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While 2D planar radiation therapy quality assurance techniques suffice for linac verification, a full 3D dosimetry measurement is ideal for robust treatment plan verification. In this study, an optical 3D dose reconstruction technique based on radioluminescence imaging is presented, using two orthogonal views provided by gantry and couch mounted cameras. Both small field and multi-target beam apertures were tested, mimicking typical 3D radiosurgery plans. Pass rates >94% for 3D gamma with 2%/2mm were achieved in all cases. Slice images were used for gamma analysis in each of transverse, sagittal and coronal planes, through the point of maximum dose. This proposed system can enable real-time imaging of beam delivery dynamics in a cylindrical water-equivalent phantom with high spatial resolution 3D reconstruction of the dose distribution, and verification of each beamlet used.

This study describes a method for producing volumetric dose profiles of proton beams from 2D slices of optical scintillation images. The method relies on a high frame rate camera acquisition (100 frames per second), the spot scanning capabilities of current proton pencil beam scanning systems, and a water equivalent scintillation screen. The acquired slices are corrected for optical blurring and ionization quenching and stacked to produce volumetric dose distribution. The volumetric optical dose profile had a pass rate of 98.3% for 2%/2mm local gamma analysis, suggesting the method can accurately measure dose profiles. The method can potentially image all clinical proton beams for pencil beam scanning systems and can extend to imaging patient plans, with further verification.

Integration of magnetic resonance imaging (MRI) and near-infrared spectral tomography (NIRST) has yielded promising diagnostic performance for breast imaging in the past. This study focused on whether MRI-guided NIRST can quantify hemoglobin concentration using only continuous wave (CW) measurements. Patients were classified into four breast density groups based on their MRIs. Optical scattering properties were assigned based on average values obtained from these density groups, and MRI-guided NIRST images were reconstructed from calibrated CW data. Total hemoglobin (HbT) contrast between suspected lesions and surrounding normal tissue was used as an indicator of the malignancy. Results obtained from simulations and twenty-four patient cases indicate that the diagnostic power when using only CW data to differentiate malignant from benign abnormalities is similar to that obtained from combined frequency domain (FD) and CW data. These findings suggest that eliminating FD detection to reduce the cost and complexity of MRI-guided NIRST is possible.

Purpose/Objective(s) In the last decade, Cherenkov imaging has been demonstrated as a useful clinical technique both for real-time surface dose visualization during patient treatment and for various high-resolution QA measurements. However there remains much work to be done in the development of Cherenkov-based in vivo dosimetry. In this work, the concept of in vivo color Cherenkov imaging is introduced. It is hypothesized that Cherenkov images with sensitivity to the spectral quality of Cherenkov emission induced inside tissue can provide increased information about tissue composition as opposed to monochromatic, red-weighted images used in prior work. Materials/Methods A custom Color Cherenkov camera was created from three time-gated intensified CMOS cameras, each with varying spectral sensitivity of the photocathode, and sharing one imaging lens. A dichroic mirror assembly allowed for incoming Cherenkov light signals to be redirected according to wavelength to the appropriate camera resulting in three raw image stacks for each acquisition. These images were then reconstructed into three-channel color images via color calibration, summed, and background subtracted. In vivo color Cherenkov images of three right-sided breast patients were acquired for one treatment fraction each as part of an IRB-approved clinical trial. These images were interpreted alongside images of liquid tissue-simulating phantoms that matched tissue optical properties. Variations in oxygenation and blood volume were mimicked in this way, and the data was used to interpret the clinical images. Impacts on Cherenkov emission spectra from tissue under these various conditions were also estimated. Results The presence of oxygenated vs deoxygenated blood in tissue has a visible impact on the color of Cherenkov emission, leading to a redder hue due to decreased attenuation of red wavelengths by oxyhemoglobin, similar to erythema or blush of tissue. This was verified in the tissue phantoms. Variations in blood concentration produce a strong blue-red trend in color space (R2 = 0.96), as verified by detailed analysis. Color Cherenkov images of right breast radiotherapy treatments displayed pink regions across the breast coincident with the treated area for all three patients, and the variations in color were interpreted relative to the phantom data. Conclusion This first investigation of color Cherenkov imaging uncovered the natural relationship between tissue composition and the spectral quality of emitted Cherenkov light. The correlation between blood content and color will be translated in future work to in vivo sensing of variations in fat and fibroglandular content in irradiated tissues. These findings will allow for the correction of Cherenkov images to produce accurate in vivo surface dose maps during patient treatments.

Purpose/Objective(s) Cherenkov imaging can uniquely record beam shapes directly on the patient, offering a brand new means of assessing patient position and treatment accuracy. We used Cherenkov imaging to assess accuracy of two patient positioning techniques, optical surfacing imaging versus traditional skin marks and room laser alignment (skin marks/lasers), during right breast irradiation. Materials/Methods All imaging data was obtained with IRB approval from patients receiving free-breathing, right breast radiation therapy with either 6X or 6X and 10X beams. Data was obtained from two separate clinics that utilize different positioning methods. Patients treated at one clinic were positioned using optical surface imaging and patients treated at a second clinic were positioned using skin marks/lasers. For each fraction imaged, DICE coefficient (% similarity) and MDC (mean distance to conformity) were measured by comparing Cherenkov imaging obtained for that fraction to the Cherenkov imaging from the initial fraction. A two-tailed t-test of unequal variance was performed to obtain P-values comparing MDC and DICE from the two positioning techniques. Results Cherenkov images taken of 127 fractions using optical surface imaging for breast setup and 47 fractions using skin marks/lasers setup showed that MDCs were found to average 2.02 mm (std dev of 0.83mm) and 2.47mm (std dev of 0.68mm), respectively, resulting in a P value of 0.07. The mean DICE coefficients averaged 97.33% (std dev of 1.13%) and 97.19% (std dev of 1.90%) for optical surface imaging and skin marks/lasers, respectively, with a P value of 0.65. The data confirms the null hypothesis in both cases. Conclusion Comparison of our Cherenkov image analytics from two centers, each using a separate positioning method (optical surface imaging and skin marks/lasers), revealed that there is no statistical difference in terms of MDC and DICE coefficient. This analysis confirms that both setup methods can be used confidently for patient positioning without compromising quality of care. This novel method for assessing alignment techniques is easy to use on a daily basis, adds no extra time or imaging dose to the patient, and analysis is automated, making this tool ideal for evaluating patient positioning for large numbers of treatments. Future work will examine different methods for alignment of more complex treatments such as deep-inspiration breath hold for left breast radiation.

Purpose/Objective(s) Cherenkov imaging is a novel technique that captures light emissions during radiation therapy, allowing for visualization of radiation treatments on patients, in real-time. We hypothesized that simply viewing the Cherenkov video images, both in real-time and with post-treatment review by radiation therapists, would identify events not previously reported in the existing QA program. Materials/Methods In December 2020, Cherenkov imaging cameras were introduced into an academic medical center with an existing QA program consisting of a hospital wide incident reporting system that is anonymous, voluntary, and non-punitive. Events are reviewed monthly by a multidisciplinary group including representatives from radiation therapy, dosimetry, nursing, physics and radiation oncologists. The Cherenkov cameras were installed in each treatment bunker, positioned laterally on each side of the couch. The cameras provided continuous, real-time video images of the patients and visualization of the irradiated tissue. Live viewing of the treatments was provided via a dedicated monitor in the console room. All treatments were imaged with the exception of treatments where optical surface imaging lights were on for SGRT. Results During this 3-month period, 12 events were reported in the hospital-based incident reporting system. Events were reviewed and categorized as 3 operational/process improvement (e.g., scheduling errors), 3 other safety events (e.g., patient falls), 3 treatment planning errors (e.g., wrong shifts calculated for setup), 1 prescription transcription error, 1 treatment delivery error (a missed treatment field), and 1 simulation error (suboptimal immobilization equipment used). Aside from a patient fall, all events were deemed to have no detectable harm to the patient. In this same time period, review of Cherenkov images identified 3 treatment delivery events, which were not identified by other means. The first was an AP-PA thoracic spine treatment and on one day, the treating therapists noted the patient's chin in the treatment field. Treatment was stopped, the patient was re-positioned for the remainder of the treatment. Second was an AP-PA lumbar spine field that on post-treatment review was noted that the patient's hands moved into the field. The third was a 3-field sacrum plan that on post-treatment review was noted that for 7 of 10 fractions, the patient's left arm was positioned over the exit RPO beam. Physics review estimated that the uninvolved arm received approximately 3 Gy. Conclusion Viewing of Cherenkov emission imaging by the treatment team identified delivery incidents due to non-ideal patient positioning during treatment and these events were not identified in the existing QA program. Future work will focus on determining incident rates detected by Cherenkov imaging and if this imaging can identify and/or avoid treatment delivery errors from reaching the patient. Automated detection and near real time notification of such events is a work in progress.

Purpose/Objective(s) Electron ultrahigh dose rate FLASH radiotherapy (UHDR/eFLASH-RT) is currently being extensively tested and modeled, and was studied in several rodent and large animal experiments and one clinical cancer patient. These studies suggest prospective dosimetry assessments are necessary to ensure safe delivery and widespread clinical translation of eFLASH-RT would clearly benefit from prior dose prediction and a treatment planning process that accounts for anatomical heterogeneity and complex geometries. In this study, a GAMOS Monte Carlo beam model was developed and implemented in a clinical treatment planning system for a modified UHDR electron LINAC to demonstrate eFLASH-RT planning of patients. Materials/Methods The gantry head was modelled without scattering foils or targets, representative of the LINAC modifications. Centered at the nominal energy of 10 MeV, the energy spectrum (σE) was varied to match the central axis percent depth dose (PDD) profiles of an open field measured with radiographic film. The beam's emittance cone angle (θcone) was determined by matching calculated and film measured lateral profiles, at several depths. The beam model and its configuration in the treatment planning system were validated with film measured lateral profiles and PDD's of the open field and nominal fields for clinical applicators. A GAMOS forward dose calculation was conducted for a mouse whole brain treatment and an eFLASH-RT plan was compared to a conventional electron plan for a human patient with a rib metastasis. Results Our eFLASH beam model agrees best with measurements at σE = 0.5MeV and θcone = 3.9o ± 0.2o. The model and its treatment planning system configuration were validated to clinically acceptable accuracy (the absolute average error was within 1.5% for in water lateral, 3% for in air lateral, and 2% for PDD's). The forward dose calculation showed dose was delivered to the entire mouse brain with adequate conformality (90% of the tumor volume receiving 90% of the prescribed dose). The comparison plans for the patient undergoing treatment for a rib metastasis demonstrated the capability to achieve an acceptable eFLASH-RT plan with routine accessories (90% of the tumor receiving 95% and 90% of the prescribed dose for eFLASH and conventional, respectively) in relatively complex geometry (right posterior oblique treatment with patient specific applicator cutout). Conclusion To the best of our knowledge, this study presents the first functional beam model commissioned in a clinical TPS for eFLASH-RT, enabling treatment planning and evaluation with minimal deviation from conventional radiotherapy workflow. By producing plans with the quality comparable to conventional plans, specifically for human patients involving complex geometries and tissue heterogeneity, the clinical translation of eFLASH-RT can be expedited. The open-source methods (described in https://github.com/mr3536/eFLASHBeamModeltoTPS ) can model other eFLASH irradiators with different beam characteristics.

Physiologic barriers to drug delivery and selection for drug resistance limit survival outcomes in cancer patients. In this study, we present preclinical evidence that a subtumoricidal photodynamic priming (PDP) strategy can relieve drug delivery barriers in the tumor microenvironment to safely widen the therapeutic window of a nanoformulated cytotoxic drug. In orthotopic xenograft models of pancreatic cancer, combining PDP with nanoliposomal irinotecan (nal-IRI) prevented tumor relapse, reduced metastasis, and increased both progression-free survival and 1-year disease-free survival. PDP enabled these durable improvements by targeting multiple tumor compartments to (i) increase intratumoral drug accumulation by >10-fold, (ii) increase the duration of drug exposure above a critical therapeutic threshold, and (iii) attenuate surges in CD44 and CXCR4 expression, which mediate chemoresistance often observed after multicycle chemotherapy. Overall, our results offer preclinical proof of concept for the effectiveness of PDP to minimize risks of tumor relapse, progression, and drug resistance and to extend patient survival. Significance: A biophysical priming approach overcomes key treatment barriers, significantly reduces metastases, and prolongs survival in orthotopic models of human pancreatic cancer. Cancer Res; 78(2); 558–71. ©2017 AACR.

We realized subsurface fluorescence LiDAR with a large format single-photon avalanche diode array capable of localizing and quantifying concentration of fluorescent molecules in heavily scattering media, such as tissue, with submillimeter depth accuracy. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Purpose: Hsp90, a chaperone to numerous molecular pathways in malignant cells, is elevated in aggressive breast cancers. We hypothesized that identifying breast cells with elevated Hsp90 activity in situ could result in early detection of aggressive breast cancers. Experimental Design: We exploited the uptake of an Hsp90 inhibitor by malignant cells to create an imaging probe (HS131) of Hsp90 activity by linking it to a near-infrared (nIR) dye. HS131 uptake into cells correlated with cell membrane expression of Hsp90 and was used to image molecular subtypes of murine and human breast cancers in vitro and in murine models. Results: HS131 imaging was both sensitive and specific in detecting the murine 4T1 breast cancer cell line, as well as subclones with differing metastatic potential. Highly metastatic subclones (4T07) had high HS131 uptake, but subclones with lower metastatic potential (67NR, 168FARN) had low HS131 uptake. We generated isogenic cell lines to demonstrate that overexpression of a variety of specific oncogenes resulted in high HS131 uptake and retention. Finally, we demonstrated that HS131 could be used to detect spontaneous tumors in MMTV-neu mice, as well as primary and metastatic human breast cancer xenografts. HS131 could image invasive lobular breast cancer, a histologic subtype of breast cancer which is often undetectable by mammography. Conclusions: An HSP90-targeting nIR probe is sensitive and specific in imaging all molecular subtypes of murine and human breast cancer, with higher uptake in aggressive and highly metastatic clones. Clinical studies with Hsp90-targeting nIR probes will be initiated shortly. Clin Cancer Res; 23(24); 7531–42. ©2017 AACR.

High tissue pressures prevent chemotherapeutics from reaching the parenchyma of pancreatic ductal adenocarcinoma, which makes it difficult to treat this aggressive disease. Researchers currently use invasive probes to monitor the effectiveness of pressure-reducing therapies, but this practice introduces additional complications. Here, we hypothesize that Young’s modulus is a good surrogate for tissue pressure because collagen density and hyaluoronic acid, the key features of the tumor microenvironment responsible for high tissue pressures, also affect modulus elastograms. To corroborate this hypothesis, we used model-based quasi-static elastography to assess how the Young’s modulus of naturally occurring AsPc-1 pancreatic tumors varies with collagen density and hyaluoronic acid concentration. We observed that Young’s moduli of orthotopically grown xenograft tumors were 6 kPa (p < 0.05) higher than that of their subcutaneously grown counterparts. We also observed a strong correlation between Young’s modulus and regions within the tumors with high collagen (R2 ≈ 0.8) and hyaluoronic acid (R2 ≈ 0.6) densities. These preliminary results indicate that hyaluronic acid and collagen density, features of the pancreatic ductal adenocarcinoma tumor microenvironment responsible for high tissue pressure, influence Young’s modulus.

The poor efficacy of systemic cancer therapeutics in pancreatic ductal adenocarcinoma (PDAC) is partly attributed to deposition of collagen and hyaluronan, leading to interstitial hypertension collapsing blood and lymphatic vessels, limiting drug delivery. The intrinsic micro -regional interactions between hyaluronic acid (HA), collagen and the spatial origins of mechanical stresses that close off blood vessels was investigated here. Multiple localized pressure measurements were analyzed with spatially-matched histochemical images of HA, collagen and vessel perfusion. HA is known to swell, fitting a linear elastic model with total tissue pressure (TTP) increasing above interstitial fluid pressure (IFP) directly with collagen content. However, local TTP appears to originate from collagen area fraction, as well as increased its entropy and fractal dimension, and morphologically appears to be maximized when HA regions are encapsulated by collagen. TTP was inversely correlated with vascular patency and verteporfin uptake, suggesting interstitial hypertension results in vascular compression and decreased molecular delivery in PDAC. Collagenase injection led to acute decreases in total tissue pressure and increased drug perfusion. Large microscopic variations in collagen distributions within PDAC leads to microregional TPP values that vary on the hundred micron distance scale, causing micro-heterogeneous limitations in molecular perfusion, and narrows viable treatment regimes for systemically delivered therapeutics.

Considerable advances in cancer-specific optical imaging have improved the precision of tumor resection. In comparison to traditional imaging modalities, this technology is unique in its ability to provide real-time feedback to the operating surgeon. Given the significant clinical implications of optical imaging, there is an urgent need to standardize surgical navigation tools and contrast agents to facilitate swift regulatory approval. Because fluorescence-enhanced surgery requires a combination of both device and drug, each may be developed in conjunction, or separately, which are important considerations in the approval process. This report is the result of a one-day meeting held on May 4, 2016 with officials from the National Cancer Institute, the FDA, members of the American Society of Image-Guided Surgery, and members of the World Molecular Imaging Society, which discussed consensus methods for FDA-directed human testing and approval of investigational optical imaging devices as well as contrast agents for surgical applications. The goal of this workshop was to discuss FDA approval requirements and the expectations for approval of these novel drugs and devices, packaged separately or in combination, within the context of optical surgical navigation. In addition, the workshop acted to provide clarity to the research community on data collection and trial design. Reported here are the specific discussion items and recommendations from this critical and timely meeting. Cancer Res; 77(9); 2197–206. ©2017 AACR.

Margin assessment in gross pathology is becoming feasible as various explanatory deep learning-powered methods are able to obtain models for macroscopic textural information, tissue microstructure, and local surface optical properties. Unfortunately, each different method seems to lack enough diagnostic power to perform an adequate classification on its own. This work proposes using several separately trained deep convolutional networks, and averaging their responses, in order to achieve a better margin assessment. Qualitative leave-one-out cross-validation results are discussed for a cohort of 70 samples. Spanish Ministry of Science, Innovation and Universities (FIS2010-19860, TEC2016-76021-C2-2-R), Spanish Ministry of Economy, Industry and Competitiveness and Instituto de Salud Carlos III (DTS17-00055, DTS15- 00238), Instituto de Investigación Valdecilla (INNVAL16/02, INNVAL18/23), Spanish Ministry of Education, Culture, and Sports (FPU16/05705).

Background: Despite the rapid growth of fluorescence imaging, accurate sampling of tissue sections remains challenging. Development of novel technologies to improve intraoperative assessment of tissue is needed. Methods: A novel contact probe-based fluorescence dosimeter device, optimized for IRDye800CW quantification, was developed. After evaluation of the device in a phantom setup, its clinical value was defined ex vivo in patients with head and neck squamous cell carcinoma who received panitumumab-IRDye800CW. Results: Ten patients were enrolled with a total of 216 data points obtained. Final histopathology showed tumor in 119 spots and normal tissue in 97 spots. Fluorescence-to-excitation ratios in tumor tissue were more than three times higher than those in normal tissue. The area under the curve was 0.86 (95% CI: 0.81-0.91) for tumor detection. Conclusions: Fluorescence-guided tissue preselection using a fluorescence dosimeter could have substantial impact on tissue sampling for frozen section analysis and potentially reduce sampling errors.

Background X-Ray induced phototherapy is highly sought after as it provides a deep tissue, synergistic method of treating cancers via standard-of-care radiotherapy. When this is combined with releasable chemotherapy agents, it can provide high target selectivity, with reduced off-target organ effects that limit current systemic therapies. We have recently developed a unique light-activated drug delivery system whereby the drug is conjugated to an alkylcobalamin scaffold. Alkylcobalamins are actively transported into cells by transcobalamin receptors (TCblR), which are overexpressed in a variety of cancer types. We hope to utilize this cobalamin scaffold technology for drug delivery in pancreatic adenocarcinoma (PDAC) cancer. Methods The ability of the cobalamin scaffold to selectively target PDAC was investigated by treating mice that had MIA PaCa-2 xenografts with an alkylcobalamin labeled with the fluorophore Bodipy650 (Bodipy650-cobalamin). The mice were imaged alive and organs as well as tumors were subsequently imaged ex vivo. In addition, we examined the potential of the cobalamin scaffold to deliver drugs to orthotopic pancreas MIA PaCa-2 tumors with Bodipy650-cobalamin. We determined the light dose required for release of cargo from the cobalamin scaffold by examining the fluorescence increase of Bodipy650-cobalamin in response to red light (650 nm). Finally, we probed the ability of the cobalamin scaffold to release cargo with increasing X-ray doses from a clinical linear accelerator. Results We have found that Bodipy650-cobalamin was shown to localize in MIA PaCa-2 tumors, both in flank and orthotopic models. We quantified a light dose for red light release from the cobalamin scaffold that is within normal clinical doses required for photodynamic therapy. This derivative was also activated with clinical X-ray doses from a linear accelerator. Conclusions Tumor selectivity combined with fluorescence detection demonstrates the effectiveness of the vitamin B12 scaffold as a theranostic targeting agent. The activation of this scaffold with radiation from a linear accelerator shows potential for action as radiation-induced chemotherapy.

PURPOSE: Treatment planning systems (TPS) for MR-linacs must employ Monte Carlo based simulations of dose deposition to model the effects of the primary magnetic field on dose. However, the accuracy of these simulations, especially for areas of tissue-air interfaces where the electron return effect (ERE) is expected, are difficult to validate due to physical constraints and magnetic field compatibility of available detectors. This study employs a novel dosimetric method based on remotely captured, real-time optical Cherenkov and scintillation imaging to visualize and quantify the ERE. METHODS: An intensified CMOS camera was used to image two phantoms with designed ERE cavities. Phantom A was a 40cm × 10cm × 10cm clear acrylic block drilled with 5 holes of increasing diameters (0.5cm, 1cm, 2cm, 3cm, 4cm). Phantom B was a clear acrylic block with 3 cavities of increasing diameter (3cm, 2cm, 1cm) split into two halves in the transverse plane to accommodate radiochromic film. Both phantoms were imaged while being irradiated by 6MV flattening filter free (FFF) beams within a MRIdian Viewray (Viewray, Cleveland, OH) MR-linac (0.34T primary field). Phantom A was imaged while being irradiated by 6MV FFF beams on a conventional linac (TrueBeam, Varian Medical Systems, San Jose, CA) to serve as a control. Images were post processed in Matlab (Mathworks Inc., Natick, MA) and compared to treatment planning system (TPS) dose volumes. RESULTS: Control imaging of Phantom A without the presence of a magnetic field supports the validity of the optical image data to a depth of 6cm. In the presence of the magnetic field, the optical data shows deviations from the commissioned TPS dose in both intensity and localization. The largest air cavity examined (3cm) indicated the largest dose differences, which were above 20% at some locations. Experiments with Phantom B illustrated similar agreement between optical and film dosimetry comparisons with TPS data in areas not affected by ERE. CONCLUSION: There are some appreciable differences in dose intensity and spatial dose distribution observed between the novel experimental data set and the dose models produced by the current clinically implemented MR-IGRT TPS. Further validation of the proposed experimental methods, as well as the magnetic field effect models within the TPS, is recommended.

The goal of our study was to determine the susceptibility of different pancreatic cell lines to clinically applicable photodynamic therapy (PDT). The efficacy of PDT of two different commercially available photosensitizers, verteporfin and sodium porfimer, was compared using a panel of four different pancreatic cancer cell lines, PANC-1, BxPC-3, CAPAN-2, and MIA PaCa-2, and an immortalized non-neoplastic pancreatic ductal epithelium cell line, HPNE. The minimum effective concentrations and dose-dependent curves of verteporfin and sodium porfimer on PANC-1 were determined. Since pancreatic cancer is known to have significant stromal components, the effect of PDT on stromal cells was also assessed. To mimic tumor–stroma interaction, a co-culture of primary human fibroblasts or human pancreatic stellate cell (HPSCs) line with PANC-1 was used to test verteporfin-PDT-mediated cell death of PANC-1. Two cytokines (TNF-α and IL-1β) were used for stimulation of primary fibroblasts (derived from human esophageal biopsies) or HPSCs. The increased expression of smooth muscle actin (α-SMA) confirmed the activation of fibroblasts or HPSC upon treatment with TNF-α and IL-1β. Cell death assays showed that both sodium porfimer- and verteporfin-mediated PDT-induced cell death in a dose-dependent manner. However, verteporfin-PDT treatment had a greater efficiency with 60× lower concentration than sodium porfimer-PDT in the PANC-1 incubated with stimulated fibroblasts or HPSC. Moreover, activation of stromal cells did not affect the treatment of the pancreatic cancer cell lines, suggesting that the effects of PDT are independent of the inflammatory microenvironment found in this two-dimensional culture model of cancers.

Purpose Patients have reported sensations of seeing light flashes during radiation therapy, even with their eyes closed. These observations have been attributed to either direct excitation of retinal pigments or generation of Cherenkov light inside the eye. Both in vivo human and ex vivo animal eye imaging was used to confirm light intensity and spectra to determine its origin and overall observability. Methods and Materials A time-gated and intensified camera was used to capture light exiting the eye of a patient undergoing stereotactic radiosurgery in real time, thereby verifying the detectability of light through the pupil. These data were compared with follow-up mechanistic imaging of ex vivo animal eyes with thin radiation beams to evaluate emission spectra and signal intensity variation with anatomic depth. Angular dependency of light emission from the eye was also measured. Results Patient imaging showed that light generation in the eye during radiation therapy can be captured with a signal-to-noise ratio of 68. Irradiation of ex vivo eye samples confirmed that the spectrum matched that of Cherenkov emission and that signal intensity was largely homogeneous throughout the entire eye, from the cornea to the retina, with a slight maximum near 10 mm depth. Observation of the signal external to the eye was possible through the pupil from 0° to 90°, with a detected emission near 2500 photons per millisecond (during peak emission of the ON cycle of the pulsed delivery), which is over 2 orders of magnitude higher than the visible detection threshold. Conclusions By quantifying the spectra and magnitude of the signal, we now have direct experimental observations that Cherenkov light is generated in the eye during radiation therapy and can contribute to perceived light flashes. Furthermore, this technique can be used to further study and measure phosphenes in the radiation therapy clinic.

Near-infrared (NIR) fluorescence combined with targeting epidermal growth factor receptor (EGFR) overexpression for surgical guidance in many cancers is gaining momentum. ABY-029 is an anti-EGFR Affibody molecule conjugated to IRDye 800CW that is FDA approved as an exploratory Investigational New Drug (eIND 122681). ABY-029 has a short plasma half-life (~15-20 minutes), which allows for administration of the imaging agent and excision surgery to occur on the same day unlike fluorescent antibodies. This fast tissue clearance may provide the means necessary to achieve clinically relevant tumor-to-normal tissue contrast levels using microdosing administration schemes. Pre-clinical studies have indicated that tumor-to-normal tissue contrast peaks between 4-8 hours depending on EGFR expression. Additionally, the No Observable Adverse Effect Level (NOAEL) was determined in pre-clinical toxicity studies to be 1,000X the microdose, or 30 micromole, whereas mild adverse events are common in antibody imaging studies. A number of promising first-in-human clinical Phase 0 trial microdose evaluation of ABY-029 have been initiated for recurrent glioma, soft-tissue sarcoma, and head and neck cancers (NCT0290925, NCT03154411, and NCT03282461, respectively). Here, we provide an update on our experience using ABY-029 for surgical resection at microdose levels and describe tissue contrast and correlation of ABY-029 fluorescence to EGFR tissue expression. Current progress indicates that moderate TBRs (~3-5) are observable at the microdose administration level but increased administration doses (3X and 6X microdoses) are being investigated. In addition, ex vivo tissue fluorescence is highly correlated to EGFR staining in both intensity and spatial localization.

Imaging Cherenkov emission during radiation therapy cancer treatments can provide a real-time, non-contact sampling of the entire dose field. The emitted Cherenkov signal generated is proportional to deposited dose, however, it is affected by attenuation from the intrinsic tissue optical properties of the patient, which in breast, ranges from primarily adipose to fibroglandular tissue. Patients being treated with whole-breast X-ray radiotherapy (n = 13) were imaged for 108 total fractions, to establish correction factors from the linear relationships between Cherenkov light and CT number (HU). This study elucidates this relationship in vivo, and a correction factor approach is used to scale each image to improve the linear correlation between Cherenkov emission intensity and dose (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{6X}^2 = 0.85,\,R_{10X}^2 = 0.95$$\end{document}R6X2=0.85,R10X2=0.95). This study provides a major step towards direct quantitative radiation dose imaging in humans by utilizing non-contact camera sensing of Cherenkov emission during the radiation therapy treatment., Imaging Cherenkov emission during radiotherapy can provide information on the delivered radiation dose, but is attenuated by optical properties of the tissue. Here the authors derive a correction factor applicable to breast X-ray radiotherapy in human subjects to improve the correlation between Cherenkov emission intensity and dose.

Structured light imaging (SLI) with high spatial frequency (HSF) illumination provides a method to amplify native tissue scatter contrast and better differentiate superficial tissues. This was investigated for margin analysis in breast-conserving surgery (BCS) and imaging gross clinical tissues from 70 BCS patients, and the SLI distinguishability was examined for six malignancy subtypes relative to three benign/normal breast tissue subtypes. Optical scattering images recovered were analyzed with five different color space representations of multispectral demodulated reflectance. Excluding rare combinations of invasive lobular carcinoma and fibrocystic disease, SLI was able to classify all subtypes of breast malignancy from surrounding benign tissues (p-value

Daylight activation for photodynamic therapy (PDT) of skin lesions is now widely adopted in many countries as a less painful and equally effective treatment mechanism, as compared to red or blue light activation. However, seasonal daylight availability and transient weather conditions complicate light dose estimations. A method is presented for dose planning without placing a large burden on clinical staff, by limiting spectral measurements to a one-time site assessment, and then using automatically acquired weather reports to track transient conditions. The site assessment tools are used to identify appropriate treatment locations for the annual and daily variations in sunlight exposure for clinical center planning. The spectral information collected from the site assessment can then be integrated with real-time daily electronic weather data. It was shown that a directly measured light exposure has strong correlation (R2 : 0.87) with both satellite cloud coverage data and UV index, suggesting that the automated weather indexes can be surrogates for daylight PDT optical dose. These updated inputs can be used in a dose-planning treatment model to estimate photodynamic dose at depth in tissue. A simple standardized method for estimating light dose during daylight-PDT could help improve intersite reproducibility while minimizing treatment times.

Photodynamic therapy (PDT) for actinic keratosis (AK) and certain non-melanoma skin cancers (NMSC) is performed with either blue light (415nm Lamp), red light (630nm LED Lamps) or with sunlight. The differences in PDT efficacy can be high when using the latter broad-spectrum activation of PpIX. The purpose of this work was to establish a predictive treatment plan approach to daylight PDT which incorporated both local weather forecast information as well as prediction of wavelength-depth dependence upon the efficacy. The concept of PpIX-weighted light fluence is now well established as a way to compare effective light doses from daylight PDT to traditional lamp PDT, but there is limited work to date considering the effects of tissue optical properties or the dynamic distribution of PpIX at depths into the tissue. Using a Monte Carlo model of light fluence in a multi-layer skin geometry we estimate the effective fluence at depth in tissue. The result of these simulations in combination with a model for PpIX production and photobleaching at a range of depths are used to generate lookup tables for the time needed to reach a specific photodynamic dose at a predicted lesion thickness. These tables are then used as the foundation of a web-based application that will better inform the dermatology team of light dosing options. GPS-derived location is used to retrieve forecasted and historical weather patterns automatically, and used as an additional input to further refine prescribed dosing of daylight-PDT. The application is currently being tested in conjunction with fluorescence dosimetry, as a method to verify and alleviate clinical variation in lesion clearing from daylight PDT.

Cherenkov excitation of molecular probes in tissue can be used for photodynamic effect or diagnostic luminescence imaging. Excitation of dendritic platinum-based metalloporphyrn molecule complexes as an oxygen sensor (PtG4) has been shown to allow oxygen measurement in vivo with spatial resolution defined by the exciting x-ray beam. By sweeping the beamlet shapes and geometries, and detecting the emitted luminscence lifetime, a highly accurate pO2 distribution can be reconstructed of the tissue volume. This has been shown in tumors as well as in normal tissues, and now for implanted microtubes. Additional imaging of luminescent agents based upon Cherenkov or direct radio-excitation could be used for molecular sensing. The combination of depth, concentration, and radiation dose have been analyzed for the tradeoffs in signal to noise, and the signal to background optimization has been completed. The use of this approach can be applied to any clinical radiation therapy linac.

Purpose The purpose of this study was to demonstrate high resolution optical luminescence sensing, referred to as Cherenkov excited luminescence scanning imaging (CELSI), could be achieved during a standard dynamic treatment plan for a whole breast radiotherapy geometry. Methods The treatment plan beams induce Cherenkov light within tissue, and this excitation projects through the beam trajectory across the medium, inducing luminescence where there can be molecular reporter. Broad beams generally produce higher signal but low spatial resolution, yet for dynamic plans the scanning of the multileaf collimator allows for a beam-narrowing strategy by recursively temporal differencing each of the Cherenkov images and associated luminescence images. Then reconstruction from each of these size-reduced beamlets defined by the differenced Cherenkov images provides a well-conditioned matrix inversion, where the spatial frequencies are limited by the higher signal-to-noise ratio beamlets. A built-in stepwise convergence relies on stepwise beam size reduction, which is associated with a widening of the bandwidth of Cherenkov spatial frequency and resultant increase in spatial resolution. For the phantom experiments, europium nanoparticles were used as luminescent probes and embedded at depths ranging from 3 to 8 mm. An intensity modulated radiotherapy (IMRT) plan was used to test this. Results The Cherenkov images spatially guided where the luminescence was measured from, providing high lateral resolution, and iterative reconstruction convergence showed that optimization of the initial and stopping beamlet widths could be achieved with 15 and 4.5 mm, respectively, using a luminescence imaging frame rate of 5/s. With the IMRT breast plan, the original lateral resolution was improved 2X, that is, 0.08-0.24 mm for target depths of 3-8 mm. In comparison, a dynamic wedge (DW) plan showed an inferior image fidelity, with relative contrast recovery decreasing from 0.86 to 0.79. The methodology was applied to a three-dimensional dataset to reconstruct Cherenkov excited luminescence intensity distributions showing volumetric recovery of a 0.5 mm diameter object composed of 0.5 μM luminescent microbeads. Conclusions High resolution CELSI was achieved with a clinical breast external beam radiotherapy (EBRT) plan. It is anticipated that this method can allow visualization and localization for luminescence/fluorescence tagged vasculature, lymph nodes, or superficial tagged regions with most dynamic treatment plans.

This letter describes a hybrid plug/compartment (HyPC) kinetic model to fit dynamic indocyanine green fluorescence data acquired in a porcine model of long bone traumatic fracture. Parametric images of periosteal blood flow, endosteal blood flow, total bone blood flow and fraction of endosteal-to-periosteal flow were obtained by applying the HyPC model on a pixel-by-pixel basis. Intraoperative discrimination between healthy and damaged bone could facilitate debridement reducing post-operative complications from non-union and infection. The ability to quantify periosteal and endosteal blood flow could inform nail vs. plate-and-screw decisions to avoid further compromising cortical blood supply.

Surface dosimetry is required for ensuring effective administration of total skin electron therapy (TSET); however, its use is often reduced due to the time consuming and complex nature of acquisition. A new surface dose imaging technique was characterized in this study and found to provide accurate, rapid and remote measurement of surface doses without the need for post-exposure processing. Disc-shaped plastic scintillators (1 mm thick × 15 mm ) were chosen as optimal-sized samples and designed to attach to a flat-faced phantom for irradiation using electron beams. Scintillator dosimeter response to radiation damage, dose rate, and temperature were studied. The effect of varying scintillator diameter and thickness on light output was evaluated. Furthermore, the scintillator emission spectra and impact of dosimeter thickness on surface dose were also quantified. Since the scintillators were custom-machined, dosimeter-to-dosimeter variation was tested. Scintillator surface dose measurements were compared to those obtained by optically stimulated luminescence dosimeters (OSLD). Light output from scintillator dosimeters evaluated in this study was insensitive to radiation damage, temperature, and dose rate. Maximum wavelength of emission was found to be 422 nm. Dose reported by scintillators was linearly related to that from OSLDs. Build-up from placement of scintillators and OSLDs had a similar effect on surface dose (4.9% increase). Variation among scintillator dosimeters was found to be 0.3 ± 0.2%. Scintillator light output increased linearly with dosimeter thickness (~1.9 × /mm). All dosimeter diameters tested were able to accurately measure surface dose. Scintillator dosimeters can potentially improve surface dosimetry-associated workflow for TSET in the radiation oncology clinic. Since scintillator data output can be automatically recorded to a patient medical record, the chances of human error in reading out and recording surface dose are minimized.

Previous work has shown that capturing optical emission from plastic discs attached directly to the skin can be a viable means to accurately measure surface dose during total skin electron therapy. This method can provide accurate dosimetric information rapidly and remotely without the need for postprocessing. The objective of this study was to: (1) improve the robustness and usability of the scintillators and (2) enhance sensitivity of the optical imaging system to improve scintillator emission detection as related to tissue surface dose. Baseline measurements of scintillator optical output were obtained by attaching the plastic discs to a flat tissue phantom and simultaneously irradiating and imaging them. Impact on underlying surface dose was evaluated by placing the discs on-top of the active element of an ionization chamber. A protective coating and adhesive backing were added to allow easier logistical use, and they were also subjected to disinfection procedures, while verifying that these changes did not affect the linearity of response with dose. The camera was modified such that the peak of detector quantum efficiency better overlapped with the emission spectra of the scintillating discs. Patient imaging was carried out and surface dose measurements were captured by the updated camera and compared to those produced by optically stimulated luminescence detectors (OSLD). The updated camera was able to measure surface dose with3 % difference compared to OSLD–Cherenkov emission from the patient was suppressed and scintillation detection was enhanced by 25 × and 7 × , respectively. Improved scintillators increase underlying surface dose on average by 5.2 ± 0.1 % and light output decreased by 2.6 ± 0.3 % . Disinfection had0.02 % change on scintillator light output. The enhanced sensitivity of the imaging system to scintillator optical emission spectrum can now enable a reduction in physical dimensions of the dosimeters without loss in ability to detect light output.

PURPOSE: The aim of this study was to create an optical imaging‐based system for quality assurance (QA) testing of a dedicated Co‐60 total body irradiation (TBI) machine. Our goal is to streamline the QA process by minimizing the amount time necessary for tests such as verification of dose rate and field homogeneity. METHODS: Plastic scintillating rods were placed directly on the patient treatment couch of a dedicated TBI (60)Co irradiator. A tripod‐mounted intensified camera was placed directly adjacent to the couch. Images were acquired over a 30‐s period once the cobalt source was fully exposed. Real‐time image filtering was used; cumulative images were flatfield corrected as well as background and darkfield subtracted. Scintillators were used to measure light‐radiation field correspondence, dose rate, field homogeneity, and symmetry. Dose rate effects were measured by modifying the height of the treatment couch and scintillator response was compared to ionization chamber (IC) measurements. Optically stimulated luminesce detector (OSLD) used as reference dosimeters during field symmetry and homogeneity testing. RESULTS: The scintillator‐based system accurately reported changes in dose rate. When comparing normalized output values for IC vs scintillators over a range of source‐to‐surface distances, a linear relationship (R(2) = 0.99) was observed. Normalized scintillator signal matched OSLD measurements with

Luminescence molecular tomography with Cherenkov excitation offers the ability to non-invasively image and quantify temporal changes in fluorescence throughout the body, and then further realize tumor localization. This can be done in radiotherapy to determine the response to treatment in fractionated therapy. To obtain high signal-to-background or signal-to-noise ratio measurement, it is critical to know the best post time point of in-vivo agent-based molecular imaging, which could account on a high signal ratio of target to skin (TSR). For this purpose, ex-vivo murine experiments were performed to quantify the biokinetics and biodistribution of the major organs, plasma, tumor, and skin.

Cherenkov-excited luminescence scanned imaging (CELSI) is achieved with a clinical linear accelerator during External Beam Radiotherapy, to map out molecular luminescence intensity or lifetime in tissue. In order to realize a deeper imaging depth with a reasonable spatial resolution in CELSI, we optimized the original scanning procedure to complete this in a similar way to x-ray computed tomography and with image reconstruction from Maximum-likelihood expectation maximization and multi-pinhole irradiation for parallelization. Resolution phantom studies showed that a 0.3 mm diameter capillary tube containing 0.01 nM luminescent nanospheres could be recognized at a depth of 21 mm into tissue-like media. Small animal imaging with a 1 mm diameter cylindrical target demonstrated that fast 3D data acquisition can be achieved by this multi-pinhole collimator approach to image high resolution luminescence through a whole animal.

This editorial reflects on the shape of biomedical engineering as a discipline, and its relation to biomedical optics.

Cherenkov-excited luminescence scanned imaging (CELSI) is achieved with External Beam Radiotherapy, to map out molecular luminescence intensity or lifetime in tissue. In order to realize a deeper imaging depth with a reasonable spatial resolution, we optimized the original scanning gesture to do in a similar way to computed tomography (CT) and the image reconstruction was instead used a customized Maximum-likelihood expectation maximization (ML-EM) for CELSI. In tomographic CELSI (TCELSI), tomographic images are generated by irradiating the subject using a sequence of programmed X-ray beams at a fixed projection angle, while sensitive measurement is to take a sum for all image pixels from an intensified charge-coupled device. By restricting the X-ray excitation to a single, narrow beam of radiation, the origin of the optical photons can be inferred regardless of where these photons were detected, and how many times they scattered in tissue. Measurement geometry was designed for clinical expectation: CT scanning was achieved by a clinical linear accelerator (LINAC), where X-ray beam sequence and multiple projections were realized with multi leaf collimator (MLC) and gantry movement, respectively. Furthermore, in most modern External Beam Radiotherapy, MLC movement is synchronized with gantry angle to release a uniform radiation, and some of treatment plans, e.g., Intensity Modulated Radiation Therapy (IMRT), have a potential to match the scanning way mentioned. By including Cherenkov imaging results, medium surface profile can be additionally acquired, which can be used as boundary reference to do depth correction and co-register with molecular images. Resolution phantom studies showed that a 0.3 mm diameter capillary tube containing 0.01 nM luminescent nanospheres could be recognized at a depth of 21 mm into tissue-like media. Small animal imaging with a 1 mm diameter cylindrical target demonstrated that fast 3D data acquisition was achieved by a multi-pinhole collimator to image local luminescence 20mm deep.

In recent years, numerous publications have documented the growing consensus among dermatologists for daylight-photodynamic therapy (dPDT) treatment of Actinic Kerasotis (AK), with additional evidence supporting treatment of certain non-melanoma skin cancers (NMSC). While these publications aim to address the minimum effective surface-irradiance required for successful clearance, our current work investigates how the tissue optical properties influence the fluence rate within tissue. While it is known red and blue light will have drastically different attenuation profiles in tissue, it is harder to quantify this for broad-spectrum light sources. Our model aims to expand the current PpIX-weighted irradiance metric by incorporating a clinically relevant depth distribution factor. Using a 7-layer skin model, Monte Carlo simulations of optical photons ranging from 350nm – 900nm provide insight into the potential depth of activation of the photosensitizer. Additionally, these models can be applied to known light spectra for both narrow-band conventional treatments (415nm, 633nm), as well as for the Sun and other white light sources (CFL, Halogen). Using this model, we show even when the effective surface-irradiance of the Sun is 4x a halogen light source, the effective fluence within the top 3mm of tissue is generally equivalent, due to the higher proportion of UV-blue light in Sun spectrum which is highly attenuated within the first 50m. We plan to use this model to inform which light source or light combinations would be most appropriate for specific lesion morphologies.

Cherenkov emission, which is generated during radiation therapy, can be utilized for imaging that is synergistic with radiation therapy. Cherenkov light can be utilized to excite phosphors, which then can be imaged utilizing Cherenkov excited luminescence scanned imaging (CELSI). Europium chelate microspheres, which exhibit bright luminescence with long luminescent lifetime, were appended with multiple copies of cetuximab. This will allow for selective imaging of EGFR overexpressing tumors during the course of radiation therapy via CELSI. We have characterized the functionality of the cetuximab loaded microspheres in vitro via ELISA, as well as via fluorescence microscopy in EGFR overexpressing A431 cells. These microspheres were intravenously injected into athymic nude mice bearing A431 flank tumors and allowed to incubate for a series of time points. They were then imaged first via standard fluorescence imaging to determine the ideal time point for visualizing tumors via CELSI. After demonstrating selective accumulation in tumors, imaging was then undertaken in vivo via CELSI. These antibody conjugated europium microspheres provide promise to image tumors selectively with CELSI. Future studies involve conjugating other antibodies to the europium microspheres to utilize in CELSI.

The discovery of new tumor targeting agents is desirable to expand imaging and drug delivery platforms. Cobalamins, vitamin B12 derivatives, selectively accumulate in tumor versus benign tissue due to overexpression of transcobalamin receptors in a variety of cancer types. Multiple forms of this vitamin are taken into cells via transport through transcobalamin receptors on the cell surface. Alkylcobalamins are light-activatable, and we have discovered that the wavelength of this light activation is tunable via appendage of a fluorophore. We have been able to harness this cobalamin platform to release drugs with a variety of wavelengths of light, including those within the optical window of tissue. This cobalamin drug delivery platform provides selective spatiotemporal activation of drug only where needed, thereby diminishing side effects of traditional chemotherapy. A Bodipy650-cobalamin was synthesized and utilized to study the tumor targeting ability of cobalamin derivatives in athymic nude mice with subcutaneous MCF-7 and MIA PaCa-2 tumors, which have been demonstrated to overexpress transcobalamin receptors. The fluorescently labeled cobalamin was injected intravenously into the mice and allowed to incubate for a series of time points. Fluorescence imaging revealed that this cobalamin conjugate selectively accumulated in both tumor types. We utilized this cobalamin platform for tumor selective, light-activated delivery of the pancreatic cancer drugs erlotinib and SN38. We determined light-induced apoptosis in MIA PaCa-2 cells in vitro and explored the reduction of MIA PaCa-2 tumors in vivo utilizing these cobalamin drug conjugates. This cobalamin platform provides potential for development of new theranostic tools for drug delivery.

In clinical delivery of PDT, in-situ measurement of PpIX concentration is rarely done, and yet point-probe measurements have shown extreme heterogeneity exists between patients and between lesions. Direct measurements of PpIX can provide guidance in PDT, informing critical decisions about treatment time and retreatment or further skin preparation. In this work, we present a smartphone-based fluorescence imaging system to map PpIX concentration onto a 2D image for the use in PDT treatment optimization. The hand-held system utilizes a custom application on an iPhone 6s in conjunction with a 3D-printed measurement base containing custom miniaturized light source and electronics and filter system. The prototype has been produced and tested in phantoms and in pre-clinical evaluation. Intralipid phantom measurements detected clinicallyrelevant concentrations of PpIX within the 0.05μM - 4μM range. Preclinical tests on mice showed the ability to detect PpIX concentration for topically applied ALA within 20-30 minute incubation. These results showcase the viability of the system to map pixel intensities to PpIX concentrations and perform in-vivo detection within a clinically relevant timeframe. Clinical trials are in preparation with results expected in the next few months.

Total Skin Electron Therapy (TSET) utilizes high-energy electrons to treat cancers on the entire body surface. The otherwise invisible radiation beam can be observed via the optical Cherenkov photons emitted from interaction between the high-energy electron beam and tissue. Cherenkov emission is used to evaluate the dose uniformity on the surface of the patient in real-time. We have utilized a structured light sensor to determine the surface contour of each patient. Each patient was also monitored during TSET via in-vivo detectors (IVD) and/or scintillating discs in nine locations. The Cherenkov image is converted to dose distribution after a two-dimensional perspective geometry correction and the IVD measured dose at umbilicus. Cumulative dose on patient surface is obtained by projecting the two-dimensional dose distribution onto a cylindrical geometry representing the patient anatomic geometry. Patients undergoing TSET in various conditions (whole body and half body) were imaged and analysed, and the cumulative dose based on Cherenkov imaging was evaluated on various patients.

Photodynamic Therapy (PDT) is a promising modality for cancer treatment. Typically, a laser is used to photo-excite a photosensitizer (PS) that subsequently collides with oxygen molecules promoting them to the metastable singlet delta state O2(1Δ). Singlet oxygen molecules are believed to be the species that destroys cancerous cells during PDT. In this paper we describe a novel 2D imaging sensor for photosensitizer fluorescence and singlet oxygen luminescence. We describe our instrument and initial results from both in-vitro and in-vivo studies that indicate that this system may be a valuable dosimeter for both PDT researchers and eventually for clinical application.

While most cancer therapy options rely on a systemic delivery of pharmacologic drugs into the tumor site, physiologic barriers intrinsic to solid tumors seriously limit drug distribution. In pancreatic ductal adenocarcinoma (PDAC) tumors, it is well-characterized that tumor stroma with a dense desmoplasia hinders drug uptake due to the overproduction of extracellular matrix (ECM) macromolecules such as collagen and hyaluronan. These major components of the ECM exert a high pressure on blood vessels thus collapsing them. This study focused on reducing the overexpression of cancer associated fibroblasts (CAF) by administering an angiotensin II receptor blocker, losartan, to examine its effects on tumor microenvironment modulation for photodynamic therapy. Treatments were conducted on orthotopic xenograft models of AsPC-1 tumor line, which represented the dense stroma of PDAC with highly disordered collagen bundles. Drug delivery efficiency was examined by quantifying verteporfin uptake and vascular patency. Results showed that pancreatic tumor stroma can be modulated by angiotensin II receptor blockers. Losartan treated mice showed an increase in verteporfin uptake and patent vessel area. Collagen structure change was observed which required more texture analysis to quantify. Tumor size between the two groups did not show significant shrinkage, which indicated the importance of treatment start time especially for malignant tumors with narrow treatment windows such as AsPC-1. The enhancement of drug uptake and vascular perfusion suggested that photodynamic therapeutic outcome could be improved by targeting the tumor stroma to improve verteporfin uptake.

Purpose.In this study, spatio-temporal beam profiling for electron ultra-high dose rate (UHDR; >40 Gy s-1) radiation via Cherenkov emission and radioluminescence imaging was investigated using intensified complementary metal-oxide-semiconductor cameras.Methods.The cameras, gated to FLASH optimized linear accelerator pulses, imaged radioluminescence and Cherenkov emission incited by single pulses of a UHDR (>40 Gy s-1) 10 MeV electron beam delivered to the isocenter. Surface dosimetry was investigated via imaging Cherenkov emission or scintillation from a solid water phantom or Gd2O2S:Tb screen positioned on top of the phantom, respectively. Projected depth-dose profiles were imaged from a tank filled with water (Cherenkov emission) and a 1 g l-1quinine sulfate solution (scintillation). These optical results were compared with projected lateral dose profiles measured by Gafchromic film at different depths, including the surface.Results.The per-pulse beam output from Cherenkov imaging agreed with the photomultiplier tube Cherenkov output to within 3% after about the first five to seven ramp-up pulses. Cherenkov emission and scintillation were linear with dose (R2 = 0.987 and 0.995, respectively) and independent of dose rate from ∼50 to 300 Gy s-1(0.18-0.91 Gy/pulse). The surface dose distribution from film agreed better with scintillation than with Cherenkov emission imaging (3%/3 mm gamma pass rates of 98.9% and 88.8%, respectively). Using a 450 nm bandpass filter, the quinine sulfate-based water imaging of the projected depth optical profiles agreed with the projected film dose to within 5%.Conclusion.The agreement of surface dosimetry using scintillation screen imaging and Gafchromic film suggests it can verify the consistency of daily beam quality assurance parameters with an accuracy of around 2% or 2 mm. Cherenkov-based surface dosimetry was affected by the target's optical properties, prompting additional calibration. In projected depth-dose profiling, scintillation imaging via spectral suppression of Cherenkov emission provided the best match to film. Both camera-based imaging modalities resolved dose from single UHDR beam pulses of up to 60 Hz repetition rate and 1 mm spatial resolution.