Evaluation of intracranial lesions with inversion recovery half-Fourier single-shot turbo spin-echo MR: initial observations.

PURPOSETo determine the value of inversion recovery half-Fourier single-shot turbo spin-echo (IR-HASTE) MR sequences in the characterization of a variety of intracranial lesions, with the focus on differentiating between epidermoids and nonneoplastic cystic lesions.METHODSWe used a 1.5-T MR unit to study five epidermoids, seven arachnoid cysts, seven other nonneoplastic cysts (three neuroepithelial cysts, two interhemispheric cysts, and two Rathke''s cleft cysts), and eight solid neoplasms (three meningiomas, two astrocytomas, one subependymoma, one cavernoma, and one metastatic tumor) using IR-HASTE sequences with variable inversion times (TI). Imaging time for each section was 2 seconds for the sequence. The TI nulling values were analyzed statistically.RESULTSThe TI nulling values were 1200 to 2300 for the epidermoids, 2800 to 3000 for the arachnoid cysts, 300 and 800, respectively, for the Rathke''s cleft cysts, 2500 to 3000 for the other nonneoplastic cysts, and 300 to 1500 for the solid neoplasms. There was no overlap of TI nulling values between the arachnoid cysts and the epidermoids; the difference was statistically significant. Both patients with interhemispheric cysts had two lesions in which the TI nulling values were different.CONCLUSIONIR-HASTE sequences provide a rapid and reliable imaging method for differentiating among epidermoids, arachnoid cysts, and solid neoplasms. This technique also provides information about the continuity of the multicystic lesions in terms of the differences in their TI nulling values. For solid intraaxial masses, the use of IR-HASTE helps to differentiate intratumoral cysts and necrosis from solid components.     

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.     

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.     

Angled oblique sagittal MR imaging of rotator cuff tears: comparison with standard oblique sagittal images

Objective. To compare the accuracy for diagnosing rotator cuff tears of oblique coronal images supplemented with standard oblique sagittal images versus thinner-section angled oblique sagittal images. Design and patients. The study included 75 consecutive patients who had a shoulder MR scan followed by arthroscopy. MR images included oblique coronal, oblique sagittal (4 mm thick, 1 mm interslice gap), and angled oblique sagittal (3 mm/0.2 mm) images perpendicular to the lateral cuff. A musculoskeletal staff radiologist and fellow separately evaluated the cuff for tears on the oblique coronal images supplemented with either the oblique sagittal or the angled sagittal images. Results. For distinguishing a cuff tear from no tear, the staff radiologist had an accuracy of 0.76 (95% confidence interval: 0.67, 0.85) with the standard sagittal set, and 0.88 (0.80, 0.95) with the angled set (P=0.04). There was a nonsignificant improvement in accuracy for the fellow, calculated as 0.73 (0.63, 0.83) on the standard sagittal set and 0.76 (0.67, 0.85) on the angled set. Both readers also improved their diagnostic accuracy for partial-thickness tears with the angled set, although the improvement was statistically significant only for the staff radiologist. Conclusion. There is a slight improvement in accuracy for diagnosing rotator cuff tears, particularly partial-thickness tears, for the more experienced radiologist using thinner-section angled oblique sagittal images. These images may be useful as a supplemental sequence in patients where it is important to identify partial-thickness tears accurately. Received: 7 August 2000 Revision requested: 13 October 2000 Revision received: 27 November 2000 Accepted: 12 December 2000     

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.     

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.     

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.     

Diffusion-weighted imaging of the spine with a non-carr-purcell-meiboom-gill single-shot fast spin-echo sequence: initial experience

BACKGROUND AND PURPOSE: To prospectively evaluate the signal-to-noise ratio (SNR) improvement in diffusion-weighted imaging (DWI) of the spine with the use of a newly developed non-Carr-Purcell-Meiboom-Gill (non-CPMG) single-shot fast spin-echo (SS-FSE) sequence and its effect on apparent diffusion coefficient (ADC) measurements. MATERIALS AND METHODS: Twenty-four patients were enrolled after written informed consent. DWI of the spine was obtained with an echo-planar imaging (EPI)-based sequence followed by a non-CPMG SS-FSE technique. SNR and ADC values were measured over a lesion-free vertebral corpus. A quality score was assigned for each set of images to assess the image quality. When a spinal lesion was present, contrast-to-noise ratio (CNR) and ADC were also measured. Student t tests were used for statistical analysis. RESULTS: Mean SNR values were 5.83 +/- 2.2 and 11.68 +/- 2.87 for EPI and non-CPMG SS-FSE DWI, respectively. SNR values measured in DWI using parallel imaging were found to be significantly higher (P < .01). Mean ADCs of the spine were 0.53 +/- 0.15 and 0.35 +/- 0.15 x 10(-3) mm(2)/s for EPI and non-CPMG SS-FSE DWI, respectively. Quality scores were found to be higher for the non-CPMG SS-FSE DWI technique (P < .05). Overall lesion CNR was found to be higher in DWI with non-CPMG SS-FSE. CONCLUSION: The non-CPMG SS-FSE technique provides a significant improvement to current EPI-based DWI of the spine. A study including a larger number of patients is required to determine the use of this DWI sequence as a supplementary tool to conventional MR imaging for increasing diagnostic confidence in spinal pathologic conditions.     

T2-weighted MR imaging of the liver: Qualitative and quantitative comparison of SPACE MR imaging with turbo spin-echo MR imaging

Objective

To qualitatively and quantitatively compare T2-weighted MR imaging of the liver using volumetric spin-echo with sampling perfection with application-optimized contrast using different flip angle evolutions (SPACE) with conventional turbo spin-echo (TSE) sequence for fat-suppressed T2-weighted MR imaging of the liver.

Materials and methods

Thirty-three patients with suspected focal liver lesions had SPACE MR imaging and conventional fat-suppressed TSE MR imaging. Images were analyzed quantitatively by measuring the lesion-to-liver contrast-to-noise ratio (CNR), and the signal-to-noise ratio (SNR) of main focal hepatic lesions, hepatic and splenic parenchyma and qualitatively by evaluating the presence of vascular, respiratory motion and cardiac artifacts. Wilcoxon signed rank test was used to search for differences between the two sequences.

Results

SPACE MR imaging showed significantly greater CNR for focal liver lesions (median = 22.82) than TSE MR imaging (median = 14.15) (P < .001). No differences were found for SNR of hepatic parenchyma (P = .097), main focal hepatic lesions (P = .35), and splenic parenchyma (P = .25). SPACE sequence showed less artifacts than TSE sequence (vascular, P < .001; respiratory motion, P < .001; cardiac, P < .001) but needed a longer acquisition time (228.4 vs. 162.1 s; P < .001).

Conclusion

SPACE MR imaging provides a significantly increased CNR for focal liver lesions and less artifacts by comparison with the conventional TSE sequence. These results should stimulate further clinical studies with a surgical standard of reference to compare the two techniques in terms of sensitivity for malignant lesions.     

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.     

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).     

Magnetic resonance cholangiopancreatography: comparison of respiratory-triggered three-dimensional fast-recovery fast spin-echo with parallel imaging technique and breath-hold half-Fourier two-dimensional single-shot fast spin-echo technique

Purpose The aim of this study was to compare magnetic resonance cholangiopancreatography (MRCP) using respiratory-triggered (resp) three-dimensional Fourier transformation (3D) fast-recovery fast spin echo (FR-FSE) sequence with array spatial sensitivity technique (ASSET) for visualization of the pancreatobiliary system with breath-hold single thick-section and multiple thin-section MRCP using 2D single shot FSE (SSFSE) sequences. Materials and methods Forty patients underwent MRCP for evaluation of pancreatobiliary abnormalities in a 1.5-T magnet. Imaging time for resp 3D FR-FSE was recorded. The ghosting and blurring artifacts, overall image quality, and delineation of the pancreatobiliary ducts were evaluated using a five-point scale. Results On multisection 2D SSFSE source images, there were the least ghosting artifacts (4.9 ± 0.3, P < 0.05). Ghosting (3.4 ± 0.6, P < 0.05) and blurring (4.4 ± 0.8; P < 0.05) artifacts were the most prominent on resp 3D FR-FSE. 3D FR-FSE MRCP provided the highest rating of overall image quality (4.3 ± 0.8, P < 0.05) and delineation of third- and second-order branches of the hepatic ducts (2.9 ± 1.6 for third-order branches and 3.9 ± 1.3 for second-order branches, P < 0.05). Extrahepatic bile ducts, including upper and middle portions and cystic and pancreatic ducts, were also better seen with resp 3D FR-FSE MRCP than others. Conclusion MRCP with resp 3D FR-FSE using ASSET can be routinely used for acquiring information from the pancreatobiliary system. This article was presented at ISMRM in 2003.     

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.     

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.     

Fast spin-echo imaging of the temporomandibular joint

The applicability of a fast spin-echo (PSE) technique for magnetic resonance imaging of the tem-poromandibular joint (TMJ) was studied, and the technique compared with a conventional spin-echo (CSE) technique. Sagittal Tl-weighted CSE and dual-echo FSE images of 50 TMJs in 25 patients with symptoms of internal TMJ derangement were compared. CSE and FSE images were diagnostically comparable in 22 TMJs (44%). The FSE technique was rated better than CSE imaging for delineation of the disk in 26 joints (52%), whereas the CSE technique was rated better in only two joints (4%). The FSE technique was preferred overall in 54% of the joints. Mild to moderate joint effusion was detected in 17 joints because additional T2-weighted data were provided with the dual-echo FSE technique. The study showed that FSE imaging is an effective technique for evaluation of the TMJ. It is faster and diagnostically comparable to or better than CSE imaging, with the added advantage of providing T2-weighted data.