Ct image quality pdf

For rt, ct has been used mainly for rt planning rtp and, in recent years, for guiding rt delivery, e. Ninety consecutive patients were randomly assigned. The one comprehensive ct image quality characteristic is visibility. A ct chest examination is one of the most common ct studies worldwide. Computed tomography ct is a technique that uses an xray beam to generate images that have a very good resolution to demonstrate anatomy. Crosssections are reconstructed from measurements of attenuation coefficients of xray beams in the volume of. Studies of ct dose and image quality using clinical and phantom. The most commonly used dose descriptor is ct dose index, which represents the dose to a location e. Conventional head ct scans were obtained in 20 patients all 65 years with history of non. Computed tomography introducing groundbreaking ct products and technologies for decades, we are known as the innovation leader in this field. With the continuing advances in technology there is the capability. Astrength of ct is its ability to visualize structures of low contrast in a subject, a task that is limited primarily by noise and is therefore closely associated with radiation dose.

This is an important starting point because it makes a clear statement about how petct is evolving in a particular country with a view to providing a routine service. Image filters improve image quality and lower patient radiation. Ct quality control manual 4 this manual is designed to help guide facilities in establishing and maintaining an effective ct quality control program. It is certainly worth trying to improve the quality of the scan. To assess the impact on image quality and dose reduction of a new deep learning image reconstruction dlir algorithm compared with a hybrid iterative reconstruction ir algorithm. Computed tomography ct imaging technology is rapidly changing the conditions of image quality optimization and radiation dose reduction.

Imaging parameters were optimized with ct data acquired for a phantom to create image quality enhancement iqe protocols, which were subsequently used to scan a prostate and a pancreatic cancer patient who underwent image guided radiotherapy igrt. Patientbased artifacts are caused by such factors as patient. We compared the image quality of lowmas head ct scans with that of conventional nonenhanced scans. Data acquisitions were performed at seven dose levels ctdi vol. However, visibility depends on a somewhat complex combination of the five 5 more specific image characteristics shown here. When combined together with a dose indicator, a generalised dose efficiency index can be explored in a. Computed tomography ct has been widely used in diagnostics and radiotherapy rt. Even if we image a perfectly uniform object there is still a variation in the hounsfield units about a mean. It commences with a chapter on a radionuclide radiologists perspective about the use of petct in his medical practice. The purpose of our study was to assess the potential benefit of ir in head ct by comparing objective and subjective image quality with standard fbp at various dose levels. Image quality assessment tools for optimization of ct images article pdf available in radiography 162. Each module is 4 cm in depth and 20 cm in diameter.

The higher the dose contributing to the image, the less apparent is image noise and the. Accreditation is required for providers that bill for ct under part b of the medicare physician fee schedule. Pulmonary ct angiography as firstline imaging for pe. The most commonly used dose descriptor is ct dose index, which. The image by the ct scanner is a digital image and consists of a square matrix of elements, each of which represents a voxel volume element of the tissue of the patient. Optimizing a ct protocol is the rather complex process of balancing the image quality characteristics both among themselves and with radiation dose. This article discusses ct radiation dose, the measurement of ct dose, and ct image quality. To provide support for facilities, physicists must understand the scanner features, and how they impact image quality and dose. Manufacturerspecific information on scanner features will be presented.

To reduce radiation yet still produce good quality ct images, more sophisticated methods are needed to process the raw data from the ct system. Almost all image quality characteristics of spiral ct are identical to those of conventional sectionbysection ct. The problem is further enhanced by the inherent property of cbct with its large conebeam geometry which makes it more prone to artifacts and scatter 15 compared to conventional ct. Effect of patient centering on patient dose and image. The purpose of this study was to assess radiation dose and overall image quality of ct examination of the neck between fixedtube current and automatic tube current modulation. Click the manual checkbox a small diamond and then click on the manual box. Spatial resolution ability to image small objects that have high subject contrast 1. The image quality is mainly determined by 3 factors. Imaging techniques in improving image quality of ct. One issue with scanning photos is one of original quality scanning emphasizes any flaws in the image photo to be scanned. This paper is structured into three separate sections that provide an overview of the most common approaches taken when dealing with image quality in ct imaging. Studies of ct dose and image quality using clinical and phantom images haytham ahmad al ewaidat a thesis presented to charles sturt university in fulfillment of the requirements for the degree of doctor of philosophy 20 school of dentistry and health sc. For diagnostic purposes, ct dose is often minimized as long as ct quality is acceptable.

Ct image quality, as in most imaging, is described in terms of contrast,spatialresolution,imagenoise,andartifacts. European guidelines on quality criteria for computed tomography these guidelines result from the cooperative effort of the following european study group of radiologists and physicists involved in diagnostic computed tomography and consultation with experts in the field. Computed tomography technology has made tremendous advances since the technique was introduced in the early 1970s. Image quality assessment tools for optimization of ct images. Noise degrades the image by degrading low contrast resolution and introducing uncertainty in the hounsefield units of the images i. The role of computed tomography ct in modern medicine is well established as a means of diagnosis and also as. Our aim was to compare ct images from native, nephrographic and excretory phases using image quality criteria as well as the detection of positive pathological findings in ct urography, to explore if the radiation burden to the younger group of patients or patients with negative outcomes can be reduced. The purpose of this presentation will be to first describe several of the components of ct image quality noise, slice thickness zaxis resolution, low contrast.

Resolution is the measure of how far two objects must be apart before they can be seen as separate details in the image. A derived model relates the projection quality measures to the actual measurement error of the ct scan. A weighted average of the ct dose index measured at the center and periphery of dose phantoms provides a convenient. Relating noise to image quality indicators in ct examinations. Pdf purposeproducing high quality images in ct is important for image interpretation and to obtain the maximum diagnostic information from the images. Radiology and ct quality control procedures workbook quality control procedures radiographycrdr 1 quality control procedures radiographycrdr safety code 35 summary. Introduction computed tomography ct is now one of the most effective and valuable imaging methods for medical diagnosis and guiding therapeutic procedures.

Ir has recently demonstrated its capacity to reduce noise and permit dose reduction in abdominal and thoracic ct applications. Factors affecting contrastdetail performance in computed. Ct imaging should only be performed in circumstances where the medical benefit outweighs any associated risk, and where the required clinical information that will support a patients treatment cannot be achieved by other imaging methods such as ultrasound or mri, which do not involve radiation exposure. Principles of petct quality control and calibration. Effect of patient centering on patient dose and image noise in. New methods for patientspecific optimization1 of image quality and radiation dose the patientcentered approach to imaging is an increasing focus in radiology departments. Set the scan resolution to no less than 300 dpi to start increase the resolution as possible for your particular printer and or the software being. All facilities must recognize the importance of a quality control program in producing diagnostic quality.

To understand some basic measurements of image quality used in ct. Fundamentally, image quality in ct, as in all medical imaging, depends on 4 basic factors. Any information contained in this pdf file is automatically generated from digital material. Image quality and pathology assessment in ct urography. Comparison of image quality between conventional and low. Pet ct atlas on quality control and image artefacts this publication is an atlas on quality control and pet ct artefacts, providing guidance on the physics and technical aspects behind pet and pet ct image distortions. That is the visibility of anatomical structures, various tissues, and signs of pathology. Resolution is measured in line pairs per centimeter lpcm i. Increasing use of ct for evaluating neurologic disease may expose patients to considerable levels of ionizing radiation. Click the image quality icon and then pick image analysis. There are, of course, much more complete definitions of noise that take into account the contrast scale of the scanner for example, the definition described. A strength of ct is its ability to visualize structures of low contrast in a subject, a task that is limited primarily by noise and is therefore closely associated with radiation dose.

Cheenu kappadath, phd aapm 2014 two functions for ct as part of petct ac of pet higher diagnostic ultralow ctac only ct dose requirement anatomic localization loss of anatomic and. Mam162 vd0203741 for image quality in mammography according to din 6868162. That requires a knowledge of both the science, especially physics, and the evolving technology that is being used. It presents an assortment of cases with examples of possible image distortions and errors, with explanations as to the causes. Pdf assessment of adult patient radiation dose and image. The atcm systems then use patient size and attenuation properties to modulate the xray tube current i. Ct has moderate spatial resolution 20 lpcm 1 contrast resolution ability to distinguish between and image similar tissues 1 ct has excellent low contrast detectability 0. These two curves are called probability density functions pdf. Our portfolio shows unique arguments with regards to artificial intelligence, low dose, workflow optimization and image quality. Evaluation of image quality iq in computed tomography ct is important to. For two objects to be seen as separate the detectors must be able to identify a gap between them. Methodology for the evaluation of ct image quality in.

Evaluation of image quality iq in computed tomography ct is. Ct image quality a summary image noise image noise, in its most simple definition, is measured as the standard deviation of voxel values in a homogenous typically water phantom. Cheenu kappadath, phd aapm 2014 ct pet wo ctac pet with ctac fused petct image courtesy. Consultation with a radiologist and medical physicist, will best assist the technologist in producing acceptable image quality at the. The technical improvements have led to excellent and reliable image quality and in turn to its ubiquitous use in clinical medicine. Principles and practice of petct part 1 a technologists guide. Image quality and dose reduction opportunity of deep learning. Finally, ct provides good image quality in a wide variety of body compositions and clinical conditions with minimal patient discomfort. The ultimate goal of ct optimization is to minimize radiation exposure while maintaining diagnostic image quality. In conclusion, a measurement made by a detector ct is proportional to the sum of the attenuation coefficients.

In ct examinations using atcm, a level of image quality is targeted by setting an image quality indicator. While image quality has always been a concern for the physics community. Image quality and dose are dependent factors generally to increase image quality, dose increases. In general, the relationship between tube current and patient dose is essentially linear, with increases in mas resulting in a comparable percentage increase in patient dose 3. Pdf image quality assessment tools for optimization of. This webinar course will provide an opportunity for medical physicists to increase their understanding of computed tomography, advanced features of scanners, and of the accreditation process. For patients undergoing ct, this includes a personalized examination, one that provides diagnostic image quality. Petct atlas on quality control and image artefacts this publication is an atlas on quality control and petct artefacts, providing guidance on the physics and technical aspects behind pet and petct image distortions. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Pdf image quality assessment tools for optimization of ct images. Dose from ct imaging has an associated risk and should be kept low.

While the benefits of ct have been well documented and. Tradeoffs in ct image quality and radiation dose influenced by. Technical methods for this purpose include the use of automatic exposure control aec i. Improving ct quality with optimized image parameters for. Interpretation of spectct myocardial perfusion images. The aim of the study was to compare radiation dose and image quality for adult routine medical ct examinations performed with automatic exposure control aec and fixed tube current ftc techniques. The advancement of multidetector ct technology has resulted in improved image quality as well as an increase in ionizing radiation dose to patient.

European guidelines on quality criteria for computed tomography. The role of computed tomography ct in modern medicine is well established as a means of diagnosis and also as an essentia. The phantom the acr ct accreditation phantom is a solid phantom containing four modules, and is constructed primarily from a waterequivalent material. Image quality and radiation dose considerations john mayo1. Comparison of image quality between conventional and lowdose. Di and reality hj, pdihj is the pdf to make a decision di when the reality is hj. Since it is still very common to state the lc performance of a ct imaging system via the visibility of single objects, we opted for an observerbased subjective image quality study involving an image quality phantom.

Evaluation of image quality for different kv conebeam ct. Dose and image quality for a conebeam carm ct system. Zeng 1 1division of imaging and applied mathematics office of science and engineering laboratories 2division of radiological devices office of in vitro diagnostic device evaluation cdrh fda challenges to ct image evaluation. Conventional head ct scans were obtained in 20 patients all 65 years with history of noncns malignancy by using a multidetector technique. This is a retrospective study of 40 patients who underwent a ct urography examination on a. All facilities must recognize the importance of a quality control program in producing diagnostic quality images at the lowest appropriate dose. Those advanced methods, called image reconstruction algorithms, can require undesirably long computing times, so they can be used only for some patients currently. Radiology david geffen school of medicine at ucla image quality image quality has many components and is influenced by many technical parameters. Computed tomography ct scanning, also known as, especially in the older literature and textbooks, computerized axial tomography cat scanning, is a diagnostic imaging procedure that uses xrays to build crosssectional images slices of the body. Ct image quality, as in most imaging, is described in terms of contrast, spatial resolution, image noise, and artifacts. To optimize image quality, it is necessary to understand why artifacts occur and how they can be prevented or suppressed. The ct accreditation program involves submission of clinical and phantom images, dose measurements and scanning protocols. For more detail about each quality control qc procedure select the relevant link in the tables below. The two major risks associated with pulmonary cta are contrast toxicity and stochastic pulmonary ct angiography as firstline imaging for pe.

Consideration must always be taken when balancing patient dose with a required level of quality. Physicsbased artifacts result from the physical processes involved in the acquisition of ct data. The patient images were compared with those scanned with standard clinical protocols, the quality of these images was assessed with various. The image analysis tool, shown in the image below, will appear e. A weighted average of the ct dose index measured at the center and periphery of dose phantoms provides a convenient singlenumber estimate. Conebeam ct david spelic, phd division of radiological health. Zeng 1 1division of imaging and applied mathematics office of science and engineering laboratories 2division of radiological devices office of in vitro diagnostic device evaluation cdrh fda.