Iterative reconstruction methods in X-ray CT

Beister, Marcel; Kolditz, Daniel; Kalender, Willi A.

doi:10.1016/j.ejmp.2012.01.003

Cited by 653 publications

(478 citation statements)

References 62 publications

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“…Hence, a new algorithm called iterative reconstruction (IR) has been proposed by manufacturers-used in the past and abandoned because of the long reconstruction time imposed by older computers-which is currently capable of additional dose reduction [21]. Beister et al [22] published an extensive review of the different modalities of dose reduction systems (Table 3).…”

Section: Dose Reduction Systemsmentioning

confidence: 99%

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CT exposure in adult and paediatric patients: a review of the mechanisms of damage, relative dose and consequent possible risks

et al. 2014

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An increase has been observed not only in the absolute number of CT examinations but also in the length of coverage and number of scanning phases, with the result that exposure to ionising radiation from CT is becoming an increasingly serious problem. The extent of the problem is not entirely known and cannot be adequately addressed without proper knowledge of all the phases that leads to the effective dose calculation. In light of the growing awareness of the issue of ionising radiation dose and the possible risk for the individual and the population, there is a need for radiologists, medical physicists and radiographers to play an active role in dose management. In this review, the authors try to delineate the problem in a consequential and multifaceted way: radiation-patient interaction, possible mechanisms of damage, main CT dose units, risk and its quantification in the population, with the aim of optimising the acquisition dose without diagnostic drawbacks. For an ''up-to-date'' use of CT, radiologists must know the dose concerns for the single patient and population, and use the CT apparatus with the best dose care; substitute CT with other diagnostic techniques when possible, especially in children; reduce the number/extension of scans and phases, and the dose in single scans and single examinations.

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Section: Dose Reduction Systemsmentioning

confidence: 99%

“…However, it is possible to divide these modalities into two types: those working on the control of the images, using a statistical method for noise reduction, and those directly managing the raw data domain. The latter allow for a further dose reduction, but imply a complex analysis with longer processing time [22].…”

Section: Dose Reduction Systemsmentioning

confidence: 99%

CT exposure in adult and paediatric patients: a review of the mechanisms of damage, relative dose and consequent possible risks

et al. 2014

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“…The educational platform has been designed to include the following features: (1) the basic concepts of the Digital Imaging and Communications in Medicine (DICOM) protocol [19] for storing and transferring medical images, (2) the principles of acquiring projections forming the sinogram of an imaged object, (3) the principles of reconstructing tomographic images from their projections using either the filtered back projection (FBP) or iterative reconstruction (IR) methods [20,21], and (4) image processing using (a) the information from the corresponding intensity histogram and (b) a number of filters applied in the spatial or frequency domains [11]. A number of options were provided for assisting users in the understanding of the parameters that affect medical image quality, quantified using the modulation transfer function (MTF) [23].…”

Section: Design Considerationsmentioning

confidence: 99%

A Web Simulation of Medical Image Reconstruction and Processing as an Educational Tool

et al. 2014

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Web educational resources integrating interactive simulation tools provide students with an in-depth understanding of the medical imaging process. The aim of this work was the development of a purely Web-based, open access, interactive application, as an ancillary learning tool in graduate and postgraduate medical imaging education, including a systematic evaluation of learning effectiveness. The pedagogic content of the educational Web portal was designed to cover the basic concepts of medical imaging reconstruction and processing, through the use of active learning and motivation, including learning simulations that closely resemble actual tomographic imaging systems. The user can implement image reconstruction and processing algorithms under a single user interface and manipulate various factors to understand the impact on image appearance. A questionnaire for pre-and post-training self-assessment was developed and integrated in the online application. The developed Web-based educational application introduces the trainee in the basic concepts of imaging through textual and graphical information and proceeds with a learning-by-doing approach. Trainees are encouraged to participate in a pre-and post-training questionnaire to assess their knowledge gain. An initial feedback from a group of graduate medical students showed that the developed course was considered as effective and well structured. An e-learning application on medical imaging integrating interactive simulation tools was developed and assessed in our institution.

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“…Moreover, such conditions are likely to produce inaccurate estimates of CT Hounsfield numbers. Recently, iterative reconstruction techniques have been developed to more effectively mitigate image artifacts and reduce image noise 2 , 3 . In radiotherapy, CT simulation images have been frequently utilized in specific tasks, including determination of tissue electron density (via CT Hounsfield numbers) and delineation of tumor and normal organ anatomy (by either manual techniques or increasingly by the use of semiautomated or automated techniques) 4 , 5 , 6 , 7 , 8 .…”

Section: Introductionmentioning

confidence: 99%

A comparative study based on image quality and clinical task performance for CT reconstruction algorithms in radiotherapy

Dolly

Chen

et al. 2016

J Applied Clin Med Phys

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CT image reconstruction is typically evaluated based on the ability to reduce the radiation dose to as‐low‐as‐reasonably‐achievable (ALARA) while maintaining acceptable image quality. However, the determination of common image quality metrics, such as noise, contrast, and contrast‐to‐noise ratio, is often insufficient for describing clinical radiotherapy task performance. In this study we designed and implemented a new comparative analysis method associating image quality, radiation dose, and patient size with radiotherapy task performance, with the purpose of guiding the clinical radiotherapy usage of CT reconstruction algorithms. The iDose4iterative reconstruction algorithm was selected as the target for comparison, wherein filtered back‐projection (FBP) reconstruction was regarded as the baseline. Both phantom and patient images were analyzed. A layer‐adjustable anthropomorphic pelvis phantom capable of mimicking 38–58 cm lateral diameter‐sized patients was imaged and reconstructed by the FBP and iDose4 algorithms with varying noise‐reduction‐levels, respectively. The resulting image sets were quantitatively assessed by two image quality indices, noise and contrast‐to‐noise ratio, and two clinical task‐based indices, target CT Hounsfield number (for electron density determination) and structure contouring accuracy (for dose‐volume calculations). Additionally, CT images of 34 patients reconstructed with iDose4 with six noise reduction levels were qualitatively evaluated by two radiation oncologists using a five‐point scoring mechanism. For the phantom experiments, iDose4 achieved noise reduction up to 66.1% and CNR improvement up to 53.2%, compared to FBP without considering the changes of spatial resolution among images and the clinical acceptance of reconstructed images. Such improvements consistently appeared across different iDose4 noise reduction levels, exhibiting limited interlevel noise (<5 HU) and target CT number variations (<1 HU). The radiation dose required to achieve similar contouring accuracy decreased when using iDose4 in place of FBP, up to 32%. Contouring accuracy improvement for iDose4 images, when compared to FBP, was greater in larger patients than smaller‐sized patients. Overall, the iDose4 algorithm provided superior radiation dose control while maintaining or improving task performance, when compared to FBP. The reader study on image quality improvement of patient cases shows that physicians preferred iDose4‐reconstructed images on all cases compared to those from FBP algorithm with overall quality score: 1.21 vs. 3.15, p=0.0022. However, qualitative evaluation strongly indicated that the radiation oncologists chose iDose4 noise reduction levels of 3–4 with additional consideration of task performance, instead of image quality metrics alone. Although higher iDose4 noise reduction levels improved the CNR through the further reduction of noise, there was pixelization of anatomical/tumor structures. Very‐low‐dose scans yielded severe photon starvation artifacts, which decreased target visu...

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Iterative reconstruction methods in X-ray CT

Cited by 653 publications

References 62 publications

CT exposure in adult and paediatric patients: a review of the mechanisms of damage, relative dose and consequent possible risks

CT exposure in adult and paediatric patients: a review of the mechanisms of damage, relative dose and consequent possible risks

A Web Simulation of Medical Image Reconstruction and Processing as an Educational Tool

A comparative study based on image quality and clinical task performance for CT reconstruction algorithms in radiotherapy

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