Highlightsd 20 inpatient adults received ultra-processed and unprocessed diets for 14 days each d Diets were matched for presented calories, sugar, fat, fiber, and macronutrients d Ad libitum intake was 500 kcal/day more on the ultraprocessed versus unprocessed diet d Body weight changes were highly correlated with diet differences in energy intake

23Na MR imaging with short echo times can be used to quantify absolute tissue sodium concentration in patients with brain tumors and shows increased sodium concentration in tumors relative to that in normal brain structures.

A new fast method of measuring kinetic reaction rates for two-site chemical exchange is described. The method employs saturation transfer magnetic resonance spectroscopy (MRS) and acquisition of only four spectra under partially saturated, high signal-to-noise ratio (SNR) conditions. In two acquisitions one of the exchanging species is saturated; the other two employ a control saturation. Each pair of acquisitions is applied with two different flip angles, and the equilibrium magnetization, relaxation times, and reaction rates are calculated therefrom. This four-angle saturation transfer (FAST) method is validated theoretically using the Bloch equations modified for two-state chemical exchange. Potential errors in the rate measurements due to the effects of exchange are evaluated for creatine kinase (CK) metabolism modeled for skeletal and heart muscle, and are found to be <5% for forward CK flux rates of 0.05 ≤ k f ≤ 1.0 s Compromised energy metabolism and energy deprivation appear to play a central role in many disease states, including ischemic heart disease (1), heart failure (2), stroke and congenital myopathies (3). The creatine kinase (CK) reaction is important in cellular energy metabolism, reversibly transferring high-energy phosphate between adenosine triphosphate (ATP) and phosphocreatine (PCr):where k f and k r are the pseudo-first-order forward and reverse rate constants. Today, the endogenous, in vivo concentrations of PCr, ATP, and H ϩ (pH) can be measured noninvasively in humans at 1.5 T with phosphorus ( 31 P) magnetic resonance spectroscopy (MRS) (4 -6), and the total concentration of phosphorylated plus unphosphorylated creatine (CR ϭ PCr ϩ Cr) with proton ( 1 H) MRS of the N-methyl resonance (7-10). If the CK flux and rate constants k could also be measured noninvasively in humans, the chemical function of the CK reaction could be completely characterized, and its role in heart failure and other disease states directly assessed.In fact, measurements of CK reaction rates have long been possible in cells and isolated perfused animal organs placed in conventional MRS spectrometers using 31 P magnetization transfer techniques (11)(12)(13)(14), and by using surface MRS detector coils placed on or sutured to the organ of interest in otherwise intact animals (15-17). In the standard experiment, the ␥-phosphate resonance of ATP (␥-ATP) is saturated (or inverted) by chemical-selective irradiation. This results in a reduction in the PCr signal to a value MЈ 0 from its fully-relaxed equilibrium value of M 0 , due to the forward flux of phosphate through the CK reaction and the replenishment of PCr with saturated (or inverted) phosphate via the reverse reaction.For the standard saturation experiment assuming a twosite exchange model, the fractional reduction in M 0 is equal to k f in units of the spin-lattice relaxation time T Ј 1 of PCr measured with the ␥-ATP saturated (designated by primes): k f TЈ 1 ϭ 1 Ϫ MЈ 0 /M 0 .[1]At equilibrium, the reverse rate constant is given by:Thus, the determination of k...

Elevated TSC in breast lesions measured by non-invasive (23)Na MRI appears to be a cellular-level indicator associated with malignancy. This method may have potential to improve the specificity of breast MRI with only a modest increase in scan time per patient.

The role of dynamic contrast material-enhanced magnetic resonance (MR) imaging of the breast as an adjunct to the conventional techniques of mammography and ultrasonography has been established in numerous research studies. MR imaging improves the detection and characterization of primary and recurrent breast cancers and allows evaluation of the response to therapy. The breast imaging lexicon published by the American College of Radiology allows a standardized and consistent description of the morphologic and kinetic characteristics of breast lesions; however, there are many challenges in the interpretation of breast enhancement patterns and kinetics, and many imaging and interpretation pitfalls must be considered. New breast MR imaging techniques that are based on the use of molecular markers of malignancy may help improve lesion characterization. The margin characteristics of a lesion and the intensity of its enhancement at MR imaging 2 minutes or less after contrast material injection are currently considered the most important features for breast lesion diagnosis.

At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B 1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B 0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T 2 preparation (T 2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T 2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast-passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Coronary magnetic resonance angiography (MRA) at 1.5 T has shown promise for the assessment of significant coronary artery disease in proximal and mid segments of the coronary arteries (1). However, low signal-to-noise ratio (SNR) limits the utilization of this imaging technique for more distal and branching vessels at 1.5 T (1). At a higher magnetic field strength, an improved SNR is expected. However, the enhanced effect of magnetic field susceptibility leads to off-resonance effects, while B 1 inhomogeneity, tissue dielectric constants, body dielectric resonances, and increased specific absorption rate (SAR) are additional limitations that must be considered at higher magnetic field strength (2-8). Therefore, to take full advantage of higher field strength and clinically realize the improved SNR, a careful sequence design that minimizes these effects is necessary.Three-dimensional (3D), free-breathing coronary MRA techniques can be used to image the tortuous path of the coronary arterial tree with improved SNR relative to twodimensional (2D) approaches. However, 3D imaging results in a lower contrast between the coronary blood and the myocardium. To overcome this problem, the use of contrast agents (9 -12) or magnetization preparation schemes (13-17) have been proposed. T 2 Prep is used in 3D coronary imaging to increase the contrast between the coronary arterial blood-pool and the surrounding tissue (13,17,18). However, increased B 1 and B 0 inhomogeneities at higher magnetic field strength pose significant challenges to uniform T 2 preparation of the magnetization across the imaged volume, thereby limiting the value of coronary MRA in general. Therefore, a novel T 2 preparation scheme in which adiabatic pulses are used to achieve B 1 and B 0 insensitive contrast enhancement was developed. Numerical simulations and an in vivo study were performed to characterize the efficacy of the technique. METHODS Background

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OBJECTIVEWe examined if chronic cannabis smoking is associated with hepatic steatosis, insulin resistance, reduced β-cell function, or dyslipidemia in healthy individuals.RESEARCH DESIGN AND METHODSIn a cross-sectional, case-control study, we studied cannabis smokers (n = 30; women, 12; men, 18; 27 ± 8 years) and control subjects (n = 30) matched for age, sex, ethnicity, and BMI (27 ± 6). Abdominal fat depots and intrahepatic fat content were quantified by magnetic resonance imaging and proton magnetic resonance spectroscopy, respectively. Insulin-sensitivity indices and various aspects of β-cell function were derived from oral glucose tolerance tests (OGTT).RESULTSSelf-reported cannabis use was: 9.5 (2–38) years; joints/day: 6 (3–30) [median (range)]. Carbohydrate intake and percent calories from carbohydrates, but not total energy intake, were significantly higher in cannabis smokers. There were no group differences in percent total body fat, or hepatic fat, but cannabis smokers had a higher percent abdominal visceral fat (18 ± 9 vs. 12 ± 5%; P = 0.004). Cannabis smokers had lower plasma HDL cholesterol (49 ± 14 vs. 55 ± 13 mg/dL; P = 0.02), but fasting levels of glucose, insulin, total cholesterol, LDL cholesterol, triglycerides, or free fatty acids (FFA) were not different. Adipocyte insulin resistance index and percent FFA suppression during an OGTT was lower (P < 0.05) in cannabis smokers. However, oral glucose insulin sensitivity index, measures of β-cell function, or incretin concentrations did not differ between the groups.CONCLUSIONSChronic cannabis smoking was associated with visceral adiposity and adipose tissue insulin resistance but not with hepatic steatosis, insulin insensitivity, impaired pancreatic β-cell function, or glucose intolerance.