Roger Berg

Photodynamic therapy of non‐melanoma malignant tumours of the skin using topical δ‐amino levulinic acid sensitization and laser irradiation

Eighty basal cell carcinomas (BCCs) in 21 patients, 10 lesions of Bowens disease in three patients, and four lesions of cutaneous T‐cell lymphoma in two patients, were treated with photodynamic laser therapy (PDT), using topical application of the haem precursor δ‐amino levulinic acid (ALA). The diagnoses were confirmed histologically prior to treatment. Fifty‐five of the BCCs were superficial lesions, and 25 were nodular. Of the 80 BCCs, 39 (49%) were located on the trunk, 36 (45%) on the head and neck region, four (15%) on the leg and one on the arm. The two principal locations of the 10 Bowens disease lesions were the leg (50%) and the trunk (40%). The T‐cell lymphoma lesions were located on the shoulder and on the arm. A water‐in‐oil based cream containing 20% ALA was applied to the lesions, with a margin of about 10–20 mm beyond the visible tumour border, 4–6 h before the laser procedure. During this period of time the highly fluorescent and photodynamically active substance protoporphyrin IX (Pp IX) is synthesized via the haem cycle. Laser‐induced fluorescence (LJF) was used for real‐time monitoring of the Pp IX distribution in the tumour and in the normal surrounding skin, before and after treatment in all patients. Before laser treatment the Pp IX distribution demonstrated by LJF showed a demarcation between tumour and normal skin of about 15:1 for BCC and Bowens disease, and 5:1 for T‐cell lymphomas. Laser light from a pulsed frequency‐ doubled Nd: YAG laser pumping a dye laser with light emission at 630 nm was used for the therapy. The power density in the irradiation was kept below 110 mW/cm2, in order to avoid hyperthermal effects. A total energy of 60 J/cm2 was delivered for 10–20 min, depending on the tumour size. A complete response rate of 100% in superficial BCCs and 64% in nodular BCCs occurred after a single laser treatment, and a response rate of 100% was achieved after one additional treatment in the nodular BCCs. In the Bowens disease lesions a complete response of 90% was obtained with a single treatment. Two of the four T‐cell lymphomas resolved completely. The follow‐up time was between 6 and 14 months.

Time-resolved Transillumination For Medical Diagnostics

A time-gated technique to improve the possibility of localizing spatial differences in absorption when transilluminating a turbid, highly scattering medium, such as human tissue, is demonstrated. When transmitting picosecond laser pulses and detecting photons on the opposite side of the object, the contrast can be strongly enhanced by detecting only the photons with the shortest traveling time. Measurements on a 35-mm-thick tissue phantom with 5-mm-diameter absorbing objects inside are reported with data for a human hand in vivo. Implications for optical mammography (diaphanography) are discussed.

Pharmacokinetic studies on 5-aminolevulinic acid-induced protoporphyrin IX accumulation in tumours and normal tissues

Laser-induced fluorescence (LIF) for in vivo point monitoring and fluorescence microscopy incorporating a CCD camera were used to study the fluorescence distribution of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) in tumours. Fluorescence in a chemically-induced adenocarcinoma in the liver of rats and in an aggressive basal cell carcinoma in a patient were studied after intravenous injection of ALA at a dose of 30 mg/kg body weight. The LIF technique demonstrated slightly more ALA-induced PpIX fluorescence in the tumour than in the surrounding normal liver and abdominal muscle of rats. The visible parts of the human basal cell carcinoma exhibited strong ALA-induced fluorescence, while this fluorescence was much weaker in the necrotic areas of the tumour and in the surrounding normal skin.

Medical transillumination imaging using short-pulse diode lasers

The recently introduced time-resolved technique for enhanced medical transillumination imaging has been demonstrated for the important case of a diode laser transmitter. This type of gated-viewing technique utilizes early received light only to reject multiply scattered, delayed light, normally blurring the image. Human breast-cancer detection is demonstrated in vitro, and the observations are explained by using theoretical modeling and tissue phantom experiments.

Measurements of the optical properties of tissue in conjunction with photodynamic therapy

A simple optical dosimeter was used to measure the light intensity in rat liver and muscle in vivo with fibers positioned at different depths to investigate whether the light penetration changed during photodynamic therapy (PDT). The results were then correlated with measurements of the three optical-interaction coefficients µ(s), µ(a) and g for wavelengths in the range 500-800 nm for PDT-treated and nontreated rat liver and muscle tissue in vitro. Adistinct increase in the absorption coefficient was seen immediately after treatment, in agreement with the decreasing light intensity observed during the treatment, as measured with the optical dosimeter. The collimated transmittance was measured with a narrow-beam setup, and an optical integrating sphere was used to measure the diffuse reflectance and total transmittance of the samples. The corresponding optical properties were obtained by spline interpolation of Monte Carlo-simulated data. To ensure that the measured values were correct, we performed calibration easurements with suspensions of polystyrene microspheres and ink.

Multispectral tissue characterization with time-resolved detection of diffusely scattered white light

A novel technique for the noninvasive measurement of tissue optical properties simultaneously at all visible and near-infrared wavelengths is presented. The technique is based on the time-resolved detection of multicolor diffusely scattered light. Short pulses of white light are produced by using self-phase modulation by focusing the light from a short-pulsed high-power laser into a cuvette filled with water. After spectral dispersion in a polychromator and temporal dispersion in a streak tube, a two-dimensional CCD camera was used as a detector, with one dimension used for time resolution and the other one for wavelength separation.

Effects of Optical-constants On Time-gated Transillumination of Tissue and Tissue-like Media

Light transillumination was used to study structures inside turbid media. Time-gated viewing was performed to suppress multiply-scattered light and thus improve spatial resolution. We demonstrate that, for the case of scattering-dominated attenuation (scattering coefficient much greater than the absorption coefficient), the detection of early transmitted light will be practically insensitive to variations in the absorption coefficient. This is an important observation for the development of time-gated optical mammography, since optical mammography using continuous-wave light is based on increased light absorption in the tumour region caused by the neovascularization surrounding a tumour. In order to detect tumours in time-gated viewing it is the scattering coefficient of the tumour that must be characteristic. The scattering coefficient is measured to be lower in the tumour region than in the surrounding breast tissue for one resected breast specimen.

Multi-colour fluorescence imaging in connection with photodynamic therapy of delta-amino levulinic acid (ALA) sensitised skin malignancies

Abstract A system for multi-colour fluorescence imaging of tissue is described. The instrument is mainly developed for tissue diagnostics to identify and localise malignant tumours, but might also be useful for real-time monitoring of the therapeutic dose delivered during photodynamic therapy. In vivo examples from various malignant skin lesions following topical I´-amino levulinic acid (ALA) administration are presented. The diagnostic system utilises both characteristics of a fluorescent tumour marker, such as a porphyrin containing substance, and the native tissue autofluorescence to characterise the tissue. A dimensionless function of three or four simultaneously recorded fluorescence intensities is formed and an optimum-contrast image is calculated pixel-by-pixel. (Less)

Laser-induced fluorescence studies of normal and malignant tumour tissue of rat following intravenous injection of delta-amino levulinic acid

Laser‐induced fluorescence was studied in normal and tumour tissue of rat after intravenous injection of δ‐amino levulinic acid (ALA). The aim of the study was to investigate the protoporphyrin IX accumulation in different tissue types in rat after systemically administered ALA.

Time-resolved white light transillumination for optical imaging

Purpose: To describe a new breast-imaging method with the potential of multi-spectral optical transillumination based on a time-resolved technique. Material and Methods: A breast phantom was irradiated with ultra-short laser pulses of white light generated by self-phase modulation of an incident high-power laser pulse in water. Time-resolved detection of the transmitted light was performed. Contrast resolution was studied using different absorbers located inside the breast phantom. Results and Conclusion: The results showed that simultaneous, multi-spectral transillumination is possible. The technique can also be used for measurements of optical properties in tissue.