Optimization of parameter values for complex pulse sequences by simulated annealing: Application to 3D MP-RAGE imaging of the brain

A number of pulse sequence techniques, including magnetization-prepared gradient echo (MP-GRE), segmented GRE, and hybrid RARE, employ a relatively large number of variable pulse sequence parameters and acquire the image data during a transient signal evolution. These sequences have recently been proposed and/or used for clinical applications in the brain, spine, liver, and coronary arteries. Thus, the need for a method of deriving optimal pulse sequence parameter values for this class of sequences now exists. Due to the complexity of these sequences, conventional optimization approaches, such as applying differential calculus to signal difference equations, are inadequate. We have developed a general framework for adapting the simulated annealing algorithm to pulse sequence parameter value optimization, and applied this framework to the specific case of optimizing the white matter-gray matter signal difference for a T₁-weighted variable flip angle 3D MP-RAGE sequence. Using our algorithm, the values of 35 sequence parameters, including the magnetization-preparation RF pulse flip angle and delay time, 32 flip angles in the variable flip angle gradient-echo acquisition sequence, and the magnetization recovery time, were derived. Optimized 3D MP-RAGE achieved up to a 130% increase in white matter-gray matter signal difference compared with optimized 3D RF-spoiled FLASH with the same total acquisition time. The simulated annealing approach was effective at deriving optimal parameter values for a specific 3D MP-RAGE imaging objective, and may be useful for other imaging objectives and sequences in this general class.     

Calcium antagonists and renal protection. Current status and future perspectives.

During the past decade, considerable attention has been focused on the effects of calcium antagonists on renal function. Direct in vivo and in vitro observations in diverse experimental models indicate that calcium antagonists antagonize preglomerular vasoconstriction. Furthermore, calcium antagonists are postulated to have additional properties that contribute to their ability to afford renal protection. These putative mechanisms include the ability to retard renal growth, and possibly to attenuate mesangial entrapment of macromolecules, and to attenuate the mitogenic effects of diverse growth factors. Although the clinical implications of the above-mentioned findings have not been fully delineated, the results of recent clinical trials indicate that calcium antagonists exert salutary effects on renal function in clinical settings characterized by impaired renal hemodynamics, including transplant-associated acute renal insufficiency and, possibly, cyclosporine nephrotoxicity. Evidence has accrued suggesting that calcium antagonists may also be protective against acute radiocontrast-induced nephrotoxicity. Finally, the renal hemodynamic and natriuretic effects of calcium antagonists commend their use as antihypertensive agents in the management of essential hypertension, renovascular hypertension, and transplant-associated hypertension.     

Categorization: a fundamental of unconscious mental activity.

Association formation and categorization, phenomena below volition and awareness, are in the unconscious domain. They reflect automatic processes of brain circuitry. The formation and maintenance of associations and categories require as well as yield neural energy, energy arising from cerebral metabolic processes. Automatic categorization is a fundamental element in perceptual, motoric, and cognitive functions as emphasized by Edelman (1987) who, further, relates categorization to dynamic cerebral cortical fields and to limbic fields for the necessary affective component.     

Self-concept dimensions of clinically depressed and anxious outpatients.

Principal components analyses of the Beck Self-Concept Test (BST) were conducted independently for 288 women with primary mood disorders, 230 women with anxiety disorders, 236 men with mood disorders, and 161 men with anxiety disorders. Four self-concept dimensions that reflected (1) Intellectual Ability; (2) Work Efficacy; (3) Physical Attractiveness; and (4) Virtues/Vices occurred within the four samples. For 5-item subscales that represent these four dimensions, a two-way MANOVA found significant effects for sex and type of disorder. Women described themselves as having less intellectual ability than men did. Outpatients with mood disorders considered their physical appearance, work efficacy, and virtues/vices to be less acceptable than did those with anxiety disorders. Findings were discussed with respect to the cognitive content-specificity theory of psychopathology.     

Glued-on, rigid gas-permeable contact lens for severe radiation-induced keratitis.

A 68-year-old woman with severe radiation-induced keratoconjunctivitis sicca became progressively unresponsive to conventional medical treatment. Her left eye deteriorated rapidly and required total tarsorrhaphy. In an attempt to stabilize the right eye and preserve some functional vision, we glued a high-Dk rigid, gas-permeable contact lens with tissue-grade cyanoacrylate adhesive to Bowman's membrane. This glued-on contact lens induced rapid and dramatic improvement of the patient's comfort and sight. Recent developments in high-permeability, rigid, contact-lens materials now make artificial replacement of the epithelium a potentially useful treatment for severe ocular surface disease when conventional treatment has failed.     

The effect of a multidisciplinary team approach on weight gain in nonorganic failure-to-thrive children

Failure-to-thrive (FTT) is a chronic symptom accounting for 1% of all patients admitted to pediatric hospitals. FTT, which is traditionally attributed to organic (OFTT) and/or nonorganic (NFTT) causes, results in undernutrition. Undernutrition has potentially serious effects on child development, behavior, and cognitive skills. We undertook a study of children with FTT to determine whether multidisciplinary team treatment resulted in improved weight gain compared with children treated in a primary care setting. Fifty-three children with NFTT referred to our outpatient FTT consultative clinic and 107 children with NFTT identified as comparison subjects from our primary care clinic (PCC) were enrolled in the study. Growth outcomes over a 6-month follow-up were analyzed using growth quotient (GQ) analysis. Children followed in the multidisciplinary team clinic grew better (GQ = 1.75 +/- 0.39 SD) than did children in the PCC (GQ = 1.18 +/- 0.42 SD, p less than .001). The use of a multidisciplinary team offers special advantages in the rapid correction of undernutrition in children with NFTT.