Thermal safety and effectiveness of tumor treating fields’ delivery to the abdomen as determined by computational simulations

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Background: Tumor Treating Fields (TTFields), an antimitotic cancer treatment, utilizes low intensity (1-3 V/cm), intermediate frequency (100-300 kHz), alternating electric fields delivered non-invasively by transducer arrays placed on skin over tumor region. Safety of TTFields has been established in pancreatic cancer (Phase II study; PANOVA; NCT01971281). A Phase 3 study in locally-advanced pancreatic cancer (PANOVA-3) and a phase 2 study in hepatocellular cancer are ongoing. Preclinical studies suggest that TTFields’ intensity correlates with treatment efficacy. Simulations can determine the thermal safety of TTFields by evaluating tissue heating due to field absorption and resultant risk of thermal damage. We used computational simulations to study the effectiveness of field distribution and associated heating in realistic phantoms during TTFields delivery to the abdomen. Methods: Delivery of TTFields to computational phantoms of a male (DUKE 3.0), a female (ELLA 3.0) and an obese male (FATS 3.0) was simulated. For each phantom, 6-8 different transducer array layouts to the abdomen were tested. Specific Absorption Rate (SAR) levels were calculated to assess the risk of thermal damage to tissues, and compared to the SAR control level of 10 W/kg per International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines for occupational exposure (Health Physics 74 (4) 494; 1998). The field intensities were measured to determine the effectiveness of treatment delivery. Results: Altering the size and position of the arrays facilitates field intensities above the therapeutic threshold of 1 V/cm. Within the abdominal internal organs, the SAR values were generally below the ICNIRP recommended level of 10 W/kg. The maximum SAR levels did not exceed 20 W/kg. Conclusions: TTFields could be delivered at intensities above therapeutic threshold of 1 V/cm by strategizing the array size and placement. TTFields to the abdomen can be delivered to target gastrointestinal cancers without causing thermal damage to abdominal tissues. These results also indicate that TTFields delivery can be optimized in gastrointestinal cancers.

PANOVA-3: A phase III study of tumor treating fields with nabpaclitaxel and gemcitabine for front-line treatment of locally advanced pancreatic adenocarcinoma (LAPC)

TPS469

Background: Tumor Treating Fields (TTFields) are a non-invasive, regional antimitotic treatment modality, which has been approved for the treatment of patients with glioblastoma by the FDA. TTFields predominantly act by disrupting the formation of the mitotic spindle during metaphase. TTFields were effective in multiple preclinical models of pancreatic cancer. The Phase 2 PANOVA study was the first trial testing TTFields in pancreatic cancer patients, and demonstrated the safety of TTFields when combined with nab-paclitaxel and gemcitabine in both metastatic and LAPC. The Phase 3 PANOVA-3 trial (NCT03377491) is designed to test the efficacy of adding TTFields to nab-paclitaxel and gemcitabine combination in LAPC. Methods: Patients (N = 556) with unresectable, LAPC (per NCCN guidelines) will be enrolled in this prospective, randomized trial. Patients should have an ECOG score of 0-2 and no prior progression or treatment. Patients will be stratified based on their performance status and geographical region, and will be randomized 1:1 to TTFields plus nab-paclitaxel and gemcitabine or to nab-paclitaxel and gemcitabine alone. Chemotherapy will be administered at standard dose of nab-paclitaxel (125 mg/m2) and gemcitabine (1000 mg/m2 once weekly). TTFields (150kHz) will be deilvered at least 18 hours/day until local disease progression per RECIST Criteria V1.1. Follow up will be performed q8w, including a CT scan of the chest and abdomen. Following local disease progression, patients will be followed monthly for survival. Overall survival will be the primary endpoint and progression-free survival, objective response rate, rate of resectability, quality of life and toxicity will all be secondary endpoints. Sample size was calculated using a log-rank test comparing time to event in patients treated with TTFields plus chemotherapy with control patients on chemotherapy alone. PANOVA-3 is designed to detect a hazard ratio 0.75 in overall survival. Type I error is set to 0.05 (two-sided) and power to 80%. Clinical trial information: NCT03377491.

Abstract CT082: TTFields concurrent with standard of care for the treatment of stage 4 non-small cell lung cancer (NSCLC) following platinum failure: phase III LUNAR study

Tumor Treating Fields (TTFields) are a non-invasive, anti-mitotic treatment modality. TTFields disrupt the formation of the mitotic spindle, and dislocation of intracellular constituents. TTFields significantly extend the survival of newly diagnosed glioblastoma patients when combined with temozolomide. Efficacy of TTFields in NSCLC has been shown preclinically and their safety in a phase I/II pilot study with pemetrexed. We hypothesize that adding TTFields to immune checkpoint inhibitor or docetaxel following platinum doublet failure will increase OS.

Methods: Patients (N=534) with squamous or non-squamous NSCLC are enrolled in the LUNAR phase III study [NCT02973789]. Patients are stratified by their selected standard therapy (immune checkpoint inhibitors or docetaxel), histology (squamous vs. non-squamous) and geographical region. Key inclusion criteria are disease progression while on or after platinum-based systemic therapy, ECOG 0-2, no electronic medical devices in the upper torso, and absence of brain metastasis. Docetaxel or immune checkpoint inhibitors are given at standard doses. TTFields are applied to the upper torso for 18 hours/day, allowing patients to maintain daily activities. TTFields are continued until progression in the thorax and/or liver. Follow up is performed every 6 weeks, including CT scans of the chest and abdomen. On progression in the thorax and/or liver, patients have three post-progression follow up visits and are later followed monthly for survival. The primary endpoint is superiority in OS between patients treated with TTFields in combination with the standard of care treatments, compared to standard of care treatments alone. Key secondary endpoints compare the OS in patients treated with TTFields and docetaxel Vs. those treated with docetaxel alone, and patients treated with TTFields and immune checkpoint inhibitors Vs. those treated with immune checkpoint inhibitors alone. An exploratory analysis will test non-inferiority of TTFields with docetaxel compared to checkpoint inhibitors alone. Secondary endpoints include progression-free survival, radiological response rate, quality of life based on the EORTC QLQ C30 questionnaire and severity & frequency of adverse events. The sample size is powered to detect a HR of 0.75 in TTFields-treated patients versus control group.

Citation Format: Uri Weinberg, Ori Farber, Moshe Giladi, Zeev Bomzon, Eilon Kirson. TTFields concurrent with standard of care for the treatment of stage 4 non-small cell lung cancer (NSCLC) following platinum failure: phase III LUNAR study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT082.

Abstract CT157: PANOVA-3: A phase III study of TTFields with nab-paclitaxel and gemcitabine for front-line treatment of locally-advanced pancreatic adenocarcinoma (LAPC)

Tumor Treating Fields (TTFields) are a non-invasive, regional antimitotic treatment modality, which has been approved for the treatment of patients with glioblastoma by the FDA. TTFields predominantly act by disrupting the formation of the mitotic spindle during metaphase. TTFields were effective in multiple preclinical models of pancreatic cancer. The Phase 2 PANOVA study was the first trial testing TTFields in pancreatic cancer patients, and demonstrated the safety of TTFields when combined with nab-paclitaxel and gemcitabine in both metastatic and LAPC. The Phase 3 PANOVA-3 trial (NCT03377491) is designed to test the efficacy of adding TTFields to nab-paclitaxel and gemcitabine combination in LAPC.

Trial Design: Patients (N=556) with unresectable, LAPC (per NCCN guidelines) will be enrolled in this prospective, randomized trial. Patients should have an ECOG score of 0-2 and no prior progression or treatment. Patients will be stratified based on their performance status and geographical region, and will be randomized 1:1 to TTFields plus nab-paclitaxel and gemcitabine or to nab-paclitaxel and gemcitabine alone. Chemotherapy will be administered at standard dose of nab-paclitaxel (125 mg/m2) and gemcitabine (1000 mg/m2 once weekly). TTFields (150kHz) will be deilvered at least 18 hours/day until local disease progression per RECIST Criteria V1.1. Follow up will be performed q8w, including a CT scan of the chest and abdomen. Following local disease progression, patients will be followed monthly for survival. Overall survival will be the primary endpoint and progression-free survival, objective response rate, rate of resectability, quality of life and toxicity will all be secondary endpoints. Sample size was calculated using a log-rank test comparing time to event in patients treated with TTFields plus chemotherapy with control patients on chemotherapy alone. PANOVA-3 is designed to detect a hazard ratio 0.75 in overall survival. Type I error is set to 0.05 (two-sided) and power to 80%.

Citation Format: Uri Weinberg, Ori Farber, Moshe Giladi, Zeev Bomzon, Gitit Lavy-Shahaf, Eilon D. Kirson. PANOVA-3: A phase III study of TTFields with nab-paclitaxel and gemcitabine for front-line treatment of locally-advanced pancreatic adenocarcinoma (LAPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT157.

First steps to creating a platform for high throughput simulation of TTFields

Tumor Treating Fields (TTFields) are low intensity alternating electric fields in the 100-500 KHz frequency range that are known to have an anti-mitotic effect on cancerous cells. In the USA, TTFields are approved by the Food and Drug Administration (FDA) for the treatment of glioblastoma (GBM) in both the newly diagnosed and recurrent settings. Optimizing treatment with TTFields requires a deep understanding of how TTFields distribute within the brain. To address this issue, simulations using realistic head models have been performed. However, the preparation of such models is time-consuming and requires a high level of expertise, limiting the usefulness of these models for systematic studies in which the testing of multiple cases is required. Here we present a platform for rapidly simulating TTFields distributions in multiple scenarios. This platform enables high throughput computational simulations to be performed, allowing comparison of field distributions within the head in multiple clinically relevant scenarios. The simulation setup is simple and intuitive, allowing non-expert users to run simulations and evaluate results, thereby providing a valuable tool for studying how to optimize TTFields delivery in the clinic.

Modelling Tumor Treating Fields for the treatment of lung-based tumors

Tumor Treating Fields (TTFields), low-intensity electric fields in the frequency range of 100-500 kHz, exhibit antimitotic activity in cancer cells. TTFields were approved by the U. S. Food and Drug Administration for the treatment of recurrent glioblastoma in 2011. Preclinical evidence and pilot studies suggest that TTFields could be effective for treating certain types of lung cancer, and that treatment efficacy depends on the electric field intensity. To optimize TTFields delivery to the lungs, it is important to understand how TTFields distribute within the chest. Here we present simulations showing how TTFields are distributed in the thorax and torso, and demonstrate how the electric field distribution within the body can be controlled by personalizing the layout of the arrays used to deliver the field.

Abstract 2051: Tumor-treating fields (TTFields) intensity in the gross tumor volume and peritumoral brain zone: implications for local recurrence in glioblastoma

The purpose of this study was to simulate the intensity of TTFields delivered to the brain during the course of glioblastoma (GBM) treatment and to determine whether therapeutic intensities are delivered to the proximal peri-tumoral brain zone (PBZ). Background: TTFields are low-intensity (1-3 V/cm), intermediate frequency (200kHz), alternating electric fields delivered orthogonally in a localized manner during the course of GBM therapy. A recent phase 3 randomized, controlled trial conducted in patients newly diagnosed with GBM was stopped early for efficacy when the end points for progression-free survival (PFS) and overall survival (OS) were met at the interim analysis. Patients receiving TTFields in combination with temozolomide (TMZ) had a significantly longer PFS and OS compared with patients receiving TMZ alone. More than 90% of GBM recur at the margin of a resection cavity or within the PBZ where the presence of infiltrating tumor cells, inflammatory cells and tumorigenic stromal cells are thought to promote recurrence. Phantom model simulation studies suggest that field intensities >1V/cm are delivered to the brain in a non-uniform distribution, however the field distribution to the gross tumor volume (GTV) and PBZ have not been previously evaluated. Methods: Two MRI cases (frontal and posterior-parietal tumors) were used to generate TTFields treatment array layout maps using NovoTAL(TM) System planning software, targeting areas of contrast enhancement on T1 sequences. Simulations for the respective array layouts were created for solid tumors, resection cavities and for tumors with a necrotic core (modified Colin27 model, meshed and solved using the Sim4Life software solver package). Two orthogonal fields (left-right and antero-posterior) at a field frequency of 200 kHz were employed for all simulations. Field intensity was determined in the GTV, tumor margin(TM) and proximal PBZ (20mm) for all models. Results: Transducer array layout maps generated by the NovoTAL software deliver therapeutic intensities of TTFields in both L-R and A-P directions. Bi-directional intensities exceed therapeutic levels (>1 V/cm) in the GTV (median 1.84 V/cm), TM (median 1.9 V/cm) and PBZ (median 2.09 V/cm) in all solid tumors and in the PBZ (median 1.83 V/cm) surrounding a gross total resection (GTR) cavity. The highest areas of field intensity are observed directly adjacent to resection cavities and the ventricles. Conclusions: The delivery of therapeutic intensities of TTFields to patients who have undergone a GTR, subtotal resection or who have inoperable GBM, targets therapy to the area of active disease and importantly, to the PBZ. TTFields target residual tumor cells in the GTV and may also disrupt infiltrating tumor cells in the PBZ. Clinically, this may decrease local GBM recurrence rates and prospective clinical studies are warranted to explore this further.

Citation Format: Aafia Chaudhry, Zeev Bomzon, Hadas Sara Hershkovich, Dario Garcia-Carracedo, Cornelia Wenger, Uri Weinberg, Yoram Palti. Tumor-treating fields (TTFields) intensity in the gross tumor volume and peritumoral brain zone: implications for local recurrence in glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2051.

Abstract B79: Translational study of tumor treating fields in combination with paclitaxel in ovarian cancer

Tumor Treating Fields (TTFields), a clinically active anticancer modality, are based on low intensity intermediate frequency alternating electric fields that exert their cytotoxicity by disrupting mitosis. The present study examines whether concomitant paclitaxel and TTFields have a beneficial impact on ovarian cancer growth both in vitro and in vivo. Moreover, on the basis of the preclinical observations, an open-label pilot clinical study evaluating the effect of the combined modalities in 30 patients with recurrent ovarian cancer was initiated.

Preclinical studies: To investigate the inhibitory effect of TTFields on ovarian cancer cell growth in vitro and determine optimal therapeutic frequency of TTFields in ovarian cancer, human ovarian cancer cell lines were treated with TTFields (100-400 kHz) for 72 hours using the inovitro system (Novocure, Haifa, Israel). To assess whether adding TTFields to paclitaxel increases the response of ovarian cancer cells to paclitaxel, we treated these cell lines with paclitaxel alone and in combination with TTFields. In vivo efficacy of the combined treatment was tested in female C57Bl/6 mice, orthotopically implanted with MOSE-L FFL luciferase positive cells. The feasibility of effective regional delivery of TTFields therapy to the ovaries, pelvis and abdomen of human subjects was examined using Finite Element Mesh (FEM) simulations performed using the Sim4life software. The FEM simulations demonstrated effective distribution of fields at intensities of 1-2 V/cm, which is above the minimal threshold required for TTFields response.

The INNOVATE Trial (NCT02244502): Based on positive preclinical studies demonstrating the combined efficacy of TTFields and paclitaxel in different ovarian cancer models, a pilot clinical trial was initiated to evaluate this therapeutic combination in recurrent ovarian carcinoma patients. In this prospective, pilot, single arm study, 30 patients will receive bi-directional TTFields at 200 kHz applied to the ovaries and surrounding intra-abdominal tissues using 4 transducer arrays located on the surface of the lower abdominal region. In addition, patients will receive concomitant paclitaxel at a standard regimen and dose. The combined treatment will be administered until further radiological progression. Inclusion criteria include ECOG score of 0-1 and no serious co-morbidities. The trial's primary endpoint is adverse events frequency and severity. The study will also collect preliminary efficacy data through the analysis of progression-free survival, 1-year survival rate and overall survival. Compliance data will be analyzed as an additional secondary endpoint. The INNOVATE study started to enroll patients in October 2014, and is currently accruing patients in Switzerland, Belgium and Spain. So far the trial has enrolled half of the planned 30 patients.

In summary, we present the first preclinical evidence in ovarian cancer of the combined efficacy of paclitaxel and TTFields, a new anticancer treatment modality. Our results suggest that it may represent a novel, effective therapeutic strategy against ovarian cancer. Pilot clinical testing is ongoing.

Citation Format: Mijal Munster, Roni Blat, Paul C. Roberts, Eva M. Schmelz, Moshe Giladi, Rosa S. Schneiderman, Yaara Porat, Zeev Bomzon, Noa Urman, Aviran Itzhaki, Tali Voloshin, Shay Cahal, Eilon D. Kirson, Uri Weinberg, Yoram Palti. Translational study of tumor treating fields in combination with paclitaxel in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B79.

Mitotic Spindle Disruption by Alternating Electric Fields Leads to Improper Chromosome Segregation and Mitotic Catastrophe in Cancer Cells

Tumor Treating Fields (TTFields) are low intensity, intermediate frequency, alternating electric fields. TTFields are a unique anti-mitotic treatment modality delivered in a continuous, noninvasive manner to the region of a tumor. It was previously postulated that by exerting directional forces on highly polar intracellular elements during mitosis, TTFields could disrupt the normal assembly of spindle microtubules. However there is limited evidence directly linking TTFields to an effect on microtubules. Here we report that TTFields decrease the ratio between polymerized and total tubulin, and prevent proper mitotic spindle assembly. The aberrant mitotic events induced by TTFields lead to abnormal chromosome segregation, cellular multinucleation, and caspase dependent apoptosis of daughter cells. The effect of TTFields on cell viability and clonogenic survival substantially depends upon the cell division rate. We show that by extending the duration of exposure to TTFields, slowly dividing cells can be affected to a similar extent as rapidly dividing cells.

Abstract 5365: Alternating electric fields (TTFields) in combination with paclitaxel are therapeutically effective against ovarian cancer cells in vitro and in vivo

Tumor Treating Fields (TTFields) are low intensity intermediate frequency alternating electric fields that disrupt mitosis. Our previous in vitro studies suggest that ovarian cancer cells are highly sensitive to TTFields treatment.

The goal of the present study was to evaluate the efficacy of the combined treatment of TTFields and paclitaxel against ovarian cancer cells in vitro and in vivo.

For in vitro studies, TTFields (1.75 V/cm) were applied for 72 hours using the inovitro system. The in vivo efficacy of the combined treatment was tested in C57Bl/6 mice, orthotopically injected with MOSE-L FFL luciferase positive cells. Finite Element Mesh (FEM) simulations were performed using the Sim4life software package (ZMT, Zurich, Switzerland) for the calculations of the electric fields intensities around the ovaries.

Our results demonstrate that in vitro application of 200 kHz TTFields led to a significant reduction in both the number of viable cells (44.6%) and the clonogenic potential (23.8%) as compared to untreated cells (p<0.001). Further reduction in the number of viable cells was achieved when TTFields were combined with paclitaxel. In vivo, the combined treatment of TTFields and Paclitaxel led to a significant reduction in tumor luminescence (40%, p<0.01) and in the tumor weight (55%, p<0.05) as compared to untreated tumor bearing mice. FEM simulations demonstrated that electric fields intensities inside and in the vicinity of the ovaries of a real human anatomy model are about 1 and 2 V/cm RMS which is above the minimal threshold required for TTFields response.

Taken together these results demonstrate that the combined treatment of TTFields and paclitaxel could serve as an effective treatment against ovarian cancer. A clinical trial testing the efficacy of the combined modalities is now underway.

Citation Format: Mijal Munster, Christopher P. Roberts, Eva M. Schmelz, Moshe Giladi, Roni Blat, Rosa S. Schneiderman, Yaara Porat, Zeev Bomzon, Noa Urman, Aviran Itzhaki, Tali Voloshin Sela, Shay Cahal, Eilon D. Kirson, Uri Weinberg, Yoram Palti. Alternating electric fields (TTFields) in combination with paclitaxel are therapeutically effective against ovarian cancer cells in vitro and in vivo. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5365. doi:10.1158/1538-7445.AM2015-5365

Abstract 3804: Disruption of spindle microtubules by TTFields result in abnormal chromosomes segregation and subsequent caspase-dependent cell death

Tumor Treating Fields (TTFields) are low intensity, intermediate frequency alternating electric fields. TTFields efficacy was demonstrated in vitro, in vivo and in clinical trials. The Optune device, designated to deliver TTFields to the tumor region, was approved by the FDA for the treatment of recurrent Glioblastoma multiforme (GBM). While there is a growing body of evidence demonstrating TTFields effect on mitotic cells, little is known about the mechanisms by which TTFields act to induce cancer cell death. The aim of the present study was to provide a mechanistic insight into the mode of action of TTFields.

Cancerous cell lines were treated with TTFields using the inovitro system. Disruption of spindle microtubules was demonstrated by confocal microscopy. Divergence from normal chromosome number was evaluated using SKY analysis and chromosome spreads. Induction of apoptosis was examined using flow cytometry based on Annexin V and Propidium Iodide staining. Detection of caspase activity was carried using poly caspase assay kit. Broad-spectrum caspase inhibitor was used in combination with TTFields to evaluate to what extent caspase dependent apoptosis was accountable for treatment efficacy.

Our results demonstrate that TTFields application prevents proper mitotic spindle assembly by interfering with microtubule polymerization. We also show that the outcomes of mitosis under TTFields application include abnormal chromosome segregation and caspase dependent apoptosis of daughter cells. Addition of caspase inhibitor completely abrogated apoptosis confirming that TTFields induced cell death is caspase dependent manner.

Taken together, our results demonstrate that TTFields treatment interfere with normal mitotic spindle formation thereby promoting mitotic catastrophe which result in caspase dependent apoptosis.

Citation Format: Tali Voloshin Sela, Rosa S. Schneiderman, Moshe Giladi, Yaara Porat, Mijal Munster, Roni Blat, Shay Sherbo, Zeev Bomzon, Noa Urman, Eilon D. Kirson, Uri Weinberg, Yoram Palti. Disruption of spindle microtubules by TTFields result in abnormal chromosomes segregation and subsequent caspase-dependent cell death. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3804. doi:10.1158/1538-7445.AM2015-3804

Chondrocyte deformation induces mitochondrial distortion and heterogeneous intracellular strain fields

Chondrocyte mechanotransduction is poorly understood but may involve cell deformation and associated distortion of intracellular structures and organelles. This study quantifies the intracellular displacement and strain fields associated with chondrocyte deformation and in particular the distortion of the mitochondria network, which may have a role in mechanotransduction. Isolated articular chondrocytes were compressed in agarose constructs and simultaneously visualised using confocal microscopy. An optimised digital image correlation technique was developed to calculate the local intracellular displacement and strain fields using confocal images of fluorescently labelled mitochondria. The mitochondria formed a dynamic fibrous network or reticulum, which co-localised with microtubules and vimentin intermediate filaments. Cell deformation induced distortion of the mitochondria, which collapsed in the axis of compression with a resulting loss of volume. Compression generated heterogeneous intracellular strain fields indicating mechanical heterogeneity within the cytoplasm. The study provides evidence supporting the potential involvement of mitochondrial deformation in chondrocyte mechanotransduction, possibly involving strain-mediated release of reactive oxygen species. Furthermore the heterogeneous strain fields, which appear to be influenced by intracellular structure and organisation, may generate significant heterogeneity in mechanotransduction behaviour for cells subjected to identical levels of deformation.

Spatial Fourier-transform polarimetry using space-variant subwavelength metal-stripe polarizers

A novel method for rapid polarization measurement is suggested. The method is based on a periodic space-variant polarizer that can be realized by use of subwavelength metal-stripe gratings. The Stokes parameters of the incident beam are determined by Fourier analysis of the space-variant intensity transmitted through the grating, thus permitting real-time polarization measurement. We discuss the design and realization of such polarizers and demonstrate our technique with polarization measurements of CO(2)-laser radiation at a wavelength of 10.6mum.

Pancharatnam--Berry phase in space-variant polarization-state manipulations with subwavelength gratings

We report the appearance of a geometrical phase in space-variant polarization-state manipulations. This phase is related to the classic Pancharatnam-Berry phase. We show a method with which to calculate it and experimentally demonstrate its effect, using subwavelength metal stripe space-variant gratings. The experiment is based on a unique grating for converting circularly polarized light at a wavelength of 10.6 mum into an azimuthally polarized beam. Our experimental evidence relies on analysis of far-field images of the resultant polarization.