Dosimetric Evaluation of Radiation Treatment Planning for Simultaneous Integrated Boost Technique Using Monte Carlo Simulation.

Monte Carlo (MC) techniques have been recognized as the gold standard for the simulation of radiation transport in radiotherapy. The aim of the study is to perform dosimetric evaluation of Simultaneous Integrated Boost (SIB) radiation treatment planning using MC simulation approach. The geometrical source modeling and simulation of 6 MV Flattening Filter Free (FFF)beam from TrueBeam linear accelerator have been carried out to simulate Volumetric Modulated Arc Therapy (VMAT) plans using MC simulation software PRIMO. All the SIB plans have been generated using VMAT techniques for patients with locally advanced postoperative head-and-neck squamous cell carcinoma in Eclipse Treatment Planning System (TPS) retrospectively. TPS plans have been compared against their respective MC-simulated plans in PRIMO. The quality assessments of plans have been performed using several dose volume parameters, plan quality indices, and methods of gamma analysis. Dmean, D50%, and D2% received by planning target volume (PTV), PTV60, and PTV52 have been found significantly lower in TPS-generated plans compared to MC-simulated plans. D100%, D98%, and D95% received by PTV60 exhibit good agreement. However, PTV52 shows a significant deviation between TPS and MC plans. The mean organ-at-risk doses have been found significantly lower in TPS plans compared to MC plans. TPS and MC plans have been found in close agreement within gamma acceptance criteria of 3% Dose Difference (DD) and 3 mm Distance to Agreement (DTA). Dose distributions computed using MC simulation techniques are reliable, accurate, and consistent with analytical anisotropic algorithm. Plan quality indices have been found slightly compromised in MC-simulated plans compared with TPS-generated plans appeared to be a true representation of real dose distribution obtained from MC simulation technique. Validation using MC simulation approach provides an independent secondary check for ensuring accuracy of TPS-generated plan.

Evaluation of the dosimetric influence of interfractional 6D setup error in hypofractionated prostate cancer treated with IMRT and VMAT using daily kV-CBCT.

INTRODUCTION: Prostate cancer is one of the most common malignant tumors in men and is usually treated with advanced intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). Significant uncorrected interfractional 6-Dimensional setup errors could impact the delivered dose. The aim of this study was to assess the dosimetric impact of 6D interfractional setup errors in hypofractionated prostate cancer using daily kilovoltage cone-beam computed tomography (kV-CBCT). METHODS: This retrospective study comprised twenty prostate cancer patients treated with hypofractionated IMRT (8) and VMAT (12) with daily kV-CBCT image guidance. Interfraction 6D setup errors along lateral, longitudinal, vertical, pitch, roll, and yaw axes were evaluated for 400 CBCTs. For targets and organs at risk (OARs), the dosimetric impact of rotational error (RError), translational error (TError), and translational plus rotational error (T+RError) were evaluated on kV-CBCT images. RESULTS: The single fraction maximum TError ranged from 12-20 mm, and the RError ranged from 2.80-3.00. The maximum mean absolute dose variation ΔD in D98% (dose to 98% volume) of CTV-55 and PTV-55 was -0.66±0.82 and -5.94±3.8 Gy, respectively, in the T+RError. The maximum ΔD (%) for D98% and D0.035cc in CTV-55 was -4.29% and 2.49%, respectively, while in PTV-55 it was -24.9% and 2.36%. The mean dose reduction for D98% in CTV-55 and D98% and D95% in PTV-55 was statistically significant (p<0.05) for TError and T+RError. The mean dose variation for Dmean and D50% in the rectum was statistically significant (p<0.05) for TError and T+RError. CONCLUSION: The uncorrected interfractional 6D setup error results in significant target underdosing and OAR overdosing in prostate cancer. This emphasizes the need to correct interfractional 6D setup errors daily in IMRT and VMAT.

Potential of luminescent materials in phototherapy.

Phototherapy is the use of light in the treatment of skin diseases that show improvement upon exposure to natural sunlight or man-made lamps. Artificial phototherapy treatments like Narrow band UVB (NB-UVB) phototherapy, Photochemotherapy by UVA (PUVA) and Targeted phototherapy are safe and widely used for several skin diseases like psoriasis, vitiligo, acne vulgaris, mycosis fungoides etc. Photodynamic therapy (PDT), a specialized phototherapy involves use of efficient photo sensitizers and optical radiations for the treatment of cancer and various other medical maladies. Efficacy of these treatments depends on proper selection of a phototherapy lamp which is decided by the wavelength of light emitted by the luminescent material present in it. These luminescent materials on account of their unique luminescence features of portability, power efficiency, lesser heat generation and durability find widespread application in bioassay and therapy. Here, we have discussed about the potential of various luminescent materials for phototherapy on the basis of their photoluminescence behaviour and also tabulated their application for various dermatoses. A few more luminescent materials are discussed in view of current developments in phototherapy and bioscience.

Study of thermoluminescence in turtle shell fossils using radiation dosimetry.

The present study describes for the first time thermoluminescence (TL) characterization of turtle shell. A fossil shell was collected from the Dongargaon area in the Chandrapur district of Maharashtra, India. TL was recorded and a comparative study of TL for the above material was performed to understand the special TL characteristics of the shell. The shell was irradiated with 60 Co γ-radiation to study its TL properties. The sample displayed two good TL peaks at 135°C and 255°C. A linear dose-response curve for the irradiated sample was produced for the dose range 0.79-28.5 kGy; this sample of turtle shell (fossil) may be useful as a high dose dosimetry phosphor in this range. This geological sample was further characterized using X-ray diffraction to confirm its phase structure and by scanning electron microscopy , Fourier transform infrared and wavelength dispersive X-ray fluorescence spectroscopy to determine morphology, vibration, and elemental composition as ppm or percentage of the sample, respectively. Kinetic parameters of the TL glow peak were calculated using three different methods.

Versatility of thermoluminescence materials and radiation dosimetry - A review.

Thermoluminescence (TL) materials exhibit a wide range of applications in different areas such as personal dosimetry, environmental dosimetry, medical research etc. Doping of different rare earth impurities in different hosts is responsible for changing the properties of materials useful for various applications in different fields. These materials can be irradiated by different types of beams such as γ-rays, X-rays, electrons, neutrons etc. Various radiation regimes, as well as their dose-response range, play an important role in thermoluminescence dosimetry. Several TL materials, such as glass, microcrystalline, nanostructured inorganic materials and recently developed materials, are reviewed and described in this article.

New UVA-emitting BaAlBO3 F2 :Eu2+ phosphor with PL and TL properties for phototherapy lamp.

We present a new phosphor material, BaAlBO3 F2 doped with Eu2+ ions, having emission in the UVA region. The phosphor material is prepared by a simple wet chemical method. Phase confirmation was carried out using the Rietveld refinement program which shows that BaAlBO3 F2 :Eu2+ has an hexagonal crystal system. Using a Fourier transform infrared spectroscopy graph, we studied the bond stretching present in the phosphor material. Photoluminescence (PL) characterization, carried out using a RF spectrofluorophotometer, shows two types of PL excitation and emission. Before reduction, emission is in the blue region at 431 nm; after reduction, excitation is at 258 nm and emission is at 361 nm, which is in the UVA region. Some thermoluminescence (TL) studies were carried out in this material for the first time, for example, determination of the trapping parameters, linearity, fading, glow curve convolution and deconvolution (GCCD) function for curve fitting and the Tm -Tstop method for confirmation of the trapped centers in the TL glow peak. Copyright © 2016 John Wiley & Sons, Ltd.

Photoluminescence and electron paramagnetic resonance properties of a potential phototherapic agent: MMgF4 :Gd3+ (M = Ba, Sr) sub-microphosphors.

Novel narrow band UVB-emitting phosphors, BaMgF4 :Gd3+ and SrMgF4 :Gd3+ phosphors, were synthesized using a co-precipitation synthesis method. X-Ray diffraction analysis was carried out to confirm compound formation, phase purity and crystallinity of the phosphor. At 274 nm excitation, phosphors show a sharp narrow band emission at 313 nm that can be assigned to 6 P7/2  â†’ 8 S7/2 transition of the Gd3+ ion. With increasing dopant concentration, intensity enhances and then decreases after a certain concentration, which is an indication of concentration quenching taking place in the phosphor. Scanning electron microscopy images of the phosphor show agglomerated particles in the sub-micron range. Particles range in size from 600 to 800 nm. Electron paramagnetic resonance studies of the phosphors were carried out to detect radicals present in the prepared phosphor. With narrow band UVB emission, phosphor seems to be a good candidate for UV phototherapy application. Copyright © 2016 John Wiley & Sons, Ltd.

UVB-emitting Gd(3+)-activated M2O2S (where M = La, Y) for phototherapy lamp phosphors.

Gd(3+)-activated oxysulphide (M2O2S) may be used to study Photoluminescence (PL) properties with respect to phototherapy. Gd(3+)-activated phosphor materials are widely used for phototherapy lamps. The Gd(3+) ion gives characteristic Narrow-Band (NB) emissions, in particular in the ultraviolet (UV) light region, that are used to treat more than 50 types of skin diseases. In this paper, M2O2S oxysulphide doped with Gd(3+) was synthesized by the solid-state flux fusion method and its down conversion spectral properties were studied as a function of different Gd(3+) concentrations. The sample was characterized by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and PL and the crystal structure was also studied. The lanthanum oxysulphide (La2O2S)-activated Gd(3+) ion showed a sharp emission peak at 314 nm when excited at 275 nm excitation, whereas the yttrium oxysulphide (Y2O2S)-activated Gd(3+) ion showed a sharp emission at 316 nm when excited by 272 nm. The effect of concentration of the Gd(3+) ion on the luminescence properties of M2O2S:Gd(3+) phosphor was also studied. These phosphor materials activated with the Gd(3+) ion may be suitable for phototherapy lamps, which are used to treat many types of skin diseases such as psoriasis, vitiligo, or scleroderma.

Influence of thiol capping on the photoluminescence properties of L-cysteine-, mercaptoethanol- and mercaptopropionic acid-capped ZnS nanoparticles.

Mercaptoethanol (ME), mercaptopropionic acid (MPA) and L-cysteine (L-Cys) having -SH functional groups were used as surface passivating agents for the wet chemical synthesis of ZnS nanoparticles. The effect of the thiol group on the optical and photoluminescence (PL) properties of ZnS nanoparticles was studied. L-Cysteine-capped ZnS nanoparticles showed the highest PL intensity among the studied capping agents, with a PL emission peak at 455 nm. The PL intensity was found to be dependent on the concentration of Zn(2+) and S(2-) precursors. The effect of buffer on the PL intensity of L-Cys-capped ZnS nanoparticles was also studied. UV/Vis spectra showed blue shifting of the absorption edge.

KCl:Dy phosphor for thermoluminescence dosimetry of ionizing radiation.

The thermoluminescence (TL) characterizations of γ-irradiated KCl:Dy phosphor for radiation dosimetry are reported. All phosphors were synthesized via a wet chemical route. Minimum fading of TL intensity is recorded in the prepared material. TL in samples containing different concentrations of Dy impurity was studied at different γ-irradiation doses. Peak TL intensities varied sublinearly with γ-ray dose in all samples, but were linear between 0.08 to 0.75 kGy for the KCl:Dy (0.1 mol%) sample. This material may be useful for dosimetry within this range of γ-ray dose. TL peak height was found to be dependant on the concentration (0.05-0.5 mol%) of added Dy in the host.

Lyoluminescence, thermoluminescence and mechanoluminescence studies in γ-ray irradiated Dy3+ activated potassium chloride phosphor for accidental radiation dosimetry.

The lyoluminescence (LL), thermoluminescence (TL) and mechanoluminescence (ML) of γ-ray-irradiated coloured powder of KCl:Dy (0.05-0.5 mol%) phosphors are reported in this paper. To understand the mechanism of LL and ML, the LL and ML spectra are compared with TL studies. The variation of intensity of respective luminescence with different γ-ray doses and with different concentrations of Dy3+ ion doped in KCl is found to be similar in nature. The intensities differ from each other, but their nature is found to be similar with γ-ray exposures. The ML glow peak intensity is linear up to high 1 kGy exposure as compared to LL (up to 0.5 kGy) and TL (up to 0.75 kGy) techniques. Therefore, according to our results, the recommendation is that KCl:Dy (0.1 mol%) phosphor prepared by wet chemical technique is useful for high-dose measurements using the ML technique for accidental radiation dosimetry.

Preparation of (K:Eu) NaSO4 phosphor for lyoluminescence dosimetry of ionising radiation.

Gamma ray dosimetry using lyoluminescence is a low cost and simple system. As sulphate based phosphors are used for TL radiation dosimetry they therefore seem to be a promising material for LL gamma ray dosimetry. A study on LL properties of Eu activated KNaSO4 and K3Na(SO4)2 gamma irradiated materials is reported. Eu doped KNaSO4 shows maximum LL yield in the above system. It shows a linear response from 0.06 to 10 C.kg(-1) and there is not much fading of LL intensity, indicating the phosphor to be suitable as a lyoluminescence dosimetry phosphor of ionising radiation. The doped Eu ion acts as an activator and thus enhances the LL intensity of the phosphor.