In Vivo Light Dosimetry For Interstitial Photodynamic Therapy: Results Of Clinical Importance.

Marijnissen, Johannes P. A.; Versteeg, A. A. C.; Star, Willem M.

doi:10.1117/12.978010

Cited by 8 publications

(7 citation statements)

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“…For a simulation of the detector probe embedded in tissue it has been shown unequivocally that the presence of the probe has a negligible influence on the surrounding tissue fluence and that the detector probe provides an accurate measure of tissue fluence. This study confirms earlier work by Marijnissen (1993) and Lilge et al (1993) which compared measurements using isotropic probes in phantoms with the theoretical prediction of diffusion theory. With the probe positioned just above the tissue surface some shadowing was observed, resulting in a reduction in the tissue fluence close to the surface.…”

Section: Discussionsupporting

confidence: 91%

Monte Carlo simulations of the use of isotropic light dosimetry probes to monitor energy fluence in biological tissues

Jode

1999

Phys. Med. Biol.

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The use of isotropic light dosimetry probes is being increasingly advocated to monitor the light dose during photodynamic therapy. In this paper Monte Carlo simulations were used to study the potential error resulting from the disturbance of the local fluence due to presence of the probe. External irradiation of a plane slab of tissue was modelled for two sets of tissue optical properties. A highly scattering, nearly spherical detector probe, approximately 1 mm in diameter, positioned just above the tissue surface and at several depths below the surface, was incorporated into the simulation. Tissue fluence distributions were generated in the absence of the detector probe, and with the probe in situ. The presence of the probe caused negligible disturbance to the ambient fluence distribution when embedded in the tissue. The fluence measured at the centre of the detector probe showed a good correlation with the tissue fluence measured in the absence of the probe. With the detector probe positioned just above the tissue surface some reduction in surface tissue fluence was observed, although this effect was negligible at greater tissue depths. It was concluded that, when embedded in tissue, isotropic detector probes produce an accurate measure of tissue fluence or fluence rate.

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Section: Discussionsupporting

confidence: 91%

Monte Carlo simulations of the use of isotropic light dosimetry probes to monitor energy fluence in biological tissues

Jode

1999

Phys. Med. Biol.

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“…It has been shown that experimental nonsuperficial tumours can be effectively treated by PDT in a single session of interstitial irradiation (34,35). In principle, the amount of light energy to be administered can be determined by measuring (13,34,36) or calculating (12,36) optical isofluence curves (or 'optical isodoses') and combining these for multiple fibre insertions (36,37). Subsequently, one estimates the energy fluence rate at the tumour boundary for the given geometry and fibre output to prescribe the treatment time.…”

Section: Interstitial Photodynamic Therapymentioning

confidence: 99%

“…Ifhyperthermia is avoided, J/cm is still not a good measure ofeffective light dose, because the latter depends on the tumour volume and on the distribution of the implanted cylindrical diffusors over this volume. In our opinion, the only way to apply interstitial PDT in a controlled fashion is to use an in situ light dosimetry probe (13,34). This is only feasible for accessible tumours.…”

Section: Interstitial Photodynamic Therapymentioning

confidence: 99%

Light delivery and light dosimetry for photodynamic therapy

Star

1990

Laser Med Sci

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Photodynamic therapy (PDT) has attracted attention because it was considered to be a selective form of cancer treatment causing minimal damage to normal tissues. This is not exactly true, because the ratio between the photosensitizer concentrations in tumour and surrounding normal tissues is not always much more than one. Nevertheless, tumour destruction by PDT with relatively little damage to normal tissue is possible in many cases. This requires sophisticated light delivery and/or light dosimetry techniques. In this respect the limited penetration of light into biological tissues can sometimes be useful. In this paper a qualitative and sometimes quantitative discussion is given of the physical phenomena determining the energy fluence in a biological tissue. Most important is light scattering, the contribution of which depends on the geometrical conditions. Finite beam surface irradiation, irradiation of hollow organs (bladder) and interstitial irradiation are discussed separately. The emphasis is on light 'dose' and light dose distribution. It is emphasized that PDT dosimetry in general is complicated by photosensitizer distribution (which is usually not known), by photobleaching of the sensitizer, by possible effects of hyperthermia, and by changes in optical properties during and as a result of PDT.

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“…In practice, E (x) is measured with an isotropic light detector and a is obtained from the c-folding length (diffusion length). •F-2Ca (5) Y=ycC (6) where y is the fluorescence yield, c the extinction coefficient, and C the concentration of fluorescent agent (P11 or HpD).…”

Section: Theorymentioning

confidence: 99%

Diagnosis of tumors by fluorescence: quantification of photosensitizer concentration

1990

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The concentration of Photofrmn II is needed to determine the dose in photodynamic therapy, and in fluorescence diagnosis of tumors. A method based on fluorescence was devised which shows promise. Diffusion theory was applied in slab geometry with closely spaced excitation and emission wavelengths. A function of the measured radiant energy fluences for excitation and emission, and the depth x, was found that canceled the dependence on depth. A function of the diffusion coefficient and attenuation coefficient was derived from the measured diffuse reflectance. This function compensated for differences in absorption and scattering in different tissues, or a calibration phantom and tissue. Comparisons should be made with the concentration derived in other ways, but the fluorescence method shows promise.

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In Vivo Light Dosimetry For Interstitial Photodynamic Therapy: Results Of Clinical Importance.

Cited by 8 publications

References 0 publications

Monte Carlo simulations of the use of isotropic light dosimetry probes to monitor energy fluence in biological tissues

Monte Carlo simulations of the use of isotropic light dosimetry probes to monitor energy fluence in biological tissues

Light delivery and light dosimetry for photodynamic therapy

Diagnosis of tumors by fluorescence: quantification of photosensitizer concentration

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