Safety and feasibility of prostate stereotactic ablative radiotherapy using multimodality imaging and flattening filter free.

OBJECTIVE: To investigate feasibility and safety of stereotactic ablative radiotherapy in the management of prostate cancer while employing MR/CT fusion for delineation, fiducial marker seeds for positioning and Varian RapidArc with flattening filter free (FFF) delivery. METHODS: 41 patients were treated for low-intermediate risk prostate cancer with initial prostate-specific antigen of ≤20 ng ml-1, Gleason score 6-7. Patients had MR/CT fusion for delineation of prostate ±seminal vesicles. CT/MR fusion images were used for delineation and planned using flattening filter free modality. Verification on treatment was cone beam CT imaging with fiducial markers for matching. Patients had Radiation Therapy Oncology Group scoring for genitourinary and gastointestinal symptoms at baseline, week 4, 10 and 18. RESULTS: Clinically acceptable plans were achieved for all patients, all plans achieved the objective clinical target volume D99% ≥ 95%, and for planning target volume D95% ≥ 95%. Rectum dose constraints were met for 95.1% for V18 Gy ≤ 35%, 80% V28 Gy ≤ 10%. A total of 32 (78.0%) plans achieved all rectum dose constraints. Grade 1 acute genitourinary symptoms were 53.7% of patients at baseline, 90.2% [95% CI (76.8-97.3%)] (p = 0.0005) at treatment 5, falling to 78.0% (62.4-89.4%) at week 4, and 75.0% (58.8-87.3%) by week 10 and 52.5% (36.1-68.5%) (p = 1.00) at week 18. Acute gastrointestinal symptoms were 5% at baseline, 46.3% [95% CI (30.7-62.6%)] at treatment 5, week 4 43.9% [95% CI (28.5-60.3%)], week 10 25.0% (11.1-42.3%), and declined slightly by week 18 [-20.095% CI (12.7-41.2)] p = 0.039. Overall 75.6% (31/41) of patients experienced Grade 1-2 toxicity during or after treatment. CONCLUSION: This planning and delivery technique is feasible, safe and efficient. A homogeneous dose can be delivered to prostate with confidence, whilst limiting high dose to nearby structures. The use of this technology can be applied safely within further randomized study protocols. Advances in knowledge: Multimodality imaging for delineation and linac-based image-guided RT with FFF for the treatment of prostate stereotactic ablative radiotherapy.

Confocal laser scanning microscopy using a frequency doubled vertical external cavity surface emitting laser.

We report on a frequency doubled 980 nm vertical external cavity surface emitting laser for applications in confocal laser scanning microscopy. The beam quality, wavelength flexibility, and low noise characteristics of this compact source make this prolific imaging technique an exemplary tool. Single pass frequency doubling via KNbO(3) was demonstrated, yielding 1.8 mW at 490 nm with a near diffraction limited beam quality. Detailed analysis and comparison of the laser performance with the current standard argon ion laser revealed clear advantages of the solid-state source for confocal imaging. Imaging of fluorescein and eGFP labeled biological samples using the attenuated solid-state source provided high-resolution images at lower cost and with improved reliability.

Characterization of microscope objective lenses from 1,400 to 1,650 nm to evaluate performance for long-wavelength nonlinear microscopy applications.

We have demonstrated a simple method for characterization of objective lens performance at longer wavelengths for 3PLSM and THG imaging. We investigated a range of air and oil-immersion objective lenses across a wavelength range of 1,400-1,650 nm using a synchronously pumped optical parametric oscillator laser source. In the first instance, we investigated the percentage light transmission across this spectral range. Second, we used a simple second harmonic autocorrelation pulse measurement technique to study the dispersion properties of these lenses at the range of input wavelengths. For the objective lenses investigated, we observed pulse broadening on the order of around 4%-7% for air immersion lenses and 9%-12% for oil immersion lenses. Even for the greater dispersion incurred by the application of the oil immersion lenses, these objectives are suitable for longer wavelength application in conjunction with a suitable light source. The same techniques could easily be applied for a larger range of objective lenses and adapted for alternative spectral windows and pulse durations.