EVALUATION OF ACCURACY AND INTRINSIC UNCERTAINTY OF AUTOMATED IMAGE REGISTRATION FOR A 6D KV-CBCT IMAGE GUIDANCE SYSTEM: A CONCURRENT ANALYSIS WITH A MACHINE PERFORMANCE CHECK.

The accuracy and uncertainty of the automated image registration (AIR) algorithm in a six-dimensional (6D) kilovoltage cone-beam computed tomography (kV-CBCT) image-guided radiation therapy (IGRT) system were evaluated with a concurrent analysis of machine performance check (MPC). The MPC was performed before (MPCpre) and after (MPCpost) each accuracy and intrinsic uncertainty measurement. The accuracy was evaluated for 25 sets of the known shifts applied to the Catphan-504 phantom through a 6D robotic couch in the head, thorax, and pelvis CBCT acquisition modes. The uncertainty was evaluated for the intensity range, soft tissue, and bone matching filters in the head, thorax and pelvis CBCT acquisition modes. The mean ΔMPC (MPCpost-MPCpre) for all test parameters was within 0.02 ± 0.08 mm and 0.00 ± 0.02°. The overall average accuracy in AIR of 6D kV-CBCT IGRT in all translational and rotational axes was within 0.05 ± 0.76 mm and 0.02 ± 0.07°, respectively, for all CBCT modes. The overall mean population (Mpop), systematic (Σ) and random (σ) errors were within 0.47, 0.53 and 0.24 mm and within 0.03, 0.08 and 0.07° in translational and rotational axes, respectively, for all matching filters in all CBCT modes. The accuracy and intrinsic uncertainty in the AIR of the 6D kV-CBCT IGRT were within acceptable limits for clinical use.

QUANTIFICATION OF 6D INTER-FRACTION TUMOUR LOCALISATION ERRORS IN TONGUE AND PROSTATE CANCER USING DAILY KV-CBCT FOR 1000 IMRT AND VMAT TREATMENT FRACTIONS.

This study aimed to evaluate the 6D inter-fraction tumour localisation errors in 20 tongue and 20 prostate cancer patients treated with intensity-modulated radiation therapy and volumetric-modulated arc therapy. The patient tumour localisation errors in lateral, longitudinal and vertical translation axes and pitch, roll and yaw rotational axes were analysed by automatic image registration of daily pretreatment kilovoltage cone-beam computed tomography (kV-CBCT) with planning CT in 1000 fractions. The overall mean error (M), systematic error (Σ), random error (σ) and planning target volume (PTV) margins were evaluated. The frequency distributions of setup errors were normally distributed about the mean except for pitch in the tongue and prostate. The overall 3D vector length ≥ 5 mm was 14.2 and 49.8% in the ca-tongue and ca-prostate, respectively. The frequency of rotational errors ≥1 degree was a maximum of 37 and 59.5%, respectively, in ca-tongue and ca-prostate. The M, Σ and σ for all translational and rotational axes decreased with increasing frequency of verification correction in ca-tongue and ca-prostate patients. Similarly, the PTV margin was reduced with no correction to alternate day correction from a maximum of 4.7 to 2.5 mm in ca-tongue and from a maximum of 8.6 to 4.7 mm in ca-prostate. The results emphasised the vital role of the higher frequency of kV-CBCT based setup correction in reducing M, Σ, σ and PTV margins in ca-tongue and ca-prostate patients.

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.

Facile synthesis and thermoluminescence properties of nano bio-ceramic ß-Ca2P2O7:Dy phosphor irradiated with 75 meV C6+ ion beam.

Dy3+ doped ß-Ca2P2O7 phosphor has been synthesized using wet chemical method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed the formation of ß-Ca2P2O7:Dy nano-phosphors. However, photoluminescence (PL) study was carried out to confirm the presence of dopant ion in the host matrix of ß-Ca2P2O7:Dy material. Thermoluminescence (TL) glow curves of ß-Ca2P2O7 were recorded for different concentrations of Dy3+ after exposure to various fluences of C6+ ion beam (75 meV). TL sensitivity of ß-Ca2P2O7:Dy3+ (0.1 mol%) phosphor was 3.79 times more than commercially available CaSO4:Dy3+. TRIM code based on the Monte Carlo simulation was used to calculate the absorbed doses, ion range and main energy loss. Glow curve de-convolution (GCD) method was used to determine the number of TL peaks and their trapping parameters. The wide linear response of ß-Ca2P2O7 nanoparticles along with high stability of TL glow curve makes this nanomaterial a good candidate for C6+ ion beam dosimetry.

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.

On the study of the C6+ ion beam and γ-ray induced effect on structural and luminescence properties of Eu doped LiNaSO4: explanation of TSL mechanism using PL, TL and EPR study.

The present paper reports on the γ-ray and C6+ ion beam induced effect on the structural and luminescence properties of Eu doped LiNaSO4 phosphors synthesized via wet the chemical method. The material was irradiated by 60Co and 137Cs γ-rays and 75 MeV C6+ ions in a fluence range varying from 2 × 1010 to 1 × 1012 ion per cm2. The ion induced modified properties were investigated using X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL), thermoluminescence (TL) and electron paramagnetic resonance (EPR) studies. The XRD and micro-Raman results confirm the loss of crystallinity and elongation of the lattice parameters after ion beam irradiation. The presence of both divalent as well as trivalent states of Eu ions at multiple sites of LiNaSO4 is observed by PL study. Irradiation of the LiNaSO4:Eu phosphor with a C6+ ion beam modifies the population of the valence state of the doped rare earth Eu ion and enhances the TL sensitivity of this phosphor. The nature of the prominent TL glow curve is identical for both γ-ray and C6+ ion beam irradiated materials while additional deep trap levels appear in the latter due to the formation of several types of cation and anion vacancy. The electron paramagnetic resonance (EPR) technique also supports the presence of the Eu ion at multiple sites and provides information regarding several types of radical produced after γ-ray and C6+ ion irradiation. Finally, a mechanism is presented for the thermally stimulated luminescence phenomenon on the basis of our observed results from the PL, TL and EPR studies. The reason behind ion beam irradiation induced modification of the TL properties and enhancement of luminescence intensity is also explained in this report.