title: Spectral filtering for improved pulsed photothermal temperature profiling in agar tissue phantoms.
abstract: We present a systematic experimental comparison of pulsed photothermal temperature profiling utilizing the customary spectral band of the InSb radiation detector (lambda=3.0 to 5.6 microm) and a narrowed acquisition band (4.5 to 5.6 microm). We use custom tissue phantoms composed of agar gel layers separated by thin absorbing layers. The laser-induced temperature profiles are reconstructed within the customary monochromatic approximation, using a custom minimization algorithm. In a detailed numerical simulation of the experimental procedure, we consider several acquisition spectral bands with the lower wavelength limit varied between 3.0 and 5.0 microm (imitating application of different long-pass filters). The simulated PPTR signals contain noise with amplitude and spectral characteristics consistent with our experimental system. Both experimental and numerical results indicate that spectral filtering reduces reconstruction error and broadening of temperature peaks, especially for shallower and more complex absorbing structures. For the simulated PPTR system and watery tissues, numerical results indicate an optimal lower wavelength limit of 3.8 to 4.2 microm.
authors.affiliation: Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Matija
authors.initials: M
authors.lastname: Milanic
authors.forename: Boris
authors.initials: B
authors.lastname: Majaron
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Nelson
mesh_terms: D000362:Agar / Q000737:chemistry*; D000465:Algorithms; D003238:Connective Tissue / Q000502:physiology* / Q000528:radiation effects; D007834:Lasers; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013057:Spectrum Analysis / Q000379:methods*; D013817:Thermography / Q000379:methods*
chemical_list: D000362:Agar