An optical method for reducing green fluorescence from urine during fluorescence-guided cystoscopy.

Photodynamic diagnosis (PDD) of bladder tumour tissue significantly improves endoscopic diagnosis and treatment of bladder cancer in rigid cystoscopes in the operating theatre and thus reduces tumour recurrence. PDD comprises the use of blue light, which unfortunately excites green fluorescence from urine. As this green fluorescence confounds the desired red fluorescence of the PDD, methods for avoiding this situation particularly in cystoscopy using flexible cystoscopes are desirable. In this paper we demonstrate how a tailor made high power LED light source at 525 nm can be used for fluorescence assisted tumour detection using both a flexible and rigid cystoscope used in the outpatient department (OPD) and operating room (OR) respectively. It is demonstrated both in vitro and in vivo how this light source can significantly reduce the green fluorescence problem with urine. At the same time this light source also is useful for exciting autofluorescence in healthy bladder mucosa. This autofluorescence then provides a contrast to the sensitized fluorescence (PDD) of tumours in the bladder.

Office-based transurethral devascularisation of low grade non-invasive urothelial cancer using diode laser. A feasibility study.

BACKGROUND AND OBJECTIVE: Frequent recurrence of non-muscle invasive bladder tumours (NMIBC) requiring transurethral resection of bladder tumour (TUR-BT) and lifelong monitoring makes the lifetime cost per patient the highest of all cancers. A new method is proposed for the removal of low grade NMIBCs in an office-based setting, without the need for sedation and pain control and where the patient can leave immediately after treatment. STUDY DESIGN/PATIENTS AND METHODS: An in vitro model was developed to examine the dose/response relationship between laser power, treatment time, and distance between laser fibre and target, using a 980 nm diode laser and chicken meat. The relationship between depth and extent of tissue destruction and the laser settings was measured using microscopy and non-parametric statistical analysis. A patient with low grade stage Ta tumour and multiple comorbidity, and therefore not fit for general anaesthesia, had a tumour devascularised using the laser at the tumour base, in the outpatient department. The tumour was left in the bladder. RESULTS: In the in vitro model, depth of tissue destruction increased with laser illumination up to 30 seconds, where median depth was 4.1 mm. With longer illumination the tissue destruction levelled off. The width of tissue destruction was 2-3 mm independent of laser illumination time. The in vivo laser treatments devascularised the tumour, which was later shed from the mucosa and passed out with the urine in the days following treatment. Pain score was 0 on a visual log scale (0-10). The tumour had completely disappeared two weeks after treatment. CONCLUSION: This diode laser technique may provide almost pain-free office-based treatment of low grade urothelial cancer using flexible cystoscopes in conscious patients. A prospective randomised study will be scheduled to compare the technique with standard TUR-BT in the operating theatre.

Characterizing a pulse-resolved dosimetry system for complex radiotherapy beams using organic scintillators.

A fast-readout dosimetry system based on fibre-coupled organic scintillators has been developed for the purpose of conducting point measurements of absorbed dose in radiotherapy beams involving high spatial and temporal dose gradients. The system measures the dose for each linac radiation pulse with millimetre spatial resolution. To demonstrate the applicability of the system in complex radiotherapy fields, output factors and per cent depth dose measurements were performed in solid water for a 6 MV photon beam and compared with Monte Carlo simulated doses for square fields down to 0.6 cm × 0.6 cm size. No significant differences between measurements and simulations were observed. The temporal resolution of the system was demonstrated by measuring dose per pulse, beam start-up transients and the quality factor for 6 MV. The precision of dose per pulse measurements was within 2.7% (1 SD) for a 10 cm × 10 cm field at 10 cm depth. The dose per pulse behaviour compared well with linac target current measurements and accumulated dose measurements, and the system was able to resolve transient dose delivery differences between two Varian linac builds. The system therefore shows promise for reference dosimetry and quality assurance of complex radiotherapy treatments.