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Biomedical subjects

G F Thomas

Publications and source records attributed to G F Thomas.

10 recordsLinked to original sources
PubMed1997

Phase I trial of photodynamic therapy in the treatment of recurrent superficial transitional cell carcinoma of the bladder.

OBJECTIVES: A Phase I trial of photodynamic therapy (PDT) in the treatment of superficial transitional cell carcinoma (TCC) of the bladder was performed. METHODS: Twenty patients with recurrent superficial TCC of the bladder after receiving a mean of 2.6 (range 1 to 6) courses of intravesical therapy were treated with PDT. The photosensitizer Photofrin II dose was 1.5 or 2.0 mg/kg. A 630-nm intravesical red laser was used to activate the photosensitizer 2 days after administration of Photofrin II. A 0.01% intralipid solution was used as a bladder-filling medium to scatter light and achieve more homogeneous light distribution. Light doses from 5.1 to 25.6 J/cm2 (total dosage 1500 to 5032 J) were used to illuminate the bladder. RESULTS: Twenty patients underwent 21 treatments with PDT. Complications included asymptomatic reflux in 4 patients. One other patient, treated at the highest total light dose, experienced bladder contraction and fibrosis. Nine patients (45%) had no tumor evident at cystoscopy, on random biopsies, or in urinary cytology at the 3-month evaluation after treatment. Four patients remained without recurrent disease for 23 to 56 months. Sixteen of 20 (80%) patients experienced recurrence, and 8 of the 16 underwent cystectomy. CONCLUSIONS: An intravenous photosensitizer dose of 1.5 mg/kg Photofrin II followed by light energy in the range of 13 J/cm2 (total light dose 2500 to 3250 J) was defined as a safe treatment parameter and resulted in tumor responses. With present technologies, administration of PDT requires careful dosimetry.

Adult↗
PubMed1995

A diffusing sphere which delivers homogeneous laser light for use in photodynamic therapy.

Photodynamic therapy (PDT) exploits the selective uptake of a photosensitizer in tumors and other hyperproliferative target tissues, as well as the ability to direct the treatment light beam to a specific region. Since the photodynamic effect depends on light dose, tissue optical properties and photosensitizer concentration, uniform delivery of light is crucial to attain optimal photodynamic effect. Many commonly used methods for delivering laser light during photodynamic therapy, such as a free fiber or microlens, require fiber and laser adjustments to obtain a highly uniform beam. In this study, we test the ability of a diffusing sphere to improve the uniformity of a light field coming from an argon laser coupled to a free fiber, in which no attempt has been made to optimize beam characteristics. Light fields from the free fiber, a microlens and the diffusing sphere are compared for uniformity via light intensity readings. An in vivo comparison between the sphere and the free fiber is also made in guinea pigs given Photofrin-II. The diffusing sphere decreases problems with shielding, allows quick and easy application of light by simply applying the device over the desired treatment area, and optimizes the desired photodynamic effect by producing ad highly uniform beam of light with no necessity to optimize light delivery by vibrating, looping or re-cleaving fibers.

Animals↗
PubMed1994

Intrathoracic photodynamic therapy: a canine normal tissue tolerance study and early clinical experience.

Surgery with intraoperative photodynamic therapy (PDT) has the potential to improve the treatment of pleural malignancies. Before embarking on such treatment in humans, however, thoracic tissue tolerance to PDT was studied. For each of three (1 week, 1 month, and 6 month) study end-points, one control (no Photofrin II [PII]) and four treated animals underwent thoracotomy 72 hours after I.V. injection (6 mg/kg) PII. Red light (630 nm) was delivered (5-40 J/cm2) to the pleural surface (1 cm diameter) of selected thoracic organs. No clinical differences were observed between PDT and control dogs. The control showed no histological changes; however, in the treated animals focal areas of coagulation necrosis were found at 1 week which progressed to fibrosis at 1 month. The extent and depth of injury was proportional to light dose. The lung was the most sensitive; the chest wall was the most resistant. Myocardium had superficial damage, whereas coronary arteries appeared normal. The results provide the basis for proceeding to phase I human trials in the evaluation of PDT as an intraoperative adjuvant treatment in the management of pleural malignancies.

Animals↗
PubMed1993

Tolerance of small bowel anastomoses in rabbits to photodynamic therapy with dihematoporphyrin ethers and 630 nm red light.

Photodynamic therapy (PDT) is being evaluated in experimental clinical trials in patients with peritoneal malignancies. Some patients require partial small bowel resection with re-anastomosis prior to PDT because of bulky tumor or focal involvement of the small bowel by tumor. To assess the safety of PDT in this setting, the tolerance of small bowel anastomoses in New Zealand white rabbits to PDT with dihematoporphyrin ethers (DHE) and 630 nm light was studied. With conventional DHE doses of 1.5-2.5 mg/kg given 24 hours prior to surgery and light doses of 0-20 J/cm2 of 630 nm light, no adverse effects were seen on the healing of small bowel anastomoses. Higher photosensitizer doses of 10 mg/kg and 20 mg/kg in conjunction with 20 J/cm2, however, induced failure and breakdown of fresh anastomoses in 2/3 and 4/4 animals, respectively.

Anastomosis, Surgical↗
PubMed1991

Technique of photodynamic therapy for disseminated intraperitoneal malignant neoplasms. Phase I study.

Patients with disseminated intraperitoneal malignant neoplasms were given intra-abdominal photodynamic therapy. Patients received dihematoporphyrin ethers intravenously 48 to 72 hours before laparotomy at doses of 1.5 to 3.0 mg/kg. At operation, as much tumor as possible was resected. Red light (630 nm) was delivered to all peritoneal surfaces from an argon-pumped dye laser at doses ranging from 0.2 to 3.0 J/cm2 in an escalating fashion. Viscera and peritoneal surfaces were anatomically isolated and exposed to light for intervals calculated to deliver the prescribed energy. Light was delivered to mesentery and bowel by a flat-cut optical fiber, while other areas, including diaphragm, viscera, omental bursa, gutters, and pelvis, were delivered light through a diffusing wand. Twenty-three patients (13 with ovarian cancer, eight with sarcoma, and two with pseudomyxoma peritoneii) underwent photodynamic therapy. Five of eight patients cleared positive peritoneal cytologies after treatment. Six patients remained clinically free of disease for up to 18 months, and five patients had treatment-related complications. Intraperitoneal phototherapy is technically feasible and deserving of clinical evaluation.

Adrenal Gland Neoplasms↗
PubMed1991

A light-diffusing device for intraoperative photodynamic therapy in the peritoneal or pleural cavity.

Light delivery to anatomic areas involved by tumor is critical for effective photodynamic therapy. The authors provide a detailed overview of a light-diffusing device which they have used for intraoperative illumination of the peritoneal and pleural cavities in patients with tumors involving the surfaces of these cavities. Their device represents an inexpensive modification of widely available endotracheal tubes. It has been used to deliver intraoperative photodynamic therapy in over 50 patients without episodes of device failure. When combined with a lipid-based, light-diffusing medium and on-line power/energy density monitoring, it allows homogeneous illumination of these complex surfaces.

Combined Modality Therapy↗
PubMed1991

Transcutaneous determination of tissue dihematoporphyrin ether content. A device to optimize photodynamic therapy.

Photodynamic therapy involves the use of light of appropriate wavelength to excite a photosensitizer resulting in tissue destruction. The photosensitizer dihematoporphyrin ether is selectively retained in tumors allowing for tumor destruction while sparing normal structures. Accessibility of skin tumors makes them well suited for photodynamic therapy. Tissue and tumor dihematoporphyrin ether content is estimated based on the amount of dihematoporphyrin ether administered. In our study, skin dihematoporphyrin ether content was measured in guinea pigs transcutaneously by a hand-held fluorometer and compared with dihematoporphyrin ether determinations done on skin biopsy specimens. Fluorometry was performed on guinea pigs receiving 0, 2.5, 5, 10, and 25 mg/kg of dihematoporphyrin ether. Transcutaneous measurements of skin fluorescence increased with increasing dihematoporphyrin ether dose and correlated well with skin dihematoporphyrin ether content as determined by extracting dihematoporphyrin ether from skin samples. Transcutaneous fluorescent measurements of guinea pigs given 0 and 2.5, 2.5 and 5, 5 and 10, and 10 and 25 mg/kg of dihematoporphyrin ether differed in a statistically significant manner. Transcutaneous fluorometric determination of dihematoporphyrin ether content and extraction of dihematoporphyrin ether from skin samples were able to reflect differences in dihematoporphyrin ether dosing and presumably skin dihematoporphyrin ether content. However, transcutaneous fluorometry provides an instantaneous estimate of tissue dihematoporphyrin ether without the need for a tissue sample. This may provide a clinical tool to predict more accurately the optimal light dose necessary to maximize photodynamic therapy.

Animals↗
PubMed1990

Response of black and white guinea pig skin to photodynamic treatment using 514-nm light and dihematoporphyrin ether.

Differences in skin pigmentation may significantly affect light penetration during photodynamic therapy. This study evaluated the effect of skin pigmentation on dermatotoxic reaction to photodynamic therapy utilizing the photosensitizer dihematoporphyrin ether. Black and white guinea pigs were given 10 mg/kg of dihematoporphyrin ether, depilated, and treated 48 hours after injection with 30 mW/cm2 of 514-nm light. Eschar formation was observed on white skin at an average light dose of 26 J/cm2, whereas black skin showed similar changes at 58 J/cm2. Microscopically, superficial necrosis corresponded to the gross changes noted. Our results agree with data describing the difficulty of treating pigmented lesions such as malignant melanoma with photodynamic therapy. This further suggests that higher light doses may be required to treat superficial lesions and produce skin photosensitivity in dark-skinned individuals.

Animals↗
PubMed1989

Photodynamic therapy of rabbit endometrial transplants: a model for treatment of endometriosis.

The potential of photodynamic therapy for endometriosis was evaluated by autotransplantation of endometrial tissue in 15 female virgin New Zealand white rabbits. After maturation, 14 animals were injected intravenously with 10 mg/kg of dihematoporphyrin ether (DHE) and, 24 hours later, transplants were exposed to 630 nm light at 100 to 210 mW/cm2. Sixteen transplants received 100 J/cm2, 10 transplants received 50 J/cm2; 13 untreated transplants served as controls. In the remaining animal that did not receive DHE, 3 transplants were irradiated with 100 J/cm2. Six days after treatment, transplants were harvested with the underlying musculature, and multiple sections were examined histopathologically. Complete endometrial epithelial destruction was seen in 13 of 16 transplants (81%) in the 100 J/cm2 group and in 6 of 10 transplants (60%) in the 50-J/cm2 group. Nearly complete endometrial epithelial destruction was seen in 2 other transplants in each group. No damage occurred in either the 3 transplants that received 100 J/cm2 without prior DHE or in the 13 transplants with DHE and no irradiation. The sensitivity of ectopic rabbit endometrial tissue encourages further evaluation of photodynamic therapy for the treatment of human endometrial disorders.

Animals↗