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Relationship between body habitus and image quality and radiation dose in chest X-ray examinations: A phantom study
摘要： Purpose: To evaluate the influence of being overweight on image quality (IQ), radiation dose and acquisition parameters when undertaking adult chest X-ray (CXR) examinations using routine acquisition protocols. Methods: The Lungman chest phantom, with and without chest plates, was used to simulate the chest region for larger size and average adult patients, respectively. Radiographic acquisitions were conducted using 17 X-ray machines located in eight hospitals using their routine clinical protocols. IQ was assessed using relative visual grading analysis (VGA) and 2 alternative forced choice (2AFC) by six observers. Incident air kerma (IAK) was measured using a solid-state dosimeter. Results: IQ mean (range) scores between the hospitals were 16.2 (12.0–21.3) with a 56.0% difference and 20.9 (14.1–23.6) with a 50.2% difference for the standard and larger size phantoms, respectively. IAK mean (range) scores 63 μGy (19–136 μGy) with a 150% difference and 159 μGy (27–384 μGy) with a 173% difference for the standard and larger size phantoms, respectively. The chest plates had a significant negative impact on IQ (P = 0.001) and lead to an increased in IAK by approximately 50%. Conclusion: Visual measures of IQ and IAK showed large differences between hospitals for standard and larger phantom sizes; differences within the hospitals was lower. Overall, Lungman with chest plates was found to degrade IQ and increase radiation dose by a factor of two. Further optimisation is required especially for the larger sized patient’s imaging protocols for all eight hospitals.
关键词： Overweight,Image quality,Obesity,Adult chest radiography,Dose optimisation,Radiation dose
更新于2025-09-23 15:23:52
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Projection X-ray Imaging
摘要： Recent advances in digital detector technology for medical radiography and fluoroscopy have resulted in improved workflow efficiency, operational flexibility, image quality, and diagnostic accuracy. This is attributed to the implementation of portable flat-panel x-ray detector devices able to provide real-time readout, processing, and display of medical images. As a result, digital radiography flat-panel detectors are rapidly replacing computed radiography passive detectors for projection imaging exams and image intensifier detectors for dynamic fluoroscopy exams. Advanced exam capabilities now include digital tomosynthesis and dual-energy radiography; the former is based on rapid acquisition of multiple angle-dependent image projections to synthesize tomographic slabs at selectable depths within the patient, and the latter is based on rapid back-to-back acquisition of the same anatomy at low and high x-ray energies to generate separate soft tissue and bone images. In both situations, superimposition of anatomy is reduced or eliminated, with the possibility of enhanced diagnostic confidence. Increased x-ray absorption efficiency and lower electronic noise of digital radiography detectors compared to computed radiography detectors enable equal image quality at lower patient dose; however, because of a disconnect between image appearance and radiation dose, lower patient dose is not always achieved. Education, training, and implementation of standards such as the International Electrotechnical Commission 62494-1 Digital Radiography Exposure Index are needed to ensure image quality at the lowest appropriate radiation dose. The National Council on Radiation Protection and Measurements can contribute to radiation responsibility in medical imaging by providing guidance on use of digital radiography, including recommendations for acquisition protocols and exposure index standards, for development of radiographic exam diagnostic reference levels, and for oversight of retake and reject analysis.
关键词： x rays,radiation dose,fluoroscopy,National Council on Radiation Protection and Measurements
更新于2025-09-23 15:23:52
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Readjustment of abdominal computed tomography protocols in a university hospital: impact on radiation dose
摘要： Objective: To assess the reduction of estimated radiation dose in abdominal computed tomography following the implementation of new scan protocols on the basis of clinical suspicion and of adjusted images acquisition parameters. Materials and Methods: Retrospective and prospective review of reports on radiation dose from abdominal CT scans performed three months before (group A – 551 studies) and three months after (group B – 788 studies) implementation of new scan protocols proposed as a function of clinical indications. Also, the images acquisition parameters were adjusted to reduce the radiation dose at each scan phase. The groups were compared for mean number of acquisition phases, mean CTDIvol per phase, mean DLP per phase, and mean DLP per scan. Results: A significant reduction was observed for group B as regards all the analyzed aspects, as follows: 33.9%, 25.0%, 27.0% and 52.5%, respectively for number of acquisition phases, CTDIvol per phase, DLP per phase and DLP per scan (p < 0.001). Conclusion: The rational use of abdominal computed tomography scan phases based on the clinical suspicion in conjunction with the adjusted images acquisition parameters allows for a 50% reduction in the radiation dose from abdominal computed tomography scans.
关键词： Contrast media,Radiation dose,Radiation protection,Computed tomography,Abdomen
更新于2025-09-23 15:23:52
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Coronary artery calcium scoring with photon-counting CT: first in vivo human experience
摘要： To evaluate the performance of photon-counting detector (PCD) computed tomography (CT) for coronary artery calcium (CAC) score imaging at standard and reduced radiation doses compared to conventional energy-integrating detector (EID) CT. A dedicated cardiac CT phantom, ten ex vivo human hearts, and ten asymptomatic volunteers underwent matched EID and PCD CT scans at different dose settings without ECG gating. CAC score, contrast, and contrast-to-noise ratio (CNR) were calculated in the cardiac CT phantom. CAC score accuracy and reproducibility was assessed in the ex vivo hearts. Standard radiation dose (120 kVp, reference mAs = 80) in vivo CAC scans were compared against dose-reduced CAC scans (75% dose reduction; reference mAs = 20) for image quality and CAC score reproducibility. Interstudy agreement was assessed by using intraclass correlation (ICC), linear regression, and Bland–Altman analysis with 95% confidence interval limits of agreement (LOA). Calcium-soft tissue contrast and CNR were significantly higher for the PCD CAC scans in the cardiac CT phantom (all P < 0.01). Ex vivo hearts: CAC score reproducibility was significantly higher for the PCD scans at the lowest dose setting (50 mAs) (P = 0.002); score accuracy was similar for both detector systems at all dose settings. In vivo scans: the agreement between standard dose and low dose CAC score was significantly better for the PCD than for the EID with narrower LOA in Bland–Altman analysis, linear regression slopes closer to 1 (0.96 vs. 0.84), and higher ICC values (0.98 vs. 0.93, respectively). Phantom and in vivo human studies showed PCD may significantly improve CAC score image quality and/or reduce CAC score radiation dose while maintaining diagnostic image quality.
关键词： Radiation dose reduction,Photon-counting CT,Coronary artery calcium score
更新于2025-09-23 15:23:52
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The Application of a New Model-Based Iterative Reconstruction in Low-Dose Upper Abdominal CT
摘要： Rationale and Objectives: To compare upper abdominal computed tomography (CT) image quality of new model-based iterative reconstruction (MBIR) with low-contrast resolution preference (MBIRNR40), conventional MBIR (MBIRc), and adaptive statistical iterative reconstruction (ASIR) at low dose with ASIR at routine-dose. Materials and Methods: Study included phantom and 60 patients who had initial and follow-up CT scans. For patients, the delay phase was acquired at routine-dose (noise index = 10 HU) for the initial scan and low dose (noise index = 20 HU) for the follow-up. The low-dose CT was reconstructed with 40% and 60% ASIR, MBIRc, and MBIRNR40, while routine-dose CT was reconstructed with 40% ASIR. CT value and noise measurements of the subcutaneous fat, back muscle, liver, and spleen parenchyma were compared using one-way ANOVA. Two radiologists used semiquantitative 7-scale (-3 to +3) to rate image quality and artifacts. Results: The phantom study revealed superior low-contrast resolution with MBIRNR40. For patient scans, the CT dose index for the low-dose CT was 3.00 ± 1.32 mGy, 75% lower than the 11.90 ± 4.75 mGy for the routine-dose CT. Image noise for the low-dose MBIRNR40 images was significantly lower than the low-dose MBIRc and ASIR images, and routine-dose ASIR images (p < 0.05). Subjective ratings showed higher image quality for low-dose MBIRNR40, with lower noise, better low-contrast resolution for abdominal structures, and finer lesion contours than those of low-dose MBIRc and ASIR images, and routine-dose ASIR images (p < 0.05). Conclusion: MBIRNR40 with low-contrast resolution preference provides significantly lower noise and better image quality than MBIRc and ASIR in low-dose abdominal CT; significantly better objective and subjective image quality than the routine-dose ASIR with 75% dose reduction.
关键词： Model-based iterative reconstruction,Abdominal CT.,X-ray computed tomography,Adaptive statistical iterative reconstruction,Radiation dose
更新于2025-09-23 15:22:29
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256-Slice Coronary Computed Tomography Angiography Using Low Tube Voltage of 100 KV
摘要： Purpose: To evaluate the image quality and radiation dose of 100 kV with 1000 mAs retrospective electrocardiography (ECG)-gated CCTA protocol, compared to the standard protocol of 120 kV with 800 mAs retrospective ECG-gated CCTA. Material and Methods: We divided 70 patients into two, a reduced dose group with 35 patients (18 M, 17 F; Mean age 56.94 ± 11.51 years) were examined by 100-kV with 1000 mAs retrospective ECG-gated CCTA, and another as a standard group of 35 patients (21, 14 F; Mean age 54.03 ± 9.81 years) were examined by 120-kV with 800 mAs retrospective ECG-gated CCTA. The two blinded radiologists analyzed the image quality of the coronary arteries independently and they accessed subjective and objective image quality. The radiation dose was also measured as effective radiation dose [ED] and was calculated using CT dose volume index [CTDIvol.], dose-length product [DLP] and conversion coefficient for chest (conversion factor k=0.014 mSv mGy-1cm-1). Results: Although the objective image quality of the 100-kV with 1000 mAs was significantly better than the 120-kV with 800 mAs (mean SNR, 36.65 ± 2.95 vs. 33.47 ± 3.86, P<0.0001; mean CNR, 34.27 ± 2.92 vs. 30.62 ± 3.90, P<0.0001). There was no significant variation in the subjective image quality between two groups (mean image score, 4.54 ± 0.37 vs. 4.56 ± 0.25 for radiologist 1, P = 0.781; 4.52 ± 0.25 vs. 4.56 ± 0.25 for radiologist 2, P=0.486). The radiation dose was found to be reduced by 28% with the 100-kV/1000 mAs protocol than with the 120-kV/800 mAs retrospective ECG-gated CCTA (7.87 ± 0.59 vs. 10.95 ± 1.67 mSv, P<0.0001). Conclusion: The protocol of low tube voltage CCTA using 100 kV/1000 mAs retrospective ECG-gated shows significant reduction of the radiation dose without disturbing the subjective image quality of CCTA.
关键词： Coronary CT angiography,Image quality,Radiation dose
更新于2025-09-23 15:21:21
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A Multiport Converter Interfacing Solar Photovoltaic Modules and Energy Storage with DC Microgrid
摘要： A novel real-time optical fibre X-Ray dosimeter for monitoring the radiation pulses delivered from a clinical linear accelerator (Linac) is presented. The primary focus of the sensor is to measure low doses of ionising X-ray radiation in real time (limited to 0.1-ms gate time of the detector). The sensor tip material scintillates upon exposure to X-ray energy and the resultant low-level visible light signal is coupled to a polymethyl methacrylate plastic optical fibre, which is used to guide it towards a distal avalanche photodiode-based detector. The detector measures the low-level scintillating light from the sensor, thereby converting the ionizing radiation energy to a measurable signal with a time resolution of 0.1 ms. Results show that the scintillating optical fibre X-ray dosimeter is capable of capturing the individual X-Ray pulses delivered by the Linac during normal operation. Further examination of the results demonstrates that the sensor is capable of measuring dose rate and, hence, dose with a linearity (R2 = 0.9995 ? 0.9999) and in a highly repeatable manner for dose rates in the range 100 to 600 monitor units/min.
关键词： optical fibre sensors,X-ray dosimetry,Clinical external beam radiotherapy,fluorescent and luminescent sensors,real time radiation dose measurement
更新于2025-09-23 15:21:01
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Combined temperature and radiation effects on radiation sensitive single-mode optical fibers
摘要： A novel real-time optical fibre X-Ray dosimeter for monitoring the radiation pulses delivered from a clinical linear accelerator (Linac) is presented. The primary focus of the sensor is to measure low doses of ionising X-ray radiation in real time (limited to 0.1-ms gate time of the detector). The sensor tip material scintillates upon exposure to X-ray energy and the resultant low-level visible light signal is coupled to a polymethyl methacrylate plastic optical fibre, which is used to guide it towards a distal avalanche photodiode-based detector. The detector measures the low-level scintillating light from the sensor, thereby converting the ionizing radiation energy to a measurable signal with a time resolution of 0.1 ms. Results show that the scintillating optical fibre X-ray dosimeter is capable of capturing the individual X-Ray pulses delivered by the Linac during normal operation. Further examination of the results demonstrates that the sensor is capable of measuring dose rate and, hence, dose with a linearity (R2 = 0.9995 ? 0.9999) and in a highly repeatable manner for dose rates in the range 100 to 600 monitor units/min.
关键词： optical fibre sensors,X-ray dosimetry,Clinical external beam radiotherapy,fluorescent and luminescent sensors,real time radiation dose measurement
更新于2025-09-23 15:21:01
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Enhanced X-ray absorption by using gold nanoparticles in a biological tissue
摘要： In recent years, application of nanoparticles (NPs) in diagnosis and treatment of cancer has been the issue of extensive research. In this study, we investigated the effect of gold nanoparticles (GNPs) in a tumor during X-ray therapy. Our simulation, based on the Monte Carlo method, shows that the GNPs injected into a tumor considerably enhanced the absorbed dose during X-ray therapy, especially in the energy range between 10 keV and 150 keV. This increase in the absorbed dose is due to a combination of increased photoelectric interaction and Auger electron generation from the gold atoms. Furthermore, the absorbed dose in a biological cell is strongly influenced by the size of the GNPs; our results show that the ideal diameter of GNPs should be around 50 nm, and this result was confirmed by several authors.
关键词： human organ,X-ray,radiation dose,tumors
更新于2025-09-23 15:21:01
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Interventional Oncology (Principles and Practice of Image-Guided Cancer Therapy) || Imaging in interventional oncology: Role of image guidance
摘要： Advances in medical imaging have created the opportunity for minimally invasive, image-guided oncologic care by allowing: (1) procedure planning; (2) device delivery; (3) intraprocedure monitoring; and (4) therapy assessment. Although most current image-guided therapy still utilizes standard diagnostic imaging equipment, interventional use of imaging equipment has in fact different priorities compared with diagnostic uses of such equipment. Therefore, interventional procedures prioritize imaging equipment that: (1) provides real-time imaging; (2) lowers radiation dose; and (3) provides greater physician access to the patient. In contrast to diagnostic imaging, lower image quality is an acceptable compromise for real-time imaging for interventional procedures. Patients have already undergone high-quality diagnostic imaging when they are referred to interventional therapies. Moreover, high-quality diagnostic imaging may require more time and more radiation dose than fast imaging of a restricted region of interest as performed for image guidance of interventions.
关键词： image-guided therapy,real-time imaging,physician access,medical imaging,radiation dose,interventional oncology
更新于2025-09-23 15:21:01