Skin dose is often the quantity of interest for radiological protection, as the skin is the organ that receives maximum dose during kilovoltage X-ray irradiations. The purpose of this study was to simulate the energy response and the depth dose water equivalence of the MOSkin radiation detector (Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia), a MOSFET-based radiation sensor with a novel packaging design, at clinical kilovoltage photon energies typically used for superficial/orthovoltage therapy and X-ray CT imaging. Monte Carlo simulations by means of the Geant4 toolkit were employed to investigate the energy response of the CMRP MOSkin dosimeter on the surface of the phantom, and at various depths ranging from 0 to 6 cm in a 30 × 30 × 20 cm water phantom. By varying the thickness of the tissue-equivalent packaging, and by adding thin metallic foils to the existing design, the dose enhancement effect of the MOSkin dosimeter at low photon energies was successfully quantified. For a 5 mm diameter photon source, it was found that the MOSkin was water equivalent to within 3% at shallow depths less than 15 mm. It is recommended that for depths larger than 15 mm, the appropriate depth dose water equivalent correction factors be applied to the MOSkin at the relevant depths if this detector is to be used for depth dose assessments. This study has shown that the Geant4 Monte Carlo toolkit is useful for characterising the surface energy response and depth dose behaviour of the MOSkin.
. (2013). Measurement of multislice computed tomography dose profile with the Dose Magnifying Glass and the MOSkin radiation dosimeter. Radiation Measurements, 55 51-55.
Measurement of multi-slice computed tomography dose profile with the Dose Magnifying Glass and the MOSkin radiation dosimeter
AbstractThis study describes the application of two in-house developed dosimeters, the Dose Magnifying Glass (DMG) and the MOSkin dosimeter at the Centre for Medical Radiation Physics, University of Wollongong, Australia, for the measurement of CT dose profiles for a clinical diagnostic 16-slice MSCT scanner. Two scanner modes were used; axial mode and helical mode, and the effect of varying beam collimation and pitch was studied. With an increase in beam collimation in axial mode and an increase of CT pitch in helical mode, cumulative point dose at scanner isocentre decreased while FWHM increased. There was generally good agreement to within 3% between the acquired dose profiles obtained by the DMG and the film except at dose profile tails, where film over-responded by up to 30% due to its intrinsic depth dose dependence at low doses.
AbstractThis study describes the application of two in-house developed dosimeters, the Dose Magnifying Glass (DMG) and the MOSkin dosimeter at the Centre for Medical Radiation Physics, University of Wollongong, Australia, for the measurement of CT dose profiles for a clinical diagnostic 16-slice MSCT scanner. Two scanner modes were used; axial mode and helical mode, and the effect of varying beam collimation and pitch was studied.With an increase in beam collimation in axial mode and an increase of CT pitch in helical mode, cumulative point dose at scanner isocentre decreased while FWHM increased. There was generally good agreement to within 3% between the acquired dose profiles obtained by the DMG and the film except at dose profile tails, where film over-responded by up to 30% due to its intrinsic depth dose dependence at low doses.
This study reports on the application of the MOSkin™ dosimeter in MSCT imaging for the real-time measurement of absorbed organ point doses in a tissue-equivalent female anthropomorphic phantom. MOSkin™ dosimeters were placed within the phantom to measure absorbed point organ doses for 2 commonly applied clinical scan protocols, namely the renal calculus scan and the pulmonary embolus scan. Measured organ doses in the imaged field of view were found to be in the dose range 4.7-9.5 mGy and 16.2-27.4 mGy for the renal calculus scan and pulmonary scan protocols respectively. For the derivation of effective dose, using the more recent ICRP 103 tissue weighting factors (w T) compared to that of the ICRP 60 wT resulted in a difference in the derived effective dose by up to 0.8 mSv (-20%) in the renal calculus protocol and up to 1.8 mSv (18%) in the pulmonary embolus protocol. This difference is attributed to the reduced radiosensitivity of the gonads and the increased radiosensitivity of breast tissue in the latest ICRP 103 assigned wT. The results of this study show that the MOSkin™ dosimeter is a useful real-time tool for the direct assessment of organ doses in clinical MSCT examinations.
Radioiodine treatment is administered radioactive iodine to treat the thyroid cancer or to ablate a thyroid remnant. However, due to the risk of radiation, there is a possibility that the patient will experience side effects. Skin dose is an important parameter for quantifying patient dose. The aim of this study is to use a MOSFET detector for real time skin dosimetry. At the Centre for Medical Radiation Physics (CMRP), University of Wollongong, a new type of MOSFET detector called MOSkin is being developed to measure the skin dose, with real-time read out. This paper discusses the pre-clinical characterization the MOSkin and phantom study with radioiodine. In this study, the MOSkin is operated in active mode during irradiation, with +5 V gate bias supplied by a Lithium battery. The Electrical characterization, temperature response, dose linearity response, energy response, and sensitivity versus gate bias for MOSkin were investigated. For the detector characterization, the MOSkin had temperature instability Vth of 0.2 mV/°C under used readout current. The MOSkin energy response was like any MOSFET detector, the dose depending on photon energy. However for a photon energy of more than 250 keV the MOSkin had a flat response that allowed calibration of the MOSkin on a 6 MV LINAC. The sensitivity of the MOSkin was 1.72 mV/cGy and 2.54 mV/cGy under gate biases of +5 V and +15 V respectively. Sensitivity was constant and within 1% when MOSkin irradiated up to 10 Gy. A phantom study was performed with radioiodine 1-131 of activity 80 MBq. The absorbed skin doses for anterior neck and posterior neck were 63.95 and 2.92 cGy respectively. In conclusion, the unique design of the MOSkin appears to show great promise as a skin dosimetry device, with the added advantage of being small in size and having real-time dosimetry capabilities for radionuclide treatment in nuclear medicine.
Peripheral artery disease (PAD) is a common and debilitating condition characterized by the narrowing of the limb arteries, primarily due to atherosclerosis. Non-invasive multi-modality imaging approaches using computed tomography (CT), magnetic resonance imaging (MRI), and nuclear imaging have emerged as valuable tools for assessing PAD atheromatous plaques and vessel walls. This review provides an overview of these different imaging techniques, their advantages, limitations, and recent advancements. In addition, this review highlights the importance of molecular markers, including those related to inflammation, endothelial dysfunction, and oxidative stress, in PAD pathophysiology. The potential of integrating molecular and imaging markers for an improved understanding of PAD is also discussed. Despite the promise of this integrative approach, there remain several challenges, including technical limitations in imaging modalities and the need for novel molecular marker discovery and validation. Addressing these challenges and embracing future directions in the field will be essential for maximizing the potential of molecular and imaging markers for improving PAD patient outcomes.
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