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Objective . With the introduction of Cherenkov imaging technology on the Halcyon O-ring linear accelerator platform, we seek to demonstrate the imaging feasibility and optimize camera placement. Approach . Imaging parameters were probed by acquiring triggering data Cherenkov image frames for simplistic beams on the Halcyon and comparing the analyzed metrics with those from the TrueBeam platform. Camera position was analyzed by performing 3D rendering of patient treatment plans for various sites and iterating over camera positions to assess treatment area visibility. Main results . Commercial Cherenkov imaging systems are compatible with the pulse timing of the Halcyon, and this platform design favorably impacts signal to noise in Cherenkov image frames. Additionally, ideal camera placement is treatment site dependent and is always within a biconical zone of visibility centered on the isocenter. Visibility data is provided for four treatment sites, with suggestions for camera placement based on room dimensions. Median visibility values were highest for right breast plans, with values of 80.33% and 68.49% for the front and rear views respectively. Head and neck plans presented with the lowest values at 26.44% and 38.18% respectively. Significance . This work presents the first formal camera positional analysis for Cherenkov imaging on any platform and serves as a template for performing similar work for other irradiation platforms. Additionally, this study confirms the Cherenkov imaging parameters do not need to be changed for optimal imaging on the Halcyon. Lastly, the presented methodology provides a framework which could be further expanded to other optical imaging systems which rely on line of sight visibility to the patient., (© 2023 Institute of Physics and Engineering in Medicine.)

Neurosurgical fluorescence guidance relies on contrast agents to identify tumor regions to aid in increasing the extent of resection. Existing contrast agents for this indication each have their own limitation: unpredictable contrast from tumor heterogeneity, significant extravasation into the background brain and long incubation times. An ideal contrast agent should have high and rapid contrast that persists well into the surgical procedure. By using a whole animal hyperspectral cryo-imaging system several CAs were screened for these favorable properties and compared to the gold standard of gadolinium enhanced MR. Herein, we briefly report on the leading candidate Rd-PEG1k, which shows high contrast within minutes of administration that persists for at least 90 minutes.

Fluorescent contrast agents targeted to cancer biomarkers are increasingly being explored for cancer detection, surgical guidance, and response monitoring. Efforts have been underway to topically apply such biomarker-targeted agents to freshly excised specimen for detecting cancer cell receptors on the surface as a method for intraoperative surgical margin assessment, including dual-probe staining methods introduce a second 'non-specific' optical agent as a control to help compensate for heterogeneous uptake and normalize the imaging field. Still, such specimen staining protocols introduce multifaceted complexity with unknown variables, such as tissue-specific diffusion, cell-specific binding and disassociation rates, and other factors, affecting the interpreted cancer-biomarker distribution across the specimen surface. The ability to recover three-dimensional dual-probe biodistributions throughout whole-specimens could offer a ground-truth validation method for examining topical staining uptake behaviors. Herein, we report on a novel method for characterizing dual-probe accumulation with 3D depth-profiles observed from a dual-probe fresh-specimen staining experiment.

The ability to directly measure whole-body fluorescence can enable tracking of labeled cells, metastatic spread, and drug bio-distribution. We describe the development of a new hyperspectral imaging whole body cryo-macrotome designed to acquire 3-D fluorescence volumes in large specimens (whole animals) at high resolution. The use of hyperspectral acquisition provides full spectra at every voxel, enabling spectral decoupling of multiple fluorohpores and autofluorescence. We present examples of tissue spectra and spectral fitting in a rodent glioma xenograft.