Uniformity Of Fat Suppression Research Articles

The application value of LAVA-flex sequences in enhanced MRI scans of nasopharyngeal carcinoma: comparison with T1WI-IDEAL.

Magnetic resonance imaging (MRI) staging scans are critical for the diagnosis and treatment of patients with nasopharyngeal cancer (NPC). We aimed to evaluate the application value of LAVA-Flex and T1WI-IDEAL sequences in MRI staging scans. Eighty-four newly diagnosed NPC patients underwent both LAVA-Flex and T1WI-IDEAL sequences during MRI examinations. Two radiologists independently scored the acquisitions of image quality, fat suppression quality, artifacts, vascular and nerve display. The obtained scores were compared using the Wilcoxon signed rank test. According to the signal intensity (SI) measurements, the uniformity of fat suppression, contrast between tumor lesions and subcutaneous fat tissue, and signal-to-noise ratio (SNR) were compared by the paired t-test. Compared to the T1WI-IDEAL sequence, LAVA-Flex exhibited fewer artifacts (P<0.05), better visualization of nerves and vessels (P<0.05), and performed superior in the fat contrast ratio of the primary lesion and metastatic lymph nodes (0.80 vs. 0.52, 0.81 vs. 0.56, separately, P<0.001). There was no statistically significant difference in overall image quality, tumor signal-to-noise ratio (SNR), muscle SNR, and the detection rate of lesions between the two sequences (P>0.05). T1WI-IDEAL was superior to LAVA-Flex in the evaluation of fat suppression uniformity (P<0.05). LAVA-Flex sequence provides satisfactory image quality and better visualization of nerves and vessels for NPC with shorter scanning times.

Water excitation with LIBRE pulses in three-dimensional variable flip angle fast spin echo for fat-free and large field of view imaging at 3 tesla

PurposeTo develop and evaluate a sequence in which water excitation with lipid insensitive binomial off-resonant radio frequency excitation (LIBRE) pulses is incorporated into three-dimensional (3D) variable flip angle fast spin echo (LIBRE-vf-FSE) for fat-free and large field of view imaging at 3 Tesla (T). Materials and methodsNumerical simulation was conducted to optimize the parameters of LIBRE pulses, including the flip angle, pulse duration, and frequency offset, for maximizing the fat suppression effect of the proposed LIBRE-vf-FSE sequence. The sequence was then implemented at 3 T and assessed in phantoms, lower extremity imaging of 8 healthy volunteers, and head/neck imaging of 5 healthy volunteers. Conventional water excitation (WE) and fat saturation (FatSat) were also performed for comparison. Signal-to-noise ratio (SNR) of fat and contrast-to-noise ratio (CNR) between fat and water were used to evaluate the level of fat suppression. Standard deviation (SD) of SNR was used to evaluate the uniformity of fat suppression. ResultsThe numerical simulation demonstrated that LIBRE-vf-FSE enables large volume imaging with uniform fat suppression, which was further confirmed by phantom and healthy volunteer experiments. LIBRE provided the lowest fat SNR and offered more uniform fat suppression compared with the WE and FatSat. Specifically, average oil SNRs obtained by LIBRE (1.10 ms, 360 Hz, and 60°), WE, and FatSat were (180.1 vs. 280.2 vs. 811.2) in phantom experiments, and average fat SNRs and SDs in legs obtained by LIBRE (1.10 ms, 360 Hz, and 60°), WE, and FatSat were (85.1 vs. 105.0 vs. 105.1) and (22.4 vs. 27.4 vs. 56.4) in vivo experiments, respectively. ConclusionThe proposed LIBRE-vf-FSE sequence allows for fat suppression and large field of view imaging at 3 T. It could be an alternative approach for fat-free vf-FSE scan.

A mask method to assess the uniformity of fat suppression in phantom studies.

Fat suppression is a technique used to suppress the signals from adipose tissues, during clinical evaluation of the tissues near the fat-tissue boundary. However, in cases where the scan area has a complicated shape, the effect of fat suppression may demonstrate poor uniformity, resulting in diagnosis-related difficulties. To improve the uniformity of fat suppression, phantom studies are more suitable than volunteer studies. In this study, we evaluated the reliability of the region of interest (ROI) dependency using an unevenness phantom, to develop a method to assess the uniformity of fat suppression while using whole magnetic resonance imaging by masking the surrounding phantom. We modulated different ROI sizes, which were eroded from 100% to approximately 50%, and observed that the normalized absolute average deviation and error increased with decreased ROI. Using our method, more objective, concrete, and accurate data could be obtained by including the whole-body phantom (whole poor uniformity area).

Benefits and pitfalls of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) imaging in clinical application of the cervical spine MR

To evaluate efficacy of T2-weighted (T2W) iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL)-fast spin echo (FSE) imaging of the cervical spine. The cervical spine of 100 symptomatic patients was imaged using routine magnetic resonance imaging (MRI) versus IDEAL-FSE imaging. The signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs), and image quality were analysed. To compare the diagnostic efficiency of degenerative spondylopathy, evaluations of spondylolisthesis, retrolisthesis, disc herniation, myelopathy, disc degeneration, and bone marrow oedema were also performed. IDEAL-FSE showed significantly higher SNRs and CNRs (all p<0.001) than fat-suppressed (FS) T2W-FSE. Sixteen of 100 patients had cervical spine instrumentation; in those patients, IDEAL-FSE provided significantly better uniformity of fat suppression (p<0.001) and fewer metallic artefacts (p<0.001). For patients without instrumentation, FS T2W-FSE showed significantly better overall image quality (p<0.001) and homogeneity of the cerebrospinal fluid (CSF; p<0.001) with fewer motion artefacts (p<0.001). IDEAL-FSE, however, provided significantly better uniformity of fat suppression (p<0.001). There were no significant differences in the diagnoses of spondylolisthesis, retrolisthesis, disc herniation, or myelopathy between IDEAL and FS T2W images. The only significant differences between the IDEAL and FS T2W images were noted when diagnosing degenerative disc disease at the C2-3 and C5-6 disc levels (p=0.019, p=0.002, respectively) and bone marrow oedema at C3 vertebral body (p=0.029). T2W IDEAL-FSE imaging should only be considered as an additional sequence to conventional FS T2W images in patients with poor fat suppression or severe metallic artefacts.

Assessment of the Quality of Breast MR Imaging Using the Modified Dixon Method and Frequency-Selective Fat Suppression: A Phantom Study.

To obtain objective and concrete data by physically assessing the quality of breast magnetic resonance images based on the fat-suppression effect by the modified Dixon method (mDixon) and frequency-selective fat suppression (e-Thrive) using an original lipid-content breast phantom that could easily reveal the influence of non-uniform fat suppression in breast magnetic resonance imaging. The fat-suppression uniformity was approximately seven times superior when using mDixon compared with when using e-Thrive. mDixon appears to have a significant advantage.

Diffusion-Weighted Imaging of the Head and Neck: Influence of Fat-Suppression Technique and Multishot 2D Navigated Interleaved Acquisitions.

DWI of the head and neck can reveal valuable information, but the effects of fat suppression and multishot acquisition on image quality have not been thoroughly investigated. We aimed to comprehensively compare the quality of head and neck DWI at 3T using 2 fat-suppression techniques, STIR, and spectral presaturation with inversion recovery, which were used with both single- and multishot EPI. Sixty-five study participants underwent 3 DWI sequences of single-shot EPI-STIR, single-shot EPI-spectral presaturation with inversion recovery, and multishot EPI-spectral presaturation with inversion recovery of the head and neck. In multiple anatomic regions, 2 independent readers assessed 5-point visual scores for fat-suppression uniformity and image distortion, and 1 reader measured the contrast-to-noise ratio and ADC. The mean visual score for fat-suppression uniformity was higher in single-shot EPI-STIR than in other sequences (all regions except for the orbital region, P < .05). The mean visual score for image distortion was higher in multishot EPI-spectral presaturation with inversion recovery than in single-shot EPI sequences (all regions, P < .001). Contrast-to-noise ratio was mostly lower in single-shot EPI-STIR than in other sequences (P < .001), and ADC was significantly higher in multishot EPI-spectral presaturation with inversion recovery than in single-shot EPI sequences (P ≤ .001). Overall, multishot EPI-spectral presaturation with inversion recovery provided the best image quality, with relatively homogeneous fat suppression, less image distortion than single-shot EPI sequences, and higher contrast-to-noise ratio than single-shot EPI-STIR. The measured ADC values can be higher in multishot EPI-spectral presaturation with inversion recovery, which necessitates cautious application of the previously reported ADC values to clinical settings.

Improved fat-suppression homogeneity with mDIXON turbo spin echo (TSE) in pediatric spine imaging at 3.0 T.

Background Robust fat suppression remains essential in clinical MRI to improve tissue signal contrast, minimize fat-related artifacts, and enhance image quality. Purpose To compare fat suppression between mDIXON turbo spin echo (TSE) and conventional frequency-selective and inversion-recovery methods in pediatric spine MRI. Material and Methods Images from T1-weighted (T1W) and T2-weighted (T2W) TSE sequences coupled with conventional methods and the mDIXON technique were compared in 36 patients (5.8 ± 5.4 years) at 3.0 T. Images from 42 pairs of T1W (n = 16) and T2W (n = 26) scans were acquired. Two radiologists reviewed the data and rated images using a three-point scale in two categories, including the uniformity of fat suppression and overall diagnostic image quality. The Wilcoxon rank-sum test was used to compare the scores. Results The Cohen's kappa coefficient for inter-rater agreement was 0.69 (95% confidence interval [CI], 0.56-0.83). Images from mDIXON TSE were considered superior in fat suppression ( P < 0.01) in 22 (rater 1) and 25 (rater 2) cases, respectively. In 13 (rater 1) and 11 (rater 2) cases, mDIXON TSE demonstrated improved diagnostic image quality ( P < 0.01). In three cases, fat suppression was superior using inversion-recovery and likewise in one case mDIXON had poorer image diagnostic quality. Lastly, mDIXON and conventional fat-suppression methods performed similarly in 17 (rater 1) and 14 (rater 2) cases, and yielded equal diagnostic image quality in 28 (rater 1) and 30 (rater 2) cases. Conclusion Robust fat suppression can be achieved with mDixon TSE pediatric spine imaging at 3.0 T and should be considered as a permanent replacement of traditional methods, in particular frequency-selective techniques.

Liver acquisition with volume acceleration flex on 70-cm wide-bore and 60-cm conventional-bore 3.0-T MRI.

This study aimed to compare the uniformity of fat suppression and image quality between liver acquisition with volume acceleration flex (LAVA-Flex) and LAVA on 60-cm conventional-bore and 70-cm wide-bore 3.0-T magnetic resonance imaging (MRI). The uniformity of fat suppression by LAVA-Flex and LAVA was assessed as the efficiency of suppression of superficial fat at the levels of the liver dome, porta, and renal hilum. Percentage standard deviation (%SD) was calculated using the following equation: %SD (%)=100×SD of the regions of interest (ROIs)/mean value of the signal intensity (SI) in the ROIs. Signal-to-noise ratio (SNR) and contrast ratio (CR) were calculated. In the LAVA sequence, the %SD in all slices on wide-bore 3.0-T MRI was significantly higher than that on conventional-bore 3.0-T MRI (P<0.01). However, there was no significant difference in fat signal uniformity between the conventional and wide-bore scanners when LAVA-Flex was used. In the liver, there were no significant differences in SNR between the two sequences. However, the SNR in the pancreas was lower for the wide-bore scanner than for the conventional-bore scanner for both sequences (P<0.05). There were no significant differences in CR for the liver and fat between LAVA-Flex and LAVA in both scanners. The CR in the LAVA-Flex images obtained by wide-bore MRI was significantly higher than that in the LAVA-Flex images recorded by conventional-bore MRI (P<0.001). LAVA-Flex offers more homogenous fat suppression in the upper abdomen than LAVA for both conventional and wide-bore 3.0-T MRI.

Breast DWI at 3 T: influence of the fat-suppression technique on image quality and diagnostic performance

To evaluate two fat-suppression techniques: short tau inversion recovery (STIR) and spectral adiabatic inversion recovery (SPAIR) regarding image quality and diagnostic performance in diffusion-weighted imaging (DWI) of breast lesions at 3 T. Ninety-two women (mean age 48 ± 12.1 years; range 21-78 years) underwent breast MRI. Two DWI pulse sequences, with b-values (50 and 1000 s/mm(2)) were performed with STIR and SPAIR. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), suppression homogeneity, and apparent diffusion coefficient (ADC) values were quantitatively assessed for each technique. Values were compared between techniques and lesion type. Receiver operating characteristics (ROC) analysis was used to evaluate lesion discrimination. One hundred and fourteen lesions were analysed (40 benign and 74 malignant). SNR and CNR were significantly higher for DWI-SPAIR; fat-suppression uniformity was better for DWI-STIR (p < 1 × 10(-4)). ADC values for benign and malignant lesions and normal tissue were 1.92 × 10(-3), 1.18 × 10(-3), 1.86 × 10(-3) s/mm(2) for DWI-STIR and 1.80 × 10(-3), 1.11 × 10(-3), 1.79 × 10(-3) s/mm(2) for SPAIR, respectively. Comparison between fat-suppression techniques showed significant differences in mean ADC values for benign (p = 0.013) and malignant lesions (p = 0.001). DWI-STIR and -SPAIR ADC cut-offs were 1.42 × 10(-3) and 1.46 × 10(-3) s/mm(2), respectively. Diagnostic performance for DWI-STIR versus SPAIR was: accuracy (81.6 versus 83.3%), area under curve (87.7 versus 89.2%), sensitivity (79.7 versus 85.1%), and specificity (85 versus 80%). Positive predictive value was similar. The fat-saturation technique used in the present study may influence image quality and ADC quantification. Nevertheless, STIR and SPAIR techniques showed similar diagnostic performances, and therefore, both are suitable for use in clinical practice.

The importance of image quality: In the eyes of the beholder?

The importance of image quality: In the eyes of the beholder?

Abdominal MRI at 3.0 T: LAVA‐flex compared with conventional fat suppression T1‐weighted images

To study liver imaging with volume acceleration-flexible (LAVA-Flex) for abdominal magnetic resonance imaging (MRI) at 3.0 T and compare the image quality of abdominal organs between LAVA-Flex and fast spoiled gradient-recalled (FSPGR) T1-weighted imaging. Our Institutional Review Board approval was obtained in this retrospective study. Sixty-nine subjects had both FSPGR and LAVA-Flex sequences. Two radiologists independently scored the acquisitions for image quality, fat suppression quality, and artifacts and the values obtained were compared with the Wilcoxon signed rank test. According to the signal intensity (SI) measurements, the uniformity of fat suppression, the contrast between muscle and fat and normal liver and liver lesions were compared by the paired t-test. The liver and spleen SI on the fat-only phase were analyzed in the fatty liver patients. Compared with FSPGR imaging, LAVA-Flex images had better and more homogenous fat suppression and lower susceptibility artifact (qualitative scores: 4.70 vs. 4.00, 4.86% vs. 7.14%, 4.60 and 4.10, respectively). The contrast between muscle and fat and between the liver and pathologic lesions was significantly improved on the LAVA-Flex sequence. The contrast value of the fatty liver and spleen was higher than that of the liver and spleen. The LAVA-Flex sequence offers superior and more homogenous fat suppression of the abdomen than does the FSPGR sequence. The fat-only phase can be a simple and effective method of assessing fatty liver.

Application of time‐resolved angiography with stochastic trajectories (twist)‐dixon in dynamic contrast‐enhanced (dce) breast mri

To evaluate a magnetic resonance imaging (MRI) technique that integrates time-resolved angiography with stochastic trajectories (TWIST) view sharing and Dixon for a breast dynamic contrast-enhanced (DCE)-MRI application. Simulation study: K-space data at six timepoints (1 pre-, 5 postcontrast) were generated by performing Fourier transform on a digital "phantom" with 3-9 mm enhancing lesions and three types of enhancement curves (persistent, plateau, washout). Images were reconstructed with and without TWIST. Clinical study: Six TWIST-Dixon image sets (one pre-, five postcontrast) were acquired in 18 patients on a 3T scanner, followed by one conventional image set. The last TWIST-Dixon and the conventional images were scored for seven criteria: perceived signal-to-noise ratio (P.SNR), visualization of anatomy, fat suppression (FS) accuracy, FS uniformity, ghosting artifact, edge ringing artifact, and overall image quality (IQ). Simulation study: With proper TWIST parameters (pA ≥33%, pB ≥50%), the enhancement underestimation was 5% or less for tumor size ≥5 mm. Clinical study: TWIST-Dixon images have significantly better scores in all criteria except for ghosting artifacts, where the difference was not significant. With proper parameters, TWIST-Dixon provides higher perceived SNR, more accurate fat suppression, and better overall image quality for breast DCE-MRI without sacrificing accuracy in the enhancement estimation.

Comparing T1-weighted and T2-weighted three-point Dixon technique with conventional T1-weighted fat-saturation and short-tau inversion recovery (STIR) techniques for the study of the lumbar spine in a short-bore MRI machine

To compare T1-weighted (W) fat-water separation (Dixon's technique) with T1W fat-saturation (FS) and T2W Dixon with short-tau inversion recovery (STIR) images for fat suppression in a short-bore MRI machine. Thirteen patients with lumbar disease were studied on using 1.5T MRI machine. The protocol included T1 FS (with contrast medium administration) and/or STIR and T1W and/or T2W Dixon, for comparison. Three neuroradiologists scored the images from the two-pairs of techniques for fat suppression uniformity and lesion conspicuity. Clinical usefulness of fat-only images was also evaluated. Regarding uniformity of fat suppression, mean scores were 2.28 (±0.49), 3.06 (±0.49), 2.39 (±0.49), and 3.15 (±0.35) for T1W FS, T1W Dixon, STIR, and T2W Dixon sequences, respectively. For the same pulse sequences, lesion conspicuity scores were 2.78 (±0.50), 2.78 (±0.27), 2.76 (±0.47), and 2.91 (±0.4), respectively. Both T1W and T2W Dixon sequences showed more homogeneous fat-suppression when compared to T1W FS (p=0.026) and STIR (p=0.008) techniques, but no significant difference was found for lesion conspicuity. Mean scores for the diagnostic utility of fat-only maps were, respectively, 1.72 (±0.39) and 2.48 (±0.50) for T1W and T2W Dixon. Fat suppression quality was superior with Dixon when compared to the conventional sequences, but not lesion conspicuity, suggesting that both techniques are reliable for diagnosis. Dixon may be advantageous in cases where inhomogeneity artefacts are an issue. Water-only maps appear to be useful in the clinical setting.

Fat suppression strategies in MR imaging of breast cancer at 3.0 T: comparison of the two-point Dixon technique and the frequency selective inversion method

To compare two fat suppression methods in contrast-enhanced MR imaging of breast cancer at 3.0 T: the two-point Dixon method and the frequency selective inversion method. Forty female patients with breast cancer underwent contrast-enhanced three-dimensional T1-weighted MR imaging at 3.0 T. Both the two-point Dixon method and the frequency selective inversion method were applied. Quantitative analyses of the residual fat signal-to-noise ratio and the contrast noise ratio (CNR) of lesion-to-breast parenchyma, lesion-to-fat, and parenchyma-to-fat were performed. Qualitative analyses of the uniformity of fat suppression, image contrast, and the visibility of breast lesions and axillary metastatic adenopathy were performed. The signal-to-noise ratio was significantly lower in the two-point Dixon method (P < 0.001). All CNR values were significantly higher in the two-point Dixon method (P < 0.001 and P = 0.001, respectively). According to qualitative analysis, both the uniformity of fat suppression and image contrast with the two-point Dixon method were significantly higher (P < 0.001 and P = 0.002, respectively). Visibility of breast lesions and metastatic adenopathy was significantly better in the two-point Dixon method (P < 0.001 and P = 0.03, respectively). The two-point Dixon method suppressed the fat signal more potently and improved contrast and visibility of the breast lesions and axillary adenopathy.

T1-weighted Fat-suppressed Imaging of the Pelvis with a Dual-Echo Dixon Technique: Initial Clinical Experience

To compare the image quality of water-only images generated from a dual-echo Dixon technique with that of standard fast spin-echo T1-weighted chemical shift fat-suppressed images obtained in patients evaluated for pelvic pain with a 1.5-T magnetic resonance (MR) system. The ethics board granted approval for this retrospective study; patient consent was not required. Twenty-five women underwent both standard axial T1-weighted fast spin-echo chemical shift fat-suppressed imaging and dual-echo Dixon imaging of the pelvis. Two readers independently scored the acquisitions for image quality, fat suppression quality, and artifact. On the basis of signal intensity measurements, the uniformity of fat suppression, the contrast between fat-suppressed and non-fat-suppressed tissue, and the contrast between pathologic lesions and suppressed fat were calculated. Values obtained with the T1-weighted fat-suppressed and dual-echo Dixon techniques were compared by using the Wilcoxon signed rank test. The images generated with the dual-echo Dixon technique were of higher quality, had better fat suppression, and had less artifact (qualitative scores: 4.4, 4.6, and 4.0, respectively) compared with the standard T1-weighted fat-suppressed images (qualitative scores: 3.4, 3.3, and 3.6, respectively; P < .01). Contrast between fat-suppressed and non-fat-suppressed tissue (contrast ratio: 0.86 for dual-echo Dixon technique vs 0.42 for T1-weighted fat-suppressed technique, P < .001) and between pathologic lesions and suppressed fat (contrast ratio: 0.88 for dual-echo Dixon technique vs 0.57 for T1-weighted fat-suppressed technique, P =.012) was significantly improved with the dual-echo Dixon technique. Twelve pathologic lesions were identified with dual-echo Dixon imaging versus eight that were identified with T1-weighted fat-suppressed imaging. Compared with standard T1-weighted fat-suppressed imaging, dual-echo Dixon imaging facilitates improved image quality of fat-suppressed images of the pelvis, enabling better delineation of pathologic lesions.

Fast three‐dimensional dual echo dixon technique improves fat suppression in breast MRI

To compare qualitative and quantitative measures of the contrast-enhanced dual-echo Dixon technique with the commonly used standard three-dimensional (3D) gradient echo (spectrally selective fat suppression) technique (SS-FS) in breast MRI exams (bMRI). A total of 19 women, with prescheduled bMRI exam, were recruited to our study between 2006 and 2008. Dixon and standard SS-SF techniques were used on both breasts of each patient. Image quality was rated in five categories: fat suppression quality, fat suppression uniformity, lesion margin clarity, lesion visibility, and axillary visibility. For quantitative assessment, we calculated the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of lesion to breast, SNR efficiency, and CNR efficiency. Of 19 patients evaluated, 13 had a primary breast malignancy and 6 had benign lesions or negative exams. Dixon images were rated higher in four of five qualitative categories (P < 0.0001) and required a shorter scan time. Dixon images yielded significantly higher SNR (43.8) and CNR (40.1) values than did 3DGRE images (SNR = 34.8, CNR = 25.3; P < 0.05). SNR efficiency (36.30) and CNR efficiency (33.79) values for Dixon images were also higher than were 3DGRE images (SNR efficiency =25.7, CNR efficiency = 19.1; P < 0.05). Dixon images were superior to the standard SS-SF images in both qualitative and quantitative assessment of 19 bMRI exams. The Dixon technique could replace standard SS-SF technique in bMRI exam, after our findings have been confirmed in future studies with a larger sample size.

Multiecho time‐resolved acquisition (META): A high spatiotemporal resolution dixon imaging sequence for dynamic contrast‐enhanced MRI

To evaluate a new dynamic contrast-enhanced (DCE) imaging technique called multiecho time-resolved acquisition (META) for abdominal/pelvic imaging. META combines an elliptical centric time-resolved three-dimensional (3D) spoiled gradient-recalled echo (SPGR) imaging scheme with a Dixon-based fat-water separation algorithm to generate high spatiotemporal resolution volumes. Twenty-three patients referred for hepatic metastases or renal masses were imaged using the new META sequence and a conventional fat-suppressed 3D SPGR sequence on a 3T scanner. In 12 patients, equilibrium-phase 3D SPGR images acquired immediately after META were used for comparing the degree and homogeneity of fat suppression, artifacts, and overall image quality. In the remaining 11 of 23 patients, DCE 3D SPGR images acquired in a previous or subsequent examination were used for comparing the efficiency of arterial phase capture in addition to the qualitative analysis for the degree and homogeneity of fat suppression, artifacts, and overall image quality. META images were determined to be significantly better than conventional 3D SPGR images for degree and uniformity of fat suppression and ability to visualize the arterial phase. There were no significant differences in artifact levels or overall image quality. META is a promising high spatiotemporal resolution imaging sequence for capturing the fast dynamics of hyperenhancing hepatic lesions and provides robust fat suppression even at 3T.

Comparison of diffusion-weighted images using short inversion time inversion recovery or chemical shift selective pulse as fat suppression in patients with breast cancer

Fat suppression is essential for diffusion-weighted imaging (DWI) in the body. However, the chemical shift selective (CHESS) pulse often fails to suppress fat signals in the breast. The purpose of this study was to compare DWI using CHESS and DWI using short inversion time inversion recovery (STIR) in terms of fat suppression and the apparent diffusion coefficient (ADC) value. DWI using STIR, DWI using CHESS, and contrast-enhanced T1-weighted images were obtained in 32 patients with breast carcinoma. Uniformity of fat suppression, ADC, signal intensity, and visualization of the breast tumors were evaluated. In 44% (14/32) of patients there was insufficient fat suppression in the breasts on DWI using CHESS, whereas 0% was observed on DWI using STIR (P < 0.0001). The ADCs obtained for DWI using STIR were 4.3% lower than those obtained for DWI using CHESS (P < 0.02); there was a strong correlation of the ADC measurement (r = 0.93, P < 0.001). DWI using STIR may be excellent for fat suppression; and the ADC obtained in this sequence was well correlated with that obtained with DWI using CHESS. DWI using STIR may be useful when the fat suppression technique in DWI using CHESS does not work well.

Fast dixon-based multisequence and multiplanar MRI for whole-body detection of cancer metastases.

To develop and demonstrate the feasibility of multisequence and multiplanar MRI for whole-body cancer detection. Two fast Dixon-based sequences and a diffusion-weighted sequence were used on a commercially available 1.5 T scanner for whole-body cancer detection. The study enrolled 19 breast cancer patients with known metastases and in multistations acquired whole-body axial diffusion-weighted, coronal T2-weighted, axial/sagittal pre- and postcontrast T1-weighted, as well as triphasic abdomen images. Three radiologists subjectively scored Dixon images of each series for overall image quality and fat suppression uniformity on a 4-point scale (1 = poor, 2 = fair, 3 = good, and 4 = excellent). Eighteen of the 19 patients completed the whole-body MRI successfully. The mean acquisition time and overall patient table time were 46 +/- 3 and 69 +/- 5 minutes, respectively. The average radiologists' scores for overall image quality and fat suppression uniformity were both 3.4 +/- 0.5. The image quality was consistent between patients and all completed whole-body examinations were diagnostically adequate. Whole-body MRI offering essentially all the most optimal tumor-imaging sequences in a typical 1-hour time slot can potentially become an appealing "one-stop-shop" for whole-body cancer imaging.

A single‐point dixon technique for fat‐suppressed fast 3D gradient‐echo imaging with a flexible echo time

To develop a single-point Dixon (SPD) technique that requires only data of a single echo with a flexible echo time, and to demonstrate its use for fat-suppressed, T1-weighted contrast agent enhancement studies. Raw data were collected using a product fast 3D gradient-echo pulse sequence. Phase-error removal and fat-suppression (FS) were achieved using a fully-automated region-growing algorithm. A water and fat phantom and the abdomen and breast of cancer patients before and after injection of gadolinium contrast agent were imaged at varying echo times. Scan time efficiency and overall FS quality were compared to those by the product fast 3D gradient-echo technique with conventional FS. In phantom, the SPD technique achieved uniform FS for a wide range of echo times corresponding to the water and fat relative phase angles between 100 degrees and 160 degrees. In patients, the technique was able to achieve approximately 30% scan time reduction and more uniform FS when compared to using the conventional FS technique but otherwise identical scan parameters. The SPD technique compares favorably in scan time efficiency and FS uniformity and can be useful for fast T1-weighted and fat-suppressed imaging with contrast agent administration.