In vivo tumor detection in small animals by hematoporphyrin-mediated fluorescence imaging.

OBJECTIVE: Noninvasive in vivo imaging of human tumors implanted in mice provides a reliable and economic tool for the investigation of tumor progression and metastasis and of the effectiveness of the antiblastic drugs on them. The purpose of this study is to report on the performance achievable by the well-known and extensively investigated HP-FRI (HematoPorphyrin (HP)-mediated Fluorescence Reflectance Imaging) when a high-quality image-acquisition device is used. BACKGROUND DATA: Previous articles of ours showed that HP-FRI still represents a useful, simple and reliable optical imaging technique to detect surface tumors. Therefore, it is particularly suitable to be used in combination with other imaging modalities in a multimodal imaging system endowed with diagnostic capabilities much better than each separate modality. MATERIALS AND METHODS: Six-week-old Crl:CD-1 nude mice were subcutaneously inoculated with tumor cells. Tumor-bearing mice were irradiated in vivo by a frequency-doubled pulsed Nd:YAG laser (lambda = 532 nm). A cooled CCD digital camera recorded fluorescence light emitted by HP injected in mice through a cut-on long-wavelength pass filter. RESULTS: The system we developed allows in vivo imaging of surface tumors on small animals with a large field of view, high photometric sensitivity, adequate space resolution, and short measurement time. The estimated spatial resolution is 730 microm for a fluorescence source placed about 0.5 mm under the mouse skin. The first exploration of the capabilities of this HP-FRI setup on few mice shows that it allows the detection of (a) both types of investigated tumors, (b) early stage and late stage but visually unrecognizable tumors, (c) the gross structure of tumors, and (d) the discrimination of necrotic and nonnecrotic tumor regions.

Hematoporphyrin-mediated fluorescence reflectance imaging: application to early tumor detection in vivo in small animals.

The in vivo early detection of subcutaneous human tumors implanted in small animals was studied by laser-induced fluorescence reflectance imaging (FRI), with a hematoporphyrin (HP) compound as an exogenous optical contrast agent. Tumor detection was shown to be possible just 3 days after the inoculation of tumor cells, when tumors were neither visible nor palpable. However, this detection capability is limited to a temporal window of approximately 100 h from HP administration and to a low optical contrast of the tumor (<2).

Determination of the concentration scaling law of the scattering coefficient of water solutions of Intralipid at 832 nm by comparison between collimated detection measurements and Monte Carlo simulations.

BACKGROUND AND OBJECTIVES: Intralipid (IP) is a scatterer extensively used in the building of phantoms for Biomedical Optics measurements. Recently, deviations from the linearity have been shown for the concentration scaling law of the scattering coefficient of IP water solutions at visible wavelengths. In this work this scaling law was determined at 832 nm. STUDY DESIGN/MATERIALS AND METHODS: Space resolved transmittance measurements of a laser beam at 832 nm through water solutions of IP and ink were performed and compared with the corresponding results of Monte Carlo simulations. RESULTS: The comparison provides a quadratic dependence of mu'(s) on the volume-to-volume scatterer concentration, C(IP), in the range of C(IP) values (0.0024