Experimental validation of alternating transillumination for imaging intramural wave propagation.

Current techniques to map intramural activation patterns in ex vivo cardiac tissue have limited spatial resolution. Here, we report on the experimental validation of a novel optical technique that was recently proposed to resolve the size and depth of intramural wave fronts using alternating transillumination (AT). AT was achieved by simultaneously mapping the epi- and endocardial surfaces with two synchronized CCD cameras and rapidly alternating LED illumination between both surfaces. Optical phantoms were made based on tissue optical properties measured using a hybrid optical spectrometer. Spherical fluorescent sources (Scarlet microspheres, Invitrogen, UK) of varying sizes were embedded at known depths in the phantoms. Coronary-perfused procine left ventricular slab preparations were stained with DI-4-ANBDQBS (n = 3) and paced at known intramural depths. In phantoms we were able to reliably estimate the depth of the center of fluorescent sources (9.6 ± 5.4% error), as well as their transmural extent (15.7 ± 11.5% error). In ventricular slabs we were able to localize the sites of origin of intramural excitation waves with a precision of ± 1.6 mm. Transmural conduction velocities were, for the first time, measured optically from the surfaces and found to be 21.0 ± 12.4 cm/s. In conclusion, alternating transillumination is a promising technique for reliable reconstruction of depth and expansion rate of intramural activation wave fronts in cardiac tissue.

Improved survival in central nervous system aspergillosis: a series of immunocompromised children with leukemia undergoing stereotactic resection of aspergillomas. Report of four cases.

Central nervous system (CNS) aspergillosis remains a daunting diagnosis. This opportunistic mycosis historically carries a mortality rate approaching 100% in immunocompromised patients, with death ensuing within days after the onset of neurological symptoms. From their literature review, the authors concluded that children contracting CNS aspergillosis while undergoing systemic chemotherapy for leukemias represent a particularly unfortunate prognostic group. Antifungal medications prove ineffective for treating CNS aspergillosis in patients immunocompromised because of their chemotherapy regimens. In contrast, withholding chemotherapy to reverse immunosuppression, thereby improving the efficacy of antifungal medications, allows for progression of the primary leukemic disease. The authors present a series of four immunosuppressed patients whose course of treatment for leukemia was complicated by CNS Aspergillus sp. abscesses. Multiple cerebral fungal abscesses developed in two patients and a single cerebral abscess developed in two. All four patients underwent frameless stereotactic resection of the aspergilloma. All children later experienced resolution of their CNS infections and full neurological recovery. At 2- to 4-year follow ups, one patient has died of leukemia and the other three continue to thrive without evidence of recurrent aspergillosis. Given the grave natural history cited in the literature for this disease when medical treatment is instituted alone, the authors stress the crucial role of stereotactic neurosurgery for the intelligent treatment of immunocompromised children suspected of harboring a CNS aspergilloma abscesses. The authors propose that the goal for successful treatment in these patients should be gross-total resection of the abscess, its wall, and its capsule.