The Physics of CT Dosimetry : CTDI and Beyond

Description

Content: Cover Half Title Series Page Title Page Copyright Page Contents Preface Acknowledgments Author About the Series Chapter 1: Introduction and History 1.1 INTRODUCTION 1.2 A HISTORICAL VIEW OF CT DOSIMETRY 1.2.1 The Early Universe 1.2.2 The Birth of CTDI -- 1981 1.2.3 Enter the Regulators -- 1989 1.2.4 The Standard Dosimetry Phantoms 1.2.5 Enter CTDI100 -- 1995 1.2.6 The Advent of Multi-Detector CT (MDCT) -- 1998 1.2.7 Enter CTDIvol (A Misnomer) but an Improvement since It Eliminates nT (N × T) 1.2.8 Dose Length Product 1.2.9 Helical Scanning -- Scanning with Continuous Table Motion -- 19901.3 SLIPPING THE SURLY BONDS OF CTDI 1.3.1 An Alternative to the Pencil Chamber -- 2003 1.3.2 AAPM TG-111 -- 2010 1.3.3 Limitations of the CTDI-Paradigm and the Pencil Chamber Acquisition 1.4 The IEC Attempts to Circumvent the Limitations of CTDI 1.4.1 For Shift-Variant Techniques 1.4.2 For the Stationary Phantom/Table 1.4.3 Wide Beam Widths 1.4.4 Use of the Scanner-Reported CTDI 1.4.5 Size-Specific Dose Estimates (SSDE) References Chapter 2: Derivation of Dose Equations for Shift-Invariant Techniques and the Physical Interpretation of the CTDI-Paradigm2.1 Introduction 2.2 Derivation of the Dose Equations and the CTDI-Paradigm on the Phantom Central Axis for a Shift-Invariant Helical Technique in Which No Parameters Vary With z (Constant Tube Current, Pitch, Aperture, etc.) 2.3 Limitations of the CTDI-Paradigm: The Requirement for Shift-Invariance 2.4 Extension of the Derivations to Axial Scans and to Helical Scans on the Peripheral Axes 2.4.1 Derivation of the Dose Equations for Axial Scans 2.4.2 Derivation of the Helical Dose Distribution on the Peripheral Axes2.4.3 Longitudinal Average vs. Angular Average for Helical Scans 2.5 Total Energy E Absorbed in the Phantom (and DLP) 2.5.1 CTDI-Aperture 2.5.2 The Physical Meaning of CTDIfree-in-air 2.5.3 Three-Dimensional Calculation of the Total Energy Deposited in the Phantom Glossary References Chapter 3: Experimental Validation of a Versatile System of CT Dosimetry Using a Conventional Small Ion Chamber 3.1 INTRODUCTION 3.2 SUMMARY OF CT DOSE THEORY IN A CYLINDRICAL PHANTOM 3.3 ACCUMULATED DOSE (OR CTDI) MEASUREMENTS 3.3.1 Pencil Chamber Acquisition Method3.3.2 Small Ion Chamber Acquisition Method 3.3.3 The Measured Quantity -- A Phantom Dose Surrogate 3.4 MATERIALS AND METHODS 3.5 MEASUREMENTS VALIDATING THE PRECISION AND ACCURACY OF TH 3.5.1 Test of the "Stem Effect" for NE 2571 Farmer Chamber 3.5.2 Effect of Phantom Cavity on Farmer Chamber Reading 3.5.3 Cross Comparison of Ion Chambers 3.5.4 Validation of the Manufacturer-Supplied Pencil Chamber Active Length ℓ 3.6 BODY PHANTOM MEASUREMENTS AND RESULTS 3.6.1 Effect of Phantom Length on CTDI100