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Purpose Accurate characterization of contrast reagent (CR) longitudinal relaxivity in whole blood is required to predict arterial signal intensity in contrast-enhanced MR angiography (CE-MRA). This study measured the longitudinal relaxation rate constants (R1) over a concentration range for non-protein-binding and protein-binding CRs in ex vivo whole blood and plasma at 1.5 and 3.0 Tesla (T) under physiologic arterial conditions. Methods Relaxivities of gadoteridol, gadobutrol, gadobenate, and gadofosveset were measured for [CR] from 0 to 18 mM [mmol(CR)/L(blood)]: the latter being the upper limit of what may be expected in CE-MRA. Results In plasma, the 1H2O R1 [CR]-dependence was nonlinear for gadobenate and gadofosveset secondary to CR interactions with the serum macromolecule albumin, and was well described by an analytical expression for effective 1:1 binding stoichiometry. In whole blood, the 1H2O R1 [CR]-dependence was markedly non-linear for all CRs, and was well-predicted by an expression for equilibrium exchange of water molecules between plasma and intracellular spaces using a priori parameter values only. Conclusion In whole blood, 1H2O R1 exhibits a nonlinear relationship with [CR] over 0 to 18 mM CR. The nonlinearity is well described by exchange of water between erythrocyte and plasma compartments, and is particularly evident for high relaxivity CRs. Magn Reson Med 72:1746–1754, 2014. © 2013 Wiley Periodicals, Inc.

Purpose: To use magnetization tagged magnetic resonance imaging (MRI) (tag-MRI) to quantify cardiac induced liver strain and compare strain of cirrhotic and normal livers. Materials and Methods: Tag-MRI was performed at 1.5T on eight subjects with no history of liver disease and 10 patients with liver cirrhosis. A breath-hold peripheral pulse-gated (PPG) conventional tag-MRI cine sequence was performed with planes to include the left lobe of the liver and the inferior wall of the heart. Commercially available software HARP (Diagnosoft, Palo Alto, CA) was used for image analysis and strain calculation. Three regions-of-interest (ROIs) were selected: segment II of the liver near the heart (A), right liver lobe far from the heart (B), and the left ventricular wall (C). The average and maximal (max) strain were measured in A, B, and C. The maximum strains were used to generate a cardiac-corrected strain gradient: (maxA-maxB)/maxC. Results were compared with Student's t-test (SPSS, Chicago, IL). Results: In subjects with no history of liver disease vs. cirrhotic patients, the average strain was 22% ± 7% vs. 4% ± 3% (P < 0.001), the max strain was 63% ± 15% vs. 17% ± 5% (P < 0.001), and the corrected strain gradient was 0.52 ± 0.16 vs. 0.11% ± 0.08%. Conclusion: There is a significant difference in liver strain measured with tag-MRI between subjects with no history of liver disease and patients with cirrhosis. J. Magn. Reson. Imaging 2012; 36:1490–1495. © 2012 Wiley Periodicals, Inc.

Background Postherpetic neuralgia, a common sequele to herpes zoster infection, is a chronic debilitating problem. The available therapeutic modalities are usually ineffective. Methods A total of 3960 patients (1326 women and 2634 men; age group, 21–84 years), with postherpetic neuralgia as the presenting complaint and with pain lasting from 2 months to 5 years, were treated with Jaipur block, consisting of local subcutaneous infiltration of 2% xylocaine, 0.5% bupivacaine, and 4 mg/mL dexamethasone solution. Patients were followed up at six-weekly intervals with subsequent injections given in non-responders. Results Twenty eight per cent of patients obtained complete relief from pain after a single injection, another 57% after a second injection, and 11% after a third injection; 4% of patients did not respond to treatment. The non-responders were either old (over 60 years) or had pain lasting for more than 2 years. The response to therapy was similar in both sexes. There were 31 left-handed patients in this study. Pain was less severe in left-handed patients and they obtained complete relief after a single injection. Side-effects including giddiness and sweating were seen, occasionally, in a few patients. Conclusions Ninety six per cent of patients obtained complete relief after the block with a follow-up of up to 19 years.