Esophageal magnetic resonance fluoroscopy: optimization of the sequence

OBJECTIVE: The purpose of this study was to try to delineate the esophageal passage under dynamic conditions and to determine optimum settings for esophageal magnetic resonance (MR) imaging. METHODS: Ten healthy volunteers underwent MR fluoroscopy with two T1-weighted sequences: turbo field echo (TFE) and T1-weighted fast field echo (T1-FFE). These sequences were compared for signal-to-noise ratios (SNRs) and image quality. To determine the optimum slice thickness, an additional 10 healthy volunteers underwent MR fluoroscopy. Results obtained for slice thicknesses of 25, 35, 45, and 55 mm were compared for delineated length of the esophagus and image quality. RESULTS: The T1-FFE sequences provided higher SNRs and better image quality than the TFE sequences (T1-FFE: 89.4 +/- 28.0, TFE: 52.4 +/- 16.7; P < 0.001). Artifacts were less prominent and delineation of the esophageal wall was better on the T1-FFE images. The delineation of the esophageal wall was best with a 35-mm slice thickness, although delineated length was the longest with a 55-mm slice thickness. CONCLUSION: This study showed T1-FFE to be a more suitable sequence than TFE and that the 35-mm slice thickness was the optimum slice thickness for esophageal MR fluoroscopy.     

Abdominal and pelvic segmented T1-weighted echo-planar imaging and MRI. Comparison with T1-TSE and T2-UTSE sequences]

PURPOSE: To assess, quantitatively and qualitatively, the diagnostic value of a segmented EPI T1W sequence compared to T1W and T2W TSE sequences. MATERIAL AND METHODS: A prospective analysis of abdominal and pelvic MRI examinations of 70 patients (44 women, 26 men, mean age of 61 years), was performed on a 0.5 T supraconductive magnet with 15 mT/m gradients. The sequences were randomized and compared in a blinded fashion by 3 independent reviewers: TSE T1W (TR/TE = 500/12 ms, NSA = 6, turbo factor 5, 3:49 min), EPI T1W (TR/TE = 500/30 ms, NSA = 6, EPI factor = 7, 2:13 min) and UTSE T2W (TR/TE = 1600-2500/100, NSA = 6, turbo factor = 31, 2:20 min). RESULTS: Quantitatively, no significant difference was found between T1W sequences for signal to noise ratio. The EPI T1W sequence had lower signal but stronger enhancement after gadolinium injection. Qualitatively, EPI T1W had significantly less flow artefacts (p < 0.001, wilcoxon test), and more chemical shift artifact (p < 0.01). For lesion detection, differences were not statistically significant between T1W sequences or between paired T1W and T2W sequences (sensitivity and specificity 84 and 86% for TSE T1W 76 and 86% for EPI T1W, 78 and 79% for UTSE T2W, 90 and 65% for TSE T1W-UTSE T2W, 88 and 65% for EPI T1W-UTSE T2W). Kappa concordance test (0.686) and Mac Nemar symmetry test (3.55) were high between T1W sequences. CONCLUSION: The segmented EPI T1W sequence used had equivalent results compared to the TSE T1W sequence, it allows a 40% reduction in acquisition time and this without difference in the diagnostic performances of the reviewers.     

Evaluation of turbo spin echo sequences for MRI of focal liver lesions at 0.5 T

To determine whether turbo spin echo (TSE) sequences can replace conventional T2-weighted spin echo (SE) sequences in MRI of the liver, 40 patients with focal liver lesions were imaged at 0.5 T. A T2-weighted SE sequences (TR/TE 1800/90 ms, number of signals averaged [NEX]=2, scan time=7:16 min), a TSE sequence (TR/TE 1800/90 ms, NEX=4, number of echos per excitation=13, echo spacing=12.9 ms, scan time=4:16 min) and a T1-weighted SE sequence (TR/TE 350/15 ms, NEX=2, scan time=4:21 min) were obtained and image quality, lesion detectability and lesion differentiation were evaluated qualitatively by subjective assessment using scores and quantitatively by lesion-liver contrast-to-noise (CNR) and tumour/liver signal intensity (SI) ratios. The image quality of the TSE sequence was substantially better compared with the T2-weighted SE sequence due to a reduction in motion artefacts and better delineation of anatomical details. Of a total of 158 visible lesions the T1-weighted SE, TSE, and T2-weighted SE sequences showed 91%, 81% and 65% of the lesions, respectively. Thus the TSE sequence depicted 24% (P< 0.001) more lesions than the T2-weighted SE sequence. In all types of pathology the lesion-liver CNR of the TSE sequence was significantly (P< 0.001) higher compared to the CNR of the T2-weighted SE sequence (+ 55–65%), indicating superior lesion conspicuity. Lesion characterization was equally good on the two T2-weighted sequences with no difference in the tumour/liver SI ratio. Using a criterion of tumour/liver SI ratio equal to or higher than 2, haemangiomas larger than 1 cm in diameter could be differentiated from other lesions with a sensitivity and specificity of 95% and 96%, respectively. Our results indicate that the TSE sequence is suitable for replacing the conventional T2-weighted SE sequence in MRI of focal liver lesions.This paper was presented at ECR 1993 Correspondence to: B. Kreft     

利用自旋回波平面成像T_2加权序列提高肝脏实性病变的检出率

目的　评价自旋回波平面成像 (SE EPI)T2 W序列对肝脏实性病变的检出能力。方法74例病人 (2 0 2个病灶 )接受肝脏 3种SE EPIT2 W序列磁共振扫描 ,评价其图像信噪比 (SNR)、肝脾对比噪声比 (L SCNR)、病灶对比噪声比 (CNR)及病变检出率 ,并与真实稳态进动快速成像 (true FISP)、快速自旋回波 (TSE)及半傅立叶采集单次激发快速自旋回波 (HASTE)等屏气T2 W序列相比较。结果SE EPI的SNR高于TSE (P <0 0 5 ) ,与true FISP相近 (P >0 0 5 ) ,但低于HASTE(P <0 0 1)。SE EPI序列的L SCNR及实性病变的CNR均显著高于true FISP、HASTE及TSE(P <0 0 1)。对于囊性病变 ,各序列间的检出率无明显差异 (P >0 0 5 )。各序列均检出所有直径大于 5cm的实性病变。直径 2～ 5cm的实性病变 ,SE EPI序列的检出率略高于true FISP、HASTE及TSE ,但无显著性差异 (P >0 0 5 )。直径小于 2cm的实性病灶 ,SE EPI序列的检出率 (93 9% )明显高于true FISP(5 7 6 % )、HASTE(71 2 % )及TSE(6 8 2 % ) (P <0 0 1)。结论　与其他屏气T2 W序列相比 ,SE EPIT2 WI有较高的病灶对比 ,能提高肝脏实性病变的检出率     

Comparison of echo planar imaging, gradient echo and fast spin echo MR scans of knee menisci.

In order to reduce the acquisition time, we compared a three-dimensional multi-shot echo-planar imaging (EPI) sequence with fat-suppression with two widely used sequences, the fat-suppressed gradient echo (GRE) and the proton-density weighted turbo spin-echo (FSE) in imaging the menisci of the knee. Sixty patients with various indications were studied prospectively with MRI. The menisci were imaged in the sagittal plane with all three sequences using a 1T MR scanner with 15mT/m gradients. The signal-to-noise ratio (SNR) of bone (b), cartilage (c), and meniscus (m) as well as contrast-to-noise ratio (CNR) and relative contrast (ReCon) between menisci and cartilage and between bone and cartilage were measured. A qualitative analysis was performed on grading of meniscal pathology (0-IV). The imaging accuracy of meniscal pathology was assessed compared to arthroscopy in 13 patients. The EPI provided the highest SNR in cartilage and meniscus (p<0.001), the highest CNR and the highest ReCon between bone and cartilage (p< or =0.001). MR grading of meniscal abnormalities showed overestimation compared to GRE and FSE. The EPI sequence could not be included in the routine protocol in imaging the menisci since the overestimation of meniscal abnormalities could lead to unnecessary arthroscopy.     

Multisection FLASH: method for breath-hold MR imaging of the entire liver.

One hundred ten patients with various focal liver lesions were imaged with a multisection fast low-angle shot (FLASH) gradient-echo sequence with an echo time of 4.6 msec. This sequence enabled the acquisition of 19 T1-weighted magnetic resonance (MR) images of the liver within a single 26-second breath hold. Patients were also examined with standard T1- and T2-weighted spin-echo (SE) sequences. The multisection FLASH sequence provided significantly higher (P less than .01) liver-spleen contrast, liver-spleen signal-difference-to-noise ratio (SD/N), liver-tumor contrast, and liver-tumor SD/N than the T1-weighted SE sequence but lower values than the T2-weighted SE sequence. Motion artifacts were reduced with the multisection FLASH sequence compared with both SE sequences (P less than .01). The overall image quality of the multisection FLASH images was similar to that of the T1-weighted SE images and superior to that of T2-weighted SE images. The most important characteristics of the multisection FLASH technique in MR imaging of the liver are the high T1 contrast, the prevention of motion artifacts, and a dramatic reduction in imaging time.     

Enhancement efficacy of magnetic starch microspheres (MSM) in conventional spin-echo and turbo spin-echo sequences at 0.5 T and 1.5 T

The efficacy of the superparamagnetic contrast agent magnetic starch microspheres (MSM) was evaluated in vitro by NMR relaxometry and in vivo by MR imaging using T2-weighted spin-echo (SE) and turbo spin-echo (TSE) sequences at 0.5 T and 1.5 T in 60 normal rats who received MSM in doses of 10–50 μmol/kg. MR imaging was performed using T2-weighted SE and TSE sequences. The relaxation rates 1/T1 and 1/T2 for liver and spleen increased linearly with MSM concentrations up to 30 μmol/kg body weight, and approached almost constant levels for higher doses. The slopes in the linear part of the 1/T2 diagram were 0.62 Hz ± 0.03 for the liver and 0.51 Hz ± 0.06 × kg/μmol for the spleen. On all T2-weighted sequences at 0.5 T and 1.5 T, liver signal-to-noise ratio (SNR) decreased by a factor of 2-3 already at the lowest dose of 10 μmol/kg. SNR values of TSE sequences exceeded values for SE sequences by 50–80%. The SNR decrease was not significantly different between SE and TSE sequences. Our results show that MSM is well suited as a T2 contrast agent at both magnetic field strengths when using conventional SE and fast TSE sequences.     

Comparison of ferucarbotran‐enhanced fluid‐attenuated inversion‐recovery echo‐planar,T2‐weighted turbo spin‐echo,T2*‐weighted gradient‐echo,and diffusion‐weighted echo‐planar imaging for detection of malignant liver lesions

Purpose:

To compare the diagnostic accuracy of superparamagnetic iron oxide (SPIO)‐enhanced fluid‐attenuated inversion‐recovery echo‐planar imaging (FLAIR EPI) for malignant liver tumors with that of T2‐weighted turbo spin‐echo (TSE), T2*‐weighted gradient‐echo (GRE), and diffusion‐weighted echo‐planar imaging (DW EPI).

Materials and Methods:

SPIO‐enhanced magnetic resonance imaging (MRI) that included FLAIR EPI, T2‐weighted TSE, T2*‐weighted GRE, and DW EPI sequences was performed using a 3 T system in 54 consecutive patients who underwent surgical exploration with intraoperative ultrasonography. A total of 88 malignant liver tumors were evaluated. Images were reviewed independently by two blinded observers who used a 5‐point confidence scale to identify lesions. Results were correlated with results of histopathologic findings and surgical exploration with intraoperative ultrasonography. The accuracy of each MRI sequence was measured with jackknife alternative free‐response receiver operating characteristic analysis. The sensitivity of each observer with each MRI sequence was compared with McNemar's test.

Results:

Accuracy values were significantly higher with FLAIR EPI sequence (0.93) than with T2*‐weighted GRE (0.80) or DW EPI sequences (0.80) (P < 0.05). Sensitivity was significantly higher with the FLAIR EPI sequence than with any of the other sequences.

Conclusion:

SPIO‐enhanced FLAIR EPI sequence was more accurate in the diagnosis of malignant liver tumors than T2*‐weighted GRE and DW EPI sequences. SPIO‐enhanced FLAIR EPI sequence is helpful for the detection of malignant liver tumors. J. Magn. Reson. Imaging 2010;31:607–616. ©2010 Wiley‐Liss, Inc.     

MR-Guided percutaneous ethanol ablation of liver tissue in a .2-T open MR system: Preliminary study in porcine model

The purpose of this study was to test the feasibility of MR-guided percutaneous ethanol ablation of liver tissue on a .2-T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then into livers of three anesthetized pigs, and injection of 10 ml of 96% alcohol was performed. T1 fast low-angle shot (FLASH), T2 turbo spin echo (TSE), and T1 spin echo (SE) images were obtained after incremental volumes of injection. In one pig, simultaneous injection of saline into normal liver was also performed with subsequent pathological correlation. Ethanol-infiltrated liver was hypointense to liver on all sequences, whereas saline caused no tissue signal changes on T1 SE and either isointense or hyperintense changes on T2 TSE images. Pathological examination confirmed ethanol-induced acute liver changes as compared with the control. MR guidance of needle placement and monitoring of ethanol effects on liver tissue is feasible. This may have implications for potential MR-guided hepatic tumor ablation.     

MR pulse sequence selection for optimal display of acrylic polymer phantoms

PurposeAcrylic phantoms are being increasingly used as an alternative to cadaveric and animal derived tissue samples in pre-clinical magnetic resonance (MR) imaging research studies. Such phantoms have been imaged using a variety of MR sequences but little effort has been devoted to determining the most appropriate MR pulse sequence. In order to address this question, a prospective comparative study was performed to determine which MR sequence optimally demonstrates acrylic polymer phantoms.MethodsNine MR imaging sequences were selected and used to image an acrylic phantom placed in a water bath. The mid-sagittal slice of each sequence was used to determine signal-to-noise (S/N) and contrast-to-noise (C/N) ratios. The signal intensity maximum gradient at the phantom/fluid interface was used as a measure of edge delineation.ResultsOf the nine sequences reviewed the T2 driven equilibrium pulse sequence (DRIVE), a 3D turbo spin echo (TSE) sequence, provided the highest S/N (72.88) and C/N (69.62) ratios, while the proton density (PD) TSE or intermediate T2 TSE sequences provided the best edge delineation (definition of the acrylic-fluid interface).ConclusionThis study suggests that selection of MR pulse sequences when evaluating a submersed acrylic phantom is dependent on which information is most important to the researcher. If S/N and C/N are considered most important, of the nine MR sequences tested, the T2 DRIVE sequence may be best employed. If edge delineation is considered most important, then PD or intermediate T2 TSE sequences may be best employed.     

A comparative analysis of double inversion recovery TFE and TSE sequences on carotid artery wall imaging

Objective

To analyze the characteristics of double inversion recovery (DIR) turbo field echo (TFE) and turbo spin echo (TSE) sequences and explore the value of double inversion recovery TFE sequence on carotid artery wall imaging.

Patients and methods

56 patients (32 males and 24 females, aged 31–76 years with a mean age of 53 years) were performed with DIR TFE and DIR TSE T1 weighted imaging (T1WI) sequences on carotid artery bifurcations. Image quality acquired by different techniques were evaluated and scored by two physicians. Whether there is significant difference is determined by SPSS 11.0 software. Paired-samples t test was used for statistics.

Results

There was no significant difference in the image quality scores between two sequences (t = 0.880, P = 0.383 > 0.05).

Conclusions

DIR TFE sequence has short scanning time and high spatial resolution. DIR TFE sequence can be used as the preferred sequence for screening carotid atherosclerotic plaque compared with DIR TSE sequence.     

Phased array breath-hold versus non-breath-hold MR imaging of focal liver lesions: A prospective comparative study

This study was undertaken to determine whether phased array breath-hold T1- and T2-weighted sequences can replace non-breath-hold spin echo (SE) sequences in the imaging of focal liver lesions by comparing overall image quality, liver-lesion contrast, and artifact. Both breath-hold and non-breath-hold T1-weighted and T2-weighted imagings of focal liver lesions were prospectively compared in 120 patients with suspected focal liver lesions imaged at 1.5 T with use of a body phased array multicoil. Breath-hold images were acquired with T1-weighted fast low-angle shot (FLASH) and T2-weighted turbo spin echo (TSE) sequences, and non-breath-hold images were made with conventional T1- and T2-weighted SE sequences. Qualitative image analysis was done by three blinded readers, and quantitative analysis was done. The highest signal-to-noise ratios were obtained with breath-hold T1-weighted FLASH sequence. The signal-to-noise ratios of breath-hold T2-weighted TSE sequence were slightly inferior to those of non-breath-hold SE sequence. Both T1-weighted and T2-weighted breath-hold sequences had less image artifact. Overall image quality of breath-hold sequences was better than that of non-breath-hold sequences for both T1- and T2-weighted sequences (P < .01). The tissue contrast of T1-weighted FLASH sequence was superior to that of SE sequence (P < .01). On T2-weighted imaging, tissue contrast of solid lesions was better on conventional SE sequence than that on breath-hold TSE sequence (P < .01). Respiratory ghost artifact was less prominent on T1-weighted FLASH sequence, although this artifact was occasionally seen on breath-hold T2-weighted TSE sequence. In a state-of-art MR unit with use of a phased array multicoil, conventional T1-weighted can be replaced by breath-hold sequences. On T2-weighted imaging, because solid tumor-liver contrast on breath-hold TSE imaging is inferior to that on non-breath-hold SE image, breath-hold imaging may not replace conventional non-breath-hold T2-weighted SE sequence.     

脂肪肝内正常肝岛及正常肝内局灶脂肪变性的CT与MR诊断

目的：探讨脂肪肝内正常肝岛及正常肝内局灶脂肪变性的ＣＴ与ＭＲ征象。方法：６例脂肪肝内正常肝组织岛（Ａ组）与７例正常肝内局灶性脂肪变性（Ｂ组）病人,ＣＴ与常规ＳＥＴ１ 及Ｔ２ 加权及梯度回波Ｔ１ 加权ｉｎ－ ｐｈａｓｅ及ｏｕｔ－ ｐｈａｓｅ ＭＲ成像。结果：增强前、后ＣＴ显示正常肝组织岛保持正常肝组织与脾脏密度关系;肝组织局灶脂肪变性呈相对低密度。ＭＲＩＳＥＴ１、Ｔ２ 加权成像及梯度回波ｉｎ－ ｐｈａｓｅＴ１ 加权成像显示正常肝组织岛相对低信号区;局灶脂肪变性区呈稍高信号。梯度回波ｏｕｔ－ ｐｈａｓｅ Ｔ１ 加权成像正常肝组织岛呈高信号;局灶脂肪变性区呈低信号。脂肪抑制Ｔ２ 加权成像均呈等信号。结论：采用ＭＲ的梯度回波ｏｕｔ－ ｐｈａｓｅＴ１ 加权及ＴＳＥＴ２ 加权脂肪抑制成像可以诊断正常肝岛及正常肝内的局灶脂肪变性。     

Fast T2*-weighted MRI of the prostate at 3 Tesla

Purpose:

To describe a rapid T2*‐weighted (T2*W), three‐dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1‐weighted turbo‐spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS).

Materials and Methods:

B₀ susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k‐space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six‐channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed.

Results:

Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W‐positive areas. Post‐biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS.

Conclusion:

The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T. J. Magn. Reson. Imaging 2011;33:902–907. © 2011 Wiley‐Liss, Inc.     

Post-operative lumbar spine: comparative study of TSE T2 and turbo-FLAIR sequences vs contrast-enhanced SE T1

AIM: To compare turbo T2 weighted spin echo (TSE T2) and turbo-FLAIR (fluid attenuated inversion recovery) vs gadolinium enhanced T1 weighted spin echo (SE T1) sequence in the differential diagnosis between disc herniation and post-surgical fibrosis. MATERIALS AND METHODS: Sixty-four patients who underwent surgical treatment for lumbar disc herniation with persistent or recurrent post-surgical symptoms were studied with a 0.5 Tesla MR system. The sequences used were TSE T2, turbo-FLAIR and T1 SE with and without intravenous gadolinium DTPA. The enhanced T1 SE sequence was considered the gold standard. Sensitivity and specificity were calculated. RESULTS: The sensitivity was 100% for both TSE T2 and turbo-FLAIR sequences. The specificity was 94% for TSE T2 and 92% for turbo-FLAIR. Negative predictive value was 100% for both sequences and positive predictive value 84% and 80% for TSE T2 and turbo-FLAIR, respectively. CONCLUSION: Although both sequences show high sensitivity, TSE-T2 presents greater specificity than turbo-FLAIR as compared to enhanced T1 SE. TSE T2 also offers the advantage of myelographic effect. We consider that the use of rapid sequences may avoid the need for intravenous contrast medium in most cases, reserving gadolinium DTPA only to those where all the criteria for hernia or fibrosis are not fulfilled.     

MRI in characterization of focal liver lesions: Comparison of T2 weighting by conventional spin-echo and turbo spin-echo sequences

Forty-one patients with 61 proved focal liver lesions underwent MRI of the liver at 1.0 T, with the aim of evaluating the usefulness of turbo spin-echo (TSE) sequences in characterizing focal liver lesions, by comparing them with conventional spin-echo (CSE) sequences. Two different TSE protocols were employed, with constant echo time and varying repetition time: TSE-S (3000 msec) and TSE-L (5100 msec). All images were evaluated quantitatively (signal-to-noise ratio ‘SNR’) and qualitatively: because benign lesions were all liquid (12 cysts and 10 hemangiomas), they were well characterized morphologically on the basis of signal intensity. Mean SNR was significantly different between metastases and benign lesions (P < .0001) with all T2 sequences. Among the single T2 sequences tested, logistic regression analysis showed TSE-L to have the best predictive ability of the nature of focal lesions, with a G value of 42.02, compared to 29.87 of TSE-S and 25.55 of CSE second echo (SE II). The combination of TSE-L with TSE-S did not modify these results, whereas the combination of TSE-L with CSE only resulted in slight improvement (G = 46.95). Comparison of the receiver operating characteristic (ROC) curves showed only SE II (area under the ROC curve of .8312) to be significantly inferior to the best single sequence, or TSE-L (area under the ROC curve of .9176; P = .027). All sequences were equivalent in qualitative evaluation, with good reproducibility, sensitivity ranging from .94 to 1.0, and specificity ranging from .86 to .93. This study confirms the value of TSE sequences in characterization of focal liver lesions. Time of acquisition is strongly reduced with these sequences, whereas results are fairly similar to those obtained with CSE. TSE sequences could therefore replace CSE for the study of focal liver lesions.     

Fat-suppressed 3D-T1-weighted-echo planar imaging: comparison with fat-suppressed 3D-T1-weighted-gradient echo in imaging the cartilage of the knee.

This study was conducted to compare a three-dimensional (3D) multi-shot echo-planar imaging (EPI) sequence with fat-suppression (FS) with the 3D-fat-suppressed gradient echo (GRE-FS) sequence in imaging the cartilage of the knee. One hundred sixty-nine patients were studied prospectively. The cartilage was imaged in the sagittal plane with: (a) 3D-T1-EPI-FS and (b) 3D-T1-GRE-FS sequences using a 1T MR scanner. The signal-to-noise ratio (SNR) of bone (b) and cartilage (c), and relative contrast (ReCon) between bone and cartilage and meniscus and cartilage were measured in 60 patients with arthroscopically normal cartilage. The imaging accuracy was assessed by comparing with linear regression analysis (length and depth) 32 defects in the cartilage of cadaveric (human and bovine) knees. The 3D-T1-EPI-FS provided better bone marrow signal suppression, better SNRc and better ReCon(bc) and ReCon(cm) (p<0.01). The 3D-T1-EPI-FS showed better accuracy concerning the depth of the defects and the 3D-T1-GRE-FS better accuracy concerning the length of the defects. In conclusion, the 3D-T1-EPI-FS pulse sequence could be included in the routine protocol in imaging the cartilage of the knee because it achieves high SNR of the cartilage and high ReCon compared to the surrounding structures, at a reduced scan time.     

Hepatic T2-weighted MRI: A prospective comparison of sequences,including breath-hold,half-Fourier turbo spin echo (HASTE)

The purpose of this study was to quantitatively compare the hepatic contrast characteristics of conventional spin-echo (CSE) and fast spin-echo (FSE) sequences with breath-hold T2-weighted images acquired with half-Fourier turbo spin echo (HASTE). Forty-five patients were examined with a phased-array surface coil. Nineteen patients had focal hepatic lesions, including eight malignant tumors, 10 cavernous hemangiomas, and one hepatic adenoma. Twenty-six patients had no focal hepatic lesions. T2-weighted images with comparable TE were acquired with CSE, FSE, and HASTE pulse sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for liver, spleen, and lesions were measured. FSE demonstrated significantly better quantitative performance than CSE for liver-spleen CNR (P = .0084). No statistically significant difference was demonstrated between FSE and CSE for liver or spleen SNR. FSE demonstrated clear scan time and resolution advantages over CSE. HASTE performed significantly poorer than CSE and FSE for liver-spleen CNR (P < .0001), liver SNR (P = .0002 for CSE and P < .0001 for FSE), and spleen SNR (P < .0001). Optimized FSE images with a short echo train length performed comparably to CSE images of equivalent TE. Liver-lesion CNR was suppressed on HASTE images, suggesting that long echo train length FSE sequences could diminish solid lesion detection compared to CSE and short echo train length FSE.     

In vivo detection of hemorrhage in human atherosclerotic plaques with magnetic resonance imaging

PURPOSE: To investigate the performance of high-resolution T1-weighted (T1w) turbo field echo (TFE) magnetic resonance imaging (MRI) for the identification of the high-risk component intraplaque hemorrhage, which is described in the literature as a troublesome component to detect. MATERIALS AND METHODS: An MRI scan was performed preoperatively on 11 patients who underwent carotid endarterectomy because of symptomatic carotid disease with a stenosis larger than 70%. A commonly used double inversion recovery (DIR) T1w turbo spin echo (TSE) served as the T1w control for the T1w TFE pulse sequence. The MR images were matched slice by slice with histology, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the MR images were calculated. Additionally, two readers, who were blinded for the histological results, independently assessed the MR slices concerning the presence of intraplaque hemorrhage. RESULTS: More than 80% of the histological proven intraplaque hemorrhage could be detected using the TFE sequence with a high interobserver agreement (Kappa = 0.73). The TFE sequence proved to be superior to the TSE sequence concerning SNR and CNR, but also in the qualitative detection of intraplaque hemorrhage. The false positive TFE results contained fibrous tissue and were all located outside the main plaque area. CONCLUSION: The present study shows that in vivo high-resolution T1w TFE MRI can identify the high-risk component intraplaque hemorrhage with a high detection rate in patients with symptomatic carotid disease. Larger clinical trials are warranted to investigate whether this technique can identify patients at risk for an ischemic attack.     

Comparison of MRI with CT for the radiotherapy planning of prostate cancer: a feasibility study

This feasibility study was performed to evaluate the suitability of MRI in defining appropriate pelvic radiotherapy treatment volumes, and to compare MRI sequences with CT for prostate cancer radiotherapy. Five patients with localized prostate cancer, imaged with four MRI sequences (spin echo (SE) T1, turbo SE (TSE) T2, high resolution TSE (HR) T2, and FLASH 3D (F3D)), compared with their corresponding CT planning scans. Segmentation ability of the following pelvic structures: prostatic apex (PA), prostate, rectum, bladder and seminal vesicles (SV), were evaluated by three independent observers. They used a five point grading scale based on the anatomical definition of the organ boundary, tissue contrast and multiplanar display. Results were averaged for the group and for each sequence. There was no significant interobserver variation in the assessed scores (p > 0.1). The average scores (+/- 1 SD) for all pelvic structures assessed by each imaging sequence were CT 1.3 +/- 0.6; SE T1 2.4 +/- 0.9; TSE T2 2.4 +/- 0.7; HR T2 2.2 +/- 0.7 and F3D 3.4 +/- 0.6. Compared with CT, the average MR score for each assessed pelvic structure was higher with a trend for all transaxial MR sequences to provide improved segmentation of the PA and rectum. The F3D sequence scored highest as it provided multiplanar views and avoided the problem of partial volume averaging. MRI, compared with CT, appears to provide improved definition of pelvic treatment volumes but further work is required to confirm this and to address the issues of MRI associated distortion and dosimetry before MRI can be used routinely for pelvic radiotherapy planning.