Scanning photoacoustic imaging of submucosal gastric tumor based on a long focused transducer in phantom and in vitro experiments

Photoacoustic imaging,which can provide the maximum intensity contrast in tissue depth imaging without ionizing radiation,will be a promising imaging trend for tumor detection.In this paper,a column diffusionfiber was employed to carry a pulsed laser for irradiating stomach directly through esophagus based on the characteristics of gastric tissue structure.A long focused ultrasonic transducer was placed outside the body to detect photoacoustic signals of gastric tissue.Phantom and in vitro experiments of submucosal gastric tumors were carried out to check the sensitivity of scanning photoacoustic tomography system,including the lateral and longitudinal resolution of the system,sensitivity of different absorption coefficient in imaging,capability of transversal detection,and probability of longitudinal detection.The results demonstrate that our innovative technique can improve the parameters of imaging.The lateral resolution reaches 2.09 mm.Then a depth of 5.5mm with a longitudinal accuracy of 0.36mm below gastric mucosa of early gastric cancer(EGC)has been achieved.In addition,the optimal absorption coefficient differences among absorbers of system are 3.3-3.9 times.Results indicate that our photoacoustic imaging(PAI)system,is based on a long focusing transducer,can provide a potential application for detecting submucosal EGC without obvious symptoms.

Correlation between Polymerization of Cyclic Butylene Terephthalate(CBT) and Crystallization of Polymerized CBT

The correlation between ring-opening polymerization(ROP) of cyclic butylene terephthalate(CBT) and crystallization of polymerized CBT(p CBT) strongly affected the final properties of p CBT and its composites.The major objective of this contribution is to pinpoint the threshold temperature between them and the interrelation is successfully disclosed.That is,crystallization during polymerization occurs below 204 °C and the crystallization properties of p CBT are determined by this isothermal ROP stage; polymerization and crystallization are gradually separated with the increase of temperature of ROP(TP) from 204 °C,and the crystallization properties of p CBT are dominated by cooling stage; only polymerization is performed above 212 °C.Moreover,quantitative analysis suggests that uniform crystal size distributions and thicker lamellar crystals derive from the stage of crystallization during polymerization.On the contrary,the crystal size distributions become wider above 204 °C of TP and lead to obvious double melting peaks during heating scan.These efforts provide a very useful guide for the related investigation and application of CBT.