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.