The low sensitivity of fluid-attenuated inversion-recovery MR in the detection of multiple sclerosis of the spinal cord

PURPOSE: To confirm the expected superiority of fluid-attenuated inversion-recovery (FLAIR) over conventional fast spin-echo MR imaging in the detection of multiple sclerosis (MS) of the spinal cord. METHODS: Fifteen subjects with known MS involving the spinal cord and brain were studied prospectively. The entire cord was imaged with a phased-array coil on a 1.5-T MR system. Sagittal T1-weighted and fast spin-echo proton density- and T2-weighted images were followed by fast FLAIR images. FLAIR parameters were varied to optimize lesion conspicuity with optimal inversion times (TIs) ranging from 2400 to 2600. Lesion conspicuity and detection were compared between the fast spin-echo and FLAIR images by three radiologists who reached agreement by consensus. RESULTS: The FLAIR technique effectively suppressed cerebrospinal fluid (CSF) signal and reduced CSF pulsation and truncation artifacts in all cases. Shorter imaging parameters (repetition time of 4000 to 6000, TI of 1500 to 2000) uniformly decreased lesion conspicuity in all subjects. Of 11 cord lesions in five subjects imaged with the longer parameters (repetition time of 8000 to 11,000, TI of 2400 to 2600), three were not seen on FLAIR images, four were less conspicuous on FLAIR images, and four were seen equally or better on FLAIR images. CONCLUSION: Although successful in suppressing CSF signal and reducing imaging artifacts, fast FLAIR imaging appears unreliable in the detection of MS lesions in the spinal cord.     

Half-fourier acquisition single-shot turbo spin-echo (HASTE) MR: comparison with fast spin-echo MR in diseases of the brain

PURPOSE: To compare an ultrafast T2-weighted (half-Fourier acquisition single-shot turbo spin-echo [HASTE]) pulse sequence with fast spin-echo T2-weighted sequences in MR imaging of brain lesions. METHODS: Fast spin-echo and HASTE images of 34 consecutive patients over the age of 50 years or with suspected demyelinating disease were reviewed independently by two neuroradiologists for the number of lesions less than 5 mm and greater than or equal to 5 mm, and for lesion conspicuity, gray-white matter differentiation, and extent of periventricular confluent signal abnormality. The reviewers also assessed for the presence of hemosiderin and extent of motion artifacts. RESULTS: Per patient, the mean number of 5-mm or larger lesions detected on fast spin-echo images (1.4) relative to the number detected on HASTE images (0.8) was not statistically significant. For lesions less than 5 mm, fast spin-echo images showed more lesions (7.5) than HASTE images did (2.4). The fast spin-echo images were better at depicting gray-white matter differentiation, conspicuity of lesions, and periventricular signal abnormality. Of four T2 hypointense lesions seen on fast spin-echo images, none was detected on HASTE images. CONCLUSION: Although the HASTE technique might be useful for rapid imaging of the brain, our study shows a diminished sensitivity for the detection of lesions less than 5 mm in diameter and for T2 hypointense lesions.     

Cultural factors in the treatment of a catatonic Chinese patient

We carried out fluid-attenuated inversion recovery (FLAIR) pulse sequences with long repetition and echo times in seven children with tuberous sclerosis, and compared them with conventional spin-echo (SE) sequences. FLAIR images exhibited higher sensitivity than conventional SE images to cortical and subcortical tubers. The low signal intensity of cerebrospinal fluid on FLAIR images allowed more accurate delineation of the cortical and subcortical tubers. However, T1-weighted imaging was still superior for delineation of subependymal nodules.     

Molecular heterogeneity and new subtypes of HCV genotype 4

We used five MRI sequences in six patients with multiple sclerosis (MS): conventional spin-echo (CSE) with 5-mm slices; 2D fast spin-echo (FSE) with 2-mm slices; multishot T2*-weighted echo-planar imaging (EPI) with 5-mm slices; fast fluid-attenuated inversion recovery (fFLAIR) with 2-mm slices; and 3D fast spin-echo with 1.5-mm-thick slices. A total of 225 lesions were detected on CSE, 274 on 2D FSE, 137 on EPI, 385 on fFLAIR and 320 on 3D FSE. The EPI sequence was clearly the least sensitive and susceptibility artefact was a problem, particularly in the brain stem and temporal lobes. Fast FLAIR displayed a much higher number of supratentorial lesions (380) than 3D FSE (297), 2D FSE (264) or CSE (211). However, in the posterior cranial fossa 3D FSE was the most sensitive sequence (23 lesions), followed by CSE (14) and 2D FSE (10), while fFLAIR (5) was extremely insensitive.     

MR identification of white matter abnormalities in multiple sclerosis: a comparison between 1.5 T and 4 T

BACKGROUND AND PURPOSE: Although MR spectroscopy and functional MR imaging of the brain have been successful at 4 T, conventional fast spin-echo imaging of the brain at 4 T has not been adequately evaluated. The purpose of this study was to compare the detection of white matter abnormalities in multiple sclerosis (MS) at 1.5 T and 4 T. METHODS: Fifteen patients with clinically definite MS were imaged at both 1.5 T and 4 T within a 1-week period. Comparison was made between fast spin-echo long-TR images at both field strengths. Pulse sequences were tailored to maximize resolution and signal-to-noise ratio in clinically relevant imaging times (< 7 min). Four interpreters independently reviewed the images obtained at both field strengths in separate sessions and evaluated them for lesion identification, size, characterization, and subjective resolution. Differences in interpretations at 1.5 T and 4 T were subsequently recorded. RESULTS: Images obtained at 4 T showed a mean of 88 more lesions as compared with images obtained at 1.5 T. All the lesions measured less than 5 mm and were typically aligned along perivascular spaces. Twenty-five consensually identified lesions on 4-T images were not seen at all on 1.5-T images. Moreover, 4-T images showed 56 additional consensually identified lesions, which were indistinct and seen only in retrospect on 1.5-T images. These lesions were frequently (n = 48) identified in large confluent areas of white matter signal intensity abnormality at 1.5 T. All observers also agreed that 4-T images subjectively enhanced the perception of normal perivascular spaces and small perivascular lesions. CONCLUSION: MR imaging at 4 T can depict white matter abnormalities in MS patients not detectable at 1.5 T through higher resolution with comparable signal-to-noise ratio and imaging times.     

Fast fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging of the brain: a comparison of multi-shot echo-planar and fast spin-echo techniques

PURPOSE: To evaluate fast spin-echo and multi-shot echo-planar fluid-attenuated inversion recovery (FLAIR) sequences in paediatric brain imaging. MATERIALS AND METHODS: Matched images from 32 patients with suspected tumour or white matter disease were independently evaluated by two paediatric neuroradiologists. The observer preferences for image quality and lesion detection were analysed for differences between fast spin-echo FLAIR and multi-shot echo-planar FLAIR. Diagnostic quality was compared with that of fast spin-echo T2-weighted images. RESULTS: Images of a diagnostic quality equivalent to that of fast spin-echo T2-weighted images were achieved with both FLAIR techniques. Grey and white matter differentiation and cerebrospinal fluid (CSF) nulling were significantly better on fast spin-echo FLAIR sequences. CSF flow artefact was reduced on multi-shot echo-planar FLAIR. There was no difference in lesion detection. Fast spin-echo FLAIR images were visually preferred at the expense of longer imaging time. CONCLUSION: Fast FLAIR techniques are complementary to fast spin-echo T2-weighted sequences in imaging of the paediatric brain. We find that the fast spin-echo FLAIR sequence is preferable to the multi-shot echo-planar technique.     

Fast fluid-attenuated inversion recovery (FLAIR) compared with T2-weighted spin-echo in the magnetic resonance diagnosis of mesial temporal sclerosis

RATIONALE AND OBJECTIVES: The authors compare coronal fast fluid-attenuated inversion recovery (FLAIR) with coronal T2-weighted spin-echo (SE) magnetic resonance (MR) techniques in the diagnosis of mesial temporal sclerosis (MTS). METHODS: In this prospective study, the authors assessed MR scans of 30 patients with drug-resistant temporal lobe epilepsy (based on clinical symptomatology and electroencephalographic registrations) with MR features suggestive of MTS. MR scans of age-, sex-, and scanner-matched patients, referred for MR assessment of white matter disease, without a history of epilepsy and with no visible abnormalities on MR, were used as controls. In 16 patients the MR diagnosis was confirmed by histologic abnormalities consistent with MTS. Coronal T2 SE and FLAIR images of patients and controls were presented to two experienced radiologists in random order for independent blinded review. Hippocampal and associated extrahippocampal temporal lobe abnormalities were used for the diagnosis of MTS. RESULTS: The sensitivity of observer A was 97% for the T2 SE sequence and 100% for the FLAIR; the specificity of observer A for both techniques was 100%. The sensitivity of observer B was 53% for T2 SE and 83% for FLAIR; the specificity for observer B was 93% for the T2 SE and 100% for FLAIR. CONCLUSION: Coronal FLAIR images provide a similar or increased yield in the detection of MTS compared with T2-weighted SE images.     

Anterior cruciate ligament injury: fast spin-echo MR imaging with arthroscopic correlation in 217 examinations

OBJECTIVE: Our objective was to evaluate the accuracy of MR imaging strategy that uses primarily fast spin-echo sequences for the diagnosis of anterior cruciate ligament tears. MATERIALS AND METHODS: The original clinical interpretations of MR images of 217 examinations of the knee joint were correlated with subsequent arthroscopic results. Each MR examination included a double-echo fast spin-echo sequence as the only imaging sequence in the sagittal plane. Subsequent discordant MR and arthroscopic examinations were then subjected to reanalysis by two observers who were unaware of arthroscopic results to determine if misinterpretations were observer or image dependent. Two hundred sixteen patients who underwent MR imaging for suspected internal derangement of the knee subsequently underwent arthroscopic surgery. Two patients had both knees evaluated. One patient was excluded because he was referred for evaluation for osteomyelitis, not internal derangement. This yielded a total number of 217 MR examinations for suspected internal derangement of the knee. RESULTS: For 56 arthroscopically proven tears, the sensitivity of MR imaging was 96%. The specificity was 98%, yielding an overall accuracy rate of 98%. The positive and negative predictive values were 95% and 99%, respectively. These values are within the ranges of previously reported MR imaging strategies using conventional spin-echo sequences. CONCLUSION: Fast spin-echo MR imaging of the knee can be an alternative to conventional spin-echo imaging for the detection of anterior cruciate ligament tears.     

Fast and ultrafast magnetic resonance imaging in renal lesions

Our purpose was to analyze and compare the image quality and contrast-to-noise ratio (CNR) of different fast T1- and T2-weighted sequences with conventional spin-echo sequences in renal MRI. Twenty-three patients with focal renal lesions were examined with a T2-weighted ultrafast turbo spin-echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient-and-spin-echo sequence (GraSE), and a conventional spin-echo sequence (SE). In addition, T1-weighted images were obtained pre- and postcontrast, using a fast spin-echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2-weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat-suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1-weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2-weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1-weighted fast sequences provided no alternative to the gradient-echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2-weighted fast techniques for improved diagnostic accuracy of renal MRI.     

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.     

Sensitivity of enhanced MR in multiple sclerosis: effects of contrast dose and magnetization transfer contrast

BACKGROUND AND PURPOSES: New strategies have been developed to improve the sensitivity of contrast-enhanced MR imaging in quantifying disease activity in patients with multiple sclerosis (MS). The goal of the present study was to evaluate the sensitivity of T1-weighted images after injection of a triple dose of contrast material and application of a magnetization transfer (MT) pulse in the detection of enhancing lesions as compared with the conventional approach. METHODS: Monthly MR images were obtained in 13 patients with relapsing-remitting MS for a period of 3 months. The MR studies were performed on two separate occasions with single- and triple-dose contrast material. In each session, T1- and T2-weighted spin-echo images with and without the MT pulse were obtained before and after contrast administration. All images were evaluated in a blinded fashion and scored in random order and consensually by two readers. The number of total and new enhancing lesions and active images was counted. RESULTS: Eighty-six percent more enhancing lesions and 54% more new enhancing lesions were detected with triple-dose as compared with single-dose non-MT sequences, whereas single-dose MT images depicted 33% more enhancing lesions and 18% more new enhancing lesions than the single-dose non-MT images. Twenty-nine percent more lesions were detected on triple-dose non-MT images than on single-dose MT images. The combination of a triple dose of contrast material and MT did not produce any significant change in detection of enhancing lesions as compared with a triple dose of contrast without MT. CONCLUSION: The use of a triple dose of contrast material is the best approach to maximize the sensitivity of enhanced MR imaging.     

MR imaging of the brain: comparison of gradient-echo and spin-echo pulse sequences

OBJECTIVE: Gradient-echo pulse sequences can reduce imaging time and decrease motion artifacts. If gradient-echo pulse sequences are shown to be comparable to spin-echo sequences in MR imaging of the brain, then gradient-echo imaging can be valuable for examining critically ill, anxious, or uncooperative patients and can increase patient throughput. The purpose of this study was to prospectively compare one fast multiplanar spoiled gradient-recalled acquisition in the steady state (GRASS) (FMPSPGR) sequence with one conventional T1-weighted spin-echo sequence to determine the reliability of the FMPSPGR sequence for detecting cerebral lesions. SUBJECTS AND METHODS: Fifty-one patients with 142 cranial lesions, including brain tumors, infarction, infection, and noninflammatory lesions, were examined. Forty-two unenhanced and 39 contrast-enhanced FMPSPGR (113-240/2.6-3.6/90 degrees/4 [TR/TE/flip angle/acquisitions]) and spin-echo T1-weighted (400-579/11-12/90 degrees/2) MR images of the head were obtained with a 1.5-T system. The visibility, margination, and extent of the lesions; image quality; contrast; and artifacts were qualitatively and quantitatively compared. RESULTS: Supratentorial lesions were more conspicuous on the unenhanced FMPSPGR images because of the higher signal-to-noise ratio of the normal brain resulting in higher lesion contrast. The higher contrast-to-noise ratio of neoplasms on the contrast-enhanced spin-echo images was not found to be significant in the independent qualitative analysis. The conspicuity and extent of other lesions evaluated with the two pulse sequences were not significantly different for either the unenhanced or the contrast-enhanced studies. Vascular pulsation artifacts were significantly reduced on the contrast-enhanced FMPSPGR images. Susceptibility and chemical-shift phase-cancellation artifacts were more pronounced on the FMPSPGR images. CONCLUSION: The FMPSPGR sequence provides high-quality images with fewer vascular pulsation artifacts three to four times faster than the spin-echo sequence. The FMPSPGR sequence can reliably show intracranial lesions and can substitute for the T1-weighted spin-echo sequence in routine brain imaging.     

MR imaging in children with nonperforated acute appendicitis: value of unenhanced MR imaging in sonographically selected cases

OBJECTIVE: The aim of this study was to describe the MR appearance of acute appendicitis and to determine the value of MR imaging for diagnosis of acute appendicitis. SUBJECTS AND METHODS: Forty-five children (28 girls, 17 boys), 7-16 years old (mean age, 13 years old), with clinically diagnosed acute appendicitis underwent independently graded compression sonography by two radiologists. MR imaging was performed when sonography revealed acute appendicitis (observer 1, 16 [36%] patients; observer 2, 18 [40%] patients), was inconclusive (observer 1, two [4%] patients; observer 2, one [2%] patient), and was interpreted as normal (observer 1, two [4%] patients; observer 2, one [2%] patient) (n = 20). Axial T1-weighted turbo spin-echo sequences, T2-weighted turbo spin-echo sequences in the axial and coronal planes, and fat-suppressed short inversion time inversion recovery turbo spin-echo sequences in the axial plane (4-mm slice thickness) were obtained and evaluated independently by two radiologists. The ability to see acute appendicitis with MR imaging was evaluated, the appearance and morphologic changes were described, and the most accurate sequence was determined. All children in whom MR imaging was performed underwent surgery. RESULTS: MR imaging revealed acute appendicitis in all cases (100%) by both observers. On T2-weighted ultra turbo spin-echo images, acute appendicitis appeared with a markedly hyperintense center, a slightly hyperintense thickened wall, and markedly hyperintense periappendiceal tissue. Unenhanced axial T2-weighted spin-echo imaging was the most sensitive sequence. CONCLUSION: In this study group, MR imaging was a valuable technique for depiction of acute appendicitis.     

Scientific role of German ophthalmology in the European telecommunication project OPHTEL]

We examined 21 patients aged 5 months to 19 years, on a 1.5 T magnet. T1-weighted spin-echo images, proton density and T2-weighted images with spin-echo and turbo spin-echo sequences, and contrast-enhanced magnetization transfer (MT) T1-weighted images were obtained in all cases. MT T1-weighted images were performed before injection in 9 patients. Subependymal nodules were found in 14, and cortical and subcortical tubers in 20 of the 21 patients. MT T1-weighted images showed tubers and subependymal nodules as higher signal than normal gray matter and revealed more tubers than conventional sequences in 11 cases. High signal intensity lesions of the white matter were found in 19 patients but were seen only on MT images in 9 cases. When MT images both before and after injection were available, tubers and white matter lesions were more easily recognised on unenhanced MT images because of their higher contrast.     

The clinical use of echoplanar MR tomography in the detection of focal liver lesions. The results of a quantitative study

The purpose of the present study was to investigate the clinical application of echoplanar MR imaging compared to conventional MR imaging in the detection of focal liver lesions. A total of three conventional and 12 echoplanar pulse sequences were acquired in 35 patients with focal liver lesions. Motion artifacts were eliminated because of short acquisition times of 32 ms subsequently improving signal-to-noise. A single-shot spin-echo technique with a TE of 26 ms provided the highest liver signal-to-noise ratio (p < 0.05) of all sequences acquired. Contrast-to-noise ratios for a single-shot SE technique with echo times of 50-100 ms were as high as 10-40.     

MR imaging of the anterior cruciate ligament: frequency of discordant findings on sagittal-oblique images and correlation with arthroscopic findings

OBJECTIVE: The purposes of this study were to determine the frequency of discordant MR findings of the anterior cruciate ligament (ACL) using sagittal-oblique images and the arthroscopic integrity of the ACL in knees with a discordant MR appearance. MATERIALS AND METHODS: The frequency of discordant MR features was determined by independently reviewing the sagittal-oblique images of 53 consecutive patients undergoing subsequent arthroscopic surgery. The first 25 consecutive knees were examined using a conventional, dual-echo, T2-weighted spin-echo (SE) sequence; the subsequent 28 consecutive knees were examined using both a T1-weighted SE(T1) and a fat-suppressed, fast spin-echo (FSE) T2-weighted sequence. Two examiners who were unaware of patient identification and arthroscopic results evaluated only the sagittal images that included the ACL. Each reviewer graded the ACL as torn or intact. The MR appearance was considered discordant when one MR sequence showed disrupted or poorly seen ACL fibers and the other sequence showed intact ACL fibers. The arthroscopic integrity of the ACL was determined for the 20 knees with a discordant MR appearance. RESULTS: A discordant MR appearance of the ACL was seen in 20 of the 53 knees (38%), including 10 knees evaluated using conventional T2-weighted sequences (40%) and 10 knees using T1/FSE T2 (36%) sequences. Arthroscopic examination of these knees showed intact ACL fibers in all 20 knees; the ACL was normal in 18 knees and a partial tear was questioned in two knees. CONCLUSION: A discordant appearance of the ACL was frequently encountered (38%) using either conventional T2-weighted sequences or T1 and FSE MR sequences in the sagittal-oblique plane. Intact ACL fibers were found during arthroscopy in all 20 knees with a discordant MR appearance.     

Fast spin-echo MR imaging of the eye

Magnetic resonance imaging of the eye usually includes T2-weighted images both for screening purposes and for characterization of melanoma. Conventional T2-weighted spin-echo (SE) imaging suffers both from long acquisition times and incomplete recovery of the vitreous' signal. A fast SE sequence was therefore compared prospectively with conventional sequences in 29 consecutive patients with lesions of the eye. Fast SE images delineated melanoma and other lesions of the eye from vitreous better than conventional T2-weighted images. Image quality and lesion conspicuity were improved on the fast sequence. Whereas melanoma appeared hypointense to vitreous on both types of images, subretinal effusion was hypointense on fast images and hyperintense on conventional T2-weighted images. Ghosting of the globe, which, however, did not decrease diagnostic value, was more pronounced on fast images. Conventional T2-weighted images may be replaced by fast SE images in MR studies of the eye with a gain in lesion conspicuity and significant time saving.     

HASTE MR cholangiography in the evaluation of hilar cholangiocarcinoma

OBJECTIVE: The objective of this study was to determine the usefulness of MR cholangiography using the half-Fourier acquisition single-shot turbo spin-echo sequence in the examination of patients with hilar cholangiocarcinoma. CONCLUSION: Half-Fourier acquisition single-shot turbo spin-echo MR cholangiography is a useful, noninvasive adjunct to other imaging techniques, particularly MR imaging, in the evaluation of hilar cholangiocarcinoma. MR cholangiography allows rapid visualization of the biliary tract without instrumentation and, therefore, without the risk of inducing sepsis in a patient with ductal obstruction. In the six patients presented. MR cholangiography allowed for determination of the proximal extent of disease and assessment of resectability and delineated the duct both proximal and distal to the stricture and isolated ductal obstructions. MR cholangiography provides three-dimensional images of the biliary tract that facilitate planning of surgery, palliative drainage, and radiation therapy.     

A comparison of dialysers with low-flux membranes: significant differences in spite of many similarities

PURPOSE: To determine whether dynamic traditional spin-echo MR imaging, with the use of routine T1 parameters during contrast infusion, is superior to standard MR imaging after contrast administration for detecting microlesions of the pituitary gland. METHODS: Sixty-four patients with pituitary microlesions 3 to 10 mm in diameter were examined with a dynamic traditional spin-echo technique; that is, a typical T1 spin-echo sequence of 500-600/20-25/2 (repetition time/echo time/excitations), 3-mm-thick sections, 16-cm field of view, 256 x 128 matrix, and a scan time ranging from 2 minutes to 2 minutes 40 seconds during contrast infusion. In addition, standard imaging with unenhanced and contrast-enhanced spin-echo sequences were obtained. The three sequences were evaluated retrospectively and graded for gland-lesion contrast conspicuity, lesion homogeneity, and delineation of lesion margin. RESULTS: The dynamic sequence was judged to be better than the standard enhanced sequence for depicting microlesions in 42% to 47% of patients. Lesions were identified only on the dynamic study in an additional 1% to 14% of patients. Lesions were seen equally well on the standard and dynamic sequences only in 16% to 23% of cases. The standard postcontrast sequence was judged better in 12.5% to 17% of cases, with lesions identified only on the standard sequence in an additional 8% to 9%. CONCLUSION: Dynamic traditional spin-echo MR imaging improved lesion detection and provided increased clarity over standard sequences after contrast infusion. Both sequences are important, since lesions were detected only on the dynamic sequence in 11% to 14% of patients and only on the standard sequence in 8% to 9% of patients.     

How to diagnose chronic rejection. A study in porcine intestinal allografts

The conventional Spin-Echo sequences have been the most used acquisition techniques on Magnetic Resonance Imaging (MRI) of the brain, since the beginning of 1990s. Recently, however, technological developments proposed such new fast acquisition techniques, with a dramatic reduction in acquisition time as Gradient Echo, Turbo Spin Echo, Gradient Spin Echo ed Echo Planar sequences. We investigated the comparative adequacy of the new fast sequences, in brain MR studies versus conventional sequences, on medium field strength MR equipment (.5 T). On in vitro exams S/N ratio was evaluated and on in vivo study C/N ratio between white substance grey substance and fluid were evaluated, in 15 healthy volunteers. All the exams were carried out on Philips NT5 Gyroscan MR unit operating at .5 T, with 15 mT/m power gradients. Both conventional and fast sequences Spin-Echo (SE), Inversion Recovery (IR), Gradient-Echo (GE), Turbo Spin-Echo (TSE), Gradient Spin-Echo (GRASE) and Echo Planar (EPI), all optimized to obtain T1, T2 and T1-IR weighted images, were performed. The sequences were evaluated separately comparing different acquisition techniques relative to the same type of contrast (T1, T2, and T1-IR). The results indicate the superiority of the fast acquisition techniques, both in terms of quality and acquisition times, except for T1-weighted images, where the conventional Spin-Echo sequences confirmed to be superior. In conclusion, the present study suggests that fast acquisition techniques can improve the conventional protocol of sequences, in the anatomical representation of the normal brain even with medium field strength equipment only on T2 and T1-IR weighted images. On T1-weighted imaging conventional SE acquisition technique is still the best choice. The time saving obtained with fast sequences can therefore be used for an overall improvement in the quality of images, and to apply accessory acquisition plans on routine exams.