flow-compensated, water-selective, short TI inversion recovery sequence with a long echo time. We experimentally evaluate the effectiveness of this sequence and present in vivo results clearly demonstrating the method's potential.

Adipose Tissue↗

PubMed2005

Apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) in pediatric hypoxic-ischemic brain injury.

BACKGROUND AND PURPOSE: a review of the literature reveals the increasing interest in using Diffusion magnetic resonance imaging, with diffusion weighted images (DWI) and ADC (Apparent Diffusion Coefficient) quantitation, in pediatric hypoxic-ischemic brain injury. However, ADC and MTR (Magnetization Transfer Ratio) as quantitative tools have not been investigated together in these pathological conditions in young pediatric patients. The aim of this study was to apply a quantitative method by using ADC and MTR calculation in order to propose a reproducible quantitation of brain parenchymal lesions. METHODS: we conducted a prospective study including all children presenting with suspected cerebral hypoxic-ischemic injury. 15 children were included, among them 10 males and 5 females aged from 36 weeks of gestation to 17 months with a median age of 10,5 months. All MR examinations were performed at 1.5 Tesla unit including conventional MR (T1, T2 and Inversion-recovery sequences) and DWI with ADC map. ADC and MTR ROI (region of interest) measurements were made, in the frontal subcortical and periventricular white matter (WM) as well as in the gray matter (GM=basal ganglia), and in focal lesions. RESULTS: ADC and MTR values were abnormal in focal lesions and in diffuse injury with no evidence of lesion on conventional MRI and DWI. We observed a strong inverse correlation between these ADC and MTR (R=0,66 in WM; R=0,61 in GM). CONCLUSION: ADC and MTR calculation may be helpful as a reproductive method to quantify the lesions and detect diffuse lesions in hypoxic-ischemic pediatric brain injury.

Diffusion Magnetic Resonance Imaging↗

PubMed1993

Deletion breakpoints associated with the Prader-Willi and Angelman syndromes (15q11-q13) are not sites of high homologous recombination.

Deletions of 15q11.2-q12 are associated with either the Prader-Willi (PWS) or Angelman (AS) syndromes. It has been suggested that excessive recombination in this region might explain the high frequency of such deletions, and the frequent involvement of chromosome 15 in translocations and nondisjunction. We have studied recombination in the PWS region by linkage analysis of non-PWS families. No recombination was found (with maximum lod scores greater than 3.0) for most pair-wise combinations of probes: 39, IR4-3R, ML34, 189-1, 3-21. A 'hotspot' of recombination is observed between loci detected by p3-21 and pIR10-1. The female recombination fraction in this region was significantly higher than that for males. Close linkage with 0.06 recombination was found for the IR10-1 and CMW-1 pair. No excess recombination was found between sites bounding common breakpoints observed in deletions associated with PWS and AS. It is suggested that these deletions form frequently because of the presence of duplicated DNA sequences and/or inversions in this region, and not because of a high rate of homologous recombination.

Angelman Syndrome↗

PubMed2003

MRI correlates of pathology in parkinsonism: segmented inversion recovery ratio imaging (SIRRIM).

The two commonest, clinically well-defined, forms of parkinsonism are idiopathic Parkinson's disease (PD) and progressive supranuclear palsy (PSP). Both involve, inter alia, pathological changes in the substantia nigra pars compacta (SN(C)). In PD there is neuronal loss with associated Lewy body pathology and microglial activation. Three morphological features have been identified [Brain 114 (1991), 2283; Greenfield's Neuropathology 2 (1997), 289]. First, there is a gradient of pathological change such that the lateral segments are more affected than the medial. Second, there is thinning of the pigmented tissue, and third, there is a broadening of the overall structure in a dorsal-ventral direction, possibly caused by the migration of melanin-laden macrophages [Greenfield's Neuropathology 2 (1997), 289]. In contrast, PSP is characterized pathologically by intraneuronal neurofibrillary tangles. There are two morphological features in the SN(C) [Brain 114 (1991), 2283]. First, the gradient of pathological change is in the opposite direction to that of PD (i.e., the medial segments are more affected than the lateral). Second, there is atrophy. Any technique sensitive to neuropathology should be capable of detecting these features. We have previously reported on a new approach to detecting signal change in the substantia nigra in PD. This makes use of a ratio of images acquired by two distinct inversion recovery sequences [J. Neurol, Neurosurg. Psychiatry 67 (1999), 815; Am. J. Neuroradiol. 21 (2000) 697]. The prior work suggests that the technique is sensitive to, but not necessarily specific for, PD. We present here a preliminary report on an extension of the work. This is a semiautomated segmentation analysis that enables the substantia nigra to be displayed as an isolated structure. The technique is now given the acronym SIRRIM (segmented inversion recovery ratio imaging). In contrast to our earlier work, it allows for a more accurate assessment of the gross abnormalities. We report typical SIRRIM images of the SN(C). Images are shown for three subjects: a normal control, a patient with PD, and a "disease control" (a patient with PSP). In these examples all three morphological features of PD, as well as both morphological features of PSP, have radiological correlates. These preliminary findings suggest that SIRRIM may be specific for both diseases.

Aged↗

PubMed1976

Geographical variability in the pericentric inversion system of the grasshopper Trimerotropis pseudofasciata.

Island and mainland populations of Trimerotropis pseudofasciata from California were compared with respect to the nature and extent of their percentric inversion systems. Island populations generally have more chromosomes polymorphic for centromere position than mainland populations and a considerably higher percentage of the genome in these island populations is in a structurally heterozygous state. Thus, although geographically peripheral, the islands provide habitats capable of supporting denser and more chromosomally polymorphic populations than the mainland. Chiasmata are generally localized to terminal positions in all classes of chromosomes and do not occur in the inverted regions of inversion heterozygotes. Chiasma frequency is highest in inversion homozygotes. It is hypothesized that the inversion system in T. pseudofasciata serves the dual synergistic function of preserving allelic sequences in the inversion region intact through inversion heterozygosity and limiting the generation of variability in regions outside the inversion by increasing terminal chiasmata. Additionally, it is argued that it is the gene sequence on only the inversion chromosome that is important in Trimerotropis. This condition contrasts with the "co-adapted" pattern seen in Drosophila where the gene sequences on both chromosomes in the inversion heterozygote are simultaneously important.

Animals↗

PubMed2006

Block lengths and block sequence of linear triblock and glycerol derivative diblock copolyethers by electrospray ionization--collision-induced dissociation mass spectrometry.

Chemical properties of ethylene oxide (EO) and propylene oxide (PO) block copolymers are strongly dependent on their sequence. Useful information about copolymer sequence can be obtained by tandem mass spectrometry (MS/MS). In this work, collision-induced dissociation (CID) of ammonium adducts of various linear triblock and glycerol derivative diblock copolyethers produced by electrospray ionization was studied under low-energy conditions. At first, homopolymers MS/MS spectra enabled us to identify the nature of the product ions and to suggest decomposition pathways. Then, it was shown that copolyethers with the same composition in each repeat unit but with inversed block sequences (i.e., PEO-b-PPO-b-PEO vs PPO-b-PEO-b-PPO and gPEO-b-PPO vs gPPO-b-PEO) can be easily distinguished with characteristic fragment ions. In the case of linear copolymers, CID spectra gave pertinent information about block lengths.

Epoxy Compounds↗

PubMed1991

NMR spin grouping and correlation exchange analysis. Application to low hydration NaDNA paracrystals.

The NMR spin-grouping technique is applied to low hydration oriented fibers of NaDNA to study the role of exchange in determining the apparent (observed) spin relaxation of the system. The analysis proceeds in three steps: first, the apparent proton relaxation is measured at high fields, with both selective and nonselective inversion pulse sequences, and in the rotating frame. The spin-grouping technique is used in all spin-lattice relaxation measurements to provide the optimum apparent relaxation characterization of the sample. Next, all apparent results are analyzed for exchange. In this analysis the results from the high field and rotating frame experiments (which probe the exchange at two different time scales) are correlated to determine the inherent (or true) spin relaxation parameters of each of the proton groups in the system. The results of selective inversion T1 measurements are also incorporated into the exchange analysis. Finally, the dynamics of each spin group are inferred from the inherent relaxation characterization. The low hydration NaDNA structure is such that the exchange between the protons on the water and those on the NaDNA is limited, a priori, to dipolar mixing. The results of the exchange analysis indicate that the dipolar mixing between water and NaDNA protons is faster than the spin diffusion within the NaDNA proton group itself. The spin-diffusion on the macromolecule is the bottleneck for the exchange between the water protons and the NaDNA protons. The water protons serve as the relaxation sink both at high fields and in the rotating frame for the total NaDNA-water spin bath. The inherent relaxation of the water is characteristic of water undergoing anisotropic motion with a fast reorientational correlation time about one axis (5 X 10(-10) less than or equal to tau r less than or equal to 8 X 10(-9)S) which is about three orders of magnitude slower than that of water in the bulk; and a slow tumbling correlation time for this axis (1.5 x 10(-7) less than or equal to tau t less than or equal to 8 x 10(-7)S) which is two orders of magnitude slower yet.

Crystallography↗

PubMed2003

Genome-based identification of cancer genes by proviral tagging in mouse retrovirus-induced T-cell lymphomas.

The identification of tumor-inducing genes is a driving force for elucidating the molecular mechanisms underlying cancer. Many retroviruses induce tumors by insertion of viral DNA adjacent to cellular oncogenes, resulting in altered expression and/or structure of the encoded proteins. The availability of the mouse genome sequence now allows analysis of retroviral common integration sites in murine tumors to be used as a genetic screen for identification of large numbers of candidate cancer genes. By positioning the sequences of inverse PCR-amplified, virus-host junction fragments within the mouse genome, 19 target genes were identified in T-cell lymphomas induced by the retrovirus SL3-3. The candidate cancer genes included transcription factors (Fos, Gfi1, Lef1, Myb, Myc, Runx3, and Sox3), all three D cyclins, Ras signaling pathway components (Rras2/TC21 and Rasgrp1), and Cmkbr7/CCR7. The most frequent target was Rras2. Insertions as far as 57 kb away from the transcribed portion were associated with substantially increased transcription of Rras2, and no coding sequence mutations, including those typically involved in Ras activation, were detected. These studies demonstrate the power of genome-based analysis of retroviral insertion sites for cancer gene discovery, identify several new genes worth examining for a role in human cancer, and implicate the pathways in which those genes act in lymphomagenesis. They also provide strong genetic evidence that overexpression of unmutated Rras2 contributes to tumorigenesis, thus suggesting that it may also do so if it is inappropriately expressed in human tumors.

Animals↗

PubMed1986

Rearrangements and insertions in the Moloney murine leukemia virus long terminal repeat alter biological properties in vivo and in vitro.

The effects of rearrangement and insertion of sequences in the Moloney murine leukemia virus (M-MuLV) long terminal repeat (LTR) were investigated. The alterations were made by recombinant DNA manipulations on a plasmid subclone containing an M-MuLV LTR. Promoter activity of altered LTRs was measured by fusion to the bacterial chloramphenicol acetyltransferase gene, followed by transient expression assay in NIH 3T3 cells. M-MuLV proviral organizations containing the altered LTRs were also generated, and infectious virus was recovered by transfection. Infectivity of the resulting virus was quantified by XC plaque assay, and pathogenicity was determined by inoculating neonatal NIH Swiss mice. Inversion of sequences in the U3 region containing the tandemly repeated enhancer sequences (-150 to -353 base pairs [bp]) reduced promoter activity approximately fivefold in the transient-expression assays. Infectious virus containing the inverted sequences (Mo- M-MuLV) showed a 20-fold reduction in relative infectivity compared with wild-type M-MuLV, but the virus still induced thymus-derived lymphoblastic lymphoma or leukemia in mice, with essentially the same kinetics as for wild-type M-MuLV. We previously derived an M-MuLV which carried inserted enhancer sequences from the F101 strain of polyomavirus (Mo + PyF101 M-MuLV) and showed that this virus is nonleukemogenic. In Mo + PyF101 M-MuLV, the PyF101 sequences were inserted between the M-MuLV promoter and the M-MuLV enhancers (at -150 bp). A new LTR was generated in which the PyF101 sequences were inserted to the 5' side of the M-MuLV enhancers (at -353 bp, PyF101 + Mo M-MuLV). The PyF101 + Mo LTR exhibited promoter activity similar (40 to 50%) to that of wild-type M-MuLV, and infectious PyF101 + Mo M-MuLV had high infectivity on NIH 3T3 cells (50% of wild type). In contrast to the nonleukemogenic Mo + PyF101 M-MuLV, PyF101 + Mo M-MuLV induced leukemia with kinetics similar to that of wild-type M-MuLV. Thus, the position of the PyF101 sequences relative to the M-MuLV LTR affected the biological behavior of the molecular construct. Furthermore, PyF101 + Mo M-MuLV induced a different spectrum of neoplastic disease. In comparison with wild-type M-MuLV, which induces a characteristic thymus-derived lymphoblastic lymphoma with extremely high frequency, PyF101 + Mo M-MuLV was capable of inducing both acute myeloid leukemia or thymus-derived lymphoblastic lymphoma, or both. Tumor DNA from both the PyF101 + Mo- and Mo- M-MuLV-inoculated animals contained recombinant proviruses with LTRs that differed from the initially inoculated virus.

Animals↗

PubMed1995

Predominant expression of invariant V alpha 14+ TCR alpha chain in NK1.1+ T cell populations.

A novel T cell subset characterized by cell surface NK1.1+ TCR alpha beta+ expression was investigated for its TCR alpha usage, particularly that of invariant V alpha 14 TCR, which was found to be preferentially used in peripheral CD4-CD8- T cells developed at extrathymic sites. We found that NK+ alpha beta T cell subsets account for 0.4% in thymocytes, 5% in the splenic T cells and 40.5% in the bone marrow T cells. Among these NK+ alpha beta T cells, two distinct subsets were detected; cell surface TCR V alpha 14+ and V alpha 14- subpopulations. Almost all of NK+ alpha beta thymocytes express V alpha 14 mRNA; however, only < 20% were positive, while > 80% were negative or undetectable for V alpha 14 TCR expression on the cell surface in the thymus. Similarly, approximately 50% of NK+ alpha beta T cells in spleen and bone marrow are V alpha 14+ as revealed by FACS. TCR repertoire analysis by nucleotide sequences on inverse PCR products demonstrated that most NK+ alpha beta T cells express an invariant TCR encoded by the V alpha 14J alpha 281 gene with a 1 base N-region in all tissues. Thus, invariant V alpha 14 TCR is uniquely expressed on NK T cells, and can be a marker to distinguish NK, NK T and T cells.

Animals↗

PubMedDate not supplied

Combined fat- and water-suppressed MR imaging of orbital tumors.

BACKGROUND AND PURPOSE: The use of a high-resolution T2-weighted MR sequence, which suppresses signal from both fat and water, has been shown to be highly effective for depicting areas of inflammatory damage within the optic nerve. The ability of this sequence to show neoplastic and inflammatory orbital lesions, which may mimic neuritis, is unknown. This study was designed to examine the characteristics of such a sequence for the investigation of orbital mass lesions. METHODS: Twenty-eight patients with known or suspected mass lesions of the orbit and six healthy volunteers were recruited for study. Imaging was performed with a 1.5-T MR unit. Participants were examined by selective partial inversion recovery (SPIR) sequences with T2-weighted fast spin-echo acquisition, selective partial inversion recovery/fluid attenuated inversion recovery (SPIR/FLAIR) sequences with fast spin-echo acquisition, short tau inversion recovery (STIR) sequences with fast spin-echo acquisition, and SPIR sequences with contrast-enhanced T1-weighted fast spin-echo acquisition. Two neuroradiologists, using a randomised, blinded method, scored images for lesion presence and extent. Lesion extent was defined as the number of images with visible abnormality, and was compared with the standard of reference established at a later date by consensus review of all imaging sequences. The ability of the sequences to show the presence and extent of pathologic lesions was compared. RESULTS: The SPIR/FLAIR sequence showed both the presence and extent of orbital masses significantly better than did either STIR or T2-weighted SPIR sequences (P<.01 and P<.001, respectively). Contrast-enhanced T1-weighted SPIR images ranked better than SPIR/FLAIR images, although the difference failed to reach statistical significance. In the orbital apex, the SPIR/FLAIR technique was superior to all other techniques used. This reflected its ability to distinguish enhancing, pathologic lesions from enhancing, normal anatomy. CONCLUSION: SPIR/FLAIR is an appropriate screening technique for orbital masses and offers significant advantages over currently used fat-suppressed sequences for the investigation of orbital disease.

Adolescent↗