[In-phase and out-of-phase single-shot magnetization-prepared gradient recalled echo: description and optimization of technique at 1.5 T]. / Secuencia de disparo único eco de gradiente en fase y fase opuesta con preparación de la magnetización: descripción y optimización de la técnica con equipo de 1,5 T.

PURPOSE: To implement in-phase and out-of-phase (IP/OP) techniques with Magnetization-Prepared Gradient Recalled Echo (MP-GRE) and to evaluate the feasibility and diagnostic image quality among pre and post-optimized MP-GRE sequences, including patients unable to cooperate with breath-hold requirements. MATERIALS AND METHODS: Institutional review board approval with waiver of informed consent was obtained for this HIPAA-compliant retrospective study. Two groups of patients were included in the study, before and after optimization of MP-GRE parameters, with seventy-three (24 noncooperative/49 cooperative) and sixty-four (22 noncooperative/42 cooperative) consecutive patients, respectively. The motion-insensitive sequence used in this study was a single-shot 2D MP-GRE. Two radiologists qualitatively evaluated the sequences to identify the presence of phase cancellation artifact in OP images and to determine image quality, extent of artifacts (respiratory ghosting, bounce-point artifact, spatial misregistration and pixel graininess) and lesion conspicuity on the various sequences. The ability to visually detect liver steatosis and fatty adrenal adenomas was evaluated. Qualitative analyses were compared using the Wilcoxon and Mann-Whitney tests. RESULTS: There were statistically significant differences between all MP-GRE sequences concerning phase cancellation artifact (P<.0001) which was present in MP-GRE OP sequences and negligible to absent in the pre (IP1) and post-optimized (IP2) MP-GRE IP sequences, respectively, in all patients. Bounce point artifacts were significantly more pronounced in MP-GRE IP1 (P<.0001). Spatial misregistration was slightly more prominent in noncooperative patients with MP-GRE IP2 (P=.0027). MP-GRE OP and MP-GRE IP2 showed significantly higher overall image quality (P<.0001). MP-GRE sequences subjectively identified hepatic steatosis (n=20) and adrenal adenomas (n=5) based on signal loss from IP to OP sequence. CONCLUSION: Single shot IP/OP MP-GRE is feasible and allows motion resistant imaging with adequate diagnostic image quality. This technique is able to provide IP and OP information in patients unable to suspend respiration.

A comparison of a T1 weighted 3D gradient-echo sequence with three different parallel imaging reduction factors, breath hold and free breathing, using a 32 channel coil at 1.5 T. A preliminary study.

PURPOSE: To investigate whether increasing temporal resolution with higher parallel imaging (PI) reduction factors (RF) in both breath-hold and free breathing approaches, using a non-contrast T1-weighted 3D gradient echo (GRE) sequence and a 32-channel phased array coil, permits diagnostic image quality, with potential application in patients unable to cooperate with breath-hold requirements. MATERIALS AND METHODS: The 9 healthy subjects (5 females and 4 males; age range was 20-49, mean 36 yrs) were recruited. A 3D GRE MR imaging of the abdomen was performed on 1.5 T MR system using a 32-element phased-array torso coil with PI RFs of 2, 4 and 6, breath hold and free breathing. Two reviewers retrospectively qualitatively evaluated all sequences for image quality, extent of artifacts, including motion, truncation, aliasing, pixel graininess and signal heterogeneity. The results were compared using Wilcoxon signed rank and a Bonferroni adjustment was applied for multiple comparisons. RESULTS: Image quality and extent of artifacts were better with breath hold than with free breathing acquisitions. The rate of artifacts increased with higher RF. The best quality was acquired with breath hold sequence using RF=2. RF=4 had lower but diagnostic rates (P=.004). The severity of artifacts, mainly pixel graininess (P=.004), rendered sequences with RF=6 non-diagnostic. All sequences were non-diagnostic in free breathing acquisitions. CONCLUSION: Breath hold sequences with RF=2 had excellent quality and RF=4 had good quality and may be potentially used in partially cooperative patients. None of the sequences was considered diagnostic in free breathing acquisitions.

Breast MRI: intraindividual comparative study at 1.5 and 3.0T; initial experience.

PURPOSE: To prospectively and intraindividually compare breast magnetic resonance imaging (MRI) at 1.5 Tesla (T) and 3.0T. METHODS: A prospective intraindividual Ethics Committee- approved study was performed in 31 women (average age 58.6±12.3 years), with 114 lesions (9 benign, 105 breast cancers; 24 patients with unilateral and 7 with bilateral cancers). Axial bilateral breast high-spatial resolution contrast-enhanced dynamic MRI was performed at 1.5T using 3 dimensional (3D) dynamic gradient-echo sequences in all patients (spatial resolution 1.1×0.7×2 mm; temporal resolution 41 sec per dynamic acquisition), and after 24-48 h at 3.0T (0.6×0.6×1.7 mm; temporal resolution 65 and 72 sec per dynamic acquisition). Contrast enhancement ratio, number and features of enhancing lesions, image quality and reliability were compared by two radiologists independently. RESULTS: 102 cancer lesions were detected at 1.5T and 105 cancer lesions were detected in 31 patients at 3.0T. One cancer lesion was observed at 1.5T which was missed at 3.0T, and 3 cancer lesions and one high-risk lesion (LCIS) were detected at 3.0T while missed at 1.5T. Enhancement rates were significantly higher at 1.5T (224.5±100.2) compared to 3.0T (133.7±38.3). Better image quality was observed at 3.0T. Interobserver reliability was higher at 3.0T (p= 0.684) compared to 1.5T (p= 0.351). CONCLUSION: Detection of breast cancer shows a trend of better performance at 3.0T than at 1.5T.

T1 signal intensity in the dentate nucleus after the administration of the macrocyclic gadolinium-based contrast agent gadoterate meglumine: An observational study.

INTRODUCTION AND AIMS: Contradictory results have been reported about hyperintensity of the globus pallidus and/or dentate nucleus on unenhanced T1-weighted magnetic resonance (MR) images after exposure to various gadolinium-based contrast agents. This change in signal intensity varies with different gadolinium-based contrast agents. We aimed to determine whether signal intensity in the dentate nucleus is increased in unenhanced T1-weighted images in patients who have undergone multiple studies with the macrocyclic gadolinium-based contrast agent gadoterate meglumine. We thoroughly reviewed the literature to corroborate our results. MATERIALS AND METHODS: We included patients who had undergone more than 10 MR studies with gadoterate meglumine. We quantitatively analyzed the signal intensity in unenhanced T1-weighted MR images measured in regions of interest placed in the dentate nucleus and the pons, and we calculated the dentate nucleus-to-pons signal intensity ratios and the differences between the ratio in the first MR study and the last MR study. We used t-tests to evaluate whether the differences between the signal intensity ratios were different from 0. We also analyzed the subgroups of patients who had been administered <15 and ≥15 doses of gadoterate meglumine. We used Pearson correlation to determine the relationships between the differences in the signal intensity ratios and the number of doses of gadoterate meglumine administered. RESULTS: The 54 patients (26 men) had received a mean of 13.8±3.47 doses (range, 10-23 doses). The difference in the dentate nucleus-pons signal intensity ratio between the first and last MR study was -0.0275±0.1917 (not significantly different from 0; p=0.2968) in the entire group, -0.0357±0.2204 (not significantly different from 0; p = 0.351 in the patients who had received <15 doses (n=34), and -0.0135±0.1332 (not significantly different from 0; p = 0.655) in those who had received ≥15 doses (n=20). Differences in signal intensity ratios did not correlate significantly with the accumulated dose of gadoterate meglumine (P = 0.9064; ρ = -0.0164 [95%]). CONCLUSIONS: Receiving more than 10 doses of gadoterate meglumine was not associated with increased signal intensity in the dentate nucleus.

T1 signal intensity in the dentate nucleus after the administration of the macrocyclic gadolinium-based contrast agent gadoterate meglumine: an observational study. / Intensidad de la señal en T1 en el núcleo dentado tras la administración del agente de contraste con gadolinio macrocíclico gadoterato de meglumina: un estudio observacional.

INTRODUCTION AND AIMS: Contradictory results have been reported about hyperintensity of the globus pallidus and/or dentate nucleus on unenhanced T1-weighted magnetic resonance (MR) images after exposure to various gadolinium-based contrast agents. This change in signal intensity varies with different gadolinium-based contrast agents. We aimed to determine whether signal intensity in the dentate nucleus is increased in unenhanced T1-weighted images in patients who have undergone multiple studies with the macrocyclic gadolinium-based contrast agent gadoterate meglumine. We thoroughly reviewed the literature to corroborate our results. MATERIALS AND METHODS: We included patients who had undergone more than 10 MR studies with gadoterate meglumine. We quantitatively analyzed the signal intensity in unenhanced T1-weighted MR images measured in regions of interest placed in the dentate nucleus and the pons, and we calculated the dentate nucleus-to-pons signal intensity ratios and the differences between the ratio in the first MR study and the last MR study. We used t-tests to evaluate whether the differences between the signal intensity ratios were different from 0. We also analyzed the subgroups of patients who had been administered<15 and ≥15 doses of gadoterate meglumine. We used Pearson correlation to determine the relationships between the differences in the signal intensity ratios and the number of doses of gadoterate meglumine administered. RESULTS: The 54 patients (26 men) had received a mean of 13.8±3.47 doses (range, 10-23 doses). The difference in the dentate nucleus-pons signal intensity ratio between the first and last MR study was -0.0275±0.1917 (not significantly different from 0; p=0.2968) in the entire group, -0.0357±0.2204 (not significantly different from 0; p=0.351 in the patients who had received <15 doses (n=34), and -0.0135±0.1332 (not significantly different from 0; p=0.655) in those who had received ≥15 doses (n=20). Differences in signal intensity ratios did not correlate significantly with the accumulated dose of gadoterate meglumine (P=0.9064; ρ=-0.0164 [95%]). CONCLUSIONS: Receiving more than 10 doses of gadoterate meglumine was not associated with increased signal intensity in the dentate nucleus.

T1 Signal-Intensity Increase in the Dentate Nucleus after Multiple Exposures to Gadodiamide: Intraindividual Comparison between 2 Commonly Used Sequences.

BACKGROUND AND PURPOSE: Different T1-weighted sequences have been used for qualitative and quantitative evaluation of T1 signal intensity related to gadolinium deposition in the dentate nucleus in patients who underwent several enhanced MR imaging studies. Our purpose was to perform an intraindividual qualitative and quantitative comparison between T1-weighted spin-echo and 3D magnetization-prepared rapid acquisition of gradient echo sequences in patients who had multiple exposures to gadodiamide. MATERIALS AND METHODS: Our retrospectively selected population included 18 patients who underwent at least 3 administrations of gadodiamide and had a baseline and a final MR imaging performed with both T1-weighted sequences. Qualitative and quantitative analyses were independently performed. Dentate nucleus/middle cerebellar peduncle signal-intensity ratios and signal changes between the baseline and final examinations were compared by using the Wilcoxon signed rank test. Correlation between quantitative and qualitative evaluations was assessed by using a polyserial correlation test. RESULTS: The differences between the 2 sequences for both baseline and last examination dentate nucleus/middle cerebellar peduncle ratios were statistically significant (P = .008 and P = .006, respectively); however, the signal-intensity changes of the ratios with time were not (P = .64). The correlation between the qualitative and quantitative analysis was very strong (near-perfect) (r = 0.9) for MPRAGE and strong (r = 0.63) for spin-echo sequences. CONCLUSIONS: T1-weighted spin-echo and MPRAGE sequences cannot be used interchangeably for qualitative or quantitative analysis of signal intensity in the dentate nucleus in patients who received gadodiamide. Baseline and final examination ratios should be evaluated across time by using the same sequence. Qualitative analysis performed with MPRAGE correlated better with quantitative analysis and may offer advantages over spin-echo sequences for research purposes.

Gadolinium-Based Contrast Agent Accumulation and Toxicity: An Update.

In current practice, gadolinium-based contrast agents have been considered safe when used at clinically recommended doses in patients without severe renal insufficiency. The causal relationship between gadolinium-based contrast agents and nephrogenic systemic fibrosis in patients with renal insufficiency resulted in new policies regarding the administration of these agents. After an effective screening of patients with renal disease by performing either unenhanced or reduced-dose-enhanced studies in these patients and by using the most stable contrast agents, nephrogenic systemic fibrosis has been largely eliminated since 2009. Evidence of in vivo gadolinium deposition in bone tissue in patients with normal renal function is well-established, but recent literature showing that gadolinium might also deposit in the brain in patients with intact blood-brain barriers caught many individuals in the imaging community by surprise. The purpose of this review was to summarize the literature on gadolinium-based contrast agents, tying together information on agent stability and animal and human studies, and to emphasize that low-stability agents are the ones most often associated with brain deposition.

Amphotericin B lipid complex for the treatment of patients with acute leukemia and hepatosplenic candidiasis.

Hepatosplenic candidiasis (HSC) is an emerging complication of the treatment of patients with acute leukemia. Treatment of this infection can be very difficult and data on the duration of antifungal therapy are not available. We evaluated the efficacy of amphotericin B lipid complex (ABLC) for the treatment of five patients with acute leukemia and HSC. The dose of the administered ABLC ranged between 5 and 11 mg/kg per day and the median duration of therapy was 4.3 months. Four patients had complete response to the above treatment with resolution of fever and improvement in the radiologic findings. One patient refused to continue treatment and subsequently died with relapsed leukemia and disseminated Candida infection. Preliminary data suggest that ABLC is a well-tolerated and effective treatment for HSC and should be considered for phase II trials as front line treatment for this type of deep seated fungal infections.

Pelvic magnetic resonance imaging in the evaluation of uterine torsion.

BACKGROUND: Uterine torsion is defined as the rotation of more than 45 degrees around the long axis of the uterus. An uncommon but potentially fatal event, uterine torsion is rarely diagnosed until the time of surgery. With magnetic resonance imaging (MRI), however, an accurate diagnosis of uterine torsion may now be made preoperatively. CASE: We describe a patient with uterine torsion in whom the correct diagnosis was made prenatally with the use of MRI, by the demonstration of an X-shaped configuration of the upper vagina. CONCLUSION: Distinctive features suggestive of uterine torsion were demonstrated by MRI and enabled an accurate preoperative diagnosis. To our knowledge, this is the first reported case of uterine torsion diagnosed on MRI.

Preoperative evaluation of intersex patients with pelvic magnetic resonance imaging in search of Y chromosome-bearing gonadal tissue.

OBJECTIVE: To illustrate the utility of preoperative magnetic resonance imaging in the evaluation of intersex patients who require gonadectomy. DESIGN: Case reports of two phenotypic females having karyotypes containing a Y chromosome whose preoperative evaluation included pelvic magnetic resonance imaging. SETTING: Tertiary academic referral center. MAIN OUTCOME MEASURE: Pelvic magnetic resonance imaging for gonadal localization. RESULTS: Preoperative evaluation with magnetic resonance imaging correctly identified the most appropriate surgical approach to gonadectomy. CONCLUSIONS: Pelvic magnetic resonance imaging can be useful in the preoperative evaluation of intersex patients having nonpalpable Y chromosome-bearing gonadal tissue.

Magnetic resonance imaging of the spleen and pancreas.

MRI of the spleen and pancreas requires specialized sequences which diminish artifacts in the upper abdomen. High temporal resolution sequences (e.g., spoiled gradient echo) acquired immediately after intravenous Gd-DTPA administration are necessary for imaging both the spleen and pancreas. In evaluating the spleen, early post Gd-DTPA images are essential as many focal disease processes (e.g., lymphomatous deposits or metastases) equilibrate rapidly (< 2 min) with splenic parenchyma. Complete pancreatic examination also requires the use of T1-weighted fat suppressed spin echo. T2-weighted images provide complementary information in a number of settings, in particular in the evaluation of islet cell tumors. Pancreatic ductal carcinoma is low signal on T1-weighted images and enhances in a diminished fashion on immediate post Gd-DTPA images. These tumors are well differentiated from focal chronic pancreatitis and islet celltumors based on their appearances on combined T1, T2-weighted and immediate post Gd-DTPA enhanced images.

Magnetic resonance imaging of the liver.

A variety of diffuse and focal disease processes affect the liver. MRI is likely the imaging modality of choice for investigation of patients suspected of having diffuse disease such as cirrhosis, hemochromatosis, or fatty infiltration. MRI is extremely effective at detecting and characterizing focal hepatic lesions. In particular, patients suspected of possessing hemangiomas, hepatocellular carcinoma, or hypervascular liver metastases are better evaluated by MRI than other imaging modalities. Immediate post gadolinium spoiled gradient echo and T2-weighted fat suppressed spin echo are very effective at lesion detection, whereas serial post gadolinium spoiled gradient echo is essential for lesion characterization. New fast T2-weighted sequences and tissue specific contrast agents may further increase the role of liver MRI by shortening exam time and increasing sensitivity and specificity, respectively.

Magnetic resonance imaging of the adrenal gland and kidney.

MR is able to detect and characterize the majority of disease entities which affect the adrenal glands and kidneys. In the evaluation of the adrenal glands in-phase and out-of-phase T1-weighted imaging may be the most effective noninvasive method to distinguish benign adenomas from malignant masses. T2-weighted images are sensitive and relatively specific for the investigation of pheochromocytoma. Although MRI is excellent at evaluating the kidneys, the lower cost and good image quality of CT render it the primary diagnostic tool for renal imaging. The major current applications for MRI of the kidneys include evaluation of patients with allergy to iodinated contrast, renal failure, and the characterization of complicated renal lesions. Evaluation of venous thrombus in the context of renal cancer is likely also a useful role for MRI.

MR imaging of the gallbladder.

Implementation of fast T1- and T2-weighted sequences on state-of-the-art magnetic resonance (MR) imagers increases the potential of MR imaging for examining the gallbladder and permits imaging of both cooperative and acutely ill patients with fewer artifacts. Comprehensive evaluation of gallbladder and biliary tract disease is feasible on new generation MR scanners using MR cholangiographic techniques in combination with tissue imaging sequences (spoiled gradient-echo and fat-suppressed spoiled gradient-echo) and dynamic intravenous gadolinium-chelate administration. Inflammatory and neoplastic diseases of the gallbladder are well shown with these techniques.

Evaluation of Crohn's disease using half-fourier RARE and gadolinium-enhanced SGE sequences: initial results.

To assess the bowel changes in Crohn's disease, 11 consecutive patients underwent magnetic resonance imaging (MRI) study using T(2)-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) and gadolinium-enhanced standard and fat suppressed spoiled gradient echo (SGE) sequences. Comparison was made between MR findings of disease extent, severity, and complications and clinical data, endoscopic findings and/or surgical specimens in all patients. We found that the half-Fourier RARE images showed bowel wall thickening, dilatation of bowel and bowel obstruction well in all patients, however severity of bowel disease could not be determined as the signal intensity of diseased bowel was comparable to normal bowel in 10/11 patients. Gadolinium-enhanced fat suppressed SGE demonstrated variations of mural enhancement that correlated well with extent of disease severity in 10/11 patients. Complications such as intraperitoneal (i. p.) abscess (2 patients), gastric outlet obstruction (1 patient), bowel obstruction (2 patients), and fistula formation (3 patient), were accurately shown. We conclude that T(2)-weighted half-Fourier RARE and gadolinium-enhanced fat suppressed SGE sequences are complementary techniques that possess different imaging features that are of value for assessing bowel changes in Crohn's disease.

Active intrahepatic gadolinium extravasation following TIPS.

A 31-year-old male patient had a transjugular intrahepatic portal systemic shunt (TIPS) placed for acute Budd-Chiari syndrome secondary to paroxysmal nocturnal hemoglobinuria (PNH). Post-procedure, he was anticoagulated for his underlying paroxysmal nocturnal hemoglobinuria. After 11 days, he complained of upper abdominal pain and underwent magnetic resonance imaging (MRI). On immediate post-gadolinium spoiled-gradient-echo (SGE) images, active extravasation of gadolinium was depicted in one of two intrahepatic hematomas. Progression of layering of high signal gadolinium was shown from early to later phase post-gadolinium images. The active arterial bleeding was confirmed by conventional angiography performed immediately following the magnetic resonance imaging.

Exophytic benign tumors of the liver: appearance on MRI.

The purpose of our study was to determine the MR imaging appearance of exophytic benign liver tumors on precontrast and postgadolinium images. We reviewed our 9.5 year experience with MRI of the liver with dynamic gadolinium enhanced imaging to identify four patients with five histologically proven exophytic benign liver tumors. The histological diagnoses were cavernous hemangioma (2), focal nodular hyperplasia (FNH) (1), and hepatocellular adenoma (HCA) (2 exophytic adenomas in a patient with adenomatosis of the liver). All MRI studies were performed at 1.5 T and included: in-phase and out-of-phase T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed echo train spin echo, single shot T2-weighted sequences, and serial postgadolinium T1-weighted SGE sequences without and with fat-suppression. Prospective interpretations were reviewed and retrospective consensus readings of all MR images were performed assessing location, size, origin, morphology, visibility of the connection to the liver, signal characteristics on precontrast T1-weighted and T2-weighted images, and enhancement patterns on serial postgadolinium images. Three of the five tumors were pedunculated and connected to the liver by a thin stalk, which was prospectively identified in one patient. On precontrast and serial postgadolinium images, all exophytic tumors showed signal characteristics comparable to imaging features of standard intraparenchymal benign liver tumors. Our findings illustrate that the characteristic T1, T2, and postgadolinium imaging findings of these tumors permit correct identification of their liver origin despite their exophytic location, even if their connection with liver is not visualized.

Adult intussusception: demonstration by current MR techniques.

We describe magnetic resonance findings in three patients with small bowel intussusception from different etiologies including idiopathic, adenomatous polyps, and hamartomatous polyps. Magnetic resonance findings showed a bowel-within-bowel appearance in two patients and a coiled-spring appearance in one patient. These findings were best shown on T2-weighted images, and clear definition was present on breathing independent T2-weighted images using half fourier acquisition snap shot turbo spin echo T2-weighted images.

Post radiation hemorrhagic cystitis: MR findings.

We report on the magnetic resonance findings in two patients with hemorrhagic cystitis secondary to radiation therapy. One patient's bladder wall was high in signal intensity on T1-weighted fat-suppressed spoiled gradient echo and low in signal intensity on T2-weighted fat-suppressed spin echo images, findings consistent with intracellular methemoglobin in the setting of subacute intramural hemorrhage. The second patient's bladder wall had regions that were low in signal intensity on T1-weighted fat-suppressed spin echo and high in signal intensity on T2-weighted fat-suppressed spin echo, and other regions that were high in signal intensity on T1-weighted fat suppressed spin echo and on T2-weighted fat-suppressed spin echo images, findings that were consistent with active bleeding and late subacute hemorrhage, respectively. Imaging findings correlated with the patients' clinical picture. Our two cases illustrate that magnetic resonance images may demonstrate changes of hemorrhagic cystitis and may permit determination of disease acuity.

Angiosarcoma of the liver: MR imaging pre- and post-chemotherapy.

Angiosarcoma of the liver is a rare tumor of mesenchymal origin. We report the MR appearance of angiosarcoma of the liver on T1-weighted, T2-weighted, and serial gadolinium enhanced spoiled gradient echo images pre- and post-intravenous chemotherapy. On pre-treatment images, angiosarcoma lesions were well defined, high signal with central regions of low signal on T2-weighted images, and showed peripheral nodular enhancement on serial post gadolinium images. Lesions resembled hemangiomas, however low signal central regions on T2-weighted images was a distinguishing feature. Post-treatment images acquired 11, 15, and 17 months after initiation of therapy, demonstrated decrease in diameter or resolution of angiosarcoma masses. Lesions increased in signal on T1 weighted images and decreased in signal on T2 weighted images approaching the signal intensity of liver. Treated liver lesions enhanced negligibly on gadolinium enhanced images.