Evaluation of locally recurrent pelvic malignancy: performance of T2- and diffusion-weighted MRI with image fusion

PURPOSE: To evaluate the performance of T2- and diffusion-weighted magnetic resonance imaging (MRI) with image fusion for detection of locally recurrent pelvic malignancy. MATERIALS AND METHODS: The study group consisted of 28 patients (27 female, 1 male) who underwent pelvic MRI at 1.5 T after treatment of pelvic malignancy. MR images were reviewed independently by three blinded readers. The performance of the four sequences for detecting local recurrence was evaluated using receiver operating characteristic analysis: T2-weighted fast spin-echo (FSE), diffusion-weighted echo-planar imaging (DWI), dynamic contrast-enhanced (DCE) fat-suppressed T1-weighted spoiled gradient echo (SPGR), and T2-DWI with image fusion, the latter created using OsiriX Medical Imaging Software. RESULTS: Local recurrence was confirmed at biopsy in 16 patients. Twelve patients showed no evidence of recurrence on two consecutive MRI studies. The Az value for T2-DWI with image fusion (0.949) was statistically greater than that for T2-weighted FSE (0.849) (P<0.05). The sensitivity and specificity was 87.5% and 47.2%, respectively, for T2-weighted FSE, 100.0% and 50.0% for DWI, 95.8% and 58.3% for DCE fat-suppressed T1-weighted SPGR, and 93.8% and 72.2% for T2-DWI with image fusion. CONCLUSION: For depicting locally recurrent pelvic malignancy, T2-DWI with image fusion outperforms standard T2-weighted FSE and DWI and is comparable to DCE fat-suppressed T1-weighted SPGR.     

Flow ghost artifact in slice-encoding direction mimicking vestibular schwannoma in contrast-enhanced 3D spoiled gradient-echo sequence

The value of MR imaging by post-contrast T1-weighted 3D spoiled gradient-echo (3D SPGR) is well established for the detection of small vestibular schwannomas in the cerebellopontine angle region. We describe a case in which a flow ghost artifact in the slice-encoding direction mimicked a vestibular schwannoma and heavily T2-weighted MR cisternography and multiplanar reconstruction images helped us to reach the correct diagnosis. In addition, we conducted a volunteer study to demonstrate that changing the k-space trajectory can reduce this artifact in post-contrast 3D SPGR images.     

MR angiography of the thoracic aorta with an electrocardiographically triggered breath-hold contrast-enhanced sequence.

An electrocardiographically (ECG) triggered breath-hold contrast material-enhanced magnetic resonance (MR) angiography sequence has been developed for imaging the thoracic aorta. A three-dimensional (3D) gradient-echo sequence is used with a contrast material bolus. Forty-nine patients with various aortic abnormalities and five healthy volunteers underwent imaging with the sequence. All studies were performed in a single breath hold. ECG-triggered breath-hold contrast-enhanced MR angiography was tolerated in 48 of the 49 patients. The images demonstrated no respiratory motion artifacts and diminished pulsation artifacts. The cardiac chambers, aortic root, ascending and descending aorta, aortic arch, proximal arch vessels, and proximal coronary arteries were clearly demonstrated and not obscured by ghost artifacts. The 3D data set allowed excellent multiplanar reformation, permitting orthogonal or oblique views of the vascular anatomy. A variety of congenital and acquired abnormalities were clearly identified. When this sequence is used, it is important to evaluate both the maximum-intensity projection and source images. Delayed imaging should be performed to detect late filling. In conjunction with cine MR and T1-weighted spin-echo imaging, ECG-triggered breath-hold contrast-enhanced MR angiography should be considered the technique of choice for imaging the thoracic aorta.     

Usefulness of IDEAL T2-weighted FSE and SPGR imaging in reducing metallic artifacts in the postoperative ankles with metallic hardware

Purpose

The aim of this work is to prospectively compare the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL), T2-weighted fast spin-echo (FSE), and spoiled gradient-echo (SPGR) MR imaging to frequency selective fat suppression (FSFS) protocols for minimizing metallic artifacts in postoperative ankles with metallic hardware.

Materials and methods

The T2-weighted and SPGR imaging with IDEAL and FSFS were performed on 21 ankles of 21 patients with metallic hardware. Two musculoskeletal radiologists independently analyzed techniques for visualization of ankle ligaments and articular cartilage, uniformity of fat saturation, and relative size of the metallic artifacts. A paired t test was used for statistical comparisons of MR images between IDEAL and FSFS groups.

Results

IDEAL T2-weighted FSE and SPGR images enabled significantly improved visualization of articular cartilage (p?<?0.05), the size of metallic artifact (p?<?0.05), and the uniformity of fat saturation (p?<?0.05). However, no significant improvement was found in the visibility of ligaments.

Conclusions

IDEAL T2-weighted FSE and SPGR imaging effectively reduces the degree of tissue-obscuring artifacts produced by fixation hardware in ankle joints and improves image quality compared to FSFS T2-weighted FSE and SPGR imaging. However, visibility of ligaments was not improved using IDEAL imaging.

     

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.     

Articular cartilage of knee: normal patterns at MR imaging that mimic disease in healthy subjects and patients with osteoarthritis

PURPOSE: To evaluate normal magnetic resonance (MR) imaging findings that may mimic articular cartilage diseases in healthy subjects and patients with osteoarthritis of the knee. MATERIALS AND METHODS: Sagittal fat-suppressed intermediate-weighted fast spin-echo (FSE) (repetition time msec/echo time [TE] msec, 4,000/13), sagittal T2-weighted FSE (4,000/39), and sagittal fat-suppressed three-dimensional (3D) spoiled gradient-echo (SPGR) (60/5, 40 degrees flip angle) MR images were acquired in 28 patients and four volunteers. FSE images with a TE of 13 msec were considered "short-TE images"; those with a TE of 39 msec were considered "long-TE images." Presence of normal MR imaging appearance of articular cartilage was determined by one author. Contrast between cartilage and adjacent structures (meniscus, joint capsule, synovial fluid, muscle) was calculated in posterior regions of the femoral condyle on images obtained with each sequence; Wilcoxon signed rank testing was performed. RESULTS: The following appearances were observed in patients with knee osteoarthritis (on short-TE FSE, long-TE FSE, and SPGR MR images, respectively): (a) ambiguity of surface contour in posterior region of the femoral condylar cartilage (in zero, zero, and 20 patients), (b) linear area of high signal intensity in deep zone adjacent to subchondral bone of femoral condyle (in zero, zero, and 26 patients), (c) pseudolaminar appearance in posterior region of femoral condylar cartilage (in seven, nine, and 24 patients), (d) truncation artifact in patellofemoral compartment (in seven, six, and 27 patients), (e) susceptibility artifact on cartilage surface caused by air or metal (in three, three, and 11 patients), (f) decreased signal intensity in distal part of trochlear cartilage (in 28, 28, and 28 patients), (g) cartilage thinning adjacent to the anterior horn of the lateral meniscus (in 19, 19, and 21 patients), and (h) focal cartilage flattening in posterior region of femoral condyle (in 16, 16, and nine patients). Cartilage-meniscus and cartilage-synovial fluid contrast was significantly higher on fat-suppressed FSE than on fat-suppressed 3D SPGR MR images (P <.001). CONCLUSION: Fat-suppressed FSE and 3D SPGR MR images showed nonuniform signal intensity arising from articular cartilage and cartilage thinning, both of which could mimic disease.     

Differentiation between hepatic cyst and hemangioma: additive value of breath-hold, multisection fluid-attenuated inversion-recovery magnetic resonance imaging using half-Fourier acquisition single-shot turbo-spin-echo sequence

PURPOSE: To evaluate the additive value of breath-hold, multisection fluid-attenuated inversion-recovery (FLAIR) magnetic resonance imaging (MRI) using half-Fourier acquisition single-shot turbo-spin-echo (HASTE) sequence as supplements to moderately and heavily T2-weighted fast-spin-echo (FSE) sequences in differentiating hepatic cyst from hemangioma. MATERIALS AND METHODS: A total of 183 lesions (127 hepatic cysts, 56 hepatic hemangiomas) in 117 patients were evaluated in this study. Three radiologists independently reviewed FLAIR MR images using a HASTE sequence and T2-weighted FSE MR images. Each radiologist used a five-point scale to rate his confidence in determination of hepatic cyst and hemangioma. RESULTS: All three reviewers were significantly better able to differentiate hepatic cyst from hepatic hemangioma with the combination of FLAIR imaging using HASTE and moderately and heavily T2-weighted FSE images (area under the receiver operating characteristic (ROC) curve, 0.99 for each reader) than with moderately and heavily T2-weighted FSE images alone (0.82-0.93; P < 0.05). FLAIR-HASTE imaging in addition to T2-weighted FSE sequences improved the diagnostic performance, including the sensitivity, specificity, accuracy, and confident diagnosis in the differentiation between hepatic hemangiomas and cysts. CONCLUSION: FLAIR-HASTE imaging is useful for distinguishing hepatic hemangioma from hepatic cyst without the use of contrast-enhanced MR images.     

Optimal Pulse Sequence for Ferumoxides-Enhanced MR Imaging Used in the Detection of Hepatocellular Carcinoma: A Comparative Study Using Seven Pulse Sequences

Objective

To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs).

Materials and Methods

Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 µmol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333 8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR∞/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis.

Results

Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others.

Conclusion

T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxides-enhanced MR imaging in the detection of HCCs.     

Evaluation of focal liver lesions: fast-recovery fast spin echo T2-weighted MR imaging

PURPOSE: To compare breath-hold fast-recovery fast spin echo (FR-FSE) and non-breath-hold fast spin echo (FSE) T2-weighted sequences for hepatic lesion conspicuity and image quality at MR imaging. MATERIALS AND METHODS: Fifty-nine patients with known or suspected liver lesions underwent hepatic MR imaging by using a breath-hold FR-FSE T2-weighted sequence with and without fat suppression and a non-breath-hold FSE T2-weighted sequence with and without fat suppression. Quantitative analysis was made with measurements of the signal intensity of the liver, spleen, background noise, and up to three liver lesions, as well as calculations of the liver signal-to-noise ratio (SNR) and the liver-to-lesion contrast-to-noise ratio (CNR) for each sequence. Qualitative analysis was made for image quality and the number of lesions identified. Statistical analysis was performed by using a single-tailed paired Student's t test with a 95% confidence interval. RESULTS: SNR and CNR were significantly higher (P<.05) for FSE with fat suppression than for FR-FSE with fat suppression. No statistically significant difference was seen in terms of SNR and CNR between non-fat-suppressed FSE and FR-FSE sequences. Lesion conspicuity, liver edge sharpness, and clarity of vessels were superior and ghosting was less with the FR-FSE sequences compared with the FSE sequences. CONCLUSION: Breath-hold FR-FSE technique is a reasonable alternative in T2-weighted imaging of the liver.     

Spatial relationship between vestibular schwannoma and facial nerve on three-dimensional T2-weighted fast spin-echo MR images

BACKGROUND AND PURPOSE: During surgical removal of a vestibular schwannoma, correct identification of the facial nerve is necessary for its preservation and continuing function. We prospectively analyzed the spatial relationship between vestibular schwannomas and the facial nerve using 3D T2-weighted and postcontrast T1-weighted spin-echo (SE) MR imaging. METHODS: Twenty-two patients with a unilateral vestibular schwannoma were examined with MR imaging. The position and spatial relationship of the facial nerve to adjacent tumor within the internal auditory canal (IAC) and cerebellopontine angle cistern (CPA) were assessed on multiplanar reformatted 3D T2-weighted fast spin-echo (FSE) images and on postcontrast transverse and coronal T1-weighted SE images. The entrance of the nerve into the bony canal at the meatal foramen and the nerve root exit zone along the brain stem were used as landmarks to follow the nerve course proximally and distally on all images. RESULTS: The spatial relationship between vestibular schwannoma and facial nerve could not be detected on postcontrast T1-weighted SE images. In 86% of the patients, the position of the nerve in relation to the tumor was discernible on multiplanar reformatted 3D T2-weighted FSE images. In tumors with a maximal diameter up to 10 mm, the entire nerve course was visible; in tumors with a diameter of 11 to 24 mm, only segments of the facial nerve were visible; and in tumors larger than 25 mm, the facial nerve could not be seen, owing to focal nerve thinning and obliteration of landmarks within the IAC and CPA. CONCLUSION: Identification of the facial nerve and its position relative to an adjacent vestibular schwannoma is possible on multiplanar reformatted 3D T2-weighted FSE images but not on postcontrast T1-weighted SE images. Detection of this spatial relationship depends on the tumor's size and location.     

MR angiography with an ultrasmall superparamagnetic iron oxide blood pool agent

The purpose of the study was to investigate the use of a dextran-coated ultrasmall superparamagnetic iron oxide (USPIO) as a blood pool contrast agent for thoracic and abdominal MR angiography. Abdominal and thoracic MR angiography was performed in six healthy volunteers using two-dimensional and three-dimensional spoiled gradient echo (SPGR) sequences before and after intravenous administration of USPIO. Doses ranged from 1.1 to 2.6 mg Fe/kg. Flip angle was varied from 20 to 60°. Subjective image quality, analysis of signal-to-noise ratio (SNR), and blood T1 relaxation times were measured. USPIO significantly lowered the T1 of blood (from 1,210 ms precontrast to 159 ms postcontrast at a dose of 2.6 mg Fe/kg) (P < .01). Image quality on coronal fast three-dimensional breath-hold SPGR images of the abdomen increased with increasing dose and was maximum at the highest dose, producing an aortic SNR of 9.6 compared to 1.8 precontrast. Axial two-dimensional time-of-flight (TOF) aortic SNR was reduced significantly from 13 on precontrast to 6 on the postcontrast images at the highest dose (P < .05) due to T2* shortening effects. There was little flip angle dependence on image quality. Due to the T1 shortening effect and long intravascular half-life, USPIO improved visualization of vascular anatomy using three-dimensional fast SPGR imaging. The echo time must be minimized to minimize signal loss from T2* shortening effects. The blood pool distribution of USPIO is useful for equilibriumphase MR angiography.     

Preoperative MRI of potential living-donor-related liver transplantation using a single dose of gadobenate dimeglumine

OBJECTIVE: This article evaluates the feasibility of single-dose gadobenate dimeglumine-enhanced MRI as both an angiographic and biliary contrast medium for making a preoperative evaluation of the donor candidates for a living-donor-related liver transplantation. SUBJECTS AND METHODS: Eleven right hepatic lobe donors underwent MRI examinations using T1- and T2-weighted imaging and T2-weighted MR cholangiography (MRC). The MR angiography (MRA) and contrast-enhanced (CE) T1-weighted MRC images then were obtained after injecting a single dose of gadobenate dimeglumine. One radiologist and one surgeon prospectively reviewed all the MRI examinations for hepatic vascular and biliary abnormalities and compared them with the surgical findings and intraoperative cholangiograms. In addition, two blinded reviewers evaluated the two sets of MRC (T2-weighted MRC set and T2-weighted MRC plus CE-T1-weighted MRC set) retrospectively and recorded the anatomic types of the hilar biliary branching pattern along with their confidence in the interpretation. RESULTS: Prospective analysis detected the following vascular variants: hepatic arterial variation in two patients, portal venous variation in one, and a significantly large accessory hepatic vein (> 5 mm) in one. Biliary variants also were identified in two patients. All the MRI findings on the vascular and biliary anatomy were corroborated intraoperatively. Retrospective analysis showed that the mean diagnostic confidence in the combined set was significantly higher than that of the T2-weighted MRC alone by both reviewers (p < 0.05). CONCLUSION: Obtaining both MRA and CE-T1-weighted MRC is feasible using a single dose of gadobenate dimeglumine. Therefore, gadobenate dimeglumine-enhanced MRI might play a role as a preoperative imaging technique for the vascular and biliary evaluation of potential living donors.     

High-resolution MR imaging of the elbow using a microscopy surface coil and a clinical 1.5 T MR machine: preliminary results

Objective To obtain high-resolution MR images of the elbow using a microscopy surface coil with a 1.5 T clinical machine and to evaluate the feasibility of its use for elbow injuries.Design and patients Five asymptomatic normal volunteers and 13 patients with elbow pain were prospectively studied with MR imaging using a microscopy surface coil 47 mm in diameter. High-resolution MR images using a microscopy coil were obtained with fast spin echo (FSE) proton density-weighted sequence, gradient recalled echo (GRE) T2*-weighted sequence, and short tau inversion recovery (STIR) sequence, with a 1–2 mm slice thickness, a 50–70 mm field of view, an imaging matrix of 140–224×512 using zero fill interpolation, and 2–6 excitations.Results High-resolution MR images of normal volunteers using a microscopy coil clearly showed each structure of the medial and lateral collateral ligaments on GRE T2*-weighted images and FSE proton-density weighted images. Partial medial collateral ligament injury, a small avulsion of the medial epicondyle, and osteochondritis dissecans were well demonstrated on high-resolution MR images.Conclusion High-resolution MR imaging of the elbow using a microscopy surface coil with a 1.5 T clinical machine is a promising method for accurately characterizing the normal anatomy of the elbow and depicting its lesions in detail.     

Comparison of breath-hold multishot echo-planar and respiratory triggered fast-spin-echo sequences for T2-weighted MRI of liver lesions

The purpose of this study was to evaluate the usefulness of multishot echo-planar imaging in detecting liver tumors in comparison with respiratory triggered T2-weighted fast-spin-echo (FSE) imaging. Thirty-two patients with 70 focal liver lesions were imaged using a 1.5-T high speed MR imager. Eight-shot echo-planar images covering the whole liver were acquired during a single breath-hold period. FSE images were acquired with respiratory triggering in approximately 4 minutes. Lesion detectability and image quality of the two pulse sequences were analyzed qualitatively. Quantitative analysis was performed by means of signal-to-noise and tumor-liver contrast-to-noise analysis. Lesion detectability was comparable in both solid (86.3% vs 90.2%: .3 < P < .5) and nonsolid lesions (89.5% vs 100%: .3 < P < .5) between echo-planar and FSE images. Echo-planar imaging provided significantly reduced image artifact, better lesion conspicuity, and anatomic detail compared with FSE imaging. The signal-to-noise and contrast-to-noise ratios of echo-planar images were significantly higher than those of FSE images. Breath-hold eight-shot echo-planar imaging can be an alternative to T2-weighted FSE imaging because it can provide comparable image quality in a substantially decreased acquisition time.     

IDEAL技术在脊柱病变的应用

目的:对IDEAL技术与频率选择饱和法FSE序列T2 WI脂肪抑制效果进行比较,探讨IDEAL技术在脊柱磁共振成像方面的应用价值.方法:35例脊柱病变患者行常规磁共振检查,频率选择饱和法进行矢状面T2 WI脂肪抑制扫描,采用IDEAL技术行矢状面T2 WI扫描,对两种方法的脂肪抑制效果、图像总体质量评分进行比较,并且比...     

Magnetic resonance imaging of the hila and mediastinum

In the diagnosis of chest diseases, MR imaging has been shown to be most helpful in the evaluation of hilar and mediastinal lesions. The detection of intrathoracic abnormalities is technique-dependent, and imaging with both short and long repetition and echo times is necessary. ECG gating and sagittal or coronal images supplement transaxial scans in some patients. MR allows the diagnosis of mediastinal vascular lesions and the differentiation of mediastinal mass and vessel without contrast agents. It provides diagnostic information quite similar to that of CT in patients with mediastinal mass, but spatial resolution is somewhat poorer. In patients with hilar mass, MR is superior to CT in identifying the mass and distinguishing it from normal structures.     

Assessment of internal auditory canal tumors: a comparison of contrast-enhanced T1-weighted and steady-state T2-weighted gradient-echo MR imaging.

BACKGROUND AND PURPOSE: Although contrast-enhanced T1-weighted MR imaging is the standard of reference for diagnosing tumor in the cerebellopontine angle, high-resolution T2-weighted imaging may show more details of the seventh and eighth cranial nerve branches, resulting in more accurate tumor volume measurements. The purpose of this study was to compare two MR sequences for their ability to delineate internal auditory canal tumors. METHODS: Twenty-seven ears in 21 patients with 16 confirmed schwannomas were studied with the 3D T2-weighted prototype segment-interleaved motion-compensated acquisition in steady state (SIMCAST) and the T1-weighted contrast-enhanced spoiled gradient-echo (SPGR) techniques. Twenty-eight axial sections were acquired using parameters of 17/3.3 (TR/TE), a 40 degrees flip angle, a 20 x 15-cm or 22 x 16-cm field of view (FOV), a 512 x 256 matrix, and a 0.4- or 1.2-mm section thickness for the SIMCAST technique, and 30/4.2, a 30 degrees flip angle, a 20 x 20-cm FOV, a 512 x 288 matrix, and a 1.5-mm section thickness for the SPGR technique. Tumor appearance and depiction of surrounding anatomy, including the cranial nerves, were evaluated. Tumor volumes were measured by manual tracing. RESULTS: Both sequences clearly identified tumors that ranged in size from 0.06 to 3.0 cm3. Measurements on both sequences agreed, on average, within 14%. The information from both sequences was complementary. SIMCAST usually delineated the CSF spaces better, whereas SPGR more clearly showed the tumor/brain boundary. CONCLUSION: SIMCAST and SPGR are suitable for tumor detection and volume measurements. SPGR has somewhat better contrast, but SIMCAST excels at depicting the surrounding anatomy and tumor involvement of the seventh and eighth cranial nerves.     

Head and neck paragangliomas: improved tumor detection using contrast-enhanced 3D time-of-flight MR angiography as compared with fat-suppressed MR imaging techniques

BACKGROUND AND PURPOSE: MR imaging techniques have proved their efficacy in imaging the head and neck region. In this study, we compared T1-weighted, dual T2-weighted, and fat-suppressed MR imaging and unenhanced and contrast-enhanced 3D time-of-flight MR angiography sequences for detection of head and neck paragangliomas. METHODS: Thirty-one patients with 70 paragangliomas were examined. Four combinations of MR images were reviewed by two neuroradiologists: T1-weighted and dual T2-weighted fast spin-echo images, T1- and T2-weighted fat-suppressed fast spin-echo images, T1-weighted and contrast-enhanced T1-weighted fat-suppressed spin-echo images, and unenhanced and contrast-enhanced 3D time-of-flight MR angiograms. The randomized examinations were independently evaluated for image quality, presence of tumor, tumor size, and intratumoral flow signal intensity. The standard of reference for presence of tumor was digital subtraction angiography. Data were analyzed by using the logistic regression method. RESULTS: Mean sensitivity, specificity, and negative predictive values, respectively, were assessed by the two observers to be as follows: for dual T2-weighted fast spin-echo, 74%/99%/86%; for T2-weighted fat-suppressed fast spin-echo, 70%/100%/85%; for contrast-enhanced T1-weighted fat-suppressed spin-echo, 73%/100%/86%; and for unenhanced and contrast-enhanced 3D time-of-flight MR angiography, 89%/99%/93%. Sensitivity was significantly better for unenhanced and contrast-enhanced 3D time-of-flight MR angiography (P =.000028). More intratumoral flow signal intensity was depicted with unenhanced and contrast-enhanced 3D time-of-flight MR angiography. CONCLUSION: A combination of unenhanced and contrast-enhanced 3D time-of-flight MR angiography is superior for detecting paragangliomas and should be added to a standard imaging protocol, especially for patients with familial paragangliomas because they are more susceptible to multicentric disease.     

Detection of hepatocellular carcinoma with ferucarbotran (resovist)-enhanced breath-hold MR imaging: feasibility of 10 minute-delayed images

PURPOSE: We evaluated the optimal timing for breath-hold MR imaging with bolus-injectable superparamagnetic iron oxide (SPIO) for detecting hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Twenty patients with 62 HCCs (52 hypervascular, 10 non-hypervascular) underwent MR imaging that included unenhanced and SPIO-enhanced T1-weighted gradient echo (GRE) and T2-weighted fast spin echo (FSE) sequences, perfusion study, and SPIO-enhanced T2*-weighted GRE sequences. We obtained SPIO-enhanced T2*-weighted sequences 10 and 30 min after injecting SPIO and made 2 image sets, comprising 10- or 30-min delayed T2*-weighted images. Three observers performed alternative free response receiver operating characteristic (AFROC) analysis, and quantitative evaluation was performed. RESULTS: Only Observers 2 and 3 recognized a significant difference in the area under the AFROC curve (Az) value in the 10-min delayed images; no significant difference was observed in the 30-min delayed images. There was no significant difference in the sensitivity of individual observers between 10- and 30-min delayed images. The contrast-to-noise (C/N) ratio of the 30-min delayed images was significantly higher than that of the 10-min delayed images. The C/N ratio of hypervascular HCCs in the 30-min delayed images was significantly higher than in the 10-min delayed images, but that of non-hypervascular HCCs showed no significant difference. Conclusion: In most cases, 10-min delayed SPIO-enhanced T2*-weighted images are sufficient to detect HCCs.     

Intracranial meningeal disease: comparison of contrast-enhanced MR imaging with fluid-attenuated inversion recovery and fat-suppressed T1-weighted sequences

BACKGROUND AND PURPOSE: Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging has been reported to have higher sensitivity for detecting leptomeningeal disease compared with contrast-enhanced T1-weighted MR imaging. The purpose of this study was to compare contrast-enhanced T1-weighted MR images with fat suppression to contrast-enhanced FLAIR images to determine which sequence was superior for depicting meningeal disease. METHODS: We reviewed MR images of 24 patients (35 studies) with a variety of meningeal diseases. The MR imaging protocol included contrast-enhanced T1-weighted MR images with fat suppression (FS) and contrast-enhanced fluid-attenuated inversion recovery (FLAIR) images that were reviewed by three neuroradiologists and were assigned a rating of positive, equivocal, or negative for abnormal meningeal enhancement. The two sequences were compared side by side to determine which better depicted meningeal disease. RESULTS: Abnormal meningeal enhancement was positive in 35 contrast-enhanced T1-weighted MR images with FS and in 33 contrast-enhanced FLAIR studies. In the first group, which had the T1-weighted sequence acquired first (21 of 33 studies), contrast-enhanced T1-weighted images with FS showed superior contrast enhancement in 11 studies (52%), inferior contrast enhancement in six studies (29%), and equal contrast enhancement in four studies (19%) compared with the contrast-enhanced FLAIR images. In the second group, which had the FLAIR sequence acquired first (12 of 33), contrast-enhanced T1-weighted images with FS showed superior contrast enhancement in seven studies (58%), inferior contrast enhancement in two studies (17%), and equal contrast enhancement in three studies (25%). CONCLUSION: Contrast-enhanced T1-weighted MR imaging with FS is superior to contrast-enhanced FLAIR imaging in most cases for depicting intracranial meningeal diseases.