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The purpose of this study was to evaluate the potential utility of texture analysis of parametric apparent diffusion coefficient (ADC) maps in quantifying hepatic fibrosis. To this end, using ex vivo murine liver tissues from a dietary model of hepatic fibrosis, an array of texture analysis techniques, including histogram-based, gray-level co-occurrence matrix-based, and gray-level run-length-based features, was used to evaluate correlations with liver fibrosis. Moderate to very strong correlation between several of the texture-based features and both subjective as well as digital image analysis-based assessments of hepatic fibrosis was demonstrated. This rigorous study of texture analysis applied to parametric ADC maps in a liver fibrosis model study demonstrates and validates the potential utility of texture-based features for the noninvasive, quantitative assessment of hepatic fibrosis.

Objectives To test the hypothesis that higher blood levels of neurotrophic proteins (proteins that support neuronal survival and function) in the first 2 weeks of life are associated with a lower risk of cognitive impairment at 10 years. Study design We evaluated 812 10-year-old children with neonatal blood specimens enrolled in the multicenter prospective Extremely Low Gestational Age Newborn Study, assessing 22 blood proteins collected on 3 days over the first 2 weeks of life. Using latent profile analysis, we derived a cognitive function level based on standardized cognitive and executive function tests. We defined high exposure as the top quartile neurotrophic protein blood level on ≥2 days either for ≥4 proteins or for a specific cluster of neurotrophic proteins (defined by latent class analysis). Multinomial logistic regression analyzed associations between high exposures and cognitive impairment. Results Controlling for the effects of inflammatory proteins, persistently elevated blood levels of ≥4 neurotrophic proteins were associated with reduced risk of moderate (OR, 0.35; 95% CI, 0.18-0.67) and severe cognitive impairment (OR, 0.22; 95% CI, 0.09-0.53). Children with a cluster of elevated proteins including angiopoietin 1, brain-derived neurotrophic factor, and regulated upon activation, normal T-cell expressed, and secreted had a reduced risk of adverse cognitive outcomes (OR range, 0.31-0.6). The risk for moderate to severe cognitive impairment was least with 0-1 inflammatory and >4 neurotrophic proteins. Conclusions Persisting elevations of circulating neurotrophic proteins during the first 2 weeks of life are associated with lowered risk of impaired cognition at 10 years of age, controlling for increases in inflammatory proteins.

SummaryObjectiveAim was to compare volumetric and semi-quantitative (SQ) measurements of subchondral bone marrow lesions (BMLs) on non-fat-suppressed (FS) T1-weighted (w), T1-w FS contrast enhanced (CE) and proton density (PD)-w FS images in order to define which sequence depicts the lesions to their maximum extent and if T1-w FS CE images and PD-w FS images may be used interchangeably to assess BMLs in a volumetric or SQ fashion.DesignThirty-two patients with clinical knee osteoarthritis (OA) were scanned on a standard 1.5 T MRI system. A total of 47 BMLs were identified and were manually segmented on all three sequences. BMLs were also assessed semiquantitatively using the Whole Organ Magnetic Resonance Imaging Score (WORMS). The volumetric and SQ results were compared across the three imaging sequences using paired t-tests.ResultsEighty-three percent of the lesions appeared largest on the PD-w FS sequence. Significant differences were observed for volumetric measurements between all three sequences (P < 0.001), however the mean volume difference between PD-w FS and T1-w FS CE (38%) was much smaller than for non-FS T1-w and PD-w FS/T1-w FS CE sequences (195% and 114%, respectively). Significant differences in WORMS scores were noted between PD-w FS and non-FS T1-w images and between T1-w FS CE and non-FS T1-w images (P < 0.001), but no significant difference was observed between PD-w FS and T1-w FS CE images.ConclusionOur findings suggest that the T1-w FS CE and PD-w FS sequences may be interchangeably used for quantitative volumetric and SQ assessment of BMLs.

The objective of this study was to determine the T1, T2 and secular-T2 relaxo-volumetric brain aging patterns using multispectral quantitative magnetic resonance imaging, both globally and regionally, and covering an age range approaching the full human lifespan. Fifty-one subjects (28 males, 23 females; age range: 0.5-87 years) were studied consisting of 18 healthy volunteers and 33 patients. Patients were selected after carefully reviewing their radiology reports to have either normal-by-MRI findings (25 patient subjects) or small focal pathology less than 6 mm in size (eight patient subjects). All subjects were MR imaged at 1.5 T with the mixed turbo spin echo pulse sequence. The soft tissues inside the cranial vault, termed intracranial matter (ICM), were segmented using a dual-clustering segmentation algorithm. ICM segments were further divided into six subsegments: bilateral anterior cerebral, posterior cerebral and cerebellar subsegments. T1, T2 and secular-T2 relaxation time histograms of all segments were generated and modeled with Gaussian functions. For each segment, the volumes of white matter, gray matter and cerebrospinal fluid were calculated from the T1 histograms. The age-related tendencies of three quantitative MRI parameters (T1, T2 and secular-T2) and the fractional tissue volumes showed four distinct periods of life, specifically a maturation period (0-2 years), a development period (2-20 years), an adulthood period (20-60 years) and a senescence period (60 years and older). For all ages, the anterior cerebral subsegment exhibited consistently longer gray matter T1s and shorter white matter T1s than the posterior cerebral and cerebellar subsegments. Volumetric age-related changes of the cerebellar subsegment were more gradual than in the cerebral subsegments. This study shows that relaxometric and volumetric age-related changes are synchronized and define the same four periods of brain evolution both globally and regionally.

The combined T 1 , T 2 and secular- T 2 pixel frequency distributions of 24 adult human brains were studied in vivo using a technique based on the mixed-TSE pulse sequence, dual-space clustering segmentation and histogram gaussian decomposition. Pixel frequency histograms of whole brains and the four principal brain compartments were studied comparatively and as function of age. For white matter, the position of the T 1 peak correlates with age ( R 2 =.7868) when data are fitted to a quadratic polynomial. For gray matter, a weaker age correlation is found ( R 2 =.3687). T 2 and secular- T 2 results are indicative of a weaker correlation with age. The technique and preliminary results presented herein may be useful for characterizing normal as well as abnormal aging of the brain, and also for comparison with the results obtained with alternative quantitative MRI methodologies.

SUMMARY The mechanisms involved in the generation of motion artifacts in MR imaging are complex and depend both on the type and direction of motion as well as on the parameters of the imaging sequence chosen. The methods used to control or reduce motion artifacts are multiple and the appropriate method for use with any given clinical situation will depend on the particular hardware and software of the MR imaging unit, the patient's clinical status, and the specific organ or disease state to be imaged. Some general guidelines for clinical use that are applicable in most scenarios can be defined, although preferences for the different techniques vary. Appropriate T1-weighted images of the upper abdomen and liver can be obtained with breath-hold T1-weighted gradient echo. These images should be acquired with inferior–superior spatial presaturation pulses to reduce vascular pulsation artifact and ghosting. The application of GMN will depend on the individual MR imaging system. If sufficient coverage cannot be obtained with gradientecho imaging, then conventional T1-weighted images with phase-encoding reordering is suggested. The addition of spatial presaturation pulses (inferior-superior) may be valuable. The use of fat suppression will further improve image quality by reducing ghost artefact and improving CNR, although SNR will decrease. T2-weighted imaging of the upper abdomen will depend greatly on the hardware and software of the MR imaging unit. Recent techniques of breath-hold T2-weighted imaging require faster and stronger gradients, and may not be universally available. If available, these techniques provide excellent anatomic detail, although image contrast (e.g., liver to spleen) may decrease. Respiratory-triggered FSE techniques are the preferred method of imaging in most centers, because the imaging time is considerably less than conventional T2-weighted imaging whereas the image quality is improved. Liver lesion detection capability of the various techniques is still under study. The addition of fat suppression appears to improve image quality further with an increase in lesion detection. By understanding the principles underlying motion artifacts, one can choose the appropriate method of artifact control tailored for the individual clinical situation. In addition, the recognition of the variable appearances of motion artifacts will prevent interpretive errors and misdiagnoses. Careful attention to motion artifact reduction techniques can greatly improve patient care.

As there are limitations in WB-MR angiography, so there are limitations in BB-MR angiography. Vessel morphology is visualized by means of the innermost nonattenuated layer of tissue, which, under ideal conditions, coincides with the luminal surface of the vessel wall. Vessel morphology may be depicted inaccurately whenever a portion of the vessel wall is undetectable with the MR imaging technique used. In such cases, vessel segments with exaggerated lumen diameter may result at locations where tissues with either a very short T2 or a low proton density are present. Another phenomenon that could potentially degrade the accuracy of vessel depiction with BB techniques is the effect of slowly flowing blood near the vessel walls. Residual blood signal would result in apparent vessel narrowing. Preliminary clinical experience in the brain, however, suggests that this adverse effect is less prominent with a turbo-SE-based BB technique than with a TOF WB technique. BB-MR angiography data sets may also present image postprocessing difficulties arising from the isointensity between the vessels and other dark structures such as bones and air-filled cavities. A limitation that is more specific to hybrid-SE-based BB-MR pulse sequences, particularly for very high spatial resolution applications, stems from the comparatively high RF specific absorption rates that result from the intensive use of 180 degrees refocusing pulses. GRASE-based BB-MR techniques that generate a fraction of the RF energy constitute a promising alternative for very high spatial resolution applications. In summary, to be effective, a BB technique must produce strong signal attenuation from flowing spins, ideally to the level of the baseline noise. Simultaneously it should produce good depiction of tissues with the comparatively short T2s characteristic of vessel walls and muscle, hence the need to operate with the shortest possible TE. Finally, high spatial resolution combined with fast data acquisition are requisites for imaging small vessels in the presence of motion, such as the carotid arteries. The flow properties of BB-MR angiographic sequences that meet these criteria were reviewed for different anatomic locations.

Objectives To compare the prevalence of cognitive, neurologic, and behavioral outcomes at 10 years of age in 428 girls and 446 boys who were born extremely preterm. Study design A total of 889 of 966 eligible children previously enrolled in the multicenter Extremely Low Gestational Age Newborns Study from 2002-2004 were evaluated at 10 years of age. Children underwent a neuropsychological battery and testing for autism spectrum disorder (ASD), and parents reported on their child's behavior, development, and seizures. Results Of the children, 28% of boys and 21% of girls exhibited moderate to severe impairment on summary measures of cognitive abilities. Boys had a higher prevalence of impairment than girls in nearly all measures of cognition, were more than twice as likely to have microcephaly (15% in boys, 8% in girls), and require more often assistive devices to ambulate (6% in boys, 4% in girls). In contrast, boys and girls had comparable risk for a history of seizure (identified in 10% of the cohort) or epilepsy (identified in 7% of the cohort). The boy-to-girl ratio of ASD (9% in boys, 5% in girls) was lower than expected compared with the overall US autism population. Conclusions In this contemporary cohort of children born extremely premature and evaluated at school age, boys had higher prevalence of cognitive, neurologic, and behavioral deficits than girls. The ratio of boys to girls among those with ASD deserves further study as does the perinatal environmental-genetic interactions that might contribute to male preponderance of deficits in this high-risk sample.

Rationale and Objectives We studied preparatory strategies for high-resolution human eye in vivo imaging with commercially available magnets and coils. Materials and Methods We imaged normal volunteers on 1.5T systems by Philips, GE, and Siemens, using commercial ∼9 cm temporomandibular joint receive coils. Subjects fixated the nonimaged eye on a target. We compared signal (S) to tissue noise (N t ) and system noise (N s ) between images acquired with the imaged eye: 1) open, 2) held closed, 3) taped closed, and 4) taped closed with overlying water-soaked gauze. We standardized technique 4 to compare studies between manufacturers using T1-weighted parameters (repetition time/echo time/flip angle/number of signal averages = 400 ms/10–17ms/90°/4–6, in-plane resolution ∼250 × 250 μm 2 ; 2–3 mm slices, image time = 4.3–5.2 min). We obtained similar images of an enucleated human eye to estimate in vivo effects of microsaccades and ocular pulsations. Results Measurements of S/N t and S/N s gave surprising results of N t s in some instances. N s /N t was ≅ 1, varying ∼20%, when the eye was taped shut and covered with water-soaked gauze. T1-weighted spin echo sequences, using technique 4, produced high-quality images with good S/N t on all systems. Images from the three manufacturers were comparable when parameters were normalized for pulse repetition time, echo time, number of signal averages, bandwidth in Hz/pixel, and reconstruction matrix. Images of the enucleated eye produced S/N t ratios that were comparable to in vivo images in some structures. Conclusions Our best preparatory technique produced images with in-plane resolution of ∼250 μm in 4–5 minutes with three commercial 1.5T systems. The in vivo S/N t was comparable to in vitro values in most solid tissues but decreased in most fluid compartments.