Computed Tomography Dose Optimization Research Articles

Establishment of baseline size-specific dose estimate (SSDE) for paediatric head computed tomography (CT) examinations

BackgroundIn recent times, size-specific dose estimate (SSDE) has been the ideal metric for accurate estimation of individual patient doses in computed tomography (CT) examinations. The objective of this study was to estimate patient radiation doses based on SSDE and the water-equivalent diameter (DW) as an effect tool for dose optimization in paediatric head CT at two facilities in Tamale Metropolis, in the northern region of Ghana. This is a preliminary retrospective study conducted on 57 paediatric patients (comprising 32 males and 25 females), aged newborns to 16 years old, who underwent head CT examinations. Patient head sizes were determined in terms DW, which was calculated by manual contouring the circumference of the CT images excluding the background to measure the region of interest (ROI) using the mid-slice axial CT images. SSDE was calculated as the product of CTDIvol and the size-specific conversion coefficients (CTDIvol, 16 to SSDE) obtained from the American Association of Physicists in Medicine (AAPM) Report 293.ResultsAt facility ‘A’, the median SSDE values for patients, aged 3 months to 1 year, 1 to 6 years, and older than 6 years were 46.1 mGy, 39.6 mGy, and 48.2 mGy, respectively. The corresponding CTDIvol values were 42.3 mGy, 39.1 mGy, and 51.7 mGy. Facility ‘B’ reported median SSDE values of 36.0, 39.2, and 43.8 mGy, with corresponding CTDIvol values of 28.7, 39.8, and 46.9 mGy for the same age categories. For all age groups, the two facilities showed significant differences in SSDE values (44.72 mGy vs. 39.77 mGy, p = 0.009) and CTDIvol values (45.72 mGy vs. 40.60 mGy, p = 0.03). Some of the age group doses were up to 25.3% in CTDIvol and 25.8% in SSDE higher than those found in published data.ConclusionsThe SSDEs estimated showed significant variations between the two facilities, indicating a possible variability of scan protocols for paediatric head CT examinations. The SSDEs obtained in this study could be useful for optimization of paediatric routine head CT examinations.

Clinical and technical challenges associated with CT dose optimization in practice

Radiation burden represents a particular issue in realizing the greater benefits of computed tomography (CT), conceptual dose levels, real-time and offline dose monitoring software being among major efforts towards optimizing the benefit. Here we share technical and clinical challenges faced on a regional scale in implementing such tools in clinical practice. Conceptual dose baselines, although not limited to the diagnostic reference level (DRL), have for CT been based on anatomical body parts such as the head, chest, abdomen etc. The methodology and calculations used in establishing DRLs have nevertheless resulted in wide variability across CT dose indices. Example, DLP based head trauma DRLs have been reported as 556 mGy cm, 753 mGy cm, and 1820 mGy cm. The suggestion is of a need to establish DRLs based on examinations sharing similar objectives, in particular focusing on clinical indications, seeking to reduce the wide dose variations associated with anatomical based DRLs. Implementing this clinically is a challenge, particularly since CT scan acquisition series are not directly linked nor labeled according to clinical indications. Alternatively, clinical indications are more applicable when linked with CT protocols which are saved on the CT console and easily retrieved. Dose variation is also seen with use of the same protocol, scan coverage and number of scan acquisition series being contributing factors. DRLs based on scan acquisition series for every protocol allows better control and elimination of confounding factors.

Advanced Computational Methods for Radiation Dose Optimization in CT.

In planning radiotherapy treatments, computed tomography (CT) has become a crucial tool. CT scans involve exposure to ionizing radiation, which can increase the risk of cancer and other adverse health effects in patients. Ionizing radiation doses for medical exposure must be kept "As Low As Reasonably Achievable". Very few articles on guidelines for radiotherapy-computed tomography scans are available. This paper reviews the current literature on radiation dose optimization based on the effective dose and diagnostic reference level (DRL) for head, neck, and pelvic CT procedures used in radiation therapy planning. This paper explores the strategies used to optimize radiation doses, and high-quality images for diagnosis and treatment planning. A cross-sectional study was conducted on 300 patients with head, neck, and pelvic region cancer in our institution. The DRL, effective dose, volumetric CT dose index (CTDIvol), and dose-length product (DLP) for the present and optimized protocol were calculated. DRLs were proposed for the DLP using the 75th percentile of the distribution. The DLP is a measure of the radiation dose received by a patient during a CT scan and is calculated by multiplying the CT dose index (CTDI) by the scan length. To calculate a DRL from a DLP, a large dataset of DLP values obtained from a specific imaging procedure must be collected and can be used to determine the median or 75th-percentile DLP value for each imaging procedure. Significant variations were found in the DLP, CTDIvol, and effective dose when we compared both the standard protocol and the optimized protocol. Also, the optimized protocol was compared with other diagnostic and radiotherapy CT scan studies conducted by other centers. As a result, we found that our institution's DRL was significantly low. The optimized dose protocol showed a reduction in the CTDIvol (70% and 63%), DLP (60% and 61%), and effective dose (67% and 62%) for both head, neck, and pelvic scans. Optimized protocol DRLs were proposed for comparison purposes.

Feasibility study for the evaluation of doses received by organs during medical exposure for pediatric patient undergoing CT scan and estimation of the potential risk of radiation-induced cancers

Computed Tomography (CT) continues to contribute a significant portion of the total collective dose delivered to the public from medical procedures involving ionizing radiation. Children are considered to be at higher risk of developing radiation induced cancer due to the young age of exposure and increased tissue radio sensitivity. Organ dose estimation is essential for pediatric patient cancer risk assessment. The aim of this study was to evaluate the excess risk of radiation induced cancer following exposure to low-dose ionizing radiation from pediatric CT scans.We collected information from Radiation Dose Structured Report (RDSR) in 2 radiology department for 3 protocols and three (3) different age group in pediatric CT scan.We estimated the excess of cancer risk by using the Radiation Risk Assessment Tool RadRAT). For that, we calculate first the organ doses with National Cancer Institute for CT (NCICT). Effective dose and Size Specific Dose Estimate were also estimated, CTDI and DLP recorded from the RDSR were compared by the ones given by the software. The doses received by 30 organs including both inside and outside the scanning range were calculated and compared for the different age groups and protocols.The excess risk observed here range between 0.6 and 10.1‰ for respectively the thorax and Abdomen protocol in boy's cohort. This can be due to the significant dose variability observed among radiological protocols defined for the same CT scan and patient of the same age. For a head examination, a ratio of 2–4, depending on the age of the child, is estimated between the maximum and minimum doses delivered to the brain. For the other types of examination, this ratio is even greater: around 9 for chest examinations, 16 for abdominopelvic explorations.Careful justification of pediatric CT scans and dose optimization should be available in hospitals to minimize risks.

A Comprehensive Review of GAN-Based Denoising Models for Low-Dose Computed Tomography Images

Computed Tomography (CT) offers great visualization of the intricate internal body structures. To protect a patient from the potential radiation-related health risks, the acquisition of CT images should adhere to the “as low as reasonably allowed” (ALARA) standard. However, the acquired Low-dose CT (LDCT) images are inadvertently corrupted by artifacts and noise during the processes of acquisition, storage, and transmission, degrading the visual quality of the image and also causing the loss of image features and relevant information. Most recently, generative adversarial network (GAN) models based on deep learning (DL) have demonstrated ground-breaking performance to minimize image noise while maintaining high image quality. These models’ ability to adapt to uncertain noise distributions and representation-learning ability makes them highly desirable for the denoising of CT images. The state-of-the-art GANs used for LDCT image denoising have been comprehensively reviewed in this research paper. The aim of this paper is to highlight the potential of DL-based GAN for CT dose optimization and present future scope of research in the domain of LDCT image denoising.

Diagnostic reference level for computed tomography abdominal examinations: A multicentre study

Computed tomography (CT) represents one of the largest sources of medical diagnostic ionizing radiation exposures to patients. As with other radiological imaging procedures, optimization leading to adoption of diagnostic reference levels (DRL) is recommended, mitigating unnecessary exposure. Present study has made evaluation of patient exposures, seeking a national DRL in Sudan for several abdominal CT techniques. In a study involving 16 radiology departments, data were obtained in imaging of a total of 321 patients examined for issues associated wtith the abdomen and pelvis. Patient weight and age ranges were 65–75 kg and 18–70 years respectively. Observed have been abdomen and abdomen-pelvis dose length products (DLP) in the range 1331 mGy cm to 3172 mGy cm and 370 mGy cm to 1687 mGy cm, respectively. The mean and range of CTDIvol (in mGy) for the abdomen and abdomen-pelvis respectively were found to be 28.2 (3.0–13.0) and 26.0 (4.0–80.0). Patient doses were observed to vary both between departments and within the same department, wide variation in technical settings suggesting need for staff training in CT dose optimization techniques. The patient doses are found to be greater than those typically observed in other studies elsewhere. DRLs are proposed for all of the investigated CT procedures.

Barriers to CT Dose Optimization: The Challenge of Organizational Change

The use of diagnostic imaging with computed tomography (CT) has risen significantly, increasing cumulative life-time exposure to ionizing radiation for patients and raising concerns about increased cancer risk. Lowering the doses would reduce concerns about associated cancer risks. To determine organizational leaders' perceptions of barriers to optimizing radiation dose in CT. An observational study using semistructured interviews conducted with 26 organizational leaders from 19 health care systems in the United States, Europe, and Japan. Interviews focused on approaches the organizations used to optimize radiation dose and barriers encountered. Data were analyzed using a directed content analysis approach. Analysis identified six primary barriers to dose optimization: (1) resistance to change, (2) limited time and resources, (3) complex organizational structure, (4) lack of leadership support, (5) variations in CT equipment, and (6) variability in CT protocols. Barriers to optimizing CT dose across diverse health care organizations were described by organizational leaders tasked with implementing and improving CT imaging. They identified six consistent themes that reflected barriers to optimizing radiation dose at the organizational level. These barriers impeded efforts by health care organizations to optimize radiation doses to patients from CT imaging. Identifying barriers early in any improvement process is an important first step in making meaningful and sustained change.

Achieving CT Regulatory Compliance: A Comprehensive and Continuous Quality Improvement Approach

Computed tomography (CT) represents one of the largest sources of radiation exposure to the public in the United States. Regulatory requirements now mandate dose tracking for all exams and investigation of dose events that exceed set dose thresholds. Radiology practices are tasked with ensuring quality control and optimizing patient CT exam doses while maintaining diagnostic efficacy. Meeting regulatory requirements necessitates the development of an effective quality program in CT. This review provides a template for accreditation compliant quality control and CT dose optimization. The following paper summarizes a large health system approach for establishing a quality program in CT and discusses successes, challenges, and future needs.

CT dose optimization

The advances in computed tomography (CT) technology have expanded the clinical applications of CT imaging. As a result the use of CT has been markedly increased over the recent years raising concerns about the stochastic risks of radiation and consequently safety in patient’s care. To comply with the “as low as reasonably achievable” principle, there is need to develop appropriate strategies to optimize CT examinations. CT manufacturers strive to develop techniques to reduce radiation dose while delivering tomographic images of diagnostic quality. Automatic exposure control systems and iterative reconstruction algorithms constitute the state of the art techniques for radiation dose optimization in CT. However, technological advancements have led to the introduction of new parameters that complicate CT examination protocols. Parameters that affect radiation dose and image quality in CT include quality reference tube current, quality reference image noise, tube voltage, quality reference contrast to noise ratio, beam width, pitch, length of z-overscan, reconstruction kernel, weight of blending between filtered back projection and iterative reconstruction algorithms. To optimize CT examination protocols, a basic understanding of CT scan parameters and their effect on image quality is required. CT radiation dose optimization is an important issue that needs to be addressed first by CT vendors and consequently by radiologists, medical physicists and radiologic technologists. In this presentation the basic principles of CT radiation exposure and the strategies followed for CT radiation dose optimization from the medical physicist’s perspective are reviewed.

The advantages of using average attenuation metrics to express patient size in computed tomography dose optimization

Introduction Dose comparisons are essential to the process of dose optimization in computed tomography (CT). Large-scale databases, and size-specific dose estimates (SSDE), made comparisons less dependent on patient size. However, quantification of patient size would still be useful, to allow comparisons between different patient populations and different scanners. Moreover, when optimizing acquisition protocols after installation of a new scanner, dose data will be collected first for a small number of patients, and it is important that this can be compared with an established standard. Purpose To assess the feasibility of using the water equivalent diameter (Dw) instead of patient weight to quantify patient size. Materials and methods Existing data from a previous survey was re-analyzed using Dw metrics. Two different values of Dw were obtained for each exam: the midscan or central Dw (Dw_c) used for calculation of SSDE, and the average value of Dw in the scanned region (Dw_a). The data pertained to adult chest and chest-abdomen-pelvis (CAP) exams, in two 16 slice CT scanners (a GE Lightspeed and a Toshiba Aquilion RXL). Results The volume CT dose index (CTDIvol) and the SSDE were plotted as a function of patient weight, body mass index (BMI), Dw_c and Dw_a. The use of Dw_a was found to reduce the dispersion of the data, relative to all the other metrics used, allowing a clearer visualization. Conclusion Dw_a proved a robust and useful metric to characterize patient size, which can be used for comparisons of both small and large data sets. Disclosure The authors have no relevant financial or non-financial relationships to disclose.

Image processing as a potential tool for CT dose optimization

Introduction Automatic tube current modulation (ATCM) is an important tool for dose optimization in computed tomography (CT). Optimization of ATCM parameters is usually done by trial and error. In a 2009 study by IAEA, image processing (noise addition) was used to simulate lower dose acquisitions. Purpose The aim of this work is to assess the potential of image processing as a routine auxiliary tool for CT dose optimization. Materials and methods In this first stage, only CT exams without iterative reconstruction (IR) were considered. A process to add noise to DICOM® images was developed, to simulate acquisitions with lower tube current (I). This was tested using phantom images, acquired with different I values, and then applied to real exams. CT images in the liver region were selected from 13 archived exams, and dose reductions of 15% and 33% were simulated. Two experienced Radiologists evaluated the original and virtual images in terms of diagnostic quality, noise and artifacts. Results Standard deviation (SD) in virtual images of phantoms agreed well with the expected values, within the range of variation observed for acquisitions with the same parameters. Diagnostic quality scores were slightly lower for the virtual images, but the results obtained highlight the subjectivity of image quality evaluation. Some virtual images were classified as having less artifacts than the original ones, as a result of reduced sampling. Conclusion This study was well received by radiologists, and implemented using commonly available software. The challenge is to develop a robust method of image quality evaluation. Disclosure The authors have no relevant financial or non-financial relationships to disclose.

MO‐DE‐204‐04: Dose Optimization in CT: Trends and Motivation in the US

The main topic of the session is to show how dose optimization is being implemented in various regions of the world, including Europe, Australia, North America and other regions.A multi‐national study conducted under International Atomic Energy Agency (IAEA) across more than 50 less resourced countries gave insight into patient radiation doses and safety practices in CT, mammography, radiography and interventional procedures, both for children and adults. An important outcome was the capability development on dose assessment and management.An overview of recent European projects related to CT radiation dose and optimization both to adults and children will be presented. Existing data on DRLs together with a European methodology proposed on establishing and using DRLs for paediatric radiodiagnostic imaging and interventional radiology practices will be shown.Compared with much of Europe at least, many Australian imaging practices are relatively new to the task of diagnostic imaging dose optimisation. In 2008 the Australian Government prescribed a requirement to periodically compare patient radiation doses with diagnostic reference levels (DRLs), where DRLs have been established. Until recently, Australia had only established DRLs for computed tomography (CT). Regardless, both professional society and individual efforts to improved data collection and develop optimisation strategies across a range of modalities continues. Progress in this field, principally with respect to CT and interventional fluoroscopy will be presented.In the US, dose reduction and optimization efforts for computed tomography have been promoted and mandated by several organizations and accrediting entities. This presentation will cover the general motivation, implementation, and implications of such efforts. Learning Objectives: Understand importance of the dose optimization in Diagnostic Radiology. See how this goal is achieved in different regions of the World. Learn about the global trend in the dose optimization and future prospectives.M. Rehani, The work was a part of the work of IAEA where I was an employee and IAEA is a United Nations organization

The application of automatic tube current modulation (ATCM) on image quality and radiation dose at abdominal computed tomography (CT): A phantom study

Multi-phase spiral Computed tomography (CT) of abdomen has been widely used as an effective imaging modality to diagnose variety of diseases. As a result, the accumulated radiation exposure on the abdomen is substantially higher than other human organ regions. According to ALARA (as low as reasonably achievable) principle, how to control radiation dose without compromising imaging quality becomes a research topic of high interest. However, how to achieve dose optimization of the abdomen CT examinations in Chinese patients have not been fully investigated in previous studies. In this study, we develop an abdomen-equivalent tissue model made by well-known CTP579 auxiliary testing model and the real CT data acquired from 68 Chinese male subjects. Combining with catphan600, we simulated the visibility of low and high contrast objects at adult abdomen under variety of x-ray dose levels. Using the automatic tube current modulation (ATCM) technique, we reduced the total radiation dose and identified a proper noise index (NI) for Chinese patients to maintain low or high contrast detectability of abdominal CT image. Our numerical experiments showed that in the phantom study for Chinese patients, when a NI was set at 10, the radiation dose reduced by 34.3% with low contrast objects detectable, while setting NI at 14 the dose level decreased by 65.1% without change the detectability of high contrast targets. The subjective ratings from three radiologists also yielded high consistence with Kappa > 0.75. This study demonstrated the feasibility of performing the CT dose optimization studies through a unique phantom with the ATCM method.

THE DEVIATION OF LIVER DOSE IN REAL PATIENTS FOR THORACIC COMPUTED TOMOGRAPHY SCANS: A NEW APPROACH TO INDIVIDUAL DOSIMETRY WITH METHODS OF RADIOTHERAPY TREATMENT PLANNING

The increasing use of computed tomography (CT) in diagnostic imaging is associated with a relevant increase in patient dose and requires CT dose optimization. Anthropomorphic phantoms and mathematical patient models have been developed to improve the dosimetry in diagnostic imaging. Nevertheless, the doses calculated in these models and the ones individual patients can receive may differ considerably. In particular, the assessment of organ doses is problematic when organs and tissues receive only a partial exposure. A typical example for this situation is the exposure of the liver within a thoracic CT. To evaluate the impact of the field boundary and the liver volume on the individual organ dose, 50 CT scans from 25 male and 25 female patients between the ages of 27 to 87 were analyzed in this study with the volumetric tools of a treatment planning system for radiotherapy. The relative volume of the liver within a thoracic CT was assessed and compared to results from dosimetry methods using standardized patient models. The differences between an individual dose and the results from standardized patients are considerable. The fraction of the liver volume within a thoracic CT with a standard lower boundary extends from 48-92%, resulting in a possible dose difference of up to a factor of 1.7. Results from mathematical phantoms can underestimate the liver dose by more than a factor of 2.6. From the determined data, correction factors for the dosimetry of the liver using standard programs can be derived.

CT Dose Index and Patient Dose: They AreNotthe Same Thing

Estimates of individual patient risk, and epidemiologic studies assessing potential late effects, must use patient size–specific dose estimates—they cannot use only scanner output (volume CT dose index or dose-length product).

Computed Tomography Radiation Dose: A Primer for Administrators

The use of computed tomography (CT) is growing, and, consequently, the associated radiation dose to patients is increasing as well. There is also increasing evidence linking the radiation dose within the range of diagnostic CT with a significantly increased risk of malignancy. These two factors combine to make radiation dose from diagnostic CT a public health concern. In order to practise to the best of our abilities and avoid harming patients, the radiation dose from CT must be minimized. Administrators, technologists, radiologists and other physicians are encouraged to work toward this goal through the use of education and a multi-faceted team approach. The objective of this paper is to educate healthcare professionals about the radiation dose from diagnostic CT, including utilization rates, typical examination doses and the risks of this radiation. Our experience in Saskatchewan is discussed. Suggestions regarding CT dose management and optimization are highlighted.