ABSTRACT
A novel light source - light blanket composed of a series of parallel cylindrical diffusing fibers (CDF) is designed to substitute the hand-held point source in the PDT treatment of the malignant pleural or intraperitoneal diseases. It achieves more uniform light delivery and less operation time in operating room. The preliminary experiment was performed for a 9cmx9cm light blanket composed of 8 9-cm CDFs. The linear diffusers were placed in parallel finger-like pockets. The blanket is filled with 0.2 % intralipid scattering medium to improve the uniformity of light distribution. 0.3-mm aluminum foil is used to shield and reflect the light transmission. The full width of the profile of light distribution at half maximum along the perpendicular direction is 7.9cm and 8.1cm with no intralipid and with intralipid. The peak value of the light fluence rate profiles per input power is 11.7mW/cm2/W and 8.6mW/cm2/W respectively. The distribution of light field is scanned using the isotropic detector and the motorized platform. The average fluence rate per input power is 8.6 mW/cm2/W and the standard deviation is 1.6 mW/cm2/W for the scan in air, 7.4 mW/cm2/W and 1.1 mW/cm2/W for the scan with the intralipid layer. The average fluence rate per input power and the standard deviation are 20.0 mW/cm2/W and 2.6 mW/cm2/W respectively in the tissue mimic phantom test. The light blanket design produces a reasonably uniform field for effective light coverage and is flexible to confirm to anatomic structures in intraoperative PDT. It also has great potential value for superficial PDT treatment in clinical application.
ABSTRACT
A large-size blanket composed of the parallel catheters and silica core side glowing fiber is designed to substitute the hand-held point source in the photodynamic therapy treatment (PDT) of the malignant pleural or intraperitoneal diseases. It produces a reasonably uniform field for effective light coverage and is flexible to conform to anatomic structures in intraoperative PDT. The size of the blanket is 30cm×20cm. The light blanket composed of several PVC layers and a series of parallel catheters attached on both sides of the intralipid layer of 0.2% concentration. On one side of the intralipid layer, the parallel fiber catheters were attached using thermal sealing technique. On the other side, the parallel detect catheters were attached along the perpendicular direction. 0.1mm aluminum foil was used to construct the reflection layer to enhance the efficiency of light delivery. The long single side-glowing fiber goes through the fiber catheters according to the specific fiber pattern design. Compared with the prototype of the first generation, the new design is more cost-efficient and more applicable for clinical applications. The light distribution of the blanket was characterized by scanning experiments which were performed in flatness and on the curved surface of tissue body phantom. The fluence rate generated by the blanket can meet requirements for the light delivery in pleural or intraperitoneal (IP) PDT. Taking the advantage of large coverage and flexible conformity, it has great value to increase the reliability and consistency of PDT.
ABSTRACT
The object of this study is to develop optimization procedures that account for both the optical heterogeneity as well as photosensitizer (PS) drug distribution of the patient prostate and thereby enable delivery of uniform photodynamic dose to that gland. We use the heterogeneous optical properties measured for a patient prostate to calculate a light fluence kernel (table). PS distribution is then multiplied with the light fluence kernel to form the PDT dose kernel. The Cimmino feasibility algorithm, which is fast, linear, and always converges reliably, is applied as a search tool to choose the weights of the light sources to optimize PDT dose. Maximum and minimum PDT dose limits chosen for sample points in the prostate constrain the solution for the source strengths of the cylindrical diffuser fibers (CDF). We tested the Cimmino optimization procedures using the light fluence kernel generated for heterogeneous optical properties, and compared the optimized treatment plans with those obtained using homogeneous optical properties. To study how different photosensitizer distributions in the prostate affect optimization, comparisons of light fluence rate and PDT dose distributions were made with three distributions of photosensitizer: uniform, linear spatial distribution, and the measured PS distribution. The study shows that optimization of individual light source positions and intensities are feasible for the heterogeneous prostate during PDT.
ABSTRACT
A compact robotic platform is designed for simultaneous multichannel motion control for light delivery and dosimetry during interstitial photodynamic therapy (PDT). Movements of light sources and isotropic detectors are controlled by individual motors along different catheters for interstitial PDT. The robotic multichannel platform adds feedback control of positioning for up to 16 channels compared to the existing dual-motor system, which did not have positioning encoders. A 16-channel servo motion controller and micro DC motors, each with high resolution optical encoder, are adopted to control the motions of up to 16 channels independently. Each channel has a resolution of 0.1mm and a speed of 5cm/s. The robotic platform can perform light delivery and dosimetry independently, allowing arbitrary positioning of light sources and detectors in each catheter. Up to 16 compact translational channels can be combined according to different operational scheme with real-time optimal motion planning. The characteristic of high speed and coordinating motion will make it possible to use short linear sources (e.g., 1- cm) to deliver uniform PDT treatment to a bulk tumor within reasonable time by source stepping optimization of multiple sources simultaneously. Advanced robotic control algorithm handles the various unexpected circumstance in clinical procedure, e.g., positiontorque/current control will be applied to prevent excessive force in the case of resistance in the fiber or motorized mechanism. The robotic platform is fully compatible with operation room (OR) environment and improves the light delivery and dosimetry in PDT. It can be adopted for diffusing optical tomography (DOT), spectroscopic DOT and fluorescent spectroscopy.