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PubMed2004

[Double inversion recovery sequence in temporal lobe epilepsy: preliminary results].

PURPOSE: DIR (double inversion recovery) is a sequence with the hybrid contrast of both FLAIR and STIR sequences, produced by the application of double inversion recovery pulse. It has been suggested that DIR provides high sensitivity to lesions with low T2 contrast. The purpose of this study was to test the hypothesis that DIR sequence is superior to conventional sequences in the identification of mesial temporal sclerosis and other temporal lobe lesions in patients with temporal lobe epilepsy. MATERIALS AND METHODS: Thirty-three subjects with a prediagnosis of temporal lobe epilepsy and ten healthy control subjects with no abnormality on magnetic resonance imaging studies have been studied with DIR, FLAIR and T2W sequences. Coronal images through temporal lobes and hippocampus were acquired. Qualitatively, overall sensitivity to the presence of lesions, hippocampal lesion detectability, temporal horn dilatation and artifacts were evaluated in temporal lobe epilepsy cases and quantitatively, hippocampal and white matter signal-to-noise ratio as well as hippocampus-white matter contrast-to-noise ratio were calculated in the healthy subjects. Subjective scores were graded on a scale of 3 or 4 points. RESULTS: Signal-to-noise ratio scores were higher on T2W sequence, however contrast-to-noise ratio scores were higher on DIR sequence compared to the other two sequences. Imaging findings were compatible with mesial temporal sclerosis in seven patients, tumoral mass in two, and chronic infarct in four. DIR sequence was less sensitive to hippocampal atrophy than the other two sequences because of cerebrospinal fluid artifacts. Overall sensitivity to the presence of lesions and hippocampal lesion detectability scores, although similar among three sequences, were highest with DIR sequence. However, lesion sensitivity scores were highest for lesions compatible with mesial temporal sclerosis and for solid masses and lowest for cystic lesions on DIR sequence. CONCLUSION: Despite the presence of artifacts, DIR is a sequence providing high sensitivity to mesial temporal sclerosis like lesions at hippocampus. DIR might be useful as an additional sequence when the other conventional sequences reveal a suspicious lesion with no accompanying hippocampal atrophy.

Adolescent↗
PubMed2000

Detection of parametrial invasion in cervical carcinoma: role of short tau inversion recovery sequence.

AIM: To investigate the role of short tau inversion recovery (STIR) sequence in the detection of parametrial invasion in patients with carcinoma of the cervix. MATERIALS AND METHODS: Axial magnetic resonance imaging (MRI) images of the cervical region using T1 weighted turbo spin echo (TSE), TSE T2, STIR and T1 weighted dynamic gadolinium enhanced SE sequences were obtained in 38 patients with cervical carcinoma. All the images were assessed for the presence or absence of parametrial invasion using a standard scoring system. The diagnostic confidence, image quality, sensitivity, specificity, positive and negative predictive values and accuracy of each sequence were compared. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for each sequence in the diagnosis of parametrial invasion were: 60%, 80%, 32%, 93% and 78% for unenhanced T1W sequence; 90%, 92%, 64%, 98% and 92% for TSE T2 sequence; 90%, 94%, 69%, 98% and 93% for STIR sequence; and 90%, 80%, 41%, 98% and 82% for dynamic T1W sequence, respectively. Image quality and diagnostic confidence were both better for STIR and T2 compared to the dynamic T1 sequence. CONCLUSION: Dynamic T1W imaging is inferior to STIR and TSE T2 sequences. STIR is of similar value in the detection of parametrial invasion in cervical carcinoma as a TSE T2W sequence; their simultaneous use is not justified.

Adenocarcinoma↗
PubMed2006

Prognostic value of hyperintense vessel signals on fluid-attenuated inversion recovery sequences in acute cerebral ischemia.

BACKGROUND: Fluid-attenuated inversion recovery (FLAIR) sequences may reveal hyperintense vessel signals (HVS) at the acute stage of cerebral ischemia. The aim of this study was to test the hypothesis that HVS are associated with a worse outcome. METHODS: We included 30 consecutive patients admitted within 12 h after onset of hemispheric cerebral ischemia. The outcome was assessed with the modified Rankin Scale at month 1. RESULTS: Proximal HVS were present in 9 patients and distal HVS in 16. All patients with proximal occlusions on time-of-flight sequences had distal HVS on FLAIR. Patients with poor outcome at month 1 (modified Rankin Scale 3-6) more frequently had had HVS on MRI (12/13 vs. 4/17; p< 0.001). CONCLUSION: Distal HVS found on FLAIR sequences within 12 h of acute cerebral ischemia are associated with a worse 1-month outcome.

Adult↗
PubMed1989

[MR characterization of breast pathology using inversion recovery sequence].

As yet, a valid tissue characterization of human breast diseases has not been possible with conventional MR techniques. On the basis of the experimental thesis according to which fibroadenomas and carcinomas have a slight, though significant, difference in T1 relaxation times, we employed specific inversion recovery sequences at the T null of the breast glandular and adipose tissues, to enhance the differences in the signal intensities of the various pathologies. We examined 16 (6 cystic dysplasias, 5 fibroadenomas, 3 carcinomas, and 1 phylloid fibroadenoma) selected patients with the above-mentioned sequences in addition to the routine T1- and T2-weighted spin echo sequences. The following conclusions were reached by evaluating the characteristic signal intensities: MR spin echo sequences allow solid lesions to be distinguished from cystic ones; MR inversion recovery sequences allow fibroadenomas to be distinguished from carcinomas with 88% accuracy.

Adenofibroma↗
PubMed1996

Adult cerebrovascular disease: role of modified rapid fluid-attenuated inversion-recovery sequences.

PURPOSE: To compare a rapid fluid-attenuated inversion-recovery (FLAIR) sequence with T1-weighted, fast spin-echo proton density-weighted, and T2-weighted images in the evaluation of cerebrovascular disease. METHODS: All patients underwent standard T1-, proton density-, and T2-weighted fast spin-echo and fast FLAIR MR imaging at 1.5 T. Images were compared for lesion size, location, and conspicuity. RESULTS: Forty-five infarctions were identified on T2-weighted and fast FLAIR sequences. Lesion size was comparable on the proton density-weighted, fast T2-weighted, and fast FLAIR sequences, although lesion conspicuity was superior on the fast FLAIR images in 43 (96%) of the lesions. Associated periventricular and pontine hyperintensities were more extensive on the fast FLAIR images. CONCLUSION: Our modified fast FLAIR technique provided improved conspicuity of infarctions and white matter disease as compared with T1-, proton density-, and T2-weighted spin-echo images, and a reduced scan time compared with conventional FLAIR sequences in patients with cerebrovascular disease.

Adult↗
PubMed1997

MR of the spine with a fast T1-weighted fluid-attenuated inversion recovery sequence.

PURPOSE: To optimize a T1-weighted fast fluid-attenuated inversion recovery (FLAIR) sequence using computer-simulated data and to study its clinical utility for imaging the spine. METHODS: Relative signal intensities and contrast of relevant normal and pathologic tissues in the spine were computed using an inversion recovery equation modified to account for a hybrid RARE (rapid acquisition with relaxation enhancement) readout. A range of inversion time (TI) and repetition time (TR) pairs that null the signal from CSF was generated. A contrast-optimized heavily T1-weighted fast FLAIR sequence, based on the generated data, was qualitatively compared with conventional T1-weighted spin-echo sequences for imaging various spinal abnormalities. RESULTS: A T1/TR pair of approximately 862/2000 was extracted from the computer-generated data to produce effective nulling of CSF signal, to achieve heavy T1 weighting, and to optimize contrast between abnormal tissues and cord/bone marrow. Clinical implementation of the optimized T1-weighted fast FLAIR sequence revealed superior contrast at the CSF-cord interface, better conspicuity of lesions of the spinal cord and bone marrow, and reduced hardware-related artifacts as compared with conventional T1-weighted spin-echo sequences. CONCLUSION: The optimized T1-weighted fast FLAIR technique has definite advantages over spin-echo sequences for imaging the spine. Comparable acquisition times render the FLAIR sequence the method of choice for T1-weighted imaging of the spine.

Adult↗
PubMed2003

Magnetic resonance imaging of normal and osteomyelitis in the mandible: assessment of short inversion time inversion recovery sequence.

OBJECTIVE: We sought to determine the suitable magnetic resonance imaging conditions for the short inversion time inversion recovery (STIR) sequence through the use of phantoms; to describe the signal characteristics of normal structures in the mandible; and to evaluate the usefulness of STIR images in enabling the identification of mandibular osteomyelitis on conventional T1- and T2-weighted spin-echo images. STUDY DESIGN: Suitable mandibular STIR imaging conditions were determined by varying inversion time and repetition time in each sequence. STIR magnetic resonance images of 162 healthy subjects and STIR and T1- and T2-weighted spin-echo images of 21 subjects with mandibular osteomyelitis were evaluated. RESULTS: In STIR imaging, the signal of oil was suppressed at an inversion time equaling 100 milliseconds and a repetition time equaling 1500 to 3000 milliseconds. In healthy subjects, the mandibular marrow was revealed to have high signal intensities (100%) and cortical bone had no signal intensities (100%) on STIR images. In surrounding soft tissue in these healthy subjects, the submandibular glands were shown to have high signal intensities (100%); the parotid glands had intermediate to high signal intensities (100%); the sublingual glands had high (88.9%) and intermediate to high (11.1%) signal intensities; lymph nodes had high signal intensities (100%); and the masseter muscles had intermediate signal intensities (100%) on STIR images. The lesions in bone marrow had low (75%) and low to intermediate (25%) signal intensities on T1-weighted images and high (54%), intermediate to high (29%), and intermediate (17%) signal intensities on T2-weighted images. On STIR images, the signal intensities resulted in high (75%), intermediate to high (21%), and intermediate (4%) signal intensities. CONCLUSIONS: STIR imaging is highly effective for the evaluation of bone marrow and surrounding soft tissue in terms of the detection of osteomyelitis in the mandible and the identification of inflammation spreading to soft tissue.

Adult↗
PubMedDate not supplied

Experience with MR cholangiopancreatography with use of a fast inversion recovery sequence during a single breath-hold period.

The purpose of this study was to evaluate the single breath-hold fast inversion recovery sequence (FIR) for depicting the biliary tract. A prospective study was performed in 40 patients with suspected diseases in the biliary tract. MRCP (magnetic resonance cholangiopancreatography) including cholecystograms of diagnostic quality was carried out in 35 patients. Impacted common duct stones were able to be distinguished from malignancies because of their characteristic shapes of obstruction in four of five cases. FIR with thick slices can provide a shorter acquisition time and fewer artifacts with better signal to noise ratio and contrast to noise ratio than MIP images obtained by means of gradient echo methods. MRCP with FIR was a useful adjunctive tool for non-invasive evaluation of patients with obstructive jaundice.

Biliary Tract↗
PubMed1991

Structure of the gas vesicle plasmid in Halobacterium halobium: inversion isomers, inverted repeats, and insertion sequences.

Halobacterium-halobium NRC-1 harbors a 200-kb plasmid, pNRC100, which contains a cluster of genes for synthesis of buoyant gas-filled vesicles. Physical mapping of pNRC100 by using pulsed-field gel electrophoresis showed the presence of a large (35 to 38-kb) inverted repeat (IR) sequence. Inversion isomers of pNRC100 were demonstrated by Southern hybridization analysis using two restriction enzymes, AflII and SfiI, that cut asymmetrically within the intervening small single-copy region and the large single-copy region, respectively, but not within the large IRs. No inversion isomers were observed for a deletion derivative of pNRC100 lacking one IR, which suggests that both copies are required for inversion to occur. Additionally, the identities and approximate positions of 17 insertion sequences (IS) in pNRC100 were determined by Southern hybridization and limited nucleotide sequence analysis across the IS element-target site junctions: ISH2, a 0.5-kb element, was found in four copies; ISH3, a 1.4-kb heterogeneous family of elements, was present in seven copies; ISH8, a 1.4-kb element, was found in five copies; and ISH50, a 1.0-kb element, was present in a single copy. The large IRs terminated at an ISH2 element at one end and an ISH3 element at the other end. pNRC100 is similar in structure to chloroplast and mitochondrial genomes, which contain large IRs and other large halobacterial and prokaryotic plasmids that are reservoirs of IS elements but lack the large IRs.

Base Sequence↗
PubMed1988

Magnetic resonance imaging of the parotid glands using inversion-recovery sequences at 0.08 T.

One hundred and eight examinations on 103 patients with suspected disease of the salivary glands were studied using a 0.08 T resistive magnet and inversion-recovery pulse sequences. Sixty-eight patients who had a mass lesion within a salivary gland later had surgery, and specimens were obtained for histological diagnosis. The remaining 35 patients were diagnosed on clinical grounds. In all cases the clinical findings were compared with the appearances on magnetic resonance imaging (MRI). The use of inversion-recovery pulse sequences allowed accurate localization of all tumour masses and, because of the clarity with which blood vessels were displayed, the precise relationship of any parotid mass to the retromandibular vessels and hence the facial nerve was possible. Whilst MRI did not display any pathognomonic features to allow the differentiation of malignant cell types or the differentiation of invasive malignant tumours from chronic inflammatory disease, it was possible to differentiate parotitis from Mikulicz's disease and to diagnose cysts and pleomorphic adenomas by their appearances on MRI.

Cysts↗
PubMed1997

[Fast spin echo and fast fluid attenuated inversion recovery sequences in multiple sclerosis].

Fast spin echo (FSE) and fast fluid attenuated inversion recovery (fast-FLAIR) MR sequences were compared with conventional spin echo (CSE) in quantitating multiple sclerosis (MS) lesion burden. For each sequence, the total number and volume of MS lesions were calculated in 38 remitting MS patients using a semiautomated lesion detection program. CSE, FSE and fast-FLAIR images were reported on randomly and at different times by two expert observers. Interobserver differences, the time needed to quantitate MS lesions and lesion signal intensity (contrast-to-noise ratio and overall contrast) were considered. The lesions were classified by site into infratentorial, white matter and cortical/subcortical. A total of 2970 lesions with a volume of 961.7 cm3 was calculated on CSE images. FSE images depicted fewer (16.6%; p < .005) and smaller (24.9%; p < .0001) lesions and the differences were statistically significant. Despite an overall nonsignificant reduction for fast-FLAIR images (.5% and 4.8% for lesion number and volume, respectively), significantly lower values (lesion number: p < .01; volume: p < .04) were observed for infratentorial lesions, while significantly higher values were seen for cortical/subcortical lesions (lesion number: p < .01; volume: p < .02). A higher lesion/white matter contrast (p < .002), a significant time saving for lesion burden quantitation (p < .05) and very low interobserver variability were found in favor of fast-FLAIR. Our data suggest that, despite the limitations regarding infratentorial lesions, fast-FLAIR sequences are indicated in MS studies because of their good identification of cortical/subcortical lesions, almost complete interobserver agreement, higher contrast-to-noise ratio and the limited time needed for semiautomated quantitation.

Adult↗
PubMed2000

Value of fluid-attenuated inversion recovery sequences in early MRI of the brain in neonates with a perinatal hypoxic-ischemic encephalopathy.

The aim of our study was to assess the usefulness of fluid-attenuated inversion recovery (FLAIR) sequences in comparison with conventional spin-echo and inversion MR imaging in neonates for evaluation of myelination and for detection of hypoxic-ischemic brain injury. We reviewed early MR scans of 18 neonates with suspected hypoxic-ischemic brain damage. Myelination could be evaluated with confidence using conventional MR imaging in all but 2 infants; however, the presence of myelin was very difficult to assess on FLAIR images. Overall, 53 lesions or groups of lesions were identified. The FLAIR technique was more sensitive in 11 of the lesions; especially (pre)cystic lesions could be identified much better and more cysts were found. Conventional MR imaging failed to identify 2 of the lesions and was more sensitive in 14 of the lesions; especially punctate hemorrhages and lesions in basal ganglia or thalami could be better determined. The FLAIR technique missed 3 of these lesions. In the remaining 28 lesions conventional MR and FLAIR images were equally diagnostic. The FLAIR technique and conventional MR imaging are complementary in detecting early sequelae of hypoxic-ischemic brain injury in neonates. The FLAIR technique is not suitable for assessing myelination of the neonatal brain; therefore, FLAIR cannot replace conventional MR imaging.

Brain↗
PubMed2004

Inherited and somatic cytogenetic variability in Palearctic populations of Chironomus riparius Meigen 1804 (Diptera, Chironomidae).

Inter- and intracytogenetic variability was analyzed in 13 natural Palearctic populations of Chironomus riparius Meigen 1804 (syn. Chironomus thummi) by examining hereditary and somatic aberrations (mainly inversions) of the salivary gland polytene chromosomes. In total, 77 different types of inherited inversion sequences and 184 different types of somatic inversions were found. The median percent frequency of inherited inversions was 1.4% and karyotypic divergence between populations was very low. Most hereditary inversions were endemic and always in a heterozygous state. Only six inversion sequences, each of them shared by two very distant populations, may be considered a relic of very ancient ancestral inversions. Unlike inherited inversions, occurrence of somatic aberrations seems to increase with the overall rise in the level of heavy metal pollution of the sediments from which larvae were sampled. In contrast with what occurs in populations of other chironomid species, populations of C. riparius do not seem to undergo a process of cytogenetic differentiation.

Animals↗
PubMed2000

A high-resolution fast spin-echo inversion-recovery sequence for preoperative localization of the internal globus pallidus.

A fast spin-echo inversion-recovery (FSE-IR) sequence is described for its utility regarding surgical planning for patients with Parkinson's disease (PD) who are undergoing microelectrode-guided internal globus pallidus (GPi) ablation. Images from thirty-seven adult patients with PD were reviewed and visualization of the GPi, globus pallidus externa (GPe), and the intervening lamina was noted. High-resolution images were acquired from all patients despite the external hardware and the patients' movement disorder. In all cases, the conventional surgical trajectory, determined indirectly by a fixed measurement from the anteroposterior commissure line, was modified by the ability to visualize the GPi and optic tract directly. This sequence facilitated accurate stereotactic targeting.

Adult↗
PubMed2004

Exclusion of brain lesions: is MR contrast medium required after a negative fluid-attenuated inversion recovery sequence?

We hypothesized that in patients with negative fluid-attenuated inversion recovery (FLAIR) images T(2) weighted fast spin-echo (FSE) images and T(1) weighted spin-echo (SE) images before and after intravenous administration of gadolinium-based contrast medium display no pathology either. Thus, we assessed the negative predictive value of FLAIR images to rule out MR-detectable brain lesions. 1026 consecutive cranial MR examinations were reviewed. Routine MRI of the brain included T(1) weighted coronal imaging before and after administration of gadopentetate dimeglumine, axial T(2) weighted FSE and fast-FLAIR imaging. The FLAIR images were rated by two radiologists into categories of 0 (without pathologic changes) and 1 (with pathologic changes). Two other radiologists analysed the complete examination. In 284 MR examinations of the brain no abnormalities were found (28%). FLAIR-ratings were false-negative in four cases and false-positive in 30 cases. Sensitivity and specificity of the FLAIR sequence for MR-detectable brain lesions were 99.5% and 89.4%. The unselective application of gadolinium avoided one false-negative MR-reading and improved the sensitivity of the MR-examination from 99.5% to 99.6%. Positive and negative predictive values were 96.1% and 98.4%, respectively. The interobserver reliability was kappa=0.93 for the FLAIR-readers and 0.89 for the readers who rated the complete examination. In conclusion, negative FLAIR images provide a high negative predictive value for MR-detectable brain lesions. Thus, in patients with negative FLAIR images the unselective application of gadolinium seems to be unnecessary.

Adolescent↗
PubMed2001

Imaging of acute subarachnoid hemorrhage with a fluid-attenuated inversion recovery sequence in an animal model: comparison with non-contrast-enhanced CT.

BACKGROUND AND PURPOSE: Fluid-attenuated inversion recovery (FLAIR) MR imaging sequences have been previously described in the evaluation of acute subarachnoid hemorrhage (SAH) in human subjects and have demonstrated good sensitivity. The purpose of this study was to evaluate a FLAIR sequence in an animal model of SAH and to compare the results with those obtained with non-contrast-enhanced CT. METHODS: SAH was experimentally induced in 18 New Zealand rabbits by injecting autologous arterial blood into the subarachnoid space of the foramen magnum. Nine animals had high-volume (1-2 mL) injections, and nine animals had low-volume (0.2-0.5 mL) injections. Four control animals were injected with 0.5 mL of saline. The animals were imaged with a FLAIR sequence and standard CT 2-5 hours after injection. Gross pathologic evaluation of seven of the animals was performed. Four blinded readers independently evaluated the CT and FLAIR images for SAH and graded the probability of SAH on a scale of 1 to 5 (1 = no hemorrhage, 5 = definite hemorrhage). RESULTS: Overall, the sensitivity of FLAIR was 89%, and the sensitivity of CT was 39% (P <.01). In animals with a high volume of SAH, the sensitivity of FLAIR was 100%, and the sensitivity of CT was 56%. In animals with a low volume of SAH, the sensitivity of FLAIR was 78%, and the sensitivity of CT was 22%. The specificity of FLAIR in animals without SAH was 100%, and the specificity of CT was 100%. The average reader score for FLAIR was 3.8, and that for CT was 2.2 (P <.001). Reader scores for FLAIR were higher than those for CT in 94% (P <.01) of animals with SAH and in 25% of animals without SAH (P >.05). Seven animals underwent gross pathologic examination, and all had blood in the subarachnoid space around the brain stem. CONCLUSION: FLAIR was more sensitive than CT in the evaluation of acute SAH in this model, especially when a high volume of SAH was present. This study provides a model for further experimentation with MR imaging in the evaluation of SAH. These findings are consistent with those of current clinical literature, which show FLAIR to be an accurate MR sequence in the diagnosis of SAH.

Acute Disease↗
PubMed1996

Determining depth of invasion of advanced colorectal cancer using MRI short inversion time inversion recovery sequences.

To examine the usefulness of magnetic resonance imaging (MRI) in the preoperative determination of cancerous invasion, we examined 39 patients with advanced colorectal cancer with 0.5T MRI. We employed short inversion time inversion recovery (STIR) sequences, in addition to ordinary spin echo sequences for T1- and T2-weighted images. Preoperatively, the estimated depth of tumor invasion was classified into three grades according to MRI findings, and confirmed on the basis of surgical and histopathologic results. The depth of tumor invasion estimated preoperatively using STIR sequences corresponded well with the surgical and histopathologic results in 85% of the cases. In contrast, assessments based on T1-weighted images corresponded well in only 62% of the cases and T2-weighted images corresponded well in only 64%.

Colon, Sigmoid↗