Dr. Rachael L. Hachadorian Profile

Dr. Rachael L. Hachadorian

at Thayer School of Engineering At Dartmouth

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Publications (6)

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

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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.

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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

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Proceedings Article | 5 March 2021 Presentation

A non-contact, quantitative dosimetry calibration using CT radiodensity and Cherenkov imaging

Rachael Hachadorian, Petr Bruza, David Gladstone, Michael Jermyn, Lesley Jarvis, Brian Pogue

Proceedings Volume 11634, 1163408 (2021) https://doi.org/10.1117/12.2582579

KEYWORDS: X-ray computed tomography, Calibration, Tissues, Signal attenuation, Breast, Computed tomography, X-rays, X-ray optics, Tissue optics, Radiotherapy

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Proceedings Article | 25 February 2020 Paper

Cherenkov emission from external beam irradiation: proportional to the dose buildup gradient and inversely affected by tissue optical attenuation

Brian Pogue, Rachael Hachadorian, Sadhya Garg, Jacqueline Andreozzi, Petr Bruza

Proceedings Volume 11224, 112240D (2020) https://doi.org/10.1117/12.2548155

KEYWORDS: Tissue optics, Natural surfaces, Tissues, Signal attenuation, Diffusion, Photons, Radiotherapy, Absorption, Scattering, Light scattering

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Proceedings Article | 1 March 2019 Presentation + Paper

Correcting Cherenkov images for large-scale tissue-optical property attenuation using SFDI and patterned light reflectance for quantitative dosimetry

Rachael Hachadorian, Petr Bruza, Michael Jermyn, Lesley Jarvis, David Gladstone, Brian Pogue

Proceedings Volume 10874, 1087414 (2019) https://doi.org/10.1117/12.2511111

KEYWORDS: Tissue optics, Reflectivity, Signal attenuation, Imaging systems, Optical properties, Calibration, Radiotherapy, Cameras, Light sources and illumination

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SPIE Journal Paper | 10 November 2018 Open Access

Correcting Cherenkov light attenuation in tissue using spatial frequency domain imaging for quantitative surface dosimetry during whole breast radiation therapy

Rachael Hachadorian, Petr Bruza, Michael Jermyn, Amaan Mazhar, David Cuccia, Lesley Jarvis, David Gladstone, Brian Pogue

JBO, Vol. 24, Issue 07, 071609, (November 2018) https://doi.org/10.1117/12.10.1117/1.JBO.24.7.071609

KEYWORDS: Tissue optics, Signal attenuation, Optical properties, Radiotherapy, Natural surfaces, Imaging systems, Blood, Calibration, Breast, Tissues

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