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.

中文翻译：

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通过环境背景光和过滤的光谱选择优化体内切伦科夫成像剂量学

意义：切伦科夫发射光谱与室内环境光源的发射光谱重叠。房间照明设备的选择极大地影响了患者治疗期间切伦科夫辐射的有效检测。目的：确定最佳室内光源，允许在正常照明的放射治疗产房中进行切伦科夫发射成像。方法：对各种商业光源和长通 (LP) 滤光片进行了调查，以确定从组织发出的红光到近红外切伦科夫光的光谱带分离。它们对信噪比 (SNR)、切伦科夫与背景信号比和图像伪影的影响通过使用增强的时间门控 CMOS 相机对辐照组织等效体模进行成像来量化。结果：因为来自组织的切伦科夫发射主要位于近红外光谱中，避免该光谱带的受控环境光选择以及对其最敏感的相机是理想的选择。在所有模拟室温的光源中，RGB LED 光源产生了最佳的 SNR。相机输入上的 675 nm LP 滤波器进一步降低了检测到的环境光（光密度 > 3），实现了接近 40 的切伦科夫发射的最大信噪比。 减少室内光信号减少了组织表面镜面反射的伪影，并最大限度地减少了杂散Cherenkov 信号来自非组织特征，例如推注。结论：近红外光图像采集过程中的 LP 滤波与窄带 LED 照明房间相结合可提高图像质量，权衡红色波长的损失以更好地去除图像中的房间光。这种光谱过滤对于消除图像中的镜面反射并允许通过清晰的团块对切伦科夫发射进行成像也至关重要。除了时间门控外部束治疗系统之外，光谱分离方法还可用于连续治疗递送方法的背景去除，包括质子笔形束扫描系统和近距离放射治疗。