ABSTRACT
Most current photoacoustic imaging (PAI) systems employ piezoelectric transducers to receive photoacoustic signals, which requires coupling medium to facilitate photoacoustic wave propagation and are not favored in many applications. Here, we report an all-optical non-contact PAI system based on a commercial heterodyne interferometer working at 1550 nm. The interferometer remotely detects ultrasound-induced surface vibration and does not involve any physical contact with the sample. The theoretically predicated and experimentally measured noise equivalent detection limits of the optical sensor are about 4.5 and 810 Pa over 1.2 MHz bandwidth. Using a raster-scan PAI system equipped with the non-contact design, stereotactic boundaries of an artificial tumor in a pig brain were accurately delineated. The non-contact design also enables the tomographic PAI of biological tissue samples in a non-invasive manner. The preliminary results and analyses reveal that the heterodyne interferometer-based non-contact PAI system holds good potential in biomedical imaging.
ABSTRACT
Laser Doppler Vibrometry (LDV) has been widely used in engineering applications involving non-contact vibration and sound measurements. This technique has also been used in some biomedical applications including hearing research. The detectable frequencies are in the range of near-DC to 1 GHz or higher. This paper reviews applications of LDV in biomedical engineering and proposes new medical imaging applications based on measuring surface vibrations of tissues and organs. Tests were conducted on human skin using single point and scanning laser vibrometers. These tests suggest that skin vibrations due to the forcing excitation from the heart can be used in imaging of blood flow. The results of these tests illustrate the potential of such vibration measurements in a variety of diagnostic medical imaging applications including blood flow/restrictions, real-time monitoring of blood pressure variations, wound healing, muscle movements, etc. The fact that the measurements can be conducted remotely (non-contact) is an important benefit that adds to the promise of this approach.
ABSTRACT
Insertion of CO(2) into the metal-N bond of a series of synthetically important alkali-metal TMP (2,2,6,6-tetramethylpiperidide) complexes has been studied. Determined by X-ray crystallography, the molecular structure of the TMEDA-solvated Li derivative shows a central 8-membered (LiOCO)(2) ring lying in a chair conformation with distorted tetrahedral lithium centres. While trying to obtain crystals of a THF-solvated derivative, a mixed carbonato/carbamato dodecanuclear lithium cluster was formed containing two central (CO(3))(2-) fragments and eight O(2)CTMP ligands with four distinct bonding modes. A bisalkylaluminium carbamato complex has also been prepared via two different methods (CO(2) insertion into a pre-formed Al-N bond and ligand transfer from the corresponding lithium reagent) which adopts a dimeric structure in the solid state.
ABSTRACT
The August 2007 earthquake in Peru resulted in the loss of critical health infrastructure and resource capacity. A regionally located United States Military Mobile Surgical Team was deployed and operational within 48 hours. However, a post-mission analysis confirmed a low yield from the military surgical resource. The experience of the team suggests that non-surgical medical, transportation, and logistical resources filled essential gaps in health assessment, evacuation, and essential primary care in an otherwise resource-poor surge response capability. Due to an absence of outcomes data, the true effect of the mission on population health remains unknown. Militaries should focus their disaster response efforts on employment of logistics, primary medical care, and transportation/evacuation. Future response strategies should be evidence-based and incorporate a means of quantifying outcomes.
