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1.
Magn Reson Imaging ; 18(2): 117-24, 2000 Feb.
Article in English | MEDLINE | ID: mdl-10722970

ABSTRACT

The purpose of this study was to develop a multi-shot dual-echo breathhold fast spin echo technique (DFSE) and compare it with conventional spin echo (T2SE) for T(2)-weighted MR imaging of liver lesions. The DFSE acquisition (EffTE1/EffTE2/TR = 66/143/2100 ms) imaged 5 sections per 17 s breathhold. T2SE imaging (TE1/TE2/TR = 60/120/2500 ms) required 16:55 (min:s) for 14 sections. Both techniques used a receive-only phased-array abdominal multicoil and provided 192 x 256 effective resolution. The results showed first and second echo relative DFSE/T2SE contrast values for 27 representative lesions (15 consecutive patients) were 1.08 +/- 0.05 and 1.16 +/- 0.09 (mean +/- STD mean), respectively. Corresponding CNR values were 1.12 +/- 0.09 and 0.97 +/- 0.12. Overall DFSE was comparable-to-superior to T2SE for lesion sizing and image artifact. DFSE lesion detection was inferior to T2SE's in several patient studies because of decreased conspicuity of lesions located near multicoil edges and because of poor breathhold-to-breathhold reproducibility and lack of breathholding. However both DFSE (and T2SE) provided lesion detection rated to be of diagnostic quality for all patient studies. In conclusion, we found that DFSE provides diagnostically useful dual-echo T(2)-weighted MR liver images in a greatly decreased acquisition time.


Subject(s)
Carcinoma, Hepatocellular/diagnosis , Echo-Planar Imaging/instrumentation , Image Enhancement/instrumentation , Liver Neoplasms/diagnosis , Magnetic Resonance Imaging/instrumentation , Adult , Aged , Artifacts , Cysts/diagnosis , Diagnosis, Differential , Fourier Analysis , Humans , Liver/pathology , Liver Diseases/diagnosis , Liver Neoplasms/secondary , Middle Aged , Sensitivity and Specificity
2.
Radiology ; 199(2): 367-73, 1996 May.
Article in English | MEDLINE | ID: mdl-8668780

ABSTRACT

PURPOSE: To compare the accuracy of a fluid-attenuated inversion-recovery (FLAIR) sequence with that of a conventional double spin-echo (SE) sequence in the identification of increased signal intensity of the hippocampus in mesial temporal sclerosis (MTS). MATERIALS AND METHODS: Three blinded reviewers independently graded the FLAIR and SE images in 36 patients with intractable complex partial seizures. Reproducibility was tested. At histopathologic examination, the criterion standard, 32 patients had MTS. RESULTS: The accuracy of FLAIR images was 97% versus 91% for SE images (P<.02). The radiologists preferred the contrast properties of FLAIR to those of SE images by a significant margin (P<.0001). Surgical to nonsurgical hippocampal contrast-to-noise ratio (C/N) measurements were better for the second echo of the SE sequence than for FLAIR (P<.002). Hippocampus-to-background tissue C/N was superior with FLAIR (P<.0001). CONCLUSION: FLAIR provides images with T2-weighted contrast and complete suppression of high signal intensity of CSF. Incorporation of a FLAIR sequence into the routine MR evaluation of patients with epilepsy is recommended.


Subject(s)
Epilepsy, Complex Partial/pathology , Hippocampus/pathology , Magnetic Resonance Imaging/methods , Temporal Lobe/pathology , Adult , Artifacts , Epilepsy, Complex Partial/surgery , Female , Humans , Image Enhancement/methods , Male , Observer Variation , Psychosurgery , Reproducibility of Results , Sclerosis , Sensitivity and Specificity , Temporal Lobe/surgery , Time Factors
3.
J Magn Reson Imaging ; 6(2): 356-62, 1996.
Article in English | MEDLINE | ID: mdl-9132102

ABSTRACT

The purpose of this paper was to develop and evaluate a fast inversion recovery (FIR) technique for T1-weighted MR imaging of contrast-enhancing brain pathology. The FIR technique was developed, capable of imaging 24 sections in approximately 7 minutes using two echoes per repetition and an alternating echo phase encoding assignment. Resulting images were compared with conventional T1-weighted spin echo (T1SE) images in 18 consecutive patients. Compared with corresponding T1SE images, FIR images were quantitatively comparable or superior for lesion-to-background contrast and contrast-to-noise ratio (CNR). Gray-to-white matter and cerebrospinal fluid (CSF)-to-white matter contrast and CNR were statistically superior in FIR images. Qualitatively, the FIR technique provided comparable lesion detection, improved lesion conspicuity, and superior image contrast compared with T1SE images. Although FIR images had greater amounts of image artifacts, there was not a statistically increased amount of interpretation-interfering image artifact. FIR provides T1-weighted images that are superior to T1SE images for a number of image quality criteria.


Subject(s)
Brain Diseases/diagnosis , Brain Neoplasms/diagnosis , Brain/pathology , Magnetic Resonance Imaging/methods , Artifacts , Brain Neoplasms/secondary , Humans , Image Processing, Computer-Assisted , Middle Aged , Time Factors
4.
Magn Reson Med ; 34(6): 868-77, 1995 Dec.
Article in English | MEDLINE | ID: mdl-8598814

ABSTRACT

The optimization of contrast is considered for the fluid-attenuated inversion recovery (FLAIR) MRI pulse sequence, specifically the contrast of multiple sclerosis (MS) to white matter (WM). A performance bound is identified at 1.5 Tesla as that provided using an inversion time (TI) of 2900 ms. It is shown that TR/TI times exceeding 11000/2600 ms provide about 90% of the MS-WM contrast possible theoretically. The commonly reported TR/TI combination of 6000/2000 provides only about 60%. For TR times exceeding 8000 ms, an echo time (TE) of 140 ms is at or near optimum. Use of TR/TI times less than 9000/2400 lacks efficiency in multisection imaging. Predicted relative contrast performance of TR/TI 11000/2600 versus 6000/2000 was evaluated in seven patients with known MS lesions, and measurements closely matched theoretical predictions. It is strongly recommended that for near optimum contrast and high multisection efficiency, FLAIR should be performed with TR/TI times exceeding 10000/2500 ms.


Subject(s)
Brain/pathology , Magnetic Resonance Imaging/methods , Multiple Sclerosis/pathology , Humans , Image Enhancement/methods , Image Processing, Computer-Assisted , Time Factors
5.
Radiology ; 195(3): 769-76, 1995 Jun.
Article in English | MEDLINE | ID: mdl-7754009

ABSTRACT

PURPOSE: To prospectively compare use of a phased-array multicoil and a conventional body coil in abdominal MR imaging. MATERIALS AND METHODS: Thirteen patients (seven men, six women; mean age, 55 years) underwent imaging with a phased-array multicoil and with a conventional body coil. Four pulse sequences were used: T2-weighted spin echo (SE), magnetization-prepared gradient-recalled echo (GRE), breath-hold fast SE, and echo planar (EP). RESULTS: Lesion detection improved the most on fast SE, multicoil-acquired images. Signal-to-noise ratio (S/N) increased 64% with fast SE (P = .0005) and EP (P < .0109) sequences. Contrast-to-noise ratio (C/N) doubled (P < .05) with T2-weighted SE sequences. Lesion conspicuity improved on multicoil-acquired images with all fast sequences (magnetization-prepared GRE, P = .015; fast SE, P = .002; EP imaging, P = .013). There was little difference in respiratory and vascular artifact. Depiction of most abdominal structures improved (P < .01). CONCLUSION: Use of the phased-array multicoil provides better MR images of the abdomen than does use of a conventional body coil.


Subject(s)
Abdomen/pathology , Magnetic Resonance Imaging/instrumentation , Abdomen/anatomy & histology , Abdominal Neoplasms/diagnosis , Adult , Aged , Artifacts , Female , Humans , Magnetic Resonance Imaging/methods , Male , Middle Aged , Prospective Studies
6.
Radiology ; 194(2): 431-7, 1995 Feb.
Article in English | MEDLINE | ID: mdl-7824723

ABSTRACT

PURPOSE: To evaluate a breath-hold fast spin-echo (SE) technique for T2-weighted magnetic resonance (MR) imaging of liver lesions. MATERIALS AND METHODS: A fast SE technique was developed that enabled six sections to be imaged per 16-second breath hold with a single echo. Resulting images were compared with those obtained with the first echo of a conventional dual-echo T2-weighted SE sequence (16 minutes 55 seconds for 18 sections). Thirty-one patients with malignant focal hepatic lesions were studied prospectively. The images were compared quantitatively and qualitatively. RESULTS: Quantitatively, the contrast and contrast-to-noise ratios for the fast SE images were 20% +/- 5 and 19% +/- 8 greater, respectively, than those for the conventional T2-weighted SE images of the 54 representative lesions. Qualitatively, fast SE images had less image artifact, enabled comparable or better lesion sizing, and greatly improved depiction of extrahepatic structures compared with conventional T2-weighted SE images. CONCLUSION: The fast SE technique with breath holding provides diagnostically useful liver images in a greatly decreased acquisition time.


Subject(s)
Liver Neoplasms/diagnosis , Magnetic Resonance Imaging/methods , Adult , Aged , Humans , Liver Neoplasms/secondary , Middle Aged
7.
Magn Reson Med ; 33(2): 264-70, 1995 Feb.
Article in English | MEDLINE | ID: mdl-7707919

ABSTRACT

An interleaved echo-planar imaging (EPI) technique is described that provides images from 20 sections of the brain at two echo times (27 and 84 ms) in 1:05. Six echoes per image per repetition are collected in 24 repetitions of the pulse sequence. MR images of the brain obtained from five volunteers using the dual-echo EPI sequence, fast spin-echo (FSE), and conventional dual-echo spin-echo were evaluated qualitatively for diagnostic use and quantitatively for relative signal-to-noise ratio (SNR), contrast, and contrast-to-noise ratios (CNR).


Subject(s)
Brain/anatomy & histology , Echo-Planar Imaging/methods , Image Enhancement/methods , Adipose Tissue , Artifacts , Cerebrospinal Fluid , Cerebrovascular Circulation , Humans , Signal Processing, Computer-Assisted , Time Factors
8.
Magn Reson Imaging ; 13(8): 1095-8, 1995.
Article in English | MEDLINE | ID: mdl-8750321

ABSTRACT

Within the last several years a number of technical developments have been made in magnetic resonance imaging (MRI) that can potentially impact clinical and research MR imaging application in epilepsy. These include developments in instrumentation and in pulse sequences. Advances in instrumentation include higher capacity gradient systems and multiple receiver coils as directed to brain imaging. Advances in pulse sequence include use of fast or turbo-spin-echo techniques, variants of echo-planar imaging, and sequences such as fluid-attenuation inversion recovery (FLAIR) targeted to specific applications of brain imaging. The purpose of this paper is to review several of these developments.


Subject(s)
Epilepsy/diagnosis , Image Processing, Computer-Assisted/instrumentation , Magnetic Resonance Imaging/instrumentation , Brain/pathology , Echo-Planar Imaging/instrumentation , Epilepsy/pathology , Humans , Magnetic Resonance Imaging, Cine/instrumentation
9.
Radiology ; 193(1): 173-80, 1994 Oct.
Article in English | MEDLINE | ID: mdl-8090888

ABSTRACT

PURPOSE: To evaluate fast fluid-attenuated inversion-recovery (FLAIR) technique for imaging brain abnormalities. MATERIALS AND METHODS: A fast FLAIR sequence was developed that provided 36 5-mm contiguous sections in 5 minutes 8 seconds. Resulting images were compared with dual-echo T2-weighted spin-echo images of 41 consecutive patients with brain abnormalities. RESULTS: Contrast and contrast-to-noise ratios (C/Ns) (for contrast between the lesion and background and between the lesion and cerebrospinal fluid) for fast FLAIR exceeded the corresponding values for T2-weighted spin-echo images for all but the second-echo lesion-to-background C/N. Fast FLAIR provided equivalent or greater overall lesion conspicuity and enabled greater lesion detection in 98% and 100%, respectively, of the evaluations. Fast FLAIR images more often had image artifact, but this did not interfere with image interpretation in a significantly (P < or = .05) greater number of evaluations. CONCLUSION: Fast FLAIR provides images that are superior to proton-density- and T2-weighted images for many image quality criteria.


Subject(s)
Artifacts , Brain Diseases/diagnosis , Brain/pathology , Magnetic Resonance Imaging/methods , Humans , Image Enhancement/methods , Middle Aged , Time Factors
10.
Radiology ; 180(2): 551-6, 1991 Aug.
Article in English | MEDLINE | ID: mdl-2068326

ABSTRACT

Use of intraacquisition modification of pulse-sequence parameters to reduce acquisition time for conventional T2-weighted spin-echo images was evaluated. With this technique (variable-rate spin-echo pulse sequence), the repetition time and echo time (TR msec/TE msec) were reduced during imaging as a function of the phase-encoding view. To maintain T2-based contrast, TR and TE for the low-spatial-frequency views were left at their prescribed values (eg, 2,000/80). TR and TE for the high-spatial-frequency views were progressively reduced during imaging (eg, to 1,000/20). Acquisition time was reduced by as much as 25%. In one pulse sequence, the duration of multisection imaging nominally performed at TR 2,000 and with 256 phase-encoding views was reduced from 9 minutes 30 seconds to 6 minutes 30 seconds. In all sequences, edges and small structures were enhanced, and T2 contrast was somewhat decreased in high spatial frequencies. Filtering of the raw data before reconstruction can suppress these effects and provide a net increase in contrast-to-noise ratio.


Subject(s)
Image Enhancement/methods , Magnetic Resonance Imaging/methods , Brain/anatomy & histology , Contrast Media , Humans , Knee Joint/anatomy & histology , Medical Laboratory Science , Models, Theoretical , Time Factors
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