Percutaneous MR imaging-guided radiofrequency interstitial thermal ablation of tongue base in porcine models: implications for obstructive sleep apnea syndrome

PURPOSE: To test the feasibility and safety of a percutaneous magnetic resonance (MR) imaging-guided technique for radiofrequency (RF) interstitial thermal ablation of the tongue base and to correlate MR appearance of induced thermal lesions with histopathologic findings in pigs in acute and chronic porcine models. MATERIALS AND METHODS: A 1-cm-tip RF electrode was inserted percutaneously into the tongue in 10 pigs with 0.2-T real-time MR guidance. The RF electrode was advanced up the midline between lingual arteries and stopped short of tongue mucosa. RF interstitial thermal ablation was performed at 90 degrees C +/- 2 and lasted 10 minutes. Postablation images were obtained with a 1.5-T MR imager. Five pigs were sacrificed immediately (acute model), while five were followed up for 1 month (chronic model) before they were sacrificed. MR-compatible fiducial coils were inserted into tongues with MR imaging guidance prior to RF ablation in the chronic group. Tongues were harvested for histopathologic analysis. Mean thermal lesion volume was compared with the Student t test on images obtained immediately, 2 weeks, and 1 month after RF ablation. Interclass correlation coefficients of lesion diameters at gross pathologic analysis and corresponding diameters with each pulse sequence were calculated. RESULTS: Successful MR imaging-guided electrode positioning was achieved in all procedures without intra- or postprocedure complications because there was high vascular conspicuity and tissue contrast. Thermal lesions appeared hypointense with hyperintense surrounding rims with all sequences in both groups. At pathologic analysis, acute lesions appeared as pale necrotic areas surrounded by hyperemic rims, while chronic lesions demonstrated progressive circumferential fibrosis and significant volume shrinkage (P <.01). Thermal lesion diameters measured at gross pathologic analysis best agreed with corresponding diameters measured on short inversion time inversion-recovery images (interclass correlation coefficient = 0.85). CONCLUSION: The results of this investigation demonstrate MR imaging-guided RF interstitial thermal ablation of the tongue base is feasible and safe and illustrate imaging and pathologic phenomena associated with creation and evolution of the induced thermal lesions.     

Preservation of place and manner cues during simultaneous communication: a spectral moments perspective

Spectral moments, which describe the distribution of frequencies in a spectrum, were used to investigate the preservation of acoustic cues to intelligibility of speech produced during simultaneous communication (SC) in relation to acoustic cues produced when speaking alone. The spectral moment data obtained from speech alone (SA) were comparable to those spectral moment data reported by Jongman, Wayland, and Wong (2000) and Nittrouer (1995). The spectral moments obtained from speech produced during SC were statistically indistinguishable from those obtained during SA, indicating no measurable degradation of obstruent spectral acoustic cues during SC. Educational objectives: As a result of this activity, the participant will be able to (1) describe SC; (2) explain the role of SC in communication with children who are deaf; (3) describe the first, third, and fourth spectral moments of obstruent consonants; and (4) identify spectral moment patterns in speech produced during SC.     

Neue Gesichtspunkte in der Heparin-Anwendung bei der extrakorporalen Hämodialyse

Ohne Zusammenfassung Mit 2 Textabbildungen VortragenderH. J. Hillenbrand.     

What is going on with vaccines: keeping up with the childhood immunization schedule.

In the last 25 years, the number of diseases prevented by vaccination in childhood has more than doubled, challenging practitioners to become familiar with a host of new vaccine recommendations. Incorporating new vaccines into practice is facilitated by an understanding of the processes that affect their use. Factors that influence the successful incorporation of a vaccine into routine practice include licensing, development of recommendations, identification of funding sources, liability coverage in the event of adverse outcomes, the development of mandates for use, and consideration of parental knowledge and attitudes. New vaccine recommendations offer increased protection against rotavirus, hepatitis A, varicella, pertussis, meningococcus, and human papillomavirus. With increasing complexity and changing recommendations, practitioners should refer to reliable resources for accessing up-to-date information.     

Dentistry's responsibility to community health through the public health dentist

Wurold Hillenbrand outlines cleurly, as usuaf, the need for cooperation between dental directors and dental societies.     

A dedicated automated injection system for dynamic contrast‐enhanced MRI experiments in mice

Purpose:

To develop a reproducible small‐animal dynamic contrast‐enhanced (DCE) MRI set‐up for mice through which volumes <100 μL can be accurately and safely injected and to test this set‐up by means of DCE measurements in resting muscle and tumor tissue.

Materials and Methods:

The contrast agent (CA) injection system comprised 2 MR‐compatible syringe pumps placed 50 cm from the 7T magnet bore where the fringe field is approximately 40 mT. Microbore tubing and T‐connector, close to the injection site, minimized dead volume (<10 μL). For DCE‐MRI measurements in 8 CB‐17 SCID mice with 1500–2500 mm³ large orthotopic neuroblastoma, a bolus of 10‐fold‐diluted Gd‐DTPA CA solution (0.1 mmol/kg) was delivered (5 μL/s), followed by a 50‐μL saline flush. Retro‐orbital injections were given instead of tail vein injections, because the peripheral vasculature was reduced because of large tumor burden.

Results:

The CA injection was successful in 19 of 24 experiments. Optical assessment showed minimal dispersion of ink‐colored CA bolus. Mean (±SD) pharmacokinetic parameters retrieved from DCE‐MRI examinations in resting muscle (K^trans = 0.038 ± 0.025 min^?1, k_ep = 0.66 ± 0.48 min^?1, v_e = 0.060 ± 0.014, v_p = 0.033 ± 0.021) and tumor (K^trans = 0.082 ± 0.071 min^?1, k_ep = 0.82 ± 0.80 min^?1, v_e = 0.121 ± 0.075, v_p = 0.093 ± 0.051) agreed with those reported previously.

Conclusion:

We successfully designed and implemented a DCE‐MRI set‐up system with short injection lines and low dead volume. The system can be used at any field strength with the syringe pumps placed at a sufficiently low fringe field (<40 mT). J. Magn. Reson. Imaging 2013;37:746–751. © 2012 Wiley Periodicals, Inc.