No abstract

Radiotherapy is a well-established and important treatment for cancer tumors, and advanced technologies can deliver doses in complex three-dimensional geometries tailored to each patient’s specific anatomy. A 3D dosimeter, based on optically stimulated luminescence (OSL), could provide a high accuracy and reusable tool for verifying such dose delivery. Nanoparticles of an OSL material embedded in a transparent matrix have previously been proposed as an inexpensive dosimeter, which can be read out using laser-based methods. Here, we show that Cu-doped LiF nanocubes (nano-LiF:Cu) are excellent candidates for 3D OSL dosimetry owing to their high sensitivity, dose linearity, and stability at ambient conditions. We demonstrate a scalable synthesis technique producing a material with the attractive properties of a single dosimetric trap and a single near-ultraviolet emission line well separated from visible-light stimulation sources. The observed transparency and light yield of silicone sheets with embedded nanocubes hold promise for future 3D OSL-based dosimetry.

In this contribution, we study the optically stimulated luminescence (OSL) exhibited by commercial $$\hbox {Lu}_{(2-x)}\hbox {Y}_x\hbox {SiO}_5$$ Lu ( 2 - x ) Y x SiO 5 :Ce crystals. This photon emission mechanism, complementary to scintillation, can trap a fraction of radiation energy deposited in the material and provides sufficient signal to develop a novel post-irradiation 3D dose readout. We characterize the OSL emission through spectrally and temporally resolved measurements and monitor the dose linearity response over a broad range. The measurements show that the $$\hbox {Ce}^{3+}$$ Ce 3 + centers responsible for scintillation also function as recombination centers for the OSL mechanism. The capture to OSL-active traps competes with scintillation originating from the direct non-radiative energy transfer to the luminescent centers. An OSL response on the order of 100 ph/MeV is estimated. We demonstrate the imaging capabilities provided by such an OSL photon yield using a proof-of-concept optical readout method. A 0.1 $$\hbox {mm}^3$$ mm 3 spatial resolution for doses as low as 0.5 Gy is projected using a cubic crystal to image volumetric dose profiles. While OSL degrades the intrinsic scintillating performance by reducing the number of scintillation photons emitted following the passage of ionizing radiation, it can encode highly resolved spatial information of the interaction point of the particle. This feature combines ionizing radiation spectroscopy and 3D reusable dose imaging in a single material.

With the introduction of highly conformal treatment modalities, dose verification in 3D is becoming more important than ever for patient-specific quality assurance of radiotherapy. Reusability of 3D dosimeters may be the path to cope with the cost-benefit issues caused by batch-to-batch fluctuations and intense calibration protocols in existing 3D systems. We present the idea of an envisioned (optically stimulated luminescence) OSL-based 3D readout system, which exploits the inherently reusable dosimetry properties of OSL. We provide the emission spectra of the OSL active material LiF:Mg, Cu, P (MCP) for three stimulation wavelengths (460 nm, 532 nm, and 664 nm), and summarize recently published optical characterization results to highlight the requirements of a readout system for an MCP-based dosimeter.

We discuss the commonly encountered problem when optimizing NMR pulses using optimal control that the otherwise very precise NMR theory does not provide as excellent agreement with experiments. We hypothesize that this disagreement is due to phase transients in the pulse due to abrupt phase-and amplitude changes resulting in a large bandwidth. We apply the GROUP algorithm that gives high fidelity pulses with a low bandwidth compared to the typical GRAPE pulses. Our results obtain a better agreement between experiment and simulations supporting our hypothesis and solution to the problem. arXiv:1912.05862v2 [quant-ph]