Difference In Signal Intensity Ratio Research Articles

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

Introduction and aimsContradictory 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 methodsWe 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. ResultsThe 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%]). ConclusionsReceiving more than 10 doses of gadoterate meglumine was not associated with increased signal intensity in the dentate nucleus.

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 aimsContradictory 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 methodsWe 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. ResultsThe 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%]). ConclusionsReceiving more than 10 doses of gadoterate meglumine was not associated with increased signal intensity in the dentate nucleus.

Pituitary adenoma consistency: Direct correlation of ultrahigh field 7T MRI with histopathological analysis

PurposeTumor consistency is a critical factor in surgical planning that influences ease of resection and risk of operative morbidity. The ability of MRI to predict tumor consistency tumor consistency has been shown to increase with higher field strength. The present study examined the utility of 7 T (7 T) MRI in predicting the tumor consistency of pituitary adenomas. MethodFifteen patients with pituitary adenomas were preoperatively scanned at 7 T MRI. Regions of interest were drawn around lesions for voxel-based signal intensity (SI) analysis. The percentage of tumor voxels with intensity higher than local gray matter was calculated on T2-weighted imaging. A single neurosurgeon rated tumor firmness for all patients. Histopathological analysis was performed. Radiological tumor features were correlated with intraoperative tumor consistency measurements and histopathology. ResultsTumors rated as ‘soft’ intraoperatively were hyperintense to local gray matter on T2-weighted imaging. ‘Firm’ tumors were hypointense to local gray matter. There was no significant difference in SI ratio between soft and firm tumors (p = 0.098). Soft tumors had a significantly higher percentage of tumor voxels greater than local gray matter compared to firm tumors (p = 0.035, Cohen’s D-effect size = 1.208). Soft tumors had higher vascularity than firm tumors, p = 0.015. ConclusionsThe signal and contrast advantage conferred by 7 T MRI may provide valuable preoperative information regarding pituitary tumor consistency and physiology. The use of granular, voxel-based analysis maximizes the potential afforded by the high resolution of 7 T imaging, and may be a valuable method of predicting consistency of pituitary adenoma.

Gadolinium deposition in the brain of dogs after multiple intravenous administrations of linear gadolinium based contrast agents.

ObjectiveTo determine the effect of a linear gadolinium-based contrast agent (GBCA) on the signal intensity (SI) of the deep cerebellar nuclei (DCN) in a retrospective clinical study on dogs after multiple magnetic resonance (MR) examinations with intravenous injections of gadodiamide and LA-ICP-MS analysis of a canine cerebellum after gadodiamide administration.Animals15 client-owned dogs of different breeds and additionally 1 research beagle dog cadaver.ProceduresIn the retrospective study part, 15 dogs who underwent multiple consecutive MR imaging examinations with intravenous injection of linear GBCA gadodiamide were analyzed. SI ratio differences on unenhanced T1-weighted MR images before and after gadodiamide injections was calculated by subtracting SI ratios between DCN and pons of the first examination from the ratio of the last examination. Additionally, 1 research beagle dog cadaver was used for LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) analysis of gadolinium in the cerebellum as an add-on to another animal study. Descriptive and non-parametrical statistical analysis was performed and a p-value of < 0.05 was considered significant.ResultsNo statistically significant differences of SI ratios, between DCN and pons, were detectable based on unenhanced T1-weighted MR images. LA-ICP-MS analyses showed between 1.5 to 2.5 μg gadolinium/g tissue in the cerebellum of the examined dog, 35 months after the last of 3 MRI examination with gadodiamide (two examinations at a dose of 1 x 0.1mmol/kg, last examination at a dose of 3 x 0.05mmol/kg).Conclusion and clinical relevanceAlthough the retrospective MRI study did not indicate any visible effect of SI increase after multiple gadodiamide exposures, further studies based on LA-ICP-MS showed that the optical threshold was not reached for a potential visible effect. Gadolinium was detectable at a level of 1.5 to 2.5 μg gadolinium/g tissue by using LA-ICP-MS in the cerebellum 35 months after last MRI examination. The general importance of gadolinium retention of subvisible contents requires further investigation.

Preliminary observation on the changes of T(1) weighted signal of globus pallidus after multiple intravenous injection of linear gadolinium contrast agent

Objective: To explore the changes in signal intensity (SI) ratios of globus pallidus (GP) on unenhanced T(1)-weighted(T(1)WI)magnetic resonance imaging (MRI) scans between the first and last MRI using the linear gadolinium-based contrast agent (GBCAs) intravenously. Methods: Clinical and imaging data of 114 patients who underwent at least 4 consecutive enhanced MRI examinations at the Affiliated Hospital of Xuzhou Medical University between January 2016 and April 2018 were analyzed. The SI ratio of GP, thalamus and cerebrospinal fluid (CSF) were measured on unenhanced T(1)WI. The GP to thalamus SI ratio was calculated by dividing the SI in the GP by that in the thalamus, and so was the GP to CSF SI ratio. The difference of SI ratio in the same patient was analyzed by nonparametric tests, linear regression analysis was used to analyze clinical factors. Results: The SI ratio of GP-to-thalamus and GP-to-CSF after multiple enhancement were higher than before, and the difference was statistically significant. The SI ratio of GP-to-thalamus and GP-to-CSF before and after repeated contrast-enhanced were 1.036(1.010, 1.075), 1.104(1.074, 1.168); 4.215(3.590, 5.614), 5.409(4.213, 6.502), all P<0.01. The SI ratio differences showed a significant positive correlation with the number of enhanced examination(pons:b=0.023, P<0.01,CSF:b=0.279,P=0.034), and a significant negative correlation with the interval (pons: b=-0.002,P< 0.01, CSF: b=-0.023, P=0.039). There was no correlation with other clinical factors (all P>0.05). Conclusions: There is an increase in SI in the GP after serial injections of linear GBCAs, and there is a positive correlation with the times of enhanced examination, and a negative correlation with time interval.

Assessment of acute obstructive pancreatitis by magnetic resonance imaging: Predicting the occurrence of pancreatic fistula following pancreatoduodenectomy.

The aim of the present study was to assess the effect of preoperative acute obstructive pancreatitis on the risk of the occurrence of pancreatic fistula (PF) following pancreaticoduodenectomy. A total of 22 patients who developed postoperative PF were carefully matched with 22 control patients without PF according to demographic data, pancreatic pathology, presenting symptoms and other surgery-associated parameters. These parameters were compared between these two groups. The mean pancreatic apparent diffusion coefficient (ADC) values in the fistula group were 1.14±0.31×10-3 mm2/s, which was significantly decreased compared with the non-fistula group (1.48±0.44×10-3 mm2/s) (P=0.005). The pancreas-muscle signal intensity (SI) ratio on fat-suppressed T1 weighted image (rT1) in the fistula group was 1.71±0.25, which was significantly increased compared with the non-fistula group (1.25±0.29) (P<0.001). The pancreas-muscle SI ratios on fat-suppressed T2 weighted image (T2WI) in the fistula group and the non-fistula group were 0.72±0.08 and 0.62±0.07, respectively (P=0.79). There was no significant difference in pancreas-muscle SI ratio on fat-suppressed T2-weighted image (rT2) value between these two groups. Based on the receiver operating characteristic curve, the optimal cut-off value of ADC as a criterion for prediction of pancreatic fistula was 1.29×10-3 mm2/s, which yielded a sensitivity of 77.3% and a specificity of 63.6%. In conclusion, the severity of acute obstructive pancreatitis was negatively associated with ADC values and pancreas-muscle SI ratio on rT1 images, which may be useful for predicting the occurrence of PF preoperatively.

Signal Changes in the Dentate Nucleus and Globus Pallidus on Unenhanced T1-Weighted Magnetic Resonance Images After Intrathecal Administration of Macrocyclic Gadolinium Contrast Agent.

The aim of this study was to evaluate signal changes in the dentate nucleus and globus pallidus (GP) on unenhanced T1-weighted magnetic resonance (MR) images (T1 WI) in a cohort of patients who have received intrathecal macrocyclic ionic gadolinium-based contrast agent (GBCA) gadoterate meglumine. A group of 20 patients (male/female ratio, 8:12; mean age, 39.5 ± 15.5 years) who had not received intravenous GBCA but had received an intrathecal macrocyclic ionic GBCA (plus baseline and an additional final magnetic resonance imaging [MRI] for reference) from 2012 to 2017 were retrospectively included in this institutional review board-approved study. Two radiologists inspected T1-weighted 2-dimensional spin echo (n = 7) and 3-dimensional isotropic turbo field echo (n = 13) images on a 3 T MRI system to conduct visual evaluation and quantitative analysis. Baseline and final examination signal intensity (SI) ratios were assessed across time by using the same pulse sequences. For visual analysis, SI changes on the GP, thalamus (Th), cerebellar peduncle (CP), and dentate nucleus (DN) were graded as a 3-point scale. For quantitative analysis, SI ratio differences between the baseline and final MR examinations were estimated for the DN-to-CP and GP-to-Th ratios. One-sample t tests were used to investigate whether they differed from 0. In addition, to investigate significant differences between the SI ratios for various pulse sequences, t tests were performed. The regression analysis was additionally used to find any correlation between SI ratio differences and various confounding variables including age, sex, or the mean interval between the baseline and final MR examinations. The SI ratio differences did not deviate significantly from 0, neither for the DN/CP ratio (0.013 ± 0.0584, P = 0.287) nor the GP/Th ratio (-0.0113 ± 0.0546, P = 0.366). The DN-to-CP and GP-to-Th SI ratio differences did not significantly deviate from 0 in the patient groups in either of the imaging sequences (P > 0.05) as well. Age, sex, and the mean interval between examinations did not influence SI ratio differences between examinations (P > 0.05). Intrathecal macrocyclic GBCA administration was not associated with measurable T1 SI changes in the GP and DN as an indicator of brain gadolinium deposition detectable by MRI.

Weekly enhanced T1-weighted MRI with Gadobutrol injections in MS patients: Is there a signal intensity increase in the dentate nucleus and the globus pallidus?

Background and PurposeGadolinium-based contrast agents (GBCAs) administration have drastically improved the accuracy of Multiple Sclerosis (MS) diagnosis by highlighting any damage to the brain blood barrier, thereby differentiating between active and non-active lesions. Following multiple administrations of GBCAs, several MS studies have reported a signal intensity (SI) increase on unenhanced T1-weighted images in certain brain regions such as the dentate nucleus (DN) and the globus pallidus (GP). Our aim was therefore to determine the accumulation of macrocyclic GBCAs on enhanced T1-weighted images SI in the DN and the GP of MS patients injected eight times. Materials and MethodsFive MS patients underwent eight weekly consecutive MRI scans. Enhanced 3D T1-weighted images with Gadobutrol as a macrocyclic GBCA, were acquired. A ROI-based approach was applied for the evaluation of SI in the DN to middle cerebellar peduncle (DN-MCP) and GP to semi-oval white matter (GP-SOWM) ratios. An analysis of variance on repeated measures was used for the statistical analysis of each ratio. ResultsNo DN-MCP and GP-SOWM SI ratio differences were observed over the eight-weeks period using the macrocyclic GBCA. ConclusionIterative and weekly injections of macrocyclic GBCAs are not associated with T1 signal increase in the DN and GP of MS patients. These results would suggest a no gadolinium accumulation in the brain using macrocyclic GBCA even after several close injections and promote the use of a macrocylcic GBCA rather than linear agents for MS patients.

Pediatric Brain: Gadolinium Deposition in Dentate Nucleus and Globus Pallidus on Unenhanced T1-Weighted Images Is Dependent on the Type of Contrast Agent.

The aim of this study was to identify the signal intensity (SI) changes in the dentate nucleus (DN) and the globus pallidus (GP) on unenhanced T1-weighted magnetic resonance (MR) images after multiple administration of gadolinium-based contrast agents (GBCAs) in children and compare those changes between linear and macrocyclic GBCAs. This retrospective study was approved by the institutional review board and the requirement for informed consent was waived. We identified 92 children who underwent at least 4 consecutive MR examinations exclusively using either linear GBCA (gadodiamide or gadopentetate dimeglumine, n = 41) or macrocyclic GBCA (gadoterate meglumine, n = 51). Signal intensity ratio changes in the DN to pons and GP to thalamus between the first and last MR examinations were calculated. The SI ratios in the linear group increased significantly between the first and last MR examinations (mean difference: DN to pons, 0.0461 ± 0.0480, P < 0.001; GP to thalamus, 0.0332 ± 0.0385, P < 0.001), but not in the macrocyclic group (mean difference: DN to pons, -0.0010 ± 0.0371, P = 0.855; GP to thalamus, 0.0007 ± 0.0294, P = 0.867). In the linear regression analysis, the numbers of administrations of gadodiamide and gadopentetate dimeglumine were highly associated with the differences in SI ratios (DN to pons, P < 0.001 and P = 0.003; GP to thalamus, P < 0.001 and P = 0.002, respectively). The SIs of the DN and GP on unenhanced T1-weighted images increased after serial administrations of linear GBCA, but not macrocyclic GBCA, in children. The number of linear GBCA administration had a linear association with the SI changes in the DN and GP.

Evaluation of Gadolinium Retention After Serial Administrations of a Macrocyclic Gadolinium-Based Contrast Agent (Gadobutrol): A Single-Institution Experience With 189 Patients.

There has been controversy as to whether gadobutrol, one of the widely used macrocyclic gadolinium-based contrast agents, can lead to gadolinium retention after serial injections. Our aim was to validate whether serial administrations of gadobutrol can cause signal increase in the dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted magnetic resonance (MR) images due to gadolinium retention. A total of 189 patients who had undergone at least 2 contrast-enhanced MR scans using only gadobutrol between August 2009 and August 2016 were retrospectively included. The DN-to-pons and GP-to-thalamus signal intensity (SI) ratio differences on unenhanced T1-weighted MR images were calculated by subtracting the SI ratios at the first MR images from those at the last MR images. One-sample t tests were used to evaluate whether the SI ratio differences differed from 0. Linear regression and Pearson correlations were performed to assess correlations between SI ratio differences and various confounding variables, including the number of MR scans, mean time interval between MR scans, age, sex, history of radiation therapy or chemotherapy, and renal and liver functions. Patients underwent a mean of 5.9 ± 6.3 contrast-enhanced MR scans with a mean interval of 42.8 ± 49.5 weeks between the scans. Sixty-three patients underwent 6 or more MR scans, whereas 126 patients underwent fewer than 6 MR scans. Neither the DN-to-pons SI nor the GP-to-thalamus SI ratio differences differed significantly from 0, with mean values of -0.012 ± 0.115 (P = 0.148) and 0.012 ± 0.111 (P = 0.126), respectively. Serial administrations of gadobutrol did not result in signal increases in the DN or GP on unenhanced T1-weighted MR images due to gadolinium retention.

Up to 52 administrations of macrocyclic ionic MR contrast agent are not associated with intracranial gadolinium deposition: Multifactorial analysis in 385 patients.

PurposeTo determine whether multiple repeated administrations of gadolinium-based macrocyclic ionic MR contrast agent (MICA) are associated with intracranial gadolinium deposition and identify the predisposing factors for deposition in various clinical situations.Materials and methodsIn this institutional review board-approved retrospective study, 385 consecutive patients who underwent MICA-enhanced MR imaging were enrolled. The dentate nucleus-to-pons (DN/P) and globus pallidus-to-thalamus (GP/Th) signal intensity (SI) ratios on unenhanced T1-weighted images were recorded by 2 independent readers and averaged. The mean DN/P and GP/Th SI ratio difference between the last and the first examinations were tested using the one-sample t-test. Student’s t-test and stepwise regression analysis were used to identify the predisposing factors for deposition based on the number of administrations, time interval, hepatic and renal function, magnetic field strength, and chemo- or radiation therapy.ResultsThe mean DN/P SI ratio difference was not different from zero (P = .697), even in patients with ≥20 administrations (n = 33). Only patients with abnormal renal function showed an increase in the mean DN/P SI ratio difference (P = .019). The mean DN/P SI ratio difference was not associated with any predisposing factors. However, the mean GP/Th SI ratio difference showed decrease (P < .001), which was associated with age (P = .007), number of administrations (P = .01) and number of radiation therapy sessions (P = .022) on multivariate analysis.ConclusionMultiple repeated administrations of MICA were not associated with increased T1 signal intensity in deep brain nuclei suggestive of Gd deposition in patients with normal renal function.

Correlation between high signal intensity in cerebrum nucleus on unenhanced T1-weighted MR images and number of previous gadolinium-based contrast agent administration

To explore the correlation between the number of previous gadolinium-based contrast agent administrations and high signal intensity (SI) in the cerebrum nucleus on unenhanced T1-weighted magnetic resonance images. Thirty-nine patients who previously underwent at least three contrast-enhanced brain MRI examinations were enrolled in the study. The right globus pallidus, right thalamus, right dentate nucleus, pons and white matter of right frontal lobe were selected as region of interests (ROI). The mean SIs of the ROI were measured on unenhanced T1-weighted images. The SI ratios of globus pallidus, right thalamus, right dentate nucleus and pons to white matter were calculated, respectively. The correlation of SI ratio variation with the number of previous contrast agent administration and clinical features was analyzed with Spearman analysis. The dentate nucleus-to-white matter SI ratios of the last and first MRI scan were 1.113±0.136 and 1.014±0.096(P<0.01), respectively; while the SI ratio differences between the last and first MRI scan of globus pallidus-to-white matter, the thalamus-to-white matter and the pons-to-white matter were not significant (all P>0.05). The dentate nucleus-to-white matter SI ratio was correlated with the number of previous gadolinium-based contrast agent administrations (r=0.329, P<0.05), but not with age, sex, underlying disease, treatment and history of diabetes (all P>0.05). High SI in the dentate nucleus on unenhanced T1-weighted images may be a consequence of the number of previous gadolinium-based contrast agent administrations.

Signal intensity change on unenhanced T1-weighted images in dentate nucleus and globus pallidus after multiple administrations of gadoxetate disodium: an intraindividual comparative study

To investigate whether there is an increased signal intensity (SI) of dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted magnetic resonance imaging (MRI), in patients who had undergone multiple administrations of gadoxetate disodium. We retrospectevely included stage III melanoma patients, who had been previously enrolled in a trial of adjuvant therapy and who had undergone whole-body contrast-enhanced MRIs with gadoxetate disodium every three months for their follow-up. The SI ratios of DN-to-pons and GP-to-thalamus on unenhanced T1-weighted images were calculated. The difference in SI ratios between the first and the last MRI examinations was assessed and a linear mixed model was performed to detect how SI ratios varied with the number of administrations. Eighteen patients were included in our study. The number of gadoxetate disodium administrations ranged from 2 to 18. Paired t-test did not show any significant difference in DN-to-pons (p=0.21) and GP-to-thalamus (p=0.09) SI ratios by the end of the study. DN-to-pons SI ratio and GP-to-thalamus SI ratio did not significantly increase with increasing the number of administrations (p=0.14 and p=0.06, respectively). Multiple administrations of gadoxetate disodium are not associated with increased SI in DN and GP in the brain. • Gadolinium may deposit in the human brain after multiple GBCA administrations. • Gadolinium deposition is associated with increased T1W signal intensity • Increase in signal intensity is most apparent within the DN and GP • Multiple administrations of gadoxetate disodium do not increase T1W signal.

Pediatric Brain: No Increased Signal Intensity in the Dentate Nucleus on Unenhanced T1-weighted MR Images after Consecutive Exposure to a Macrocyclic Gadolinium-based Contrast Agent.

Purpose To determine the effect of at least five serial injections of the macrocyclic gadolinium-based contrast agent (GBCA) gadoterate meglumine on the signal intensity (SI) of the dentate nucleus (DN) of the pediatric brain on nonenhanced T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 41 pediatric patients (age range, 3-17 years) who were imaged in at least five consecutive 1.5-T MR examinations with the exclusive use of gadoterate meglumine (plus a final additional nonenhanced MR imaging examination) were evaluated. SI ratio differences between the first and last MR examination were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios in a region-of-interest-based analysis, and one-sample t tests were used to examine if the SI ratio differences differed from 0. Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 8.6 ± 3.9 GBCA administrations (mean accumulated dose, 32.07 mmol ± 17.62, with an average of 16.7 weeks ± 7.9 between every administration). Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0012 ± 0.0101, P = .436; DN-to-MCP ratio: 0.0007 ± 0.0088, P = .604), and one-sided Bayes factors provided substantial evidence against an SI ratio increase (0.10 for DN-to-pons ratio; 0.27 for DN-to-MCP ratio). Conclusion No increase of the SI in the DN was found after a mean of 8.6 serial injections of the macrocyclic GBCA gadoterate meglumine in pediatric patients, confirming previous studies that did not find this effect after serial injections of macrocyclic GBCAs in adults. © RSNA, 2017.

No Signal Intensity Increase in the Dentate Nucleus on Unenhanced T1-weighted MR Images after More than 20 Serial Injections of Macrocyclic Gadolinium-based Contrast Agents

Purpose To determine the effect of more than 20 serial injections of macrocyclic gadolinium-based contrast agents (GBCAs) on the signal intensity (SI) of the dentate nucleus (DN) on unenhanced T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 33 patients who underwent at least 20 consecutive MR imaging examinations (plus an additional MR imaging for reference) with the exclusive use of macrocyclic GBCAs gadoterate meglumine and gadobutrol were analyzed. SI ratio differences were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios by subtracting the SI ratio at the first MR imaging examination from the SI ratio at the last MR imaging examination. One-sample t tests were used to examine if the SI ratio differences differed from 0, and Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 23.03 ± (standard deviation) 4.20 GBCA administrations (mean accumulated dose, 491.21 mL ± 87.04 of a 0.5 M GBCA solution) with an average of 12.09 weeks ± 2.16 between every administration. Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0032 ± 0.0154, P = .248; DN-to-MCP ratio: -0.0011 ± 0.0093, P = .521), and one-sided Bayes factors provided substantial to strong evidence against an SI ratio increase (Bayes factor for DN-to-pons ratio = 0.09 and that for DN-to-MCP ratio = 0.12). Conclusion The study indicates that 20 or more serial injections of macrocyclic GBCAs administered with on average 3 months between each injection are not associated with an SI increase in the DN. © RSNA, 2016.

Intraindividual Analysis of Signal Intensity Changes in the Dentate Nucleus After Consecutive Serial Applications of Linear and Macrocyclic Gadolinium-Based Contrast Agents.

Recent studies reported an increase in the dentate nucleus (DN)-to-pons signal intensity (SI) ratio (DN-pons SI ratio) on unenhanced T1-weighted images in patients who received consecutive serial injections of linear gadolinium-based contrast agents (GBCAs). In contrast, most studies found no increase in the DN-pons SI ratio when patients were treated with consecutive serial injections of macrocyclic GBCAs. However, the potential difference between macrocyclic and linear GBCAs has never been assessed in individuals who received subsequent applications of both contrast agents. In this retrospective study, we assessed the evolution of the DN-pons SI ratio change in patients that were treated with a comparable number of serial consecutive injections of the linear GBCA gadopentetate dimeglumine and subsequent serial injections of the macrocyclic GBCAs gadobutrol and gadoterate meglumine. Data of 36 patients was analyzed. All patients underwent at least 5 consecutive administrations of the linear GBCA gadopentetate dimeglumine followed by an equal number of consecutive administrations of the macrocyclic GBCA gadobutrol. In 12 of the 36 patients, 5 or more final consecutive injections of the macrocyclic GBCA gadoterate meglumine were analyzed additionally. The difference of DN-pons SI ratios on unenhanced T1-weighted images was calculated by subtracting the ratio at the first examination from the ratio at the last examination in each of the 3 periods. The mean DN-pons SI ratio difference in the gadopentetate dimeglumine period was significantly greater than 0 (mean ± SD, 0.0448 ± 0.0345; P < 0.001), whereas the mean DN-pons SI ratio difference in the subsequent gadobutrol and gadoterate meglumine period was significantly smaller than 0 (gadobutrol: -0.0178 ± 0.0459, P = 0.026; gadoterate meglumine: -0.0250 ± 0.0284, P = 0.011). In this observational study, the application of the linear GBCA gadopentetate dimeglumine was associated with a DN-pons SI ratio increase, whereas subsequent applications of the macrocyclic GBCAs gadobutrol or gadoterate meglumine in the same patients were not. Rather, the current data tentatively suggest a decrease in preexisting hyperintensities over time when linear GBCAs are changed to macrocyclic GBCAs, potentially indicating a washout effect or precipitation of gadolinium. Future patient studies need to include control groups to replicate the present results, and additional animal studies should be conducted to clarify the underlying mechanism of the proposed SI decrease.

Increased Signal Intensity in the Dentate Nucleus on Unenhanced T1-Weighted Images After Gadobenate Dimeglumine Administration

The aim of this study was to compare changes in signal intensity (SI) ratios of the dentate nucleus (DN) to pons and cerebrospinal fluid (CSF) on unenhanced T1-weighted magnetic resonance imaging (MRI) scans between the first and last MRI using the linear gadolinium-based contrast agent gadobenate dimeglumine. The study was approved by the ethical committee of the University of Heidelberg (S-324/2014), and written informed consent was waived due to the retrospective character of the study. Fifty patients who underwent at least 5 consecutive MRI examinations (plus an additional last MRI for reference) with the exclusive use of gadobenate dimeglumine were analyzed retrospectively. The difference of DN-to-pons and DN-to-CSF mean SI ratios was calculated on unenhanced T1-weighted images between the first and last examination. Results were compared with previously published data on gadopentetate dimeglumine and gadoterate meglumine. Signal intensity ratio differences for DN-to-pons and DN-to-CSF were significantly greater than 0 (pons: 0.0399 ± 0.0307, P < 0.001; CSF: 0.1439 ± 0.1524, P < 0.001). No control variable consistently predicted the SI ratio difference for the DN-to-pons and the DN-to-CSF ratio. Compared with previously published data, the difference in SI increase between gadopentetate dimeglumine and gadobenate dimeglumine was not significant for the DN-to-pons ratio (P = 0.906). In contrast, the DN-to-CSF ratio difference was significantly lower (P < 0.001) for gadobenate dimeglumine. Dentate nucleus-to-pons (P < 0.001) and DN-to-CSF (P = 0.017) ratio differences were both significantly higher for gadobenate dimeglumine than for gadoterate meglumine. The present study found an increase in SI in the DN after serial injections of gadobenate dimeglumine. Further studies are needed to clarify the potential of different linear gadolinium-based contrast agents to cause SI increase in the DN.

Application of diffusion weighted magnetic resonance imaging for the diagnosis of pancreatic cancer

Objective To investigate the value of diffusion weighted magnetie resonance imaging and apparent diffusion coefficient (ADC) value in the diagnosis of pancreatic cancer.Methods The clinical data of 36 patients with pancreatie cancer who were admitted to the Wuxi No.2 People's Hospital from March 2009 to June 2011 were retrospectively analyzed,and the clinical data of 30 healthy volunteers were collected.All candidates received diffusion weighted magnetie resonance imaging examination.The signal intensity ratios ( SIRs ) of the cancer and the pericancerous tissues in the T1 weighted-images (T1WI),T2 weighted-images (T2WI) and diffusion weighted-images (DWI) were compared by using one-way analysis of variance.The ADC values of the cancer and the paricancerous tissues were compared using the paired t test.The differences of the ADC values of the cancer and pericancerous tissues compared with those of healthy individuals were analyzed using an independent sample t test.Results The accuracy rate of preoperative magnetic resonance imaging examination was 92％.The relative SIRs were 0.203 ± 0.190 in the T2 WI,0.399 ± 0.201 in the T1 WI and 0.579 ± 0.291 in the DWI,respectively,with no significant differences across the 3 kinds of images (F=5.92,6.15,6.83,P ＜ 0.05 ),while SIRs of the T1 WI and DWI were significantly higher than that of the T2 WI ( P ＜ 0.05 ).There was no significant difference in SIRs when comparing T1 WI and DWI ( P ＞ 0.05 ).The mean ADC values of the cancer and pericancerous tissues of the pancreatic cancer patients and the pancreatic tissues of healthy individuals were (1.40±0.24) ×10 3 mm2/s,(1.71 ±0.10) ×10-3 mm2/s and (1.73±0.30) ×10-3 mm2/s,respectively,with significant differences across the 3 modes of images (t =10.54,12.08,P ＜ 0.05).Conclusion DWI can show high quality images of the lesions,and ADC value is helpful in the diagnosis of pancreatic cancer. Key words: Pancreatic neoplasms; Magnetic resonance imaging; Diffusion-weighted imaging

Assessment of pulmonary parenchyma perfusion with FAIR in comparison with DCE-MRI—Initial results

Objective The aim of this study was to assess pulmonary parenchyma perfusion with flow-sensitive alternating inversion recovery (FAIR) in comparison with 3D dynamic contrast-enhanced (DCE) imaging in healthy volunteers and in patients with pulmonary embolism or lung cancer. Materials and methods Sixteen healthy volunteers and 16 patients with pulmonary embolism (5 cases) or lung cancer (11 cases) were included in this study. Firstly, the optimized inversion time of FAIR (TI) was determined in 12 healthy volunteers. Then, FAIR imaging with the optimized TI was performed followed by DCE-MRI on the other 4 healthy volunteers and 16 patients. Tagging efficiency of lung and SNR of perfusion images were calculated with different TI values. In the comparison of FAIR with DCE-MRI, the homogeneity of FAIR and DCE-MRI perfusion was assessed. In the cases of perfusion abnormality, the contrast between normal lung and perfusion defects was quantified by calculating a normalized signal intensity ratio. Results One thousand milliseconds was the optimal TI, which generated the highest lung tagging efficiency and second highest PBF SNR. In the volunteers, the signal intensity of perfusion images acquired with both FAIR and DCE-MRI was homogeneous. Wedged-shaped or triangle perfusion defects were visualized in five pulmonary embolisms and three lung cancer cases. There was no significant statistical difference in signal intensity ratio between FAIR and DCE-MRI ( P > 0.05). In the rest of eight lung cancers, all the lesions showed low perfusion against the higher perfused pulmonary parenchyma in both FAIR and DCE-MRI. Conclusion Pulmonary parenchyma perfusion imaging with FAIR was feasible, consistent and could obtain similar functional information to that from DCE-MRI.

Signal intensity changes in anterior cruciate ligament autografts: Relation to magnetic field orientation

The purpose of this study was to use magnetic resonance (MR) imaging to investigate the contribution of graft alignment to changes in signal intensity in anterior cruciate ligament (ACL) autografts. Forty patients who had undergone reconstruction of the ACL with an autograft underwent MR examinations of the knee in extension and flexion. The signal intensity of the intratibial bone tunnel and intraarticular portions of ACL graft were measured, and signal intensity ratios were defined by dividing the mean signal intensity of the graft by the mean signal intensity of the fatty marrow. The angles from the intraarticular and intratibial bone tunnel portions of the graft to the static magnetic field were measured for each signal intensity ratio. The Hotteling T2 test was used to evaluate the differences in signal intensity ratios to the differences in angles from flexion to extension for the intratibial bone tunnel and intraarticular portions of the graft. Significant increases occurred in the signal intensity of the graft and the angle with the change in position from flexion to extension for both the intratibial bone tunnel (P < .01) and intraarticular (P < .01) portions of the graft. Changes in signal intensity ratios were greater than zero, and these values differed significantly for the intraarticular and the intratibial bone tunnel (P < .01) portions of the graft. The signal intensity changes of the ACL graft related to changes in its alignment are likely a result of the magic-angle effect.