Assessment of Fat Fractions in the Tongue, Soft Palate, Pharyngeal Wall, and Parapharyngeal Fat Pad by the GOOSE and DIXON Methods.

Objective: The 2-point DIXON method is widely used to assess fat fractions (FFs) in magnetic resonance images (MRIs) of the tongue, pharyngeal wall, and surrounding tissues in patients with obstructive sleep apnea (OSA). However, the method is semiquantitative and is susceptible to B0 field inhomogeneities and R2* confounding factors. Using the method, although several studies have shown that patients with OSA have increased fat deposition around the pharyngeal cavity, conflicting findings was also reported in 1 study.

Imaging Modalities for Early Detection of Pancreatic Cancer: Current State and Future Research Opportunities.

Pancreatic cancer, one of the most lethal malignancies, is increasing in incidence. While survival rates for many cancers have improved dramatically over the last 20 years, people with pancreatic cancer have persistently poor outcomes. Potential cure for pancreatic cancer involves surgical resection and adjuvant therapy.

Free-breathing radial magnetic resonance elastography of the liver in children at 3 T: a pilot study.

Background: Magnetic resonance (MR) elastography of the liver measures hepatic stiffness, which correlates with the histopathological staging of liver fibrosis. Conventional Cartesian gradient-echo (GRE) MR elastography requires breath-holding, which is challenging for children. Non-Cartesian radial free-breathing MR elastography is a potential solution to this problem.

Haemorrhage and Calcification on Susceptibility-Weighted Imaging : A Quick and Reliable Qualitative Technique for Differentiating Lesions with Ambiguous Phase.

Purpose: Haemorrhage and calcification can be qualitatively distinguished on susceptibility-weighted imaging (SWI) using phase information, but it is unclear how to make this distinction in a subset of lesions with ambiguous phase, containing a mixture of positive and negative values. This work investigates the validity of qualitative phase assessment at the cranial or caudal margins in classifying such lesions as haemorrhagic or calcific, when quantitative susceptibility mapping is not available to the neuroradiologist.

Methods: In a retrospective review of magnetic resonance imaging examinations acquired between July 2015 and November 2019, 87 lesions with ambiguous phase which could be confidently determined to be haemorrhagic or calcific were identified.

Hepatic Iron Quantification Using a Free-Breathing 3D Radial Gradient Echo Technique and Validation With a 2D Biopsy-Calibrated R Relaxometry Method.

Background: Hepatic iron content (HIC) is an important parameter for the management of iron overload. Non-invasive HIC assessment is often performed using biopsy-calibrated two-dimensional breath-hold Cartesian gradient echo (2D BH GRE) R -MRI. However, breath-holding is not possible in most pediatric patients or those with respiratory problems, and three-dimensional free-breathing radial GRE (3D FB rGRE) has emerged as a viable alternative.

Quantitative Susceptibility Mapping Using a Multispectral Autoregressive Moving Average Model to Assess Hepatic Iron Overload.

Background: R2*-MRI is clinically used to noninvasively assess hepatic iron content (HIC) to guide potential iron chelation therapy. However, coexisting pathologies, such as fibrosis and steatosis, affect R2* measurements and may thus confound HIC estimations.

Purpose: To evaluate whether a multispectral auto regressive moving average (ARMA) model can be used in conjunction with quantitative susceptibility mapping (QSM) to measure magnetic susceptibility as a confounder-free predictor of HIC.

Cerebral microbleeds in adult survivors of childhood acute lymphoblastic leukemia treated with cranial radiation.

Cranial radiation therapy is associated with white matter-specific brain injury, cortical volume loss, mineralization, microangiopathy and neurocognitive impairment in survivors of childhood acute lymphoblastic leukemia. In this retrospective cross-sectional analysis, neurocognitive testing and 3 T brain MRI's were obtained in 101 survivors treated with cranial radiation. Small focal intracerebral hemorrhages only visible on exquisitely sensitive MRI sequences were identified and localized using susceptibility weighted imaging.

and Liver Iron Content in Children with Sickle Cell Anemia and Iron Overload.

Chronic blood transfusions in patients with sickle cell anemia (SCA) cause iron overload, which occurs with a degree of interpatient variability in serum ferritin and liver iron content (LIC). Reasons for this variability are unclear and may be influenced by genes that regulate iron metabolism. We evaluated the association of the copy number of the glutathione S-transferase M1 () gene and degree of iron overload among patients with SCA.

Autoregressive moving average modeling for hepatic iron quantification in the presence of fat.

Background: Measuring hepatic R2* by fitting a monoexponential model to the signal decay of a multigradient-echo (mGRE) sequence noninvasively determines hepatic iron content (HIC). Concurrent hepatic steatosis introduces signal oscillations and confounds R2* quantification with standard monoexponential models.

Purpose: To evaluate an autoregressive moving average (ARMA) model for accurate quantification of HIC in the presence of fat using biopsy as the reference.

Ultrashort echo time imaging for quantification of hepatic iron overload: Comparison of acquisition and fitting methods via simulations, phantoms, and in vivo data.

Background: Current R2*-MRI techniques for measuring hepatic iron content (HIC) use various acquisition types and fitting models.

Purpose: To evaluate the accuracy and precision of R2*-HIC acquisition and fitting methods.

Study Type: Signal simulations, phantom study, and prospective in vivo cohort.

Fast quantitative parameter maps without fitting: Integration yields accurate mono-exponential signal decay rates.

Purpose: To develop a computationally fast and accurate algorithm for mono-exponential signal modelling and validate the new technique in the context of R2* mapping for iron overload assessment.

Methods: An algorithm is introduced that directly calculates R2* values from a series of images based on integration of the mono-exponential signal decay curve. The algorithm is fast, because fitting is avoided and only arithmetic computations without iterations are applied.

Automated vessel exclusion technique for quantitative assessment of hepatic iron overload by R2*-MRI.

Background: Extraction of liver parenchyma is an important step in the evaluation of R2*-based hepatic iron content (HIC). Traditionally, this is performed by radiologists via whole-liver contouring and T2*-thresholding to exclude hepatic vessels. However, the vessel exclusion process is iterative, time-consuming, and susceptible to interreviewer variability.

Removal of Arterial Vessel Contributions in Susceptibility-Weighted Images for Quantification of Normalized Visible Venous Volume in Children with Sickle Cell Disease.

Purpose: To evaluate a new postprocessing framework that eliminates arterial vessel signal contributions in the quantification of normalized visible venous volume (NVVV, a ratio between venous and brain volume) in susceptibility-weighted imaging (SWI) exams in patients with sickle cell disease (SCD).

Materials And Methods: We conducted a retrospective study and qualitatively reviewed for hypointense arterial vessel contamination in SWI exams from 21 children with SCD. We developed a postprocessing framework using magnetic resonance angiography in combination with SWI to provide a more accurate quantification of NVVV.

Removal of Arterial Vessel Contributions in Susceptibility-Weighted Images for Quantification of Normalized Visible Venous Volume in Children with Sickle Cell Disease.

Purpose: To evaluate a new postprocessing framework that eliminates arterial vessel signal contributions in the quantification of normalized visible venous volume (NVVV, a ratio between venous and brain volume) in susceptibility-weighted imaging (SWI) exams in patients with sickle cell disease (SCD).

Materials And Methods: We conducted a retrospective study and qualitatively reviewed for hypointense arterial vessel contamination in SWI exams from 21 children with SCD. We developed a postprocessing framework using magnetic resonance angiography in combination with SWI to provide a more accurate quantification of NVVV.

Radial Ultrashort TE Imaging Removes the Need for Breath-Holding in Hepatic Iron Overload Quantification by R2* MRI.

Objective: The objective of this study is to evaluate radial free-breathing (FB) multiecho ultrashort TE (UTE) imaging as an alternative to Cartesian FB multiecho gradient-recalled echo (GRE) imaging for quantitative assessment of hepatic iron content (HIC) in sedated patients and subjects unable to perform breath-hold (BH) maneuvers.

Materials And Methods: FB multiecho GRE imaging and FB multiecho UTE imaging were conducted for 46 test group patients with iron overload who could not complete BH maneuvers (38 patients were sedated, and eight were not sedated) and 16 control patients who could complete BH maneuvers. Control patients also underwent standard BH multiecho GRE imaging.

Quantitative ultrashort echo time imaging for assessment of massive iron overload at 1.5 and 3 Tesla.

Purpose: Hepatic iron content (HIC) quantification via transverse relaxation rate (R2*)-MRI using multi-gradient echo (mGRE) imaging is compromised toward high HIC or at higher fields due to the rapid signal decay. Our study aims at presenting an optimized 2D ultrashort echo time (UTE) sequence for R2* quantification to overcome these limitations.

Methods: Two-dimensional UTE imaging was realized via half-pulse excitation and radial center-out sampling.

Can multi-slice or navigator-gated R2* MRI replace single-slice breath-hold acquisition for hepatic iron quantification?

Background: Liver R2* values calculated from multi-gradient echo (mGRE) magnetic resonance images (MRI) are strongly correlated with hepatic iron concentration (HIC) as shown in several independently derived biopsy calibration studies. These calibrations were established for axial single-slice breath-hold imaging at the location of the portal vein. Scanning in multi-slice mode makes the exam more efficient, since whole-liver coverage can be achieved with two breath-holds and the optimal slice can be selected afterward.

Paired self-compensated spin-lock preparation for improved T1ρ quantification.

Purpose: Spin-lock (SL) imaging allows quantification of the spin-lattice relaxation time in the rotating frame (T1ρ). B0 and B1 inhomogeneities impact T1ρ quantification because the preparatory block in SL imaging is sensitive to the field heterogeneities. Here, a modified preparatory block (PSC-SL) is proposed that attempts to alleviate SL sensitivity to field inhomogeneities in scenarios where existing approaches fail, i.

Measurement of glomerular filtration rate by dynamic contrast-enhanced magnetic resonance imaging using a subject-specific two-compartment model.

Measuring glomerular filtration rate (GFR) by dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) as part of standard of care clinicalMRIexams (e.g., in pediatric solid tumor patients) has the potential to reduce diagnostic burden.

Does fat suppression via chemically selective saturation affect R2*-MRI for transfusional iron overload assessment? A clinical evaluation at 1.5T and 3T.

Purpose: Fat suppression (FS) via chemically selective saturation (CHESS) eliminates fat-water oscillations in multiecho gradient echo (mGRE) R2*-MRI. However, for increasing R2* values as seen with increasing liver iron content (LIC), the water signal spectrally overlaps with the CHESS band, which may alter R2*. We investigated the effect of CHESS on R2* and developed a heuristic correction for the observed CHESS-induced R2* changes.

Incidental detection of late subsequent intracranial neoplasms with magnetic resonance imaging among adult survivors of childhood cancer.

Purpose: Survivors of childhood cancer are at an increased risk of developing subsequent neoplasms. In long-term survivors of childhood malignancies treated with and without cranial radiation therapy (CRT), undergoing unenhanced magnetic resonance imaging (MRI) of the brain, we estimated detection of intracranial neoplasms.

Methods: To investigate neurocognitive outcomes, 219 survivors of childhood cancer underwent unenhanced screening MRI of the brain.

Evaluation of memory impairment in aging adult survivors of childhood acute lymphoblastic leukemia treated with cranial radiotherapy.

Background: Cranial radiotherapy (CRT) is a known risk factor for neurocognitive impairment in survivors of childhood cancer and may increase risk for mild cognitive impairment and dementia in adulthood.

Methods: We performed a cross-sectional evaluation of survivors of childhood acute lymphoblastic leukemia (ALL) treated with 18 Gy (n = 127) or 24 Gy (n = 138) CRT. Impairment (age-adjusted score >1 standard deviation below expected mean, two-sided exact binomial test) on the Wechsler Memory Scale IV (WMS-IV) was measured.

Automated T(2) * measurements using supplementary field mapping to assess cardiac iron content.

Purpose: To develop and evaluate an algorithm that automatically identifies high-susceptibility areas and excludes them from T(2) * measurements in the left ventricle (LV) for myocardial iron measurements.

Materials And Methods: An autoregressive moving average (ARMA) model was implemented on multigradient echo scans of 24 patients (age range 3-45 years, 10 male/14 female). Voxels with relatively high susceptibility (>3 Hz/mm) were flagged and deselected from the T(2) * calculations for iron quantification.