Pulse sequence optimization for MR imaging using a paramagnetic hepatobiliary contrast agent

Paramagnetic agents enhance contrast between tissues in magnetic resonance (MR) imaging by altering tissue relaxation times. The effect of these changes on MR image intensity depends in part on the choice of operator-controlled pulse sequence parameters. With the newly described paramagnetic hepatobiliary contrast agent, iron(III) ethylenebis-(2-hydroxyphenylglycine), Fe(EHPG)-, an in vivo experimental analysis of pulse sequence optimization was performed on the rat. We compared the enhancement of the liver divided by background noise, EL/N, of standard inversion-recovery (IR) and spin-echo (SE) T1-weighted pulse sequences and several pulse sequences theoretically predicted to have improved EL/N. Optimization of the echo time (TE = TEmin) gave a substantial (greater than 60%) increase in EL/N over the standard IR and SE pulse sequences. Images obtained with optimized repetition rate and inversion time gave only a slight additional improvement. Within the uncertainties of our relaxation measurements, the measured changes in EL/N with pulse sequence optimization corresponded well with theoretical predictions. With the experimental and theoretical data, the importance of using a short echo time to obtain maximal T1 contrast in contrast-enhanced MR imaging and the relative merits of optimized SE versus IR pulse sequences for contrast-enhanced MR imaging are discussed.     

Surgical management of the hypodynamic palate.

The most successful surgical correction of velopharyngeal insufficiency (VPI) has been achieved in those patients in whom residual dynamic function of the soft palate/nasopharyngeal sphincter mechanism exists. In spite of the obvious need for rehabilitation, surgical reconstruction has often been advised against in those cases where the palate was hypodynamic or adynamic. We have developed a surgical procedure for these patients by utilizing a modification of Hogan's lateral port control pharyngeal flap method. We present the surgical considerations along with the initial application and results in four patients with hypodynamic palates of differing origins. We think that this technique extends surgical correction of VPI to the previously neglected group of patients in whom this condition is the result of a hypodynamic palate.     

Cochlear implants

Cochlear implants are cost-effective auditory prostheses that safely provide a high-quality sensation of hearing to adults who are severely or profoundly deaf. In the past 5 years, progress has been made in hardware and software design, candidate selection, surgical techniques, device programming, education and rehabilitation,and, most importantly, outcomes. Cochlear implantation in the elderly is well tolerated and provides marked improvement in auditory performance and psychosocial functioning.     

Dexamethasone protects organ of corti explants against tumor necrosis factor-alpha-induced loss of auditory hair cells and alters the expression levels of apoptosis-related genes

Objective: Determine the molecular mechanism(s) behind tumor necrosis factor-alpha (TNFα)–induced loss of auditory hair cells and the ability of dexamethasone base (DXMb) to protect against TNFα ototoxicity.