Evaluation of kV-CBCT based 3D dose calculation accuracy and its validation using delivery fluence derived dose metrics in Head and Neck Cancer.

PURPOSE: The purpose of this study is to evaluate the dosimetric impact of Hounsfield unit (HU) variations in kilovoltage cone-beam computed tomography (kV-CBCT) based 3D dose calculation accuracy in the treatment planning system and its validation using measured treatment delivery dose (MTDD) derived dose metrics for Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiotherapy (IMRT) plans in Head and Neck (HN) Cancer. METHODS: CBCT dose calculation accuracy was evaluated for 8 VMAT plans on inhomogeneous phantom and 40 VMAT and IMRT plans of HN Cancer patients and validated using ArcCHECK diode array MTDD derived 3D dose metric on CT and CBCT. RESULTS: The mean percentage dose difference between CBCT and CT in TPS (ΔD(CBCT-CT)TPS) and 3DVH (ΔD(CBCT-CT)3DVH) were compared for the corresponding evaluation dose metrics (D98%, D95%, D50%, D2%, Dmax, D1cc, D0.03cc, Dmean) of all PTVs and OARs in phantom and patients. ΔD(CBCT-CT)TPS and ΔD(CBCT-CT)3DVH for all evaluation dose points of all PTVs and OARs were less than 2.55% in phantom and 2.4% in HN patients. The Pearson correlation coefficient (r) between ΔD(CBCT-CT)TPS and ΔD(CBCT-CT)3DVH for all dose points in all PTVs and OARs showed a strong to moderate correlation in phantom and patients with p < 0.001. CONCLUSIONS: This study evaluated and validated the potential feasibility of kV-CBCT for treatment plan 3D dose reconstruction in clinical decision making for Adaptive radiotherapy on CT in Head and Neck cancer.

Solid state diffusion and amalgamating anionic exchange at a KNaSO4 phosphors activated with Eu3+ , Dy3+ and Sm3+ rare earth ions to enhance w-LED performance.

In present work, KNa(SO4 ) phosphors doped with different concentrations of rare earth Eu3+ , Sm3+ and Dy3+ ions (0.05, 0.1, 0.3, 0.5, 0.7, 1 mol%) were synthesized using a solid-state diffusion technique. Photoluminescence (PL) investigations were carried out for the whole range of Eu3+ , Sm3+ and Dy3+ -doped phosphors; rare earth ions that retained maximum PL intensity were selected for advanced anionic exchange. In the present investigation, phosphors KNa(SO4 ):Eu3+ (1 mol%), KNa(SO4 ):Dy3 + (0.5 mol%) and KNa(SO4 ):Sm3+ (0.3 mol%) had the highest PL intensity, and were therefore selected for further anionic substitution of sulphate anions with different concentrations of vanadate, phosphate, and tungstate anions, such as KNa(SO4 )1-x (MO4 )x : W (where W = Eu3+ 1 mol%, Dy3+ 0.5 mol% and Sm3+ 0.3 mol%; MO4 = PO4 , VO4 , WO4 ; and x = 0.1, 0.3, 0.5, 0.7, 1). Structural and molecular environments of the substituted phosphors were characterized individually using X-ray diffraction and Fourier transform infrared spectroscopy. In-depth morphological investigations of the prepared phosphors were undertaken using scanning electron microscopy. For the principal investigation on enhancement of white light-emitting diode (w-LED) performance, the PL properties of all the synthesized phosphors were studied analytically. Emission intensity ratios for KNa(SO4 ):Eu3+ 1 mol%, KNa(SO4 )0 (PO4 )1 :Eu 1 mol%, KNa(SO4 )0.9 (VO4 )1 :Eu 1 mol%, and KNa(SO4 )0.9 (WO4 )0.1 :Eu 1 mol% were 1:1.15:1.23:0.08. PL intensity ratios for the phosphors KNaSO4 :Dy 0.5 mol% and KNa(SO4 )0.9 (PO4 )0.1:Dy 0.5 mol% was 1:2. The ratio of PL intensity was 1:3.2:0.8 for KNa(SO4 ):Sm 1 mol%, KNa(SO4 )0.5 (PO4)0.5 :Sm 0.3 mol%, and KNa(SO4 )0.7 (VO4 )0.3 :Sm 0.3 mol% phosphors, respectively. Chromaticity investigations were carried out using Commission Internationale de l'Éclairage colour co-ordinate diagrams, which suggested that the prepared Eu3+ -doped and Sm3+ -doped phosphors would be prospective candidates for red and green LEDs, respectively, whereas Dy3+ -doped phosphors showed emission in the blue and yellow regions. The entire study indicated that amalgamation of anionic exchange at a KNaSO4 phosphor activated with Eu3+ , Dy3+ and Sm3+ rare earth ions could generate and enhance white light emission.

Luminescence properties of nanocrystalline Mg2 P2 O7 :Eu phosphor.

Thermoluminescence (TL) measurements were carried out on europium (Eu) doped magnesium pyrophosphate (Mg2 P2 O7 ) nanopowders using gamma irradiation in the dose range of 0.1 to 3 kGy. The powder samples were successfully synthesized by chemical co-precipitation synthesis route. The formation and crystallinity of the compound was confirmed by powder X-ray diffraction (PXRD) pattern. The estimated particle size was found to be in nanometer scale by using Debye Scherer's formula. A scanning electron microscopy (SEM) study was carried out for the morphological characteristics of as synthesized Mg2 P2 O7 :Eu phosphor. Photoluminescence (PL) study was carried out to confirm the presence of the rare-earth ion and its valence state. The TL analysis of synthesized samples were performed after the irradiation of Mg2 P2 O7 :Eu with cobalt-60 (60 Co) gamma rays. The high and low intensity peaks of TL glow curve appeared at around 400 K, 450 K, 500 K and 596 K respectively. The appreciable shift in peak positions has been observed for different concentrations of Eu ion. The trapping parameters, namely activation energy (E), order of kinetics (b) and frequency factor (s) have been determined using thermal cleaning process, peak shape (Chen's) method and glow curve deconvolution (GCD) functions.