Singlet oxygen (1O2) is the major cytotoxic agent for type II photodynamic therapy (PDT). The production of 1O2 involves the complex reactions among light, oxygen molecule, and photosensitizer. From universal macroscopic kinetic equations which describe the photochemical processes of PDT, the reacted 1O2 concentration, [1O2]rx, with cell target can be expressed in a form related to time integration of the product of 1O2 quantum yield and the PDT dose rate. The object of this study is to develop optimization procedures that account for the optical heterogeneity of the patient prostate, the tissue photosensitizer concentrations, and tissue oxygenation, thereby enable delivery of uniform reacted singlet oxygen to the gland. We use the heterogeneous optical properties measured for a patient prostate to calculate a light fluence kernel. Several methods are used to optimize the positions and intensities of CDFs. The Cimmino feasibility algorithm, which is fast, linear, and always converges reliably, is applied as a search tool to optimize the weights of the light sources at each step of the iterative selection. Maximum and minimum dose limits chosen for sample points in the prostate constrain the solution for the intensities of the linear light sources. The study shows that optimization of individual light source positions and intensities is feasible for the heterogeneous prostate during PDT. To study how different photosensitizer distributions as well as tissue oxygenation in the prostate affect optimization, comparisons of light fluence rate were made with measured distribution of photosensitizer in prostate under different tissue oxygenation conditions.
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.
Light dosimetry for photodynamic therapy requires a knowledge of the optical absorption spectrum of the tissue being
treated Here, we present a theoretical and experimental analysis of the capabilities of a system using interstitial linear
light sources ranging in length from 2 to 5 cm to illuminate the tissue interstitially, and isotropic point-like detectors to
measure the resulting diffusely transmitted light. The sources and detectors are translated in transparent plastic catheters
under the control of a motorized positioning system designed for interstitial measurements in the prostate. The light
source is a quartz-tungsten-halogen (QTH), and the spectrally resolved detection is accomplished using a CCD-based
grating spectrometer. The data are analyzed using an approximation to the radiative transport equation, assuming
homogeneous scattering and heterogeneous absorption spectra Absorption spectra are reconstructed independently for
individual source-detector channel pairs. Sequential reconstruction can then be used to create a 3-dimensional
reconstruction. The results of simulated data, measurements made in multi-component phantoms, and synthetic data
reconstructed from in vivo measurements made with point sources demonstrate the feasibility of this method.
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 fingerlike
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.
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.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.