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Spie Press Book

Computed Tomography: Principles, Design, Artifacts, and Recent Advances, Second Edition
Author(s): Jiang Hsieh

Book Description

X-ray computed tomography (CT) continues to experience rapid growth, both in basic technology and new clinical applications. Seven years after its first edition, Computed Tomography: Principles, Design, Artifacts, and Recent Advancements, Second Edition, provides an overview of the evolution of CT, the mathematical and physical aspects of the technology, and the fundamentals of image reconstruction algorithms. Image display is examined from traditional methods used through the most recent advancements. Key performance indices, theories behind the measurement methodologies, and different measurement phantoms in image quality are discussed. The CT scanner is broken down into components to provide the reader with an understanding of their function, their latest advances, and their impact on the CT system. General descriptions and different categories of artifacts, their causes, and their corrections are considered at length.

Given the high visibility and public awareness of the impact of x-ray radiation, the second edition features a new chapter on x-ray dose and presents different dose reduction techniques ranging from patient handling, optimal data acquisition, image reconstruction, and post-process. Based on the advancements over the past five years, the second edition added new sections on cone beam reconstruction algorithms, nonconventional helical acquisition and reconstruction, new reconstruction approaches, and dual-energy CT. Finally, new to this edition is a set of problems for each chapter, providing opportunities to enhance reader comprehension and practice the application of covered material.


Book Details

Date Published: 19 November 2009
Pages: 572
Volume: PM188

Table of Contents
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Contents

Preface xi
Nomenclature and Abbreviations xiii
1 Introduction 1
1.1 Conventional X-ray Tomography 2
1.2 History of Computed Tomography 7
1.3 Different Generations of CT Scanners 14
1.4 Problems 19
2 Preliminaries 23
2.1 Mathematics Fundamentals 23
    2.1.1 Fourier transform and convolution 23
    2.1.2 Random variables 27
    2.1.3 Linear algebra 30
2.2 Fundamentals of X-ray Physics 34
    2.2.1 Production of x-rays 34
    2.2.2 Interaction of x-rays with matter 37
2.3 Measurement of Line Integrals and Data Conditioning 42
2.4 Sampling Geometry and Sinogram 47
2.5 Problems 49
3 Image Reconstruction 55
3.1 Introduction 55
3.2 Several Approaches to Image Reconstruction 57
3.3 The Fourier Slice Theorem 61
3.4 The Filtered Backprojection Algorithm 65
    3.4.1 Derivation of the filtered back-projection formula 68
    3.4.2 Computer implementation 71
    3.4.3 Targeted reconstruction 85
3.5 Fan Beam Reconstruction 88
    3.5.1 Reconstruction formula for equi-angular sampling 89
    3.5.2 Reconstruction formula for equal-spaced sampling 95
    3.5.3 Fan-beam to parallel-beam rebinning 97
3.6 Iterative Reconstruction 101
    3.6.1 Mathematics verses reality 102
    3.6.2 The general approach to iterative reconstruction 103
    3.6.3 Modeling of scanner's optics and physics 105
    3.6.4 Updating strategy 109
3.7 Problems 112
4 Image Presentation 119
4.1 CT Image Display 119
4.2 Volume Visualization 123
    4.2.1 Multiplanar reformation 123
    4.2.2 MIP, minMIP, and volume rendering 128
    4.2.2 Surface rendering 136
4.3 Impact of the Visualization Tools 137
4.4 Problems 140
5 Key Performance Parameters of the CT Scanner 143
5.1 High-Contrast Spatial Resolution 143
    5.1.1 In-plane resolution 144
    5.1.2 Slice sensitivity profile 150
5.2 Low-Contrast Resolution 154
5.3 Temporal Resolution 160
5.4 CT Number Accuracy and Noise 167
5.5 Performance of the Scanogram 172
5.6 Problems 174
6 Major Components of the CT Scanner 179
6.1 System Overview 179
6.2 The X-ray Tube and High-Voltage Generator 180
6.3 The X-ray Detector and Data-Acquisition Electronics 190
6.4 The Gantry and Slip-Ring 197
6.5 Collimation and Filtration 199
6.6 The Reconstruction Engine 202
6.7 Problems 203
7 Image Artifacts: Appearances, Causes, and Corrections 207
7.1 What Is an Image Artifact? 207
7.2 Different Appearances of Image Artifacts 209
7.3 Artifacts Related to System Design 214
    7.3.1 Aliasing 214
    7.3.2 Partial volume 226
    7.3.3 Scatter 231
    7.3.4 Noise-induced streaks 235
7.4 Artifacts Related to X-ray Tubes 239
    7.4.1 Off-focal radiation 239
    7.4.2 Tube arcing 242
    7.4.3 Tube rotor wobble 244
7.5 Detector-induced Artifacts 244
    7.5.1 Offset, gain, nonlinearity, and radiation damage 244
    7.5.2 Primary speed and afterglow 248
    7.5.3 Detector response uniformity 253
7.6 Patient-induced Artifacts 258
    7.6.1 Patient motion 258
    7.6.2 Beam hardening 270
    7.6.3 Metal artifacts 280
    7.6.4 Incomplete projections 283
7.7 Operator-induced Artifacts 288
7.8 Problems 291
8 Computer Simulation and Analysis 301
8.1 What is Computer Simulation 301
8.2 Simulation Overview 303
8.3 Simulation of Optics 305
8.4 Computer Simulation of Physics-related Performance 316
8.5 Problems 323
9 Helical or Spiral CT 327
9.1 Introduction 327
    9.1.1 Clinical needs 327
    9.1.2 Enabling technology 331
9.2 Terminology and Reconstruction 332
    9.2.1 Helical pitch 332
    9.2.2 Basic reconstruction approach 333
    9.2.3 Selection of the interpolation algorithm and reconstruction plane 339
    9.2.4 Helical fan-to-parallel rebinning 343
9.3 Slice-Sensitivity Profile and Noise 348
9.4 Helically Related Image Artifacts 355
    9.4.1 High-pitch helical artifacts 355
    9.4.2 Noise-induced artifacts 360
    9.4.3 System-misalignment-induced artifacts 364
    9.4.4 Helical artifacts caused by object slope 368
9.5 Problems 371
10 Multislice CT 375
10.1 The Need for Multislice 375
10.2 Detector Configurations of Multislice CT 378
10.3 Nonhelical Mode of Reconstruction 385
10.4 Multislice Helical Reconstruction 396
    10.4.1 Selection of interpolation samples 398
    10.4.2 Selection of region of reconstruction 402
    10.4.3 Reconstruction algorithms with 3D backprojection 405
10.5 Multislice Artifacts 410
    10.5.1 General description 410
    10.5.2 Multislice CT cone-beam effects 411
    10.5.3 Interpolation-related image artifacts 414
    10.5.4 Noise-induced multislice artifacts 416
    10.5.5 Tilt artifacts in multislice CT 417
    10.5.6 Distortion in step-and-shoot mode SSP 419
    10.5.7 Artifacts due to geometric alignment 421
    10.5.8 Comparison of multislice and single-slice helical CT 422
10.6 Problems 424
11 X-ray Radiation and Dose-Reduction Techniques 435
11.1 Biological Effects of X-ray Radiation 436
11.2 Measurement of X-ray dose 437
    11.2.1 Terminologies and the measurement Standard 438
    11.2.2 Other measurement units and methods 444
    11.2.3 Issues with the current CTDI 445
11.3 Methodologies for Dose Reduction 446
    11.3.1 Tube-current modulation 448
    11.3.2 Umbra-penumbra and overbeam issues 449
    11.3.3 Physiological gating 452
    11.3.4 Organ-specific dose reduction 455
    11.3.5 Protocol optimization and impact of the operator 458
    11.3.6 Postprocessing techniques 463
    11.3.7 Advanced reconstruction 464
11.4 Problems 465
12 Advanced CT Applications 471
12.1 Introduction 471
12.2 Cardiac Imaging 473
    12.2.1 Coronary artery calcification (CAC) 474
    12.2.2 Coronary artery imaging 478
      12.2.2.1 Data acquisition and reconstruction 480
      12.2.2.2 Temporal resolution improvement 487
      12.2.2.3 Spatial resolution improvement 494
      12.2.2.4 Dose and coverage 494
12.3 CT Fluoroscopy 498
12.4 CT Perfusion 505
12.5 Screening and Quantitative CT 513
    12.5.1 Lung cancer screening 514
    12.5.2 Quantitative CT 518
    12.5.3 CT colonography 520
12.6 Dual-Energy CT 523
12.7 Problems 533
Glossary 545
Index 551

Preface

Since the release of the first edition of this book in 2003, x-ray computed tomography (CT) has experienced tremendous growth thanks to technological advances and new clinical discoveries. Few could have predicted the speed and magnitude of the progress, and even fewer could have predicted the diverse nature of the technological advancement. The second edition of this book attempts to capture these advances and reflect on their clinical impact.

The second edition provides significant changes and additions in several areas. The first major addition is a new chapter on radiation dose. In the last few years, significant attention has been paid to this subject by academic researchers, radiologists, the general public, and the news media. An increased awareness of the impact of radiation dose on human health has led to the gradual adoption of the "as low as reasonably achievable" (ALARA) principle, the implementation of American College of Radiology (ACR) accreditation and other dose reference levels, and the development of many advanced dose-saving features for CT scanners. The new Chapter 11 briefly describes some of the known biological effects of radiation dose, then presents different dose definitions and measurements, and concludes with an illustration of various dose-reduction techniques. At the time the first edition was published, the term "multislice" CT was an accurate description of state-of-the-art scanners. Sixteen-slice scanners had just been introduced commercially, and their clinical utilities and advantages had just begun to be discovered. Since then, the "slice war" has continued, and now 64-, 128-, 256-, and 320-slice scanners are the new state of the art. These scanners can be easily labeled as "cone-beam" CT. They require not only a detector with wider coverage, but also other technologies such as new calibration techniques and reconstruction algorithms. Chapter 10 has been significantly expanded to discuss the technologies associated with these scanners and the new image artifacts created by them.

Since the first edition, CT advancement has not been limited to the technology. Advances also have been made in many areas of clinical applications, including the rapid development of cardiac CT imaging and new applications inspired by the reintroduction of dual-energy CT. Chapter 12 presents these advances and the fundamental physics and technologies behind them.

Image artifacts have accompanied x-ray CT ever since its birth over 30 years ago. Some artifacts are caused by the characteristics of the physics involved, some are caused by technological limitations, some are created by new technologies, some are related to the patient, some result from suboptimal design, and some are introduced by the operator. Chapter 7 has been expanded to reflect the ever-evolving nature of these artifacts and various efforts to overcome them.

Historically, CT advances were driven by the development of new hardware. However, it has become increasingly clear that hardware alone cannot solve all of the technical and clinical problems that CT operators face. The second edition includes significant updates to the section on statistical iterative reconstruction technology and presents some of the exciting new developments in this area.

To enhance readers' understanding of the material and to inspire creative thinking about these subjects, a set of "problems" concludes each chapter. Many problems are open-ended and may not have uniquely correct solutions. Hopefully readers will find these problems useful and will develop new problems of their own.

At the time of this writing, the world is experiencing an unprecedented financial crisis—that some call a financial "tsunami." It is impossible to estimate or predict the impact of this crisis on the market for x-ray CT. However, CT technology is unlikely to remain stagnant. Many new exciting advances will take place in both the technology and its clinical applications.

Jiang Hsieh
May 2009


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