Dr. Daniel A. Alexander Profile

Dr. Daniel A. Alexander

at Penn Medicine

SPIE Involvement:

Author

Area of Expertise:

Medical Physics , Cherenkov Imaging

Publications (7)

Proceedings Article | 13 March 2024 Presentation

Validation of the Cherenkov converted dose using multiple Cherenkov images on TSET patients

Yifeng Zhu, Brook Byrd, Daniel Alexander, Amit Maity, John Plastaras, Michael LaRiviere, Brian Pogue, Timothy Zhu

Proceedings Volume PC12823, PC1282302 (2024) https://doi.org/10.1117/12.3003498

KEYWORDS: Monte Carlo methods, Cameras, Skin, Reliability, In vivo imaging, Dosimetry, 3D modeling, Calibration

Read Abstract +

Proceedings Article | 13 March 2024 Presentation + Paper

Improving Cherenkov-to-dose linearity in tissue for quantitative surface dosimetry during whole breast radiation therapy

Brook Byrd, Daniel Alexander, Mario Gallardo, Baozhu Lu, Dennis Sourvanos, Taoran Li, Neil Taunk, Gary Freedman, Timothy Zhu

Proceedings Volume 12834, 1283405 (2024) https://doi.org/10.1117/12.3000357

KEYWORDS: Breast, Optical properties, Cameras, Skin, Radiotherapy, Tissues, Photons, Dosimetry, Color, Natural surfaces

Read Abstract +

Proceedings Article | 14 March 2023 Presentation + Paper

Evaluation of the cumulative Cherenkov converted dose on TSET patients with multiple Cherenkov cameras

Yifeng Zhu, Daniel Alexander, Tianshun Miao, Amit Maity, John Plastaras, Ima Paydar, Michael LaRiviere, Brian Pogue, Timothy Zhu

Proceedings Volume 12359, 1235907 (2023) https://doi.org/10.1117/12.2651177

KEYWORDS: Cameras, 3D modeling, 3D scanning, Finite element methods, Cerenkov radiation imaging

Read Abstract +

SPIE Journal Paper | 13 March 2023 Open Access

Color-resolved Cherenkov imaging allows for differential signal detection in blood and melanin content

Vihan A. Wickramasinghe, Savannah M. Decker, Samuel S. Streeter, Austin M. Sloop, Arthur F. Petusseau, Daniel A. Alexander, Petr Bruza, David J. Gladstone, Rongxiao Zhang, Brian W. Pogue

JBO, Vol. 28, Issue 03, 036005, (March 2023) https://doi.org/10.1117/12.10.1117/1.JBO.28.3.036005

KEYWORDS: Blood, Tissues, Cameras, Color imaging, Signal attenuation, RGB color model, Biological imaging, Skin, Signal detection, Color

Read Abstract +

SignificanceHigh-energy x-ray delivery from a linear accelerator results in the production of spectrally continuous broadband Cherenkov light inside tissue. In the absence of attenuation, there is a linear relationship between Cherenkov emission and deposited dose; however, scattering and absorption result in the distortion of this linear relationship. As Cherenkov emission exits the absorption by tissue dominates the observed Cherenkov emission spectrum. Spectroscopic interpretation of this effects may help to better relate Cherenkov emission to ionizing radiation dose delivered during radiotherapy.AimIn this study, we examined how color Cherenkov imaging intensity variations are caused by absorption from both melanin and hemoglobin level variations, so that future Cherenkov emission imaging might be corrected for linearity to delivered dose.ApproachA custom, time-gated, three-channel intensified camera was used to image the red, green, and blue wavelengths of Cherenkov emission from tissue phantoms with synthetic melanin layers and varying blood concentrations. Our hypothesis was that spectroscopic separation of Cherenkov emission would allow for the identification of attenuated signals that varied in response to changes in blood content versus melanin content, because of their different characteristic absorption spectra.ResultsCherenkov emission scaled with dose linearly in all channels. Absorption in the blue and green channels increased with increasing oxy-hemoglobin in the blood to a greater extent than in the red channel. Melanin was found to absorb with only slight differences between all channels. These spectral differences can be used to derive dose from measured Cherenkov emission.ConclusionsColor Cherenkov emission imaging may be used to improve the optical measurement and determination of dose delivered in tissues. Calibration for these factors to minimize the influence of the tissue types and skin tones may be possible using color camera system information based upon the linearity of the observed signals.

DOWNLOAD PAPER

Proceedings Article | 6 March 2023 Presentation + Paper

Comparison of surface dose during whole breast radiation therapy on Halcyon and TrueBeam using Cherenkov imaging

Daniel Alexander, Olivia Certa, Allison Haertter, Taoran Li, Neil Taunk, Timothy Zhu

Proceedings Volume 12371, 1237108 (2023) https://doi.org/10.1117/12.2652588

KEYWORDS: Breast, Monte Carlo methods, Cameras, Radiotherapy, Tissues, In vivo imaging, Optical imaging, Optical medical imaging

Read Abstract +

SPIE Journal Paper | 13 October 2021 Open Access

Optimization of in vivo Cherenkov imaging dosimetry via spectral choices for ambient background lights and filtering

Mahbubur Rahman, Petr Bruza, Rachael Hachadorian, Daniel Alexander, Xu Cao, Rongxiao Zhang, David Gladstone, Brian Pogue

JBO, Vol. 26, Issue 10, 106003, (October 2021) https://doi.org/10.1117/12.10.1117/1.JBO.26.10.106003

KEYWORDS: Light sources, Optical filters, Signal to noise ratio, Light, Image filtering, In vivo imaging, Tissue optics, Image quality, Light emitting diodes, Cameras

Read Abstract +

Significance: The Cherenkov emission spectrum overlaps with that of ambient room light sources. Choice of room lighting devices dramatically affects the efficient detection of Cherenkov emission during patient treatment. Aim: To determine optimal room light sources allowing Cherenkov emission imaging in normally lit radiotherapy treatment delivery rooms. Approach: A variety of commercial light sources and long-pass (LP) filters were surveyed for spectral band separation from the red to near-infrared Cherenkov light emitted by tissue. Their effects on signal-to-noise ratio (SNR), Cherenkov to background signal ratio, and image artifacts were quantified by imaging irradiated tissue equivalent phantoms with an intensified time-gated CMOS camera. Results: Because Cherenkov emission from tissue lies largely in the near-infrared spectrum, a controlled choice of ambient light that avoids this spectral band is ideal, along with a camera that is maximally sensitive to it. An RGB LED light source produced the best SNR out of all sources that mimic room light temperature. A 675-nm LP filter on the camera input further reduced ambient light detected (optical density > 3), achieving maximal SNR for Cherenkov emission near 40. Reduction of the room light signal reduced artifacts from specular reflection on the tissue surface and also minimized spurious Cherenkov signals from non-tissue features such as bolus. Conclusions: LP filtering during image acquisition for near-infrared light in tandem with narrow band LED illuminated rooms improves image quality, trading off the loss of red wavelengths for better removal of room light in the image. This spectral filtering is also critically important to remove specular reflection in the images and allow for imaging of Cherenkov emission through clear bolus. Beyond time-gated external beam therapy systems, the spectral separation methods can be utilized for background removal for continuous treatment delivery methods including proton pencil beam scanning systems and brachytherapy.

DOWNLOAD PAPER

SPIE Journal Paper | 20 September 2021 Open Access

Estimation of diffuse Cherenkov optical emission from external beam radiation build-up in tissue

Savannah Decker, Daniel Alexander, Rachael Hachadorian, Rongxiao Zhang, David Gladstone, Petr Bruza, Brian Pogue

JBO, Vol. 26, Issue 09, 098003, (September 2021) https://doi.org/10.1117/12.10.1117/1.JBO.26.9.098003

KEYWORDS: Tissue optics, Natural surfaces, X-rays, Tissues, Scattering, Photons, Signal attenuation, Optical properties, Laser scattering, Diffusion

Read Abstract +

DOWNLOAD PAPER

Showing 5 of 7 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years