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The ability to detect photosensitisers in tissue at a microscopical level is important when studying photodynamic therapy (PDT) in both normal and malignant tissue. We have studied the fluorescence distribution of aluminium sulphonated phthalocyanine (A1SPc) in the normal rat bladder using a cooled CCD (charge coupled device) imaging system with computerised image processing. This system makes it possible to carry out a quantitative assessment of photosensitiser fluorescence in the various layers of the bladder wall. The highest fluorescence intensities were obtained within 1 h of intravenous administration but there was little selectivity of uptake between layers. A1SPc was eliminated from the deeper muscle layers more quickly than from the superficial layers of the bladder wall so that by 24 h a 4:1 ratio of fluorescence intensity was apparent which persisted at least until 72 h, although the absolute amount of photosensitiser declined. Following irradiation by red light (675 nm), photobleaching of the sensitiser in the deeper layers further increased this ratio. Direct absorption of A1SPc by the bladder wall following intravesical administration proved unreliable. Images Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Forty nine patients with rectosigmoid carcinoma considered unsuitable for surgery underwent endoscopic Nd:YAG laser treatment for palliation of symptoms and tumour eradication, if feasible. Altogether 25 (51%) of the lesions had distal margins less than 7 cm from the anus and 36 (73%) extended above the peritoneal reflection. In seven patients with tumours less than 3 cm in diameter, symptomatic improvement was achieved in all (mean follow up 16 months) and complete tumour eradication in three. In the remaining 42 patients with larger tumours (34 greater than 2/3 circumferential, mean length 5.5 cm), symptomatic improvement was achieved with repeated treatments (average 3.4) in 31 (74%) over a mean follow up of 19 weeks. Of the parameters assessed, only circumferential tumour extent proved significant in predicting functional outcome after treatment. All treatment failures (eight initial, three late) occurred in patients with extensive tumours, and only seven of these patients were considered fit for colostomy. Bowel perforation occurred in two patients (5%) but there was no treatment-related mortality. Mean stay in hospital for all laser treatments was nine days (30% were outpatient attendances). These results suggest that laser therapy may be the palliative treatment of choice in patients with rectal carcinoma unsuitable for surgery.

Ten patients with colorectal cancers unsuitable for operation were treated with endoscopic photodynamic therapy (PDT). The patients were assessed before treatment, and at 1 week and 1 month after treatment by colonoscopy with biopsy and endoluminal ultrasound examination. The depth of tumour was measured and the effect of PDT was quantified by measuring the reduction in tumour depth. All patients were sensitized with 2·5mg kg−1 of haematoporphyrin derivative, 48h before phototherapy. A standard treatment protocol of light exposure was used. Up to four parts of the tumour were treated with 50 J of red light (630 nm) from a tuneable dye laser, through a flexible optical fibre passed through the colonoscope and inserted into the tumour. Two patients with small lesions are tumour-free 20 and 28 months after PDT. One treatment of an advanced tumour was complicated by a haemodynamically significant secondary haemorrhage. PDT may be most suitable for the treatment of small tumours or for small areas of persistent tumour where the bulk has been removed by alternative techniques.

For effective photosensitization of malignant tumours, a sensitizer should exhibit appreciable absorption at red to near-infrared wavelengths and generate cytotoxic species via oxygen-dependent photochemical reactions. These photosensitization mechanisms rely on the excitation of the sensitizer from its electronic ground state to the fluorescent singlet state, which is in turn transformed into the longer-lived triplet state. Efficient formation of this metastable state is required because it is the interaction of the triplet state with tissue components that generates cytotoxic species such as singlet oxygen. Measurement of fluorescence provides a useful means of probing the sensitizer, particularly because detection sensitivities for both the triplet state and the cytotoxic singlet oxygen are much lower. With the development of chemically well-defined sensitizers, in vivo fluorescence detection has the potential to provide quantitative assessment of photoactive sensitizer distributions. The reactive properties of sensitizer triplet states and species such as singlet oxygen can result in significant sensitizer photodegradation, which may appear undesirable but can be exploited in vivo under certain conditions.

Recent reports suggest that the effect of photodynamic therapy (PDT) can be enhanced by fractionating the light dose or reducing the light fluence rate. We assessed these options on two tissues in rats (normal colon and a transplanted fibrosarcoma) using the photosensitiser meta-tetrahydroxyphenylchlorin (mTHPC). Animals were sensitised with 0.3 mg/kg mTHPC, 3 days prior to illumination with red light (652 nm) using a single fibre touching the target tissue and killed 1–3 days later for quantitative measurement of the extent of PDT necrosis. Results were similar for both tissues, although the differences between illumination regimens were less marked in tumour tissue. Using continuous illumination and a fixed low energy in colon, the extent of necrosis was up to almost three times larger with 5 mW than with 100 mW, although the maximum attainable necrosis was independent of power. The long treatment time using 5 mW could be halved without loss of effect by increasing the power during treatment. Dividing the light into two equal fractions at 100 mW increased the lesion size by up to 20% in colon (independent of the timing of the dark interval), but by only 10% in tumour and had no effect at 20 mW. Previous studies using 5-aminolaevulinic acid (ALA) showed a much larger effect of fractionation that was critically dependent on the timing of the dark interval. We postulate that enhancement of PDT by fractionation is due to improved oxygen supply to the treated area which may be due to reversal of temporary vascular occlusion (more likely with ALA) or less rapid photochemical consumption of oxygen (more likely with mTHPC). At lower fluence rates, the oxygen consumption rate is not fast enough to be improved by fractionation. We conclude that fractionated or low power light delivery can enhance PDT with mTHPC. Although the effects are not large, this may be of value for interstitial treatment of solid tumours when multiple sites are treated simultaneously.

Background: Many patients with advanced malignant dysphagia are not suitable for definitive treatment. The best option for palliation of dysphagia varies between patients. This paper looks at a simple technique for enhancing laser recanalisation. Aim: To assess the value of adjunctive brachytherapy in prolonging palliation of malignant dysphagia by endoscopic laser therapy. Patients: Twenty two patients with advanced malignant dysphagia due to adenocarcinoma of the oesophagus or gastric cardia, unsuitable for surgery or radical chemoradiotherapy. Methods: Patients able to eat a soft diet after laser recanalisation were randomised to no further therapy or a single treatment with brachytherapy (10 Gy). Results were judged on the quality and duration of dysphagia palliation, need for subsequent intervention, complications, and survival. Results: The median dysphagia score for all patients two weeks after initial treatment was 1 (some solids). The median dysphagia palliated interval from the end of initial treatment to recurrent dysphagia or death increased from five weeks (control group) to 19 weeks (brachytherapy group). Three patients had some odynophagia for up to six weeks after brachytherapy. There was no other treatment related morbidity or mortality. Further intervention was required in 10 of 11 control patients (median five further procedures) compared with 7/11 brachytherapy patients (median two further procedures). There was no difference in survival (median 20 weeks (control), 26 weeks (brachytherapy)). Conclusions: Laser therapy followed by brachytherapy is a safe, straightforward, and effective option for palliating advanced malignant dysphagia, which is complementary to stent insertion.

5-Aminolaevulinic acid (ALA)-induced protoporphyrin IX (PpIX) is proving to be a useful photosensitizer for photodynamic therapy (PDT). Conversion of PpIX to haem requires catalysed chelation with iron, and thus the presence of an iron chelator should, in theory, lead to an increase in cellular PpIX accumulation. This paper assesses the in vivo effect of a new iron chelator, 1,2-diethyl-3-hydroxypyridin-4-one (CP94), on the kinetics of PpIX in different layers of the bladder wall. Wistar rats were given 1% or 10% ALA intravesically with or without intraperitoneal CP94. The biodistribution of ALA-induced PpIX in the bladder was evaluated using fluorescence microscopy. Photodynamic effects on the bladder were compared in rats receiving various drug dosimetries. In CP94-treated rats, 5-7 h after administration of 10% ALA solution, the fluorescence intensity of PpIX in the urothelium was doubled compared with animals given ALA alone, whereas in the muscle layer PpIX remained at a low level similar to that found without the iron chelator. At an ALA concentration of 1%, although the PpIX concentration was not increased with CP94, the urothelial selectivity of PDT compared with the muscle layer was enhanced. In conclusion, by using CP94, a further reduction in skin photosensitization may be possible as similar photodynamic effects can be achieved with a lower dose of ALA. The addition of CP94 seems to be an effective and convenient way to potentiate ALA-induced PpIX tissue selectivity between the urothelium and the underlying layers of the bladder wall.

BACKGROUND/AIMS: A major drawback of laser endoscopy in the palliation of malignant dysphagia is the need for repeated treatments. This study was designed to test whether external beam radiotherapy would reduce the necessity for repeated laser therapy. PATIENTS/METHODS: Sixty seven patients with inoperable oesophageal or gastric cardia cancers and satisfactory swallowing after initial laser recanalisation were randomised to palliative external beam radiotherapy (30 Gy in 10 fractions) or no radiotherapy. All patients underwent a 'check' endoscopy five weeks after initial recanalisation and were subsequently reendoscoped only for recurrent dysphagia, which occurred in 59 patients. RESULTS: Dysphagia was relieved equally well in both groups and the improvement was maintained with further endoscopic treatment. The initial dysphagia controlled interval and the duration between procedures required to maintain lifelong palliation (treatment interval) increased from five to nine weeks (median) in the radiotherapy group (p < 0.01 both parameters). Radiotherapy was well tolerated in all but three patients. One perforation occurred and two fistulae opened after dilatation in patients who received radiotherapy. CONCLUSION: Additional radiotherapy reduces the necessity for therapeutic endoscopy for a patient's remaining life. It has an important role in relatively well patients who are likely to survive long enough to benefit.

Photodynamic therapy (PDT) is a promising technique for the treatment of small tumours in organs where it is essential to minimise damage to immediately adjacent normal tissue as PDT damage to many tissues heals by regeneration rather than scarring. As preservation of function is one of the main aims of treating laryngeal tumours, this project studied the effects of PDT on the normal rabbit larynx with two photosensitisers, endogenous protoporphyrin IX (PPIX) induced by the administration of 5-aminolaevulinic acid (ALA) and disulphonated aluminium phthalocyanine (AIS2Pc). The main aims of the study were to examine the distribution of protoporphyrin IX and AIS2Pc by fluorescence microscopy in the different regions of the larnyx and to assess the nature and subsequent healing of PDT damage. Peak levels of PPIX were found 0.5-4 h after administration of ALA (depending on dose) with highest levels in the epithelium of the mucosa. With 100 mg kg-1, PDT necrosis was limited to the mucosa, whereas with 200 mg kg-1 necrosis extended to the muscle. With 1 mg kg-1 AIS2Pc, 1 h after administration, the drug was mainly in the submucosa and muscle, whereas after 24 h, it was predominantly in the mucosa. PDT at 1 h caused deep necrosis whereas at 24 h it was limited to the mucosa. All mucosal necrosis healed by regeneration whereas deeper effects left some fibrosis. No damage to cartilage was seen in any of the animals studied. The results of this study have shown that both photosensitisers are suitable for treating mucosal lesions of the larynx, but that for both it is important to optimise the drug dose and time interval between drug and light to avoid unacceptable changes in normal areas. Images Figure 2 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8

Surgery is the only effective treatment for dysplasia in the gastrointestinal tract with considerable associated morbidity and mortality and is difficult to justify without confirmed malignancy. Photodynamic therapy (PDT) produces localised necrosis, which can be limited to the mucosa. This study examined the mechanical properties of the normal rat stomach after PDT. The aim of this study was to measure the bursting pressure of PDT lesions in the stomach and to assess gastric emptying after producing circumferential mucosal necrosis at the pylorus by PDT. Two photosensitising agents were used--5-aminolaevulinic acid (ALA), and aluminium disulphonated phthalocyanine (A1S2Pc). Normal rats were sensitised and PDT lesions created in the stomach with red light. The bursting pressure was measured and compared with that in thermal control lesions. In further experiments, circumferential mucosal necrosis was produced at the pylorus, and animals observed for subsequent eating and weight gain. It was found that gastric bursting pressure was reduced after thermal injury, but not at any time after PDT (with A1S2Pc, but not ALA, adhesive omental reinforcement was required to maintain the gastric wall strength at one week). For the pyloric lesions, gastric emptying was permanently impaired using A1S2Pc, but with low dose ALA (20 mg/kg) had returned to normal by three days. With ALA, but not A1S2Pc, necrosis could be limited to the mucosa. In conclusion, using ALA, selective ablation of the gastric mucosa is possible, which does not reduce the strength of the stomach and only temporarily delays gastric emptying. PDT is a promising technique for the circumferential ablation of dysplastic mucosa.

5-Aminolaevulinic acid (ALA)-induced prophyrin photosensitisation is an attractive option for photodynamic therapy (PDT) since skin photosensitivity is limited to 1-2 days. However, early clinical results on colon tumours using the maximum tolerated oral dose of 60 mg kg-1 showed only superficial necrosis, presumably owing to insufficient intratumoral porphyrin levels, although inadequate light dosimetry may also be a factor. We undertook experiments using ALA, 25-400 mg kg-1 intravenously, to establish the threshold doses required for a PDT effect. Laser light at 630 nm (100 mW, 10-200 J) was delivered to a single site in the colon of photosensitised normal Wistar rats at laparotomy. The animals were killed 3 days later and the area of PDT-induced necrosis measured. No lesion was seen with 25 mg kg-1. The lesion size increased with larger ALA doses and with the light dose but little benefit was seen from increasing the ALA dose above 200 mg kg-1 or the light dose above 100 J. Thus there is a fairly narrow window for optimum doses of drug and light. Further experiments showed that the PDT effect can be markedly enhanced by fractionating the light dose. A series of animals was sensitized with 200 mg kg-1 ALA and then treated with 25 J. With continuous irradiation, the lesion area was 13 mm2, but with a single interruption of 150 s the area rose to 94 mm2 with the same total energy. Results were basically similar for different intervals between fractions (10-900 s) and different numbers of fractions (2-25). This suggests that a single short interruption in the light irradiation may dramatically reduce the net light dose required to achieve extensive necrosis. Images Figure 3

Photodynamic therapy (PDT) produces localised necrosis with light after prior administration of a photosensitising drug. As PDT lesions in the gastrointestinal tract heal so well, the technique is suitable for repeated endoscopic use. In this study, PDT was used to treat large polyps (four duodenal and two colorectal) unsuitable for surgery in 6 patients with familial adenomatous polyposis (FAP). Patients were sensitised with 60 mg/kg 5-aminolaevulinic acid (ALA) orally or intravenous (i.v.) 2.0 mg/kg Photofrin. Laser treatment was performed 6 h after ALA or 48 h after Photofrin using a gold vapour laser. Necrosis was only superficial (up to 1.8 mm) using ALA but much deeper using Photofrin. The one malignant polyp (8 mm diameter in the colon) showed a complete response using Photofrin. All healed safely with no complications. Photofrin worked better, but caused cutaneous photosensitivity lasting up to 3 months. ALA cleared within 2 days, but its use is limited by the superficial effect. Better results with ALA may be obtained using higher drug doses or modified light dosimetry. Fluorescence microscopy showed no evidence of selectivity of photosensitisation between neoplastic and normal tissue. PDT is a promising treatment for inoperable polyps in patients with FAP, but further work is required to optimise the treatment conditions.

The first study of photodynamic therapy in the human gastrointestinal tract using 5 aminolaevulinic acid (ALA) induced protoporphyrin IX as the photosensitising agent is described. Eighteen patients with colorectal, duodenal, and oesophageal tumours were studied. After 30-60 mg/kg of ALA given orally, biopsy specimens of tumour and adjacent normal mucosa were taken 1-72 hours later. These specimens were examined by quantitative fluorescence microscopy for assessment of sensitisation with protoporphyrin IX. Ten patients were given a second dose of ALA a few weeks later and their tumours were treated with red laser light (628 nm). With 30 mg/kg ALA, the highest fluorescence values were detected in the duodenum and oesophagus, and the lowest in the large bowel. Doubling the ALA dose in patients with colorectal tumours gave protoporphyrin IX fluorescence intensities similar to those in patients with upper gastrointestinal lesions and improved the tumour:normal mucosa protoporphyrin IX sensitisation ratio. The treated patients showed superficial mucosal necrosis in the areas exposed to laser light. Six patients had transient rises in serum aspartate aminotransferases, two mild skin photosensitivity reactions, and five mild nausea and vomiting. In conclusion, photodynamic therapy with systemically administered ALA may be a promising technique for the treatment of small tumours and areas of dysplasia such as in Barrett's oesophagus.

Photodynamic therapy of cancer exposes adjacent arteries to the risk of injury and the possibility of haemorrhage and thrombosis. The nature of photodynamic injury to normal arteries has not been satisfactorily defined, and the ability of arteries to recover with time is unclear. To clarify these issues, we have investigated the effects of PDT on rat femoral arteries, using a second-generation photosensitiser, disulphonated aluminium phthalocyanine, and a new method of photosensitisation, using endogenous synthesis of protoporphyrin IX following systemic administration of 5-aminolaevulinic acid (ALA). Pharmacokinetic studies of sensitiser fluorescence were carried out to determine peak levels of sensitiser. Subsequently photodynamic therapy at times corresponding to maximal fluorescence was performed using two light doses, 100 and 250 J cm-2. The nature of injury sustained and recovery over a 6 month period was investigated. Three days following PDT, all vessels treated showed complete loss of endothelium, with death of all medial smooth muscle cells, leaving an acellular flaccid artery wall. No vascular occlusion, haemorrhage or thrombosis was found. A striking feature was the lack of inflammatory response in the vessel wall at any time studied. Re-endothelialisation occurred in all vessels by 2 weeks. The phthalocyanine group showed repopulation of the media with smooth muscle cells to be almost complete by 3 months. However, the ALA group failed to redevelop a muscular wall and remained dilated at 6 months. Luminal cross-sectional area of the ALA-treated group was significantly greater than both control and phthalocyanine groups at 6 months. All vessels remained patent. This study indicates that arteries exposed to PDT are not at risk of catastrophic haemorrhage or occlusion, a finding that is of significance for both the local treatment of tumours and the use of PDT as an intraoperative adjunct to surgery for the ablation of microscopic residual malignant disease. Images Figure 1 Figure 3

The accumulation of endogenous porphyrins in rats following systemic administration of 5-aminolaevulinic acid (ALA) has been examined to assess the photosensitization characteristics of this technique for photodynamic therapy (PDT) and chemical extraction assays with fluorescence and absorbance detection of the porphyrin content have been carried out. We compared the results obtained using quantitative microfluorimetry on normal gastric and colonic tissues in rats at 0.5, 1, 2, 4 and 6 h and chemically induced duodenal tumours 2 and 4.5 h after intravenous administration of ALA at a dose of 200 mg kg-1. With chemical extraction followed by high performance liquid chromatography analysis, protoporphyrin IX (PpIX) was found to be the predominant porphyrin present, reaching peak levels of several microgrammes per gramme at 2-4 h in each type of tissue; a small amount of coproporphyrin was detected at 0.5 and 2 h in normal gastric mucosa and duodenal tumour respectively. Both the extraction assay and quantitative microfluorimetry showed that the porphyrin fluorescence builds up rapidly in the mucosal layers of the colon and stomach, reaching a maximum at 2 h, whereas lower fluorescence levels were found with a slower rate of accumulation in the corresponding muscularis layers. A significant PpIX content was found in the duodenal tumour, with a maximum of 7.1 micrograms g-1 4.5 h after ALA administration. We conclude that systemic administration of ALA can induce effective tissue sensitization with protoporphyrin IX and appears to be a promising technique for PDT.

Introduction With the advent of capsule endoscopy, automated detection of Barrett9s columnar lined oesophagus (BE) becomes achievable. This might allow screening to be undertaken in a non-specialist setting. We have shown that elastic scattering spectroscopy, which could be incorporated into a capsule, accurately differentiates squamous from columnar mucosa but cannot reliably differentiate gastric from oesophageal columnar mucosa. We hypothesise that the shape of BE distribution may hold a key to this. The aim of this study, therefore, was to determine whether there are distinctive macroscopic shapes of Barrett9s columnar lined oesophagus which could be used for automated detection. Methods Sixty-five patients (53 men, median age 69, range 45–83) with dysplastic BE, who were being assessed for endoscopic therapy between 2006 and 2009, had visual mapping of each quadrant of BE every 1 cm at endoscopy. The maps were reconstructed in electronic format, as two-dimensional, colour-coded visual representations, using Microsoft Excel programming. This allows for easy observation and interpretation of the macroscopic BE pattern distribution. BE patterns were described as Circumferential, Islands and Tongues and basic parametric statistics were applied. Results Fifty-nine patients (92%) had a hiatus hernia (mean length 2.9 cm). Mean length BE was 7.6 cm; only two patients had short segment ( Conclusion We have developed an electronic mapping tool which provides a quick and simple method of describing macroscopic visual patterns in BE. The morphology of BE usually involves tongues or islands. Automated detection based on these features would identify 80% of cases. We need to apply this mapping to patients with non-dysplastic and short segment BE, as well as to patients with oesophagitis, to see if its use is more widely applicable.

Laser therapy offers rapid relief of dysphagia for patients with cancers of the oesophagus and gastric cardia but repeat treatments are required approximately every five weeks to maintain good swallowing. To try to prolong the treatment interval, 22 elderly patients were given additional external beam radiotherapy. Nine had squamous cell carcinoma and 13 adenocarcinoma: five had documented metastases. Six received 40 Gy and 16,30 Gy in 10-20 fractions. A 'check' endoscopy was performed three weeks after external beam radiotherapy. Dysphagia was graded from 0-4 (0 = normal; 4 = dysphagia for liquids). The median dysphagia grade improved from 3 to 1 after laser treatment. This improvement was maintained in the 30 Gy group but there was a noticeable deterioration in three of those who had received the higher radiation dose. A lifelong dysphagia grade of 2 or better was enjoyed by 14 of 16 patients in the 30 Gy group but only two of six in the 40 Gy group. The dysphagia controlled interval was 9 weeks (median) after check endoscopy and subsequent endoscopic procedures were required every 13 weeks to maintain good swallowing. There were no endoscopy related complications. Combined treatment is a promising approach for reducing the frequency of endoscopic treatments. The 30 Gy dose seems more appropriate and may prolong survival. A randomised study to test these conclusions is in progress.

Aminolaevulinic acid (ALA) is the first committed step in haem synthesis. In the presence of excess ALA the natural regulatory feedback system is disrupted allowing accumulation of protoporphyrin IX (PP IX) the last intermediate product before haem, and an effective sensitiser. This method of endogenous photosensitisation of cells has been exploited for photodynamic therapy (PDT). We have studied the fluorescence distribution and biological effect of induced PP IX in normal and tumour tissue in the rat colon. Fluorescence in normal colonic tissue was at a peak of 4 h with a rapid fall off by 6 h. The fluorescence had returned to background levels by 24 h. All normal tissue layers followed the same fluorescence profile but the mucosa showed fluorescent levels six times higher than the submucosa, with muscle barely above background values. At 6 h the ratio of fluorescence levels between normal mucosa and viable tumour was approximately 1:6. At this time laser treatment showed necrosis of normal mucosa and tumour with sparing of normal muscle. There was good correlation between the fluorescence distribution and the biological effect of ALA-induced photosensitisation on exposure to red light. ALA may be superior to conventional sensitisers for tumours that produce haem as the PP IX is synthesised in malignant cells while the other sensitisers mainly localise to the vascular stroma of tumours. There is also a greater concentration difference between the PP IX levels in tumours and in normal mucosa and normal muscle than with the other photosensitisers raising the possibility of more selective necrosis in tumours. Images p820-a Figure 2 Figure 3 Figure 4 Figure 7 Figure 8

We have previously reported photodynamic therapy of normal rat colon using aluminium sulphonated phthalocyanine (AISPc). In that study, the AISPc used was a mixture of phthalocyanines of different degrees of sulphonation. Phthalocyanines of defined degrees of sulphonation have recently become available and we compared the distribution of the di- and tetra-sulphonates (AIS2Pc and AIS4Pc) in rat colon and colon wall structures employing both chemical extraction and fluorescence photometry using a charge coupled device imaging system. Also, the photodynamic effects produced by these components in rat colon were compared at various times after photosensitization. After intravenous photosensitizer administration using equimolar doses, the concentration of AIS2Pc in colon fell off more rapidly with time than AIS4Pc. Differences were noted in the microscopic distribution of these compounds, with the di-sulphonate exhibiting peak fluorescence in colon wall structures by 1 h after photosensitization, while mucosal fluorescence with the tetra-sulphonate peaked at 5 h. Fluorescence was also lost from the colon wall much more slowly with the tetra-sulphonate, which tended to be retained in the submucosa. Maximum photosensitizing capability was seen at 1 h with AIS2Pc and no lesions could be produced with photodynamic therapy at 1 week, with up to 5.65 mumol/kg. With AIS4Pc (5.65 mumol/kg), while no lesions could be produced with light treatment at 1 h, photodynamic therapy at 1 week produced lesions only slightly smaller than those produced with treatment at 48 h (the time of maximum effect), and significant photosensitization was present at 2 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

— —Radioprotective agents have been found to protect normal tissues during photodynamic therapy (PDT). We have investigated a phosphorylated thiol protectant WR-77913 (W7) with the photosensitizer aluminium sulphonated phthalocyanine (AlSPc). We compared the effects of PDT on normal and tumour tissue in the rat colon, with and without this protectant. In normal colon no necrosis was seen in sites treated after administration of the W7. Necrosis of mean diameter 4.2 mm was seen in those given the protectant after light exposure. At tumour sites the area of necrosis was similar after light exposure before and after the administration of the protective agent. These results suggest a possible role for W7 in enhancement of selectivity of PDT action. Several mechanisms of protection against porphyrin phototoxicity by these drugs have been proposed, including acceleration of photobleaching. We used fluorescence to detect AlSPc in strips of rat colon before and after laser treatment, with and without W7. However, a primary role for the photobleaching of AlSPc as the mechanism for the protection shown is not supported by these observations.

Photodynamic therapy (PDT) depends on the interaction of light with an administered photosensitiser to produce a local cytotoxic effect. The most widely used photosensitiser is haematoporphyrin derivative (HpD), but newer photosensitisers such as aluminium sulphonated phthalocyanine (A1SPc) are promising. HpD and A1SPc have been compared as photosensitisers for colonic PDT in the rat. Quantitative analysis showed that following injection of a standard photosensitiser dose, A1SPc produced more damage than HpD with increasing energy (fluence). Alteration of the injected dose of photosensitiser did not produce a clear difference. There was a loss of reciprocity for photosensitiser/light combinations at low injected dose (0.5 mg kg-1), both HpD and A1SPc producing no damage. Similarly at high photosensitiser dosage (25 mg kg-1) there was no quantitative difference between A1SPc and HpD. Photosensitiser photodegradation at low photosensitiser doses, and light attenuation by high tissue concentrations of A1SPc account for these findings. PDT with either agent produced the same histological damage and full thickness necrosis produced no mechanical weakening of the colon measured by the bursting pressure. The submucosal collagen was preserved and healing was by regeneration. Images Figure 5 Figure 6 Figure 7

Menorrhagia1 is a common and debilitating symptom among women but methods for local endometrial destruction have met with limited success. Not until Goldrath2 3 ablated the endometrium using a high powered (55–60W) Nd-YAG laser under hysteroscopic control did a successful local method become available. This procedure had a 93% success rate after one application and had minimal morbidity.

Background—Intestinal metaplastic mucosa in Barrett's oesophagus can be replaced by squamous epithelium after mucosal thermal ablation associated with acid suppression therapy. Aims—To assess whether restoration of squamous epithelium can be obtained after ablation of Barrett's oesophagus using argon plasma coagulation (APC) associated with proton pump inhibitor (PPI) therapy. Methods—Thirty one patients with Barrett's oesophagus received APC. Omeprazole (40 mg/day) was given from the first APC application to one month after completion of the treatment, then given symptomatically. Twenty four hour pH-metry was performed during endotherapy. Results—Complete re-epithelialisation was visualised at endoscopy in 25/31 patients (81%) after a mean number of 2.4 APC sessions (range 1-4). Only partial squamous re-epithelialisation was observed in three patients and three others had no eradication. At histological assessment, eradication of Barrett's oesophagus was only confirmed in 19/31 patients (61%) due to the presence of a few residual Barrett's glands under the new squamous epithelium. Complete eradication was related to a Barrett's oesophagus segment length of less than 4 cm and the absence of circumferential extension but not to the normalisation of oesophageal acid exposure under PPI therapy. Seventeen patients with apparently complete endoscopic and histological eradication of Barrett's oesophagus were re-evaluated at one year; eight (47%) disclosed relapsing islands of Barrett metaplasia despite continuous omeprazole therapy (10-40 mg/day). Conclusions—APC combined with 40 mg omeprazole daily can eradicate Barrett's mucosa with apparent squamous re-epithelialisation in the majority of patients even in the absence of normalisation of oesophageal acid exposure. However, one year after endotherapy for Barrett's oesophagus, relapse is frequent but limited in extent.

Photodynamic therapy with intravenous photosensitising drugs has been shown to be effective in the ablation of superficial cancers, but long-lasting photosensitivity is a serious disadvantage. Similar photosensitivity is a feature of certain types of porphyria. We present the first report of tumour necrosis brought about by photodynamic activation of a temporary endogenous porphyrin accumulation, after an oral dose of the haem precursor, 5-aminolaevulinic acid. In 4 patients, quantitative fluorescence microscopy showed that accumulation of the photoactive intermediate protoporphyrin IX peaked after 4-6 h in 4 oral cavity squamous cell carcinomas, returning to background in 24 h. Irradiation with non-thermal red laser light caused tumour necrosis in 3 patients.

To investigate the effect of pulsing on neodymium-YAG laser-induced hyperthermia we have exposed rat liver to low-power Nd-YAG laser light delivered via an interstitially inserted fibre. This was either continuous wave excitation or pulsed excitation at 10 or 40 Hz (pulse duration 100μs) with an average power of 1W and exposure durations of 400 s. No differences were seen with respect to overall diameter of the histological damage, diameter of the central cavitation, or intrahepatic temperatures, as measured by an embedded array of microthermocouples. We conclude that with 100-μs pulses, within the range of parameters studied, the pulsing rate does not influence the nature or the extent of damage seen after low-power interstitial Nd-YAG laser hyperthermia.

Photodynamic therapy (PDT) involves the parenteral administration of a photosensitising agent with some selectivity for malignant tissue. When activated by light, usually from a laser, local tissue destruction occurs. The amount of tissue destruction is dependent on the concentration of the photosensitising agent in the tissue and the light energy delivered. By careful manipulation of laser energy and photosensitiser dosage true selective destruction of malignant tissue can be produced in experimental colon cancers with total sparing of normal colon although under these conditions, the extent of necrosis in the tumour is only 2-3 mm from the light source. In addition, PDT has been shown not to reduce the mechanical strength of the colon even if full thickness necrosis is produced in normal areas. In contrast, thermal full thickness laser damage of the colon considerably weakens the colonic wall and may cause perforation. Light microscopy with specific collagen stains and electron microscopy have shown that the submucosal collagen layer is preserved following PDT, but is destroyed by thermal laser therapy. An initial clinical trial of PDT has been performed in ten patients with inoperable tumours because of advanced metastatic disease or severe medical problems. PDT has been shown to be safe and some small colorectal cancers can be totally eradicated.

Since December 1986, 40 laser angioplasty procedures have been performed using the energy from a pulsed NdYAG laser, delivering near infrared light (1064 nm) in 100-μs pulses of approximately 300 mJ per pulse, directly through a transparent sapphire tipped device. All patients had total occlusion of the superficial femoral artery and symptoms severe enough to warrant surgery, with ulceration or gangrene in eight, rest pain in 14 and severe claudication interfering with life-style in the others. The device was introduced through an antegrade puncture of the superficial or common femoral artery and laser recanalization was followed by attempted balloon angioplasty in all cases. Occlusions were a median length of 15 cm (range 2–35 cm); ten patients had previously undergone failed attempts at conventional balloon angioplasty and four had occluded femoropopliteal grafts. Thirty-seven legs of 34 patients were treated with an average of 60 J (range 10–235 J) with successful recanalization in 27 and immediate reocclusion in seven. The 20 successful recanalizations have been followed up for up to 24 months (median 7 months) with only one late occlusion at 5 months. Failed recanalization was due to poor transmission by the delivery device in the early part of the series (five cases), repeated passage of the device down a collateral branch (four cases), dissection at the site of previous surgery (two cases) or no apparent reason (two cases). Immediate reocclusion was due to very poor run off in patients with severely ischaemic limbs (three cases) or technical difficulties with balloon dilatation (two cases). Complete symptomatic relief was obtained in all the cases of radiologically successful laser angioplasty. Early surgery was required in one case following reocclusion of the artery when an angioplasty balloon failed to deflate, and one patient suffered a skin reaction thought to be due to inadequate removal of the sterilizing solution. A different sterilizing procedure is now followed. Laser angioplasty can reduce the number of patients requiring bypass surgery and improvements in the device and access methods may reduce the number of untreatable cases.

The total damage caused by equivalent doses of energy given to human cadaver vascular tissue over the same time scale from three Nd-YAG lasers of different pulse lengths is quantified. The continuous wave (c.w.) laser produces vacuolation and coagulation around a vaporized crater; the 100 μs pulsed laser produces less surrounding damage and the 10 ns pulsed laser none at all. The areas of damage in five craters made with 10 J energy were measured from histology slides using a digitising platten, and it was found that in each case the total amount of damage was the same, even though the depth of the craters made varied. The dose response for vaporization of the 10 ns pulsed laser was the greatest at 35 μm/J and that of the c.w. laser was least at 8 μm/J. A pulse length of 100 μs may not be the optimum for limiting surrounding tissue damage during laser angioplasty but it produces much less damage than a c.w. laser and unlike the 10 ns pulses is easily transmissible down an optical fibre.

Photodynamic therapy (PDT) is a promising approach to the local destruction of malignant tumours, but little work has been done to determine which factors control the extent of tissue necrosis produced. Using a new photosensitiser, a sulphonated aluminium phthalocyanine (AlSPc) and light from an argon ion pumped dye laser at 675 nm, we quantified the effects of interstitial PDT in a transplantable fibrosarcoma in rats. At 100mW laser power, thermal effects were comparable to those of PDT, so subsequent studies were carried out at 50 mW, where thermal effects were minimal. The depth of PDT necrosis increased with the logarithm of the applied energy. Tissue concentration of AlSPc was measured by alkali extraction and at all times after sensitisation, correlated well with the necrosis produced with a given light dose. Peak tumour concentration of AlSPc occurred 24-48 h after sensitisation compared with a peak at 3 h in muscle. The peak ratio tumour:muscle was 2:1 at 24 h. Apart from a different time interval to reach the peak sensitiser concentration, the extent of tumour damage varied with the light and sensitiser parameters in a similar way to that found in normal liver, although the optical penetration depth was greater in the tumour (2.5 mm vs. 1.8 mm). At doses of AlSPc below 1 mg kg-1 the diameter of necrosis increased with the logarithm of the dose of sensitiser, and doubling the dose from 0.25 to 0.5 mg kg-1 increased the depth of necrosis by 50%. However, at higher doses, the changes were smaller and increasing the dose from 2.5 to 5 mg kg-1 only increased the necrosis by 10% for the same light dose. In all dose ranges, a given percentage increase in the tissue concentration of AlSPc gave a much smaller percentage increase in the extent of necrosis for the same light dose, suggesting that selectivity of necrosis between tumour and normal tissue is likely to be much less than the selectivity of retention of the photosensitiser. From these results, the extent of PDT necrosis in this fibrosarcoma is as predictable as it is in normal liver if the light dose, tissue concentration of AlSPc and optical penetration depth of the tissue are known. Further studies are now required on different tumour models to establish how tumours respond compared with adjacent normal tissue when the tumour is growing in its organ of origin rather than the non-physiological situation using a transplantable tumour as in this study. Images Figure 2

The effects of three ultraviolet excimer laser wavelengths on normal and atheromatous human cadaver aortic wall are presented. Ultraviolet radiation successfully ablates vessel wall; the dose response is greatest at 249 nm followed by 193 nm and 351 nm, where the effect is negligible for the equivalent energy dose. Wavelengths 249 and 193 nm have a selective effect on fibrous atheroma; ablation proceeds at a higher rate in this tissue. Non-linear effects observed at 249 nm may be due to thermal as well as photoablative mechanisms. In addition, blood samples were exposed to all three wavelengths and potassium concentrations were measured; the dose of energy required to produce tissue ablation may also produce significant haemolysis and hyperkalaemia at 249 and 193 nm but not with 351 nm. This finding may be important for coronary angioplasty but less so for peripheral work. The wavelength that produces the strongest dose response is 249 nm; this is the wavelength for which a fibre-optic delivery system should be developed.

Detection of photosensitizers at the microscopic level is fundamental to understanding the mechanism of photodynamic therapy. Fluorescence microscopy is capable of high sensitivity using photometric detectors which enable quantitative measurements of photosensitizer fluorescence intensity. The use of a cooled slow-scan CCD (charge-coupled device) imaging system is particularly suitable for this application since the image can be time-integrated by the CCD sensor. Using the digital image processing a wide range of signal levels may be quantitatively compared, and the high sensitivity eliminates interference from photobleaching. In this work a CCD camera system has been used to obtain fluorescence images of aluminium sulphonated phthalocyanine in normal and malignant colonic rat tissue sections. Correlation of relative fluorescence intensities with concentration is discussed with regard to phthalocyanine sensitizers.

Three different lasers were compared under the same conditions for their effectiveness at producing photodynamic damage to normal colon following sensitization with aluminium sulphonated phthalocyanine (AlSPc). One laser was an argon ion pumped continuous wave (CW) dye laser and the other two were pulsed at 10 kHz (copper vapour laser pumped dye laser, and 5 Hz (flashlamp pumped dye laser). The CW and 10 kHz laser were equally effective at producing damage. The 5 Hz laser failed to produce a photodynamic effect, although occasionally caused a photomechanical effect when the laser fibre was placed touching the colonic mucosa. Quantitative analysis suggests that the high energy pulses of the flashlamp pumped dye laser saturate AlSPc, so very little of the available energy can be used to produce a photodynamic effect, in contrast to the two other lasers which do not produce saturation conditions.