MRI in pregnancy: Indications and practical considerations.

There is a constantly evolving knowledgebase regarding the safety of MRI in pregnant patients, as well as the safety of gadolinium administration, given potential fetal risks. This review provides an overview of national and international recommendations for patient screening and safety by trimester, evaluates the most recent literature regarding administration of gadolinium in pregnant patients, and discusses technical requirements when imaging pregnant patients. A protocol for imaging pregnant patients is provided, and multiple common indications for MRI in pregnancy are discussed. Level of Evidence 5. Technical Efficacy Stage 5. J. Magn. Reson. Imaging 2019;49:621-631.

MRI features of primary rare malignancies of the liver: A report from four university centres.

PURPOSE: To determine if rare primary malignancies of the liver may have consistent features on magnetic resonance imaging (MRI). MATERIALS AND METHODS: This IRB-compliant retrospective study reviewed the records from the pathology departments of four university centres over an 11-year period from 2005-2016 to identify rare primary malignant tumours, which were cross-referenced with MRI records. MRI studies of these patients were reviewed to determine if these tumours exhibited consistent and distinctive features. RESULTS: Sixty patients were identified with rare primary liver tumours. The following distinctive features and frequency of occurrence were observed: mixed hepatocellular carcinoma-cholangiocarcinoma showed regions of wash-out in 7/19 of patients; 6/6 of fibrolamellar carcinomas demonstrated large heterogeneous lesions with large heterogeneous central scars; epithelioid haemangioendothelioma larger than 2 cm showed target-like enhancement in late-phase enhancement in 9/13; sarcomas excluding angiosarcoma had central necrosis in 3/9 and haemorrhage in 5/9; angiosarcomas showed centripedal progressive nodular enhancement in 3/6 and showed regions of haemorrhage in 3/6; and 7/7 of primary hepatic lymphomas showed encasement of vessels. CONCLUSION: Although helpful features for the differentiation of rare primary malignancies of the liver are identified, no MRI features appear to be specific and therefore histopathological confirmation is usually required for definitive diagnosis. KEY POINTS: • No MRI features appear to be specific for rare primary liver malignancies. • Haemorrhage is a helpful sign in diagnosis of primary hepatic sarcomas. • Angiosarcomas may show progressive nodular enhancement towards the centre mimicking haemangioma. • Vessel encasement is a helpful sign in diagnosis of primary hepatic lymphoma.

Liver imaging reporting and data system category 4 observations in MRI: Risk factors predicting upgrade to category 5.

PURPOSE: To identify demographic and imaging features in magnetic resonance imaging (MRI) that are associated with upgrade of Liver Imaging Reporting and Data System (LI-RADS) category 4 (LR-4) observations to category 5 (LR-5), and to assess their effects on risk of upgrade and time to upgrade. MATERIALS AND METHODS: Institutional Review Board approval was obtained for this retrospective, dual-institution Health Insurance Portability and Accountability Act (HIPAA)-compliant study. Radiologists reviewed 1.5T and 3T MRI examinations for 181 LR-4 observations in 139 patients, as well as follow-up computed tomography (CT) and MRI examinations and treatment. A stepwise multivariate Cox proportional hazards model analysis was performed to identify predictive risk factors for upgrade to LR-5, including patient demographics and LI-RADS imaging features. Overall cumulative risk of upgrade was calculated by using the Kaplan-Meier method. The cumulative risks were compared in the presence/absence of significant predictive risk factors using the log-rank test. RESULTS: The independent significant predictive risk factors in the 56 LR-4 observations that upgraded to LR-5 were mild-moderate T2 hyperintensity (P < 0.001; hazard ratio = 1.84), growth (P < 0.001; hazard ratio = 3.71), and hepatitis C infection (P = 0.02; hazard ratio = 1.69). The overall 6-month cumulative risk of upgrade was 32.7%. The 6-month cumulative risk rate was significantly higher in the presence of T2 hyperintensity (P = 0.03; 48.1% vs. 25.4%). CONCLUSION: For LR-4 observations, mild-moderate T2 hyperintensity, threshold growth, and hepatitis C infection are associated with significantly higher risk of upgrade to LR-5. Although mild-moderate T2 hyperintensity was the most useful risk factor for predicting upgrade, actual risk level was only mildly elevated, and the risk of upgrade associated with LR-4 observations is similar across subtypes. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 5 J. MAGN. RESON. IMAGING 2017;46:783-792.

Enhancement of abdominal structures on MRI at 1.5 and 3 T: a retrospective intraindividual crossover comparison.

OBJECTIVE: To quantitatively compare the extent of enhancement of abdominal structures on MRI in an intraindividual fashion at 1.5 and 3 T. METHODS: HIPAA-compliant, retrospective, longitudinal, intraindividual, crossover study, with waived informed consent, of consecutive individuals scanned at both 1.5 and 3 T closed-bore magnets using gadobenate dimeglumine during different phases of enhancement at tightly controlled arterial phase timing. Quantitative ROI measurements and qualitative sub-phase arterial phase assignments were independently performed by two radiologists. Qualitative discrepancies were resolved by a senior radiologist. RESULTS: Final population included 60 patients [41 female and 19 male; age, 49.35 ± 18.31 years (range 16-81); weight, 78.88 ± 20.3 kg (range 44.5-136)]. Similar enhancement peak patterns were noted at both field strengths. Interobserver agreement of quantitative evaluations was substantial. Significantly higher amplitudes of enhancement peaks were noted for all abdominal solid organs during all phases at 3 T, except for the pancreas (p = 0.17-0.30). Significantly higher amplitudes of enhancement peaks of the abdominal aorta at 1.5 T were noted. CONCLUSION: Similar peak patterns of enhancement for abdominal structures were observed at 1.5 and 3 T, with solid abdominal organs showing a higher percentage enhancement at 3 T, while unexpectedly higher aortic higher percentage enhancement was observed at 1.5 T. KEY POINTS: • Similar enhancement peak patterns at both field strengths for studied abdominal structures. • Significantly higher percentage enhancement of most abdominal organs at 3 T. • Non-statistically significant trend of higher pancreatic percentage enhancement at 3 T. • Significantly lower abdominal aortic percentage enhancement at 3 T.

Signal intensity change on unenhanced T1-weighted images in dentate nucleus following gadobenate dimeglumine in patients with and without previous multiple administrations of gadodiamide.

OBJECTIVES: To evaluate the impact of previous administration of gadodiamide and neural tissue gadolinium deposition in patients who received gadobenate dimeglumine. METHODS: Our population included 62 patients who underwent at least three administrations of gadobenate dimeglumine, plus an additional contrast-enhanced last MRI for reference, divided into two groups: group 1, patients who in addition to gadobenate dimeglumine administrations had prior exposure to multiple doses of gadodiamide; group 2, patients without previous exposure to other gadolinium-based contrast agent (GBCAs). Quantitative analysis was performed on the first and last gadobenate dimeglumine MRIs in both groups. Dentate nucleus-to-middle cerebellar peduncle signal intensity ratios (DN/MCP) and relative change (RC) in signal over time were calculated and compared between groups using generalized additive model. RESULTS: Group 1 showed significant increase in baseline and follow-up DN/MCP compared to group 2 (p < 0.0001). The RC DN/MCP showed a non-statistically significant trend towards an increase in patients who underwent previous gadodiamide (p = 0.0735). CONCLUSION: There is increased T1 signal change over time in patients who underwent gadobenate dimeglumine and had received prior gadodiamide compared to those without known exposure to previous gadodiamide. A potentiating effect from prior gadodiamide on subsequent administered gadobenate dimeglumine may occur. KEY POINTS: • Neural gadolinium deposition is associated with multiple administrations of less stable GBCAs. • Less stable GBCA effect on subsequent more stable GBCA administrations is undetermined. • Significant increase of DN/MCP was seen in patients with previous gadodiamide exposure. • RC DN/MCP showed a non-significant increase in patients who received previous gadodiamide. • Potentiating effects from prior gadodiamide on subsequent administered gadobenate dimeglumine may occur.

Gadolinium in Humans: A Family of Disorders.

OBJECTIVE: The literature informs us that gadolinium can cause health issues. At least four major gadolinium disorders, including the two well-recognized nephrogenic systemic fibrosis and severe acute adverse event, have been identified. CONCLUSION: We propose naming the histopathologically proven presence of gadolinium in brain tissue "gadolinium storage condition," and we describe a new entity that represents symptomatic deposition of gadolinium in individuals with normal renal function, for which we propose the designation "gadolinium deposition disease."

Bone Metastases of Hepatocellular Carcinoma: Appearance on MRI Using a Standard Abdominal Protocol.

OBJECTIVE: The purpose of this study is to describe the MRI features of hepatocellular carcinoma (HCC) bone metastases. MATERIALS AND METHODS: Thirty-three consecutive patients were included. Two radiologists performed qualitative and quantitative analysis. The coordinator searched for clinical and epidemiologic features related to patients and their primary liver tumors. Earlier MRI studies were also reviewed to determine whether bone metastases were already present and prospectively identified. Descriptive statistics and the Lin concordance correlation coefficient were used. RESULTS: Chronic hepatitis C virus infection was the most common cause of liver disease (20/32; 62.5%), and diffuse and multifocal HCC were the most frequent types of liver HCCs (28/33; 84.8%). Most lesions were located at the spine (109/155; 70.3%), with high signal intensity on fat-suppressed T1-weighted (54/62; 87.1%) and T2-weighted (53/62; 85.5%) images. Bone metastases were predominantly nodular (48/62; 77.4%), confined to the vertebral body (40/60; 66.7%), and best visualized at the arterial phase (40/62; 64.5%). The ring pattern of enhancement was present in 23 of 62 lesions, and the remaining lesions showed diffuse enhancement. Thirty-five of 62 (56.4%) bone metastases showed arterial peak of enhancement. In 13 of 33 (39.9%) patients, bone metastases were not prospectively reported. CONCLUSION: Most patients with bone metastases had chronic hepatitis C virus infection and diffuse or multifocal HCC. Metastases are most commonly appreciated as hypervascular focal moderately intensely enhancing nodular masses on the hepatic arterial dominant phase images, with concomitant moderately high signal intensity on fat-suppressed T1- and T2-weighted images.

Surrogate arterial phase imaging using a long duration (≈1.5 min) radial acquisition T1-weighted sequence: an alternative in patients unable to breath-hold.

BACKGROUND: Pediatric and adult patients unable to suspend respiration generally undergo magnetic resonance (MR) examinations that lack arterial phase imaging, which is a phase that provides substantial information on disease processes. An MR strategy that provides this type of information may be of considerable value. PURPOSE: To describe and assess the feasibility and enhancement quality of early-phase imaging utilizing long-duration radial 3D-GRE imaging by initiating the sequence prior to starting contrast injection. MATERIAL AND METHODS: Thirty-three consecutive patients (10 men, 23 women; 50.7 ± 25.5 years) underwent free-breathing gadolinium-enhanced radial 3D-GRE, with sequence initiation 30 s prior to contrast injection. Late hepatic arterial (LHA) phase was chosen for comparison. Images were evaluated for enhancement and overall image quality. Organ enhancement was calculated. Sub-group analysis was performed. RESULTS: Twenty-two examinations of radial 3D-GRE sequences were acquired during the LHA phase. Organ enhancement scores were of satisfactory to good quality (range, 3.32-3.82). There was a significant trend of superior overall enhancement quality scores in pediatrics and examinations performed at 3 T (P = 0.0225 and 0.0001, respectively). CONCLUSION: Arterial phase abdominal MR imaging is feasible using conventional radial 3D-GRE by adopting this simplistic proposed approach, which may allow arterial-phase imaging in patients unable to breath-hold.

Radiologist income, receipts, and academic performance: an analysis of many nations.

Background Considerable interest exists in comparison between healthcare systems across multiple countries, especially where cost enters the discussion. Purpose To evaluate the relationship between radiologists' income, receipts for studies, and academic performance across multiple countries. Material and Methods The annual income of radiologists and receipts for computed tomography (CT) and magnetic resonance imaging (MRI) were obtained based on a survey sent to expert radiologists practicing in 23 countries of varying developmental status. Articles published in generalist radiology journals determined the academic performance of each country. Results Among the developed countries, Canada has the highest estimated annual income for both private ($700,000/year) and university radiologists ($600,000/year) while Spain has the lowest income for private practice ($68,000/year) and Portugal has the lowest income for university practice ($57,300/year). Among the developing countries, Saudi Arabia has the highest incomes for both private ($210,000/year) and university ($140,000/year) radiologists and Vietnam has the lowest incomes for both private ($30,000/year) and university ($6,000/year) radiologists. Total receipts for CT and MRI studies ranged from $80/study (Portugal) to $1000/study (USA) in developed countries, and ranged from $30/study (Egypt) to $700/study (Saudi Arabia) in developing countries. A moderate correlation ( r = 0.482) was seen between radiologist's income and the receipts for combined practice in all countries. The radiology journal academic quotient was highest in The Netherlands among developed countries, and Turkey among developing countries. Conclusion A relatively broad range of radiologists' income is observed among developed and developing countries, which shows correlation with the receipts for advanced imaging studies. Countries with an acceptable compromise between income, receipts, and academic performance, may be the best models for other countries to emulate.

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.

Magnetic resonance imaging of acute appendicitis in pregnancy: a 5-year multiinstitutional study.

OBJECTIVE: The purpose of this study was to determine the diagnostic performance of magnetic resonance imaging (MRI) in the diagnosis of acute appendicitis during pregnancy in a multiinstitutional study. STUDY DESIGN: In this multicenter retrospective study, the cases of pregnant women who underwent MRI evaluation of abdominal or pelvic pain and who had clinical suspicion of acute appendicitis between June 1, 2009, and July 31, 2014, were reviewed. All MRI examinations with positive findings for acute appendicitis were confirmed with surgical pathologic information. Sensitivity, specificity, negative predictive values, and positive predictive values were calculated. Receiver operating characteristic curves were generated, and area under the curve analysis was performed for each participating institution. RESULTS: Of the cases that were evaluated, 9.3% (66/709) had MRI findings of acute appendicitis. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive values were 96.8%, 99.2%, 99.0%, 92.4%, and 99.7%, respectively. There was no statistically significant difference between centers that were included in the study (pair-wise probability values ranged from 0.12-0.99). CONCLUSION: MRI is useful and reproducible in the diagnosis of suspected acute appendicitis during pregnancy.

High-resolution 3D-GRE imaging of the abdomen using controlled aliasing acceleration technique - a feasibility study.

OBJECTIVES: To assess the feasibility of high-resolution 3D-gradient-recalled echo (GRE) fat-suppressed T1-weighted images using controlled aliasing acceleration technique (CAIPIRINHA-VIBE), and compare image quality and lesion detection to standard-resolution 3D-GRE images using conventional acceleration technique (GRAPPA-VIBE). MATERIALS AND METHODS: Eighty-four patients (41 males, 43 females; age range: 14-90 years, 58.8 ± 15.6 years) underwent abdominal MRI at 1.5 T with CAIPIRINHA-VIBE [spatial resolution, 0.76 ± 0.04 mm] and GRAPPA-VIBE [spatial resolution, 1.17 ± 0.14 mm]. Two readers independently reviewed image quality, presence of artefacts, lesion conspicuity, and lesion detection. Kappa statistic was used to assess interobserver agreement. Wilcoxon signed-rank test was used for image qualitative pairwise comparisons. Logistic regression with post-hoc testing was used to evaluate statistical significance of lesions evaluation. RESULTS: Interobserver agreement ranged between 0.45-0.93. Pre-contrast CAIPIRINHA-VIBE showed significantly (p < 0.001) sharper images and lesion conspicuity with decreased residual aliasing, but more noise enhancement and inferior image quality. Post-contrast CAIPIRINHA-VIBE showed significantly (p < 0.001) sharper images and higher lesion conspicuity, with less respiratory motion and residual aliasing artefacts. Inferior fat-suppression was noticeable on CAIPIRINHA-VIBE sequences (p < 0.001). CONCLUSION: High in-plane resolution abdominal 3D-GRE fat-suppressed T1-weighted imaging using controlled-aliasing acceleration technique is feasible and yields sharper images compared to standard-resolution images using standard acceleration, with higher post-contrast image quality and trend for improved hepatic lesions detection. KEY POINTS: • High-resolution imaging of the upper abdomen is clinically feasible using 2D-controlled aliasing acceleration technique. • High-resolution imaging yields significantly sharper images and increased hepatic lesions conspicuity. • High-resolution imaging yields significantly less respiratory motion and residual aliasing artefacts. • Controlled-aliasing offers substantial acquisition-time reduction in patients with breath-holding difficulties.

Accuracy of MRI skeletal age estimation for subjects 12-19. Potential use for subjects of unknown age.

INTRODUCTION: In forensic practice, there is a growing need for accurate methods of age estimation, especially in the cases of young individuals of unknown age. Age can be estimated through somatic features that are universally considered associated with chronological age. Unfortunately, these features do not always coincide with the real chronological age: for these reasons that age determination is often very difficult. Our aim is to evaluate accuracy of skeletal age estimation using Tomei's MRI method in subjects between 12 and 19 years old for forensic purposes. MATERIAL AND METHODS: Two investigators analyzed MRI images of the left hand and wrist of 77 male and 74 female caucasian subjects, without chronic diseases or developmental disorders, whose age ranged from 12 to 19 years. Skeletal maturation was determined by two operators, who analyzed all MRI images separately, in blinded fashion to the chronological age. Inter-rater agreement was measured with Pearson (R (2)) coefficient. One of the examiners repeated the evaluation after 6 months, and intraobserver variation was analyzed. Bland-Altman plots were used to determine mean differences between skeletal and chronological age. RESULTS: Inter-rater agreement Pearson coefficient showed a good linear correlation, respectively, 0.98 and 0.97 in males and females. Bland-Altman analysis demonstrated that the differences between chronological and skeletal age are not significant. Spearman's correlation coefficient showed good correlation between skeletal and chronological age both in females (R (2) = 0.96) and in males (R (2) = 0.94). CONCLUSIONS: Our results show that MRI skeletal age is a reproducible method and has good correlation with chronological age.

Prospective Cohort Study of Nephrogenic Systemic Fibrosis in Patients With Stage 3-5 Chronic Kidney Disease Undergoing MRI With Injected Gadobenate Dimeglumine or Gadoteridol.

OBJECTIVE: The purpose of this study was to determine the incidence of nephrogenic systemic fibrosis (NSF) in patients with chronic kidney disease (CKD) and moderate-to-severe impairment of kidney function who had not previously been exposed to gadolinium-based contrast agents (GBCAs) or referred to undergo contrast-enhanced MRI with gadobenate dimeglumine or gadoteridol. SUBJECTS AND METHODS: Two multicenter prospective cohort studies evaluated the incidence of unconfounded NSF in patients with stage 3 CKD (estimated glomerular filtration rate [eGFR] in cohort 1, 30-59 mL/min/1.73 m(2)) or stage 4 or 5 CKD (eGFR in cohort 2, < 30 mL/min/1.73 m(2)) after injection of gadobenate dimeglumine (study A) or gadoteridol (study B). A third study (study C) determined the incidence of NSF in patients with stage 4 or 5 CKD who had not received a GBCA in the 10 years before enrollment. Monitoring for signs and symptoms suggestive of NSF was performed via telephone at 1, 3, 6, and 18 months, with clinic visits occurring at 1 and 2 years. RESULTS: For studies A and B, the populations evaluated for NSF comprised 363 and 171 patients, respectively, with 318 and 159 patients in cohort 1 of each study, respectively, and with 45 and 12 patients in cohort 2, respectively. No signs or symptoms of NSF were reported or detected during the 2 years of patient monitoring. Likewise, no cases of NSF were reported for any of the 405 subjects enrolled in study C. CONCLUSION: To our knowledge, and consistent with reports in the literature, no association of gadobenate dimeglumine or gadoteridol with unconfounded cases of NSF has yet been established. Study data confirm that both gadoteridol and gadobenate dimeglumine properly belong to the class of GBCAs considered to be associated with the lowest risk of NSF.

Inter- and intra-individual comparative study of two gadolinium-based agents: A pilot study.

PURPOSE: The aim of the study was to evaluate the acute adverse events rate and enhancement properties of gadoterate meglumine (Dotarem(®)) and gadobenate dimeglumine (MultiHance(®)) in a small-scale controlled double-blinded study, using inter- and intra-individual comparisons. MATERIALS AND METHODS: Forty-one randomly selected patients were scanned with Dotarem(®). The rate of adverse reactions, qualitative and quantitative image evaluation was performed vs. a control group of 46 patients who underwent MultiHance(®) over the same 1-month time period (population 1), and 27 patients who underwent both Dotarem(®) and MultiHance(®)-enhanced body MRI studies within an 18-month period (population 2). Data were subjected to statistical analysis. RESULTS: Only 1 mild acute adverse event (vomiting) was observed in population 1 (with Dotarem(®)). Blinded assessment of image quality was good for both agents in all patients. Population 1 showed significantly higher liver percentage enhancement with MultiHance(®) (p < 0.0001). There was a trend to higher pancreas-to-liver enhancement with Dotarem(®), significant in population 2 (p = 0.0333). CONCLUSION: This small-scale multi-blinded study characterizes a strategy to objectively assess intravenous contrast agents, which may be an ideal method to evaluate whether a new contrast agent should be introduced for clinical use at any institution, and to re-evaluate the agent in standard use. Whenever available, intra-individual assessment may be ideal.

MR-PET evaluation of 1-month post-ablation therapy for hepatocellular carcinoma: preliminary observations.

PURPOSE: The purpose of the study was to evaluate the feasibility and protocol optimization of whole-body hybrid MR-PET system performed 1-month after post-locoregional thermoablative procedures for hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: Eight patients (6 men and 2 women; mean age, 56.6 ± 5.5 years) with 9 ablated HCCs constituted our study population. Three readers interpreted the studies to determine the presence or absence of residual malignancy. Two readers independently assessed the fused MR-PET images to compare registration accuracy of two types of T2-weighted (triggered T2 half-Fourier acquisition single-shot turbo spin-echo and turbo spin-echo) and T1-weighted [Cartesian and radial 3D gradient echo (GRE)]. Image quality evaluation of both 3D-GRE T1-weighted sequences was evaluated. Kappa statistics were used to measure inter-observer agreement. Non-parametric Kruskal-Wallis and Wilcoxon signed-rank tests were used for qualitative data analysis. RESULTS: Definite residual tumor was observed in 3/9 ablations; two were PET positive. All residual tumors were isovascular on MRI. Radial 3D-GRE demonstrated significantly superior MR-PET subjective co-registration in comparison with the remaining sequences and showed a non-significant trend toward higher image quality scores than Cartesian GRE. CONCLUSION: Whole-body hybrid MR-PET is feasible as a part of 1-month follow-up post-locoregional thermoablative treatment for HCC. Radial 3D-GRE offers improved co-registration with PET data, with overall good image quality.

MR-PET co-registration in upper abdominal imaging: quantitative comparison of two different T1-weighted gradient echo sequences: initial observations.

PURPOSE: The purpose of this study is to quantitatively compare the accuracy of spatial registration of Cartesian breath-hold 3D-GRE and non-respiratory-triggered free-breathing radial 3D-GRE images with PET data acquisition on whole-body hybrid MR-PET system. MATERIALS AND METHODS: Eight patients (six men and two women; mean age, 56.6 ± 5.5 years) with nine ablated hepatocellular carcinomas constituted our study population. Spatial coordinates (x, y, z) of the estimated isocenters of the ablated areas were independently determined by two radiologists. Both T1-weighted sequences were performed in the axial plane. Distance between the isocenter of the lesion on PET images and on both T1-weighted images was measured, and misregistration was calculated. Statistical analysis was performed using Student t test. RESULTS: Misalignment values of the hepatic ablation zones between PET and MR images were calculated at 4.94 ± 1.35 mm (reader 1) and 4.89 ± 2.21 mm (reader 2) for Cartesian 3D-GRE sequence, and 2.48 ± 0.65 mm (reader 1) and 2.72 ± 0.44 mm (reader 2) for the radial 3D-GRE sequence, with p values of 0.0011 and 0.0133, respectively. CONCLUSION: Radial 3D-GRE offers improved registration accuracy with PET, supporting the use of this T1-weighted sequence in upper abdominal MR-PET studies.

Value of MRI of the hand and the wrist in evaluation of bone age: preliminary results.

PURPOSE: To evaluate bone age determination using MRI of the hand and wrist. MATERIALS AND METHODS: A total of 179 (78 female and 101 males, 11 to 16 years old) subjects of 252 normal volunteers met entrance criteria. A low field open magnet (0.2 Tesla) was used for this study; coronal T1-weighted images with a slice thickness of 1.3mm were acquired. Two blinded radiologists evaluated the studies and the following elements were considered: the appearance of cartilage, vacuolization of cartilage, provisional calcification, progression of ossification, and complete ossification. Correlation between chronologic age and MR bone age was determined by means of simple linear regression analysis. RESULTS: Strong correlation between MR skeletal age and chronological age was observed for both investigators, Pearson correlation R2 = 0.9 for each. CONCLUSION: Determination of bone age with MRI is feasible and shows good interobserver reproducibility. Data from this study may be useful to develop an atlas of skeletal development and bone age.

Combined chemical shift imaging with early dynamic serial gadolinium-enhanced MRI in the characterization of adrenal lesions.

OBJECTIVE: The purpose of this study was to retrospectively evaluate early dynamic serial gadolinium-enhanced and chemical-shift imaging (CSI) MRI to distinguish benign from malignant adrenal tumors. MATERIALS AND METHODS: Between July 2007 and December 2011, 205 patients with 239 adrenal lesions (177 adenomas, 54 metastases, 5 pheochromocytomas, and 3 adrenal cortical carcinomas) underwent early dynamic serial gadolinium-enhanced MRI and CSI. CSI was assessed qualitatively and by calculating the adrenal index, and enhancement patterns were evaluated qualitatively and quantitatively. Statistical analyses were performed. RESULTS: Most adenomas exhibited either an arterial blush or homogeneous enhancement, whereas most metastases showed early peripheral or heterogeneous enhancement. Visualization of higher enhancement on arterial and venous phases enabled differentiation of adenomas from metastases in most cases. Moderate to high signal intensity drop on CSI was seen in 95.4% of adenomas and 14.8% of metastases. In lesions with this level of signal intensity drop, 87 of 88 lesions with a capillary blush were adenomas. Early dynamic serial imaging alone was a significant (p < 0.0001) indicator of nonadenoma (area under the curve [AUC], 0.912) with optimal sensitivity of 81% and specificity of 93% for differentiating adenomas from nonadenomas. Combined analysis (CSI and early dynamic serial imaging) was also significant (p < 0.0001 and p=0.0014, respectively) for diagnosing nonadenomas (AUC, 0.983) with optimal sensitivity of 94% and specificity of 98%. CONCLUSION: Early dynamic serial gadolinium-enhanced MRI aids in characterization of adrenal tumors, especially lesions that are categorized as indeterminate on the basis of CSI.

Perilesional enhancement of liver cavernous hemangiomas in magnetic resonance imaging.

OBJECTIVE: To evaluate on magnetic resonance imaging (MRI) the occurrence rate of temporal perilesional parenchymal enhancement (PPE) associated with hepatic hemangiomas in a large consecutive series and to determine which aspects are associated with this observation. MATERIALS AND METHODS: Institutional review board approved this retrospective study. A computerized search of the MRI database was performed for consecutive patients between January 2008 and January 2012. The study population included 513 liver hemangiomas in 224 patients (104 males and 120 females; mean age of 55.2 ± 13.5 years; age range 24-89 years). Two readers independently reviewed the frequency of PPE, size, speed of enhancement and location of each hemangioma. Marginal models with generalized estimating equation were used. Wald test was applied to verify if the model coefficients were significant. RESULTS: 80/513 (15.6%) hemangiomas showed PPE. The incidence of PPE was significantly higher (p < 0.05) in hemangiomas with Type1 speed of enhancement (51/80, 63.8%) than in those with Type2 or Type3. 66/80 (82.5%) hemangiomas with PPE were subcapsular (p < 0.05). Conversely, the majority (280/433, 64.7%) of hemangiomas without PPE were deep in location (p < 0.001). Lesser proportion of hemangiomas with PPE was located in segment IVa (p < 0.05). CONCLUSION: PPE is not uncommonly seen along with hepatic hemangiomas. This appearance is most frequently observed in rapidly enhancing small lesions with a subcapsular location.