System for interstitial photodynamic therapy with online dosimetry: first clinical experiences of prostate cancer

Hybrid heterogeneous phantoms for biomedical applications: a demonstration to dosimetry validation

Phantoms simultaneously mimicking anatomical and optical properties of real tissues can play a pivotal role for improving dosimetry algorithms. The aim of the paper is to design and develop a hybrid phantom model that builds up on the strengths of solid and liquid phantoms for mimicking various anatomical structures for prostate cancer photodynamic therapy (PDT) dosimetry validation. The model comprises of a photosensitizer-embedded gelatin lesion within a liquid Intralipid prostate shape that is surrounded by a solid silicone outer shell. The hybrid phantom was well characterized for optical properties. The final assembled phantom was also evaluated for fluorescence tomographic reconstruction in conjunction with SpectraCure's IDOSE software. The developed model can lead to advancements in dosimetric evaluations. This would improve PDT outlook as a clinical treatment modality and boost phantom based standardization of biophotonic devices globally.

High Sensitivity Singlet Oxygen Luminescence Sensor Using Computational Spectroscopy and Solid-State Detector

This paper presents a technique for high sensitivity measurement of singlet oxygen luminescence generated during photodynamic therapy (PDT) and ultraviolet (UV) irradiation on skin. The high measurement sensitivity is achieved by using a computational spectroscopy (CS) approach that provides improved photon detection efficiency compared to spectral filtering methodology. A solid-state InGaAs photodiode is used as the CS detector, which significantly reduces system cost and improves robustness compared to photomultiplier tubes. The spectral resolution enables high-accuracy determination and subtraction of photosensitizer fluorescence baseline without the need for time-gating. This allows for high sensitivity detection of singlet oxygen luminescence emission generated by continuous wave light sources, such as solar simulator sources and those commonly used in PDT clinics. The value of the technology is demonstrated during in vivo and ex vivo experiments that show the correlation of measured singlet oxygen with PDT treatment efficacy and the illumination intensity on the skin. These results demonstrate the potential use of the technology as a dosimeter to guide PDT treatment and as an analytical tool supporting the development of improved sunscreen products for skin cancer prevention.

First in human measurements of abscess cavity optical properties and methylene blue uptake prior to photodynamic therapy by in vivo diffuse reflectance spectroscopy

Significance

Efficacious photodynamic therapy (PDT) of abscess cavities requires personalized treatment planning. This relies on knowledge of abscess wall optical properties, which we report for the first time in human subjects.

Aim

The objective was to extract optical properties and photosensitizer concentration from spatially-resolved diffuse reflectance measurements of abscess cavities prior to methylene blue (MB) PDT, as part of a Phase 1 clinical trial.

Approach

Diffuse reflectance spectra were collected at the abscess wall of 13 human subjects using a custom fiber-optic probe and optical spectroscopy system, before and after MB administration. A Monte Carlo lookup table was used to extract optical properties.

Results

Pre-MB abscess wall absorption coefficients at 665 nm were 0.15±0.1 cm -1 (0.03-0.36 cm -1 ) and 10.74±15.81 cm -1 (0.08-49.3 cm -1 ) post-MB. Reduced scattering coefficients at 665 nm were 8.45±2.37 cm -1 (4.8-13.2 cm -1 ) and 5.6±2.26 cm -1 (1.6-9.9 cm -1 ) for pre-MB and post-MB, respectively. Oxygen saturations were found to be 58.83±35.78% (5.6-100%) pre-MB and 36.29±25.1% (0.0001-76.4%) post-MB. Determined MB concentrations were 71.83±108.22 µM (0-311 µM).

Conclusions

We observed substantial inter-subject variation in both native wall optical properties and methylene blue uptake. This underscores the importance of making these measurements for patient-specific treatment planning.

The Use of Photodynamic Therapy for Head, Neck, and Brain Diseases

Head-neck cancers as a group have the 7th highest rate of incidence worldwide. The most often diagnosed disease of the head and neck is squamous cell carcinoma (90% of cases). Another specific group of tumors is brain tumors. These can be divided into primary tumors and secondary tumors associated with metastasis. Research shows that treating head and neck cancers continues to be problematic and challenging, and researchers are actively seeking new treatments that would improve survival rates and reduce side effects. Irradiation of tumor tissue with the optimal wavelength of light in photodynamic therapy (PDT) generates predominantly singlet oxygen in tissue-based photosensitizers (PSs) or reactive oxygen radicals in the case of vascular PSs leading to cellular apoptosis and necrosis. A very important feature of PDT is that cells cannot become immune to the effects of singlet oxygen or reactive oxygen radicals. However, photosensitizer (PS) transport is influenced by the specific structures of cancer tumors and the concentration of PS decreases in cells far from the vessel lumen. Therefore, PSs may not reach tumor interiors, which decreases therapy effectiveness. The use of drug carriers and 3rd generation PSs that contain biocompatible functional groups makes it possible to control transport. This review of the current literature on PDT was conducted through databases such as PubMed and Scopus. The types of publications considered included clinical studies and most of the articles included were published in English. Based on the publications collected, we conclude that researchers have demonstrated the potential of PDT as a therapeutic platform for head, neck, and brain diseases.

Computational Optimization of Irradiance and Fluence for Interstitial Photodynamic Therapy Treatment of Patients with Malignant Central Airway Obstruction

There are no effective treatments for patients with extrinsic malignant central airway obstruction (MCAO). In a recent clinical study, we demonstrated that interstitial photodynamic therapy (I-PDT) is a safe and potentially effective treatment for patients with extrinsic MCAO. In previous preclinical studies, we reported that a minimum light irradiance and fluence should be maintained within a significant volume of the target tumor to obtain an effective PDT response. In this paper, we present a computational approach to personalized treatment planning of light delivery in I-PDT that simultaneously optimizes the delivered irradiance and fluence using finite element method (FEM) solvers of either Comsol Multiphysics® or Dosie™ for light propagation. The FEM simulations were validated with light dosimetry measurements in a solid phantom with tissue-like optical properties. The agreement between the treatment plans generated by two FEMs was tested using typical imaging data from four patients with extrinsic MCAO treated with I-PDT. The concordance correlation coefficient (CCC) and its 95% confidence interval (95% CI) were used to test the agreement between the simulation results and measurements, and between the two FEMs treatment plans. Dosie with CCC = 0.994 (95% CI, 0.953-0.996) and Comsol with CCC = 0.999 (95% CI, 0.985-0.999) showed excellent agreement with light measurements in the phantom. The CCC analysis showed very good agreement between Comsol and Dosie treatment plans for irradiance (95% CI, CCC: 0.996-0.999) and fluence (95% CI, CCC: 0.916-0.987) in using patients' data. In previous preclinical work, we demonstrated that effective I-PDT is associated with a computed light dose of ≥45 J/cm2 when the irradiance is ≥8.6 mW/cm2 (i.e., the effective rate-based light dose). In this paper, we show how to use Comsol and Dosie packages to optimize rate-based light dose, and we present Dosie's newly developed domination sub-maps method to improve the planning of the delivery of the effective rate-based light dose. We conclude that image-based treatment planning using Comsol or Dosie FEM-solvers is a valid approach to guide the light dosimetry in I-PDT of patients with MCAO.

A Monte Carlo simulation for Moving Light Source in Intracavity PDT

We developed a simulation method for modeling the light fluence delivery in intracavity Photodynamic Therapy (icav-PDT) for pleural lung cancer using a moving light source. Due to the large surface area of the pleural lung cavity, the light source needs to be moved to deliver a uniform dose around the entire cavity. While multiple fixed detectors are used for dosimetry at a few locations, an accurate simulation of light fluence and fluence rate is still needed for the rest of the cavity. We extended an existing Monte Carlo (MC) based light propagation solver to support moving light sources by densely sampling the continuous light source trajectory and assigning the proper number of photon packages launched along the way. The performance of Simphotek GPU CUDA-based implementation of the method - PEDSy-MC - has been demonstrated on a life-size lung-shaped phantom, custom printed for testing icav-PDT navigation system at the Perlman School of Medicine (PSM) - calculations completed under a minute (for some cases) and within minutes have been achieved. We demonstrate results within a 5% error of the analytic solution for multiple detectors in the phantom. PEDSy-MC is accompanied by a dose-cavity visualization tool that allows real-time inspection of dose values of the treated cavity in 2D and 3D, which will be expanded to ongoing clinical trials at PSM. PSM has developed a technology to measure 8-detectors in a pleural cavity phantom using Photofrin-mediated PDT that has been used during validation.

First-In-Human Computer-Optimized Endobronchial Ultrasound-Guided Interstitial Photodynamic Therapy for Patients With Extrabronchial or Endobronchial Obstructing Malignancies

Objective

Patients with inoperable extrabronchial or endobronchial tumors who are not candidates for curative radiotherapy have dire prognoses with no effective long-term treatment options. To reveal that our computer-optimized interstitial photodynamic therapy (I-PDT) is safe and potentially effective in the treatment of patients with inoperable extra or endobronchial malignancies inducing central airway obstructions.

Methods

High-spatial resolution computer simulations were used to personalize the light dose rate and dose for each tumor. Endobronchial ultrasound with a transbronchial needle was used to place the optical fibers within the tumor according to an individualized plan. The primary and secondary end points were safety and overall survival, respectively. An exploratory end point evaluated changes in immune markers.

Results

Eight patients received I-PDT with planning, and five of these received additional external beam PDT. Two additional patients received external beam PDT. The treatment was declared safe. Three of 10 patients are alive at 26.3, 12, and 8.3 months, respectively, after I-PDT. The treatments were able to deliver a prescribed light dose rate and dose to 87% to 100% and 18% to 92% of the tumor volumes, respectively. A marked increase in the proportion of monocytic myeloid-derived suppressor cells expressing programmed death-ligand 1 was measured in four of seven patients.

Conclusions

Image-guided light dosimetry for I-PDT with linear endobronchial ultrasound transbronchial needle is safe and potentially beneficial in increasing overall survival of patients. I-PDT has a positive effect on the immune response including an increase in the proportion of programmed death-ligand 1-expressing monocytic myeloid-derived suppressor cells.

Photodynamic therapy for prostate cancer: Recent advances, challenges and opportunities

Over the past two decades, there has been a tendency toward early diagnosis of prostate cancer due to raised awareness among the general public and professionals, as well as the promotion of prostate-specific antigen (PSA) screening. As a result, patients with prostate cancer are detected at an earlier stage. Due to the risks of urine incontinence, erectile dysfunction, etc., surgery is not advised because the tumor is so small at this early stage. Doctors typically only advise active surveillance. However, it will bring negative psychological effects on patients, such as anxiety. And there is a higher chance of cancer progression. Focal therapy has received increasing attention as an alternative option between active monitoring and radical therapy. Due to its minimally invasive, oncological safety, low toxicity, minimal effects on functional outcomes and support by level 1 evidence from the only RCT within the focal therapy literature, photodynamic treatment (PDT) holds significant promise as the focal therapy of choice over other modalities for men with localized prostate cancer. However, there are still numerous obstacles that prevent further advancement. The review that follows provides an overview of the preclinical and clinical published research on PDT for prostate cancer from 1999 to the present. It focuses on clinical applications of PDT and innovative techniques and technologies that address current problems, especially the use of nanoparticle photosensitizers in PDT of prostate cancer.

Innovative light sources for phototherapy

The use of light for therapeutic purposes dates back to ancient Egypt, where the sun itself was an innovative source, probably used for the first time to heal skin diseases. Since then, technical innovation and advancement in medical sciences have produced newer and more sophisticated solutions for light-emitting sources and their applications in medicine. Starting from a brief historical introduction, the concept of innovation in light sources is discussed and analysed, first from a technical point of view and then in the light of their fitness to improve existing therapeutic protocols or propose new ones. If it is true that a “pure” technical advancement is a good reason for innovation, only a sub-system of those advancements is innovative for phototherapy. To illustrate this concept, the most representative examples of innovative light sources are presented and discussed, both from a technical point of view and from the perspective of their diffusion and applications in the clinical field.

Effects of patient-specific treatment planning on eligibility for photodynamic therapy of deep tissue abscess cavities: retrospective Monte Carlo simulation study

SIGNIFICANCE

Antimicrobial photodynamic therapy (PDT) effectively kills bacterial strains found in deep tissue abscess cavities. PDT response hinges on multiple factors, including light dose, which depends on patient optical properties.

AIM

Computed tomography images for 60 abscess drainage subjects were segmented and used for Monte Carlo (MC) simulation. We evaluated effects of optical properties and abscess morphology on PDT eligibility and generated treatment plans.

APPROACH

A range of abscess wall absorptions (μa  ,  wall) and intra-cavity Intralipid concentrations were simulated. At each combination, the threshold optical power and optimal Intralipid concentration were found for a fluence rate target, with subjects being eligible for PDT if the target was attainable with <2000  mW of source light. Further simulations were performed with absorption within the cavity (μa  ,  cavity).

RESULTS

Patient-specific treatment planning substantially increased the number of subjects expected to achieve an efficacious light dose for antimicrobial PDT, especially with Intralipid modification. The threshold optical power and optimal Intralipid concentration increased with increasing μa  ,  wall (p  <  0.001). PDT eligibility improved with patient-specific treatment planning (p  <  0.0001). With μa  ,  wall  =  0.2  cm  -  1, eligibility increased from 42% to 92%. Increasing μa  ,  cavity reduced PDT eligibility (p  <  0.0001); modifying the delivered optical power had the greatest impact in this case.

CONCLUSIONS

MC-based treatment planning greatly increases eligibility for PDT of abscess cavities.

Perspective on the integration of optical sensing into orthopedic surgical devices

SIGNIFICANCE

Orthopedic surgery currently comprises over 1.5 million cases annually in the United States alone and is growing rapidly with aging populations. Emerging optical sensing techniques promise fewer side effects with new, more effective approaches aimed at improving patient outcomes following orthopedic surgery.

AIM

The aim of this perspective paper is to outline potential applications where fiberoptic-based approaches can complement ongoing development of minimally invasive surgical procedures for use in orthopedic applications.

APPROACH

Several procedures involving orthopedic and spinal surgery, along with the clinical challenge associated with each, are considered. The current and potential applications of optical sensing within these procedures are discussed and future opportunities, challenges, and competing technologies are presented for each surgical application.

RESULTS

Strong research efforts involving sensor miniaturization and integration of optics into existing surgical devices, including K-wires and cranial perforators, provided the impetus for this perspective analysis. These advances have made it possible to envision a next-generation set of devices that can be rigorously evaluated in controlled clinical trials to become routine tools for orthopedic surgery.

CONCLUSIONS

Integration of optical devices into surgical drills and burrs to discern bone/tissue interfaces could be used to reduce complication rates across a spectrum of orthopedic surgery procedures or to aid less-experienced surgeons in complex techniques, such as laminoplasty or osteotomy. These developments present both opportunities and challenges for the biomedical optics community.

High optical-throughput spectroscopic singlet oxygen and photosensitizer luminescence dosimeter for monitoring of photodynamic therapy

We report a high light-throughput spectroscopic dosimeter system that is able to noninvasively measure luminescence signals of singlet oxygen (¹ O₂ ) produced during photodynamic therapy (PDT) using a CW (continuous wave) light source. The system is based on a compact, fiber-coupled, high collection efficiency spectrometer (>50% transmittance) designed to maximize optical throughput but with sufficient spectral resolution (~7 nm). This is adequate to detect ¹ O₂ phosphorescence in the presence of strong luminescence background in vivo. This system provides simultaneous acquisition of multiple spectral data points, allowing for more accurate determination of luminescence baseline via spectral fitting and thus the extraction of ¹ O₂ phosphorescence signal based solely on spectroscopic decomposition, without the need for time-gating. Simultaneous collection of photons at different wavelengths improves the quantum efficiency of the system when compared to sequential spectral measurements such as filter-wheel or tunable-filter based systems. A prototype system was tested during in vivo PDT tumor regression experiments using benzoporphyrin derivative (BPD) photosensitizer. It was found that the treatment efficacy (tumor growth inhibition rate) correlated more strongly with ¹ O₂ phosphorescence than with PS fluorescence. These results indicate that this high photon-collection efficiency spectrometer instrument may offer a viable option for real-time ¹ O₂ dosimetry during PDT treatment using CW light.

Photodynamic Therapy: A Compendium of Latest Reviews

Photodynamic therapy (PDT) is a promising therapy against cancer. Even though it has been investigated for more than 100 years, scientific publications have grown exponentially in the last two decades. For this reason, we present a brief compendium of reviews of the last two decades classified under different topics, namely, overviews, reviews about specific cancers, and meta-analyses of photosensitisers, PDT mechanisms, dosimetry, and light sources. The key issues and main conclusions are summarized, including ways and means to improve therapy and outcomes. Due to the broad scope of this work and it being the first time that a compendium of the latest reviews has been performed for PDT, it may be of interest to a wide audience.

Light Technology for Efficient and Effective Photodynamic Therapy: A Critical Review

Photodynamic therapy (PDT) is a cancer treatment with strong potential over well-established standard therapies in certain cases. Non-ionising radiation, localisation, possible repeated treatments, and stimulation of immunological response are some of the main beneficial features of PDT. Despite the great potential, its application remains challenging. Limited light penetration depth, non-ideal photosensitisers, complex dosimetry, and complicated implementations in the clinic are some limiting factors hindering the extended use of PDT. To surpass actual technological paradigms, radically new sources, light-based devices, advanced photosensitisers, measurement devices, and innovative application strategies are under extensive investigation. The main aim of this review is to highlight the advantages/pitfalls, technical challenges and opportunities of PDT, with a focus on technologies for light activation of photosensitisers, such as light sources, delivery devices, and systems. In this vein, a broad overview of the current status of superficial, interstitial, and deep PDT modalities-and a critical review of light sources and their effects on the PDT process-are presented. Insight into the technical advancements and remaining challenges of optical sources and light devices is provided from a physical and bioengineering perspective.

Perspectives on interstitial photodynamic therapy for malignant tumors

SIGNIFICANCE

Despite remarkable advances in the core modalities used in combating cancer, malignant diseases remain the second largest cause of death globally. Interstitial photodynamic therapy (IPDT) has emerged as an alternative approach for the treatment of solid tumors.

AIM

The aim of our study is to outline the advancements in IPDT in recent years and provide our vision for the inclusion of IPDT in standard-of-care (SoC) treatment guidelines of specific malignant diseases.

APPROACH

First, the SoC treatment for solid tumors is described, and the attractive properties of IPDT are presented. Second, the application of IPDT for selected types of tumors is discussed. Finally, future opportunities are considered.

RESULTS

Strong research efforts in academic, clinical, and industrial settings have led to significant improvements in the current implementation of IPDT, and these studies have demonstrated the unique advantages of this modality for the treatment of solid tumors. It is envisioned that further randomized prospective clinical trials and treatment optimization will enable a wide acceptance of IPDT in the clinical community and inclusion in SoC guidelines for well-defined clinical indications.

CONCLUSIONS

The minimally invasive nature of this treatment modality combined with the relatively mild side effects makes IPDT a compelling alternative option for treatment in a number of clinical applications. The adaptability of this technique provides many opportunities to both optimize and personalize the treatment.

Optimizing Interstitial Photodynamic Therapy Planning With Reinforcement Learning-Based Diffuser Placement

Interstitial photodynamic therapy (iPDT) has shown promising results recently as a minimally invasive stand-alone or intra-operative cancer treatment. The development of non-toxic photosensitizing drugs with improved target selectivity has increased its efficacy. However, personalized treatment planning that determines the number of photon emitters, their positions and their input powers while taking into account tissue anatomy and treatment response is still lacking to further improve outcomes.

OBJECTIVE

To develop new algorithms that generate high-quality plans by optimizing over the light source positions, along with their powers, to minimize the damage to organs-at-risk while eradicating the tumor. The optimization algorithms should also accurately model the physics of light propagation through the use of Monte-Carlo simulators.

METHODS

We use simulated-annealing as a baseline algorithm to place the sources. We propose different source perturbations that are likely to provide better outcomes and study their impact. To minimize the number of moves attempted (and effectively runtime) without degrading result quality, we use a reinforcement learning-based method to decide which perturbation strategy to perform in each iteration. We simulate our algorithm on virtual brain tumors modeling real glioblastoma multiforme cases, assuming a 5-ALA PpIX induced photosensitizer that is activated at [Formula: see text] wavelength.

RESULTS

The algorithm generates plans that achieve an average of 46% less damage to organs-as-risk compared to the manual placement used in current clinical studies.

SIGNIFICANCE

Having a general and high-quality planning system makes iPDT more effective and applicable to a wider variety of oncological indications. This paves the way for more clinical trials.

Mechanisms for Tuning Engineered Nanomaterials to Enhance Radiation Therapy of Cancer

Engineered nanomaterials that produce reactive oxygen species on exposure to X- and gamma-rays used in radiation therapy offer promise of novel cancer treatment strategies. Similar to photodynamic therapy but suitable for large and deep tumors, this new approach where nanomaterials acting as sensitizing agents are combined with clinical radiation can be effective at well-tolerated low radiation doses. Suitably engineered nanomaterials can enhance cancer radiotherapy by increasing the tumor selectivity and decreasing side effects. Additionally, the nanomaterial platform offers therapeutically valuable functionalities, including molecular targeting, drug/gene delivery, and adaptive responses to trigger drug release. The potential of such nanomaterials to be combined with radiotherapy is widely recognized. In order for further breakthroughs to be made, and to facilitate clinical translation, the applicable principles and fundamentals should be articulated. This review focuses on mechanisms underpinning rational nanomaterial design to enhance radiation therapy, the understanding of which will enable novel ways to optimize its therapeutic efficacy. A roadmap for designing nanomaterials with optimized anticancer performance is also shown and the potential clinical significance and future translation are discussed.

Photodynamic Therapy for Photodamage, Actinic Keratosis, and Acne in the Cosmetic Practice

Photodynamic therapy is the combination of the initial application of a photosensitive chemical on the skin and then using typically a blue filter light of varying spectrums. This treatment protocol has been more useful and functional than other chemical peels and lasers for a variety of conditions. There has been efficacy in antiviral treatments, such as herpetic lesions; malignant cancers of the head and neck; and lung, bladder, and skin cancers. It has been tested for prostate cancers, cervical cancer, colorectal cancer, lung cancer, breast cancer, esophageal cancer, stomach cancer, pancreatic cancer, vaginal cancer, gliomas, and erythroplasia of Queyrat.

Irradiance, Photofrin® Dose and Initial Tumor Volume are Key Predictors of Response to Interstitial Photodynamic Therapy of Locally Advanced Cancers in Translational Models

The objective of the present study was to develop a predictive model for Photofrin® -mediated interstitial photodynamic therapy (I-PDT) of locally advanced tumors. Our finite element method was used to simulate 630-nm intratumoral irradiance and fluence for C3H mice and New Zealand White rabbits bearing large squamous cell carcinomas. Animals were treated with light only or I-PDT using the same light settings. I-PDT was administered with Photofrin® at 5.0 or 6.6 mg kg-1 , 24 h drug-light interval. The simulated threshold fluence was fixed at 45 J cm-2 while the simulated threshold irradiance varied, intratumorally. No cures were obtained in the mice treated with a threshold irradiance of 5.4 mW cm-2 . However, 20-90% of the mice were cured when the threshold irradiances were ≥8.6 mW cm-2 . In the rabbits treated with I-PDT, 13 of the 14 VX2 tumors showed either local control or were cured when threshold irradiances were ≥15.3 mW cm-2 and fluence was 45 J cm-2 . No tumor growth delay was observed in VX2 treated with light only (n = 3). In the mouse studies, there was a high probability (92.7%) of predicting cure when the initial tumor volume was below the median (493.9 mm3 ) and I-PDT was administered with a threshold intratumoral irradiance ≥8.6 mW cm-2 .

Optical characterization of porcine tissues from various organs in the 650-1100 nm range using time-domain diffuse spectroscopy

We present a systematic characterization of the optical properties (µ_a and µ_s') of nine representative ex vivo porcine tissues over a broadband spectrum (650-1100 nm). We applied time-resolved diffuse optical spectroscopy measurements for recovering the optical properties of porcine tissues depicting a realistic representation of the tissue heterogeneity and morphology likely to be found in different ex vivo tissues. The results demonstrate a large spectral and inter-tissue variation of optical properties. The data can be exploited for planning or simulating ex vivo experiments with various biophotonics techniques, or even to construct artificial structures mimicking specific pathologies exploiting the wide assortment in optical properties.

The Yin and Yang of PDT and PTT

In Chinese philosophy, yin and yang ("dark-bright," "negative-positive") describe how seemingly opposite or contrary forces may actually be complementary, interconnected and interdependent. This paper provides this perspective on photodynamic and photothermal therapies, with a focus on the treatment of solid tumors. The relative strengths and weaknesses of each modality, both current and emerging, are considered with respect to the underlying biophysics, the required technologies, the biological effects, their translation into clinical practice and the realized or potential clinical outcomes. For each specific clinical application, one or the other modality may be clearly preferred, or both are effectively equivalent in terms of the various scientific/technological/practical/clinical trade-offs involved. Alternatively, a combination may the best approach. Such combined approaches may be facilitated by the use of multifunctional nanoparticles. It is important to understand the many factors that go into the selection of the optimal approach and the objective of this paper is to provide guidance on this.

Validation of combined Monte Carlo and photokinetic simulations for the outcome correlation analysis of benzoporphyrin derivative-mediated photodynamic therapy on mice

We compare previously reported benzoporphyrin derivative (BPD)-mediated photodynamic therapy (PDT) results for reactive singlet oxygen concentration (also called singlet oxygen dose) on mice with simulations using a computational device, Dosie™, that calculates light transport and photokinetics for PDT in near real-time. The two sets of results are consistent and validate the use of the device in PDT treatment planning to predict BPD-mediated PDT outcomes in mice animal studies based on singlet oxygen dose, which showed a much better correlation with the cure index than the conventional light dose.

An Implantable Ultrasonically-Powered Micro-Light-Source (µLight) for Photodynamic Therapy

Photodynamic therapy (PDT) is a promising cancer treatment modality that can selectively target unresectable tumors through optical activation of cytotoxic agents, thus reducing many side effects associated with systemic administration of chemotherapeutic drugs. However, limited light penetration into most biological tissues have so far prevented its widespread adoption beyond dermatology and a few other oncological applications in which a fiber optic can be threaded to the desired locations via an endoscopic approach (e.g., bladder). In this paper, we introduce an ultrasonically powered implantable microlight source, μLight, which enables in-situ localized light delivery to deep-seated solid tumors. Ultrasonic powering allows for small receiver form factor (mm-scale) and power transfer deep into the tissue (several centimeters). The implants consist of piezoelectric transducers measuring 2 × 2 × 2 mm3 and 2 × 4 × 2 mm3 with surface-mounted miniature red and blue LEDs. When energized with 185 mW/cm2 of transmitted acoustic power at 720 kHz, μLight can generate 0.048 to 6.5 mW/cm2 of optical power (depending on size of the piezoelectric element and light wavelength spectrum). This allows powering multiple receivers to a distance of 10 cm at therapeutic light output levels (a delivery of 20-40 J/cm2 light radiation dose in 1-2 hours). In vitro tests show that HeLa cells irradiated with μLights undergo a 70% decrease in average cell viability as compared to the control group. In vivo tests in mice implanted with 4T1-induced tumors (breast cancer) show light delivery capability at therapeutic dose levels. Overall, results indicate implanting multiple µLights and operating them for 1-2 hours can achieve cytotoxicity levels comparable to the clinically reported cases using external light sources.

A Novel Prospective Study Assessing the Combination of Photodynamic Therapy and Proton Radiation Therapy: Safety and Outcomes When Treating Malignant Pleural Mesothelioma

Malignant pleural mesothelioma remains difficult to treat, with high failure rates despite optimal therapy. We present a novel prospective trial combining proton therapy (PT) and photodynamic therapy (PDT) and the largest-ever mesothelioma PT experience (n = 10). PDT photosensitizers included porfimer sodium (2 mg·kg-1 ; 24 h drug-light interval) or 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) (4 mg·m-2 ;48 h) with wavelengths of 630 nm to 60J·cm-2 and 665 nm to 15-45J·cm-2 , respectively. With a median age of 69 years, patients were predominantly male (90%) with epithelioid histology (100%) and stage III-IV disease (100%). PT was delivered to a median of 55.0 CGE/1.8-2.0 CGE (range 50-75 CGE) adjuvantly (n = 8) or as salvage therapy (n = 2) following extended pleurectomy/decortication (ePD)/PDT. Two-year local control was 90%, with distant and regional failure rates of 50% and 30%, respectively. All patients received chemotherapy, and four received immunotherapy. Surgical complications included atrial fibrillation (n = 3), pneumonia (n = 2), and deep vein thrombosis (n = 2). Median survival from PT completion was 19.5 months (30.3 months from diagnosis), and 1- and 2-year survival rates were 58% and 29%. No patient experienced CTCAEv4 grade ≥2 acute or late toxicity. Our prolonged survival in very advanced-stage patients compares favorably to survival for PT without PDT and photon therapy with PDT, suggesting possible spatial or systemic cooperativity and immune effect.

Optimizing interstitial photodynamic therapy with custom cylindrical diffusers

Interstitial photodynamic therapy (iPDT) has shown promise recently as a minimally invasive cancer treatment, partially due to the development of non-toxic photosensitizers in the absence of activation light. However, a major challenge in iPDT is the pre-treatment planning process that specifies the number of diffusers needed, along with their positions and allocated powers, to confine the light distribution to the target volume as much as possible. In this work, a new power allocation algorithm for cylindrical light diffusers including those that can produce customized longitudinal (tailored) emission profiles is introduced. The proposed formulation is convex to guarantee the minimum over-dose possible on the surrounding organs-at-risk. The impact of varying the diffuser lengths and penetration angles on the quality of the plan is evaluated. The results of this study are demonstrated for different photosensitizers activated at different wavelengths and simulated on virtual tumors modeling virtual glioblastoma multiforme cases. Results show that manufacturable cylindrical diffusers with tailored emission profiles can significantly outperform those with conventional flat profiles with an average damage reduction on white matter of 15% to 55% and on gray matter of 23% to 58%.

Reconstruction of a Deformed Tumor Based on Fiducial Marker Registration: A Computational Feasibility Study

Interstitial photodynamic therapy has shown promising results in the treatment of locally advanced head and neck cancer. In this therapy, systemic administration of a light-sensitive drug is followed by insertion of multiple laser fibers to illuminate the tumor and its margins. Image-based pretreatment planning is employed in order to deliver a sufficient light dose to the complex locally advanced head-and-neck cancer anatomy, in order to meet clinical requirements. Unfortunately, the tumor may deform between pretreatment imaging for the purpose of planning and intraoperative imaging when the plan is executed. Tumor deformation may result from the mechanical forces applied by the light fibers and variation of the patient’s posture. Pretreatment planning is frequently done with the assistance of computed tomography or magnetic resonance imaging in an outpatient suite, while treatment monitoring and control typically uses ultrasound imaging due to considerations of costs and availability in the operation room. This article presents a computational method designed to bridge the gap between the 2 imaging events by taking a tumor geometry, reconstructed during preplanning, and by following the displacement of fiducial markers, which are initially placed during the preplanning procedure. The deformed tumor shape is predicted by solving an inverse problem, seeking for the forces that would have resulted in the corresponding fiducial marker displacements. The computational method is studied on spheres of variable sizes and demonstrated on computed tomography reconstructed locally advanced head and neck cancer model. Results of this study demonstrate an average error of less than 1 mm in predicting the deformed tumor shape, where 1 mm is typically the order of uncertainty in distance measurements using magnetic resonance imaging or computed tomography imaging and high-quality ultrasound imaging. This study further demonstrates that the deformed shape can be calculated in a few seconds, making the proposed method clinically relevant.

Effects of Ultraviolet Radiation on Glioma: Systematic Review

Glioblastoma multiforme is the most aggressive primary brain tumor. Treatment is largely palliative, with current strategies unable to prevent inevitable tumor recurrence. Implantable micro-electromechanical systems are becoming more feasible for the management of several human diseases. These systems may have a role in detecting tumor recurrence and delivering localized therapies. One potential therapeutic tool is ultraviolet (UV) light. This systematic review assesses the effects of UV light on glioma cells. A total of 47 publications are included. The large majority were in vitro experiments conducted on human glioblastoma cell lines in monolayer. In these cells, UV light was shown to induce apoptosis and the expression of genes or activation of proteins that modulate cell death, repair, and proliferation. The nature and magnitude of cellular response varied by UV wavelength, dose, cell line, and time after irradiation. UVC (wavelength 100-280 nm) was most effective at inducing apoptosis, and this effect was dose dependent. The included studies had varied methodologies, complicating reconciliation of results. Further work will be required to determine the best regime of UV irradiation for therapeutic use. J. Cell. Biochem. 118: 4063-4071, 2017. © 2017 Wiley Periodicals, Inc.

Advances in antimicrobial photodynamic inactivation at the nanoscale

The alarming worldwide increase in antibiotic resistance amongst microbial pathogens necessitates a search for new antimicrobial techniques, which will not be affected by, or indeed cause resistance themselves. Light-mediated photoinactivation is one such technique that takes advantage of the whole spectrum of light to destroy a broad spectrum of pathogens. Many of these photoinactivation techniques rely on the participation of a diverse range of nanoparticles and nanostructures that have dimensions very similar to the wavelength of light. Photodynamic inactivation relies on the photochemical production of singlet oxygen from photosensitizing dyes (type II pathway) that can benefit remarkably from formulation in nanoparticle-based drug delivery vehicles. Fullerenes are a closed-cage carbon allotrope nanoparticle with a high absorption coefficient and triplet yield. Their photochemistry is highly dependent on microenvironment, and can be type II in organic solvents and type I (hydroxyl radicals) in a biological milieu. Titanium dioxide nanoparticles act as a large band-gap semiconductor that can carry out photo-induced electron transfer under ultraviolet A light and can also produce reactive oxygen species that kill microbial cells. We discuss some recent studies in which quite remarkable potentiation of microbial killing (up to six logs) can be obtained by the addition of simple inorganic salts such as the non-toxic sodium/potassium iodide, bromide, nitrite, and even the toxic sodium azide. Interesting mechanistic insights were obtained to explain this increased killing.

Endobronchial ultrasound-guidance for interstitial photodynamic therapy of locally advanced lung cancer-a new interventional concept

Recent advances in interventional pulmonology led to a significant expansion of the diagnostic and therapeutic role of endobronchial ultrasound. In this paper, we describe a new concept for using endobronchial ultrasound to guide interstitial photodynamic therapy (PDT). For this purpose, we conducted in vitro and in vivo experiments using a phantom and animal models, respectively. A new 0.5 mm optical fiber, with cylindrical diffuser end, was used to deliver the therapeutic light through the 21-gauge endobronchial ultrasound needle. The animal experiments were performed under real-time ultrasonography guidance in mice and rabbits' tumor models. Safe and effective fiber placements and tumor illumination was accomplished. In addition, computer simulation of light propagation suggests that locally advanced lung cancer tumor can be illuminated. This study demonstrates the potential feasibility of this new therapeutic modality approach, justifying further investigation in the treatment of locally advanced lung cancers.

Vascular targeted photodynamic therapy with TOOKAD® Soluble (WST11) in localized prostate cancer: efficiency of automatic pre-treatment planning

Vascular targeted photodynamic therapy (VTP) with WST11 is a novel non-thermal focal treatment for localized prostate cancer that has shown favorable and early efficacy results in previously published studies. In this work, we investigate the efficiency of automatic dosimetric treatment planning. An action model established in a previous study was used in an image-guided optimization scheme to define the personalized optimal light dose for each patient. The calculated light dose is expressed as the number of optical cylindrical fibers to be used, their positions according to an external insertion grid, and the lengths of their diffuser parts. Evaluation of the method was carried out on data collected from 17 patients enrolled in two multi-centric clinical trials. The protocol consisted of comparing the method-simulated necrosis to the result observed on day 7 MR enhanced images. The method performances showed that the final result can be estimated with an accuracy of 10%, corresponding to a margin of 3 mm. In addition, this process was compatible with clinical conditions in terms of calculation times. The overall process took less than 10 min. Different aspects of the VTP procedure were already defined and optimized. Personalized treatment planning definition remained as an issue needing further investigation. The method proposed herein completes the standardization of VTP and opens new pathways for the clinical development of the technique.

Nanoparticles as Theranostic Vehicles in Experimental and Clinical Applications-Focus on Prostate and Breast Cancer

Prostate and breast cancer are the second most and most commonly diagnosed cancer in men and women worldwide, respectively. The American Cancer Society estimates that during 2016 in the USA around 430,000 individuals were diagnosed with one of these two types of cancers, and approximately 15% of them will die from the disease. In Europe, the rate of incidences and deaths are similar to those in the USA. Several different more or less successful diagnostic and therapeutic approaches have been developed and evaluated in order to tackle this issue and thereby decrease the death rates. By using nanoparticles as vehicles carrying both diagnostic and therapeutic molecular entities, individualized targeted theranostic nanomedicine has emerged as a promising option to increase the sensitivity and the specificity during diagnosis, as well as the likelihood of survival or prolonged survival after therapy. This article presents and discusses important and promising different kinds of nanoparticles, as well as imaging and therapy options, suitable for theranostic applications. The presentation of different nanoparticles and theranostic applications is quite general, but there is a special focus on prostate cancer. Some references and aspects regarding breast cancer are however also presented and discussed. Finally, the prostate cancer case is presented in more detail regarding diagnosis, staging, recurrence, metastases, and treatment options available today, followed by possible ways to move forward applying theranostics for both prostate and breast cancer based on promising experiments performed until today.

Oncologic Photodynamic Therapy: Basic Principles, Current Clinical Status and Future Directions

Photodynamic therapy (PDT) is a clinically approved cancer therapy, based on a photochemical reaction between a light activatable molecule or photosensitizer, light, and molecular oxygen. When these three harmless components are present together, reactive oxygen species are formed. These can directly damage cells and/or vasculature, and induce inflammatory and immune responses. PDT is a two-stage procedure, which starts with photosensitizer administration followed by a locally directed light exposure, with the aim of confined tumor destruction. Since its regulatory approval, over 30 years ago, PDT has been the subject of numerous studies and has proven to be an effective form of cancer therapy. This review provides an overview of the clinical trials conducted over the last 10 years, illustrating how PDT is applied in the clinic today. Furthermore, examples from ongoing clinical trials and the most recent preclinical studies are presented, to show the directions, in which PDT is headed, in the near and distant future. Despite the clinical success reported, PDT is still currently underutilized in the clinic. We also discuss the factors that hamper the exploration of this effective therapy and what should be changed to render it a more effective and more widely available option for patients.

Interstitial Photodynamic Therapy-A Focused Review

Multiple clinical studies have shown that interstitial photodynamic therapy (I-PDT) is a promising modality in the treatment of locally-advanced cancerous tumors. However, the utilization of I-PDT has been limited to several centers. The objective of this focused review is to highlight the different approaches employed to administer I-PDT with photosensitizers that are either approved or in clinical studies for the treatment of prostate cancer, pancreatic cancer, head and neck cancer, and brain cancer. Our review suggests that I-PDT is a promising treatment in patients with large-volume or thick tumors. Image-based treatment planning and real-time dosimetry are required to optimize and further advance the utilization of I-PDT. In addition, pre- and post-imaging using computed tomography (CT) with contrast may be utilized to assess the response.

Photodynamic Therapy of Non-Small Cell Lung Cancer. Narrative Review and Future Directions

Photodynamic therapy (PDT) is an established treatment modality for non-small cell lung cancer. Phototoxicity, the primary adverse event, is expected to be minimized with the introduction of new photosensitizers that have shown promising results in phase I and II clinical studies. Early-stage and superficial endobronchial lesions less than 1 cm in thickness can be effectively treated with external light sources. Thicker lesions and peripheral lesions may be amenable to interstitial PDT, where the light is delivered intratumorally. The addition of PDT to standard-of-care surgery and chemotherapy can improve survival and outcomes in patients with pleural disease. Intraoperative PDT has shown promise in the treatment of non-small cell lung cancer with pleural spread. Recent preclinical and clinical data suggest that PDT can increase antitumor immunity. Crosslinking of signal transducer and activator of transcription-3 molecules is a reliable biomarker to quantify the photoreaction induced by PDT. Randomized studies are required to test the prognosis value of this biomarker, obtain approval for the new photosensitizers, and test the potential efficacy of interstitial and intraoperative PDT in the treatment of patients with non-small cell lung cancer.

Recovery of optical properties using interstitial cylindrical diffusers as source and detector fibers

We demonstrate recovery of optical properties using arrays of interstitial cylindrical diffusing fibers as sources and detectors. A single 1-cm diffuser delivered laser illumination at 665 nm, while seven 1- and 2-cm diffusers at 1-cm grid spacing acted as detectors. Extraction of optical properties from these measurements was based upon a diffusion model of emission and detection distributions for these diffuser fibers, informed by previous measurements of heterogeneous axial detection. Verification of the technique was performed in 15 liquid tissue-simulating phantoms consisting of deionized water, India ink as absorber, and Intralipid 20% as scatterer. For the range of optical properties tested, mean errors were 4.4% for effective attenuation coefficient, 12.6% for absorption coefficient, and 7.6% for reduced scattering coefficient. Error in recovery tended to increase with decreasing transport albedo. For therapeutic techniques involving the delivery of light to locations deep within the body, such as interstitial photodynamic and photothermal therapies, the methods described here would allow the treatment diffuser fibers also to be used as sources and detectors for recovery of optical properties. This would eliminate the need for separately inserted fibers for spectroscopy, reducing clinical complexity and improving the accuracy of treatment planning.

Revisiting photodynamic therapy dosimetry: reductionist & surrogate approaches to facilitate clinical success

Photodynamic therapy (PDT) can be a highly complex treatment, with many parameters influencing treatment efficacy. The extent to which dosimetry is used to monitor and standardize treatment delivery varies widely, ranging from measurement of a single surrogate marker to comprehensive approaches that aim to measure or estimate as many relevant parameters as possible. Today, most clinical PDT treatments are still administered with little more than application of a prescribed drug dose and timed light delivery, and thus the role of patient-specific dosimetry has not reached widespread clinical adoption. This disconnect is at least partly due to the inherent conflict between the need to measure and understand multiple parameters in vivo in order to optimize treatment, and the need for expedience in the clinic and in the regulatory and commercialization process. Thus, a methodical approach to selecting primary dosimetry metrics is required at each stage of translation of a treatment procedure, moving from complex measurements to understand PDT mechanisms in pre-clinical and early phase I trials, towards the identification and application of essential dose-limiting and/or surrogate measurements in phase II/III trials. If successful, identifying the essential and/or reliable surrogate dosimetry measurements should help facilitate increased adoption of clinical PDT. In this paper, examples of essential dosimetry points and surrogate dosimetry tools that may be implemented in phase II/III trials are discussed. For example, the treatment efficacy as limited by light penetration in interstitial PDT may be predicted by the amount of contrast uptake in CT, and so this could be utilized as a surrogate dosimetry measurement to prescribe light doses based upon pre-treatment contrast. Success of clinical ALA-based skin lesion treatment is predicted almost uniquely by the explicit or implicit measurements of photosensitizer and photobleaching, yet the individualization of treatment based upon each patients measured bleaching needs to be attempted. In the case of ALA, lack of PpIX is more likely an indicator that alternative PpIX production methods must be implemented. Parsimonious dosimetry, using surrogate measurements that are clinically acceptable, might strategically help to advance PDT in a medical world that is increasingly cost and time sensitive. Careful attention to methodologies that can identify and advance the most critical dosimetric measurements, either direct or surrogate, are needed to ensure successful incorporation of PDT into niche clinical procedures.

Online dosimetry for temoporfin-mediated interstitial photodynamic therapy using the canine prostate as model

Online light dosimetry with real-time feedback was applied for temoporfin-mediated interstitial photodynamic therapy (PDT) of dog prostate. The aim was to investigate the performance of online dosimetry by studying the correlation between light dose plans and the tissue response, i.e., extent of induced tissue necrosis and damage to surrounding organs at risk. Light-dose planning software provided dose plans, including light source positions and light doses, based on ultrasound images. A laser instrument provided therapeutic light and dosimetric measurements. The procedure was designed to closely emulate the procedure for whole-prostate PDT in humans with prostate cancer. Nine healthy dogs were subjected to the procedure according to a light-dose escalation plan. About 0.15 mg/kg temoporfin was administered 72 h before the procedure. The results of the procedure were assessed by magnetic resonance imaging, and gross pathology and histopathology of excised tissue. Light dose planning and online dosimetry clearly resulted in more focused effect and less damage to surrounding tissue than interstitial PDT without dosimetry. A light energy dose-response relationship was established where the threshold dose to induce prostate gland necrosis was estimated from 20 to 30  J/cm2.

A new finite element approach for near real-time simulation of light propagation in locally advanced head and neck tumors

Background and Objectives

Several clinical studies suggest that interstitial photodynamic therapy (I‐PDT) may benefit patients with locally advanced head and neck cancer (LAHNC). For I‐PDT, the therapeutic light is delivered through optical fibers inserted into the target tumor. The complex anatomy of the head and neck requires careful planning of fiber insertions. Often the fibers' location and tumor optical properties may vary from the original plan therefore pretreatment planning needs near real‐time updating to account for any changes. The purpose of this work was to develop a finite element analysis (FEA) approach for near real‐time simulation of light propagation in LAHNC.

Methods

Our previously developed FEA for modeling light propagation in skin tissue was modified to simulate light propagation from interstitial optical fibers. The modified model was validated by comparing the calculations with measurements in a phantom mimicking tumor optical properties. We investigated the impact of mesh element size and growth rate on the computation time, and defined optimal settings for the FEA. We demonstrated how the optimized FEA can be used for simulating light propagation in two cases of LAHNC amenable to I‐PDT, as proof‐of‐concept.

Results

The modified FEA was in agreement with the measurements (P = 0.0271). The optimal maximum mesh size and growth rate were 0.005–0.02 m and 2–2.5 m/m, respectively. Using these settings the computation time for simulating light propagation in LAHNC was reduced from 25.9 to 3.7 minutes in one case, and 10.1 to 4 minutes in another case. There were minor differences (1.62%, 1.13%) between the radiant exposures calculated with either mesh in both cases.

Conclusions

Our FEA approach can be used to model light propagation from diffused optical fibers in complex heterogeneous geometries representing LAHNC. There is a range of maximum element size (MES) and maximum element growth rate (MEGR) that can be used to minimize the computation time of the FEA to 4 minutes. Lasers Surg. Med. 47:60–67, 2015. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Comparison of flat cleaved and cylindrical diffusing fibers as treatment sources for interstitial photodynamic therapy

PURPOSE

For interstitial photodynamic therapy (iPDT) of bulky tumors, careful treatment planning is required in order to ensure that a therapeutic dose is delivered to the tumor, while minimizing damage to surrounding normal tissue. In clinical contexts, iPDT has typically been performed with either flat cleaved or cylindrical diffusing optical fibers as light sources. Here, the authors directly compare these two source geometries in terms of the number of fibers and duration of treatment required to deliver a prescribed light dose to a tumor volume.

METHODS

Treatment planning software for iPDT was developed based on graphics processing unit enhanced Monte Carlo simulations. This software was used to optimize the number of fibers, total energy delivered by each fiber, and the position of individual fibers in order to deliver a target light dose (D90) to 90% of the tumor volume. Treatment plans were developed using both flat cleaved and cylindrical diffusing fibers, based on tissue volumes derived from CT data from a head and neck cancer patient. Plans were created for four cases: fixed energy per fiber, fixed number of fibers, and in cases where both or neither of these factors were fixed.

RESULTS

When the number of source fibers was fixed at eight, treatment plans based on flat cleaved fibers required each to deliver 7180-8080 J in order to deposit 90 J/cm(2) in 90% of the tumor volume. For diffusers, each fiber was required to deliver 2270-2350 J (333-1178 J/cm) in order to achieve this same result. For the case of fibers delivering a fixed 900 J, 13 diffusers or 19 flat cleaved fibers at a spacing of 1 cm were required to deliver the desired dose. With energy per fiber fixed at 2400 J and the number of fibers fixed at eight, diffuser fibers delivered the desired dose to 93% of the tumor volume, while flat cleaved fibers delivered this dose to 79%. With both energy and number of fibers allowed to vary, six diffusers delivering 3485-3600 J were required, compared to ten flat cleaved fibers delivering 2780-3600 J.

CONCLUSIONS

For the same number of fibers, cylindrical diffusers allow for a shorter treatment duration compared to flat cleaved fibers. For the same energy delivered per fiber, diffusers allow for the insertion of fewer fibers in order to deliver the same light dose to a target volume.

Focal therapy for prostate cancer. Alternative treatment

CONTEXT

The great controversy surrounding the treatment of localized prostate cancer is related with its possibilities of radical treatment or active surveillance. The objective of this paper is to analyze the rationale selection among current focal therapy modalities regarding tumor and patient selection.

EVIDENCE ACQUISITION

Current articles about advantages and disadvantages on the treatment of localized prostate cancer as well as information about focal therapy regarding tumour selection, characteristics and indications cited in MEDLINE search were reviewed.

SUMMARY OF EVIDENCE

Focal therapy standardized criteria must be: low risk tumors, PSA<10-15, Gleason score ≤ 6, and unilateral presentation all supported by image-guided biopsy and nuclear magnetic resonance (NMR). There are doubts about the suitability of focal therapy in cases of bilateralism or in those with Gleason score 3+4 or PSA>15.

CONCLUSIONS

Focal therapy is an alternative for localized prostate cancer treatment. However, some aspects of their diagnosis and selection criteria should be defined by prospective studies which should provide knowledge about the indication for focal therapy.

Design and validation of a fiber optic point probe instrument for therapy guidance and monitoring

Optical techniques for tissue diagnostics currently are experiencing tremendous growth in biomedical applications, mainly due to their noninvasive, inexpensive, and real-time functionality. Here, we demonstrate a hand-held fiber optic probe instrument based on fluorescence/reflectance spectroscopy for precise tumor delineation. It is mainly aimed for brain tumor resection guidance with clinical adaptation to minimize the disruption of the standard surgical workflow and is meant as a complement to the state-of-the-art fluorescence surgical microscopy technique. Multiple light sources with fast pulse modulation and detection enable precise quantification of protoporphyrin IX (PpIX), tissue optical properties, and ambient light suppression. Laboratory measurements show the system is insensitive to strong ambient light. Validation measurements of tissue phantoms using nonlinear least squares support vector machines (LS-SVM) regression analysis demonstrate an error of <5% for PpIX concentration ranging from 400 to 1000 nM, even in the presence of large variations in phantom optical properties. The mean error is 3% for reduced scattering coefficient and 5% for blood concentration. Diagnostic precision of 100% was obtained by LS-SVM classification for in vivo skin tumors with topically applied 5-aminolevulinic acid during photodynamic therapy. The probe could easily be generalized to other tissue types and fluorophores for therapy guidance and monitoring.

Stability enhanced polyelectrolyte-coated gold nanorod-photosensitizer complexes for high/low power density photodynamic therapy

Photodynamic therapy (PDT) is a promising treatment modality for cancer and other malignant diseases, however safety and efficacy improvements are required before it reaches its full potential and wider clinical use. Herein, we investigated a highly efficient and safe photodynamic therapy procedure by developing a high/low power density photodynamic therapy mode (high/low PDT mode) using methoxypoly(ethylene glycol) thiol (mPEG-SH) modified gold nanorod (GNR)-AlPcS4 photosensitizer complexes. mPEG-SH conjugated to the surface of simple polyelectrolyte-coated GNRs was verified using Fourier transform infrared spectroscopy; this improved stability, reduced cytotoxicity, and increased the encapsulation and loading efficiency of the nanoparticle dispersions. The GNR-photosensitizer complexes were exposed to the high/low PDT mode (high light dose = 80 mW/cm(2) for 0.5 min; low light dose = 25 mW/cm(2) for 1.5 min), and a high PDT efficacy leads to approximately 90% tumor cell killing. Due to synergistic plasmonic photothermal properties of the complexes, the high/low PDT mode demonstrated improved efficacy over using single wavelength continuous laser irradiation. Additionally, no significant loss in viability was observed in cells exposed to free AlPcS4 photosensitizer under the same irradiation conditions. Consequently, free AlPcS4 released from GNRs prior to cellular entry did not contribute to cytotoxicity of normal cells or impose limitations on the use of the high power density laser. This high/low PDT mode may effectively lead to a safer and more efficient photodynamic therapy for superficial tumors.

Investigation of photodynamic therapy optimization for port wine stain using modulation of photosensitizer administration methods

To raise photosensitizer concentration level during the photodynamic therapy process, two new methods of photosensitizer administration were investigated. The first method involves the slow intravenous injection of photosensitizer throughout the first 15 min of irradiation, and the second method involves 30 min fomentation before photosensitizer injection and irradiation. The fluorescence spectra of port wine stain skin were monitored and the therapeutic effect correlated index was calculated with a previously published spectral algorithm. Thirty cases were divided into group A (slow injection of photosensitizer during the first 15 min), group B (fomentation), and group C (control group, traditional injection method), with 10 cases in each group. To analyze the effect of these two new methods, the change of therapeutic effect correlated index values of two photodynamic therapy sessions for each patient were calculated, and the photodynamic therapy outcome was compared. The results showed that the change of therapeutic effect correlated index in group A was slightly more remarkable than that in the control group. The change of therapeutic effect correlated index in group B was similar to that in the control group. Slow injection of photosensitizer during photodynamic therapy has a potential to increase photosensitizer concentration level during photodynamic therapy. However, fomentation before photodynamic therapy has no such potential. There is a need for new methods to be attempted.

Experimental spectro-angular mapping of light distribution in turbid media

We present a new approach to the analysis of radiance in turbid media. The approach combines data from spectral, angular and spatial domains in a form of spectro-angular maps. Mapping provides a unique way to visualize details of light distribution in turbid media and allows tracking changes with distance. Information content of experimental spectro-angular maps is verified by a direct comparison with simulated data when an analytical solution of the radiative transfer equation is used. The findings deepen our understanding of the light distribution in a homogenous turbid medium and provide a first step toward applying the spectro-angular mapping as a diagnostic tool for tissue characterization.

A review of in-vivo optical properties of human tissues and its impact on PDT

A thorough understanding of optical properties of biological tissues is critical to effective treatment planning for therapies such as photodynamic therapy (PDT). In the last two decades, new technologies, such as broadband diffuse spectroscopy, have been developed to obtain in vivo data in humans that was not possible before. We found that the in vivo optical properties generally vary in the ranges μ(a) = 0.03-1.6 cm⁻¹ and μ'(s) = 1.2-40 cm⁻¹, although the actual range is tissue-type dependent. We have also examined the overall trend of the absorption spectra (for μ(a) and μ'(s)) as a function of wavelength within a 95% confidence interval for various tissues in vivo. The impact of optical properties on light fluence rate is also discussed for various light application geometries including superficial, interstitial, and within a cavity.