Monte Carlo simulation of light transport in dark-field confocal photoacoustic microscopy

A modified MC convolution method for integration extension of MC simulation is developed for finite photon beam with random shape of translational or rotational invariance, which is proven consistent with the conventional convolution extension of MC simulation for normal incident finite beam. The method is applied to analyze the positions of fluence foci and ratios of fluence at the focus and surface which are two key factors in the application of dark-field confocal and some interesting points are presented including: 1) The fluence profile has a saddle-like shape with highest peak in the bright field and low valley near the surface and a second rise in the center of dark field which is defined as the effective optical focus; 2) Besides a little peak near zero inner radius, the ratio of fluences at the focus and surface increases linearly with the inner radius, suggesting the large inner radius more advantageous to image at the effective optical focus; 3) The position of effective optical foci deepens linearly with the increase of the inner radius, suggesting that to get a high quality image of deeper target, a dark-field with larger size is more beneficial. But the position of fluence foci are far away from the foci of geometrical laser beam in high scattering tissue, so aligning the foci of geometrical laser beam and acoustic transducer doesn't guarantee that effective optical focus is accurately overlapping with the acoustic focus. An MC simulation with integration extension presented in this paper maybe helpful to determine where the acoustic focus should be to maximize the SNR in tissue imaging; 4) incident angle makes little difference to ratio of fluences at the focus and surface and an incident angle between 30 and 50 degrees gives the highest fluence at the effective optical focus; 5) the depth of fluence focus is insensitive to the incident angle

Monte Carlo simulation of light transport in dark-field confocal photoacoustic microscopy

A modified MC convolution method for integration extension of MC simulation is developed for finite photon beam with random shape of translational or rotational invariance, which is proven consistent with the conventional convolution extension of MC simulation for normal incident finite beam. The method is applied to analyze the positions of fluence foci and ratios of fluence at the focus and surface which are two key factors in the application of dark-field confocal and some interesting points are presented including: 1) The fluence profile has a saddle-like shape with highest peak in the bright field and low valley near the surface and a second rise in the center of dark field which is defined as the effective optical focus; 2) Besides a little peak near zero inner radius, the ratio of fluences at the focus and surface increases linearly with the inner radius, suggesting the large inner radius more advantageous to image at the effective optical focus; 3) The position of effective optical foci deepens linearly with the increase of the inner radius, suggesting that to get a high quality image of deeper target, a dark-field with larger size is more beneficial. But the position of fluence foci are far away from the foci of geometrical laser beam in high scattering tissue, so aligning the foci of geometrical laser beam and acoustic transducer doesn't guarantee that effective optical focus is accurately overlapping with the acoustic focus. An MC simulation with integration extension presented in this paper maybe helpful to determine where the acoustic focus should be to maximize the SNR in tissue imaging; 4) incident angle makes little difference to ratio of fluences at the focus and surface and an incident angle between 30 and 50 degrees gives the highest fluence at the effective optical focus; 5) the depth of fluence focus is insensitive to the incident angle

Optical fluence distribution study in tissue in dark-field confocal photoacoustic microscopy using a modified Monte Carlo convolution method

We have modified the existing convolution method of the Monte Carlo simulation for finite photon beams with both translational and rotational invariance. The modified convolution method was applied to simulate the optical fluence distribution in tissue in dark-field confocal photoacoustic microscopy. We studied the influence of the size of the dark field and the illumination incident angle on the depth position of the effective optical focus (the region with the highest fluence) and the fluence ratio (the ratio of the optical fluence at the effective optical focus inside the tissue to the optical fluence on the tissue surface along the ultrasonic axis). Within the reach of diffuse photons, the depth position of the effective optical focus increases with the size of the dark field and is much less sensitive to the incident angle. The findings show that, while the fluence at the effective optical focus decreases, the fluence ratio increases with the size of the dark field. The incident angle has a weaker influence on the fluence ratio than the size of the dark field does. An incident angle between 30 and 50 degrees gives the highest fluence at the effective optical focus

Early detection of spontaneous combustion disaster of sulphide ore stockpiles

Opasnost od vatre izazvane spontanim izgaranjem sulfidnih rudača važno je sigurnosno, ekološko i ekonomsko pitanje za rudarstvo i metalurgiju, a postalo je jedan od najvažnijih problema u rudarstvu, posebice kada je potrebno dugotrajno uskladištiti sulfidne rudače ili ih prenositi na velike udaljenosti. Osnovna je svrha ovoga rada odabir odgovarajućeg indikatora detekcije kroz cjelokupni proces spontanog izgaranja od oksidacije do vatre uz točno određivanje mjesta nastanka vatre kod spontanog izgaranja naslaga sulfidne rude u ranom stadiju. Proveli smo terenske i laboratorijske eksperimente koristeći pet pokazatelja kako bi odredili karakteristike oksidacije sulfidnih rudača. Eksperimentalni rezultati pokazuju da bi promjena površinske temperature na naslagama sulfidne rudače mogla indirektno odražavati prirodu oksidacije sulfidne rudače te da je usko povezana s različitim stadijima spontanog izgaranja. Na temelju analiza temperaturnih anomalija i tehnologije infracrvene termografije, predložena je nova metoda za otkrivanje izvora vatre, kojom se može pratiti najviša točka temperature na površini samozapaljivih rudača. Rezultat istraživanja pokazuje da su maksimalne razlike temperature 0,5; 0,16 i 0,04 °C na dubinama detekcije od 2,3 i 5 m, i površine od 1 × 1m kada su blizu samozapaljenju. Pod istim uvjetima, maksimalne razlike temperature su 1,39; 0,53 i 0,14 °C površine od 2 × 2 m. Stoga se sustav infracrvene termografije može koristiti s dovoljno visokom točnošću za mjerenje temperaturnih razlika na površini naslaga rudača, rezultirajući određivanjem položaja mjesta nastanka vatre.The fire hazards induced by the spontaneous combustion of sulphide ores pose safety, environmental, and economic concerns to the mining and metallurgical industries and have become one of the most important problems in mining, particularly when sulphide ores have to be stored for a long time or transported for a long distance. The first purpose of this paper is the selection of a suitable detection indicator for running through the entire process of spontaneous combustion from oxidation to fire and accurately determining the position of the fire source of the spontaneous combustion of sulphide ore stockpiles at an early stage. We conducted on-site and laboratory experiments by using five indices to assess the oxidation characteristics of sulphide ores. Experimental results show that the change of surface temperature on sulphide ore stockpiles could indirectly reflect the nature of sulphide ore oxidation and is closely related to the various stages of spontaneous combustion. On the basis of the temperature anomaly analyses and infrared thermal imaging technology, a new fire source detection method, which can monitor the highest temperature point on the surface of self-igniting ores, was proposed. The investigation result shows that the maximum temperature differences are 0,5; 0,16 and 0,04 °C at the detection depths of 2, 3, and 5 m, respectively, and a scope of 1 × 1 m when close to the self-ignition duration. Under the same condition, the maximum temperature differences are 1,39; 0,53 and 0,14 °C at a scope of 2 × 2 m. Therefore, the infrared thermal imaging system with a sufficiently high accuracy can be used to measure the temperature differences on the surface of ore stockpiles, thus resulting in the determination of fire source position

Plasmonic Nanoparticles with Quantitatively Controlled Bioconjugation for Photoacoustic Imaging of Live Cancer Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135410/1/advs216_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135410/2/advs216-sup-0001-S1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135410/3/advs216.pd