T1-Weighted MR imaging of the brain using a fast inversion recovery pulse sequence

The purpose of this paper was to develop and evaluate a fast inversion recovery (FIR) technique for T1-weighted MR imaging of contrast-enhancing brain pathology. The FIR technique was developed, capable of imaging 24 sections in approximately 7 minutes using two echoes per repetition and an alternating echo phase encoding assignment. Resulting images were compared with conventional T1-weighted spin echo (T1SE) images in 18 consecutive patients. Compared with corresponding T1SE images, FIR images were quantitatively comparable or superior for lesion-to-background contrast and contrast-to-noise ratio (CNR). Gray-to-white matter and cerebrospinal fluid (CSF)-to-white matter contrast and CNR were statistically superior in FIR images. Qualitatively, the FIR technique provided comparable lesion detection, improved lesion conspicuity, and superior image contrast compared with T1SE images. Although FIR images had greater amounts of image artifacts, there was not a statistically increased amount of interpretation-interfering image artifact. FIR provides T1-weighted images that are superior to T1SE images for a number of image quality criteria.     

Characterization of Focal Liver Lesions with Superparamagnetic Iron Oxide-Enhanced MR Imaging: Value of Distributional Phase T1-Weighted Imaging

Objective

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

Materials and Methods

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas [HCC], 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

Results

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p < .05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

Conclusion

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.     

Detection of Malignant Primary Hepatic Neoplasms with Gadobenate Dimeglumine (Gd-BOPTA) Enhanced T1-Weighted Hepatocyte Phase MR Imaging: Results of Off-site Blinded Review in a Phase-II Multicenter Trial

Objective

To investigate the efficacy of gadobenate dimeglumine (Gd-BOPTA) enhanced MR imaging for the detection of liver lesions in patients with primary malignant hepatic neoplasms.

Materials and Methods

Thirty-one patients with histologically proven primary malignancy of the liver were evaluated before and after administration of Gd-BOPTA at dose 0.05 or 0.10 mmol/kg. T1-weighted spin echo (T1W-SE) and gradient echo (T1W-GRE) images were evaluated for lesion number, location, size and confidence by three off-site independent reviewers and the findings were compared to reference standard imaging (intraoperative ultrasound, computed tomography during arterial portography or lipiodol computed tomography). Results were analyzed for significance using a two-sided McNemar''s test.

Results

More lesions were identified on Gd-BOPTA enhanced images than on unenhanced images and there was no significant difference in lesion detection between either concentration. The largest benefit was in detection of lesions under 1 cm in size (7 to 21, 9 to 15, 16 to 18 for reviewers A, B, C respectively). In 68% of the patients with more than one lesion, Gd-BOPTA increased the number of lesions detected.

Conclusion

Liver MR imaging after Gd-BOPTA increases the detection of liver lesions in patients with primary malignant hepatic neoplasm.     

MR imaging of the liver: Effect of portal hypertension on hepatic parenchymal enhancement using a gadolinium chelate

The purpose of this study was to prospectively investigate the extent to which reduced portal blood flow in patients with hepatic cirrhosis and portal hypertension affects hepatic parenchymal enhancement during gadolinium-chelate-enhanced dynamic MR imaging. Breath-hold three-dimensional (3D) spoiled gradientrecalled echo (GRE) MR imaging technique obtained after intravenous administration of a gadolinium chelate was used to measure hepatic parenchymal enhancement and time to peak enhancement in 20 patients with hepatic cirrhosis and clinical evidence of portal hypertension (group 1) and in 20 control subjects without portal hypertension (group 2) who were matched for age, sex, and body weight. Mean peak hepatic enhancement values ± SD and times to peak enhancement ± SD were determined for both groups of patients. Mean peak enhancement value (±SD) was 78.7% ± 36.2 in group 1 and 91.6% ± 46.2 in group 2 (not significant). However, in the nine patients in group 1 with splenomegaly, mean peak enhancement value was 61.3% ± 14.4, whereas it was 93.0% ± 42.7 in the 11 patients without splenomegaly (P < .05). Mean time to peak enhancement was 84 seconds ± 23 in group 1 and 54.0 sec ± 25.0 in group 2 (P < .01). Our results show that mean peak enhancement value of hepatic parenchyma after intravenous administration of a gadolinium chelate is significantly altered for patients with portal hypertension and splenomegaly. In addition, the time to peak enhancement is delayed significantly when portal hypertension is present. Thus, it is possible that the optimal time for imaging the liver during the portal phase must be tailored to the status of the portal system of the patient.     

Malignant lesions of the liver identified on T1- but not T2-weighted MR images at 1.5 T

The authors reviewed their 21/2-year experience with a magnetic resonance (MR) imaging protocol for a 1.5-T MR imager that included T2-weighted fat-suppressed spin-echo, T1-weighted breath-hold gradient-echo, and serial dynamic gadolinium-enhanced T1-weighted gradient-echo imaging to identify histologic types of malignant liver lesions more apparent on T1- than on T2-weighted images. MR images of 212 consecutive patients with malignant liver lesions were reviewed. T2-weighted, T1-weighted, and dynamic contrast-enhanced T1-weighted images were examined separately in a blinded fashion. Seven patients demonstrated liver lesions (lymphoma [two patients] and carcinoid, hepatocellular carcinoma, colon adenocarcinoma, transitional cell carcinoma, and melanoma [one patient each]) on T1-weighted images that were inconspicuous on T2-weighted images. In all cases, the lesions were most conspicuous on T1-weighted images obtained immediately after administration of contrast agent. Histologic confirmation was present for all seven patients. The consistent feature among these lesions was that they were hypovascular, due either to a fibrous stroma or to dense monoclonal cellularity. These results suggest that in some patients with hypovascular primary neoplasms, the lesions may be identified only on T1-weighted images, and that immediate postcontrast T1-weighted images are of particular value in demonstrating lesions.     

Diffusion-Weighted Imaging with Sensitivity Encoding (SENSE) for Detecting Cranial Bone Marrow Metastases: Comparison with T1-Weighted Images

Objective

This study was designed to determine whether diffusion-weighted imaging (DWI) with sensitivity encoding (SENSE) could detect bone marrow involvement in patients with cranial bone marrow (CBM) metastases. DWI results obtained were compared with T1-weighted imaging (T1WI) findings.

Materials and Methods

DWI with sensitivity encoding (SENSE; b value = 1,000) was performed consecutively in 13 patients with CBM metastases diagnosed pathologically and radiologically. CBM lesions were dichotomized according to the involved site, i.e., skull base or calvarium. Two radiologists qualitatively evaluated the relative conspicuousness of CBM lesions and image qualities in B0 and in isotropic DWI and in T1WI. According to region of interest analysis of normal and pathologic marrow for these three sequences, absolute signal difference percentages (SD%) were calculated to quantitatively analyze lesion contrast.

Results

All 20 lesions in 13 patients with CBM metastases revealed abnormal DWI signals in areas corresponding to T1WI abnormalities. Both skull base and calvarial lesions provided better lesion conspicuousness than T1WI and B0 images. Although the image quality of DWI was less satisfactory than that of T1WI, relatively good image qualities were obtained. Quantitatively, B0 images (SD%, 82.1 ±7.9%) showed better lesion contrast than isotropic DWI (SD%, 71.4 ±13.7%) and T1WI (SD%, 65.7 ±9.3%) images.

Conclusion

For scan times of less than 30 seconds, DWI with SENSE was able to detect bone marrow involvement, and was superior to T1WI in terms of lesion conspicuity. DWI with SENSE may be helpful for the detection of cranial bone/bone marrow metastases when used in conjunction with conventional MR sequences.     

Comparison of multishot turbo spin echo and HASTE sequences for T2-weighted MRI of liver lesions

The purpose of this study was to compare the relative usefulness of multishot turbo spin echo (TSE) and half-Fourier single-shot turbo spin echo (HASTE) for determination of optimal breath-hold fast T2-weighted technique in terms of lesion detection, lesion-to-liver contrast-to-noise ratio (CNR), and image quality. The images of TSE with and without fat suppression (FS) and of HASTE with and without FS were retrospectively reviewed for 49 patients with 128 lesions. Without FS, TSE and HASTE images allowed depiction of focal hepatic masses (112 of 128, sensitivity = 87.5%) at the same rate. TSE with FS depicted more focal lesions (115 of 128, 89.8%) than HASTE with FS (109 of 128, 85.2%), but the difference was not statistically significant (P > .05). The CNR of each lesion on HASTE sequences was greater (P < .01) than that on TSE sequences. The CNR of hemangioma was distinct from that of solid tumors and cystic lesions in all sequences, and the range of CNR in each group of pathologies overlapped less and were well separated in the HASTE sequences. HASTE sequences produced better image quality with fewer artifacts (P < .0001). The results of this study suggest that HASTE sequences allow differentiation between solid tumors, hemangiomas, and cystic lesions in terms of CNR, producing fewer image artifacts, with acceptable sensitivity in lesion detection.     

HASTE MR imaging: Description of technique and preliminary results in the abdomen

HASTE (HAlf fourier Single-shot Turbo spin-Echo) is a single-section T2-weighted sequence that acquires images in less than 1 second. Images are breathing independent and possess a variety of other features useful for imaging the abdomen. The design of this technique is described. Clinical studies of 38 consecutive patients were performed using this technique. HASTE images were considered good in 28 and fair in 10 patients, including five patients who could not suspend respiration. Definition of liver and bowel was particularly clear.     

Effects of ami-25 on liver vessels and tumors on T1-weighted turbo-field-echo images: Implications for tumor characterization

This study was devoted to tumor differentiation in liver MR T1-weighted imaging with superparamagnetic iron oxide (SPIO). Twenty-one patients with 40 liver lesions were studied at 1.5 T. Before and at least 45 minutes after SPIO administration, turbo-field-echo (TFE) T1-weighted, TFE T1 × T2*-weighted (MXT), and fat-suppressed turbo-spin-echo T2-weighted images were acquired. A quantitative analysis was performed blindly. On TFE T1-weighted images, the signal enhancement was ?33% ± 12 for the liver, ?24% ± 2 for adenomas and focal nodular hyperplasia, +60% ± 33 for the hemangiomas; metastases and cyst enhancement were not significant. After SPIO on TFE T1-weighted images, the hemangioma-to-liver signal ratio (149% ± 18) was definitely higher than the mean metastasis-to-liver signal ratio (90% ± 16). This T1-related differentiation ability lacked dramatically on TFE MXT images and, in one case, was reduced on post-SPIO TFE T1-weighted images by a long imaging delay after SPIO administration (2 hours).     

T1rho MR imaging of the human wrist in vivo

RATIONALE AND OBJECTIVES: The purpose of this study was (a) to demonstrate the feasibility of computing T1rho maps of, and T1rho dispersion in, human wrist cartilage at MR imaging in vivo and (b) to compare T1rho and T2 weighting in terms of magnitude of relaxation times and signal intensity contrast. MATERIALS AND METHODS: T2 and T1rho magnetic resonance images of wrist joints in healthy volunteers (n = 5) were obtained with a spin-echo sequence and a fast spin-echo sequence pre-encoded with a spin-lock pulse cluster. A 1.5-T clinical imager was used (Signa; GE Medical Systems, Milwaukee, Wis) with a 9.5-cm-diameter transmit-receive quadrature birdcage coil tuned to 63.75 MHz. RESULTS: T1rho relaxation times at a spin-lock frequency of 500 Hz vary from 40.5 msec +/- 0.85 to 56.6 msec +/- 4.83, and T2 relaxation times vary from 28.1 msec +/- 1.88 to 34.5 msec +/- 2.63 (mean +/- standard error of the mean, n = 5, P < .016) in various regions of the wrist. T1rho dispersion was observed in the range of spin-lock frequencies studied. T1rho-weighted images not only have higher signal-to-noise ratios but also show better fluid and fat signal suppression than T2-weighted images. CONCLUSION: It was possible to perform T2- and T1rho-weighted MR imaging of human wrist cartilage in vivo with standard clinical imagers. The higher signal-to-noise ratio and improved contrast between cartilage and surrounding fat achieved with T1rho imaging may provide better definition of lesions and accurate quantitation of small changes in cartilage degeneration.     

MR imaging of the internal auditory canal and inner ear at 3T: comparison between 3D driven equilibrium and 3D balanced fast field echo sequences

OBJECTIVE: To compare the use of 3D driven equilibrium (DRIVE) imaging with 3D balanced fast field echo (bFFE) imaging in the assessment of the anatomic structures of the internal auditory canal (IAC) and inner ear at 3 Tesla (T). MATERIALS AND METHODS: Thirty ears of 15 subjects (7 men and 8 women; age range, 22-71 years; average age, 50 years) without evidence of ear problems were examined on a whole-body 3T MR scanner with both 3D DRIVE and 3D bFFE sequences by using an 8-channel sensitivity encoding (SENSE) head coil. Two neuroradiologists reviewed both MR images with particular attention to the visibility of the anatomic structures, including four branches of the cranial nerves within the IAC, anatomic structures of the cochlea, vestibule, and three semicircular canals. RESULTS: Although both techniques provided images of relatively good quality, the 3D DRIVE sequence was somewhat superior to the 3D bFFE sequence. The discrepancies were more prominent for the basal turn of the cochlea, vestibule, and all semicircular canals, and were thought to be attributed to the presence of greater magnetic susceptibility artifacts inherent to gradient-echo techniques such as bFFE. CONCLUSION: Because of higher image quality and less susceptibility artifacts, we highly recommend the employment of 3D DRIVE imaging as the MR imaging choice for the IAC and inner ear.     

MR arterial portography with gadolinium-DOTA: Analysis of nontumoral perfusion abnormalities

The purpose of this article was to determine the frequency and imaging characteristics of nontumoral perfusion abnormalities observed on magnetic resonance imaging (MRI) obtained during arterial portography (MRAP). MRAP examinations done in 23 consecutive patients with malignant hepatic tumors were retrospectively and blindly reviewed by two readers for the presence of nontumoral perfusion abnormalities. MR images were assessed for the presence, location, shape, and type of nontumoral perfusion abnormalities, and correlated with intraoperative findings or follow-up imaging studies. Fourteen nontumoral perfusion abnormalities were found in 10 patients (43%). Nontumoral perfusion abnormalities were categorized into these five types: triangular nontumoral perfusion defects not associated with a more proximal tumor (n = 6), triangular nontumoral perfusion abnormalities distal to a tumor (n = 2), hypoperfusion involving 1 or >1 segment (n = 2), hyperenhancement of the posterior part of the right hemiliver (n = 2), and gravity-effect-related perfusion abnormality (n = 2). Nontumoral perfusion abnormalities are seen frequently on MRAP examination. Recognition of these abnormalities remains crucial to avoid misdiagnosis.     

MR demonstration of mesencephalic lesions in osmotic demyelination syndrome (central pontine myelinolysis)

Summary A case of CPM/ODS with mesencephalic involvement is presented. The lesions were nonenhancing on CT and were homogeneous and well-defined on MR with prolonged T1- and T2-relaxation times. MR is recommended for imaging the pontomesencephalic demyelinating lesions associated with this disease.     

Human in-vivo 31P MR Spectroscopy of Benign and Malignant Breast Tumors

Objective

To assess the potential clinical utility of in-vivo 31P magnetic resonance spectroscopy (MRS) in patients with various malignant and benign breast lesions.

Materials and Methods

Seventeen patients with untreated primary malignant breast lesions (group I), eight patients with untreated benign breast lesions (group II) and seven normal breasts (group III) were included in this study. In-vivo 31P MRS was performed using a 1.5 Tesla MR scanner. Because of the characteristics of the coil, the volume of the tumor had to exceed 12 cc (3×2×2 cm), with a superoinferior diameter at least 3 cm. Mean and standard deviations of each metabolite were calculated and metabolite ratios, such as PME/PCr, PDE/PCr, T-ATP/PCr and PCr/T-ATP were calculated and statistically analyzed.

Results

Significant differences in PME were noted between groups I and III (p=0.0213), and between groups II and III (p=0.0213). The metabolite ratios which showed significant differences were PME/PCr (between groups II and III) (p=0.0201), PDE/PCr (between groups I and III, and between groups II and III) (p=0.0172), T-ATP/PCr (between groups II and III) (p=0.0287), and PCr/T-ATP (between groups II and III) (p=0.0287). There were no significant parameters between groups I and II.

Conclusion

In-vivo 31P MRS is not helpful for establishing a differential diagnosis between benign and malignant breast lesions, at least with relatively large lesions greater than 3 cm in one or more dimensions.     

Contrast-enhanced three-dimensional MR angiography with an elliptical centric view for the evaluation of intracranial aneurysms

The purpose of this study was to assess the feasibility of high spatial resolution, selective arterial phase, 3D contrast-enhanced (CE) MR angiography with first pass bolus, software-trigger, elliptical centric view ordering in the detection of intracranial aneurysms. Our study included nine consecutive patients with ten intracranial aneurysms. 3D TOF MR angiography and 3D CE MR angiography were carried out with a 1.5-T MR scanner. 3D CE MR angiography was performed with an automated bolus detection algorithm and elliptical centric view order using ultrafast SPGR with a spatial resolution of 0.63×0.83×0.5 mm and imaging time of 55 s. Observers detected seven of ten aneurysms on 3D TOF MR angiograms and nine of ten aneurysms on 3D CE MR angiograms. 3D CE MR angiography clearly revealed an IC-PC aneurysm with a relatively smaller neck, a broad-based small aneurysm originating from tortuous and dilated MCA bifurcation, and a residual aneurysm and parent vessels adjacent to metallic aneurysmal clips, which had relatively low signal intensities on 3D TOF MR angiograms. 3D CE MR angiography was found to be a good and promising technique for detecting intracranial aneurysms with small necks and slow flow, vasculature with aneurysmal clips and tortuous vasculature with disturbed flow.     

Quantitative P-31 MR spectroscopy of the liver in alcoholic cirrhosis.

To determine the cause of reduced urea synthesis in cirrhosis, absolute concentrations of phosphorus metabolites in the human liver have been measured in vivo with magnetic resonance (MR) spectroscopy. One-dimensional chemical shift imaging was used to obtain phosphorus-31 spectra from five healthy volunteers and five patients with alcoholic cirrhosis. A reference standard included in all studies enabled the calculation of absolute concentrations. In contrast to hepatic metabolite ratios, absolute concentrations reveal that in the cirrhotic patients, concentrations of adenosine triphosphate (ATP) were significantly reduced and concentrations of phosphomonoesters slightly reduced. Intracellular pH was unchanged. Histologic evidence suggests that the amount of ATP per cell was unchanged and could not account for the reduced urea production. Instead, urea synthesis depends on the functional liver cell mass, which was reduced by 31% in alcoholic cirrhosis. Quantitative in vivo P-31 MR spectroscopy of liver has potential clinical applications and can supplement the more generally used P-31 metabolite ratios.