| 1. |
- Daniel, M., et al.
(författare)
-
Impact of androgen deprivation therapy on apparent diffusion coefficient and T2w MRI for histogram and texture analysis with respect to focal radiotherapy of prostate cancer
- 2019
-
Ingår i: Strahlentherapie und Onkologie (Print). - : Springer Berlin/Heidelberg. - 0179-7158 .- 1439-099X. ; 195:5, s. 402-411
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: Accurate prostate cancer (PCa) detection is essential for planning focal external beam radiotherapy (EBRT). While biparametric MRI (bpMRI) including T2-weighted (T2w) and diffusion-weighted images (DWI) is an accurate tool to localize PCa, its value is less clear in the case of additional androgen deprivation therapy (ADT). The aim of this study was to investigate the value of a textural feature (TF) approach on bpMRI analysis in prostate cancer patients with and without neoadjuvant ADT with respect to future dose-painting applications.Methods: 28 PCa patients (54–80 years) with (n = 14) and without (n = 14) ADT who underwent bpMRI with T2w and DWI were analyzed retrospectively. Lesions, central gland (CG), and peripheral zone (PZ) were delineated by an experienced urogenital radiologist based on localized pre-therapeutic histopathology. Histogram parameters and 20 Haralick TF were calculated. Regional differences (i. e., tumor vs. PZ, tumor vs. CG) were analyzed for all imaging parameters. Receiver-operating characteristic (ROC) analysis was performed to measure diagnostic performance to distinguish PCa from benign prostate tissue and to identify the features with best discriminative power in both patient groups.Results: The obtained sensitivities were equivalent or superior when utilizing the TF in the no-ADT group, while specificity was higher for the histogram parameters. However, in the ADT group, TF outperformed the conventional histogram parameters in both specificity and sensitivity. Rule-in and rule-out criteria for ADT patients could exclusively be defined with the aid of TF.Conclusions: The TF approach has the potential for quantitative image-assisted boost volume delineation in PCa patients even if they are undergoing neoadjuvant ADT.
|
|
| 2. |
- Alqedra, Mohammed K., et al.
(författare)
-
Optical coherence properties of Kramers' rare-earth ions at the nanoscale for quantum applications
- 2023
-
Ingår i: Physical Review B. - 2469-9950. ; 108:7
-
Tidskriftsartikel (refereegranskat)abstract
- Rare Earth (RE) ion doped nanomaterials are promising candidates for a range of quantum technology applications. Among RE ions, the so-called Kramers' ions possess spin transitions in the GHz range at low magnetic fields, which allows for high-bandwidth multimode quantum storage, fast qubit operations as well as interfacing with superconducting circuits. They also present relevant optical transitions in the infrared. In particular, Er3+ has an optical transition in the telecom band, while Nd3+ presents a high-emission-rate transition close to 890 nm. In this paper, we measure spectroscopic properties that are of relevance to using these materials in quantum technology applications. We find the inhomogeneous linewidth to be 10.7 GHz for Er3+ and 8.2 GHz for Nd3+, and the excited state lifetime T1 to be 13.68 ms for Er3+ and 540μs for Nd3+. We study the dependence of homogeneous linewidth on temperature for both samples, with the narrowest linewidth being 379 kHz (T2=839 ns) for Er3+ measured at 3 K, and 62 kHz (T2=5.14μs) for Nd3+ measured at 1.6 K. Further, we investigate time-dependent homogeneous linewidth broadening due to spectral diffusion and the dependence of the homogeneous linewidth on magnetic field to get additional clarity of mechanisms that can influence the coherence time. In light of our results, we discuss two applications: single qubit-state readout and a Fourier-limited single photon source.
|
|
| 3. |
- Guillot-Noel, O., et al.
(författare)
-
Hyperfine structure, optical dephasing, and spectral-hole lifetime of single-crystalline Pr3+: La-2(WO4)(3)
- 2007
-
Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 75:20
-
Tidskriftsartikel (refereegranskat)abstract
- Most of the experiments related to quantum information applications, involving rare-earth doped inorganic crystals, are performed on yttrium orthosilicate single crystals. The work presented here is motivated by the search of new compounds which can be used in the field of quantum computing and/or quantum storage. Relaxation times and hyperfine structure of the H-3(4)(0)-> D-1(2)(0) transition in 1.4% Pr3+:La-2(WO4)(3) at 4 K have been measured by photon-echo and spectral-hole-burning techniques. The hyperfine splittings of the ground H-3(4)(0) and the excited D-1(2)(0) states are 14.9 +/- 0.1 MHz, 24.6 +/- 0.1 MHz and 5.0 +/- 0.1 MHz, 7.3 +/- 0.1 MHz, respectively. An inhomogeneous linewidth of 18.8 +/- 0.1 GHz was measured. A homogeneous linewidth of 25.3 +/- 2.0 kHz was obtained with or without an external magnetic field of about 14 mT. The fluorescence dynamics of the D-1(2) level obtained by a direct excitation in the H-3(4)-> D-1(2) transition gives a nonexponential decay which indicates energy-transfer processes. This decay can be accurately fitted by the Inokuti-Hirayama model [J. Chem. Phys. 43, 1978 (1965)] with a radiative lifetime of 61 +/- 1 mu s giving a minimal homogeneous linewidth of 2.6 kHz. The spectral-hole lifetime due to population redistribution within the ground hyperfine levels is 16 +/- 2 s. The results obtained for the La-2(WO4)(3) compound make this crystal an interesting host for quantum applications.
|
|
| 4. |
- Moncorge, R, et al.
(författare)
-
Linear and non-linear spectroscopy of Ho3+-doped YVO4 and LuVO4
- 2005
-
Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 17:42, s. 6751-6762
-
Tidskriftsartikel (refereegranskat)abstract
- Rare-earth-doped crystals can be attractive materials for quantum information processing, because of the long coherence times that can be expected, in particular, from non-Kramers ions. In this paper, Ho3+-doped yttrium and lutetium vanadate single crystals have been investigated using linear and coherent optical spectroscopy. For Ho3+:YVO4, the crystal-field levels of the I-5(8), F-5, F-5(4) and S-5(2) multiplets have been determined and compared with crystal-field level calculations. This allowed us to unambiguously assign most of the observed transitions, although some results suggest that the site symmetry of the Ho3+ ion could deviate from D-2d. Similar conclusions were reached for Ho3+:LuVO4. Hole burning measurements indicate that the coherence time of the I-5(8)-F-5(5) optical transitions is rather short in both compounds (around 40 ns). Assuming that the coherence is limited by spin interactions, this is accounted for by the high nuclear moment of the nearby vanadium ions, since the large crystal-field level splittings of the I-5(8) and F-5(5) multiplets do not favour a large enhanced nuclear Zeeman effect.
|
|
| 5. |
- Serrano, Diana, et al.
(författare)
-
Impact of the ion-ion energy transfer on quantum computing schemes in rare-earth doped solids
- 2014
-
Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 151, s. 93-99
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze the Ce3+-Pr3+:Y2SiO5 emission spectra obtained under selective excitation of the two Ce3+ sites in Y2SiO5 and we show clear evidence of direct energy transfer from Ce3+ to Pr3+. Energy transfer microparameters were calculated from the experimental spectral overlap between the Ce3+ emission and the Pr3+ and Eu3+ absorptions from which, the transfer mechanisms Ce3+-> Pr3+ are concluded to be more efficient than the transfer mechanisms Ce3+-> Eu3+. The energy transfer processes demonstrated here are potentially detrimental for an efficient qubit readout, using Ce3+ as readout ion, as they lead to a quenching of the Ce3+ luminescence and can give rise to the unwanted change of Pr3+ and Eu3+ qubit states. The quantum computing readout scheme is based on permanent electric dipole interactions scaling as R-3, where R is the distance between the Ce3+ and the qubit ion. The non-radiative energy transfer processes also depend on the ion-ion distances, however as R-6. A discussion about the microscopic dopant distributions leading to an efficient single-ion readout quantum computing scheme is here presented. The likely existence of energy transfer paths between the qubits or, as in this case, between the readout ion and the qubit ions, has not been taken into account so far by the rare-earth based quantum computing approaches. The results of this study suggest the need to consider them in order to design realistic and efficient quantum computing schemes for rare-earth doped solids. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 6. |
- Serrano, Diana, et al.
(författare)
-
Satellite line mapping in Eu3+-Ce3+ and Pr3+-Ce3+ codoped Y2SiO5
- 2016
-
Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 170, s. 102-107
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we perform a high-resolution spectroscopic investigation of Eu3+-Ce3+ and Pr3+-Ce3+ codoped Y2SiO5 crystals. Satellite line spectra were recorded at low temperatures around the Eu3+:F-7(0) -> D-5(0) and the Pr3+:H-3(4) -> D-1(2) transitions. It is observed that the incorporation of Ce3+ as a codopant notably changes the Eu3+ and Pr3+ satellite line patterns. Satellite lines measured in singly doped Eu3+:Y2SiO5 were found at the same spectral positions in Eu3+-Ce3+ codoped crystals. These coincident lines were concluded to be due to pairs of Eu3+ ions. Extra satellite lines appeared in the codoped crystals, which were assigned to Ce3+ related structures such as Ce3+-Eu3+ pairs. The analysis of the Pr3+ satellite line spectra presents further challenges. Satellite lines associated to Pr3+ pairs show weaker intensity, presumably due to the efficient quenching of the Pr3+ D-1(2) emission through cross-relaxation paths (D-1(2) -> (1)G(4); H-3(4) -> F-3(4)). The investigation of the Eu3+ and Pr3+ satellite line patterns in Y2SiO5 is particularly interesting for their exploitation in rare-earth based quantum computation schemes. (C) 2015 Elsevier B.V. All rights reserved.
|
|
