MR sialography using half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences.

We describe our preliminary experience with the half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences for MR imaging of the salivary gland ducts. In the majority of patients, the main parotid and/or submandibular gland ducts and large branches within the glands were detectable on MR images obtained in 2 seconds per section and within 3 minutes for the entire examination. MR sialography using HASTE sequences can be combined with conventional MR studies for the salivary glands.     

Centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo sequence: improvement of the image quality of oxygen-enhanced MRI

PURPOSE: The purpose of the study presented here was to determine the improvement in image quality of oxygen-enhanced magnetic resonance (MR) subtraction imaging obtained with a centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo (c-IR-HASTE) sequence compared with that obtained with a conventional sequentially reordered inversion recovery single-shot HASTE (s-IR-HASTE) sequence for pulmonary imaging. MATERIALS AND METHODS: Oxygen-enhanced MR imaging using a 1.5 T whole body scanner was performed on 12 healthy, non-smoking volunteers. Oxygen-enhanced MR images were obtained with the coronal two-dimensional (2D) c-IR-HASTE sequence and 2D s-IR-HASTE sequence combined with respiratory triggering. For a 256x256 matrix, 132 phase-encoding steps were acquired including four steps for phase correction. Inter-echo spacing for each sequence was 4.0 ms. The effective echo time (TE) for c-IR-HASTE was 4.0 ms, and 16 ms for s-IR-HASTE. The inversion time (TI) was 900 ms. To determine the improvement in oxygen-enhanced MR subtraction imaging by c-IR-HASTE, CNRs of subtraction image, overall image quality, and image degradation of the c-IR-HASTE and s-IR-HASTE techniques were statistically compared. RESULTS: CNR, overall image quality, and image degradation of c-IR-HASTE images showed significant improvement compared to those s-IR-HASTE images (P<0.05). CONCLUSION: Centrically reordered inversion recovery half-Fourier single-shot turbo spin-echo (c-IR-HASTE) sequence enhanced the signal from the lung and improved the image quality of oxygen-enhanced MR subtraction imaging.     

Oxygen-enhanced lung magnetic resonance imaging: influence of inversion pulse slice selectivity on inversion recovery half-Fourier single-shot turbo spin-echo signal

Purpose  

The purpose of this study was to evaluate in vivo the influence of inversion pulse slice selectivity on oxygen-enhanced magnetic resonance imaging (MRI).     

MR imaging of pulmonary parenchyma with a half-Fourier single-shot turbo spin-echo (HASTE) sequence.

OBJECTIVE: To evaluate the utility of a half-Fourier single-shot turbo spin-echo sequence (HASTE) at depicting lung parenchyma and lung pathology. METHODS AND PATIENTS: A HASTE sequence was applied to five normal volunteers and 20 patients with various pulmonary disorders to depict the lung parenchyma. Images were acquired with ECG-triggering and breath-holding. In three volunteers, signal intensity measurements from lung parenchyma were performed using four sequences: (a) HASTE; (b) conventional spin echo; (c) fast spin echo; and (d) gradient echo. T2 maps were produced using the HASTE acquisition. RESULTS: Minimal respiratory or cardiac motion artifacts were observed. The signal-to-noise ratios from lung parenchyma were 27.8 +/- 5.4, 22.0 +/- 3.0, 15.3 +/- 0.9, and 6.0 +/- 1.9 for HASTE, spin-echo, fast spin-echo, and gradient echo sequences, respectively. The scan time for HASTE was 302 ms for each slice. The T2 values in the right lung and the left lung were 61.2 +/- 4.1 and 79.1 +/- 8.9 ms in systole and 92.6 +/- 5.8 and 97.5 +/- 12.2 ms in diastole, respectively (P < 0.05 diastole versus systole). The HASTE sequence demonstrated clearly various pulmonary disorders, including lung cancer, hilar lymphadenopathy, metastatic pulmonary nodules as small as 3 mm, pulmonary hemorrhage, pulmonary edema and bronchial wall thickening in bronchiectasis. CONCLUSION: Our preliminary results indicate that the HASTE sequence provides a practical means for breath-hold MR imaging of lung parenchyma.     

Dynamic sagittal half-Fourier acquired single-shot turbo spin-echo MR imaging of the temporomandibular joint: initial experience and comparison with sagittal oblique proton-attenuation images

BACKGROUND AND PURPOSE: Our aim was to assess dynamic half-Fourier acquired single-shot turbo spin-echo (HASTE) MR imaging of the temporomandibular joint (TMJ) using parallel imaging, in comparison with static proton density (Pd) imaging. MATERIALS AND METHODS: Thirty-four TMJs from 17 subjects (7 volunteers, 10 patients) were imaged in a multichannel head coil on a 1.5 T magnet by using a 35-second dynamic sagittal HASTE acquisition (TR/TE, 1180/65 msec; matrix, 128 x 128; section thickness, 7 mm; 30 images) and sagittal oblique Pd in closed- and open-mouthed positions (TR/TE, 1800/12 msec; matrix, 256 x 256; section thickness, 2 mm; 15 sections). Images were reviewed by 3 readers and rated for confidence of disk position, presence of motion artifact, range of motion, and presence of disk displacement on a 5-point scale. Consensus review of cases was also performed to assess disk dislocation and limited range of motion. RESULTS: More static examinations were rated as having motion artifact (19.6% versus 6.9%, P=.016), limited range of motion (30.4% versus 17.7%, P=.016), and disk dislocations (31.4% versus 22.6%, P=.071). Confidence ratings were higher on dynamic examinations (4.11 versus 3.74, P=.018). Chi-squared tests demonstrated no significant difference in consensus reviews of the 2 examination types. CONCLUSION: Dynamic HASTE TMJ MR imaging is a time-efficient adjunct to standard MR imaging protocols, producing fewer motion artifacts, additional range of motion information, and a dynamic assessment of disk position, when compared with static imaging. Further study is needed to evaluate the role of this sequence in diagnosing disk displacement.     

MR cisternography using a three-dimensional half-Fourier single-shot fast spin-echo sequence

Application of a three-dimensional half-fourier single-shot fast spin-echo sequence to MR cisternography is presented. This technique is capable of demonstrating normal cranial nerves. It is also useful in screening for acoustic neuroma as well as in the diagnosis of neurovascular compression. Received 13 March 1997; Revision received 17 July 1997; Accepted 27 August 1997     

Comparison of ultrafast half-Fourier single-shot turbo spin-echo sequence with turbo spin-echo sequences for T2-weighted imaging of the female pelvis

So that we might evaluate the ultrafast half-Fourier single-shot turbo spin-echo (HASTE) sequence in T2-weighted MRI of the female pelvis and compare it with the turbo spin-echo (TSE) sequence, we prospectively studied 60 consecutive females with suspected abnormalities of the pelvis. For all MR examinations, we used a 1.5-T superconductive magnet with a phased array coil. The HASTE sequence was applied with TR/effective TE/echo train = ∞/90/64 and a 128 × 256 matri× (acquisition time: .3 sec/slice), conventional TSE imaging with 3,400 to 5,000/132/15 and a 128 × 256 matri× (mean acquisition time: 2 min 4 sec), and high-resolution TSE imaging with 3,400 to 5,000/132/15 and a 300 × 512 matri× (6 min 4 sec). Although the lesion conspicuity for the HASTE sequence was less than that for the high-resolution TSE sequences, artifacts (including ghosting, bowel motion, susceptibility difference, and chemical shift) were negligible on HASTE images of all patients. The lesion conspicuity for the HASTE sequence was significantly better than for the conventional TSE sequence. In spite of the very short acquisition time, the subjective scoring of the overall image quality for the HASTE sequence was significantly higher than for the conventional TSE sequence (P < .01) and were slightly lower than for the high-resolution TSE sequence. Compared with high-resolution TSE, HASTE provided clearer visualization of large leiomyomas and ovarian tumors but slightly poorer visualization of uterine cancer. In occlusion, HASTE sequence generates higher contrast and is free from motion and chemical shift artifact with much higher time efficacy. Because of limited image resolution, the HASTE sequence should be used when the high-resolution TSE imaging is suboptimal.     

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

PURPOSETo 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.METHODSFast 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.RESULTSPer 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.CONCLUSIONAlthough 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.     

Influence of inversion pulse type in assessing lung-oxygen-enhancement by centrically-reordered non-slice-selective inversion-recovery half-Fourier single-shot turbo spin-echo (HASTE) sequence

PURPOSE: To demonstrate the influence of inversion pulse type and inversion time for assessment of oxygen-enhancement on centrically-reordered non-slice-selective inversion-recovery (IR) half-Fourier single-shot turbo spin-echo (HASTE) sequence. MATERIAL AND METHODS: Phantoms with and without 100% oxygen and three healthy volunteers were studied with two-dimensional (2D) centrically-reordered non-slice selective IR-HASTE sequence with either composite or block inversion-recovery pulse at increasing inversion times from 200 to 1800 msec. Signal-to-noise ratios (SNRs) of phantom, real signal differences, and relative enhancement ratios of lung parenchyma between oxygen-enhanced and non-oxygen-enhanced MR images on composite and block pulse type were statistically compared at each TI. RESULTS: SNRs at TIs of 200 and 400 msec using the composite inversion pulse type were significantly lower than those with the block inversion pulse in the in vivo study (P < 0.05), although no significant differences were observed in the phantom study and in the in vivo study at inversion times greater than or equal to 600 msec. Real signal intensity (SI) differences at 400 and 600 msec of the composite inversion pulse type were significantly higher than those with the block inversion pulse type (P < 0.05). Relative enhancement ratio at 800 msec with the composite inversion pulse were significantly lower than that with the block inversion pulse (P < 0.05). CONCLUSION: IR pulse type and inversion time have influence on assessment of oxygen-enhancement by centrically-reordered non-slice-selective IR-HASTE sequence.     

Pancreaticobiliary diseases. Comparison of 2D single-shot turbo spin-echo MR cholangiopancreatography with endoscopic retrograde cholangiopancreatography

PURPOSE: To compare the diagnostic value of MR cholangiopancreatography (MRCP) to that of endoscopic retrograde cholangiopancreatography (ERCP) in the diagnosis of various obstructive and nonobstructive pancreaticobiliary diseases. MATERIAL AND METHODS: We retrospectively reviewed 153 patients who had undergone both MRCP and ERCP Breath-hold, heavily T2-weighted images using 2D single-shot turbo spin-echo technique were obtained. MRCP and ERCP results were correlated with the final clinical diagnoses. Accuracy of MRCP and ERCP in the diagnosis of pancreaticobiliary diseases, detecting the cause and site of biliary obstruction, if present, and distinguishing malignant from benign cause of obstruction were compared. RESULTS: Success rates of MRCP and ERCP were 98.7% and 89.5%, respectively. The accuracy of MRCP and ERCP in detecting the site of biliary obstruction was 89.7% and 96.2%, and in detecting the cause of biliary obstruction 69.2% and 71.8%, respectively. The sensitivity, specificity and likelihood ratios for positive and negative tests for MRCP and ERCP in distinguishing malignant biliary obstruction from benign causes were 86.4%, 82.4%, 4.9, 0.2 and 88.6%, 94.1%, 15.1, 0.1, respectively. Concordance between the two tests was 91% (kappa coefficient 0.82, standard error of kappa 0.113, p<0.001). In the group of nonobstructive biliary diseases, accuracy of MRCP and ERCP in detecting cholecystolithiasis were 100% and 73.7%, and in detecting pancreatitis 57% and 14%, respectively. CONCLUSION: 2D single-shot turbo spin-echo MRCP can be performed as a complement to ERCP and can replace ERCP in high-risk patients and in case of unsuccessful cannulation.     

Analysis of cystic intracranial lesions performed with fluid-attenuated inversion recovery MR imaging.

BACKGROUND AND PURPOSE: T1-, T2-, and proton density (PD)-weighted sequences are used to characterize the content of cystic intracranial lesions. Fluid-attenuated inversion recovery (FLAIR) MR sequences produce T2-weighted images with water signal saturation. Therefore, we attempted to verify whether FLAIR, as compared with conventional techniques, improves the distinction between intracranial cysts with a free water-like content versus those filled with a non-free water-like substance and, consequently, aids in the identification of these lesions as either neoplastic/inflammatory or maldevelopmental/porencephalic. METHODS: Forty-five cystic intracranial lesions were studied using T1-weighted, T2-weighted, FLAIR, and PD-weighted sequences. By means of clustering analysis of the ratio in signal intensity between the cystic intracranial lesions and CSF, the intracranial lesions were classified as filled with a free water-like content or with a non-free water-like substance. The results were compared with their true content as evaluated either histologically or on the basis of clinical, neuroradiologic, and follow-up features (necrotic material, 13 cases; accumulation of intercellular proteinaceous/myxoid material, eight cases; keratin, five cases; CSF, 19 cases). Cystic intracranial lesions were divided into two clinical groups, neoplastic/inflammatory and maldevelopmental/porencephalic, to evaluate the level of accuracy of each MR technique. The difference in absolute value signal intensity between CSF and cystic intracranial lesion content was calculated on FLAIR and PD-weighted images. RESULTS: PD-weighted and FLAIR sequences, unlike T1- and T2-weighted sequences, accurately depicted all cystic intracranial lesions containing necrotic or myxoid/proteinaceous intercellular material (non-free water-like) and most CSF-containing cystic intracranial lesions (free water-like). All imaging techniques inaccurately showed some of the keratin-containing cystic intracranial lesions and pineal cysts. The overall error rate was 22% for T1-weighted, 27% for T2-weighted, 9% for FLAIR, and 13% for PD-weighted sequences. The signal intensity difference between CSF and cystic intracranial lesion content was higher with FLAIR imaging. CONCLUSIONS: FLAIR imaging depicts far more accurately the content of cystic intracranial lesions and better reveals the distinction between maldevelopmental/porencephalic and neoplastic/inflammatory lesions than do conventional sequences. FLAIR has the added advantage of a higher signal intensity difference between cystic intracranial lesions and CSF.     

Characterization of focal liver lesions with half-Fourier acquisition single-shot turbo-spin-echo (HASTE) and inversion recovery (IR)-HASTE sequences

The half-Fourier acquisition single-shot turbo-spinecho (HASTE) sequence allows for heavily T2-weighted images, and the inversion recovery (IR)-HASTE sequence represents the T1 value of the tissue in a very short time. This study was undertaken to determine whether characterizing focal liver lesions can be made by combination with these very fast sequences. Seventy-four patients (33 cysts, 28 hemangiomas, and 33 malignant solid liver masses [15 metastatic tumors, 14 hepatocellular carcinomas, and 4 cholangiocarcinomasl]) underwent dynamic CT and breath-hold abdominal MRI using turbo-spin-echo (TSE), HASTE, and IR-HASTE sequences with variable TI values on a 1.5-T MR unit. The imaging time for each slice was 2 seconds for HASTE imaging and 2 to 4 seconds for IR-HASTE imaging. Lesion detection and qualitative characterization were evaluated. Quantitative analysis was performed by measuring the contrast-to-noise ratios (CNRs) as well as visual analysis. The inversion time (TI) nulling values were also statistically analyzed. All cystic lesions were detected on both TSE and HASTE imagings. For solid lesions, TSE failed to detect one small solid lesion and HASTE sequence failed to detect three lesions. With HASTE sequences, all cysts and hemangiomas were markedly hyperintense in comparison with malignant solid masses. CNRs of hemangiomas or cysts were significantly higher than those of malignant solid masses (P < .01), and there was no overlap. The TI nulling value was 1,100 ± 100 msec for hemangiomas, 1,900 ± 110 msec for cysts, and 740 ± 140 msec for malignant solid masses. There was no overlap between the TI nulling values of hemangiomas and cysts (P < .01). By combining the CNR from the HASTE sequence and the TI nulling value from the IR-HASTE sequence, complete discrimination among malignant solid masses, hemangiomas, and cysts of the liver could be made. Application of HASTE (representing T2 values) and IR-HASTE (representing T1 values) sequences provided a rapid and reliable imaging method for characterizing focal liver lesions without the use of contrast medium.     

Comparison of single-shot fast spin-echo and conventional spin-echo sequences for MR imaging of the heart: initial experience

A conventional T1-weighted spin-echo (SE) magnetic resonance (MR) imaging sequence was compared with breath-hold and non-breath-hold half- Fourier single-shot fast SE MR sequences with black-blood preparation and high spatial resolution for imaging of various cardiac diseases. The optimized single-shot fast SE sequence provided better or equal image quality in less time. Breath-hold and non-breath-hold single-shot fast SE sequences may replace the conventional T1-weighted SE sequence for first-line cardiac MR imaging.     

Magnetic resonance imaging with true fast imaging with steady-state precession and half-Fourier acquisition single-shot turbo spin-echo sequences in cases of suspected placenta accreta

Purpose: To present the magnetic resonance imaging (MRI) findings of placenta accreta in suspected cases of placenta accreta with true fast imaging with steady-state precession (True FISP) and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences.

Material and Methods: Five patients underwent MRI with HASTE (n=5) and/or True FISP (n=4) sequences for suspected placenta accreta. Retrospective review of MRI was performed to define the location and extent of the implantation abnormality.

Results: The uteroplacental interface was visualized as three layers; inner low signal intensity layer, middle high signal intensity layer of myometrium, and outer low signal intensity layer of uterine serosa. Three cases were diagnosed with placenta accreta on MRI and focal non-visualization of the inner layer was demonstrated.

Conclusion: The finding of focal non-visualization of the inner layer between the placenta and myometrium by MRI with True FISP and HASTE sequences was the diagnostic finding for placenta accreta.     

T2-weighted MR imaging for focal hepatic lesion detection: supplementary value of breath-hold imaging with half-Fourier single-shot fast spin-echo and multishot spin-echo echoplanar sequences

The purpose of our study was to evaluate the supplementary value of breath-hold fat-suppressed T2-weighted magnetic resonance (MR) imaging with half-Fourier single-shot fast spin-echo (SE) or multishot SE echoplanar (EP) sequences combined with respiratory-triggered fat-suppressed fast SE T2-weighted MR imaging for detection and characterization of focal hepatic lesions. MR images in 42 patients with 82 solid, malignant and 77 nonsolid, benign lesions were analyzed. Image review was conducted on a segment-by-segment basis; in all, 333 liver segments were reviewed separately for solid and nonsolid lesions by three independent radiologists. For solid lesions, observer performance with receiver-operating-characteristic (ROC) analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. For nonsolid lesions, observer performance with ROC analysis in one radiologist and specificity in another significantly improved after adding single-shot fast SE images. Combining breath-hold half-Fourier single-shot fast SE imaging with respiratory-triggered fast SE imaging may be recommended for improved detection and characterization of focal hepatic lesions. J. Magn. Reson. Imaging 2000;12:444-452.     

The value of single-shot turbo spin-echo diffusion-weighted MR imaging in the detection of middle ear cholesteatoma

Introduction Single-shot (SS) turbo spin-echo (TSE) diffusion-weighted (DW) magnetic resonance imaging (MRI) is a non echo-planar imaging (EPI) technique recently reported for the evaluation of middle ear cholesteatoma. We prospectively evaluated a SS TSE DW sequence in detecting congenital or acquired middle ear cholesteatoma and evaluated the size of middle ear cholesteatoma detectable with this sequence. The aim of this study was not to differentiate between inflammatory tissue and cholesteatoma using SS TSE DW imaging. Methods A group of 21 patients strongly suspected clinically and/or otoscopically of having a middle ear cholesteatoma without any history of prior surgery were evaluated with late post-gadolinium MRI including this SS TSE DW sequence. Results A total of 21 middle ear cholesteatomas (5 congenital and 16 acquired) were found at surgery with a size varying between 2 and 19 mm. Hyperintense signal on SS TSE DW imaging compatible with cholesteatoma was found in 19 patients. One patient showed no hyperintensity due to autoevacuation of the cholesteatoma sac into the external auditory canal. Another patient showed no hyperintensity because of motion artifacts. Conclusion This study shows the high sensitivity of this SS TSE DW sequence in detecting small middle ear cholesteatomas, with a size limit as small as 2 mm.     

Single-shot turbo spin-echo MR myelography: comparison with 3D-turbo spin-echo MR myelography and T2-turbo spin-echo at 1 T.

In order to reduce the acquisition time, we compared the single-shot-TSE-MR myelography (MRm) and 3D-TSE-MRm. The T2-TSE sequence was the standard of reference. Fifty patients with low back pain, sciatica or cervical radiculopathy were examined at 1.0 T. The shortest AP diameter of the spinal canal, signal-to-noise ratio (SNR) for CSF and cord, contrast-to-noise ratio (CNR) and relative contrast (ReCon) between CSF and cord were calculated. No statistically significant difference was found between the three sequences with regard to the AP diameter of the spinal canal. A significant difference was found in: (i) SNRcord; (ii) SNRCSF; (iii) SS-TSE-MRm (showed the highest CNR) and (iv) SS-TSE-MRm (showed higher ReCon compared to 3D-TSE-MRm). In conclusion, SS-TSE-MRm can be used alternatively to 3D-TSE-MRm reducing the acquisition time down to only 8 s per image.     

Contrast enhancement of intracranial lesions: conventional T1-weighted spin-echo versus fast spin-echo MR imaging techniques.

BACKGROUND AND PURPOSE: The T1-weighted fast spin-echo (T1-FSE) MR imaging sequence is not used routinely, since the speed advantage is not as dramatic as it is in T2-weighted imaging. We evaluated the T1-FSE sequence to determine whether this technique can replace the conventional T1-weighted spin-echo (T1-SE) sequence for routine contrast-enhanced imaging. METHODS: Sixty-nine patients with intracranial enhancing lesions underwent both T1-SE and T1-FSE sequences in a random order after administration of contrast agent. Acquisition time was 55 seconds for the T1-FSE sequence and 2 minutes 38 seconds for the SE sequence. The conspicuity of enhancing lesions, peritumoral edema, and gray-to-white matter contrast as well as motion and flow artifacts were analyzed. Signal-to-noise ratios of enhancing lesions, gray matter, and white matter as well as contrast-to-noise ratios (CNRs) of enhancing lesions, with gray matter with white matter as the standard, were calculated. RESULTS: The conspicuity of enhancing lesions was better on T1-FSE sequences than on T1-SE sequences, although the difference in the CNRs of enhancing lesions did not reach significance. Images obtained with the T1-FSE sequence showed less flow and motion artifacts than did those obtained with the T1-SE sequence. The conspicuity of peritumoral edema and gray-to-white matter contrast was lower on the T1-FSE images than on the T1-SE images. CONCLUSION: The T1-FSE sequence reduces imaging time and has the potential to replace the conventional T1-SE sequence for the evaluation of enhancing lesions in the brain when time is a consideration.