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Special Considerations in Pediatric Nuclear Medicine
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Sofie Lindskov Hansen, Søren Holm, Liselotte Højgaard, Lise Borgwardt
A whole-body CT scan of a child between 2 and 5 years old, where the CT scan is of diagnostic image quality will result in CTDI values of around 2–3 mGy. This will result in effective doses in the order of 3–5 mSv. The same scan procedure performed on 5–10 year old children will result in CTDI values of around 3–5 mGy corresponding to effective doses of approximately 4–7 mSv. Children aged 15 and older will usually have a CTDI of around 5–7 mGy resulting in effective doses on the order of 7–10 mSv.
Quality Control of High-Energy External Beams
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Edwin Aird, W. P. M. Mayles, Cephas Mubata
The periodic monitoring of the radiation dose is dependent on the imaging modality. For MV imaging, the electronic image is acquired using the treatment beam. Usually, there is no need for direct measurement of the dose, since the MUs set for image acquisition are related to dose via the linac calibration. For kV systems, the dose is dependent on the kV or tube current settings. The imaging dose can be monitored indirectly by measuring the mAs, kVp and HVL of the different planar imaging protocols, using detectors such as the Unfors/RaySafe® (see Figure 46.12). In some cases, the dose in mGy can be directly measured. The values can then be compared with the baselines measured during commissioning. The CT dose from the imaging systems can also be monitored using ionisation chambers such as the Raysafe X2 or GafChromic XRQA2 film. The CT dose can be expressed as the computed tomography dose index (CTDI) or dose length product (DLP). The CTDI represents the total dose deposited at a point within a single scan slice during a complete examination and takes into account the scatter contributions from slices above and below the measurement point in question. The DLP is derived as the product of the CTDI and scan length. Dose issues for CBCT are discussed in Section 61.2.2.2 (see also Section 48.2.10).
Introduction and History
Published in Robert L. Dixon, The Physics of CT Dosimetry, 2019
Despite these differences, CTDI has been widely interpreted and used as an indicator of clinical patient dose by regulators and medical physicists alike, in national dose surveys, in imaging literature, in the clinic, etc., and on the CT monitor for every patient scan.
Effect of exposure to ionizing radiation on competitive proliferation and differentiation of hESC
Published in International Journal of Radiation Biology, 2023
Irina V. Panyutin, Paul G. Wakim, Roberto Maass-Moreno, William F. Pritchard, Ronald D. Neumann, Igor G. Panyutin
Cell irradiations were performed using a single X-ray tube of a dual-source CT scanner (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany) as described before (Hanu et al. 2019; Loeliger et al. 2020). Flasks with cells were irradiated with either 50 mGy CT dose index (CTDIvol) delivered as one scan or with 500 mGy CTDIvol, delivered as 10 consecutive axial scans at 120 kVp and a tube current of 666 mAs. As CTDIvol values may not reflect the true absorbed dose to the samples, the absorbed dose was measured using a calibrated, 10 cm long ionization chamber (Fluke, Victoreen 660 with 660-6 probe, Columbus, OH). The doses measured by the probe were calculated as 52 mGy and 572 mGy for low- and high-dose exposures, respectively. The 0 mGy control samples were mock-irradiated with the same scan procedure, but with no actual scan activation. We used a real CT scan exposure as it produces a unique quality of IR. The dose of 50 mGy CTDIvol is a bit higher than a typical dose received by a patient during a CT scan, however, is not unfeasible (Kanal et al. 2017). We anticipated a small effect of IR in our experiments, therefore, we used this higher dose. The dose of 500 mGy CTDIvol was used as an example of the high dose exposure.
The value of iterative metal artifact reduction algorithms during antenna positioning for CT-guided microwave ablation
Published in International Journal of Hyperthermia, 2019
Thuy Duong Do, Claudius Melzig, Dominik F. Vollherbst, Philippe L. Pereira, Hans-Ulrich Kauczor, Marc Kachelrieß, Christof M. Sommer
In the second study, the results of the first study could be confirmed with the overall interaction of the different acquisition and image reconstruction parameters [33]. In both studies, the rationale for choosing the provided CT parameters was operator experience with the intention to optimize image quality and reduce metal artifacts. What remains unclear, however, is why the CT scans were performed with such a high radiation exposure (as can be estimated from the provided tube potential and tube current). Because the nationwide reference values for diagnostic abdominal CT scans define the maximum CTDIvol at 15 mGy for each CT series, we adapted exposure settings so that the CT scan with the highest radiation exposure met this upper threshold [34]. Furthermore, multiple other CT scans feature a markedly lower radiation exposure that also may be used in clinical settings.
The benefits of folic acid-modified gold nanoparticles in CT-based molecular imaging: radiation dose reduction and image contrast enhancement
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Jaber Beik, Maryam Jafariyan, Alireza Montazerabadi, Ali Ghadimi-Daresajini, Parastoo Tarighi, Alireza Mahmoudabadi, Habib Ghaznavi, Ali Shakeri-Zadeh
CTDI value is the most common parameter for estimating radiation dose from a CT examination, developed by Shop et al. [27]. In order to estimate the radiation dose by changing the tube current–time product in a head CT protocol, CTDI value was measured with ion chamber. To this end, a CT ion chamber (RTI Electronics, Mölndal, Sweden) was placed in the centre hole of a CT head phantom (16 cm in diameter and 15 cm in length) and connected to a chamber adaptor and chamber adaptor connected to black piranha (Piranha, RTI Electronics). The phantom was aligned to the centre of the gantry using positioning lasers. Axial scanning of the phantom was performed in all five embedded holes one by one, centre, 12 o’clock, 3 o’clock, 6 o’clock and then 9 o’clock positions under different tube current–time products, ranging from 60–250 mAs and fixed peak tube voltage of 130 KVp. Dosimetry information was stored on a Tablet running Ocean software (RTI Electronics).