Miguel Ramalho

High Signal Intensity in Globus Pallidus and Dentate Nucleus on Unenhanced T1-weighted MR Images: Evaluation of Two Linear Gadolinium-based Contrast Agents.

PURPOSE To determine if a correlation exists between the number of previous enhanced magnetic resonance (MR) imaging examinations and high signal intensity in the globus pallidus (GP) and dentate nucleus (DN) in patients who received gadodiamide (Omniscan), a linear nonionic gadolinium-based contrast agent, and in those who received gadobenate dimeglumine (MultiHance), a linear ionic contrast agent. MATERIALS AND METHODS Institutional review board approval was obtained for this single-center retrospective study, with waiver of informed consent. The study population included 69 patients divided into two groups: Group 1 included patients who underwent gadodiamide-enhanced MR imaging, and group 2 included patients who underwent gadobenate dimeglumine-enhanced MR imaging. Two radiologists conducted a quantitative analysis of unenhanced T1-weighted images by using region of interest measurements. The GP-to-thalamus (TH) signal intensity ratio, DN-to-middle cerebellar peduncle (MCP) signal intensity ratio and relative percentage change (Rchange) between the first and last examinations for each patient were calculated. Relation between the signal intensity ratios and Rchange and the number of enhanced MR imaging examinations was analyzed by using a generalized additive model. Inter- and intraobserver agreement was evaluated with the Lin concordance correlation coefficient test. RESULTS Group 1 included 23 patients (19 female), with a mean of 5.0 doses ± 2.4 (standard deviation) (range, 3-11 doses) administered. Group 2 included 46 patients (24 female) with a mean of 4.6 doses ± 2.2 (range, 3-11 doses) administered. The interval between the first and last examination was 1500.1 days ± 780.2 (range, 98-3097 days) for group 1 and 1086.2 days ± 582.9 (range, 94-2633) for group 2. All patients had normal liver and renal function. Gadodiamide showed a significant increase in DN:MCP and GP:TH (P < .001 for both) and in Rchange (P = .001 for GP:TH, P < .001 for DN:MCP). In group 2, there was no significant increase in DN:MCP or GP:TH over time or in Rchange for GP:TH, but there was a significant trend toward an increase in Rchange for DN:MCP (P = .013). Interobserver agreement was almost perfect (0.99; 95% confidence interval: 0.99, 0.99) for all evaluated structures. Intraobserver agreement was substantial to almost perfect for both readers. CONCLUSION A significant increase in GP:TH and DN:MCP is associated with multiple gadodiamide-enhanced studies but not with gadobenate dimeglumine-enhanced studies, likely reflecting differences in stability and elimination of both contrast agents. Rate-of-change data indirectly suggest gadolinium deposition in the DN with gadobenate dimeglumine use, although it is considerably less than that with gadodiamide use.

Gadolinium-Based Contrast Agent Accumulation and Toxicity: An Update

SUMMARY: 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.

Free-Breathing 3D T1-Weighted Gradient-Echo Sequence With Radial Data Sampling in Abdominal MRI: Preliminary Observations

OBJECTIVE The purposes of this study were to evaluate the feasibility of a free-breathing 3D gradient-recalled echo sequence with radial data sampling (radial 3D GRE) in abdominal MRI compared with a standard 3D GRE volumetric interpolated breath-hold examination (VIBE) sequence for imaging of cooperative patients and to perform a preliminary assessment in imaging of noncooperative patients. MATERIALS AND METHODS Fifty-five consecutively registered patients who underwent unenhanced and contrast-enhanced abdominal MRI with the free-breathing radial 3D GRE technique constituted the study population. Two readers independently and blindly evaluated the images. RESULTS Overall image quality with the contrast-enhanced radial 3D GRE sequence was lower than but rated at least nearly as good as that with the 3D GRE VIBE sequence (p < 0.0001). Higher scores were recorded for 3D GRE VIBE images with respect to pixel graininess, streaking artifact, and sharpness (p = 0.0009 to p < 0.0001). Except for sharpness of vessels on unenhanced images, results for the radial 3D GRE sequence did not differ significantly in the comparison of cooperative and noncooperative patients (p = 0.004). For imaging of noncooperative patients, radial 3D GRE images of children had higher ratings for shading (unenhanced, p = 0.0004; contrast-enhanced, p < 0.0001) and streaking artifacts on contrast-enhanced images (p = 0.0017) than did those of adults. Overall image quality was higher for pediatric patients. In lesion analysis, use of the 3D GRE VIBE sequence was associated with significantly greater detectability, confidence, and conspicuity than was use of the radial 3D GRE sequence (p = 0.00026-0.011). CONCLUSION A free-breathing radial 3D GRE sequence is feasible for abdominal MRI and may find application in imaging of patients who are unable to suspend respiration, especially children.

Quantitative and qualitative comparison of 1.5 and 3.0 Tesla MRI in patients with chronic liver diseases.

To compare the quantitative and qualitative image quality intra‐individually, at 1.5 and 3.0 Tesla (T) in patients with chronic liver diseases.

Combined hepatocellular carcinoma-cholangiocarcinoma: Report of MR appearance in eleven patients

To describe the magnetic resonance imaging (MRI) appearance of hepatic combined hepatocellular‐cholangiocarcinoma (cHCC‐CC) in 11 patients.

Gadolinium- and superparamagnetic-iron-oxide-enhanced MR findings of intrapancreatic accessory spleen in five patients

PURPOSE The purposes of this study were to describe dynamic gadolinium-enhanced magnetic resonance imaging (MRI) findings of intrapancreatic accessory spleen(s) (IPAS) in five patients and to show how superparamagnetic iron oxide (SPIO) enhancement can be used for definite characterization in two cases. MATERIALS AND METHODS An MRI database was searched for patients who had pancreatic tail lesions with imaging features compatible with IPAS between June 2005 and July 2007. Five (four male, one female) patients (age: mean+/-S.D., 58+/-9.8 years; range, 50-75 years) were identified. All patients were examined with standard gadolinium-enhanced MRI protocol. Additionally, two patients were examined with SPIO-enhanced MRI protocol. All MRI examinations were retrospectively and blindly evaluated by two radiologists for the predetermined findings, and their final diagnoses were noted. RESULTS One pancreatic tail lesion was detected in each patient. All of these lesions were single, focal, well-marginated and located within 3 cm of the distal tail of the pancreas. The mean size (mean+/-S.D.) of the lesions was (2.02+/-0.64)x(1.72+/-0.42) cm2, and all lesions had a rounded morphology. The signal intensity of all lesions was similar to that of the spleen on all sequences, including precontrast, postgadolinium and post-SPIO sequences. The reviewers confidently diagnosed IPAS in two patients who had SPIO-enhanced MRI. In the remaining three patients, the reviewers favored the diagnosis of IPAS based on the findings of standard gadolinium-enhanced MRI; however, they could not definitively exclude the other differential diagnoses. CONCLUSION The discovery of a well-marginated, rounded mass in the distal aspect of the tail of the pancreas with signal intensity features of the spleen on all precontrast and postgadolinium sequences suggests the diagnosis of IPAS. However, SPIO-enhanced MRI can be used to characterize the lesion and to establish the definite diagnosis of IPAS in case of clinical doubt.

Self-reported gadolinium toxicity: A survey of patients with chronic symptoms

PURPOSE This study aims to describe the self-reporting symptoms experienced by individuals with self-reported normal renal function after gadolinium based contrast agent (GBCA) administration. MATERIALS AND METHODS This HIPAA-compliant, IRB-approved study consisted of an anonymous online survey of patients who believe that they suffer from gadolinium toxicity. 50 respondents completed the nine-question survey. RESULTS Fifty (100%) of the subjects ascribed their complaints to gadolinium exposure. Thirty-three (66%) described the onset immediately following GBCA administration and 16 (32%) within 6weeks. The most common symptoms included bone/joint pain and head/neck symptoms including headache, vision change, and hearing change (77.6% each). Other symptoms occurred with lesser incidence. CONCLUSIONS This survey represents an initial description of patients with normal renal function who self-described toxicity related to GBCA administration. Bone and joint complaints and skin changes are two of the most common complaints.

Quarter-Dose (0.025 mmol/kg) Gadobenate Dimeglumine for Abdominal MRI in Patients at Risk for Nephrogenic Systemic Fibrosis: Preliminary Observations

OBJECTIVE The purpose of this study is to evaluate the feasibility of 0.025 mmol/kg gadobenate dimeglumine, which is one quarter of the standard dose, for abdominal 3-T MRI studies in patients considered to be at risk for nephrogenic systemic fibrosis, using qualitative and quantitative measures and comparison with higher doses. MATERIALS AND METHODS The MRI database was retrospectively searched to select consecutive patients who underwent quarter-dose gadobenate dimeglumine-enhanced abdominal MRI at 3 T, between January 1, 2009, and January 15, 2010, and who underwent half-dose (0.05 mmol/kg) gadobenate dimeglumine-enhanced abdominal MRI at 3 T during one randomly chosen month. There were 25 patients in the final quarter-dose group (16 men and nine women; mean age, 57 years) and 44 patients in the half-dose group (21 men and 23 women; mean age, 58 years). The enhancement of abdominal organs and aorta was evaluated qualitatively and quantitatively on contrast-enhanced images. The overall quality of abdominal enhancement was also evaluated. RESULTS Reviewers rated the diagnostic enhancement of the evaluated organs in all phases of enhancement for both studied doses, but the half dose had significantly higher ratings than did the quarter dose in all comparisons (p, 0.034 to < 0.0001), except in the pancreas in the early hepatic venous phase (p = 0.095 for reviewer 1; p = 0.0611 for reviewer 2). The overall enhancement quality of the quarter dose was rated as good in all phases of enhancement, although it was significantly lower than that for the half dose (p ≤ 0.0001). The liver, pancreas, renal cortex, and aorta had 1.52-1.93-fold, 1.53-1.90-fold, 1.46-1.77-fold, and 1.58-1.84-fold, respectively, higher percentages of enhancement with the half dose than with the quarter dose (p, 0.0049 to < 0.0001). CONCLUSION A one-quarter dose of gadobenate dimeglumine at 3 T is a feasible alternative for abdominal MRI in patients at risk for nephrogenic systemic fibrosis. Our results might have important clinical implications, because greater safety may be conferred on patients with poor renal function with this low dose of contrast agent.

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

The authors performed intraindividual qualitative and quantitative comparison between T1-weighted spin-echo and 3D MPRAGE images in 18 patients who had multiple exposures to gadodiamide. Differences in signal between the 2 sequences for both baseline and last examination dentate nucleus/middle cerebellar peduncle ratios were statistically significant. They conclude that T1-weighted spin-echo and MPRAGE sequences cannot be used interchangeably for qualitative or quantitative signal intensity analysis of the dentate nucleus in patients who received gadodiamide. 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.

Magnetic resonance imaging of pancreatitis: An update

Magnetic resonance (MR) imaging plays an important role in the diagnosis and staging of acute and chronic pancreatitis and may represent the best imaging technique in the setting of pancreatitis due to its unmatched soft tissue contrast resolution as well as non-ionizing nature and higher safety profile of intravascular contrast media, making it particularly valuable in radiosensitive populations such as pregnant patients, and patients with recurrent pancreatitis requiring multiple follow-up examinations. Additional advantages include the ability to detect early forms of chronic pancreatitis and to better differentiate adenocarcinoma from focal chronic pancreatitis. This review addresses new trends in clinical pancreatic MR imaging emphasizing its role in imaging all types of acute and chronic pancreatitis, pancreatitis complications and other important differential diagnoses that mimic pancreatitis.